JP2006293080A - Image heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a best paper supplying condition according to variation in Curie points of an exoergic member in a manufacturing process. <P>SOLUTION: An image heating apparatus heats an image on supplied recording material P by using the exoergic member 1 provided with a specified Curie point and generating heat by an action of magnetic flux. The image heating apparatus includes a detecting means 11 detecting the Curie point characteristic of the exoergic member and a varying means 104 varying the supplying condition of the recording material toward the exoergic member according to the result of detection by the detecting means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image heating apparatus that has an induction heating member having a Curie point characteristic and heats an image on a recording material by heat generated by the induction heating member due to magnetic flux generated by magnetic flux generation means.

  2. Description of the Related Art An electrophotographic copying machine or the like is provided with a fixing device that fixes a toner image formed by a transfer method or a direct method on a sheet of recording paper or transfer material as a recording medium.

  As the fixing device, for example, an induction heating type fixing device using high-frequency induction as a heating source has been proposed. (For example, see Patent Document 1) In this induction heating fixing device, a coil is concentrically arranged inside a hollow fixing roller made of a metal conductor, and fixing is performed by a high frequency magnetic field generated by flowing a high frequency current through the coil. An induced eddy current is generated in the roller, and the fixing roller itself generates Joule heat by the skin resistance of the fixing roller itself. According to this induction heating type fixing device, since the electric-heat conversion efficiency is greatly improved, the warm-up time (the time from when the power is turned on until the temperature of the fixing roller reaches a predetermined temperature suitable for fixing) is increased. Shortening is possible.

  Even with such an electromagnetic induction heating type fixing device, since it operates to fix the entire area of the maximum size of the recording material that can be passed through at the fixing temperature, it requires more energy than actually fixing the toner. In addition, depending on the size of the recording material, an area that is not the paper passing area is abnormally heated, causing temperature rise in the apparatus and thermal deterioration of the non-heating member.

As a countermeasure, a fixing roller having a Curie point near the fixing temperature has been proposed. (For example, refer to Patent Document 2) The temperature rise is weak above the permeability change point, which is a characteristic of the Curie point, and an area that is not more than necessary and a non-heating member does not rise.
JP 59-33787 JP 2000-39797 A

However, the Curie point roller may vary in the actual Curie point with respect to the set Curie point in the manufacturing process. As the Curie point varies, the heat generation characteristics differ. For example, in a fixing machine in which the Curie point is set to the fixing temperature and the temperature is adjusted by itself, a fixing roller having a Curie point lower than the set temperature may be used. In this case, for example, in order to satisfy the fixability of the unfixed toner image in the morning, the lower limit of the Curie point variation must be anticipated, and the productivity (throughput) must be reduced uniformly. Here, the throughput refers to the number of heat-fixed processes per unit time. However, there is a possibility that a fixing roller having a Curie point higher than the normal set temperature may be used. In this case, it is desirable to set a paper feed condition that alleviates a decrease in productivity.
Similarly, in the case of a fixing machine in which the Curie point is set higher than the fixing temperature and lower than the predetermined temperature for the purpose of preventing or reducing the excessive temperature rise when the roller is abnormally heated above the fixing temperature, Since the heat generation characteristics are different due to variations in the Curie point characteristics (characteristics in which the heat generation characteristics change as the roller temperature approaches the Curie point), depending on the actual Curie point variations of the fixing roller (differences in the Curie point characteristics) It is necessary to set the optimum paper feeding conditions (recording material feeding conditions, conveying conditions).

  Accordingly, an object of the present invention is to provide an image heating apparatus and an image forming apparatus that can set an optimum sheet feeding condition in accordance with variations in Curie point of a heat generating member in a manufacturing process.

  The configuration of a typical heating device according to the present invention is an image heating device that heats an image on a recording material fed using a heat generating member that has a predetermined Curie point and generates heat by the action of magnetic flux. Detecting means for detecting a Curie point characteristic of the heat generating member; and changing means for changing a feeding condition for feeding the recording material toward the heat generating member according to a detection result of the detecting means. An image heating apparatus.

  A typical image forming apparatus according to the present invention includes: an image forming unit that forms an image on a recording material; and a heat generating member that generates heat by the action of magnetic flux and has a predetermined Curie point. In an image forming apparatus that heats an image formed by the image forming unit using a member, a detecting unit that detects a Curie point characteristic of the heat generating member, and a detection unit that detects a Curie point characteristic of the heat generating member An image forming apparatus comprising: a changing unit that changes a recording material feeding condition. It is.

  According to the present invention, it is possible to provide an image heating apparatus and an image forming apparatus that can set an optimum sheet feeding condition according to variations in the Curie point of the heat generating member in the manufacturing process.

  Hereinafter, the present invention will be described with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration model diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus 100 of this example is a digital image forming apparatus (a copying machine, a printer, a facsimile, a composite function machine thereof, etc.) equipped with a transfer type electrophotographic process, a laser scanning exposure method, and an induction heating method fixing device. is there.

  Reference numeral 101 denotes a document reading device (image scanner), and 102 denotes an area designating device (digitizer), both of which are arranged on the upper surface side of the image forming apparatus 100. The document reading device 101 scans a document surface placed on the document table of the device by a scanning illumination optical system including a light source provided therein, and reads reflected light from the document surface by an optical sensor such as a CCD line sensor. The image information is converted into a time series electric digital pixel signal. The area designating device 102 sets a document reading area and outputs a signal. A print controller 103 outputs a print signal based on image data of a personal computer (not shown). A control unit (CPU, control unit) 104 receives signals from the document reading device 101, the area designating device 102, the print controller 103, and the like, and performs signal processing for sending commands to each unit of the image output mechanism and various image forming sequence controls. Means, Curie point (Curie temperature) discrimination means).

  The following is a description of the image output mechanism section (image forming mechanism section) as the image forming means. Reference numeral 105 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) serving as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed. In the rotation process, the photosensitive drum 105 is uniformly charged by a charging device 106 with a predetermined polarity and potential, and the uniformly charged surface is uniformly charged by receiving image exposure L by an image writing device 107. The potential of the exposed bright portion of the surface is attenuated, and an electrostatic latent image corresponding to the exposure pattern is formed on the surface of the photosensitive drum 105. In this example, the image writing device 107 is a laser scanner, which outputs a laser beam L modulated in accordance with the image data signal-processed by the control unit (CPU) 104, and applies the uniformly charged surface of the rotating photosensitive drum 105. An electrostatic latent image corresponding to the document image information is formed by scanning exposure.

  Next, the electrostatic latent image is developed as a toner image by the developing device 108. The recording medium feed in which the toner image is fed at a predetermined control timing from the paper feed mechanism unit to the transfer unit T which is the opposite part of the photosensitive drum 105 and the transfer charging device 109 at the position of the transfer charging device 109. In the case of the image forming apparatus of this example, the mechanism unit includes a first cassette paper feeding unit 110 that stacks and accommodates small-size recording materials as heated materials, and a second cassette that stacks and accommodates large-sized recording materials as heated materials. Recording paper P as a heated material selectively fed separately from the first or second cassette paper feeding unit 110 or 111 to the transfer unit T at a predetermined timing. A registration roller 112 is provided.

  The recording material P that has received the transfer of the toner image from the surface of the photosensitive drum 105 at the transfer unit T is separated from the surface of the photosensitive drum 105, conveyed to the fixing device 114, and subjected to fixing processing of the unfixed toner image. The paper is discharged onto the paper discharge tray 115.

  On the other hand, the surface of the photosensitive drum 105 after separation of the recording material is cleaned by the cleaning device 113 after removal of adhering contaminants such as untransferred toner, and is repeatedly used for image formation.

(2) Fixing device 114
FIG. 2 is an enlarged cross-sectional model view of a main part of the fixing device 114 as an image heating device. The fixing device 114 is a heating roller type and induction heating type heating device, and is a pair of heating members (a fixing nip portion N having a predetermined nip length (nip width) formed by pressure contact with each other with a predetermined pressing force ( A heating medium, a fixing member) and two heating rollers 1 and 2 as pressure members are used as main components.

  A heating roller (hereinafter referred to as a fixing roller) 1 as a heating member is formed of an induction heating element (conductive magnetic material) such as iron, nickel, SUS430, and has a thickness of about 0.1 mm to 1.5 mm. This roller has a hollow (cylindrical) metal layer (conductive layer, cored bar) and has a Curie point characteristic. The outer surface of the roller is coated with a fluororesin or the like, and a heat-resistant release layer (heat transfer material) ) 1a is formed. Here, the Curie point characteristic means a characteristic in which the magnetic property is lost and the heat generation characteristic is changed when the temperature of the fixing roller 1 approaches the Curie point. By using this characteristic, excessive temperature rise is prevented. Alternatively, reduction can be performed.

  In this embodiment, the fixing device 114 has a fixing temperature of 230 ° C., and the fixing roller 1 is a fixing roller 1 having a Curie point characteristic in which the Curie point is set to substantially the fixing temperature. That is, the metal layer that is the induction heating element of the fixing roller 1 in this embodiment is a magnetic shunt alloy that has a permeability change point at 200 ° C. and has a permeability of 1 at 230 ° C. as shown in FIG. . The temperature at which the permeability reaches 1 is the so-called Curie point at which the induction heating element loses magnetism. The magnetic shunt alloy is an iron-nickel alloy whose Curie point is adjusted as desired, as disclosed in JP 2000-39797 A.

  The fixing roller 1 is disposed such that both end portions thereof are rotatably supported via bearings between front and back side plates of the fixing device. In addition, a coil assembly 3 serving as a magnetic flux generating means for inserting an induction current (eddy current) in the fixing roller 1 to generate Joule heat is generated in the inner space.

  The pressure roller 2 is an elastic roller including a shaft core 2a and a silicone rubber layer 2b, which is a surface releasable heat-resistant rubber layer concentrically formed around the outer periphery of the shaft core. The pressure rollers 2 are arranged in parallel below the fixing roller 1 so that both end portions of the cored bar 2a are rotatably held via bearings between the front and back side plates of the fixing device. Further, a fixing nip portion N having a predetermined nip length as a heating portion is pressed against the lower surface of the fixing roller 1 with a predetermined pressing force against the elasticity of the elastic body layer 2b by a biasing means (not shown). Is formed.

  A coil assembly 3 as a magnetic flux generating means inserted in the inner space of the fixing roller 1 includes a bobbin 4, a core (core material) 5 made of a magnetic material, an induction coil (excitation coil, induction heat source) 6, and an insulating member. This is an assembly of the stay 7 and the like. The core 5 is inserted into a through hole formed in the bobbin 4, and the induction coil 6 is formed by winding a copper wire around the bobbin 4. The unit of the bobbin 4, the core 5 and the induction coil 6 is fixedly supported on the stay 7.

  The above-described coil assembly 3 is inserted into the inner space of the fixing roller 1 so as to maintain a constant gap between the inner surface of the fixing roller 1 and the induction coil 6 at a predetermined angle and posture. Both ends are fixedly supported non-rotatingly by holding members (not shown) on the front side and the back side of the fixing device, respectively. The units of the bobbin 4, the core 5 and the induction coil 6 are accommodated so as not to be exposed to the outside of the fixing roller 1.

  The core 5 is preferably made of a material having a large magnetic permeability and a small self-loss. For example, ferrite, permalloy, sendust, etc. are suitable. The bobbin 4 also functions as an insulating part that insulates the core 5 from the induction coil 6.

  On the outer periphery of the fixing roller 1, a central temperature detecting device (detecting means) 11 for detecting the temperature of the fixing roller 1 is provided. The central temperature detection device 11 is in pressure contact with the surface of the fixing roller 1 so as to face the induction coil 6 across the fixing roller 1. The central temperature detection device 11 is composed of, for example, a thermistor.

  Reference numeral 13 denotes a separation claw, which is introduced into the fixing nip portion N and serves to separate the recording material P as a heated material from the fixing nip portion N from being wound around the fixing roller 1 and separated from the fixing roller 1. .

  The bobbin 4, the stay 7, and the separation claw 14 are made of heat-resistant and electrically insulating engineering plastic.

  In the present embodiment, the sheet passing is performed based on the central reference. That is, for any recording material size, the central portion of the recording material passes through the central portion in the fixing roller axial direction.

  The control unit 104 of the image forming apparatus starts the apparatus by turning on the main power switch SW (FIG. 4) of the apparatus and starts predetermined image forming sequence control.

  For the fixing device 114, the control unit 104 drives the fixing roller 1 to rotate at a predetermined speed in a clockwise direction indicated by an arrow A in FIG. Following the rotation of the fixing roller 1, the pressure roller 2 also rotates in the counterclockwise direction indicated by the arrow B. Further, energization of a high frequency current having a predetermined fixed value is started from the excitation circuit 116 to the induction coil 6 of the coil assembly 3 at a predetermined control timing. As a result, a high-frequency alternating magnetic field is generated around the induction coil 6, and the fixing roller 1 is heated by electromagnetic induction heat generation. The temperature of the fixing roller 1 rises rapidly, and converges to a temperature at which the magnetic permeability of the fixing roller 1 becomes 1, that is, a so-called Curie point, through a temperature at which the magnetic permeability changes. As long as the above-described high-frequency current is continuously applied to the induction coil 6, the fixing roller 1 is maintained in a heated state at the Curie point (self-temperature control state).

As described above, the fixing device 114 in this embodiment has a fixing temperature of 230 ° C., and the fixing roller 1 is a fixing roller 1 having a Curie point characteristic in which the Curie point is set to substantially the fixing temperature. The heating temperature substantially converges to the fixing temperature of 230 ° C. and becomes a self-temperature control state.
The temperature change of the fixing roller 1 over time is detected by the thermistor 11, and the detected temperature information is input to the control unit 104. The control unit 104 detects that the temperature of the fixing roller 1 has converged to the Curie point based on the input detected temperature information.
In the self-temperature control state of the fixing roller 1, the recording material P carrying the unfixed toner image t is introduced from the image forming mechanism side to the fixing nip portion N, and is nipped and conveyed through the fixing nip portion N. Thus, the unfixed toner image t is heated and pressure-fixed on the surface of the recording material P by the heat of the fixing roller and the pressing force of the fixing nip portion N. In this embodiment, the heat treatment can be performed when the temperature of the fixing roller 1 reaches a predetermined temperature after energization of the coil is started.

(3) Curie point measurement mode Depending on the device, the set Curie point (Curie point characteristic) may vary. Therefore, in this embodiment, a detecting means for detecting a Curie point (Curie point characteristic) is provided, and the recording material feeding condition can be changed according to the detection result. That is, the image forming apparatus according to the present exemplary embodiment is configured to set an optimum sheet feeding condition (feeding condition of the recording material P) according to variations in manufacturing of the setting Curie point of the fixing roller 1 that is an induction heating member. The following Curie point measurement mode is provided.

  FIG. 5 is a basic flowchart of the Curie point measurement mode. FIG. 6 is a flow chart showing a Curie point and paper feed condition (recording material P feed condition, transport condition) determination process in the Curie point measurement mode. FIG. 7 is a diagram showing the temperature rise of the fixing roller 1 in the Curie point measurement mode in time series.

  The Curie point measurement mode of this embodiment is executed when the mode is selected by the mode selection switch 117 (FIG. 4) provided in the operation unit (not shown) of the image forming apparatus. The Curie point measurement mode may be executed at the time of shipment of the image forming apparatus from the factory, installation, replacement of the fixing member, power-on, return to standby, or elapse of a predetermined time.

  As shown in the basic flowchart of the Curie point measurement mode in FIG. 5, the control unit 104 determines whether or not the Curie point measurement mode is selected by the mode selection switch 117 in S200. If the Curie point measurement mode is not selected (N in S200), the process ends without doing anything. When the Curie point measurement mode is selected (Y in S200), the control unit 104 starts to supply power to the fixing device 114 (S201). That is, as in the normal image forming operation, the fixing roller 1 is driven to rotate, and energization of a high frequency current having a predetermined fixed value is started from the excitation circuit 116 as energization means to the induction coil 6 of the coil assembly 3. Then, a determination process for measuring a Curie point (or Curie point characteristic) and determining a paper feed condition is executed (Seq1). Detailed description of this determination process (Seq1) will be described later.

  When the determination process is completed, the power supply to the fixing device 114 is stopped (S202).

  The above is the basic flow of processing in the Curie point measurement mode.

  Next, the measurement of the Curie point (or Curie point characteristics) and the paper feed condition determination process (Seq1) will be described in detail with reference to FIGS.

  As shown in FIG. 6, first, it is determined whether or not the time Time1 required for the determination process has elapsed (S300). This time Time1 is the same as when the normal image forming operation is performed. After the energization of the high frequency current from the excitation circuit 116 to the induction coil 6 of the coil assembly 3, the surface temperature of the fixing roller 1 changes from the environmental temperature to the fixing target. The time is set to be somewhat longer than the general required time required to rise to the temperature (= approximately the set Curie point). This fixing target temperature can be set to an appropriate temperature depending on the environment such as room temperature and humidity.

Further, the surface temperature transition information of the fixing roller 1 is input to the control unit 104 continuously (time series) with time from the thermistor 11 serving as the Curie point characteristic detecting means. The control unit 104 serving as a determining unit that determines whether or not the Curie point of the fixing roller is within a predetermined range is based on the fixing roller surface temperature transition information that is continuously input from the thermistor 11 until the time Time1 elapses. At the time, it is determined whether or not the inclination of the temperature rise of the fixing roller 1 has become smaller than a predetermined inclination (S301). Here, it is confirmed whether or not the temperature rise of the fixing roller 1 has converged until the time Time1 has elapsed. That is, it is confirmed whether or not the Curie point has been reached.
If the temperature does not converge even after a predetermined time has elapsed, it is regarded as abnormal and the power supply to the coil is stopped. (S300)
Next, in S301, if it is determined that the Curie point has been reached (Y), the process proceeds to S302. If it is determined that the Curie point has not been reached (N), the process returns to S300 and the same processing is performed. Specifically, the determination as to whether or not the Curie point has been reached will be described. The temperature rise rate is obtained from the difference between the temperature information before and after the temperature information input from the thermistor is taken at regular intervals. At this time, the controller 104 (discriminating means) discriminates whether or not the temperature increase rate is equal to or less than a predetermined value (whether or not it has a predetermined Curie characteristic). In this embodiment, the rate of temperature increase was obtained from the difference between the temperature information before and after, but not limited to this, the average value of some sampled values (average value for a predetermined time) was calculated, and the calculated average value The temperature increase rate may be obtained from the transition.
As described above, in this embodiment, the temperature at which the rate of temperature rise is a predetermined value or less is regarded as the Curie point.

  In S <b> 302, it is determined which zone of the temperature ranges Zone 1, Zone 2, and Zone 3 is predetermined as the surface temperature TEMP of the fixing roller 1 at that time as a predetermined range. In this embodiment, three temperature ranges Zone 1 to 3 constitute a temperature tolerance allowable range in the design of the fixing roller 1. In the temperature ranges Zone 1 to 3, Zone 2 is a Zone that determines a Curie point corresponding to a set Curie point (230 ° C. in this embodiment) based on the surface temperature TEMP of the fixing roller 1. Zone 1 is a Zone that determines a Curie point that is higher than the set Curie point based on the surface temperature TEMP of the fixing roller 1. The upper limit value (first temperature in the figure) Temp1 of the temperature range Zone1 is set to a temperature at which there is a risk of failure, smoke generation, or ignition of surrounding components. Zone 3 is a zone for determining a Curie point lower than the set Curie point based on the surface temperature TEMP of the fixing roller 1. The lower limit value (second temperature in the figure) Temp2 of the temperature range Zone3 is set to a limit temperature that can satisfy the image fixing property. These upper limit value Temp1 and lower limit value Temp2 can be set to appropriate values depending on the environment such as room temperature and humidity.

  When it is determined in S302 that the surface temperature TEMP of the fixing roller 1 attached to the fixing device 114 and having the Curie point characteristic is in the temperature range Zone1, the Curie point of the fixing roller 1 is near the upper limit of the temperature crossing allowable range. Judge that there is. In this case, since the Curie point is higher than the set Curie point of the temperature range Zone 2, more power can be supplied to the fixing roller 1, and the unfixed toner image t is fixed on the recording material P in the morning. It is possible to secure a margin for sex. Therefore, the feeding condition for feeding the recording material P to the fixing roller 1 can be changed according to the Curie point.

  Here, as the feeding conditions, for example, the number of recording materials to be heat-treated by the fixing roller 1 per unit time or the timing of changing the number of recording materials to be heat-treated per unit time can be cited. .

  Specifically, in the control unit 104, after the warm-up is finished (after the power of the apparatus main body is turned on and the recording material is ready to be heated), the productivity (throughput) is measured as the Curie point. Is set higher than when Curie point is set, and the copy operation is started. Here, the copying operation is an operation in which the unfixed toner image t is heated and fixed on the recording material P by the fixing roller 1 and the pressure roller 2. Specifically, the productivity (the number of sheets heated by the fixing roller per unit time) is changed by changing the interval of the paper to be conveyed or changing the conveyance speed.

  Next, in S302, when it is determined that the surface temperature TEMP is in the temperature range Zone2 in the fixing roller 1, it is determined that the Curie point of the fixing roller 1 is near the center of the temperature crossing allowable range. In this case, since the Curie point is substantially equal to the set Curie point, the control unit 104 serving as a changing unit that changes the feeding condition fixes the fixing property of the unfixed toner image t on the recording material P in the morning. A copy operation is started by applying a predetermined paper feed condition setting (a condition in which the productivity is lower than that in Zone 1), which is the minimum productivity reduction for satisfying the defect.

  Here, “morning first” refers to a time immediately after the image forming apparatus main body or the fixing device is turned on, and the fixing roller 1 is not sufficiently heated. In this embodiment, the feeding condition is changed in the morning. However, the present invention is not limited to this, and feeding for a predetermined time after returning from a standby operation (standby state) in which image formation is not performed. The conditions may be changed.

  Next, in S302, when it is determined that the surface temperature TEMP is in the temperature range Zone3 in the fixing roller 1, it is determined that the Curie point of the fixing roller 1 is near the lower limit of the temperature crossing allowable range. In this case, since the Curie point is lower than the set Curie point of the temperature range Zone2, there is little margin for satisfying the first fixing failure in the morning with respect to the fixability of the unfixed toner image t on the recording material P. For this reason, the control unit 104 applies a predetermined paper feed condition setting that is slower than the temperature range Zone2 and starts the copy operation.

  Next, in S303, a predetermined calculation formula is applied according to the surface temperature TEMP of the fixing roller 1 determined in the preprocessing S301, and the paper supply condition holding time Time2 for applying the paper supply condition setting determined in S302 is calculated. To do. An example of a calculation formula for obtaining the paper feed condition holding time Time2 is given below.

Feeding condition holding time: Time2 = (210−Fixing roller surface temperature TEMP) × 10 [SEC]
In FIG. 7, A is a morning copy operation in the temperature range Zone1, and the copy operation is started at a normal copy speed without setting the paper feed condition holding time. B is a copy operation in the temperature range Zone2, a predetermined paper feed condition holding time Time2 is set, and the copy operation is started at a copy speed slower than the normal copy speed. C is a copy operation in the temperature range Zone3. A paper feed condition holding time Time2 longer than that in the temperature range Zone2 is set, and the copy operation is started at a copy speed slower than the copy speed in the Zone2. In the temperature ranges Zone 2 and 3, the normal copy speed is restored after the holding time Time2 has elapsed.

  In the present embodiment, the number of sheets heated by the fixing roller 1 per unit time is changed in Zone 2 and Zone 3, but the time or timing until the throughput is reduced without changing the throughput reduction amount in Zone 2 and Zone 3. The feeding condition may be changed by changing.

  The flow in the paper feed condition determination process is thus completed.

  In the paper supply condition holding time Time2, the registration roller 112 is controlled to change the paper supply interval of the recording material P, that is, the interval between the trailing edge of the preceding recording material and the leading edge of the succeeding recording material, or The time for controlling the feeding interval of the recording material P is changed.

Here, a method for measuring the Curie point will be described. The Curie point can be measured from the temperature dependence of the magnetic permeability. The magnetic permeability is measured as follows. The measurement was performed using a BH analyzer (model number: SY-8232) manufactured by Iwatsu Measurement Co., Ltd. A predetermined primary coil and secondary coil of the apparatus are wound around the measurement sample, and measurement is performed at a frequency of 20 kHz. The measurement sample may be any shape as long as the coil is wound around it. (The ratio between the temperatures with different magnetic permeability hardly changes)
After setting the coil to the sample, put the sample in a constant temperature room to saturate the temperature, and plot the permeability at that temperature. The temperature dependence curve of permeability can be obtained by changing the temperature of the temperature-controlled room. At this time, the temperature at which the magnetic permeability is 1 is defined as the Curie temperature. Here, the temperature at which the magnetic permeability is 1 is obtained as follows. The temperature of the temperature-controlled room is raised, and the permeability does not change at a certain temperature. This temperature is regarded as the temperature at which the magnetic permeability is 1 (Curie temperature).

  In this embodiment, the morning feeding condition has been described as an example. However, the present invention is not limited to this. For example, the present invention can also be applied at the time of standby (heating processing operation standby state).

  In addition to the morning one, the present invention can also be applied when an arbitrary time has elapsed since the apparatus was turned on and reached the heat treatment possible state. For example, in the heat processing enabled state, when the throughput is lowered when the temperature of the roller is lowered when continuous paper is passed, the throughput down start timing and the amount of throughput down may be changed according to the variation in Curie characteristics. In this case, the feeding condition is appropriately changed from the difference in heat generation capability of the fixing roller 1 due to the difference in Curie point characteristics.

  In this embodiment, the convergence temperature of the heat generating member is detected to detect the Curie point characteristic (Curie point). However, the present invention is not limited to this. For example, the temperature change of the permeability of the fixing roller 1 is measured to measure the Curie point characteristic. The temperature (Curie point characteristic) may be detected indirectly.

  In the first embodiment, an example in which the Curie point is set to the fixing temperature and the self-temperature control is described, but in this embodiment, the Curie point is set to a temperature higher than the predetermined fixing temperature and lower than the heat resistance temperature of the apparatus. This is different from the first embodiment in that abnormal temperature rise at the difference area between the maximum size paper and small size paper when small size paper is continuously passed, that is, so-called non-sheet passing temperature rise is prevented or reduced. . The heat-resistant temperature of the device is a temperature at which the electric power supplied to the heating device is increased and the device components rise when the temperature of the heating roller rises and exceeds the destruction or heat-resistance limit. In the present invention, the heat resistance temperature of the coating resin of the coil of the heating device is 235 degrees, and the heat resistance temperature of the heating apparatus of the present embodiment is 235 degrees.

  In this embodiment, the temperature of the fixing roller 1 is detected by the thermistor 11, and the temperature is adjusted so that the detected temperature becomes a predetermined target temperature. In this case, the time to reach a predetermined fixing temperature varies due to the difference in Curie point characteristics. Therefore, the time from the start of energization to the coil until it reaches the specified fixing temperature is detected by a timer as a Curie point characteristic detection means, and if the time to reach the fixing temperature is long, the throughput is reduced compared to the short case. Reduce the amount of The longer the time from when the coil is energized until the predetermined fixing temperature is reached, the greater the amount of heat stored in the roller, so that the throughput reduction can be reduced.

  In this embodiment, the heat resistance temperature of the apparatus is 235 ° C., but the present invention is not limited to this.

  FIG. 8 is a schematic configuration diagram of an induction heating type fixing device in the present embodiment. The fixing device of the present embodiment is a film heating type fixing device using a fixed induction heating member as a heater (heating body).

  Reference numeral 10 denotes a fixing film assembly as a heating member. The assembly 10 includes a horizontally long and thin plate-like induction heating member 1A as a heater, a heater support member 8 that supports the heater 1A fixed along the length of the lower surface, and is disposed inside the heater support member 8. A coil assembly 3 composed of a magnetic core 5, an induction coil 6 and the like; a fixing film 9 made of a cylindrical heat-resistant resin loosely fitted on the heater 1A-heater support member 8-coil assembly 3 assembly; It comprises a thermistor 11 as a temperature measuring element for detecting the temperature of the heater 1A.

  In the present embodiment, the fixing device has a fixing temperature of 230 ° C., and the heater 1A as the induction heating member has a Curie point characteristic in which the Curie point is set to substantially the fixing temperature.

  Reference numeral 2 denotes a pressure roller as a pressure member. The pressure roller 2 is an elastic roller comprising a shaft core 2a and a silicone rubber layer 2b, which is a surface-releasing heat-resistant rubber layer formed concentrically and integrally around the shaft core. The pressure roller 2 holds both ends of the metal core 2a rotatably between the front and back side plates of the fixing device via bearings.

  Above the pressure roller 2, the fixing film assembly 10 is arranged in parallel with the pressure roller 22 with the heater 1A facing downward, and biasing means (not shown) is provided at the left and right ends of the heater support member 8. The pressing force is applied. As a result, the heater 1A on the lower surface of the heater support member 8 is pressed against the pressure roller 2 against the elasticity of the elastic layer 2b with the fixing film 9 in between, and a predetermined width is provided between the fixing film 9 and the pressure roller 2. The fixing nip portion N is formed.

  The pressure roller 21 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the cylindrical fixing film 9 by the frictional force in the fixing nip N between the pressure roller 2 and the outer surface of the fixing film 9 by the rotational driving of the pressure roller 2. As a result, the fixing film 9 rotates around the heater support member 8 in the clockwise direction indicated by an arrow while sliding in close contact with the lower surface of the heater 1A in the fixing nip portion N (pressure roller driving method). The fixing film 9 is in a rotational state having a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 2.

  The inner surface of the fixing film 9 is coated with fluorine-based grease as a lubricant to ensure the sliding property between the fixing film 9 and the heater 1A / heater support member 8.

  The control unit 104 rotationally drives the pressure roller 2 by the driving source M at a predetermined control timing, and at a predetermined control timing, a high frequency current having a predetermined fixed value is applied from the excitation circuit 116 to the induction coil 6 of the coil assembly 3. Start energization. As a result, a high-frequency alternating magnetic field is generated around the induction coil 6, and the heater 1A, which is an induction heating member, generates heat by electromagnetic induction and the temperature rises. The temperature of the heater 1A rises quickly, and converges to a so-called Curie point at which the permeability of the heater 1A becomes 1 after passing through the change point temperature of the permeability. As long as the above-described high-frequency current is continuously supplied to the induction coil 6, the heater 1 </ b> A is maintained substantially in the heated state at the Curie point (self-temperature control state). In the fixing device in this embodiment, as described above, the fixing temperature is set to 230 ° C., and the heater 1A is an induction heating member having a Curie point characteristic in which the Curie point is set to substantially the fixing temperature. Almost converges to a fixing temperature of 230 ° C. and enters a self-temperature control state.

  The temperature change of the heater 1A with time is detected by the thermistor 11, and the detected temperature information is input to the control unit 104. The control unit 104 detects that the temperature of the heater 1A has converged to the Curie point based on the input detected temperature information.

  In the self-temperature control state of the heater A1, the recording material P carrying the unfixed toner image t is introduced from the image forming unit side to the fixing nip portion N and is nipped and conveyed through the fixing nip portion N. The unfixed toner image t is heated and pressure-fixed on the surface of the recording material P by the heat of the heater 1A via the fixing film 9 and the pressure of the fixing nip N.

  By providing the image forming apparatus including such a fixing device with the Curie point measurement mode as in the first embodiment, an actual heater 1A having a Curie point characteristic as an induction heating member mounted on the apparatus is provided. It is determined whether the Curie point is in any temperature range Zone 1 to 3 of the temperature tolerance allowable range of the set Curie point. When the Curie point is in the temperature range Zone 1 or 3, the corresponding paper feed condition setting is applied.

  As described above, according to each embodiment, it is possible to set an optimum sheet feeding condition according to variations in the Curie point of the fixing roller 1 or the heater A1 as the induction heating member in the manufacturing process.

[Others]
1) The present invention is also applied to an image forming apparatus including a magnetic flux shielding plate for preventing a temperature rise at a non-sheet-passing portion and an induction heating type fixing device having a driving means for induction. It is possible to set an optimum sheet feeding condition according to variations in the Curie point of the heat generating member.

2) In the fixing device according to the first or second embodiment, the coil assembly 3 as the magnetic flux generating unit may be arranged outside the fixing roller 1 as the induction heating member.
In the fixing device according to the first exemplary embodiment, instead of the fixing roller, a belt-like heat generating member may be stretched between a plurality of suspension members and rotated by a driving roller.

  3) In the fixing device according to the second embodiment, the fixing film 9 may be configured to be stretched between a plurality of suspension members and rotated by a drive roller. Further, the fixing film 9 may be a long-end member having a roll wound around the feeding shaft, and may be configured to travel and move to the winding shaft side.

  4) The heating device of the present invention is not limited to the fixing device of the embodiment, but an image heating device that is supposed to be worn, and an image heating device that reheats a recording medium carrying an image to improve surface properties such as gloss The sheet-like heated material other than the recording medium can be passed through and used as a heat treatment apparatus such as drying, heat laminating, hot press wrinkle removal, hot press curl removal and the like.

  In the first embodiment, the fixing temperature is the temperature of the heating roller when fixing the toner on the paper. In this embodiment, the fixing temperature is 230 ° C., but the present invention is not limited to this.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. Expanded cross-sectional model view of the fixing device Explanatory drawing of change in magnetic permeability with temperature of metal layer (induction heating member) of fixing roller Block diagram of control system Basic flowchart of Curie point measurement mode The flowchart figure which showed the Curie point at the time of Curie point measurement mode, and paper feed condition judgment processing Diagram showing the temperature rise of the fixing roller and the paper feed condition settings in time series in the Curie point measurement mode Enlarged cross-sectional model view of the fixing device in Example 2

Explanation of symbols

1 ... Heating member (fixing roller), 1a ... Metal layer (induction heating member), 2 ... Pressure member (pressure roller), 3 ... Coil assembly (magnetic flux generating means), 4 ... Bobbin, 5 .. Magnetic core, 6 .... induction coil, 7 .... stay, 1A ... heater (induction heating member), 8 .... heater support member, 9 .... fixing film, 10 .... fixing film assembly, 11 .... Temperature sensor, 13 ... Separation claw, 100 ... Image forming device, 101 ... Document reading device, 102 ... Digitizer, 103 ... Print controller, 104 ... Control unit (CPU), 105 ... Photosensitive drum, 107 ..Image writing device 105 ..Photosensitive drum 108 ..Development device 109 ..Transfer device 114 ..Fixing device 116 ..Excitation circuit, S200 to S304 ..Curie point measurement mode Each processing step, Seq1 ·· Curie point measurement mode paper feed condition determination processing, TEMP ·· Curie point measurement mode measured Curie point, Temp1 ·· Temperature tolerance allowable range, Temp2 ·· Temperature tolerance Minimum allowable temperature in allowable range, Time1 ... Curie point measurement mode processing time, Time2 ... Morning one feeding condition holding time, Zone1 ... Upper range of temperature tolerance range, Zone2 ... Central range of temperature tolerance range, Zone3 ... Lower range of temperature tolerance range

Claims (13)

  In an image heating apparatus for heating an image on a recording material fed using a heat generating member having a predetermined Curie point and generating heat by the action of magnetic flux, detecting means for detecting the Curie point characteristic of the heat generating member An image heating apparatus comprising: a changing unit that changes a feeding condition for feeding the recording material toward the heat generating member according to a detection result of the detecting unit.   2. The image heating apparatus according to claim 1, wherein the feeding condition is the number of recording materials to be heat-treated by the heat generating member per unit time.   The image heating apparatus according to claim 1, wherein the feeding condition is a timing for changing a number of recording materials per unit time subjected to heat treatment by the heat generating member.   The image according to any one of claims 1 to 3, wherein the detection means detects a temperature at which a rate of temperature increase of the heat generating member per unit time after the heat generating member starts to generate heat is a predetermined value or less. Heating device.   5. The image heating apparatus according to claim 4, wherein when the temperature at which the temperature increase rate is equal to or lower than a predetermined temperature is lower than the predetermined temperature, the number of recording materials to be heat-treated by the heat generating member per unit time is reduced. .   5. The image heating apparatus according to claim 4, wherein when the temperature at which the temperature increase rate is equal to or lower than a predetermined temperature is higher than the predetermined temperature, the number of recording materials to be heat-treated by the heat generating member per unit time is increased. .   5. The period of decreasing the number of recording materials per unit time subjected to heat treatment by the heat generating member when the temperature at which the temperature increase rate is equal to or lower than a predetermined temperature is lower than a predetermined temperature. Image heating device.   5. The period for reducing the number of recording materials per unit time subjected to heat treatment by the heat generating member when the temperature at which the temperature increase rate is equal to or lower than a predetermined temperature is higher than a predetermined temperature. Image heating device.   A temperature adjusting means for adjusting the temperature of the heat generating member to a predetermined temperature control temperature, and the feeding condition according to a time from the start of heating the heat generating member until the predetermined temperature control temperature is reached. The image heating apparatus according to claim 1, wherein the image heating apparatus is changed.   10. The image heating according to claim 1, wherein the changing unit changes a feeding condition within a predetermined period after the power of the main body of the apparatus is turned on according to the detection result. apparatus.   11. The image heating apparatus according to claim 1, wherein the Curie point is set to a temperature not lower than a fixing temperature and not higher than a heat resistant temperature of the apparatus.   An image formed by the image forming unit using the heat generating member, the image forming unit forming an image on the recording material, and a heat generating member that generates heat by the action of magnetic flux and has a predetermined Curie point. In the image forming apparatus that heats the recording medium, a detecting unit that detects a Curie point characteristic of the heating member, and a changing unit that changes a feeding condition of the recording material to the heating member according to a detection result of the detecting unit. An image forming apparatus comprising: The image forming apparatus according to claim 12, wherein the changing unit changes a feeding condition within a predetermined period after the power of the image forming apparatus main body is turned on according to the detection result.

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