JP2016024366A - Fixation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device of an electromagnetic induction heating system, which facilitates temperature control of an area of a rotor, through which a recording material passes, while forming heat generation distribution according to the size of the recording material.SOLUTION: A fixation device includes: a converter driving a resonance circuit; a switch member controlling electric power supplied to the converter; a frequency control unit setting the drive frequency of the converter according to at least one of the size of a recording material and the temperature of the paper non-passing part of a rotor; and an electric power control unit controlling the switch member according to the temperature of the paper passing part of the rotor, and controlling electric power supplied to the converter.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer.

  A fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer is a recording material that carries an unfixed toner image at a nip formed by a heating rotator and a pressure roller that contacts the heating rotator. In general, a toner image is fixed on a recording material by heating while conveying the toner.

  In recent years, an electromagnetic induction heating type fixing device capable of generating heat in a conductive layer of a heating rotator has been developed and put into practical use. The electromagnetic induction heating type fixing device has an advantage that the warm-up time is short.

  Patent Document 1 discloses a fixing device in which the restrictions on the thickness of the conductive layer and the material of the conductive layer are small.

JP 2014-026267 A

  Also in the fixing device disclosed in Japanese Patent Application Laid-Open No. 2004-133620, the temperature rise of the non-sheet passing portion when fixing a small size recording material becomes a problem.

  An object of the present invention is to provide a fixing device that can easily control the temperature of a region through which a recording material of a rotating body passes while forming a heat generation distribution according to the size of the recording material.

  The present invention for solving the above-described problems includes a cylindrical rotating body having a conductive layer, a coil disposed inside the rotating body and having a helical axis substantially parallel to the generatrix direction of the rotating body, and a resonant capacitor An image formed on the recording material by the heat of the rotating body, wherein the conductive layer causes electromagnetic induction heat generation by the magnetic flux generated by the coil. In the fixing device for fixing the recording material to the recording material, a switch member for controlling the power supplied to the converter, and driving of the converter according to at least one of the size of the recording material and the temperature of the non-sheet passing portion of the rotating body A frequency control unit that sets a frequency, and a power control unit that controls the switch member in accordance with the temperature of the sheet passing portion of the rotating body and controls the power supplied to the converter. The features.

  It is possible to provide a fixing device that can easily control the temperature of a region through which a recording material of a rotating body passes while forming a heat generation distribution according to the size of the recording material.

Schematic sectional view of the image forming apparatus Cross section of fixing unit Front view of fixing unit Perspective view of coil unit provided in fixing unit Example 1 Coil unit drive circuit diagram Diagram showing the relationship between the drive frequency and the heat distribution of the fixing sleeve Diagram explaining TRIAC voltage waveform Flow chart of the first embodiment Example 2 Coil unit drive circuit diagram Diagram explaining FET voltage waveform Flow chart of embodiment 2

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments for carrying out the invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

Example 1
FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 of this embodiment is a laser beam printer using an electrophotographic process.

  A controller 31 is a control unit of the image forming apparatus, and includes a CPU (Central Processing Unit) 32 having a ROM 32a, a RAM 32b, a timer 32c and the like, various input / output control circuits (not shown), and the like. Reference numeral 101 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) serving as an image carrier, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed. The photosensitive drum 101 is uniformly charged to a predetermined polarity and potential by the contact charging roller 102 during the rotation process. Reference numeral 103 denotes a laser beam scanner, which outputs laser light L that is on / off modulated in accordance with image information input from an external device such as an image scanner or a computer (not shown). The charged surface of the photosensitive drum 101 is exposed by the laser light L, and an electrostatic latent image corresponding to image information is formed on the surface of the photosensitive drum 101. A developing device 104 supplies developer (toner) to the surface of the photosensitive drum 101 from the developing roller 104a, and develops the electrostatic latent image on the surface of the photosensitive drum 101 as a toner image. Reference numeral 105 denotes a paper feed cassette in which the recording material P is stored. A registration roller 107 conveys the recording material P so that the leading end of the toner image formed on the photosensitive drum and a predetermined position of the recording material are aligned. When a paper feed start signal is input, the paper feed roller 106 is driven to feed the recording material P in the paper feed cassette 105 one by one. The fed recording material is adjusted in conveyance timing by a registration roller 107 and then introduced into a transfer portion 108T where the photosensitive drum 101 and the transfer roller 108 abut. While the recording material P is nipped and conveyed at the transfer site 108T, a transfer bias is applied to the transfer roller 8 from a power source (not shown). The transfer roller 108 is applied with a transfer bias having a polarity opposite to the charging polarity of the toner, whereby the toner image on the photosensitive drum 101 is transferred to the recording material P. Thereafter, the recording material P onto which the toner image has been transferred is separated from the surface of the photosensitive drum 101 and is introduced into the fixing unit A through the conveyance guide 109. The toner image on the recording material is heated by the fixing unit and fixed on the recording material. The recording material P that has passed through the fixing unit is discharged onto the paper discharge tray 112 through the paper discharge port 111. On the other hand, the surface of the photosensitive drum 101 after the recording material P is separated is cleaned by the cleaning unit 110.

  The fixing unit A is an electromagnetic induction heating type fixing device. Specifically, the fixing device fixes the image formed on the recording material to the recording material by the electromagnetic induction heat generation of the conductive layer of the rotating material by the magnetic flux generated by the coil. 2 is a cross-sectional view of the fixing unit, FIG. 3 is a front view of the fixing unit, and FIG. 4 is a perspective view of a coil unit provided in the fixing unit. The fixing unit A includes a heating unit having a fixing sleeve 1 and a coil unit, which will be described later, and a pressure member 8, and sandwiches and conveys a recording material P carrying an unfixed toner image between the heating unit and the pressure member. A fixing nip N is formed.

  The pressure roller 8 as a pressure member includes a cored bar 8a, an elastic layer 8b formed of silicone rubber or the like, and a release layer 8c formed of fluorine resin or the like. Both ends of the cored bar 8a are rotatably held via bearings between device chassis (not shown) of the fixing unit. Also, pressure springs (compression springs in this example) 17a and 17b are provided between both ends of the pressure stay (metal reinforcing member) 5 shown in FIG. 3 and the spring receiving members 18a and 18b on the apparatus chassis side, respectively. By providing, a pressing force is applied to the pressurizing stay 5. In the fixing unit A of this embodiment, a total pressure of about 100 N to 250 N (about 10 kgf to about 25 kgf) is applied. As a result, the lower surface of the sleeve guide member 6 made of a heat resistant resin (PPS or the like) and the pressure roller 8 are pressed against each other with the fixing sleeve 1 interposed therebetween to form the fixing nip portion N. The pressure roller 8 is driven in a direction indicated by an arrow by a driving unit (not shown), and the fixing sleeve 1 rotates following the rotation of the pressure roller. Reference numerals 12a and 12b denote flange members that rotate following the rotation of the fixing sleeve. The flange member is rotatably disposed at the longitudinal end portion of the sleeve guide 6. When the fixing sleeve moves toward the generatrix while rotating, it abuts against the flange member, and the flange member pushed by the fixing sleeve abuts against the regulating member 13a (13b). Thereby, the shift movement of the fixing sleeve is regulated by the regulating member. The flange member is formed of a material having good heat resistance such as LCP (Liquid Crystal Polymer).

  The fixing sleeve 1 as a rotatable cylindrical rotating body preferably has a diameter of 10 to 50 mm, and includes a heat generating layer (conductive layer) 1a as a base layer, an elastic layer 1b laminated on the outer surface, and a release layer 1c on the sleeve surface. Have. The heat generating layer 1a is a metal film (the material of the sleeve in this example is stainless steel), and the film thickness is preferably 10 to 50 μm. The elastic layer 1b is made of silicone rubber, and preferably has a hardness of about 20 degrees (JIS-A, 1 kg load) and a thickness of 0.1 mm to 0.3 mm. The release layer is a fluororesin tube, and the thickness is preferably 10 to 50 μm. An induced current is generated in the heat generating layer 1a by the action of an alternating magnetic flux described later. The heat generation layer generates heat by this induced current, and this heat is transmitted to the elastic layer 1b and the release layer 1c, and the entire circumferential direction of the fixing sleeve 1 is heated. The temperature detection elements 9, 10, and 11 for detecting the temperature of the fixing sleeve will be described later.

  Next, a mechanism for generating an induced current in the heat generating layer 1a will be described in detail. FIG. 4 is a perspective view of a coil unit provided in the heating unit. The coil unit has a spiral-shaped portion that is disposed inside the rotating body (fixing sleeve) and has a spiral axis that is substantially parallel to the generatrix direction of the rotating body, and generates an alternating magnetic field for causing the conductive layer of the rotating body to generate electromagnetic induction heat. It has a coil 3 to be formed. Furthermore, the core 2 for arrange | positioning in a spiral shape part and guide | inducing a magnetic flux is provided. The magnetic core 2 as a magnetic core material is disposed through the hollow portion of the fixing sleeve 1 by fixing means (not shown). NP and SP indicate the magnetic poles of the core 2. The core 2 has an end shape, and the magnetic flux generated by the coil forms an open magnetic path. The material of the core is composed of a material having a small hysteresis loss and a high relative magnetic permeability, for example, a sintered ferrite, a ferrite resin, an amorphous alloy (amorphous alloy), a high permeability oxide such as permalloy, an alloy, or the like. Ferromagnetic materials are preferred. In this example, sintered ferrite having a relative magnetic permeability of 1800 is used. The core of this example has a cylindrical shape, and the diameter is preferably 5 to 30 mm. In the case of a fixing device mounted on an A4 printer, the length of the core is preferably about 240 mm. The core 2 around which the coil 3 is wound is covered with a resin cover 4.

  The exciting coil 3 is formed by spirally winding a single conducting wire around the magnetic core 2 in the hollow portion of the fixing sleeve 1. In that case, it winds so that a space | interval may become denser in an edge part rather than a core center part. The exciting coil 3 is wound 18 times around the magnetic core 2 having a longitudinal dimension of 240 mm. The winding interval is 10 mm at the end, 20 mm at the center, and 15 mm in the middle. Thus, the coil is wound in a direction intersecting the axis X of the core.

  When a high frequency current is passed through the exciting coil 3 by the high frequency converter through the power supply contact portions 3a and 3b, a magnetic flux is generated. In the apparatus of this example, most of the magnetic flux that emerges from the end of the core 2 (70% or more, preferably 90% or more, more preferably 94% or more) passes outside of the heat generation layer of the fixing sleeve and other than the core. Designed to return to the edge. For this reason, an induced current flowing in the circumferential direction is generated in the heat generating layer of the fixing sleeve so that a magnetic flux that cancels the magnetic flux passing outside the sleeve is generated. Thereby, the whole circumferential direction of the heat generating layer generates heat. As described above, the configuration in which the induced current flows in the circumferential direction of the fixing sleeve generates heat in the entire circumferential direction of the fixing sleeve, so that there is an advantage that the time for warming up the fixing device to a temperature at which fixing can be performed can be shortened. Further, the core 2 is formed in an end shape, so that most of the magnetic flux passes through the outside of the heat generating layer by an open magnetic path. For this reason, there is also an advantage that the size can be reduced as compared with an apparatus having a configuration in which the core is formed in a loop shape to form a closed magnetic circuit.

  As shown in FIG. 2, the temperature detection elements 9, 10, and 11 of the fixing unit A are disposed upstream of the fixing nip portion N in the fixing sleeve rotation direction and detect the surface temperature of the fixing sleeve. Further, in the longitudinal direction of the fixing unit, as shown in FIG. 3, the temperatures of the center and both ends of the fixing sleeve are detected. The temperature detection elements 9, 10, and 11 are configured by a thermistor or the like. The power supply to the coil is controlled so that the temperature detected by the temperature detecting element 9 at the center maintains a control target temperature suitable for fixing. Further, the temperature detection elements 10 and 11 disposed near the end of the fixing sleeve 1 can detect the temperature rise in the non-sheet passing area of the fixing sleeve when the small size recording material P is continuously printed. . The temperature detecting elements 10 and 11 are arranged at the end of the pressure roller 8 in the axial direction to detect the temperature rise in the non-sheet passing area of the pressure roller when the small size recording material P is continuously printed. Also good.

  FIG. 4 is a block diagram showing the relationship among the CPU 32, the printer controller 41, and the host computer which are control means for performing printer control. The printer controller 41 communicates with the host computer 42 described later, receives image data, and develops the received image data into information that can be printed by the image forming apparatus 100. Furthermore, signal exchange and serial communication are performed with the engine control unit 43. The engine control unit 43 exchanges signals with the printer controller 41, and further controls the units 44 to 46 of the image forming apparatus 100 through serial communication. The fixing temperature control unit 44 controls the temperature of the fixing unit A based on the temperatures detected by the temperature detecting elements 9, 10, 11, and detects abnormality of the fixing unit A. The frequency control unit 45 as a frequency control means controls the driving frequency of the high-frequency converter 16, and the power control unit 46 controls the power of the high-frequency converter 16 by turning on / off the driving of the high-frequency converter 16. Specifically, the drive of the high-frequency converter 16 is turned ON / OFF so that the detected temperature of the temperature detecting element 9 maintains the control target temperature. The host computer 42 transfers image data to the printer controller 41 and sets various printing conditions such as the size of the recording material P in the printer controller 41 in response to a request from the user.

  FIG. 5 is a circuit diagram for explaining a drive circuit including the high-frequency converter 16 in the present embodiment. The commercial power source 50 is a commercial power source (AC power source) that connects the image forming apparatus 100, and supplies AC power to the image forming apparatus 100 via the inlet 51. This circuit includes a primary side directly connected to the commercial power source 50 and a secondary side connected to the commercial power source 50 in a non-contact manner. The waveform of the commercial power supply 50 is a waveform like waveform 1 when the horizontal axis is time and the vertical axis is voltage. The electric power input from the commercial power supply 50 is input and rectified to the diode bridges 81 to 84 as an example of the rectification unit via the inlet 51, the AC filter 52, and the triac 161 as an example of the switch member. The rectified voltage is charged in the capacitor 85. Subsequently, the signal is input to a high frequency converter (current resonance control circuit) 16 including FETs 86 and 87 and a voltage resonance capacitor 88. As a result, power is supplied to a resonance circuit (current resonance circuit) 191 including the equivalent inductance L and equivalent resistance R of the fixing unit A and the resonance capacitor 89.

  Reference numeral 71 denotes a power supply device (power supply unit), which receives power from the commercial power supply 50 via the AC filter 52 and outputs a predetermined voltage to a secondary load (such as a motor) not shown. The CPU 32 is also used for the operation of the high-frequency converter 16, and is composed of input / output ports, ROM 32a, RAM 32b, and the like. The power supply device (power supply unit) 71 for supplying power to the high-frequency converter 16, the resonance circuit 191, and the secondary side is directly connected to the commercial power supply 50 before the primary winding of the transformer. It is a primary circuit. Further, after the secondary winding of the transformer in the power supply device 71, for example, a motor or unit that operates during image formation, such as a motor (not shown) that rotates the photosensitive drum 101, a laser scanner 103, etc. It is connected to the contact and is an electrical secondary circuit.

  On the other hand, the electric power of the commercial power supply 50 is input to the ZEROX generation circuit 75 via the AC filter 52. The ZEROX generation circuit 75 outputs a high level (or low level) signal when the commercial power supply voltage is equal to or lower than a certain threshold voltage near 0 V, and otherwise, the low level (or high level). The signal is output. A pulse signal having a cycle substantially equal to the cycle of the commercial power supply voltage is input to the input port PA1 of the CPU 32 via the resistor 76. The CPU 32 detects an edge of the ZEROX signal that changes from High → Low or Low → High, and uses this as a trigger for driving the drive circuit 160 described later.

  Next, the power control drive circuit 160 will be described. The drive circuit 160 is controlled by the power control unit 46 (see FIG. 4) of the CPU 32. When the output port PA2 becomes high level at the timing determined by the CPU 32, the transistor 165 via the base resistor 67 is turned on. When the transistor 165 is turned on, the phototriac coupler 162 is turned on. The phototriac coupler 162 is a device for securing a creepage distance between the primary side circuit and the secondary side circuit. The resistor 166 is a resistor for limiting the current flowing through the light emitting diode in the phototriac coupler 162.

  Resistors 163 and 164 are bias resistors for the triac (switch member) 161, and the triac 161 is turned on when the phototriac coupler 162 is turned on. Since the triac 161 is an element that keeps the ON state until it reaches the next ZEROX point of the commercial power supply 50 once it is turned ON, power corresponding to the ON timing is input to the fixing unit A via the high-frequency converter 16.

  Next, the high frequency converter 16 will be described. When the CPU 32 outputs a pulse signal having a frequency described later from the output port PA 3 to the Hi-gate drive circuit 77, the Hi-gate drive circuit 77 outputs a gate waveform to the switching element 86. The switching element 86 is turned on between the drain and source while the gate waveform is Hi, and is turned off during the Lo period. Similarly, when the CPU 32 outputs a pulse signal having the same frequency as the pulse signal to the Hi-gate drive circuit 77 from the output port PA 4 to the Lo-gate drive circuit 78, the Lo-gate drive circuit 78 supplies the switching element 87. Output the gate waveform. The switching element 87 turns on between the drain and the source while the gate waveform is Hi, and turns off during the Lo period. The switching element 86 and the switching element 87 are alternately turned ON at the frequency of the pulse signal, and supply a square wave to the resonance circuit 191. As a result, the equivalent inductance L of the fixing unit A and the resonance capacitor 61 resonate, and the rotating body 1 of the fixing unit A generates heat. Note that the ON duty ratio of the pulse signal to the Hi-gate drive circuit 77 (the ON time ratio per one cycle of the pulse signal) and the ON duty ratio of the pulse signal to the Lo-gate drive circuit 78 are determined by the frequency of the pulse signal. Regardless, it is set to about 50%. When the pulse signal to the switching element 86 and the switching element 87 stops, the heat generation of the fixing unit A is stopped.

  The temperature detecting element 9 arranged in the fixing unit A has one end connected to the power supply Vcc1 through the ground and the other end connected through the resistor 73, and further connected to the analog input port AN0 of the CPU 32 through the resistor 74. . Note that the outputs of the temperature detection elements 10 and 11 for detecting the temperature at the end of the fixing unit are also input to the analog input port of the CPU 32 (not shown in FIG. 5), similarly to the temperature detection element 9. The thermistor used as the temperature detecting element 9 has a characteristic that the resistance value decreases at a high temperature. The CPU 32 detects the temperature of the fixing unit A (more precisely, the temperature of the fixing sleeve) by converting the divided voltage with the fixed resistor 73 into a temperature by a preset temperature table (not shown). As will be described later, the CPU 32 controls the drive circuit 160 so that the temperature of the fixing unit A (detected temperature of the temperature detecting element 9) maintains a predetermined temperature (control target temperature) during the fixing process.

  By the way, in order to generate an induced current flowing in the sleeve circumferential direction in the conductive layer of the sleeve, most of the magnetic flux emitted from the end of the core passes outside the heat generation layer of the fixing sleeve and returns to the other end of the core. The designed fixing device has been found to have the following problems.

  A general electromagnetic induction type fixing device is provided with a high-frequency converter that drives a resonance circuit including a coil. In a fixing device that couples the magnetic flux generated by the coil to the conductive layer of the rotor and generates heat by generating an eddy current in the conductive layer, the driving frequency of the high-frequency converter (described above) is used to keep the sleeve temperature constant. Adjust the pulse signal frequency) to adjust the amount of heat generation.

  However, in a fixing device that generates an induced current that flows in the circumferential direction of the sleeve as in this example, it has been found that when the drive frequency of the high-frequency converter is changed, the heat generation distribution in the direction of the bus of the sleeve changes. FIG. 6 shows the temperature distribution of the sleeve when the drive frequency of the high-frequency converter is changed in the range of 21 kHz to 50 kHz so that the center of the rotor body (sleeve) in the busbar direction (longitudinal direction) is maintained at 200 ° C. . It can be seen that the lower the drive frequency, the lower the amount of heat generated at both ends of the sleeve. Therefore, for example, in a case where the drive frequency must be set to 21 kHz in order to keep the temperature of the central portion at 200 ° C., the amount of heat generated at both ends of the sleeve is insufficient. As a result, when fixing a large size recording material, the image on the recording material corresponding to both ends of the sleeve is insufficiently fixed.

  In this embodiment, therefore, the driving frequency is not set according to the temperature of the central portion of the fixing sleeve, but is driven according to the size of the recording material P and the temperature of the non-sheet passing region of the fixing sleeve 1 (hereinafter referred to as driving). Frequency fk). The non-sheet passing area is an area through which a recording material having a maximum size that can be used by the apparatus passes but does not pass a recording material having a size smaller than the maximum size. By setting the drive frequency fk in this way, when fixing a large size recording material, the entire length of the fixing sleeve 1 is uniformly heated, and when fixing a small size recording material, the sleeve It is possible to set a heat generation distribution that suppresses the heat generation amount at the end. Further, the power supplied to the high-frequency converter 16 is controlled by controlling the drive circuit 160 described above according to the temperature of the central portion of the fixing sleeve so that the temperature of the central portion of the fixing sleeve maintains the control target temperature. Yes.

  With reference to FIG. 7, each operation waveform for four cycles of the commercial power supply voltage when 50% of power is input will be described. The CPU 32 of the present embodiment sets power corresponding to the detected temperature of the temperature detecting element 9 for each control period, with four cycles of the commercial power supply voltage as one control period.

  In FIG. 7, the voltage 701 of the commercial power supply 50, the ZEROX signal waveform 702, the voltage waveform 703 of the triac 161, the gate waveform 704 of the switching element 86, and the gate waveform 705 of the switching element 87 are shown with time on the horizontal axis. . When a voltage 701 is input from the commercial power supply 50, a ZEROX signal 702 is generated by the ZEROX generation circuit 75 and input to the CPU 32. The switching elements 86 and 87 are alternately switched as shown by the gate waveforms 704 and 705 at a driving frequency fk determined according to the paper size and the temperature rise degree of the non-sheet passing portion.

  When power is input by 50%, the CPU 32 determines the input power for each half wave so that the average power input for four cycles is 50%. In FIG. 7, the input power pattern of the triac 161 is 50% input power in the entire half-wave.

  A ROM 32a in the CPU 32 stores a table of lighting timing coefficients for phase control corresponding to the input power ratio. The CPU 32 calculates the lighting timing using the table, the ZEROX signal 702, and the information of the temperature detection element 9. The table is, for example, as shown in Table 1. The lighting timing coefficient 0 is when the phase of the voltage waveform 701 of the commercial power supply 50 is 0 °, and 1 is 180 °.

  The CPU 32 determines the timing for turning on the drive circuit 160 using the detected temperature of the temperature detecting element 9 and the table in Table 1. For example, in the case of a commercial power supply 50 at 50 Hz, the ON timing of the triac 161 for turning on 50% of power is 5.0 ms (= 20 ms / 2 × 0) from the falling edge (or rising edge) of the zero cross signal waveform 702. .50) after. In the case of odd-numbered waveforms D1, D3, D5, and D7 shown in FIG. 7, the CPU 32 outputs 50% by outputting a High level to the output port PA2 after 5 ms from the time when the ZEROX signal 702 changes from High to Low. Power will be supplied. As a result, 50% input power can be supplied to the rectifier circuits 81 to 84 in 4 cycles of the commercial power supply voltage. In this embodiment, four cycles are defined as one control cycle, and power control is performed using phase control every four cycles. However, one control cycle may be other than four cycles. The control waveform may also be a control waveform other than phase control, such as wave number control or control combining phase control and wave number control.

  The flow of the power input sequence by the CPU 32 will be described with reference to the flowchart of FIG. First, when the power input sequence is started, the input power duty ratio D by the triac 61 is determined from the detected value of the temperature detecting element 9 and the control target temperature in S101. Next, in S102, the drive frequency fk of the switching elements 86 and 87 is determined according to at least one of the size of the recording material P and the end temperature of the sleeve 1. Subsequently, a counter k (the number of half cycles of the commercial power supply voltage) is initialized (k = 1) in S103, and the rising or falling edge of the ZEROX signal 702 is monitored in S104. The counter k is incremented at the timing when the rising or falling edge of the ZEROX signal 702 is detected (S105), and half-wave power is input to the fixing unit A at the phase angle D% by the triac 161 (S106). If the counter k is less than 8 in S107, since one control period (four cycles) has not been reached, S104 to S106 are continuously repeated. On the other hand, when the counter k reaches 8 in S107, the power input in one control cycle is completed. Until S <b> 108 determines the end of power-on, steps S <b> 101 to S <b> 107 are repeated and power-on is performed while switching the power-on duty ratio every four cycles.

  As described above, the triac 161 is disposed in front of the diode bridges 81 to 84, and the effective voltage input to the subsequent circuit is adjusted by the triac 161, so that the driving frequency fk of the switching elements 86 and 87 is not changed. It becomes possible to adjust the power. In the present embodiment, an example in which the triac 161 is disposed in front of the diode bridges 81 to 84 as a power control switch member has been described. However, the switch member only needs to be a switchable component such as an FET, IGBT, or relay, and is not limited to a triac.

(Example 2)
In the present embodiment, an example will be described in which an FET is arranged in the subsequent stage of the diode bridges 81 to 84 and the power is controlled by turning the FET on and off. In the following, the present embodiment will be described mainly with respect to differences from the first embodiment, and the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 9 is a circuit diagram including the high-frequency converter 16 in the present embodiment. The effective input voltage to be input to the high-frequency converter 16 is adjusted by turning on and off the FET 93 which is an example of a switch member arranged after the rectifier circuits 81 to 84 and before the high-frequency converter 16. When the CPU 32 outputs a signal for turning on the FET from the output port PA5, the FET drive circuit 95 outputs a gate waveform toward the FET 93. By adopting such a configuration, the power can be adjusted without changing the drive frequency of the switching elements 86 and 87.

  In FIG. 10, the voltage 701 of the commercial power supply 50, the ZEROX signal waveform 702, the voltage waveform 1001 of the FET 93, the gate waveform 704 of the switching element 86, and the gate waveform 705 of the switching element 87 are shown with time on the horizontal axis. When a voltage 701 is input from the commercial power supply 50, a ZEROX signal 702 is generated by the ZEROX generation circuit 75 and input to the CPU 32. The switching elements 86 and 87 are alternately switched as indicated by the gate waveforms 704 and 705 at the drive frequency fk corresponding to the paper size and the temperature rise in the non-sheet passing portion.

  When power is input by 50%, the CPU 32 determines the input power for each half wave so that the average power input for four cycles is 50%. In the case of the example in FIG. 10, the FET 93 sequentially turns on power for each half wave in the order of 100% → 0% → 0% → 100% → 100% → 0% → 0% → 100% from the first half wave. . As a result, the average input power in one control cycle (4 cycles) is 50%. In the present embodiment, power control is performed using wave number control, but the phase control described in the first embodiment or a control waveform in which phase control and wave number control are mixed may be used.

  The flow of the power-on sequence by the CPU 32 will be described using the flowchart of FIG. The same parts as those in FIG. A half-wave ON-OFF (D1 to D8) is set from the half-wave ON-OFF table corresponding to each input power duty ratio prepared in advance and the half-wave ON-OFF table corresponding to each input power duty ratio prepared in advance. S201). After detecting the rising or falling edge of the ZEROX signal 702, in step S202, it is determined whether the FET 93 is turned on or off for each half wave. If Dk = ON based on the ON / OFF set value for each half wave set in S201, the FET 93 is turned ON in S203. If Dk = OFF, the FET 93 is turned OFF in S204. The counter k is incremented in S205, and S104 to S205 are repeated until the counter k reaches 8. As described above, the FET 93 is disposed in the subsequent stage of the diode bridges 81 to 84, and the effective voltage input to the subsequent circuit is adjusted by the FET 93. As a result, the input power can be adjusted without changing the drive frequency of the switching elements 86 and 87. In the present embodiment, the example in which the FET 93 is disposed as the switch member has been described. However, the disposed component may be any component that can be turned on and off, such as an IGBT and a relay, and is not limited to the present embodiment.

  In the first embodiment, power control is performed using phase control, and in the second embodiment, wave number control is used. However, both the configuration of the first embodiment and the configuration of the second embodiment can apply any of the phase control, the wave number control, and the control pattern in which the phase control and the fractional control are mixed, and are limited to the first and second embodiments. Is not to be done.

86, 87 Switching element 89 Resonant capacitor 161 Triac 81-84 Diode bridge 93 FET

Claims (9)

A resonant circuit comprising: a cylindrical rotating body having a conductive layer; a coil disposed inside the rotating body and having a helical axis substantially parallel to a generatrix direction of the rotating body; and a resonant capacitor;
A converter for driving the resonant circuit;
In the fixing device for causing the conductive layer to generate electromagnetic induction heat by the magnetic flux generated by the coil and fixing the image formed on the recording material by the heat of the rotating body on the recording material,
A switch member for controlling the power supplied to the converter;
A frequency control unit that sets the drive frequency of the converter according to at least one of the size of the recording material and the temperature of the non-sheet passing portion of the rotating body;
A power control unit that controls the switch member according to the temperature of the sheet passing portion of the rotating body and controls the power supplied to the converter;
A fixing device.   The fixing device according to claim 1, wherein the power control unit controls the switch member so that a temperature of a sheet passing portion of the rotating body maintains a target temperature.   The fixing device according to claim 1, wherein the resonance circuit is a current resonance circuit.   4. The fixing device according to claim 1, further comprising a rectifying unit configured to rectify a commercial power supply voltage, wherein the switch member is provided upstream of the rectifying unit.   The fixing device according to claim 4, wherein the switch member is a triac.   The fixing device according to claim 1, further comprising a rectifying unit that rectifies a commercial power supply voltage, wherein the switch member is provided between the rectifying unit and the converter.   The fixing device according to claim 6, wherein the switch member is an FET or an IGBT.   The coil-shaped spiral part has a core for inducing magnetic flux, and an induced current flowing in the circumferential direction of the rotating body is generated in the conductive layer. The fixing device according to claim 1.   The fixing device according to claim 8, wherein the core has an end shape.