JP2019124950A - Fixation device - Google Patents

Abstract

Kind Code: A1 An electromagnetic induction heating type fixing device is provided that facilitates temperature control of a region of a rotating body through which a recording material passes while forming a heat generation distribution according to the size of the recording material. SOLUTION: A converter for driving a resonance circuit, a switch member for controlling power supplied to the converter, and a driving frequency of the converter according to at least one of the size of a recording material and the temperature of a non-sheet passing portion of a rotating body. and a power control unit for controlling the power supplied to the converter by controlling the switch member according to the temperature of the paper passing portion of the rotating body. [Selection drawing] Fig. 5

Description

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

  A fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer is a recording material carrying an unfixed toner image at a nip portion formed by a heating rotating body and a pressure roller in contact therewith. In general, the toner image is fixed on the recording material by heating while conveying the toner image.

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

  Patent Document 1 discloses a fixing device in which 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 Patent Document 1, the temperature rise of the non-sheet-passing portion at the time of fixing the recording material of a small size becomes an issue.

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

  The present invention for solving the above-mentioned problems comprises: 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 converter for driving the resonance circuit, the magnetic flux generated by the coil causes the conductive layer to generate heat by electromagnetic induction, and the image of the recording material is formed by the heat of the rotating body. A fixing member for fixing the toner to the recording material, the switch member for controlling the power supplied to the converter, the driving of the converter according to at least one of the size of the recording material and the temperature of the non-sheet A frequency control unit configured to set a frequency, and a power control unit configured to control the switch member according to the temperature of the sheet passing unit of the rotating body and to control power supplied to the converter The features.

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

Schematic cross-sectional view of the image forming apparatus Cross section of fixing unit Front view of fixing unit A perspective view of a coil unit provided in a fixing unit Coil Unit Driving Circuit of Embodiment 1 Diagram showing the relationship between the drive frequency and the heat generation distribution of the fixing sleeve Diagram to explain the triac voltage waveform Flow chart of the first embodiment Coil Unit Driving Circuit of Embodiment 2 Diagram to explain FET voltage waveform Flow chart of the second embodiment

  Hereinafter, with reference to the drawings, a mode for carrying out the present invention will be exemplarily described in detail based on examples. However, the dimensions, materials, shapes, etc. of the components described in this embodiment should be changed as appropriate depending on the configuration of the apparatus to which the invention is applied and various conditions. That is, the scope of the present invention is not intended to be limited to the following embodiments.

Example 1
FIG. 1 is a schematic block 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.

  Reference numeral 31 denotes a controller which is a control unit of the image forming apparatus, and comprises a CPU (central processing unit) 32 equipped with 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 rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven at a predetermined circumferential speed in the clockwise direction indicated by the arrow. The photosensitive drum 101 is uniformly charged to a predetermined polarity and potential by the contact charging roller 102 in the process of its rotation. Reference numeral 103 denotes a laser beam scanner, which outputs laser light L on / off modulated corresponding to 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 beam 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 a developer (toner) from the developing roller 104a to the surface of the photosensitive drum 101 and develops the electrostatic latent image on the surface of the photosensitive drum 101 as a toner image. A paper feed cassette 105 accommodates the recording material P therein. A registration roller 107 conveys the recording material P so that the front end of the toner image formed on the photosensitive drum and the predetermined position of the recording material are aligned. When a feed start signal is input, the feed roller 106 is driven to feed the recording materials P in the feed cassette 105 one by one. After the conveyance timing of the fed recording material is adjusted by the registration roller 107, the recording material is introduced to the 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 supply (not shown). A toner image on the photosensitive drum 101 is transferred onto the recording material P by applying to the transfer roller 108 a transfer bias having a polarity opposite to the charging polarity of the toner. Thereafter, the recording material P to which the toner image has been transferred is separated from the surface of the photosensitive drum 101 and 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 having passed through the fixing unit is discharged onto the discharge tray 112 via the 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 is configured to cause the conductive layer of the rotating body to generate electromagnetic induction heat by magnetic flux generated by the coil, and fix the image formed on the recording material to the recording material by the heat of the rotating body. 2 is a 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 nips and conveys a recording material P carrying an unfixed toner image between the heating unit and the pressure member. A fixing nip portion N is formed.

  The pressure roller 8 as a pressure member has a cored bar 8a, an elastic layer 8b formed of silicone rubber or the like, and a release layer 8c formed of fluorocarbon resin or the like. Both ends of the cored bar 8a are rotatably held between the unshown device chassis of the fixing unit via bearings. Further, pressure springs (in this example, compression springs) 17a and 17b are respectively 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. By providing the pressure stay 5, a pressing force is applied to the pressure stay 5. In the fixing unit A of this embodiment, a pressing force 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 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 the direction of the arrow by driving means (not shown), and the fixing sleeve 1 is rotated by 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 of the sleeve guide 6. When the fixing sleeve is displaced in the generatrix direction while rotating, it abuts against the flange member, and the flange member pressed by the fixing sleeve abuts against the regulating member 13a (13b). Thus, the shift movement of the fixing sleeve is restricted by the restricting member. The flange member is formed of a heat-resistant material such as LCP (Liquid Crystal Polymer: liquid crystal polymer).

  The fixing sleeve 1 as a rotatable cylindrical rotary member preferably has a diameter of 10 to 50 mm, and 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 1 b is formed 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 fluorocarbon resin 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 the alternating magnetic flux described later. The heat generation layer generates heat due to the induction current, and the heat is transmitted to the elastic layer 1 b and the release layer 1 c, and the entire circumferential direction of the fixing sleeve 1 is heated. The temperature detection elements 9, 10, 11 for detecting the temperature of the fixing sleeve will be described later.

  Next, the 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 disposed inside the rotating body (fixing sleeve) and having a helical axis substantially parallel to the generatrix direction of the rotating body, and generates an alternating magnetic field for electromagnetically generating heat in the conductive layer of the rotating body. It has the coil 3 to form. Furthermore, a core 2 is provided which is disposed in the spiral shape and which guides the magnetic flux. A magnetic core 2 as a magnetic core material is disposed through a 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 circuit. The core material is composed of a material having a small hysteresis loss and a high relative permeability, such as a fired ferrite, a ferrite resin, an amorphous alloy (amorphous alloy), an oxide of high permeability such as permalloy, an alloy, etc. Ferromagnetics are preferred. In the present example, a fired ferrite of relative permeability 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 cover 4 made of resin.

  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. At that time, it is wound so that the spacing is closer at the end than at the center of the core. The exciting coil 3 is wound 18 times on the magnetic core 2 having a longitudinal dimension of 240 mm. The winding distance 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 caused to flow to the exciting coil 3 by the high frequency converter through the feeding contact portions 3a and 3b, a magnetic flux is generated. In the device of this example, most (70% or more, preferably 90% or more, more preferably 94% or more) of the magnetic flux emitted from the end of the core 2 passes outside the heat generating layer of the fixing sleeve and the other It is designed to return to the end. For this reason, an induced current flowing in the circumferential direction is generated in the heat generating layer of the fixing sleeve so as to generate a magnetic flux which cancels out the magnetic flux passing through the outside of the sleeve. As a result, the entire circumferential direction of the heat generating layer generates heat. As described above, when the induction current flows in the circumferential direction of the fixing sleeve, the entire circumferential direction of the fixing sleeve generates heat, so that the time for warming up the fixing device to a temperature at which the fixing device can fix can be shortened. Further, the core 2 is formed into an end shape, and most of the magnetic flux passes through the outside of the heat generating layer by the open magnetic circuit. For this reason, there is also a merit that the core can be miniaturized as compared with a device configured to form a closed magnetic path with a loop shape.

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

  FIG. 4 is a block diagram showing the relationship between the CPU 32, which is control means for controlling the printer, the printer controller 41, and the host computer. The printer controller 41 communicates with the host computer 42 described later, receives image data, and expands the received image data into information that can be printed by the image forming apparatus 100. Furthermore, exchange of signals with the engine control unit 43 and serial communication are performed. The engine control unit 43 exchanges signals with the printer controller 41, and further controls each unit 44 to 46 of the image forming apparatus 100 via serial communication. The fixing temperature control unit 44 controls the temperature of the fixing unit A based on the temperatures detected by the temperature detection elements 9, 10 and 11 and performs abnormality detection of the fixing unit A and the like. The frequency control unit 45 as the frequency control means controls the drive frequency of the high frequency converter 16, and the power control unit 46 turns on / off the drive of the high frequency converter 16 to control the power 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 detection element 9 maintains the control target temperature. The host computer 42 transfers image data to the printer controller 41, and sets various print 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 describing a drive circuit including the high frequency converter 16 in the present embodiment. The commercial power supply 50 is a commercial power supply (AC power supply) connecting the image forming apparatus 100, and supplies AC power to the image forming apparatus 100 through the inlet 51. The circuit is configured of a primary side directly connected to the commercial power supply 50 and a secondary side connected to the commercial power supply 50 in a noncontact manner. The waveform of the commercial power supply 50 is a waveform like the waveform 1 when the horizontal axis is time and the vertical axis is voltage. The power input from the commercial power supply 50 is input and rectified to the diode bridges 81 to 84 as an example of the rectifying 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 to the capacitor 85. Subsequently, the signal is input to a high frequency converter (current resonance control circuit) 16 composed of FETs 86 and 87 and a voltage resonance capacitor 88. As a result, power is supplied to the resonance circuit (current resonance circuit) 191 including the equivalent inductance L and the equivalent resistance R of the fixing unit A, and the resonance capacitor 89.

  A power supply unit (power supply unit) 71 receives the power of the commercial power supply 50 through the AC filter 52, and outputs a predetermined voltage to a load (such as a motor) on the secondary side (not shown). The CPU 32 is also used for the operation of the high frequency converter 16, and includes each input / output port, the ROM 32a, the RAM 32b, and the like. The high frequency converter 16, the resonance circuit 191, and the primary winding of the transformer in the power supply unit (power supply unit) 71 for supplying power to the secondary side are directly connected to the commercial power supply 50, and electrically It is a primary side circuit. Further, after the secondary winding of the transformer in the power supply device 71, for example, a motor (not shown) for rotating the photosensitive drum 101, a motor or a unit operating at the time of image formation such as the laser scanner 103, etc. It is connected to the contact and electrically forms a secondary circuit.

  On the other hand, the 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 a voltage below a certain threshold voltage near 0 V, and in other cases, it is low level (or high level). Is configured to output a signal of Then, 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 changing from high to low or from low to high, and uses this as a trigger for driving the drive circuit 160 described later.

  Next, the drive circuit 160 for power control 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 photo triac coupler 162 is turned on. The photo triac coupler 162 is a device for securing a creeping distance between the primary side circuit and the secondary side circuit. The resistor 166 is a resistor for limiting the current flowing to the light emitting diode in the photo triac coupler 162.

  Resistors 163 and 164 are bias resistors for the triac (switch member) 161. The triac 161 is turned on when the phototriac coupler 162 is turned on. Once the TRIAC 161 is turned on, it is an element that holds the ON state until it reaches the next ZEROX point of the commercial power supply 50. Therefore, the power corresponding to the ON timing is supplied 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 of a frequency to be described later from the output port PA3 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 turns on between the drain and the source while the gate waveform is Hi, and turns 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 PA4 to the Lo-gate drive circuit 78, the Lo-gate drive circuit 78 outputs the same signal to the switching element 87. Output the gate waveform to the direction. The switching element 87 turns on between the drain and 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 to supply a square wave to the resonant circuit 191. Thereby, 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. The ON duty ratio of the pulse signal to the Hi-gate drive circuit 77 (ON time ratio per pulse signal cycle) and the ON duty ratio of the pulse signal to the Lo-gate drive circuit 78 are equal to 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 is stopped, the heat generation of the fixing unit A is stopped.

  The temperature detection element 9 disposed in the fixing unit A is connected to ground at one end and the power supply Vcc1 via the resistor 73 at the other end, and is further connected to the analog input port AN0 of the CPU 32 via the resistor 74. . Similarly to the temperature detection element 9, the outputs of the temperature detection elements 10 and 11 for detecting the temperature of the end portion of the fixing unit are also input to the analog input port of the CPU 32 (not shown in FIG. 5). The thermistor used as the temperature detection element 9 has a characteristic that the resistance value decreases when the temperature becomes high. 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 according to a preset temperature table (not shown). Although described later, the CPU 32 controls the drive circuit 160 so that the temperature of the fixing unit A (the detected temperature of the temperature detection element 9) maintains a predetermined temperature (the control target temperature) during the fixing process.

  By the way, most of the magnetic flux from the end of the core passes outside the heat generating layer of the fixing sleeve and returns to the other end of the core so that an induced current flowing in the circumferential direction of the sleeve is generated in the conductive layer of the sleeve. It was found that the designed fixing device had the following problems.

  In a general electromagnetic induction type fixing device, a high frequency converter is provided which drives a resonant circuit including a coil. Then, in a fixing device of a system in which a magnetic flux generated by a coil is coupled to a conductive layer of a rotating body and an eddy current is generated in the conductive layer to generate heat, a driving frequency of a high frequency converter (described above Adjust the frequency of the pulse signal) to adjust the heat generation amount.

  However, it has been found that the heat generation distribution in the generatrix direction of the sleeve changes when the driving frequency of the high frequency converter is changed in the fixing device in which the induced current flows in the sleeve circumferential direction as in this example. 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 generator (sleeve) in the generatrix direction (longitudinal direction) is maintained at 200.degree. . It can be seen that the amount of heat generation at both ends of the sleeve decreases as the drive frequency decreases. Therefore, for example, in the case where the drive frequency has to 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, an image on the recording material corresponding to both ends of the sleeve is insufficiently fixed.

  Therefore, in the present embodiment, the drive frequency is not set according to the temperature of the central portion of the fixing sleeve, but the drive frequency (hereinafter referred to as drive frequency) according to the size of the recording material P and the temperature of the non-sheet passing area of the fixing sleeve 1. Set the frequency fk). The non-sheet passing area is an area through which the recording material of the largest size available in the apparatus passes but the recording material of a size smaller than the largest size does not. By setting the driving frequency fk in this manner, when fixing a large size recording material, the entire area in the longitudinal direction of the fixing sleeve 1 is uniformly heated, and when fixing a small size recording material, the sleeve is used. The heat generation distribution can be set so as to suppress the amount of heat generation at the end. Furthermore, by controlling the drive circuit 160 described above according to the temperature of the central portion of the fixing sleeve, the power supplied to the high frequency converter 16 is controlled, and the temperature of the central portion of the fixing sleeve maintains the control target temperature. There is.

  Each operation waveform during four cycles of the commercial power supply voltage in the case of supplying 50% of power will be described with reference to FIG. The CPU 32 of this embodiment sets power corresponding to the detected temperature of the temperature detection element 9 every control cycle, with four cycles of the commercial power supply voltage as one control cycle.

  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 represented 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 of the non-sheet passing portion.

  When the power is applied 50%, the CPU 32 determines the input power for each half wave so that the average input power of 4 cycles is 50%. In FIG. 7, the input power pattern of the TRIAC 161 is 50% input power for all half waves.

  The ROM 32a in the CPU 32 stores a table of lighting timing coefficients of phase control according 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 when it is 180 °.

  The CPU 32 uses the detected temperature of the temperature detection element 9 and the table of Table 1 to determine the timing at which the drive circuit 160 is turned on. For example, in the case of the 50 Hz commercial power supply 50, the ON timing of the TRIAC 161 for applying 50% power is 5.0 ms (= 20 ms / 2 × 0) from the falling edge (or rising edge) of the zero cross signal waveform 702. .50) calculated after. In the case of the 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 5 ms after the time when the ZEROX signal 702 changes from high to low. It will supply power. Thereby, 50% of input power can be supplied to the rectifier circuits 81 to 84 in four cycles of the commercial power supply voltage. In the present embodiment, four cycles are 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-on 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 detection value of the temperature detection element 9 and the control target temperature in S101. Next, in step 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 (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 the half-wave power is applied to the fixing unit A at the phase angle D% by the triac 161 (S106). If the counter k is less than 8 at S107, one control cycle (4 cycles) has not been reached, so S104 to S106 are repeated continuously. On the other hand, when the counter k reaches 8 at S107, the power supply in one control cycle is completed. S101 to S107 are repeated until it is determined in S108 that the end of the power supply has ended, and the power supply is performed while switching the power supply duty ratio every four cycles.

  As described above, the TRIAC 161 is disposed at the front stage of the diode bridges 81 to 84, and the effective voltage input to the circuit at the rear stage is adjusted by the TRIAC 161, thereby changing the drive frequency fk of the switching elements 86 and 87 without changing it. It is possible to adjust the power. In this embodiment, an example in which the TRIAC 161 is disposed at the front stage of the diode bridges 81 to 84 as a power control switch member has been described. However, the switch member may be a switchable component such as an FET, an IGBT, or a relay, and is not limited to the triac.

(Example 2)
In the present embodiment, an example will be described in which an FET is disposed downstream of the diode bridges 81 to 84 and power control is performed by turning on and off the FET. In the following, points different from the first embodiment will be mainly described in the present embodiment, and the same reference numerals are given to the same configuration and the description will be omitted.

  FIG. 9 is a circuit diagram including the high frequency converter 16 in the present embodiment. The input effective voltage 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 disposed downstream of the rectifier circuits 81 to 84 and at the front stage of the high frequency converter 16. When the CPU 32 outputs a signal to turn on the FET from the output port PA5, the FET drive circuit 95 outputs a gate waveform to the FET 93. With such a configuration, power adjustment can be performed 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 represented 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 gate waveforms 704 and 705 at a driving frequency fk according to the paper size and the temperature rise of the non-sheet-passing portion.

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

  The flow of the power input sequence by the CPU 32 will be described with reference to the flowchart of FIG. The same parts as in FIG. 8 are assigned the same reference numerals and descriptions thereof will be omitted. Set ON-OFF (D1 to D8) for each half wave from the ON-OFF table for each half wave according to the input power duty ratio D determined according to the detected temperature and each prepared half-power ON / OFF according to each input power duty ratio S201). After detecting the rising or falling edge of the ZEROX signal 702, it is determined in S202 whether the FET 93 is turned on or off for each half wave. In the case of 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. In step S205, the counter k is incremented, and steps S104 to S205 are repeated until the counter k becomes eight. As described above, the FET 93 is disposed at the rear stage of the diode bridges 81 to 84, and the FET 93 adjusts the effective voltage input to the circuit at the rear stage. As a result, the input power can be adjusted without changing the drive frequency of the switching elements 86 and 87. Although the example which arrange | positioned FET93 as a switch member was demonstrated in the present Example, components to arrange | position should just be components which can be turned ON-OFF, such as IGBT and a relay, and it is not limited to a present Example.

  In the first embodiment, power control is performed using phase control, and in the second embodiment, wave number control. However, for both the configuration of the first embodiment and the configuration of the second embodiment, any of the phase control, the wave number control, and the control pattern in which the phase control and the fraction control are mixed can be applied, and is limited to the first embodiment and the second embodiment. It is not something to be done.

86, 87 switching element 89 resonant capacitor 161 triac 81 to 84 diode bridge 93 FET

The present invention for solving the above-mentioned problems comprises: 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 converter for driving the resonance circuit, the magnetic flux generated by the coil causes the conductive layer to generate heat by electromagnetic induction, and the image of the recording material is formed by the heat of the rotating body. In the fixing device for fixing the toner to the recording material, the number of coils disposed inside the rotating body is one, and the conductive layer is formed of the same material and with the same thickness from one end to the other end in the generatrix direction cage, a switch member for controlling the power supplied to the converter peripheral to set the drive frequency of the converter according to at least one of the temperature of the non-sheet passing portion of the size of the recording material and the rotating member The number control unit, the controls said switch member in accordance with the temperature of the sheet passing portion of the rotary member, have a, a power control unit for controlling the power supplied to said converter, said to lower the driving frequency When the frequency control unit controls the converter, the heat generation distribution of the conductive layer is changed so that the amount of heat generation of the conductive layer at the end in the generatrix direction is reduced .

Claims (9)

A resonant circuit including: 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;
A fixing device for fixing the image formed on the recording material to the recording material by the heat of the rotating body by causing the conductive layer to generate electromagnetic induction heat by the magnetic flux generated by the coil;
A switch member for controlling power supplied to the converter;
A frequency control unit which sets a drive frequency of the converter in accordance with 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 characterized by having:   The fixing device according to claim 1, wherein the power control unit controls the switch member such 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.   The fixing device according to any one of claims 1 to 3, further comprising: a rectifying unit configured to rectify a commercial power supply voltage, wherein the switch member is provided on a front side of the rectifying unit.   The fixing device according to claim 4, wherein the switch member is a triac.   The fixing device according to any one of claims 1 to 3, further comprising a rectifying unit configured to rectify 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 spiral shaped portion of the coil has a core for inducing a 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 any one of the preceding claims.   The fixing device according to claim 8, wherein the core has an end shape.