JP2007052176A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating apparatus wherein it is unnecessary to keep a distance of a heat generating body as a primary side circuit away from a temperature detecting body as a secondary side circuit, and also, which is made more compact and inexpensive than the conventional constitution of a temperature detecting element arranged on the primary side, and to provide a fixing apparatus and an image forming apparatus equipped with the fixing apparatus. <P>SOLUTION: A pulse generated by a pulse generator arranged on a secondary side is transmitted to a primary side through a transmitting means which insulates the primary side from the secondary side, then, the pulse is converted to an analog voltage value, and then, compared with the output value of a temperature detecting element arranged on the primary side, the comparison result is transmitted to the secondary side through the transmitting means again, then, inputted to an engine controller as two values such as high or low values. Besides, a duty outputted from a PWM port and a detection temperature table by the temperature detecting element at that time are incorporated with the engine controller, and the temperature of the temperature detecting element is detected based on the outputted duty and high or low level of the I/O port, and a heater temperature control or a printing sequence control is carried out by the engine controller based on the detected temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heating apparatus for a material to be heated and an image forming apparatus including the heating apparatus as an image fixing unit.

  For the sake of convenience, a fixing device (image heating device) as a heating device that is provided in an image forming apparatus such as an electrophotographic copying machine or a printer and that thermally fixes an unfixed image will be described as an example.

  A heat fixing device of an image forming apparatus fixes an unfixed image (toner image) formed on a transfer paper by an image forming means such as an electrophotographic process on the transfer paper, and a heat roller using a halogen heater as a heat source A heat fixing device of the type, a film heating type heat fixing device using a ceramic surface heater as a heat source, and the like are used.

  As a conventional heating device, a heating device as shown in FIG. 12 is known and put into practical use. Such a heating device includes a heating element 507 that generates heat when energized from a commercial power source 501, a thermistor 508 that is a temperature detection body for detecting the temperature of the heating element 507, and energization and disconnection from the commercial power source 501 to the heating element 507. There is provided switching means 504 that can be switched to any one of them, and a temperature control circuit 503 that is control means for controlling energization from the commercial power source 501 to the heating element 507 in accordance with the temperature detected by the thermistor 508.

  The switching means 504 includes a triac 504B that switches between energization to the heating element 507 from the commercial power source 501 and a phototriac 504A that switches to the triac 504B in response to a control signal from the temperature control circuit 503. have.

  The commercial power source 501 is connected to the heating element 507 via the triac 504B and converts the AC power source from the commercial power source 501 into a DC power source, and then supplies the DC current to the temperature control circuit 503. It is connected to the.

  The thermistor 508 detects the temperature of the heating element 507 that has generated heat by energization from the commercial power source 501, and then the temperature control circuit 503 controls the triac 504B by driving the phototriac 504A according to the detected temperature of the thermistor 508. Furthermore, the temperature control of the ceramic heater 506 is performed by the triac 504B switching the conduction from the commercial power source 501 to the heating element 507 to either conduction or interruption.

  FIG. 13 is a schematic view of the ceramic heater 506 shown in FIG. 12, where (A) is a perspective view showing one surface of the ceramic heater 506, while (B) shows the other surface of the ceramic heater 506. It is a perspective view.

  In the ceramic heater 506, a thermistor 508, a conductive pattern 603 for applying a voltage to the thermistor 508, and a conductive pattern 604 are provided on the back surface 601 of the substrate mainly composed of ceramics. A heating element 507 is provided, and the heating element 507 generates heat when a voltage is applied to the end 605 and the end 606 of the heating element 507.

  The thermistor 508 may be provided in the primary side circuit, and by controlling the heater energization based on the detected temperature, the distance between the heating element as the primary side circuit and the thermistor 508 as the secondary side circuit is controlled. For example, Patent Document 1 and Patent Document 2 are used which can eliminate the need to reduce the size and reduce the size.

  Further, the thermistor 508 provided in the primary side circuit may be used as an auxiliary role of the temperature control thermistor, for example, for print sequence control or as a safety circuit. In the above configuration, a comparison circuit with a reference voltage, for example, an electric element such as a comparator is required for each detected temperature, and the configuration is complicated.

Further, when used for temperature control, as shown in FIG. 14, the one-chip IC 509 for digitizing the detected temperature information of the thermistor 508 and the detected temperature information from the one-chip IC 509 are transmitted to the temperature control circuit. The transformer 510 has a temperature control circuit 503 and a one-chip IC 509 connected by inductive coupling, and the temperature control circuit 503 supplies power to the one-chip IC 509 via the transformer 510. Has been achieved.
Japanese Patent Laid-Open No. 10-69208 Japanese Patent Laid-Open No. 11-344901

  However, in such a heating device, the configuration is expensive and complicated in order to take a safety distance between the primary side circuit that is the heating element and the secondary side circuit that is the temperature detection body. It was.

  In addition, in the configuration in which a plurality of temperature detectors are provided on the secondary side, complicated control is required such that the printer engine control means, for example, the CPU A / D port input is required for each temperature detector. And it was an expensive configuration.

  In addition, when the temperature detector is provided in the primary circuit, in order to know the desired detection temperature, a plurality of comparison circuits for each detection temperature, for example, comparators are required, and the circuit configuration becomes complicated. In addition, when trying to perform linear control as a temperature control application, an expensive one-chip IC is required, and it is difficult to reduce costs and complicated control is required. .

  In the present invention, it is not necessary to take the distance between the primary side circuit that is the heating element and the secondary side circuit that is the temperature detection body, and the number of electronic components is more than the conventional configuration in which the temperature detection element is provided on the primary side. An object of the present invention is to provide a small and inexpensive image forming apparatus that can be greatly reduced and that the control method is simple.

  In order to achieve the above object, the present invention has the following features.

[1] heating means including a heating element that generates heat upon receiving power from a power source;
Temperature detection means provided on the primary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Switching means switchable to either conduction or interruption from the power source to the heating element;
A first transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
A second transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
Pulse generating means provided on the secondary side for generating a pulse signal with variable duty;
A pulse conversion means for converting the pulse signal emitted from the pulse generation means transmitted to the primary side via the first transmission means into an electric signal corresponding to the duty;
In an image forming apparatus having a temperature control means for controlling switching of the switching means,
The electrical signal from the pulse converter and the electrical signal detected by the temperature detector are input to a determination circuit that indicates whether or not the temperature provided on the primary side is equal to or higher than a predetermined temperature. The output determination signal is configured to be supplied to the temperature control unit via the second transmission unit, and the temperature control unit controls the switching unit based on the determination signal. An image forming apparatus.

[2] heating means including a heating element that generates heat upon receipt of power supplied from a power source;
Switching means switchable to either conduction or interruption from the power source to the heating element;
First temperature detection means provided on the primary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Second temperature detection means provided on the secondary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Temperature control means for controlling switching of the switching means based on the electrical signal detected by the second temperature detection means;
A first transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
A second transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
Pulse generating means provided on the secondary side for generating a pulse signal with variable duty;
A pulse conversion means for converting the pulse signal emitted from the pulse generation means transmitted to the primary side via the first transmission means into an electric signal corresponding to the duty;
In an image forming apparatus having a print control means for performing print sequence control,
The electrical signal from the pulse converter and the electrical signal detected by the temperature detector are input to a determination circuit that indicates whether or not the temperature provided on the primary side is equal to or higher than a predetermined temperature. The output determination signal is configured to be supplied to the print control unit via the second transmission unit, and the print control unit performs print sequence control based on the determination signal from the determination circuit. An image forming apparatus.

[3] An abnormality determination circuit provided on the primary side for determining that the temperature detected by the temperature detection means exceeds a predetermined upper limit temperature;
A third transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary, and is provided on the primary side;
The electrical signal from the pulse conversion means and the electrical signal from the first temperature detection means are input to the abnormality determination circuit,
An abnormality determination signal output from the abnormality determination circuit is configured to be supplied to the switching unit via the third transmission unit, and when the switching unit receives the abnormality determination signal, the heating unit 3. The image forming apparatus according to 1 or 2, wherein energization of the means is stopped.

  [4] The image forming apparatus according to [2] or [3], wherein the print control unit reduces throughput based on a signal from the determination circuit.

  [5] The image forming apparatus according to any one of [2] to [4], wherein the print control unit cuts off power from the power source to the heating unit based on a signal from the determination circuit.

  [6] The image formation according to any one of 2 to 5, wherein the print control unit changes an on / off ratio of the temperature control unit to the switching unit based on a signal from the determination circuit. apparatus.

As explained above,
According to the first invention,
Heating means including a heating element that generates heat upon receipt of power from a power source;
Temperature detection means provided on the primary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Switching means switchable to either conduction or interruption from the power source to the heating element;
A first transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
A second transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
Pulse generating means provided on the secondary side for generating a pulse signal with variable duty;
A pulse conversion means for converting the pulse signal emitted from the pulse generation means transmitted to the primary side via the first transmission means into an electric signal corresponding to the duty;
In an image forming apparatus having a temperature control means for controlling switching of the switching means,
The electrical signal from the pulse converter and the electrical signal detected by the temperature detector are input to a determination circuit that indicates whether or not the temperature provided on the primary side is equal to or higher than a predetermined temperature. The output determination signal is configured to be supplied to the temperature control unit via the second transmission unit, and the temperature control unit controls the switching unit based on the determination signal.
Thus, the configuration between the heating unit and the temperature detection unit can be made inexpensive and easy.

  That is, since the temperature detecting means is provided on the primary side, there is no need to secure an insulation distance from the heating means such as a primary heating element, and the temperature detecting means for detecting the temperature of the heating means; As compared with the conventional circuit configuration in which the temperature detecting means is provided on the primary side, the number of parts can be reduced and a heating device having a simple configuration can be provided.

According to the second invention,
Heating means including a heating element that generates heat upon receipt of power from a power source;
Switching means switchable to either conduction or interruption from the power source to the heating element;
First temperature detection means provided on the primary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Second temperature detection means provided on the secondary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Temperature control means for controlling switching of the switching means based on the electrical signal detected by the second temperature detection means;
A first transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
A second transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
Pulse generating means provided on the secondary side for generating a pulse signal with variable duty;
A pulse conversion means for converting the pulse signal emitted from the pulse generation means transmitted to the primary side via the first transmission means into an electric signal corresponding to the duty;
In an image forming apparatus having a print control means for performing print sequence control,
The electrical signal from the pulse converter and the electrical signal detected by the temperature detector are input to a determination circuit that indicates whether or not the temperature provided on the primary side is equal to or higher than a predetermined temperature. The output determination signal is configured to be supplied to the print control unit via the second transmission unit, and the print control unit performs print sequence control based on the determination signal from the determination circuit. thing,
Thus, temperature detection means that are not used for temperature control can be installed on the primary side. Therefore, the configuration between the heating unit and the heating unit can be facilitated.

  In other words, since the temperature detection means other than the temperature control is provided on the primary side, it is not necessary to secure an insulation distance from the heating means such as a heating element on the primary side. The configuration can be facilitated.

  Conventionally, the outputs of all temperature detection elements are input to a temperature control means, for example, an A / D port of a CPU, and complicated software processing is performed. Since the output of the temperature detection element other than the control application is output as binary information, the CPU input port can be used as an I / O port input corresponding to the binary information, thus reducing the load on the CPU. In addition, the A / D port can be reduced, and the cost can be reduced. Specifically, the sequence controller corresponds to the CPU described above, and the control operation can be performed only by inputting an ON signal. Therefore, the burden on the control circuit can be reduced, and the configuration is inexpensive and simple. It can be.

According to the third invention,
Furthermore, an abnormality determination circuit provided on the primary side for determining that the temperature detected by the temperature detection means exceeds a predetermined upper limit temperature,
A third transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary, and is provided on the primary side;
The electrical signal from the pulse conversion means and the electrical signal from the first temperature detection means are input to the abnormality determination circuit,
An abnormality determination signal output from the abnormality determination circuit is configured to be supplied to the switching unit via the third transmission unit, and when the switching unit receives the abnormality determination signal, the heating unit Stop energizing the means,
Thus, it is not necessary to take the distance between the heating element as the primary circuit and the temperature detection element as the secondary circuit, and a small and inexpensive heating device can be provided.

  Further, by adopting such a configuration, it is possible to stop the power supply to the heating means by a mechanism that does not involve a CPU or the like in which a failure occurs at random, and thus it is possible to provide a highly reliable and safe device. It becomes.

According to the fourth invention,
The print control means is configured to reduce throughput based on a signal from the determination circuit;
Thus, the temperature of the heating element can always be controlled below a desired temperature, and a safe and inexpensive image forming apparatus can be provided.

According to the fifth invention,
The print control means shuts off the energization from the power source to the heating means based on a signal from the determination circuit;
Thus, the temperature of the heating element can always be controlled below a desired temperature, and a safe and inexpensive image forming apparatus can be provided.

According to the sixth invention,
The print control means changes an on / off ratio of the temperature control means to the switching means based on a signal from the determination circuit;
Thus, the temperature of the heating element can always be controlled below a desired temperature, and a safe and inexpensive image forming apparatus can be provided.

  Hereinafter, description will be given with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus using an electrophotographic process, and shows a case of a laser printer, for example.

  The laser printer main body 101 (hereinafter referred to as the main body 101) has a cassette 102 for storing the recording paper S, a cassette presence / absence sensor 103 for detecting the presence / absence of the recording paper S in the cassette 102, and a size of the recording paper S in the cassette 102. There are provided a cassette size sensor 104 (consisting of a number of micro switches), a paper feed roller 105 for feeding the recording paper S from the cassette 102, and the like. A registration roller pair 106 that synchronously conveys the recording paper S is provided downstream of the paper supply roller 105. Further, an image forming unit 108 that forms a toner image on the recording paper S based on the laser beam from the laser scanner unit 107 is provided downstream of the registration roller pair 106. Further, a fixing device 109 that thermally fixes the toner image formed on the recording paper S is provided downstream of the image forming unit 108, and a discharge unit that detects the conveyance state of the paper discharge unit is provided downstream of the fixing device 109. A paper sensor 110, a paper discharge roller 111 for discharging the recording paper S, and a stacking tray 112 for stacking the recording paper S on which recording has been completed are provided. The conveyance reference of the recording paper S is set so as to be centered with respect to the length of the recording paper S in the direction orthogonal to the conveyance direction of the image forming apparatus, that is, the width of the recording paper S.

  The laser scanner 107 emits a laser beam modulated based on an image signal (image signal VDO) sent from an external device 131 (to be described later), and the laser beam from the laser unit 113 is described later. It comprises a polygon motor 114 for scanning on the photosensitive drum 117, an imaging lens 115, a folding mirror 116, and the like.

  The image forming apparatus 108 includes a photosensitive drum 117, a primary charging roller 119, a developing device 120, a transfer charging roller 121, a cleaner 122, and the like necessary for a known electrophotographic process. The fixing device 109 includes a fixing film 109a, a pressure roller 109b, a ceramic heater 109c provided inside the fixing film, and a thermistor 109d that detects the surface temperature of the ceramic heater.

  The main motor 123 applies a driving force to the paper feed roller 105 via a paper feed roller clutch 124, and a resist roller pair 106 via a resist roller 125, and further includes an image forming unit including a photosensitive drum 117. Driving force is also applied to each unit 108, the fixing device 109, and the paper discharge roller 111.

  An engine controller 126 controls the electrophotographic process by the laser scanner unit 107, the image forming unit 108, and the fixing unit 109, and controls the conveyance of the recording paper in the main body 101.

  Reference numeral 127 denotes a video controller, which is connected to an external device 131 such as a personal computer via a general-purpose interface (Centronics, RS232C, etc.) 130, and develops image information sent from the general-purpose interface into bit data. The bit data is sent to the engine controller 126 as a VDO signal.

  FIG. 2 shows a ceramic heater driving and control circuit according to the present invention. Reference numeral 1 denotes an AC power source for connecting the image forming apparatus. The image forming apparatus supplies AC power to the heating element 3 and the heating element 20 of the ceramic heater 24 via the AC filter 2 to thereby connect the ceramic heater 24. The heat generating body 3 and the heat generating body 20 that are configured are caused to generate heat.

  The supply of electric power to the heating element 3 is controlled by energization and interruption of the triac 4. The resistors 5 and 6 are bias resistors for the triac 4, and the phototriac coupler 7 is a device for securing a creepage distance between the primary and secondary. The triac 4 is turned on by energizing the light emitting diode of the phototriac coupler 7. A resistor 8 is a resistor for limiting the current of the phototriac coupler 7, and the phototriac coupler 7 is turned on / off by the transistor 9. The transistor 9 operates according to the ON1 signal from the engine controller 11 via the resistor 10.

  Supply of electric power to the heating element 20 is controlled by energization and interruption of the triac 13. The resistors 14 and 15 are bias resistors for the triac 13, and the phototriac coupler 16 is a device for ensuring a creepage distance between the primary and secondary. The triac 13 is turned on by energizing the light emitting diode of the phototriac coupler 16. The resistor 17 is a resistor for limiting the current of the phototriac coupler 16, and the phototriac coupler 16 is turned on / off by the transistor 18. The transistor 18 operates according to the ON2 signal from the engine controller 11 via the resistor 19.

  The AC power supply 1 is input to the zero cross detection circuit 12 via the AC filter 2. The zero-cross detection circuit notifies the engine controller 11 as a pulse signal that the commercial power supply voltage is equal to or lower than a certain threshold value. Hereinafter, this signal sent to the engine controller 11 is referred to as a ZEROX signal. The engine controller 11 detects the edge of the pulse of the ZEROX signal, and turns ON / OFF the triac 4 or 13 by phase control or wave number control.

  In the case where power is supplied to the heating elements 3 and 20 and the controlling means breaks down and the heating elements 3 and 20 are in a thermal runaway state, an excessive temperature rise prevention means 23 is provided as one means for preventing excessive temperature rise. It is arranged on the ceramic heater 24. The excessive temperature rise prevention means 24 is, for example, a thermal fuse or a thermo switch. When the heating elements 3 and 20 reach thermal runaway due to a failure of the power supply control means and the excessive temperature rise prevention means 23 exceeds a predetermined temperature, the excessive temperature rise prevention means 23 becomes OPEN, and the heating elements 3 and 20 Power is cut off.

  An outline of the ceramic heater 24 in this embodiment is shown in FIG. A is a sectional view of the ceramic surface heater, B is a surface on which the heating elements 3 and 20 are formed, and C is a surface opposite to the surface indicated by B.

  The ceramic surface heater 24 protects a ceramic insulating substrate 31 such as SiC, AlN, Al 2 O 3, the heating elements 3 and 20 formed on the surface of the insulating substrate 31 by paste printing, and the two heating elements. The protective layer 34 is made of glass or the like. On the protective layer 34, a temperature detection element 46 for detecting the temperature of the ceramic surface heater 24 and an excessive temperature rise prevention means 23 are provided with respect to the conveyance reference of the recording paper, that is, the center in the length direction of the heat generating portions 3a and 20a. It is a symmetrical position and is disposed at a position inside the minimum recording paper width that can be passed.

  The heating element 3 includes a portion 3a that generates heat when electric power is supplied, a conductive portion 3b that connects the electrode portions 3c and 3d to the heating element, and electrode portions 3c and 3d to which electric power is supplied via a connector. ing. The heating element 20 includes a portion 20a that generates heat when power is supplied, a conductive portion 20b that is connected to the electrode portions 20c and 20d, and electrode portions 20c and 20d that are supplied with power via a connector. The electrode portion 20 c is connected to the two heating elements 3 and 20 and serves as a common electrode for the heating elements 3 and 20. In addition, a glass layer may be formed on the surface facing the insulating substrate 31 on which the heating elements 3 and 20 are printed in order to improve slidability.

  The common electrode 3 c is connected from the HOT side terminal of the AC power supply 1 through the excessive temperature rise prevention means 23. The electrode portion 3 d is connected to a triac 4 that controls the heating element 3, and is connected to a neutral terminal of the AC power supply 1. The electrode portion 20 d is electrically connected to the triac 13 that controls the heating element 20, and is connected to the neutral terminal of the AC power supply 1. The ceramic heater 24 is supported by a film guide 62 as shown in FIG. Reference numeral 61 denotes a fixing film made of a cylindrical heat-resistant material, and is externally fitted to a film guide 62 that supports the ceramic heater 24 on the lower surface side.

  Then, the ceramic heater 24 on the lower surface of the film guide 62 and the elastic pressure roller 63 as a pressure member are pressed against each other with a predetermined pressure against the elasticity of the elastic pressure roller 63 with the fixing film 61 interposed therebetween. Thus, a fixing nip portion having a predetermined width as a heating portion is formed. An excessive temperature rise prevention means 23, for example, a thermostat is in contact with the surface of the insulating substrate 31 or the protective layer 34 of the ceramic heater 24. The thermostat 23 is corrected in position by the film guide 62, and the thermosensitive surface of the thermostat 23 is in contact with the surface of the ceramic heater 24. Although not shown, the temperature detection element 46 is also in contact with the surface of the ceramic heater 24 in the same manner. Here, as shown in FIG. 4, the ceramic heater 24 may have the heating elements 3 and 20 on the side opposite to the nip part or the heating element on the nip part side. In order to improve the slidability of the film 61, slidable grease may be applied to the interface between the film 61 and the ceramic heater 24.

  Next, in this embodiment, reference numeral 46 denotes a temperature detection element for detecting the temperature of the ceramic heater 24, for example, a thermistor temperature sensing element, and secures an insulation distance from the heating elements 3 and 20 on the ceramic heater 24. It arrange | positions through the insulator which has a dielectric strength voltage so that it can. The temperature detecting element 46 is characterized in that it is installed on the primary side of the power source. The temperature detected by the temperature detection element 46 is detected as a partial pressure between the resistor 37 and the temperature detection element 46, and is compared with a signal from the engine controller 11 by a comparator 38 such as a comparator. Here, 30 connected to the PWM port of the engine controller 11 is a current limiting resistor for limiting the base current of the transistor 31, 32 is a current limiting resistor for limiting the current of the photocoupler 33, and one end is the secondary side. It is connected to a constant power source Vcc. These elements are installed on the secondary side of the power source. Further, a primary side circuit is provided via the photocoupler 33, 34 is a current limiting resistor for limiting the current of the phototransistor in the photocoupler 33, and one end is connected to the primary side constant power source Vac. A smoothing circuit is constituted by 35 resistors and 36 capacitors, and the PWM signal is converted into an analog voltage value corresponding to the output duty.

  The pulse signal output from the PWM port of the engine controller 11 is transmitted from the secondary side to the primary side by these circuit units, converted into an analog voltage value corresponding to the output duty width, and the resistor 37 and the temperature detecting element. 46 is compared with the partial pressure value of 46. The comparator 38 outputs high when the partial pressure value is higher, and outputs low when it is lower. The output of the comparator 38 is determined to be high or low by a resistor 39 having one end connected to Vac, and is input to the base of the transistor 41 via the base current limiting resistor 40. When high is input to the transistor 41 and turned on, the photocoupler 43 provided to insulate the secondary side from the primary side is also turned on, and the I / O port of the engine controller 11 is connected to the I / O port of the engine controller 11 via the resistor 45. low is input. Further, when low is input to the transistor 41, both the transistor 41 and the photocoupler 43 are turned off, and high is input to the I / O port of the engine controller 11 via the resistor 45. Reference numerals 42 and 44 denote resistors for limiting the currents of the photodiode and the phototransistor in the photocoupler 43, respectively.

  In this way, the pulse output from the PWM port of the engine controller 11 installed on the secondary side is transmitted to the primary side via the photocoupler 33, and the temperature detection element 46 installed on the primary side. Is compared with the output value of. The comparison result is transmitted again to the secondary side via the photocoupler 43, and is input to the I / O port in the engine controller 11 as a binary value of high or low.

  The engine controller 11 has a ROM (not shown) in which a table of the duty output from the PWM port and the temperature detected by the temperature detection element 46 at that time is built-in. The temperature of the temperature detection element 46 is detected at a high or low level.

  The temperature of the ceramic heater 24 is monitored by the engine controller 11, and is compared with the set temperature of the ceramic heater 24 set inside the engine controller 11, whereby the heating elements 3, 20 constituting the ceramic heater 24. The engine controller 11 sends an ON1 signal to the transistor 9 or an ON2 signal to the transistor 18 according to the control condition.

  Next, a flow chart for carrying out the present invention is shown in FIG.

  When the apparatus is turned on, heater control is started (S1).

  Thereafter, the engine controller 11 checks print information such as the number of sheets to be passed and the paper type (S2). Based on the print information checked in S2, the engine controller 11 adjusts the temperature to a temperature adjusted according to the information. The pulse width based on the temperature information in the table previously held in the engine controller 11 is output from the PWM port (S3).

  Thereafter, the engine controller 11 checks the I / O port input signal (S4). If it remains at the low level, the engine controller 11 turns on the energization of the ceramic heater 24 (S5) and waits for the output inversion of the I / O port. If the level is high, the engine controller 11 stops energizing the ceramic heater 24 (S6).

  Thereafter, it is checked whether or not the print job is completed (S7). If the print job is not completed, the print information is checked again, and the routines from S2 to S7 are repeated. If the print job is finished, the heater energization is turned off (S8), and the print operation is finished.

  As described above, the engine controller 11 controls the temperature of the ceramic heater 24 so as to perform an optimal printing operation.

  In this embodiment, by controlling the heating device with the above-described configuration, it is not necessary to take a distance between the primary side circuit that is a heating element and the secondary side circuit that is a temperature detection body, and the number of electronic components is also reduced. Therefore, it is possible to provide a safe heating device with an inexpensive configuration that can be reduced as compared with the configuration of the temperature detector provided on the primary side.

  A duplicated point with the first embodiment is omitted.

  FIG. 6 shows a drive and control circuit for the ceramic heater in this embodiment. In FIG. 6, the same points as those in the first embodiment are omitted. In FIG. 6, reference numeral 50 denotes a temperature detection element for detecting the temperature of the ceramic heater 24, for example, a thermistor temperature sensing element, which is insulated on the ceramic heater 24 so as to secure an insulation distance from the heating elements 3 and 20. It arrange | positions through the insulator which has a proof pressure. Unlike the temperature detection element 46 in the first embodiment, the temperature detection element 50 is installed on the secondary side of the power source. The temperature detected by the temperature detection element 50 is detected as a partial pressure between the resistor 51 and the temperature detection element 50 and input to the A / D port of the engine controller 11 as a TH signal.

  Reference numeral 46 denotes a temperature detection element for detecting the temperature of the ceramic heater 24 as in the first embodiment, for example, a thermistor temperature sensing element, and provides an insulation distance from the heating elements 3 and 20 on the ceramic heater 24. It arrange | positions through the insulator which has a withstand voltage so that it can ensure. This temperature detection element 46 is arranged on the primary side of the power supply, as in the first embodiment.

  The temperature of the ceramic heater 24 detected by the temperature detection element 50 is monitored by the engine controller 11 and compared with the set temperature of the ceramic heater 24 set inside the engine controller 11, thereby generating heat that constitutes the ceramic heater 24. The power ratio to be supplied to the bodies 3 and 20 is calculated, converted into a phase angle (phase control) or wave number (wave number control) corresponding to the supplied power ratio, and the engine controller 11 turns on the transistor 9 according to the control conditions. A signal or an ON2 signal is sent to the transistor 18. For example, in the case of phase control, the following table is provided in the engine controller 11, and temperature control is performed based on this control table.

  As described above, since the normal heater temperature control is performed at the temperature detected by the temperature detection element 50 provided on the secondary side, as shown in the first embodiment, the heater temperature control is performed on the primary side. The provided temperature detecting element 46 is not used.

  Further, the temperature detecting element 50 used for controlling the heater temperature is normally disposed near the center of the heater and efficiently detects the temperature.

  However, the end of the printing paper (end of the ceramic heater 24) is easily deprived of heat, and if the pattern of the heating element 3 or 20 has a straight shape, it is difficult to raise the temperature, and the end of the printing paper is not fixed properly. Sometimes it becomes. Therefore, there is a ceramic heater in which the end pattern of the heating element 3 or 20 is narrowed more than the central portion, the resistance value is increased, the electric power is increased, and countermeasures for fixing failure are taken.

  In that case, for example, when printing on narrow paper represented by an envelope or the like, the heat at the end of the ceramic heater 24 is not taken away by the printing paper, so that the temperature rises more easily than in the central part. In the case where a pattern stop is further inserted at the end, the temperature rise is further severe, and as a result, the heater may be damaged.

  For this reason, it is more effective to provide the temperature detection element 46 at the end and perform print sequence control based on the detected temperature. Normally, a sequence controller that performs print sequence control operates based on information incorporated in the CPU 11 (not shown).

  In the present embodiment, the case where the temperature detection element 46 provided on the primary side is provided in the end diaphragm will be described.

  Next, an outline of the ceramic heater 24 in the present embodiment is shown in FIG. A is a sectional view of the ceramic surface heater, B is a surface on which the heating elements 3 and 20 are formed, and C is a surface opposite to the surface indicated by B.

The ceramic surface heater 24 includes a ceramic insulating substrate 31 such as SiC, AlN, and Al ₂ O _3, heating elements 3 and 20 formed on the surface of the insulating substrate 31 by paste printing or the like, and two heat generations. It consists of a protective layer 34 such as glass that protects the body. In addition, the heating element 20 has a configuration in which the end pattern is narrowed in order to secure the paper end fixing property as described above. On the protective layer 34, a temperature detecting element 50 for detecting the temperature of the ceramic surface heater 24 and controlling the energization ratio to the heating element 3 or 20 based on the detected temperature, and an excessive temperature rise prevention means 23 are provided. The recording paper is provided at a position symmetrical to the conveyance reference of the recording paper, that is, the center in the length direction of the heat generating portions 3a and 20a, and at a position inside the minimum recording paper width through which the paper can pass.

  The temperature detection temperature detecting element 50 for controlling the energization ratio is provided in the secondary circuit of the power source. Reference numeral 46 denotes a temperature detection element for countermeasure against temperature rise at the end as described above, and is provided at a position where the temperature of the pattern diaphragm portion of the heating element 20 can be detected.

  The heating element 3 includes a portion 3a that generates heat when electric power is supplied, a conductive portion 3b that connects the electrode portions 3c and 3d to the heating element, and electrode portions 3c and 3d to which electric power is supplied via a connector. ing. The heating element 20 includes a portion 20a that generates heat when power is supplied, a conductive portion 20b that is connected to the electrode portions 3c and 20d, and electrode portions 3c and 20d that are supplied with power via a connector. The electrode portion 3 c is connected to the two heating elements 3 and 20 and serves as a common electrode for the heating elements 3 and 20. In addition, a glass layer may be formed on the surface facing the insulating substrate 31 on which the heating elements 3 and 20 are printed in order to improve slidability.

  The common electrode 3 c is connected from the HOT side terminal of the AC power supply 1 through the excessive temperature rise prevention means 23. The electrode portion 3 d is connected to a triac 4 that controls the heating element 3, and is connected to a neutral terminal of the AC power supply 1. The electrode portion 20 d is electrically connected to the triac 13 that controls the heating element 20, and is connected to the neutral terminal of the AC power supply 1. The ceramic heater 24 is supported by a film guide 62 as shown in FIG. Reference numeral 61 denotes a fixing film made of a cylindrical heat-resistant material, and is externally fitted to a film guide 62 that supports the ceramic heater 24 on the lower surface side. Then, the ceramic heater 24 on the lower surface of the film guide 62 and the elastic pressure roller 63 as a pressure member are pressed against each other with a predetermined pressure against the elasticity of the elastic pressure roller 63 with the fixing film 61 interposed therebetween. Thus, a fixing nip portion having a predetermined width as a heating portion is formed. An excessive temperature rise prevention means 23, for example, a thermostat is in contact with the surface of the insulating substrate 31 or the protective layer 34 of the ceramic heater 24. The thermostat 23 is corrected in position by the film guide 62, and the thermosensitive surface of the thermostat 23 is in contact with the surface of the ceramic heater 24. Although not shown, the temperature detecting element 46 or 50 is also in contact with the surface of the ceramic heater 24. Here, as shown in FIG. 7, the ceramic heater 24 may be configured such that the heating elements 3 and 20 are on the side opposite to the nip part or the heating element is on the nip part side. In order to improve the slidability of the film 61, slidable grease may be applied to the interface between the film 61 and the ceramic heater 24.

  Further, the engine controller 11 has a ROM (not shown) in which a table of the duty output from the PWM port and the temperature detected by the temperature detection element 46 at that time is built, and the output duty and the I / O port. The temperature of the temperature detecting element 46 is detected at a high or low level.

  The sequence controller in the engine controller 11 controls the print sequence based on the detected temperature.

  Next, the relationship between the pattern of the ceramic heater 24 and the paper type is shown in FIG.

  Due to the characteristics of the ceramic heater 24 and the roller in contact with the ceramic heater 24, the end of the printing paper is open, so that heat is easily taken away and the temperature is not easily raised. For this reason, the end portion of the printing paper may not reach the temperature necessary for fixing as compared with the central portion, resulting in fixing failure. Moreover, if it is going to satisfy the temperature of an edge part, the temperature of a center part will become high more than needed, and the member which contact | abuts a heater and a heater will be damaged. Also, in terms of power, it is disadvantageous because more power than necessary is input. Therefore, the end pattern of the heating element 20 is narrower than the center part, the resistance value is increased, the electric power is increased, and the end temperature rise is satisfied to satisfy the end fixing failure countermeasure. There is also a heater.

  In that case, for example, when printing on narrow paper represented by an envelope or the like, the heat at the end of the ceramic heater 24 is not taken away by the printing paper, so that the temperature rises more easily than in the central part. In the case where a pattern stop is further inserted at the end, the temperature rise is further severe, and as a result, the heater may be damaged.

  In the case of printing a wide paper such as LTR or A4 paper, the end pattern aperture is effective for ensuring fixability, but in the case of narrow paper printing such as a width size of B5 paper or less, Abnormal temperature rise at the edge becomes a problem.

  Therefore, for example, by providing a temperature detection element 46 in the end diaphragm and detecting the temperature, abnormal temperature rise at the end is prevented by executing a print throughput reduction at the time of narrow paper printing.

  FIG. 9 shows a flowchart in the present embodiment.

  When the apparatus is turned on, the engine controller 11 sets the outputs of the ON1 and ON2 ports to high (S11) and starts energizing the heater (S12).

  When the heater energization is started, based on the detected temperature of the heater temperature adjusting temperature detecting element 50 provided on the secondary side, the CPU 11 sets the energization power ratio to the heater as described in the above table. Control is performed based on (S13).

  Thereafter, the PWM port in the engine controller 11 outputs a duty pulse based on the detected temperature table so as to be set to a first detected temperature set in advance assuming that narrow paper is printed ( S14). Next, the input of the I / O port at the low level in the normal state is observed (S15). Here, when the I / O port is at the high level, the engine controller 11 detects the current temperature from the above-described table based on the current pulse width (S16).

  In S15, if the I / O port remains at the low level, pulses of the same duty are continuously output until the high level is reached.

  After that, the sequence controller in the engine controller 11 that has detected the first temperature reduces the print speed to the preset first speed throughput (S17).

  Next, throughput reduction is performed, and a pulse of duty based on the detected temperature table is output so as to become the second detected temperature (S18). The second temperature is set to a temperature higher than the first temperature.

  Next, the engine controller 11 looks at the input of the I / O port at the low level in the normal state (S19). Here, when the I / O port is at the high level, the engine controller 11 detects the current temperature from the above-described table based on the current pulse width (S20). The fact that the high level has been detected means that even if the throughput is reduced to the first speed, the temperature at the end is further increased. Therefore, here, the throughput is reduced to the second speed that is further slower than the first speed (S21) to prevent the end temperature from rising.

  In S19, if the I / O port remains at the low level, pulses of the same duty are continuously output until the high level is reached, and the throughput speed is not changed.

  Next, in S22, a duty pulse based on the detected temperature table is output so as to be the third detected temperature. Here, the third detected temperature is a temperature at which the ceramic heater 24 and a member in contact therewith may be damaged if the temperature further increases. Needless to say, the temperature is set higher than the first detection temperature and the second detection temperature. After setting the third detected temperature, the engine controller 11 looks at the input of the I / O port that is at the low level in the normal state (S23).

  If the I / O port is at a high level, the engine controller 11 determines that the end temperature has reached a dangerous temperature due to some abnormality and forcibly turns off the energization to the ceramic heater 24 (S25). ). Normally, when the throughput is reduced to the second speed, the power during the heater temperature adjustment can be reduced, and the gap between the papers becomes wider and the cooling time becomes longer. Go.

  If the throughput is reduced in S23 and the subsequent end temperature does not reach the abnormal level, it is checked whether or not the print job is completed (S24). If not, the routines from S14 to S24 are repeated again. .

  If the print job is finished, the heater energization is turned off (S25), and the print operation is finished.

  While the above flow is repeated, the temperature control by the temperature detection element 50 provided on the secondary side is performed as usual.

  In the present embodiment, by using the image forming apparatus configured as described above, a temperature detection element that is not used for temperature control, in this case, the temperature detection element 50 can be installed on the primary side. Therefore, the configuration between the heating unit and the heating unit can be facilitated. In other words, since the temperature detection means other than the temperature control is provided on the primary side, it is not necessary to secure an insulation distance from the heating means such as a heating element on the primary side. The configuration can be facilitated.

  Also, by setting the first throughput speed and its temperature detection, and the second throughput speed and its temperature detection, it is possible to know the state of the edge temperature rise after the throughput is reduced to the first speed. Therefore, it is possible to increase the throughput and reliably prevent the heater from being turned off.

  Conventionally, the outputs of all temperature detection elements are input to the temperature control means, for example, the A / D port of the CPU 11, and complicated software processing is performed. Since the output of the temperature detection element other than the control application is output as binary information, the input port of the CPU 11 can be an I / O port input corresponding to the binary information, thus reducing the load on the CPU. In addition, the A / D port can be reduced, and the cost can be reduced. Specifically, the sequence controller corresponds to the CPU 11 described above, and can perform a control operation only by inputting an ON signal. Therefore, the load on the control circuit can be reduced, and the configuration is inexpensive and simple. It can be.

  The place which overlaps with Example 1 and 2 is abbreviate | omitted.

  The circuit configuration in this embodiment is the same as that in the second embodiment.

  FIG. 10 shows a flowchart in the present embodiment.

  When the apparatus is turned on, the engine controller 11 sets the output of the ON1 and ON2 ports to high (S31) and starts energizing the heater (S32).

  When the heater energization is started, based on the detected temperature of the heater temperature adjusting temperature detecting element 50 provided on the secondary side, the CPU 11 sets the energization power ratio to the heater as described in the above table. Control is performed based on (S33).

  Thereafter, the PWM port in the engine controller 11 outputs a duty with an ON width of 95% (S34), and the input of the I / O port at the low level in the normal state is viewed (S35). Here, when the I / O port is at a high level, comparison is made with the PWM duty output from the table previously held in the engine controller 11 (S38), and the temperature is detected (S39).

  In S35, if the I / O port remains at the low level, the engine controller 11 determines whether the PWM duty is 5% (S36). If the PWM duty is 5%, the same routine is repeated with 95% again. If the PWM duty is not 5%, the duty is decreased by 5% (S37), the level of the I / O port is monitored, and the same routine is repeated.

  Here, it is determined whether or not the detected temperature is equal to or higher than a first detection temperature set in advance assuming that narrow paper is printed and equal to or lower than a second (described later) detection temperature ( S40). If it is within the above range, there is a possibility that narrow paper printing is in progress, so the throughput is reduced to the first speed (S41), and then it is checked whether the print job is finished (S45). ) If not, the routine from S34 is repeated again.

  If not within the above range, it is determined whether the temperature is equal to or higher than the second detected temperature and equal to or lower than a third (described later) detected temperature (S42). The second temperature is set to a temperature higher than the first temperature. The fact that the temperature is within the range of the second detection temperature or more and the third detection temperature or less means that even if the throughput is reduced to the first speed, the temperature at the end is further increased. Therefore, here, the throughput is reduced to the second speed that is further slower than the first speed (S43) to prevent the end temperature from rising. Thereafter, it is checked whether or not the print job is finished (S45). If the print job is not finished, the routine from S34 is repeated again.

  If the detected temperature range is not within the above-described range, it is determined whether the temperature is equal to or higher than the third detected temperature (S44). Here, the third detected temperature is a temperature at which the ceramic heater 24 and the roller in contact therewith may be damaged if the temperature further increases. Needless to say, the temperature is set higher than the first detection temperature and the second detection temperature. If the engine controller 11 determines that the temperature is the third detected temperature, the engine controller 11 determines that the end temperature has reached a dangerous temperature due to some device abnormality, and forcibly turns off the energization of the ceramic heater 24. (S46). Normally, when the throughput is reduced to the second speed, the temperature can be reduced as compared with the case where the electric power for adjusting the heater temperature is not used. Therefore, the temperature is set so that the temperature of the end portion decreases. If none of the detected temperatures correspond, the routine from S34 is repeated again.

  While the above flow is repeated, the temperature control by the temperature detection element 50 provided on the secondary side is performed as usual.

  In the present embodiment, by using the image forming apparatus configured as described above, a temperature detection element that is not used for temperature control, in this case, the temperature detection element 50 can be installed on the primary side.

  Therefore, the configuration between the heating unit and the heating unit can be facilitated. In other words, since the temperature detection means other than the temperature control is provided on the primary side, it is not necessary to secure an insulation distance from the heating means such as a heating element on the primary side. The configuration can be facilitated.

  Also, by setting the first throughput speed and its temperature detection, and the second throughput speed and its temperature detection, it is possible to know the state of the edge temperature rise after the throughput is reduced to the first speed. Therefore, it is possible to increase the throughput and reliably prevent the heater from being turned off.

  Conventionally, the outputs of all temperature detection elements are input to the temperature control means, for example, the A / D port of the CPU 11, and complicated software processing is performed. Since the output of the temperature detection element other than the control application is output as binary information, the input port of the CPU 11 can be an I / O port input corresponding to the binary information, thus reducing the load on the CPU. In addition, the A / D port can be reduced, and the cost can be reduced. Specifically, the sequence controller corresponds to the CPU 11 described above, and can perform a control operation only by inputting an ON signal. Therefore, the load on the control circuit can be reduced, and the configuration is inexpensive and simple. It can be.

  Moreover, since the temperature detection range and the width of the detection temperature can be arbitrarily set, more accurate temperature detection can be performed.

  The place which overlaps with Examples 1-3 is abbreviate | omitted.

  The circuit configuration in this embodiment is the same as those in the second and third embodiments.

  FIG. 11 shows a flowchart in the present embodiment.

  When the apparatus is turned on, the engine controller 11 sets the outputs of the ON1 and ON2 ports to high (S51) and starts energizing the heater (S52).

  When the heater energization is started, based on the detected temperature of the heater temperature adjusting temperature detecting element 50 provided on the secondary side, the CPU 11 sets the energization power ratio to the heater as described in the above table. Control is performed based on (S53).

  Thereafter, the PWM port in the engine controller 11 outputs a duty pulse based on the detected temperature table so as to be set to a first detected temperature set in advance assuming that narrow paper is printed ( S54). Next, the input of the I / O port at the low level in the normal state is observed (S55). Here, when the I / O port is at the high level, the engine controller 11 detects the current temperature from the above-described table based on the current pulse width (S56).

  In S15, if the I / O port remains at the low level, pulses of the same duty are continuously output until the high level is reached.

  After that, the sequence controller in the engine controller 11 that has detected the first temperature is a phase control table (Example 2) set on the secondary side and set based on the detected temperature of the temperature detecting element for temperature control. From the power ratio duty based on the temperature detected by the current temperature adjustment temperature detecting element (S57).

  Next, a duty pulse based on the detected temperature table is output so as to be the second detected temperature (S58). Here, the second detected temperature is a temperature at which the ceramic heater 24 and the roller in contact therewith may be damaged if the temperature further increases. Needless to say, the temperature is set higher than the first detected temperature. If the engine controller 11 determines that the temperature is the second detected temperature, the engine controller 11 determines that the end temperature has reached a dangerous temperature due to some abnormality in the device, and forcibly turns off the ceramic heater 24. (S61). Normally, in the phase control, when the heater input power ratio duty is reduced, the power at the time of adjusting the heater temperature can be reduced as compared with the case where the heater temperature is not reduced.

  Next, the engine controller 11 determines whether the print job is finished (S60). If the print job is finished, the heater energization is turned off (S61), and the printing operation is finished.

  While the above flow is repeated, the temperature control by the temperature detection element 50 provided on the secondary side is performed as usual.

  As described above, the present invention can be implemented even when the print sequence control is a reduction in heater energization power.

  In the present embodiment, by using the image forming apparatus configured as described above, a temperature detection element that is not used for temperature control, in this case, the temperature detection element 50 can be installed on the primary side. Therefore, the configuration between the heating unit and the heating unit can be facilitated. In other words, since the temperature detection means other than the temperature control is provided on the primary side, it is not necessary to secure an insulation distance from the heating means such as a heating element on the primary side. The configuration can be facilitated.

  Also, by setting the first throughput speed and its temperature detection, and the second throughput speed and its temperature detection, it is possible to know the state of the edge temperature rise after the throughput is reduced to the first speed. Therefore, it is possible to increase the throughput and reliably prevent the heater from being turned off.

  Conventionally, the outputs of all the temperature detection elements are input to the temperature control means, for example, the A / D port of the CPU 11, and complicated software processing is performed. Since the output of the temperature detection element other than for the purpose of adjusting control is output as binary information, the input port of the CPU 11 can be used as an I / O port input corresponding to the binary information, thus reducing the load on the CPU. In addition, the A / D port can be reduced, and the cost can be reduced. Specifically, the sequence controller corresponds to the above-described CPU 11 and can perform a control operation only by inputting an ON signal. Therefore, the load on the control circuit can be reduced, and the configuration is inexpensive and simple. It can be.

1 is a diagram illustrating an image forming apparatus in Embodiment 1. FIG. FIG. 3 is a diagram illustrating a control and drive circuit of a fixing device in Embodiment 1. FIG. 2 is a diagram illustrating an outline of a ceramic heater which is a heating unit in the first embodiment. FIG. 3 is a diagram illustrating a schematic configuration of a fixing device according to the first exemplary embodiment. FIG. 3 is a diagram illustrating a flowchart of fixing device control according to the first exemplary embodiment. FIG. 6 is a diagram illustrating a control and drive circuit of a fixing device in Embodiment 2. FIG. 6 is a diagram showing an outline of a ceramic heater which is a heating means in Embodiment 2. FIG. 6 is a diagram showing a ceramic heater which is a heating means in Embodiment 2. FIG. 6 is a diagram illustrating a flowchart of fixing device control in Embodiment 2. FIG. 10 is a diagram illustrating a flowchart of fixing device control in Embodiment 3. FIG. 10 is a diagram illustrating a flowchart of fixing device control in Embodiment 4. The figure which showed the control and drive circuit of the conventional fixing device in this invention. The figure which showed the outline of the ceramic heater which is the conventional heating means in this invention. The figure which showed the control and drive circuit of the conventional fixing device in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Laser beam printer main body 102 Paper feed cassette 105 Paper feed roller 107 Laser scanner part 109 Fixing device 111 Paper discharge roller 112 Paper discharge tray 117 Photosensitive drum 119 Primary charging roller 120 Developer 121 Transfer charging roller 123 Main motor 126 Engine controller 127 Video Controller 131 External device

Claims (6)

Heating means including a heating element that generates heat upon receipt of power from a power source;
Temperature detection means provided on the primary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Switching means switchable to either conduction or interruption from the power source to the heating element;
A first transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
A second transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
Pulse generating means provided on the secondary side for generating a pulse signal with variable duty;
A pulse conversion means for converting the pulse signal emitted from the pulse generation means transmitted to the primary side via the first transmission means into an electric signal corresponding to the duty;
In an image forming apparatus having a temperature control means for controlling switching of the switching means,
The electrical signal from the pulse converter and the electrical signal detected by the temperature detector are input to a determination circuit that indicates whether or not the temperature provided on the primary side is equal to or higher than a predetermined temperature. The output determination signal is configured to be supplied to the temperature control unit via the second transmission unit, and the temperature control unit controls the switching unit based on the determination signal. An image forming apparatus. Heating means including a heating element that generates heat upon receipt of power from a power source;
Switching means switchable to either conduction or interruption from the power source to the heating element;
First temperature detection means provided on the primary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Second temperature detection means provided on the secondary side for detecting the temperature of the heating element and outputting the temperature detection information as an electrical signal;
Temperature control means for controlling switching of the switching means based on the electrical signal detected by the second temperature detection means;
A first transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
A second transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary sides;
Pulse generating means provided on the secondary side for generating a pulse signal with variable duty;
A pulse conversion means for converting the pulse signal emitted from the pulse generation means transmitted to the primary side via the first transmission means into an electric signal corresponding to the duty;
In an image forming apparatus having a print control means for performing print sequence control,
The electrical signal from the pulse converter and the electrical signal detected by the temperature detector are input to a determination circuit that indicates whether or not the temperature provided on the primary side is equal to or higher than a predetermined temperature. The output determination signal is configured to be supplied to the print control unit via the second transmission unit, and the print control unit performs print sequence control based on the determination signal from the determination circuit. An image forming apparatus. An abnormality determination circuit provided on the primary side for determining that the temperature detected by the temperature detection means exceeds a predetermined upper limit temperature;
A third transmission means that insulates the primary side from the secondary side and enables signal transmission between the primary and secondary, and is provided on the primary side;
The electrical signal from the pulse conversion means and the electrical signal from the first temperature detection means are input to the abnormality determination circuit,
An abnormality determination signal output from the abnormality determination circuit is configured to be supplied to the switching unit via the third transmission unit, and when the switching unit receives the abnormality determination signal, the heating unit The image forming apparatus according to claim 1, wherein the power supply to the means is stopped.   The image forming apparatus according to claim 2, wherein the print control unit reduces the throughput based on a signal from the determination circuit.   The image forming apparatus according to claim 2, wherein the print control unit cuts off power supply from the power source to the heating unit based on a signal from the determination circuit.   6. The image forming apparatus according to claim 2, wherein the print control unit changes an on / off ratio of the temperature control unit to the switching unit based on a signal from the determination circuit. .