JPH1069208A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the high reliability of a protective means as for the temperature control and thermorunaway of a device by reducing a burden for controlling the heating device of a controlling means, making a constitution between a heating means and the temperature detecting means of the heating means easy and informing of the fault of the device at an image forming device which possesses the heating device having the heating means heating material to be heated by being supplied with electric power from an electric power supplying means as a fixing device. SOLUTION: At the heating device where the temperature detecting means 13 of the heating means 2 and the driving and control circuits of the device are constituted on a primary side, the controlling means 30 sends an ON signal 40 instructing the control circuit 27 to drive, and a temperature discriminating circuit, for instance, a wind comparator discriminates that the temperature of the heating means is within the range of specified temperature, and the control circuit sends a discriminating signal 41 to the controlling means and informs the controlling means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a heating device for a material to be heated and an image forming apparatus provided with the heating device as image fixing means.

[0002]

2. Description of the Related Art For convenience, a fixing device (image heating device) as a heating device provided in an image forming apparatus such as an electrophotographic copying machine or a printer for thermally fixing an unfixed image will be described as an example.

A fixing device of an image forming apparatus is provided with a recording material (recording medium; transfer material sheet, electrostatic recording paper, electrofax paper) by an appropriate image forming means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. A non-fixed image (toner image) corresponding to the target image information formed and carried on a printing paper or the like by a transfer method or a direct method, and thermally fixed as a permanent image on a recording material surface. A heat roller type heat fixing device using a heat source as a heat source is often used.

As shown in FIG. 13, this fixing device of the heat roller type uses a fixing roller 8 as a heating roller (heat roller).
1 and a pressure roller 82 in parallel, the roller pair is rotated, and a recording medium S to be subjected to image fixing processing is introduced and nipped into a heating nip portion N which is a pressure contact portion of the roller pair. The unfixed image t is heated and melted by the heat of the fixing roller 81 and the pressing force of the nip portion N so that the recording medium S
It is to be soaked into the surface and heat-fixed.

The fixing roller 81 is generally formed by using a hollow metal roller of aluminum as a base and forming a heat-resistant rubber layer or the like as a release layer (offset prevention layer) on the outer peripheral surface thereof.
A halogen heater 8 as a heat source is provided at a substantially central portion in the hollow.
3 is inserted and arranged. The halogen heater 83 is an elongated rod-shaped one sealed with glass.

The pressure roller 82 is composed of a core metal and a heat-resistant elastic layer made of silicone rubber or the like formed concentrically around the core metal, and has a predetermined width between the fixing roller 81 and the elastic layer due to elastic deformation of the elastic layer. A heating nip N is formed.

[0007] The halogen heater 83 of the fixing roller 81 generates heat by electric power, and the heat is conducted to the hollow metal roller base of the fixing roller 81 by radiation and convection to heat the metal roller base. The metal roller base has a function of uniformly transmitting the received heat to the entire roller, and the fixing roller 81 has a uniform temperature distribution.

The halogen heater 81 is connected to an AC power supply (line input power supply) via a switching control element such as a triac, and power is supplied from the AC power supply.

A temperature detecting element 84, generally a thermistor thermosensitive element (thermosensitive element) is brought close to or in contact with the fixing roller 81, and the temperature of the fixing roller 81 is detected as a voltage by the element 84 and a voltage dividing resistor. Digitally converted and monitored by the CPU that controls the engine. The CPU controls ON / OFF of a switching element, for example, a triac in order to control electric power supplied to the halogen heater 84 based on the detected temperature so that the temperature of the fixing device becomes a predetermined constant. Reference numeral 85 denotes a safety element (temperature fuse, thermoswitch, etc.) for urgently shutting off power supply to the heater when the apparatus is overheated (runaway of the heater).

FIG. 14 shows a driving circuit of the halogen heater 83. Reference numeral 90 denotes a commercial power supply (AC power supply) for connecting the image forming apparatus. The image forming apparatus supplies commercial power to the halogen heater 83 to turn on the halogen heater. The power supply to the halogen heater 83 is turned on / off by a triac 91 and cut off. Resistance 92
Numeral 93 denotes a bias resistor for the triac 91, and a phototriac coupler 94 is a device for securing a creepage distance between the primary and the secondary. By energizing the light emitting diode of the phototriac coupler 94, the triac 91 is turned on. The resistor 95 is a resistor for limiting the current of the phototriac coupler 94, and is turned on / off by the transistor 96. The transistor 96 operates according to a signal from the control means 97. Also,
Reference numeral 98 denotes an inrush current reducing thermistor, which has an effect of reducing the inrush current immediately after the heater is turned on.

[0011]

In the control system of the heating device as described above, the halogen heater as a heat source is one in number.
On the secondary side, the CPU and the thermistor temperature sensing element are on the secondary side, so that a phototriac coupler or the like is provided, and an insulation distance is secured between the fixing roller and the thermistor temperature sensing element. It needs to be insulated. In particular, the configuration between the thermistor temperature sensing element and the fixing roller has been complicated.

Further, since the temperature of the fixing unit is managed by the CPU and the temperature of the fixing unit is kept constant by on / off control of the triac, the control of the CPU is complicated. Therefore, the present invention relates to a heating apparatus having heating means for heating a material to be heated by receiving power supply from the power supply means. The burden on the heating device control of the control means (for example, the CPU of the sequence controller for controlling the image forming apparatus) is reduced. The configuration between the heating means and the temperature detecting means of the heating means is facilitated. To be able to report the failure of the heating device. The purpose is to control the temperature of the heating device and to ensure high reliability of protection means against thermal runaway.

[0013]

According to the present invention, there is provided a heating apparatus and an image forming apparatus having the following constitutions.

(1) Heating means for heating the material to be heated by receiving power supply from the power supply means, control means for controlling the apparatus, and energization from the power supply means to the heating means,
Mechanical protection circuit for mechanical disconnection, at least two protection means of electronic protection circuit for electrical disconnection, temperature detection means for detecting the temperature of the heating means, and a first for setting the temperature of the heating means Temperature determination means, a first determination means for comparing the temperature detected by the temperature detection means with the temperature determined by the first temperature setting means, and a first determination means for determining the temperature by the first determination means. Power control means for controlling the power supply means on the basis of the first temperature setting means, a second temperature setting means for setting a temperature range including a temperature set by the first temperature setting means, and a temperature detected by the temperature detection means. A second temperature determining means for determining that the temperature is within a temperature range set by the second temperature setting means, wherein the control means instructs the apparatus to drive. And when the temperature detected by the temperature detecting means is within the temperature range set by the second temperature setting means, the control means is informed based on the judgment result of the second temperature judging means. A heating device for notifying a first determination signal as true.

(2) When the control means issues a drive signal for instructing the apparatus to drive, and after a predetermined time has elapsed, if the first determination signal based on the second temperature determination means is false, the drive means Characterized by turning off the signal (1)
A heating device according to claim 1.

(3) a third temperature setting means in which a temperature higher than the temperature range set by the second temperature setting means is set; a temperature detected by the temperature detecting means; And a third temperature judging unit for comparing and judging the temperature set by the temperature setting unit, wherein the control unit issues a drive signal for instructing the apparatus to drive, and the third temperature judgment unit When the means determines that the temperature detected by the temperature detection means is higher than the temperature set by the third temperature setting means, the electronic protection circuit is turned off, and the control means outputs a second signal to the control means. The heating device according to (1), wherein the determination signal is reported as true, and the control unit turns off the drive signal.

(4) The heating device according to any one of (1) to (3), wherein the heating means is an electromagnetic induction heating means.

(5) The material to be heated is a recording material on which an unfixed image is formed, and the apparatus is a fixing device for heating and fixing the unfixed image on the recording material. The heating device according to any one of (1) to (4).

(6) In an image forming apparatus having an image forming means for forming and carrying an unfixed image on a recording medium and a fixing means for heating and fixing the unfixed image to a recording material, the fixing means may be any of (1) to (5) An image forming apparatus, which is the heating apparatus according to any one of (1) to (4).

<Operation> Control means for controlling the apparatus (for example, a CPU of a sequence controller for controlling the image forming apparatus) has a drive signal for instructing the heating apparatus to drive, and the temperature of the heating means is controlled to a predetermined value. Means for determining that the temperature is within the temperature range, and having a determination signal for notifying the control means that the heating means is in that state, that is, a temperature detecting means of the heating means, for example, a thermistor thermosensitive element In a heating device in which the driving and control circuit of the device is configured on the primary side, the control means sends an ON signal to instruct the control circuit to drive, and determines that the temperature of the heating means is within a predetermined temperature range. The judgment is made by a judgment circuit, for example, a window comparator, and the control circuit sends the judgment signal to the control means and notifies the control means, thereby: 1. The burden on the control of the heating device by the control means is reduced. Since the temperature of the heating device need not be monitored by the control means, the temperature detecting element can be configured on the primary side, and the configuration between the temperature detecting element, the heating device, and the electronic protection circuit is facilitated. 3. The failure of the heating device can be notified, the failure and runaway can be detected and prevented, and it can be one of the protection circuits against thermal runaway of the heating device. Further, a temperature higher than the temperature range as a set temperature, means for determining that the temperature is equal to or higher,
By providing a determination signal that notifies the sequence controller of the state, that is, a temperature determination circuit that sets a temperature higher than the temperature range determined by the above-described window comparator as a set temperature, for example, a comparator The control circuit determines that the temperature of the heating means is much higher than the predetermined temperature, and the control circuit notifies the control means of the state, and operates the electronic protection circuit with the determination signal to thereby heat the heating means. It is possible to configure a plurality of protection circuits against thermal runaway of the device, and it is possible to control the temperature of the heating device and ensure high reliability of the protection means against thermal runaway.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 5) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus 501 of this example is a laser printer using a transfer type electrophotographic process.

Reference numeral 517 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which is driven to rotate at a predetermined peripheral speed (process speed) clockwise as indicated by an arrow a. .

The photosensitive drum 517 is uniformly charged to a predetermined polarity and potential by the primary charging roller 519 during the rotation process. A laser beam output from the laser scanner unit 507 to the uniformly charged surface of the rotating photosensitive drum 517 and subjected to modulation control (ON / OFF control) corresponding to a time-series electric digital pixel signal of target image information. The scanning exposure L is performed, and an electrostatic latent image of target image information is formed on the surface of the rotating photosensitive drum 517.

The formed latent image is developed by a toner in a developing unit 520 and is visualized. As a development method, a jumping development method, a two-component development method, an FEED development method, or the like is used, and a combination of image exposure and reversal development is often used.

On the other hand, the recording paper (transfer material) S as a recording medium stored in the paper supply cassette 502 is fed out one by one by driving the paper supply roller 505, and a registration roller pair 506 is provided.
Is fed at a predetermined control timing to a transfer nip portion which is a pressure contact portion between the photosensitive drum 517 and the transfer charging roller 521, and the toner image on the photosensitive drum 517 surface side is sequentially transferred to the surface of the fed recording paper S. To go.

The recording paper S exiting the transfer nip is sequentially separated from the surface of the rotating photosensitive drum 517, and is introduced into a fixing device A as a heating device for thermally fixing the toner image, thereby thermally fixing the toner image. Receive processing. The fixing device A of this embodiment is an apparatus of an electromagnetic induction heating system, and its configuration and control system will be described in detail in the following items (2) and (3).

The recording paper exiting from the fixing device A is discharged from a paper discharge roller 511.
Is printed out on the stacking tray 512.

The rotating photosensitive drum surface after the recording paper is separated is cleaned by a cleaner 522 to remove adhering contaminants such as untransferred toner, and is repeatedly provided for image formation.

The printer 501 of the present embodiment includes a photosensitive drum 51
7. Primary charging roller 519, developing unit 520, cleaner 5
The four process devices 22 are collectively provided as a process cartridge (image forming unit) 508 that is detachable from the printer main body.

In the laser scanner unit 507, 513
Denotes a laser unit, and an image signal (image signal VD) transmitted from an external device 531 such as a personal computer.
The laser light modulated based on O) is emitted. 514
Represents the laser light from the laser unit 513
Reference numeral 514a denotes a polygon mirror for scanning the mirror 17, reference numeral 514a denotes a motor for rotating the mirror, reference numeral 515 denotes an imaging lens group, and reference numeral 516 denotes a folding mirror.

Reference numeral 503 denotes a cassette paper presence / absence sensor for detecting the presence / absence of the recording paper S in the cassette 502, reference numeral 504 denotes a cassette size sensor for detecting the size of the recording paper S in the cassette 502 (composed of a plurality of micro switches), 51
Reference numeral 0 denotes a paper discharge sensor that detects the recording paper conveyance state of the paper discharge unit. Reference numeral 529 denotes a heat exhaust fan.

Reference numeral 523 denotes a main motor which applies a driving force to the paper feed roller 505 via a paper feed roller clutch 524 and a driving force to the pair of registration rollers 506 via a registration clutch 525, and further includes a photosensitive drum 517. Driving force is also applied to each device in the process cartridge 508, the fixing device A, the paper discharge roller 511, and the like.

Reference numeral 526 denotes an engine controller, which includes a laser scanner 507, a process cartridge 508,
The control of the electrophotographic process by the fixing unit A and the control of the conveyance of the recording paper in the printer are performed.

Reference numeral 527 denotes a video controller, which is connected to an external device 531 such as a personal computer via a general-purpose interface (Centronics, RS232C, etc.) 530, and develops image information sent from the general-purpose interface into bit data The bit data is transmitted as a VDO signal to the engine controller 526 via the interface 528.

(2) Fixing Unit A FIG. 2 is a schematic cross-sectional view showing a schematic configuration of the fixing unit A in this embodiment. The fixing device A of this embodiment is a heating device of an electromagnetic induction heating system, and uses an electromagnetic induction heating film. This fixing device A is an image forming apparatus main body (printer main body).
It is detachable with respect to.

A) Outline of Apparatus Configuration and Fixing Operation 1 is a fixing film assembly, which is a cylindrical heating film 2 of electromagnetic induction heat generation as a rotary heating member, and supports the cylindrical fixing film 2 from the inside. It comprises a cylindrical film support member 3 (film guide), an exciting coil 4 for generating a high-frequency magnetic field (alternating magnetic field) as a magnetic field generating means disposed inside the cylindrical film guide 3, a core 5, and the like. . The cylindrical fixing film 2 is loosely fitted to a cylindrical film guide 3. The fixing film assembly 1 is arranged such that both ends of the film guide 3 are held between the front and rear side plates of the apparatus.

Numeral 6 denotes an elastic pressure roller as a pressure rotating member, which comprises a metal core 6a and a silicone rubber layer 6b formed concentrically around the metal core. The bearing is held between the side plate on the side and the back side substantially in parallel with the fixing film assembly 1,
Further, the fixing film 2 is sandwiched between the lower surfaces of the film guides 3 of the fixing film assembly 1, and a fixing nip portion (heating nip portion) N having a predetermined width is formed with a predetermined pressing force and pressed against the fixing film 2.

The driving of the pressure roller 6 is transmitted from a drive source M via a drive transmission system, and the pressure roller 6 is rotated at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow (pressure roller driving type). With the rotation of the pressure roller 6, a cylindrical shape loosely fitted to the film guide 3 of the fixing film assembly 1 at a fixing nip portion N which is a pressure contact portion between the fixing film assembly 1 and the pressure roller 6. The rotational force acts on the cylindrical fixing film 2 by the frictional force between the rotating pressure roller 6 and the outer surface of the fixing film 2 with respect to the fixing film 2 so that the cylindrical fixing film 2 moves around the film guide 3. At the fixing nip portion N, the film guide 3 is rotated in the clockwise direction indicated by the arrow at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 6 while sliding closely on the lower surface of the film guide 3.

The excitation coil 4 generates a high-frequency magnetic field by a high-frequency current (alternating current) supplied from the excitation circuit.
The high-frequency magnetic field is concentrated and distributed near the fixing nip N by the core 5 corresponding to the position of the fixing nip N.
As shown in FIG. 4, the magnetic flux a of the high-frequency magnetic field is applied to a metal layer (resistor layer, magnetic layer) 2 as a heating layer of the fixing film 2 which will be described later.
An eddy current b is generated in a. This eddy current b is generated by the metal layer 2a.
Joule heat is generated in the metal layer 2a by the specific resistance (heat generation due to eddy current loss). That is, the fixing film 2 generates electromagnetic induction heat.

The electromagnetically induced heat of the fixing film 2 is generated intensively in the vicinity of the fixing nip N where the alternating magnetic flux is concentrated and distributed, and the fixing nip N is heated with high efficiency.
The temperature of the fixing nip N is controlled such that a predetermined temperature is maintained by controlling power supply (current supply) to the exciting coil 4 by a temperature control system including a temperature detecting element.

In the present embodiment, the generated magnetic field can be passed through a desired heating area of the metal layer 2a of the fixing film 2 by distributing the exciting coil 4 in a concentrated manner in the vicinity of the fixing nip portion N. High fixing device can be realized.

Thus, the pressure roller 6 is driven to rotate, and the cylindrical fixing film 2 is accordingly moved by the film guide 3.
And the fixing nip portion N rises to a predetermined temperature and the temperature is controlled in the state where the fixing film 2 is heated by the electromagnetic induction as described above by the power supply from the excitation circuit to the excitation coil 4. The recording sheet S on which the unfixed toner image t conveyed from the image forming unit is formed has the image surface facing upward between the fixing film 2 and the pressure roller 6 in the fixing nip portion N, that is, the image surface is the fixing film surface. And the image surface is fixed at the fixing nip portion N to the fixing film 2.
The fixing nip N is conveyed together with the fixing film 2 in close contact with the outer surface of the fixing nip N. In the process in which the recording paper S is nipped and conveyed along the fixing nip portion N together with the fixing film 2, the unfixed toner image t on the recording paper S is heated and fixed by heating by the electromagnetic induction heat of the fixing film 2. After passing through the fixing nip N, the recording paper S is separated from the outer surface of the rotary fixing film 2 and is discharged and conveyed.

B) Fixing Film 2 FIG. 4 is a schematic diagram of the layer structure of the fixing film 2 having electromagnetic induction and heat generation. (A) has a two-layer structure of a 50 μm-thick cylindrical nickel film material as a metal layer (heating layer) 2a that generates electromagnetic induction heat and a fluororesin release layer 2b covering the outer peripheral surface thereof. belongs to. (B) has a three-layer structure in which an elastic layer 2c made of silicone rubber or the like is interposed between the metal layer 2a and the release layer 2b.

As described above, the alternating magnetic flux a is applied to the metal layer 2a.
Acts, an eddy current b is generated in the metal layer 2a, and the metal layer 2a generates heat. The heat heats the fixing nip portion N via the release layer 2b or the elastic layer 2c / release layer 2b, and heats the recording paper as a material to be passed through the fixing nip portion N to form a toner image. Heat fixing of t is performed.

A desired functional layer can be added to the inner surface of the metal layer 2a. The metal layer 2a may be a single layer.

The metal layer 2a is made of 10 ^-5 to
Any metal or metal compound that is a good electrical conductor of 10 ⁻¹⁰ Ω · m may be used. More preferably, a pure gold layer such as iron or cobalt having high magnetic permeability and exhibiting ferromagnetism or a compound thereof can be used. A layer in which a metal filler is mixed in a resin can also be used.

The release layer 2b is made of PFA, PTFE, FEP
In addition to such fluororesins, materials having good releasability and heat resistance such as silicone resin, silicone rubber, fluororubber, and silicone rubber can be selected. The thickness is 20-10
0 μm is preferred.

The elastic layer 2c functions to cause the fixing film surface to follow the unevenness of the toner layer even in the case of a four-color superimposed color toner image having a thick toner layer. The hardness is preferably 60 ° (JIS-A) or less, more preferably 45 ° (JIS-A) or less. Thermal conductivity λ is 6 × 1
0 ^{-4 to} 2 × 10 ^-3 [cal / cm · sec · deg. ]
Is good.

C) Excitation coil 4 and core 5 FIG. 3 is a perspective view showing the inside of the film guide 3 with the upper half cut away. At the center of the inner bottom surface of the film guide 3, two rib plates 3a are arranged in parallel along the length of the film guide.
.3a are provided at intervals, and the rib plate 3a
The core 5 is dropped and held in the space between 3a. The core 5 is a horizontally long ferromagnetic / high-permeability member having a length in the longitudinal direction of the film guide 3, and is preferably made of a material used for a transformer core, such as ferrite or permalloy. It is better to use

In this embodiment, the exciting coil 4 is formed by winding an electric wire in a boat shape substantially corresponding to the substantially lower half surface of the inner surface of the cylindrical film guide 3. Is positioned and held at a substantially lower half surface portion in the cylindrical film guide 3. The core 5 is located substantially at the center of the boat-shaped exciting coil 4.

(3) Control System of Fixing Unit A FIG. 5 is a circuit configuration diagram of the fixing unit control system.

The fixing device A is provided with a temperature detecting element 13 (for example, a thermistor temperature-sensitive element) for detecting the temperature of the fixing device in proximity to the fixing film 2 as a rotating heating member. Also, by interposing in series with the electric path of the exciting coil 4,
Mechanically cut off the current to the exciting coil 4 (ie, the fixing device);
A mechanical protection circuit 14 as a first protection means (for example,
Thermoswitch, thermal fuse, etc.).

The AC input 15 is rectified by the diode bridge 16 via a fuse 21 and a relay 22 which is an electronic protection circuit as a second protection means and electrically cuts off power supply to the exciting coil 4. It is smoothed by the capacitor 17.

Reference numeral 18 denotes a resonance capacitor for performing a resonance operation with the exciting coil 4. The rectified AC input 15 is connected to the switching element 19 (MOSFET, transistor, IGBT) via the exciting coil 4 and the resonance capacitor 18.
Etc.), and is connected to the overcurrent detection resistor 20. The rectified AC input 15 is turned on / off by the switching element 19, and a high-frequency current is supplied to the exciting coil 4. The exciting coil 4 generates a high-frequency magnetic field, and as described above, an eddy current loss occurs in the metal layer 2a of the fixing film which is electromagnetically induced and heat-generating, and the fixing film 2 generates heat to heat the fixing nip portion N.

The fixing unit control unit controls the switching element 19 so that the fixing unit temperature sent out by the thermistor 13 as the fixing unit temperature detecting element is maintained at the target temperature. Also, an ON signal for instructing driving of the fixing device sent from the CPU 30 of the sequence controller for controlling the image forming apparatus.
(Low active) The switching element 19 is driven / stopped in accordance with ON / OFF of 40.

The detected voltage as the fixing temperature of the thermistor 13 is a result of dividing the reference voltage Vref by the resistor 26 and the thermistor 13, and this detected voltage is compared and amplified by the error amplifier 23 with the target voltage V1 (target temperature). You. The output of the error amplifier 23 is input to the control IC 27, and a PWM waveform suitable for the temperature condition is output. This output drives the switching element 19 on / off via the resistor 25.

When the CPU 30 sends an ON signal (Low) 40, the transistor 43 is turned off via the resistor 42 and the transistor of the photocoupler 44 is turned on, so that an ON signal is sent to the fixing device. Here, the photocoupler 44
Is a device for ensuring the creepage distance between the primary and secondary.

The detected voltage of the thermistor 13 is determined by the comparators 31 and 32 and the NAND circuit 33 to be within the target voltage range (predetermined temperature range).

The comparator 31 compares the temperature with the high temperature set by the voltage V2, and the comparator 32 compares the temperature with the low temperature set by the voltage V3. That is, V2 <V1 <V3.

When the temperature detected by the thermistor 13 is within the temperature range set by the voltages V2 and V3, the output of the NAND circuit 33 becomes High,
4. The transistor 36 is turned on via the resistor 35.

When the transistor 36 is turned on, the transistor of the photocoupler 37 is turned on.
An ow (true) signal 41 is sent. This signal 41 is an RDY signal (Low active) that notifies the sequence controller that the temperature of the fixing device is within a predetermined temperature range.
It is. Here, the photocoupler 37 is a device for ensuring the creepage distance between the primary and secondary.

When it is determined that the temperature detected by the thermistor 13 is out of the temperature range set by the comparators 31 and 32, the output of the NAND circuit 33 becomes Low and the transistor of the photocoupler 37 is turned off.
The RDY signal 41 is High, that is, false.

The CPU 30 sends an ON signal 40 to the fixing device controller.
And after a predetermined time elapses, the RDY signal 41 from the fixing device
Is false, the sequence controller determines that the fixing device has failed or runs away, and turns the ON signal 40 off.

When the ON signal 40 from the CPU 30 is turned off, the control IC 27
By turning off the output to 9, the driving of the fixing device is stopped.

Further, when the ON signal 40 from the CPU 30 is turned off (High), the output of the NOT circuit 50 becomes Low, and the transistor 52 is turned off via the resistor 51 to provide the second protection means. The relay 22 as the electronic protection circuit is turned off, and the power supply to the fixing device is cut off. O
When the N signal 40 is on (Low), the relay 22 is on.

The relay 22 is connected to the switching element 19
ON / OFF operation can be performed without the intervention of the control IC 27, which is particularly effective when the control IC fails.

The temperature fuse 14 as a mechanical protection circuit, which is the first protection means, is provided with the above-described temperature detection element 1.
3 is a protection circuit against a thermal runaway of the fixing device, which cuts off the power supply to the fixing device when the temperature of the fixing device becomes higher than a certain temperature regardless of the temperature detected by the fixing device.

With the above configuration and control, the burden on the fixing device control of the CPU of the sequence controller for controlling the image forming apparatus is reduced.

Since the thermistor 13, the fixing device, and the thermal fuse 14 (other than a thermoswitch) are formed on the primary side, the thermistor 13, the exciting coil 4, the fixing film 2, which generates heat by electromagnetic induction, and the thermal fuse It is not necessary to secure a creepage space distance between the primary and the secondary according to the safety standard of 14 and a simple configuration as a fixing device can be obtained.

<Embodiment 2> (FIGS. 6 and 7) FIG. 6 is another circuit configuration diagram of the control system of the fixing device A. The difference from the circuit configuration of the first embodiment shown in FIG. 5 is that the fixing device temperature detected by the thermistor 13 is set to a temperature criterion (voltage V4) higher than the temperature (voltage V2) used as a criterion for the comparator 31. Based on the comparator 60 to be compared and the determination result, Er to the sequence controller
An r signal 67 (Low active) is provided.
Other circuit configurations are the same.

Hereinafter, only the different points will be described. That is, the fixing device temperature detected by the thermistor 13 is compared with the temperature set by the voltage V4 by the comparator 60 as a voltage value. When the temperature is higher than the temperature set by the voltage V4, the output of the comparator 60 becomes H
It becomes igh. Here, there is a relationship of V4 <V2 <V1 <V3.

The output of the comparator 60 is O
The signal is input to the NAND circuit 50 together with the N signal (Low active). The output from the comparator 60 is High (false)
Therefore, the output from the NAND circuit 50 becomes Low, and the transistor 52 is turned off via the resistor 51. When the transistor 52 is turned off, the relay 22 as an electronic protection circuit, which is the second protection circuit, is turned off, and the power supply to the exciting coil 4 is cut off.

The temperature detected by the thermistor 13 is the voltage V4
, The relay 22 is ON only when the ON signal is ON.

Further, when the fixing device temperature detected by the thermistor 13 is higher than the temperature set by the voltage V4, the High output from the comparator 60 turns on the transistor 63 via the amplifier circuit 61 and the resistor 62. I do. When the transistor 63 is turned on, the photocoupler 64
Are turned on, and the CPU 30 sends Low (tru
The signal 67 of e) is sent. This signal 67 is an Err signal (Low) which indicates that the temperature of the fixing device is extremely high.
active).

If the Err signal 67 is true, CP
U30 considers that the fixing device is running out of heat, and turns off the ON signal 40 sent to the fixing unit control unit.

Accordingly, the control IC 27 turns off the switching element 19 and also turns off the relay 22, thereby preventing the thermal runaway of the fixing device.

FIG. 7 is a graph showing the state of the above-mentioned temperature control.
It is a temperature graph.

As described above, apart from the window comparator for judging that the temperature of the fixing device is within a predetermined temperature range, a comparator having a temperature higher than the temperature range as the judgment temperature is provided. By reporting the result to the sequence controller, a plurality of protection circuits against thermal runaway of the fixing device can be configured.

<Embodiment 3> (FIGS. 8 to 12) This embodiment is another example of various configurations of a heating device (fixing device).

1) The apparatus shown in FIG. 8 is a film guide 3 holding an endless belt-shaped fixing film 2 of electromagnetic induction heat generation and an exciting coil 4 and a core 5 as magnetic field generating means.
, Film drive roller 71, tension roller 72
The film guide 3 is rotatably driven while the lower surface of the film guide 3 is slid by the rotation of the drive roller 71 by the rotation of the drive roller 71. The pressure roller 6 presses against the lower surface of the film guide 3 across the fixing film 2 to form a fixing nip portion N. The pressure roller 6 rotates following the rotation of the fixing film 2.

2) The apparatus shown in FIG. 9 feeds a rolled endless fixing film 2 having an electromagnetic induction heating property and wound into a roll.
From the side, the running movement is performed while sliding the lower surface of the film guide 3 at a predetermined speed toward the winding shaft 74 via the lower surface of the film guide 3 holding the exciting coil 4 and the core 5 as the magnetic field generating means. It is of a configuration. The pressure roller 6 presses against the lower surface of the film guide 3 across the fixing film 2 to form a fixing nip portion N. Pressure roller 6
Rotates following the rotation of the fixing film 2. The fixing film 2 can be used repeatedly by being rewound from the take-up shaft 74 side to the pay-out shaft 73 side.

3) The apparatus shown in FIG. 10 is a heating apparatus of a heating roller type, in which a roller base of a heating roller (fixing roller) 2A is a cylindrical metal roller of electromagnetic induction heat generation.
Excitation coil 4 and core 5 as magnetic field generating means
Are inserted and arranged to cause the heat roller 2A to generate heat by electromagnetic induction. The pressure roller 6 is in pressure contact with the heat roller 2A to form a fixing nip N.

4) In the apparatus shown in FIG. 11, the fixing film F is a heat-resistant, cylindrical or endless belt-shaped or end-elongated film having no electromagnetic induction heat generation. On the lower surface of the film guide 3, a metal plate 2 </ b> C having electromagnetic induction and heat is fixed and held with the lower surface exposed. An exciting coil 4 and a core 5 as magnetic field generating means are held inside the film guide 3. The pressure roller 6 is a metal plate 2
A fixing nip portion N is formed with the fixing film F interposed therebetween. The fixing film F rotates or travels in close contact with the lower surface of the metal plate 2C. The metal plate 2C generates electromagnetically induced heat by the high-frequency magnetic field generated by the exciting coil 4 and the core 5. The recording paper S is introduced between the fixing film F in the fixing nip N and the pressure roller 6 and is nipped and conveyed together with the fixing film F by the electromagnetic induction heating of the metal plate 2C. The toner image t is thermally fixed by receiving the heat via the fixing film F.

5) Also in the apparatus shown in FIG. 12, the fixing film F is a heat-resistant, cylindrical or endless belt-shaped or end-elongated film having no electromagnetic induction heat generation. On the lower surface of the film guide 3, a ceramic heater 7 as a heat source is fixedly held by exposing the lower surface. The pressure roller 6 forms a fixing nip portion N with the fixing film F interposed between the pressure roller 6 and the ceramic heater 7. The fixing film F rotates or travels in close contact with the lower surface of the ceramic heater 7. The ceramic heater 7 quickly enters a heating and heating state when a current is applied to the heating resistor. The recording paper S is introduced between the fixing film F in the fixing nip portion N and the pressure roller 6, and generates heat of the ceramic heater 7 in the process of nipping and conveying the fixing nip portion N together with the fixing film F. The toner image t is heat-fixed by receiving through the F.

The ceramic heater 7 in this embodiment is composed of a heater substrate 7a made of alumina or the like, and the front side (lower side) of this substrate.
Current-generating resistor pattern 7b of Ag / Pd (silver palladium) or the like,
b) A surface protection layer 7c such as a glass layer formed by covering the surface of the heater substrate 7a, a temperature detecting element 13 such as a thermistor provided on the back side of the heater substrate 7a, and a safety element 14 such as a thermal fuse. The heating element is a linear heating element having a low heat capacity as a whole, and quickly rises in temperature by being energized to the energized heating resistor pattern 7b.

The present invention provides a heating device having various configurations as described in 1) to 5) above, and a control device of a heating roller type heating device using the halogen heater 83 as a heat source in FIG. Is also effective.

<Others> 1) The pressure rotating member 6 may be a rotating belt type. The pressure rotating member 6 may also be of an electromagnetic induction heating type, or may be provided with a heat source such as a halogen heater or a surface heating element to be heated to a predetermined temperature. This configuration is effective, for example, for fixing a color toner image having a thick toner layer.

2) The heating device of the present invention is not limited to the fixing device of the embodiment, but may be a device for heating a recording material carrying an image to improve the surface properties such as gloss, an image heating device to be supposedly applied, and others. It can be widely used as a means / apparatus for heat-treating a material to be heated, such as a device for heating and drying the material to be heated, a heating laminating device, and the like.

[0089]

As described above, according to the present invention, a heating device having a heating means for heating a material to be heated by receiving power supply from a power supply means, and an image forming apparatus having the heating device as a fixing device In. Reducing the burden on the control of the heating device by the control means; Facilitating the configuration between the heating means and the temperature detection means of the heating means;
To be able to report the failure of the heating device,
. The temperature control of the heating device and the high reliability of the protection means against thermal runaway can be secured, and the intended purpose is well achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 2 is a schematic diagram illustrating a configuration of a fixing device of an electromagnetic induction heating system according to a first embodiment.

FIG. 3 is a cutaway perspective view of a film guide.

FIGS. 4 (a) and (b) are schematic diagrams of a layer structure of a fixing film having an electromagnetic induction heating property.

FIG. 5 is a circuit configuration diagram of a fixing device control system.

FIG. 6 is a circuit configuration diagram of a fixing device control system according to a second embodiment.

FIG. 7 is a time-temperature graph showing a state of temperature control.

FIG. 8 shows another configuration example of the heating device (fixing device) (part 1).

FIG. 9 shows another configuration example of the heating device (part 2).

FIG. 10 shows another configuration example of the heating device (part 3).

FIG. 11 shows another configuration example of the heating device (part 4).

FIG. 12 shows another configuration example of the heating device (part 5).

FIG. 13 is a schematic diagram of a heating roller type heating device.

FIG. 14 is a drive circuit diagram of a halogen heater.

[Explanation of symbols]

Reference Signs List A Fixing device (heating device) 1 Fixing film assembly 2 Cylindrical fixing film having electromagnetic induction and heat 3 Film guide 4 Exciting coil 5 Core 6 Pressure roller S Recording material (material to be heated) t Unfixed toner image 13 Temperature detecting means (Thermistor, etc.) 14 Mechanical protection circuit (Temperature fuse, Thermo switch, etc.) 22 Electronic protection circuit (Relay, etc.) 30 CPU of sequence controller 31, 32, 60 Comparator 40 ON signal of fixing device 41 RDY signal of fixing device 67 Err signal of fixing unit

Claims (6)

[Claims] 1. A heating means for heating a material to be heated by receiving power supply from a power supply means, a control means for controlling a device, and a machine for mechanically disconnecting the power supply from the power supply means to the heating means. A protection circuit, at least two protection means of an electronic protection circuit that is electrically disconnected, a temperature detection means for detecting a temperature of the heating means, and a first temperature setting means for setting a temperature of the heating means. A first determining unit that compares and determines a temperature detected by the temperature detecting unit with a temperature determined by the first temperature setting unit; Power control means for controlling the means; second temperature setting means for setting a temperature range including the temperature set by the first temperature setting means; and a temperature detected by the temperature detection means, A second temperature determining unit for determining that the temperature is within a temperature range set by the second temperature setting unit, wherein the control unit issues a drive signal for instructing the device to drive, When the temperature detected by the temperature detecting means is within the temperature range set by the second temperature setting means, the control means makes a first judgment based on the judgment result of the second temperature judging means. A heating device for notifying a signal as true. 2. The method according to claim 1, wherein the control unit issues a drive signal for instructing the apparatus to drive, and after a lapse of a predetermined time, when the first determination signal based on the second temperature determination unit is false, the drive signal is output. 2. The device according to claim 1, wherein
A heating device according to claim 1. A third temperature setting means for setting a temperature higher than a temperature range set by the second temperature setting means; a temperature detected by the temperature detecting means; Third temperature determining means for comparing and determining the temperature set by the temperature setting means, wherein the control means issues a drive signal for instructing the apparatus to drive, and the third temperature determining means When it is determined that the temperature detected by the temperature detecting means is higher than the temperature set by the third temperature setting means, the electronic protection circuit is turned off, and the control means makes a second determination. True signal
The heating device according to claim 1, wherein the control unit turns off the drive signal. 4. The heating device according to claim 1, wherein the heating means is an electromagnetic induction heating means. 5. The fixing device according to claim 1, wherein the material to be heated is a recording material on which an unfixed image is formed, and the apparatus is a fixing device for heating and fixing the unfixed image on the recording material. A heating device according to any one of the preceding claims. 6. An image forming apparatus comprising: an image forming unit for forming and carrying an unfixed image on a recording medium; and a fixing unit for heating and fixing the unfixed image to a recording material, wherein the fixing unit is any one of claims 1 to 5. An image forming apparatus, which is the heating device according to any one of the above.