CN210605363U - Heating device for image forming apparatus and image forming apparatus - Google Patents
Heating device for image forming apparatus and image forming apparatus Download PDFInfo
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- CN210605363U CN210605363U CN201921494023.7U CN201921494023U CN210605363U CN 210605363 U CN210605363 U CN 210605363U CN 201921494023 U CN201921494023 U CN 201921494023U CN 210605363 U CN210605363 U CN 210605363U
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Abstract
The application discloses a heating device for an image forming device and the image forming device, wherein the image forming device comprises a fixing unit, the heating device comprises a heating circuit, a detection circuit, a switch circuit, a hardware control circuit, a first resistor and a controller, the heating circuit is used for heating the fixing unit, and the detection circuit is used for detecting the temperature of the fixing unit; the input end of the controller is respectively connected with the detection circuit and the hardware control circuit through a first resistor and is used for controlling the on-off of the heating circuit through the switch circuit according to the detection result of the detection circuit; the hardware control circuit is used for controlling the on or off of the heating circuit through the switch circuit according to the detection result of the detection circuit. According to the application, when the software control circuit is abnormal and the temperature detection result of the detection circuit is influenced, the hardware control circuit can still output correct control signals to control the on or off of the heating circuit, so that the fusing unit is prevented from being burnt due to overhigh temperature.
Description
Technical Field
The application relates to the technical field of image forming equipment, in particular to a heating device for the image forming equipment and the image forming equipment with the heating device.
Background
In an image forming apparatus such as a printer, a fixing unit is generally provided for fixing a toner image on a sheet after transfer. At the time of fixing, the fixing unit needs to be heated.
In the prior art, a heating circuit is generally provided for heating a fixing unit, and a software control circuit and a hardware control circuit are provided, where the software control circuit and the hardware control circuit are respectively used for controlling the on/off of the heating circuit to control the heating condition of the fixing unit and prevent the fixing unit from being burnt due to an over-high temperature.
However, in the prior art, when the software control circuit is abnormal, both the software control circuit and the hardware control circuit may malfunction, that is, both the software control circuit and the hardware control circuit cannot control the on/off of the heating circuit, thereby causing the fusing unit to be burned due to an over-high temperature.
SUMMERY OF THE UTILITY MODEL
In order to overcome the problems of the prior art described above, a primary object of the present application is to provide a heating device for an image forming apparatus capable of preventing a fixing unit from being burned out due to an excessively high temperature.
In order to achieve the above purpose, the following technical solutions are specifically adopted in the present application:
the application discloses a heating device for an image forming apparatus, the image forming apparatus includes a fixing unit, the heating device includes a heating circuit, a detection circuit, a switch circuit, a hardware control circuit, a first resistor, and a controller; the heating circuit is used for heating the fixing unit, and the detection circuit is used for detecting the temperature of the fixing unit; the switch circuit is connected with the loop of the heating circuit, the hardware control circuit is connected with the loop of the switch circuit and used for controlling the on and off of the switch circuit, and the input end of the controller is respectively connected with the detection circuit and the hardware control circuit through the first resistor.
The controller is used for outputting a software control signal according to the detection result of the detection circuit, and the software control signal is used for controlling the on/off of the heating circuit through the switch circuit.
The hardware control circuit is used for outputting a hardware control signal according to the detection result of the detection circuit, and the hardware control signal is used for controlling the on/off of the heating circuit through the switch circuit.
Preferably, the controller has an ADC input terminal, the hardware control circuit includes at least one comparator, and the ADC input terminal is connected to the input terminal of the comparator and the detection circuit through the first resistor.
When the detection circuit detects that the temperature of the fixing unit is greater than a preset temperature T1, the controller outputs a first software control signal for controlling the heating circuit to be switched off through the switch circuit.
When the detection circuit detects that the temperature of the fixing unit is higher than a preset temperature T2, the hardware control circuit outputs a first hardware control signal for controlling the heating circuit to be switched off through the switch circuit, and T2 is larger than or equal to T1.
Preferably, the detection circuit comprises a second resistor and a thermistor, and the input end of the ADC is respectively connected to the second resistor and the thermistor through the first resistor; when the input end of the ADC is in fault, and the detection circuit detects that the temperature of the fixing unit is higher than a preset temperature T3, the hardware control circuit outputs a second hardware control signal for controlling the heating circuit to be switched off, wherein T3 is more than or equal to T2.
Preferably, the detection circuit includes a second resistor, a thermistor and a first triode, the input end of the ADC is connected to the second resistor and the thermistor via the first resistor, the emitter and the base of the first triode are connected to two ends of the first resistor, respectively, and the collector of the first triode is connected to the hardware control circuit and/or the switch circuit.
Preferably, the collector of the first triode is connected with the input end of the comparator of the hardware control circuit.
Preferably, the switch circuit comprises a relay control circuit and/or a thyristor control circuit, and the relay control circuit and/or the thyristor control circuit are respectively connected with the loop of the heating circuit.
And the collector of the first triode is connected with the relay control circuit and/or the silicon controlled rectifier control circuit, and the on-off of the heating circuit loop is controlled by controlling the relay control circuit and/or the silicon controlled rectifier control circuit.
Preferably, when the switching circuit includes both the relay control circuit and the thyristor control circuit.
If the hardware control circuit comprises a comparator, the comparator is connected with the relay control circuit and/or the silicon controlled rectifier control circuit.
If the hardware control circuit comprises two comparators, the two comparators are respectively connected with the relay control circuit and the silicon controlled rectifier control circuit.
Preferably, when the switching circuit includes a relay control circuit, the relay control circuit includes a relay and a first switch, and a collector of the first transistor is connected to the first switch and the relay loop.
Preferably, when the switching circuit comprises a thyristor control circuit, the thyristor control circuit comprises a thyristor and a second switch, and the collector of the first triode is connected with the second switch and the thyristor loop.
Accordingly, the application also discloses an image forming apparatus including the heating device.
Compared with the prior art, this application is through being provided with first resistance, the input of controller links to each other respectively through first resistance and detection circuitry and hardware control circuit, make the voltage of the input of controller different with the voltage of hardware control circuit's input, it is unusual when software control circuit appears, like the voltage of the input of controller risees, when influencing detection circuitry's temperature detection result, hardware control circuit still can export correct control signal, with the switch-on or the turn-off of control heating circuit, and then avoid the high temperature of photographic fixing unit and burn out.
Drawings
Fig. 1 is a circuit block diagram of a heating device according to an embodiment of the present application.
Fig. 2 is a schematic circuit diagram of a heating device according to an embodiment of the present application.
Fig. 3 is an equivalent circuit of the embodiment of the present application under a normal condition of the controller.
Fig. 4 is an equivalent circuit of the embodiment of the present application in the case of an abnormality of the controller.
Fig. 5 is a schematic circuit diagram of a heating device according to another embodiment of the present application.
Fig. 6 is a schematic circuit diagram of a heating device according to another embodiment of the present application.
Fig. 7 is a schematic circuit diagram of a heating device according to another embodiment of the present application.
Fig. 8 is a schematic circuit diagram of a heating device according to another embodiment of the present application.
Fig. 9 is a schematic diagram of an image forming apparatus according to an embodiment of the present application.
The attached drawings are as follows:
100-a carton;
101-a paper feed roller;
102-a first transport roller;
103-a second conveying roller;
104-a process cartridge;
105-a laser;
106-a transfer roller;
107-a fixing unit;
108-a third transport roller;
109-a fourth conveying roller;
110-a fifth carrying roller;
111-discharge carton;
112-a photosensitive drum;
113-a charging roller;
114-a developer roller;
115-paper.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In the description of the present application, unless explicitly stated or limited otherwise, the terms "first" software, "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless specified or indicated otherwise; the terms "connected," "fixed," and the like are to be construed broadly and may, for example, be fixedly connected, detachably connected, integrally connected, or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Embodiments of the present application disclose a heating device for an image forming apparatus including a fixing unit, the heating device being configured to heat the fixing unit.
As shown in fig. 1, the heating device includes a heating circuit 1, a switching circuit 2, a controller 3, a hardware control circuit 4, a detection circuit 5, and a first resistor R1, the heating circuit 1 being for heating the fixing unit. The switch circuit 2 is connected with the loop of the heating circuit 1, the input end of the controller 3 is respectively connected with the detection circuit 5 and the hardware control circuit 4 through the first resistor R1, and the output end of the controller 3 and the output end of the hardware control circuit 4 are respectively connected with the switch circuit 2. The detection circuit 5 is used for detecting the temperature of the fixing unit, and the controller 3 is used for outputting a software control signal according to the detection result of the detection circuit 5, wherein the software control signal is used for controlling the on or off of the heating circuit 1 through the switch circuit 2; the hardware control circuit 4 is configured to output a hardware control signal according to a detection result of the detection circuit 5, where the hardware control signal is configured to control the heating circuit 1 to be turned on or off through the switch circuit 2.
This application is through being provided with software control circuit and hardware control circuit, when detection circuitry 5 detected the fusing unit temperature and exceeded predetermined temperature, through software control circuit or hardware control circuit control switch circuit 2 shutoff, and then control heating circuit 1 shutoff, and then stop the heating to the fusing unit, avoid the fusing unit to be burnt out because of the high temperature. Meanwhile, by arranging the first resistor R1, the input end of the controller 3 is connected with the detection circuit 5 and the hardware control circuit 4 through the first resistor R1, respectively, when the controller 3 is abnormal and the voltage of the ADC input end of the controller 3 is increased, the voltage of the input end of the hardware control circuit 4 is lower than the voltage of the ADC input end of the controller 3, so that the hardware control circuit 4 can still output a normal control signal to control the turn-off of the heating circuit 1.
As shown in fig. 2, the detection circuit 5 includes a second resistor R2 and a thermistor TH, and the hardware control circuit 4 includes a comparator U1, a third resistor R3, and a fourth resistor R4. The input end of the ADC of the controller 3 is connected to one end of the second resistor R2, the non-inverting input end of the comparator U1 and one end of the thermistor TH through the first resistor R1, the other end of the second resistor R2 is connected to the voltage Vref1, the other end of the thermistor TH is connected to the ground GND, one end of the third resistor R3 and one end of the fourth resistor R4 are connected to the inverting input end of the comparator U1, the other end of the third resistor R3 is connected to the power supply Vref2, and the other end of the fourth resistor R4 is connected to the ground GND.
The switch circuit 2 comprises a relay control circuit and a silicon controlled rectifier control circuit, the relay control circuit comprises a fifth resistor R5, a second triode Q2, a diode D1 and a relay RL, and the silicon controlled rectifier control circuit comprises a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a third triode Q3, a silicon controlled rectifier SCR and an optical coupler OC. The heating circuit comprises a power supply AC and a heater LD, wherein the power supply AC is connected with the heater LD and is used for supplying power to the heater LD. The controller 3 has a first output end and a second output end, the first output end of the controller 3 is respectively connected with one end of a fifth resistor R5 and the base of a second triode Q2 through a sixth resistor R6, the other end of the fifth resistor R5 and the emitter of the second triode Q2 are respectively grounded GND, the collector of the second triode Q2 is connected with the anode of a diode D1 and one end of a relay RL, the cathode of the diode D1 and the other end of the relay RL are connected with a power source VCC, and the relay RL is arranged on a current loop of the heating circuit 1. A second output end of the controller 3 is connected with an output end of a comparator U1 and one end of an eleventh resistor R11 through a twelfth resistor R12, the other end of the eleventh resistor R11 is connected with one end of a tenth resistor R10 and a base of a third triode Q3, the other end of the tenth resistor R10 and an emitter of the third triode Q3 are grounded GND, a collector of the third triode Q3 is connected with one end of a ninth resistor R9 through an optical coupler OC, the other end of the ninth resistor R9 is connected with a power supply VCC, a silicon controlled SCR is arranged in a current loop of the heating circuit 1, a seventh resistor R7 is connected with the silicon controlled SCR, the seventh resistor R7 is connected with one end of an eighth resistor R8 through the optical coupler OC, and the other end of the eighth resistor R8 is connected with the silicon controlled SCR.
In the present embodiment, the heater LD is a halogen lamp, the controller is a CPU controller, and the thermistor TH is a contact thermistor, and detection of the temperature of the fixing roller is realized by bringing the thermistor TH into close contact with the fixing roller in the fixing unit. Only one comparator U1 is provided, and the comparator U1 is connected to the thyristor and is used for controlling the on/off of the thyristor. It is understood that, in other embodiments, the heater LD may also be a ceramic heater, the controller may also be an SoC controller, the thermistor TH may also be a non-contact thermistor, and two comparators may also be provided, where the two comparators are respectively connected to the relay and the thyristor.
Contacts of a power supply AC, the heater LD, the silicon controlled rectifier SCR and the relay RL form an alternating current loop, and the silicon controlled rectifier SCR and the relay RL are used as switches and used for controlling the connection or disconnection of the power supply AC of the heater LD. The power source VCC, the coil of the Relay RL, the second triode Q2 and the first output end of the controller 3 form a direct current loop, and the software control signal Relay output by the first output end of the controller 3 is used for controlling the Relay RL to be switched on or switched off.
The thermistor TH serves as a temperature sensor for detecting the surface temperature of the fixing roller in the fixing unit. The higher the temperature, the smaller the resistance of the thermistor TH. The power source Vref1, the thermistor TH, the second resistor R2 and the ground GND form a dc loop, and the voltage VP at the point P is rTH/(R2+ rTH) Vref1, where rTH is the resistance of the thermistor TH and R2 is the resistance of the second resistor R2.
On one hand, the temperature detection signal TH _ Read is transmitted to the ADC input end of the controller 3, the ADC module inside the controller 3 performs analog-to-digital conversion on the received analog signal, and according to the conversion result, if the detection circuit 5 detects that the temperature of the fuser roller exceeds the preset temperature T1, the controller 3 outputs a first software control signal, and controls the heating circuit 1 to be turned off through the switch circuit 2, that is, software protection of the heating device is realized, and the fuser roller is prevented from being burnt out due to overheating.
On the other hand, the temperature detection signal TH _ Read is input to one input terminal of the comparator U1, in this embodiment, the temperature detection signal TH _ Read is a voltage signal with a magnitude VP (voltage value of P point), the other input terminal of the comparator U1 is connected to the reference voltage Vref3, Vref3 is R4/(R3+ R4) × Vref2, where R3 and R4 are resistance values of the third resistor R3 and the fourth resistor R4, respectively. The comparator U1 compares the detection voltage VP with the reference voltage Vref3, when the thermistor TH detects that the surface temperature of the fusing roller is higher than the preset temperature T2, the voltage VP is lower than the reference voltage Vref3, the comparator U1 outputs a low level, the third triode Q3 is cut off, the optical coupler OC is cut off, the silicon controlled rectifier SCR is further cut off, and the power supply AC of the heater LD is cut off. Namely, the hardware protection of the heating device is realized. When the controller 3 is out of control, the switch control signal Light _ on may be continuously in an active level state (e.g. high level), the hardware protection circuit acts to avoid the fusing roller from being burnt due to overheating, and the hardware protection temperature is generally higher than the software protection temperature, that is: t2 is more than or equal to T1.
However, if the first resistor R1 is not provided and the ADC input terminal of the controller 3 is directly connected to the comparator U1 and the thermistor TH, under normal conditions, the voltages at two points P, Q are equal, that is, VP is equal to VQ, when the ADC input terminal of the controller 3 is abnormal, the voltage VQ at the point Q is abnormally increased and the voltage VP at the point P is also increased, even if the thermistor TH detects that the surface temperature of the fixing roller is too high and the resistance value is small, the voltage VP is still higher than the reference voltage Vref3 of the comparator U1 due to the influence of the voltage at the point Q, and the comparator U1 remains inactive, and at this time, the controller 3 cannot acquire the normal temperature detection signal TH _ Read, that is, both software protection and hardware protection may cause the fixing roller to be burned due to the temperature failure, and the image forming apparatus may generate smoke and fire.
By arranging the first resistor R1, after the ADC input end of the controller 3 breaks down, the hardware control circuit can still act when the heating temperature of the fixing roller is greater than the preset temperature T3, and the reliability of the hardware protection circuit is ensured.
Wherein, T3 is more than or equal to T2 is more than or equal to T1, when the temperature of the fixing roller exceeds T1, the controller 3 outputs a first software control signal to control the power supply AC of the heater LD to be turned off, when the software control of the controller fails and the temperature of the fixing roller exceeds T2, the hardware control circuit 4 outputs a first hardware control signal to control the power supply AC of the heater LD to be turned off, and when the ADC input end of the controller fails and the temperature of the fixing roller exceeds T3, the hardware control circuit 4 outputs a second hardware control signal to control the power supply AC of the heater LD to be turned off.
Further, the resistance value of the thermistor TH corresponding to the heating temperature T2 is rTH, and the resistance value of the thermistor TH corresponding to the heating temperature T3 is krTH, where k is equal to the ratio of the resistance value of the thermistor at T3 to the resistance value of the thermistor at T2, and k is (0, 1), the resistance value R1 of the first resistor R1, and the resistance values R2 and k of the second resistor R2 need to satisfy the following relationships: r1// r2 is not less than kr 2. The specific reasoning is as follows:
when the ADC input terminal of the controller 3 is normal, the equivalent circuit is as shown in fig. 3, at this time, the resistance value of the ADC input terminal of the controller 3 is much larger than the resistance value of the first resistor R1, VP is VQ, the protection temperature is T2, the resistance value of the corresponding thermistor TH is rTH, and the maximum value Vmax of the operation voltage of the comparator U1 is rTH/(rTH + R2). When the ADC input of the controller 3 is abnormal, the equivalent circuit is as shown in fig. 4, generally Vab is Vref1, the protection temperature is T3 which is greater than T1 and T2, the corresponding thermistor TH has a value krTH, r 2' r1// r2, that is,
then, VP ═ krTH/(krTH + r 2') ≦ Vmax ═ rTH/(rTH + r2), i.e., r1// r2 ≧ kr 2.
In the present embodiment, the same principle is applied to not only the case where Vab is Vref1 but also the case where Vab is not equal to Vref 1.
Based on the above embodiment, as shown in fig. 5, in this embodiment, the heating device includes a first transistor Q1, an emitter of the first transistor Q1 is connected to an ADC input of the controller 3, a base of the first transistor Q1 is connected to a non-inverting input of the comparator U1, and a collector of the first transistor Q1 is connected to an inverting input of the comparator U1.
When the ADC input terminal of the controller 3 is abnormal, the voltage VQ at the point Q becomes high level, and at this time, because there is a voltage difference across the first resistor R1 and it is greater than the on-state voltage of the base of the first transistor Q1, the first transistor Q1 is turned on, the voltage at the non-inverting input terminal of the comparator U1 is lower than the inverting input voltage thereof, the comparator U1 outputs low level, and the thirteenth diode Q10 is turned off, thereby disconnecting the heating signal and protecting the fixing unit.
In the present embodiment, the first resistor R1 and the second resistor R2 need to satisfy the following conditions: r1// r2
The voltage of the first triode Q1 is not less than rTH VQ1/(Vref1-VQ1), and VQ1 is the turn-on voltage of the first triode Q1.
Based on the above embodiments, the present application further discloses a specific implementation manner, as shown in fig. 6, in this embodiment, the heating device further includes a fourth triode Q4, a thirteenth resistor R13, and a fourteenth resistor R14, an emitter of the first triode Q1 is connected to an ADC input terminal of the controller, a substrate of the first triode Q1 is connected to a non-inverting input terminal of the comparator U1, a collector of the first triode Q1 is connected to a base of the fourth triode Q4 through the thirteenth resistor R13, a base of the fourth triode Q4 is further connected to the ground through the fourteenth resistor R14, an emitter of the fourth triode Q4 is connected to the ground, and a collector of the fourth triode Q4 is connected to the second output terminal of the controller 3.
When the controller is abnormal and the Q point is changed to high level, the first triode Q1 and the fourth triode Q4 are both turned on, the Light _ on signal output by the second output end of the controller 3 is pulled to low level, the silicon controlled rectifier SCR is turned off, and the fixing unit is protected.
Based on the above embodiments, the present application further discloses a specific implementation manner, as shown in fig. 7, in this embodiment, the heating device further includes a fifth triode Q5, a fifteenth resistor R15 and a sixteenth resistor R6, an emitter of the first triode Q1 is connected to the ADC input terminal of the controller 3, a base of the first triode Q1 is connected to the non-inverting input terminal of the comparator U1, a collector of the first triode Q1 is connected to the base of the fifth triode Q5 through the fifteenth resistor R15, a base of the fifth triode Q5 is connected to an emitter of the fifth triode Q5 through the sixteenth resistor R16, an emitter of the fifth triode Q5 is grounded, and a collector of the fifth triode Q5 is connected to the first output terminal of the controller 3.
When the voltage at the ADC input of the controller 3 is abnormal and becomes high, the first transistor Q1 and the fifth transistor Q5 are both turned on, the signal at the first output of the controller 3 is pulled to low, the relay RL is turned off, and the fixing unit is protected.
Based on the above embodiments, the present application further discloses a specific implementation manner, as shown in fig. 8, in this embodiment, an emitter of the first triode Q1 is connected to an ADC input terminal of the controller 3, a base of the first triode Q1 is connected to a non-inverting input terminal of the comparator U1, a collector of the first triode Q1 is connected to a base of the fourth triode Q4 through a thirteenth resistor R13, a base of the fourth triode Q4 is connected to an emitter of the fourth triode Q4 through a fourteenth resistor R14, an emitter of the fourth triode Q4 is grounded, and a collector of the fourth triode Q4 is connected to a second output terminal of the controller 3. The collector of the first triode Q1 is also connected to the base of the fifth triode Q5 through a fifteenth resistor R15, the base of the fifth triode Q5 is also connected to the emitter of the fifth triode Q5 through a sixteenth resistor R16, the emitter of the fifth triode Q5 is grounded, and the collector of the fifth triode Q5 is connected to the first output terminal of the controller 3.
When the voltage at the ADC input of the controller 3 is abnormal and becomes high, the first transistor Q1, the fourth transistor Q4 and the fifth transistor Q5 are all turned on, the signals at the first output end and the second output end of the controller 3 are pulled to low level, the relay RL and the silicon controlled rectifier SCR are both turned off, and the fixing unit is protected.
Accordingly, an embodiment of the present application also discloses an image forming apparatus, as shown in fig. 9, including a paper cassette 100, a paper feed roller 101, a first conveying roller 102, a second conveying roller 103, a process cartridge 104, a laser 105, a transfer roller 106, a fixing unit 107, a third conveying roller 108, a fourth conveying roller 109, a fifth conveying roller 110, a discharge paper cassette 111, a photosensitive drum 112, a charging roller 113, a developing roller 114, and the above-described heating device. The photosensitive drum 112, the charging roller 113, and the developing roller 114 are provided in the process cartridge 104, the first conveying roller 102 and the second conveying roller 103 are provided in a paper feeding path of the image forming apparatus, respectively, and the third conveying roller 108, the fourth conveying roller 109, and the fifth conveying roller 110 are provided in a paper discharging path of the image forming apparatus, respectively.
The paper cassette 100 stores paper 115, the paper feed roller 101 conveys the paper 115 stored in the paper cassette 100 to a paper feed path, and the first conveying roller 102 and the second conveying roller 103 convey the paper 115 to a nip of the photosensitive drum 112 and the transfer roller 106. The charging roller 113 is used for charging the surface of the photosensitive drum 112, the laser 105 is used for emitting laser beams to form an electrostatic latent image on the surface of the photosensitive drum 112, and the developing roller 114 is used for developing and forming a carbon powder image on the surface of the photosensitive drum 112. The heating device is used to heat the fixing unit 107. When the paper 115 passes through the nip between the photosensitive drum 112 and the transfer roller 106, the photosensitive drum 112 transfers the toner image formed on the surface thereof to the paper by the transfer roller 106 or the like. The fixing unit 107 is configured to convey the sheet 115, on which the toner image is fixed on the sheet 115, to the discharge paper cassette 111 via the third conveying roller 108, the fourth conveying roller 109, and the fifth conveying roller 110.
The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A heating device for an image forming apparatus including a fixing unit, characterized by comprising:
a heating circuit for heating the fixing unit;
a detection circuit for detecting a temperature of the fixing unit;
the switching circuit is connected with a loop of the heating circuit;
the hardware control circuit is connected with the loop of the switch circuit and is used for controlling the on and off of the switch circuit;
a first resistor;
the input end of the controller is respectively connected with the detection circuit and the hardware control circuit through the first resistor;
the controller is used for outputting a software control signal according to a detection result of the detection circuit, and the software control signal is used for controlling the on/off of the heating circuit through the switch circuit;
the hardware control circuit is used for outputting a hardware control signal according to the detection result of the detection circuit, and the hardware control signal is used for controlling the on/off of the heating circuit through the switch circuit.
2. The heating device of claim 1, wherein the controller has an ADC input, the hardware control circuit comprises at least one comparator, and the ADC input is connected to the input of the comparator and the detection circuit via the first resistor;
when the detection circuit detects that the temperature of the fixing unit is higher than a preset temperature T1, the controller outputs a first software control signal for controlling the heating circuit to be switched off through the switch circuit;
when the detection circuit detects that the temperature of the fixing unit is higher than a preset temperature T2, the hardware control circuit outputs a first hardware control signal for controlling the heating circuit to be switched off through the switch circuit, and T2 is larger than or equal to T1.
3. The heating device of claim 2, wherein the detection circuit comprises a second resistor and a thermistor, and the ADC input terminal is connected to the second resistor and the thermistor via the first resistor, respectively;
when the input end of the ADC is in fault, and the detection circuit detects that the temperature of the fixing unit is higher than a preset temperature T3, the hardware control circuit outputs a second hardware control signal for controlling the heating circuit to be switched off, wherein T3 is more than or equal to T2.
4. The heating device according to claim 2, wherein the detection circuit comprises a second resistor, a thermistor and a first triode, the ADC input terminal is connected to the second resistor and the thermistor via the first resistor, the emitter and the base of the first triode are connected to two ends of the first resistor, respectively, and the collector of the first triode is connected to the hardware control circuit and/or the switch circuit.
5. The heating device of claim 4, wherein a collector of the first transistor is coupled to an input of a comparator of the hardware control circuit.
6. The heating device according to claim 4, wherein the switching circuit comprises a relay control circuit and/or a thyristor control circuit, and the relay control circuit and/or the thyristor control circuit are respectively connected with a loop of the heating circuit;
and the collector of the first triode is connected with the relay control circuit and/or the silicon controlled rectifier control circuit, and the on-off of the heating circuit loop is controlled by controlling the relay control circuit and/or the silicon controlled rectifier control circuit.
7. The heating device of claim 6, wherein when the switching circuit includes both the relay control circuit and the thyristor control circuit;
if the hardware control circuit comprises a comparator, the comparator is connected with the relay control circuit and/or the silicon controlled rectifier control circuit;
if the hardware control circuit comprises two comparators, the two comparators are respectively connected with the relay control circuit and the silicon controlled rectifier control circuit.
8. A heating device as claimed in any one of claims 6 or 7, wherein, when the switching circuit comprises a relay control circuit, the relay control circuit comprises a relay and a first switch, and the collector of the first transistor is connected to the first switch and the relay loop.
9. The heating device of any one of claims 6 or 7, wherein when the switching circuit comprises a thyristor control circuit, the thyristor control circuit comprises a thyristor and a second switch, and the collector of the first transistor is connected to the second switch and the thyristor loop.
10. An image forming apparatus characterized by comprising the heating device according to any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201921494023.7U CN210605363U (en) | 2019-09-06 | 2019-09-06 | Heating device for image forming apparatus and image forming apparatus |
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| CN201921494023.7U CN210605363U (en) | 2019-09-06 | 2019-09-06 | Heating device for image forming apparatus and image forming apparatus |
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| CN210605363U true CN210605363U (en) | 2020-05-22 |
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| Country | Link |
|---|---|
| CN (1) | CN210605363U (en) |
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2019
- 2019-09-06 CN CN201921494023.7U patent/CN210605363U/en active Active
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| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20221221 Address after: No. 1, Northwest Corner, Intersection of Dianzhong Road and Fanhua Avenue, Cuozhen Town, Feidong County, Hefei City, Anhui Province, 231600 Patentee after: Hefei Bentu Intelligent Manufacturing Co.,Ltd. Address before: 519060 Central District A, Building 3, 01, 3883 Zhuhai Avenue, Zhuhai City, Guangdong Province Patentee before: ZHUHAI PANTUM ELECTRONICS Co.,Ltd. |
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| TR01 | Transfer of patent right |