KR910007443B1 - Protection circuit and method for temperature control accident of copymachine's roller - Google Patents

Abstract

The microcomputer detects the abnormality of the fixing temperature rising or the circuit break and turns off the relay to stop the AC power. The circuit includes a break signal generator (100) for comparing the voltage of the thermister (Rth) and a break reference voltage to discriminate the break of the thermister (Rth), a temperature controller (200) for generating and transmitting heater on/off signal to a heater on/off signal input terminal (PA) of the micro computer, a temperature limiter (300) for discriminating the over rising of the fixing temperature, for transmitting the discrimination signal to an AC break deciding terminal (PB) and for generating an AC break signal, a detector for detecting the outputs of the break signal generator and the temperature controller, and a relay for controlling the AC current, supplied to the thermister.

Description

Protection circuit and method in case of abnormal control of copier fixing temperature

1 is a circuit diagram of the present invention.

2 is a thermistor temperature versus voltage relationship.

3 is a related figure inside the copier.

4 is a diagram illustrating input of a heater temperature / MIC heater on / off determination terminal (PA) signal.

5 is a flow chart of the present invention.

* Explanation of symbols for main parts of the drawings

10, 20, 30: comparator H: heater

40: Micom Rth: Thermistor

INV1, INV2: Inverter RY1: Relay

R1-R22: resistor D1, D2: diode

D3: Light Emitting Diode TRC: Triac

31: photosensitive drum 32: transfer machine

33: separator 34: conveying unit

35: heater roller 36: compression roller

The present invention relates to a protection circuit and method in the case of an abnormal temperature control due to overheating of a fixing unit in a copier. In case of danger of fire due to overheating of the copier, or thermal breakdown element, the input power should be cut off to stabilize the system.

Accordingly, an object of the present invention is to provide a protection circuit and method in the case of an abnormality in the copier fixing temperature control to shut off the AC power by detecting an abnormal state such as an overheating of the fixing temperature and a disconnection in the microcomputer.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. A microcomputer 40 for controlling the system, a heater H which is a heating element for controlling the temperature of the heater roller, a relay switch RY1 connected between the AC 100 volt supply terminal, the heater H, and the node point 4, respectively. A temperature sensing thermistor (Rth) connected between the node point (1) and the control supply power supply (5V) and indicating a resistance change according to a temperature change, and a resistor (R1) connected in series between the node point (1) and ground. And the non-inverting input by setting the first supply power level of the variable resistor VR1 and the inverting input terminal (-) connected to the node point 1 and adjusted by the resistors R2 and R3 as the reference voltage. The first comparator 10 inputted to the terminal (+), the resistor R4 and the base connected between the output terminal of the first comparator 10 and the first supply power supply are connected to the first comparator (R5) through the resistor R5. 10) Determination of disconnection of the thermistor (Rth) is composed of a transistor (TR1) connected to the output terminal and the emitter is connected to the terminal of the first power supply (5V). Inputs the disconnection control unit 100 and the first supply power level adjusted by the resistor R6 and the resistor R7 to the non-inverting terminal to set a reference voltage level, and an inverting terminal inverts the first comparator 10. A resistor R8 connected between the second comparator 20 connected to the terminal and the second comparator output terminal and the non-inverting terminal, a resistor R9 connected between the second comparator output terminal and the first supply power and the first comparator; The inverter INV1 connected to the resistor R9 and the node point 2 connected between the output terminal of the first comparator 20 and the first supply power and inverting the output of the second comparator 20 supplied through the resistor R10. ) And a resistor (R14) connected between the second node point (2) and the first supply power source (5V) to the set voltage of the second comparator 20 and the thermistor (Rth) distribution voltage (Vth). Triac (TRC) connected in parallel between the set temperature controller 200 for generating the heater H on-off output signal and the node points 3 and 4 according to the comparison result. A resistor (R21) and a capacitor (C1) connected in series with each other and connected in parallel with the triac (TRC), a resistor (R20) connected in parallel between one end of the triac (TRC) and the node point (4); A light emitting diode having an anode connected to a capacitor C2, an internal triac OP-TRC connected to the node point 3 through a resistor R22, and a collector terminal of the disconnection control unit 100 transistor TR1. Opto triac OP composed of D3), a resistor R19 connected between the light emitting diode D3 and the node point 2, and a resistor R12 and a resistor R13 through non-inverting input terminals. A third comparator 30 and a first comparable power supply and the third comparator 30 for comparing and inputting the first supply power level adjusted by the reference voltage as a reference voltage and inputting and comparing a thermistor distribution voltage Vth with an inverting input terminal. Resistor R15 connected between the output terminal and the third comparator 30 output terminal and the third comparator 30 non-inverting input terminal. A resistor R14, a resistor R16 connected between the output terminal of the third comparator 30 and the node point 3, and a resistor R18 connected between the node point 3 and the supply power supply 5V. A diode D1 having an anode connected to the node point 3, a resistor R17 connected between a relay control signal of the diode D1 and the microcomputer 40 between a sending terminal PC, Inverter INV2 for inverting the output of the third comparator 30 and a temperature rise controller comprising a diode D2 connected in parallel between the inverter INV2 and the second supply power and an anode connected to the inverter side. It consists of 300.

2 is a thermistor temperature vs. voltage relationship, FIG. 3 is a copier internal relationship, FIG. 4 is a relationship between set temperature and heater sensing temperature, 4b is a relationship between PA input and detection time, and FIG. As a flowchart of the present invention, a first process of checking whether a signal input state through the heater on / off determination input terminal PA of the microcomputer 40 is in a "low" state when the power is turned on, and the signal input state in the first process In the "low" state, it is determined whether the "low" state has elapsed more than the first disconnection detection time, and the second process of looping to the first process at the time of preheating, and detecting that the detection time has elapsed in the second process. The microcomputer 40 outputs a "low" status signal to the relay control signal transmission terminal PC to turn off the relay to cut off the AC power applied to the heater H, and the heater in the first process. On / Off Judgment Input Signal is Low The fourth process proceeds to the third process if the state of the AC blocking decision terminal (PB) input state is " low " when the state is not " low " The fifth step of determining whether the heater on / off determination terminal (PA) signal input of the microcomputer 40 is in the "low" state at the time of "high" state; and the second disconnection detection time at the time of the "low" state as the determination result. A sixth process of checking whether the process proceeds to the third process, and when the heater on / off determination input signal is high when the fifth process is performed and the on / off determination input signal is "low" in the sixth process. When the state does not pass more than the second disconnection detection time (t2), it performs a different function and loops to the fourth process.

Based on the above-mentioned, this invention is demonstrated in detail.

In FIG. 1, the output of the first comparator 10 comparing the divided voltages of the voltage Vth distributed to the thermistor Rth and the resistors R1 and VR1 and the disconnection voltage setting resistors R2 and R3 outputs the thermistor divided voltage ( If Vth) is higher than the disconnection voltage, it becomes OV (Volt) in a "low" state. As a result, the base potential of the PNP-type transistor TR1 is also set to the "low" level, so that the transistor TR1 is turned on so that the first supply power applied to the emitter of the transistor TR1 is passed through the collector and the opto. A 5V power supply is applied to the anode of the diode D3 of the triac OP.

At this time, the temperature increase control unit 300 has the relay control signal transmission terminal PC of the initial microcomputer 40 in the "high" state (5V), and the oversetting set voltage distributed by the two resistors R12 and R13 is thermistor Rth. ) Higher than the distribution voltage Vth, the output of the third comparator 30 is in a "high" state.

Therefore, 5V is applied to the input of the inverter INV2 through the resistor R16 so that the inverter INV2 output becomes the "low" state OV. As a result, the relay RY1 conducts, so that the AC100V is connected to the heater H and the triac. It is applied to one side of (TRC). On the other hand, in the set temperature controller 200, when the thermistor Rth distribution voltage is lower than the heater off voltages distributed to the resistors R6 and R7, the output of the comparator 20 comparing the two divided voltages becomes a “high” state. . Therefore, a voltage of 5 V is applied to the input of the inverter INV1 through the resistors R9 and R10 so that one side of the resistor R9 connected to the cathode of the diode D3 of the optotriac OP is connected to the inverter INV1. It becomes OV by the output. As a result, the diode D3 of the optotriac OP becomes conductive, and the internal triac OP-TRC conducts and is applied to the gate of the triac TRC through the resistor R22, thereby applying the triac TRC. ) Conducts and the heater H is energized to generate heat.

At the same time, the inverter INV1 output state is applied to the heater on / off determination input terminal PA of the microcomputer 40, and when the input state is "low" in the microcomputer 40, the triac TRC is driven so that the heater is turned on. It knows that it is on and judges that the heater is off when it is in the "high" state. Next, the temperature of the heater roller 35 is increased.

×5V)보다 높게 되면 비교기(20)의 출력은 로우(OV)상태가 되고 비교기(30)출력은 "하이"상태로 되어 저항(R19)의 일측에는 저항(R11)을 통해 5V가 인가되어 옵토트라이악(OP)의 다이오드(D1)은 오프되고 트라이악(TRC)도 오프되어 히터(H)가 오프된다. 그러므로 서미스터 분배전압(Vth)이 히터온전압(

×5V) 이하가 되어야만 히터(H)가 다시 온된다.Thermistor distribution voltage (Vth) is the heater off voltage (

X 5V), the output of the comparator 20 is in a low (OV) state, and the output of the comparator 30 is in a "high" state, and 5V is applied to one side of the resistor (R19) through the resistor (R11), thereby providing opto. The diode D1 of the triac OP is turned off and the triac TRC is also turned off so that the heater H is turned off. Therefore, the thermistor distribution voltage (Vth)

The heater H is turned on again only when it becomes less than * 5V).

Here, the resistance RS is for hysteresis of the difference between the heater on voltage and the heater off voltage. In another case, when the thermistor Rth is generated, the thermistor Rth distribution voltage Vth becomes OV. On the other hand, the set temperature control unit 200 and the disconnection detection voltage is the same as the formula (1) below.

×5V...............................................(1)

× 5V ........................... ( One)

×5V)보다 낮게 되면 비교기(10)의 출력은 히터오프전압보다 서미스터 분배전압(Vth)이 낮으므로 "하이"상태인 출력이 발생된다.The thermistor (Rth) distribution voltage (Vth) is a disconnection detection voltage (

When the output voltage of the comparator 10 is lower than x 5 V), the output of the comparator 10 is lower than the heater-off voltage, so that the output of the "high" state is generated.

The output of the INV1 is in a low state, but the output of the first comparator 10 is in a high state, and 5 V is applied through the base resistors R4 and R5 of the transistor TR1 to be in an off state. As a result, the optotriac OP is also turned off, and electricity is not supplied to the heater H, so that it is turned off.

×5V) 이하의 상태이므로 비교기(30)의 출력이 하이상태가 되어 인버터(INV2)의 입력에는 저항(R18)을 통해 5V가 인가되어 릴레이(RY1)는 온되어 있는 상태가 되어 (마이컴의 PC출력이 "High(5V)"상태로 Diode(D1)이 off되어 있음) 단선검출 제1시간(T1)이상 경과되면 서미스터의 단선(Open)상태를 검출하고 마이컴의 릴레이 제어신호 송출단자(PC)을 로우(OV)로 하여 인버터(INV2)의 입력에는 "로우"상태가 되어 인버터(ONV2)의 출력은 하이상태로 되어 릴레이(RY1) 오프되어 히터(H) 구동회로에 흐르는 AC전원을 차단시킨다. (이때 저항R18은 R16,R17보다 큰값으로 수정하고 제2비교기 출력과 마이컴(40)의릴레이 제어신호 송출단자(PC)출력이 로우상태일 때 분배되는 전압이 인버터(INV2)의 입력에도 로우상태가 되게 형성) 또한 서미스터 분배전압이 히터 오프전압 이하에 고정되어 있는 경우에도 초기 파워온시 단선 제1시간(T1)이상 경과시에도 릴레이 제어신호 송출단자(PC)출력은 로우상태로 하여 강제로 AC100V를 차단시킨다.At this time, a low state is input to the heater on / off determination particle stage PA of the microcomputer 40, and the thermistor distribution voltage Vth is a multiplier detection voltage (

Since the output of the comparator 30 becomes high, 5V is applied to the input of the inverter INV2 through the resistor R18, and the relay RY1 is turned on (the microcomputer's PC). Diode (D1) is turned off with output “High (5V)”) Disconnection Detection After the first time (T1) has elapsed, thermistor disconnection (Open) is detected and the microcomputer relay control signal output terminal (PC) is detected. To OV, the input of inverter INV2 becomes "low" state, and the output of inverter ONV2 becomes high state, relay RY1 is turned off to cut off AC power flowing to heater H driving circuit. . (At this time, the resistor R18 is modified to a value larger than R16 and R17. When the second comparator output and the relay control signal sending terminal (PC) output of the microcomputer 40 are in a low state, the divided voltage is also low in the input of the inverter INV2. Also, even when the thermistor distribution voltage is fixed below the heater off voltage, the relay control signal output terminal (PC) output is forced to be low even when the initial power-on disconnection first time (T1) has elapsed. Shut off AC100V.

In addition, once the heater is turned on again when the set voltage (heater off voltage) is increased, the heater on / off determination terminal (PA) input of the microcomputer 40 goes low and becomes equal to or greater than the second disconnection detection time T2. Judgment due to abnormality of triac (TRC), heater (H), etc. Set the relay control signal sending terminal (PC) of the microcomputer 40 to the "low" state, turn off the relay RY1, and cut off the AC100V power supply. Do this.

×5V) 이상이 되면 제2비교기(20)출력은 "로우"상태가 되고 인버터(INV1)출력은 "하이"상태로 릴레이(RT1)가 오프되어 AC전원을 차단시킨다.The heater H is continuously energized by a short of the triac TRC, or the both ends of the thermistor RT11 are shorted so that the thermistor distribution voltage V becomes the heater over-sensing voltage (

X 5V) or more, the second comparator 20 outputs a "low" state and the inverter INV1 outputs a "high" state, and the relay RT1 is turned off to cut off the AC power.

×5V) 이하가 되면 다시 릴레이(RY1)이 온될수 있으므로 제2비교기(20)의 출력은 마이컴(IC6)의 (PB)입력으로 받아들여 로우상태로 인지되면 릴레이 제어신호 송출(PC)출력을 "로우"상태로 출력시켜 릴레이(RY1)를 오프시켜 계속 AC전원을 차단케한다.Thermistor distribution voltage (V) is heater over-return voltage (

The relay RY1 may be turned on again when the voltage is less than 5 V), so that the output of the second comparator 20 is received as the (PB) input of the microcomputer IC6. It outputs in the "low" state and turns off the relay (RY1) to keep the AC power off.

Referring to the above-described operation process in detail with reference to the flowchart of FIG. 5, when the power is turned on, the microcomputer 40 determines whether the heater ON / OFF determination input terminal PA state is "low" in step 5a.

As a result of the determination, the process proceeds to the step of "low" state (5b) and checks whether the "low" state input has elapsed more than the first disconnection detection time (T1). Detecting the occurrence of the abnormal state due to the abnormal progress, proceeds to step (5c) to turn off the relay (RY1) to terminate the relay control signal sending terminal (PC) output of the microcomputer 40 to the "low" state.

In step (5a), if the heater on / off determination terminal (PA) input is not in the "low" state, the process proceeds to step (5d) and checks whether the (PB) input is in the "low" state. After determining that the process proceeds to step 5c to turn off the heater (H).

When the heater on / off determination terminal PA is not in the low state in step 5d, the process proceeds to step 5e to check whether the heater on / off determination PA is in the low state.

If the test result is low, it detects that the heater is on and proceeds to step (5f) to check whether the second disconnection detection time (T2) or more has elapsed and proceeds to step (5c) when the second disconnection detection time is elapsed. When the heater on / off determination (PA) input is not low in step (5e) and when the detection time is not exceeded in step (5f), proceed to step (5g) to perform another function (5d). Loop to step

As described above, the heater H on / off control is configured to turn on / off the optotriac OP in a circuit at the set temperature controller 200 to drive the triac TRC to turn on / off the heater H. The microcontroller turns off and inputs the on / off signal to the (PA) terminal to determine disconnection. When the heater roller 35 is overheated, the output of the second comparator 20 is " low " OFF to cut off the AC power and at the same time, it is input to the AC disconnection determination terminal (PB) of the microcomputer 40, and the microcomputer 40 relays the control signal transmitting terminal (PC) to cut off the AC power when overheating and disconnection. Outputs a signal of the "low" state to the terminal so that the relay RY1 is "off".

By operating as described above, there is an advantage that a malfunction due to overheating of the delivery copier can be prevented.

Claims (2)

In the protection circuit at the time of fixing temperature control abnormality of the copying machine provided with the microcomputer 40, thermistor Rth, and the heater H, the thermistor Rth distribution voltage Vth to determine the disconnection of the thermistor Rth. ) And the disconnection control unit 100 to generate a disconnection control signal by comparing the disconnection set voltage, and generate a heater on / off signal by comparing a predetermined set temperature and thermistor distribution voltage (Vth) to generate the heater on of the microcomputer 40. Determining the transient rise of the fixing temperature by comparing the set temperature controller 200 outputted to the on / off determination input terminal PA with a predetermined set voltage and the thermistor distribution voltage Vth, determines whether the microcomputer 40 cuts off the AC. The temperature increase control unit 300 which transmits to the terminal PB and generates an AC power cutoff signal under the control of the microcomputer 40, and the disconnection control output of the disconnection control unit 100 and the set temperature control unit 200. Sensing means for detecting output state And a switching means for controlling the current according to the sensing means, and a relay unit for turning on / off the relay under the control of the temperature rise controller (300). A protection method in the case of an abnormality in the copier fixing temperature control, comprising: a first process of checking whether a signal input state through a heater on / off determination input terminal PA of the microcomputer 40 is in a low state when power is turned on; A second process of determining whether the "low" state has elapsed more than a first disconnection detection time when the signal input state is "low" in the process and looping to the first process during preheating; and detecting in the second process A third process of cutting off the AC power applied to the heater by turning off the relay by outputting a "low" status signal to the relay control signal transmission terminal PC when the microcomputer 40 detects that the time has elapsed; A fourth process of checking whether the AC blocking decision terminal (PB) input state is “low” when the heater on / off determination input signal is not “low” in the first process, and proceeding to a third process when the heater on / off determination input signal is not “low”; AC power difference in the fourth process When the determination terminal (PB) input is in the "high" state The fifth process of determining whether the heater on / off determination terminal (PA) signal input of the microcomputer 40 in the "low" state, and when the determination result "low" state The sixth process of checking whether or not the second disconnection detection time has elapsed and proceeding to the third process, and when the heater on / off determination input signal is high when the fifth process is performed, and the heater on / off in the sixth process And a seventh step of performing another function and looping to a fourth step when the OFF determination input signal does not pass the "low" signal for more than the second disconnection detection time (t2).

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