KR940007343B1 - Automatic adjustment circuit of fixing temperature - Google Patents

Abstract

The circuit for preventing the abnormal operation caused by the fault of the temp. sensor includes a temp. detector (10) measuring the fixing temp. with a thermistor (THR), a multiplier (20) multiplying the region of the measured voltage with a preset constant, a comparator (30) comparing the multiplied voltage to the reference ones having various steps, a controller (40) controlling a fixing lamp driver (2) and a fixing fan (3) selectively with the compared result and detecting the fault of the thermistor, and a CPU (50) providing the alarm if the fault of the thermistor is detected.

Description

Automatic Control of Fixture Temperature of System Using Electrophotographic Development Method

1 is a conventional fixing temperature automatic control circuit diagram

2 is a detection characteristic diagram of the fixing temperature according to FIG.

3 is a circuit diagram for automatically adjusting the settling temperature according to the present invention.

4 is a detection characteristic diagram of the fixing temperature according to FIG.

* Explanation of symbols for main parts of the drawings

1: fixing lamp 2: fixing lamp driving part

3: fixing fan 10: temperature detection unit

20: detection voltage expansion unit 30: comparison unit

40: fixing temperature control unit 50: CPU

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system using an electrophotographic development method, and more particularly, to a fixing temperature automatic control circuit for automatically detecting and stably adjusting a fixing temperature.

In general, electrophotographic development is widely adopted for recording images on recording paper in systems such as laser beam printers and plain paper facsimile machines as well as copiers. It is well known that such an electrophotographic development method is performed in the order of charging → exposure → development → transfer → separation → settlement → cleaning → removal removal. In this case, the fixing means fixing the toner adhered to the recording paper by the development by heating by a heat roller and pressurizing by a pressure roller. At this time, the heat of the heat roller is generated by the fixing lamp installed in the heat roller. Therefore, the fixing temperature is determined by the heat generated by the fixing lamp.

If the fixing temperature is too high, there is a risk of fire if there is paper due to jam or the like in the fixing unit. On the contrary, if the fixing temperature is too low, the toner is not fixed to the recording paper.

Accordingly, in the related art, as a fixing temperature control circuit configured as shown in FIG. 1, the fixing temperature is controlled to maintain an appropriate level.

The circuit of FIG. 1 includes a fixing lamp 1 that is a heating source for fixing, a fixing lamp driver 2 for driving the fixing lamp 1, a fixing fan 3 for lowering the fixing temperature, and a heat roller. The temperature detector 4 which is installed in close contact with the thermistor THR and the voltage divider R0 for detecting the fixing temperature and generates the detection voltage Vo according to the temperature change, and the detection voltage Vo A / D (Analog-to-Digital) converter 5 and digital conversion data are compared to a predetermined value to determine " on " / of the fixing fan 3 and the fixing lamp driver 2. The CPU 6 controls the " off ". In the configuration of FIG. 1, the fixing lamp driver 2 typically uses a solid state relay (SSR).

2 is a view showing the fixing temperature detection characteristics according to the first diagram.

Referring to FIG. 1 and FIG. 2, the conventional fixing temperature adjusting operation is described as follows. First, the fixing temperature of the fixing unit is detected by a thermistor (THR) having a negative resistance characteristic with respect to the temperature. And the detection voltage Vo caused by the voltage division of the power supply voltage Vcc of the resistor R0 are changed. The detection voltage Vo is input to the A / D converter 5, and the A / D converter 5 converts the input detection voltage V0 to n bits at a resolution of 2 ⁿ steps within the range of the reference voltage. Convert to digital data. At this time, the range of the reference voltage of the A / D converter 5 is the range of the power supply voltage Vcc and the ground voltage connected to the reference voltage input terminals Vref (+) and Vref (-), respectively.

The CPU 6 then inputs the digitally converted data and compares it with a value preset by the program to perform the following operation to adjust the fixing temperature to maintain the proper level. In the CPU 6, the first and second reference voltages V1 and V2 are set in advance by a program within the range of the ground voltage 0V and the power supply voltage Vcc with respect to the input detection voltage Vo value as shown in FIG. Release.

In the above state, when V0 <V1, that is, when the fixing temperature is lower than A ° C., it is determined that the temperature is abnormally low. The fixing lamp driving unit 2 is turned on to increase the temperature, and the AC lamp is applied to the fixing lamp 1. The power is applied to generate heat and the driving of the fixing fan 3 is stopped.

Secondly, when V1 &lt; V0 &lt; V2, that is, when the fixing temperature is between A ° C and B ° C, it is determined to be in a normal state, and the fixing lamp 1 and the fixing fan 3 are kept in the present state.

Thirdly, when V0> V2, that is, when the fixing temperature is higher than or equal to B ° C, it is determined to be in an abnormally high temperature state, and the fixing lamp driver 2 is turned off to cut off the power supply of the fixing lamp 1, and the fixing fan 3 Drive.

Accordingly, the fixing temperature is maintained at a steady state.

In the conventional fixing temperature control circuit as described above, it is impossible to detect the fixing temperature when a failure occurs due to an open or short of the thermistor which is a temperature detection sensor. As a result, if the fixing lamp is "on" continuously, there is a risk of fire if there is paper due to jams in the fixing unit, and if the fixing lamp is "off", the toner does not fuse to the recording paper. There was a problem. In addition, as the resistance change of the thermistor between the normal temperature and the abnormal temperature is minute, the difference between the set reference voltage and the temperature detection voltage is also small, which may cause the case of misrecognition of the fixing temperature state due to a sudden change in the power supply voltage. .

Accordingly, an object of the present invention is to provide a fixing temperature automatic control circuit which can prevent the malfunction due to the failure of the temperature detection sensor.

Another object of the present invention is to provide a fixing temperature automatic control circuit which can prevent the misunderstanding of the fixing temperature state due to the detection error by extending the range of the temperature detection voltage according to the fixing temperature detection.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is a circuit diagram for automatically adjusting the fixing temperature according to the present invention, which includes a fixing lamp 1 for generating fixing heat, a fixing lamp driver 2 for driving the fixing lamp 1, and a fixing fan for lowering the fixing temperature. (3) and a thermistor (THR) and resistors (R1-R3) for detecting the fixing temperature installed in close contact with the heat roller, and detecting the fixing temperature as the thermistor (THR) to generate the detection voltage (Vo). The detection unit 10, the detection voltage expansion unit 20 for generating the extended detection voltage Vo 'by extending the voltage range of the detection voltage Vo generated by the temperature detection unit 10 to a set multiple, and the extended detection voltage ( The comparator 30 for comparing Vo ') with a plurality of reference voltages set in predetermined steps differently from each other, and determining a fixing temperature state according to the comparison result of the comparator 30. Selective control of the drive of the fixing fan 3 and failure of the thermistor THR And detecting the fixing temperature control section 40 that, interrupted (interrupt) by which the failure of the thermistor (THR) detected by the fixing temperature control section 40 is composed of a CPU (50) so that to the alarm.

In the configuration of FIG. 3, the detection voltage expansion unit 20 includes an A / D converter 22 for digitally converting the output detection voltage Vo of the temperature detection unit 10 to 6 bits of resolution, and 6 bits of a preset value. 16-bit multiplier generating 8-bit extended detection voltage data by multiplying the digitally converted data of the A / D converter 22 and the multiplier adjustment data by the multiple adjustment data generation unit 24 that generates multiple adjustment data. (multiplier) 26 and a digital-to-analog (D / A) converter 28 for converting the extended detection voltage data of the multiplier 26 to analog conversion and outputting the extended detection voltage Vo '. Here, the sump data generator 24 is pulled up to the power supply voltage Vcc by a pull up resistor R4 commonly connected to the output side using a DIP switch.

The comparator 30 is composed of resistors R5-R6 and is configured to set a first reference voltage Vth1 for providing a reference for an open state of the thermistor THR by dividing the power supply voltage Vcc by a predetermined voltage. A second voltage consisting of a voltage dividing circuit 32 and resistors R7-R8 and setting a second reference voltage Vth2 for providing a reference for an abnormal low temperature state of the fixing temperature by dividing the power supply voltage Vcc by a constant voltage; A third voltage consisting of a voltage dividing circuit 34 and resistors R9-R10 and setting a third reference voltage Vth3 for providing a reference for an abnormal high temperature state of the fixing temperature by dividing the power supply voltage Vcc by a constant voltage; A voltage divider circuit 36 and resistors R11-R12, and for setting a fourth reference voltage Vth4 for providing a reference for a short-circuit state of the thermistor THR by dividing the power supply voltage Vcc by a constant voltage. The quadrature voltage circuit 36 and the extended detection voltage Vo 'of the D / A converter 28 are commonly input to the inverting input terminal (-), and the first, First and second and third generations of the second, third, and third reference voltages Vth1, Vth2, and Vth3, respectively, and generating comparison results as first, second, and third comparison detection signals DT1, DT2, and DT3. The comparator COMP1, COMP2, and COMP3 and the extended detection voltage Vo 'of the D / A converter 28 are input to the non-inverting input terminal (+), and the fourth reference voltage Vth4 is input to the inverting input terminal (-). The comparison result is composed of a fourth comparator COMP4 generated by the fourth comparison detection signal DT4.

The fixing temperature control unit 40 is composed of an ora gate G1-G2 and an inverter IN1-IN2, and detects the fixing temperature as an abnormally low temperature state by a predetermined logical combination of the first to third comparison detection signals DT1-DT3. The first temperature control signal 42 for generating the first temperature control signal FLC for driving the fixing lamp driver 2 only when the second lamp is driven, and the OA gates G3-G4. A second control section 44 for generating a second temperature control signal FFC for driving the fixing fan 3 only when the fixing temperature is detected as an abnormal high temperature state by a predetermined logical combination of the DT1-DT3; The third control unit 46 detects a fault in which the thermistor THR is shorted or opened by the fourth comparison detection signals DTl and DT4 and applies the fault detection signal ARM to the interrupt terminal INT of the CPU 50. It is composed of In this case, the third controller 46 includes a logic sum gate G5.

FIG. 4 is a diagram illustrating the fixing temperature detection characteristics of FIG. 3, wherein the first to fourth reference voltages Vth1 to Vth4 are applied to the extended detection voltage Vo 'according to the temperature detection voltage V0 when the fixing temperature is increased. Shows the detection of the fixing temperature state by comparison with.

Hereinafter, an operation example of FIG. 3 according to the present invention will be described in detail with reference to FIG. 4.

First, the fixing temperature of the fixing unit is detected by the thermistor THR of FIG. 3 having a negative resistance characteristic in which the resistance value decreases as the temperature increases. The detection voltage Vo due to the resistance value of the thermistor THR and the voltage division of the power supply voltage Vcc of the resistors R1-R2 is applied to the analog input terminal Ain of the A / D converter 22 to provide a reference voltage. The first input terminal A0 of the 16-bit multiplier 26 for digitally converting the voltage range of the detection voltage Vo after digital conversion with 64 steps of 6-bit resolution within the range of the ground voltage and the power supply voltage Vcc. -A5). At this time, the multiplicity adjustment data generation unit 24, which is a DIP switch, generates 6-bit multiple adjustment data previously set by the switch operation and is input to the second input terminals B0-B5 of the multiplier 26.

Then, the multiplier 26 multiplies the output digital data of the A / D converter 22 by the multiple adjustment data and outputs an 8-bit multiplication result as extended detection voltage data.

In this case, the voltage range of the detection voltage Vo is extended to prevent the misunderstanding of the fixing temperature state due to the detection error, and the setting of the drainage adjustment value of the drainage adjustment data generator 24 and the corresponding D / The expansion factor is set by setting the reference voltage Vcc 'applied to the A converter 28. At this time, assuming that the power supply voltage Vcc is 5V, the temperature detection voltage Vo ranges from 0V to 5V. If the multiplier adjustment is set to 3 times, the reference voltage Vcc 'applied to the D / A converter 28 and Set the ground voltage range to 0V-15V. The grounding of the multiplier 26 without using the first two bits of the first and second input terminals A6-A7 and B6-B7 is carried out if the multiplication result is too large, so that a carry occurs. It is configured to take 8-bit multiplication and produce 8-bit output. Therefore, the resolutions of the front and rear A / D converters 22 and D / A converters 28 are also set to match this.

The 8-bit extended detection voltage data output from the multiplier 26 is analog-converted to 256-bit 8-bit resolution by the D / A converter 28 and output as the extended detection voltage Vo ', and the fourth comparator COMP4. Is applied in common to the non-inverting input terminal (+) and the inverting input terminal (−) of the first to third comparators COMP1 to COMP3.

On the other hand, in the first to fourth voltage dividing circuits 32 to 38, the first to fourth reference voltages Vth1 to Vth4, which are set by dividing the power supply voltage Vcc, are respectively determined by the first to fourth comparators COMP1 to COMP4. It is input to the type force terminal. At this time, the first to fourth reference voltages Vth1 to Vth4 are set to different sizes within the range of the extended detection voltage Vo 'as shown in FIG. 4 and set in a relationship of Vth4> Vth3> Vth2> Vth1> 0. .

The first-fourth comparators COMP1-COMP4 respectively output the comparison results to the fixing temperature controller 40 as first-fourth comparison detection signals DT1-DT4. Then, the fixing temperature controller 40 performs a logical combination with the first to fourth comparison detection signals DT1 to DT4 as shown in the following formulas (1) to (3) and fails with the first and second temperature control signals FLC and FFC. The detection signal ARM is generated in the logical state as shown in Table 1 below to detect the fixing temperature adjustment and the failure of the thermistor THR.

By referring to the equations (1)-(3) and Table (1), the fixing lamp 1 and the fixing fan 3 are selectively driven according to the extended temperature detection voltage Vo 'to automatically adjust the fixing temperature. At the same time, the operation of detecting the failure of the thermistor THR will be described as follows.

First, when Vo '<Vth1, that is, when the fixing temperature is below T1 ° C as shown in FIG. 4, the fixing lamp 1 and the fixing fan 3 cannot be detected because the temperature detection in the thermistor (THR) opening state is impossible in the above table (1). ) Is " off " and the fault detection signal ARM is activated with logic " 1 " and applied to the interrupt terminal INT of the CPU 50. The CPU 50 is then interrupted to stop the operation of the system according to the setting program and to repair the thermistor THR by alerting the user. At this time, the alarm method can be appropriately alarmed according to the visible, audible and the like. It can also be used to shut down the system's mains supply.

Secondly, when Vth2 <Vo '<Vth1, that is, when the fixing temperature is between T1 ° C and T2 ° C as shown in FIG. 4, the fixing lamp 1 is turned "on" because the temperature is abnormally low in Table (1). (3) "off" to raise the fixing temperature.

Thirdly, when Vth3 <Vo '<Vth2, that is, when the fixing temperature is between T2 ° C and T3 ° C as shown in Fig. 4, the fixing lamp 1 and the fixing fan 3 are replaced with the normal state in Table 1 above. Off "to maintain the present state. At this time, it may be possible to maintain the current state of the fixing lamp 3 without changing it.

Fourth, when Vth3 <Vo '<Vth4, that is, when the fixing temperature is higher than T3 ° C as shown in FIG. 4, the fixing lamp 1 is turned off because the abnormal high temperature is in the table (1). "On" to lower the fixing temperature.

Fifth, when Vo '> Vth4, that is, when the fixing temperature is T3 ° C or higher and the temperature detection in the thermistor (THR) short-circuit state is impossible, the fixing lamp 1 is " off " Is turned on to lower the fixing temperature, and the fault detection signal ARM is activated to logic " 1 " as in the first case described above, and applied to the interrupt terminal INT of the interrupt terminal INT of the CPU 50. Inform fault detection.

By controlling the fixing temperature of the fixing unit by the operation as described above, by detecting the failure of the thermistor (THR), which is a temperature detection sensor, by expanding the temperature detection voltage recognition range, it is possible to prevent the misunderstanding due to the detection error caused by the external voltage fluctuation. .

In addition, although the above description exemplifies controlling the fixing temperature by selectively controlling the fixing lamp 1 and the fixing fan 3, the same applies to a system in which the fixing fan 3 is not used. Thus, when applied to a system that does not use the fixing fan 3, the second control unit 44 is also unnecessary. In addition, it will be appreciated that the present invention can be easily applied to temperature control of a system employing a heater as well as a system using an electrophotographic developing method such as a copying machine and a laser beam printer.

As described above, the present invention can cope with a risk that may occur when a temperature detection sensor malfunctions, and has an advantage of preventing misrecognition due to a detection error by extending a temperature detection voltage recognition range.

Claims (7)

A fixing temperature automatic control circuit for a system using an electrophotographic development method, comprising: a fixing lamp (1) for emitting a fixing heat, a fixing lamp driver (2) for driving the fixing lamp (1), and fixing according to the fixing heat A temperature detection unit 10 for detecting a temperature as a temperature detection sensor and generating a detection voltage, a detection voltage expansion unit 20 for extending a voltage range of the detection voltage generated by the temperature detection unit 10 by a set multiple, and the expansion A first comparator C0MP1 for comparing the original detection voltage with a first group voltage set to provide a reference for the open state of the temperature detection sensor, and a reference for an abnormal low temperature state of the fixing temperature; A second comparator COMP2 comparing the second reference voltage set to provide a second reference voltage, and a third reference voltage set to provide a reference for the abnormal high temperature state of the fixing temperature with the extended detection voltage; A third comparator COMP3 to compare with and a fourth comparator COMP4 to compare the extended detection voltage with a fourth reference voltage set to provide a reference for the short-circuit state of the temperature detection sensor; A control unit 42 for driving the fixing lamp driver 2 only when the fixing temperature is detected as an abnormally low temperature from the comparison result of the third comparators OMP1-COMP3, and the first and fourth comparators COMP1, And a control unit (46) for detecting a failure of the temperature detection sensor from the comparison result of COMP4). 2. The fixing according to claim 1, wherein the fixing temperature automatic adjustment circuit further comprises a CPU 50 which interrupts when the failure of the temperature detection sensor is detected in the control section 46 and generates an alarm. Temperature automatic control circuit. The A / D converter 22 of claim 1 or 2, wherein the detection voltage extension unit 20 converts the output detection voltage of the temperature detection unit 10 into digital data, and adjusts a multiple of a preset value. A multiplier adjustment data generation unit 24 for generating data, a multiplier 26 for generating an extended detection voltage data by multiplying the digitally converted data of the A / D converter 22 and the multiple adjustment data; And a D / A converter 28 which analog-converts the extended detection voltage data of (26) and outputs the extended detection voltage to the first to fourth comparators (COMP1-COMP4). Automatic control circuit. 4. The fixing temperature automatic control circuit according to claim 3, wherein the magnitude of the first to fourth reference voltages is set in a relationship of first reference voltage <second reference voltage <third reference voltage <fourth reference voltage. . In a fixing temperature automatic control circuit of a system using an electrophotographic development method, a fixing lamp (1) for emitting a fixing heat, a fixing lamp driver (2) for driving the fixing lamp (1), and fixing according to the fixing heat A temperature detector 10 for detecting a temperature as a temperature detection sensor and generating a detection voltage, a comparator C0MP1 for comparing the detected voltage with a reference voltage set to provide a reference for an open state of the temperature detection sensor, Detecting a failure of the temperature detection sensor from a comparison result of the comparator COMP4 and the comparators COMP1 and COMP4 for comparing the detected voltage with a reference voltage set to provide a reference for a short-circuit state of the temperature detection sensor. Fixing temperature automatic control circuit, characterized in that the control unit 46. 6. The fixing according to claim 5, wherein the fixing temperature automatic adjusting circuit further comprises a CPU 50 which interrupts by detecting a failure of the temperature detecting sensor in the control unit 46 and generates an alarm. Temperature automatic control circuit. 7. A comparator (COMP2) according to claim 5 or 6, wherein said settling temperature automatic regulation circuit compares said detected voltage with a reference voltage set to provide a reference for an abnormally low temperature state of said settling temperature; Comparator COMP3 comparing the detected voltage with a reference voltage to provide a reference for the abnormal high temperature state of the fixing temperature, and only when the fixing temperature is detected as the abnormal low temperature state from the comparison result of the comparators COMP1-COMP3. Fixing temperature automatic control circuit characterized in that it further comprises a control unit 42 for driving the fixing lamp drive unit (2).