JPS598024A - Temperature controller - Google Patents

Abstract

PURPOSE:To prevent chattering and to increase the temperature control accuracy for a heat fixing device of a copying machine, a printer, etc. as well as a temperature controller of a drying device, etc., by changing the reference voltage for a fixed period after an object to be heated reaches a fixed temperature. CONSTITUTION:For a temperature controller which supplies the electric power to an object to be heated in response to the output signal of a comparator, a differentiating circuit consisting of a capacitor C1 is connected between an output terminal and a plus (+) input terminal of a comparator IC1 and in series to a feedback resistance R6. Then the differential waveform is fed back in both rise and fall modes of the output of the comparator IC1. Therefore the difference between reference voltage of the plus (+) input terminal and the voltage of the minus (-) input terminal of the IC1 becomes large. Thus the chattering of the output of the IC1 is never generated owing to the ripple of the thermistor voltage.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a temperature control device for a heat fixing device such as a copying machine or a printing machine or a drying device. PRIOR ART A conventional temperature control device of this type, as shown in FIG.
It is composed of a temperature control circuit using heater cello cross ON-OFF control. For example, a thermistor (old 11) that detects the surface temperature of a regular roller (not shown) is connected to the power supply 1) S via a resistor R1, and the connection point between this thermometer THI and resistor R1 is one input of the ratio device IC1. Connected to the terminal, a reference voltage corresponding to the temperature setting is applied. A resistor I is obtained by dividing the power supply voltage of the power supply O5 by a resistor I and a resistor I which generates this reference voltage. The connection point between and resistor R3 is connected to the input terminal of comparator TCI. ratio"
It is connected to the tenth input terminal f of the nuclear layer ICI. The output terminal of the comparator IC1 is connected to the base of a transistor Q1 via a resistor, and the collector of this transistor Q1 is connected to the J terminal of a zero-cross control solid state relay (hereinafter referred to as SSR). . A heater II for applying a constant 5-row roller is connected to the output end of this SSR, and the SSR becomes conductive when the binary state of the output terminal of the comparator ICI is LOW. Sungen A
When the output terminal of the comparator TCI is IIIGII, it becomes non-conductive and stops power supply to the heater I-1. In the above circuit, for example, if the temperature of the fixing roller is low and the resistance value of the thermistor Tljl is high, the comparator IC
If the voltage at one input terminal of I is higher than the base voltage at the 1-input terminal, the output terminal of comparator ICI is LOW and SSR is activated.
becomes conductive and power is supplied to heater [1]. As power is supplied to the heater 11, the temperature of the fixing roller gradually increases, the resistance value of the thermistor TIII gradually decreases, and the voltage at one input terminal of the comparator ICH gradually decreases. This ratio 1 articulator ICI
Conventionally, when the voltage at one input terminal decreases to become equal to the base l'11 voltage at the input terminal of comparator IC1 and further becomes lower than the reference voltage, the output of comparator IC1 instantly goes LOW.
to 111 G Vl, or from IIIGH to L
The reversal movement from number 10,772 to OW to 20,077
This causes a so-called chattering phenomenon that repeats for approximately 2 seconds. This chattering phenomenon is caused by the power supply 1) S
This is caused by the presence of ripples of about 20 to 5 Q 7n V in the power supply voltage when a rectified commercial power supply is used. Next, the reason why this chatter link occurs will be explained. As shown in FIGS. 2 and 3, the signal voltage V applied to one input terminal of the operational amplifier A that operates as an IT axis device
If s includes a ripple of several 7nV, this voltage v
At the moment when 5 cuts the base Q voltage VL, the output voltage vO of the operational amplifier A repeats 111G11°L OW many times. Therefore, the power supply 1) shown in FIG.
Since the voltage of S includes a ripple, the output voltage of the thermistor Tfil includes a ripple. Therefore, as shown in FIG. 4C, the output voltage of the comparator rc1 becomes T-11G many times
Chattering occurs by repeating I(・r-o~■). As mentioned above, chattering occurs in the output of the comparator ICI, and the output signal of the comparator IC1 is sent to the SSR through the transistor Ql. As shown in Fig. 4, half-wave power may be applied to the heater H between JtJI where this chattering occurs.In this case, an abnormal current flows to the commercial power supply As, There was a problem in that the waveform distortion of the power supply was caused, and the fluorescent lights connected to this commercial power supply system flickered momentarily, making people in the room feel uncomfortable. , as shown in FIG. 5, the output terminal to the operational amplifier that operates as a comparator is connected to the input terminal of the operational amplifier A to which the reference voltage is input via the feedback resistor Rf. The inversion operation of the comparator output with respect to changes in the signal input now has hysteresis, and chattering does not occur when the comparator output is inverted.In other words, as shown in FIG. 6, the signal voltage Vs rises and the reference voltage V, %
When the output voltage reaches the reference voltage Vtl, the output voltage to the operational amplifier is inverted from HIGH to LOW. At this time, the LOW signal at the output terminal of operational amplifier A is connected to the resistor R.
(is fed back to the tenth input terminal through
Lower it to 2. Therefore, the reference voltage VLl, Vt
If the level difference between the two levels is made sufficiently larger than the ripple of the signal voltage Vs, the output of the operational amplifier A will continue to be LOW and no chattering will occur. Furthermore, when the signal voltage Vs drops and reaches the reference voltage VLl, the reference voltage at the input terminal of the operational amplifier A is V2, so the output voltage of the operational amplifier A is not inverted. I, 0
Continuing ~■, when the signal voltage 1 voltage VS reaches the reference voltage VL2, the output of the operational amplifier A changes from LOW to IIIGIIj
At the same time as this inversion, the reference voltage VL2 rises above Vtt. Therefore, the rise of the signal vS is based on the voltage V t ]
(The output to the operational amplifier is IITG)
Chattering does not occur by continuing the state of l. When the above-mentioned means is applied to a temperature control device, as shown in FIG. Voltage”
- Feedback to the input terminal. In this circuit, the temperature of the fixing roller is in the upper row,
As shown in FIG. 3, the output chamber of the mister'ri11. The voltage 1'l (gradually decreases, and this thermistor voltage ~'TI1 reaches the reference voltage V, and then from the base 7 + 7 - city pressure VL2 to 1) ((2, Fig. 8 1). As shown, ratio) 119 藷■ 0
1's output voltage is inverted from LOW to HIGH. At this time, this comparator I
The output voltage of C□ is applied to the tenth input terminal of the comparator IC1, and the base voltage of the tenth input terminal of the comparator ICI is increased from VH2 to VTL, as shown in FIG. 8a. Therefore, at this time, the difference between the thermistor voltage and the reference voltage becomes large, and chattering of the output of the comparator ICI due to ripples in the thermistor voltage does not occur. In addition, when the temperature of the fixing roller decreases and the thermistor voltage increases, the output of the comparator ICI is reversed from IITGH to LOW when the thermistor voltage reaches the double raised reference voltage Vt1. , at this time, the output voltage of the comparator IC1 is applied to the input terminal through the feedback resistor 6, and the reference voltage input to the comparator IC1 becomes Vt, as shown in FIG. 8a.
1 to Vt2, the difference between the thermistor voltage and the reference voltage becomes large, and no chattering occurs in the output of the ratio 1 articulator IC1. However, in this temperature control device, as shown in FIG. 8a, the reference voltage input to the comparator C1 changes depending on whether the temperature of the fixing roller increases or decreases, The difference between the parts, that is, the hysteresis voltage △V
As a result, when the temperature of the constant volume roller drops and the thermistor voltage slides upward to reach the lower reference voltage V12, the output of the comparator IC1 becomes IIICI (as shown in FIG. 8).
−+1 of the 8th
As shown in Figure C, He! No power is supplied to H. Therefore, as shown in FIG. 8d, the temperature of the fixing roller passes through the set temperature To and further decreases. The reference voltage vtl when the temperature of the fixing roller further decreases and the thermistor voltage changes
When reaching LO, the output of comparator IC1 becomes HIGf (from LO
At this point, the SSR becomes conductive and power supply to the heater T-I starts, but at this time the temperature of the fixing roller is lower than the set temperature To by Δ'F. In this way, since power supply to the heater is started when the temperature of the fixing roller becomes lower than the set temperature by a certain value F, there is a drawback that temperature ripple becomes large and highly accurate temperature control cannot be performed. Purpose The present invention has been made in view of the above-mentioned drawbacks of the conventional technology. In this way, it is an object of the present invention to provide a temperature control device which can prevent chattering of the output of a comparator and can control the temperature of the first floor of a guard with high precision. The comparator is equipped with a ratio calculator that compares the corresponding signal voltage with a reference voltage corresponding to the temperature setting value and outputs a signal corresponding to the magnitude relationship between the signal voltage and the reference voltage. output signal of

[Accordingly, in order to supply power to the object to be heated, a differentiating circuit is provided on the output side of the comparator so that the output voltage attenuates with a predetermined time constant. It is characterized in that the differential output is connected to one input terminal of the comparator, and the differential waveform is returned at the rising and falling edges of the output of the comparator. EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. As shown in FIG. 9, a differentiating circuit consisting of a capacitor C1 is connected in series with a feedback resistor 1 (6) between the output terminal of the comparator ICI and the input terminal. The circuit is similar to the conventional circuit shown in Fig. 7, and the same circuit parts as in Fig. 7 are given the same reference numerals. When the temperature of the fixing roller rises, as shown in Figure 1A, the thermistor voltage ■・n-■
decreases and the temperature of the fixing roller reaches the set value TO, the thermistor voltage "n" becomes equal to the basic voltage V at the input terminal of the comparator IC1, and as shown in FIG.
Output voltage of comparator IC1 changes from LOW to HI G II
Then, the power supply to the heater [1 is stopped. At this time, the output voltage of the comparator ICI is applied to the input terminal of the comparator IC1 through the series circuit of the foot-knocking resistor R6 and the capacitor CI, and as shown in FIG. The reference voltage at the tenth input terminal of the comparator Ic1 is increased to V(3. Therefore, at this time, the voltage at the thermistor voltage at the single terminal of the comparator Ic1 and the reference voltage at the tenth input terminal of the comparator rc1 are The difference becomes large, and chattering of the output of the comparator ICI due to the ripple of the thermistor voltage does not occur.However, although the output of the comparator 1cI is LOW, the HTG
When reversed to I-1, capacitor c1 is charged with a constant running time constant by the resistance value of feedback resistor 1 to 6 and the capacitance value of capacitor CI, and capacitor C1
As the charging voltage increases, the voltage at the input terminal of the comparator ICI gradually drops. When the charge of the capacitor C1 becomes equal to the voltage difference at the output terminal T of the comparator ICI, the voltage at the input terminal of the comparator IC1 becomes the original reference voltage V (FIG. 10a). That is, the reference voltage at the input terminal of the comparator IC1 is increased for a certain period of time after the temperature of the fixer l cola reaches the set value TO and the thermistor voltage becomes equal to the reference voltage V. In addition, when the power supply to heater 1 is stopped (J-), the temperature of the fixing roller decreases, and the thermistor voltage decreases, and the temperature of the fixing roller reaches the set value 1. becomes equal to the voltage V[, the output voltage of the comparator TC1 changes from Ir1G11 to LO~), and the heater I
- Power supply to T is started. At this time, the output voltage of the comparator IC1 is applied to the input terminal of the comparator rc through the 1i'j column circuit of the feedback resistor R6 and the capacitor c1, and the output voltage of the comparator ICI is applied to the input terminal of the comparator ICI. 'The quasi-pressure is lowered to Vt4 (101st Tla). Therefore, at this time, the difference between the thermister voltage, which is the voltage at the -manual terminal r- of the comparator IC1, and the base voltage, which is the voltage at the input terminal of the articulator TC1, becomes large, and the thermistor voltage No chattering occurs in the output of the comparator TC1 due to ripples. Furthermore, when the output of the comparator ICI is reversed from TNGI4 to low, the capacitor c1 is charged in a manner opposite to that described above, and as the charging pressure of the capacitor CI increases according to the above-mentioned time constant, the comparison is made. When the voltage at the input terminal of the ratio ICI rises smoothly and the charging voltage of the capacitor C1 becomes equal to the voltage drop at the output terminal of the comparator C1, the voltage at the top of the input terminal of the ratio ICI 01 increases. Is it the original base? (/1 voltage Vt
(Figure 1O a). In other words, the temperature of the fixing roller is the set value T. After the thermistor voltage becomes equal to the reference voltage V, the reference voltage at the input terminal of the comparator IC1 is lowered for a certain period of time. In this case, as shown in FIG. 1O, when the temperature of the fixing roller decreases to the set value To, the -reamister voltage becomes V[, and the output voltage of the comparator IC1 changes from TIIGI-1 to LOW. Then, the power supply to the heater 1 is started. That is, as soon as the temperature of the fixing roller drops to the set value, power supply to the heater is started. fart. By the way, the resistance values of the resistors R4, R5, and R6 and the capacitance value of the capacitor C1, which determine the change period of the reference voltage according to the time constant of the change in the reference voltage mentioned above, that is, the hysteresis voltage and the time constant of the change in the reference voltage, are as follows. , so that the output of the ratio 1 interpolator ICI has a hysteresis characteristic sufficient to prevent chap IJ when the output of the comparator C1 is inverted, and
The change period of the reference voltage is the capacity of the heater, and the fixing roller! 7
``!) The fixing temperature recovery time is set to be sufficiently shorter than the fixing temperature recovery time determined by the product, the usage environment temperature of the copying machine, the copying operation mode, etc.
Is it about 3 seconds to 3 seconds, and is it a conventional temperature system? The inheritance period of the chatter link of the output of the comparator in the a11 device is 50 to 10
Since it is about 0m5eC, the time constant of the change in the reference voltage is set to 2.
00 to 300772S (at the IC position)
the law of nature,. It is sufficient to determine the resistance values of R5 and R6 and the electrostatic capacitance of capacitor c1. Another embodiment of the present invention, as shown in FIG. 11, feeds back the differential wave of the output of the comparator IC1 to the signal voltage side of the thermistor r Hl to prevent output chatter.
] Two. In this case, as shown in FIG. 12, the comparator ICI
The voltage at the ten input terminals of changes like the waveform Δ. In this example, even if there is a ripple on the reference voltage, the comparator output is stable, the reference level is kept constant once a month, and accurate control can be achieved. Effects As explained above, in the present invention, the signal voltage corresponding to the temperature of the heated object is compared with the base 7% voltage corresponding to the temperature setting value, and the signal voltage is compared with the reference voltage. In a temperature control device that is equipped with a comparator that outputs a signal according to the magnitude relationship of A differentiating circuit is provided in which the output voltage attenuates with a predetermined time constant, and this differential output is connected to one input terminal of the comparator, so that the differential waveform is fed back at the rise and fall of the output of the ratio 1 oscillator. From this, the chattering of the comparator output can be eliminated to create a commercial T; ? In addition, the temperature ripple of the heated object is reduced and temperature control can be performed with high precision.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional temperature control device, Figure 2 is a circuit diagram showing a comparator, Figure 3 is a waveform diagram showing the operation of the circuit in Figure 2, and Figure 4 is a diagram of the circuit in Figure 1. A waveform diagram of the main part, FIG. 5 is a circuit diagram showing another comparator, FIG. 6 is a waveform diagram showing the operation of the circuit in FIG. 5, FIG. 7 is a circuit diagram of another conventional temperature control device, 8 is a waveform diagram of the main part of the circuit of FIG. 7, FIG. 9 is a circuit diagram showing an embodiment of the present invention, FIG. 10 is a waveform diagram of the main part of the circuit of FIG. 9, and FIG. 12 is a circuit diagram showing another embodiment of the present invention, and FIG. 12 is a waveform diagram of the main part of the circuit of FIG. 11. ICI...Comparator, +11...Heater,
R6...Resistor, C1...Capacitor. Patent applicant: Minolta Camera Co., Ltd.

Claims (1)

[Claims] (1) The signal voltage corresponding to the temperature of the heated object is compared with the reference voltage corresponding to the temperature setting value, and a signal is output according to the magnitude relationship between this signal voltage and the reference voltage. In the temperature control device, the temperature control device is equipped with a comparator and controls the power supply to the heated object according to the output signal of the comparator, and a predetermined time interval is provided between one input terminal of the comparator and the comparator output. 1. A temperature control device characterized by being provided with a differentiation circuit that attenuates by a constant, and feeding back the differentiation waveform when the comparator output is changed.