JPS58197524A - Temperature controller - Google Patents

Abstract

PURPOSE:To perform heating in a short time and to prevent overshooting by powering up a heater with a 100% duty cycle for abrupt heating up to critical temperature set between set temperature and control point temperature, and then performing heating with an about 50% duty cycle. CONSTITUTION:The detection output of a temperature detector 1 is supplied to a circuit 2 which varies in duty cycle with temperature and a circuit 3 for commanding the start of proportional control. The outputs of the circuits 2 and 3 are supplied to a solid-state relay SSR5 through an OR circuit 4 to intermit a current to a heater 6. Quick heating with a 100% duty cycle is carried out initially, but the output of the commanding circuit 3 goes down to L when the temperature attains to the critical temperature between the set temperature and control temperature to reduce the output to about 50% under the control of the duty cycle varying circuit 2, so that the temperature rises gradually. Consequently, the temperature rises in a short time and no overshoot occurs. This is suitable for the fixing device of a copying machine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device that detects the temperature of an object heated by a heater and controls the temperature to a set temperature, and is particularly applicable to an fB4A fixing device of a copying machine. The present invention relates to a temperature control device that can be used.

Taking the heated roll fixing device of a horizontal copying machine as an example,
This heating roll has a non-adhesive layer such as silicone rubber on its outer surface, and since there is a limit to the heat resistance of this non-adhesive layer, it is necessary to reduce unnecessary high temperatures as much as possible in terms of fixing performance. be. For this reason, k should be adjusted to reduce overshading when the temperature rises and ripples when the temperature stabilizes.

Conventionally, proportional control has generally been performed in order to reduce overgage during temperature rise and temperature ripple during stabilization. This changes the duty cycle of heater conduction from 1001% to 99% as the temperature rises.
8%... and so on. Therefore, the point at which the duty cycle begins to change must be at a low temperature.

In such a conventional example, overshoot and temperature ripple could certainly be suppressed to a certain extent compared to on/off control.

However, such conventional proportional control has the disadvantage that the temperature rise time becomes long.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a temperature control device that can minimize overshading and temperature ripples without increasing the rise time to a set temperature.

For this purpose, a judgment temperature is set between the set temperature and the control point temperature (duty cycle change point temperature), and the heater is fully energized until this judgment temperature reaches this judgment temperature. After reaching this point, the heater is turned on and off at a duty cycle that drops to about 50.

The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a basic configuration block diagram of a temperature control device according to the present invention. In the figure, reference numeral 1 denotes a temperature detector, and its output is manually inputted to a variable duty cycle circuit 2 whose duty cycle is varied according to the temperature, and a command circuit 3 which commands the start of the proportional -1 phrase.

4 is an OR circuit that inputs these two outputs, and OR circuit 4
The output is inputted to the heater 6 via an 88R (solid state relay) 5, whereby the heater 6 is controlled to be turned on and off.

That is, only when a low level output is output from the command circuit 3, the heater 6 is proportionally controlled with a duty cycle corresponding to the temperature.

FIG. 2 is an actual control circuit diagram. In the figure, a 1M degree detector 1 is composed of a thermistor. In addition, the date cycle variable circuit 2 includes an operational amplifier 7 and an I/O circuit for a timer.
11#1J121 is supplied from a V/F converter IC (predetermined in response to the output of this V/F converter section) consisting of C1 and a nest stabilizing multivibrator IC that generates a pulse. Further, the command circuit is composed of a controller 8. The heater 6 is configured to be supplied with squid by a power source 9.

Next, the operation of this circuit will be explained in detail. First, the voltage at the 0 point (voltage at the ten terminals of the operational amplifier 7) is high when the temperature is low, and low when the temperature is high.

The waveform (actually inverted by the inverter Il) of the output waveform of the IC No. 103, which is the waveform of the waveform (actually, it is inverted by the inverter Il), is approximately proportional to the voltage at the zero point. The reason for this is that the 3rd terminal of the IC is set to Hi by the 6th terminal (threshold terminal).
gh, Low VC is controlled, but when the capacitor CI becomes V, this No. 6 terminal makes the No. 3 terminal Low.
When K #; binding, ■, it becomes High K (Vt>Vt), and as a result, Nokurusu is generated from No. 3 熇子. In this case, the decrease in the potential of the capacitor CI is proportional to the collector current IcK of the transistor Q, and this 1. Since K is proportional to the voltage at the 0 point, the pulse dark wave number at the 0 point is proportional to the potential at the 0 point.

The pulse output at point 0 is the trigger terminal of the IC, 2
input to the number terminal. In this case, resistor R, and capacitor C3
If the trigger pulse interval T1 is shorter than the time constant determined by , Therefore, a high level signal is input to one input terminal of the OR circuit 4,
81R5 should be operated to provide complete communication to the heater 6. Then, as the temperature rises, the pulse interval of the first pulse P1 output from the No. 3 terminal of IC1 changes to the resistance R1,
When the number of time points determined by the capacitor CI is greater than the time constant, the capacitor c, nv1. v, the second node (rus) of the arrival time width is output from the 3$4 child of IC,.

(This coincides with the control point temperature). Usually at this point 8
8) A control signal with a gradually lowered duty cycle is applied to the heater 6 via t5, but in the present invention, one input terminal of the OR circuit 4 receives a judgment temperature set higher than this control point temperature. It is connected to the comparator 8 for detection. 1 for this is this comparator 8 and #41
Detects the constant temperature and connects High to one input of the OR circuit 4.
The heater 6 is now fully energized by changing the level signal that was being sent to the Low level Kg.

After the determination temperature is detected, since the t3 signal is not output from the controller 8 (T, OW level good number), starting from this point, the heater 6 is turned on by the second pulse P.
This means that off control will begin.

FIG. 3 is a temperature characteristic diagram, where t is the set temperature dissipation to be controlled, t is the control point source +W at which the duty cycle starts to change in the variable duty cycle circuit 2, and t is the point at which the heater 6 is actually turned on. , is the determination temperature at which off control starts.

As is clear from this characteristic diagram, full current is applied until the determination temperature t, and from the point when the determination temperature is reached, the duty cycle is rapidly lowered to perform on/off control.

FIG. 4 is a timing chart of waveforms of various parts.

(1) is the voltage waveform of capacitor CI, (2) is the third terminal output of IC, that is, the first pulse Ps, (3) is the output of inverter I, that is, the waveform of the 0 point, and (4) is the capacitor C
1 voltage waveform, (5) is the third terminal output O1 of ICt, that is, the second pulse P, (6) is the output obtained by inverting the output of converter 8 with inverter I, (7) is the output of OR circuit 4 The waveform [F] and (8) are the positive pressure waveforms of the heater 6.

=lrAs mentioned above, when the temperature is low (A), (
Since the output of 5) remains at T (igl+ level and does not become a pulse), all heaters 6 are energized, and even when the temperature is high (b), the output level of (6) remains low K.
Even if the second pulse P is output until the temperature drops, the heater 6
is fully energized.

As described above, when the present invention performs proportional control by changing the duty cycle, the duty cycle is not gradually reduced from 100 inches, but is suddenly reduced suddenly, so that the rise time is not extended. K is set to prevent overshoot and temperature ripple.

[Brief explanation of the drawing]

Figure 1 is a basic block diagram showing the principle of the stomach filling according to the present invention.
, FIG. 2 is an electric circuit diagram showing a practical example, FIG. 3 is a temperature characteristic diagram according to the present invention, and FIG. 4 is a timing chart of each part in the electric circuit diagram of FIG. 2. 1...Temperature detector, 2...Duty cycle 0T
Variation circuit, 4.8... OR circuit and Hi-comparator as a judgment circuit, 5-... -Relay, 6... Fist heater, 9 units...
・1 growth. Bu/IZ 135-

Claims (1)

[Claims] (1) A heater, a temperature detector that detects the temperature of the object heated by the heater, and a duty cycle whose duty cycle is varied in proportion to the output of the temperature detector from a control point temperature lower than the set temperature. The cycle variable circuit detects the judgment @ degree between the set temperature and the control point temperature, and when this judgment temperature is reached, the duty cycle ``■ variable circuit outputs the heater and 1 to the relay in the source 111. (2. In claim (1), the object heated by the heater is a fixing device of a copying machine. A temperature control device that is used as a samurai.