JPS598025A - Controlling system of temperature for heat fixing device - Google Patents

Abstract

PURPOSE:To decrease the rise time and to avoid overshoot, by having a rise with ON/OFF control when the temperature of the heat fixing device is higher than a fixed level. CONSTITUTION:When the heater temperature is lower than a fixed level, the ON/OFF control signal (c) is set at L. At the same time, a phase control signal (b) having large width is generated from a phase signal generating circuit A2 since a large output is generated from an amplifying circuit A1. The signal (b) is applied to a triac TR and gives phase control to the electric power of a heater H. When the heater temperature reaches a fixed level, a heater power supply is turned off. Thus the signal (c) is set at H to consecutively turn on the triac TR. As a result, the heater temperature rises quickly up to a set level. Then the output of a detecting circuit A6 is set at L. Thus the output (c) is set at L again, and the TR undergoes phase control again with the output (b). Therefore the heater temperature is kept at a set level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control system for a heat fixing device in a copying machine or the like.

As a temperature control method for heat fixing devices, ON-
Two methods are known: an OFF control method and a phase control method, and conventionally, one of these two methods has been adopted to control the temperature of the heat fixing device. However, the ON-OFF control system has the problem that the start-up speed is fast, but the overshoot is harsh, as shown in the characteristic curve (A) of FIG. Further, the phase control method has the problem that although the O-G shoot is small, the rise speed is slow, as shown in the characteristic curve (b). Therefore, when the phase control method is adopted, it takes 71 seconds from the Tl temperature to reach the set temperature.
It takes a long time, and there is a problem in that, for example, it takes a long time to recover after the heat fixing device is turned off due to a jam in the copying machine or a door opening. On the other hand, ON
- In the case of the OFF electric 11r wholesale method, the time τ2 (<τ1) from 'F1γ1 temperature to the set temperature is shortened, but when starting up from room temperature, the heat fixing device greatly increases the set temperature due to its heat storage effect. There was a problem.

The present invention solves the above-mentioned problems, and provides a heat fixing device that can turn off the heat fixing device for a short time due to jam etc., shorten the time to return afterward, and suppress overshoot at initial start-up. The purpose is to provide a temperature control method.

In order to achieve this objective, the present invention uses an ON-OFF control method to raise the temperature of the heat fixing device to the set temperature when it is above a certain temperature, and then switches to the phase control method. Since the phase control method is used to start up hot dust, the overshoot is determined by the temperature at the time of start-up, and is shown by the curve (c) in Figure 2.
, 2) and (e), the temperatures T2 and T at startup are
3. It was found that the closer T4 is to the set temperature, the smaller the overshoot will be. Therefore, in the present invention, the temperature of the heat fixing device is detected using this relationship, and when the temperature is higher than a certain temperature, the ON-OFF control method is used to shorten the time for the temperature to return after the above-mentioned short time OFF. If the temperature is lower than that, a phase control method is used to prevent over-sheeting when the initial temperature is raised.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a power saving circuit according to an embodiment of the present invention, which increases the reference voltage VR and lowers the heater set temperature during standby by returning the heat fixing device temperature.

Th is a thermistor for temperature detection.

A1 is when the temperature detection voltage vT exceeds the reference voltage VR,
This is a non-inverting amplifier circuit that outputs a positive signal.

A2 is a phase that compares the A, output with a triangular wave signal synchronized with a half cycle of the heater power AC generated from the triangular generator circuit S, and outputs a phase control signal that becomes 1-H at the A, output > S output. This is a signal generation circuit.

01 is an OR circuit that outputs a phase control signal or an ON-OFF control signal, TR is a triac, H is a heater for a heat fixing device, AC is a commercial 100V heater power supply, and L
is the reactance.

2 is a zero cross detection circuit which generates a zero cross signal every half cycle of the power supply AC, and resets the integral operation by turning on the transistor Q2 of the triangle generation circuit S. As a result, the triangular generating circuit S generates a triangular wave signal synchronized with the AC half cycle.

A3 is a high temperature detection circuit that sets the output d to rHJ when the heater temperature rises to a high temperature of two constant values due to a short circuit in the triac TR, etc. A4 is a thermistor disconnection that detects the disconnection of thermistor Th and sets the output e to rHJ It is a detection circuit.

A5 is a 100°C detection circuit that sets the output f to "■(" when the heater temperature reaches 100°C or higher, and A6 sets the output g to "L" when the detected temperature reaches 180°C or higher and warm-up is completed. This is a 180°C detection circuit.

A7 is now a, , p signal rHJ, r of A6 output g
This is an ON-OFF control signal generation circuit that generates an ON-OFF control signal according to the LJ state. That is, as shown in FIG.
This is the signal that goes to rHJ when it is LJ, and goes to rLJ when it is r'HJ. Also, the ON-OFF control signal generation circuit A7 (
1) The A6 output g is applied directly to the terminal, while the control voltage Vcc and the 1,000-warf 0 signal are applied to the (→terminal) via resistors R2 and R3.As a result, ON-OFF control signal generation circuit A7 generates an ON-OFF control signal that becomes rHJ between 100°C and 180°C, and the OR circuit 01
The signal is input to the TRIAC TR gate 9 through the TRIAC TR.

With the above configuration, when the heater temperature is 100℃ or less, the ON
-OFF control signal rLJ. On the other hand, the temperature detection voltage V is much higher than the reference voltage VR, and the amplifier circuit A
1 generates a large output. Phase signal generation circuit A2
As a result of comparing the output of the driver 1 and the output of S, a wide phase control signal shown by the chain line in Fig. 5 is applied to the triac 1'R via the OR circuit 01, and the power of the heater H is applied. Control phase. Therefore, when , power is supplied to the heater H in an almost continuous ON state as indicated by the chain line in FIG. 5, and the heater H is rapidly heated. As a result, the thermistor Th
As it warms up, its resistance value decreases, and as a result, the temperature detection voltage vT also decreases. Therefore, by lowering the AI specific output, the width of the A2 output, that is, the phase control signal, becomes narrower as shown by the solid line in FIG. 5, the heater power also decreases, and the temperature rise rate slows down.

In this way, when the heater temperature reaches 100℃,
Alternatively, once the warm-up is completed, turn off the heater power in case of a jam, etc.
When the temperature exceeds 0°C, the A7 output c becomes "H" and the trier and tsTR are turned on continuously. As a result, the heater temperature quickly rises again and reaches the set temperature of 180℃ in a short time.
reach. Then, the A6 output g becomes rLJ, which is input as it is to the (4) terminal of the 0N-OFF control signal generation circuit A7, while the (→ terminal) has Vcc and power-up signal rLJ divided by resistors R2 and R3. As a result, the terminal voltage becomes higher and the A7 output C becomes rLJ.

Therefore, as a result of the triac TR being phase-controlled again by the A2 output, the heater temperatures i and J exceed somewhat 180°C, and then are held constant at the set temperature of 180°C.

In this way, when starting up the heater temperature from 100°C or higher, start up using the 0N-OFF control method,
By switching to the open phase control method when the temperature reaches 180℃, the heater temperature startup time can be shortened, and
This makes it possible to suppress overshoot within an acceptable range.

In addition, the switching temperature of 100°C and the set temperature of 180°C for switching from phase control to 0N-OFF interval opening shown in the above example.
is just an example, and it is clear that the switching temperature should be set to a constant value that allows overshoot from the set temperature to fall within the standard range, even if the set temperature is set arbitrarily.

As described above, according to the present invention, when the temperature of the heat fixing device is above a certain value, the heat fixing device is started up by ON-OFF control, so that the startup time can be shortened and auto-coupling can be suppressed. be able to.

[Brief explanation of the drawing]

Figure 1 is the start-up characteristic curve of the ON-OFF'F control method and phase control method. A circuit diagram of a heat fixing temperature control device according to an embodiment of the invention, FIG. 4 is an explanatory diagram of various circuit output changes corresponding to warm changes to explain the operation of FIG. 3, and FIG. FIG. 2 is a time chart for explaining the operation of FIG.

Claims (1)

[Claims] (1) In a method of controlling the temperature according to a set value by controlling the AC power supply supplied to the heat fixing device, ON-OFF control is used when the temperature of the heat fixing device is started from a certain temperature or higher. A temperature control method for a heat fixing device, characterized in that a phase control method is used when starting up from below the certain temperature. (2. Claim 1, wherein the constant temperature is a temperature within an allowable range of overshoot. A temperature control method for a thermal fixing device according to item 1, characterized in that after the temperature of the thermal fixing device is raised to a set temperature, the temperature of the thermal fixing device is controlled to the set value by a phase control method.