JPS60103418A - Temperature control method - Google Patents

Abstract

PURPOSE:To assure temperature control by detecting directly the temperature of a heating element based on the resistance value of the heating element and thereby detecting an accurate temperature without using a temperature detecting element. CONSTITUTION:A temperature control part 4a stops the working of a constant voltage type power supply part 5a in case the input current is larger than the current value corresponding to the set temperature of a cylindrical semiconductor ceramic heater 1. Then the part 5a is started again when a prescribed period of time elapsed from a time point when the part 5a is stopped. A temperature control part 4a detects again the input current and compares this current with above-mentioned corresponding current value. These actions are repeated successively. Thus the temperature of the heater 1 is controlled to the set level.

Description

DETAILED DESCRIPTION OF THE INVENTION [111 Fields] The present invention relates to a method for controlling the temperature of a heating element using Joule heat generation.

[Prior art] Conventionally, in order to control the temperature of a heating element using Joule heat generation to a constant value, the temperature of this heating element is measured with a temperature detection element (for example, a thermistor, etc.), and the measured value is adjusted to a predetermined value. controlled the supply of power to the

Since such conventional methods use temperature sensing elements, the following problems occur.

When detecting temperature with a temperature sensing element in contact with a heating element 1 For example, in the fusing section of a copying machine, the heating element gets dirty with l/ner, etc., and this dirt adheres to the surface of the sensing part of the temperature sensing element and accumulates. However, as a result, the temperature detection error increases.

Furthermore, when detecting the temperature of a fixing roller whose surface is made of a material to which toner does not easily adhere (for example, silicone rubber, tetrafluoroethylene, etc.), the surface of the fixing roller is damaged by the temperature detection element.

When detecting temperature with the temperature sensing element separated from the heating element, it is susceptible to environmental influences such as ambient temperature and convection.

Moreover, in either case, since the overshoe 1- is large, it is difficult to control the temperature to a desired temperature.

In particular, since the surface of the fixing roller is made of a thermal insulator, overshoot is large and control tends to become unstable.

[Purpose] The present invention has been made in order to solve the above-mentioned drawbacks of the conventional technology. The purpose is to provide a temperature control method that does not require any elements.

[Configuration] 1. Embodiments of the present invention kJY with reference to the attached drawings
Explain in detail.

FIG. 1 illustrates a temperature control device according to an embodiment of the present invention. In this embodiment, the temperature of the fixing machine of a copying machine is controlled.

In the figure, 1 is a cylindrical semiconductive ceramic heater;
Reference numeral 2 denotes electrodes fixed to both sides of the semiconductive ceramic heater 1, and the electrodes 2 are provided with ventilation holes 3.

Note that the semiconductive ceramic heater 1 is made of titanium oxide (Ti
The main component is titanium oxide (1"io), which has metal titanium encapsulated during the ring treatment of 02), and exhibits semiconductivity.

Reference numeral 4 designates a temperature control unit that controls the temperature of the semiconductive ceramic heater 1 to a predetermined fixing temperature, and 5 designates a power supply unit that supplies power to the semiconductive ceramic heater 1.

FIG. 2 shows the relationship between the specific resistance ρ and the temperature Tc of the semiconducting ceramic heater l. This relationship is expressed by the following formula (1) where ρ is the specific resistance of the semiconducting ceramic heater 1, and ρ0
and are constants, and T is temperature (absolute temperature). In addition,
Tc in the figure is Serra's display, so in this case 1'c = 27
3+T(K).

Here, the power supply unit is a constant voltage positive type power supply 5 as shown in FIG.
If a, then the inflow current of the semiconducting ceramic heater 1 ■
changes with temperature as shown in Figure 4. Note that the power supply voltage is 100 (V).

Therefore, the temperature control section 4a controls the heater's set temperature T.
When the inflow current I becomes larger than the current value Io corresponding to o, the constant current injection power source 5a is stopped, and after a predetermined time (for example, 2 minutes) has elapsed from this point, the constant current injection power source 5a is restarted. do.

Then, the temperature control section 4a detects the inflow current again and compares it with the value Io, and thereafter repeats the above process in sequence.

The temperature of the semiconducting ceramic heater 1 is controlled to the set value To by such an action of the temperature control section 4a.

Note that 6 is a shunt resistance.

FIG. 5 shows an example of a circuit when a constant current type power source section 5b is used as the power source section.

In this case, since the inflow current is constant, the voltage V applied to the conductive ceramic heater 1 changes with temperature.

Therefore, in the temperature control section 4b, the applied voltage V is the set temperature 1.
When the value corresponding to 'o is exceeded, the constant current type power supply unit 5b is controlled in the same manner as described above. Note that resistors '1 and 8 are voltage dividing resistors.

FIG. 6 shows an example of a circuit when a power supply for temperature detection is separately provided.

As shown in the figure, the output of the detection power supply section 10 is applied to the semiconducting ceramic heater 1, and the temperature control section 4C detects the current or voltage on this circuit to control the temperature of the semiconducting ceramic heater 1. I am doing it.

In this way, the temperature of the semiconductive ceramic heater 1 can be continuously monitored.

By the way, in the embodiments described above, the temperature of the semiconducting ceramic heater is controlled, but the object to be controlled is not limited to this. In general, metals (conductors) have the characteristic that their specific resistance increases as the temperature rises, and this characteristic can be utilized to perform temperature control similar to that described above.

[Effects] As described above, according to the present invention, the temperature of the heating element is directly detected based on the resistance value of the heating element, so a temperature detection element is not required. As a result, temperature detection can be performed reliably and without time delay, making temperature control reliable.

[Brief explanation of the drawing]

Fig. 1 is a perspective view illustrating a temperature control device according to an embodiment of the present invention, Fig. 2 is a graph showing the temperature-specific resistance characteristics of a semiconducting ceramic heater, and Fig. 3 is a constant voltage power supply. 11 is a graph showing the relationship between temperature and inflow current, FIG. 5 is a block diagram showing a device using a constant current type power supply, and FIG. FIG. 2 is a block diagram showing a device including a power source for temperature detection. 1 ・+11: Conductive ceramic heater, 4. /Ia, 4
b, 4c - Temperature control section, 5... Power supply section, 5a...
Constant voltage power supply section, 5b - Constant current power supply section. Agent Patent Attorney Crest 1) '$ij し ・j Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] (1) In a temperature control method for controlling the temperature of a Joule heating element to a predetermined value, the electrical resistance of the heating element is detected, the temperature of the heating element is determined from the detected value, and the temperature is determined to be a predetermined value. A humidity control method characterized by stopping the power supply for a predetermined time and then determining the temperature again if the temperature exceeds the temperature. (2. A humidity control method as set forth in claim 1, characterized in that the Joule heating element is made of a semiconducting ceramic material. (3) A humidity control method as set forth in claim 2, wherein the The temperature control method is characterized in that the conductive ceramic material is made of titanium oxide as the main raw material, and is made conductive by an egg treatment.