JPS6319915Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a compensated spot type sensor, which uses a temperature sensing element such as a thermistor or diode instead of the conventional diaphragm or bimetal, and uses a conventional contact cap. It is an object of the present invention to provide a compensation type spot-type sensor that does not require high mechanical dimensional accuracy such as leak holes, and can cope with adverse environments and aging.

An embodiment of the compensated spot type sensor of this invention will be explained with reference to the drawings.

In Fig. 1, the anode side of the voltage comparison element PUT ₁ is connected to point A where the voltage is divided by thermistor Th ₁ of the temperature sensing element and fixed resistor R ₂ , and it has the same characteristics as the thermistor Th ₁ mentioned above and a heat capacity. A voltage dividing point B is connected to the gate of the voltage comparison element PUT ₁ by means of a small temperature sensing element Th ₂ and a fixed resistor R ₃ . Moreover, point B is another voltage comparison element PUT ₂
It is connected to the gate. This voltage comparison element
The anode of PUT ₂ is connected to a reference voltage point C that divides the voltage by fixed resistors R ₄ and R ₅ .
The cathodes of PUT1 and PUT2 are both connected to the transistor Q, and the output side of the transistor is connected to the gate of the thyristor SCR.

A constant temperature is detected by comparing the voltages at point A and point B, and comparing the temperature increase rate at point B and point C.

Now, when the temperature rises rapidly, the thermistor Th ₁
Since the resistance value of A gradually decreases, the voltage at point A gradually decreases. On the other hand, the resistance value of Th ₂ rapidly decreases, and the voltage at point B rapidly drops. Therefore, a circuit is created in which the voltages at points A and B are compared by the voltage comparison element PUT ₁ , the transistor Q is switched, and the output triggers the thyristor SCR, which switches when the temperature rise rate exceeds a certain level. Also, by comparing point B and point C, which is a reference voltage point, a circuit that switches when a certain temperature is reached can be created.

Next, as a trigger method for the switching circuit, conventionally, as shown in Figure 2, a capacitor C is inserted into the anode of the voltage comparison element PUT.
When the PUT was turned on, the current that flowed when the charged charge was discharged was used to flow the trigger current, but when the power was turned off, this circuit
Due to the discharge of the capacitor, the anode potential does not drop immediately and becomes higher than the gate potential, and the voltage comparison element PUT turns on. This state continues until the capacitor finishes discharging, so if the power is turned on again immediately after being turned off, the voltage comparison element remains on.

In this invention, as shown in Figure 1, we used a transistor Q instead of a capacitor, so the voltage comparison element
When PUT ₁ or PUT ₂ is turned on, bias is applied to transistor Q, and current flows between collector and emitter, supplying trigger current to the switching circuit, so malfunction of the voltage comparison element due to power on/off does not occur. do not have.

Furthermore, in the conventional circuit shown in Figure 2, when the ambient temperature is high, the divided voltage of the thermistors Th ₁ and Th ₂ becomes small, and the voltage applied to the capacitor is low, so the amount of charge charged is small and the trigger current is also small. The trigger current flowing through the switching circuit is always constant because it is supplied from the emitter of the transistor Q.

Note that C ₁ and R ₁ in FIG. 1 are for absorbing leakage current and noise, R ₆ is for absorbing noise to the transistor Q, and R ₇ is a resistor for adjusting the trigger current to the thyristor SCR.

As explained above, the present invention uses a reference voltage circuit for the power supply consisting of resistor R ₂ , thermistor Th ₁ , resistor R ₃ , and thermistor Th ₂ , which has the same characteristics as thermistor Th ₁ but has a small heat capacity, resistor R ₄ , and resistor R ₅ . The divided voltage of thermistor Th ₁ and the divided voltage of thermistor Th ₂ are compared with the voltage comparison element PUT ₁ , and a differential temperature detection signal is triggered at a predetermined voltage difference, and the thermistor Th ₂
The divided voltage and the reference voltage are compared by voltage comparison element PUT ₂ , and a constant temperature detection signal is triggered at a predetermined voltage difference, and
Since the sensing output is output from a switching element with both trigger outputs OR-connected, it eliminates the need for high mechanical dimensional precision such as contact gaps and leak holes in conventional mechanical sensors, making it less susceptible to harsh environments. correspondence,
In addition to being able to cope with changes over time, the temperature rise rate can be detected by connecting two temperature-sensing elements in series as a semiconductor-based compensated spot sensor to create a structural difference in thermal response. However, compared to the method that uses one more thermistor to maintain a constant temperature, this method uses two temperature sensing elements and one voltage comparison element to detect the temperature rise rate, and uses one of the elements in common to detect a different voltage. Since a constant temperature is detected using a comparison element, the circuit becomes simple. Furthermore, since one transistor is used for the trigger of the switching circuit, the trigger voltage becomes constant, switching becomes smooth, and the phenomenon of inoperation when the power is turned on and off is eliminated.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention. Second
The figure is a circuit diagram of a conventional example. In the drawing, Th ₁ , Th ₂ are thermistors, R ₂ , R ₃ ,
R ₄ and R ₅ are fixed resistors, PUT ₁ and PUT ₂ are voltage comparison elements, Q is a transistor, and SCR is a thyristor.

Claims (1)

[Scope of utility model registration request] Connect resistor R ₂ and thermistor Th ₁ , resistor R ₅ and the reference voltage circuit of thermistor Th ₂ , which has the same characteristics as thermistor Th ₁ but has a small heat capacity, resistor R ₄ and resistor R ₅ to the power supply, and connect the thermistor Th ₁ to the reference voltage circuit. The divided voltage and the divided voltage of thermistor Th ₂ are compared with the voltage comparison element PUT ₁ , and a differential temperature detection signal is triggered and output at a predetermined voltage difference, and the divided voltage of thermistor Th ₂ and the reference voltage are compared with the voltage comparison element PUT. This is a compensated spot type sensor that outputs a fixed temperature detection signal as a trigger based on a predetermined voltage difference compared _between