JPS6239738A - Temperature switch apparatus - Google Patents

Abstract

PURPOSE:To impart no effect to detected temp., by providing a differential amplifier consisting of two transistors to an apparatus and varying the comparing voltage applied to one input of the differential amplifier even if the voltage of a power source varies. CONSTITUTION:The titled apparatus is constituted of a battery 1, a switch 2, a lamp 3, a capacitor 4, a thyristor 5, resistors 6, 12, 13, 15, 17, PNP transistors 14, 16 constituting a differential amplifier and a negative characteristic thermistor 18. When the voltage of the battery 1 changes, the middle point voltage necessary for turning the thyristor 5 ON changes but, at the same time, comparing voltage obtained by voltage dividing resistors 11, 13 also changes and temp. dependence when the thyristor 5 is turned ON is eliminated. Therefore, even if the voltage of the battery 1 varies, it can be accurately informed that the temp. of cooling water reached predetermined temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature switch device, and more particularly to a temperature switch device that operates by detecting the temperature of cooling water in an engine of an automobile or the like.

[Industrial Application Field] FIG. 3 is a circuit diagram showing an example of a conventional temperature switch device. First, the configuration of a conventional temperature switch device will be explained with reference to FIG. The first of the automobile battery 1
The positive side as the potential of is connected to lamp 3 via switch 2.
The negative side of the automobile battery 1 as the second potential is grounded. The lamp 3 lights up when the cooling water reaches a predetermined temperature. The other end of the lamp 3 is connected to a positive temperature coefficient thermistor 9 via a resistor 8. Resistor 8 is for current limiting. The positive temperature coefficient thermistor 9 has a positive temperature coefficient whose resistance value increases as the temperature increases. The positive temperature coefficient thermistor is housed in a case 10, and the case 10 is immersed in cooling water 11.

A capacitor 4 for absorbing surges and the like and a thyristor 5 are connected between the other end of the lamp 3 and the ground. The gate terminal of the thyristor 5 is grounded via a resistor 6, and is also connected to a resistor 8 via a Zener diode 7.
and the positive temperature coefficient thermistor 9 at the point P:. The Zener diode 7 levels-shifts the gate voltage required to trigger the thyristor 5.

In the temperature switch device configured as described above, when the cooling water 11 is cold, the resistance value of the positive temperature coefficient thermistor 9 is small, so even if the switch 2 is closed, no gate current is supplied to the gate terminal of the Cyrisk 5. . Therefore, the thyristor 5 is turned off. When the automobile engine is started, the temperature of the cooling water 11 rises, and the resistance value of the positive temperature coefficient thermistor 9 changes in the positive direction. Following this, the voltage at the midpoint between the resistor 8 and the positive temperature coefficient thermistor 9 also increases. This midpoint voltage V gate is (the gate voltage of the thyristor) + (the Zener voltage of the Zener diode)
When the water temperature reaches , a gate current begins to flow to the gate terminal of the thyristor 5, thereby turning on the thyristor 5. When the thyristor 5 is turned on, current flows from the battery 1 to the lamp 3 via the switch 2, and the lamp 3 lights up, indicating that the cooling water has reached a predetermined temperature.

[Problems to be Solved by the Invention] In the conventional temperature switch device configured as described above, the midpoint voltage V between the resistor 8 and the positive temperature coefficient thermistor 9 necessary for turning on the thyristor 5 is Vr+ -(value of positive characteristic thermistor 9 x battery voltage)/<value of resistor 8 + value of positive characteristic thermistor 9) -1 x battery voltage...(1),
When the voltage of battery 1 changes J, the midpoint voltage i becomes 1X (
As a result, the temperature at which the thyristor 5 is turned on corresponds to a change in the temperature at which the thyristor 5 turns on. In other words, the temperature of the cooling water 11 when the thyristor 5 is turned on greatly influences the voltage change of the battery 1, resulting in a drawback as a temperature sensor.

Therefore, the main objective of this invention, Na'a! !
To provide an inexpensive temperature switch device that does not affect detected temperature even when pressure changes.

[Means for Solving the Problems] The temperature switch device according to the present invention includes two transistors connecting the midpoint between a resistor and a thermistor connected in series between a first potential and a second potential. The midpoint of two resistors connected in series between the first potential and the second potential is connected to the input of the differential amplifier. One output of the amplifier is connected to the gate terminal of the thyristor, and a load is connected to the anode terminal of the thyristor. When the value changes and the voltage at the connection point of the resistor and thermistor changes more than the voltage at the connection point of the two resistors, a gate current flows from one output of the differential amplifier to the gate terminal of the thyristor, and the thyristor is activated. Turns on and supplies current to the load. the first potential and the second potential
Even if the potential changes, the voltage at the midpoint of the two resistors also changes, so it does not affect the detected temperature.

[Embodiment] FIG. 1 is an electrical circuit diagram of an embodiment of the present invention. 1st
In the figure, the same battery 1, switch 2, lamp 3, capacitor 4, thyristor 5, and resistor 6 as in FIG. 1 are used. And from battery 1 to switch 2
A resistor 17 is connected between the positive potential as the first potential supplied via the lamp 3 and the ground as the second potential.
A first series circuit consisting of a negative characteristic thermistor 18 and a negative characteristic thermistor 18 are connected, and a second series circuit consisting of two resistors 12 and 13 is connected. The negative characteristic thermistor 18 is placed in a case in the same manner as in FIG. 3 described above, and the case is immersed in cooling water.

The base of one PNP transistor 16 constituting the differential amplifier is connected to the connection point between the resistor 17 and the negative characteristic thermistor 18, and the base of the other PNP transistor 16 constituting the differential amplifier is connected to the connection point between the resistors 12 and 13. The base of PNP transistor 14 is connected. the first potential and the PNP transistor 14.
A current limiting resistor 15 is connected between the emitter 16 and the emitter 16.

Further, the collector of the PNP transistor 14 is grounded, and the collector of the PNP transistor 16 is connected to the gate terminal of the thyristor 5.

In the temperature switch device configured as described above, when the switch 2 is closed, the temperature from the switch 2 via the lamp 3 ( )
Therefore, current flows through resistors 12 and 13. Then, the 'N voltage divided by the resistors 12 and 13 is applied to the base of the PNP transistor 14 as a comparison voltage.
Since a forward bias voltage is applied between the base and emitter of the NP transistor 14, it is turned on or off. On the other hand, PNP
When the cooling water is cold, the resistance of the negative characteristic thermistor 18 is large in the transistor 16, so the base
A reverse bias voltage is applied across the emitters, turning it off. Since PNP1 to transistor 16 are in the off state, thyristor 5 is also off.

When the automobile engine is started, the temperature of the cooling water begins to rise by 1 degree, and the resistance value of the negative characteristic thermistor 18 also decreases. Following it, resistor 17 and negative characteristic thermistor 18
The midpoint voltage V- also decreases, and when the water temperature reaches a point where the midpoint voltage V becomes the same voltage as the comparison voltage V obtained by the two voltage dividing resistors 12 and 13, it is in the on state. The PNP transistor 14 turns off, and the PNP transistor 16, which was in the off state, begins to turn on.As a result, a gate current begins to flow to the gate terminal of the thyristor 5, turning on the thyristor 5.When the thyristor 5 turns on, , current flows through lamp 3,
This lamp 3 lights up to notify that the cooling water has reached the predetermined temperature of 1a degree.

Here, when the voltage of the battery 1 changes, the midpoint voltage required to turn on the thyristor 5 is V gate - (value of negative characteristic thermistor 18 x battery voltage), -' (value of resistor 17 + 1ffl) of the negative characteristic thermistor 18) -2 x battery voltage...<2), and K2 x (change in battery voltage) changes, but at the same time, the comparison voltage VF obtained by the voltage dividing resistor 12.13 Also, -(value of resistor 13 x battery voltage)/(value of resistor 72 + fa of resistor 13) -3 x battery voltage...(3),
When the thyristor 5 turns on, the voltage division ratio (K2-K3 is selected) is set so that Vr=Vn, so the same change occurs.

For this reason, there is almost no temperature deviation of the cooling water when the thyristor 5 is turned on.

In other words, the dependence of the temperature when the thyristor 5 turns on on the voltage fluctuation of the battery 1 is eliminated. Therefore, even if the voltage of the automobile battery 1 fluctuates, it is possible to accurately notify that the temperature of the cooling water has reached a predetermined temperature.

FIG. 2 is an electric circuit diagram showing another embodiment of the present invention. In the embodiment shown in FIG. 2, a positive temperature coefficient thermistor 19 is connected in place of the resistor 17 shown in FIG. 1 resistor 20 in place of the negative characteristic thermistor 18! Continuation t: Something. When one positive temperature coefficient thermistor is used in this way, when the cooling water is cold λC, the resistance is small, so the voltage between the base and emitter of the range transistor 16 is low, and this transistor 16 does not conduct. And cold 1
1 f'l as the water temperature rises! As a result, the resistance MN of the positive characteristic transistors 1 and 9 increases, and the transistor 16
The base-emitter voltage of the transistor 16 becomes conductive, and the thyristor 5 also becomes conductive.

In addition, in the above-mentioned actual tA example;
Although the case of detecting the temperature of ff coolant water has been described, it goes without saying that it can also be used to detect the temperature of the pond.

[Effect of the Invention] As described above, according to the present invention, the midpoint between the resistor and the thermistor connected between the first potential and the second potential is
It is connected to one input of a stationary 11!1 width converter mixed with two transistors, and the midpoint of two resistors connected in series between the first potential and the second potential is connected to the difference 111111 width divider. , one output of the differential amplifier is connected to the gate terminal of the thyristor, and the load is connected to the anode terminal of the thyristor, so that there is no difference between the first potential and the second potential. Even if the potential changes, the comparison voltage applied to one input of the differential amplifier changes, so the detected concentration is not affected.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of an embodiment of the present invention. Second
The figure is an electrical circuit diagram of another embodiment of the invention. FIG. 3 is a circuit diagram showing a conventional temperature switch device. In the figure, 1 is a battery, 2 is a switch, 3 is a lamp, 4 is a capacitor, 5 is a silicon risk, 6°12.13.
15, 17, 20 are resistors, 14, 16 are P NP )-
A transistor, 18 indicates a mouth↑ji1 raw thermistor, and 19 indicates a positive characteristic thermistor.

Claims (3)

[Claims] (1) Consists of a resistor and a thermistor, with a first potential and a second potential.
a first series circuit connected between the first potential and the second potential; a second series circuit in which two resistors are connected in series between the first potential and the second potential; The input of one transistor is connected to the connection point between the resistor and the thermistor of the first series circuit, and the input of the other transistor is connected to the connection point of the two resistors of the second series circuit. A temperature switching device, comprising: a differential amplifier having a differential amplifier, a thyristor having a gate terminal connected to an output terminal of the one transistor of the differential amplifier, and a load connected to an anode terminal of the thyristor. (2) The thermistor is a negative characteristic thermistor, and the resistor of the first series circuit is connected between the input terminal of the one transistor and the first reference potential, and the negative characteristic thermistor is a negative characteristic thermistor. The temperature switch device according to claim 1, wherein the temperature switch device is connected between the input terminal of the transistor and the second reference potential. (3) The thermistor is a positive characteristic thermistor, the positive characteristic thermistor is connected between the input terminal of the one transistor and the first reference potential, and the resistance of the first series circuit is connected to the one transistor. The temperature switch device according to claim 1, wherein the temperature switch device is connected between the input terminal of the transistor and the second reference potential.