JP2781312B2 - Compensated heat detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compensation type heat sensor in which a thermosensitive element such as a thermistor is provided inside and outside a sensor to detect a fire by a constant temperature function and a differential function.

[0002]

2. Description of the Related Art Conventionally, as a compensation type heat sensor of this kind, a temperature of a guard zone is set in advance by using a heat sensitive element such as a semiconductor thermistor element whose resistance changes according to a temperature change. It has both a constant temperature function that issues an alarm when the temperature reaches the specified temperature and a differential function that issues an alarm when the temperature of the alert zone rises above a predetermined temperature rise rate.

FIG. 5A shows a main circuit portion of a conventional compensation type heat sensor, which comprises an external thermosensitive element 1 and an internal thermosensitive element 2 using a semiconductor thermistor element or the like. The external thermal element 1 is installed outside the sensor, and the thermal time constant is small because the resistance value always changes following the change of the ambient temperature. The internal thermal element 2 is provided inside the sensor, and has a large thermal time constant because there is a delay in temperature change with respect to a change in ambient temperature.

[0004] External heat sensitive element 1 sets the base voltage V _b1 of the transistor Q1 connected in series with the resistor R1. The internal thermosensitive element 2 is connected in series with a resistor R2 to connect a transistor Q
The second base voltage _Vb2 is set. Transistors Q1, Q
Numeral 2 connects the emitters in common and is connected to a positive power supply line via a resistor R3. These transistors Q1 and Q2 constitute a comparison circuit for fire detection by a differential function.

[0005] divided voltage by the external thermal element 1 and the resistor R1 sets the base voltage V _b3 of the transistor Q3 at the same time. A transistor Q4 is differentially connected to the transistor Q3, and both emitters are connected to a positive power supply line via a resistor R6. A constant base voltage _Vb4 is set at the base of the transistor Q4 by the resistors R4 and R5. The transistors Q3 and Q4 constitute a comparison circuit for detecting a fire by the constant temperature function.

[0006] FIG. 5 (b) shows the constant temperature characteristics, the base voltage of the transistor Q1~Q4 at constant temperature, has a _{V b4> V b2 (= V} b3)> V b1, the transistor Q1, Q3 is on. If the temperature in the alert area rises slowly due to a fire,
The temperature change of the external thermal element 1 and the internal thermal element 2 is almost the same, the resistance value is also changed in the same manner, and the base voltage V _b1 ,
V _b2 increases while maintaining the difference.

For this reason, when the base voltage V _b3 rises to the constant temperature alert temperature Tc at which the base voltage V _b4 reaches the constant base voltage V _b4 , the transistor 3 is turned off from on and at the same time the transistor Q is turned off.
4 turns on from off, and outputs a fire detection signal by a constant temperature function to a switching circuit (not shown) to issue an alarm. FIG. 5 (c) shows the differential characteristic, the base voltage of the transistor Q1~Q4 at constant temperature, has a _{V b4> V b2 (= V} b3)> V b1, the transistors Q1, Q3 is Turned on. When the temperature of the alert area rises sharply due to a fire, the resistance value of the external thermosensitive element 1 rapidly decreases according to the temperature rise, but the temperature of the internal thermosensitive element 2 does not change much, and the base voltage _Vb1 rises in temperature. , But the rise of the base voltage V _b2 is small. Therefore, when the base voltage V _b1 reaches the differential alarm temperature Td exceeding the base voltage V _b2 , the transistor Q1 is turned on from off, and at the same time the transistor Q2 is turned on from off. Outputs a detection signal and issues an alarm.

[0008]

However, in such a conventional compensation type heat sensor, a comparison circuit for realizing a constant temperature function and a differential function are realized as shown in FIG. 5 (a). Since the comparison circuit and the comparison circuit were separately provided, two transistors Q1 and Q3 of each comparison circuit were always in the ON state in the steady monitoring state, the current consumption per sensor was large, and the comparison circuit was drawn from the receiver. Since the current capacity of one sensor line is determined, the number of connected lines per line is limited, which is a factor that increases the overall cost of the fire alarm system.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and provides a compensation type heat sensor capable of reducing equipment cost by reducing current consumption and simplifying a circuit configuration. The purpose is to:

[0010]

In order to achieve this object, the present invention is configured as follows. The reference numerals in the drawings of the embodiments are also shown. First, according to the present invention, an external thermosensitive element 1 having a small thermal time constant with respect to a temperature change in a caution area is provided outside the sensor, and an internal thermosensitive element 2 having a large thermal time constant with respect to a temperature change in a caution area is provided inside the sensor. A constant-temperature function for detecting that the temperature of the guard zone has reached a predetermined temperature based on the detection signals of the thermosensitive elements 1 and 2 and issuing an alarm, and a warning zone exceeding a predetermined temperature rise rate. And a differential function for detecting and notifying that the temperature of the sensor has risen sharply.

According to the present invention, such a compensation type heat sensor is provided with an external thermosensitive element 1 in a base bias circuit and a base voltage V _b6 based on a change (decrease) in a resistance value with a rise in temperature.
And a first transistor Q6 that is connected in parallel with the first transistor Q6 and has an internal thermosensitive element 2 in the base bias circuit. The base voltage V _b7 rises due to a change (decrease) in the resistance value caused by the temperature rise. And a third transistor Q3 differentially connected to each of the first and second transistors Q6 and Q7 and having a fixed reference base voltage V _b3 set by a base bias circuit.

First to third transistors Q6, Q7, Q3
Are commonly connected to a power supply line via a pull-up resistor R4. An output circuit is provided for extracting a fire detection signal by the constant temperature function when the second transistor Q2 is turned on and extracting a fire detection signal by the differential function when the third transistor Q3 is turned on. Here, the first to third transistors Q
6, Q7 and Q3 use PNP transistors, and the emitters of the PNP transistors are commonly connected and connected to a power supply line via a pull-up resistor R4.

Further, the values of the resistors R9 and R10 connected in series to the external thermosensitive element 1 and the internal thermosensitive element 2 are changed so that the temperature of each thermosensitive element 1 and 2 is the same and the resistance value is the same in the steady monitoring state. by varying the first and base voltage V _b6, V _b7 of the second transistor Q6, Q7 of the first transistor Q6 on, and the second transistor Q7 is turned off.

[0014]

According to the compensation type heat sensor of the present invention having such a configuration, a comparison circuit for realizing fire detection by the constant temperature function and a comparison circuit for realizing fire detection by the differential function are shared. Although four transistors are used, only three transistors are required, and the circuit configuration including the bias circuit can be simplified.

Further, since all the transistors constituting the comparison circuit are commonly connected and connected to the power supply line via one pull-up resistor, the current flowing through the transistor has a value restricted by a single resistor, Further, in the steady monitoring state, only one transistor is in the ON state, and the current consumption of the detection circuit can be reduced to about half of the conventional circuit. For this reason, if the number of connections per line is increased, or if the number of connections is the same, the power supply capacity of the receiver can be reduced, which can greatly contribute to a reduction in overall equipment costs.

[0016]

FIG. 1 is a block diagram of an embodiment showing a main circuit portion of a compensation type heat sensor according to the present invention. In FIG. 1, an external thermosensitive element 1 and an internal thermosensitive element 2 are provided. For example, a semiconductor thermistor element having the same characteristic that the resistance value decreases with increasing temperature is used. The external thermal element 1 has a resistance R
9, and the _divided voltage is applied to the base of the transistor Q6 (first transistor) as the base Vb6. The internal thermosensitive element 2 uses the divided voltage generated by the series connection with the resistor R10 as the base voltage _Vb7 to set the transistor Q
7 (second transistor).

The emitters of the transistors Q6 and Q7 are commonly connected, and the collector of the transistor Q6 is connected to a negative power supply line. The collector of the transistor Q7 is connected via a resistor R18 to an output line to a switching circuit (not shown). Here the internal thermal element 2
Has the same resistance value as the external thermosensitive element 1, but the values of the resistors R9 and R10 in the base bias circuit satisfy R10 <R9. For this reason, in the steady monitoring state in which the temperature of the external thermosensitive element 1 and the internal thermosensitive element 2 are the same and the resistance value is the same,
Creating a difference as a V _b7> V _b6 between the transistors Q6, Q7 base voltage V _b6 of, V _b7, and the transistor Q6 is set to base voltage V _b6 of lower to be always on.

On the other hand, a transistor Q3 is provided in which a divided voltage generated in a series circuit of the resistors R5, R6 and R7 is set as a base voltage _Vb3 , and the transistor Q3 is differentially connected to each of the transistors Q6 and Q7. I have. That is, the emitter of the transistor Q3 is commonly connected to the emitters of the transistors Q6 and Q7. When one of the transistors Q6 and Q7 is turned on, the transistor Q3 is always turned off. When both the transistors Q6 and Q7 are turned off, the transistor Q3 is turned off. Q3 is turned on.

After the emitter of the transistor Q3 is commonly connected to the emitters of the transistors Q6 and Q7, it is commonly connected to a positive power supply line via a single pull-up resistor R4. Therefore, the transistor Q3, Q6 or Q
The current flowing through 7 has a value limited by a single pull-up resistor R4. The collector of the transistor Q3 is a resistor R
17 is connected to an output line for a switching circuit (not shown).

Here, the base voltage V _b3 of the transistor Q3 set in the series circuit of the resistors R5, R6 and R7 is a specified voltage higher than the base voltages V _b6 and V _b7 of the transistors Q6 and Q7 in the steady monitoring state. It is set as follows. Therefore, during the transistors Q3, Q6, the base voltage V _b3 of Q7, V _b6, V _b7 is set to relation of V _b3> V _b7> V _b6 at steady monitoring state.

FIG. 2 is an explanatory diagram showing constant temperature characteristics in the embodiment of FIG. First In the steady monitoring state in the normal temperature range, the base voltage of the transistor Q3, Q6, Q7 are increased in the order of V _b6, V _b7 and V _b3, there Therefore the transistor Q6 is turned on, the transistor Q
7 and Q3 are off. In this state, if the temperature of the alert area slowly rises due to the fire, even if the thermal time constant of the external thermosensitive element 1 is small and the thermal time constant of the internal thermosensitive element 2 is large, the temperature rises of both are almost the same, and the resistance value becomes the temperature. It changes in the same way as it rises.

[0022] Therefore, as shown in the characteristic of FIG. 2, the transistors Q6, each base voltage remains magnitude of the base voltage V _b6, V _b7 was maintained at Q7 rises as well. Base voltage V of transistor Q6 due to temperature rise
_{When b6} reaches a constant base voltage _Vb3 set at the transistor Q3 at the constant temperature alert temperature Tc, the transistor Q6
When the transistor is turned off, the transistor Q3 is turned on. When the transistor Q3 is turned on, a fire detection signal by the constant temperature function is output to the switching circuit via the resistor R17, and an alarm signal is sent from the sensor to the receiver.

FIG. 3 is an explanatory diagram showing the differential characteristics of FIG. In the steady monitoring state First, as in the constant temperature characteristics of FIG. 2, the base voltage of the transistor Q3, Q6, Q7 has a high relationship in the order of V _b6, V _b7 and V _b3.
Therefore, only the transistor Q6 is turned on, and the transistors Q3 and Q7 are turned off.

In this state, the temperature of the guard area is suddenly increased due to the fire.
If it rises, the external thermal element 1 having a small thermal time constant
Although the resistance value decreases sharply, the internal thermal sensitivity with a large thermal time constant
The resistance value of element 2 decreases slowly with a time lag.
Base voltage V as shown in FIG. _b6, V_b7Changes. Immediately
In addition, the base voltage V by the internal thermal element 2_b7Is a gentle top
The base voltage V due to the external thermal element 1_b6Is steep
Drastically increases, the base voltage V_b6Is the base voltage V _b7Reach
Transistor Q6 is turned off from on at differential alarm temperature Td
Transistor Q7 switches from off to on at the same time
Switches to the switching circuit via resistor R18
It outputs a fire detection signal by the differential function and
Then, an alarm signal is transmitted.

FIG. 4 is a block diagram showing the specific embodiment of FIG. 1 together with the entire sensor circuit. In FIG. 4, terminals L and C are connected to a power / signal line drawn from a receiver. Following the terminals L and C, the connection polarity to the power / signal line is made non-polarized by the diode bridges 3 and S.
A CR circuit 7, a constant voltage circuit 4, and a comparison circuit unit 5 having the basic configuration shown in FIG. 1 are provided. The comparison circuit section 5 is basically the same as that of FIG. 1 except that a noise absorbing capacitor C8 is connected between the base and the emitter of the transistor Q3, and a noise absorbing capacitor C11 is connected in parallel with the external thermal element 1.
, A capacitor C12 for absorbing noise is connected between the base and collector of the transistor Q6, and a capacitor C13 for absorbing noise is connected between the emitter and base of the transistor Q7.

Subsequent to the comparison circuit section 5, a switching circuit 6 for triggering the SCR circuit 7 is provided.

[0027]

As described above, according to the present invention, the comparison circuit for realizing the constant temperature function and the comparison circuit for realizing the differential function are made common, and the conventional configuration composed of four transistors is reduced to three. It can be composed of transistors, and the circuit configuration can be significantly reduced. In addition, the three transistors provided in the comparison circuit for realizing the constant temperature function and the differential function are connected to the power supply line via a single resistor to limit the current. Since only one transistor is on, current consumption can be significantly reduced.

Further, the simplification of the circuit configuration and the reduction in current consumption not only reduce the cost of the sensor itself, but also reduce the power supply capacity of the receiver accompanying the reduction in current consumption and increase the number of connections to the sensor line. This can greatly contribute to a reduction in the overall cost of the fire abandonment facility.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a main circuit unit of the present invention.

FIG. 2 is an explanatory diagram showing a constant temperature characteristic of the present invention.

FIG. 3 is an explanatory diagram showing a differential characteristic of the present invention.

FIG. 4 is a configuration diagram of an embodiment of a specific detector circuit of the present invention.

FIG. 5 is an explanatory view of a conventional technique.

[Explanation of symbols]

 1: External thermal element 2: Internal thermal element 3: Diode bridge 4: Constant voltage circuit 5: Comparison circuit section 6: Switching circuit 7: SCR circuit Q6: First transistor Q7: Second transistor Q3: Third transistor R4: Pull Up resistance

Claims (3)

(57) [Claims] (1) Heat is supplied to the outside of the sensor in response to a temperature change in a warning area.
Provide an external thermal element (1) with a small time constant and sense
The inside of the vessel has a large thermal time constant for the temperature change in the alert area.
A thermosensitive element (2) is provided, and each thermosensitive element (1, 2) is
A regulation that sets the temperature of the alert area based on the detection signal in advance
A constant temperature function that detects when the temperature has reached and issues an alert
The temperature in the alert area rises sharply beyond the predetermined temperature rise rate
Compensation formula with differential function that detects and alerts
In the heat detector, the external heat sensitive element (1) is provided in a base bias circuit.
Base voltage (V_b6)upon
A first transistor (Q6) that receives the rise, and a transistor connected in parallel with the first transistor (Q6).
A source bias circuit including the internal thermosensitive element (2);
Base voltage (V _b7)upon
A second transistor (Q7) that receives the rise, and each of the first and second transistors (Q6, Q7)
And a constant reference base voltage (V_b3)
The third transistor (Q
3) and the first to third transistors (Q6, Q7, Q3)
Pull-up resistors (R
4) and a constant temperature function by turning on the second transistor (Q2).
A fire detection signal is taken out and the third transistor
Turn on (Q3) to extract fire detection signal by differential function
Compensated heat sensing characterized by having an output circuit
vessel. 2. The compensation type heat sensor according to claim 1, wherein
PNP transistors are used as the first to third transistors (Q6, Q7, Q3), and the emitters of the PNP transistors are connected in common to connect the pull-up resistor (R
4) A compensation type heat sensor connected to a power supply line via 4). 3. The compensation type heat sensor according to claim 1, wherein
The resistances of the resistors (R9, R10) connected in series to the external thermosensitive element (1) and the internal thermosensitive element (2) are made different from each other. When the values are the same, the first and second transistors (Q
6, Q7), the first transistor (Q6) is turned on by _changing the base voltages ( _Vb6 , _Vb7 ), and the second transistor (Q6) is turned on.
7) A compensation type heat sensor characterized by turning off.