JP2012208556A - Differential heat detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential heat detector that does not issue a fire alarm erroneously, even if a huge difference occurs between a temperature determined by a temperature measurement section when a temperature detection element is disconnected and a temperature determined by the temperature measurement section when the temperature detection element is normally connected.SOLUTION: A differential heat detector comprises: a temperature measurement section for measuring a temperature of a monitoring area based on a temperature detection element temperature of a temperature detection element whose state changes according to an ambient temperature; a CPU inner temperature measurement section for measuring a CPU inner temperature; a storage section for storing the temperature detection element temperature detected by the temperature detection element and the CPU inner temperature measured by the CPU inner temperature measurement section; and a control section that, when the temperature detection element temperature detected by the temperature measurement section is lower than the CPU inner temperature measured by the CPU inner temperature measurement section by a predetermined value or more, makes the storage section store the CPU inner temperature instead of the temperature detection element temperature, and determines a fire based on the temperature stored by the storage section.

Description

  The present invention relates to a differential heat sensor that can prevent a false alarm when the temperature detection element is normally connected after the temperature detection element such as a thermistor is disconnected.

  Conventionally, the ambient temperature of a fire detector is measured at a predetermined cycle, and a temperature gradient is calculated based on the difference between the maximum and minimum temperatures measured within a predetermined period, and the temperature gradient exceeds the threshold value. In such a case, there is known a differential heat sensor that determines that the temperature has rapidly increased and issues a fire alarm (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 07-092032

  However, in the conventional differential heat detector, when the temperature detection element is disconnected, the temperature measurement unit determines that the minimum temperature that can be detected by the temperature detection element is being measured, and then the temperature detection element is properly operated. When connected, the temperature measurement unit measures the temperature of the monitoring region detected by the temperature detection element. And, based on the difference between the temperature measured when the temperature detecting element is disconnected and the temperature measured in the normal connection state after that, a temperature gradient that does not actually occur is generated. The temperature measurement unit determines.

  In the conventional example, as described above, there is a large difference between the temperature determined by the temperature measurement unit when the temperature detection element is disconnected and the temperature determined by the temperature measurement unit when the temperature detection element is normally connected. In this case, there is a problem that it is determined that there is a fire and a fire alarm may be erroneously issued.

  Even if there is a large difference between the temperature determined by the temperature measurement unit when the temperature detection element is disconnected and the temperature determined by the temperature measurement unit when the temperature detection element is normally connected, It is an object of the present invention to provide a differential heat sensor that does not emit a fire alarm.

  The present invention includes a temperature measurement unit that measures the temperature of a monitoring area based on the temperature detection element temperature of a temperature detection element whose state changes depending on the ambient temperature, a CPU internal temperature measurement unit that measures the temperature in the CPU, and the temperature detection described above. A temperature detecting element temperature detected by the element and a CPU internal temperature measured by the CPU internal temperature measuring unit, and a temperature detecting element temperature detected by the temperature measuring unit were measured by the CPU internal temperature measuring unit. A control unit that stores the CPU internal temperature in the storage unit instead of the temperature detection element temperature when the temperature is lower than the CPU internal temperature by a predetermined value or more, and determines a fire based on the temperature stored in the storage unit; Have

  According to the present invention, when the temperature detection element is disconnected, the temperature in the CPU is stored in the storage unit instead of storing the temperature detected by the temperature measurement unit that measures the temperature of the monitoring region based on the temperature detection element. Therefore, during a non-fire, there is a large temperature difference between the temperature data stored in the storage unit when the temperature detection element is disconnected and the temperature data detected by the temperature measurement unit after the temperature detection element is normally connected. Therefore, there is an effect that a fire alarm is not erroneously issued.

It is a circuit diagram which shows the outline | summary of the differential thermal sensor 100 which is Example 1 of this invention. 3 is a flowchart showing the operation of the differential heat sensor 100.

  The modes for carrying out the invention are the following examples.

  FIG. 1 is a circuit diagram showing an outline of a differential heat detector 100 according to a first embodiment of the present invention.

  The differential heat sensor 100 includes a series circuit of a thermistor 10 and a resistor 11, a CPU 20, a transmission circuit 30, and an indicator lamp 40.

  The thermistor 10 is a temperature detection element and is provided so as to protrude outside the differential heat sensor 100, and its resistance value changes according to the ambient temperature of the differential heat sensor 100. The temperature around the differential heat sensor 100 is detected, one end of which is connected to the + B power source, one end of the resistor 11 is grounded, and the other end of the thermistor 10 and the other end of the resistor 11 are connected.

  Here, the thermistor 10 is a so-called NTC thermistor whose resistance value decreases with increasing temperature. If the thermistor 10 is a so-called PTC thermistor whose resistance value increases as the temperature rises, the disconnection state of the thermistor 10 is a state in which no current flows through the thermistor 10. Since the value is increased, that is, when the thermistor 10 is normal, the temperature is the same as when the temperature is increased. Therefore, when the thermistor 10 is disconnected, it is determined that a fire has occurred and a fire alarm is erroneously issued. .

  The CPU 20 is a so-called microcomputer, and includes a control unit 21, an A / D converter 22, a storage unit 23, and a CPU internal temperature measurement unit 24.

  The control unit 21 controls the entire CPU 20. The control unit 21 determines that the thermistor temperature (the temperature corresponding to the voltage generated at the connection point between the thermistor 10 and the resistor 11, that is, the temperature detection element temperature that is the temperature detected by the thermistor 10) is the CPU internal temperature (CPU internal When the temperature is lower than a predetermined value by a temperature measurement unit 24, the CPU temperature is used as the detected temperature instead of the thermistor temperature. The control unit 21 determines that the thermistor 10 is disconnected when the thermistor temperature is lower than the CPU internal temperature by a predetermined value or more for a predetermined time.

  The A / D converter 22 inputs a voltage (thermistor voltage) obtained by dividing the + B power source generated at the connection point between the thermistor 10 and the resistor 11 by the resistance value of the thermistor 10 and the resistance value of the resistor 11 into the digital signal. Convert.

  The memory | storage part 23 memorize | stores the value of the voltage which sampled the thermistor voltage, for example for every 3 second for 4 minutes and a half. That is, the storage unit 23 stores the thermistor temperature detected by the thermistor 10. When the thermistor temperature is lower than the CPU temperature measured by the CPU temperature measuring unit 24 by a predetermined value or more, the CPU temperature is stored instead of the thermistor temperature under the control of the control unit 21.

  The CPU internal temperature measurement unit 24 corresponds to the temperature measurement function of the CPU 20 and outputs a value corresponding to the temperature characteristics of the semiconductor constituting the CPU 20, that is, measures the internal temperature of the CPU 20 (CPU internal temperature).

  The temperature measurement unit 25 includes the thermistor 10, the resistor 11, and the A / D converter 22.

  Next, the operation of the differential heat sensor 100 will be described.

  FIG. 2 is a flowchart showing the operation of the differential heat sensor 100.

  In S1, the thermistor temperature (the temperature detected by the thermistor 10) and the CPU internal temperature (the temperature measured by the CPU 20) are acquired by the control unit 21, and in S2, whether the thermistor temperature is, for example, −30 ° C. or less. to decide. If it is determined that the thermistor temperature is higher than −30 ° C., it is determined that the thermistor 10 has not failed. At this time, if the thermistor disconnection failure flag indicating that the thermistor 10 has a disconnection failure is set, in S3, the thermistor disconnection failure flag is lowered to store that the thermistor 10 is normally connected.

  In S4, it is determined whether the thermistor temperature is lower than the CPU internal temperature by, for example, 20 ° C. or more. If the thermistor temperature is not lower than the CPU temperature by 20 ° C. or more, it is determined that the thermistor temperature is reliable (the thermistor 10 is not disconnected), and the thermistor temperature is stored in the storage unit 23 in S5.

  Then, in S6, it is checked whether or not the thermistor disconnection failure flag is set. If it is determined that the thermistor disconnection failure flag is not set, the temperature stored in the storage unit 23 (in the past four and a half minutes) is determined in S7. Whether the difference between the highest value and the lowest value before the highest value is equal to or greater than a predetermined threshold value. If it is determined that the difference between the maximum value of the temperature stored in the storage unit 23 and the minimum value of the time before the maximum value is equal to or greater than a predetermined threshold, that is, the temperature is equal to or greater than the threshold, that is, the past 4 minutes. If it is determined that the temperature has risen above the threshold value in half, a fire alarm is generated in S8.

  If it is determined in S6 that the thermistor disconnection failure flag is set, the process returns to S1.

  On the other hand, if it is determined in S2 that the thermistor temperature is −30 ° C. or lower, it is determined in S11 whether this state has continued for a predetermined time. If it is determined in S11 that the thermistor temperature is −30 ° C. or lower for a predetermined time, it is determined that the thermistor 10 is normally connected, and the process proceeds to S4. That is, even if the detected temperature of the thermistor 10 (temperature corresponding to the voltage input to the input terminal of the A / D converter 22) is lower than −30 ° C., if it does not continue for a predetermined time, Proceed to S4.

  If it is determined in S11 that the thermistor temperature is −30 ° C. or lower for a predetermined time, it is determined that the thermistor 10 is surely disconnected, and the thermistor 10 is disconnected in S12. The thermistor disconnection failure flag indicating is set, and the process proceeds to S4.

  If it is determined in S4 that the thermistor temperature is 20 ° C. or more lower than the CPU internal temperature, the CPU internal temperature is stored in the storage unit 23 instead of storing the thermistor temperature. That is, in reality, there is very little temperature difference of 20 ° C. or more even though the position where the thermistor 10 is installed is not so far from the position where the CPU 20 is installed. Therefore, it is determined that the thermistor 10 has a disconnection failure. Therefore, it is determined that the temperature corresponding to the input voltage of the A / D converter 22 is abnormal, and instead of storing the thermistor temperature, the CPU internal temperature is stored in the storage unit 23. The CPU internal temperature stored later in the storage unit 23 is prepared for use in place of the thermistor temperature.

  By doing in this way, when the thermistor 10 which constitutes a part of the differential heat sensor 100 breaks down, it is possible to prevent the occurrence of a false alarm that a fire alarm is issued even if no fire has occurred. it can. That is, when the temperature detection element is disconnected, the A / D converter 22 is grounded via the resistor 11, as if the resistance value of the thermistor 10 is increased and the thermistor voltage is decreased, and the lowest temperature that can be detected by the temperature detection element. Since the CPU internal temperature measured by the CPU internal temperature measurement unit 24 is stored in the storage unit 23 in place of the temperature measured by the temperature measurement unit 25 in the same state as when measuring the temperature, the temperature detecting element is normally operated. There is no significant difference between the temperature data detected by the temperature detection element after being connected, and therefore a fire alarm is not erroneously issued.

  In addition, when the differential heat sensor 100 is installed in the entrance of a house or the like, especially in winter, when the entrance door is opened, extremely low temperature outside air enters the entrance, When the thermistor 10 provided in the dynamic heat sensor 100 detects a low temperature and then closes the entrance door and the temperature inside the entrance rises rapidly toward room temperature, it is usually determined that a fire has occurred. However, according to the above embodiment, it is possible to prevent the occurrence of false alarms.

  In addition, when the differential heat sensor 100 is installed in the vicinity of the large refrigerator, the cold air reaches the differential heat sensor 100 by opening the door of the large refrigerator, and the thermistor temperature rapidly decreases, Thereafter, when the refrigerator door is closed, the temperature may rise rapidly toward the room temperature. In this case as well, the occurrence of false alarms can be prevented.

  In the above embodiment, other temperature detection elements may be used instead of the thermistor 10. In this case, the thermistor temperature is the temperature detection element temperature.

  In the above embodiment, both the thermistor temperature and the CPU temperature are stored in the storage unit 23, and whether or not the thermistor temperature is lower than the CPU temperature by a predetermined value or more is stored. It may be determined whether to use the CPU temperature or the CPU temperature.

  In the above embodiment, the controller 21 determines that the thermistor 10 is disconnected when the thermistor temperature is lower than the CPU internal temperature by a predetermined value or more for a predetermined time. Is the extreme temperature, it is determined that the thermistor 10 is disconnected, and therefore the disconnection of the thermistor 10 can be reliably detected.

  Furthermore, since the temperature measurement function of the control unit 21 is used as the CPU temperature measurement unit 24, a temperature measurement function that has recently been provided as a standard function in microcomputers and the like can be used, and thus the CPU temperature is measured. Therefore, there is an advantage that it is not necessary to provide a separate configuration.

DESCRIPTION OF SYMBOLS 100 ... Differential heat sensor, 10 ... Thermistor, 20 ... CPU, 21 ... Control part,
24 ... Temperature measurement part in CPU, 25 ... Temperature measurement part.

Claims (3)

A temperature measuring unit for measuring the temperature of the monitoring region based on the temperature detecting element temperature of the temperature detecting element whose state changes according to the ambient temperature;
A CPU temperature measuring unit for measuring the temperature in the CPU;
A storage unit for storing the temperature detection element temperature detected by the temperature detection element and the CPU internal temperature measured by the CPU internal temperature measurement unit;
When the temperature detection element temperature detected by the temperature measurement unit is lower than the CPU internal temperature measured by the CPU internal temperature measurement unit by a predetermined value or more, the CPU internal temperature is stored in the storage unit instead of the temperature detection element temperature. A control unit for storing and determining a fire based on the temperature stored in the storage unit;
A differential heat sensor. In claim 1,
The control unit is means for determining that the temperature detection element is disconnected when a state where the temperature detection element temperature is lower than a CPU internal temperature by a predetermined value or more continues for a predetermined time. Differential heat sensor. In claim 1 or claim 2,
The CPU internal temperature measurement unit uses a temperature measurement function of the control unit.

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