JPH0331731A - Disconnection detection method and disconnection detection circuit of thermistor temperature sensor circuit - Google Patents

Abstract

PURPOSE:To easily and rapidly check the disconnection of a thermistor temperature sensor circuit by measuring the resistance values of thermistors sensing heating bodies after a prescribed time from the start of operation. CONSTITUTION:The thermistors 1 to 3 and a dummy resistor 4 for a heater driving structure increasing its temperature by its operation are arranged in positions indicating the temperature rise similar to a body to be measured of the structure and a dummy position. Voltage is impressed from a power supply 5 for measuring the resistance values of respective thermistors 1 to 3 respectively through resistors 6 to 9. The voltage of the power supply 5 is divided by the resistance values of the resistor 6 and the thermistor 1 e.g. and supplied to an analog-digital converter 11. Even when the resistance value is high at the time of a low temperature, the disconnection of the temperature sensor circuit to which the thermistor 1 is connected can be easily and surely detected by detecting the resistance value of the thermistor 1 after a prescribed time from the start of operation by the analog-digital converter 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to temperature measurement using a thermistor as a temperature sensor used in a machinery device having a structure whose temperature increases with operation, such as an engine or a torque converter. The present invention relates to methods and devices, and particularly relates to a disconnection detection method for a thermistor temperature sensor circuit and a disconnection detection circuit for the thermistor temperature sensor circuit, which can reliably and easily confirm disconnection in the thermistor temperature sensor circuit.

[Prior Art] As is well known, in power machinery such as construction machinery that uses an engine to generate driving force and uses a torque converter to change the torque for running, it is necessary to prevent machine failure. In order to display to the operator the temperature rise of the engine cooling water and the oil used in the torque converter, the engine is equipped with a temperature measurement and display device.

These temperatures are extremely low in the cryogenic region (4) When the machine is at rest, the temperature is extremely low, but as time passes after the start of operation, the temperature rises by -1-1, and when the temperature is balanced, it drops to 1 degree Celsius.
The temperature rises to about 00 degrees.

Therefore, thermistors are used as economical sensors suitable for measuring temperatures near 100 degrees Celsius during operation.9 [Problems to be Solved by the Invention] As is well known, the resistance value of thermistors is Although it varies depending on the composition of the hill, the resistance value at zero degrees is generally about 20 times greater than the resistance value at 100 degrees, and the temperature coefficient of resistance is =t near zero degrees, and the temperature coefficient is small near 100 degrees.

If you try to judge the resistance value near 100 degrees using an economical circuit using υC, you will not be able to measure and judge the change in resistance near zero degrees, and therefore you will find out whether the thermistor circuit is disconnected or not. It was difficult to judge.

It would be nice to have a thermistor whose temperature resistance coefficient does not become extremely large even at low temperatures, but it is difficult to develop a thermistor with such characteristics, and by connecting a resistor in parallel with the thermistor, the equivalent resistance at low temperatures can be reduced. Lowering the value also makes it more difficult to determine if the thermistor itself is disconnected.

Therefore, an object of the present invention is to provide a disconnection detection method for a thermistor temperature sensor circuit and a disconnection detection circuit for the thermistor temperature sensor circuit, which can easily and quickly determine whether or not the thermistor circuit is disconnected.

[Means for Solving the Problems] In order to achieve the above object, in the disconnection detection method and disconnection detection circuit for a thermistor temperature sensor circuit according to the present invention, the first invention provides a method for detecting a disconnection in a thermistor temperature sensor circuit and a disconnection detection circuit according to the present invention. In a temperature measuring circuit using a provided thermistor as a sensor, disconnection of the sensor circuit is detected by measuring the resistance value of the sensor circuit after a predetermined period of time from the start of the first operation. In a second invention, in a temperature measurement circuit using a thermistor as a sensor provided in a structure whose temperature increases due to operation, there is provided a thermistor for measuring the temperature of the target structure, and a dummy resistor having a temperature coefficient similar to that of the thermistor. , a comparison judgment circuit that measures and compares the resistance value of the dummy resistor and the resistance value of the thermistor, and a timer circuit.

In a third invention, in a temperature measurement circuit that uses a thermistor as a sensor provided in a structure whose temperature increases due to operation, the thermistor that measures the temperature of the target structure and a predetermined temperature sensor that measures the temperature of the target structure and a The device includes a memory that stores a resistance value that is to be reached after a certain time, a determination circuit that measures and compares the value read from the memory with the resistance value of the thermistor, and a timer circuit.

In a fourth invention, in a temperature measurement circuit using a thermistor as a sensor provided in a structure whose temperature increases due to operation, a thermistor that measures the temperature of the target structure and a thermistor installed in the measurement circuit at the start of operation of the target structure are provided. The device includes a memory device that stores a measured value of the thermistor resistance, a determination circuit that measures and compares the value read from the memory device and the resistance value of the thermistor, and a timer circuit. Furthermore, in a fifth invention, in a temperature measurement circuit using as sensors thermistors provided at at least two places on an operating system whose temperature increases due to operation, a circuit for comparing output values of the plurality of temperature sensors and a timer circuit are provided. By measuring and comparing the resistance values of the plurality of sensor circuits after a predetermined period of time from the start of operation, a disconnection in any one of the plurality of sensor circuits is detected.

[Operation] According to the present invention, in a temperature measuring circuit that uses a thermistor as a sensor for a heat generating drive structure whose temperature increases due to operation, the temperature of the sensor circuit is measured by measuring the resistance value of the thermistor after a predetermined time from the start of operation. Since disconnection is detected, it is possible to easily and reliably detect disconnection of the thermistor temperature sensor circuit even if the resistance is high at low temperatures, which is an excellent effect.

[Example] Embodiments of the present invention will be described in detail with reference to the drawings.

1 to 4 show characteristic diagrams, FIGS. 5 and 6 show block diagrams, and FIG. 7 shows a simple operation flow.

FIG. 1(a) shows an example of the temperature characteristics of a thermistor, where the horizontal axis shows the time since the structure started operating, and the vertical axis shows the temperature rise and the temperature change associated with the temperature rise. It shows the resistance value increase characteristic of a thermistor, which is a sensor that measures temperature changes in a structure, with respect to temperature rise.

That is, the curve a shows the temperature increase over time, and the curve a shows the change in the resistance value of the thermistor as the temperature rises. Point t5 indicates the resistance value determination time after a predetermined time has elapsed after the start of operation of the structure based on the present invention.

FIG. 1(b) shows the disconnection determination criteria at time t shown in FIG. 1(a).

In other words, it is sufficient if the measured value at time t falls within α between curve a and curve a2 in the resistance temperature characteristic, but if the thermistor or sensor circuit is disconnected, it may show a high resistance as shown in curve a3. become.

Next, an embodiment of a disconnection detection circuit for a thermistor temperature sensor circuit according to the present invention will be described with reference to the block diagram shown in FIG.

The figure shows an example of a circuit when the present invention is applied to construction machinery. In the figure, 1 is for measuring engine cooling water temperature, 2 is for measuring torque converter oil temperature, and 3 is for working machine system hydraulic oil. Thermistors for temperature measurement are shown, and 4 is a resistor having the same characteristics as each thermistor, which is mounted as a dummy at a predetermined location. That is, for example, a thermistor having the same characteristics as those for measuring each part is attached to a part of the structure exhibiting a temperature rise similar to that of the object to be measured.

5 is an applied power source for measuring the resistance value of each thermistor, and the applied power source 5 is applied to each thermistor 1.2.3 and dummy resistor 4 via a resistor 6.7.8.9. Applying voltage.

The voltage of the applied power source 5 is divided by the resistance values of the resistor 6 and thermistor 1 and supplied to the analog-to-digital converter 11 . Therefore, when the temperature is low and the resistance value of the thermistor is large, a large voltage is supplied to the analog-to-digital converter 11, and if the sensor circuit is not disconnected, the voltage supplied to the analog-to-digital converter becomes smaller as the temperature rises.

Similarly to the above, the terminal voltage of the thermistor 2 is supplied to the analog-to-digital converter 12, and when the temperature is low and the resistance value of the thermistor 2 is large, a large voltage is supplied to the analog-to-digital converter 12, and if the sensor circuit is not disconnected. As the temperature increases, the voltage supplied to the analog-to-digital converter decreases.

Similarly, the terminal voltage of the thermistor 3 is supplied to the analog-to-digital converter 13, and when the temperature is low and the resistance value of the thermistor 3 is large, a large voltage ((1) is supplied to the analog-to-digital converter 13 and the 5 sensor circuit is disconnected. Otherwise, as the temperature increases, the voltage supplied to the analog-to-digital converter will decrease.

Similarly to the above, the terminal voltage of the dummy resistor 4 is supplied to the analog-to-digital converter 14, and when the temperature is low and the resistance value of the thermistor 4 is large, a large voltage is supplied to the analog-to-digital converter 14, causing the sensor circuit to break. Otherwise, as the temperature increases, the voltage supplied to the analog-to-digital converter will decrease.

The terminal voltage values from each thermistor and the dummy resistor supplied to the analog-to-digital converter 4 input to each analog-to-digital converter, 11, 12, and 13, are converted from analog values to digital values and are converted to digital values by the computer 5.
The measured values are compared and evaluated.

That is, the measured values are evaluated according to the flow shown in FIG.

In FIG. 7, when the flow is started, the measured values of the four thermistors digitized in the first step are input. When a timer provided inside the computer 5 reaches time L indicating that a predetermined time has elapsed since the start of the operation of the mechanism, in a third step, the voltage value indicating the resistance value of the first thermistor and the dummy thermistor are measured. A voltage value indicating a resistance value is compared.

If it is determined that there is an abnormality in the fourth step, an alarm is issued, and if there is no abnormality, the flow returns to the beginning and the third step knob shows the voltage value indicating the resistance value of the second thermistor and the resistance value of the thermistor as a dummy. is compared with the voltage value indicating .

If it is determined that there is an abnormality in the 4th step, a W signal will be issued, and if there is no abnormality, the flow will return to the beginning and the voltage value indicating the resistance value of the 3rd thermistor will be displayed using the 3rd step knob. A voltage value indicating a resistance value is compared.

If it is determined that there is an abnormality in the 71st step, an alarm will be issued,
If there is an abnormality, return to the beginning of the flow and repeat the operation of this flow.

In the second [A, bd is the temperature characteristic of the dummy attachment part, b
is the temperature characteristic of engine cooling water, a.

indicates the resistance value-temperature characteristic of the dummy thermistor, and ae indicates the resistance value-temperature characteristic of the thermistor for measuring the temperature of engine cooling water. If the deviation width of the temperature measurement comparison of the resistance value is larger than α, the one with the larger resistance value is determined to be a disconnection. By sequentially comparing the 0-wire determination for three thermistors, a disconnection is clearly determined. be able to.

Next, another embodiment based on the present invention will be described.

Fig. 6 shows an example of a circuit when the present invention is applied to construction machinery. In Fig. 9, 1 is for measuring engine cooling water temperature, 2 is for measuring torque converter oil temperature, and 3 is for working machine system. Each thermistor is shown for measuring the temperature of the hydraulic fluid.

Reference numeral 5 denotes an application power source for measuring the resistance value of each thermistor, and the application power source 5 applies a voltage to each thermistor 1°2.3 via a resistor 6.7.8.

The voltage of the power supply 5 is divided by the resistance values of the resistor 6 and thermistor 1 and supplied to the analog-to-digital converter 11 . Therefore, when the temperature is low and the resistance value of the thermistor is large, a large voltage is supplied to the analog-to-digital converter 11, and if the sensor circuit is not disconnected, the voltage supplied to the analog-to-digital converter becomes smaller as the temperature rises.

'' Similar to the two-legged case, the terminal voltage of the thermistor 2 is supplied to the analog-to-digital converter 12, and when the temperature is low and the resistance value of the thermistor 2 is large, a large voltage is supplied to the analog-to-digital converter 12, and the sensor circuit is disconnected. Otherwise, as the temperature increases, the voltage supplied to the analog-to-digital converter will decrease.

Similarly, the terminal voltage of the thermistor 3 is supplied to the analog-to-digital converter 13, and when the temperature is low and the resistance value of the thermistor 3 is large, a large voltage is supplied to the analog-to-digital converter 13, and if the sensor circuit is not disconnected, As the temperature increases, the voltage supplied to the analog-to-digital converter decreases.

The voltage from each thermistor input to each analog-to-digital converter 11, 12, 13 is digitally converted and input to the computer 15.

In FIG. 6, the computer 15 is made to record in advance a voltage value corresponding to the resistance value that the construction machine is supposed to reach after a predetermined period of time. As previously mentioned, the digitized voltage values representing the measured resistance of each thermistor are input into the computer and the input values are compared with the recorded values.

In FIG. 3, S indicates the above-mentioned recorded value, and a indicates the resistance value temperature characteristic of the thermistor for measuring the temperature of engine cooling water at one time t.

The deviation width when comparing the recorded value and the input resistance value is α
If it is larger than , it is determined that the resistance value is disconnected.

Another embodiment will be described. That is, in FIGS. 3 and 6 described above, the voltage value a indicates the resistance value of the thermistor at the time when the structure starts operating.

is input into the computer 5 and stored.

According to the flow shown in FIG. 7, a timer installed in the computer indicates the passage of a predetermined time and starts the comparison circuit of the computer 5, and in the third step of the flow, the measured value a of the thermistor and the Memory value a. Compare and evaluate.

The voltage value a indicating the resistance value of the thermistor at the start of operation is the stored value a. If there is no change, the computer 5 determines that there is a disconnection.

inform.

Next, other embodiments will be described. When the flow is started as shown in FIG. 7 in FIG. 6 and explained above, each measurement value of the three thermistors digitized in the first step is input, and each measurement value corresponds to the respective temperature rise. The temperature rise characteristics per hour of the body are different, as shown in Fig. 4. That is, bt is the temperature characteristic of torque converter oil, b.

is the temperature characteristic of engine cooling water. Therefore, the resistance value-temperature characteristic of the thermistor for measuring the temperature of torque converter oil is as shown in a, and the resistance value-temperature characteristic of the thermistor for measuring the temperature of the engine cooling water is as shown in a8. 3 in FIG. 7 after a predetermined time t has elapsed from the start of operation of the mechanism.
If the deviation width obtained by comparing the resistance values of the two misters and comparing the temperature measurement of the resistance values in each step is larger than β shown in Fig. 4, the computer 5 determines that the wire with the larger resistance value is broken and issues an alarm. One judgment is made for three thermistors, one for engine cooling water temperature measurement, one for torque converter oil temperature measurement, and one for work equipment system hydraulic oil temperature measurement, according to the flowchart shown in Figure 7, according to a predetermined program. By comparing the results with each other, it is possible to clearly determine a disconnection. Furthermore, it is also possible to determine that the thermistor is not broken but is in an abnormal state by mutually comparing the resistance values.

As explained above, when it is determined that there is a disconnection or an abnormality, the computer 15 sends a signal to the alarm circuit 16, and as a result, the alarm device 16 notifies the abnormality.

[Effects of the Invention] As explained above, according to the present invention, in a temperature measurement circuit using a thermistor as a sensor for a heat-generating elliptical body whose temperature increases due to operation, the resistance value of the thermistor is measured after a predetermined time from the start of operation. Since the disconnection of the sensor circuit is detected by doing this, it is possible to easily and reliably detect the disconnection of the thermistor temperature sensor circuit even if the resistance is high at low temperatures, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment according to the present invention. 2nd [21 is another explanatory diagram of the embodiment shown in FIG. 1. Figure 3 is another real Bf! , an illustration of an example. FIG. 1 is an explanatory diagram of another embodiment. FIG. 5 is a circuit diagram of an embodiment according to the present invention. FIG. 6 is a circuit diagram of another embodiment according to the present invention. Fig. 7 is an operation flow diagram of an embodiment according to the present invention 9 Thermistor 2... Thermistor 3... Thermistor 1... Thermistor 5 - Power supply 6 - Resistor 7... Resistor 8 - Resistor () - Resistor Body 11 Analog-digital converter 12-ana 1 cog-digital recon bark 13...7'
1'1G digital converter 1, 1...Analog to digital converter 15/Computer 16...Alarm circuit

Claims (1)

[Scope of Claims] 1. In a temperature measurement circuit whose sensor is a thermistor provided in a structure whose temperature increases due to operation, the sensor circuit is measured by measuring the resistance value of the sensor circuit after a predetermined period of time from the start of operation. 1. A method for detecting disconnection in a thermistor temperature sensor circuit, characterized in that a disconnection in a thermistor temperature sensor circuit is detected. 2. In a temperature measurement circuit whose sensor is a thermistor installed in a structure whose temperature increases due to operation, a thermistor that measures the temperature of the target structure, a dummy resistor having a temperature coefficient similar to that of the thermistor, and the dummy 1. A disconnection detection circuit for a thermistor temperature sensor circuit, comprising a comparison judgment circuit that measures and compares the resistance value of a resistor and the resistance value of the thermistor, and a timer circuit. 3. In a temperature measurement circuit whose sensor is a thermistor installed in a structure whose temperature increases due to operation, a thermistor that measures the temperature of the target structure and a predetermined period of time after the target structure starts operating. a memory device that stores a resistance value that is to be reached later; a determination circuit that measures and compares the value read from the memory device and the resistance value of the thermistor;
A disconnection detection circuit for a thermistor temperature sensor circuit, comprising a timer circuit. 4. In a temperature measurement circuit whose sensor is a thermistor installed in a structure whose temperature increases due to operation, a thermistor that measures the temperature of the target structure and a thermistor resistor installed in the measurement circuit at the start of operation of the target structure Disconnection detection in a thermistor temperature sensor circuit, comprising: a memory device that stores a measured value of the temperature sensor; a determination circuit that measures and compares a value read from the memory device with a resistance value of the thermistor; and a timer circuit. circuit. 5. In a temperature measurement circuit using as sensors thermistors provided at at least two locations on an operating system whose temperature increases due to operation, the temperature measurement circuit includes a circuit for comparing the output values of the plurality of temperature sensors and a timer circuit, A thermistor temperature sensor circuit, characterized in that a disconnection of any one of the plurality of sensor circuits is detected by measuring and comparing the resistance values of the plurality of sensor circuits after a predetermined period of time from the start. Disconnection detection method.