JPH0528946U - Temperature detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a temperature detecting device capable of easily determining whether an abnormal temperature rise of a motor as a heat source is generated or a thermistor is short-circuited. [Configuration] The thermistor 1 attached to the motor 2, an interface 8 for converting the resistance value of the thermistor 1 into a voltage value, and when the output voltage from the interface 8 is lower than a set voltage value, the output voltage from the interface 8 The calculating means 11 for calculating the voltage change rate and the judging means 12 for comparing the voltage change rate calculated by the calculating means 11 and judging whether the motor is overheated or the thermistor 1 is short-circuited are provided. .

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a device for detecting the temperature of a heat source such as a motor.

[0002]

[Prior Art]

 Conventionally, among this type of temperature detecting device, a device for detecting the temperature of a motor of an automobile converts a resistance value of the thermistor 1 into a voltage value by an interface 8 as shown in FIG. 4, and based on the voltage value, Whether the temperature of the motor 2 is within the normal temperature range (generally, the motor is used in the range of -40 ° C to 150 ° C) or whether the thermistor 1 is abnormal (disconnection or short circuit) The judgment means 12 is used for judgment.

That is, the magnitude relation of the output voltage values from the interface 8 is expressed as follows, and the above judgment is made by comparing the magnitude of the values.

[0004]

[Equation 1]

However, V _CC is a reference voltage.

The thermistor 1 exhibits a resistance value change as shown in FIG. 5 with respect to a temperature change, and the resistance value change is expressed by the following equation.

[0007]

[Equation 2]

Therefore, the resistance value of the thermistor 1 at the lower limit (-40 ° C.) and the upper limit (150 ° C.) of the temperature of the motor 2 is as follows.

[0009]

[Equation 3]

[0010]

[Equation 4]

As a result, the output voltage value from the interface 8 is as described above.

[0012]

[Equation 5]

[0013]

[Equation 6]

[0014] The detected voltage with respect to temperature is as shown in FIG.

[0015]

[Problems to be solved by the device]

 However, as described above, if it is determined whether the thermistor 1 is abnormal or the temperature of the motor 2 is abnormal only by comparing the output voltage values from the interface 8, it is easy to determine whether the thermistor 1 is disconnected. Although it can be judged, it was difficult to judge whether the temperature was abnormal (whether the upper limit was exceeded) or the thermistor 1 was short-circuited (see equation (1)).

The present invention is intended to solve the problems of the prior art.

[0017]

[Means for Solving the Problems]

 That is, the temperature detecting device of the present invention includes a thermistor attached to a heat source, an interface for converting the resistance value of the thermistor into a voltage, and an output from the interface when the output voltage value from the interface is lower than the set voltage value. It is determined whether the heat source is overheated or the thermistor is short by comparing the voltage change rate calculated by this calculating means with the voltage change rate calculated by this calculating means and the preset voltage change rate. It is characterized in that it is provided with a determining means for performing.

[0018]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a temperature detecting device of the present invention. In this figure, reference numeral 1 is a thermistor whose resistance value changes in accordance with a temperature change (see FIG. 5). This thermistor 1 is attached to a motor 2 as a heat source, one end of which is connected to the terminal 4 of the A / D converter 3 and the other end of which is connected to the terminal 5 of the A / D converter 3. I am doing it. A resistor R ₂ is arranged between the thermistor 1 and the terminal 4.

The power supply 6 is connected to the terminal 7 of the A / D converter 3 and also connected between the resistor R ₂ and the terminal 4 via the resistor R ₁ . The resistor R ₁ and the resistor R ₂ form an interface 8. The interface 8 converts the resistance value change of the thermistor 1 into a voltage value change (see FIG. 6).

Reference numeral 9 is a microcomputer, and this microcomputer 9 includes an A / D converter 3 and a CPU 10. The CPU 10 has a computing means 11 and a judging means 12.

Next, the function of the microcomputer 9 will be described based on the flowchart shown in FIG. That is, the microcomputer 9 reads the temperature of the motor 2 as a voltage value (temperature data) via the thermistor 1 and the interface 8 (S ₁ ), and judges the preset value A and the latest temperature data stored in advance. The comparison is made according to 12 (S ₂ ). When the latest temperature data is larger than the set value A, it is judged that the sensor is broken and a control signal is output to an external device (for example, a warning lamp).

When the latest temperature data is equal to the set value A or smaller than the set value B, the previously stored set value B and the latest temperature data are compared by the judging means 12 (S ₃ ). When the latest temperature data is equal to or smaller than the set value B, it is determined that the motor temperature is normal, the latest temperature data is stored, and the above procedure is repeated from the beginning. As the temperature data, at least n data before the latest temperature data is stored.

On the other hand, when the latest temperature data is smaller than the set value B, as shown in FIG. 3, the difference ΔV ₁ (or voltage conversion rate; ΔV ₁₎ between the latest temperature data and the nth previous temperature data. / T) is calculated by the calculating means 11 (S ₄ ). Then, the difference ΔV ₁ is compared with the predetermined value C (or the voltage change rate; c / t shown in FIG. 3) stored in advance by the judging means 12 (S ₅ ). The predetermined value C is a voltage change amount with respect to a temperature change of the motor 2 within a unit time.

When the difference ΔV ₁ is larger than the predetermined value C, it is determined that the thermistor 1 is short-circuited, and a control signal is output to an external device (for example, a warning lamp). On the other hand, when the difference ΔV ₁ is equal to or smaller than the predetermined value C, it is determined that the motor 2 is overheated and a control signal is output to an external device (for example, a motor ON / OFF switch) to The operation of the motor 2 is stopped until 2 is cooled to a predetermined temperature.

As described above, in the present embodiment, the difference ΔV ₁ (voltage change rate; ΔV ₁ / t) between the latest temperature data and the nth previous temperature data is calculated by the calculation means 11, and the difference ΔV ₁ is calculated. The determination means 12 compares the predetermined value C (preset voltage change rate; c / t) with the determination means 12 to determine whether the motor 2 is overheated or the thermistor 1 is short-circuited. Therefore, as shown in FIG. 3, the difference between the case where the thermistor 1 is short-circuited with a rapid voltage change and the case where the voltage is changed due to the temperature rise of the motor 2 becomes remarkable, and the above judgment becomes extremely easy.

[0027]

[Effect of the device]

 As will be apparent from the above description, the present invention is directed to a thermistor attached to a heat source, an interface for converting the resistance value of the thermistor into a voltage value, and an interface if the output voltage from this interface is lower than the set voltage value. And a determining means for comparing the voltage conversion rate of the output voltage from the device and the voltage change rate calculated by this calculating means to determine whether the heat source is overheated or the thermistor is short-circuited. Since it is equipped with, the abnormal temperature rise of the heat source and the short circuit of the thermistor can be very easily distinguished.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a temperature detection device showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the functions of the device.

FIG. 3 is a diagram showing a continuous voltage change state.

FIG. 4 is a schematic configuration diagram of a conventional temperature detection device.

FIG. 5 is a resistance value change state diagram of the thermistor.

FIG. 6 is a detection voltage value change state diagram corresponding to a resistance value change of the thermistor.

[Explanation of symbols]

1 ... Thermistor, 2 ... Heat source (motor), 8 ... Interface, 11 ... Arithmetic means, 12 ... Judgment means.

Claims (1)

[Scope of utility model registration request] 1. A thermistor attached to a heat source, an interface for converting a resistance value of the thermistor into a voltage value, and a rate of change of output voltage from the interface when the output voltage from the interface is lower than a set voltage value. And a determining means for comparing the voltage change rate calculated by the calculating means with a preset voltage change rate to determine whether the heat source is overheated or the thermistor is short-circuited. A temperature detecting device characterized in that