JP7043339B2 - Temperature measuring device and temperature measuring method - Google Patents

Description

The present invention relates to a temperature measuring device and a temperature measuring method.

Conventionally, in a vehicle such as an automobile, the outside air, the environmental temperature in the vehicle interior, and the temperature of parts such as an engine and electronic parts are measured, and necessary control is performed according to the temperature measurement result. However, in a vehicle, since the environmental change is large, the temperature measurement result may vary greatly due to the influence of various noises. Therefore, for example, a technique has been proposed in which the temperature inside a vehicle is measured by a plurality of temperature elements, and even if one of the measured values changes significantly, it is ignored to suppress the influence of noise (for example, Patent Document 1). reference).

In recent years, semiconductor parts have been used in drive units of electric vehicles and the like. Semiconductor parts generally generate heat due to overcurrent or the like and may fail. Therefore, for example, there is a device that constantly monitors the temperature of a semiconductor component and shuts off the energization when the threshold temperature is exceeded.

Japanese Unexamined Patent Publication No. 2006-11302

By the way, in the above-mentioned prior art, a plurality of temperature sensors are required for one semiconductor component, and a plurality of A / D converters may have to be prepared according to a plurality of temperature sensors. Therefore, in terms of cost and size. There is room for improvement.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a temperature measuring device and a temperature measuring method capable of accurately measuring the temperature of an object to be measured at low cost.

In order to achieve the above object, the temperature measuring device according to the present invention includes a temperature measuring means for measuring the temperature of the object to be measured and an acquisition means for acquiring the measured temperature of the object to be measured at predetermined time intervals. And the determination means for determining whether or not the absolute value of the difference between the acquired current temperature of the object to be measured and the previous temperature of the object to be measured is equal to or less than the threshold value, and the difference based on the determination result by the determination means. When the absolute value of is equal to or less than the threshold value, the output means for outputting the temperature of the object to be measured this time and the holding means for holding the temperature of the object to be measured this time as the temperature of the object to be measured last time. The threshold value is characterized by being the maximum value of the temperature change of the measured object calculated based on at least the calorific value, the thermal resistance, and the heat capacity of the measured object in the predetermined time.

In the temperature measuring device, the threshold value is R * P * {1-exp (1), where P is the calorific value of the object to be measured, R is the thermal resistance, C is the heat capacity, and ts is the predetermined time. -Ts / (C * R))}.

In the temperature measuring device, the object to be measured is a semiconductor component mounted on a vehicle and driven by energization, and the temperature measuring device further measures an energizing current when the object to be measured is in an energized state. When the current measuring means to be measured and the energization current are outside the allowable energization current range of the object to be measured and the temperature of the object to be measured exceeds the permissible temperature of the object to be measured, the energization of the object to be measured is energized. A current interrupting means for interrupting is provided, and the threshold value is the temperature of the object to be measured, which is calculated based on at least the thermal resistance, the heat capacity, the electric resistance, and the energization current of the object to be measured in the predetermined time. It shall be the maximum value of change.

In the temperature measuring device, the threshold value is R *, where R is the thermal resistance of the object to be measured, _C is the heat capacity, RL is the electrical resistance, I is the energizing current, and ts is the predetermined time. I ² * _RL * {1-exp (-ts / (C * R))}.

In order to achieve the above object, the temperature measuring method according to the present invention includes a temperature measuring step of measuring the temperature of the object to be measured and an acquisition step of acquiring the measured temperature of the object to be measured at predetermined time intervals. And the determination step of determining whether or not the absolute value of the difference between the acquired current temperature of the object to be measured and the previous temperature of the object to be measured is equal to or less than the threshold value, and the difference based on the determination result by the determination step. When the absolute value of is equal to or less than the threshold value, the output step of outputting the temperature of the object to be measured this time and the holding step of holding the temperature of the object to be measured this time as the temperature of the object to be measured last time in the holding means. The threshold value is the maximum value of the temperature change of the measured object calculated based on at least the calorific value, the thermal resistance, and the heat capacity of the measured object in the predetermined time. ..

According to the temperature measuring device and the temperature measuring method according to the present invention, there is an effect that the temperature of the object to be measured can be measured accurately at low cost.

FIG. 1 is a block diagram showing a schematic configuration of a temperature measuring device according to a first embodiment. FIG. 2 is a flowchart showing an example of a temperature measurement process executed by the temperature measuring device according to the first embodiment. FIG. 3 is a diagram showing an example of heat generation temperature characteristics of the object to be measured according to the first embodiment. FIG. 4 is a diagram showing an example of heat dissipation temperature characteristics of the object to be measured according to the first embodiment. FIG. 5 is a diagram showing an example of the maximum value of the heat generation temperature of the object to be measured according to the first embodiment. FIG. 6 is a diagram showing an example of the maximum value of the heat dissipation temperature of the object to be measured according to the first embodiment. FIG. 7 is a block diagram showing a schematic configuration of the temperature measuring device according to the second embodiment. FIG. 8 is a flowchart showing an example of the temperature measurement process executed by the temperature measuring device according to the second embodiment. FIG. 9 is a diagram showing an example of the signal acquisition timing of the CPU in the first and second embodiments.

Hereinafter, embodiments of the temperature measuring device and the temperature measuring method according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to the present embodiment. Further, the components in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. In addition, the components in the following embodiments can be omitted, replaced, or modified in various ways without departing from the gist of the invention.

[First Embodiment]
The temperature measuring device 1 according to the first embodiment of the present invention is mounted on a vehicle such as an automobile, for example. The temperature measuring device 1 measures the temperature of the object to be measured 3 (hereinafter, also referred to as “the temperature of the object to be measured”), and outputs temperature data corresponding to the measured temperature of the object to be measured to the outside. Here, the object 3 to be measured is a temperature measurement object, and includes, for example, outside air, indoor air, engine parts, electronic parts, and the like. The temperature measuring device 1 is connected to, for example, an ECU (Electronic Control Unit) mounted on a vehicle, and outputs temperature data to the ECU. As shown in FIG. 1, the temperature measuring device 1 includes a temperature sensor 11, an I / F circuit 13, an analog filter 15, an A / D converter 17, and a CPU 19.

The temperature sensor 11 is an example of a temperature measuring means, and is placed in contact with or in the vicinity of the measured object 3 to measure the temperature of the measured object 3. The temperature sensor 11 is roughly classified into a contact type and a non-contact type, but any of them may be used. When the temperature sensor 11 is a contact type, it is arranged in contact with the object to be measured 3. Examples of the contact type temperature sensor include a thermocouple, a thermistor, and the like. When the temperature sensor 11 is a non-contact type, it is arranged in the vicinity of the object to be measured 3. Some non-contact temperature sensors measure infrared rays emitted from the object 3 to be measured and measure the temperature from the amount of infrared rays. The temperature sensor 11 is electrically connected to the I / F circuit 13 and outputs a temperature signal corresponding to the temperature of the object to be measured. This temperature signal may be, for example, a voltage value.

The I / F circuit 13 is an interface circuit that inputs a temperature signal from the temperature sensor 11 and converts the temperature signal into a format that can be read by the CPU 19. The I / F circuit 13 is electrically connected to the analog filter 15 and outputs the converted temperature signal to the analog filter 15.

The analog filter 15 is a filter circuit for inputting a temperature signal from the I / F circuit 13 and reducing the influence of noise contained in the temperature signal. The analog filter 15 removes unnecessary frequency components in, for example, a temperature signal. The analog filter 15 is electrically connected to the A / D converter 17, and outputs a temperature signal from which unnecessary frequency components have been removed to the A / D converter 17.

The A / D converter 17 is a conversion circuit that inputs a temperature signal from the analog filter 15 and converts the temperature signal from an analog signal to a digital signal. The A / D converter 17 is electrically connected to the CPU 19, converts a temperature signal into temperature data readable by the CPU 19, and outputs the temperature signal. Although the A / D converter 17 of the present embodiment is configured separately from the CPU 19, it may be integrally configured with the CPU 19.

The CPU 19 is a control unit that performs predetermined processing based on the temperature data input from the A / D converter 17. The CPU 19 is, for example, a central processing unit such as an MPU (Micro Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), a ROM (ReadOnMemory) Including electronic circuits mainly composed of well-known microcomputers.

The CPU 19 has a function as an acquisition means for acquiring temperature data corresponding to the measured object temperature of the object 3 to be measured every predetermined time (hereinafter, also referred to as “sampling cycle time”). Specifically, as shown in FIG. 9, the CPU 19 acquires temperature data from the temperature data input from the A / D converter 17 for each sampling cycle in which the sampling cycle time is ts [sec].

The CPU 19 has a function as a determination means for determining whether or not the absolute value of the difference ΔT between the acquired current temperature data Now and the previous temperature data Tbefore is equal to or less than the threshold value ΔTmax. For example, the CPU 19 stores the current temperature data Tnow on one side and the previous temperature data Tbefore on the other side for two data addresses, and sets the absolute value of the difference ΔT between the temperature data Tnow and the temperature data Tbefore. Calculate. The CPU 19 compares the absolute value of the difference ΔT with the threshold value ΔTmax previously held in the ROM or the like, and determines whether or not the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax.

The CPU 19 has a function as an output means for outputting the current temperature data Now when the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax based on the determination result by the above-mentioned function as the determination means. Specifically, when the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax, the CPU 19 outputs the temperature data Tnow to an external device, for example, an ECU or the like. Further, the CPU 19 has a function as a holding means for holding the current temperature data Tnow as the previous temperature data Tbefore. Specifically, the CPU 19 replaces the value of the data address in which the temperature data Tbefore is stored with the temperature data Tnow.

The threshold value ΔTmax of the present embodiment is the maximum value of the temperature change of the measured object 3 calculated based on the calorific value, the thermal resistance, and the heat capacity of the measured object 3 in the sampling cycle time. Specifically, the threshold value ΔTmax is P [W] for the calorific value of the object 3 to be measured, R [° C / W] for the thermal resistance, C [J / ° C] for the heat capacity, and ts [sec] for the sampling cycle time. Then, it is expressed by the following equation (1).
ΔTmax = R * P * {1-exp (-ts / (C * R))} ... (1)

As shown in FIGS. 3 to 6, the object 3 to be measured has thermal characteristics based on a calorific value P, a thermal resistance R, and a heat capacity C. The thermal characteristics shown in FIGS. 3 and 5 are heat generation characteristics when the object to be measured 3 generates heat, and the temperature of the object to be measured 3 rises from the ambient temperature Ta [° C.] to the upper limit temperature (Ta + R * P) [° C.]. This is an example of the case. The heat generation characteristics shown are represented by the following formula (2).
T = Ta + R * P * {1-exp (-t / (C * R))} ... (2)
Here, the temperature change ΔT (ct) after the lapse of time ct [sec] from the start of heat generation of the object 3 to be measured is expressed by the following equation (3).
ΔT (tc) = R * P * {1-exp (-tc / (C * R))} ... (3)
Therefore, the maximum value of the temperature change for each sampling cycle of the object 3 to be measured from the start of heat generation can be expressed by the above equation (1).
The thermal characteristics shown in FIGS. 4 and 6 are heat dissipation characteristics when heat is released from the object 3 to be measured, and the temperature of the object 3 to be measured is from the upper limit temperature (Ta + R * P) [° C] to the ambient temperature Ta [° C]. This is an example of a descent. The illustrated heat dissipation characteristics are represented by the following equation (4).
T = Ta + R * P * exp (-t / (C * R)) ... (4)
Here, the temperature change ΔT (tc) after the lapse of time ct from the start of heat dissipation of the object 3 to be measured is expressed by the following equation (5).
ΔT (tc) = R * P * {1-exp (-tc / (C * R))} ... (5)
Therefore, the maximum value of the temperature change for each sampling cycle of the object 3 to be measured after heat dissipation from the upper limit temperature can be expressed by the above equation (1).

Next, the temperature measurement operation in the temperature measuring device 1 will be described with reference to FIG.

First, in step S1, the temperature of the object to be measured 3 is measured. In step S1, for example, after the vehicle is started (for example, the ignition switch is turned on), the temperature measurement operation of the object 3 to be measured by the temperature sensor 11 is repeated.

Next, in step S2, the CPU 19 acquires the temperature data of the object to be measured 3 for each sampling cycle.

Next, in step S3, the CPU 19 substitutes the initial temperature data Ti (i = 0) among the temperature data acquired in step S2 into the previous temperature data Tbefore.

Next, in step S4, the CPU 19 substitutes the current temperature data Ti (i = i + 1) into the current temperature data Tnow.

Next, in step S5, the CPU 19 compares the absolute value of the difference ΔT between the current temperature data Now and the previous temperature data Tbefore with the threshold value ΔTmax, and determines whether or not the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax. do. As a result of this determination, if the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax, the process proceeds to step S6. On the other hand, when the absolute value of the difference ΔT exceeds the threshold value ΔTmax, the process proceeds to step S9.

Next, in step S6, the CPU 19 outputs the current temperature data Now.

Next, in step S7, the CPU 19 substitutes the current temperature data Now into the previous temperature data Tbefore.

Next, in step S8, the CPU 19 determines whether or not the measurement is completed. For example, the CPU 19 determines whether or not the vehicle has stopped (for example, the ignition switch is turned off), executes the steps after step S4 if the vehicle has not stopped, and performs this process if the vehicle has not stopped. finish.

In step S9, the CPU 19 discards the current temperature data Now and proceeds to step S8. For example, in step S9, the CPU 19 deletes the value of the data address in which the current temperature data Now is stored.

In the temperature measuring device 1 described above, the CPU 19 acquires the temperature of the object to be measured measured by the temperature sensor 11 for each sampling cycle, and the difference between the temperature of the object to be measured (Tnow) and the temperature of the object to be measured (Tbefore). When the absolute value is equal to or less than the threshold value ΔTmax, the temperature of the object to be measured this time is output, and the temperature of the object to be measured this time is held as the temperature of the object to be measured last time. The threshold value ΔTmax is the maximum value of the temperature change of the measured object 3 calculated based on at least the calorific value P, the thermal resistance R, and the heat capacity C of the measured object 3 in the sampling cycle time ts. According to the above configuration, when the temperature of the object to be measured that is measured in a certain cycle changes beyond the threshold value ΔTmax due to the influence of noise, the changed object temperature to be measured is not used and only the temperature of the object to be measured that is equal to or less than the threshold value ΔTmax is used. Can be used. As a result, even if there is an influence of noise at the time of temperature measurement, it is possible to measure with high accuracy. Further, since it is not necessary to add various functional parts for reducing the influence of noise, the temperature measurement accuracy can be improved at low cost. When the conventional temperature measuring device is affected by noise, for example, the temperature signal itself output from the temperature sensor or the analog signal output from the I / F circuit changes. If this change cannot be removed by the noise filter, a signal with a large change like the waveform on the right side of the graph shown in FIG. 9 is input to the CPU 19. Even if smoothing is attempted by moving average processing or the like in the CPU 19, it is difficult to remove the noise from the signal changed by the noise. Therefore, if the absolute value of the difference between the temperature of the object to be measured this time and the temperature of the object to be measured last time exceeds the threshold value ΔTmax, it is judged that the temperature has changed significantly due to noise, and the temperature of the object to be measured this time is discarded. The accuracy can be improved.

Further, the temperature measuring method of the temperature measuring device 1 is a step of acquiring the temperature of the object to be measured measured by the temperature sensor 11 for each sampling cycle, and the difference between the temperature of the object to be measured (Tnow) and the temperature of the object to be measured (Tbefore). When the absolute value of is equal to or less than the threshold value ΔTmax, a step of outputting the temperature of the object to be measured this time and a step of holding the temperature of the object to be measured this time as the temperature of the object to be measured last time are included. The threshold value ΔTmax is the maximum value of the temperature change of the measured object 3 calculated based on at least the calorific value P, the thermal resistance R, and the heat capacity C of the measured object 3 in the sampling cycle time ts. As a result, the same effect as that of the temperature measuring device 1 can be obtained.

Further, the temperature measuring device 1 has the above equation (1) when the threshold value ΔTmax is P for the calorific value of the object 3 to be measured, R for the thermal resistance, C for the heat capacity, and ts for the sampling cycle time. Thereby, the threshold value ΔTmax can be calculated based on at least the calorific value P, the thermal resistance R, and the heat capacity C of the object 3 to be measured at the sampling cycle time ts.

[Second Embodiment]
Next, the temperature measuring device 1A according to the second embodiment of the present invention will be described with reference to FIGS. 7 and 8. The temperature measuring device 1A differs from the temperature measuring device 1 in that a current measuring circuit for measuring the energization current I of the object to be measured 3A is added to the temperature measuring device 1. The object to be measured 3A of the present embodiment is composed of, for example, a semiconductor component (for example, a semiconductor switch or the like) mounted on a vehicle and driven by energization. In the following, the same components as those in the first embodiment described above will be designated by a common reference numeral, and the common configurations, actions, and effects will be omitted as much as possible.

The temperature measuring device 1A includes a current sensor 21, an I / F circuit 13A, an analog filter 15A, an A / D converter 17A, and a CPU 19A, in addition to the configuration of the temperature measuring device 1 described above. .. The current sensor 21, the I / F circuit 13A, the analog filter 15A, and the A / D converter 17A constitute a current measurement circuit.

The current sensor 21 is an example of a current measuring means, and measures an energized current I when the object to be measured 3A is in an energized state. The current sensor 21 is, for example, a shunt resistor connected in series with an electric wire 31 connected to the object to be measured 3A. The current sensor 21 may be a CT (current transformer) type or a Hall element type configured so as to sandwich the electric wire 31. The current sensor 21 is electrically connected to the I / F circuit 13A and outputs a current value signal corresponding to the energization current I to the I / F circuit 13A.

The I / F circuit 13A is an interface circuit that inputs a current value signal from the current sensor 21 and converts the current value signal into a format that can be read by the CPU 19A. The I / F circuit 13 is electrically connected to the analog filter 15A and outputs the converted current value signal to the analog filter 15A.

The analog filter 15A is a filter circuit for inputting a current value signal from the I / F circuit 13A and reducing noise included in the current value signal. The analog filter 15A removes unnecessary frequency components in, for example, a current value signal. The analog filter 15A is electrically connected to the A / D converter 17A, and outputs a current value signal from which unnecessary frequency components have been removed to the A / D converter 17A.

The A / D converter 17A is a conversion circuit that inputs a current value signal from the analog filter 15A and converts the current value signal from an analog signal to a digital signal. The A / D converter 17A is electrically connected to the CPU 19, converts a current value signal into current value data readable by the CPU 19, and outputs the current value signal. Although the A / D converter 17A of the present embodiment is configured separately from the CPU 19A, it may be integrally configured with the CPU 19A. Further, the A / D converter 17 may also be integrally configured with the CPU 19A.

The CPU 19A is a control unit that performs predetermined processing based on the temperature data input from the A / D converter 17 and the current value data input from the A / D converter 17A. The CPU 19A has the following functions in addition to the various functions of the CPU 19 described above. That is, in the CPU 19A, when the absolute value of the difference ΔT between the current temperature data Now and the previous temperature data Tbefore exceeds the threshold value ΔTmax, the current value data corresponding to the energization current I is the permissible energization current of the object 3A to be measured. It has a function as another determination means for determining whether or not it is out of the range of. Here, the range of the allowable energizing current of the object to be measured 3A is, for example, the range of the rated current of the semiconductor switch when the object to be measured 3A is a semiconductor switch. Further, the CPU 19A has a function as a current cutoff means for cutting off the current supply of the object to be measured 3A when the current value data is out of the allowable current current range. Further, the CPU 19A has a function as a calculation means for calculating the threshold value ΔTmax. The threshold value ΔTmax of the present embodiment is the maximum value of the temperature change of the measured object 3A calculated based on the thermal resistance, heat capacity, electric resistance, and energization current of the measured object 3A during the sampling cycle time. Specifically, the threshold value ΔTmax is expressed by the following equation (6), where R is the thermal resistance of the object 3A to be measured, C is the heat capacity, I is the energization current, and ts is the sampling cycle time. Equation (6) replaces the calorific value P (= I ² * _RL ) in the above equation (1) with an equation based on the energization current I.
ΔTmax = R * I ² * _RL * {1-exp (-ts / (C * R))} ... (6)

The CPU 19A compares the current temperature data Tnow with the predetermined maximum permissible temperature data Tth of the object to be measured 3A, and determines whether or not the current temperature data Tnow exceeds the maximum permissible temperature data Tth. It has a function as a determination means. Here, the maximum allowable temperature data Tth of the object to be measured 3A is, for example, an upper limit of the operating temperature range (allowable temperature range) of the semiconductor switch when the object to be measured 3A is a semiconductor switch.

Next, the temperature measurement and the current value measurement operation in the temperature measuring device 1A will be described with reference to FIG. Note that steps S12, S13, S16, S19 to S22 in FIG. 8 are the same as steps S2, S3, S4, S6 to S9 shown in FIG. 2, and their description will be omitted.

First, in step S11, the temperature of the object to be measured 3A and the energization current are measured. In step S11, after the vehicle is started (for example, the ignition switch is turned on), the temperature measurement operation of the object to be measured 3A by the temperature sensor 11 is repeated, and the measurement operation of the energization current I by the current sensor 21 is repeated.

In step S14, the CPU 19A acquires the current value data of the object to be measured 3A. The CPU 19A may be configured to acquire the current value data in synchronization with the acquisition timing of the temperature data, or may be configured to acquire the current value data at different timings.

In step S15, the CPU 19A calculates the threshold value ΔTmax. The CPU 19A has the above equation (6) based on the energization current I corresponding to the current value data acquired in step S14, the thermal resistance R, the heat capacity C, the electric resistance _RL , and the sampling cycle time ts of the object to be measured 3A. ) To calculate the threshold value ΔTmax. As a result, ΔTmax calculated in real time can be used as a threshold value, and the accuracy of detection can be improved.

In step S17, the CPU 19A determines whether or not the energization current I is within the normal range. Specifically, the CPU 19A determines whether or not the energization current I corresponding to the current value data acquired in step S14 is included in the rated current range of the object to be measured 3A. As a result of this determination, if the energizing current I is out of the rated current range, the process proceeds to step S23. On the other hand, when the energization current I is included in the rated current range, the process proceeds to step S18.

In step S18, the CPU 19A compares the absolute value of the difference ΔT between the current temperature data Now and the previous temperature data Tbefore with the threshold value ΔTmax, and determines whether or not the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax. As a result of this determination, if the absolute value of the difference ΔT is equal to or less than the threshold value ΔTmax, the process proceeds to step S19. On the other hand, when the absolute value of the difference ΔT exceeds the threshold value ΔTmax, the process proceeds to step S22.

In step S23, the CPU 19A compares the current temperature data Tnow with the predetermined maximum permissible temperature data Tth of the object to be measured 3A, and determines whether or not the current temperature data Tth exceeds the maximum permissible temperature data Tth. .. As a result of this determination, if the current temperature data Tnow exceeds the maximum allowable temperature data Tth, the process proceeds to step S24. On the other hand, when the current temperature data Now is equal to or less than the maximum allowable temperature data Tth, the process proceeds to step S18.

In step 24, the CPU 19A executes the energization cutoff process to stop the operation of the object to be measured 3A. Specifically, the CPU 19A outputs a notification signal to an external ECU, and the ECU shuts off the energization of the object to be measured 3A to stop the operation.

In the temperature measuring device 1A described above, the CPU 19A acquires the temperature of the object to be measured measured by the temperature sensor 11 for each sampling cycle, and the energization current I is outside the allowable energization current range of the object 3A to be measured. When the temperature of the object to be measured (Tnow) exceeds the allowable temperature (Tth) of the object to be measured, the energization of the object to be measured 3A is cut off. Further, the threshold value ΔTmax is the maximum value of the temperature change of the measured object 3A calculated based on the thermal resistance, the heat capacity, the electric resistance, and the energization current of the measured object 3A in the sampling cycle time. With the above configuration, the same effect as that of the temperature measuring device 1 can be obtained. Further, the temperature measuring device 1A can prevent a failure due to an overcurrent of the object to be measured 3A and can improve the accuracy of the temperature measurement by distinguishing between a temperature rise due to the overcurrent and a temperature change due to noise. In the case of a semiconductor component in which the object to be measured 3A is energized and driven, there is a possibility that the temperature of the object to be measured (Tnow) this time exceeds the allowable temperature (Tth) of the semiconductor component due to heat generation more than expected due to a short circuit. There is. In such a case, it leads to the failure of the semiconductor component. Therefore, when the energization current I of the object to be measured 3A is monitored and the energization current I is out of the rated current range and the temperature of the object to be measured (Tnow) this time exceeds the allowable temperature (Tth) of the semiconductor component, It is determined that heat is generated due to a short circuit, etc., and the current is cut off to prevent the failure of semiconductor parts. On the other hand, when the energizing current I is within the rated current range, or when the energizing current I is outside the rated current range and the temperature of the object to be measured (Tnow) this time is the allowable temperature (Tth) or less, the measured objects this time and the previous time are measured. When the absolute value of the difference in the object temperature exceeds the threshold value ΔTmax, it is determined that the temperature has changed significantly due to noise, and the temperature of the object to be measured this time is discarded, so that the accuracy of the temperature measurement can be improved.

Further, the temperature measuring method of the temperature measuring device 1A is a step of acquiring the temperature of the object to be measured measured by the temperature sensor 11 for each sampling cycle, and the energization current I is outside the range of the allowable energization current of the object to be measured 3A. If the temperature of the object to be measured (Tnow) exceeds the allowable temperature (Tth) of the object to be measured 3A, the step of shutting off the energization of the object to be measured 3A is included. Further, the threshold value ΔTmax is the maximum value of the temperature change of the measured object 3A calculated based on at least the thermal resistance, the heat capacity, the electric resistance, and the energization current of the measured object 3A in the sampling cycle time. As a result, the same effect as that of the temperature measuring device 1A can be obtained.

Further, in the temperature measuring device 1A, assuming that the threshold value ΔTmax is R for the thermal resistance of the object 3A, C for the heat capacity, _RL for the electrical resistance, I for the energization current, and ts for the sampling cycle time, the above equation ( 6). As a result, the threshold value ΔTmax can be calculated in real time from the energization current I of the object to be measured 3A, and the temperature change due to noise and the temperature change due to abnormal heat generation of the object to be measured 3A are excluded by using the threshold value ΔTmax. be able to. As a result, the accuracy of temperature measurement can be further improved.

In the second embodiment, the CPU 19A calculates the threshold value ΔTmax in step S15 of FIG. 8, but the present invention is not limited to this. For example, even if the CPU 19A holds the table information of the threshold value ΔTmax having the energization current I as a parameter in advance, and calculates ΔTmax by referring to the table information based on the acquired current value data (energization current I). good.

(Modification example)
In the first and second embodiments, the CPUs 19 and 19A output the current temperature data Now in step S6 of FIG. 2 and step S19 of FIG. 8, but the present invention is not limited thereto. For example, the CPUs 19 and 19A may perform arithmetic processing using a plurality of temperature data including the current temperature data Now in steps S6 and S19, and output the processing result. This arithmetic processing includes, for example, a moving average processing of a plurality of temperature data including the current temperature data Now in which the absolute value of the difference ΔT is equal to or less than the threshold value. In this case, the temperature data Tm is calculated as the processing result of the moving average processing of the temperature data in steps S6 and S19, and the temperature data Tm is output. Further, in step S7 of FIG. 2 and step S20 of FIG. 8, the CPUs 19 and 19A substitute the temperature data Tm for the current temperature data Tnow and substitute the temperature data Tm for the previous temperature data Tbefore. With the above configuration, the temperature data whose temperature has changed due to noise can be excluded, and the temperature of the object to be measured can be estimated using a plurality of temperature data before the temperature change, so that the temperature measurement accuracy can be maintained.

1,1A Temperature measuring device 3,3A Object to be measured 11 Temperature sensor 13,13A I / F circuit 15,15A Analog filter 17,17A A / D converter 19,19A CPU
21 Current sensor

Claims (5)

A temperature measuring means for measuring the temperature of the object to be measured, and
An acquisition means for acquiring the measured temperature of the object to be measured at predetermined time intervals, and
A determination means for determining whether or not the absolute value of the difference between the acquired temperature of the object to be measured this time and the temperature of the object to be measured last time is equal to or less than the threshold value.
When the absolute value of the difference is equal to or less than the threshold value based on the determination result by the determination means, the output means for outputting the temperature of the object to be measured this time and the output means.
A holding means for holding the temperature of the object to be measured this time as the temperature of the object to be measured last time is provided.
The threshold is
It is the maximum value of the temperature change of the measured object calculated based on at least the calorific value, the thermal resistance, and the heat capacity of the measured object in the predetermined time.
A temperature measuring device characterized by that. The threshold is
Assuming that the calorific value of the object to be measured is P, the thermal resistance is R, the heat capacity is C, and the predetermined time is ts.
R * P * {1-exp (-ts / (C * R))}
The temperature measuring device according to claim 1. The object to be measured is
It is a semiconductor component that is mounted on a vehicle and driven by energizing.
The temperature measuring device further
A current measuring means for measuring the energizing current when the object to be measured is in an energized state, and
When the energization current is outside the allowable energization current range of the object to be measured and the temperature of the object to be measured exceeds the permissible temperature of the object to be measured, a current cutoff means for cutting off the energization of the object to be measured and Equipped with
The threshold is
It is the maximum value of the temperature change of the object to be measured calculated based on at least the thermal resistance, the heat capacity, the electric resistance, and the energization current of the object to be measured in the predetermined time.
The temperature measuring device according to claim 1. The threshold is
Assuming that the thermal resistance of the object to be measured is R, the heat capacity is C, the electric resistance is _{RL, the} energization current is I, and the predetermined time is ts.
R * I ² * _RL * {1-exp (-ts / (C * R))}
The temperature measuring device according to claim 3. A temperature measurement process that measures the temperature of the object to be measured, and
An acquisition process for acquiring the measured temperature of the object to be measured at predetermined time intervals, and
A determination step for determining whether or not the absolute value of the difference between the acquired temperature of the object to be measured this time and the temperature of the object to be measured last time is equal to or less than the threshold value.
When the absolute value of the difference is equal to or less than the threshold value based on the determination result by the determination step, the output step of outputting the temperature of the object to be measured this time and the output step.
The holding step of holding the temperature of the object to be measured this time as the temperature of the object to be measured last time in the holding means,
Equipped with
The threshold is
It is the maximum value of the temperature change of the measured object calculated based on at least the calorific value, the thermal resistance, and the heat capacity of the measured object in the predetermined time.
A temperature measuring method characterized by that.

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