JP2003294543A - Temperature detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature detection device capable of taking temperature information at a plurality of spots through one port of a microprocessor. <P>SOLUTION: A plurality of temperature sensors 4u, 4w thermally combined respectively on a plurality of heating spots of a detection object are connected in parallel to constitute a temperature detection part 4, and a temperature detection signal Vt acquired by converting a parallel resistance combined value of the temperature sensors 4u, 4w into a voltage signal is inputted into one A/D port of the microprocessor 5. A determination value used as a criterion when determining whether the temperature at the heating spot exceeds a tolerance or not is differentiated between the steady state wherein the temperatures at all the heating spots of the detection object show an equal value and the unsteady state wherein the temperature at one heating spot shows a higher value than the temperature at another heating spot, to thereby determine whether overheat is generated or not in the detection object. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting device used to obtain information on the temperature of an object to be detected having a plurality of heat generation points.

[0002]

2. Description of the Related Art Conventionally, in order to protect an object having a plurality of heat-generating points, the temperature of each of the heat-generating points is individually detected and input to a microprocessor. When the temperature of a predetermined heat generation point exceeds the allowable range by the microprocessor, measures are taken to lower the temperature of the heat generation point.

For example, in a brushless DC motor having a plurality of phases of armature coils, when the motor is in a locked state (stopped state) due to an increase in load during driving, a specific position determined by the stop position of the rotor is specified. Since a state in which a current flows in the armature coil of a phase for a long time may cause the armature coil of the specific phase to burn out. In addition, even if the motor does not lock due to an increase in load, or even when it is in an extremely low speed rotation state close to lock, a state in which a current flows for a long time in the armature coil of a specific phase similarly causes the armature coil to move. There is a risk of burning. In this way, when there is a risk that the armature coil will burn out, a temperature sensor is attached to each of the multiple-phase armature coils, and the temperature information detected by each temperature sensor is input to the microprocessor. When it is detected that the temperature detected by the temperature sensor exceeds the allowable range, the armature current is shut off or its value is reduced.

FIG. 9 shows an armature (stator) of a three-phase brushless DC motor as an example of an object to be detected for temperature detection.
1 is shown. The illustrated armature 1 is an armature core 2 having three tooth portions 2u, 2v and 2w, and a three-phase electric machine wound around the tooth portions 2u, 2v and 2w of the armature core and star-connected. Child coils 3u, 3v and 3w
The magnetic pole portions at the tips of the tooth portions 2u, 2v, and 2w are opposed to the magnetic poles of the magnetic field provided on the rotor (not shown).

In this brushless DC motor, 3
A three-phase position sensor (not shown) for obtaining rotational angle position information of the magnetic poles of the rotor is provided for each of the three-phase armature coils 3u, 3v, and 3w, and the outputs of these three-phase position sensors are provided. The drive current is supplied to the armature coil of the excitation phase determined in accordance with. As a result, the drive current is commutated to the three-phase armature coils 3u to w in a predetermined phase order, and a rotating magnetic field is generated from these armature coils,
Rotate the rotor.

In this type of electric motor, when the rotor is stopped due to an excessive load, a state in which a drive current continuously flows through the armature coil of a specific phase determined by the stop position of the rotor occurs, and the armature coil A local overheat condition occurs in which the temperature rises above that of the armature coils of the other phases.
If such a state is left as it is, the temperature of the armature coil in the phase in which the driving current flows rapidly increases, and eventually the armature coil is burnt out. Similarly, when the rotation speed of the rotor drops to a speed just before the stop, the time for the drive current to flow through the armature coil of each phase becomes long, so the temperature of the armature coil of a specific phase is different from that of other phases. There is a possibility that the temperature of the armature coil becomes higher than the temperature of the armature coil, and the armature coil is burned out.

When there is no risk of a locked state or a state close to a locked state and the temperature of all armature coils rises evenly, a temperature sensor is attached to any one of the armature coils, The temperature of the armature coil can be managed by controlling the drive current when the detected temperature exceeds the allowable value.

However, when only the temperature of the armature coils of some phases may rise, as shown in FIG. 9, the temperature sensors 4u to 4w are attached to the three-phase armature coils 3u to 3w, respectively. Control to detect the temperature of the armature coils of all phases and limit or cut off the drive current when the temperature of the armature coils of any phase exceeds the allowable value. Need to do.

In the case of performing the above control, normally, the output of the temperature sensor is input to the microprocessor for controlling the electric motor, and the temperature detected by each temperature sensor in the microprocessor is compared with the determination value to obtain It is determined whether or not the temperature of the armature coil exceeds the allowable value.

FIG. 10 shows a conventional circuit for inputting the temperature information detected by the temperature sensors 4u to 4w shown in FIG. 9 to the microprocessor 5. In this example, the temperature sensor is composed of a temperature sensitive resistance element such as a thermistor, and fixed resistors 6u to 6w are connected in series to the temperature sensors 4u to 4w, respectively. The terminals of the fixed resistors 6u to 6w opposite to the temperature sensor are grounded, and a constant DC voltage V is applied across the series circuits of the temperature sensors 4u to 4w and the fixed resistors 6u to 6w.
c is applied. Further, capacitors 8u to 8w are connected to both ends of the fixed resistors 6u to 6w through resistors 7u to 7w, and the voltage signals obtained at both ends of the capacitors 8u to 8w include temperature information of the armature coils 3u to 3w, respectively. The signals are input to the three A / D input ports (input ports of the A / D converter) of the microprocessor 5 as signals.

In FIG. 10, resistors 7u to 7w and capacitors 8u to 8w constitute a noise absorbing filter circuit.

The microprocessor 5 is programmed so as to constitute means for controlling the drive current of the electric motor, and compares the temperature of the armature coil detected by the temperature sensors 4u to 4w with a judgment value to determine which one of them. When the temperature detected by the temperature sensor exceeds the judgment value, the current flowing through the armature coil is cut off or reduced.

In this example, the temperature sensors 4u to 4w are used.
And the fixed resistors 6u to 6w, the power supply circuit for applying the DC voltage Vc to the series circuit of each temperature sensor and the fixed resistor, and the microprocessor 5, the temperature of the detected object having a plurality of heat generation points. And a temperature detection device that determines whether or not the temperature of any of the heat generation points exceeds an allowable value.

[0014]

As described above, in the conventional temperature detecting device, the temperature detection signal including the temperature information detected by each of the plurality of temperature sensors attached to the plurality of heat generating points of the object to be detected is detected. Since it was individually input to the microprocessor, it was necessary to use the microprocessor ports for the number of temperature sensors in order to read the temperature information of the object to be detected (the motor in the above example). It was necessary to use a different microprocessor.

Further, in the above configuration, since two connection lines are required for each temperature sensor to connect the temperature sensor and the microprocessor, the temperature information detected by each of the plurality of temperature sensors is read into the microprocessor. Therefore, there is a problem that the number of connection lines required is large and the configuration of the input circuit of the microprocessor becomes complicated.

Instead of individually inputting the temperature information detected by the plurality of temperature sensors into the plurality of ports of the microprocessor as described above, a plurality of voltage signals including the temperature information detected by the plurality of temperature sensors are switched. A method is known in which signals are sequentially switched by a signal switching circuit equipped with a switch and input to one input port of a microprocessor. However, in the case of such a configuration, a switching circuit is provided between the temperature sensor and the microprocessor. Since it has to be provided, there is a problem that the circuit configuration of the temperature information input circuit becomes complicated.

An object of the present invention is to provide a temperature required for temperature control of an object to be detected having a plurality of heat generating points without using a signal switching circuit and using only one port of a microprocessor. An object of the present invention is to provide a temperature detecting device capable of obtaining information.

Another object of the present invention is to provide one port of a microprocessor in a motor having a multi-phase armature coil in which only a part of the phase armature coils may be overheated. It is possible to detect whether the temperature of the entire polyphase armature coil exceeds the allowable range and to detect whether only the temperature of some armature coils exceeds the allowable range just by using it. Another object of the present invention is to provide a temperature detecting device for an electric motor.

[0019]

SUMMARY OF THE INVENTION The present invention is a temperature detecting device for obtaining information on the temperature of an object to be detected, wherein a plurality of temperature sensors having a characteristic that a resistance value changes according to the temperature are detected. A temperature detecting section that is arranged in a state of being thermally coupled to a plurality of heat generating points of the object, and is configured by connecting the plurality of temperature sensors in parallel; and a circuit that applies a voltage to both ends of the temperature detecting section. A temperature detection circuit that outputs a voltage signal whose magnitude changes in accordance with a change in resistance value at both ends of the temperature detection unit as a temperature detection signal including information on an average value of the temperatures of the plurality of heat generation points. It is characterized by having.

As described above, when a plurality of temperature sensors for detecting the temperatures of a plurality of heat generating points are connected in parallel to form a temperature detecting section, when the temperatures detected by the plurality of temperature sensors are equal, It is possible to detect the temperature of each heat generation point from the resistance value at both ends of the temperature detection unit (parallel combined resistance value of a plurality of temperature sensors). In this case, if there is a difference in temperature between a plurality of heat-generating points, the temperature at each heat-generating point cannot be accurately detected, but if the difference is slight, the information on the temperature at each heat-generating point may have a slight error. Since the temperature can be obtained within the range, when the temperature is detected for the purpose of protecting the object to be detected from overheating, the purpose of temperature detection can be sufficiently achieved.

On the other hand, a local overheat state occurs in which the temperature of some heat generating points is higher than the temperature of other heat generating points, and the resistance value between some temperature sensors and the resistance value of other temperature sensors is increased. If there is a large difference in the temperature, it is not possible to detect the temperature of each heat generation point from the resistance values at both ends of the temperature detection unit,
At this time, it is possible to obtain information from the resistance values at both ends of the temperature detection unit whether or not the temperature of a part of the heat generation point where the temperature is high reaches the upper limit of the allowable range. When detecting the temperature for the purpose of protecting the vehicle from local overheating, the purpose can be sufficiently achieved.

When the temperature detecting device is constructed as described above,
When inputting temperature information of a plurality of heat generation points of the object to be detected to the microprocessor for determination processing, only one port of the microprocessor needs to be assigned to input the temperature information. It is possible to use a microprocessor with a small number, and to allocate an extra port of the microprocessor for input of information other than temperature information.

In the present invention, an object in which a temperature of some heat generating points becomes higher than the temperature of other heat generating points when a non-steady state occurs and a local overheating state may occur is set as a detected object. It is particularly useful when obtaining information as to whether or not the temperature of each heat generation point of the detected object is within the allowable range.

In this case, the temperature detecting device according to the present invention includes a plurality of temperature sensors having a characteristic that the resistance value changes according to the temperature, and a plurality of temperature sensors including a heat generating portion where local overheating of the object to be detected may occur. Of the temperature detection unit, each of which is thermally coupled to each of the heat generation points, and includes a temperature detection unit configured by connecting the plurality of temperature sensors in parallel to each other and a circuit for applying a voltage to the temperature detection unit. A temperature detection circuit that outputs a voltage signal whose magnitude changes in accordance with changes in resistance values at both ends as a temperature detection signal corresponding to the average value of the temperatures of the plurality of heat generation points, and the state of the detected object is a steady state. In the state in which the object to be detected is determined to be in a steady state by the object to be detected state determining means for determining whether the object to be detected is in the steady state or the unsteady state, When the temperature of each of the plurality of heat generation points is equal to the upper limit value of the allowable temperature range, the first determination value having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit and the magnitude of the temperature detection signal are set. In comparison, it is determined from the magnitude relationship between the magnitude of the temperature detection signal and the first determination value whether or not the temperature of each heat generation point of the detected object exceeds the allowable range, and the detected object state determination means. In the state where the detected object is determined to be in an unsteady state by the temperature detection signal output from the temperature detection circuit when the temperature of a part of the plurality of heat generation points reaches the upper limit value of the allowable range. Is compared with the magnitude of the temperature detection signal and the temperature of a part of the plurality of heat generation points is determined from the magnitude relationship between the magnitude of the temperature detection signal and the second determination value. Temperature to determine whether it exceeds the allowable range It can be configured to include a judgment means.

The present invention also includes n phases (n is an integer of 2 or more).
Of the armature coil of another phase when the rotation speed becomes less than the set value or becomes zero while the armature current is being applied. This is useful for obtaining information as to whether or not the temperature of the armature coil of the electric motor is within the allowable range, with the electric motor in which a local overheat state becomes higher than the coil temperature as a detection target.

In this case, the temperature detecting device according to the present invention is a state in which n temperature sensors having the characteristic that the resistance value changes according to the temperature are thermally coupled to the n armature coils of the electric motor, respectively. And a circuit for applying a constant voltage to the temperature detection unit and a circuit for applying a constant voltage to the temperature detection unit. Temperature detection circuit that outputs a voltage signal whose magnitude changes with temperature as a temperature detection signal having a magnitude corresponding to the average value of the temperature of the n-phase armature coil, and rotation speed detection that detects the rotation speed of the electric motor. Means, a rotation speed determination means for determining whether or not the rotation speed of the electric motor detected by the rotation speed detection means exceeds a set value set sufficiently low, and the rotation speed of the electric motor by the rotation speed determination means. When it is determined that the temperature exceeds the set value, the magnitude corresponding to the temperature detection signal output from the temperature detection circuit when the temperature of each of the n-phase armature coils is equal to the upper limit value of the allowable temperature range. First having
Of the n-phase armature coils, the temperature of some of the armature coils of the n-phase is allowed when the rotation speed determination means determines that the rotation speed of the electric motor is not higher than the set value. Judgment reference signal generating means for generating a second judgment reference signal having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit when the upper limit value of the range is reached, the temperature detection signal and the first judgment. It is determined whether the temperature of each of the n-phase armature coils exceeds the allowable range based on the magnitude relationship with the reference signal, and the n-phase armature is determined based on the magnitude relationship between the temperature detection signal and the second determination reference signal. The temperature determination means may be configured to determine whether or not the temperature of some of the armature coils of the coil exceeds the allowable range.

The temperature detection circuit includes a resistor connected in series to the temperature detection unit, and a constant voltage power supply circuit for applying a constant DC voltage across the series circuit of the temperature detection unit and the resistor. In addition, the voltage signal may be output from both ends of the resistor or the temperature detection unit.

The rotation speed detecting means includes a signal generator for generating a pulse signal whose frequency is proportional to the rotation speed of the electric motor, and a rotation speed for converting the frequency or generation period of the signal generated by the signal generator into the rotation speed. And a conversion means.

Further, the temperature judging means is composed of a voltage comparing circuit for comparing the temperature detection signal and the judgment reference signal and generating outputs of different levels according to the magnitude relation between the temperature detection signal and the judgment reference signal. You can

The temperature determining means can also be constituted by a microprocessor programmed to perform a determination process of the magnitude relation between the temperature detection signal and the determination reference signal.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a temperature detecting device according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 shows a hardware configuration according to the first embodiment of the present invention. In FIG. 1, 4u to 4w are thermally coupled to different heat generation points of an object to be detected. It is a temperature sensor.

In the present embodiment, the armature of the three-phase brushless DC motor shown in FIG. 9 is the object to be detected. In this case, since the three-phase armature coils 3u to 3w are heat generating points, the temperature sensors 4u to 4w are attached to the armature coils 3u to 3w in a thermally coupled state.

Each of the temperature sensors has a characteristic that the resistance value seen from both ends thereof changes according to the change of the sensed temperature. The temperature sensor has a negative or positive temperature coefficient, such as a thermistor. Outside, as shown in FIG. 2 (A),
A composite resistor configured by connecting a fixed resistor R1 in series to the temperature-sensitive resistance element Rth, and a composite resistor configured by connecting a fixed resistor R2 in parallel to the temperature-sensitive resistance element Rth as shown in FIG. 2B. A resistor, as shown in FIG. 2C, a temperature-sensitive resistance element Rt
A composite resistor formed by connecting resistors R1 and R2 to h in series and parallel respectively, or in FIG. 2A to 2C, a fixed resistor is partially replaced by a variable resistor. It can be composed of a composite resistor or the like.

As shown in FIGS. 2A to 2C, when a resistor is connected in series or in parallel to the temperature sensitive resistance element, the resistance value at both ends of the temperature sensor and the temperature of the resistance value are compared. The characteristics of change (change rate, etc.) can be adjusted appropriately.

As described above, each temperature sensor can have various configurations, but the temperature sensors 4u to 4w attached to one object to be detected have the same configuration and have a resistance value-temperature characteristic. Use as close as possible (preferably the same). Temperature sensor 4u to 4w
Are connected in parallel to each other, and the temperature detection unit 4 is configured by a parallel circuit of these temperature sensors. Temperature detector 4
A resistor 6 is connected in series with the resistor 6, and the terminal of the resistor 6 on the opposite side of the temperature detecting unit 4 is grounded. Also, the temperature detector 4
Is connected to the positive side output terminal of a constant voltage power supply circuit (not shown) whose negative side output terminal is grounded, and the temperature detection unit 4 and the resistor 6 are connected in series from the power supply circuit. A constant DC voltage Vc is applied to both ends of the circuit.

A resistance voltage dividing circuit is constituted by a series circuit of the temperature detecting section 4 and the resistor 6, and a temperature detecting circuit composed of a voltage signal showing a value corresponding to the temperature sensed by the temperature detecting section 4 at both ends of the resistor 6. The signal Vt is obtained.

Assuming that the temperature-sensitive resistance elements constituting the temperature sensors 4u to 4w are thermistors having a negative temperature coefficient, the temperature detection signal Vt obtained at both ends of the resistor 6 is It shows the characteristic that the level increases with the increase.

The temperature detection signal Vt is input to a noise absorbing filter circuit 9 composed of a resistor 7 and a capacitor 8. The temperature detection signal Vt 'from which noise has been removed by the filter circuit 9 is one of the microprocessors 5. It is being input to the A / D input port.

In the present embodiment, a constant voltage power supply circuit (not shown) that outputs a DC voltage Vc and a resistor 6 constitute a voltage application circuit that applies a constant DC voltage across the temperature detector 4. The voltage applying circuit and the temperature detecting section 4 constitute a temperature detecting circuit.

In FIG. 1, 10 is 3 as shown in FIG.
A DC brushless motor having a three-phase armature coil, and on the armature (stator) side of the motor, position sensors hu to hw for detecting the rotational angle position of the rotor with respect to the U-phase to W-phase armature coils. Is provided. The position sensors hu to hw are Hall ICs that output signals having different levels according to the polarities of the magnetic poles of the rotor, and are arranged at positions having a predetermined phase relationship with the U-phase to W-phase armature coils. Has been done. Position sensor hu
To hw output rectangular wave-shaped position detection signals indicating a high level (H level) state or a low level (L level) state depending on whether the polarity of the rotor magnetic pole detected by each is N or S. To do. The position detection signals Hu to Hw output from these position sensors are input to the ports Bu to Bw of the microprocessor 5.

Reference numeral 11 denotes an encoder attached to the electric motor 10. The encoder generates a pulse every time the electric motor rotates by a certain angle. The pulse Vp generated by the encoder 11 is input to the port Bp of the microprocessor 5. The microprocessor 5 detects the rotation speed of the electric motor from the pulse generation interval.

Reference numeral 12 denotes an inverter circuit provided between a DC power source such as a battery Bat and the electric motor 10. The inverter circuit is, for example, as shown in FIG. 5, a switch element Fu or a switch element constituting the upper side of the bridge. It is composed of a switch element bridge circuit including Fw and switch elements Fx to Fz forming the lower side of the bridge. Switch elements Fu to Fw and F of the inverter circuit 12
The control terminals of x to Fz are connected to the ports Cu to Cw and Cx to Cz of the microprocessor 5, and drive signals V from the microprocessor 5 to the switching elements Fu to Fw and Fx to Fz of the inverter circuit.
u to Vw and Vx to Vz are provided. The microprocessor 5 turns on a predetermined switch element of the inverter circuit in order to pass a drive current to the armature coil of the phase determined based on the rotational angle position information of the rotor given by the position sensors hu to hw, and the direct current is turned on. A drive current that commutates in a predetermined phase sequence is supplied from the power supply Bat to the armature coil of the electric motor.

In the example shown in FIG. 5, the switch element forming the inverter circuit is a MOSFET. A parasitic diode is formed between the drain and source of each MOSFET, but the diode is not shown.

In the brushless DC motor shown in FIG. 1, when the load of the motor becomes excessive and the motor is in a locked state (when the rotor is stopped while the drive current is flowing), the rotor is stopped. A drive current flows only in a specific armature coil determined by the stop position of the armature coil, the temperature of the armature coil rises rapidly, and local overheating occurs. Also, even if the rotor does not stop, even when the rotation speed becomes very low and it is about to lock,
Since the driving current flows through each armature coil for a long time, the temperature of the armature coil of the phase in which the driving current is flowing becomes higher than the temperature of the armature coils of the other phases, resulting in local overheating.

In the present invention, as described above, the state in which local overheating occurs is set to an unsteady state, and the same heat is generated at all heat generating points (the armature coils in this embodiment), and all heat generating points are generated. The steady state is a state where the temperatures are almost equal.

As described above, when a plurality of temperature sensors 4u to 4w for detecting the temperatures of a plurality of heat generating points are connected in parallel to constitute the temperature detecting section 4, the temperatures detected by the plurality of temperature sensors are detected. When is equal, it is possible to detect the temperature of each heat generation point from the resistance values (the parallel combined resistance values of the plurality of temperature sensors) at both ends of the temperature detection unit.
Here, assuming that the resistance values of the temperature sensors 4u to 4w are Ru to Rw, respectively, when the temperatures of all the heat generating points are equal, Ru = Rv = Rw. If the combined value) is Rx, then Rx = Ru / 3 (1) If the resistance value of the resistor 6 is R1 and the multiplication symbol is *,
At this time, the temperature detection signal Vt output from the temperature detection circuit
Vt = {R1 / (R1 + Rx)} * Vc (2) On the other hand, local overheating of the armature coil 3u occurs, and only the resistance value Ru of the temperature sensor 4u becomes low, and the other two temperature sensors When the resistance values Rv and Rw of 4v and 4w are equal, Rx = (Ru * Rv) / (2Ru + Rv) (3) Vd = {R1 / (R1 + Rx)} * Vc (4) FIG. Temperature sensor 4 when the condition continues
It shows an example of changes in resistance values Ru to Rw of u to 4w and their parallel combined resistance value Rx (= Ru / 3). In this case, Ru to Rw are equal, but in the figure, an example of changes in these resistance values is shown by three polygonal lines that are displayed close to each other for convenience. Initially, since the temperature of the armature coil was constant, the resistance values Ru to Rw of the temperature sensors 4u to 4w show constant values Rb, but since the temperature of the armature coil increased from the middle, the resistance values Ru to Rw. Rw is decreasing linearly. In the illustrated example, when the temperature of the armature coil reaches the upper limit value of the allowable range, the resistance values Ru to Rw become equal to Ra, and the parallel combined resistance value Rx becomes Ra ′ (= Ra / 3). Will be equal. Therefore, a value equal to the value of the temperature detection signal Vt when the parallel combined resistance value Rx of the temperature detection unit 4 becomes equal to Ra ′ is set as a set value, and the temperature detection signal Vt is set.
It is possible to prevent the armature coil from burning out by performing a protective operation such as interruption of the armature current when t exceeds this set value.

As described above, when the steady state continues, the parallel combined resistance value Rx of the temperature sensors becomes 1/3 of the resistance value of each temperature sensor, but at this time, the temperatures of all armature coils are equal. Therefore, the temperature of each armature coil can be detected from the parallel combined resistance value Rx.

Even in the steady state, there may be a case where Rx = Ru / 3 does not hold due to a slight difference between the temperatures of the three-phase armature coils, variations in the characteristics of the temperature sensor, etc. If the difference between the resistance values of the sensors is small, each armature coil (heating point) can be calculated from the parallel combined resistance values of the temperature sensors that detect the temperatures of the three-phase armature coils.
The temperature information can be obtained within a slight error range, and if the setting value is determined in consideration of this error range, the protection operation can be performed accurately.

Next, FIG. 7 shows an example of changes in the resistance value of the temperature sensor when a local overheat condition occurs in which only some of the armature coils rise in temperature. In the example of FIG. 7, time t
Since the temperature of the armature coil 3u rises from a, time t
Only the resistance value Ru of the temperature sensor 4u has dropped from a. At this time, at time tb, the temperature of the armature coil 3u reaches the upper limit value of the allowable range and becomes Ru = Ra, but the parallel combined resistance value Rx of the temperature detection unit is Ra ″, and all armature coils are in the steady state. Shows a value higher than the parallel combined resistance value Ra ′ when the temperature of reaches the upper limit of the allowable range.
At time tc, the parallel combined resistance value Rx becomes equal to Ra ′. However, since the temperature of the armature coil 3u in which local overheating occurs at this time greatly exceeds the upper limit value of the allowable range, it is the same as in the steady state. If the protection operation is performed when Rx becomes equal to Ra ′, the armature coil cannot be protected. In order to properly perform the protective operation when the local overheat occurs, it is necessary to perform the protective operation when the parallel combined resistance value Rx of the temperature detection unit becomes equal to Ra ″ at time tb. . Armature coil 3
If local overheating occurs in u, the temperatures of the other armature coils 3v and 3w are equal, and Rv = Rw = Rb, Ra ″ is given by the following equation.

Ra ″ = (Ra * Rb) / (2Ra + Rb) (5) In the non-steady state, the value of the temperature detection signal when the parallel combined resistance value of the temperature detection unit is equal to Ra ″ is set as the set value. In advance, by performing the protective operation when the temperature detection signal Vt exceeds this set value, it is possible to prevent the armature coil from burning due to local overheating.

Next, while the temperature of the three-phase armature coil is rising, an unsteady state occurs, and the temperature of the one-phase armature coil 3u becomes higher than the temperature of the other-phase armature coils. FIG. 8 shows the change in the resistance value of the temperature sensor when the temperature rises and the change in the parallel combined resistance value of the temperature detection unit.

In the example shown in FIG. 8, because local overheating occurs in the armature coil 3u at the time ta, the resistance value Ru of the temperature sensor 4u falls at a steeper slope than the resistance values of the other temperature sensors, and At tb, the resistance value Ru reaches the value Ra corresponding to the upper limit value of the allowable range of the temperature of the armature coil. In this case, the value of the temperature detection signal when the parallel combined resistance value Rx of the temperature detection unit becomes equal to Ra ″ is set as a set value, and protection is performed when the temperature detection signal exceeds this set value. By performing the operation, the armature coil 3u can be protected from local overheating.

That is, in the case where the temperature detecting device is constructed as shown in FIG. 1, in the state in which the object to be detected state judging means judges that the object to be detected is in the steady state,
A first determination value having a magnitude corresponding to the magnitude of the temperature detection signal Vt output from the temperature detection circuit when the temperature of each of the plurality of heat generation points of the detected object is equal to the upper limit of the allowable temperature range. And the magnitude of the temperature detection signal Vt are compared to determine whether or not the temperature of each heat generation point of the detected object exceeds the allowable range based on the magnitude relationship between the magnitude of the temperature detection signal and the first determination reference value. In the state in which the object to be detected is determined to be in an unsteady state by the object to be detected state determination means, when the temperature of a part of the plurality of heat generation points reaches the upper limit value of the allowable range. The second determination value having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit is compared with the magnitude of the temperature detection signal to compare the magnitude of the temperature detection signal with the second determination value. From the temperature of some of the multiple heat generation points By configuring the temperature determination means to determine whether exceeds the capacity range, it is possible to obtain temperature information necessary in order to protect the detection object. This temperature determining means can be realized by causing a microprocessor to execute a predetermined program.

Since the steady state and the non-steady state of the object to be detected can be detected in almost all cases, when the object to be detected is protected from overheating, the state of the object to be detected is as described above. Even if the comparison and determination process of the temperature detection signal and the determination reference signal is performed after the detection of the temperature detection result, there is no practical problem.

When the object to be detected is an electric motor as in the present embodiment, the rotational speed of the electric motor is compared with a set value (a value corresponding to the rotational speed immediately before the electric motor stops),
The state where the rotation speed is above the set value is detected as a steady state, and the state where the rotation speed is not above the set value (the state where the rotation speed is lower than the set value and the rotation speed is zero) is not detected. The detected object state detecting means can be configured to detect the steady state.

The detected object state detecting means can be realized, for example, by causing the microprocessor to execute a process of comparing and determining the rotational speed of the electric motor detected from the output pulse of the encoder 11 with the set value.

In the case of a brushless DC motor, since the cycle in which the level change occurs in the output of the position detectors hu to hw is inversely proportional to the rotation speed of the motor, instead of measuring the output pulse generation interval of the encoder 11. In addition, the rotation speed of the electric motor can also be detected by measuring the cycle in which the level change of the output signals of the position detectors hu to hw appears.

In the above example, the A /
Since the D input terminal is provided, the output of the temperature detection circuit is input to the microprocessor through the filter circuit 9, and the microprocessor performs the determination processing as to whether or not the temperature of the object to be detected exceeds the allowable range. However, this determination processing may be performed by a hardware circuit.

FIG. 3 shows a second embodiment of the present invention in which the above determination processing is performed by a hardware circuit. In this example, the temperature detection signal Vt obtained from the temperature detection circuit is The temperature detection signal Vt ′ is input to the inverting input terminal of the comparator 15 through the filter circuit 9. A resistor 16 having one end connected to the positive output terminal of the constant voltage power supply circuit (not shown), a resistor 17 connected between the other end of the resistor 16 and the ground circuit, and a resistor 16
A resistor voltage divider circuit comprising a resistor 18 connected between the connection point of the resistor divider 17 and the port D1 of the microprocessor is provided, and the voltage obtained across the resistor 17 of the resistor voltage divider circuit is the criterion. It is input to the non-inverting input terminal of the comparator 15 as a signal.

By executing the program stored in the ROM, the microprocessor 5 sets the rotational speed detecting means for detecting the rotational speed of the electric motor and the rotational speed of the electric motor detected by the rotational speed detecting means to a sufficiently small value. Rotational speed determining means (corresponding to the detected object state determining means) for determining whether or not it is equal to or more than the set value (determination value for determining whether the electric motor is in a locked state or a state close to a locked state) And a judgment reference signal switching for changing the value of the judgment reference signal given to the comparator 15 from the voltage dividing circuit composed of the resistors 16 to 18 according to the judgment result of the rotation speed judging means. Realize means and.

Here, the determination reference signal switching means sets the potential of the port D1 to the non-ground potential (H level) when the rotation speed determination means determines that the rotation speed is equal to or higher than the set value. Is separated from the ground circuit, the temperature of the determination reference signal input to the comparator 15 is detected when the temperature of the three-phase armature coil reaches the upper limit of the allowable range in the state where local overheating does not occur. The first determination reference signal Vrf1 having a value corresponding to the magnitude of the temperature detection signal obtained from the above, and when the rotation speed determination means determines that the rotation speed is not higher than the set value (less than the set value or zero), Set the potential of port D1 to the ground level (L
By connecting the resistor 18 in parallel with the resistor 17 as a level), the temperature of the determination reference signal input to the comparator 15 is changed in a state where local overheating occurs in any armature coil. The second determination reference signal Vrf2 (<Vrf having a value corresponding to the magnitude of the temperature detection signal obtained from the temperature detection circuit when the upper limit of the allowable range is reached.
1).

The judgment reference signal switching means and the resistor 16
In the state in which the rotation speed determination means determines that the rotation speed of the electric motor exceeds the set value, the temperature of each of the n-phase armature coils falls within the allowable temperature range. When it is equal to the upper limit value, a first determination reference signal Vrf1 having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit is generated, and the rotation speed determination means determines that the rotation speed of the electric motor is not equal to or higher than the set value. The second determination criterion having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit when the temperature of a part of the n-phase armature coil reaches the upper limit value of the allowable range in the state where Judgment reference signal generating means for generating the signal Vrf2 is configured.

When the resistance value of the resistor 6 is R1, the first judgment reference signal Vrf1 can be set by the following equation.

Vrf1 = {R1 / (R1 + Ra ′)} * Vc (6) The second determination reference signal Vrf2 can be set by the following equation. Vrf2 = {R2 / (R1 + Ra ″)} * Vc (7) That is, Vrf1 and Vrf2 are expressed by the equations (6) and (7).
The resistance values of the resistors 16, 17 and 18 may be determined so that the values are determined by the equation.

When the initial value Rb of the resistance value of the temperature sensor shown in FIGS. 6 to 8 changes, the Ra 'and Ra "are changed.
Since the value of Ra 'and Ra "is changed,
It may be obtained by experiment.

The comparator 15 detects the temperature of the temperature detection signal Vt 'when the detection object state determining means determines that the state of the detection object is in a steady state (when the potential of the port D1 is at H level). Is compared with the first determination reference signal Vrf1 and the potential of the port A1 of the microprocessor is set to a high level (H level) when the magnitude of the temperature detection signal Vt ′ is equal to or less than the magnitude of the first determination reference signal Vrf1. ) And the magnitude of the temperature detection signal Vt ′ is the first determination reference signal Vrf.
When the value exceeds 1, the potential of the port A1 of the microprocessor is set to the low level (L level).

The comparator 15 also determines that the detected object determining means determines that the detected object is in a non-steady state (when the potential of the port D1 is at L level).
Then, the magnitude of the temperature detection signal Vt ′ is compared with the magnitude of the second determination reference signal Vrf2 to determine the temperature detection signal Vt ′.
Of the second judgment reference signal Vrf2 is equal to or smaller than the second judgment reference signal Vrf2, the potential of the port A1 of the microprocessor is set to a high level (H level), and the magnitude of the temperature detection signal Vt 'is set to the second judgment. When the magnitude of the reference signal Vrf2 is exceeded, the potential of the port A1 of the microprocessor is set to the low level (L level) state.

In the state where the state of the object to be detected is determined to be the steady state, the microprocessor 5 makes the temperatures of the heat generating points of the object to be detected almost equal when the potential of the port A1 is at the H level. Then, it is determined that the average temperature is within the allowable range. The microprocessor also has a local overheat that exceeds the allowable temperature range of the detected object when the potential of the port A1 is at the H level when the detected object is in the non-steady state. Is determined not to occur.

Further, the microprocessor 5 determines that all the objects to be detected are detected when the electric potential of the port A1 is at the L level in a state where the state of the electric motor (state of the objects to be detected) is in the steady state. It is determined that the temperature of the armature coil (heat generation point) exceeds the allowable range. The microprocessor also determines that the temperature of the motor is locally overheated in any one of the armature coils when the potential of the port A1 is at the L level in the state where the state of the electric motor is determined to be the unsteady state. It is determined that the allowable range has been exceeded.

When it is determined that the temperature of all the heat generating points of the object to be detected or the temperature of any heat generating point exceeds the allowable range, the microprocessor takes necessary measures to reduce the temperature. As in the present embodiment, when the detected object is the armature coil of the electric motor, the drive current of the electric motor is cut off when it is detected that the temperature of the armature coil exceeds the allowable range, or Alternatively, the control for reducing the average value of the drive current is performed to protect the armature coil from overheating.

In the example shown in FIG. 3, the comparator 15
From the magnitude relationship between the temperature detection signal and the first determination reference signal or the magnitude relationship between the detection signal and the second determination reference signal, n
A temperature determination unit is configured to determine whether the average value of the temperature of the armature coils of the phases is within the allowable range.

In the above example, the rotation speed detecting means and the detected object state detecting means are realized by causing the microprocessor to execute a predetermined program, but the microprocessor is provided with an A / D input port. If not, these can be configured by hardware circuits.

FIG. 4 shows a third embodiment of the present invention in which the rotation speed detecting means and the detected object state detecting means are constituted by hardware circuits. In this example, a pulse signal V obtained from an encoder attached to the motor
The frequency of p (which is proportional to the rotation speed) is converted into a voltage signal whose magnitude is inversely proportional to the frequency, and the speed detection signal V
The rotation speed detecting means is constituted by the frequency / voltage conversion circuit (F / V conversion circuit) 20 which outputs as n, and divides the output voltage Vc of the constant voltage power supply circuit to serve as a reference for judging the state of the electric motor. The detection target object state detection means 23 is configured by the reference signal generation circuit 21 that generates the reference signal Vs giving the set value and the comparator 22 that compares the speed detection signal Vn with the reference signal Vs.

The frequency / voltage conversion circuit shown in FIG.
A capacitor 26 charged with a constant time constant through a resistor 25 by a constant DC voltage Vc, a voltage follower circuit 27 to which a pulse signal Vp obtained from an encoder attached to the motor is input, and a differential capacitor 28.
And a resistor 29, and a differential circuit 30 that differentiates the rising edge of the pulse applied through the voltage follower circuit 27 to generate a narrow differential pulse, a transistor 31, and resistors 32 to 34. hand,
Each time a differentiating pulse is given from the differentiating circuit 30, the transistor 31 is turned on to charge the capacitor 26 with the resistor 34.
Between the collector and the emitter of the transistor 31 and the resistor 34
A discharge circuit 35 for discharging with a constant time constant through
The voltage follower circuit 36 outputs a voltage equal to the terminal voltage of the capacitor 26. This frequency /
In the voltage conversion circuit, the time interval in which the capacitor 26 is discharged is shortened as the rotation speed of the electric motor increases, so that the size of the capacitor 26 changes at both ends in inverse proportion to the rotation speed of the electric motor. The speed detection signal Vn composed of the voltage signal is obtained.

In the example shown in FIG. 4, the speed detection signal Vn and the reference signal Vs are input to the inverting input terminal and the non-inverting input terminal of the comparator 22, respectively, and the speed detection signal Vn
Is greater than the magnitude of the reference signal Vs [when the rotation speed of the electric motor is less than or equal to a set value (non-steady state)], the comparator 2
The potential of the output terminal of 2 becomes L level, and the speed detection signal V
When the magnitude of n is less than the magnitude of the reference signal Vs [when the rotation speed exceeds the set value (steady state)], the comparator 22
The potential of the output terminal of is at H level.

Similarly to the example shown in FIG. 3, the resistors 16,
A resistance voltage dividing circuit constituted by 17 and 18, a judgment reference signal Vrf2 obtained from this voltage dividing circuit, and a temperature detection signal Vt ′ obtained from a temperature detection circuit configured similarly to the example shown in FIG. And a comparator 15 input to the non-inverting input terminal and the inverting input terminal.
The output of 5 is input to the port A1 of the microprocessor 5. In this example, the resistor 18 of the resistance voltage dividing circuit is connected between the connection point of the resistors 16 and 17 and the output terminal of the comparator 22.

Although the brushless DC electric motor controlled by the microprocessor and the position sensor provided in the electric motor are not shown in FIG. 4, in the example shown in FIG. The position detection signals Hu to Hw are input to the ports Bu to Bw, respectively, and the ports Cu and C of the microprocessor are input.
Drive signals Vu, Vv, V are supplied from v, Cw, Cx, Cy and Cz to the inverter circuits for controlling the armature currents, respectively.
w, Vx, Vy and Vz are given.

In the example shown in FIG. 4, when the rotation speed of the electric motor exceeds the set value for determining the locked state or the state close to the locked state (when the electric motor is in the steady state), the comparator 22 Since the output terminal of is disconnected from the ground circuit, the resistor 18 of the resistance voltage dividing circuit is disconnected from the resistor 17. At this time, the judgment reference signal given to the non-inverting input terminal of the comparator 15 becomes the first judgment reference signal Vrf1. In this state, when the temperature detection signal Vt ′ is equal to or lower than the first determination reference signal Vrf1, the potential of the port A1 of the microprocessor becomes H level, and the temperature detection signal Vt ′ is changed to the first determination reference signal Vrf1.
Is exceeded, the potential of the port A1 of the microprocessor becomes L level.

When the rotation speed of the electric motor is equal to or lower than the set value (when the electric motor is in an unsteady state in which the electric motor may be locked), the output terminal of the comparator 22 is grounded. The resistor 18 of the pressure circuit is connected to the resistor 17 in parallel. At this time, the determination reference signal given to the non-inverting input terminal of the comparator 15 becomes the second determination reference signal Vrf2. In this state, when the temperature detection signal Vt ′ is equal to or lower than the second determination reference signal Vrf2, the potential of the port A1 of the microprocessor becomes H level,
When the temperature detection signal Vt ′ exceeds the second determination reference signal Vrf2, the potential of the port A1 of the microprocessor is L
Become a level.

The microprocessor 5 is in a state in which it is determined that the state of the object to be detected is in a steady state, and when the potential of the port A1 is at the H level, the temperatures of the heat generating points of the object to be detected are substantially equal. Then, it is determined that the temperature is within the allowable range. The microprocessor also has a local overheat that exceeds the allowable temperature range of the detected object when the potential of the port A1 is at the H level when the detected object is in the non-steady state. Is determined not to occur.

Further, the microprocessor 5 determines that the temperature of all the heat generating points of the detected object is low when the potential of the port A1 is L level in the state where the state of the detected object is determined to be the steady state. It is determined that the values are equal and that the value exceeds the allowable range. The microprocessor also determines that the state of the detected object is in a non-steady state,
When the potential of the port A1 is at the L level, it is determined that local overheating has occurred at any heat generation point of the detected object and the temperature exceeds the allowable range.

In the above example, in order to protect the brushless DC motor from overheating, the armature is used as the object to be detected. However, in addition to the armature, another portion that generates heat may be used as the object to be detected. Good. For example, when a drive current is passed through the armature coil through the inverter circuit as shown in FIG. 5, heat is also generated in the switch element that constitutes the inverter circuit, and thus this inverter circuit may be the detection target. When the inverter circuit is the detection target, for example, the temperature sensor 4u is thermally coupled to the switch elements Fx to Fz forming the lower stage of the bridge.
Place 4 to 4w.

In the above example, the brushless DC motor is used as an object to be detected. However, since local overheating occurs in an unsteady state (abnormal state), temperatures at a plurality of heat generating points are detected. The present invention can be widely applied when necessary.

In the above description, the thermistor having a negative temperature coefficient is used as the temperature-sensitive resistance element which constitutes the temperature sensor, but the temperature sensor can also be constituted using a thermistor having a positive temperature coefficient.

In the above example, the temperature detection signal is obtained from both ends of the resistor 6 connected in series to the temperature detection unit 4, but the positions of the temperature detection unit 4 and the resistor 6 are switched,
You may make it obtain a temperature detection signal from the both ends of the temperature detection part 4.

The temperature detection signal Vt may be a signal whose level rises as the temperature rises, or a signal whose level falls as the temperature rises.

When the temperature sensor is constructed by using a thermistor having a positive temperature coefficient, the temperature detector 4 is located on the ground circuit side, and the resistor 6 is located on the positive output terminal side of the power source to measure the temperature. If the temperature detection signals are obtained from both ends of the detection unit 4, it is possible to obtain the temperature detection signals whose level increases with the temperature rise.

[0089]

As described above, according to the present invention, a plurality of temperature sensors for respectively detecting the temperatures of a plurality of heat generation points of an object to be detected are connected in parallel, and the parallel combined value is converted into a voltage signal. Since the temperature detection signal is obtained by the conversion, when the temperature information of the plurality of heat generation points of the object to be detected is input to the microprocessor to perform the determination process,
Only one port of the microprocessor need be assigned to input temperature information. Therefore, it is possible to use a microprocessor having a smaller number of ports than the conventional one, or to allocate the remaining ports of the microprocessor to the input of information other than temperature information. In addition, since the number of wires connecting the temperature sensor and the microprocessor can be reduced, the structure can be simplified.

Further, when the temperature judgment processing is performed by using the comparator composed of the hardware circuit, only one comparator needs to be prepared for the plurality of temperature sensors, so that the structure of the hardware circuit is simple. Can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a first exemplary embodiment of the present invention.

2A to 2C are circuit diagrams showing different configuration examples of a temperature sensor.

FIG. 3 is a circuit diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration example of an inverter circuit used in the embodiment of the present invention.

FIG. 6 is a graph showing an example of changes in the resistance value of each temperature sensor and the parallel combined resistance value of the temperature detection units when the electric motor is in a steady state in each embodiment of the present invention.

FIG. 7 is a graph showing an example of changes in the resistance value of each temperature sensor and the parallel combined resistance value of the temperature detection units when the electric motor enters an unsteady state during operation in each embodiment of the present invention. .

FIG. 8 is a graph showing another example of changes in the resistance value of each temperature sensor and the parallel combined resistance value of the temperature detection units when the electric motor enters an unsteady state during operation in each embodiment of the present invention. Is.

FIG. 9 is a front view showing an armature of a brushless DC electric motor as an object to be detected in each embodiment of the present invention.

FIG. 10 is a configuration diagram showing a configuration of a conventional temperature detection device.

[Explanation of symbols]

3u to 3w ... Armature coil, 4u to 4w ... Temperature sensor, 4 ... Temperature detector, 5 ... Microprocessor, 6
... resistor, 15 ... comparator, 16,17,18 ... resistor forming a resistance voltage dividing circuit, 20 ... frequency / voltage conversion circuit forming a speed detection circuit, 21 ... reference signal generating circuit, 22
... comparator.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuichi Muramatsu             3744 Ooka, Numazu City, Shizuoka Prefecture             In the company (72) Inventor Yutaka Inaba             3744 Ooka, Numazu City, Shizuoka Prefecture             In the company F-term (reference) 2F056 RG01 RG02 RG04 RG08                 5H560 BB04 BB12 DA02 DB07 DC05                       EB01 JJ06 TT15 UA05 XA04                       XA05

Claims (7)

[Claims] 1. A temperature detection device for obtaining information on the temperature of an object to be detected, wherein a plurality of temperature sensors having a characteristic that a resistance value changes according to temperature are provided at a plurality of heat generating points of the object to be detected. The temperature detection unit includes a temperature detection unit that is arranged in a state of being thermally coupled and that is configured by connecting the plurality of temperature sensors in parallel, and a circuit that applies a DC voltage to both ends of the temperature detection unit. Temperature detecting device comprising a temperature detecting circuit for outputting a voltage signal whose magnitude changes in accordance with a change in resistance value at both ends of the section as a temperature detecting signal including information on an average value of temperatures of the plurality of heat generating points. . 2. An object that is subject to local overheating, in which the temperature of some heat generating points becomes higher than the temperature of other heat generating points when an unsteady state occurs, A temperature detection device for obtaining information on whether or not the temperature of each heat generation point of an object to be detected is within an allowable range, wherein a plurality of temperature sensors having a characteristic that a resistance value changes according to temperature are A temperature detection unit that is thermally coupled to each of a plurality of heat generation points including a heat generation point where local overheating of an object may occur, and that is configured by connecting the plurality of temperature sensors in parallel with each other, and the temperature detection section. And a circuit for applying a voltage to the temperature detection unit as a temperature detection signal corresponding to the average value of the temperature of the plurality of heat generation points voltage signal that changes with the change of the resistance value of both ends of the temperature detection unit. Output temperature detection circuit, The detected object state determining means for determining whether the state of the detected object is in a steady state or a non-steady state, and the detected object is in a steady state by the detected object state determining means. In the state determined to be, the magnitude corresponding to the temperature detection signal output from the temperature detection circuit when the temperature of each of the plurality of heat generation points of the detected object is equal to the upper limit value of the allowable temperature range. First having
Of the temperature detection signal is compared with the magnitude of the temperature detection signal, and whether the temperature of each heat generation point of the detected object exceeds the allowable range based on the magnitude relationship between the magnitude of the temperature detection signal and the first determination value. In the state in which it is determined whether or not the detected object is in the unsteady state by the detected object state determination means, the temperature of a part of the plurality of heat generation points is the upper limit value of the allowable range. When the temperature reaches the temperature detection signal, the second determination value having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit is compared with the magnitude of the temperature detection signal to compare the magnitude of the temperature detection signal with the second value. A temperature detecting device, comprising: temperature determining means for determining whether or not the temperature of a part of the plurality of heat generating points exceeds an allowable range based on the magnitude relationship with the determination value. 3. An n-phase (n is an integer of 2 or more) armature coil is provided, which is partially provided when the rotation speed becomes less than a set value or becomes zero in a state where an armature current is applied. The temperature of the armature coil of the phase is higher than the temperatures of the armature coils of the other phases, and the temperature of the armature coil of the electric motor is within the allowable range, as the detection target is an electric motor in which local overheating occurs. A temperature detecting device for obtaining information as to whether or not n temperature sensors having a characteristic that a resistance value changes according to temperature are thermally coupled to n armature coils of the electric motor, respectively. And a circuit for applying a constant voltage to the temperature detection unit, the temperature detection unit being configured by connecting the n temperature sensors in parallel with each other.
A temperature detection circuit that outputs a voltage signal whose magnitude changes in accordance with a change in resistance value at both ends of the temperature detection unit as a temperature detection signal having a magnitude corresponding to an average value of the temperatures of the n-phase armature coils. And a rotation speed detection unit that detects the rotation speed of the electric motor, and a rotation speed determination unit that determines whether or not the rotation speed of the electric motor detected by the rotation speed detection unit exceeds a set value that is set to be sufficiently small. And a state in which the rotation speed determination means determines that the rotation speed of the electric motor exceeds a set value, when the temperature of each of the n-phase armature coils is equal to the upper limit value of the allowable temperature range. A first determination reference signal having a magnitude corresponding to the temperature detection signal output from the temperature detection circuit, and the rotation speed determination means determines the rotation speed of the electric motor. In the state that is determined not to be above,
A second magnitude having a magnitude corresponding to a temperature detection signal output from the temperature detection circuit when the temperature of a part of the armature coils of the n-phase reaches the upper limit value of the allowable range. Based on the magnitude relationship between the temperature detection signal and the first determination reference signal, it is determined whether the temperature of each of the n-phase armature coils exceeds an allowable range based on the magnitude relation between the temperature detection signal and the first determination reference signal. Temperature determining means for determining whether or not the temperature of the part of the armature coils exceeds an allowable range based on the magnitude relationship between the temperature detection signal and the second determination reference signal. Temperature detection device. 4. The rotation speed detecting means converts a signal generator that generates a pulse signal whose frequency is proportional to the rotation speed of the electric motor and a frequency or a generation cycle of the signal generated by the signal generator into a rotation speed. The temperature detecting device according to claim 3, wherein the temperature detecting device comprises a rotating speed converting means. 5. The temperature detecting circuit comprises a resistor connected in series to the temperature detecting section, and a constant voltage for applying a constant DC voltage across the series circuit of the temperature detecting section and the resistor. The temperature detecting device according to claim 1, further comprising a power supply circuit, which outputs the voltage signal from both ends of the resistor or both ends of the temperature detecting unit. 6. The temperature determining means comprises a voltage comparator that compares the temperature detection signal with the determination reference signal and generates outputs of different levels according to the magnitude relation between the temperature detection signal and the determination reference signal. Claims 3, 4, or 5
The temperature detection device according to. 7. The temperature determining means is constituted by a microprocessor programmed to perform a determination process of the magnitude relationship between the temperature detection signal and the determination reference signal, as claimed in claim 3, 4, or 5. Temperature detection device.