JP2003143750A - Overload protective device of motor drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overload protective device of a motor drive system for carrying out protection by fully detecting an increase in winding temperature of a motor caused by the generation of an overload state. SOLUTION: The temperature of a current-detecting resistor 44 at the feeding path of a drive power supply to a motor 3 for rotating an air-blowing fan 2 is detected by a thermistor 45. When the temperature of the current-detecting resistor 44 reaches a prescribed temperature of 150 deg.C, the level of a drive control signal generated from an ECU of an air conditioner to a drive control unit 34 is made to decrease by 10% by the temperature-detecting circuit 43A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload protection device for a system for driving a motor, which detects when the motor is in an overload state and performs protection.

[0002]

2. Description of the Related Art FIG. 7 shows an electrical configuration of a drive system of a motor used in a vehicle for rotating a blower fan. In FIG. 7, a fan motor drive system 1 is configured such that a brushless motor 3 that rotates a blower fan 2 and a drive device 4 that is formed on a substrate and that controls the brushless motor 3 are housed in a casing (not shown). ing. The blower fan 2 blows the cooling air of the vehicle air conditioner into the passenger compartment, and the fan motor drive system 1 and the blower fan 2 are arranged in the air conditioner unit.

A power supply terminal + B of the drive unit 4 is connected to a positive side terminal of a battery 7 mounted on a vehicle through a relay or a switch 8, and a ground terminal E is a negative side terminal (earth) of the battery 7. Terminal) (also connected to the body ground terminal). In addition, the drive device 4
A control signal Sa for instructing the rotation speed of the brushless motor 3 (that is, the blower fan 2) is input to the signal input terminal SI of the air conditioner ECU 9.

The brushless motor 3 has, for example, a three-phase 6
A stator (not shown), which has a pole structure and in which Δ-connected windings 3u, 3v, 3w are wound, and a permanent magnet (a plastic magnet is arranged for position detection by the Hall element 10) are provided. The rotor 3r is arranged (shown as a two-pole structure in FIG. 7). The blower fan 2 is attached to the rotary shaft of the rotor 3r. The terminals of the windings 3u, 3v, 3w are respectively the output terminals 4u, 4v, 4w of the driving device 4.
It is connected to the.

In the casing, the rotor 3r is arranged on the upper surface side of the substrate on which the drive unit 4 is formed, and the Hall element 10 for detecting the magnetic pole position of the rotor 3r is mounted on the substrate. Has been. In addition to the Hall element 10, the driving device 4 is composed of an inverter circuit 11, a constant voltage circuit 12, a one-chip IC 13 customized for control, a temperature sensor 36, and the like.

The inverter circuit 11 is a P-channel type M
OSFETs 16 to 18, N-channel type MOSFET 1
9 to 21 and the free wheeling diodes 22 to 27 are the positive power supply line 1
4 has a configuration of a voltage type inverter circuit connected in a three-phase bridge between the negative side power source line 15 and the negative side power source line 15. The free wheeling diodes 22 to 27 are incorporated in the respective elements of the FETs 16 to 21, respectively. Here, the FETs 16 to 18 and the free wheeling diodes 22 to 24 constitute an upper arm, and the FETs
19 to 21 and the free wheeling diodes 25 to 27 form a lower arm. U phase, V in the inverter circuit 11
The phase-phase and W-phase output terminals 11u, 11v, and 11w are connected to the output terminals 4u, 4v, and 4w, respectively.

The IC 13 includes an input signal processing unit 28, a rotation speed setting unit 29, an energization pattern generation unit 30, and a lock protection unit 3.
1, current limiter 32, temperature protector 33, drive controller 34
Etc. Further, the constant voltage circuit 12 is configured to generate a control power supply from the voltage of the battery 7 and supply it to the IC 13.

The input signal processing unit 28 is the air conditioner ECU 9
The drive control signal of the motor 3 output as a PWM signal is buffered and output to the rotation speed setting unit 29.
The rotation point setting unit 29 converts the drive control signal into a DC voltage signal, and based on the position detection signal of the rotor 3r output from the Hall element 10, the rotation number setting signal is supplied to the drive control unit 34.
Output to. The energization pattern generation unit 30 uses the Hall element 1
The energization pattern signal is generated based on the position detection signal output from 0 and output to the drive control unit 34.

When the lock protector 31 detects a locked state in which the rotation of the rotor 3r is stopped due to an external factor based on the position detection signal output from the Hall element 10, it outputs a stop signal to the energization pattern generator 30. Then, the output of the energization pattern signal is stopped. When the current limiter 32 detects that an excessive current is flowing based on the terminal voltage of the galvanic resistor 35 arranged on the negative power supply line 15, the current limiter 32 outputs a stop signal to the drive controller 34 to output the motor 3 to the motor 3.
The drive of is stopped.

Further, the temperature sensor 36 has a chip thermistor arranged near the FETs 16 to 21 to detect their temperatures. When the temperature sensor 36 detects that the temperature of the FETs 16 to 21 has excessively increased by the temperature sensor 36, the temperature protection unit 33 outputs a stop signal to the energization pattern generation unit 30 to stop the output of the energization pattern signal. ing.

[0011]

However, in such a protection mode, the motor 3 does not lock up, and the overcurrent (the detection level is set to be considerably larger than the steady-state current level). There is a possibility that protection cannot be provided for an overload condition in which even the above) is not detected. For example, the motor 3 continues to rotate with some foreign matter caught between the blower fan 2 and the case,
If the rotation of the motor 3 is continued while the ventilation resistance is changed by opening a part of the case to check the rotation state of the motor 3 during maintenance, the current increases and the temperature of the windings 3u to 3w of the motor 3 increases. May rise and its heat generation may be a problem.

Further, the power supply voltage of the battery 7 is usually about 12V in a general passenger car, but the battery 7 having a voltage of about 24V is used in a shared car (bus). When the voltage of the battery 7 becomes high, in the motor 3, in order to suppress the amount of current flowing, the winding 3
The diameters of u to 3w are reduced and the resistance value is set to be high.

When the resistance value of the windings 3u to 3w becomes high, the degree of increase in the amount of heat generated becomes large when the amount of flowing current slightly increases. On the other hand, on the drive device 4 side, the amount of current in the steady state decreases due to the increase in the voltage of the battery 7, and the amount of heat generation of the entire circuit section tends to decrease. Therefore, there is a problem that even if the temperature of the FETs 16 to 21 is detected by the temperature sensor 36, the correlation with the temperatures of the windings 3u to 3w of the motor 3 is low, and it becomes difficult to perform appropriate temperature detection.

In addition, in a passenger car having a large vehicle body, a plurality of air-conditioning blowers 2 are arranged and used. In that case, the plurality of blower fans 2 are often arranged and used in one housing together with ducts for a blower path. In such an arrangement, for example, when performing maintenance, in order to confirm whether or not each blower fan is rotating, the operator opens the door provided in the housing and visually confirms. There must be. At that time, since the blowing resistance for each blower fan 2 is temporarily reduced, the rotation speed of the motor 3 tends to fall below the normal operating state, but the winding 3u is increased in order to increase the energization by the rotation speed control. Since the amount of current flowing through ~ 3w increases and the temperature of the winding rises, the above-mentioned problems associated with heat generation easily occur.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to appropriately detect that the winding temperature of a motor has risen due to the occurrence of an overload condition and perform protection. An object is to provide an overload protection device for a motor drive system.

[0016]

According to another aspect of the present invention, there is provided an overload protection device for a motor drive system, wherein a temperature detecting means detects the temperature of a galvanic resistance arranged in a supply path of a drive power source for the motor. . That is, since a current proportional to the current flowing through the winding of the motor flows through the galvanic resistance arranged in the supply path of the driving power source, the temperature of the galvanic resistance has a high correlation with the temperature of the winding. . When the detected temperature of the galvanic resistance reaches a predetermined temperature, the signal level lowering unit lowers the level of the command signal output by the control command output unit to the drive control unit. Then, the number of rotations of the motor that rotates the blower fan decreases, so that the amount of current flowing through the winding can be suppressed. Therefore, the occurrence of an overload condition when the motor is not locked can be detected based on the temperature rise of the galvanic resistance, and the winding of the motor and its peripheral circuits can be appropriately protected.

According to another aspect of the motor drive system overload protection device of the present invention, the signal level lowering means lowers the level of the command signal, and thereafter, the temperature of the galvanic resistance is constant with reference to a predetermined temperature. When it is detected that there is a difference, the level of the command signal is returned to the original state. That is, if the level of the command signal is lowered by the action of the signal level lowering means, and if it can be estimated that the temperature of the winding of the motor has dropped to some extent, the command signal level can be restored to the original state by returning to the original state. The drive can be continued.

According to another aspect of the motor drive system overload protection device of the present invention, the signal output stopping means outputs the command signal when the temperature of the galvanic resistance detected by the temperature detecting means reaches the upper limit temperature. Stop output. That is, even if the level of the command signal is lowered by the action of the signal level lowering means, if the current detection resistance, that is, the temperature of the winding of the motor further rises, the output of the command signal is stopped to rotate the motor. Can be stopped and the winding of the motor can be surely protected.

According to another aspect of the motor drive system overload protection device of the present invention, the signal output stopping means stops the output of the command signal and then the temperature of the galvanic resistance is a constant temperature based on the upper limit temperature. When it is detected that there is a difference, the level of the command signal is returned to the original state. In other words, the level of the command signal is not returned to the original state unless the temperature of the galvanic resistance decreases with the constant temperature difference.

That is, when the temperature of the winding of the motor reaches the upper limit temperature, it is assumed that a serious problem has occurred in the drive system of the motor. Therefore, even if the detected temperature is slightly lowered, the level of the command signal is not returned to the original state, the operation of the motor is substantially stopped, and the worker can check the drive system. . In this case, it goes without saying that the "constant temperature difference" in claim 4 is set to be larger than the temperature difference in claim 2.

According to the overload protection device for the motor drive system of the fifth or sixth aspect, even if the signal level lowering means is not provided as in the first or the second aspect, the signal output stopping means is the third or the third aspect. 4 can be operated in the same manner. Incidentally, the upper limit temperature in this case may be set without being restricted by the predetermined temperature in claim 1 or 2. Further, the "constant temperature difference" in claim 6 does not necessarily need to be set to be larger than the temperature difference in claim 2, and may be set to an optimum temperature difference in the configuration having only the signal output stopping means. Good.

According to another aspect of the motor drive system overload protection device of the present invention, the temperature detecting means and the galvanic resistance are previously configured as an integrated component, and the component is a circuit board on which a drive circuit is formed. It is mounted by soldering. That is, in order to detect the temperature of the galvanic resistance more accurately by the temperature detecting means, it is desirable to arrange them so that they are in close contact with each other. Therefore, if both are configured as an integral part in advance, the above-described form can be easily achieved, and the temperature detection accuracy of the galvanic resistance can be improved.

According to another aspect of the motor drive system overload protection device of the present invention, the galvanic resistance is constituted by a conductor having a slight resistance component, and the conductor has a cross-sectional area which is in contact with the temperature detecting means. It is formed so that it is relatively small and the cross-sectional area of the portion to be soldered to the circuit board is relatively large.

That is, regarding the portion where the temperature is detected in the galvanic resistance, the amount of current flowing through the galvanic resistance changes if the resistance of the portion is increased by reducing the cross-sectional area of the conductor. Since the temperature change due to the increase in temperature becomes large, the temperature can be easily detected by the temperature detecting means. Also, by increasing the conductor cross-sectional area of the portion to be soldered to the circuit board, it is possible to suppress the degree of temperature rise when the amount of current flowing through the galvanic resistance increases. In addition, since heat dissipation efficiency is also increased, it is possible to prevent thermal stress from being applied to the soldered portion due to heat generation.

According to another aspect of the motor drive system overload protection device of the present invention, the galvanic resistance has a shape in which the portion in contact with the temperature detecting means is along the outer shape of the temperature detecting means. According to this structure, the contact area between the galvanic resistance and the temperature detecting means can be increased, so that the temperature of the galvanic resistance can be detected with higher accuracy.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. The same parts as those in FIG. 7 are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. FIG. 1 shows a motor drive system 41.
2 shows an electrical configuration of the above. The drive system 41 is
The IC 13 in the drive system 1 is replaced with an IC 42, and two sets of temperature detection circuits 43A (signal level lowering means) and 43B (signal output stopping means) are arranged outside the IC 42.

Further, a galvanic resistor 44 instead of the galvanic resistor 35 is used.
And a thermistor (temperature detecting means) 4 for detecting the temperature
5 are arranged. In addition, these are the lock protection unit 3
1, the current limiting unit 32, the temperature protection unit 33, and the like are arranged as an alternative to protection means.

The IC 42 has an input signal processing unit 28 and a drive control unit 34, and in FIG.
8 is illustrated by a concrete circuit. Further, the rotation speed setting unit 29 and the energization pattern generation unit 30 are also provided, but they are not shown. The input signal processing unit 28 uses the air conditioner E
When the drive control signal (command signal) Sa from the CU (control command output unit) 9 is received via the resistor 46, simple signal processing is performed, and the processed signal is transmitted to the rotation speed setting unit 29. .

The air conditioner ECU 9 outputs the drive control signal Sa in a PWM format signal and controls the rotation speed of the motor 3 by the duty of the signal pulse. The input signal processing unit 28 includes a signal level converting unit 28a and a first integrating circuit 28.
b and the second integrating circuit 28c.

The signal level converter 28a is mainly composed of a comparator 47 and an NPN type transistor 48. The output terminal of the comparator 47 is connected to the base of the transistor 48.
Is the reference voltage V applied to the inverting input terminal of the drive control signal Sa received through the resistor 49 at the non-inverting input terminal.
Outputs a signal based on the result of comparison with ref. The non-inverting input terminal of the comparator 47 is connected to the control power supply Vcc via the resistor 40.

The collector of the transistor 48 is connected to the control power supply Vcc through the resistor 50, and the emitter of the transistor 48 is
It is connected to the ground via the resistor 51, and is also connected to the input terminal of the first integrating circuit 28b. The signal level conversion unit 28a outputs a signal in which the maximum value of the PWM signal is converted to a level divided by the resistors 50 and 51.

First integrating circuit 28b connected in series
And the second integrator circuit 28c, the resistor 52 (b,
c), capacitor 53 (b, c) and operational amplifier 54
It is composed of (b, c). The output terminal of the operational amplifier 54c of the second integrating circuit 28c is connected to the input terminal of the drive control unit 34. The capacitor 5
3b and 53c are externally attached to the IC 42.

At the common connection point of the resistor 52b and the capacitor 53b in the first integration circuit 28b, an integration signal in which a ripple of a high frequency component included in the PWM signal is slightly observed is observed, and in the second integration circuit 28c. At the common connection point of the resistor 52c and the capacitor 53c, an integrated signal from which the ripple is substantially removed is observed. That is, a DC voltage signal corresponding to the duty of the PWM signal output from the air conditioner ECU 9 is input to the input terminal of the drive control unit 34.

Further, the resistor 5 in the second integrating circuit 28c
The common connection point of 2c and the capacitor 53c is connected to the output terminals of the two sets of temperature detection circuits 43A and 43B.
Hereinafter, the circuit configurations of the temperature detection circuits 43A and 43B will be described. However, since the circuit connection configurations of the two are the same, the symbols "A, B" are omitted unless it is necessary to distinguish them. One end of the thermistor 45 described above is connected to the control power supply Vcc via the resistor 55, and the other end is connected to the ground line GL connected to the ground terminal E. The common connection point between the thermistor 45 and the resistor 55 is connected to the inverting input terminal of the comparator 56 that constitutes the temperature detection circuit 43.

The non-inverting input terminal of the comparator 56 is connected to the ground line GL via the resistor 57 and is also connected to the collector of the NPN type transistor 59 via the resistor 58. The emitter of the transistor 59 is connected to the ground line GL. Further, the non-inverting input terminal of the comparator 56 is connected to the power supply terminal + B via the resistor 60.

The output terminal of the comparator 56 is connected to the bases of the NPN type transistors 61 and 62, connected to the control power supply Vcc via the resistor 63, and further connected to the ground line GL via the capacitor 64. It is connected. The emitters of the transistors 61 and 62 are both connected to the ground line GL, and the collector of the transistor 61 is connected via the resistor 65 to the common connection point of the resistor 52c and the capacitor 53c in the second integrating circuit 28c described above. There is.

The collector of the transistor 62 is connected to the base of the transistor 59, and is also connected to the power source VBO for each operational amplifier via the resistor 66. Note that VBO is set to be substantially equal to the voltage of the constant voltage circuit 12 (for example, 12V). However, the resistors 57A, 58A, 60A, 65A in the temperature detection circuit 43A
Resistance value and the resistance 57B in the temperature detection circuit 43B,
It is set to a value different from the resistance values of 58B, 60B and 65B.

FIG. 2 shows a galvanic resistor 44 and a thermistor 45.
Is a concrete configuration example centered on. The galvanic resistor 44 and the thermistor 45 are PPS (Polyphenyle) in advance.
ne Sulfide) is integrally assembled to a holder 67 composed of a plate, and in that state is electrically connected by soldering to a circuit board on which the inverter circuit (driving circuit) 11 and the IC 42 are mounted. It has become so.

The galvanic resistor 44 is made of a conductor (for example, Ni-Cu alloy) having a slight resistance, and its resistance value is set to about 15 mΩ. The shape of the galvanic resistor 44 is formed so that the cross-sectional area of the portion where the temperature is detected by contacting the thermistor 45 is relatively small and the cross-sectional area of the portion of the circuit board which is soldered to the ground pattern is relatively large. Has been done. By forming the shape of the galvanic resistance 44 in this way, the sensitivity to temperature changes is improved, and the temperature rise is suppressed and heat is radiated to the portion where the soldering with the circuit board is performed, and the thermal resistance is improved. I try to avoid stress as much as possible.

The galvanic resistor 44 and the thermistor 45 are arranged in a form orthogonal to each other on the holder 67 as shown in FIG. 2 (a), and the portion where the galvanic resistor 44 and the thermistor 45 contact each other is As shown in FIG. 2 (b), it is formed in an arcuate substantially U-shape so as to follow the outer shape of the thermistor 45 having a circular cross section. With such a shape, the contact area between the galvanic resistance 44 and the thermistor 45 is maximized, so that the temperature can be properly detected. Further, the galvanic resistor 44 and the thermistor 45 are adhered to each other by dropping a silicone adhesive or the like. In the above configuration, the galvanic resistor 44, the thermistor 45, and the temperature detection circuits 43A and 43B form an overload protection device 68. In addition, the inverter circuit 11,
The constant voltage circuit 12 and the IC 42 to which the overload protection device 68 is added constitute a drive device 69 which replaces the drive device 4.

Next, the operation of this embodiment will be described with reference to FIGS. The thermistor 45 generally has a negative resistance characteristic (see FIG. 3), and its resistance value tends to decrease as the temperature rises. Therefore, the divided potential VT at the inverting input terminal of the comparator 56 forming the temperature detection circuit 43 decreases as the temperature of the galvanic resistor 44 rises.

When the output terminal of the comparator 56 is at the low level, the transistor 62 is off, so that the base current is flowing to the transistor 59 through the resistor 66 and the transistor 59 is on. Therefore, the non-inverting input terminal of the comparator 56 and the ground line GL
The resistors 57 and 58 are connected in parallel between and, and as a result, the divided potential at the non-inverting input terminal of the comparator 56 is low.

When the output terminal of the comparator 56 becomes high level, the capacitor 64 is charged and its terminal voltage rises, and the base current is supplied to the transistor 62 to turn it on. Then, the base current of the transistor 59 stops flowing and the transistor 59 is turned off.
Between the non-inverting input terminal 6 and the ground line GL,
Only the resistor 57 is connected. As a result, the divided potential at the non-inverting input terminal of the comparator 56 rises.

As described above, the resistance values of the resistors 57A, 58A, 60A in the temperature detection circuit 43A and the resistance values of the resistors 57B, 58B, 60B in the temperature detection circuit 43B are set to different values. The divided potentials when the respective transistors 59A and 59B are turned on and off are set to the levels shown in FIG. 4, for example. That is, the levels are set in the following order from higher level to lower level. VBH temperature detection circuit 43B: transistor 59B (OFF) VAH temperature detection circuit 43A: transistor 59A (OFF) VAL temperature detection circuit 43A: transistor 59A (ON) VBL temperature detection circuit 43B: transistor 59B (ON)

The setting of these four partial potentials is
The temperature is set to correspond to the temperature shown in FIG. Temperature of thermistor 45 Winding temperature of motor 3 (estimation) VBL 195 ° C 230 ° C VAL 150 ° C 185 ° C VAH 40 ° C −VBH −30 ° C or lower −30 ° C or lower Since a current proportional to the current flowing in 3u to 3w flows, the temperature of the galvanic resistor 44 detected by the thermistor 45 has a high correlation with the temperatures of the windings 3u to 3w of the motor 3. Therefore, the windings 3u to 3w of the motor 3 are detected based on the temperature detected by the thermistor 45.
It is possible to reasonably estimate the temperature of. It should be noted that the temperature of the thermistor 45 and the estimated value of the winding temperature of the motor 3 are examples based on the actual measurement results performed by the inventors of the present invention.

Now, the case shown in FIG. 4 will be described. When the motor 3 is in a normal operating state, the winding temperature of the motor 3 is 185 ° C. or lower, the temperature detected by the thermistor 45 is low, and its resistance value is high. Therefore, the comparator 56
The divided potential VT at the inverting input terminal of is also high. Then, for example, as described above, the motor 3 continues to rotate in a state in which some foreign matter is caught between the blower fan 2 and the case, or a part of the case is checked to check the rotation state of the motor 3 during maintenance. When the motor 3 is overloaded and the amount of current flowing through the windings 3u to 3w increases by operating the device while the ventilation resistance is reduced by opening it, the amount of current flowing through the galvanic resistor 44 also increases. To increase. Then, since the temperature of the resistor 44 rises, the temperature detected by the thermistor 45 rises and its resistance value drops, and the divided potential VT also drops with the drop.

Then, the divided potential VT is compared with the comparator 56.
When it becomes lower than the divided potential VAL at the non-inverting input terminal of A, the output terminal of the comparator 56A becomes high level and the transistor 61A is turned on. Then IC42
The electric charge charged in the capacitor 53c in the internal second integrating circuit 28c is the resistance 65A and the transistor 6
It is discharged via 1A.

The resistor 52 in the second integrating circuit 28c
The resistance ratio between c and the resistor 65A is set to 1: 9, and the air conditioner ECU 9 provided to the drive control unit 34 by discharging the capacitor 53c through the resistor 65A.
The level of the drive control signal is reduced by about 10%.

When the output terminal of the comparator 56A becomes high level, the transistor 62 as described above.
A turns on, transistor 59A turns off, and the divided potential at the non-inverting input terminal of comparator 56A is VAL.
Changes from VAH to VAH. After that, the motor 3 continues to be driven by the drive control signal that is lowered by 10%, so that the winding 3u.
When the temperature of 3w tends to decrease, the partial potential VT increases. And the galvanic resistance 4 detected by the thermistor 45
When the temperature of 4 becomes 40 ° C. or less, the temperature difference of 150 ° C. corresponding to the partial voltage potential VAL decreases by 110 ° C. and exceeds the partial voltage potential VAH, the output terminal of the comparator 56A becomes low level, and the air conditioner ECU 9 The level of the drive control signal is output as it is.

Next, the case shown in FIG. 5 will be described. When the motor 3 is in an overload state that is heavier than in the case described above and the amount of current flowing through the windings 3u to 3w increases significantly, the divided potential VT decreases, and the divided potential VAL on the non-inverting input terminal side is lower than the divided potential VAL. By lowering the level of the drive control signal to 1
Even if the temperature is reduced by 0%, the rise in temperature detected by the thermistor 45 does not decrease, the divided potential VT continues to decrease, the detected temperature becomes 195 ° C (upper limit temperature), and the estimated value of the winding temperature exceeds 230 ° C. In this state, the voltage falls below the divided potential VBL on the comparator 56B side.

Then, the output terminal of the comparator 56B becomes high level, and the transistor 61B also turns on. In this case, the capacitor 53c in the second integrating circuit 28c
The electric charge charged in the capacitor is discharged through the resistor 65B and the transistor 61B. Here, the resistance value of the resistor 65B is the resistance value of the resistor 5 in the second integrating circuit 28c.
It is set to be extremely smaller than 2c, and the capacitor 53c is almost completely discharged through the resistor 65B. Therefore, the level of the drive control signal of the air conditioner ECU 9 provided to the drive control unit 34 becomes substantially 0%, and the drive signal output is substantially stopped.

When the winding temperature of the motor 3 rises to this level, it is assumed that a serious abnormality has occurred in the drive system of the motor 3. Therefore, when the output terminal of the comparator 56B becomes high level, 62B is turned on and the transistor 59B is turned off to change the divided potential at the non-inverting input terminal of the comparator 56B from VBL to VBH. The divided potential VBH is set corresponding to a state in which the temperature detected by the thermistor 45 is −30 ° C. or lower, that is, a state in which the temperature difference is decreased by 225 ° C. with respect to the upper limit temperature of 195 ° C. The temperature setting is not possible in the operating environment of the motor 3. That is, in this case, the operation of the motor 3 is substantially stopped, the drive system is checked, and the cause of the abnormality is removed.

As described above, the temperature detecting circuits 43A, 4A
By setting the temperature by 3B, the temperature detected by the thermistor 45, the estimated temperature of the winding of the motor 3, and the drive control unit 34
The relationship with the input level of the drive control signal viewed from the side is as shown in FIG. 6, and the temperature detection circuits 43A and 43B have a hysteresis in the temperature characteristic due to the circuit operation.

As described above, according to this embodiment, the temperature of the galvanic resistor 44 arranged in the supply path of the driving power source to the motor 3 for rotating the blower fan 2 is detected by the thermistor 45, and the temperature detecting circuit 43A is detected. When the temperature of the galvanizing resistor 44 reaches a predetermined temperature of 150 ° C., the air conditioner E
The level of the drive control signal that the CU 9 outputs to the drive control unit 34 is reduced by 10%.

That is, since the temperature of the galvanic resistor 44 has a high correlation with the temperatures of the windings 3u to 3w of the motor 3, an overload occurs when the motor 3 does not lock due to the temperature reaching a predetermined temperature. It is possible to detect the occurrence of the state, reduce the rotation speed of the motor 3 and suppress the amount of current flowing through the windings 3u to 3w, and appropriately protect the windings 3u to 3w of the motor 3 and its peripheral circuits. it can.

Then, the temperature detecting circuit 43A lowers the temperature of the galvanic resistor 44 to 1 after reducing the level of the drive control signal.
When it is detected that the temperature has dropped from 50 ° C. to 40 ° C., the level of the drive control signal is returned to the original state.
When it can be estimated that the temperature of 3w has dropped to some extent, the drive control signal level is returned to the original state and the motor 3
Can be continuously driven.

Further, according to the present embodiment, the temperature detection circuit 4
3B is a galvanic resistance 4 detected by the thermistor 45.
When the temperature of No. 4 reaches the upper limit temperature of 195 ° C., the output of the drive control signal is stopped. That is, the level of the drive control signal is 10% by the action of the temperature detection circuit 43A.
Even if lowered, the galvanic resistance 44, that is, the winding 3u of the motor 3
When the temperature of 3 to 3w further rises, the output of the drive control signal is stopped to stop the rotation of the motor 3 and the windings 3u to 3w of the motor 3 can be reliably protected.

Then, the temperature detecting circuit 43B stops the output of the drive control signal, and then the temperature of the galvanic resistor 44 becomes-.
The level of the drive control signal is not returned to the original state unless the temperature drops to 30 ° C. That is, when the temperature of the windings 3u to 3w of the motor 3 reaches the upper limit temperature, it is assumed that a serious malfunction has occurred in the drive system of the motor 3, so that the temperature detected by the thermistor 45 is It is possible to prevent the level of the drive control signal from returning to the original state by a slight decrease and to substantially stop the operation of the motor 3 so that the operator can check the drive system.

Further, according to the present embodiment, the thermistor 45.
The galvanic resistor 44 and the galvanic resistor 44 are assembled into the holder 67 to form an integrated component in advance, and the component is mounted on the circuit board on which the inverter circuit 11 is formed by soldering. That is, in order to detect the temperature of the galvanic resistance 44 more accurately by the thermistor 45, it is desirable to arrange them so that they are in close contact with each other. This can be easily done and the temperature detection accuracy of the galvanic resistor 44 can be improved.

The galvanic resistor 44 is composed of a conductor having a slight resistance, and the conductor has a relatively small cross-sectional area in contact with the thermistor 45 and a cross-sectional area in a portion to be soldered to the circuit board. Was formed to be relatively large. That is, regarding the portion where the temperature is detected by the thermistor 45, the resistance of the portion can be increased by reducing the conductor cross-sectional area, and the temperature can be easily detected by the thermistor 45. Further, regarding the portion soldered to the circuit board, it is possible to suppress the degree of temperature rise when the amount of current flowing through the galvanic resistance 44 rises and improve the heat dissipation efficiency. Therefore, it is possible to prevent the heat generated at that portion from exerting a thermal stress on the soldered portion.

In addition, the galvanic resistor 44 is connected to the thermistor 45.
Since the portion contacting with the thermistor 45 is shaped so as to follow the outer shape of the thermistor 45, that is, it is formed in a substantially U-shaped arc shape so as to follow the outer shape of the thermistor 45 having a circular cross section, the galvanic resistance 44 The area where the thermistor 45 and the thermistor 45 contact each other can be increased, and the temperature of the galvanic resistor 44 can be detected with higher accuracy.

The present invention is not limited to the embodiments described above and shown in the drawings, but the following modifications or expansions are possible. In addition to the configuration of the present embodiment, a lock protection unit 31, a current limiting unit 32, and a temperature protection unit 33 in the conventional configuration may be provided to improve the fail safe function. The setting of the detection temperature and the like are merely examples, and may be appropriately changed and implemented according to the individual design. Further, the decrease amount of the drive control signal in the temperature detection circuit 43A is not limited to 10% and may be changed appropriately. The temperature detection circuits 43A and 43B may be configured to respectively latch a state in which the signal level is lowered and a state in which the signal output is stopped when the detected temperature exceeds the predetermined temperature and the upper limit temperature.

Either one of the temperature detection circuits 43A and 43B may be deleted. When only the temperature detection circuit 43B is provided, the upper limit temperature is set to the same temperature as the predetermined temperature of the temperature detection circuit 43A, and the signal output is stopped when the detected temperature exceeds the predetermined temperature (= upper limit temperature). You may comprise so that it may be made. The temperature difference for returning the signal output to the original state may be set similarly to the temperature detection circuit 43A. If there is no problem with the thermal stress applied to the soldered portion, the galvanic resistor 44 may be shaped so that its conductor cross-sectional area is uniform. Galvanic resistance 44 and thermistor 45
If the two can be sufficiently contacted, they may be directly attached to the circuit board. The present invention is not limited to the motor 3 that rotates the blower fan 2, and can be applied to any motor that can change the load amount to be driven.

[Brief description of drawings]

FIG. 1 is a diagram showing an electric configuration of a motor drive system, which is an embodiment in which the present invention is applied to a motor for rotating a blower fan.

2A and 2B show a state in which a galvanic resistance and a thermistor are assembled to a holder, where FIG. 2A is a plan view and FIG. 2B is a front view.
(C) Side view

FIG. 3 is a diagram showing temperature characteristics of a thermistor.

FIG. 4 is a diagram showing an example of a change in temperature detected by a thermistor, showing a case where the detected temperature exceeds a predetermined temperature.

FIG. 5 is a diagram showing an example of a change in temperature detected by a thermistor, showing a case where the detected temperature exceeds an upper limit temperature.

FIG. 6 is a diagram showing temperature characteristics of two temperature detection circuits.

FIG. 7 is a diagram corresponding to FIG. 1 showing a conventional technique.

[Explanation of symbols]

3 is a motor, 3u to 3w are windings, 9 is an air conditioner ECU
(Control command output unit), 11 is an inverter circuit (drive circuit), 34 is a drive control unit, 41 is a motor drive system,
43A is a temperature detection circuit (signal level lowering means), 43B
Is a temperature detecting circuit (signal output stopping means), 44 is a galvanic resistance, 45 is a thermistor (temperature detecting means), and 68 is an overload protection device.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kennobu Shimoda             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Toshiyuki Morimoto             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F term (reference) 5G044 AA04 AB03 AC05 AE01 CA01                       CA11 CC02 CE05                 5H560 AA01 BB04 BB08 BB12 DA02                       DA08 EB01 HB10 JJ02 JJ06                       SS02 UA05

Claims (9)

[Claims] 1. A drive control unit for driving a motor winding by energizing a winding of the motor through a drive circuit, and a command signal for controlling the rotation speed of the motor is output to the drive control unit. A motor drive system including a control command output unit, which is an overload protection device for preventing an overcurrent from flowing in a winding of the motor when the motor is in an overload state, A current detection resistor arranged in a path through which a drive circuit supplies drive power to the motor, temperature detection means for detecting the temperature of the current detection resistance, and the detection current detected by the temperature detection means. An overload protection device for a motor drive system, comprising: signal level lowering means for lowering the level of the command signal when the temperature of the flow resistance reaches a predetermined temperature. 2. When the signal level lowering means detects that the temperature of the galvanic resistance has dropped with a constant temperature difference with respect to the predetermined temperature as a reference after lowering the level of the command signal, the command 2. The overload protection device for a motor drive system according to claim 1, wherein the overload protection device is configured to restore the level of the signal to the original state. 3. A signal output stopping means for stopping the output of the command signal when the temperature of the galvanic resistance detected by the temperature detecting means reaches an upper limit temperature. Item 3. An overload protection device for a motor drive system according to Item 1 or 2. 4. The command output stop means, after stopping the output of the command signal, detects that the temperature of the galvanic resistance has decreased with a constant temperature difference with respect to the upper limit temperature as a reference. 4. The configuration according to claim 3, wherein the signal level is restored to the original state.
An overload protection device for the described motor drive system. 5. A drive control section for driving the motor by energizing the winding of the motor via a drive circuit, and a command signal for controlling the rotational speed of the motor is output to the drive control section. A motor drive system including a control command output unit, which is an overload protection device for preventing an overcurrent from flowing in a winding of the motor when the motor is in an overload state, A current detection resistor arranged in a path through which a drive circuit supplies drive power to the motor, temperature detection means for detecting the temperature of the current detection resistance, and the detection current detected by the temperature detection means. An overload protection device for a motor drive system, comprising: a signal output stopping means for stopping the output of the command signal when the temperature of the flow resistance reaches the upper limit temperature. 6. The command output stop means, after stopping the output of the command signal, detects that the temperature of the galvanic resistance has decreased with a constant temperature difference with respect to the upper limit temperature as a reference. 6. The configuration according to claim 5, wherein the signal level is restored to the original state.
An overload protection device for the described motor drive system. 7. The temperature detecting means and the galvanic resistor are previously configured as an integrated component, and the component is mounted by soldering on a circuit board on which the drive circuit is formed. The overload protection device for a motor drive system according to any one of claims 1 to 6. 8. The galvanic resistance is composed of a conductor having a slight resistance component, and the conductor has a relatively small cross-sectional area in contact with the temperature detecting means and is soldered to the circuit board. The overload protection device for a motor drive system according to claim 7, wherein the cross-sectional area of the portion is formed to be relatively large. 9. The overload protection of a motor drive system according to claim 8, wherein a portion of the galvanic resistance in contact with the temperature detecting means has a shape along an outer shape of the temperature detecting means. apparatus.