JP2000078880A - Controller for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for a brushless motor which can evade the state of high temperature of a drive control part. SOLUTION: An ambient temperature of a control microcomputer 1 which is detected with a thermistor 2 connected with a constant current circuit 3 and a temperature detecting part 11 is inputted in a high temperature judging part 12 and a low temperature judging part 13. When a flag 13 is 'normal state' and a detected temperature is at least a temperature threshold value of a high temperature value storage part 12a, the high temperature judging part 12 makes the flag 14 'reduced state'. In this state, a command speed inputted in a command speed input part 15 is corrected by a command speed correction part 17 so as to be lower than or equal to an upper limit speed reduced from the normal state which is stored in an upper limit speed storage part 15. A pulse output part 18 outputs a pulse signal corresponding to a command speed, and decreases a rotational speed. As a result, the heating value of a driving element and the like is reduced, and a continuous state of high temperature of the control microcomputer 1 or the like can be evaded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a brushless motor, and more particularly to a technology for avoiding a high temperature of a drive control unit.

[0002]

2. Description of the Related Art Conventionally, a brushless motor has been used for a blower fan for an air conditioner and a radiator cooling fan mounted on a vehicle, and a current is supplied to a control circuit including a control microcomputer and an armature winding. The field effect transistor (MOSFET) is housed in a single case, forms a drive control unit, and is fixed to the motor body.

[0003] Inside the case, an appropriate mounting layout is made, and the MOSFET and the control IC are kept at an appropriate temperature.

Further, a part of the current path of the armature winding is cut off, and a temperature fuse for detecting the temperature of the MOSFET is inserted at the cut off point. The fuse was blown to protect the windings and circuit elements such as MOSFETs.

[0005]

As described above, the conventional brushless motor has a control microcomputer and an MO.
It had a drive control unit that housed the SFET in a single case.

However, in order to increase the mounting efficiency inside the case and to reduce the size of the drive control unit, a control microcomputer (control circuit) is required at the time of high-speed rotation.
However, there was a concern that the operation would be unstable due to the high temperature inside the case. In addition, since the MOSFET (drive element) becomes hot at the time of high-speed rotation, improvement has been demanded.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a brushless motor control device capable of avoiding a high temperature of a drive control unit of the brushless motor.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, a brushless motor control device according to the present invention is a brushless motor control device for rotating a brushless motor at a command speed. Temperature detection means for detecting the temperature of the drive control unit, a maximum speed reduction means for reducing the maximum speed of the brushless motor when the detected temperature is equal to or higher than a predetermined temperature, and a command exceeding the reduced maximum speed. Command speed correcting means for correcting the command speed to be equal to or less than the reduced upper limit speed when a speed is input.

The present invention reduces the upper limit speed of the brushless motor when the temperature of a drive control unit including a drive element for driving the brushless motor and a control circuit for controlling the drive element is high. The purpose of the present invention is to reduce the heat generated from the driving elements constituting the control unit and the circuit patterns thereof and to avoid the continuous high temperature state of the drive control unit. That is, when the high temperature state of the drive control unit is detected by the temperature detection unit, the upper limit speed reduction unit reduces the upper limit speed of the brushless motor, and the command speed correction unit sets the command speed to
The correction is made so as to be equal to or less than the reduced upper limit speed. Then, the brushless motor rotates at the corrected command speed. Accordingly, the brushless motor does not rotate beyond the reduced upper limit speed, the amount of heat generated from the drive elements and the circuit patterns and the like is reduced, and the continuous high temperature state of the drive control unit can be avoided.

[0010]

According to the control device for a brushless motor of the present invention, when the high temperature state of the drive control unit is detected,
Since the upper deceleration is reduced and the command speed is corrected to be equal to or lower than the upper limit speed, the amount of heat generated from the drive elements and circuit patterns is reduced, and the drive control unit is not continuously exposed to a high temperature. Therefore, the operation of the drive control unit is stabilized, and occurrence of a failure is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for a brushless motor according to the present invention will be described below in detail with reference to FIGS.

FIG. 1 is a block diagram of a first embodiment of a control device for a brushless motor according to the present invention. The apparatus according to the present embodiment includes a control microcomputer 1
(Hereinafter referred to as “control microcomputer”)
When this temperature exceeds a predetermined temperature, the upper deceleration of the brushless motor is set lower than usual, and this speed is set as an upper limit,
Control the rotation speed.

The control microcomputer 1 is a main component of the control device, and detects a voltage across the thermistor 2 which receives a constant current from the constant current circuit 3.

As shown in FIG. 2, the control microcomputer 1 has a surface mount type shape, and the thermistor 2 is mounted on a printed wiring board and detects the ambient temperature of the control microcomputer 1.
When the ambient temperature changes, the internal resistance value of the thermistor 2 changes, and the voltage between both ends changes accordingly. Therefore, the ambient temperature of the control microcomputer 1 can be obtained from this voltage.

In FIG. 1, the temperature detecting section 11
This is an input unit for A / D converting the voltage signal (temperature detection signal) to obtain a detected temperature value.

The high temperature value storage section 12a and the low temperature value storage section 13a are both constituted by a ROM inside the control microcomputer 1, and the high temperature value storage section 12a has a temperature threshold value (high temperature threshold value) for reducing the upper deceleration. Is an area for storing. In this embodiment, a value corresponding to 85 ° C. is stored in consideration of the operating temperature range of the control microcomputer 1.
On the other hand, the low temperature value storage unit 13a is an area for storing a temperature threshold value (low temperature threshold value) for canceling the reduction of the upper limit speed, and stores a value corresponding to 75 ° C.

The flag 14 is a flag indicating whether or not the upper limit speed is reduced. When the control microcomputer 1 is started, it is initialized to a "normal state", that is, a state where the upper limit speed is not reduced. At the time of reduction, invert,
It becomes "reduced state".

The high temperature judging section 12 and the low temperature judging section 13 are both functions constituted by a program on the control microcomputer 1, and the high temperature judging section 12 sets the flag 14 to the "normal state".
At this time, the high temperature threshold value (85 ° C.) stored in the high temperature value storage unit 12a is compared with the detected temperature value output from the temperature detection unit 11, and the detected temperature value is equal to or higher than the high temperature threshold value (85 ° C.). , The flag 14 is set to the “reduced state”.

When the flag 14 is in the "reduced state", the low temperature judging section 13 compares the detected temperature value with the low temperature threshold value (75.degree. C.) stored in the low temperature value storage section 13a. When the temperature is equal to or lower than the low temperature threshold (75 ° C.), the flag 14 is set to “normal state”.

A voltage signal is input to the control microcomputer 1 as a speed command signal from an air-conditioning control device or a radiator control device. It is to find the speed.

The upper limit speed storage section 16 is a storage area constituted by a ROM inside the control microcomputer 1 for storing an upper limit speed set lower than the maximum rotation speed in the motor characteristics. In this embodiment, 1800 rpm
(Every minute) is stored. Hereinafter, this speed is referred to as “reduced upper limit speed”.

The command speed correcting section 17 is a function for correcting the command speed. When the flag 14 is in the "reduced state" and the command speed exceeds 1800 rpm, the command speed corresponding to 1800 rpm is forcibly changed. The program is set in the control microcomputer 1 so as to output the corrected value.

The pulse output unit 18 is a command speed correction unit 17
And outputs a pulse signal having a duty corresponding to the command speed output from the controller (pulse signal output means). The MOSFET is driven by this signal, and the rotation of the brushless motor is controlled.

Next, the control procedure in this embodiment will be described with reference to the flowcharts of FIGS.

FIG. 3 is a flowchart showing a procedure from the detection of the ambient temperature of the control microcomputer to the determination of the state of the flag 14.

First, the temperature detector 11 A / D converts the temperature detection signal to obtain a detected temperature value (S21). Next, it is determined whether the flag 14 is in the “reduced state” (S
22). When it is determined that the state is not the “reduced state” (N
O), it is determined whether the detected temperature value is equal to or higher than the high temperature threshold value stored in the high temperature value storage unit 12a (S23). When it is determined that the temperature is equal to or higher than the high temperature threshold (YES),
The flag 14 is inverted (S25), and then the step S
The control shifts to 21. On the other hand, if it is determined in step S22 that the temperature is in the “reduced state” (YES), it is determined whether the detected temperature value is equal to or less than the low temperature threshold value stored in the low temperature value storage unit 13a (S24). If it is determined that the temperature is equal to or lower than the low temperature threshold (YES), the flag 14 is inverted (S25), and the process proceeds to step S21. In addition, when it is determined NO in steps S23 and S24, the control shifts to step S21.

FIG. 4 is a flowchart showing a procedure for correcting the command speed.

First, the command speed input unit 15 detects a command speed (S31). Next, it is determined whether the flag 14 is in the “reduced state” (S32). If it is determined that the state is not the “reduced state” (NO), the pulse output unit 18
Outputs a pulse signal having a duty corresponding to the command speed (S35).

On the other hand, in step S32, the "reduced state"
Is determined (YES), that is, if the ambient temperature of the control microcomputer is determined to be high, whether the commanded speed has exceeded the “reduced upper limit speed” stored in the upper limit speed storage unit 16 is determined. Is determined (S33). If it is determined that the speed does not exceed the “reduced upper limit speed” (NO),
The process moves to S35. On the other hand, if it is determined that the speed has exceeded (YES), the command speed is corrected to the “reduced upper limit speed”, and the process proceeds to S35.

As described above, when the high temperature state of the ambient temperature of the control microcomputer is detected, the flag 14 is set to the "reduced state", and the high temperature state is determined from the state of the flag 14,
The command speed exceeding the “reduced upper limit speed” is corrected to be the “reduced upper limit speed”. Therefore, the brushless motor is prevented from rotating beyond its upper limit speed, and the amount of heat generated from the driving elements and circuit patterns is reduced, so that the temperature rise of the control microcomputer can be suppressed.

When it is determined that the detected temperature value is equal to or lower than the low temperature threshold value, that is, when the ambient temperature of the control microcomputer has sufficiently decreased, the flag 14 is inverted and the state automatically returns to the "normal state". Therefore, the rotation speed can be increased again.

FIG. 5A shows the structure of this embodiment.
FIG. 7 is a diagram illustrating a transition characteristic of an upper limit speed with respect to an ambient temperature of a control microcomputer.

Point S indicates the upper limit speed and the ambient temperature of the control microcomputer 1 at the time when the brushless motor starts at normal temperature (25 ° C.).

Even if the ambient temperature rises, the high temperature value storage unit 1
Until the high temperature threshold (85 ° C.) stored in 2a is reached,
The upper limit speed is not reduced, and the rotation speed can be increased up to the maximum rotation speed 2200 rpm of the motor as shown in the route.

When the temperature of the control microcomputer 1 reaches 85 ° C., the high temperature judging section 12 sets the flag 14 to the “reduced state”.
By setting to, the upper limit speed is 180 as shown in
Transition to 0 rpm.

Once the flag 14 is in the "reduced state",
Until the ambient temperature of the control microcomputer becomes equal to or lower than the low temperature threshold value (75 ° C.) stored in the low temperature value storage section 13a, this reduced state is maintained as shown in FIG.

When the ambient temperature of the control microcomputer falls and reaches 75 ° C., the low-temperature judging unit 13 sets the flag 14 from the “reduced state” to the “normal state”.
As shown in the above, the reduction of the upper limit speed is released, and thereafter, the rotation speed exceeds 1800 rpm, and the maximum is 2200 rpm.
Can be raised up to

By the way, the inside of the car parked under the hot sun becomes extremely hot, and the environment becomes severe even for the brushless motor of the air conditioner. The actual rotation speed is controlled so as to rise smoothly with a predetermined inclination.
Ambient temperature of the control microcomputer rises rapidly due to radiant heat from a MOSFET driving a brushless motor, a common mode choke coil, a bus bar or a circuit pattern of a printed wiring board, and solar heat.

FIG. 5B is a graph schematically showing the change of the actual rotation speed with respect to the elapsed time in such an actual use environment. , The transition timing of the upper limit speed is shown.

When the motor starts at time t0, the actual rotation speed increases from 200 rpm with the above-mentioned predetermined slope. Then, at time t1, the maximum speed 2 on the motor characteristics
When the rotation speed is increased to 200 rpm, the rotation speed is maintained thereafter. During this time, the ambient temperature of the control microcomputer is MO
The temperature rises due to the radiation heat of the SFET and the like.
Then, the state shifts to the “reduction state”, and the upper limit speed becomes 180
It becomes 0 rpm. After that, the actual rotational speed is suppressed up to 1800 rpm of the “reduced upper limit speed”. Therefore, during this period, the radiant heat from the MOSFET and the like is suppressed to be low, so that the ambient temperature of the control microcomputer also decreases. Then, at time t3, when the temperature reaches 75 ° C., the state returns to the “normal state” and the reduction of the upper limit speed is canceled, so that the rotation speed increases again. By repeating such a cycle, the temperature in the vehicle interior gradually becomes stable, and finally the ambient temperature of the control microcomputer also becomes stable, so that the actual rotation speed gradually approaches a constant speed.

Therefore, in this embodiment, while the upper deceleration in the rotation speed region is reduced, the amount of heat generated from the MOSFET, the common mode choke coil, the bus bar, the circuit pattern of the printed wiring board, etc. is reduced, and the control is performed. It is possible to prevent the microcomputer from continuously being in a high temperature state, and to stabilize its operation.

Since the transition between the reduced state and the normal state is performed with a hysteresis characteristic as described above,
The state in which the upper limit speed is reduced is not intermittent, but continues for a long time, and the ambient temperature of the control microcomputer can be sufficiently reduced.

In addition, when the ambient temperature drops sufficiently, the reduction of the upper limit speed is canceled, so that the rotation speed can be increased again.

In this embodiment, the "reduced upper limit speed" is stored in the ROM in advance. However, the same effect can be obtained by programming this to be calculated according to the detected temperature value. .

In the first embodiment, the device is configured to reduce the upper deceleration in the rotational speed range based on the ambient temperature of the control microcomputer. Since the armature winding current flows, if the current increases due to, for example, a short circuit in the winding, the MOSFET will be in a dangerously high temperature state. Therefore, a description will be given of a second embodiment of the brushless motor control device according to the present invention, in which the temperature of the MOSFET is detected and the rotation of the motor is stopped before the temperature becomes dangerously high.

FIG. 6A is a top view showing a method of mounting a surface mounted thermistor for detecting the temperature of a MOSFET on a printed wiring board, and FIG. 6B is a sectional view taken along the line AA of FIG. It is.

4 is a MOS for supplying a current to the armature winding.
FET 4a is its drain terminal. The drain terminal 4a is fixed to the terminal area C1a of the circuit pattern C1 formed on the surface of the printed wiring board B with solder S.

Reference numeral 5 denotes a surface mount type thermistor having electrodes 5a, 5a at both ends, and a circuit pattern C at the center.
1 and the terminal areas C2a of the circuit patterns C2 and C3,
Both electrodes 5a, 5a are fixed to C3a with solder S.

The thermistor 5 is connected to a constant current circuit similarly to the thermistor 2 used in the first embodiment, and is connected to the thermistor 5 in response to a temperature rise of the circuit pattern C1 due to heat transmitted from the MOSFET 4. When the internal resistance value changes, the voltage across it also changes proportionally.

As described above, the thermistor 5 is replaced with the one shown in FIG.
By mounting on a printed wiring board as shown in (b),
The temperature of the MOSFET 4 can be detected indirectly.

In this embodiment, the voltage signal across the thermistor 5 is input to the temperature detection unit 11 as the temperature detection signal shown in FIG. In the high temperature value storage unit 12a,
In consideration of the junction temperature of the MOSFET 4 and the heat capacity of the package, a high temperature threshold of 100 ° C. is set so as to avoid a failure due to a high temperature, and as in the control device of the first embodiment, a high temperature determination unit is provided. If it is determined at 12 that the detected temperature value is higher than the high temperature threshold value (100 ° C.), the flag 14 is set to “reduced state”.

Then, the value 0 is stored in the upper limit speed storage unit 16, and when the flag 14 is in the "reduced state", the command speed correction unit 17 forcibly sets the command speed to this value 0. to correct. Upon receiving the command speed, the pulse output unit 18 stops outputting the pulse signal, stops supplying current to the motor, and stops rotation.

Thereafter, if the cause of the temperature rise is eliminated, the detected temperature value becomes equal to or lower than the low temperature threshold value (80 ° C.) stored in the low temperature value storage unit 13a, and the flag 14 returns to the “normal state”. Then, the brushless motor can be rotated again.

Therefore, in the second embodiment of the brushless motor control device according to the present invention, even if the temperature of the MOSFET rises, the supply of current to the brushless motor is stopped before a failure occurs. The failure of the MOSFET can be avoided.

Also, without using a thermal fuse, a MOS
The FET can be protected, and the trouble of repair in the event of a failure is reduced. In addition, the use of a surface mount thermistor facilitates mounting on a printed wiring board. By adopting such a mounting form, the temperature of the MOSFET could be detected without variation.

As described above, in the first embodiment, the ambient temperature of the control microcomputer is detected, and in the second embodiment, the temperature of the circuit pattern connected to the MOSFET is detected. The location is not limited to these locations. For example, an effect can be obtained by detecting the temperature of the control microcomputer main body, the housing, or the radiator plate to which the drive element is attached.

As described above, according to the brushless motor control device of the present invention, the upper limit speed of the motor is reduced even if the temperature of the drive control unit is high, so that the drive control unit is continued. As a result, it is not exposed to high temperature, its operation is stabilized, and the occurrence of failure is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of a control device for a brushless motor according to the present invention.

FIG. 2 is a side view showing an attached state of a thermistor in the apparatus of FIG.

FIG. 3 is a flowchart showing a procedure for determining a flag state in the apparatus of FIG. 1;

FIG. 4 is a flowchart showing a procedure for correcting a command speed in the apparatus of FIG. 1;

5 (a) is a graph showing a transition characteristic of an upper limit speed in the apparatus of FIG. 1, and FIG. 5 (b) is a graph showing a change of an actual rotation speed with respect to an elapsed time.

6A and 6B are mounting diagrams of a MOSFET and a thermistor according to a second embodiment of the control device for a brushless motor according to the present invention, wherein FIG. 6A is a top view and FIG. 6B is a cross-sectional view taken along line AA. .

[Description of Signs] 1 control microcomputer (control microcomputer) 11 temperature detection unit 12 high temperature determination unit 12a high temperature value storage unit 13 low temperature determination unit 13a low temperature value storage unit 14 flag 15 command speed input unit 16 upper limit speed storage unit 17 Command speed correction unit 18 Pulse output unit 2 Thermistor 3 Constant current circuit 4 MOSFET 5 Thermistor

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor F. Shinki 5-24-15 Minamidai, Nakano-ku, Tokyo Calsonic Corporation F-term (reference) 5H560 AA01 DC05 FF14 GG04 JJ06

Claims (6)

[Claims] A brushless motor control device for rotating a brushless motor at a command speed, comprising: a drive control unit (1;
Temperature detecting means (2, 3, 5) for detecting the temperature of 4), and upper limit speed reducing means (11, 12,...) For reducing the upper limit speed of the brushless motor when the detected temperature is equal to or higher than a predetermined temperature. 12a, 14, 16) and command speed correcting means (15, 17) for correcting the command speed to be equal to or less than the reduced upper speed when a command speed exceeding the reduced upper speed is input. A control device for a brushless motor, comprising: 2. The temperature detecting means (2, 3, 5) detects a temperature of a drive element (4) constituting the drive control unit or a control circuit (1) for controlling the drive element. The control device for a brushless motor according to claim 1, wherein: 3. An upper limit speed reducing means (11, 12, 1).
2a, 14, 16), wherein when the detected temperature is lower than the predetermined temperature, the reduced upper speed is returned to the non-reduced upper speed. A control device for a brushless motor according to claim 2. 4. An upper limit speed reducing means (11, 12, 1).
2a, 14, 16) according to any one of claims 1 to 3, wherein when the detected temperature is equal to or higher than the predetermined temperature, the rotation of the brushless motor is stopped. A control device for the brushless motor according to the above. 5. The temperature detection means (2, 3, 5) includes a circuit pattern connected to an armature current terminal among terminals of a drive element (4) constituting the drive control section (1, 4). 5. The control device for a brushless motor according to claim 1, comprising a thermistor (5) in contact with the brushless motor. 6. The thermistor (5) is a surface mount type thermistor (5) having electrodes at both ends, wherein each electrode is a pair of terminal regions arranged outside both ends of the circuit pattern. The control device for a brushless motor according to claim 5, wherein the control device is connected to each terminal region.