JP3531563B2 - Brushless motor control device, brushless motor control method, and compressor - Google Patents

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 sensorless control of a brushless motor used in a compressor of an air conditioner, and particularly to reduce the starting current and improve the starting probability.

[0002]

2. Description of the Related Art A conventional brushless motor control device used in a hermetic compressor such as an air conditioner shown in FIG. 4 is disclosed in, for example, Japanese Patent Laid-Open No. 9-327194.
As shown in FIG. In the case of this type of brushless motor, it is necessary to know the rotor position without using a magnetic pole position detection element such as a Hall element. One of them is generated in the non-energized phase (non-energized armature winding) of the brushless motor. The detected induced voltage is used to detect the position of the rotor, and the energization of the armature winding current of the brushless motor is switched based on the detected position. Further, since the rotor is stopped at the start of starting the brushless motor, an induced voltage is not generated, so that it is necessary to perform synchronous operation or the like.

In this control device, an AC / DC converter 2 converts an AC power source 1 into a predetermined DC power source, and this DC power source is switched into switching elements Ua, Va, Wa, X, and X of an inverter unit 3.
Brushless motor (DCM) switching by Y, Z
4 armature windings.

When the brushless motor 4 is controlled by an analog system, the position detection circuit 5 passes the terminal voltage (chopped induced voltage) of the brushless motor 4 through an integrating circuit or the like and compares it with a reference level as a triangular wave. To output a position detection signal to the control circuit (microcomputer) 6.

The control circuit 6 switches the energization of the armature winding current of the brushless motor 4 with the position detection signal as the timing of the intersection of the triangular wave and the reference level.
WM signal) is output to the drive circuit 7 to drive the switching elements Ua, Va, Wa, X, Y, Z of the inverter unit 3 in a predetermined manner.

The position detection circuit 8 directly compares the induced voltage generated in the armature winding with the reference voltage, and outputs a position detection signal of the comparison result (intersection point; position detection point) to the control circuit 9. The control circuit 9 detects the position of the rotor based on the position detection signal, calculates the energization switching timing of the armature winding current based on this position detection, and uses the calculated energization switching timing to calculate the armature winding of the brushless motor 4. A drive signal (PWM signal) for switching the energization of the line current is output to the drive circuit 7, and the switching elements Ua, V of the inverter unit 3 are output.
a, Wa, X, Y, Z are driven in a predetermined manner.

As described above, in order to control the motor of a hermetic compressor such as an air conditioner, it is necessary to control without using a magnetic pole position detecting element such as a Hall element. A general method is to control by using velocity electromotive force induced in the non-energized phase. In this method, the position of the rotor is obtained by detecting the zero cross point of the speed electromotive force, and the energization of the stator winding of the brushless motor is switched so that torque is generated in a desired rotation direction.

In this method, a predetermined starting pulse is generated from the positioning state to rotate the rotor by an electrical angle of 120 degrees and permit the position detection of the non-energized phase, and when the position can be detected (electrical angle π / (Corresponding to 6), the operation shifts to the position detection operation. The above method will be described below with reference to FIGS. 6 to 11.

FIG. 7 is a flowchart showing the operation of the conventional brushless motor control device. The control device first performs a predetermined energization pattern (UV phase → UW phase → UV phase) to position the rotor (steps 1 to 3). Step 3
In the positioning state (hereinafter, referred to as a state) due to the UV phase energization, the positional relationship between the rotor 11b and the armature 11a is as shown in FIG. That is, the magnetic poles facing the magnetic field generated by the armature 11a face each other.

Next, the control unit electrically changes the state to 2π /
3 The phase is advanced (VW phase energization), and the terminal voltage of the non-energized phase (U phase) is started to be monitored (steps 4 and 5, hereinafter, this energized state is referred to as a state). Since the magnetic field of the armature 11a changes its direction to the position advanced by 2π / 3 by the operation of step 4, the rotor starts to rotate in this direction (see FIG. 8). In the case of the DC brushless motor (see FIG. 9), the speed electromotive force of the following formula (1) is generated in the non-energized phase (U phase in this case).

[0011] V = kωsin (θ + 5π / 6) (1) However, V: velocity electromotive force induced in U phase k: Induced voltage constant of permanent magnet ω: rotational speed θ: Electrical rotation angle (based on the stop position in the state)

That is, the U-phase induced voltage crosses zero at the boundary of θ = π / 6, and the induced voltage is detected in step 5. The position detection operation is started from the timing detected thereafter (step 6).

Since the system can shift to the position detecting operation in a relatively short time, it has advantages that the starting time is short and the starting current is small. This requires acceleration to a speed sufficient to detect the induced voltage by rotation of only the electrical angle π / 6, and thus there is a problem that it cannot be used when the load inertia or the load torque is large.

When the load inertia and the load torque are large, the acceleration becomes relatively small, so that ω in the equation (1) becomes small. This means that the amplitude of the voltage induced in the non-energized phase decreases, so that the position detection accuracy decreases and the possibility of starting failure increases (see FIG. 10 and FIG. 1).
0 is a diagram showing the induced voltage waveform of the non-energized phase at the time of startup. Also, in the case of a load that needs to be rotated up to a high rotation speed, the induced voltage constant of the motor needs to be made small, but this means that k in the formula (1) becomes small, so that position detection at startup becomes difficult as in the above. .

In the activation control method in the above conventional example, there is a process of advancing energization control by 2π / 3 (step 3 → 4), but this energization switching involves turning on the V-phase upper arm switch and turning off the lower arm switch. It will be performed simultaneously (see FIG. 11). For example, if the turn-off of the upper arm drive circuit is delayed due to circuit variations or the like, the elements of the inverter may be short-circuited and the elements may be destroyed.

[0016]

As described above, when the general cylindrical DC brushless motor is started by the conventional start control method, the speed electromotive force obtained by accelerating in the angular range up to the electrical angle π / 6. Therefore, the velocity electromotive force can obtain only a very small amplitude. further,
When the inertia is large, the speed at the time of rotating the electrical angle of 30 degrees becomes relatively small, so that there is a problem that the position cannot be detected and the position detection operation cannot be started.
In addition, even in high-speed rotating load applications and multi-pole motor applications where it is necessary to reduce the induced voltage constant (the amount of speed electromotive force generated per 1 Hz of electrical frequency), the non-energized phase detection voltage at startup is small, so the startup performance is low. There was a problem such as a drop.

Further, there is a possibility that the inverter may be short-circuited at the time of startup. Also, for example, if the load is a compressor,
When the pressure difference between the suction side and the discharge side is large, the load torque at startup becomes large, and there is a problem that the probability of startup failure increases.

The present invention has been made in order to solve the above problems, and provides a brushless motor control device capable of accurately starting in a short time even with a load having a large inertia and preventing element short circuit at the time of starting. The purpose is to

[0019]

A brushless motor control device according to the present invention starts a three-phase brushless motor, and then activates a rotor by an induced voltage generated in a non-energized phase of an armature winding of the brushless motor. In a brushless motor control device that detects a position and switches the energization of the armature winding current based on the position detection to perform a position detection operation, the energization pattern of the start control means is: An energization pattern A for positioning the rotor at a specific position, an energization pattern B for energizing for a minute time in a phase electrically advanced by π / 3 from the energization pattern A, and an electrically further π / from the energization pattern B. And the energization pattern C for energizing the advanced phase and detecting the induced voltage in the non-energized phase.

Further, after starting the three-phase brushless motor, the position of the rotor is detected by the induced voltage generated in the non-energized phase of the armature winding of the brushless motor, and the position is detected based on the detected position. In a brushless motor control device including a start control means for switching the energization of armature winding current to perform position detection operation, the energization pattern of the start control means is an energization pattern D for positioning the rotor at a specific position, An energization pattern E for stopping the energization of all phases for a very short time, and an energization pattern F for energizing the phase electrically advanced by 2π / 3 from the energization pattern D and detecting the induced voltage of the non-energized phase. It is a thing.

The brushless motor is composed of a q-axis inductance larger than the d-axis inductance.

The brushless motor comprises an armature, a rotor having a magnet on the outside and a core made of a ferromagnetic material inside, and the magnet is thick in the d-axis direction and thin in the q-axis direction. It was done.

Further, the compressor according to the present invention comprises a brushless motor which is drive-controlled by a brushless motor control device.

The brushless motor control according to the present invention
The method is as follows after starting the three-phase brushless motor.
Induction that occurs in the non-energized phase of the armature winding of a brushless motor
The position of the rotor is detected by the electromotive voltage, and based on this position detection
Position detection by switching energization of the armature winding current
Brushless motor control method with start control for driving
In the starting control, the rotor is positioned at a specific position.
When the position is set and then the phase is advanced π / 3 electrically
For a short period of time, and then electrically in a phase that leads π / 3
And the induced voltage of the non-energized phase is detected.
Move to position detection operation.

Also, the three-phase brushless motor was started.
Then, in the non-energized phase of the armature winding of the brushless motor,
The position of the rotor is detected by the induced voltage generated and the position is detected.
Switch the energization of the armature winding current based on the output
Brushless model equipped with start control means for position detection operation
In the data control method, the start control is performed at a specific position.
Position the rotor and then energize all phases at a minute
Stop for a while, then energize at a phase that is electrically advanced by 2π / 3
And the induced voltage in the non-energized phase is detected, and then
Move to position detection operation.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1. 1 is a configuration diagram showing an example of a motor form in a brushless motor control device according to Embodiment 1 of the present invention. In the figure, 11 is a DC brushless motor, 11
a is an armature, 11b is a rotor, 11c is a magnet, and 11d is a rotor core made of a ferromagnetic material. In the figure, the direction of the magnetic flux is defined as the d-axis, and the phase that is electrically deviated from the d-axis by 90 degrees (the phase that is mechanically deviated by 90/2 = 45 degrees in the figure) is the q-axis. At this time, since there is a magnetic gap due to the magnet in the d-axis direction, the magnetic resistance is high, that is, the inductance is small. On the other hand, in the q-axis direction, since there is no gap due to the magnet, the magnetic resistance is low and the inductance is large. Hereinafter, this motor is referred to as a salient pole type motor.

The brushless motor shown in FIG. 9 in the description of the conventional example is called a cylindrical type because the thickness of the rotor magnet is uniform, and the winding inductance is constant regardless of the rotor phase. It has a characteristic of (Ld = Lq).

FIG. 2 shows a waveform of the induced voltage when the salient pole motor described above is started by the control device shown in FIG. 5 of the conventional example. As shown in FIG. 2, the salient-pole motor has a large terminal voltage change in the non-conduction phase. Since this is Ld ≠ Lq (that is, the magnetic flux of the armature differs depending on the position of the rotor), the magnetic flux generated on the armature side changes due to rotation and is observed as an induced voltage in the non-energized phase. by. If Ld <Lq, the magnetic attraction torque acting between the iron core of the rotor and the magnetic field of the armature acts in the motor rotating direction during the period up to π / 6 after starting, so that the motor is accelerated. Promoted,
The induced voltage becomes higher.

Even if Ld> Lq, the neutral point voltage of the motor changes, but in that case, since the neutral point voltage acts in the opposite direction to the speed electromotive force, it is detected in reverse. Will be difficult. That is, the inductance is Ld <Lq
Is a necessary condition for improving the position detection accuracy.

As described above, in the present embodiment, the type of the material forming the motor can be achieved without complicating it, so that the dismantling process similar to the conventional one can be performed and the recyclability is excellent.

Embodiment 2. FIG. 3 is a flowchart showing the operation of the brushless motor control device according to the second embodiment of the present invention. In addition,
The same functions as those of the conventional brushless motor control device are designated by the same reference numerals, and the description thereof will be omitted. The configuration of the brushless motor control device is the same as that of the conventional example shown in FIG.

In FIG. 3, after the positioning energization in step 3, the energization pattern (U → W phase energization) electrically advanced by π / 3 is energized for a minute time (step 3a). This minute energization time is a period during which the motor does not rotate or the electrical angle is within several degrees due to the energization. At this time, the upper and lower arms of the V phase are switched off. Immediately after that, energization from step 4 onward is performed, and the startup control similar to the conventional one is performed. By inserting the process of step 3a, the V-phase element short circuit is avoided.

Also, since there is no short circuit of the U-phase and W-phase even when the energization is switched from step 3a to step 4,
A safe start-up method that does not cause a short circuit of the element when switching all the energization steps is realized.

In the above embodiment, an example in which the energization pattern of step 3a is a π / 3 advanced energization pattern has been described, but the same effect can be obtained even in the all-element energization off state.

That is, the energization pattern of the control device includes an energization pattern A for positioning the rotor at a specific position, an energization pattern B for energizing a phase electrically advanced by π / 3 from the energization pattern A for a minute time, and an energization pattern. And a conduction pattern C for electrically conducting a phase further advanced by π / 3 from B and detecting an induced voltage in a non-conduction phase, and the conduction pattern of the control device is as described above. Separately, an energization pattern D for positioning the rotor at a specific position, an energization pattern E for stopping energization of all phases for a very short time, and an electrical conduction of 2π / 3 from the energization pattern D.
The same effect can be obtained with the energization pattern F that energizes the advanced phase and detects the induced voltage of the non-energized phase.

In the above description, the energizing pattern for positioning has been described in the steps 1 to 3, but the present invention is not limited to this. For example, step 1 may be omitted.

[0037]

As described above, according to the present invention, after the three-phase brushless motor is started, the position of the rotor is detected by the induced voltage generated in the non-energized phase of the armature winding of the brushless motor. In a brushless motor control device having a start control means for performing position detection operation by switching energization of armature winding current based on position detection, the energization pattern of the start control means positions the rotor at a specific position. Energization pattern A, energization pattern B that energizes a phase that is electrically advanced by π / 3 from the energization pattern A for a minute time, and energizes a phase that is electrically advanced by π / 3 from the energization pattern B and is non-energized. By including the energization pattern C for detecting the induced voltage of the energized phase, it is possible to prevent the element short circuit at the time of startup.

After starting the three-phase brushless motor, the position of the rotor is detected by the induced voltage generated in the non-energized phase of the armature winding of the brushless motor, and the armature winding is detected based on the detected position. In a brushless motor control device provided with a start control means for switching the energization of a line current to perform a position detection operation, the energization pattern of the start control means includes an energization pattern D for positioning the rotor at a specific position and energization of all phases. An energization pattern E for stopping for a minute time, and an energization pattern F for energizing a phase electrically advanced by 2π / 3 from the energization pattern D and detecting an induced voltage in a non-energized phase,
By being composed of, it is possible to prevent element short circuit at the time of startup.

Further, since the brushless motor is constituted by the q-axis inductance being larger than the d-axis inductance, it is possible to accurately detect the starting position at a low speed when the inertia is large.

The brushless motor comprises an armature, a rotor having a magnet on the outside and a core made of a ferromagnetic material inside, and the magnet is thick in the d-axis direction and thin in the q-axis direction. Therefore, the brushless motor is configured with a q-axis inductance larger than the d-axis inductance.

Further, since the compressor according to the present invention is provided with the brushless motor which is drive-controlled by the brushless motor control device, it is possible to realize a compressor with few start failures.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a motor form in a brushless motor control device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing an induced voltage when the motor is started in the brushless motor control device of FIG.

FIG. 3 is a flowchart showing an operation of the brushless motor control device according to the second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a general compressor.

FIG. 5 is a configuration diagram showing a brushless motor control device.

FIG. 6 is a flowchart showing the operation of a conventional brushless motor control device.

FIG. 7 is a schematic relationship diagram (1) of a rotating magnetic field and a rotor for explaining the operation of a conventional brushless motor control device.
Is.

FIG. 8 is a schematic relationship diagram (2) of a rotating magnetic field and a rotor for explaining the operation of the conventional brushless motor control device.
Is.

FIG. 9 is a configuration diagram showing a motor configuration in a conventional brushless motor control device.

FIG. 10 is a waveform diagram showing an induced voltage when the motor is started in the conventional brushless motor control device.

FIG. 11 is an operation explanatory diagram of a V-phase arm in the conventional brushless motor control device.

[Explanation of symbols]

11 DC brushless motor, 11a armature, 11b
Rotor, 11c magnet, 11d rotor core.

Front page continued (72) Inventor Hitoshi Kawaguchi 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (56) Reference JP-A-9-327194 (JP, A) JP-A-5-137386 ( JP, A) JP 56-38988 (JP, A) JP 63-144788 (JP, A) JP 8-336269 (JP, A) JP 10-23782 (JP, A) (58 ) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 6/18 F04C 29/10

Claims (7)

(57) [Claims] 1. After starting a three-phase brushless motor,
The position of the rotor is detected by the induced voltage generated in the non-energized phase of the armature winding of the brushless motor, and the position detection operation is performed by switching the energization of the armature winding current based on the detected position. In the brushless motor control device including the start-up control unit, the energization pattern of the start-up control unit is an energization pattern A for positioning the rotor at a specific position, and a phase electrically advanced by π / 3 from the energization pattern A. An energization pattern B for energizing for a very short time, and an energization pattern C for electrically energizing a phase further advanced by π / 3 from the energization pattern B and detecting an induced voltage in a non-energized phase. Brushless motor controller. 2. After starting a three-phase brushless motor,
The position of the rotor is detected by the induced voltage generated in the non-energized phase of the armature winding of the brushless motor, and the position detection operation is performed by switching the energization of the armature winding current based on the detected position. In the brushless motor control device including the start control means, the energization pattern of the start control means includes an energization pattern D for positioning the rotor at a specific position, and an energization pattern E for stopping energization of all phases for a very short time. A brushless motor control device comprising: an energization pattern F for energizing a phase electrically advanced by 2π / 3 from the energization pattern D and detecting an induced voltage in a non-energization phase. 3. The brushless motor control device according to claim 1, wherein the brushless motor is configured so that the q-axis inductance is larger than the d-axis inductance. 4. A brushless motor comprises an armature, a rotor having a magnet outside and a core made of a ferromagnetic material inside, and the magnet is thick in the d-axis direction and thin in the q-axis direction. The brushless motor control device according to claim 3, wherein the brushless motor control device is provided. 5. A compressor comprising a brushless motor which is drive-controlled by the brushless motor control device according to any one of claims 1 to 4. 6. After starting a three-phase brushless motor,
It occurs in the non-energized phase of the armature winding of the brushless motor.
The position of the rotor is detected by the induced voltage
Switch the energization of the armature winding current based on the position
Brushless motor control with start control for detection operation
In the method, the activation control is the rotor at a specific position.
Position, and then the phase is advanced by π / 3 electrically.
Energize for a short period of time, and then pass it in a phase that is electrically advanced by π / 3.
And the induced voltage of the non-energized phase is detected.
Brushless characterized by shifting to position detection operation later
Motor control method. 7. After starting a three-phase brushless motor,
It occurs in the non-energized phase of the armature winding of the brushless motor.
The position of the rotor is detected by the induced voltage
Switch the energization of the armature winding current based on the position
Brushless motor with start control means for detecting operation
In the control method, the activation control is performed at the specific position.
Position the trochanter and then stop energizing all phases for a short time
Stop and energize in a phase that is an electrical advance of 2π / 3
The induced voltage of the non-energized phase is detected along with the
Brushless motor characterized by shifting to position detection operation
Control method.