JP3389300B2 - Operating method of brushless motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a change in induced voltage generated in a stator winding that is not energized by rotation of a rotor having permanent magnets having a plurality of poles, and energizes based on this detection signal. The present invention relates to a method of operating a brushless motor that sequentially switches combinations of stator windings.

[0002]

2. Description of the Related Art As a conventional brushless motor operating method, a rotor position of a rotor is detected from an induced voltage generated in a non-energized stator winding, and a stator is energized when a detection signal is obtained. Generally, an operation method in which the delay time until the winding is changed is set to a constant electrical angle. (Patent Fair 5-1
(See Japanese Patent No. 0039)

[0003]

However, in such a conventional operation method, when the load of the brushless motor increases and the voltage applied to the stator winding increases, the combination of the stator windings to be energized is changed. A large spike voltage is generated during commutation, which adversely affects the position detection by the induced voltage, making accurate position detection operation difficult.

If the load of the brushless motor becomes larger, the position detection itself may become impossible. Therefore, it has been one of the factors that reduce the reliability of the operation based on the induced voltage.

Further, during the period from the energization start to the brushless motor until it reached a steady-state operation, since the rotor is low speed, the induced voltage generated in the stator winding is small,
In many cases, the rotational speed of the rotor during rotation is very unstable, and when the constant electrical angle is set as the delay time, such as during steady operation of the brushless motor, the energization is switched and the rotor does not rotate. It could be stable.

Therefore, the present invention has been made in order to solve the above problems, and accurately detects the rotor position without being affected by the spike voltage generated during commutation even when the load of the brushless motor increases. In addition to being able to perform operation based on the following (hereinafter referred to as position detection operation), it enables reliable position detection even when a very large load is applied to the brushless motor, and an unstable state from the start of energization of the brushless motor to steady operation. It is an object of the present invention to provide a method for operating a brushless motor that enables stable position detection operation.

[0007]

Therefore, the present invention has a rotor having permanent magnets having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Then, some of the plurality of stator windings are energized to obtain a rotating magnetic field, and changes in induced voltage caused by rotation of the rotor are detected in the stator windings that are not energized. Then, in the brushless motor operating method in which the stator windings that are energized after an appropriate delay time from the time when the detection signal obtained based on this change in the induced voltage is generated are switched sequentially, the current is applied when the detection signal is generated. the delay before changing cut stator winding, a driving method of a brushless motor and changes the driving current to the brushless motor.

Further, the present invention has a rotor having permanent magnets having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Some of the child windings are energized to obtain a rotating magnetic field, and changes in the induced voltage caused by the rotation of the rotor are detected in the stator windings that are not energized. In a brushless motor operating method that sequentially switches the stator windings that are energized after an appropriate delay time from when the detection signal obtained based on the change occurs, cut the stator winding that energizes from when the detection signal occurs. It is a method of operating a brushless motor, characterized in that the delay time until the replacement is changed according to the rotation speed of the rotor or the rotation speed of the rotor.

In the present invention, preferably, the delay time is changed according to the rotor speed or the rotation speed.
In the present invention, preferably, the delay time is not changed from the start of energization of the brushless motor until the rotor reaches a predetermined rotation speed or until the rotor reaches a predetermined rotation speed.

Further, in the present invention, preferably, the delay time is not changed until a predetermined time has passed since the start of energization of the brushless motor.

Further, in the present invention, preferably, the delay time is not changed until the number of times of sequentially switching the stator winding to be energized from the start of energization of the brushless motor reaches a predetermined number.

[0012] detecting the rotor position from the induced voltage generated in the stator windings, the delay time from the detection time detection signal is obtained until changing cut combination of the stator winding commutation time for energizing, the brushless motor Change according to the operating current or rotor speed.

In addition, after the start of energization of the brushless motor, in the operation until a predetermined rotor speed is reached, a predetermined time is reached, or a commutation operation is performed a predetermined number of times, the rotation is started from the detection time. The delay time until the flow time is fixed to a predetermined time, and after reaching a predetermined rotor speed, after reaching a predetermined time, or after performing a commutation operation a predetermined number of times, the delay time is set to a predetermined electrical angle. Change to.

[0014]

According to the above construction, according to the operating state such as the operating current of the brushless motor or the rotating speed of the rotor,
By adjusting the delay time until the switching of the energization of the stator windings from the rotational position detection time of the rotor, it is possible to adjust the phase of the induced voltage waveform generated in the stator winding, the stator winding is energized The position of the rotor can be detected without being affected by the spike voltage generated at the time of commutation for changing the combination of wires. The position of the brushless motor can be reliably detected even when the load becomes very large.

Further, in an unstable operating state from the start of energization of the brushless motor to the steady operation of the motor, the delay time is fixed to a predetermined time unlike the steady operation, so that the same stable operation as in the steady operation is achieved. Position detection operation is possible.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a brushless motor driving apparatus for carrying out the brushless motor operating method of the present invention.

In FIG. 1, an AC power source 1 is connected to a three-phase brushless motor 4 through a semiconductor switching element group 3 in which a rectifying / smoothing circuit 2 and six switching elements are connected in a three-phase bridge shape. There is. Current detector C
T5 is attached to an AC wiring connecting the AC power supply 1 and the rectifier circuit 2, and this current detector CT5 is connected to the microprocessor 8 and, after converting the voltage induced by the AC current flowing through the AC wiring into a DC voltage. It is applied to the microprocessor 8. Also, this microprocessor 8
It is connected to the semiconductor switching element group 3 and the position detection circuit 7, and controls ON / OFF of each switching element of the semiconductor switching element group 3 after performing arithmetic processing based on the output from the position detection circuit 7.

The induced voltages 6a, 6b, 6c generated in the stator windings of the brushless motor 4 are applied to the position detection circuit 7.

The brushless motor 4 has a rotor having a plurality of permanent magnets and a three-phase stator winding arranged so as to give a rotating magnetic field to the rotor when energized.

In this brushless motor 4, the plurality of brushless motors
A rotating magnetic field is obtained by energizing some of the stator windings to detect a change in the induced voltage that occurs in the stator winding that is not energized, and detection based on this induced voltage change An appropriate delay time is provided from the detection time when the signal is obtained, and the combination of the stator windings to be energized is sequentially switched. The combination of energized stator windings is O of the switching elements of the semiconductor switching element group 3.
Any combination of N / OFF can be set.

In the position detection circuit 7 of FIG. 1, the position of the rotor is detected by the change of the induced voltages 6a to 6c of the brushless motor 4. Then, based on this detected signal, the microprocessor 8 sequentially switches the energization to the stator winding to continue the operation and calculates the rotational speed of the rotor.

The current detector CT5 shown in FIG. 1 detects the operating current. This operating current is
Be transmitted to. The microprocessor 8 calculates and measures the operating current, the rotor speed, the time after the start of motor energization, and the number of commutations after the start of motor energization, and further detects the rotor position and energizes the stator winding. Processing such as determining the delay time until commutation for switching

Next, referring to FIG.

FIG. 2 is a flow chart showing an outline of each processing performed by the microprocessor 8. This process is performed by a predetermined constant delay time (fixed delay time) after the start of energization of the brushless motor 4 until a predetermined rotation speed is reached.
As a result, after reaching the predetermined rotation speed, a case where a delay time corresponding to an electrical angle of 30 degrees or an electrical angle of 20 degrees is provided by the motor operating current (delay time change) is shown.

In FIG. 2, when the brushless motor 4 is energized and started to detect a position (position detection processing step, step S1), the rotor speed is a predetermined speed Ns in the speed detection processing step (step S2). To determine if you have reached.

When the predetermined speed Ns has not been reached,
The delay time T0 from the position detection processing step (step S1) to the commutation is set in the delay setting processing step (step S4), and the delay time T0 is set in the next processing step (step S6).
After the elapse of time is determined (time-up), commutation is performed in the commutation processing stage (step S7).

On the other hand, speed detection processing stage (step S2)
When it is determined that the rotor speed has reached the predetermined speed Ns, it is determined whether the motor operating current has reached Is in the current detection processing step (step S3).

If the motor operating current has not reached Is, the delay time from position detection to commutation is set to 30 electrical degrees in the delay setting processing step (step S4). If the motor operating current has reached Is, the delay time from position detection to commutation is changed to 20 electrical degrees and set in the delay setting processing step (step S5). After that, the processes after the above-mentioned next processing step (step S6) are performed.

FIG. 3 schematically shows a motor induced voltage waveform when the delay time from position detection to commutation is 30 electrical degrees.

In FIG. 3, after switching the energization of the stator winding by commutation 17, the rotor position is detected by the detector 18, and the delay time T corresponding to an electrical angle of 30 degrees is set. It is indicated that the commutation 19 switches the energization of the stator winding after the delay time T has elapsed. This commutation 17
Is when the spike voltage 20 rises.

FIG. 6 shows an outline of a motor induced voltage waveform when the motor is operated at a predetermined constant delay time T0 after the start of energization.

FIGS. 4 and 5 schematically show the induced voltage waveform of the brushless motor 4 when the brushless motor 4 is operated with a larger motor load than the operation example shown in FIG.

FIG. 4 shows the outline of the motor induced voltage waveform when the delay time is 30 electrical degrees. The spike voltage 22 has a wider pulse width than the spike voltage 20 generated during commutation in FIG. Therefore, the margin 2 for position detection at the end of the pulse voltage of the spike voltage 22
3 is much smaller than the position detection margin 21 at the end of the pulse voltage of the spike voltage 20 shown in FIG. 3, which makes reliable position detection difficult.

When the motor load further increases and the spike voltage width becomes wider, the margin is zero, that is, the neutral point voltage 24 and the motor induced voltage do not cross each other, and position detection becomes impossible. It will be.

Therefore, when the motor load is large, the delay time from position detection to commutation is set to, for example, 20 electrical degrees, as shown in FIG. As a result, the phase of the position detection period 28 with respect to the motor induced voltage waveform is advanced by 10 degrees in electrical angle, and the margin 27 for position detection at the end of the spike voltage 26 can be increased, so that reliable position detection can be performed. It is a thing.

The present invention is not limited to the above embodiment.

Instead of detecting the rotor speed, for example, the time after the start of energization of the brushless motor 4 may be detected in the speed detection processing step (step S2).
The number of commutations after the start of energization to the brushless motor 4 may be detected.

Further, the current detection processing stage (step S3)
In, in place of detecting the operating current, the rotation speed of the rotor may be detected.

Further, in the embodiment of the present invention, the delay time after the current detection processing step (step S3) is set to the electrical angle 2
There are two types, 0 degrees and 30 degrees.

However, as shown in FIG. 7, the relationship between the operating current or the rotational speed of the rotor (horizontal axis) and the delay time (vertical axis) changes with the increase of the operating current or the rotational speed of the rotor. The delay time may be set to be reduced.

In this case, the upper limit of the delay time is 30 degrees in electrical angle and the lower limit is T1. In addition to the above, the delay time may be set by combining the operating current and the rotation speed.

[0043]

As described above, according to the present invention, even when the load of the brushless motor becomes large,
Together they make accurate position detection operation is not affected by the spike voltage generated at the time of commutation, also enabling reliable position detection in a very large brushless motor load, from energization start to the brushless motor until it reached a steady-state operation It enables stable position detection operation in an unstable state.

[Brief description of drawings]

FIG. 1 is a diagram showing a brushless motor driving device for carrying out a method of operating a brushless motor of the present invention.

FIG. 2 is a flowchart showing a preferred embodiment of the method of operating the brushless motor of the present invention.

FIG. 3 is a diagram showing an example of an induced voltage waveform during normal motor load operation.

FIG. 4 is a diagram showing an example of an induced voltage waveform during overload operation.

FIG. 5 is a diagram showing an example of an induced voltage waveform during overload operation.

FIG. 6 is a diagram showing an example of an induced voltage waveform (delay time fixed) immediately after the start of energization of a motor.

FIG. 7 is a diagram showing an example of setting a delay time.

[Explanation of symbols]

1 AC power supply 2 rectifier circuit 3 Semiconductor switching element group 4 brushless motor 5 Current detector CT 6a, 6b, 6c Motor induced voltage 7 Position detection circuit 8 microprocessors

Claims (3)

(57) [Claims] 1. A rotor having a permanent magnet having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Some of the stator windings are energized to obtain a rotating magnetic field, and the changes in the induced voltage caused by the rotation of the rotor are detected in the stator windings that are not energized, and based on this change in the induced voltage. in the stator windings are sequentially switched operation method of a brushless motor in which detection signal obtained is energized after a suitable time delay from the time it occurred, delay before changing cut stator winding is energized from the time when the detection signal is generated Time, the operating current to this brushless motor , or the rotation speed of the rotor
Degree or delay time
The rotor has been running for a certain period from the start of energizing the brushless motor.
Until the rotation speed is reached or the rotor reaches the specified rotation speed
A method of operating a brushless motor, which is characterized by not changing until the time . 2. A rotor having a plurality of permanent magnets and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Some of the stator windings are energized to obtain a rotating magnetic field, and the changes in the induced voltage caused by the rotation of the rotor are detected in the stator windings that are not energized, and based on this change in the induced voltage. in the stator windings are sequentially switched operation method of a brushless motor in which detection signal obtained is energized after a suitable time delay from the time it occurred, delay before changing cut stator winding is energized from the time when the detection signal is generated Time, the operating current to this brushless motor , or the rotation speed of the rotor
Degree or delay time
Has reached the specified time since the brushless motor was energized.
A method of operating a brushless motor, which is characterized by not changing until the time . 3. A rotor having a permanent magnet having a plurality of poles, and a plurality of stator windings arranged to give a rotating magnetic field to the rotor when energized. Some of the stator windings are energized to obtain a rotating magnetic field, and the changes in the induced voltage caused by the rotation of the rotor are detected in the stator windings that are not energized, and based on this change in the induced voltage. in the stator windings are sequentially switched operation method of a brushless motor in which detection signal obtained is energized after a suitable time delay from the time it occurred, delay before changing cut stator winding is energized from the time when the detection signal is generated Time, the operating current to this brushless motor , or the rotation speed of the rotor
Degree or delay time
Is a stator that energizes from the start of energizing the brushless motor
Until the number of times the windings are switched sequentially reaches a predetermined number
A method of operating a brushless motor, characterized by not changing .