JPH07108112B2 - How to start brushless DC motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for starting a brushless DC motor in which a rotor is prevented from rotating in the reverse direction at the time of starting.

[Prior Art] After starting, when the counter electromotive voltage induced in the stator coil is increased by increasing the rotation speed of the rotor equipped with a permanent magnet, when the value required to detect at the rotor rotation position is reached, the stator coil is Detect the rotational position of the rotor with the induced back electromotive force,
With a brushless DC motor that uses this detection output to switch the drive current to the stator coil group to generate a rotating magnetic field to drive the rotor in rotation, a counter electromotive voltage does not occur at startup, so some method is used to force startup. Need to let.

This method of forcibly starting is conventionally performed as follows.

A rotor 1 having permanent magnets N and S as shown in FIG.
And stator coils u ₁ and u ₂ , v ₁ and v ₂ , w ₁ and
When starting a three-phase four-pole brushless DC motor including the stator core 2 provided with w _2, as shown in FIG. 3, by a known circuit that switches the switching circuit by a switching signal from the microcomputer, The driving current I flowing through the three-phase stator coils u ₁ and u ₂ , v ₁ and v ₂ , w ₁ and w ₂ is switched in a fixed order of ,,, to generate a rotating magnetic field, and a permanent magnet N, The rotor 1 provided with S was rotationally driven.

That is, in, the current is applied from U to V for t ₁ hours, and the magnetic poles of the stator coils u ₁ and u ₂ , v ₁ and v ₂ are set to N and S. In, the current is applied from W to V for t ₂ hours and the stator coils w ₁ and
The magnetic poles of w ₂ , v ₁ and v ₂ are N and S, then from W to U
Stator coils w ₁ and w ₂ , u ₁ and u ₂ by energizing for ₃ hours
The magnetic poles of N and S are applied to V and U for t ₄ hours, and the magnetic poles of stator coils v ₁ and v ₂ , u ₁ and u ₂ are N and S.
And then, energize from V to W for t ₅ hours and then the stator coil
The magnetic poles of v ₁ and v ₂ , w ₁ and w ₂ are N and S, and U
From W to W for t ₆ hours and stator coils u ₁ and u ₂ , w ₁
A rotating magnetic field is generated by setting the magnetic poles of w ₂ and w ₂ to N and S, and the energization time is sequentially shortened while repeating energization of the following items 1 to 3 to increase the rotational speed of the rotor 1.

Then, the rotation speed of the rotor 1 increases, and the counter electromotive voltage induced in the stator coils u ₁ and u ₂ , v ₁ and v ₂ , or w ₁ and w ₂ in which the drive current I does not flow is generated in the rotor 1. When the value required to detect the rotational position is reached, this counter electromotive voltage detects the rotational position of the rotor ₁ and drives the stator coils u ₁ and u ₂ , v ₁ and v ₂ , w ₁ and w ₂ . The current was switched to a closed loop that generated a rotating magnetic field.

[Problems to be Solved by the Invention] However, in the conventional starting method shown in FIG. 3 and FIG. 4, the rotor 1 is in the original direction (clockwise direction) depending on the stop position of the rotor 1 at the start of starting. However, there is a problem in that it cannot be used for a fan or the like that may rotate in the opposite direction (counterclockwise direction), and it is difficult to reversely rotate at startup. That is, in FIG. 3, the rotor 1
When the rotor 1 is stopped at the positions indicated by (a) and (e), and when the rotor 1 is stopped at the position indicated by (f), the rotors rotate in opposite directions. Is.

The present invention has been made in view of the above problems, and provides a starting direction of a brushless DC motor that can always rotate the rotor in a predetermined direction regardless of where the rotor is stopped at the time of starting the starting. The purpose is to do.

[Means for Solving the Problems] In the method for starting a brushless DC motor according to the present invention, at the time of startup, the drive current to the stator coil group is switched according to a preset energization switching pattern to rotationally drive the rotor, and after startup, When the number of rotations of the rotor rises and reaches a predetermined value, the rotational position of the rotor is detected by the counter electromotive voltage induced in the stator coil, and the detection output is used to switch the drive current to the stator coil group. In a brushless DC motor configured to rotationally drive a rotor, a plurality of energization switching patterns for always rotationally driving the rotor in a predetermined direction are set in advance corresponding to stop positions of the rotor, and the rotor is stopped. A magnetic-electric conversion element for detecting the position is provided, and at the time of startup, the plurality of energization switching patterns are based on the detection output of the magnetic-electric conversion element. A corresponding energization switching pattern is selected from the loops, and the drive current to the stator coil group is switched according to the selected energization switching pattern to rotationally drive the rotor.

[Operation] At startup, the magnetoelectric conversion element detects the stop position of the rotor. Based on the detection output of the magnetoelectric conversion element, a predetermined energization switching pattern corresponding to the stop position of the rotor is selected from among a plurality of energization switching patterns set for starting in advance. With this selected energization switching pattern, the drive current to the stator coil group is switched to generate a rotating magnetic field to drive the rotor to rotate. Therefore, at the time of start-up, the rotor is always rotationally driven in the predetermined direction regardless of where the stop position is. After the start-up, the rotation speed of the rotor increases and the back electromotive force induced in the stator coil reaches a predetermined value necessary to detect the rotation position of the rotor. The rotational position of the rotor is detected by the electromotive voltage, and the detected output is used to switch the drive current to the stator coil group to generate a rotating magnetic field to rotationally drive the rotor. It demonstrates using.

1 and 2 show an embodiment of the present invention.
In these figures, the same parts as those in FIGS. 3 and 4 are designated by the same reference numerals.

In FIGS. 1 and 2, reference numeral 1 denotes a rotor rotatably supported by a bearing device and having drive permanent magnets N and S attached thereto. A stator core 2 is provided around the rotor 1.
The stator core 2 is provided with three-phase stator coils u ₁ and u ₂ , v ₁ and v ₂ , w ₁ and w ₂ of a predetermined connection and having an electrical angle of 240 °. A magnetoelectric conversion element (for example, a hold element) 3 for detecting the rotational position of the rotor 1 is provided.

Next, the starting method will be described.

(A) The stop position of the rotor 1 at the start of startup is the first
In the cases of (a), (e), and (f) in the figure, the magnetoelectric conversion element 3 faces the N pole of the permanent magnet of the rotor 1, and therefore its detection output Hv is H. Based on this detection output Hv = H, two energization switching patterns P ₁ , which are set in advance for activation,
P ₁ is selected from P ₂ . This energization switching pattern
As shown in the upper part of FIG. ₁ , P ₁ is the drive current I −
The rotating magnetic field is generated by switching in the order of 1, -1, -2, ..., And the rotor 1 is rotationally driven. That is, at -1, electricity is applied from V to U for t ₁₁ hours, and as shown in (a) (e) (f), the magnetic poles of the stator coils v ₁ and v ₂ , u ₁ and u ₂ are set to N and S, -1 is U
From W to W for t ₂₁ hours, the magnetic poles of the stator coils u ₁ and u ₂ , w ₁ and w ₂ are set to N and S as shown in (g),
-2, electricity is passed from W to V for t ₂₂ hours, and the magnetic poles of the stator coils w ₁ and w ₂ , v ₁ and v ₂ are set to N and S as shown in (h), and then from W to U t Energize for ₃ hours (j)
As shown in (k), the magnetic poles of the stator coils W ₁ and W ₂ , u ₁ and u ₂ are N and S. Then, when V to U are energized for t ₄ hours, as shown in (k), the stator coils v ₁ and v ₂ , the magnetic poles of u ₁ and u ₂ are N and S, and then, from V to W for t ₅ hours, the stator coils v ₁ and v ₂ , as shown in (m),
If the magnetic poles of w ₁ and w ₂ are N and S, then from U to W t ₆
After energizing for a period of time, the magnetic poles of the stator coils u ₁ and u ₂ , w ₁ and w ₂ are set to N and S as shown in (n), and a clockwise rotating magnetic field is generated to rotate the rotor 1 in the original rotating direction. Rotate in a clockwise direction. Similarly to the conventional example shown in FIG. 3, the energization switching is repeated, and the energization time is sequentially shortened to increase the rotation speed of the rotor 1 and the stator coil u ₁ in which the drive current I does not flow. And when the counter electromotive force induced in u ₂ , v ₁ and v ₂ , or w ₁ and w ₂ reaches the value required to detect the rotational position of the rotor 1, this counter electromotive voltage causes the rotor 1 to rotate. Rotational position is detected and stator coils u ₁ and u ₂ , v ₁ and v ₂ , w ₁ and
Switch to a closed loop that generates a rotating magnetic field by switching the drive current to w ₂ .

(B) The stop position of the rotor 1 at the start of starting is the first
In the cases of (b), (c), and (d) in the figure, since the magnetoelectric conversion element 3 faces the S pole of the permanent magnet of the rotor 1, its detection output Hv becomes L. Based on this detection output Hv = L, two energization switching patterns P ₁ set for starting in advance,
P ₂ is selected from P ₂ . This energization switching pattern
As shown in the lower part of FIG. 1, P ₂ has a drive current I of −
The rotating magnetic field is generated by switching in the order of 2, -3, ..., And the rotor 1 is rotationally driven. That is,
-2, energize from V to U for t ₁₂ hours (b) (c)
As shown in (d), the magnetic poles of the stator coils u ₁ and u ₂ , v ₁ and v ₂ are N and S, and at −3, from W to V t ₂₃
After energizing for a time, as shown in (p), the magnetic poles of the stator coils w ₁ and w ₂ , v ₁ and v ₂ are set to N and S. Then, energizing from W to U for t ₃ hours, as shown in (j). On stator coil
The magnetic poles of w ₁ and w ₂ , u ₁ and u ₂ are N and S, and
Energize from V to U for t ₄ hours and set the magnetic poles of the stator coils v ₁ and v ₂ , u ₁ and u ₂ to M and S as shown in (k),
Then, energize V to W for t ₅ hours, and set the magnetic poles of stator coils v ₁ and v ₂ , w ₁ and w ₂ to N and S as shown in (m), and energize U to W for t ₆ hours. Then, as shown in (n), the magnetic poles of the stator coils u ₁ and u ₂ , w ₁ and w ₂ are N and S, and a clockwise rotating magnetic field is generated to rotate the rotor 1 in the original direction. Rotate around. Similarly to the conventional example shown in FIG. 3, the energization switching is repeated, and the energization time is sequentially shortened to increase the rotation speed of the rotor 1 and the stator coil u ₁ in which the drive current I does not flow. And when the counter electromotive force induced in u ₂ , v ₁ and v ₂ , or w ₁ and w ₂ reaches the value required to detect the rotational position of the rotor 1, this counter electromotive voltage causes the rotor 1 to rotate. The closed loop which detects the rotational position and switches the drive current to the stator coils u ₁ and u ₂ , v ₁ and v ₂ , w ₁ and w ₂ to generate a rotating magnetic field is switched.

In the above (A) and (B), after the two energization switching pattern P _1, the predetermined energization switching pattern P ₁ or P ₂ from the P ₂ is started is selected, the detection output Hv of the magnetoelectric converting element 3 Is used as an FG (frequency generator) signal for detecting the number of revolutions of the rotor 1 and the like.

In the above embodiment, the permanent magnet for causing the magnetoelectric conversion element to detect the rotational position of the rotor is a permanent magnet for driving attached to the rotor. However, the present invention is not limited to this, and the permanent magnet is attached to the rotor. It may be a permanent magnet for position detection.

In the above-described embodiment, one magnetic-electric conversion element is used, and a predetermined energization switching pattern is selected from the two energization switching patterns preset for activation based on the detection output of this magnetic-electric conversion element. However, the present invention is not limited to this, and a plurality (for example, two) of magnetoelectric conversion elements are provided, and a plurality of (for example, four) preset for activation based on the detection outputs of these magnetoelectric conversion elements. A predetermined energization switching pattern may be selected from among the energization switching patterns.

In the above-described embodiment, the case where the present invention is applied to the three-phase four-pole inner rotor type brushless DC motor has been described, but the present invention is not limited to this, and may be, for example, a two-phase type or a four-phase type. It can also be applied to an inner rotor type or an outer rotor type brushless DC motor.

[Effects of the Invention] As described above, the brushless DC motor starting method according to the present invention presets a plurality of energization switching patterns for constantly rotating the rotor in a predetermined direction in accordance with the rotor stop position. Every time, based on the detection output of the magnetoelectric conversion element that detects the stop position of the rotor, a predetermined energization switching pattern is selected from among the set energization switching patterns, and the stator coil group is selected according to the selected energization switching pattern. The rotor is driven to rotate by generating a rotating magnetic field by switching the drive current to the rotor. Therefore, at the time of startup, the rotor can always be rotationally driven in a predetermined direction regardless of where the rotor is stopped, and the rotor does not reversely rotate at startup. Therefore, the brushless DC motor can be used for an electric fan or the like that is difficult to reversely rotate at startup.

[Brief description of drawings]

1 and 2 show an embodiment of a method for starting a brushless DC motor according to the present invention. FIG. 1 is an explanatory view for explaining the starting method for the present invention, and FIG. 2 is a brushless DC according to the present invention. Motor part configuration diagram, FIG. 3 and FIG.
FIG. 3 shows a conventional example, FIG. 3 is an explanatory view for explaining a conventional starting method, and FIG. 4 is a configuration diagram of a brushless DC motor in the conventional example. 1 ... Rotor, 2 ... Stator core, 3 ... Magnetoelectric conversion element (Hall element), Hv ... Detection output of magnetoelectric conversion element 3,
u ₁ , u ₂ , v ₁ , v ₂ , w ₁ , w ₂ ...... stator coil, P ₁ ......
An energization switching pattern for switching energization in the order of -1, -1, -2, ..., P ₂ ...- 2, -3,
An energization switching pattern in which energization is switched in the order of ,,,.

Claims (1)

[Claims] 1. At the time of start-up, the drive current to the stator coil group is switched according to a preset energization switching pattern to rotate the rotor, and after the start-up, when the rotational speed of the rotor increases and reaches a predetermined value, In the brushless DC motor, which detects the rotational position of the rotor by the counter electromotive voltage induced in the stator coil and switches the drive current to the stator coil group by this detection output to rotate the rotor. In advance, a plurality of energization switching patterns for driving the rotor to rotate in a predetermined direction corresponding to the stop position are preset, and a magnetoelectric conversion element for detecting the stop position of the rotor is provided. Select a corresponding energization switching pattern from the plurality of energization switching patterns based on the detection output of the magnetoelectric conversion element,
A method for starting a brushless DC motor is characterized in that the rotor is rotationally driven by switching the drive current to the stator coil group according to the selected energization switching pattern.