JPH0723027Y2 - Brushless motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a two-phase brushless motor using a hall element for detecting the position of a rotor.

[Background Art] Conventionally, a brushless motor as shown in FIG.
-177016. In this brushless motor, two poles 5a and 5b in diagonal positions are displaced from the equiangular position to the rotational direction side inside a 4-pole annular permanent magnet rotor 10 which is magnetized alternately at NS and at equal intervals. At the same time, the four pole salient pole type stators 3 in which the magnetic pole widths of the displaced magnetic poles 5a and 5b are narrower than the magnetic pole widths of the other two magnetic poles 4a and 4b are arranged, and they are adjacent to each other through a wide magnetic pole space. Wide magnetic pole and narrow magnetic pole, that is, magnetic pole
Magnetic poles of 4a, 5a and 4b, 5b have different polarities.
Windings 6 (L ₁ , L ₂ ) are wound around 4a, 4b, 5a, 5b, and the rotation of the permanent magnet rotor 10 is detected by the hall element 11 as a position detecting element, and the output of the hall element 11 is detected. In response to this, a current switching circuit selectively supplies a current to either one of the windings 6. Here, the salient pole type stator 3 has a narrow magnetic pole 5
20 to 40 degrees (electrical angle) from a, 5b to the rotation direction side from the equiangular position
The magnetic pole widths of the narrow magnetic poles 5a and 5b are changed while being displaced.
It is 30 to 60% narrower than the magnetic pole width of a and 4b.

FIG. 6 shows the operation of the brushless motor,
The main torque curve T ₁ due to only the interaction between the magnetic flux due to the coil current and the rotor has a waveform of only the upper half because the fundamental wave is switched every half cycle, and the permanent magnet and the stator in the state where the coil current is zero. The auxiliary torque curve T ₂ due to the interaction with the salient magnetic pole has a half cycle of the fundamental wave T ₁ , and points θ ₁ and θ ₂ that cross the coordinate axis from positive to negative are stable stop points. If the magnetic poles of the stator are evenly spaced,
This stable stop point coincides with the zero point of the fundamental wave T ₁ , but the auxiliary torque curve T ₂ is shifted in the forward rotation direction by displacing the narrow magnetic poles 5a, 5b, and the stable stop points θ ₁ , θ ₂ is positioned slightly to the right of the zero point of the fundamental wave T ₁ , and the combined torque curve T ₁ + T ₂ is always positive and has no dead point. Thus, the rotor is stopped at a position slightly rotated in the forward rotation direction at the time of starting, that is, when the coil current is zero.

According to this configuration, the stop position of the rotor 10 is mainly regulated by the narrow magnetic poles 5a, 5b during non-excitation, and evenly attracted by both magnetic poles 4a, 4b and 5a, 5b during excitation.
The advantage is that the starting characteristics can be easily obtained without using a rotor with 4 poles or 8 poles or providing a stator with a compensating pole, but the magnetomotive force generated in the stator coil during startup is sufficiently large. If you do not do so, you will not be able to start up, and therefore a high starting voltage is required, and in addition, there are large fluctuations in rotation and vibration noise, and the features of the DC brushless motor that have the original advantages of wide operating voltage range and wide range of rotation speed are There was a problem that I could not make good use of it.

This is a method of eliminating the dead center by narrowing one magnetic pole and displacing it, and it is considered that this is because the gap between the magnetic poles becomes large and the magnitude of the auxiliary torque T ₂ becomes excessive. As a countermeasure against this, reducing the deflection angle of the narrow magnetic pole is because the phase of the auxiliary torque curve T _{2 in} FIG. 6 is out of phase.
There is a problem that a dead point is likely to occur in the combined torque curve T ₁ + T ₂ , and it is also possible to change only the size without changing the ratio of the magnetic pole widths of both. Then, there is a problem that winding of the coil becomes difficult.

[Object of the Invention] The present invention has been made in view of the above problems, and an object of the present invention is to improve the operating voltage range and the rotation speed variable width by a simple modification in a two-phase brushless motor of this type. This is to reduce uneven rotation and vibration.

DISCLOSURE OF THE INVENTION NS NS two magnetic poles in diagonal positions are displaced from the equiangular position in the direction of rotation in the interior of a four-pole annular permanent magnet rotor magnetized alternately and at equal intervals. A four-pole salient-pole stator in which the magnetic pole width of the displaced magnetic pole is narrower than the magnetic pole widths of the other two magnetic poles is arranged, and the wide magnetic pole and the narrow magnetic pole adjacent to each other through a wide magnetic pole space have different polarities. Windings are wound around each magnetic pole so that the rotation of the permanent magnet rotor is detected by the position detection element, and one of the windings is switched by the current switching circuit according to the output of the position detection element. In a brushless motor that supplies a constant current, the side edges of the wide magnetic pole and the narrow magnetic pole that are adjacent to each other through a wide magnetic pole space are connected by a thin plate made of a magnetic material. Is concentrated, that is, the magnetic flux of the narrow magnetic pole is widely dispersed. Thereby decreasing the assist torque, reducing the starting voltage. By thus widely dispersing the magnetic flux of the narrow magnetic poles, the fluctuation of the auxiliary torque is reduced, the rotation unevenness and the vibration are reduced, and the starting voltage is reduced to widen the operating voltage range.

[Embodiment] FIGS. 1 to 4 show an embodiment of the brushless motor of the present invention. In FIGS. 1 and 2, four pole salient pole type stators 3 made of laminated iron cores are fixed around the cylindrical support 2 fixed to the main body casing 1, and each magnetic pole 4a, 4b, Two-phase armature windings 6 are provided on 5a and 5b. The cylindrical support 2 holds a rotary shaft 8 via a bearing 7 inside, and a cup-shaped yoke 9 fixed to one end of the rotary shaft 8 and a cylindrical permanent magnet 10 fixed to the inner peripheral surface thereof. And constitute a rotor. The permanent magnet 10 has the same number of poles as the stator, that is, four poles, and is magnetized on the circumferential surface at equal intervals and alternately with NS, while the stator has a magnetic pole width (=
The wide magnetic poles 4a and 4b having a large D ₁ ) and the narrow magnetic poles 5a and 5b whose magnetic pole width (= D ₂ ) is formed to be about 1/2 of the wide magnetic pole, and the narrow magnetic poles 5a and 5b are equal to each other. The electric angle is offset from the spacing position by 20 to 40 degrees to the rotation direction side. In this way, a wide space and a narrow space are formed between the magnetic poles 4a, 4b, 5a, 5b, but at least in the wider space between the magnetic poles, the adjacent magnetic poles 4a, 5a are formed.
The side edges of 4b and 5b are connected by a thin plate 12 made of a magnetic material and having a thickness of 0.5 mm, as shown in FIG.

Further, a Hall element 11 for detecting the polarity of the rotor magnetic pole passing therethrough is arranged at a position distant from the center of one of the wide magnetic poles 4a in the rotation direction by an electrical angle of about 90 degrees. Output of the current switching circuit 2 shown in FIG.
Control the _two transistors Q ₁ and Q ₂ ,
Current is alternately supplied to the windings L ₁ and L ₂ respectively wound around the NS pole. This Hall element 11 detects one polarity (N pole in this embodiment), outputs a signal, and
When the Q ₃ is turned on, and the transistor Q ₁ on and off Q _2, electric current to the coil L _1, since no current flows in the L _2, wound windings L ₁ in FIG. 2 Magnetic poles 4a and 5a
Only is excited, the magnetic pole 4b and 5b which are wound windings L ₂ is not excited. In this way, any two poles of the four poles of the stator magnetic pole are always excited.

The basic operation of the present invention is the same as that of the conventional example described in FIG. 6, but the auxiliary torque curve T ₂ has a steeper waveform because the magnetic pole width of the stator is narrow and the magnetic pole interval is large. As a result, the unevenness of the combined torque curve T ₁ + T ₂ becomes severe, and there is a portion where the starting torque is insufficient. Therefore, in the present invention, the thin plate 12 made of a magnetic material is provided in the space between the magnetic poles to disperse the magnetic flux during non-excitation, reduce the auxiliary torque, and reduce the starting voltage. Further, at the time of excitation in which the main magnetic flux increases, the thin plate 12 is magnetically saturated so that the main magnetic flux generated in the winding 6 does not interfere with the action of the permanent magnetic pole 10 and the generated torque is prevented from decreasing. That is, the starting voltage is reduced without reducing the generated torque. Further, by widely dispersing the magnetic fluxes of the narrow magnetic poles 5a and 5b, the fluctuation of the auxiliary torque is reduced, the rotation unevenness and the vibration are reduced, and the starting voltage is reduced, so that the operating voltage range is widened. Moreover, by connecting only the side edges of the wide magnetic poles and the narrow magnetic poles adjacent to each other through the wide magnetic pole space, that is, the side edges of the magnetic poles 4a, 5a and 4b, 5b with a thin plate made of a magnetic material, the auxiliary torque is increased more than necessary. Does not lower. As a result, the effect of the basic structure of the brushless motor of the present invention that the width of the magnetic pole is formed to be wide and narrow and the narrow magnetic pole is displaced, that is, the combined torque curve of the main torque curve and the auxiliary torque curve It does not prevent the effect of preventing dead points from occurring.

The thin plate 12 may be formed by cutting and raising it from the casing 1, or a separate member may be fixed to the casing 1. Further, the axial length of the thin plate 12 does not necessarily have to be the same as the magnetic pole length.

[Advantage of the Invention] NS The two magnetic poles in diagonal positions are displaced from the equiangular position to the rotation direction side inside the four-pole annular permanent magnet rotor magnetized alternately and at equal intervals. A four-pole salient-pole stator in which the magnetic pole width of the displaced magnetic pole is narrower than the magnetic pole widths of the other two magnetic poles is arranged, and the wide magnetic pole and the narrow magnetic pole adjacent to each other through a wide magnetic pole space have different polarities. Windings are wound around each magnetic pole so that the rotation of the permanent magnet rotor is detected by the position detection element, and one of the windings is switched by the current switching circuit according to the output of the position detection element. In a brushless motor that supplies a constant current, since the side edges of the wide magnetic pole and the narrow magnetic pole that are adjacent to each other are connected via a wide magnetic pole space with a thin plate made of a magnetic material, the magnetic flux of the narrow magnetic pole is not excited. Can be relaxed, that is, the magnetic flux of the narrow magnetic pole can be widened. Can be dispersed, and thus assist torque is reduced, it is possible to reduce the starting voltage. In addition, when the main magnetic flux increases, the thin plate is magnetically saturated, and the main magnetic flux generated in the winding does not hinder the action of the permanent magnet rotor.
There is an advantage that the generated torque can be reduced less and the starting voltage can be reduced without reducing the generated torque. Furthermore, by widely dispersing the magnetic flux of the narrow magnetic pole, it is possible to reduce the fluctuation of the auxiliary torque, reduce the rotation unevenness and vibration, and reduce the starting voltage to widen the operating voltage range. can do. Moreover, since only the side edges of the wide magnetic pole and the narrow magnetic pole that are adjacent to each other through the wide magnetic pole space are connected by the thin plate made of a magnetic material, the auxiliary torque is not reduced more than necessary, and therefore the magnetic pole is The effect of the basic structure of forming the width of the wide and narrow widths and displacing the narrow magnetic poles, that is, the effect of preventing a dead point from occurring in the combined torque curve of the main torque curve and the auxiliary torque curve. It doesn't get lost.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the brushless motor of the present invention, FIG. 2 is a lateral sectional view of the same, FIG. 3 is a circuit diagram of the same, FIG. 4 is a perspective view of essential parts of the same, and FIG. FIG. 6 is a transverse sectional view of a conventional example, and FIG. 6 is an operation explanatory view of the same. 1 is a main body casing, 2 is a cylindrical support, 3 is a stator,
4a and 4b are wide magnetic poles, 5a and 5b are narrow magnetic poles, 6 is a winding, 7 is a bearing, 8 is a rotating shaft, 9 is a cup-shaped yoke, 10 is a permanent magnet, 11 is a Hall element, and 12 is a thin plate.

Claims (1)

[Scope of utility model registration request] 1. An NS permanent magnet rotor having four poles magnetized alternately and at equal intervals, with two magnetic poles at diagonal positions being displaced from the equiangular position toward the direction of rotation. A four-pole salient-pole stator in which the magnetic pole width of the displaced magnetic poles is narrower than the magnetic pole widths of the other two magnetic poles is arranged, and the adjacent wide magnetic poles and narrow magnetic poles have different magnetism through a wide magnetic pole space. Windings are wound around each magnetic pole so that the rotation of the permanent magnet rotor is detected by the position detection element, and one of the windings is switched by the current switching circuit according to the output of the position detection element. A brushless motor for supplying a constant current, characterized in that side edges of the wide magnetic pole and the narrow magnetic pole which are adjacent to each other through a wide magnetic pole space are connected by a thin plate made of a magnetic material.