JPH0713427Y2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a brushless motor.

[Conventional technology and its problems]

In the conventional brushless motor, the stator is composed of a stator core and a coil. The stator core has teeth arranged at intervals in the circumferential direction, and coils are wound around the teeth as required.

In such a motor, teeth and slots for defining the teeth are alternately arranged. Therefore, when a large cogging torque is generated and extremely smooth rotation is required, it is difficult to use the stator having such a configuration. . For example, when it is necessary to reduce the starting current, the reduction of this current also reduces the magnetic field generated in the stator. As a result, the ratio of the cogging torque to the generated torque increases, the apparent torque clipple increases, and it is difficult to obtain smooth rotation.

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a brushless motor that has a very small cogging torque and rotates smoothly.

[Means for solving problems]

In a brushless motor including a stator including a toroidal core around which a coil is wound, and a rotor magnet that rotates relative to the stator, the coil is
The coil pitch α is set to π / P radians when the number of detected magnetic poles for switching control of the current supplied to the coils is set to π / P radians, and the coils are wound on trochoidal cores without overlapping each other. The magnetic pole angle β is (π−
π / P) radians or less, current is supplied to the coil so that it becomes a two-phase motor, and the current supplied to the coil 4 is the non-magnetized part of the rotor magnet and the specific magnetic pole part on the upstream side. When facing the portion of the toroidal core that is excited by the opposite magnetic pole of the specific magnetic pole portion of the rotor magnet, one coil 4a is switched in the rotating direction of the rotor magnet 1.

[Action]

In the brushless motor of the present invention, the coil pitch α is π
/ P radian, rotor magnet magnetic pole angle β
Is set to (π−π / P) radian or less, and the coil is supplied with current so as to form a two-phase motor. Therefore,
In relation to the presence of the non-magnetized portion corresponding to the coil pitch α in the rotor magnet, the non-magnetized portion of the rotor magnet and the specific magnetic pole portion on the upstream side of the non-magnetized portion of the rotor magnet It can be opposed to a portion excited by the magnetic pole and the opposite magnetic pole. Therefore,
When the toroidal core and the rotor magnet have the above-mentioned positional relationship, if the current of the coil existing on the downstream side in the rotation direction of the rotor magnet is switched, the rotor magnet is magnetically attracted to the part where the magnetic pole of the toroidal core is switched. To rotate. Then, even when the current is switched, the specific magnetic pole portion of the rotor magnet does not overlap with the portion of the toroidal core on the downstream side that is excited by the same magnetic pole as the magnetic pole of the specific magnetic pole portion,
Only the non-magnetized portion of the rotor magnet approaches the above-mentioned portion of the toroidal core. As a result, almost no rotation torque is generated in the opposite direction to the rotation direction of the rotor magnet, and the rotor magnet rotates smoothly and stably.

〔Example〕

Hereinafter, an embodiment of a brushless motor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 schematically shows an embodiment of a brushless motor according to the present invention. In FIG. 1, the illustrated brushless motor includes a rotor magnet 1 and a stator 3 arranged outside the rotor magnet 1.
The rotor magnet 1 has two magnetic poles, and non-magnetized portions 2 and 2 are provided between the N pole and the S pole facing each other.

This rotor magnet 1 has a toroidal core (annular body)
The stator 3 made of is externally fitted to the toroidal core, and eight coils 4a are wound around the toroidal core without overlapping each other. As shown in FIG. 1, all the coils 4a are wound in a right-handed manner, and are configured as a two-phase motor in the embodiment.

In the vicinity of the stator 3, a rotor position detector 5 including a Hall element or the like for detecting the rotation angle position of the rotating rotor,
6 is provided. A position sensor magnet (not shown) is coaxially directly connected to the rotor magnet 1, and the position sensor magnet rotates integrally with the rotor magnet 1. As shown in FIG. 2, this magnet position sensor has N poles and S poles that are arranged alternately at substantially equal intervals, and a total of 4 N poles / S poles are provided.

The pitch of the rotor magnet 1, the coils 4a, etc. are set as follows. That is, the number of detected magnetic poles of the sensor magnet is P
(P = 4 in the embodiment) and the number of phases of the coils 4a ... Is A (A = 2 in the embodiment), the pitch α of each of the coils 4a is about 2π / (A · P). ) Set to radians,
The coils 4a ... Are wound over almost the entire pitch angle. The pitch γ between the coils 4a is set to about 2π / P radian. The position detectors 5 and 6 are arranged at an interval of π / 4 radian. Furthermore, the magnetic pole angle β of the rotor magnet 1 is approximately [π−2π / (A ·
P)] Radian or less.

In this embodiment, the number of detected magnetic poles P is P = 4, as described above.
And the number of phases A of the coils 4a is A = 2,
The pitch α of each coil 4a is α≈2π / (2 × 4) = π / 4
It is set to radians, and the pitch γ between the coils 4a is γ
≈2π / 4 = π / 2 is set. Further, the magnetic pole angle β of the rotor magnet 1 is β≈ [π−2π / (2 × 4)] = 3
Set to π / 4 radians. That is, with this motor,
The individual coils 4a are provided, and the pitch α of these coils 4a is
Is π / 4 radians. On the other hand, the magnetic pole angle β of the rotor magnet 1 is 3π / 4 radians, and this rotor magnet 1 has one pitch (π / 4) between the adjacent magnetic poles of the coil 4α.
There is non-magnetization corresponding to radians. Therefore, the non-magnetized portion of the rotor magnet and the specific magnetic pole portion on the upstream side thereof can face the portion of the toroidal core that is excited by the magnetic pole opposite to the magnetic pole of the specific magnetic pole portion of the rotor magnet.

FIG. 3 is a simplified diagram sequentially showing the rotational driving state of the brushless motor described above. In FIG. 3, the portions a, b ... H of the stator 3 show the portions of the toroidal core around which the coils 4a are wound. Here, in order to explain the operating principle of the present invention more simply, the excitation state of the stator 3 is defined as follows. That is, as schematically shown in FIG. 4, when the S pole of the rotor magnet 1 approaches the toroidal winding 7, the exciting current i is applied to the winding 7 so that the rotor magnet 1 moves in the direction of arrow F. The flow of current is hereinafter referred to as "exciting the N pole". The arrow B shown in FIG.
Indicates the direction of the magnetic field.

In order to drive this brushless motor to rotate, first,
As shown in FIG. 3 (I), the portion a of the toroidal core,
Each of the coils 4a, 4b, 4c, 4d wound on b, c, d is excited to the N pole, and e, f of the portion of the toroidal core,
The coils 4e, 4f, 4g, and 4h wound around g and h are excited by the S pole. The N pole of the rotor magnet 1 faces the S pole of the stator, and the S pole of the rotor magnet faces the N pole of the stator 3. Next, the rotor magnet 1 rotates to the angular position of FIG. 3 (I) (in other words, the S pole of the rotor magnet 1 faces the portions a, b, c, d of the toroidal core, and its N pole is toroidal. (Rotate to an angular position facing the core parts e, f, g), and as shown in FIG. 3 (II), the angular coils 4b, 4c wound around the toroidal core parts b, c, d, e. 4d and 4e are excited to the N pole, and f of the toroidal core part,
The coils 4f, 4g, 4h, and 4a wound around g, h, and a are excited by the S pole. Therefore, as can be easily understood from FIGS. 3 (I) and (II), the toroidal core portion is excited to the north pole (or south pole) in the clockwise direction, so that the south pole (or north pole) of the rotor magnet 1 is excited. The pole) is magnetically attracted to the N pole (or S pole) of the rotor magnet 1. Therefore, a rotational force in the direction indicated by the arrow X (clockwise in FIG. 3) is generated in the rotor magnet 1, and the rotor magnet 1 rotates clockwise to be in the state shown in FIG. 3 (II). . The rotor magnet 1 rotates to the state shown in FIG. 3 (II) (that is, the non-magnetized portion of the rotor magnet is located at the portion e of the toroidal core, and the specific magnetized portion (for example, N pole magnetized portion) is located in the toroidal core. 2), the position detectors 5 and 6 detect position sensor magnets (not shown), as can be easily understood from FIG.
Their output signals change. When the signal changes,
The exciting current supplied to the coils 4a ... Is switched. That is, at this time, as shown in FIG. 3 (III), the coils 4c, 4d wound around the portions c, d, e, f of the toroidal core,
4f is excited by the N pole, and the coils 4g, 4h, 4a and 4b wound around the toroidal core parts g, h, a and b are S-shaped.
Excited by the poles. Therefore, in the rotor magnet 1,
Further, the rotational force in the direction indicated by the arrow ZX acts, and the rotor magnet 1 rotates to the state shown in FIG. 3 (III). Then, when rotating to this state, the position detectors 5 and 6 detect the position sensor magnets (not shown) again in the same manner as described above, and their output signals change. Upon detection in this way, the exciting current supplied to the coils 4a ... Is switched, and as shown in FIG. 3 (IV), the portion d of the toroidal core,
The coils 4d, 4e, 4f and 4g wound around e, f and g are excited to the N pole, and h, a and
The coils 4h, 4a, 4b and 4c wound around b and c are excited to the S pole, and the rotor magnet 1 is rotated to the state shown in FIG. 3 (IV). As described above, when the excitation of each coil 4a ... is sequentially changed in the direction indicated by the arrow X, the rotor magnet 1 rotates in the direction indicated by the arrow X as shown in FIGS. 3 (I) to (VIII). To do.

In the embodiment, the eight coils 4a ... Are wound independently, but when the coils 4a ... Are energized, for example, the coils 4a, 4b, 4c, 4d are excited to the N pole. And coil 4
e, 4f, 4g, and 4h are excited by the south pole. At this time, coil 4
a, 4b, 4c, 4d act as the first phase, and coils 4e, 4f, 4
g and 4h act as the second phase. Also, for example, coil 4
b, 4c, 4d, 4e are excited by the N pole, and coils 4f, 4g, 4h, 4
When a is excited by the south pole, coils 4b, 4c, 4d, 4e
Acts as the first phase, and the coils 4b, 4c, 4d, 4e act as the second phase. Therefore, in the embodiment, the coils 4a ... Of this motor are excited in two phases and driven in two-phase bipolar, and each phase thereof is sequentially changed depending on the position of the rotor magnet 1. Incidentally, in FIG. 3, the hatched portion shows the portion excited by the N pole. Further, although the wound coils are shown in a simplified manner, in reality, a larger number of coils are wound.

In this brushless motor, the output of one position detector 5 becomes a waveform signal as shown by outputs I and II as the position sensor magnet (not shown) (hence, the rotor magnet 1) rotates, and the other position Output of detector 6 is output II
The waveform signal is as shown in I and IV. Then, the exciting currents supplied to the coils 4a to 4h are switched in order based on the output signals I to IV of the position detectors 5 and 6, and the coils 4a to 4h are located at the portions a to h of the toroidal core.
Is excited to the N or S pole as indicated by coil excitation a to h in FIG. That is, 4 out of 8 sites are N
The remaining four parts are excited to the S pole, and the part excited to the N pole and the part excited to the S pole are sequentially moved in the rotation direction of the rotor magnet 1, whereby the rotor is rotated. The magnet 1 is rotationally driven in a predetermined direction. The starting torque (combined torque) generated by the rotation of the rotor magnet 1 has a waveform as shown in FIG. More specifically, the parts a to h of the toroidal core
Is excited, the magnetic pole angle of the rotor magnet 1 becomes 3 /
Since it is set to 4π radians, the area of the N pole of the rotor magnet 1 does not correspond to the exciting N pole of the stator 3, and the area corresponding to the S pole of the rotor magnet 1 is the exciting S of the stator 3. It does not correspond to the pole portion, and therefore a constant and stable driving torque is obtained.
In addition, in the stator having the conventional teeth, the slots exist at intervals in the circumferential direction, which causes torque ripple. On the other hand, in this motor, the stator 3 rotates in the circumferential direction. Direction, and the portions a to h of the stator 3 are sequentially excited to the N pole (or S pole), the torque ripple is reduced, and the rotor magnet 1 rotates stably and smoothly.

The present invention can be applied not only to the inner rotor type but also to the outer rotor type.
Further, not only the radial type in which the magnet and the stator face each other in the radial direction but also the axial type in which the magnet and the stator face each other in the shaft direction can be similarly applied.

[Effect of device]

In the brushless motor of the present invention, the coil pitch α is π
/ P radian, rotor magnet magnetic pole angle β
Is set to (π−π / P) radian or less, and the coil is supplied with current so as to form a two-phase motor. Therefore,
In relation to the presence of the non-magnetized portion corresponding to the coil pitch α in the rotor magnet, the non-magnetized portion of the rotor magnet and the specific magnetic pole portion on the upstream side of the non-magnetized portion of the rotor magnet It can be opposed to a portion excited by the magnetic pole and the opposite magnetic pole. Therefore,
When the toroidal core and the rotor magnet have the above-mentioned positional relationship, if the current of the coil existing on the downstream side in the rotation direction of the rotor magnet is switched, the rotor magnet is magnetically attracted to the part where the magnetic pole of the toroidal core is switched. So that it rotates in a predetermined direction. Then, even when the current is switched, the specific magnetic pole portion of the rotor magnet does not overlap with the portion of the toroidal core on the downstream side that is excited by the same magnetic pole as the magnetic pole of the specific magnetic pole portion (in other words, in other words). , The north pole of the rotor magnet does not correspond to the north pole of the toroidal core on the downstream side, and the south pole of the rotor magnet does not correspond to the south pole of the toroidal core on the downstream side). As a result, almost no rotational torque in the direction opposite to the rotational direction of the rotor magnet is generated, a constant drive torque is obtained, and the rotor magnet rotates smoothly and stably.

[Brief description of drawings]

FIG. 1 is a simplified plan view showing a specific example of the brushless motor according to the present invention. FIG. 2 is a graph for explaining various characteristics of the motor shown in FIG. FIG. 3 is a simplified plan view showing the order of rotation of the rotor magnet in the motor of FIG. FIG. 4 is an explanatory diagram showing a magnetizing method of the stator. 1 ... Rotor magnet, 3 ... Stator, 4a to 4h ... Coil, α ... Coil pitch, β ... Rotor magnet magnetic pole angle, γ ... Coil pitch

Claims (1)

[Scope of utility model registration request] 1. A brushless motor comprising a stator 3 comprising a toroidal core around which coils 4a are wound, and a rotor magnet 1 which rotates relative to the stator 3, wherein the coils 4a. When the number of detected magnetic poles that are wound around the trochoidal core and do not overlap each other and control the switching of the current supplied to the coils 4a is P, the pitch α of the coils 4a is set to π / P radian. Further, the magnetic pole angle β of the rotor magnet 1 is (π−π /
P) is set to be less than or equal to radian so that the non-magnetized portion is defined between the adjacent magnetic pole portions, the current is supplied to the coil 4a so as to form a two-phase motor, and the current supplied to the coil 4a ... Of the rotor magnet 1 when the non-magnetized portion of the rotor magnet 1 and the specific magnetic pole portion on the downstream side of the rotor magnet 1 face a portion of the toroidal core that is excited by a magnetic pole opposite to the magnetic pole of the specific magnetic pole portion. A brushless motor characterized in that one coil 4a can be switched in the rotating direction for each coil.