JPS6311865B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC motor that obtains continuous rotational force in a predetermined direction by alternately passing current through two-phase coils.

U.S. Pat. No. 3,299,335 discloses that two-phase coils are disposed in the stator, a fixed magnet is attached to the rotor, and the current applied to the two-phase coils is switched according to the rotation of the rotor. A brushless DC motor that obtains rotational power by is described. In such a motor, it is necessary to arrange N poles, S poles, and inorganic poles on the rotor, and it is difficult to arrange these N poles, S poles, and non-magnetic poles alternately in the required angular width on a single magnet. However, magnetization variations are likely to occur particularly in the non-magnetic pole portion and the boundary portion.

Also, in Japanese Patent Publication No. 54-41406,
The configuration of the magnetic poles of the magnet is to provide an N pole and a S pole with equal angular width, and to provide an S pole within the N pole and an N pole within the S pole adjacent to each other at a part of the border on one side of the N pole and the S pole. so that the N pole only part, the first part where both poles coexist, and the first part and the magnetic pole are reversed,
Moreover, a brushless DC motor is described in which four parts are alternately arranged, including a second part where both poles coexist and a part with only an S pole.
In this example as well, rotational force is obtained by disposing two-phase coils on the stator, attaching the aforementioned magnets to the rotor, and switching the current flowing to the two-phase coils according to the rotation of the rotor. That's what I do.

However, in this type of magnet configuration, the S pole is provided within the N pole and the N pole is provided within the S pole, so it is difficult to magnetize these small magnetic poles into the magnet, and it is difficult to magnetize the magnet with multiple poles and miniaturization. There are problems in trying to achieve this goal.

The present invention takes these points into consideration and provides a DC motor that simplifies the structure of the magnetic poles of the magnet, reduces variations in magnetization, and is suitable for multipolarization and miniaturization. Hereinafter, the present invention will be explained based on illustrated embodiments. FIGS. 1 to 4 show the basic principle of the DC motor of the present invention, and FIGS. 5 and 6 show specific configurations of embodiments of the present invention, respectively.

In FIG. 1, a is a vertical cross-sectional view of the structure showing the basic principle of the DC motor of the present invention, and b is a cross-sectional view taken along line X--X at a. In the figure, a rotating shaft 2 of a rotor 1 is rotatably supported by a stator 6 through bearings 3 and 4, and a fixed magnetized annular magnet 5 is attached to the inner surface of the rotor 1. Two-phase coils 8 and 9 are provided on the outer periphery of the armature core 7, facing the magnetic pole surface of the magnet 5. Further, a Hall element 10 for position detection is fixedly arranged on the stator 6 so as to face the lower end surface of the magnet 5. Note that illustration of the specific mounting structure is omitted.

FIG. 2a shows a developed plan view of the magnet 5 and two-phase coils 8 and 9 shown in FIG. 1, illustrating the basic principle of the present invention. In the figure, the magnet 5 has an inner peripheral surface (inner periphery) as an N pole (N pole area) and an S pole (S pole area).
It is bipolarly magnetized, and the N-pole part where the N-pole exists alone, the S-pole part where the S-pole exists alone, and the effective non-magnetic pole part where the N-pole and S-pole coexist are alternately arranged at equal angles. One set each has a width (120°) or approximately equal angular width.
Field magnetic flux density B _r (Ψ, Z) generated by magnet 5
Average magnetic flux density _r (Ψ) =
The characteristics of 1/h∫ ^h _p B (Ψ, Z) dZ are shown in Figure 2b.

The solid line in the figure is a characteristic that approximates a rectangular wave shape, and the broken line is a characteristic that accompanies actual changes in poles. Here,
Ψ is an angular variable, Z is an axial variable, and h is the effective opposing length of the coil. /dS).

Since the north and south poles coexist in the effective non-magnetic pole, the average magnetic flux density _r (Ψ) is zero or considerably small, and is considerably smaller than the average magnetic flux density at the north and south poles. I'm keeping it small. usually,
Compared to the absolute maximum value _r1 of the average magnetic flux density _r (Ψ) of the north and south pole parts, the absolute maximum value _r2 of the average magnetic flux density _r (Ψ) of the effective non-magnetic pole part is _r2 < _r1/2 …(1) It is done. Of course, it is desirable that _r2 be smaller, but sufficiently good characteristics can be obtained if _r2 ≦ _r1/4 .

The center lines of the two-phase coils 8 and 9 are shown by dashed lines in FIG. 2a. The effective pitch of each coil 8, 9 is the angular width of the effective non-magnetic pole part of the magnet 5 (120°)
The coils 8 and 9 have a phase difference of 1/2 of the magnetic pole period of 360° (one set of angles of the N pole part, the effective non-magnetic pole part, and the S pole part).
It is arranged on the armature core so that it has an angle of 180°.

FIG. 2c is a plan development view of the lower end surface of the magnet 5 (the surface facing the Hall element 10), which is equal to the number of sets of the N pole part, the effective non-magnetic pole part, and the S pole part on the circumferential surface. A set of N poles and S poles are magnetized to have equal angular width or approximately equal angular width and are used for position detection. Figure 2 d shows the magnetic flux density in the axial direction of the lower end surface of magnet 5.
This is a characteristic of B _a (Ψ).

Next, the operation of the DC motor shown in FIGS. 1 and 2 will be explained. The torque T generated when current is passed through the coils 8 and 9 is proportional to the product of the average magnetic flux density at the effective coil sides A, B, C, and D and the current value I (Fleming's left-hand rule). That is, T ₁ ∝I・[ _r (θ) − _r (θ+120°)]…(2) T ₂ ∝I・[ _r (θ+180°) − _r (θ+300°)]…(3
) becomes. Here, θ is the rotation angle between the point R _p of the magnet 5 and the point K _p of the coils 8 and 9 when viewed from the rotation axis. Average magnetic flux density difference between the effective coil sides of two-phase coils 8 and 9 _r (θ) − _r (θ + 120°) and _r
(θ+180°) − _r (θ+300°) changes as shown in FIGS. 3a and b. Therefore, as shown in Fig. 3d and e, constant values of currents i ₁ and i ₂ are changed according to the rotation angle θ,
If the coil to be energized is switched every 1/2 rotation of the magnetic pole period of the magnet 5 (one set of angles of the N pole part, the effective non-magnetic pole part, and the S pole part), the result will be as shown in Figure 3 f. Therefore, even rotational torque T can be obtained.

FIG. 4 shows an example of a drive circuit. In the figure, since the Hall element 10 faces the position detection magnetic pole on the lower end surface of the magnet 5, its Hall voltage E ₁ ,
E ₂ changes depending on the rotation angle θ as shown in FIG. 3c. The Hall voltages E ₁ and E ₂ are applied to the bases of transistors Q ₃ and Q ₄ constituting the differential circuit, and the transistor with a lower base voltage, for example, Q ₃ is turned on, and Q ₄ is turned off. As a result, the drive transistor Q ₁ is turned on, supplying the current i ₁ to the first phase coil 8, and the drive transistor Q ₂ is turned off, so that no current flows through the second phase coil 9. As the rotor rotates, the output voltages E ₁ and E ₂ of the Hall element 10 change, selectively and complementarily switching the coils to be energized, as shown in Fig. 3 d and e.
Current is always supplied to one of the coils as shown below.

In addition, 11 in FIG. 4 is a current controller, which detects the supplied current by the voltage drop of the resistor _R1 , compares it with the command signal 12, and adjusts the supplied current according to the command signal 12. It controls the emitter current _Ie of the transistors Q ₃ and Q ₄ , that is, the base current of the drive transistors Q ₁ and Q ₂ . As a result, the current i ₁ ,
The switching of i ₂ becomes smooth and the transistor
h Fluctuations in supply current due to _FE variations become smaller.

In this way, if unidirectional current is supplied to the two-phase coils 8 and 9 in a complementary manner, there is no discontinuity in the generated torque, and uniform rotation can be obtained.

Note that the position detection element is not limited to a Hall element, but a general magnetoelectric transducer can be used.

In this way, the field magnetic pole surface of the magnet 5 is covered with alternating N poles (N pole area) and S poles (S
By making part of the N pole and part of the S pole coexist in the direction perpendicular to the rotation direction, an effective non-magnetic pole with a predetermined angular width is formed, and the N pole part is magnetized. , the effective non-magnetic pole part, and the S pole part are arranged in sequence, it is possible to obtain a two-phase DC motor with a simple current-carrying configuration. Further, magnetization of the magnet 5 is extremely easy from the following point.

(1) Since the north and south poles coexist and cancel each other's magnetic effects to form an effective non-magnetic pole, the north and south poles are completely magnetized (residual flux density is maximum). It is sufficient to perform magnetization such that

(2) Since the N-pole area and S-pole area can be made larger, the salient pole of the magnetizing yoke of the magnet can be made larger.
Further, the winding process becomes easy, and uniform magnetization can be obtained. This effect is particularly significant when multipolar and miniaturized.

FIG. 5 shows a developed plan view of an embodiment of the present invention. In this embodiment, the number of poles of the magnet and the number of coils are doubled in the basic principle diagrams shown in FIGS. 1 to 4, and the structure and arrangement thereof are further improved.

In the same figure a, the inner peripheral surface of the magnet 21 has four N poles (N pole area) and S poles (S pole area) alternately.
Pole magnetized, two sets of N pole part, effective non-magnetic pole part,
S-pole portions are formed one after another. In this example, the adjacent N
The polar region and the south pole region are provided symmetrically or approximately symmetrically with respect to the boundary line between the north and south poles (0° line and 180° line in Figure 5) (this effect will be discussed later). do). The characteristics of the average magnetic flux density B _r (Ψ) on the inner peripheral surface of the magnet 21 are as shown in FIG. 5b. The solid line in the figure is an approximation to a rectangular waveform, and the broken line is a characteristic associated with actual changes in poles.

A coil 22 is placed opposite the magnetic pole of the magnet 21.
The first phase coil consisting of a and 22b and the coil 23
The second phase coils consisting of a and 23b are arranged so as to have a phase difference (90 degrees) that is half the magnetic pole period (180 degrees) of the magnet 21.

In this example as well, as shown in Fig. 5c, two N and S poles are placed on the lower end surface of the magnet 21 at equal angular widths (90 degrees).
It is assembled and magnetized and used for position detection. Figure 5d
is the characteristic of its magnetic flux density B _a (Ψ). Therefore,
The rotor can be rotationally driven by the drive circuit shown in FIG.

Next, the adjacent N of the magnet 21 of this embodiment
The effect of making the polar region and the S-pole region symmetrical or substantially symmetrical with respect to the boundary line between the N-pole portion and the S-pole portion will be described in detail. In FIG. 5a, coils 22a, 23a,
Consider a case where the magnets 22b, 23b and the magnet 21 are shifted in the axial direction, and the magnet 21 moves a predetermined distance toward the bottom of the drawing. At this time, the N-pole flux linkage of the coil 22a increases, and the coil 22a increases.
3a also increases the magnetic flux of the N pole, and conversely the magnetic flux of the coil 22b becomes S.
The magnetic flux of the pole increases (the magnetic flux of the N pole decreases), and the coil 2
3b also increases the magnetic flux of the S pole (the magnetic flux of the N pole decreases).
Since the coil 22a and the coil 22b are connected in series to form the first phase coils 22a and 22b, changes in the interlinkage magnetic flux of the coil 22a and the coil 22
The changes in the flux linkage of b cancel each other out. That is, the first
The magnetic flux linkage to the phase coil is the same as in the case where there is no shift in the axial direction. Second phase coil 23
The same applies to a and 23b. The torque generated by a DC motor is related to the change in the interlinkage magnetic flux of the coils due to the rotation of the magnet 21, but if the configuration is as described above, even if there is an axial shift, the linkage to the coils of each phase will be maintained. Since the alternating magnetic flux does not change, it is possible to obtain the same uniform generated torque as in the case where there is no deviation in the axial direction.

FIG. 6 shows a developed plan view of another embodiment of the present invention. This example is an example in which the position detecting magnetic pole part provided at the lower end of the magnet is arranged on the field magnetic pole surface (inner peripheral surface) of the magnet in the embodiment shown in FIG. 5 described above.

In the same figure a, the inner peripheral surface of the magnet 31 has four N poles (N pole region) and four S poles (S pole region) alternately.
Pole magnetized and two sets of N pole parts, effective non-magnetic pole parts,
The point that the S pole parts are formed sequentially is similar to the embodiment shown in FIG. Two sets of N and S poles are provided on a circle with equal angular width (90°) or approximately equal angular width, and the Hall element 10
I am facing it. As a result, there is no need for a magnetic pole for detecting the position of the lower end surface of the magnet, etc. The coils 22a and 22b constitute a first-phase coil group, and the coils 23a and 23b constitute a second-phase coil group, as in the embodiment shown in FIG. 5 described above. In addition, Fig. 6b shows the average magnetic flux density of the magnet 31.
This is a characteristic of _r (Ψ).

In the above embodiment, a brushless DC motor was explained in which the rotor was equipped with a magnet and the stator was equipped with an armature consisting of two-phase coils. Alternatively, a magnet may be provided in the drive phase, and the drive phase may be switched by a brush commutator.

Furthermore, in the present invention, by providing a groove in the armature core and storing two sets of coils in the groove,
It is also possible to increase efficiency.

As is clear from the above description, in the DC motor of the present invention, the magnetic poles of the magnets have a simple configuration, and the driving configuration thereof is also extremely simple. Therefore, if a brushless DC motor for audio equipment is constructed based on the present invention, it becomes possible to realize an inexpensive and high-performance audio equipment.

[Brief explanation of the drawing]

Figures 1a and b are longitudinal and cross-sectional views of the structure showing the basic principle of the DC motor of the present invention, and Figures 2a and 2 are
Figures b, c, and d are developed diagrams showing the relationship between the magnet and the coil along with the magnetic flux density, showing the basic principle of the DC motor of the present invention. Figure 3 a, b, c, d, e, and f are the DC motor of the present invention FIG. 4 is a wiring diagram showing an example of a drive circuit; FIGS. 5 a, b, c, and d are plan development views showing an embodiment of the present invention; FIG. 6 a , b are plan development views showing other embodiments of the present invention. 5, 21, 31...Magnet, 8, 9, 22
a, 22b, 23a, 23b...coil.

Claims (1)

[Claims] 1. A magnet having fixed magnetized magnetic poles;
an armature having two-phase coils interlinked with field magnetic flux generated by magnetic poles magnetized in the radial direction of the magnet; and switching energization to the two-phase coils according to relative positions of the magnet and the armature. A direct current motor comprising an energization switching means, wherein the magnetic poles of the magnet and the armature are opposed to each other in the radial direction, and one of the magnet and the armature is freely rotatable relative to the other. , the magnet has m sets (where m is an even number of 2 or more) of N-pole regions and S-pole regions magnetized alternately in the rotation direction, a part of the N-pole region and a part of the S-pole region; are made to coexist in the direction of the rotation axis to form an effective non-magnetic pole part with a predetermined angular width, and m sets of N-pole part, effective non-magnetic pole part, and S-pole part are sequentially formed in the rotation direction, A direct current motor characterized in that the shapes of the adjacent N-pole region and S-pole region are symmetrical or substantially symmetrical with respect to the boundary line between the N-pole portion and the S-pole portion of the magnet. 2. The magnet is an annular magnet, and has m sets of N pole part, effective non-magnetic pole part, and S pole part on the circumferential surface of the magnet, and m sets of N pole part and S pole part on the end face of the magnet. 2. The DC motor according to claim 1, wherein the DC motor has equal angular width or approximately equal angular width. 3. The N-pole region and the S-pole region of the magnet have m pairs of N-pole portions, effective non-magnetic pole portions, and S-pole portions, and m pairs on a circle centered on the rotation axis of the magnetic pole surface of the magnet. 2. The DC motor according to claim 1, further comprising a portion in which sets of N poles and S poles are alternately arranged with equal angular width or approximately equal angular width.