JPH08242568A - Brushless DC motor - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the delay of detection of the magnetic detection element due to the load current of the motor and improve the motor characteristics. A brushless DC motor according to the present invention includes a rotor 15 having a rotor magnet 20 and a stator 14 having a stator core 12 facing the rotor magnet 15.
In a brushless DC motor including a rotor position detecting magnet 20a provided in a part of the rotor magnet 20 and a hall element 22 for detecting the polarity of the rotor position detecting magnet 20a, the rotor position detecting magnet 20a Of the magnetic pole center portion 24 of the rotor magnet 20 with respect to the magnetic pole center portion 23
It is configured to be shifted by 0 degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor configured to detect the position of a rotor by a magnetic sensing element and to control energization of a stator coil based on a detection signal from the magnetic sensing element.

[0002]

2. Description of the Related Art Generally, a brushless DC motor of this type is provided with three-phase stator coils U, V and W, and, for example, three Hall elements u and v are used as magnetic detection elements for detecting the position of a rotor. , W, and is configured to control energization by, for example, a three-phase full-wave drive method. FIG. 12 is a development view showing the rotor and the stator of the brushless DC motor. In (1) of FIG. 12, the stator 1 is composed of a stator core 2 and a stator coil 3 wound around the stator core 2. This stator coil 3 is a three-phase stator coil 3
It consists of U, 3V and 3W. Also, the rotor 4
Has a rotor magnet 5.

A hall element 6 is arranged substantially in the middle of the teeth 2a of the stator core 2. In this case, the hall elements 6 are three hall elements 6u, 6v, 6w.
The Hall element 6u is arranged substantially in the middle of the W-phase teeth 2a and the U-phase teeth 2a, and the Hall element 6v is composed of the U-phase teeth 2a and the V-phase teeth 2a.
The hall element 6w is arranged substantially in the middle of the a, and the hall element 6w is arranged substantially in the middle of the V-phase teeth 2a and the W-phase teeth 2a.

Here, (1), (2), and
(3) and (4) show the rotor 4 in the forward (CW) direction (see FIG. 1).
2 shows each state rotated by 30 degrees in electrical angle when rotated to the left in the middle (2). Then, when energizing the brushless DC motor having the above-described configuration by the three-phase full-wave drive method, the three-phase stator coils 3U, 3V, and 3W are connected in accordance with the outputs of the three Hall elements 6u, 6v, and 6w in the following table. As shown by 1, the energization is controlled. When each output (input to the control device) of the hall elements 6u, 6v, 6w is "1" (high level), the hall element 6
This is the case where the N pole of the rotor magnet 5 is close to u, 6v, and 6w. And Hall elements 6u, 6v, 6w
When the output of each is 0 (low level), the S pole of the rotor magnet 5 is close to the Hall elements 6u, 6v, 6w. In addition, the stator coils 3U, 3V,
When outputting "H" to 3W, a positive voltage is applied, when outputting "L" to stator coils 3U, 3V, 3W, a negative voltage is applied, and stator coils 3U, 3V, When outputting "M" to 3W, the applied voltage is set to zero.

[0005]

[Table 1] In Table 1 above, when the rotor 4 is rotated in the normal direction, each output of the Hall element 6 and each output of the stator coil 3 are S
The order of switching is 1, S2, S3, S4, S5, S6, S1, ... Further, when the rotor 4 is rotated in the reverse direction, the outputs of the Hall element 6 and the stator coil 3 are S11, S12, S13, S14, S15, S1.
It switches in the order of 6, S11, ... here,
A case where the state of S1 is switched to the state of S2 will be specifically described. Now, the state shown in (1) of FIG. 12 is the state of S1, that is, the outputs of the Hall elements 6u, 6v, 6w are (“1”, “0”, “1”), and the stator coil 3U, Output of 3V, 3W (“H”, “L”,
"M"). Then, when switching from this state to the state of S2, the outputs of the hall elements 6u, 6v, 6w switch to (“0”, “0”, “1”), and
The output of the stator coils 3U, 3V, 3W is (“M”,
"L", "H"). The switched rotor 4 and stator 1 are shown in (1 ′) of FIG.

[0006]

Attention is now paid to the Hall element 6u in which the detection output is switched when the state is switched in the above-mentioned conventional configuration. At a point before the S pole of the rotor magnet 5 approaches the hall element 6u, the hall element 6
The stator coil 3U is energized so that (the magnetic pole portion of) the U-phase tooth 2a near u becomes the N pole. When the S pole of the rotor magnet 5 approaches the hall element 6u, the W-phase tooth 2a near the hall element 6u becomes N.
The stator coil W is energized so as to form a pole. Furthermore,
Even after the energization of the stator coil 3 is switched, the U-phase tooth 2a is held as the N pole for a short time due to the influence of the inductance L of the stator coil 3. Therefore, due to the influence of the N pole teeth 2a, the timing at which the Hall element 6u detects the S pole of the rotor magnet 5 is delayed.

A mode in which the detection of the Hall element 6u is delayed is shown in FIG. 13 (a). The solid line curve shown in FIG. 13A shows the change in the detection (output) voltage of the Hall element 6u, and the broken line curve shows the case without the above delay (ideal case). . Note that FIG. 13B shows the current flowing through the stator coil 3U, and FIG.
Indicates the voltage applied to the stator coil 3U.

The other two Hall elements 6v and 6w
Regarding the above, when the detection output is switched, the same detection delay as in the case of the hall element 6u occurs. Also,
Such a detection delay occurs when the rotation direction of the motor is in the reverse rotation (CCW) direction as shown in FIG.
As shown in, the hall elements 6u, 6v, 6w are teeth 2
The same occurs when it is arranged directly under a. Therefore, it can be seen that the detection delay of the Hall elements 6u, 6v, 6w is delayed by the influence of the current flowing through the stator coil 3, that is, the load current. When such a delay in the detection timing of the Hall elements 6u, 6v, 6w occurs, the position detection of the rotor 4 is delayed, which causes a problem that the motor characteristic (for example, starting torque) deteriorates. Particularly, as the magnitude of the load current increases, the detection timing of the Hall elements 6u, 6v, 6w is delayed by that amount, and the motor characteristics tend to be further deteriorated.

Therefore, an object of the present invention is to provide a brushless DC motor which can prevent the delay of the detection of the magnetic detection element due to the load current of the motor and can improve the motor characteristics.

[0010]

Brushless DC of the present invention.
The motor includes a rotor having a rotor magnet, a stator having a stator core facing the rotor magnet, a rotor position detecting magnet provided on the rotor magnet, and a magnetic detecting element for detecting the polarity of the rotor position detecting magnet. And the magnetic pole of the rotor position detecting magnet is displaced from the magnetic pole of the rotor magnet by one tooth interval of the stator core.

In this structure, it is also preferable that the rotor position detecting magnet is composed of a magnet separate from the rotor magnet. It is also conceivable to provide the rotor position detecting magnet on a surface of the rotor magnet different from the surface of the stator core facing the teeth. Furthermore, N of the rotor magnet
It is also a preferable configuration that the poles and the S poles are alternately magnetized in an angular state inclined in the circumferential direction. In this case, it is more preferable that the number of teeth of the stator core is larger than the number of magnetic poles of the rotor magnet. Further, the magnetic sensing element may be arranged substantially in the middle of two adjacent teeth of the stator core, or may be arranged substantially directly below the teeth of the stator core.

Another brushless DC motor of the present invention is a rotor having a rotor magnet, a stator having a stator core facing the rotor magnet, a rotor position detecting magnet provided on the rotor magnet, and the rotor position detecting device. And a magnetic detecting element for detecting the polarity of the magnet, and the magnetic pole of the rotor position detecting magnet is configured to be shifted by an electrical angle of 180 degrees with respect to the magnetic pole of the rotor magnet.

In the case of this construction, it may be considered that the rotor position detecting magnet is composed of a magnet separate from the rotor magnet. It is also preferable that the rotor position detecting magnet is provided on a surface of the rotor magnet different from a surface facing the teeth of the stator core. Furthermore, N of the rotor magnet
The poles and the S poles may be alternately magnetized in an angular state inclined in the circumferential direction. Furthermore, the magnetic sensing element may be arranged substantially in the middle of two adjacent teeth of the stator core, or may be arranged substantially directly below the teeth of the stator core.

[0014]

According to the above-mentioned means, the magnetic pole of the rotor position detecting magnet is equivalent to one tooth interval of the stator core with respect to the magnetic pole of the rotor magnet, specifically, 120 electrical angle.
Since the magnetic sensing element is configured to be shifted by a degree, when the detection output of the magnetic sensing element is switched, the magnetic force from the teeth that have become magnetic poles by energizing the stator coil does not affect the magnetic sensing element, and Will not be delayed. For this reason, it becomes possible to prevent the delay of the detection of the magnetic detection element due to the load current of the motor, and therefore the motor characteristics are improved.

In the above structure, if the rotor position detecting magnet is composed of a magnet separate from the rotor magnet, the structure in which the magnetic poles are displaced as described above can be easily realized with a simple structure. Further, the rotor position detecting magnet can be easily realized by providing the rotor magnet on a surface different from the surface of the rotor magnet facing the teeth of the stator core.

On the other hand, a configuration in which the N poles and S poles of the rotor magnet are alternately magnetized in an angular state inclined in the circumferential direction, that is, in a so-called skew magnetization configuration, can be easily and easily realized. In the case of this configuration, if the number of teeth of the stator core is set to be larger than the number of magnetic poles of the rotor magnet, when skew magnetized,
Since the skew angle can be reduced, the manufacture of the magnetizing yoke and the like becomes easy, and the effective magnetic flux amount can be increased to improve the motor characteristics.

Further, in the brushless DC motor having the above structure, the magnetic pole of the rotor position detecting magnet is displaced from the magnetic pole of the rotor magnet by one tooth interval between the stator cores (specifically, 120 electrical degrees). However, instead of this, the magnetic pole of the rotor position detecting magnet may be displaced by 180 electrical degrees with respect to the magnetic pole of the rotor magnet. According to this structure, it is possible to obtain the effect that the detection by the magnetic detection element becomes faster.

Also in this structure, the rotor position detecting magnet is composed of a magnet separate from the rotor magnet, and the rotor position detecting magnet is different from the surface of the rotor magnet facing the teeth of the stator core. A simple structure can be obtained by arranging the magnets on the surface or alternately by magnetizing the north pole and the south pole of the rotor magnet in an angular state inclined in the circumferential direction (that is, skew magnetization). Can be easily achieved with.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. First, brushless D
In FIGS. 2 and 3 showing the schematic configuration of the C motor, a stator core 12 is attached to the upper part of the fixed side (stator side) support cylinder 11. A three-phase stator coil 13 is wound around the stator core 12, for example. A stator 14 is composed of the stator core 12 and the stator coil 13.

A shaft 16 of the rotor 15 is rotatably provided in the support cylinder 11 via bearings 17, 17. At the upper end of the shaft 16, the rotor 1
The rotor yoke 18 of No. 5 is attached via an attaching member 19. The rotor yoke 18 is configured to have a shallow cylindrical container shape, and an annular rotor magnet 20 is provided on the inner peripheral portion thereof to form the teeth 1 of the stator core 12.
It is arranged so as to face 2a.

On the other hand, a printed wiring board 21 on which electronic parts constituting a control circuit, a drive circuit, etc. are mounted is attached to the lower part of the support cylinder 11. On the upper surface of the printed wiring board 21, for example, a Hall element 22 is attached as a magnetic sensing element so as to be disposed substantially in the middle of two adjacent teeth 12a of the stator core 12. In this case, the Hall element 22 includes three Hall elements 22u and 22u so as to correspond to the three-phase stator coil 13.
v, 22w. The Hall elements 22u, 22v, 22w are configured to mainly detect the polarity of the magnetic poles of the lower end surface portion 20a of the rotor magnet 20, as shown in FIGS. That is, the lower end surface portion 20a of the rotor magnet 20 constitutes the rotor position detecting magnet 20a.

Further, as shown in (1) of FIG.
Of the Hall elements 22u, 22v, and 22w, the Hall element 22u includes the tooth 12a (the magnetic pole portion of which) the V-phase stator coil 13V is wound and the tooth 12a (where the W-phase stator coil 13W is wound). The magnetic pole portion) is disposed substantially in the middle. Furthermore, Hall element 22v
Is disposed substantially in the middle of the tooth 12a wound with the W-phase stator coil 13W and the tooth 12a wound with the U-phase stator coil 13U. The hall element 22w is arranged substantially in the middle of the tooth 12a around which the U-phase stator coil 13U is wound and the tooth 12a around which the V-phase stator coil 13V is wound.

The rotor magnet 20 shown in FIG.
As shown in FIG. 5, the north pole and the south pole are alternately magnetized in an angular state inclined in the circumferential direction, that is, a so-called skew magnetized structure. In this case, the teeth 12 of the stator core 12 of the rotor magnet 20
a of the magnetic pole center portion 23 (position indicated by a broken line A) of the inner peripheral surface (main magnetic field) that is a portion facing a, and the magnetic pole of the rotor position detection magnet 20a that is the lower end surface portion 20a portion of the rotor magnet 20. The center portion 24 (the position indicated by the broken line B) is set so as to deviate by an electrical angle of 120 degrees. In other words, the rotor position detection magnet 20a
(The central portion 24 of the magnetic pole) of the stator core 1 with respect to (the central portion 23 of) the magnetic pole of the rotor magnet 20 (main magnetic field).
The two teeth 12a are configured to be offset by one interval.

Next, the operation of the above structure will be described with reference to FIGS. (1), (2), (3) of FIG.
(4) is a diagram showing each state of rotating the rotor 15 in the forward rotation (CW) direction (left direction in FIG. 4) by 30 degrees in electrical angle. In addition, (1) of FIG.
(2), (3), and (4) reverse the rotor 15 (CC
FIG. 6 is a diagram showing each state in which the electrical angle when rotated in the W) direction (the right direction in FIG. 5) is rotated by 30 degrees. When controlling the energization of the brushless DC motor having the above structure, the brushless DC motor is energized by the three-phase full-wave drive method. Specifically, three Hall elements 22u, 22v, 2
Three-phase stator coils 13U, 1 according to each output of 2w
The configuration is such that 3 V and 13 W are energized and controlled at the same energizing timing as in Table 1 shown in the column of the conventional configuration.

Here, in the case of rotating the rotor 15 in the normal direction, in the state shown in (1) of FIG. 4, that is, when the state of S1 in Table 1 is switched to the state of S2, the Hall elements 22u, 22v, 22w are changed. The detection outputs and the energized states of the stator coils 13U, 13V, and 13W will be specifically examined. Now, in the state of S1, that is, in the state shown in (1) of FIG. 4, the outputs of the hall elements 22u, 22v, 22w are (“1”, “0”, “1”), and the stator coil 13U, The output of 13V, 13W ("H",
"L", "M"). Then, when the state is switched to the state of S2, the hall elements 22u, 22v, 22
The output of w switches to ("0", "0", "1"), and the outputs of the stator coils 13U, 13V, 13W switch to ("M", "L", "H"). A development view of the rotor 15 and the stator 14 in this switched state is
It shows in (1 ') of FIG.

Here, let us focus on the Hall element 22u whose detection output is switched at the time of switching the state. Before the S pole of the rotor position detecting magnet 20a approaches the Hall element 22u, the stator coil 13V is energized so that the V-phase tooth 12a near the Hall element 22u becomes the S pole. And the hall element 22u
When the S pole of the rotor position detecting magnet 20a comes close to, the W-phase teeth 12 near the Hall element 22u.
The stator coil W is energized so that a becomes the N pole.
Further, the V-phase tooth 12a remains S after the energization is switched.
The stator coil 13V is energized so as to form a pole.

In this case, the polarity of one V-phase tooth 12a near the Hall element 22u (left side in the figure) is the S pole, and the Hall element 22u has the same polarity as the S pole to be detected. The Hall element 22u never delays the timing of detecting the S pole of the rotor position detection magnet 20a, and on the contrary, it becomes faster.

Next, when the rotor 15 is rotated in the reverse direction, in the state shown in (1) of FIG. 5, that is, when the state of S11 in Table 1 is switched to the state of S12, each of the Hall elements 22u, 22v, 22w. The detection output and the energization states of the stator coils 13U, 13V, 13W will be specifically examined. Now, in the state of S11, that is, the state shown in (1) of FIG. 5, the outputs of the hall elements 22u, 22v, 22w are (“0”, “0”, “1”), and the stator coil 13U, The output of 13V, 13W is ("M",
"H", "L"). And from this state, S! Two
When switching to the state of, the hall elements 22u, 22v, 2
The output of 2w is switched to ("1", "0", "1"), and the outputs of the stator coils 13U, 13V, 13W are switched to ("L", "H", "M"). A development view of the rotor 15 and the stator 14 in this switched state is shown in (1 ′) of FIG.

Attention is paid to the Hall element 22u whose detection output is switched at the time of switching the state. Before the N pole of the rotor position detecting magnet 20a approaches the Hall element 22u, the stator coil 13W is energized so that one W-phase tooth 12a near the Hall element 22u becomes the S pole, and the other one. The stator coil 13V is energized so that the V-phase tooth 12a has the N pole. When the N pole of the rotor position detection magnet 20a approaches the hall element 22u, the energization of the stator coil W is switched so that the polarity of one W-phase tooth 12a near the hall element 22u is switched, and the other one is switched. As for the V-phase tooth 12a, the stator coil 13V is set so that the polarity is maintained as the N-pole.
Is energized.

In this case, when the polarity of one of the W-phase teeth 12a (right side in the figure) near the hall element 22u is switched from the S pole to the non-polarized state, the stator coil 13
Due to the influence of the inductance L of W, the teeth 12a of the W phase are held as the S pole for a short time. For this reason,
At the time of switching the state, since both the W-phase teeth 12a and the V-phase teeth 12a near the hall element 22u are the S pole and the N pole, these S poles and N poles cancel each other. The hall element 22u is hardly adversely affected. Therefore, the Hall element 22u never delays the timing of detecting the N pole of the rotor position detection magnet 20a, and the detection timing becomes accurate.

According to the present embodiment having such a configuration, the magnetic poles of the rotor position detecting magnet 20a are set to the teeth 12 of the stator core 12 with respect to the magnetic poles of the rotor magnet 20.
Since it is configured such that the distance a is one, specifically, the electrical angle is shifted by 120 degrees, the Hall elements 22u, 22v, 22w
When the detection output of 1 is switched, the magnetic force from the tooth 12a, which has become a magnetic pole due to the energization of the stator coil 13, does not affect the Hall elements 22u, 22v, 22w. For this reason, it is possible to prevent delay in detection of the Hall elements 22u, 22v, 22w due to the load current of the motor, and therefore it is possible to improve motor characteristics such as starting torque.

Further, in the above embodiment, when the magnetic poles of the rotor position detecting magnet 20a are displaced by 120 electrical degrees with respect to the magnetic poles of the rotor magnet 20, the N and S poles of the rotor magnet 20 are circumferentially moved. Since the magnets are alternately magnetized in a tilted angle state, that is, skew magnetized, they can be easily realized with a simple structure. Further, in the case of the above-mentioned embodiment, since the rotor magnet 20 is skew-magnetized, so-called cogging torque and torque ripple can be reduced.

By the way, in the brushless DC motor which is energized by the three-phase full-wave drive method, the rotor magnet 2 is used.
The number of magnetic poles of 0 and the number of teeth 12a of the stator core 12 are, for example, 16 poles and 24 slots (teeth), 16 poles and 1 pole.
It is often set as 2 slots (teeth). Here, when the rotor magnet 20 is skew-magnetized, if the number of teeth 12a of the stator core 12 is configured to be larger than the number of magnetic poles of the rotor magnet 20, the skew angle becomes small when skew-magnetized. This makes it easier to manufacture magnetizing yokes and
The effective magnetic flux amount can be increased, and the motor characteristics can be improved.

In the above embodiment, the rotor 15 is configured to be able to rotate in the forward and reverse directions. However, in the case where the rotor 15 can be rotated in only one of the directions, either one of FIG. 4 or FIG. The drive method of 1 may be adopted. In this case, when the drive system of FIG. 4 is adopted, it is suitable when a large current is passed through the stator coil 13, that is, when the load current is a large current. On the other hand, when the drive system shown in FIG.
This is suitable for accurately controlling the rotation of No. 5.

6 to 9 show a second embodiment of the present invention, and the difference from the first embodiment will be described. The same parts as those in the first embodiment are designated by the same reference numerals. First, in FIGS. 6 to 8, the rotor magnet 25, which replaces the rotor magnet 20, has an N pole and an S pole.
The poles are magnetized alternately at equal intervals in the circumferential direction. An annular rotor position detecting magnet 26 is arranged on the lower end surface of the rotor magnet 25. The rotor position detection magnet 26 has N poles and S poles alternately magnetized at equal intervals in the circumferential direction.

Here, the rotor position detecting magnet 26
The magnetic pole center portion 27 (the position indicated by the broken line C) is the magnetic pole center portion 28 of the rotor magnet 25 (the broken line D).
The position is set so as to deviate by 120 degrees in electrical angle. In other words, the rotor position detection magnet 26
The center portion 27 of the magnetic pole is displaced from the center portion 28 of the magnetic pole of the rotor magnet 25 (main magnetic field) by one space between the teeth 12a of the stator core 12.

In the case of the above construction, each magnetic pole of the rotor position detecting magnet 26 is connected to the hall elements 22u, 22v, 22w.
Is configured to detect. Further, each magnetic pole of the rotor magnet 25 is connected to each tooth 12 of the stator core 12.
It is configured to face a. In the case of this configuration, the Hall element 22 of the rotor position detection magnet 26
The surface (lower surface) facing u, 22v, 22w is the tooth 12 of the stator core 12 of the rotor magnet 25.
It is configured to be a surface different from the surface (inner peripheral surface) facing a.

Also in the case of the second embodiment, a table showing the three-phase stator coils 13U, 13V, 13W according to the outputs of the three Hall elements 22u, 22v, 22w is shown in the column of the conventional structure. The configuration is such that energization is controlled at the same energization timing as in No. 1. 9 (1), (2),
(3) and (4) are diagrams showing each state in which the rotor 15 is rotated in the forward rotation (CW) direction (left direction in FIG. 9) by 30 degrees in electrical angle. It should be noted that the illustration corresponding to FIG. 9 in the case of reversing the rotor 15 is omitted. The configuration of the second embodiment other than that described above is the same as that of the first embodiment.
The configuration is the same as that of the above embodiment.

Therefore, also in the second embodiment, it is possible to obtain substantially the same operational effects as in the first embodiment.
Particularly, in the case of the second embodiment, since the rotor position detecting magnet 26 is composed of a magnet which is separate from the rotor magnet 25, it is possible to easily realize the structure in which the magnetic poles are displaced as described above with a simple structure. You can

In the second embodiment, the rotor position detecting magnet 26 and the rotor magnet 25 are separate magnets, but instead of this, they may be integrated magnets. In this case, the integral annular member for the magnet may be magnetized so as to obtain the magnetized regions having the polarities as shown in FIGS. 6 and 8.

Further, in the first and second embodiments, the center portions 24 and 27 of the magnetic poles of the rotor position detecting magnets 20a and 26 are arranged relative to the center portions 23 and 28 of the magnetic poles of the rotor magnets 20 and 25 and the stator core. 12 Teeth 12
In the case of the configuration in which the distance a is shifted by one, the central portion 2 of the magnetic poles of the rotor position detection magnets 20a and 26
Although 4, 4 and 27 are configured to be displaced by 120 electrical degrees from the central portions 23 and 28 of the magnetic poles of the rotor magnets 20 and 25, they may be configured to be displaced by 240 electrical degrees instead.

FIG. 10 shows a third embodiment of the present invention, and the difference from the first embodiment will be described. still,
The same parts as those in the first embodiment are designated by the same reference numerals.
In the third embodiment, as shown in FIG. 10, the Hall elements 22u, 22v, 22w are arranged so as to be disposed substantially directly below the teeth 12a of the stator core 12.
Further, (1), (2), (3), and (4) in FIG. 10 show the case where the rotor 15 is rotated in the reverse rotation (CCW) direction (right side in FIG. 10). The configuration of the third embodiment other than this is the same as the configuration of the first embodiment. Therefore, also in the third embodiment described above, it is possible to obtain substantially the same operational effects as in the first embodiment.

FIG. 11 shows a fourth embodiment of the present invention, and the difference from the second embodiment will be described. still,
The same parts as those in the second embodiment are designated by the same reference numerals.
In the fourth embodiment, as shown in FIG. 11, the center portion 27 of the magnetic pole of the rotor position detecting magnet 26 is 18 electrical degrees from the center portion 28 of the magnetic pole of the rotor magnet 25.
It is configured to be shifted by 0 degree. Further, (1), (2), (3), and (4) in FIG. 11 show the case where the rotor 15 is rotated in the reverse rotation (CCW) direction (right side in FIG. 11). The configuration of the fourth embodiment other than this is
It has the same configuration as that of the second embodiment.

Therefore, also in the above-mentioned fourth embodiment, it is possible to obtain substantially the same operational effects as in the second embodiment.
In particular, in the fourth embodiment, the center portion 27 of the magnetic pole of the rotor position detecting magnet 26 is displaced by 180 degrees in electrical angle with respect to the center portion 28 of the magnetic pole of the rotor magnet 25, which is the opposite of the conventional configuration. Hall elements 22u, 22
The detection timing of v and 22w can be advanced.
Incidentally, in the case of the fourth embodiment, unlike the first or second embodiment (the structure in which the electrical angle is shifted by 120 degrees), the rotor 1
The same action and effect can be obtained regardless of the rotation direction of 5.

[0045]

As is apparent from the above description, the present invention makes the magnetic poles of the rotor position detecting magnet correspond to one tooth interval of the stator core with respect to the magnetic poles of the rotor magnet, specifically, 120 electrical angle. Since the configuration is shifted by a degree, when the detection output of the magnetic detection element is switched, it is possible to prevent the delay of the detection of the magnetic detection element due to the load current of the motor and improve the motor characteristics. It has an excellent effect.

Further, in the case of the above construction, if the rotor position detecting magnet is composed of a magnet separate from the rotor magnet, the construction in which the magnetic poles are displaced as described above can be easily realized with a simple construction. Further, even if the rotor position detecting magnet is provided on a surface of the rotor magnet different from the surface facing the teeth of the stator core, it can be easily realized in the same manner.

On the other hand, a structure in which the N poles and S poles of the rotor magnet are alternately magnetized in an angular state inclined in the circumferential direction, that is, a so-called skew magnetization structure can be easily and easily realized. In the case of this configuration, if the number of teeth of the stator core is set to be larger than the number of magnetic poles of the rotor magnet, when skew magnetized,
Since the skew angle can be reduced, the manufacture of the magnetizing yoke and the like becomes easy, and the effective magnetic flux amount can be increased to improve the motor characteristics.

In the brushless DC motor having the above structure, the magnetic pole of the rotor position detecting magnet is displaced from the magnetic pole of the rotor magnet by one tooth interval between the stator cores (specifically, 120 electrical degrees). However, instead of this, the magnetic pole of the rotor position detecting magnet may be displaced by 180 electrical degrees with respect to the magnetic pole of the rotor magnet. According to this structure, it is possible to obtain the effect that the detection by the magnetic detection element becomes faster.

Also in this configuration, the rotor position detecting magnet is formed of a magnet separate from the rotor magnet, or the rotor position detecting magnet is different from the surface of the rotor magnet facing the teeth of the stator core. A simple structure can be obtained by arranging the magnets on the surface or alternately by magnetizing the north pole and the south pole of the rotor magnet in an angular state inclined in the circumferential direction (that is, skew magnetization). Can be easily realized in.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of the present invention in which an inner peripheral surface of a rotor magnet and a Hall element are shown in a developed state.

FIG. 2 is a partial vertical sectional view of a brushless DC motor.

FIG. 3 is a partial perspective view of a brushless DC motor.

4 (1), (2), (3), and (4) are rotor 1
The figure which shows each state rotated by 30 degrees in electrical angle when 5 is rotated in the forward direction (left direction in the figure).

5 (1), (2), (3) and (4) are rotors 1;
The figure which shows each state rotated by 30 degrees in electrical angle when 5 is rotated in the reverse direction (left direction in the figure)

FIG. 6 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 7 is a view corresponding to FIG.

FIG. 8 is a view corresponding to FIG.

FIG. 9 is a view corresponding to FIG.

FIG. 10 is a view corresponding to FIG. 5, showing a third embodiment of the present invention.

FIG. 11 is a view corresponding to FIG. 5 showing a fourth embodiment of the present invention.

FIG. 12 is a view corresponding to FIG. 4 showing a conventional configuration.

[Fig. 13] Time chart

FIG. 14 is a view corresponding to FIG.

FIG. 15 is a view corresponding to FIG.

[Explanation of symbols]

12 is a stator core, 13 is a stator coil, 14 is a stator, 15 is a rotor, 16 is a shaft, 18 is a rotor yoke, 20 is a rotor magnet, 20a is a rotor position detecting magnet, 22 is a Hall element (magnetic detecting element), 23, 24 is a central part, 25 is a rotor magnet,
Reference numeral 26 is a rotor position detecting magnet, and 27 and 28 are central portions.

Claims (13)

[Claims] 1. A rotor having a rotor magnet, a stator having a stator core facing the rotor magnet, a rotor position detecting magnet provided on the rotor magnet, and a magnet for detecting the polarity of the rotor position detecting magnet. A brushless DC motor, comprising: a detecting element, wherein the magnetic pole of the rotor position detecting magnet is displaced from the magnetic pole of the rotor magnet by one tooth interval between the stator cores. 2. The brushless DC motor according to claim 1, wherein the rotor position detecting magnet is composed of a magnet separate from the rotor magnet. 3. The brushless DC motor according to claim 1, wherein the rotor position detecting magnet is provided on a surface different from a surface of the rotor magnet facing the teeth of the stator core. . 4. The brushless DC motor according to claim 1, wherein the north pole and the south pole of the rotor magnet are alternately magnetized in an angular state inclined in the circumferential direction. 5. The number of teeth of the stator core is
The brushless DC motor according to claim 4, wherein the number of magnetic poles is greater than that of the rotor magnet. 6. The brushless DC motor according to claim 1, wherein the magnetic sensing element is arranged substantially in the middle of two adjacent teeth of the stator core. 7. The brushless DC device according to claim 1, wherein the magnetic sensing element is arranged substantially below the teeth of the stator core.
motor. 8. A rotor having a rotor magnet, a stator having a stator core facing the rotor magnet, a rotor position detecting magnet provided on the rotor magnet, and a magnet for detecting the polarity of the rotor position detecting magnet. A brushless DC motor, comprising: a detecting element, wherein the magnetic pole of the rotor position detecting magnet is displaced by 180 electrical degrees with respect to the magnetic pole of the rotor magnet. 9. The brushless DC motor according to claim 8, wherein the rotor position detecting magnet is composed of a magnet separate from the rotor magnet. 10. The rotor position detecting magnet comprises:
10. The brushless DC motor according to claim 8, wherein the brushless DC motor is provided on a surface of the rotor magnet different from a surface of the stator core facing the teeth. 11. The brushless DC motor according to claim 8, wherein the north pole and the south pole of the rotor magnet are alternately magnetized in an angular state inclined in the circumferential direction. 12. The brushless DC motor according to claim 8, wherein the magnetic sensing element is arranged substantially in the middle of two adjacent teeth of the stator core. 13. The brushless DC motor according to claim 8, wherein the magnetic sensing element is arranged substantially directly below the teeth of the stator core.