JPS622847A - Brushless motor - Google Patents

Abstract

PURPOSE:To enlarge stator coils in area and position the coils easily, by providing the outer periphery of an auxiliary magnet with magnetization tracks which are magnetized with rotational frequency informations and positional signal informations respectively, and by arranging magnetic reluctance elements confronting the tracks respectively. CONSTITUTION:On the outer peripheral section of a magnet case 2 made of ferromagnetic substance formed and fixed to contain a rotor magnet 1, an auxiliary magnet 3 is fitted. The auxiliary magnet 3 is provided with a plurality of independent magnetization tracks 7, and on the respective magnetization tracks 7, rotational frequency informations and positional signal informations having respective specified phase differences are magnetized. Via the auxiliary magnet 3 and a space, a plurality of magnetic reluctance elements 5 are supported on the side of a stator, and each of the magnetic reluctance elements is arranged to confront the magnetization tracks 7 respectively and independently. By this organization, a stator coil surface is not required to be provided with the magnetic reluctance elements 5, and so coils 4 can be formed to be large, and torque can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a brushless motor having rotational frequency detection means (hereinafter referred to as FG) that outputs frequency information according to the number of rotations of a rotor. It is effective when used as a drive source for audio, video, and information processing equipment.

BACKGROUND OF THE INVENTION In recent years, miniaturization of brushless motors has become important as equipment itself becomes smaller.

An example of the conventional brushless motor mentioned above will be described below with reference to the drawings.

FIG. 3 shows a sectional view of the structure of a conventional brushless motor. In FIG. 4, reference numeral 1 denotes a rotor magnet magnetized into multiple poles, which is fixed to a magnet case 2 made of ferromagnetic material. Reference numeral 3 denotes an auxiliary magnet made of a resin magnet, which is formed on the outer periphery of the magnet case 2. A plurality of coils 4 are fixed to the stator 6. Reference numeral 5 denotes a magnetoresistive element (hereinafter abbreviated as MR element), which is fixed to the stator 6 so as to face the auxiliary magnet 3 at a certain distance. A portion of the auxiliary magnet 3 at a height opposite to the magnetic sensing portion of the MR element 6 is an FG magnetization track 7, and FG information is magnetized in this portion. 8 is a Hall element, which faces the magnetized surface of the rotor magnet 1;
A plurality of coils are fixed to the stator 6 in a constant phase with the plurality of coils 4. A shaft 9 is supported by a bearing 1o, rotates with the rotor magnet 1 and the magnet case 2, and constitutes a rotor 14. A chassis 11 supports the stator 6 with a bearing 1o and fixed legs 12 interposed therebetween.

The operation of the conventional brushless motor configured as described above will be described below. As is well known, first, the plurality of Hall elements 8 detect the magnetic flux of the magnetized surfaces of the rotor magnets 1 facing each other. This detected signal is
It is amplified and waveform-shaped as a position signal of stator 6.
A current is passed through the plurality of coils 4 on the top. The energized coil 4 generates magnetic flux, attracts and repels the magnetic flux of the opposing rotor magnet 1, and the rotor 14 rotates. As the rotor 14 rotates, the position signal output from the Hall element 8 changes, the current flowing through the coil 4 is commutated, and the rotor 14 continues to rotate.

Problems to be Solved by the Invention However, in the above configuration, since the Hall element 8 for detecting a position signal is set at a position opposite to the rotor magnet 1, the Hall element 8 is placed on the inner circumference or outer circumference of the coil 4.
must be set.

For this purpose, the number of turns of the coil must be reduced by 40, or the number of coils in one phase must be reduced by one, resulting in a problem that the starting torque and torque constant of the motor are reduced. Another problem is that a plurality of Hall elements must be set at different angles from each other with respect to the coil.

In view of the above problems, the present invention removes the plurality of Hall elements 8, which conventionally detect position signals, from the stator e facing the rotor magnet 1, and positions each of the plurality of position signal detection elements independently. The purpose of the present invention is to provide a brushless motor that can detect a predetermined position signal even when the brushless motor is not in use.

Means for Solving the Problems In order to solve the above problems, the brushless motor of the present invention provides a plurality of magnetized tracks at different heights on the outer periphery of the auxiliary magnet, and divides the auxiliary magnet into each magnetized track. Frequency information and 1. MR elements each magnetized with position signal information having a predetermined phase difference and having the same number as the magnetized tracks are formed independently on the same substrate, and are opposed to each other at approximately the same height as the magnetized tracks. It has a configuration that allows it to be installed.

According to the above-described structure, the present invention eliminates the need to oppose the position signal detection element to the rotor magnet, and the opposing area of the coil facing the rotor magnet increases, so that the starting torque and torque constant of the motor can be reduced. It can be made much larger. Moreover, this makes it possible to reduce the number of main magnets used to obtain the necessary starting torque and torque constant, making it easier to downsize the motor.

Embodiments Hereinafter, brushless motors according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a sectional view of a first embodiment of the invention.

In FIG. 1, 1 is a rotor magnet, 2 is a magnet case, and 3 is an auxiliary magnet formed on the outer periphery of the magnet case 2. In FIG. The auxiliary magnet 3 is provided with a plurality of magnetized tracks at different heights on its outer periphery. Among these, the magnetized track farther from the magnet case opening is designated as the FG magnetized track 7, and the FG information is magnetized. The remaining magnetized tracks are used as position signal magnetized tracks 13, and position signals each having a predetermined phase difference with respect to the magnetization of the rotor magnet 1 are magnetized. 4 is a plurality of coils, 6 is a device in which the same number of MR elements as the magnetization tracks are independently formed on the same substrate, and the magnetization track on the auxiliary magnet 3, that is, F
It faces the G magnetized track 7 and the position signal magnetized track 13.

The operation of the brushless motor configured as described above will be described below with reference to FIG. MR element 6 facing each of the plurality of position signal magnetized tracks 13
detects the magnetized pole of that track. This detected signal is transmitted to each MR element 6 because the position signal magnetized tracks 13 are magnetized with a predetermined phase difference from each other.
A position signal indicating the rotational position of the rotor 14 is obtained.

This position signal is amplified and shaped into a waveform, and a current is passed through the plurality of coils 4 on the stator θ, and the generated magnetic field causes attraction and repulsion with the rotor magnet 1, and the rotor 14
repeats rotation. The rotation speed is controlled by FG magnetized track 7.
This is done by detecting rotational frequency information magnetized by an MR element facing it.

As described above, according to this embodiment, a plurality of position signals that maintain a predetermined phase difference are magnetized to the magnetization track provided on the auxiliary magnet, and the plurality of position signals are detected on a one-to-one basis. By forming the same number of MR elements on one substrate, it becomes easy to set the phase of the elements, and the area of the coil facing the rotor magnet can be increased, so that the motor characteristics can be improved.

Refer to the drawings below regarding the second embodiment of the present invention.
- Explain with reference.

FIG. 2 is a sectional view of a second embodiment of the invention.

In the figure, the difference from the configuration in FIG. 1 is that a plurality of MR elements 6 are formed on one substrate, and the one MR element closest to the stator 6 is located between the stator 6 and the opening of the magnet case 2. It is installed at a height between Also, the remaining MR
The element was set to auxiliary magnet 3. It is installed at a height that faces the same number of magnetized tracks as the remaining MR elements on a one-to-one basis. The rest of the structure is the same as that shown in FIG.

The operation of the brushless motor configured as described above will be described below. Of the MR elements 6, the stator 6
Since the one closest to the magnet case 2 is installed at a height between the opening of the magnet case 2 and the stator 6, it detects the leakage magnetic flux of the magnetization pattern of the rotor magnet 10. ◇Of the remaining MRg elements, One or more position signal magnetized tracks 1
3, the position signal magnetization track 13 magnetizes a signal with a predetermined phase difference from the magnetization pattern of the rotor magnet 1, so the magnetization is in a different phase. Detect the signal. Since the outputs of these MR elements have a predetermined phase difference from each other, even if each MR element is made on one substrate and installed at the same rotational phase, it will not be possible to indicate the rotational position of the rotor 14. It becomes a position signal. This position signal causes the rotor 14 to rotate.

As described above, among the plurality of MR elements, the one closest to the stator 6 is placed at a height between the opening of the magnet case 2 and the stator 6, and the remaining MR elements are placed on the auxiliary magnet 3.
By installing it at a height that opposes the upper magnetized track one-on-one, it is possible to reduce the number of magnetized tracks by one compared to the first embodiment, and the height of the auxiliary magnet can be reduced accordingly. , a thinner rotor is achieved. Moreover, magnetization of the auxiliary magnet 30 is also facilitated.

1st. In the second embodiment, the upper part of the magnetized track is FG
Magnetized track 7 was set, but the topmost magnetized track was set to FG.
By using the magnetized track 7, the influence of leakage magnetic flux of the rotor magnet 1 is minimized. This makes it possible to obtain highly accurate FG information.

Further, the reason why a plurality of MR elements are provided on one substrate is to make it easier to attach the MR element to the stator and to reduce relative variations among the plurality of MR elements.

Effects of the Invention As described above, according to the present invention, the element for detecting a position signal can be easily positioned, and the area of the coil facing the rotor magnet can be increased. This makes it possible to improve motor characteristics and also facilitate miniaturization of the motor.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the invention, FIG. 2 is a sectional view of a second embodiment of the invention, and FIG. 3 is a sectional view of a conventional brushless motor. 1... Rotor magnet, 2... Magnet case, 3... Auxiliary magnet, 4...
... Coil, 6... Magnetoresistive element, 6...
...Stator, 7...FG magnetized track,
13a, b, c...Position signal magnetized track, 1
4...Rotor.

Claims (3)

[Claims] (1) A rotor magnet magnetized into multiple poles, a ferromagnetic magnet case molded and fixed to enclose the rotor magnet, an auxiliary magnet formed on the outer periphery of the magnet case, and a ferromagnetic magnet case formed around the rotor magnet. The magnet includes a plurality of coils installed to face the magnetized surface, a plurality of magnetoresistive elements set to face the auxiliary magnet, and a stator that supports and fixes the coils and the magnetoresistive element. The same number of magnetized tracks as the magnetoresistive elements are provided on the outer periphery of the auxiliary magnet at different heights, and the magnetized tracks are divided into magnetized tracks to each carry rotational frequency information and position signal information having a predetermined phase difference. The plurality of magnetoresistive elements are each independently formed on the same substrate, and are placed opposite each other at substantially the same height as the magnetized track on the auxiliary magnet. brushless motor. (2) Provide one less magnetized track than the number of magnetic resistance elements on the outer circumference of the auxiliary magnet by changing the height, and divide it into each magnetized track to record rotational frequency information, rotor magnet magnetization, and predetermined information. position signal information having a phase difference of and the remaining magnetoresistive elements are installed at substantially the same height as the magnetized tracks on the auxiliary magnet, respectively, facing each other. brushless motor. (3) Among the plurality of magnetized tracks on the auxiliary magnet, the rotational frequency information is magnetized to the farthest magnetized track from the opening of the magnet case. The brushless motor according to item 2.