JPH04197071A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To realize production of a rotor position signal for switching the phase of a three-phase motor through a single position detecting element by disposing a Hall element at a position opposing to a part where a driving magnet is covered with the protruding part of a rotor. CONSTITUTION:A Hall element 1 is disposed oppositely to a protrusion 11 which covers a position where N and S poles are arranged adjacently with a pair of N and S poles of a driving magnet 3 as a reference. Upon counterclockwise rotation of a rotor 4, viewed from the direction of a stator 7, with the Hall element 1 opposing to N pole, output voltage of the Hall element has maximum positive value at a position opposing to N pole, has an intermediate value at a position opposing to a part where the driving magnet 3 is covered with the protrusion 11 of the rotor 4, and has maximum negative value at a position opposing to S pole. According to the constitution, the single Hall element 1 can produce three types of rotor position signals for electrical angle of 360 deg. of the N and S poles of the driving magnet 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a brushless DC motor in which a single position detection element generates a rotor position signal for phase switching in a three-phase motor.

Conventional technology In recent years, with the spread of inexpensive and high-performance ferrite magnets, and advances in small and high-performance Hall elements, integrated circuits, and power devices, AV equipment such as video tape recorders and digital audio tape recorders, and even laser printers have become popular. Brushless DC motors are used in OA equipment such as, and the range of their applications continues to expand.

Normally, a brushless DC motor requires one position detection element and one drive coil energization control circuit for each phase, and generally a two-phase or three-phase half-wave drive method or full-wave drive method is the main method. used in

Conventionally, many attempts have been made to reduce the number of position detection elements in three-phase drive systems, and a representative technique is the one disclosed in U.S. Patent No. 3.577°053 (hereinafter referred to as
This is abbreviated as Document 1. ) is shown. In this document 1, there are 3
In a phase-half-wave drive type brushless DC motor, a first motor with different light reflectance is mounted on the rotor. Second. An identification band having a third component is provided, a light beam is irradiated onto this identification band, and the reflected light is detected by a light receiving element, thereby detecting a change in the rotational position of the rotor as a three-step change in the output level of the light receiving element. It is outputting.

In addition, as another attempt, we installed a north pole section on the rotor.

A section where the magnet, which is the intermediate pole, is partially excluded.

By providing a magnet that constitutes the S-pole section and detecting changes in the magnetic flux of this magnet with a magneto-electric transducer (for example, a Hall element), the output level of the magneto-electric transducer can be adjusted to 3.
Changes in the rotational position of the rotor are output as changes in stages. The output waveform is shown in FIG. It is most desirable that no magnetic flux jumps into the magnetoelectric conversion element in the section where the magnet is partially removed, but in reality, the magnetic flux jumps into the magnetoelectric conversion element, and the output waveform becomes Changes gradually.

Problems to be Solved by the Invention However, in the method shown in Document 1, it is necessary to provide three identification bands with different light reflectances, a light emitting element that irradiates the identification band with a light beam, and a light receiving element that receives the reflected light. , the number of components increases and becomes more complex, and the light emitting elements and light receiving elements are currently more expensive than position sensing elements that use magnetoelectric transducers, etc. Therefore, there is no advantage in reducing the number of position sensing elements in terms of cost. do not have.

Also, as mentioned above, it is most desirable that no magnetic flux jumps into the magnetoelectric conversion element in the section where the magnet is partially excluded, but in reality, the magnetic flux jumps into the magnetoelectric conversion element, and as a result, the section of the intermediate pole However, there was a problem in that the output waveform of the magnetoelectric conversion element fluctuated, making it difficult to distinguish between the intermediate poles.

The present invention solves the above-mentioned problems, and aims to provide a brushless DC motor that has a simple structure and method and is inexpensive.

Means for Solving the Problems In order to achieve the above objects, the brushless DC motor of the present invention has, as a first configuration, a drive magnet in which a plurality of N poles and S poles are magnetized alternately in the circumferential direction. , a rotor that fixes the driving magnet and has a protrusion for covering the position where the N and S poles are adjacent to each other based on the pair of N and S poles of the driving magnet, and a rotor at a position facing the driving magnet. Consists of a drive coil installed in multiple phases, a position detection element installed in a position facing the protrusion of the rotor that covers the drive magnet, and a stator made by fixing the drive coil and position detection element. be done.

Furthermore, as a second configuration, a plurality of N poles and S poles are divided and magnetized alternately in the circumferential direction, and the magnets at positions where the N pole and S pole are adjacent are partially magnetized with a pair of N pole and S pole as a reference. The removed drive magnet, a rotor with the drive magnet fixed to it, a drive coil installed in multiple phases in a position facing the drive magnet, and a drive magnet facing the cut end of the removed part of the drive magnet. The magnet is composed of a position detection element installed at a position where the drive magnet is removed, a stator formed by fixing the drive coil and the position detection element, and a magnetic flux blocking plate that covers the removed portion of the drive magnet.

Operation The present invention has the above-mentioned configuration, so that only one position detecting element can detect three positions.
A stable rotor position signal for phase switching of phase motors can be generated.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a brushless DC motor according to a first embodiment of the present invention, in which (a) is a cross-sectional view, and (b) is a view of the rotor from the stator side (rotor from below). FIG.

In FIGS. 1 and 2, the drive magnet 3 is magnetized in four pairs of N and S poles alternately in the circumferential direction. The rotor 4 has a protrusion 11 for covering a position where the N and S poles of the drive magnet 3 are adjacent to each other with respect to the pair of N and S poles as a reference. The driving coil 5 is installed on the axis, and the driving coil 2 is installed in three phases at a position facing the driving magnet 3. A Hall element 1, which is a position detection element, is installed at a position opposite to a portion of the drive magnet 3 covered by the protrusion 11 of the rotor 4.

7 is a stator formed by fixing the drive coil 2 and the Hall element 1; 6 is a bearing fixed to the stator 7 and supporting the rotor 4;

The operation of the brushless DC motor of this embodiment configured as described above will be explained below, but before that, the operating principle of the Hall element 1 will be briefly explained.

Hall element 1 has four terminals, and Hall element 1
Two terminals that supply bias current to the Hall element 1
It consists of two terminals that output an output voltage of . Here, the Hall output voltage due to magnetic flux per unit area can be expressed by the following equation (1).

Kl'! EH= □・iH@B@cO5θ+VO...(1)
However, E)l: Hall output voltage KH: Hall element packing density B: Magnetic flux density IH: Hall element bias current VO2 Hall element unbalance voltage d: Hall element thickness θ: Magnetic flux incident angle Equation (1) , it can be seen that the Hall output voltage is proportional to the magnetic flux passing through the Hall element 1 and the bias current. Also,
When the direction of the magnetic flux changes, the Hall output voltage in equation (1) has a reverse polarity, making it possible to detect a change in magnetic pole.

In FIG. 1, the Hall element 1 is installed in a position opposite to the part where the protrusion of the rotor 4 covers the driving magnet 3. Therefore, depending on the rotational position, the magnetic flux of the driving magnet 3 is transferred to the Hall element 1. Furthermore, depending on the rotational position, the magnetic flux of the driving magnet 3 is blocked by the protrusion of the rotor 4, so that the magnetic flux does not pass through the Hall element 1. Now, suppose that when the magnetic flux of the north pole is at a position where it passes through the Hall element 1 (a position opposite to the north pole of the driving magnet 3), a constant bias current is applied so that the Hall output voltage is output to the positive pole side. We will proceed with the explanation below. First, when the Hall element 1 is located at a position facing the N pole, the maximum Hall output voltage is generated on the positive pole side. Next, when the Hall element 1 is located at a position facing the portion of the driving magnet 3 covered by the projection 11 of the rotor 4, the magnetic flux of the driving magnet 3 is blocked by the projection of the rotor 4, Since no magnetic flux passes through the Hall element 1, a Hall output voltage at an intermediate potential is generated. Furthermore, when the Hall element 1 is located at a position facing the S pole, the maximum Hall output voltage is generated on the negative pole side.

FIG. 2 shows the Hall effect when the Hall element 1 is initially located at a position facing the N pole in FIG. FIG. 3 is a waveform diagram showing output voltage.

As mentioned above, the Hall output voltage has the maximum value on the positive side at the position facing the N pole, the intermediate potential at the position facing the part where the protrusion 11 of the rotor 4 covers the drive magnet 3, and the S The maximum value is generated on the negative pole side at the position facing the pole.

As described above, by providing the protrusion 11 on the rotor 4 so as to cover the position where the N pole and the S pole are adjacent to each other with respect to the pair of N and S poles of the drive magnet 3, the drive magnet 3 can be Without changing the magnetization method or increasing the number of parts, the only Hall element 1 can generate three types of rotor position signals for the 360-degree electrical angle between the north and south poles of the drive magnet 3. It is possible for this to occur.

Next, FIG. 3 shows a second embodiment of the present invention.

This will be explained with reference to FIG.

FIG. 3 shows the configuration of a brushless DC motor according to a second embodiment of the present invention, in which (a) is a sectional view, and (b) is a view of the rotor from the stator side (rotor from below). It is a plan view,
FIG. 4 is a waveform diagram showing the operation of FIG. 3.

The operation of the brushless DC motor of this embodiment configured as described above will be explained below.

In FIG. 3, the same parts as in FIG. 1 are denoted by the same reference numerals, and their explanation will be omitted.

The drive magnet 8 is magnetized into a plurality of N-poles and S-poles alternately in the circumferential direction, and partially magnetizes the magnet at the position where the N-pole and S-pole are adjacent to each other based on a pair of N-pole and S-pole. Excluded. Reference numeral 9 indicates an iron plate serving as a magnetic flux blocking plate that covers the cut end of the removed portion of the drive magnet 8, and 10 indicates a rotor to which the drive magnet 8 is fixed.

The difference between this embodiment and the first embodiment is that the magnet at the position where the N pole and the S pole are adjacent to each other is partially excluded based on the pair of N and S poles of the driving magnet 8, and this part By covering the cut end with an iron plate, three types of Hall output voltages are generated.

In FIG. 3, since the Hall element 1 is installed so as to face the removed portion of the driving magnet 8,
Depending on the rotational position, the magnetic flux of the driving magnet 8 passes through the Hall element 1, and depending on the rotational position, no magnetic flux passes through the Hall element 1 in the excluded portion of the driving magnet 8. Now, if the Hall element 1 is located at a position where the N-pole magnetic flux passes through the Hall element 1 (a position facing the N-pole of the driving magnet 8), a constant voltage is applied so that the Hall output voltage is output to the positive pole side. The following explanation will be based on the assumption that a bias current is flowing. First, when the Hall element 1 is located at a position facing the N pole, the maximum Hall output voltage is generated on the positive pole side. Next, when the Hall element 1 is located at a position facing the removed portion of the driving magnet 8, no magnetic flux passes through the Hall element 1, so a Hall output voltage of an intermediate potential is generated.

Moreover, at this time, even if the driving magnet 8 is removed, a small amount of magnetic flux may pass through the Hall element 1.
The intermediate potential may shift to either the north pole or the south pole. Therefore, in the present invention, leakage magnetic flux is prevented by providing an iron plate 9 at the cut end of the excluded portion of the drive magnet 8.

Next, when the Hall element 1 is located at a position facing the S pole, the maximum Hall output voltage is generated on the negative pole side.

FIG. 4 shows the Hall effect when the Hall element 1 is initially located at a position facing the N pole in FIG. FIG. 3 is a waveform diagram showing output voltage.

As mentioned above, the Hall output voltage has a maximum value on the positive side at the position facing the N pole, an intermediate potential at the position facing the excluded part of the driving magnet 8, and a negative pole side at the position facing the S pole. The maximum value occurs.

As described above, by removing a predetermined portion of the driving magnet 8 and covering the cut end of the removed portion with an iron plate, it is possible to avoid adding any expensive parts without changing the method of magnetizing the driving magnet at all. Only Hall element 1
This makes it possible to generate three types of accurate and stable rotor position signals for 360 degrees of electrical angle between the north and south poles of the driving magnet 8.

In the first and second embodiments, the position detection element is a Hall element, but the same effect can be obtained if it is a magnetoelectric conversion element. Further, in the above two embodiments, the planar opposed type motor was explained, but the same effect can be obtained with the circumferential opposed type motor. Therefore, it goes without saying that the present application is not limited to the examples only.

Effects of the Invention As described above, the present invention provides, as a first configuration, a rotor having a protrusion for covering a position where an N pole and an S pole are adjacent to each other with respect to a pair of N pole and S pole of a driving magnet. By installing a position detection element in a position opposite to the part where the protrusion of the rotor covers the drive magnet, the only position detection element can generate a rotor position signal for phase switching of a three-phase motor. It becomes possible to generate. Therefore, it becomes possible to realize an inexpensive brushless DC motor with a simple configuration and method, and its practical effects are great.

Furthermore, as a second configuration, the magnet at the position where the N pole and the S pole are adjacent to each other is partially removed based on the pair of N pole and S pole, and a plurality of N poles and S poles are alternately formed in the circumferential direction. By providing a separately magnetized drive magnet and a magnetic flux blocking plate that covers the cut end of the removed portion of the drive magnet, and installing a position detection element at the opposing position, it is possible to operate a three-phase motor with the only position detection element. It becomes possible to generate accurate and stable rotor position signals for phase switching. Therefore, it becomes possible to realize an inexpensive brushless DC motor with a simple configuration and method, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a sectional view and a plan view showing the configuration of a brushless DC motor according to a first embodiment of the present invention, FIG. 2 is an operating waveform diagram of the same embodiment, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is an operating waveform diagram of the embodiment, and FIG. 5 is an operating waveform diagram of a conventional example. 1... Position detection element (Hall element), 2... Drive coil, 3, 8... Drive magnet, 4゜10
...Rotor, 7...Stator, 9...Magnetic flux blocking plate. Name of agent: Patent attorney Akira Okaji and two others (Figure 2, Figure 4) IInH Hayabusa, Ito

Claims (2)

[Claims] (1) A drive magnet in which a plurality of N poles and S poles are magnetized alternately in the circumferential direction, and a N pole with the drive magnet firmly fixed to the pair of N and S poles of the drive magnet. a rotor having a protrusion for covering a position where the south pole and the south pole are adjacent to each other; a drive coil installed in multiple phases at a position facing the drive magnet; and a protrusion of the rotor that covers the drive magnet. 1. A brushless DC motor comprising: a position detecting element installed at a position facing the part; and a stator formed by fixing the driving coil and the position detecting element. (2) Drive in which multiple N-poles and S-poles are alternately magnetized in the circumferential direction, and the magnets at positions where the N-pole and S-pole are adjacent are partially excluded based on a pair of N-pole and S-pole. a rotor to which the driving magnet is fixed; a driving coil installed in multiple phases in a position facing the driving magnet; and a rotor facing the cut end of the removed portion of the driving magnet. A device comprising: a position detection element installed at a position where the drive magnet is removed; a stator formed by fixing the drive coil and the position detection element; and a magnetic flux blocking plate that covers the removed portion of the drive magnet. Brush DC motor.