JPS6339450A - Brushless motor - Google Patents

Abstract

PURPOSE:To flatten a motor and to reduce a diameter thereof by forming the thin-film of a pattern for detecting the number of revolution consisting of a magnetoresistance element onto a yoke or a base oppositely faced to a rotor magnet. CONSTITUTION:A yoke 12, a substrate 14 for holding an MR element and a magnetizing booster coil 16 are fixed integrally through an insulating material, thus shaping a stator for a motor. An output shaft 20 is fitted vertically to a magnet 18. A rotor for the motor is formed by the output shaft 20, the magnet 18 and a rotor yoke 22. The thin-film of the magnetoresistance element is shaped to the substrate 14 for holding the MR element, faced oppositely to the rotor magnet 18 as a means for detecting a positional signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to position detection or rotation detection of a brushless motor, and particularly to performing each of the above detections using a magnetoresistive element (hereinafter referred to as an MR element).

<Prior Art> (Description of Prior Art) Conventionally, speed detection means include a coil power generation type using magnetic induction and an optical type. A device using a magnetoresistive element is usually constructed as shown in FIG. 2. 4
．． 7. 8 constitutes a rotor, and a signal magnet 2.8 is provided on the outer periphery of the rotor. is attached, the signal magnet is magnetized with multiple poles on the outer periphery, and is fixed at a predetermined position relative to the MR element. The MR element detects the signal magnetic field from the signal magnet and detects the rotation speed.

(Problems with the prior art) In such single-point detection, as the signal wavelength becomes shorter, the influence of machine precision (axial runout, outer peripheral surface runout, etc.) causes noticeable fluctuations in the detection level. As the wavelength becomes shorter, the strength of the signal magnetic field becomes smaller, and therefore the output from the MR element also becomes smaller.The FG frequency needs to be increased in order to cope with the reduction in rotor inertia and the reduction in speed due to the miniaturization of motors in recent years. To do this, in the above example, the number of magnetizations on the outer periphery must be increased.In other words, the wavelength must be shortened.However, there is a limit to shortening the wavelength, and mechanical precision must also be used to keep errors small. There are limits to what you can do.

Therefore, the above-mentioned detection level fluctuation and measurement error occur.

The rotational position detecting means uses a Hall element to pick up leakage magnetic flux from the main magnet 4 shown in FIG. 7, determines the polarity of the magnetic pole, and switches the current flowing to the coil 5 of the motor. This switching using a Hall element is most common, but in order to pick up leakage magnetic flux from the main magnet 4, for example, a hole or notch is provided in the stator yoke 6, and the Hall element is placed there. However, this hole or notch causes the motor torque to fluctuate.
Becomes a cogging ingredient. In addition, mechanical precision is required, and errors in the position of the Hall element arrangement result in switching errors in the current flowing to the coil 5, causing torque fluctuations. This is undesirable as it may worsen uneven rotation. Therefore, when the yoke 6 does not have a hole or notch for the Hall element, and the Hall element is placed between the Macnet and the stator yoke 6, in the case of a small diameter, flat motor, the problem is the size of the element, It is thick. Further, although the motor not shown in FIG. 7 is a three-phase full-wave drive, three Hall elements are normally required to switch the three-phase coils. In this case, there are a total of eight wires from the Hall element, which takes up space on the wiring board.

<Problems to be solved by the present invention> The present invention solves the above-mentioned conventional problems by forming a magnetoresistive element as a means for detecting a position signal as a thin film on a flat substrate facing the rotor magnet.

Furthermore, the present invention provides a brushless morph in which a thin film can be formed on the same plane as the position signal detection MR element for detecting the rotational speed of the rotor as well as detecting the position signal necessary for drive control of the brushless morph.

Means for Achieving the Object> In order to achieve the above object, the present invention provides a structure that is provided on a flat base or yoke facing the rotor magnet and surrounded by a concentric circle of an inner diameter Ra and an outer diameter Rb, with the center of the output shaft as the radial center. An MR element having a length Rb-Ra and a predetermined width is fixed on the radiation line, and the lower end of the MR element is connected in series with an adjacent MR element using a conductive wire to form a zigzag arc pattern. The structure is such that both ends of the circular arc pattern are guided to the rotor magnet position signal output terminal.

Furthermore, the MR element for detecting the rotational speed is connected to the MR element for detecting the position signal.
A thin film is formed on the inner or outer diameter of the element, and both ends of the MR element are connected to output terminals for signal detection.

<Description of Examples> FIG. 1 is a sectional view of the motor of the present invention. FIG. 2 is a plan view of a flat plate to which an MR element is fixed. FIG. 3 shows a partially enlarged view of the zigzag pattern of the MR element.

In the figure, 10 indicates a motor, and 12 is a yoke made of a magnetic material and has a disk shape. Reference numeral 14 denotes a base for holding the MRR element, and the MR element is fixed by vapor deposition or the like as shown in FIG. 16 indicates a field coil, and the coil I6
A coil or the like is used, which is formed by etching a copper foil fixed onto an insulating substrate into a spiral coil shape. Said yoke 12・MRR
The child holding base 14 and the magnetizing coil 16 are integrally fixed via an insulating material to form a stator of the motor. 18
is a magnet (Mg) magnetized as shown in Figure 4.
Then, the output shaft 20 is vertically fitted into the mucknet. 2
2 indicates the rotor yoke. Output shaft 20/magnet 1
8. The rotor yoke 22 forms the rotor of the motor, and a portion of the stator and the output shaft 20 are rotationally fitted together by a bearing member (not shown).

Next, the MR element shown in FIGS. 2 and 3 will be explained.

An insulation treatment is performed on the plane of a substrate 14 such as a printed wiring board, and an MRR element material is deposited and fixed as shown in the third figure.

14A・14. B・14D is 1 centered around the center O of the output shaft.
It is distributed at an angle of 20 degrees, and the 14A and 14
Each MR element of B.14r) forms a position detection element.

Each MR element 14A, 14B, 14D is formed as shown in FIG.

That is, each MR element draws a concentric arc with the radial center O as the axis of the output shaft, the inner radius Ra and the outer radius Rb, and the pitch of the inner arc part is Dl and the pitch of the outer arc part is D2. Each MR element 14a, 14a2...
... is fixed on the substrate by a thin film forming technique such as vapor deposition or sputtering. The inner and outer diameter sides of each MR element are connected in series by conducting wires 24A and 24B, respectively.

Other MR elements 14B and 14D are also formed in the same manner as 14A. Reference numeral 14P indicates a signal extraction terminal portion protruding from the circular base 14, and the terminal portion 14P is provided with terminals A-B-C-D-E for signal extraction. The terminal A is connected to the outermost conductor section 26 on the base, and the other end of the conductor section 26 is connected to a part of the inner diameter side or the outer diameter side of the MR element 14A. The other end of the MR element 14A is connected to a conductor 28, and the conductor 28 is connected to a ground terminal E. One end of the MR element 14B is connected to the extraction terminal B, and the other end of the MR element 14B is connected to the conductor 28 and the ground terminal E.
Continued. One end 14D of the MR element 14D is connected to the conducting wire 28, and the other end of the MR element 14D is connected to the extraction terminal.

Through the above wiring connections, each of the MR elements 14A, 14B, and 14D is connected between the output terminal A-B-D and the ground terminal E, respectively. 30 indicates a rotation speed detection pattern, and the pattern 2
Reference numeral 8 is formed in the same manner as the MR element for position detection described above. That is,
Centered on the radial center O, the inner radius RC1 and the outer radius RD
Then, fix each MR element in a pattern with a constant width in the area surrounded by concentric circles with a radius Rc-RD along the radial line from the center of the circle O, and connect the upper and lower ends of each MR element with conductive wires. Connect in series. One end of the rotational speed detection MR element is connected to a take-out terminal C, and the other end is connected to a grounding terminal E.

Here, each resistance of each element connected in series in the MR pattern will be referred to as MRk. k is 1.k in order from the element at the start point to the element at the end point. 2. 3゜・・・・・・
shall be. In other words, when β elements are connected in series from the starting point to the ending point, MR,, MR2゜-...
MRk, MR, fl' represent the resistance value of each element.

FIG. 4 is a diagram showing the surface of the main magnet 4 of this embodiment that faces the MR pattern, and is magnetized into eight poles, with N and S poles arranged alternately. It is assumed that the center point O of the inner diameter and outer diameter of the magnet is the same and coincides with the center point O of the MR pattern. Further, the number of magnetized poles is not limited to eight.

The specific resistance value of the MR element is ρ, and the rate of change due to the magnetic field H is 1.
00γ%. Now, the signal magnetic field H from the main magnet is H(θ)=H(, sinθ (θ is the electrical angle of the main magnet, Ho is a constant)...
(1), where ρ is a function of θ, ρ(θ)
-P, )-7Po” H,2* 5in2θ ・
−(2) (', 'H,, Po are constants) Defined as follows. Transform (2).

/:1(0)”Po [(1-7H1”/2)+(7H
1”/2) CO32θ) = Pl + P2 cos
2θ...(3)(°p, -p.(1
7H1”/2), P2=POγH1”/2) Here MR
Each element! When arranged at intervals, MRk(θ)=R,+R2cos2 io+(k-1
)A+ -(4) ('-'R1 and R2 are constants).

The MR pattern 30 will be explained.

The pattern 30 extends all the way around. The number of magnetized main magnets is 2N. Now, 0≦θkuπ and m with interval l
MR elements are connected in series. Total resistance M in this section
From (4), R[o, yr co(θ) is MR[oπ](θ
)=ΣiR, 1R2cos2 (θ+(k-1) f)
]k=1 ・・・・・・(5) (However, m!≠nπ (n=0.1.2・・・・・・)
) can be expressed as If it is repeated over the interval [0, 2Nπ), it can be expressed as follows.

Therefore, the resistance value between the series-connected starting point and ending point of the MR pattern becomes a periodic function, and the rotational position can be detected by examining this change.

MR pattern 14A, 14B, 1.4
D will be explained.

(2n+] MR patterns are connected in series and have a capacity of 14A.

14B, ], (n+1)th MR of each pattern of 4D
The elements are connected to each other by (-+mπ) the main magnet (m=
The phase is shifted by an electrical angle of o, I, 2・). Further, the elements of each pattern are connected in series to each other at equal intervals of d, which is the electrical angle of the main magnet. Therefore, the total resistance MRaEl of each pattern
is MRall(θ)=(2n+1)R++R2cos2θ
+R2Σcos2 (θ+(k-1)d)k=1 ......(7) Hence, the patterns of 14A, ]4B, +4D are signal waveforms that are shifted by %π in electrical angle from the obtained waveforms ( (See Figure 5) A signal for detecting the rotational position of the main magnet can be obtained and can be used as a signal for switching the motor coil phase.

FIG. 6 shows another embodiment of the invention. The concept of the pattern is exactly the same, especially when a high frequency signal is required using a pattern for rotational speed detection, the magnet 32 is fixed to the output shaft 20 separately from the main magnet, and multi-pole magnetization is performed as necessary. This is done to obtain a signal for detecting the rotational speed.

Reference numeral 34 indicates a substrate fixed to the output shaft 20, and 36 indicates a rotational speed detection pattern fixed to the substrate 34-A by vapor deposition.

(6) As explained above, the pattern is not a single element but an integral type arranged over a certain range, so the signal obtained from this pattern is caused by uneven magnetization and eccentricity of the magnet.
It is possible to obtain highly accurate signals that are less susceptible to disturbances. In particular, the present invention allows the MR element to be formed as a thin film on the yoke or flat plate by vapor deposition, etc., so that the motor can be flattened.
It is possible to achieve smaller diameters, reduce the number of parts, and potentially reduce costs.

Furthermore, since the position detection signal is output in three phases, it is possible to determine whether the motor is rotating forward or reverse.

In this embodiment, the base of the MR pattern was configured to face the magnet in a plane, but in principle, it may be in a configuration that faces the magnet in the circumferential direction.

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention, and FIG. 1 is a sectional view of a motor incorporating an MR element according to the present invention. Figure 2 shows the base 14. , J: is a pattern plan view of an MR element arranged in. FIG. 3 shows the MR elements 14A, ], 4B, and
14D and 30 partially enlarged views. FIG. 4 is a diagram showing the magnetization direction of the magnet 14. FIG. 7 is a sectional view of a motor with a prior art configuration.

Claims (2)

[Claims] (1) In a brushless motor in which a rotor magnet and a magnetizing coil are arranged facing each other in a direction substantially perpendicular to the output shaft, a rotation speed detection pattern made of a magnetoresistive element is provided on a yoke or a base that faces the rotor magnet. A brushless motor characterized by thin film formation. (2) The magnetoresistive element has a radial length Rb-Ra surrounded by a concentric circle with an inner diameter Ra and an outer diameter Rb with the center of the output shaft as the radial center, and the inner diameter side and the outer diameter of the magnetoresistive element are The brushless motor according to claim 1, wherein the side ends are connected by conductive wires having an inner diameter Ra and an outer diameter Rb, respectively.