JPH06209552A - Motor with built-in magnetic position detector - Google Patents

Abstract

PURPOSE:To improve the accuracy in positional detection in a motor with a built-in magnetic position detector, and further achieve high output. CONSTITUTION:A stator pole 14 is formed around the rotor of a stator. One part of it is used as a torque pole, and the other is used as a sensor pole 14. The ratio alpha/beta of the width alpha of the stator pole 14 to the width of the rotor pole 34 is 0.2-0.5, and the air gap g between the stator pole 14 and the rotor pole 34 is 0.4mm smaller, and the ratio of the thickness of the rotor pole 34 to the width beta is designed to be 0.2-0.5. By the above design, the change of the inductance of a sensor pole 14 resembles a sine wave, and highly accurate detection of position becomes possible. Moreover, high output can be gotten at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for optimally designing main dimensions of a motor with a built-in magnetic position detector.

[0002]

2. Description of the Related Art Brushless DC motors are widely used in production automation systems, industrial robots, XY tables, semiconductor circuit manufacturing devices and magnetic disk devices. The main evaluation criteria for these devices are high accuracy, high output, responsiveness,
It is reliable and easy to manufacture. In particular, JP-A-62-1
The brushless DC motor disclosed in No. 244265 is one of the most improved brushless DC motors today in terms of accuracy, response characteristics and reliability.

A brushless DC motor disclosed in Japanese Patent Laid-Open No. 62-244265 will be briefly described below with reference to FIGS. 1 to 3 attached for explaining an embodiment. FIG. 1 shows a sectional shape of a stator and its coil structure. The stator (10) has an annular part (12) formed by punching out a thin steel plate, rectangular stator poles (14) (16) arranged at equal intervals on the inner circumference of the annular part (12) and each pole. Wound coil
It is indicated by (18) and (20).

The stator poles of the illustrated motor operating in two phases are circled numbers 1, 2, 4, 5, 7, 8, 9, 10, 1.
1st and 12th groups of torque poles
(14), also 13, 14, 15, 16, 17, 18, 1
A second group of torque poles (14) is shown at 9, 21, 22 and 24 and is further divided into three groups of sensor poles (16) at 3, 6, 20 and 23.

A coil (20) is wound around the sensor pole (16) with a polarity as shown in the figure. This coil (20) is bridge-connected, and a high frequency of about 100 kHz is applied to its terminals (50) (52). Then, the inductance change of the sensor pole (16) due to the rotation of the rotor (30) has a phase difference of π / 2 with each other, and the terminal (54) (56) as a sine wave signal that changes corresponding to the rotor rotation angle. ) Is output.

Referring to FIG. 2, the rotor is a cylindrical core,
It is shown with 18 rotor poles and shafts. The rotor pole is formed of a high magnetic force permanent magnet such as samarium / cobalt alloy, and is arranged and fixed to the outer peripheral surface of the cylindrical core by an appropriate means so that the polarities are alternately different. FIG. 3 is a block diagram of a system for digital PID control of a brushless DC motor having the above structure.

The first and second groups of torque poles (14) of the motor M are supplied with first and second phase power from amplifiers HA and HB, respectively. Further, a high frequency signal of about 100 KHz is supplied from the oscillator circuit (60) to the terminals (50) and (52) of the bridge circuit shown in FIG. 1, and the inductance change of the sensor pole (16) due to the rotation of the rotor changes. Two sine wave signals having a phase difference of π / 2 and changing with the rotation of the rotor are output from the terminals (54) and (56).
The two sine wave signals are converted into a sine function and a cosine function of the rotation angle of the rotor by the synchronous detection circuit (62), and converted into a rotor angle signal by the angle determination circuit (64). This rotor angle signal is added to the external reference signal input to the terminal (84) or the reference signal internally output by the microprocessor (66) in the addition circuit (68), and the PID control circuits (70) (72) (74)
And the well-known digital PID control is performed.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
When the brushless DC motor disclosed in No. 65 and its control system were prototyped and experimented, the overall characteristics of the motor and control system such as position controllability, stability and quick response were below expected values, and , It turned out that the main reason was not in the control system but in the circumstances specific to that kind of motor. In particular, it has turned out to be due to the main dimensions of the magnetic circuit of such a motor.

Therefore, the problem to be solved by the present invention is based on the elucidation of the above-mentioned cause, and the optimization of the main dimensions of the magnetic circuit of the motor improves the overall characteristics of the motor with a built-in magnetic detector. It is in.

[0010]

According to a first aspect of the present invention, at least two groups of torque poles having a spatial phase difference and two or more groups in which the phase difference of the inductance for detecting the rotor rotation angle is 90 degrees. The main feature is that the stator is provided with a sensor pole, and the rotor pole is composed of a permanent magnet, and the ratio of the width of the stator pole to the width of the rotor pole is 0.2 or more and 0.5 or less.

According to a second aspect of the present invention, at least two groups of torque poles having a spatial phase difference and an inductance phase difference for detecting a rotor rotation angle have a phase difference of about 90.
A stator with two or more sensor poles,
The rotor pole is composed of permanent magnets, and the air gap between the stator and rotor is 0.4mm.
The main features are as follows.

According to a third aspect of the present invention, there is provided a stator having at least two groups of torque poles having a spatial phase difference and two or more sensor poles having a phase difference of 90 degrees in inductance for detecting a rotor rotation angle. The rotor pole is composed of permanent magnets, and the ratio of the stator pole width to the rotor pole width is 0.2.
.About.0.5, and the thickness / width ratio of the rotor pole is 0.4.about.0.
8. The main feature is that the rotor skew is 0.2 to 0.5.

[0013]

According to the structure of claim 1, wherein the ratio of the width of the stator pole to the width of the rotor pole is 0.2 or more and 0.5 or less, the change in the inductance of the sensor pole is made sinusoidal to reduce the static angle error and to reduce a large static angle. Achieve torque. Air gap value between stator and rotor is 0.4mm
In the configuration of claim 2 set forth below, the inductance change of the sensor pole is made sinusoidal to reduce the static angle error and realize a large static torque.

The ratio of the stator pole width to the rotor pole width is 0.2 to 0.5, and the ratio of the rotor pole thickness to the width is 0.
The configuration of claim 3 in which the rotor skew is 4 to 0.8 and the rotor skew is 0.2 to 0.5 realizes a realistic motor having a good static angle error and static torque.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The main dimensions of the motor characteristic of the present invention will be described after the description of the general structure and operation of the embodiment. FIG. 1 shows the cross-sectional shape of the stator 10 of the embodiment and its coil structure. The stator (10) is formed by punching out a thin steel plate, an annular portion (12), rectangular stator poles (14) (16) arranged at equal intervals on the inner circumference of the annular portion (12), and this stator pole. (14) Coil wound around (16) (1
8) Consists of (20).

The stator pole (1) of the illustrated motor with built-in magnetic position detector (hereinafter simply referred to as "motor") that operates in two phases
4) (16) are circled numbers 1, 2, 4, 5, 7, 8, 9,
A first group of torque poles (14), designated 10, 11, and 12, also 13, 14, 15, 16, 1
Second designated 7, 18, 19, 21, 22 and 24
Group of torque poles (14) and even 3, 6, 20
And 23 are classified into three groups of sensor poles (16).

A coil (18) is wound around the first group of torque poles (14) with a polarity as shown in the drawing, and the coils (18) are connected to each other and supplied to the terminals (40) and (42). Powered by electricity. Similarly, the second group of torque poles (1
4) is energized by the electric power of the second phase supplied to the terminals (44) and (46) to generate torque in the rotor. The feature of this motor is that each adjacent pair of torque poles (14) has a coil (1
8) is connected and its coil (18) is energized,
The point is that the coil (18) is wound in the opposite direction so that the magnetic flux flows between the pair of torque poles (14). Further, the sensor pole (16) arranged adjacent to the torque pole (14) other than the pair of adjacently arranged magnetically coupled torque poles (14) has a coil (20) wound in the polarity shown in the drawing, and the sensor pole (16) is bridged. Connected. The sum of the numbers of the torque poles (14) and the sensor poles (16) is divided by the number of phases to obtain an even number.

FIG. 2 shows a sectional structure of the rotor (30) of the embodiment. The rotor (30) comprises a cylindrical core (32), 18 rotor poles (34) and a shaft (36). The rotor pole (34) is formed of a high magnetic force permanent magnet such as samarium / cobalt alloy, and is arranged and fixed to the outer peripheral surface of the cylindrical core (32) by a proper means so that the polarities are alternately different. The number of stator poles (14) (16) and this rotor pole
The ratio of the numbers of (34) is 4: 3 or 4: 5. As will be described later, the width of the stator poles (14) (16) and the rotor poles (34)
To the width of 0.20 to 0.50.

FIG. 3 is a block diagram of a system for digital PID control of the motor M having the above structure. The first and second groups of torque poles (14) of the motor M are supplied with first and second phase power from amplifiers HA and HB, respectively. The bridge circuit terminals (50) and (52) shown in FIG.
A high frequency signal of about KHZ is supplied, and the inductance change of the sensor pole (16) due to the rotation of the rotor has a phase difference of π / 2, and the terminals are two sine wave signals that change with the rotation of the rotor. Output from (54) and (56). The two sine wave signals are converted into a sine function and a cosine function of the rotation angle of the rotor by the synchronous detection circuit (62), and converted into a rotor angle signal by the angle determination circuit (64) composed of a ROM table or the like. This rotor angle signal is an external reference signal or microprocessor (66) input to the terminal (84).
Is added to the reference signal internally output by the adder circuit (68), and P
It is output to the ID control circuits (70) (72) (74) and the well-known digital PID control is performed.

Next, referring to FIGS. 4 to 6, the air gap value between the stator and the rotor, the ratio of the width of the stator pole to the width of the rotor pole, and the ratio of the thickness of the rotor pole to its width, which are characteristic of the present invention. The main dimensions such as the skew pitch will be described. Performance evaluation of a motor driven by a PID control system is usually extremely difficult. However, the present inventor succeeded firstly in clarifying the relationship between the static angle error and the main dimension of the motor of the above-described system. That is, in a motor that has a phase difference of π / 2 with each other and derives the rotation angle of the rotor by obtaining a sine function and a cosine function of the rotation angle of the rotor from a sine wave signal that changes with the rotation of the rotor. It was discovered that the harmonics contained in the sine wave signal contribute to the static angle error. And the stator pole
(14) (16) width α and rotor pole (34) width β (see Fig. 4)
It has been found that the inductance change of the sensor pole (16) becomes non-sinusoidal when the ratio α / β of 1 approaches 1. Therefore, the inventor of the present application prototyped several kinds of samples in which the stator pole width was designed in a range where the inductance change of the sensor pole became sinusoidal and was predicted to be a high output motor, and the static angle error and static torque were measured. .

In FIG. 5, the rotor diameter is 30 mm, the rotor skew is 0.33, and the air gap value is fixed, and the ratio between the width α of the stator poles (14) and (16) and the width β of the rotor pole (34) (see FIG. 4). α / β is 0.20, 0.36, 0.39, 0.
It is a plot of static angle error and static torque of a plurality of motors changed to 50. As shown, α /
When β = 0.20 or less, the static torque decreases greatly, and α /
At β = 0.20 to 0.50, a practical motor was obtained for both static angle error and static torque. The static angle error is defined by max / 2-min / 2 (unit: minutes) using the maximum value max and the minimum value min of the angle error,
When α / β = 0.50 or more, the harmonic components contained in the above sine wave signal increase rapidly, resulting in a sharp deterioration.

Secondly, the present inventor
4) Air gap value g (Fig. 4) between (16) and rotor pole (34)
We also succeeded in clarifying the relationship between the reference angle) and the static angle error. FIG. 6 shows that the rotor skew is 0.33, the ratio α / β = 0.36 of the width α of the stator poles (14) (16) and the width β of the rotor poles (34) (see FIG. 4) is fixed, and the rotor diameter is fixed. Change the air gap value g to 0.15mm, 0.25mm,
It is a plot of the static torque and static angle error of four types of motors of 0.35 mm and 0.7 mm. As shown in the figure, when the air gap value g = 0.4 mm or more, the static angle error worsens and the static torque decreases remarkably, and the superiority of the motor with the air gap value g = 0.4 mm or less and the manufacturing limit air gap value is confirmed. Was done.

Further, the inventor of the present invention conducted a similar experiment with respect to the rotor skew, and also derived the relationship between the ratio of the thickness and the width of the rotor pole and the motor characteristic. As a result, regarding the rotor skew, it was found that by setting the rotor skew to 0.2 to 0.5, a motor with a small static angle error can be obtained, and the ratio of the rotor pole thickness to the width is 0.4.
It was found that a high output motor with a small static angle error can be obtained by setting it to 0.8.

[0024]

As described above, according to the present invention, the ratio of the width of the stator pole to the width of the rotor pole is 0.2 to 0.5,
The air gap value between the stator and the rotor is 0.4 mm or less, the width ratio to the thickness of the rotor pole is 0.4 to 0.8,
Since the rotor skew is set to 0.2 to 0.5, the inductance change of the sensor pole becomes sinusoidal, and it is possible to realize a motor with a built-in magnetic position detector having good overall characteristics such as static angle error and static torque.

[Brief description of drawings]

FIG. 1 is a sectional view of a stator according to an embodiment of the present invention.

FIG. 2 is a sectional view of a rotor according to an embodiment of the present invention.

FIG. 3 is a control circuit diagram of the embodiment.

FIG. 4 is a partially enlarged view of a stator and a rotor according to an embodiment.

FIG. 5 is an actual measurement diagram illustrating a relationship between a ratio of a stator pole width and a rotor pole width and a motor characteristic.

FIG. 6 is an actual measurement diagram illustrating a relationship between an air gap between a stator and a rotor and motor characteristics.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 stator 12 annular part 14, 16 stator pole 18, 20 coil 30 rotor 32 rotor core 34 rotor pole 36 rotor shaft

Claims (3)

[Claims] 1. A stator comprising at least two groups of torque poles having a spatial phase difference and two or more sensor poles having a phase difference of inductance of about 90 degrees for detecting a rotor rotation angle, and a permanent magnet. A motor with a built-in magnetic position detector, characterized in that the rotor pole comprises a rotor, and the ratio of the width of the stator pole to the width of the rotor pole is 0.2 or more and 0.5 or less. 2. A stator comprising at least two groups of torque poles having a spatial phase difference and two or more sensor poles having a phase difference of inductance of about 90 degrees for detecting a rotor rotation angle, and a permanent magnet. A motor with a built-in magnetic position detector, characterized in that the rotor pole is composed of a rotor, and the air gap value between the stator and the rotor is 0.4 mm or less. 3. A stator having at least two groups of torque poles having a spatial phase difference and two or more sensor poles having a phase difference of inductance of about 90 degrees for detecting a rotor rotation angle, and a permanent magnet. The rotor pole is composed of a rotor, and the ratio of the stator pole width to the rotor pole width is 0.2-
0.5, and the rotor pole thickness-width ratio is 0.4-
A magnetic position detector built-in motor having a rotor skew of 0.2 to 0.5.