JPH06331306A - Angle-of-rotation detector - Google Patents

Abstract

PURPOSE:To provide the title detector having the characteristic of a conventional resolver, simple in structure and suitable for miniaturization (flattening) and cost reduction. CONSTITUTION:An angle-of-rotation detector has the rotor 8 integrated with a rotary shaft and different in the diameter from the center of the shaft to the outer periphery thereof at every half periphery and a stator having four ring-shaped magnetic yokes 4-7 concentric to the rotor 8 and formed by superposing three coils 1-3 positioned around the rotor in the axial direction of the rotor 8 and holding three coils therebetween in the axial direction of the rotor 8 and the inner peripheries of the yokes 1-4 protrude toward the rotary shaft from the inner peripheries of the coils 1-3 and the protruding quantities thereof are formed into diameters different at every half periphery and the yokes 4-7 are overlapped so as to form a structure wherein large and small diameters are reversed every one and the coil 2 positioned at the center among three coils 1-3 are excited by an AC signal and the induced voltages from the upper and lower coils 1, 3 are subjected to analogue/digital conversion and the ratio of two digital values is operated to obtain an angle-of-rotation detection signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle detecting device for detecting a rotation angle of a rotating body.

[0002]

2. Description of the Related Art A rotation angle detecting device such as an encoder for detecting a rotation angle of a rotating body is roughly classified into an incremental type and an absolute type. The former obtains rotational position information by counting the number of pulses output for each unit rotational angle. On the other hand, in the absolute type rotation angle detection device, since the rotating body itself in the measuring instrument has rotational position information by some means, it is necessary to store the count data in a counter or the like in the signal processing circuit. There is no. Therefore, even if the power supply to the circuit is interrupted due to a power failure or the like during the rotation, the position within one rotation is not lost, and it has an advantage over the incremental type. Among such absolute type rotation angle detectors, the resolver is mechanically more robust and resistant to vibration than other detectors such as optical encoders, and also resistant to environment such as dust / oil droplets. Because of its strong character, it is widely used in machine tools.

[0003]

However, in the conventional resolver, the winding structure is complicated and the device is miniaturized (especially flattened).
It was not easy to do, and it was difficult to apply it to small motors. In addition, the circuit for signal processing is complicated, which has been an obstacle to cost reduction. Therefore, an object of the present invention is to provide a rotation angle detection device having a simple structure, a small size (flattened), and a low cost while having the characteristics of a conventional resolver that is robust and has excellent environment resistance. It is a thing.

[0004]

A rotation angle detecting device according to the present invention is a rotor which is integral with a rotary shaft and has a diameter different from the center of the shaft to the outer circumference every half circumference, and a rotor which is concentric with the rotor and surrounds the rotor. The three positioned coils are stacked in the axial direction, and the three
And a stator provided with four magnetic yokes in a ring shape so as to sandwich one coil from the axial direction, and the inner circumference of the yoke protrudes toward the rotary shaft side from the inner circumference of the coil. Is formed to have a different diameter for each half circumference, and the size of the yoke is inverted for each one, and the central coil of the three coils is excited by an AC signal to After the induced voltage from the coil is converted into a digital signal by an analog / digital converter, a signal processing circuit for calculating a ratio of the two digital values to obtain a rotation angle detection signal is provided.

[0005]

In the device having such a structure, the amount of the magnetic flux generated by the exciting coil that interlinks with each of the two detection coils depends on the rotational position of the rotor.
The output voltage from both sensing coils is a function of rotor angle. By performing A / D conversion of these two detection voltages and then taking the ratio of the two, the effects of electrical and magnetic drift are canceled out, and signal data dependent on the rotor angle can be obtained with good reproducibility. From this data, the rotor rotational position can be obtained.

[0006]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a schematic structural diagram of an angle detection device according to an embodiment of the present invention. The overall configuration is composed of a rotor 8 that rotates together with a rotating body (not shown) to be measured, and a stator that is concentric with the rotor and that faces the rotor around the rotor. The stator is 1 sandwiched between two detection coils 1 and 3.
A basic unit is composed of three coils, which are one exciting coil 2, and is arranged concentrically with the rotor 8. A ring-shaped yoke 4 that sandwiches these coils 1 to 3 from the axial direction.
To 7 are provided, and the inner circumference of the yoke is smaller than the inner circumference of the coil and protrudes inward, and the protrusion amount is large half portions 4a to 7a and small diameter portions 4b to 7b every half circumference. It is different, and the degree of unevenness is reversed one by one. The yokes 4 to 7 are magnetic plates.
On the other hand, the rotor 8 is fixed to the rotating shaft 8c and has a small diameter portion 8a and a large diameter portion 8b having different outer diameters for each half circumference (a cross-sectional shape like two semicircles 8a, 8b having different diameters attached to each other. ). The rotor 8 and the rotary shaft 8c may be an integrally molded product.

The outline of the angle detection principle of such a structure will be described with reference to FIGS. Both figures are schematic vertical sectional views showing the positional relationship between the outer circumference of the rotor 8 and the inner circumferences of the yokes 4 to 7 of the stator. The large diameter portion 8b of the rotor 8 is the small diameter portion 4 of the yoke 4.
In the state of FIG. 2 in which b and the small diameter portion 6b of the yoke 6 are opposed to each other, the magnetic reluctance to the magnetic path for magnetically coupling the exciting coil 2 and the detecting coil 1 is minimum (“air gap length / air gap width” is (Minimum), and conversely excitation coil 2 and detection coil 3
The magnetic resistance is maximum for the magnetic path that couples and.
Therefore, in this state, the exciting coil 2 and the detecting coil 1 are tightly coupled, and the exciting coil 2 and the detecting coil 3 are loosely coupled, so that a magnetic path is formed as shown by a dotted arrow in FIG.

On the other hand, in the state where the rotor has half rotated to the position shown in FIG. 3, the relationship of the above-mentioned magnetic resistance is exchanged, and the exciting coil 2 and the detecting coil 3 are tightly coupled and the exciting coil 2 and the detecting coil 1 are loosely coupled. Therefore, a magnetic path is formed as shown by the dotted arrow in FIG. Due to the rotor angle dependence of the density of the magnetic coupling between the exciting coil and the detecting coil as described above, each detected voltage from the detecting coils 1 and 3 with respect to the exciting signal increases or decreases depending on the rotor angle.・ 2 in Figure 3
From the two states, two voltage patterns (angle dependence of the detected voltage) obtained by shifting the rotor angle by 1/2 rotation are obtained.

In order to explain the behavior of this voltage pattern, a diagram schematically showing the overlapping state of the large diameter portion 8b and the small diameter portions 4b to 7b by expanding the positional relationship between the rotor and the stator yoke in a plane is shown in the figure. 4 shows. Since the detection voltage of the detection coils 1 and 3 can be approximated to be proportional to the permeance, the unevenness (the amount of change in the diameter of each of the rotor and the stator yoke) is sufficiently large, and the distance between the rotor and the stator yoke is large or small. In the case of stepwise switching to one value, the permeance value is determined by the width of the region where the protrusions 8b, 4b of the rotor and the stator face each other. Therefore, the detected voltage value exhibits a linear change in proportion to the length of the overlapping region (narrow interval region) of the convex portions.

FIG. 5 shows the rotor angle dependence of the output voltage from the two detection coils 1 and 3. Each detection voltage (e
Both 1, 1 and e2) and the ratio of both (e1 / e2) take the same value twice during one revolution of the rotor, and the angle-signal relationship is "two-to-one correspondence". Is θ <180
Since it is possible to correct “one-to-one correspondence” by discriminating ∘orθ ≧ 180 ° with a complementary 1P / R encoder or the like, it is possible to read the rotor angle from these values. The independent values of the detection voltages e1 and e2 are directly affected by electric (magnetic) drift such as temperature characteristics and are inferior in reproducibility, but by taking the ratio (e1 / e2) of the two, this fluctuation effect is canceled, Angle detection with excellent reproducibility can be performed.

However, as can be seen from FIG. 5, non-linearity appears in the ratio pattern (the angle dependency becomes non-linear), and therefore data processing for correction is necessary to improve accuracy. However, since the reproducibility (stability) of data is high, it can be easily corrected by means such as ROM correction.

FIG. 6 shows a schematic system configuration of an angle detection device using the above configuration. Data obtained by A / D converting the output voltages of the two detection coils 1 and 3 is divided to obtain the ratio (FIG. 7), and then θ <by the angle determination sensor 9 is set.
From the determination result of 180 ° or θ ≧ 180 °, data processing is added so that the angle-signal relationship is “one-to-one correspondence”. In this embodiment, a ring having a low magnetic permeability / high conductivity (ex. Brass) and having the same shape (different thickness) as the stator yoke is adjacent to the coil unit for "judgment around 180 °". Then, the method of measuring the capacitance change between the ring and the rotor was used. By shifting the uneven position (large and small diameter parts) of this brass ring from the uneven condition of the yoke by 1/4 rotation, the capacitance signal of the angle dependent pattern shifted by 1/4 rotation from the coil voltage ratio signal can be obtained. It is possible to perform "one-to-one correspondence (correct the value of θ ≧ 180 ° to the reverse slope as shown in FIG. 8)" by processing the signal of 1 in the calculation 1 portion, and the coordinates are corrected by calculation 2 (Fig. 9). After that, data processing such as ROM correction may be added if necessary. Most of the signal processing circuit 10 is a digital circuit and can be easily configured.

[0013]

As described above, the rotation angle detection device according to the present invention has a structure,
The circuit configuration is extremely simple and compact (flat),
Excellent in responding to cost reduction.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a rotation speed detection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between a rotor and a stator in the above embodiment.

FIG. 3 is an explanatory diagram showing a positional relationship between a rotor and a stator in the above embodiment.

FIG. 4 is a characteristic diagram showing a relationship between a rotor voltage and a stator large-small diameter portion overlapping state in the above-described embodiment in a plan view and a relationship with a detection voltage at each position.

FIG. 5 is a characteristic diagram showing the rotor angle dependence of the detected voltage in the above embodiment.

FIG. 6 is a block diagram showing a schematic system configuration of a rotation speed detection device according to an embodiment of the present invention.

7 is a characteristic diagram showing the rotor angle dependence of the output signal at point A in FIG.

8 is a characteristic diagram showing the rotor angle dependency of the output signal at point B in FIG.

9 is a characteristic diagram showing the rotor angle dependence of the output signal at point C in FIG.

[Explanation of symbols]

 1, 3 Detection coil 2, Excitation coil 4-7 Yoke 8 Rotor 10 Signal processing circuit

Claims (2)

[Claims] 1. A rotor, which is integral with a rotating shaft and has a diameter from the center of the shaft to the outer periphery which is different for each half circumference, and three coils which are concentric with the rotor and which are positioned around the rotor are overlapped in the axial direction.
A stator provided with four magnetic yokes in a ring shape so as to sandwich the three coils from the axial direction, and the inner circumference of the yoke projects toward the rotary shaft side from the inner circumference of the coil. A rotation angle detecting device characterized in that the protrusion amount is formed to have a different diameter for each half circumference, and the large and small diameters of the yokes are overlapped one by one. 2. A coil located in the center of the three coils is excited by an AC signal, and induced voltages from the upper and lower coils are converted into digital signals by an analog / digital converter, and then the two digital values are converted. The rotation angle detection device according to claim 1, further comprising a signal processing circuit that calculates a ratio to obtain a rotation angle detection signal.