JP2002310725A - Rotational position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the number of components of a rotary body which has a train of teeth arranged repeatedly having unevenness at the outer periphery and a position detecting device which detects the rotational position of the rotary body by obtaining a signal corresponding to the shape of the unevenness and to make them small-sized and lightweight. SOLUTION: Tooth grooves of the train of teeth formed on the rotary body are tooth grooves 12 of normal depth and one deeper tooth groove 13 on the circumference. A range shallower than the tooth grooves 12 is included in a measurement range and for a deeper range, a 1st magnetic sensor 3a having characteristics outside the measurement range is provided. Further, a 2nd magnetic sensor 3b is provided which is characterized by that a range deeper than the depth of the tooth grooves 12 and shallower than the depth of the tooth groove 13 is within the measurement range. The 2nd magnetic sensor 3b has as a reference position the position where the deeper tooth groove 13 is detected and detects the angle of rotation from the reference position which is based upon the output of the 1st magnetic sensor 3a as a rotational position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation position detector mounted on a rotating body such as a main shaft or a motor of a machine tool and detecting a rotating position of the rotating body.

[0002]

2. Description of the Related Art The operation principle of this type of position detector will be described with reference to FIG. The position detection gear 101 is
It is attached coaxially to a rotating shaft of a rotating body such as a motor, and is generally made of a magnetic material such as steel. The first magnetic sensor 103a includes two magneto-resistive elements and a bias magnet arranged near the tooth row. The magnetoresistive elements are arranged at intervals of about １ ／ of the circumferential length of the convex portion (teeth) of the position detecting gear 101. When the position detection gear 101 rotates, a change in magnetic flux generated according to the unevenness of the gear is output from the sensor 103a as electric signals x and y as shown by a waveform A in FIG.

[0003] The electric signal is supplied to a first magnetic sensor 103a.
The size differs depending on the gap between the gear and the position detecting gear 101. Usually, it is necessary to adjust the gap to about 0.1 to 0.2 mm in order to secure a stable output signal. These electric signals x and y are generally two-phase AC signals, and are represented by the following equations (1) and (2).

[0004]

X = V · sin θ + Va (1) y = V · cos θ + Vb (2)

Here, V is the amplitude of the two-phase signal, Va is the DC component included in the signal x, and Vb is the DC component included in the signal y. is the phase of the two-phase signal. If the rotation angle of the position detecting gear 101 is φ and the number of teeth is n, the phase θ is expressed by the following equation (3).

[0006]

(2) θ = n · φ (3)

The amplitudes of these two-phase signals x and y are sampled by AD converters 106a and 106b and converted into instantaneous values (x, y). The instantaneous values (x, y) converted by the AD converters 106a and 106b are input to a divider 107. In a general rotational position detecting device, the DC components Va and Vb shown in the above equations (1) and (2) are ignored, and at this time, the output of the divider 107 is expressed by the following equation (4). .

[0008]

X / y = sinθ / cosθ = tanθ (4)

The rotational position θ of the output of the divider 107 is detected by the converter 108 by the inverse function of the tan function as follows.

[0010]

## EQU4 ## θ = tan ^-1 (x / y) (5)

The rotational position θ detected as described above is a minute position in which one unit of the convex portion (teeth) of the position detecting gear 101 is defined as one unit. On the other hand, the two-phase signals x and y are converted into pulse signals by the comparators 104a and 104b and input to the counter circuit 105. The counter circuit 105 counts the pulse signal to detect the upper digit of the rotational position in a range exceeding one cycle of the rotational position θ. The upper digit of the rotational position and the above rotational position θ are added in the adder 109, and a rotational position detection value φ over the entire circumference of the detection gear 101 is obtained.

Since the above-described position is incremental (only increases unilaterally), usually, the disk 102 having the concave portion (tooth groove) 111 only at one place on the circumference as shown in FIG. Is coaxially fixed to the position detecting gear 101 and attached to the rotating body. A second magnetic sensor 103b including a magnetoresistive element and a bias magnet is arranged near the disk. This second magnetic sensor 103b
As a result, the concave portion 111 of the disk 102 like the waveform B in FIG.
The electric signal z corresponding to the fluctuation of the magnetic field at the time can be detected. As described above, the tooth groove 111 is provided in the position detecting gear 10.
Since one point is formed in one round of one, the electric signal Z
The signal indicates the reference position in the rotation. The signal for detecting the reference position is obtained by comparing the output of the sensor 103b with the comparator 1
The signal is pulsed at 04c and input to the counter circuit 105. The pulse signal, which is the output signal of the sensor 103b, resets the counter circuit and uses the incremental amount from the reference position as the absolute position (absolute position) within one rotation.

FIGS. 7 and 8 are diagrams showing the configuration of the position detecting rotating body (gear 101, disk 102) of the conventional position detector shown in FIG. FIG. 7 shows a gear having a large number of teeth 110, which is the gear 101 in FIG. FIG. 8 shows one recess 1
11 is a disk separate from the gear having the gear 11, and is the disk 102 in FIG. The gear 101 and the disk 102 are concentrically joined, and the concave portion of the disk 102 is set as a reference position within one rotation.

FIGS. 9 and 1 show another conventional rotating body for position detection.
0, shown in FIG. When the position detecting gear is formed by cutting as shown in FIG. 9, only one of the teeth of the position detecting gear,
There is a method in which the gear 112 is processed so as to remain over the entire width of the gear, and the tooth 112 is detected as a reference position within one rotation. In the case where the position detecting rotator shown in FIG. 9 is used, a reference position within one rotation is detected by detecting an electric signal z corresponding to a change in the magnetic field at the convex 112 in FIG. FIG. 12 shows an electric signal output by the magnetic sensor when the position detecting rotator of FIG. 9 is used.

Further, as shown in FIG. 10, there is a method in which a portion of the position detecting gear convex portion is machined so as to be cut off, and the tooth 116 is detected as a reference position within one rotation. FIG.
In the case where the rotating body for position detection shown in FIG. 10 is used, the concave portion 11 is formed by cutting off a part of the convex portion of the detection gear of FIG.
The reference position within one rotation is detected by detecting the electric signal z corresponding to the fluctuation of the magnetic field at 5. FIG. 13 shows an electric signal output from the magnetic sensor when the position detecting rotator of FIG. 10 is used. An electric signal waveform B ′ which is a difference between the electric signal y of the waveform A and the electric signal z of the waveform B is converted to an arbitrary reference signal Vre.
The signal f is compared with the signal f in the comparator 104c shown in FIG.

Further, as shown in FIG. 11, there is also a method in which only a portion of the position detecting gear convex portion is processed to be higher than the other convex portions, and this tooth 116 is detected as a reference position within one rotation. . When the rotating body for position detection shown in FIG. 11 is used, a reference position within one rotation is detected by detecting an electric signal z corresponding to a change in the magnetic field at the convex portion 116 in FIG. FIG. 14 shows an electric signal output from the magnetic sensor when the position detecting rotator shown in FIG. 11 is used. The waveform B is compared with an arbitrary reference signal Vref and the comparator 104 shown in FIG.
The comparison is made by c, and a pulse signal to be input to the counter circuit 5 is generated.

[0017]

Since the structure of the conventional rotary body for position detection shown in FIGS. 5, 7 and 8 is constructed as described above, it is necessary to mount the disk 102 having the concave portion 111. However, there is a problem that the number of parts increases and costs increase. Further, when the mounting position of the disk having the concave portion is shifted, the reference position is changed, and there is a problem that the positional accuracy is reduced.

Further, the structure of the rotating body of the conventional position detector shown in FIG. 9 can solve the problem that the reference position in rotation is shifted from the structure shown in FIG. But,
In order to form the reference position 112, gear cutting is performed over the entire thickness of the disk, and then unnecessary cutting portions are cut, so that there is a problem in that much time and cost are required.

Further, in the structure of the rotating body of the conventional position detector shown in FIG. 10, the problem that the reference position in rotation is shifted from the structure shown in FIG. Since it is necessary to perform gear cutting over almost the entire circumference also in the portion for detecting the position, there is a problem that it takes a lot of time and cost.

Further, in recent years, a motor having a low inertia has been manufactured due to a reduction in the size of the motor. There is a problem that the influence is increased and the acceleration / deceleration performance of the motor is deteriorated.

Further, the magnetic sensor 103a for detecting a magnetic flux change that changes in accordance with the unevenness of the position detecting gear and the magnetic sensor 103b for detecting a magnetic flux change in a concave or convex portion of the disk are provided with a position detecting gear and a reference. It was necessary to arrange the position detecting disks in the circumferential direction. for that reason,
Since the sensor array is two rows, there is a problem that the width of the sensor cannot be reduced.

Next, the structure of the conventional rotary body for position detection shown in FIG. 11 has only a gear for position detection and does not require a disk for reference position detection. Therefore, the problem relating to the inertia and the problem of reducing the width of the sensor can be solved. However, the reference position detecting projection 11 shown in FIG.
6, the electric signals x,
A large distortion occurs in the signal of y. The detection accuracy of the rotational position θ in this distorted portion is significantly deteriorated. Therefore, the gear shown in FIG. 11 cannot be used as a detection gear of the high-precision position detector.

The present invention has been made in view of the above circumstances, and can reduce the influence of inertia on the motor of the position detecting rotating body, and can achieve high accuracy without increasing the processing time of the position detecting gear. It is another object of the present invention to provide a position detector which can be manufactured at a lower cost.

[0024]

In order to solve the above-mentioned problems, a position detecting device according to the present invention has two types of sensors having different characteristics. Further, these sensors are sensors that can output a signal corresponding to the distance to the uneven surface of the tooth row, and are preferably sensors that generate a signal based on a change in a magnetic field according to the distance. The first sensor is, for example, a measurement range relatively near the sensor,
When the object to be measured is located further away, the output has no characteristic. That is, while the distance to the measurement target is short, a signal that decreases as the distance increases is output, but when the distance exceeds a certain level, the signal does not change any more. On the other hand, the second
Has a measurement range relatively far away.

The unevenness of the tooth row of the rotating body is determined corresponding to the two kinds of sensors having different characteristics, and the rotating body is provided with a plurality of recesses having different depths. These recesses are formed from a number of first tooth spaces having a first depth, preferably a common depth, and a small number of second tooth spaces having a second depth greater than this. . More preferably, the second tooth space is provided at one place on the circumference.

For the first sensor, a range shallower than the first depth falls within the detectable range, and a range deeper than the first depth and shallower than the second depth falls outside the detectable range. For the second sensor, a range that is at least deeper than the first depth and shallower than the second depth is a detectable range.

As described above, for the first sensor, since the range deeper than the first depth and shallower than the second depth is outside the measurable range, the output of the first sensor is the second deeper.
The effect of the tooth space does not appear. Therefore, even in the deep tooth space portion, it is possible to output a waveform having substantially the same cycle and amplitude as the other portions. Further, the second sensor can detect the depth of the second tooth space.
It is possible to detect the provided deep tooth spaces. The position of the deep tooth space detected by the second sensor is set as a reference position, and the rotation angle detected by the first sensor from this position is set as the rotation position of the rotating body.

As described above, the reference position can be provided by changing the tooth space depth in one tooth row.
The rotating body can be small or thin. In addition, it is relatively easy to perform processing to partially increase the depth of the tooth space.

[0029]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are diagrams showing a schematic configuration of the embodiment. Rotating body 14 for position detection
Has a gear shape in which irregularities are formed on the outer periphery of a substantially disk shape. One of the tooth spaces of the rotating body 14 is a tooth space 13 deeper than the other tooth spaces 12. A first magnetic sensor 3a is arranged adjacent to the outer periphery of the position detecting rotator 14. The first magnetic sensor 3a includes two magnetic resistance elements and a bias magnet. The two magnetoresistive elements are arranged in the circumferential direction of the position detecting rotator 14 at an interval of １ ／ of the circumferential pitch of the projections (teeth) of the rotator. When the position detecting rotator 14 rotates, a change in magnetic flux generated by unevenness on the outer periphery of the rotator 14 is detected by the two magnetic resistance elements of the first magnetic sensor 3a. The detection signals are electric signals x and y, which are two-phase AC signals shown in FIG. The electric signals x and y are represented by the following equations (6) and (7).

[0030]

X = V · sin θ + Va (6) y = V · cos θ + Vb (7)

Here, V is the amplitude of the two-phase signal, and Va and Vb are the DC components included in the signals x and y, respectively. Also,
θ is the phase of the two-phase signal. Assuming that the rotation angle of the position detection gear 14 is φ and the number of teeth is n, the phase θ is expressed by the following equation (8).

[0032]

(6) θ = n · φ (8)

The amplitudes of these two-phase signals x and y are sampled by AD converters 6a and 6b, and instantaneous x and y are
Convert to y value. This instantaneous value (x, y) is calculated by the divider 7
Is input to If the DC components Va and Vb are neglected, the output of the divider 7 is expressed by the following equation (9), and further converted by the converter 8 into the phase θ, that is, the rotational position θ within the pitch of the unevenness of the rotating body 14. You. This is shown in equation (10).

[0034]

X / y = sin θ / cos θ = tan θ (9) θ = tan ⁻¹ (x / y) (10)

The second sensor 3b is a sensor capable of detecting a deep portion of the tooth space with respect to the first sensor 3a, and uses a sensor having a wider magnetic flux detection range than the sensor 3a.
FIG. 14 shows the gap-sensor output characteristics between the sensor surfaces of the sensors 3a and 3b and the magnetic material. In FIG. 14, a characteristic curve a indicates the characteristic of the sensor 3a, and a characteristic curve b indicates the characteristic of the sensor 3b. Regarding the characteristics of the sensor 3a, when the gap between the sensor surface and the magnetic body is 1 mm or more, almost no change in output characteristics is observed. On the other hand, the characteristics of the sensor 3b show changes in output characteristics even when the gap is 1 mm or more.

FIG. 3 shows an output signal of the present embodiment. The signals x and y are signals obtained from the first magnetic sensor 3a as described above. The signal z is the second magnetic sensor 3b
This is the signal obtained from As the first magnetic sensor 3a, one having a gap of 0.1 to 0.2 mm and capable of obtaining an output of linear characteristics is used. Therefore, in the present embodiment, the first magnetic sensor 3a has a value of 0.2 mm in this range. It is arranged with a gap. Further, as described above, the output of the first magnetic sensor 3a hardly changes when the gap becomes 1 mm or more. The depth of the tooth space of the position detecting gear 14 is 0.8 mm for a normal tooth space (tooth space 12),
Is 1.3 mm. Therefore, the gap of the first magnetic sensor 3a with respect to the tooth bottom is 1 m with respect to the normal tooth bottom.
m, 1.5 mm for the tooth bottom of the deep tooth space 13.
This value is, as described above, the dead zone of the first magnetic sensor 3a, and the output of the first magnetic sensor 3a is
3 is not affected.

On the other hand, the output of the second magnetic sensor 3b varies from a gap of 1 mm or more to about 2 mm. Therefore, even if a gap of 0.2 mm between the position detecting rotator 14 and the tooth tip 10 is considered, Tooth groove depth 1mm and 1.5
mm is also a sufficiently detectable range. Therefore, as shown in FIG. 3B, the output of the second magnetic sensor 3b has a lower value when facing the deep tooth space 13. The rotational position of the position detecting rotator 14 at this time is set as a reference position, and the rotational position of the rotator 14 is obtained from the number of irregularities and the phase obtained from Expression (10).

The calculation of the position within one rotation of the position detecting rotator 14 is performed as follows. The two-phase signals x and y are also input to the comparators 4a and 4b, where they are converted into pulse signals and sent to the counter circuit 5. In this counter circuit 5, by counting the pulse signal,
The upper digits of the rotational position in a range exceeding one cycle of the rotational position θ are detected. This rotational position upper digit and the rotational position θ
Are added by the adder 9, and the rotational position of the position detecting rotator 14 is detected. The signal z is sent to the counter circuit 5 via the comparator 4c, and the pulse signal z resets the counter circuit 5. Therefore, each time the deep tooth space 13 is detected, that is, the rotating body 1
The count value is reset each time the motor 4 rotates once, and the rotation position from this position (reference position) is calculated.

As shown in FIGS. 1 and 2, a feature of the present invention is that concave portions (tooth grooves) integrally formed at predetermined intervals on the outer periphery of the position detecting rotating body shown in FIGS. Of the recesses, only one recess 13 has a groove deeper than other recesses.
That is,

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a position detector according to the present embodiment.

FIG. 2 is a diagram showing a rotating body for detecting a rotational position according to the embodiment;

FIG. 3 is a diagram showing an output waveform of the magnetic sensor according to the embodiment.

FIG. 4 is a characteristic diagram of two types of magnetic sensors of the present embodiment.

FIG. 5 is a diagram illustrating an example of a configuration of a conventional position detector.

6 is a diagram showing an output waveform of a magnetic sensor of the position detector of FIG.

FIG. 7 is a diagram showing a rotating body for detecting a rotational position of the position detector of FIG. 5 together with FIG. 7;

8 is a diagram showing a rotating body for detecting a rotational position of the position detector of FIG. 5 together with FIG. 8;

FIG. 9 is a diagram showing a configuration of another conventional example.

FIG. 10 is a diagram showing a configuration of still another conventional example.

FIG. 11 is a diagram showing a configuration of still another conventional example.

12 is a diagram showing an output waveform of a magnetic sensor of the position detector of FIG.

13 is a diagram showing an output waveform of a magnetic sensor of the position detector in FIG.

14 is a diagram showing an output waveform of a magnetic sensor of the position detector of FIG.

[Explanation of symbols]

3a Magnetic sensor (first sensor), 3b Magnetic sensor (second sensor), 10 tooth tip (tip of rotating body convex portion), 1
2 General tooth groove (rotary body concave part), 13 deep tooth groove (deep concave part of rotary body), 14 position detecting rotary body.

Continued on the front page F term (reference) 2F063 AA35 CA40 DD08 EA03 GA32 GA69 KA02 KA04 2F077 AA38 CC02 CC08 NN22 PP14 QQ11 VV01

Claims (2)

[Claims] 1. A rotator having a tooth row in which tooth grooves of a first depth are repeatedly arranged on a circumference and irregularities are arranged, and a rotating body having a center of the tooth row as a rotation axis; and a rotating body disposed near the tooth row. A rotation position calculation unit configured to calculate a rotation position of the rotating body based on a change in the distance to the dentition surface, based on a change in the distance to the dentition surface; In the detecting device, the tooth row of the rotating body has a tooth groove having a second depth deeper than a first depth at a predetermined position on a circumference, and the sensor is located at a position shallower than the first depth. Is a detectable range, and a first sensor having a characteristic in which a position deeper than the first depth and shallower than the second depth is out of the detectable range, at least deeper than the first depth and the second sensor Sensor having a characteristic in which a position shallower than the depth of the sensor is within a detectable range The rotation position calculation means calculates a relative value of a rotation angle of the rotating body based on an output of the first sensor, and
A rotation position detection device that calculates a reference position serving as a reference for rotation of the rotating body based on an output of the sensor. 2. The rotating body position detecting device according to claim 1, wherein the tooth groove having the second depth of the rotating body is provided at one place on a circumference.