JPH06147813A - Position detector for rotary body - Google Patents

Abstract

PURPOSE:To detect position highly accurately by eliminating interference at least between a pair of capacitors used for noncontact positional detection of a rotary body. CONSTITUTION:At least a pair of electrodes 93 are disposed symmetrically to a rotary body 91 thus constituting a capacitor between the rotary body 91 and each electrode 93. Furthermore, a plurality of protrusions 92 are formed at predetermined positions, not opposing simultaneously to a plurality of electrodes 93, on the rotary body 91 so that only such electrode 93 and protrusion 92 as opposing each other functions as an effective capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor position detecting device, and more particularly to a rotor position detecting device suitable for a magnetic bearing mechanism that magnetically supports a rotor in a non-contact manner.

[0002]

2. Description of the Related Art Magnetic bearings have been conventionally used as bearings for ultra-high speed motors and the like. In this magnetic bearing, at least one pair, preferably two pairs of electromagnets are arranged at a target position with a rotating shaft made of a magnetic material sandwiched therebetween, and each pair of electromagnets is excited to generate an attractive force. When exciting the electromagnets of each pair alternately, shorten the excitation period to equivalently obtain a state in which the electromagnets of each pair simultaneously exert an attractive force on the rotating body, thus making the rotating body strong. Can be supported by. Further, in the case of exciting each pair of electromagnets with direct current, it is possible to generate an attractive force in a desired direction by changing the level of direct current to be excited.

Even when the rotating body is held by the magnetic bearing, the position of the rotating body may be displaced for some reason. In this case, the direction of displacement of the rotating body and The position shift can be eliminated by controlling the electromagnets so that the attraction force of one of the electromagnets of each pair becomes larger than the vibration attraction force of the other in accordance with the amount. Further, as is clear from the above description, in order to control the electromagnet, it is essential to detect the position of the rotating body. Therefore, even in the conventional magnetic bearing, a device for detecting the position of the rotating body has been added. Since such a position detecting device is required to detect the position of the rotating body in a non-contact manner, does a sensor using a coil like an eddy current sensor be used (see Japanese Patent Laid-Open No. 63-214519). ) Or using a sensor using a capacitor (see Japanese Patent Application Laid-Open No. 2-201101). However, if the former sensor is adopted, the magnetic field is likely to be affected by the magnetic flux leaked from the motor, so that the position detection accuracy inevitably decreases, or a magnetic shield or the like is required to suppress the decrease in position detection accuracy. Therefore, there is an inconvenience that the structure becomes complicated and the size becomes large. On the other hand, the latter sensor is essentially unaffected by the magnetic flux, so that the above-mentioned inconvenience of the former sensor can be eliminated.

[0004]

However, in a sensor using a capacitor, a DC voltage is applied to the capacitor, and an impedance change caused by a position change of the rotating body is based on the divided voltage of the DC voltage. However, since one electrode of all capacitors also serves as the rotating body, interference between the capacitors inevitably occurs (the smaller the diameter of the rotating body, the greater the interference. Occurs).

As a result, although the capacitors themselves are hardly affected by noise, the accuracy of the obtained position detection signal is lowered due to the interference between the capacitors.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in detecting the position of a rotating body based on the impedance change of a capacitor, interference between the capacitors can be eliminated, and a highly accurate position can be obtained. An object of the present invention is to provide a position detecting device for a rotating body that can achieve detection.

[0007]

In order to achieve the above object, a position detecting device for a rotating body according to claim 1 is in a state in which a predetermined position of the rotating body is directly opposed to an electrode of any variable capacitance capacitor. In the above, at least one protrusion and / or recess is formed so that the distance to the electrode is smaller than the distance to the other electrode of the other variable capacitor.

According to a second aspect of the present invention, there is provided a rotary body position detecting device, wherein a predetermined range in the axial direction of the rotary body is constituted by a plurality of rotary body constituent portions electrically insulated from each other, and one rotation is performed. One electrode is arranged at a predetermined position directly facing the body constituent portion. In the position detecting device for a rotating body according to a third aspect of the present invention, each electrode is surrounded by a large area auxiliary electrode for grounding which is arranged in a state of being close to the rotating body.

According to a fourth aspect of the present invention, there is provided a position detecting device for a rotary body in which a conductive rotary body and a plurality of adjacent electrodes electrically connected to each other form one variable capacitor group which cooperates with each other. Is.

[0010]

According to the position detecting device for a rotating body of claim 1, the inter-electrode distance of the variable capacitor constituted by the rotating body and the electrode arranged at a predetermined position close to the rotating body is equal to that of the rotating body. Due to the relative position of the protruding portion and / or the recessed portion formed at a predetermined position, only one of the variable capacitance capacitors becomes smaller than the other variable capacitance capacitors. The capacitance is sufficient for position detection, and the capacitances of all other variable capacitors are substantially zero. As a result, it is possible to prevent interference between the variable capacitors. Therefore, when a voltage change is detected by applying a voltage to a plurality of variable capacitors arranged with the conductive rotating body as a reference and a position detection signal of the rotating body is obtained, another variable capacitor is used. It is possible to achieve highly accurate position detection that is not interfered with.

According to another aspect of the position detecting device of the rotating body of the present invention, a predetermined range in the axial direction of the rotating body is constituted by a plurality of rotating body constituent parts which are electrically insulated from each other.
Since the one electrode is arranged in one rotary body constituent portion, all the variable capacitors are electrically separated from each other, and the interference between the variable capacitors can be prevented in advance. Therefore, when a voltage change is detected by applying a voltage to a plurality of variable capacitors arranged with the conductive rotating body as a reference and a position detection signal of the rotating body is obtained, another variable capacitor is used. It is possible to achieve highly accurate position detection that is not interfered with.

According to another aspect of the position detecting device of the rotating body, a plurality of electrodes are arranged in the vicinity of the surface of the rotating body, and each electrode is arranged in the state of being close to the rotating body. Since it is surrounded by the electrodes, the electrostatic capacity of the capacitor composed of the auxiliary electrode and the rotating body is remarkably increased, and the corresponding portion of the rotating body can be grounded equivalently. As a result,
The variable capacitance capacitors are separated from each other by the equivalent grounded portion, and the interference between the variable capacitance capacitors can be prevented. Therefore, when a voltage change is detected by applying a voltage to a plurality of variable capacitors arranged with the conductive rotating body as a reference and a position detection signal of the rotating body is obtained, another variable capacitor is used. It is possible to achieve highly accurate position detection that is not interfered with. Further, since the rotating body is not processed at all, it is most suitable for detecting the position of the rotating body rotating at an ultrahigh speed.

According to the rotating body position detecting device of the fourth aspect, the capacitance as a whole can be increased by the cooperation of the plurality of variable capacitors, the spatial resolution can be improved, and the position detecting can be performed with high sensitivity. Can be achieved.

[0014]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 7 is an electric circuit diagram showing an application example of the position detecting device of the present invention, in which a high-frequency voltage from the high-frequency oscillator 1 is passed through a buffer circuit 7 to a matching circuit 2 including resistors and a coaxial cable of a predetermined length. Three
Is applied to each of the pair of variable capacitors 4 in series. Then, the voltage at the connection point between each matching circuit 2 and the coaxial cable 3 is taken out through the matching circuit 5 and supplied to the detector 6. Here, both detectors 6 detect the opposite phases of each other, and adder 8
Thus, both detection signals are added to obtain a position detection signal. still,
The variable-capacitance capacitor 4 is configured by arranging one of the electrodes facing each other with a rotating body and disposing the other electrode so as to be close to the rotating body. Therefore, the capacity changes due to the displacement of the position of the rotating body. The oscillation frequency of the high frequency oscillator 1 is set to a sufficiently high frequency so that the impedance can be sufficiently reduced even if the capacitance of the variable capacitor 4 is extremely small.

The operation of the above electric circuit is as follows. When a high-frequency voltage is applied to the coaxial cable 3 having the variable capacitor 4 as a load connected to the end through the matching circuit 2, a standing wave voltage is generated in the coaxial cable 3. Then, when the capacitance of the variable capacitor 4 changes due to the positional displacement of the rotating body, the phase of the standing wave voltage changes within a quarter wavelength range. Therefore, if the extraction position of the standing wave voltage is determined in advance, the value of the extracted standing wave voltage changes according to the phase change. The value of this standing wave voltage is taken out through the matching circuit 5,
By detecting with the detector 6, an impedance of the variable capacitor 4, that is, a position detection signal indicating the relative position of the rotating body can be obtained.

Although the length of the coaxial cable 3 can be freely set, the variable capacitor 4 can be set based on the upper and lower limits of the positional displacement limit amount of the rotor which is allowed in the magnetic bearing or the like. Since the variable capacity range is predetermined, the rotation by the coaxial cable 3 (rotation on the Smith chart) should be performed so that the value of the standing wave voltage changes the most corresponding to the variable capacity range. The detection sensitivity can be improved by changing the length of the cable 3.

Further, since each standing wave voltage is detected and added in opposite phases, only one detection output is:
Even if there is almost no linearity with respect to the positional displacement of the rotating body, a considerably high linearity can be provided by adding both detection signals to obtain the difference. FIG. 1A is a schematic cross-sectional view showing a main part of an embodiment of the position detecting device of the present invention, in which a protruding portion 92 is formed at a predetermined position of a rotating body 91 and the rotating body 91 is sandwiched between them. It is arranged that both electrodes 93 arranged in step 3 do not face the protrusion 92 at the same time. Incidentally, FIG.
As shown in (B), when the electrodes are arranged at positions separated from each other in the axial direction of the rotating body 91, two or more electrodes 93 including these electrodes and the protrusion 92 and the positive electrode are formed at the same time. Try not to. Further, the protrusion distance of the protrusion 92 is set to a distance sufficiently smaller than the maximum distance between the electrode 93 and the protrusion 92 within the positional displacement allowable limit of the rotating body 91.

In this case, the capacitance has a capacitance that can be detected only when the protrusion 92 and the electrode 93 face each other, and in other cases, the capacitance becomes substantially zero, so that all the capacitances can be obtained. Despite sharing one electrode of the variable capacitor 4, interference between the variable capacitors 4 can be eliminated. For example, by applying the electric circuit of FIG.
The position of can be detected with high accuracy.

Of course, instead of forming the projection 92, it is also possible to form a recess that can achieve the same effect.

[0020]

[Embodiment 2] FIGS. 2A and 2B are schematic vertical sectional views showing the main part of another embodiment of the position detecting device of the present invention, in which a large number of protrusions are formed on the outer periphery of the rotating body 91 at predetermined intervals. The portion 92 is formed and two pairs of variable capacitance capacitor groups 4g are arranged. Each variable capacitor group 4g has three electrodes 93 whose relative positions are set so as to face the protruding portion 92 at the same time or not to face the protruding portion 92 at the same time.
The three electrodes 93 are connected in parallel with each other. Further, the pitch between the variable capacitor groups 4g is, for example, the protrusion 9
It is set to be larger or smaller by 1/4 of the pitch between the protrusions 92 with reference to an integral multiple of the pitch between the two. Note that FIG. 2 (A) shows only a component part for detecting a position in one direction, and FIG. 2 (B) shows only a component part for detecting a position in a direction orthogonal to the position detecting direction in FIG. 2 (A). Is shown.

In the case of this embodiment, the electrostatic capacity of one variable capacitor group 4g is three times as large as the electrostatic capacity of the variable capacitor alone, so that the spatial resolution of the position detection signal can be improved and, in turn, the position. The detection accuracy can be improved. However, it is preferable to arrange the three electrodes 93 so as to be located on the extension lines of the corresponding projecting portions 92 in the facing state.
In addition, it is possible to increase or decrease the number of electrodes 93 that configure the variable capacitance capacitor group 4g, and it is possible to set a pitch different from the above.

[0022]

[Embodiment 3] FIG. 3 is a schematic vertical sectional view showing a main part of still another embodiment of the position detecting apparatus of the present invention.
Are electrically separated from each other in the axial direction to form the rotor component parts 91a, 9a.
1b, 91c, and 91d are formed, and the electrodes 93 of the respective variable capacitors 4 are arranged corresponding to the respective rotary body constituent parts.

In this case, the variable capacitors 4 can be completely separated, and the interference between the variable capacitors 4 can be eliminated. Therefore, for example, the position of the rotating body 91 can be detected with high accuracy by applying the electric circuit shown in FIG.

[0024]

[Fourth Embodiment] FIG. 4 is a schematic vertical cross-sectional view showing a main part of still another embodiment of the position detecting device of the present invention, and FIG. 5 is a side view of the same main part as above, which surrounds an electrode 93 of a variable capacitor 4. In this state, the auxiliary electrode 94 having a large area is arranged in a close state, and the auxiliary electrode 94 is grounded. The arrow in FIG. 4 corresponds to the arrow in FIG.

In this case, the auxiliary electrode 94 and the rotating body 91
Since the electrostatic capacitance of the capacitor constituted by and becomes sufficiently large and the corresponding portion of the rotating body 91 is equivalently grounded, interference between the variable capacitors 4 can be eliminated. Therefore, for example, the position of the rotating body 91 can be detected with high accuracy by applying the electric circuit shown in FIG.
Further, this embodiment is most preferable when it is applied to the rotating body 91 that rotates at an extremely high speed, since it is not necessary to process the rotating body 91.

[0026]

[Embodiment 5] FIG. 6 is a schematic side view showing a main part of still another embodiment of the position detecting apparatus of the present invention. The difference from Embodiment 4 is that auxiliary electrodes 94 extend in parallel with each other. Instead of the pair of electrodes, an electrode having an opening having a diameter slightly larger than that of the electrode 93 is adopted, and the electrode 93 is located in the opening.

Therefore, in the case of this embodiment, it is possible to increase the equivalently grounded portion of the rotating body 91, and to extend in all directions at a position apart from the portion directly facing the electrode 93. An equivalent grounding state can be achieved, and interference between the variable capacitors 4 can be eliminated more reliably. In addition, even in the third to fifth embodiments,
As in the second embodiment, it is possible to configure the variable capacitance capacitor group 4g with a plurality of electrodes connected in parallel with each other. Of course, since the third to fifth embodiments do not have the projecting portion 92, each electrode 93 does not correspond to the projecting portion 92, but corresponds to the corresponding component of each embodiment. .

[0028]

As described above, according to the first aspect of the present invention, only the variable capacitors having a reduced distance have sufficient electrostatic capacity for position detection, and all other variable capacitors have electrostatic capacities. Is substantially 0, the interference between the variable capacitors can be prevented, and a highly accurate position detection can be achieved without interference with other variable capacitors.

According to the second aspect of the present invention, since all the variable capacitors are electrically separated from each other, the interference between the variable capacitors can be prevented, and the interference with the other variable capacitors is prevented. It has a unique effect of achieving highly accurate position detection. According to the invention of claim 3, the capacitance of the capacitor composed of the auxiliary electrode for grounding and the rotating body becomes remarkably large, and the corresponding portion of the rotating body can be grounded equivalently. With this, the variable capacitors are separated from each other, so that the interference between the variable capacitors can be prevented, and as a result, highly accurate position detection can be achieved without being interfered with other variable capacitors.

According to the fourth aspect of the present invention, since a plurality of variable capacitors that cooperate with each other constitute one variable capacitor group, it is possible to improve the spatial resolution of the position detection signal, which in turn results in highly sensitive position detection. Has the unique effect of achieving

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a main part of an embodiment of a position detecting device of the present invention.

FIG. 2 is a schematic vertical cross-sectional view showing the main parts of another embodiment of the position detecting device of the present invention.

FIG. 3 is a schematic vertical sectional view showing a main part of still another embodiment of the position detecting device of the present invention.

FIG. 4 is a schematic vertical sectional view showing a main part of still another embodiment of the position detecting device of the present invention.

FIG. 5 is a side view of the main part of the same.

FIG. 6 is a schematic side view showing a main part of still another embodiment of the position detecting device of the present invention.

FIG. 7 is an electric circuit diagram showing an application example of the position detecting device of the present invention.

[Explanation of symbols]

4, Variable Capacitor 4g Variable Capacitor Group 91 Rotating Body 91a, 91b, 91c, 91d Rotating Body Constituent Section 92 Projection 93 Other Electrode of Variable Capacitor 94 Auxiliary Electrode

Claims (4)

[Claims] 1. A conductive rotating body (91) and a plurality of electrodes (9) provided close to the surface of the rotating body (91).
3) and a plurality of variable capacitors (4) are formed, and a voltage is applied to the variable capacitors (4) to rotate the rotating body (9).
In the position detecting device for a rotating body, which detects a capacitance that changes following the position displacement of 1) and obtains a position detection signal of the rotating body (91), any one of the variable positions is set at a predetermined position of the rotating body (91). At least the distance between the capacitor (4) and the other electrode (93) of the other variable capacitor (4) should be smaller than the distance between the electrode (93) and the other electrode (93) of the variable capacitor (4). A position detecting device for a rotating body, wherein one protrusion (92) and / or a recess is formed. 2. A conductive rotating body (91) and a plurality of electrodes (9) provided close to the surface of the rotating body (91).
3) and a plurality of variable capacitors (4) are formed, and a voltage is applied to the variable capacitors (4) to rotate the rotating body (9).
In the position detecting device for a rotating body, which detects a capacitance that changes in accordance with the position displacement of 1) and obtains a position detection signal of the rotating body (91), a predetermined range in the axial direction of the rotating body (91) is mutually offset. It is composed of a plurality of rotary body constituent parts (91a) (91b) (91c) (91d) electrically insulated from other portions, and one electrode (93) is provided at a predetermined position facing one rotary body constituent part. ) Is arranged, the position detecting device for the rotating body. 3. A conductive rotating body (91) and a plurality of electrodes (9) provided close to the surface of the rotating body (91).
3) and a plurality of variable capacitors (4) are formed, and a voltage is applied to the variable capacitors (4) to rotate the rotating body (9).
In the position detecting device for a rotating body, which detects the capacitance that changes following the position displacement of 1) and obtains the position detection signal of the rotating body (91), each electrode (93) is brought close to the rotating body (91). A large area auxiliary electrode for earth (9
4) A position detecting device for a rotating body, which is surrounded by 4. A variable capacitance capacitor group (4g) that cooperates with a conductive rotating body (91) and a plurality of electrically connected adjacent electrodes (93). The position detecting device for a rotating body according to any one of claims 1 to 3.