JP3047099B2 - Position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional linear pulse motor (hereinafter, referred to as a "pulse motor") for moving a moving body on a plane.
It is called “two-dimensional LPM”. The present invention relates to a position detecting device for detecting the position of (1).

[0002]

2. Description of the Related Art An LPM (linear pulse motor) is a linear motor that linearly moves in a linear direction by a constant pitch (step amount) each time the excitation condition of a coil is changed by an input pulse signal. The principle of operation is the same as that of a rotary type pulse motor that rotates at a constant rotation angle in response to an input signal. Therefore, there is a similarity between the two characteristics, and when moving a moving body in the same manner as a rotary type pulse motor. Can be used for In the LPM, since the linear movement of the moving body can be obtained linearly, the LPM has a direct drive system without a movement conversion mechanism such as a belt and a chain, and can perform open control.

[0003] A two-dimensional LPM is constructed using such an LPM in an orthogonal coordinate system of the X-axis and the Y-axis, and is used on a two-dimensional plane, for example, for a precision positioning mechanism of a semiconductor processing apparatus. The two-dimensional LPM is represented by 2
The moving body can be moved in an arbitrary direction on a three-dimensional plane. This two-dimensional LPM has a fixed yoke (hereinafter, referred to as a yoke).
"Platen". ) And a moving element on the moving side. As shown in a plan view and a cross section in FIG. 20, one yoke on the fixed side is formed of a pure iron plate in which grooves are cut in a lattice shape. The groove of the fixed yoke, the interval between the grooves, and the depth of the groove are, for example, 0.5 mm.

[0004] The moving element on the other moving side has a permanent magnet and a yoke wound with a coil. And
The compressed air is sent between the movable element and the platen so that the movable element does not adhere to the platen, so that the movable element floats from the platen with a gap of about 20 μm. Further, as shown in FIG. 21, the mover has a permanent magnet PM, two cores EMA and a core EMB, and each core has four magnetic poles, two in each core. However, the winding direction is also reversed for each of the two magnetic poles, and coils a and b are connected in series to each of the two magnetic poles.

[0005] The two-dimensional LPM thus configured operates as follows. Since the operations on the X axis and the Y axis are the same, here, the LPM of one of the X axis and the Y axis is used.
Only the operation will be described. In the state of FIG. 21A, when an exciting current is applied to the coil a in one direction indicated by an arrow, the magnetic flux generated by the permanent magnet PM and the coil a
And a magnetic flux generated by adding the magnetic flux due to the magnetic field. In the magnetic pole 2, the magnetic flux from the coil a is subtracted from the magnetic flux from the permanent magnet PM, and the magnetic flux becomes zero. The magnetic flux from the magnetic poles 3 and 4 is balanced. Thereby, in the state of FIG. 21A, the position of the magnetic pole 1 becomes a stable position. This state is referred to as mode 1.

Next, in the state of FIG. 21B, when an exciting current is applied to the coil b in one direction of the arrow, the magnetic fluxes of the magnetic poles 1 and 2 are balanced. In the magnetic pole 3, the magnetic flux from the coil b is subtracted from the magnetic flux from the permanent magnet PM, and the magnetic flux becomes zero. The magnetic pole 4 generates a magnetic flux obtained by adding the magnetic flux of the permanent magnet PM and the magnetic flux of the coil b. Thereby, in the state of FIG. 21B, the position of the magnetic pole 4 becomes a stable position. This state is referred to as mode 2.

In the state shown in FIG. 21C, when an exciting current is applied to the coil a in the other direction of the arrow, the magnetic flux from the permanent magnet PM is subtracted from the magnetic flux from the permanent magnet PM to the magnetic pole 1 so that the magnetic flux becomes zero. become. The magnetic pole 2 has a permanent magnet P
A magnetic flux is generated by adding the magnetic flux of M and the magnetic flux of the coil a. The magnetic flux from the magnetic poles 3 and 4 is balanced. Thereby, in the state of FIG. 21C, the position of the magnetic pole 2 becomes a stable position. This state is referred to as mode 3.

Next, in the state of FIG. 21D, when the exciting current is applied to the coil b in the other direction of the arrow, the magnetic fluxes of the magnetic poles 1 and 2 are balanced. A magnetic flux is generated in the magnetic pole 3 by adding the magnetic flux generated by the permanent magnet PM and the magnetic flux generated by the coil b. In the magnetic pole 4, the magnetic flux from the coil b is subtracted from the magnetic flux from the permanent magnet PM, and the magnetic flux becomes zero. Thereby, the position of the magnetic pole 3 becomes a stable position in the state of FIG. 21D. This state is referred to as mode 4.

In this manner, the repetition of the modes 1 to 4 in FIGS. 21A to 21D adjusts the magnetic flux of the magnetic poles 1 to 4 with the magnetic flux of the permanent magnet, and changes the stable position of the moving element and the stator. That is, one cycle is completed in four modes (four steps), and the mover moves by the pitch P of the stator and returns to the original positional relationship. Therefore, the movement amount (step amount) per mode is P / 4. Here, only the operation by one-phase excitation in which the excitation current always flows to any one coil is shown, but the same applies to the operation by two-phase excitation.

[0010]

However, in the conventional two-dimensional LPM, a so-called out-of-synchronization of the moving element, which causes a difference between the feed amount by the control signal and the actual moving amount of the moving element, is detected.
In order to enhance the reliability of the system, a demand for a 1 mm pitch high-precision position feedback has been increased. Further, when the position of the moving element is detected by the reflection type optical sensor, there is a disadvantage that the platen is erroneously operated due to dirt or rust on the platen.
Further, in the high-frequency proximity switch, since the resolution is several mm or more, there is an inconvenience that it is not possible to discriminate the unevenness of the platen of 1 mm pitch. Further, in a sensor called a gear sensor for detecting unevenness of a gear, a pitch of the module 1 is limited to 3.14 mm, and a pitch of 1 mm cannot be detected. Further, even if a high-resolution sensor is developed, there is a disadvantage that the X-axis direction and the Y-axis direction cannot be distinguished.

The present invention has been made in view of the above points, and has as its object to provide a position detecting device which can discriminate the X-axis direction and the Y-axis direction individually with high resolution and has a sufficient response speed. .

[0012]

A position detecting device according to the present invention enables a moving body to move in an arbitrary direction on a two-dimensional plane by an X axis and a Y axis orthogonal to the X axis. Moving-side mover having a predetermined gap between the platen and a platen that is a fixed-side yoke and has a lattice-shaped groove, and a detection coil provided with a permanent magnet and a yoke wound with a coil. And 2 of the mover on the platen
A detection circuit for detecting a position on a two-dimensional plane, the position detection device detecting a position of a moving body due to movement of the moving element on the two-dimensional plane, wherein a high-frequency voltage is supplied to the detection coil. The detection circuit detects a change in voltage of the detection coil by detecting a change in inductance of the detection coil, and detects a detection direction of the detection coil.
The thickness of the yoke is thinner than the groove width of the platen.
It is intended to make it. Also, the position detection of the present invention
The device is provided with the yaw which is orthogonal to the detection direction of the detection coil.
Plate width should be an integral multiple of the platen groove pitch.
Those were Unishi.

According to the position detecting device of the present invention, the following operations are performed. When the detection coil detects the groove of the platen, the inductance changes due to the change in the magnetic resistance. The change in inductance is converted to a change in voltage by the detection circuit. This detection circuit supplies a high frequency voltage to a detection coil from a high frequency oscillator via a series resistor,
A change in the inductance of the detection coil is converted into a change in the detection voltage by a detection circuit.

When the detection coil moves on the platen in the detection direction, the signal waveform of each part in the detection circuit is as follows. The high-frequency voltage is a voltage supplied to the detection coil, and the detection voltage is a voltage obtained by detecting a positive voltage of the high-frequency voltage. Here, the threshold value is set at the center of the voltage amplitude, and compared with this threshold value for output,
A quantified pulse signal is obtained. By further counting this pulse signal by a counter, the moving distance of the detection coil can be obtained.

[0015]

The present embodiment will be described below. In the present embodiment, a detection element is provided on the above-described two-dimensional LPM mover, and the shape of the detection element is characterized by applying a high-frequency proximity switch technology.
High resolution that can discriminate the irregularities of the platen with mm pitch, and the X-axis direction and the Y-axis direction are individually discriminated to have directivity in the detection direction so that the irregularities in the perpendicular direction are not detected. Is obtained.

First, the basic configuration and operation principle of the position detecting device according to the present embodiment will be described. First, the shape of the detection element and the arrangement with respect to the platen will be described with reference to FIGS. 1 shows a front view of the detection element and the platen, FIG. 2 shows a side view of the detection element and the platen, and FIG. 3 shows a plan view of the detection element and the platen. The detecting element 1 has a substantially E-shaped plate-shaped magnetic core 2 of high magnetic permeability having a height h, a width d, and a thickness t, and a coil 3 wound around a central constricted portion. . A high-frequency current described later is applied to the coil 3 via terminals 4 and 5. The platen 6 has grooves formed in a lattice pattern at a pitch P, and the detection element 1 uses two-dimensional LPM so that the detection side end of the detection element 1 and the upper surface of the platen 6 have a predetermined gap G. It is configured to be movable in the detection direction. When detecting a position in a direction orthogonal to the detection direction illustrated in FIGS. 1 to 3, the detection element 1 is arranged by rotating the detection element 1 by 90 degrees with the height h direction as a rotation axis. I just need. In this case, for example, the height h of the detection element 1 is 5 mm, the width d is 4 mm, and the thickness t is 0.05 mm.
The pitch P of the platen 6 is 1, and the gap G between the detection element 1 and the platen 6 is 0.1.

When a high-frequency current is applied to the detecting element 1 (hereinafter, referred to as a “detecting coil”) configured as described above to approach the platen 6 via a predetermined gap G, a gap between the detecting coil 1 and the platen 6 is generated. The following two physical phenomena act on. The first physical phenomenon is an eddy current generated on the surface of the platen 6 by the magnetic flux generated from the detection coil 1.
Since this eddy current flows in a direction to cancel the magnetic flux generated from the detection coil 1, the magnetic resistance increases and the inductance of the coil decreases. The second physical phenomenon is a main operation principle of the position sensor using the detection coil 1 and is an operation relating to a magnetic circuit formed between the yoke of the core 2 of the detection coil 1 and the platen 6. If there is nothing around the sensing coil 1, the magnetic flux exits one end of the yoke and returns to the other end. If the path of this magnetic flux is represented by a magnetic circuit, it will be as shown in FIG. 4 below, and the magnetic flux of the coil will be as shown in Equation 1. Where Ф is the magnetic flux passing through the coil, N is the number of turns of the coil, I is the current flowing through the coil, Rr is the magnetic resistance of the yoke, _RA is the magnetic resistance of the path in the air, and NI is the voltage of the electric circuit. Is called the magnetomotive force.

[0018]

Ф = NI / (Rr + R _A )

In this case, the magnetic resistance R _A of the path in the air is large, and the magnetic resistance Rr of the yoke has a small value because the magnetic permeability of the yoke is large. (R _A >> Rr) Here, when the detection coil 1 is brought close to the platen 6, the magnetic circuit can be represented as shown in FIG. 5 below, and the magnetic flux of the coil 1 is represented by the following equation (2). Here, Ф ′ is a magnetic flux passing through the coil 1 when the platen 6 is near, R _A ′ is a magnetic resistance of a path in the air when the platen 6 is near, and _RG is a gap between the yoke of the detection coil 1 and the platen 6. Magnetoresistance, R _P is platen 6
Is the magnetoresistance.

[0020]

Ф ′ = NI / (Rr + _RA ′ + _RG + _RP )

In this case, if the gap G between the yoke of the detection coil 1 and the platen 6 shown in FIG. 5 is sufficiently small, the relationship between the equations (1) and (2) is as follows. In other words, the magnetic resistance R _P of the platen 6 for the material of the platen 6 is pure iron, like the magneto-resistance Rr of the yoke described above small. Further, since the platen 6 is interposed in the path of the magnetic flux, the path in the air is shortened, so that the following equations (3) and (4) are obtained.

[0022]

## EQU3 ## _RA > _RA '+ _RG + _RP

[0023]

数 <Ф ’

The relationship between the inductance L of the coil, the magnetic flux 通 る passing through the coil, and the current i of the coil is given by the following equation (5).
It looks like an expression.

[0025]

L = N (dФ / di)

That is, when the detection coil 1 approaches the platen 6, the magnetic flux の of the coil increases, and the inductance L of the coil increases. The two effects acting between the detection coil 1 and the platen 6, that is, the decrease in inductance due to the eddy current and the increase in inductance due to the decrease in the magnetic resistance are in a contradictory relationship. Therefore, in the position sensor of the position detection device according to the present embodiment, the oscillation frequency is set appropriately (for example, lower) in order to reduce the effect of the eddy current.

As described above, the shape of the yoke of the detection coil 1 is an important factor in reading the fine grooves of the platen 6 and providing directivity in the detection direction. The values of the plate thickness t and the width d are important in the shape of the detection coil 1 shown in FIGS. First, the thickness t of the detection coil 1 needs to be sufficiently smaller than the groove width (0.5 mm) in order to discriminate the groove of the platen 6. In the position sensor of the position detection device according to the present embodiment, the width is 0.05 mm, which is 1/10 of the groove width. When the detection coil 1 is moved in the detection direction indicated by the arrow in the side view of FIG. 2, the magnetic resistance changes at the peaks and valleys of the groove, and the amount of movement can be read based on the change in the magnetic resistance.

Next, consider the case where the detection coil 1 moves in a direction perpendicular to the detection direction. In the front view of FIG. 1, the magnetic resistance between the yoke of the detection coil 1 and the platen 6 is the total (parallel connection) of the magnetic resistance of each peak and valley within the range of the yoke width d. In order to prevent the magnetic resistance from changing when the detection coil 1 moves left and right in the figure, the width d of the yoke is set to the period of the peak and valley of the platen 6 (pitch P ). Here, n is an integer of 0, 1, 2,..., D is the width of the yoke, and P is the width pitch of the platen.

[0029]

D = (1 + n) P

Further, the larger the value of n, the smaller the fluctuation due to the pitch error. In the position sensor of the position detecting device according to the present embodiment, the width d of the yoke was set to four times the groove pitch (n = 3). Also, as mentioned above,
In the magnetic circuit shown in FIG. 5, the magnetic resistance R _A ′ of the path in the air
Is considerably large with respect to the _RG between the yoke and the platen 6, so that it is not possible to efficiently detect the change in the _RG . Therefore, as shown in FIG. 6, the detection sensitivity can be further improved by making the yoke and the platen 6 magnetically dense by forming an efficient yoke shape. In this case, as shown in FIG. 6, a plurality of detection ends facing the platen 6 of the substantially U-shaped core 8 of the detection coil 7 are provided in the detection direction, and a width d between the detection ends is provided.
The coil 9 is wound around the constricted part of 2 so that n = 0, 1, 2,.
.., P = the groove pitch of the platen 6, and the width d1 of each detection end may be (1 + n) P, d2 = arbitrary.

Next, the basic principle of the configuration and operation of the detection circuit will be described. As shown in FIG. 7, the detection circuit includes a high-frequency oscillator OSC1 for generating a high-frequency current, a detection coil L1, a series resistor _R1 for detecting the high-frequency voltage VR1, and a diode D constituting the detection circuit 10.
1, a capacitor C1, and a resistor _R2 for detecting a detection voltage _VR2 .

The detection circuit 10 thus configured operates as follows. As described above, the detection coil L
When 1 detects a groove in the platen 6, the inductance changes due to a change in its magnetic resistance. The change in inductance is converted into a change in voltage by the detection circuit of FIG. This detection circuit supplies a high-frequency voltage V _R1 from a high-frequency oscillator OSC1 to a detection coil L1 via a series resistor R1, and converts a change in inductance of the detection coil L1 into a change in the detection voltage V _R2 by a detection circuit. ing.

FIGS. 8 and 9 show that the detection coil L1 is
8 is a signal waveform of each part in the detection circuit of FIG. In FIG. 8, the high-frequency voltage V _R1
Is a voltage supplied to the detection coil L1, and in FIG. 9, a detection voltage V _R2 is a voltage detected by detecting a voltage in the plus direction of the high frequency voltage V _R1 . Here, the threshold value V _TH is set at the center of the voltage amplitude, and is input to, for example, a comparator circuit (not shown), whereby a binarized pulse signal is obtained. The pulse signal is further counted by a counter (not shown), whereby the moving distance of the detection coil L1 can be obtained.

The operation principle of the detection circuit has been described above.
The configuration and operation of a practical detection circuit will be described below. The detection voltage V _R2 shown in FIG. 9 fluctuates due to the gap between the detection coil and the platen, and changes in the frequency and amplitude of the high-frequency oscillator OSC1. Therefore, when the threshold value V _{TH of} the comparator is a fixed value, the operating environment is more restricted, and a more practical detection circuit is required. Therefore, in order to satisfy such a demand, a detection coil and two detection circuits shown in FIG. 7 are provided, and a detection circuit that combines their outputs differentially has been developed.

First, the arrangement of the detection coils will be described with reference to FIG. Two detection coils 11 (L1, L2)
Are arranged so that the respective inductance changes are in opposite phases (180 degrees phase). The arrangement pitch Q of the detection coils 11 is such that P is the groove pitch of the platen 6, and n = 0, 1,.
Then, the following formula is obtained.

[0036]

[Mathematical formula-see original document] Q = (1/2) (1 + 2n) P

In the position sensor of the position detecting device according to the present embodiment, n = 1, Q = (3/2) P, and the two detection coils are arranged so as to have opposite phases.

Next, a differential detection circuit will be described with reference to FIG.
explain. This differential detection circuit, as shown in FIG.
A high-frequency oscillator OSC1 for generating a high-frequency current;
, A series resistor R1, a detection coil L2,
A first resistor for detecting the voltage of the column resistor R1 and the detection coil L1
And the second detection circuit for detecting the voltage of the detection coil L2.
2 detection circuit 13 and the detection output V of the first detection circuit 12
_D1And the detection output V of the second detection circuit 13_D2Output the difference with
And the differential output V of the differential circuit 14 _DEFIncrease
Width of the amplifier 15 and the amplified output V of the amplifier 15_AToshiki
High value V_THAnd the detection output V_OComparing to output
Data 16. Note that the first detection circuit 12 and
The configuration of the second detection circuit 13 is the same as that shown in FIG.
Therefore, the description is omitted.

The operation of the practical detection circuit configured as described above will be described below. The detection output V _D1 of the detection coil L1 has an amplitude voltage waveform centered on a predetermined positive potential as shown in FIG. 12A. Detection output V _D2 by the detection coil L2 is centered the same predetermined positive potential and the detection output V _D1 as shown in FIG. 12B, the amplitude voltage waveform of the detection output V _D1 and opposite phase. The voltage of the difference between the detection output V _D1 and the detection output V _D2 becomes the differential output V _DEF shown in FIG. 12C. The differential output is amplified in the amplifier output V _A, the detection output V _O is compared with a threshold value V _TH.

Here, the center voltage (offset voltage) of the amplitude of the detection output V _D1 and the detection output V _D2 changes according to the following operating conditions. First, the air gap between the detection coils L1, L2 and the platen, second, the magnetic characteristics of the platen, third, the frequency of the oscillation circuit, and fourth, the output amplitude of the oscillation circuit.

The detection output that can be represented by these condition changes
Voltage V_D1And V_D2Are the same absolute value and opposite direction
The differential output voltage V_DEFCenter voltage is always zero
Is kept. Here, the threshold value V of the comparator 16_TH
By setting to zero, changes in the operating conditions described above
Detection output pulse V without being affected by _O
Can be obtained.

FIG. 13 shows an actually measured waveform of the amplified output _VA which is the output of the amplifier 15 in this case. Here, the gain of the amplifier 15 is 10 times, the gap between the detection coils L1 and L2 and the platen 6 is 0.05 mm, and the amplitude of the oscillator is 5 times.
When V _PP (peak-to-peak), the detection coil L
1 shows waveforms when the user slides the platen 6 in the detection direction while holding the L1 (head) by hand.

On the premise of the above-described detection coil and detection circuit, the configuration and operation when used in a linear encoder (linear scale) as a position detection device actually mounted on a head driven by a two-dimensional LPM explain. The detection coil shown in FIG. 10 and the differential detection circuit shown in FIG. 11 can measure the moving distance of the moving body, but cannot measure the moving direction. Therefore, as shown in FIG.
For (L1, L2, L3, L4), two sets of detection coils shown in FIG. 10 are provided in order to discriminate the moving direction, and the respective phase differences are arranged at 90 degrees (1 / 4.P). To Here, n = 0, 1, 2,...
When the pitch of the groove is given by, the interval d between the respective detection coils 17 can be expressed by the following equation (8).

[0044]

D = (1/4) (1 + 2n) P

Next, as shown in FIG. 15, the encoder output circuit combines the voltage change of one pair of the detection coils L1 and L2 by the differential detection circuit A18 and outputs the voltage change of one pair of the detection coils L3 and L4. In the differential detection circuit B19. Here, the configuration and operation of the differential detection circuit A18 and the differential detection circuit B19 correspond to those shown in FIG. The encoder output circuit thus configured includes a differential detection circuit A18 and a differential detection circuit B1.
9, an A-phase output and a B-phase output are obtained. FIG. 16 shows the waveforms of the A-phase output and the B-phase output obtained from the differential detection circuits A18 and B19. FIG.
6, the A-phase output and the B-phase output each have a (1/4) · P phase difference (the A-phase output is ahead of the B-phase output) with the pitch P of the groove of the platen 6 as one cycle. Become. When the moving direction of the moving body is reversed at the position indicated by the one-dot chain line, the phases of the A-phase output and the B-phase output are reversed, and the A-phase output has a waveform with a delayed phase with respect to the B-phase output. In this way, an encoder output capable of distinguishing the moving direction can be obtained.

The above description of FIGS. 14 to 16 has been described with respect to one axis of the two-dimensional plane, but the moving distance of the moving body on the two-dimensional plane is separately measured for the X-axis component and the Y-axis component. 17, the detection coils 20 and 21 shown in FIG. 14 may be arranged so as to have an angle of 90 degrees on a two-dimensional plane as shown in FIG. 17.

In order to obtain a higher resolution encoder output, the following configuration may be adopted. The resolution of the encoder circuit shown in FIGS.
/ 4) · P (= 0.25 mm). Where LPM
With the step pitch, a considerably high resolution can be obtained by performing micro-step driving. Therefore, the possibility of high resolution in the linear encoder as the position detecting device of the present embodiment will be examined.

As shown in FIG. 18, the outputs of the A-phase and B-phase amplifiers 25 and 29 are different from the differential detection circuits A18 and B19 shown in FIG. 15 except for the final stage comparator 16 shown in FIG. A higher resolution may be supplied to the interpolation circuit 30. Here, the outputs of the A-phase and B-phase amplifiers 25 and 29 are, as shown in FIG.
Since it is a sine or cosine trigonometric function,
The interpolation (high resolution) by the interpolation circuit 30 can be performed. The interpolation circuit 30 can be configured, for example, as shown in FIG. The interpolation circuit 30 is described in the specification of Japanese Patent Application No. 64-49914. The interpolation circuit 30 amplifies the signal A and the signal B having different phases from the signal source by the amplification circuits 31 and 33, and then supplies the signals to the A / D conversion circuits 32 and. The A / D conversion circuits 32 and 34 convert the supplied analog signals into digital signals and supply the digital signals to storage means such as the ROM 35. The storage means such as the ROM 35 stores the interpolated angle data, uses the digital signals from the A / D conversion circuits 32 and 34 as addresses, and outputs angle data corresponding to the addresses. The angle data output from the storage means such as the ROM 35 is supplied to the processing circuit 36, where the signal is processed.

Here, the relationship between the addresses and storage contents of the A / D conversion circuits 32 and 34 and the storage means such as the ROM 35 will be described. The horizontal axis is an address in the X direction, and the vertical axis is an address in the Y direction, and each address is an A / D conversion circuit 32, 34.
Corresponding to the values of the sine and cosine waves converted into digital signals. For example, when each address is represented by 8 bits, the value of each axis is 25 from 0 to 255.
The storage contents are stored at the positions corresponding to each grid constituted by six addresses. Such stored contents are obtained in advance as follows. Here, angle data corresponding to the address when one cycle of the detection signal is divided into a plurality of periods is obtained as interpolation data corresponding to the phase of the signal. As another method, for example, A
Even without using the / D conversion circuits 32 and 34 and the ROM 35,
From the A-phase sine wave signal and the B-phase cosine wave signal, an inverse A-phase signal having a phase angle of 180 degrees with the A-phase sine wave signal is obtained. And
A phase having phase angles of 0 degree, 90 degrees, and 180 degrees, respectively.
An intermediate phase angle signal is created by weighting and adding the three-phase signals of the B phase and the inverse A phase. A pulse signal may be generated by detecting a zero cross of the sine wave thus formed. As another method, a weighted addition method by resistance division may be used. By multi-decomposition in this way, the number of divisions can be increased in principle, and a high-resolution output can be obtained.

Here, the resolution and position accuracy by interpolation are limited by the function accuracy of the trigonometric function, but it has been experimentally confirmed that if the gap between the detection coil and the platen is considerably reduced, the waveform distortion increases. Therefore, by providing a restriction on the effective range of the gap, a detection signal without waveform distortion can be obtained.

As described above, the position detecting device of the present embodiment has the following features. First, the detection coil has the following three points. First, in order to increase the resolution, the thickness of the yoke of the detection coil must be sufficiently smaller than the groove width of the platen. Second, in order to provide directivity in the detection direction, the width of the yoke plate of the detection coil should be an integral multiple of the groove pitch of the platen. Third, the peaks and valleys of the groove of the platen are captured as a change in magnetic resistance between the yoke of the detection coil and the platen, and converted into a change in inductance of the detection coil.

Next, the detection circuit has the following three points. First, a voltage is supplied to the detection coil from a high-frequency oscillation circuit via a series resistor, and a change in inductance of the detection coil is extracted as a voltage change by a detection circuit.
Second, the two detection coils are connected to the platen peak and valley positions (18).
(A phase difference of 0 degrees), and the difference between the two detection output voltages is used as a detection signal, thereby eliminating the effects of changes in the gap between the detection coil and the platen, the oscillation frequency, and the like.
Third, to increase the resolution by interpolating the detection signal.

[0053]

According to the position detecting device of the present invention, a movable body can be moved in an arbitrary direction on a two-dimensional plane by an X axis and a Y axis orthogonal to the X axis. A movable side moving element having a predetermined gap between the platen and a platen having a lattice-shaped groove, a detection coil provided with a permanent magnet and a yoke wound with a coil, and A detection circuit for detecting the position of the child on the two-dimensional plane on the platen, and detecting the position of the moving body due to the movement of the moving element on the two-dimensional plane on the platen; A high-frequency voltage is supplied to the coil, and the detection circuit detects a change in inductance of the detection coil to take out the change as a voltage change .
The plate thickness should be thinner than the platen groove width.
Application of conventional high-frequency proximity switch detection circuit
High-resolution position detection with a simple configuration
X and Y directions can be individually discriminated,
The position can be detected with a sufficient response speed, and the detection direction can be detected.
The thickness of the output coil does not interfere with the detection
There is an effect that detection can be performed.

Further, in the position detecting device according to the present invention, the yoke orthogonal to the detecting direction of the detecting coil is provided.
Plate width should be an integral multiple of the platen groove pitch.
Therefore, there is an effect that directivity can be provided in the detection direction .

[0055]

[0056]

[0057]

[0058]

[Brief description of the drawings]

FIG. 1 is a front view showing a basic shape and an arrangement of a detection coil according to an embodiment of the present invention.

FIG. 2 is a side view showing a basic shape and an arrangement of a detection coil according to the embodiment of the present invention.

FIG. 3 is a plan view showing a basic shape and an arrangement of a detection coil according to the embodiment of the present invention.

FIG. 4 is a diagram showing a magnetic circuit based on the operation principle of the detection coil according to the embodiment of the present invention.

FIG. 5 is a diagram showing a magnetic circuit in consideration of a path in the air as an operation principle of the detection coil according to the embodiment of the present invention.

FIG. 6 is a diagram showing a yoke shape of an efficient detection coil according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating a detection circuit according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating signal waveforms of the detection circuit according to the embodiment of the present invention.

FIG. 9 is a diagram showing signal waveforms of the detection circuit according to the embodiment of the present invention.

FIG. 10 is a diagram showing a practical arrangement of detection coils according to the embodiment of the present invention.

FIG. 11 is a diagram illustrating a differential detection circuit according to an embodiment of the present invention.

FIG. 12 shows a signal wave of the differential detection circuit according to the embodiment of the present invention.
FIG. 12A is a view showing a shape, and FIG. _D1And FIG._D2,
FIG. 12C shows V_DEFIs shown.

FIG. 13 is a diagram showing a detection signal waveform of an amplifier output voltage of the differential detection circuit according to the embodiment of the present invention.

FIG. 14 is a diagram showing an arrangement of detection coils for two-phase output according to the embodiment of the present invention.

FIG. 15 is a diagram showing an encoder output circuit for two-phase output according to the embodiment of the present invention.

FIG. 16 is a diagram showing a two-phase output signal waveform according to the embodiment of the present invention.

FIG. 17 is a diagram showing an arrangement of a detection coil as a two-dimensional sensor according to the embodiment of the present invention.

FIG. 18 is a diagram illustrating a high-resolution encoder output circuit according to an embodiment of the present invention.

FIG. 19 is a diagram illustrating a configuration of an interpolation circuit according to an embodiment of the present invention.

FIG. 20 is a view showing a structure of a fixed side yoke (platen) of a conventional two-dimensional LPM.

21A and 21B are diagrams showing the operation principle of a conventional two-dimensional LPM, wherein FIG. 21A is a mode 1, FIG. 21B is a mode 2, FIG.
C shows mode 3, and FIG. 21D shows mode 4.

[Explanation of symbols]

1 detection element, 2 cores, 3 coils, 4, 5 terminals,
6 platen, d width, h height, P pitch, G gap, t thickness, 7 detection coil, 8 core, 9 coil, d1 width, 10 detection circuit, OSC1 high frequency oscillator, L1 detection coil, R1 series resistor, 11 (L
1, L2) detection coil, 12, 13 detection circuit, 14
Differential circuit, 15 amplifier, 16 comparator, 17
(L1, L2, L3, L4) Detection coil, 18 differential detection circuit A, 19 differential detection circuit B, 20, 21 detection coil, 22, 23, 24, 26, 27 detection circuit, 2
4, 28 differential circuit, 25, 29 amplifier, 30 interpolation circuit, 31, 33 amplifier circuit, 32, 34 A / D conversion circuit, 35 ROM, 36 processing circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B ⁷ /00-7/34 G01D 5/12 G01D 5/245 101 H02P 5/00 101

Claims (2)

(57) [Claims] 1. A fixed-side yoke having a lattice-shaped groove, wherein a movable body can be moved in an arbitrary direction on a two-dimensional plane by an X axis and a Y axis orthogonal to the X axis. Platen,
A moving element having a predetermined gap between the platen and a moving coil having a detection coil provided with a permanent magnet and a yoke wound with a coil, and a moving element on a two-dimensional plane on the platen. A detection circuit for detecting a position, wherein the position detection device detects a position of a moving body due to movement of the moving element on a two-dimensional plane on the platen, and supplies a high-frequency voltage to the detection coil; is to take out as a change in voltage by detecting the inductance change of the detection coil, the thickness of the detection direction of the yoke of the detection coil, the
A position detecting device characterized in that it is made thinner with respect to a groove width of a platen . 2. An X-axis and a Y-axis orthogonal to the X-axis.
A mobile object in any direction on a two-dimensional plane
A platen , which is a fixed-side yoke and has a lattice-like groove,
Detection coil with permanent magnet and yoke wound coil
Having a predetermined gap between the platen and the platen.
Moving side moving element and two-dimensional moving element on the platen
A detection circuit for detecting a position on a plane, wherein the moving element moves on a two-dimensional plane on the platen.
In a position detection device that detects a position of a moving body , a high-frequency voltage is supplied to the detection coil, and the detection circuit includes:
To detect the change in inductance of the detection coil
The width of the yoke is perpendicular to the detection direction of the detection coil so as to be taken out as a voltage change.
Is a position detecting device wherein the pitch is an integral multiple of the groove pitch of the platen .