JPH04157315A - Detecting apparatus of linear position - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy by providing a coil part within one pitch of a scale of a scale part. CONSTITUTION:A position detector 11 comprise a coil assembly accommodated in a bobbin 13 and a rod 12 inserted in the bobbin 13 in a movable way in the straight direction. A part 15 of magnetic substance and a part 16 of nonmagnetic substance are alternately arranged in a magnetic scale part 17. A coil part constituting the coil assembly is provided within one pitch of the scale part 17. The coil assembly is constituted of primary coils 1A-1D and secondary coils 1a-1d wound around the grooves of the bobbin 13. The reluctance of a magnetic circuit in each coil is periodically changed with a pitch P as one cycle in accordance with the linear displacement of the rod 12. The phase of the reluctance can be shifted 90 deg. (pi/2) for every coil. Since the phase thetaof the change of the reluctance is proportional to the linear position of the magnetic part 15 according to a predetermined function of proportion, if the phase shift of an output, signal from a reference signal is measured, the linear position can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a linear position detection device that utilizes changes in magnetic resistance, and particularly to a linear position detection device that detects changes in magnetic resistance as changes in the electrical phase angle of an output AC signal. This invention relates to a shift type linear position detection device.

[Prior Art] A differential transformer has been well known as a linear position detection device that utilizes changes in magnetic resistance.

Since this converts a linear position into a voltage level, it has the disadvantage that it is easily affected by external disturbances and causes errors.For example, the resistance of the coil changes due to the influence of temperature changes, which causes The signal level fluctuates,
Another disadvantage is that the level attenuation in the signal transmission path from the detector to the circuit that uses the detection signal varies depending on the transmission distance, and level fluctuations due to noise directly manifest as detection errors. have.

Therefore, the applicant of the present invention has previously proposed a phase shift type linear position detection device that can accurately detect the linear position without being affected by output level fluctuations due to disturbances, etc. Publication No. 57-135917, Utility Model No. 1983
Publication No. 8-136718 or Utility Model Application Publication No. 1983-175105
Publications, etc.).

This phase shift type linear position detection device will be described below with reference to FIG. 6.

The position detector 61 detects a linear position using a phase shift method, and is composed of a coil assembly housed in a bobbin 63 and a rod 62 inserted into the bobbin 63 so as to be movable linearly.

The rod 62 includes a plurality of cores 65 provided at predetermined intervals in the axial direction, a non-magnetic spacer 66 provided between each core 65, and a sleeve 67 surrounding the cores 65 and spacers 66. It consists of The core 65 and the spacer 66 are repeatedly provided at a predetermined pitch P, and for example, the length in the axial direction of each is P/2 (P is an arbitrary value), and constitute a magnetic scale of 1 pitch P. .

The coil assembly consists of four coils wound around each groove of a resin bobbin 63 formed at predetermined intervals in the axial direction of the rod 62.
primary coils A, B, C, and D, and corresponding secondary coils a, b, and c.

It consists of d. The bobbin 63 is housed in a cylindrical case 64 made of a magnetic material such as iron.

Depending on the relative positional relationship of the core 65 with respect to each of the primary coils A, B, C, and D, magnetic resistance of different magnitude is generated in each coil. This is because the center of primary coil B is shifted to the right by rp(n-1/4) with respect to primary coil A, and the center of primary coil C is shifted to the right with respect to primary coil A by rp(n-1/4).
It is shifted to the right by (n −2/4) J,
The center of the primary coil D is r P (
This is because it is shifted to the right by J. Here, n is any natural number.

The magnetic scale section consisting of a repeating core 65 and spacer 66 can be dimensioned and shaped so that the magnetic resistance produced in the magnetic circuit of the coil varies trigonometrically. Here, if the repetition pitch "P" of the core 65 is 2π in phase angle, the axial length ['/4J corresponds to π/2 in phase angle. Therefore, the primary coil A whose center is located at the center of the spacer 66 as shown in FIG.
Assuming that the magnitude of the magnetic resistance generated in the primary coils B, C,
The thickness of each magnetic resistance generated in D is αcosθ,
It changes at a rate of -αsinθ and -αCosθ.

The position detector 71 shown in FIG. 7 has the same configuration as that in FIG. 6 except that the configuration of the coil assembly is different. 7th
The position detector 71 shown in the figure is different from the one shown in FIG. 6 in the primary coil A and the primary coil C.

The primary coil B and the primary coil D are each "P(n-2
/4) The points are located adjacent to each other with an interval of J.

In order to obtain an output signal by the phase shift method using a position detector such as that shown in FIGS. 6 and 7, primary coils A and C, whose magnetic resistance changes are in opposite phases, are connected to a common primary AC signal ( For example, the secondary coil a is excited by a sine wave signal).
, Q to obtain a differential output. Similarly, the primary coils B and D, whose magnetoresistance changes are in opposite phases, are also excited by a common primary alternating current signal (for example, a cosine wave signal) to obtain differential outputs from the secondary coils b and d. As a result, each secondary coil a, Q.

From b and d, the electrical angle of the primary AC signal is calculated by the phase angle θ corresponding to the linear position (linear displacement 'I & within 1 pitch) of the core 65 (75) as a signal obtained by adding and combining each differential output signal. A phase-shifted secondary signal output is obtained.

[Problem to be solved by the invention]

In the linear position detectors shown in FIGS. 6 and 7, each core 65 (75) of the rod 62 (72) is machined into a predetermined shape and completely identical, and each spacer 66 (76) is also made into the same size. When the resistance and inductance values of each coil of the coil assembly are completely the same, theoretically, position detection without detection errors can be performed.

However, when a position detector like the one shown in FIG. 6 or 7 is actually manufactured, manufacturing errors may occur.

Each core does not have completely the same shape and dimensions, but has a slightly irregular shape, and the spacing between the spacers also varies, causing variations in the magnetic resistance changes that occur for each coil. Further, the resistance value and inductance value of each of the primary and secondary coils are not completely the same, but have different values. The error caused by the difference in the shape of the magnetic scale part in the rod 62 (72) is called the rod error (
or scale error), and the error caused by differences in coil characteristics is called head error.

When the length in the axial direction of the coil assembly is set in the range of 2 to 3 times the pitch P (2P to 3P) as in the position detector shown in Figs. There are four cores, and the combinations of cores 65 (75) that cause magnetic resistance changes in each of the primary coils A, B, C, and D are different for each coil.

Therefore, in the case of the position detectors shown in Figs. 6 and 7, the magnetic resistance changes occurring in the respective primary coils A, B, C, and D vary due to the influence of the rod error, resulting in poor position detection accuracy. This will have a large error.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a linear position detecting device that can suppress rod errors caused by differences in the shapes of the rods constituting the position detecting device.

[Means to solve the problem]

The linear position detection device of the present invention includes a coil portion having at least a primary coil excited by a predetermined alternating current signal, and a coil portion configured to be linearly displaceable relative to the coil portion.
A magnetic scale section provided along the linear displacement direction and a relative position between the magnetic scale section and the coil section so that the magnetic resistance in the magnetic circuit of the coil section changes with this linear displacement. position detection accuracy for extracting data indicating the position of the magnetic scale part from the coil part based on a change in magnetic resistance of the magnetic circuit of the coil part caused by the relationship, It is characterized by being provided within the pitch.

[Effect]

Since the coil part of the present invention is provided within one pitch of the scale of the scale part, there is one position where only one scale of the magnetic scale part, which is involved in changes in magnetic resistance, exists for the coil part. The detection circuit extracts data indicating the position of the magnetic scale based on the change in magnetic resistance of the magnetic circuit of the coil section caused by the relative positional relationship between one scale of the magnetic scale section and the coil section. Therefore, even if there is a manufacturing error in the magnetic scale part and the shape etc. of the magnetic scale part are not completely the same, the linear position detection device of the present invention is accurate for one scale existing in the coil part. It becomes possible to detect the position, and the detection accuracy can be greatly improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention.

The position detector 11 detects a linear position using a phase shift method, and is composed of a coil assembly housed in a bobbin 13 and a rod 12 inserted into the bobbin 13 so as to be movable linearly. The features of the embodiment are as follows:
Power is distributed to the coil parts constituting the coil assembly within an interval rPJ corresponding to one pitch in the alternate arrangement of the magnetic material parts 15 and the non-magnetic material parts 16.

The rod 12 is provided with a magnetic scale part 17 around the circumference thereof, which is made up of magnetic parts 15 and ring-shaped non-magnetic parts 16 of a predetermined width provided alternately in the axial direction around the rod 12 . The magnetic material portion 15 and the non-magnetic material portion 16 may be made of any material as long as they are configured to provide a change in magnetic resistance to the magnetic circuit formed in the coil assembly. For example, the non-magnetic material portion 16 may be made of non-magnetic material or air, or by laser burning the iron rod 12.

By changing the magnetic properties, magnetic portions 15 and non-magnetic portions 16 having different magnetic permeabilities may be alternately formed.

The interval of one pitch in the alternate arrangement of the magnetic material portions 15 and the non-magnetic material portions 16 is "P". In that case, for example, the lengths of the magnetic part 15 and the non-magnetic part 16 are equal rP/2.
may be, and they do not necessarily have to be equal.

The coil assembly consists of four coils wound around a valve groove of a resin bobbin 13 formed at predetermined intervals in the axial direction of the rod 12.
primary coils IA, IB, IC.

1D and correspondingly the primary coils LA, IB.

Secondary coils 1a, 1b, l wound around the outside of IC and LD
It consists of c and ld. The bobbin 13 is housed in a cylindrical case 14 made of a magnetic material such as iron.

Depending on the relative positional relationship of the magnetic body portion 15 and the non-magnetic body portion 16 with respect to each of the primary coils IA, IB, IC, and LD, magnetic resistance of different magnitude is generated in each coil. it is,
The primary coil ID is shifted to the right by rP/4J with respect to the primary coil IA, and the primary coil IC is shifted to the right by rP/4J with respect to the primary coil IA.
This is because the primary coil ID is shifted to the right by 12P/4 relative to A, and the primary coil ID is shifted rightward by r3P/4J relative to the primary coil IA.

Here, if the alternating arrangement pitch rPJ of the magnetic material part 15 and the non-magnetic material part 16 is 2π in phase angle, the axial length rP
/4J is a phase angle of π/2.

Therefore, the magnitude of the magnetic resistance generated in the primary coil IA is α
Assuming that the primary coil IB changes at a rate of sin θ (α is the magnetoresistance change coefficient, θ is the phase angle indicating the linear position between the coil and the magnetic part 15 (non-magnetic part 16)), The magnitude of each magnetic resistance generated in the IC and 10 changes at a rate of αcosθ, −αsinθ, and −αcosθ, respectively.

In this embodiment, the primary coils IA, IB, Ic, and ID forming the coil assembly are configured to operate in four phases. Each primary coil IA.

IB, IC, ID and secondary coils la, lb, 1c, l
The lengths of d in the axial direction are each "P/4" or less.

With this configuration, the reluctance of the magnetic circuit in each coil changes periodically with the distance rPJ as one cycle in accordance with the linear displacement of the rod 12, and the phase of the reluctance change is 90 degrees (π/2) for each coil. Therefore, the primary coils IA and IC
The difference is 180 degrees (π), and the primary coil ID
and ID are also deviated by 180 degrees (π).

Primary coil LA, IB, IC, LD and secondary coil LA
, lb, lc, and ld are shown in FIG. In FIG. 2, the primary coils IA and IC are connected to a sine signal sinω
They are excited in opposite phases to each other at t.

The outputs of the secondary coils 1a and 1c are connected so that they are added in phase. Similarly, the primary coils IB and ID are excited by the cosine signal cosωt in opposite phases, and the outputs of the secondary coils 1b and 1d are connected so that they are added in phase. The outputs of the secondary coils la, lb, lc, and ld are finally added together and sent to the phase difference detection circuit 2 as an output signal Y.
Incorporated into 2.

This output signal Y is converted into a reference AC signal (sinω
or QO8ωt) with a phase shift. The reason is that the roughtance of each coil is different by 90 degrees (π/2), and one pair (primary coils IA, iC)
This is because the electrical phases of the excitation signals of the first coil and the other pair (primary coils IB and ID) are shifted by 90 degrees. Therefore, the output signal Y becomes Y=Ks in ((1) is 10),
Here, is a constant.

Since the phase θ of the reluctance change is proportional to the linear position of the magnetic body portion 15 according to a predetermined proportionality coefficient (or function), the reference signal Sinωt (or cos
The linear position can be detected by measuring the phase shift θ from ωt). However, 5 phase shift amount θ is full width 2
When π, the fecal line position corresponds to the distance rPJ for one pitch described above. That is, according to the electrical phase shift amount θ in the output signal Y, an absolute linear position within the range of rPJ can be detected. By measuring this electrical phase shift amount θ, it becomes possible to accurately determine the linear position within the range of rPJ with considerably high resolution.

Note that the magnetic scale portion 17 of the rod 12 is not limited to the magnetic material portion 15 and the non-magnetic material portion 16, but may be made of other materials capable of producing a change in magnetic resistance. For example, a conductive material such as copper may be used. The magnetic scale part 17 is formed by a combination of a material with a high conductivity and a material with a low conductivity (a non-conductor may also be used) such as iron (materials with different conductivities), and magnetic scale according to the eddy current loss is formed. It may also be arranged to cause a change in resistance.

In that case, a pattern of a good conductor may be formed on the surface of the rod 12 made of iron or the like by copper plating or the like. The pattern may have any shape as long as it can efficiently change the magnetic resistance.

Output signal Y and reference signal sinωt (or cosωt)
The means for determining the amount of phase shift θ with respect to θ can be configured as appropriate. FIG. 2 is a diagram showing an example of a circuit in which the phase shift amount θ is determined as a digital amount. Although not particularly shown in Figure 5, the phase shift amount θ can also be determined as an analog quantity by determining the 0-phase time difference between the reference AC signal sinωt and the output signal Y=Kgin (ωt+θ) using an integrating circuit.

In FIG. 2, the oscillator 21 generates a reference sine signal sinω
t and a cosine signal QO8ωt, and the phase difference detection circuit 22 is a circuit for measuring the amount of phase shift θ.

Clock pulse CP oscillated from clock oscillator 23
is counted by the counter 24. The counter 24 is, for example, modulo M (M is any integer), and its count value is given to the register 45. 4/ of counter 24
From the way the frequency is divided by M, the clock pulse CP is divided by 4/M.
The frequency-divided pulse Pc is taken out and applied to the C input of the flip-flop 25 for 1/2 frequency division.

The pulse p output from the Q output of the flip-flop 25
b is added to the flip-flop 29, and the pulse P output from the output side of the umbrella Q (the umbrella in front of Q means an inverted output)
a is added to the flip-flop 26, and the outputs of these flip-flops 26 and 29 are connected to the low-pass filter 27.4.
0 and the amplifier 28.41, the sinusoidal signal sinωt
and a cosine signal aosωt are supplied to each of the primary coils IA, IB, IC, and ID of the coil assembly.

M counts in the counter 23 are these reference signals si
This corresponds to a phase angle of 2π radians of nωt and cosωt. That is, one count value of the counter 23 is 2π/M
It shows the phase angle in radians.

The combined output signal Y of the secondary coils la, lb, 4c, and ld is applied to the comparator 43 via the amplifier 42, and a square wave signal corresponding to the positive/negative polarity of the output signal Y is applied to the comparator 4.
Output from 3. In response to the rise of the output signal of the comparator 43, the rise detection circuit 44 outputs a pulse Ts, and in response to this pulse Ts, the counter 3
A count value of 4 is written to the register 45. the result.

A digital value Dθ corresponding to the phase shift amount θ is taken into the register 45. This makes it possible to detect the linear position of the cylinder rod 12 absolutely and with high precision.

FIG. 3 is a diagram showing a second embodiment of the present invention.

In FIG. 3, the same components as in FIG. 1 are denoted by the same reference numerals, so their explanation will be omitted.

The position detector 36 of this embodiment is different from the one shown in FIG.
The point is that 00, OA, and IB are wound. That is,
Dummy primary coils OD and OC are provided on the left side of the primary coil LA, and dummy primary coils OA and OB are provided on the right side of the primary coil ID.

In Figure 1, the primary coil IB is placed on both sides of the primary coil IB.
A and IC, and the primary coil IC has primary coils IB and LD on both sides, but there is no such coil on the left side of the primary coil IA and on the right side of the primary coil ID. , the magnetic balance between each coil deteriorates, which appears as a detection error. Therefore, in this embodiment, a dummy primary coil is provided in the coil assembly to correct the magnetic balance. In addition, 2 wires are installed outside the dummy primary coil.
A dummy secondary coil that is not directly related to the outputs of the secondary coils la, lb, lc, and ld may be provided.

Primary coil OA~OD, 1. A~ID and secondary coil 1
The connection format for a = 1 d is the same as in Figure 2.

That is, the primary coils QC, IA, 1C, OA are connected in series in order, and the primary coils OC and IA, 1A and IC,
The IC and OA are connected so that they are excited in opposite phases by a sine signal sinωt. Similarly, the primary coil OD, IB,
ID and OB are also connected in series in order, and the primary coil OD and I
B, IB and ID, ID and OB are mutually cosine signals e08ω
Connect the wires so that they are excited in opposite phase at t. Secondary coil 1a
~1d are sequentially connected in series and wired so that their outputs are added in phase. Therefore, the secondary coil 18
The outputs of ~1d are finally added together and taken in as an output signal Y to the phase difference detection circuit 22.

FIG. 4 is a diagram showing a third embodiment of the present invention.

In FIG. 4, the same components as in FIG. 1 are denoted by the same reference numerals, so their explanation will be omitted.

Note that the bobbin and cylindrical case are not shown in this figure.

The position detector 41 of this embodiment differs from the one shown in FIG.
A plurality of coil assemblies provided within the pitch rPJ are provided in the axial direction of the rod 12, and dummy primary coils are provided at both ends thereof.

The position detector 41 of this embodiment is a primary coil IA shown in FIG.
~In addition to ID and secondary coils 18-1d.

Primary coils 2A to 2D, 3A arranged within one pitch rPJ in an alternate arrangement of magnetic parts 15 and non-magnetic parts 16
~3D, secondary coils 2a~2d, 3a~3d, and dummy primary coils OA~OD, respectively. The primary coils IA-ID and secondary coils 18-1d form a first position detector, and the primary coils 2A-2D and secondary coils 2a-2
d and the second position detector, and the primary coils 3A to 3D and 2
The secondary coils 38 to 3d constitute a third position detector. That is, the position detector 41 of this embodiment has a configuration in which three position detectors 11 shown in FIG. 1 are provided in the axial direction of the rod 12.

Primary coils IA to LD, 2A to 2D, 3A to 3D, dummy primary coils OA to OD and secondary coils l a to 1
d, 2a to 2d, and 3a to 3d The wiring format is the same as that shown in FIG. That is, the primary coil O
Connect C, IA, IC, 2A, 2G, 3A, 3C, OA in series in order, primary coil OC and IA, IA and IC1
IC and 2A, 2A and 2C12C and 3A, 3A and 3C13
C and OA are connected so that they are excited in opposite phases by a sine signal Sinωt. Similarly, the primary coils OD, IB, L
D, 2B, 2D.

Connect 3B, 3D, and OB in series in order, and connect the primary coil O.
D and IB, IB and ID, ID and 2B, 2B and 2D, 2D
and 3B, 3B, 3D, 3D and OB are each a cosine signal CO8
Connect the wires so that they are excited in the opposite phase at ωt. Secondary coil 1
8-ld, 2a-2d.

38 to 3d are connected in series in order and wired so that their outputs are added in phase. Therefore.

The outputs of the secondary coils 1a to 1d, 2a to 2d, and 3a to 3d are finally added together and taken into the phase difference detection circuit 22 as an output signal Y.

In this way, the secondary coils 1a to ld, 2a to 2d.

By adding and outputting the output signals from 3a to 3d, the rod errors detected by the first, second, and third position detectors are averaged, and the output signal Y with reduced rod errors is converted to a phase difference. It becomes possible to output to the detection circuit 22.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

In FIG. 5, the same components as in FIG. 1 are denoted by the same reference numerals, so the explanation thereof will be omitted.

Note that the bobbin and cylindrical case are not shown in this figure.

The position detector 51 of this embodiment differs from the one shown in FIG.
Pitch "Six primary coils and a secondary coil are provided in the PJ, and the primary coil is excited with a three-phase AC signal. Multiple coils are provided in the axial direction of the rod 12, and a dummy one is installed at both ends of the coil.
The next point is the provision of a coil.

The position detector 51 of this embodiment has primary coils IA to IF and secondary coils 18 to 1f within one pitch rPJ in an alternate arrangement of magnetic parts 15 and nonmagnetic parts 16, and similarly has primary coils IA to IF and secondary coils 18 to 1f. Coils 2A to 2F and secondary coils 2a to 2f are also provided within one pitch.

Primary coil ID is rP/6 with respect to primary coil IA",
The primary coil IC is r2P/6J for the primary coil IA.
, the primary coil ID is r3F/ for the primary coil IA.
6", the primary coil IE is "4P" for the primary coil IA.
/6J, primary coil IF is r5 with respect to primary coil IA
It is shifted to the right by P/6J.

The primary coils IA to IF and the secondary coils 1a to 1f
The position detector is connected to the primary coils 2A to 2F and the secondary coil 2.
8 to 2f respectively constitute a second position detector. That is, the position detector 51 of this embodiment has a configuration in which two position detectors that are excited in three phases are provided in the axial direction of the rod 12.

Primary coils IA-IF, 2A-2F, dummy primary coils OA-OF, and secondary coils 1a-1f.

The wiring format for 2a to 2f is as follows. That is, the primary coils/L10D, LA, LD, 2A, 2D, and OA are connected in series in order, and the primary coils OD and IA, IA and ID,
The LD and 2A, 2A and 2D, and 2D and OA are connected so that they are excited in opposite phases by a sine signal sinωt. Similarly, connect the primary coils OE, IB, IE, 2B, 2E, OB in series in order, and connect the primary coils OE and IB, IB and IE
, IE and 2B, 2B and 2E, and 2E and OB are connected so that they are excited in opposite phases by a sinusoidal signal sin (ω is 1π/3), and the primary coils OF, IC, IF, and 2C are connected.

2F, QC are connected in series in this order, and the primary coil OF and I
C1IC and IF, IF and 2C12C and 2F, 2F and OC
are connected so that they are mutually excited in opposite phases by a sine signal sin (ωt-2π/3). Secondary coil 1a~if, 2
A to 2f are sequentially connected in series and wired so that their outputs are added in phase. Therefore, the secondary coil 1
The outputs of a to 1f and 2a to 2f are finally added and taken into the phase difference detection circuit 22 as an output signal Y.

By adding and outputting the output signals from the secondary coils 1a-if and 2a-2f in this way.

The rod errors detected by the first and second position detectors are averaged, and it becomes possible to output an output signal Y with reduced rod errors to the phase difference detection circuit 22. Furthermore, by exciting the primary coil in three phases as in the embodiment shown in FIG. 5, errors in harmonic components can be reduced.

゛In the example, the case where the coil part has 4 phases A-D and 6 phases A-F has been explained, but it is not limited to 2-phase, 3-phase,
It is also possible to configure with other phase numbers.

In this embodiment, a case has been described in which the magnetic scale part is formed directly on the rod, but it may be formed separately at a position that is linked to the movement of the rod.

Further, the shape of the rod is not limited to a cylindrical shape, but may be any shape as long as it causes a change in slip roughtance, such as sin θ or COS θ, in response to linear displacement.

〔Effect of the invention〕

According to the present invention, it is possible to suppress rod errors caused by differences in the shapes of rods that constitute a position detection device, and it is possible to significantly improve position detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the linear position detecting device of the present invention, and FIG. 2 is a diagram showing the configuration of a position converting means for converting a detection signal from the linear position detecting device of FIG. 1 into a position signal. FIG. 3 is a diagram showing a second embodiment of the linear position detection device of the present invention. FIG. 4 is a diagram showing a third embodiment of the linear position detection device of the present invention. FIG. 5 is a diagram showing a fourth embodiment of the linear position detecting device of the present invention, and FIGS. 6 and 7 are diagrams showing the configuration of a conventional linear position detecting device. 11.36, 41.51...Position detector, 12...
Rod, 13...Bobbin, 14...Cylindrical case, 1
5... Non-magnetic material part, 16... Magnetic material part, 17...
Magnetic scale patent applicant Nisgy Co., Ltd. Patent attorney Yoshihito Iizuka

Claims (7)

[Claims] (1) A coil portion having at least a primary coil excited by a predetermined alternating current signal; and a coil portion that is provided so as to be linearly displaceable relative to the coil portion, and that the magnetic circuit of the coil portion is A magnetic scale part provided with scales at a plurality of pitches along the linear displacement direction so that the magnetic resistance changes periodically with one pitch of the scale as one cycle; and a magnetic scale part between the magnetic scale part and the coil part. a position detection circuit that extracts data indicating the position of the magnetic scale part from the coil part based on a change in magnetic resistance of the magnetic circuit of the coil part caused by the relative positional relationship, A linear position detection device characterized by being provided within one pitch of a scale. (2) The coil portion includes a plurality of primary coils that are individually excited by a plurality of reference AC signals whose phases are shifted from each other, and the excitation of the primary coils causes the coil unit to adjust the voltage according to the relative position of the reference AC signal. 2. The linear position detection device according to claim 1, further comprising a plurality of secondary coils that generate phase-shifted output signals. (3) The linear position detection device according to claim 1, wherein a plurality of the coil portions are provided within one pitch of the scale of the scale portion in the linear displacement direction. (4) The linear position detection device according to claim 1, further comprising dummy primary coils on both sides of the primary coil in the linear displacement direction. (5) The position detection circuit sums up the outputs of a circuit that individually excites each of the primary coils using a plurality of phase-shifted reference AC signals and a secondary coil corresponding to each of the primary coils, an output circuit that generates an output signal whose phase is shifted from the reference AC signal according to the relative linear position of the magnetic scale; and detecting a phase difference between a predetermined one of the reference AC signals and an output signal from the output circuit. 3. The linear position detection device according to claim 2, further comprising a circuit for outputting detected phase difference data as position data of the magnetic scale section. (6) The linear position detection device according to claim 2, wherein the magnetic scale portion is made of a repetition of two types of materials having different magnetic permeabilities. (7) The linear position detection device according to claim 2, wherein the magnetic scale portion is made of a repetition of two types of materials having different electrical conductivities.