JPH09264758A - Straight line position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily manufacture by easily separating a coil assembly from a rod. SOLUTION: A magnetic core is an integral core 30 in which a plurality of pectinated tooth-like thin plates are laminated. Phases having primary coils 1a to 1d excited by a predetermined AC signal and secondary coils 2a to 2d magnetically coupled to the primary coils are provided at least at four positions of the pectinated tooth-like core part of the magnetic core. A magnetic scale part has a plurality of scales provided along the linearly displacing direction so that magnetoresistance on a magnetic circuit formed between the cores provided relatively linearly displaceably to the magnetic core upon the movement is periodically varied per the one pitch of the scale as one cycle. A position detecting circuit supplies predetermined AC signal to the coils 1a to 1d, and takes out the data for indicating the position of the scale from the coils 2a to 2d based on the relative positional relationship between the scale and the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear position detecting device using a change in magnetic resistance, and more particularly to a phase shift type linear position detecting device for detecting a change in magnetic resistance as a change in an electrical phase angle of an output AC signal. Regarding

[0002]

2. Description of the Related Art A differential transformer has been well known as a linear position detecting device based on a change in magnetic resistance.
Since this converts the linear position into a voltage level, it has a drawback that an error is likely to occur due to the influence of disturbance. For example, the resistance of the coil changes under the influence of temperature change, which changes the detection signal level,
In addition, the level attenuation amount in the signal transmission path from the detector to the circuit that uses the detection signal varies depending on the transmission distance, and further, the level fluctuation due to noise becomes a detection error as it is. Have Therefore, the applicant of the present invention has previously proposed a phase shift type linear position detection device capable of accurately detecting a linear position without being affected by output level fluctuations due to disturbances (for example, actual Kaisho 57-135
No. 917 G13, No. 58-136718 G22, or No. 59-175105 G4.
3).

A schematic configuration of this phase shift type linear position detecting device will be described below with reference to FIG. This linear position detecting device detects the linear position of the rod 6 by the phase shift method, and the coil assembly 6
4 and a rod 6 inserted in the cylindrical space in the coil assembly 64 so as to be linearly movable. The coil assembly 64 includes four primary coils 1a, 1c, 1b, 1d formed at predetermined intervals in the axial direction of the rod 6.
And the secondary coils 2 provided corresponding to these
a, 2c, 2b, 2d. The coil assembly 64 is fixed inside the cylinder block 67. The rod 6 is made of a magnetic material such as iron, and has a bearing 68,
It is held by 69. The rod 6 includes a ring-shaped non-magnetic material portion 66 having a predetermined width, which is alternately provided in the axial direction.
On the outer circumference. The magnetic body portion 65 and the non-magnetic body portion 66
The magnetic graduation portion 6S is formed on the outer peripheral surface of the rod 6 by the repeating pattern. The axial length of one coil is “P / 2” (P is an arbitrary value), and the magnetic body portion 6
The interval for one pitch in the alternate arrangement of the 5 and the non-magnetic material portion 66 is “P”, which is twice that. In this case, the magnetic material portion 65 and the non-magnetic material portion 66 have the same length “P / 2”.
It is. Coil assembly 64 is configured to operate in four phases. In the drawings, these phases are shown with reference numerals A, C, B, and D for convenience.

The positional relationship between the rod 6 and the coil assembly 64 is such that the reluctance generated in each phase A to D of the coil assembly 64 is deviated by 90 degrees depending on the position of the magnetic body portion 65 of the rod 6. For example, assuming that the A phase is a cosine phase, the C phase is a minus cosine phase, the B phase is a sine phase, and the D phase is a minus sine phase. There is. In FIG. 4, the primary coil 1 is individually provided for each of the phases A to D.
a, 1c, 1b, 1d and secondary coils 2a, 2c, 2
b and 2d are provided respectively. The secondary coils 2a, 2c, 2b and 2d of the phases A to D are wound around the corresponding primary coils 1a, 1c, 1b and 1d, respectively.
Each primary coil 1a, 1c, 1b, 1d and secondary coil 2
The axial length of a, 2c, 2b, 2d is "P / 2" as described above. In FIG. 4, A-phase coils 1a and 2a
And C-phase coils 1c and 2c are provided adjacent to each other, and B-phase coils 1b and 2b and D-phase coils 1d and 2d are provided.
And are placed next to each other. Also, A phase and B phase or C
The coil spacing between the phase and the D phase is “P (n ± 1/4)” (n is an arbitrary natural number). In FIG. 4, n is “2” and the coil interval is 7P / 4.

According to this structure, the rod 6 has the bearing 6
By sliding and moving 8, 69, the relative positional relationship between the rod 6 and the coil assembly 64 changes, and the reluctance of the magnetic circuit in each of the phases A to D periodically changes with "P" as one cycle. The phase of the reluctance change changes by 90 degrees for each of the phases A to D. That is, the reluctance change phase is shifted by 180 degrees between the A phase and the C phase, and the reluctance change phase is shifted by 180 degrees between the B phase and the D phase. Phase A and Phase 1
The secondary coils 1a and 1c are excited in phase with each other by the sine signal sinωt, and the outputs of the secondary coils 2a and 2c are connected so as to be added in antiphase. Similarly, the B-phase and D-phase primary coils 1b and 1d are excited in the same phase by the cosine signal cosωt, and the outputs of the secondary coils 2b and 2d are connected so as to be added in opposite phases. Secondary coil 2
The outputs of a, 2c, 2b and 2d are finally added and taken out as an output signal Y.

This output signal Y is applied to the magnetic body portion 6 of the rod 6.
5 and the coil assembly 64, a reference AC signal (sinωt, co
sωt) is phase-shifted. The reason is that the reluctance of each phase A to D is deviated by 90 degrees, and the electrical phase of the excitation signal of one pair (A, C) and the other pair (B, D) is deviated by 90 degrees. This is because. Therefore, the output signal Y is Y = Ksin (ωt + φ). here,
K is a constant. Since the phase φ of the reluctance change is proportional to the linear position of the magnetic body portion 65 according to a predetermined proportional coefficient (or function), the reference signal sin in the output signal Y
The linear position can be detected by measuring the phase shift φ from ωt (or cosωt). However, when the phase shift amount φ is the full angle 2π, the linear position corresponds to the distance P described above. That is, the absolute linear position within the range of the distance P can be detected by the electrical phase shift amount φ in the output signal Y. By measuring this electrical phase shift amount φ, it becomes possible to accurately determine the linear position within the range of the distance P with high resolution.

[0007]

In the linear position detecting device shown in FIG. 4, when the wiring of the coil assembly 64 or the like fails, the rod 6 to the coil assembly 6 are removed.
It suffices to remove 4 for repairing. However, since both ends of the rod 6 are normally fixed to a machine or the like, it is easy to say that the coil assembly 64 has a problem such as wiring. Could not be pulled out from the rod 6, and there was a problem in terms of maintenance. Therefore, the applicant of the present invention has proposed a linear position detecting device as shown in FIG. 5 in order to solve such a problem (Japanese Unexamined Patent Publication No. 60-168017). In this linear position detecting device, a coil has a U-shaped core (a laminated body of iron plates) 3
The primary coil and the secondary coil wound around a to 3d constitute a coil assembly, and the coil assembly is provided along the side surface of the rod 6 so that the coil assembly can be easily removed. That is, the phase A is the primary coils 1a1 and 1a wound around the U-shaped core 3a.
2 and secondary coils 2a1 and 2a2, and phase B is a primary coil 1b1 and 1b2 wound around a U-shaped core 3b.
And the secondary coils 2b1 and 2b2, the C phase is composed of the primary coils 1c1 and 1c2 and the secondary coils 2c1 and 2c2 wound around the U-shaped core 3c, and the D phase is composed of the U-shaped core 3d. The wound primary coils 1d1 and 1d2 and 2
It consists of secondary coils 2d1 and 2d2. The position detecting principle of this linear position detecting device is the same as that of FIG. In addition,
Although not disclosed in JP-A-60-168017, these U-shaped cores have a predetermined cylinder block 3 size.
Fixed to 1.

However, in the case of the linear position detecting device of FIG. 5, four U-shaped cores 3a to 3d having the same shape must be manufactured, and a primary coil and a secondary coil are provided. The U-shaped cores 3a to 3d are attached to the cylinder block 3
1 must be accurately attached at a predetermined position, and it takes a lot of time to manufacture and attach the same, and there is a problem in that the cost becomes high. The present invention has been made in view of the above points, and provides a linear position detection device that can easily separate a coil assembly and a rod and can be manufactured easily and inexpensively. With the goal.

[0009]

A linear position detecting device according to the present invention is excited by a predetermined AC signal and a magnetic core portion formed by laminating a plurality of comb-teeth-shaped thin plates. A primary coil and a secondary coil that is magnetically coupled to the primary coil at at least four positions in the toothed core portion of the comb; The magnetic resistance on the magnetic circuit formed between the magnetic core portion and the magnetic core portion is periodically changed with one pitch of the scale as one cycle. And a magnetic graduation portion having a plurality of graduations provided along the linear displacement direction, and supplying the predetermined AC signal to the primary coil and between the magnetic graduation portion and the magnetic core portion. Due to relative position Resulting Te based on said magnetoresistive change is obtained by a position detection circuit for taking out data indicating a position of the magnetic graduation section from the secondary coil.
The magnetic core portion is formed by laminating a plurality of comb-teeth-shaped thin iron plates. Therefore, since each tooth of the comb becomes an iron core, it is only necessary to wind the primary coil and the secondary coil around it.
A coil assembly can be constructed. Further, since it is only necessary to set the spacing between the teeth of the combs to a predetermined pitch in advance at the stage of the thin iron plate, it is not necessary to adjust the pitch between the phases after the coil winding as in the conventional one shown in FIG. Therefore, the manufacturing is simplified and the cost is reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A linear position detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a linear position detecting device according to the present invention, and FIG.
Is a view showing the cross-sectional structure thereof, and FIG.
It is a figure which shows the cross-section structure in the XX line of (A). FIG. 2 is a diagram showing a cross-sectional structure taken along line YY of FIG. This linear position detecting device is an absolute type position detecting device including an inductive phase shift type linear position sensor. The position detection principle of this linear position detection device is shown in FIG.
And the conventional one shown in FIG. The linear position detecting device of the present invention is different from that of FIG. 5 in that the core around which the primary winding and the secondary winding are wound is formed of an integrally molded core. That is, the integrally molded core 30 is
A plurality of comb-teeth-shaped core iron plates are laminated, and the primary coil 1a,
1c, 1b, 1d and secondary coils 2a, 2c, 2b, 2
Each d is wound. Coil assembly 34
Are the integrally molded core 30 and the primary coil 1a,
1c, 1b, 1d and secondary coils 2a, 2c, 2b, 2
and d. The axial pitch in the alternating arrangement of the magnetic material portions 65 and the non-magnetic material portions 66 of the rod 6 is "P".
Then, the axial pitches of the tooth portions of the comb around which the primary coils 1a, 1c, 1b, 1d and the secondary coils 2a, 2c, 2b, 2d are wound, that is, the core portions of the A phase to D phase are both 3.
It is P / 4. Further, the integrally-molded core 30 has a phase A-B
The phases, the B-phase and the C-phase, and the C-phase-D are separated by a part of the teeth of the comb (an iron core part where the coil is not wound). By separating the phases with the iron cores in this manner, the degree of magnetic coupling between the rod 6 and the core portions of the A-phase to the D-phases is improved as compared with the case where there is no iron core for phase separation between the phases. The effect is that you can.

The rod 6 is made of a magnetic material such as iron as in the conventional one, and is held by bearings 68 and 69. That is, since the rod 6 penetrates the cylindrical space in the bearings 68, 69, the rod 6 is not supported by the bearings 68, 6.
In order to separate the rod 9, it is necessary to move it to one end of the rod 6 and pull it out. However, the integrally molded core 30 is simply fixed to these bearings 68 and 69 by screwing, so that the rod 6 can be easily pulled. Therefore, there is an effect that it can be easily repaired even when a problem occurs in wiring or the like. The rod 6 has ring-shaped non-magnetic material portions 66 of a predetermined width, which are alternately provided in the axial direction, on the outer circumference. Due to the repeating pattern of the magnetic material portion 65 and the non-magnetic material portion 66, the magnetic scale portion 6 is formed on the outer peripheral surface of the rod 6.
S is formed. The magnetic material portion 65 and the non-magnetic material portion 66 may be made of any material as long as the magnetic circuit formed by the coil assembly 64 is configured to change the magnetic resistance. Good. For example,
The non-magnetic material portion 66 may be made of non-magnetic material, air, or the like. Further, the magnetic properties may be changed by performing laser baking on the iron rod 6 to alternately form the magnetic material portions 65 and the non-magnetic material portions 66 having different magnetic permeability. The positional relationship between the rod 6 and the coil assembly 64 is such that the reluctance generated in each of the phases A to D of the coil assembly 64 deviates by 90 degrees depending on the position of the magnetic body portion 65 of the rod 6.
For example, if the A phase is a cosine (cos) phase, the C phase is a minus cosine (-cos) phase and the B phase is a sine (si).
The n) phase and the D phase are configured to be minus sign (-sin) phases.

According to this structure, the rod 6 has the bearing 6
By sliding and moving 8, 69, the relative positional relationship between the rod 6 and the coil assembly 64 changes, and the reluctance of the magnetic circuit in each of the phases A to D periodically changes with "P" as one cycle. The phase of the reluctance change changes by 90 degrees for each of the phases A to D. That is, the reluctance change phase is shifted by 180 degrees between the A phase and the C phase, and the reluctance change phase is shifted by 180 degrees between the B phase and the D phase. Phase A and Phase 1
The secondary coils 1a and 1c are excited in phase with each other by the sine signal sinωt, and the outputs of the secondary coils 2a and 2c are connected so as to be added in antiphase. Similarly, the B-phase and D-phase primary coils 1b and 1d are excited in the same phase by the cosine signal cosωt, and the outputs of the secondary coils 2b and 2d are connected so as to be added in opposite phases. Secondary coil 2
The outputs of a, 2c, 2b, and 2d are finally added, and taken as an output signal Y into the position conversion unit of FIG.

This output signal Y is applied to the magnetic body portion 6 of the rod 6.
5 and the coil assembly 64, a reference AC signal (sinωt, co
sωt) is phase-shifted. The reason is the same as the conventional one, and the reluctance of each phase A to D is 9
This is because they are deviated by 0 degree, and the electrical phases of the excitation signals of one pair (A, C) and the other pair (B, D) are deviated by 90 degrees. Therefore, the output signal Y is Y = Ksin (ω
t + φ). Here, K is a constant. Since the phase φ of the reluctance change is proportional to the linear position of the magnetic body portion 65 according to a predetermined proportional coefficient (or function), the phase shift φ from the reference signal sin ωt (or cos ωt) in the output signal Y is measured. The linear position can be detected. However, when the phase shift amount φ is full angle 2π,
The straight line position corresponds to the distance P described above. That is, the absolute linear position within the range of the distance P can be detected by the electrical phase shift amount φ in the output signal Y. By measuring this electrical phase shift amount φ,
It is possible to accurately determine the linear position within the range of the distance P with high resolution. The magnetic scale portion 6S of the rod 6 is not limited to the magnetic body portion 65 and the non-magnetic body portion 66,
Other materials capable of producing a change in magnetic resistance may be used. For example, a material with high conductivity such as copper and a material with low conductivity such as iron (non-conductive material is also acceptable)
The magnetic graduation portion 6S may be formed by a combination with the above (materials having different electric conductivity) to cause a change in magnetic resistance according to eddy current loss. In that case, a pattern of a good conductor may be formed on the surface of the rod 6 made of iron or the like by copper plating or the like. The shape of the pattern or the like may be any shape as long as it can efficiently cause a change in magnetic resistance.

FIG. 3 shows a detailed configuration of a position conversion device for supplying a primary AC signal to the induction type phase shift type linear position detection device of FIG. 1 and measuring an electrical phase shift φ based on an output signal Y thereof. FIG. This position conversion device unit includes a reference signal generation unit that generates the primary AC signal sinωt or cosωt, and a phase difference detection unit that measures the electrical phase shift φ of the combined output signal Y and calculates the position of the rod 6. . The reference signal generator includes a clock oscillator 9A, a synchronous counter 9B,
ROM 93a, 93b, D / A converters 94a, 94b, and amplifiers 95a, 95b, and a phase difference detection unit includes an amplifier 96, a zero-cross circuit 97, and a latch circuit 98. The clock oscillator 9A generates a high-speed and accurate clock signal, and other circuits operate based on this clock signal. The synchronous counter 9B is a clock oscillator 9
The clock signal of A is counted, and the count value is output to the ROM 93a and the latch circuit 98 as an address signal. The ROMs 93a and 93b store amplitude data corresponding to the reference AC signal, and generate amplitude data of the reference AC signal according to the address signal (count value) from the synchronous counter 9B. The ROM 93a stores the amplitude data of sin ωt, and the ROM 93b stores the amplitude data of cos ωt. Therefore, the ROMs 93a and 93b output two types of reference AC signals sinωt and cosωt by inputting the same address signal from the synchronous counter 9B. Even if the ROM having the same amplitude data is read by the address signals having different phases, two kinds of reference AC signals can be similarly obtained.

The D / A converters 94a and 94b are the ROM 9
The digital amplitude data from 3a and 93b is converted into an analog signal and output to the amplifiers 95a and 95b. The amplifiers 95a and 95b amplify the analog signal from the D / A converter and use it to amplify the reference AC signals sinωt and cos.
ωt is applied to each of the primary coils 1a, 1c and 1b, 1d. Assuming that the frequency division number of the synchronous counter 9B is M, that M count is the maximum phase angle 2 of the reference AC signal.
This corresponds to π radian (360 degrees). That is, one count value of the synchronization counter 9B indicates a phase angle of 2π / M radian.

The amplifier 96 amplifies the combined value Y = Ksin (ωt + φ) of the secondary voltage induced in the secondary coils 2a to 2d and outputs it to the zero cross circuit 97. The zero-cross circuit 97 detects the zero-cross point from the negative voltage to the positive voltage based on the mutual induction voltage (secondary voltage) induced in the secondary coils 2a to 2d of the rotational position detecting means 5, and latches the detection signal. Output to. The latch circuit 98 latches the count value of the synchronous counter started by the rising clock signal of the reference AC signal at the output point (zero cross point) of the detection signal of the zero cross circuit 97. Therefore, the value latched by the latch circuit 98 is exactly the phase difference (phase shift amount) between the reference AC signal and the mutual induction voltage (combined secondary output).
It becomes MP. That is, the combined output signal Y = sin (ωt + φ) of the secondary coils 2 a to 2 d is the zero-cross circuit 97.
Given to. The zero cross circuit 97 outputs the pulse L to the latch circuit 98 in synchronization with the timing when the electric phase angle of the combined output signal Y is zero. The pulse L is used as a latch pulse for the latch circuit 98. Therefore, the latch circuit 9
8 latches the count value of the synchronous counter 9B in response to the rising of the pulse L. The period in which the count value of the synchronization counter 9B makes one cycle is synchronized with one cycle of the sine wave signal sinωt. Then, the reference AC signal s is sent to the latch circuit 98.
The count value corresponding to the phase difference φ between inωt and the combined output signal Y = sin (ωt + φ) will be latched. Therefore, the latched value is the digital position data M
Output as P. The latch pulse L may be appropriately used as a timing pulse.

In the above embodiment, the case where the coil assembly 34 including the integrally molded core 30 is provided only on one side in the axial direction has been described. However, this is provided at a position where the axis of the rod 6 is line symmetrical. An error due to the axial deviation of the rod 6 may be compensated by providing a conical assembly composed of the same integrally-molded core and taking the average value of the signals of both. Further, three or more integrally molded cores may be provided and the average value thereof may be taken. Further, in the above-described embodiment, the case where the coil shape is a square as shown in FIG. 1B has been described, but a circular shape, a rectangular shape whose longitudinal direction coincides with the axial direction of the rod 6, an elliptical system, or the like. Needless to say, the shape may be. The cross-sectional shape of the rod may be other than circular. Further, the scale portion may be provided only on the surface facing the coil assembly.
In addition, in FIG. 1, the case where the distance between the A and D phases is equal to 3P / 4 has been described. However, since the A phase and the D phase are on both sides, the structurally unbalanced position compared to the B phase and the C phase. Therefore, the distance between the B phase and the C phase is actually set to about 90% of 3P / 4, and the distance between the A phase and the B phase and C
-The distance between the D phases should be about 110% of 3P / 4, and the number of turns of the A and D phase primary and secondary coils should be different from that of the B and C phases to balance each phase. You may The shape of the integrally-molded core 30 shown in FIG. 2 is substantially straight at the portion in contact with the rod 6, but the shape is not limited to this, and it is processed so that the shape of the contact surface matches the outer peripheral shape of the rod 6. It goes without saying that it is okay.

[0018]

According to the present invention, since the coil assembly and the rod can be easily separated from each other, maintenance is facilitated, and since the integral molding core is adopted, the manufacturing is easy and the cost is low. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a linear position detecting device according to the present invention, and FIG. 1 (A) is a diagram showing a sectional structure.
FIG. 1B is a diagram showing a cross-sectional structure taken along line XX of FIG.

FIG. 2 is a diagram showing a cross-sectional structure taken along line YY of FIG.

FIG. 3 is a diagram showing a detailed configuration of a position conversion device that supplies a primary AC signal to the induction type phase shift type linear position detection device of FIG. 1 and measures an electrical phase shift φ based on an output signal Y thereof. Is.

FIG. 4 is a diagram showing a schematic configuration of a conventional linear position detection device.

FIG. 5 is a diagram showing a schematic configuration of a conventional linear position detection device.

[Explanation of symbols]

1a, 1b, 1c, 1d ... Primary coil, 2a, 2b, 2
c, 2d ... secondary coil, 30 ... integrally molded core, 34 ...
Coil assembly, 6 ... Rod, 65 ... Magnetic body part, 6
6 ... Non-magnetic body part, 6S ... Magnetic scale part

Claims (3)

[Claims] 1. A magnetic core portion formed by laminating a plurality of comb-teeth thin plates, a primary coil excited by a predetermined AC signal, and
A coil portion having a phase composed of a secondary coil magnetically coupled to a secondary coil in at least four positions of the tooth-shaped core portion of the comb, and linear displacement movement relative to the magnetic core portion. And a magnetic resistance on the magnetic circuit formed between the magnetic core portion and the magnetic core portion along with this linear displacement movement is 1
A magnetic graduation portion having a plurality of graduations provided along a linear displacement direction so as to periodically change with a pitch as one cycle; and a magnetic graduation portion for supplying the predetermined AC signal to the primary coil. A position detection circuit for extracting data indicating the position of the magnetic scale portion from the secondary coil based on the change in the magnetic resistance caused by the relative positional relationship with the magnetic core portion. Linear position detector. 2. The linear position detecting device according to claim 1, wherein the magnetic core portions are provided at positions that are line-symmetric with respect to the linear movement direction with the magnetic scale portion interposed therebetween. 3. The linear position detecting device according to claim 1, wherein the magnetic core is configured to separate the coils of each phase by the tooth-shaped iron core of the comb.