JP3592835B2 - Linear position detector - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a linear position detecting device using a magnetoresistive change, and more particularly to a phase shift type linear position detecting device that detects a magnetoresistive change as a change in an electrical phase angle of an output AC signal.
[0002]
[Prior art]
2. Description of the Related Art A differential transformer has been well known as a linear position detecting device due to a change in magnetoresistance. Since this converts a linear position into a voltage level, there is a disadvantage that an error is likely to occur due to the influence of disturbance. For example, the resistance of the coil changes due to the effect of temperature change, which causes the detection signal level to fluctuate. Also, the level attenuation in the signal transmission path from the detector to the circuit using the detection signal indicates the transmission level. It varies depending on the distance, and further has a drawback that a level variation due to noise appears as a detection error as it is.
Accordingly, the applicant of the present invention has previously proposed a phase shift type linear position detecting device capable of accurately detecting a linear position without being affected by output level fluctuation due to disturbance or the like (for example, an actual position detecting device). JP-A-57-135917, G13, JP-A-58-136718, G22, or JP-A-59-175105, G43).
[0003]
Hereinafter, a schematic configuration of the phase shift linear position detecting device will be described with reference to FIG.
This linear position detecting device detects a linear position of the rod 6 by a phase shift method, and includes a coil assembly 64 and a rod 6 inserted into the cylindrical space in the coil assembly 64 so as to be linearly movable. Is done.
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 secondary coils 2a, 2c, 2b, 2d. The coil assembly 64 is fixed in the cylinder block 67.
The rod 6 is made of a magnetic material such as iron, and is held by bearings 68 and 69. The rod 6 has a ring-shaped non-magnetic material portion 66 of a predetermined width alternately provided in the axial direction on the outer periphery. A magnetic scale portion 6S is formed on the outer peripheral surface of the rod 6 by the repetitive pattern of the magnetic portion 65 and the non-magnetic portion 66.
The axial length of one coil is “P / 2” (P is an arbitrary value), and the interval of one pitch in the alternating arrangement of the magnetic portion 65 and the non-magnetic portion 66 is twice as long. P ". In this case, the lengths of the magnetic part 65 and the non-magnetic part 66 are equal to each other and are “P / 2”.
Coil assembly 64 is configured to operate in four phases. In the drawings, these phases are denoted by reference numerals A, C, B, and D for convenience.
[0004]
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 is shifted by 90 degrees according to the position of the magnetic body 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, the B phase is a sine (sin) phase, and the D phase is a minus sine (-sin) phase. I have.
In FIG. 4, primary coils 1a, 1c, 1b, 1d and secondary coils 2a, 2c, 2b, 2d are provided individually for each of the phases A to D. The secondary coils 2a, 2c, 2b, 2d of the respective phases A to D are wound around the corresponding primary coils 1a, 1c, 1b, 1d, respectively.
The axial length of each of the primary coils 1a, 1c, 1b, 1d and the secondary coils 2a, 2c, 2b, 2d is "P / 2" as described above. In FIG. 4, the A-phase coils 1a and 2a and the C-phase coils 1c and 2c are provided adjacent to each other, and the B-phase coils 1b and 2b are provided adjacent to the D-phase coils 1d and 2d. Has been. The coil interval between the A phase and the B phase or between the C phase and the D phase is “P (n ± １ ／)” (n is an arbitrary natural number). In FIG. 4, n is “2”, and the coil interval is 7P / 4.
[0005]
With this configuration, when the rod 6 slides on the bearings 68 and 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 becomes “P”. ) As one cycle, and the phase of the reluctance change is shifted by 90 degrees for each of the phases A to D. That is, the phase of the reluctance change is shifted by 180 degrees between the A phase and the C phase, and the phase of the reluctance change is shifted by 180 degrees between the B phase and the D phase.
The A-phase and C-phase primary coils 1a and 1c are excited in the same phase by a sine signal sinωt, and the outputs of the secondary coils 2a and 2c are connected in opposite phases. Similarly, the B-phase and D-phase primary coils 1b and 1d are excited in the same phase by a cosine signal cosωt, and the outputs of the secondary coils 2b and 2d are connected so as to be added in opposite phases. The outputs of the secondary coils 2a, 2c, 2b, 2d are finally added and taken out as an output signal Y.
[0006]
The output signal Y is obtained by phase-shifting the reference AC signal (sinωt, cosωt) by a phase angle φ corresponding to a relative linear position between the magnetic body portion 65 of the rod 6 and the coil assembly 64. The reason is that the reluctance of each phase A to D is shifted by 90 degrees, and the electrical phases of the excitation signals of one pair (A, C) and the other pair (B, D) are shifted by 90 degrees. That's why. 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 65 according to a predetermined proportionality coefficient (or function), by measuring the phase shift φ of the output signal Y from the reference signal sinωt (or cosωt). A straight line position can be detected. However, when the phase shift amount φ is 2π full angle, 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 according to the electric phase shift amount φ in the output signal Y. By measuring the electrical phase shift amount φ, it is possible to accurately determine the linear position within the range of the distance P with high resolution.
[0007]
[Problems to be solved by the invention]
In the linear position detecting device shown in FIG. 4, if a problem occurs in the wiring of the coil assembly 64 or the like, the coil assembly 64 may be removed from the rod 6 and repaired. Since the coil assembly 64 is fixed to a machine or the like, the coil assembly 64 cannot be easily removed from the rod 6 even if a problem occurs in the wiring of the coil assembly 64, which has 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 Patent Laid-Open No. 60-168017).
In this linear position detecting device, a coil assembly is constituted by a primary coil and a secondary coil wound around a U-shaped core (laminated body of iron plates) 3a to 3d, and these are arranged on a rod 6 along a side surface. With this arrangement, the coil assembly can be easily removed. That is, the A phase is composed of the primary coils 1a1 and 1a2 and the secondary coils 2a1 and 2a2 wound on the U-shaped core 3a, and the B phase is the primary coil 1b1 wound on the U-shaped core 3b. And 1b2 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 the U-shaped core. It comprises primary coils 1d1 and 1d2 wound around 3d and secondary coils 2d1 and 2d2. The principle of position detection of this linear position detecting device is the same as that of FIG. Although not described in JP-A-60-168017, these U-shaped cores are fixed to a predetermined cylinder block 31.
[0008]
However, in the case of the linear position detecting device shown in FIG. 5, four U-shaped cores 3a to 3d having the same shape must be manufactured, and the U-shaped core provided with the primary coil and the secondary coil is required. The character-shaped cores 3a to 3d must be accurately mounted at predetermined positions on the cylinder block 31, and the manufacturing and mounting operations thereof require a great deal of time, resulting in high costs.
The present invention has been made in view of the above points, and provides a linear position detecting device that can easily separate a coil assembly and a rod, and that can be manufactured easily and inexpensively. With the goal.
[0009]
[Means for Solving the Problems]
The linear position detecting device according to the present invention includes a magnetic core formed by laminating a plurality of comb-shaped thin plates, a primary coil excited by a predetermined AC signal, and a primary coil. A coil portion having a phase composed of a secondary coil magnetically coupled to the coil at at least four positions of the comb-shaped iron core portion; and a linear displacement movable relative to the magnetic core portion. Provided along the linear displacement direction so that the magnetic resistance on the magnetic circuit formed between the magnetic core portion and the magnetic core along with the linear displacement moves periodically with one pitch of the scale as one cycle. A magnetic graduation section having a plurality of graduations provided, and the magnetic resistance generated by a relative positional relationship between the magnetic graduation section and the magnetic core section while supplying the predetermined AC signal to the primary coil. To change Hazuki, constituting a position detection circuit for taking out data indicating a position of the magnetic scale unit from said secondary coil, said magnetic core, so as to separate the coils of each phase in the toothed core of the comb It was done.
The magnetic core is formed by laminating a plurality of comb-shaped thin iron plates. Accordingly, since each of the teeth of the comb becomes an iron core, a coil assembly can be formed only by winding the primary coil and the secondary coil therearound. Further, since it is only necessary to previously set the interval between the teeth of the comb at the stage of the thin iron plate at a predetermined pitch, it is not necessary to adjust the pitch between the phases after winding the coil as in the conventional case shown in FIG. This simplifies manufacturing and reduces costs. Then, by separating each phase with an iron core, the degree of magnetic coupling between the rod and the core portion of each phase is improved as compared with the case where there is no iron core for phase separation between the phases.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a linear position detecting device according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a linear position detecting device according to the present invention, FIG. 1 (A) is a diagram showing a cross-sectional structure thereof, and FIG. 1 (B) is a line XX of FIG. 1 (A). FIG. 3 is a diagram showing a cross-sectional structure in FIG. 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 type phase shift linear position sensor.
The principle of position detection of this linear position detecting device is the same as the conventional one shown in FIGS. 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 constituted by an integrally molded core. That is, the integrally molded core 30 is formed by laminating a plurality of comb-shaped core iron plates, and the primary coils 1a, 1c, 1b, 1d and Secondary coils 2a, 2c, 2b, 2d are wound respectively. The coil assembly 34 is constituted by the integrally molded core 30, the primary coils 1a, 1c, 1b, 1d and the secondary coils 2a, 2c, 2b, 2d. Assuming that the axial pitch in the alternating arrangement of the magnetic body portion 65 and the non-magnetic body portion 66 of the rod 6 is "P", the winding of the primary coils 1a, 1c, 1b, 1d and the secondary coils 2a, 2c, 2b, 2d. The axial pitches of the comb teeth to be turned, that is, the core portions of the A-phase to D-phase are all 3P / 4. In addition, the integrally molded core 30 is configured to separate the phases A-B, B-C, and C-D by a part of the teeth of the comb (an iron core part where the coil is not wound). I have. By separating the phases with the iron core in this way, the degree of magnetic coupling between the rod 6 and the core portions of the A-phase to D-phase is improved as compared with the case where there is no iron core for phase separation between the phases. There is an effect that can be.
[0011]
The rod 6 is made of a magnetic material such as iron like the conventional one, and is held by bearings 68 and 69. That is, since the rod 6 penetrates through the cylindrical space inside the bearings 68 and 69, it is necessary to move the rod 6 to one end of the rod 6 and remove it in order to separate the bearings 68 and 69 from the rod 6. Since the integrally molded core 30 is merely fixed to the bearings 68 and 69 by screws, the core 30 can be easily separated from the rod 6 and can be easily repaired even if a problem occurs in wiring or the like. This has the effect.
The rod 6 has a ring-shaped nonmagnetic portion 66 of a predetermined width alternately provided in the axial direction on the outer periphery. A magnetic scale portion 6S is formed on the outer peripheral surface of the rod 6 by the repetitive pattern of the magnetic portion 65 and the non-magnetic portion 66. The magnetic member 65 and the non-magnetic member 66 may be made of any material as long as the magnetic circuit formed by the coil assembly 64 changes the magnetic resistance. Good. For example, the non-magnetic member 66 may be made of a non-magnetic material or air. Alternatively, the magnetic properties may be changed by performing laser baking on the iron rod 6 to alternately form the magnetic portions 65 and the non-magnetic 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 is shifted by 90 degrees according to the position of the magnetic body 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, the B phase is a sine (sin) phase, and the D phase is a minus sine (-sin) phase. I have.
[0012]
With this configuration, when the rod 6 slides on the bearings 68 and 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 becomes “P”. ) As one cycle, and the phase of the reluctance change is shifted by 90 degrees for each of the phases A to D. That is, the phase of the reluctance change is shifted by 180 degrees between the A phase and the C phase, and the phase of the reluctance change is shifted by 180 degrees between the B phase and the D phase.
The A-phase and C-phase primary coils 1a and 1c are excited in the same phase by a sine signal sinωt, and the outputs of the secondary coils 2a and 2c are connected in opposite phases. Similarly, the B-phase and D-phase primary coils 1b and 1d are excited in the same phase by a cosine signal cosωt, and the outputs of the secondary coils 2b and 2d are connected so as to be added in opposite phases. The outputs of the secondary coils 2a, 2c, 2b, 2d are finally added and taken in as an output signal Y in the position conversion unit of FIG.
[0013]
The output signal Y is obtained by phase-shifting the reference AC signal (sinωt, cosωt) by a phase angle φ corresponding to a relative linear position between the magnetic body portion 65 of the rod 6 and the coil assembly 64. The reason is the same as the conventional one, the reluctance of each phase A to D is shifted by 90 degrees, and the electric signals of the excitation signals of one pair (A, C) and the other pair (B, D) are different. This is because the target phase is shifted by 90 degrees. 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 65 according to a predetermined proportionality coefficient (or function), by measuring the phase shift φ of the output signal Y from the reference signal sinωt (or cosωt). A straight line position can be detected. However, when the phase shift amount φ is 2π full angle, 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 according to the electric phase shift amount φ in the output signal Y. By measuring the 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 material portion 65 and the non-magnetic material portion 66, but may be made of any other material capable of causing a change in magnetic resistance. For example, the magnetic scale 6S is formed by a combination (a material having a different conductivity) of a material having a high conductivity such as copper and a material having a low conductivity (may be a non-conductive material) such as iron. A change in magnetic resistance according to the current loss may be caused. In this 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 and the like may be any shape as long as the change in the magnetoresistance is efficiently generated.
[0014]
FIG. 3 is a diagram showing a detailed configuration of a position conversion device that supplies a primary AC signal to the inductive type phase shift linear position detection device of FIG. 1 and measures an electrical phase shift φ based on the output signal Y. is there. 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 comprises a clock oscillator 9A, a synchronous counter 9B, ROMs 93a and 93b, D / A converters 94a and 94b, and amplifiers 95a and 95b. The phase difference detector comprises 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 the clock signal.
The synchronous counter 9B counts the clock signal of the clock oscillator 9A, and outputs the count value 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 amplitude data of sinωt, and the ROM 93b stores amplitude data of cosωt. Accordingly, 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. It should be noted that two types of reference AC signals can be obtained in the same manner by reading ROMs having the same amplitude data with address signals having different phases.
[0015]
The D / A converters 94a and 94b convert digital amplitude data from the ROMs 93a and 93b into analog signals and output the analog signals to the amplifiers 95a and 95b. The amplifiers 95a and 95b amplify the analog signal from the D / A converter and apply it to the primary coils 1a, 1c and 1b, 1d as reference AC signals sinωt and cosωt, respectively. Assuming that the frequency division number of the synchronous counter 9B is M, the M count corresponds to the maximum phase angle 2π radian (360 degrees) of the reference AC signal. That is, one count value of the synchronous counter 9B indicates a phase angle of 2π / M radian.
[0016]
The amplifier 96 amplifies the combined value Y = Ksin (ωt + φ) of the secondary voltages induced in the secondary coils 2a to 2d and outputs the amplified value to the zero cross circuit 97.
The zero-crossing circuit 97 detects a zero-crossing point from a negative voltage to a 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 time when the detection signal of the zero cross circuit 97 is output (zero cross point). Therefore, the value latched by the latch circuit 98 is exactly the phase difference (phase shift amount) MP between the reference AC signal and the mutual induction voltage (synthetic secondary output).
That is, the combined output signal Y = sin (ωt + φ) of the secondary coils 2a to 2d is supplied to the zero cross circuit 97. The zero cross circuit 97 outputs a pulse L to the latch circuit 98 in synchronization with the timing when the electric phase angle of the composite output signal Y is zero. The pulse L is used as a latch pulse of the latch circuit 98. Therefore, the latch circuit 98 latches the count value of the synchronous counter 9B in response to the rise of the pulse L. A 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 latch circuit 98 latches the count value corresponding to the phase difference φ between the reference AC signal sinωt and the composite output signal Y = sin (ωt + φ). Therefore, the latched value is output as digital position data MP. Note that the latch pulse L may be appropriately used as a timing pulse.
[0017]
In the above-described embodiment, the case where the coil assembly 34 made of the integrally molded core 30 is provided only on one side in the axial direction has been described. It is also possible to provide a control assembly composed of a mold core and take an average value of both signals to compensate for an error due to the axial deviation of the rod 6. Further, three or more integrally molded cores may be provided, and an average value thereof may be taken. In the above-described embodiment, the case where the coil shape is a square as shown in FIG. 1 (B) has been described. However, a rectangular shape, an elliptical shape in which the circular shape and the longitudinal direction coincide with the axial direction of the rod 6, and other shapes are used. It goes without saying that the shape may be any of the above. The cross-sectional shape of the rod may be other than circular. The scale portion may be provided only on the surface facing the coil assembly. FIG. 1 illustrates the case where the distance between each of the A to D phases is equal to 3P / 4. However, since the A and D phases are on both sides, the positions are structurally unbalanced as compared with the B and C phases. it means that in actually or is a distance B phase -C phase and 90 percent of the 3-Way / 4, the distance between the a phase -B phase and C-D interphase and 110 percent of the 3-Way / 4 , A-phase and D-phase primary coils and secondary coils may have different numbers of turns from those of the B-phase and C-phase to balance each phase. In addition, although the shape of the portion in contact with the rod 6 is substantially straight in the integrally molded core 30 shown in FIG. Needless to say, there is no problem.
[0018]
【The invention's effect】
According to the present invention, since the coil assembly and the rod can be easily separated from each other, maintenance becomes easy, and since the integrally formed core is employed, the production is easy and the cost can be reduced. Further, by separating the phases with an iron core, the degree of magnetic coupling between the rod and the core portion of each phase can be improved as compared with the case where there is no iron core for phase separation between the phases.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a linear position detecting device according to the present invention, FIG. 1 (A) is a diagram showing a cross-sectional structure, and FIG. 1 (B) is a line XX of FIG. 1 (A). FIG. 3 is a diagram showing a cross-sectional structure of FIG.
FIG. 2 is a diagram showing a cross-sectional structure taken along line YY of FIG. 1 (B).
FIG. 3 is a diagram showing a detailed configuration of a position conversion device that supplies a primary AC signal to the inductive type phase shift linear position detection device of FIG. 1 and measures an electrical phase shift φ based on an output signal Y thereof. It is.
FIG. 4 is a diagram showing a schematic configuration of a conventional linear position detecting device.
FIG. 5 is a diagram showing a schematic configuration of a conventional linear position detecting device.
[Explanation of symbols]
1a, 1b, 1c, 1d: primary coil, 2a, 2b, 2c, 2d: secondary coil, 30: integral molded core, 34: coil assembly, 6: rod, 65: magnetic body, 66: non-magnetic Body, 6S: Magnetic scale

Claims (2)

A magnetic core formed by laminating a plurality of comb-shaped thin plates;
A primary coil excited by a predetermined AC signal;
A coil portion having a phase composed of a secondary coil magnetically coupled to the primary coil at at least four positions of the tooth-shaped core portion of the comb;
The magnetic resistance is provided on the magnetic circuit formed between the magnetic core portion and the magnetic core portion in accordance with the linear displacement movement. A magnetic scale portion having a plurality of scales provided along the linear displacement direction so as to periodically change as one cycle;
The data indicating the position of the magnetic scale portion based on the change of the magnetic resistance generated by the relative positional relationship between the magnetic scale portion and the magnetic core portion while supplying the predetermined AC signal to the primary coil. And a position detection circuit for taking out from the secondary coil ,
The linear position detecting device , wherein the magnetic core is configured to separate coils of each phase by a toothed iron core of the comb . 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.

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