JPH037765Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field This invention relates to a phase shift type linear position detection device using a variable magnetic resistance method.

Prior Art A phase shift type linear position detection device has a plurality of sensors arranged at predetermined positions in a linear displacement direction.
It includes a primary coil, a secondary coil provided corresponding to the primary coil, and a magnetic core disposed so as to be linearly displaceable relative to the primary coil and the secondary coil, By individually exciting each of the primary coils with a plurality of phase-shifted reference AC signals, an output signal obtained by shifting the phase of the reference AC signal according to the relative linear position of the magnetic core is sent to the secondary coil. I'm trying to make it happen. Since the configuration is such that multiple primary coils are excited with alternating current signals of different phases, if crosstalk occurs between the coils, the phase of the excitation signal will be distorted, and as a result, the detection accuracy will be reduced. There was a problem with the decline. If the primary coil spacing is relatively wide, such crosstalk will not be much of a problem, but the coil spacing must be narrowed due to the need to downsize the detection device or restrictions on the installation location. This is especially a problem in cases where

The idea of magnetic shielding to prevent crosstalk is well known, for example,
No. 58-50418. In this system, a detection head senses the scale of a permanent magnet according to the relative displacement of a magnetic scale in which a large number of permanent magnets are arranged in a scale, generates a pulse output, and obtains position data by counting the pulse output. At that time,
A reference point magnet is provided corresponding to a predetermined scale position, and a reference point detection head is separately provided to sense the magnetism of this reference point magnet.In order to prevent crosstalk, a scale detection head and a reference point detection head are installed. The head is magnetically shielded separately.

In addition, conventionally known phase shift type linear position detection devices are disclosed in Japanese Patent Application Laid-Open No. 53-106065 and
There is something shown in Publication No. 55-13891 etc.
In these, only one core was provided, and the primary coil was provided over the entire linear position detectable range. Therefore, it has been difficult to expand the linear position detectable range.

Purpose of the invention Therefore, this invention makes it possible to easily expand the detectable range of linear position in a phase-shift type linear position detection device using a variable magnetic resistance method, and also enables the linear position detection device to be excited by alternating current signals of different phases. The purpose of this is to prevent crosstalk from occurring between the coils.

Summary of the invention A phase shift type linear position detection device according to the invention is arranged at a predetermined distance from each other in the direction of linear displacement, and has a predetermined phase difference other than 180° or 360°. at least two primary coils that are individually excited by a reference AC signal with /d degrees), a secondary coil provided corresponding to the primary coil, and the primary coil and the secondary coil. and a core portion having a plurality of members that cause a change in magnetic resistance arranged at predetermined pitches in the direction of linear displacement, the core portion being disposed so as to be linearly displaceable relative to the primary coil. The separation distance is calculated as P×{n±
(1/d)} (where n is any integer),
As a result, an output signal whose phase is shifted from the reference AC signal according to the linear position of the core portion with respect to the coil is generated in the secondary coil, and from each primary coil and its corresponding secondary coil. Each coil group is coated with a magnetic material, and the magnetic material coating provides mutual magnetic shielding between the coil groups excited by primary alternating current signals having different phases. This is a characteristic feature.

If the phase difference of the reference AC signal is 360/d degree, then
The arrangement of each primary coil is determined by P×{n
±(1/d)}. Thereby, it is possible to obtain an output signal whose phase is shifted according to the linear position. For example, if the reference AC signal is a sine wave and a cosine wave, and the phase difference between them is 90 degrees, d=4, and the coil arrangement interval is P×
It is determined to satisfy the condition {n±(1/4)}.

By selecting the coil arrangement in this way, in the core part,
By arranging a plurality of members that cause magnetic resistance changes at predetermined pitches, periodic phase changes occur repeatedly for each linear displacement amount P, and linear position detection can be performed over a plurality of pitches P. The linear position detectable range can be easily expanded by arbitrarily changing the arrangement number of members that cause magnetic resistance changes in the core portion without changing the coil configuration.

When excitation is performed using multiple AC signals with different phases, the effect of crosstalk becomes a particularly big problem. This problem can be solved by providing magnetic shielding.

Embodiments This invention will be described in detail below based on embodiments shown in the accompanying drawings.

In FIG. 1, the detector 20 includes a primary coil and a secondary coil that are relatively fixed in a predetermined arrangement, and a core section 3 that is inserted into these coils so as to be relatively linearly movable. I'm here. Core part 3
consists of a plurality of magnetic cores 3a arranged at predetermined intervals in the linear displacement direction and non-magnetic spacers 3b interposed therebetween. As an example, the core 3a has a cylindrical shape with a length of approximately "P/2", and the length of the spacer 3b also has a length of approximately "P/2".

In this embodiment, the coils are arranged to operate in four phases. These phases are distinguished using symbols A, B, C, and D as appropriate. Each phase A depends on the relative position of the core 3a with respect to the coil.
~The magnetic resistance generated at D is shifted by 90 degrees. For example, if phase A is a cosine phase, then B
The arrangement of each coil and the size and shape of the core 3a are determined so that the phase is a sine phase, the C phase is a minus cosine phase, and the D phase is a minus sine phase. The A-phase and C-phase coil groups, whose magnetic resistance changes are in opposite phases, are excited by a common primary AC signal, and the B-phase and D-phase coil groups, whose magnetic resistance changes are also in opposite phases, are excited by a common primary AC signal. Excited by a primary AC signal, there is an electrical phase shift between the primary AC signals of the A and C phase coil groups and the B and D phase coil group corresponding to a 90 degree phase shift of their magnetic resistances. exist. For example, the A and C phase coil groups are excited by a sine signal, and the B and D phase coil groups are excited by a sine signal.
The phase coil groups are energized by cosine signals.

In the example shown in Fig. 1, the primary coil 1A of each phase A to D is
~1D and the secondary coils 2A~2D are wound in the same position, and the coil length of each coil is approximately "P/2". The A-phase and C-phase coils 1A, 2A, 1C, and 2C are installed next to each other, and the B-phase and D-phase coils 1B, 2B, and 2C are installed next to each other.
1D and 2D are also provided next to each other, and the interval between the A and C phase coil groups and the B and D phase coil groups is "P(n±1/4)" (n is any natural number). There is.

A magnetic material 4 is coated around the A and C phase coil groups that are excited by a common primary signal (for example, a sine wave). Similarly, another magnetic material 5 is coated around the B and D phase coil groups. As a result, the coil groups of A and C phases and B,
The D-phase coil groups are each magnetically shielded, and crosstalk between them can be prevented. Therefore, the interval "P(n±1/4)" between both coil groups can be set to the minimum value (n=1, and P can be made as small as necessary).

In the embodiment shown in FIG. 2, the core portion 30 is a round bar 31.
It differs from FIG. 1 in that it consists of a ring-shaped magnetic core 30a and a spacer 30b that are fitted onto the outside, but otherwise is the same as FIG. 1.

In the embodiment shown in FIG. 3, the core portion 32 has a plurality of conical or truncated conical tapered portions 32a,
2b... are formed alternately in opposite directions at a constant pitch P along the relative linear change direction. A first magnetic taper portion 32a whose cross-sectional area gradually decreases over a constant length P/2 and a second magnetic taper portion 32b whose cross-sectional area gradually increases over a constant length P/2 are aligned. As a group, they contribute to bringing about one cycle of trigonometric function-shaped magnetoresistance change within the displacement amount P range. Primary coil 1A for each phase A to D
1D, secondary coils 2A to 2D are A, B, C, D
They are provided at intervals of "P/4" in this order. Then, the coil groups for each phase are magnetic materials 6, 7, 8, 9.
They are each coated with

In the embodiment shown in FIG. 4, the core portion 3 is the same as that in FIG. 1, but the coil configuration is slightly different. In other words,
A common primary coil 1AC is used for A phase and C phase,
A common primary coil 1BD is used for B phase and D phase. In the A and C phase coil groups, the secondary coil 2A, the primary coil 1AC, and the secondary coil 2C are arranged in this order, and their total length is approximately "P". B,D
The same applies to the phase coil groups, and the arrangement interval between both groups is "P(n±1/4)". The A and C phase coil groups are covered with a magnetic material 10, and the B and D phase coil groups are covered with a magnetic material 1.
1.

Primary coils 1A to 1 in Figures 1 to 3
D and the secondary coils 2A to 2D are connected as shown in FIG. 5 or 6. Figure 5 shows A phase and C phase.
This shows a wiring configuration in which the primary coils 1A and 1C of the phase are excited in opposite phases to each other by a sine signal sinωt, and the outputs of the secondary coils 2A and 2C are added in the same phase. B phase and D phase are also similar to the above,
The primary coils 1B and 1D are excited in opposite phases with the cosine signal cosωt, and the outputs of the secondary coils 2B and 2D are added in phase. On the other hand, in the connection format shown in FIG. 6, the A-phase and C-phase primary coils 1A, 1C are excited in the same phase by the sine signal sinωt, and the secondary coils 2A, 2C are connected in opposite phases. In addition, the primary coils 1B and 1D of B phase and D phase
are excited in the same phase by a cosine signal cosωt, and the secondary coils 2B and 2D are connected in opposite phases.

The coil connection format in FIG. 4 is as shown in FIG. 7. That is, the primary coil 1 of A phase and C phase
Excite AC with sine signal sinωt, secondary coil 2A,
Connect 2C in reverse phase. Further, the B-phase and D-phase primary coils 1BD are excited by the cosine signal cosωt, and the secondary coils 2B and 2D are connected in opposite phases.

In short, the wiring formats shown in FIGS. 5 to 7 can be expressed as follows. In other words, the reluctance change
Two phases shifted by 180 degrees (A and C or B and D)
are operated in opposite phases to each other, and one of two pairs (a pair of A and C and a pair of B and D) whose reluctance changes are shifted by 90 degrees is excited by a sine signal sinωt, and the other is excited by a cosine signal cosωt. It is excited by The output signal Y of the detector 20 is obtained by adding the secondary coil outputs of the A and C phase pair and the B and D phase pair. This output signal Y is converted into a reference AC signal (sinωt or
cosωt) with a phase shift. The reason for this is that the reluctances of each phase A to D are shifted by 90 degrees, and one pair (A, C) and the other pair (B,
This is because the electrical phase of the excitation signal in D) is shifted by 90 degrees. This point can be expressed briefly as follows.

In other words, if the phase corresponding to the linear position of the core parts 3, 30, 32 is φ, the function of reluctance change according to the linear position is cosφ for phase A and cosφ for phase B.
sinφ, the C phase is −cosφ, and the D phase is −sinφ. The A phase and C phase are sinusoidal signals sinωt
The output signal Y is It can be substantially expressed in the following shorthand form.

Y=sinωt cosφ−(−sinωt cosφ) +cosωt sinφ−(−cosωt sinφ) =2sinωt cosφ+2cosωt sinφ =2sin(ωt+φ) The coefficient indicated as “2” in the above formula for convenience is a constant determined according to various conditions. When replaced by K, it can be expressed as Y=Ksin(ωt+φ). Here, since the phase φ of the reluctance change is proportional to the linear position l of the core according to a predetermined proportionality coefficient (or function), the output signal Y
The linear position l can be detected by measuring the phase shift φ from the reference signal sinωt (or cosωt) at . However, the phase shift amount φ is full-width
2π, the linear position l is the aforementioned distance P (1 of the core
Pitch length).

Output signal Y of the detector 20 and reference AC signal sinωt
(or cosωt) can be constructed as appropriate. FIG. 8 shows an example of a circuit in which the phase shift φ is determined as a digital quantity. Although not particularly shown, the reference AC signal sinωt and the output signal Y=Ksin(ωt+φ) are generated using an integrating circuit.
The phase shift φ can also be determined as an analog quantity by determining the time difference between the zero phase and the zero phase time difference.

In FIG. 8, the oscillation unit 29 is a reference sine signal.
A circuit for generating sinωt and a cosine signal cosωt, and a phase difference detection circuit 37, is a circuit for measuring the phase shift φ. A counter 27 counts clock pulses CP generated by a clock oscillator 33. The counter 27 is, for example, Modulo M,
The count value is given to register 28. From the 4/M frequency-divided output of the counter 27, a pulse P _c obtained by 4/M cycles of the clock pulse CP is taken out and applied to the C input of a flip-flop 34 for 1/2 frequency division. The pulse P _b output from the Q output of this flip-flop 34 is applied to the flip-flop 35,
The pulse P _a output from the flip-flop 36
The outputs of these 35 and 36 pass through the low-pass filters 21 and 22 and the amplifiers 23 and 24 to obtain a cosine signal cosωt and a sine signal sinωt. The M count in the counter 27 corresponds to the phase angle of 2π radians of these reference signals cosωt and sinωt. That is, one count value of the counter 27 indicates a phase angle of 2π/M radians.

The output signal M of the detector 20 is applied to a comparator 26 via an amplifier 25, and a square wave signal corresponding to the positive or negative polarity of the signal Y is output from the comparator 26. In response to the rise of the output signal of the comparator 26, a pulse is sent from the rise detection circuit 28.
T _s is output, and the count value of the counter 27 is loaded into the register 28 in response to this pulse T _s .
As a result, the digital value D〓 according to the phase shift φ
is taken into the register 28.

Effects of the invention As described above, according to this invention, it is possible to obtain a complete phase change over 360° within a displacement range corresponding to one pitch P, and moreover, it is possible to obtain a complete phase change over a range of 360° by simply reducing the number of members that cause a change in magnetic resistance in the core. This simple increase has the advantageous effect of allowing such a 360° phase change to occur continuously for many cycles over an infinitely long measuring range. At the same time, since the periphery of each coil group is coated with a magnetic material, crosstalk between coil groups excited by AC signals of different phases is prevented, which improves detection accuracy and improves the arrangement of each coil group. The installation interval can be narrowed, which is advantageous when downsizing the entire device.

[Brief explanation of the drawing]

1 to 4 are axial sectional views showing embodiments of the phase shift type linear position detection device according to the invention, and FIGS. 5 to 7 are circuit diagrams showing coil connection types in each of the above embodiments. 8 are electrical block diagrams showing an example of a circuit for supplying a reference AC signal to a primary coil and a circuit for measuring a phase shift of a secondary coil output signal. 20...Detector, 1A to 1D, 1AC, 1BD
...Primary coil, 2A~2D...Secondary coil,
3, 30, 32...Core part, 3a, 30a...Magnetic core, 3b, 30b...Nonmagnetic spacer,
31...Round bar, 4-11...Magnetic material covering each coil group.

Claims (1)

[Claims for Utility Model Registration] Reference alternating currents having a predetermined phase difference (360/d degree) that are arranged apart from each other by a predetermined distance in the direction of linear displacement and have a predetermined phase difference other than 180° or 360°. at least two primary coils individually excited by a signal; a secondary coil provided corresponding to the primary coil; and a linear displacement relative to the primary coil and the secondary coil. a core portion having a member that causes a change in magnetic resistance and arranged in plurality at a predetermined pitch in a linear displacement direction, and the separation distance between the arrangement of each of the primary coils is determined by the distance between each primary coil. The phase difference (360/d degree) of the excitation AC signal of
Based on the distance P of one pitch of the arrangement of the members in the core part, P×{n±(1/d)} (however,
n is an arbitrary integer), thereby causing the secondary coil to generate an output signal whose phase is shifted from the reference AC signal according to the linear position of the core portion with respect to the coil, and Each coil group consisting of a coil and its corresponding secondary coil is coated with a magnetic material, and the coil groups excited by primary alternating current signals of different phases are mutually magnetically generated by the magnetic material coating. A phase shift type linear position detection device characterized in that shielding is achieved.