JPH057522Y2 - - Google Patents

Description

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

[Conventional technology]

A variable magnetic resistance type and phase shift type linear position detection device is disclosed in U.S. Pat.
Disclosed in the issue. The linear position detection device disclosed therein includes a plurality of primary coils arranged in a predetermined arrangement shifted from each other in the direction of linear displacement, a secondary coil provided corresponding to the primary coil, and a secondary coil provided corresponding to the primary coil. a core portion including a plurality of cores arranged to be linearly displaceable relative to the secondary coil and the secondary coil and provided at predetermined intervals in the linear displacement direction;
Each of the primary coils is individually excited by a plurality of phase-shifted reference AC signals, whereby an output signal obtained by phase-shifting the reference AC signal according to the linear position of the core portion with respect to the coil is generated as the second output signal. This is generated in the next coil. The reference AC signal consists of two phases, a sine wave and a cosine wave, and the coil consists of a total of four phases: two phases corresponding to the sine wave and the cosine wave, and a phase opposite to each phase.

[Problem that the invention attempts to solve]

The function of the change in magnetoresistance that occurs in each phase in response to the displacement of the core, with one pitch of the core as one period, is ideally derived from a simple sine wave or cosine wave (that is, a trigonometric function consisting of only the fundamental wave) without distortion. It is hoped that this will happen. In particular, as a function of the magnetoresistive displacement of each phase, 3
If harmonic components are included, the relationship between the amount of electrical phase shift of the output AC signal and the displacement of the core section will not be linear, and the
Error of 4 cycles as shown in the figure (hereinafter referred to as 4 cycles)
(called a harmonic phase error) occurs. However, in conventional detection devices, it was not possible to eliminate the third harmonic component from being included in the function of magnetoresistance change in each phase, so it was not possible to eliminate the problem of the fourth harmonic phase error as described above. I couldn't do it.

This idea was made in view of the above points,
It is an object of the present invention to provide a linear position detection device that can solve the problem of fourth harmonic phase error.

[Means for solving problems]

The linear position detection devices according to this invention are arranged at a predetermined distance from each other in the direction of linear displacement, and are individually excited by three-phase reference AC signals having a predetermined phase difference (120 degrees). The primary coil of the phase and the 2nd coil provided corresponding to this primary coil.
a secondary coil; and a plurality of core elements disposed so as to be linearly displaceable relative to the primary coil and the secondary coil, and repeatedly provided at a predetermined pitch in the linear displacement direction; and a core portion that produces magnetic resistance in the magnetic circuit of each of the primary coils according to the relative position with respect to the core element, and the separation distance between each phase of the arrangement of the primary coils is set to P×{ n±(1/6)} (where P is the distance of 1 pitch of the array of core elements in the core part, n is an arbitrary arrangement), and the output is phase-shifted according to the linear position of the core part. The present invention is characterized in that a signal is generated in the secondary coil.

[Effect]

Due to the three-phase structure, signal components based on third harmonic components included in the function of magnetoresistance change of each phase cancel each other out when the secondary outputs of each phase are combined. Therefore, the function of magnetoresistance change of each phase is 3
In principle, a fourth harmonic phase error caused by the inclusion of harmonic components does not occur.

〔Example〕

Hereinafter, one embodiment of this invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a linear position detection device according to this invention. This linear position detection device 1 has primary coils 1A to 1F and secondary coils 2A to 2F corresponding to six phases A to F, and is inserted so as to be relatively linearly movable within the coil space of each of these phases. It includes a core part 3.

For each phase A to F, those corresponding to primary coils 1A to 1F and secondary coils 2A to 2F are wound at the same position, and the coil length of each coil is approximately P/
2 (P is an arbitrary number). Coils 1A, 2A, 1D, 2D for A phase and D phase are installed next to each other, and coils 1B, 2B, 1E, 2E for B phase and E phase are installed next to each other.
are provided adjacent to each other, and C-phase and F-phase coils 1C, 2C, 1F, and 2F are provided adjacent to each other. The interval between the A and D phase coil groups and the B and E phase coil groups is "P(n±(1/6)" (n is an integer greater than or equal to 1), and the distance between the C and D phase coil groups is ``P(n±(1/6)''). , the interval between the F-phase coil groups is also “(n±
(1/6)P".

The core portion 3 includes a plurality of magnetic cores 3 arranged at predetermined intervals in the linear displacement direction (direction of arrow L in the figure).
a, and a conductive core 3b interposed therebetween. The magnetic core 3a has a cylindrical shape with a length of approximately P/2, and the length of the conductor portion 3b also has a length of approximately P/2.
It is 2. The magnetic core 3a is made of iron or other ferromagnetic material, and the conductive core 3b is made of a material that is less magnetic or non-magnetic than the magnetic core 3a and has a relatively good conductivity (for example, copper, aluminum, or (or a mixture of a good conductor material such as those in the middle and other materials).

Due to the arrangement of the coils and the structure of the core part 3 as described above, the permeance Pa~
The relationship between Pf is expressed in the following informal way. Here, the phase angle φ corresponds to the relative linear position of the core portion 3, and 360 degrees corresponds to the distance P.
G ₀ and G ₁ are appropriate constants.

Pa=G ₀ +G ₁ sinφ……(1) Pb=G ₀ +G ₁ sin (φ+60°) =G ₀ +G ₁ sin (φ+240°−180°) =G ₀ −G ₁ sin (φ+240°) Pc=G ₀ +G ₁ sin (φ+120°) Pd=G ₀ +G ₁ sin (φ+180°) =G ₀ −G ₁ sinφ Pe=G ₀ +G ₁ sin (φ+240°) Pf=G ₀ +G ₁ sin (φ+300°) =G ₀ +G ₁ sin (φ+120°+180°) =G ₀ −G ₁ sin (φ+120°) In other words, the permeances of the two phases in the same coil group are in opposite phases,
The permeance in each coil group is shifted by 120 degrees.

The primary signals of the A and D phases are designated as ia, the primary signals of the B and E phases are designated as ia, and the primary signals of the C and F phases are designated as ia, and these are set as follows.

ia=sinωt……(2) ib=sin(ωt+240°) ic=sin(ωt+120°) In other words, the primary coil of each coil group is controlled by an AC signal having a phase shift corresponding to the phase shift of its permeance. Excite each.

Under the conditions of equations (1) and (2) above, the output signals of the secondary coils of the two phases within the same coil group are differentially added, and the differential output signals of each coil group are added and synthesized to form the final Find Y as a typical output signal. Then, the output signal Y can be expressed in the following short form. However, K is an appropriate constant.

Y=Ksin(ωt−φ) In other words, Y is a signal obtained by shifting the phase of the primary signal ia by φ. Here, φ corresponds to the relative linear position of the core portion, so by evaluating this φ with an appropriate evaluation means (phase difference detection circuit), the linear position of the core portion 3 can be detected. .

By the way, the function of permeance change at each pole is
In reality, it is not as simple as the above equation (1), but includes a third harmonic error component G ₃ sin3 (φ+β). Then, the above equation (1) can be rewritten as follows.

Pa=G ₀ +G ₁ sinφ+G ₃ sin3 (φ+β) Pb=G ₀ − {G ₁ sin (φ+240°) +G ₃ sin3 (φ+β+240°)} Pc=G ₀ +G ₁ sin (φ+120°) +G ₃ sin3 (φ+β+120° ) Pd=G ₀ −{G ₁ sinφ+G ₃ sin3(φ+β)} Pe=G ₀ +G ₁ sin(φ+240°) +G ₃ sin3(φ+β+240°) Pf=G ₀ −{G ₁ sin(φ+120°) +G ₃ sin3 (φ+β+120°)}...(3) However, if we calculate the composite value Y of the secondary coil output signals of each phase under the conditions of this equation (3) and the above equation (2), it will not include the third harmonic error component. As in the case, Y=Ksin(ωt−φ), and it was confirmed that the error due to the third harmonic component can be eliminated in principle. To explain this point, the output signal Y is synthesized as shown in equation (4) below.

Y=d/dt {ia (Pa-Pd) + ib (Pe-Pb) + ic (Pc-Pf)}...(4) Substitute the above equation (2) for each term in the differential term of the above equation (4) When rearranged, we get the following formula.

ia (Pa-Pd) + ib (Pe-Pb) + ic (Pc-Pf) = (Pa-
Pd)・sinωt+(Pe−Pb)・sin(ωt+240)+
(Pc−Pf)・sin(ωt+120)=(Pa−Pd)・
sinωt+(Pe−Pb)・sinωt・cos240+(Pe−
Pb)・cosωt・sin240＋(Pc−Pf)・sinωt・
cos120+(Pc−Pf)・cosωt・sin120={(Pa−
Pd)−0.5(Pe−Pb)−0.5(Pc−Pf)}・sinωt+
{−0.866(Pe−Pb)+0.866(Pc−Pf)}・cosωt
...(5) However, cos120=0.5, cos240=-0.5, sin120=0.866, sin240=-0.866.

Substituting the above equation (3) into the multiplier term of sinωt in the above equation (5) and rearranging it, we get the following.

(Pa−Pd)−0.5(Pe−Pb)−0.5(Pc−Pf)={G ₀
＋G ₁ sinφ＋G ₃ sin3(φ＋β)−G ₀ ＋G ₁ sinφ＋
G ₃ sin3(φ+β)}−0.5{G ₀ +G ₁ sin(φ+240)
+G ₃ sin3 (φ+β+240) −G ₀ +G ₁ sin (φ+
240) +C ₃ sin3(φ+β+240)}−0.5{G ₀ +G ₁
sin(φ+120)+G ₃ sin3(φ+β+120)−G ₀₊
G ₁ sin (φ + 120) + G ₃ sin 3 (φ + β + 120)} = 2
{G ₁ sinφ＋C ₃ sin3(φ＋β)}−{G ₁ sin(φ＋
240) +G ₃ sin3(φ+β+240)}−{G ₁ sin(φ+
120) +G ₃ sin3 (φ+β+120)}=G ₁ {2sinφ−
sin(φ+240)−sin(φ+120)}+G ₃ {2sin3(φ
+β)-sin3(φ+β+240)-sin3(φ+β+
120)}=G ₁ {2sinφ−sinφcos240−cosφsin240
−sinφcos120−cosφsin120}+G ₃ {2sin3(φ+
β) − sin3 (φ + β) cos720 − cos3 (φ + β)
sin720−sin3(φ+β)cos360−cos3(φ+
β) sin360}=G ₁ {2sinφ+0.5sinφ+
0.866cosφ＋0.5sinφ−0.866cosφ}＋G ₃ {2sin3
(φ+β)−sin3(φ+β)−sin3(φ+β)=
3G ₁ sinφ+0……(6) However, cos720=1, cos360=1, sin720=0,
sin=360=0.

Similarly, by substituting the above equation (3) into the multiplier term of cosωt in the above equation (5) and converting it into an integer, the following is obtained.

−0.866(Pe−Pb)+0.866(Pc−Pf)=0.866[−
{G ₀ +G ₁ sin(φ+240)+G ₃ sin3(φ+β+
240) −G ₀ +G ₁ sin(φ+240)+G ₃ sin3(φ+β
+240)}+{G ₀ +G ₁ sin(φ+120)+G ₃ sin3(φ
+β+120)−G ₀ +G ₁ sin(φ+120)+G ₃ sin3
(φ+β+120)}=0.866[2G ₁ {sin(φ+120)−
sin(φ+240)}+2G ₃ {sin3(φ+β+120)−
sin3(φ+β+240)}]=0.866[2G ₁
{sinφcos120＋cosφsin120−sinφcos240−
cosφsin240}+2G ₃ {sin3(φ+β)cos360+
cos3 (φ+β) sin3660 sin3 (φ+β) cos720
−cos3(φ+β)sin720}]=0.866[2G ₁
(0.866cosφ+0.866cosφ)+2G ₃ {sin3(φ+β)
−sin3(φ+β)}=3G ₁ cosφ……(7) However, 0.866=sin120=(√3)/2.

Substituting equations (6) and (7) above into equation (5) and rewriting equation (4) above, Y=d/dt3G ₁ (sinφ・sinωt+cosφ・cosωt)=
3G ₁ (sinφ・cosωt−cosφ・sinωt)=−3G ₁
(sinωt・cosφ−cosωt・sinφ)=Ksin(ωt−
φ) becomes. Note that −3G ₁ =K is set.

As described above, it has been confirmed that the third harmonic component can be removed in principle. Therefore, a fourth harmonic phase error caused by the third harmonic component does not occur in principle, and the relationship between the phase shift amount φ in the output signal Y and the linear position x becomes linear as shown in FIG.

Each coil group may be housed in a magnetic case. An example is shown in FIG. 3. In the same figure, the A-phase primary coil and secondary coils 1A, 2A and the D-phase primary coil and secondary coils 1D, 2D are housed in a cylindrical magnetic case 4 through a partition wall, and the B-phase The primary coil and secondary coil 1B, 2B and the E-phase primary coil and secondary coil 1E, 2E are connected to the cylindrical magnetic case 5 through the partition wall.
is housed in the C-phase primary coil and secondary coil 1.
C, 2C and F phase primary coil and secondary coil 1
F and 2F are housed in a cylindrical magnetic case 6 via a partition wall. By accommodating each coil group in a magnetic case in this manner, crosstalk between the coils is prevented, the magnetic lines of force of each coil are concentrated, and the coupling of the magnetic circuits is enhanced.

FIG. 4 shows another example of the core part 3.
In the figure, the base material of the core part 3 is made of a magnetic material, and a magnetic core 3a protruding in a ring shape is provided around the base material with a predetermined width P/2 in the linear displacement direction. A plurality of body cores 3a are provided at predetermined intervals P/2 in the linear displacement direction. A plurality of conductor cores 3b are provided in a ring shape in each ring-shaped recess between each magnetic core 3a.
The width of each ring-shaped conductor core 3b is also P/2.

In the examples shown in Figures 1, 3, and 4, a conductor and a magnetic material are alternately provided as the core element, and the magnetic resistance is small in the magnetic part, and the magnetic resistance is reduced due to eddy current loss in the conductor part. As the resistance increases, the range of change in magnetic resistance increases synergistically. However, the core portion 3 may consist only of the magnetic core 3a or only the conductive core 3b.

Next, a method for forming the core element in the core portion 3 will be described using several examples. Good conductor or magnetic material 3a, 3 constituting the core element
b is an appropriate surface treatment technique (for example, plating,
It may be attached or formed on the substrate using thermal spraying, baking, painting, welding, vapor deposition, electroforming, photoetching, etc.). Recently, micro-processing technology that can form even minute patterns using this kind of processing technology has been established, so it is possible to form precise patterns using such technology.

FIG. 5 shows an example in which a repeating pattern of core elements 3b is formed around a base material 3c of the core part 3 using a good conductor material such as copper, and a surface coating 3d such as chrome plating is provided thereon. ing. In this case, the pattern formation method is to apply copper plating to the entire circumference of the base material 3c, and then remove unnecessary parts using a removal technique such as etching. is formed. Finally, a surface coating 3d such as chrome plating is applied for surface finishing. It is preferable to use a magnetic material such as iron for the base material 3c because it improves the passage of magnetic flux. However, resin such as plastic or other materials can also be used as the base material 3c. In that case, a metal film such as copper may be plated on the surface of the preformed plastic base material 3c. Alternatively, a metal film such as copper may be preformed in the mold cavity by electroforming, and then plastic may be injection molded to integrate with the metal film. In the case of FIG. 5, the core element consists only of a repeating pattern of conductors and no magnetic material is provided, but since a change in magnetic resistance occurs due to eddy current loss, the core element operates in the same manner as described above.

By the way, if the surface coating 3b is buried in the recesses between the patterns 3b as shown in FIG.
The surface often sinks and the finished surface is not smooth. Therefore, as shown in FIG. 6, it is preferable to fill the recesses between each core 3b with a suitable filler 3e, and then apply a surface coating 3d thereon. As the filler 3e, for example, nickel plating or the like can be used.

Note that when the base material 3c is plated with a metal film such as copper and then etched in a desired pattern, there is a risk that the surface of the base material 3c may be attacked by the etching agent. This problem is particularly serious when the base material 3c is made of metal such as iron. In order to solve such problems, as shown in FIG. 7, a thin film of a predetermined material 3f (for example, resin) that is resistant to etching chemicals is formed on the entire surface of the base material 3c, and then a thin film is formed on the entire surface of the base material 3c. It is preferable to perform copper plating or the like and further perform a predetermined etching to form the pattern 3b of the core element.

[Effect of idea]

As described above, according to this invention, by adopting a three-phase structure, the signal components based on the third harmonic components contained in the function of the magnetic resistance change of each phase cancel each other out when the secondary outputs of each phase are combined, so that it is possible in principle to eliminate the fourth harmonic phase error in the output phase caused by the third harmonic components being included in the function of the magnetic resistance change of each phase.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the linear position detection device according to this invention, and FIG. 2 is a graph illustrating the relationship between the amount of electrical phase shift of the output AC signal and the displacement of the core portion in the same embodiment. , FIG. 3 is a cross-sectional view showing another embodiment of the linear position detection device according to the invention, FIG. 4 is a cross-sectional view showing still another embodiment, and FIG.
7 to 7 are cross-sectional views showing the method of forming the core part,
FIG. 8 is a graph illustrating the relationship between the electrical phase shift amount of the output AC signal and the displacement of the core portion in a conventional two-phase or four-phase linear position detection device. 1... Linear position detection device, 1A to 1F... Primary coil, 2A to 2F... Secondary coil, 3... Core portion, 3a... Magnetic core, 3b... Conductor core,
3c...Base material.

Claims (1)

[Claims for Utility Model Registration] (1) Disposed apart from each other by a predetermined distance in the direction of linear displacement, and individually excited by three-phase reference AC signals having a predetermined phase difference (120 degrees). a three-phase primary coil; a secondary coil provided corresponding to the primary coil; and a secondary coil disposed so as to be linearly displaceable relative to the primary coil and the secondary coil, and in the direction of linear displacement. A core portion including a plurality of core elements repeatedly provided at a predetermined pitch and causing magnetic resistance in the magnetic circuit of each of the primary coils in accordance with the relative position of the primary coil and the core element. The separation distance between each phase of the arrangement of the primary coil is P×{n±(1/6)} (where P is the distance of one pitch of the arrangement of the core elements in the core part, n
(arbitrary arrangement), and generates in the secondary coil an output signal whose phase is shifted according to the linear position of the core portion. (2) The primary coil for each phase is P×{n±(1/
2) 1 arranged with a separation distance of
The linear position detection device according to claim 1, which is comprised of a pair of coils.