JPH0323526Y2 - - Google Patents

Description

[Detailed description of the invention] Technical field This invention relates to a variable magnetic resistance type linear position detector, and in particular, a plurality of magnetic scales are repeatedly formed at predetermined intervals on a scale part that is linearly movable relative to a coil. The present invention relates to a magnetic scale in which the magnetic scale is formed of a magnetic coating.

Prior Art A differential transformer has been well known as a variable magnetic resistance type linear position detector. However, conventionally known differential transformers have only one magnetic core.
However, the measurable range was limited to minute lengths. On the other hand, in the "phase shift type linear position detection device" shown in Utility Application No. 57-32127, a plurality of magnetic cores are provided at predetermined intervals, and each core has a periodic magnetic resistance. Try to get a change,
It has been proposed to expand the measurable range.
However, in the case shown in this prior application, a plurality of cylindrical magnetic cores and non-magnetic spacers are arranged alternately to assemble a rod-shaped core body, so the number of parts is large. However, processing and assembly were time-consuming and tended to be relatively expensive.

Purpose of the invention This invention was made to eliminate the above-mentioned drawbacks, and aims to provide a variable magnetic resistance type linear position detector that is easier to process and assemble by improving the structure of the magnetic core. It is.

Structure of the invention The variable magnetic resistance type linear position detector according to the invention includes a coil part having a plurality of primary coils and secondary coils provided at predetermined intervals in the direction of linear displacement, and a scale portion that can be relatively linearly displaced by a non-magnetic base, and is formed by repeatedly forming a plurality of magnetic scales made of a magnetic coating on the surface of a non-magnetic base at predetermined intervals along the direction of linear displacement; and the primary coil. are individually excited by a plurality of phase-shifted reference AC signals, whereby the reference AC signal is applied to the repeating pitch of the magnetic scale according to the relative linear position of the scale with respect to the coil. and a circuit that allows the secondary coil to provide an electrically phase-shifted output according to its relative linear position within one cycle of the secondary coil.

According to this invention, a plurality of magnetic scales made of a magnetic film are formed on the surface of a non-magnetic base in the scale portion. The formation of the magnetic coating can be achieved with a much smaller number of steps and parts than when assembling a plurality of cylindrical cores and spacers arranged alternately. In other words, manufacturing becomes easier and costs can be lowered. The magnetic film can be formed by selectively applying various metal film forming techniques such as plating, sputtering, vapor deposition, liquid rapid freezing, printing, and coating. Note that the magnetic coating in this invention is not limited to one made only of magnetic metal, but may be a mixture with other substances or a nonmetallic ferromagnetic coating.

Embodiment An embodiment of this invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, a coil section 1 includes four primary coils 2, which are arranged in a predetermined arrangement offset in the axial direction.
3, 4, 5 and correspondingly provided secondary coils 6, 7, 8, 9 are housed in a casing 10. The rod part 11, which corresponds to a scale part, is equipped with a plurality of ring-shaped magnetic cores 11a, which correspond to magnetic scale parts, at predetermined intervals, and is inserted concentrically into the coil space of the coil part 1. It is possible to move in a straight line relative to 1. The core of the rod portion 11 is a non-magnetic rod 11
The plurality of ring-shaped magnetic cores 11a described above are made of a magnetic coating formed around the non-magnetic rods 11b. In order to make the outermost circumferential surface of the rod portion 11 smooth, the outermost circumference is coated with a non-magnetic coating 11c. In addition, in FIG. 1, the non-magnetic rod 11b
Only one part is shown in a side view, and the other part is shown in a cross-sectional view.

As an example, a plurality of ring-shaped magnetic coatings corresponding to the ring-shaped magnetic core 11a can be simultaneously formed around the non-magnetic rod 11b by "plating". After the magnetic core 11a has been plated, a nonmagnetic coating 11c on the outermost periphery is formed by plating with a nonmagnetic metal such as copper or hard chrome. In this case, the peripheral surface of the non-magnetic rod 11b is smooth, and the ring-shaped magnetic core 11a is raised on the surface of the rod 11b to form a coating due to the ring-shaped magnetic metal plating.
Each core 1 is plated with non-magnetic metal from above.
The space between 1a is filled with a nonmagnetic coating, and a nonmagnetic coating 11c is formed on the entire outermost periphery of the rod portion 11.

Figures 2a, b, and c are diagrams showing another manufacturing procedure for the rod portion 11. In this case, magnetic metal plating 11a' is first applied to the entire circumferential surface of the non-magnetic rod 11b (see a). , then from above the ring-shaped magnetic core 1
Etching resist material 12 is applied in a ring shape corresponding to the planned position 1a (see b), and etching is performed in this state to finally obtain a ring-shaped magnetic core 11a as shown in c. Thereafter, a non-magnetic coating 11c is formed by chrome plating or the like.

3a and 3b are diagrams showing another example of the structure of the rod part 11 according to the manufacturing procedure, in which the non-magnetic rod 11 is
b' has ring-shaped projections and depressions formed at predetermined intervals on its circumferential surface. In this case, first, magnetic metal plating 11a' is applied to the entire circumferential surface of the non-magnetic rod 11b' (see a), and then the plating 11a' is scraped off to the height of the convex part of the rod 11b'. A ring-shaped magnetic film 11a is formed so as to fill the recess (b
reference). The outermost non-magnetic coating 11c does not need to be particularly formed, but if necessary, this non-magnetic coating 11c may be formed.
1c may be formed by chrome plating or the like.

As an example, the length (width) of each ring-shaped magnetic core 11a is "P/2" (P is arbitrary), the mutual interval is also "P/2", and the 1-pitch interval of the core arrangement is " P”. In this example, the coils are arranged to operate in four phases.
For convenience, these phases are distinguished using symbols A, B, C, and D. Magnetic core 11a of rod portion 11
The reluctance generated in each phase A to D is shifted by 90 degrees depending on the position of Sign phase,
It is becoming like this. In the embodiment of FIG.
Primary coils 2 to 5 and secondary coils 6 to 9 are individually provided for each phase A to D. 2 for each phase A to D
The primary coils 6 to 9 correspond to the respective primary coils 2 to 9.
5 are wrapped around the outside of each. The length of each coil is approximately equal to the length of the ring-shaped magnetic core 11a,
It is "P/2". In the example shown in Fig. 1, the A-phase coils 2, 6 and the C-phase coils 3, 7 are installed adjacent to each other, and the B-phase coils 4, 8 and the D-phase coils 5, 9 are also installed adjacent to each other. It is set up. Also, the interval between the A-phase and B-phase or C-phase and D-phase coils is “P(n
±1/4)” (n is any natural number). With this configuration, the rod portion 11 (more specifically, the magnetic core)
The reluctance of the magnetic circuit in each phase A to D changes according to the linear displacement of and D phase and 180
It is becoming like this. Primary coil 2-5
The secondary coils 6 to 9 are connected as shown in FIG. Figure 4 shows a wiring configuration in which the A-phase and C-phase primary coils 2 and 3 are excited in opposite phases by a sine signal sinωt, and the outputs of the secondary coils 6 and 7 are added in phase. It shows. B phase and D
As for the phase, the primary coils 4 and 5 are connected to cosine signals as described above.
Antiphase excitation is performed at cosωt, and the outputs of the secondary coils 8 and 9 are added in phase. The outputs of the secondary coils are finally summed to obtain the output signal Y. On the other hand, not limited to this,
The A-phase and C-phase primary coils 2 and 3 are connected to the sine signal sinωt.
The secondary coils 6 and 7 are connected in reverse phase, the B-phase and D-phase primary coils 4 and 5 are excited in the same phase by the cosine signal cosωt, and the secondary coils 8,
9 may be connected in reverse phase and the secondary coil outputs may be added finally.

In short, the wiring format shown in FIG. 4 can be expressed as follows. In other words, two phases (A and C or B and D) whose reluctance changes are shifted by 180 degrees are operated in opposite phases, and two pairs whose reluctance changes are shifted by 90 degrees (a pair of A and C and a pair of B and One of the pair D) is excited by a sine signal sinωt, and the other is excited by a cosine signal cosωt. In other words, the two pairs (the pair A and C and the pair B and D) are the same as two differential transformers whose reluctance changes are out of phase by 90 degrees; Each is individually excited by two types of alternating current signals (sinωt, cosωt) with corresponding electrical phase shifts. The output signal Y is the sum of the secondary coil outputs of the A, C phase pair and the B, D phase pair.
becomes. This output signal Y is converted into a reference AC signal (sinωt or conωt) by a phase angle φ corresponding to the linear position of the ring-shaped magnetic core 11a in the rod portion 11.
It is a phase-shifted version of . The reason for this 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. It's for a reason. This point can be summarized as follows.

That is, if the phase corresponding to the linear position of one magnetic core 11a is φ, the function of reluctance change according to the linear position is cosφ for A phase, sinφ for B phase, -cosφ for C phase, and -cosφ for D phase. It can be expressed in the short form -sinφ. A and C phases are sine signals
The output signal Y can be effectively expressed in the following shorthand form:

Y=sinωtcosφ−(−sinωtcosφ) +cosωtsinφ−(−cosωtsinφ) =2sinωtcosφ+2cosωtsinφ =2sin(ωt+φ) If we replace the coefficient indicated as “2” in the above formula with a constant K determined according to various conditions, we get 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 magnetic core 11a according to a predetermined proportionality coefficient (or function),
Reference signal sinωt (or
By measuring the phase shift φ from cosωt), the linear position l can be detected. However, when the phase shift amount φ is 2π in full width, the linear position l corresponds to the distance P described above. That is, according to the electrical phase shift amount φ in the signal Y, an absolute linear position within the range of the distance P can be detected. When it is desired to obtain an absolute linear position beyond the distance P, an appropriate arbitrary means (the detection accuracy may be rough with distance P as one unit) is installed to detect the individual magnetic cores 11 in the rod portion 11.
What is necessary is to find the absolute address of a, and use a combination of this absolute address of each core 11a and the detected linear position value based on the above-mentioned phase shift φ. By measuring the electrical phase shift φ, it is possible to accurately determine the absolute linear position within the range of distance P with fairly high resolution. Furthermore, as shown in Japanese Patent Application No. 188865/1983, it is also possible to determine the absolute linear position exceeding P by using a plurality of detectors with different lengths of one pitch P.

Output signal Y and reference AC signal sinωt (or
cosωt) can be constructed as appropriate. Although not particularly shown in the drawings, the phase shift φ can be determined as a digital quantity by counting the time difference of a predetermined phase angle (for example, 0 degrees) between the reference AC signal sinωt and the output signal Y=Ksin(ωt+φ) using a counter. Further, by integrating this time difference, the phase shift φ can also be obtained as an analog quantity.

Of course, the non-magnetic coating 11 on the outermost periphery of the rod portion 11
c is not essential to the present invention and can be omitted.

Effects of the invention As described above, according to this invention, since the magnetic scale is formed by a magnetic coating, the number of parts and manufacturing steps can be reduced, and manufacturing costs can be lowered.

[Brief explanation of the drawing]

Figure 1 is an axial sectional view showing one embodiment of this invention, Figure 2 is a diagram showing an example of the formation of the ring-shaped magnetic core of the rod part in Figure 1, and Figure 3 is another configuration of the rod part. FIG. 4 is a circuit diagram showing an example of the coil connection format in FIG. 1. 1...Coil part, 2~5...Primary coil, 6~
9... Secondary coil, 10... Casing, 11...
...Rod part, 11a...Ring-shaped magnetic core, 1
1b, 11b'...Nonmagnetic rod, 11c...Nonmagnetic coating, 11a'...Magnetic metal coating, 12...Etching resist material.

Claims (1)

[Claims for Utility Model Registration] 1. A coil section having a plurality of primary coils and secondary coils spaced apart from each other at predetermined intervals in the direction of linear displacement, and a coil section capable of linear displacement relative to the coil section. a scale portion formed by repeatedly forming a plurality of magnetic scales made of a magnetic coating on the surface of a non-magnetic base at predetermined intervals along the linear displacement direction; The reference AC signal is individually excited by a reference AC signal of the magnetic scale according to the relative linear position of the scale part with respect to the coil part. and a circuit for obtaining an electrically phase-shifted output from the secondary coil according to the linear position. 2. The variable magnetic resistance type linear position detection device according to claim 1, wherein the magnetic coating is formed by plating. 3. The variable magnetoresistive linear position detection device according to claim 1 or 2, wherein the magnetic film is formed on the surface of the non-magnetic base having a smooth surface. 4. Utility model registration claim 1, wherein the magnetic coating is formed to fill a convex portion of the non-magnetic base, the surface of which is formed with predetermined irregularities corresponding to the pattern of a scale; or 2. The variable magnetic resistance type linear position detection device according to item 2. 5. The variable magnetoresistive linear position detection device according to claim 3 or 4, wherein the outermost periphery of the scale portion on which the magnetic coating is formed is covered with a non-magnetic coating.