JPS6131802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement-to-electrical converter that converts rotational changes into electrical signals, and particularly to a displacement-to-electrical converter that can detect rotational displacement over a wide angle with high precision.

The applicant previously developed a non-contact displacement-to-electrical converter using a double annular iron core system using magnetic induction, and filed a patent application. Already proposed displacement −
An example of an electrical converter is shown in FIGS. 1 and 2. That is, two annular cores 10 and 12 made of a laminated core, a ferrite core, etc., and having substantially the same dimensions and arranged coaxially apart, and a gap 14 formed between these annular cores 10 and 12. A pair of yoke 16, an excitation coil 18 with a number of turns N ₁ [T] wound around the yoke 16, and a pair each with a number of turns N ₂ [T] wound around the annular iron core 10 so as to sandwich the yoke 16. detection coil 2
0 and 20, and a short-circuit ring 22 provided on an annular iron core so as to interlink therewith, and the short-circuit ring 22 is mechanically coupled to a rotating shaft 26 via an arm 24. In the displacement-electrical converter configured in this way, if an AC voltage E ₁ [V] is supplied to the excitation coil 18 and an excitation current I ₁ [A] is caused to flow, the excitation coil 1
8 and the annular iron cores 10 and 12 form a magnetic circuit, and the total magnetic flux Φ [wb] generated at this time is expressed by the following equation.

Φ=N ₁ I ₁ /R ……………(1) However, R is the magnetic resistance of the gap 14. However, in the gap 14, this total magnetic flux Φ flows from the annular core 12 to the annular core 10, and the joint The iron 16 flows from the annular core 10 to the annular core 12. Therefore, the material of the annular cores 10 and 12 is uniform, the relative magnetic permeability _μs is very large, the gap 1 [m] of the cavity 14 between the annular cores 10 and 12 is constant, and the cross section of each core is If the areas are equal and uniform over the entire circumference, the annular cores 10, 12
The gap 14 between the two can be made to have a uniform magnetic flux distribution. As a result, the cavity 1 centered around the rotating shaft 26
The magnetic flux φ [wb/rad] per unit angle of 4 is expressed by the following formula.

φ=Φ/2π ……………(2) Therefore, the magnetic fluxes φ ₁ and φ ₂ interlinking with the detection coils 20 and 20 have different flow directions with the position of the short circuit ring 22 as a branching point, and are expressed by the following equation. It can be done.

φ ₁ = (x−θ)φ ……………(3) φ ₂ = (x+θ)φ ……………(4) In this case, the number of turns of the detection coils 20 and 20 is N ₂ [T], respectively. By connecting differentially, the sum of interlinking magnetic fluxes φ ₀ is expressed by the following equation.

φ ₀ =φ ₂ −φ ₁ =2θφ (5) Therefore, the induced voltage E ₂ [V] induced by the detection coils 20, 20 is expressed by the following equation.

E ₂ =N ₂ dφ ₀ /dt (6) The above equation (6) is transformed into the following equation from equations (1) and (5).

E ₂ =θ/π·N ₂ ·dΦ/dt (7) Here, assuming that the total magnetic flux Φ interlinks with the excitation coil 18, the following equation holds true.

N ₁ Φ=LI ₁ , that is, Φ=LI ₁ /N ₁ ……………(8) However, the self-inductance of the L excitation coil 18 Also, the AC impedance component ωL [Ω] and the DC impedance component r of the excitation coil 18 [Ω] If the following formula ωL≫r ……………(9) holds true, the excitation voltage of the excitation coil 18
The following equation holds true between E ₁ and excitation current I ₁ .

E ₁ =LdI ₁ /dt (10) Therefore, the above equation (7) is transformed as shown in the following equation based on equation (8) and equation (10).

E ₂ = θ/π・N ₂ /N ₁・E ₁ =Kθ(K=E ₁ /π・N
₂ /N ₁ ) ……………(11) In addition, from the detection coils 20, 20 to the rotating shaft 26
The AC output voltage _E2 is linearly proportional to the rotation angle θ of
However, in order for the output signal obtained for the input angle θ to have a linear relationship as shown in equation (11) above, each component configuration must be ideally manufactured. is the condition. For this reason, sufficient care must be taken in selecting the materials for the parts, the processing accuracy of the parts must be increased, and advanced technology is required for assembly work.

For this reason, the input angle θ has a wide range, and in order to obtain the required accuracy (linearity), component material costs and manufacturing costs increase, and problems such as a decrease in yield due to an increase in defective products and the inability to miniaturize are caused. arise.

In addition, in the displacement-electrical converter having the configuration shown in FIGS. 1 and 2, the rotation bearings and the holders that hold the annular cores 10 and 12, etc. (not shown) have an inclination (see FIG. 3) and an eccentricity Δr. (See Figure 4) tends to occur during processing and assembly. In such a case, if the magnetic flux flowing through the air gap 14 no longer has a uniform magnetic flux distribution, or if eccentricity Δr occurs as shown in FIG. The electrical signals generated will no longer have a linear relationship. In addition, the yoke 16 and the annular core 10,1
There are drawbacks such as loss of linearity due to leakage magnetic flux generated in the gap between the two.

Therefore, the present inventors proposed the conventional displacement method described above.
As a result of various studies and trial production in order to overcome the various problems of electrical converters, we installed a magnetic shield plate made of conductive material with an appropriate thickness in the gap between two opposing annular iron cores, and installed a magnetic shield plate made of a conductive material with an appropriate thickness. It has been found that the above-mentioned problems can be solved at once by configuring the shielding plate so that the opposing surfaces of the annular cores facing each other starting from the position of the excitation coil gradually decrease or increase.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a displacement-to-electrical converter which has a simple configuration, controls the magnetic flux distribution state in the gap, and has highly accurate input/output characteristics.

In order to achieve the above object, the present invention includes two annular cores arranged on the same axis,
an excitation coil to which an alternating current voltage is supplied and forms a magnetic circuit with the two annular cores; a magnetic flux detection element arranged so as to be able to detect magnetic flux passing through the interior of the one annular core; a short-circuit ring provided on the iron core, one of the excitation coil, the magnetic flux detection element, and the short-circuit ring is fixed, and the other is rotated around the axis of the one annular iron core to output from the magnetic flux detection element. In a displacement-electrical converter configured to extract a signal, a magnetic flux interlinking with a magnetic flux detection element is applied to a gap formed between two opposing annular cores by the action of a short-circuit ring on the opposing surface of the annular core. The magnetic shielding plate is characterized in that a magnetic shielding plate configured to be a function of the changing length of the magnetic shielding plate is fixedly arranged.

In the above-mentioned displacement-electrical converter, the magnetic flux detection element can be composed of a detection coil or a magnetoresistive element provided on one of the annular cores so as to sandwich the excitation coil.

The shorting ring can be configured such that the shorting ring is fixed in position on one of the annular iron cores, and the shorting ring and the magnetic detection element are rotated together with respect to the excitation coil.
Alternatively, the shorting ring may be fixed in position on one of the annular cores, and the magnetic flux detection element and the exciting coil may be rotated together. Furthermore, it is also possible to configure the shorting ring to be movable with respect to one of the annular cores so that the magnetic detection element and the excitation coil rotate together with the annular core.

Next, embodiments of the displacement-to-electricity converter according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 5 shows the basic configuration of the displacement-to-electrical converter according to the present invention. For convenience of explanation, the same reference numerals are given to the same components as those of the conventional displacement-to-electrical converter shown in FIGS. 1 and 2, and detailed explanation thereof will be omitted. That is,
In this embodiment, in the air gap of the magnetic circuit having an alternating magnetic field, the opposing surfaces of the two annular cores 10 and 12 gradually decrease or increase along the annular core 10 or 12 starting from the center of the excitation coil 18. The magnetic shielding plates 30 are arranged as shown in FIG. Note that the magnetic shielding plate 30 can be made of a conductive material having an appropriate thickness. In this way, when the magnetic shielding plate 30 is arranged in the gap between the annular cores 10 and 12, when the annular core 10 or 12 is developed in the circumferential direction, the short-circuit ring 22 interlinks with the annular cores 10 and 12. The opposing area is as shown in FIG. Therefore, now the short circuit ring 22 has a rotation angle θ=
θ ₁ (see FIG. 5), the magnetic flux generated in the excitation coil 18 is transmitted to the detection coils 20, 2.
0 to form a magnetic circuit that passes through the opposing surfaces of the annular cores 10 and 12. In this magnetic circuit,
The magnetic fluxes φ ₁ and φ ₂ that interlink with the detection coils 20 and 20 due to the action of the short circuit ring 22 are divided into two at the position of the short circuit ring 22 by the opposing areas of the annular cores 10 and 12.
It is proportional to S ₁ and S ₂ respectively. As a result, it is understood that when the opposing areas S ₁ and S ₂ of the annular cores 10 and 12 have a relationship as shown in FIG. 6, the magnetic fluxes φ ₁ and φ ₂ become integral values of the function of the length l. It will be. Therefore,
In FIG. 6, if the function of the length l is l=aθ+b, the magnetic fluxes φ ₁ and φ ₂ can be obtained by the following equations.

φ ₁ =∫〓 ₋ 〓(aθ+b)dθ
……………(12) φ ₂ =∫〓〓(aθ+b)dθ
……………(13) From the above formulas (12) and (13), the detection coils 20, 20
The sum φ ₀ of the magnetic fluxes interlinked with φ 0 is determined by the following equation based on the above equation (5).

φ ₀ =φ ₁ −φ ₂ =∫〓 ₋ 〓(aθ+b)dθ−∫〓〓(aθ+b) dθ=[a/2θ ² +bθ+C−(a/2π ²
-b
π+C)] −[a/2π ² +bπ+C−(a/2θ ² +bθ+C)]=aθ ² +2bθ−aπ ² ……………(14) Additionally, the above equation (14) and the above equation (11) From the relationship, it is preferable to find a function by differentiating the characteristic curve of the sum of the required magnetic fluxes, and to manufacture the magnetic shielding plate 30 so that this function becomes a curve as shown in the developed diagram of FIG. Incidentally, the relationships among the above equations (12) to (14) are illustrated in FIG. 7. Further, since some leakage elements are added to the magnetic circuit, the present invention can be easily implemented by appropriately using a correction coefficient.

In this way, by applying magnetic shielding to the gap portion of the magnetic circuit having an alternating magnetic field, the magnetic shielding plate 30
When an alternating magnetic field interlinks with the magnetic field, eddy currents flow there, generating magnetic flux that cancels the magnetic flux flowing in the magnetic circuit. Therefore, in this embodiment, the annular iron cores 1 facing each other along the annular iron core with the excitation coil 18 as the starting point are
By configuring the facing surfaces of 0 and 12 to gradually decrease or increase, the function of the magnetic fluxes φ ₁ and φ ₂ interlinking with the detection coils 20 and 20 can be made a function of the length l of the changing facing surfaces. This makes it possible to easily improve the linearity of the output characteristics.

Moreover, the magnetic shielding plate 30
Even if there is inclination or eccentricity at 0 or 12, the magnetic shielding plate 3
0 in the plane direction and insert the annular cores 10 and 1.
By controlling the magnetically shielded area with respect to 2, the linearity of the output characteristics can be easily improved.

FIG. 8 and FIG. 9 show an embodiment of a displacement-to-electrical converter specifically constructed based on the principle of the displacement-to-electrical converter according to the present invention described above. That is, in this embodiment, one of the annular cores 12 is housed in a core holder 36 having an inverted concave cross section, fixedly held by a fixing member 38, and the opposing annular core 10 is inserted into the core holder via the yoke 16. 40, and the core holder 40 is connected to the fixing member 38 via a fixture 42. In this embodiment, the core holders 36 and 40 are all made of magnetically shielding material.
Further, a spring 44 is appropriately disposed at the bottom of the core holder 36 to press the annular iron core 12 to the yoke 16. A rotating shaft insertion portion 38a extending to the center of the opposing annular core 10 is provided at the center of the fixed member 38, and the rotating shaft 26 is rotatably inserted through the insertion portion 38a via a bearing 46. Ru. Therefore, the arm 24 is located at the tip of the rotating shaft 26.
One end of the arm 24 is fixed, and a shorting ring 22 surrounding the annular core 10 is fixed to the other end of the arm 24. An excitation coil 18 is arranged surrounding the yoke 16, and a pair of detection coils 20, 20 are provided in the core holder 40 in correspondence with the excitation coil 18. The displacement-to-electrical converter configured in this way has a gap 14 in opposing annular cores 10 and 12.
In this case, a magnetic shielding plate 30 is arranged along the annular iron core 12. Note that the outer peripheral portion of the core holder 40 on the annular core 10 side is covered with a cover 48 as appropriate. In particular, the displacement-to-electricity converter of this embodiment can be adjusted by adjusting the fixing device 42 as appropriate.
The magnetic flux distribution state can be controlled as described above by sliding the lower half of the annular core 10 side including the magnetic shield 0 and the magnetic shield in the horizontal direction with respect to the annular core 12.

FIGS. 10 to 12 show the displacement according to the present invention.
2 shows another embodiment of an electrical converter. 1st
Figure 0 shows the characteristics of thermoelectromotive force e versus temperature t from 0 to 1700°C of a thermocouple (JISC 1602). The characteristic curve shown in FIG. 10 is as follows.

y=Δe/Δt ……………(15) However, Δe=e _o −e _o-1 Δt=t _o −t _o-1 Therefore, based on the function obtained by differentiating the characteristics obtained from Fig. 10, FIG. 11 shows the developed shape of the magnetic shielding plate 30. Therefore, the first
According to the developed view shown in FIG. 1, the magnetic shielding plate 30 of the embodiment shown in FIG. 5 can be easily manufactured.

The magnetic shielding plate 30 obtained in this way is placed in the gap between the two opposing annular cores, and the magnetic shielding plate 30 is displaced -
As a result of measuring the output characteristics of the electrical converter, as shown in FIG. 12, it was found that the output characteristics of the displacement-electrical converter are extremely similar to the nonlinear characteristics of the thermocouple having the characteristics shown in FIG. confirmed. That is, in FIG. 12, the characteristic curve indicated by the broken line is
It shows the nonlinearity (%) of the thermoelectromotive force output e with respect to the temperature t of the thermocouple (JISC 1602) from 0 to 1700°C, and the characteristic curve shown by the solid line is the characteristic curve of the rotation axis of the displacement-electrical converter It shows the nonlinearity (%) of the output with respect to the displacement angle θ.

As is clear from this example, the displacement-to-electrical converter according to the present invention has a characteristic curve (first
(see Figure 0) can be easily obtained that has characteristics that are extremely similar to that of By the way, the first
In the measurement example shown in Figure 2, it was confirmed that there was extremely high similarity with an accuracy of about 0.1%.

As is clear from the embodiments described above, the displacement-to-electricity converter according to the present invention can control the magnetic flux distribution of the magnetic circuit by applying magnetic shielding to the air gap. Magnetic permeability _μs
(inversely proportional to) can be compensated for.
Restrictions imposed on materials can be alleviated, making it possible to reduce material costs.Moreover, restrictions on machining can also be alleviated, making mass production possible and significantly reducing manufacturing costs.

Further, according to the present invention, by controlling the magnetic flux distribution of the magnetic circuit in the air gap, it is possible to arbitrarily set the output characteristic curve, and the present invention can be applied to the feedback signal generating section of the servo mechanism of automatic balancing equipment.
It has many advantages, such as being applied to a means for measuring a physical quantity that converts a measured quantity into a rotational displacement, etc., and making it easy to linearize its characteristics.

In the above-mentioned embodiment, a case has been described in which the shorting ring 22 is rotated with respect to the annular core 10, but the shorting ring 22 is fixed to the annular core 10, and magnetic flux detection that can detect the magnetic flux passing through the inside of this core is also possible. Detection coils 20, 20 or magnetoresistive elements as elements are attached or embedded in the annular core 10 so as to sandwich the excitation coil 18, and the annular core 10 is mechanically coupled to the rotating shaft 26 via the arm 24, and the rotating shaft 26 The rotation of the annular core 10 and the short-circuit ring 22
The desired purpose can also be achieved by configuring the excitation coil 18 to rotate integrally with the excitation coil 18.

Further, the short circuit ring 22 is fixed to the annular iron core 10, and the detection coil 2 is arranged so as to sandwich the excitation coil 18.
0 and 20 are configured to be movable, and the detection coils 20,
20 and the excitation coil 18 (including the yoke 16) are mechanically coupled to the rotating shaft 26 via the arm 24, and the rotation of the rotating shaft 26 causes the detection coil 2
It is electromagnetically clear that the desired objective can be achieved even if the excitation coil 18 and the excitation coil 18 are configured to rotate integrally.

Further, the shorting ring 22 is movably arranged with respect to the annular core 10, the yoke 16 is mechanically coupled to the annular cores 10 and 12, and the yoke 16 is mechanically connected to the rotating shaft 26 via the arm 24. The annular iron cores 10 and 12 and the excitation coil 18 are connected by rotation of the rotating shaft 26.
Of course, the desired purpose can also be achieved even if the magnetic flux detection element (including the yoke 16) and the magnetic flux detection element (detection coil or magnetoresistive element) are configured to rotate integrally.

In the above embodiments, a case has been described in which annular cores having substantially the same dimensions are used, but it is electromagnetically clear that the opposing annular cores do not have to have the same dimensions.

Furthermore, although the case has been described in which two opposing annular iron cores are coaxially arranged vertically and parallel to each other, the case where annular iron cores with different diameters are arranged concentrically on the same plane inside and outside is also possible in the same manner as in the above embodiment. Of course, the desired purpose can be achieved by providing a magnetic shielding plate or a magnetic shielding plate to the annular core.

Although preferred embodiments of the present invention have been described above, within the scope of the spirit of the present invention,
Of course, various design changes can be made.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of a conventional displacement-to-electricity converter;
FIG. 2 is a partially sectional plan view of FIG. 1, and FIG. 3 is a side sectional view showing an abnormal state of a conventional displacement-electrical converter.
FIG. 4 is a plan view of a displacement-electrical converter showing another abnormal state, FIG. 5 is a plan view of essential parts showing an embodiment of the displacement-electrical converter according to the present invention, and FIG. A developed view showing the opposing areas of the opposing annular cores shown in
FIG. 7 is an output characteristic curve diagram of the displacement-electrical converter shown in FIG. 5, and FIG. 8 is a side view of the displacement-electrical converter materialized based on the principle of the embodiment shown in FIGS. 5 to 7. 9 is a sectional view of the main part taken along the line - in FIG. 8, FIGS. 10 to 12 show another embodiment of the displacement-electrical converter of the present invention, and FIG. 10 shows a cross-sectional view of a thermocouple. Output characteristic curve diagram, Figure 11 is a developed view of the magnetic shielding plate set based on the characteristics of Figure 10, Figure 12
The figure is a characteristic diagram comparing and displaying the nonlinearity between the output characteristics of a displacement-electrical converter using a magnetic shielding plate designed based on FIG. 11 and the output characteristics of a thermocouple. 10, 12...Annular iron core, 14...Gap portion, 1
6... Yoke, 18... Excitation coil, 20... Detection coil, 22... Short circuit ring, 24... Arm, 26
... Rotating shaft, 30 ... Magnetic shielding plate, 36 ... Core holder, 38 ... Fixing member, 40 ... Core holder, 42 ... Fixture, 44 ... Spring, 46
...Bearing, 48...Cover.

Claims (1)

[Claims] 1. Two annular iron cores arranged on the same axis,
an excitation coil to which an alternating current voltage is supplied and forms a magnetic circuit with the two annular cores; a magnetic flux detection element arranged to detect magnetic flux passing through the interior of the one annular core; and one of the annular cores. one of the excitation coil and magnetic flux detection element and the shorting ring is fixed, and the other is rotated about the axis of the one annular iron core to generate an output signal from the magnetic flux detection element. In a displacement-to-electrical converter configured to take out the magnetic flux, the magnetic flux interlinking with the magnetic flux detection element is transferred to the gap formed between two opposing annular cores by the action of the short circuit ring, and the magnetic flux is transferred to the opposite surface of the opposing annular core. 1. A displacement-to-electrical transducer characterized by a fixed arrangement of magnetic shielding plates configured to be a function of varying length. 2. The displacement-to-electrical converter according to claim 1, wherein the magnetic flux detection element comprises a detection coil or a magnetoresistive element provided on one of the annular cores so as to sandwich the excitation coil. 3. In the displacement-to-electrical converter according to claim 1 or 2, the shorting ring is fixed in position on one of the annular cores, and the shorting ring and the magnetic flux detection element are integrally rotated with respect to the excitation coil. A displacement-to-electrical converter configured as follows. 4. In the displacement-to-electrical converter according to claim 1 or 2, the short circuit ring is fixed in position on one of the annular cores, and the magnetic flux detection element and the exciting coil are configured to rotate integrally. Displacement-to-electrical converter. 5. In the displacement-to-electrical converter according to claim 1 or 2, the shorting ring is movably arranged with respect to one of the annular cores, and the magnetic flux detection element and the exciting coil are arranged together with the annular core. A displacement-electrical converter configured to rotate integrally.