JPS6131803B2 - - 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, this total magnetic flux Φ flows from the annular core 12 to the annular core 10 in the gap 14, and flows in the yoke 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 l [m] of the cavity 14 between the annular cores 10 and 12 is constant, and the cross-sectional area of each core is are equal and uniform over the entire circumference, the annular cores 10, 12
The gap 14 can be made to have a uniform magnetic flux distribution.
As a result, the magnetic flux φ [wd/rad] per unit angle of the air gap 14 centered on the rotating shaft 26 is expressed by the following equation.

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 branch point, and are expressed by the following equation.

φ ₁ = (x−θ)φ ...(3) φ ₂ = (x+θ)φ ...(4) In this case, the detection coils 20 and 20 each have a number of turns of N ₂ [T] and are differentially By connecting, the sum of interlinking magnetic flux 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) can be 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, L is the self-inductance of the excitation coil 18. Also, the AC impedance component ωL [Ω] and the DC impedance component r [Ω] of the excitation coil 18 ] 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) Also, 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
can be taken out.

However, in order for the output signal obtained with respect to the input angle θ to have a linear relationship as shown in equation (11) above, it is a condition that each component configuration is ideally manufactured. For this reason, sufficient care must be taken in selecting the materials for the parts, the processing precision 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 the displacement-to-electrical converter having the configuration shown in FIGS. 1 and 2, inclination (see FIG. 3) and eccentricity (see FIG. 3) and eccentricity ( (see Figure 4) is likely 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 occurs as shown in FIG. 4, the input angle θ and the detection coils 20, 20
The electrical signals generated at the end of the line no longer have a linear relationship. Further, there are other problems such as loss of linearity due to leakage magnetic flux generated in the gap between the yoke 16 and the annular cores 10 and 12.

The applicant first discovered that leakage magnetic flux was generated directly from the excitation coil 18 to the air gap 14, and as a result, the uniformity of the magnetic flux distribution in the air gap 14 was lost in the vicinity of the excitation coil 18, and the output voltage in the vicinity decreased. In order to solve the problem of poor linearity of the excitation coil 18 and the yoke 16 around which it is wound,
It was proposed to cover the outer circumferential surfaces of the two annular cores 10 and 12 with magnetic shielding plates except for the opposing surfaces.

However, in this case, if the short-circuit ring exists so as to surround the magnetic flux path, an eddy current flows in the short-circuit ring, increasing the magnetic resistance of the short-circuit ring portion, and the magnetic flux passes through the short-circuit ring of the path. As a result, the magnetic flux flowing from both the left and right sides to the short circuit ring returns to zero at the short circuit ring. Therefore, as mentioned above, when the entire circumference of the excitation coil is surrounded by a magnetic shielding plate, this magnetic flux shielding plate has the same effect as the short circuit ring described above, and prevents the magnetic flux from flowing to the yoke. There is a drawback that the function of the converter is degraded due to the blocking.

Therefore, the present inventors proposed the conventional displacement method described above.
As a result of repeated studies and trial production in order to overcome the various problems of electrical converters, we have developed an annular magnetic shield made of conductive material with an appropriate thickness and with a slit formed in a part, which can be used in an alternating magnetic field. It has been found that by arranging the excitation coil to surround the excitation coil located in the gap of a magnetic circuit having a magnetic circuit, the magnetic flux distribution state in the gap can be controlled and the above problems can be solved at once.

That is, by providing a slit in the magnetic shield surrounding the excitation coil, it is possible to prevent eddy currents from flowing through the magnetic shield.

Furthermore, by connecting a magnetic shielding body surrounding the excitation coil and placing a magnetic shielding plate in contact with one of the annular cores along the opposing surface of the other annular core, the magnetic shielding plate can be slid in the plane direction. If so, the magnetic flux distribution state can be controlled by changing the magnetically shielded area of the annular core, and the output characteristic curve can be arbitrarily set.

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 that is supplied with an alternating current voltage and forms a magnetic circuit with two annular cores, a magnetic shield that surrounds the excitation coil, and a magnetic flux that passes through the interior of one of the annular cores can be detected. a magnetic flux detection element arranged as shown in FIG. In the displacement-to-electrical transducer configured to rotate around the axis of the magnetic flux detecting element and to extract an output signal from the magnetic flux detection element, the magnetic shield is constituted by a ring-shaped body having a slit that is not completely closed; It is characterized in that a magnetic shielding plate is disposed in connection with the magnetic shielding body and in contact with one of the annular cores along the opposing surface of the other annular core.

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.

Further, in the present invention, the shorting ring can be fixed in position on one of the annular iron cores, and the shorting ring and the magnetic flux detection element can be configured to rotate integrally 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 arrange the shorting ring to be movable with respect to one of the annular cores, and to rotate the magnetic flux detection element and the excitation coil integrally with the annular core.

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

5 to 7 show the basic structure 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, the gap portion of the magnetic circuit having an alternating magnetic field, particularly the outer periphery of the excitation coil 18, is surrounded by an annular magnetic shield 30.
Note that the magnetic shield 30 can be made of a conductive material having an appropriate thickness. The magnetic shield 30 also has a slit 3 in a part so as not to affect the operation of the excitation coil 18 forming the magnetic circuit.
2 (see Figure 7). In this case, the position of the slit 32 of the magnetic shield 30 is not limited to the illustrated example, and can be arbitrarily set as long as it surrounds the excitation coil 18. Furthermore, in this embodiment, the opposing annular cores 10, 12
In this case, an annular magnetic shielding plate 34 having a substantially equal width is arranged over the entire circumference of the opposing surface on the gap 14 side of the annular core 12 that faces the annular core 10 around which the short-circuiting ring 22 rotates. Like the magnetic shield 30, this magnetic shield plate 34 can also be made of a conductive material having an appropriate thickness.

In this way, by magnetically shielding the air gap 14 of the magnetic circuit having an alternating magnetic field, when the alternating magnetic field interlinks with the magnetic shielding body 30 and the magnetic shielding plate 34, an eddy current flows there, and the magnetic flux flowing in the magnetic circuit is A magnetic flux is generated that cancels out the Therefore, the excitation coil 18
When excited with an alternating current voltage having an appropriate frequency, the magnetic shield 30 and the magnetic shield plate 3
4, the magnetic flux in the air gap 14 can be controlled.

As described above, by providing the magnetic shield 30 and the magnetic shield plate 34 in the gap 14 of the magnetic circuit, the magnetic flux distribution state of the gap 14 can be controlled and the magnetic flux can be distributed equally. In particular, the excitation coil 18
The magnetic shield 30 is arranged to surround the yoke 16 around which the excitation coil 18 is wound, the annular iron core 10,
Disturbances in magnetic flux distribution due to leakage magnetic flux generated at the connection point with 12 can be controlled. For this reason,
Dimension Δl of slit 32 provided in magnetic shield 30
The smaller the slit 32, the better, and an insulating sheet or the like may be inserted into the slit 32. In addition, if the error component that inevitably occurs during machining in the relationship between the opposing annular cores 10 and 12 is relatively small, the annular magnetic shield 34 may be omitted and the center of the rotating shaft 26 and the center of the annular core 10 may be Eccentricity makes it possible to sufficiently compensate for error components.

In addition, when the magnetic shield 30 and the magnetic shield plate 34 are used together, even if the opposing annular cores 10, 12 are tilted or eccentric, the magnetic shield plate 34 can be slid in the planar direction and the annular cores 10, 12 By controlling the magnetically shielded area, 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 arranged at the bottom of the core holder 36 to press the annular iron core 12 against 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 2 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 iron 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-electrical converter configured in this manner includes a magnetic shield 3 surrounding the excitation coil 18 in the gap 14 between the opposing annular cores 10 and 12.
0 and a magnetic shield 3 arranged along the annular iron core 12
4 are integrally constructed and arranged. Note that the outer peripheral portion of the core holder 40 on the side of the annular core 10 is covered with a cover 48 as appropriate. In particular, the displacement-to-electrical converter of this embodiment can be configured such that the magnetic shield 30 and the magnetic shield plate 3 can be adjusted by appropriately adjusting the fixture 42.
4 on the annular iron core 10 side, the annular iron core 1
2, the magnetic flux distribution state can be controlled as described above.

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. In particular, according to the present invention, magnetic shielding around the excitation coil can eliminate leakage magnetic flux and prevent the generation of nonlinear components.

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, 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 even if the excitation coil 18 and the excitation coil 18 are configured to rotate integrally, the desired purpose can be achieved.

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 intended purpose can be achieved by applying a magnetic shield or a magnetic shield 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 side sectional view showing an embodiment of the displacement-electrical converter according to the present invention, and FIG. 7 is a perspective view of the magnetic shielding body and magnetic shielding plate shown in FIGS. 5 and 6, and FIG. 8 is a partially cutaway plan view based on the principle of the embodiment shown in FIGS. 5 to 6. Side cross-sectional view of the embodied displacement-to-electrical converter, No. 9
The figure is a sectional view of the main part taken along the line - in FIG. 8. 10... annular iron core, 12... annular iron core, 14...
... air gap, 16 ... yoke, 18 ... excitation coil,
20...detection coil, 22...short circuit ring, 24...
Arm, 26...rotation shaft, 30...magnetic shield,
32...slit, 34...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 shield surrounding the excitation coil, and a magnetic flux passing through the one of the annular cores can be detected. a magnetic flux detection element disposed in the annular core, and a short circuit ring provided on the one annular core, one of the excitation coil, the magnetic flux detection element, and the short circuit ring is fixed, and the other is fixed to the one annular core. In a displacement-to-electrical transducer configured to rotate around an axis and extract an output signal from a magnetic flux detection element, the magnetic shield is configured of a ring-shaped body with a slit that is not completely closed; A displacement characterized in that a magnetic shielding plate is disposed in contact with one of the annular cores along the opposing surface of the other annular core in connection with the shielding body.
electrical converter. 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-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 rotated integrally. A displacement-to-electrical converter configured as follows. 5. In the displacement-to-electricity converter according to claim 1 or 2, the short circuit ring is movably positioned relative 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.