JP2001099680A - Detecting apparatus for angle of relative rotation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting apparatus, for an angle of relative rotation, which is small, in which a detection output has a linear characteristic and which is of high sensitivity. SOLUTION: This detecting apparatus 10 for an angle of relative rotation is provided with a first rotor 11 which is molded of an insulating magnetic material and which is attached to a prescribed position in the axial line direction of a first turning shaft. The detecting apparatus is provided with a fixed core 12 which is fixed to a fixation member, which comprises a core body 12a and which comprises an exciting coil 12b to which an AC current is made to flow and which forms a magnetic circuit in cooperation with the insulating magnetic material. The detecting apparatus is provided with a second rotor 13 which is adjacent to the first rotor, which is attached to a second relatively turning shaft with reference to the first shaft and which is arranged between the first rotor and the fixed core. In the first rotor 11, metal shielding layers 11d are formed at prescribed intervals along the circumferential direction. In the second rotor 13, metal teeth 13b are formed at intervals corresponding to those of the metal shielding layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a relative rotation angle detecting device.

[0002]

2. Description of the Related Art A fixed magnetic member uniformly distributed in a circumferential direction around a coil through which an alternating current is passed, and a movable magnetic member having magnetic shielding portions formed at predetermined intervals in a circumferential direction are fixed. Arrange through the gap. By arranging the members in this manner, a magnetic circuit is formed including the gap, and when the gap is changed by increasing or decreasing the gap, the spatial distribution in the circumferential direction of the gap is changed. It is known that a non-uniform alternating magnetic field is formed.

Therefore, as shown in FIG. 10, a metal rotor 3 having a plurality of shielding teeth 3a is provided with a predetermined gap between a fixed magnetic member 1 having a coil and a magnetic material rotor 2 having an uneven outer periphery. For example, there is known a relative rotation angle detecting device which is arranged and used for detecting a torque acting on a steering shaft of an automobile. In this detection device, when a plurality of shield teeth 3a are arranged at equal intervals in the circumferential direction and the shield teeth 3a cross the AC magnetic field having a non-uniform distribution due to the relative rotation of the two rotors 2 and 3, Generates an eddy current. This eddy current varies depending on the relative rotation angle between the rotors 2 and 3. Therefore, this detecting device measures the impedance change of the coil caused by the fluctuation of the eddy current induced in these members, and thereby determines the relative rotation angle of the rotors 2 and 3, that is, the two members rotating relatively. The relative rotation angle between the two is detected.

[0004]

By the way, the above-described relative rotation angle detecting device using an alternating magnetic field having a non-uniform distribution has a variation in magnetic flux density in the circumferential direction in the gap as shown in FIG. The characteristics are influenced by two parameters, a variation ΔB of the magnetic flux density and a strong / weak boundary region Δθ in the generated magnetic field distribution. That is, the relative rotation angle detecting device has a higher rotation angle detection sensitivity as the variation ΔB of the magnetic flux density is larger, and the linearity of the detection output is better as the boundary region Δθ of the magnetic field distribution is smaller.

However, the relative rotation angle detecting device has the following problems in order to increase the degree of uneven distribution of the AC magnetic field depending on the size of the gap. As is well known, in the magnetic circuit, the variation of the effective relative permeability due to the size of the gap deviates from a linear characteristic. That is, in a magnetic circuit, the smaller the gap,
The variation of the effective relative permeability is large. Since the metal rotor 3 is arranged between the gaps as described above, the relative rotation angle detection device normally sets the gap G1 to 1 mm or more as shown in FIG. 10 in consideration of the manufacturing accuracy and the rotation accuracy of the rotor. It is desirable. However, the relative rotation angle detection device requires a gap variation of about several mm to obtain an appropriate detection sensitivity. That is, the relative rotation angle detecting device calculates the gap variation ΔG due to the unevenness of the magnetic material rotor 2.
(= G2−G1) needs to be set to a size that is several mm.

On the other hand, in the relative rotation angle detecting device shown in FIG. 10, the thickness of the magnetic material rotor 2 is periodically changed along the circumferential direction in correspondence with the plurality of shielding teeth 3a. For this reason, the detection device comprises a fixed magnetic member 1 and a magnetic material rotor 2.
When the magnetic flux flows from the core material having a high magnetic permeability into the air having a low magnetic permeability, the magnetic flux is concentrated at the corners of the core material.
For this reason, in the detection device, the boundary region Δθ of the magnetic field distribution is increased due to the magnetic flux concentrated at the corners, which adversely affects the linear characteristic of the detection output.

The present invention has been made in view of the above points, and has as its object to provide a relative rotation angle detecting device which is small, has a linear detection output characteristic, and has high detection sensitivity.

[0008]

According to the present invention, in order to achieve the above object, a first rotor formed of an insulating magnetic material and fixed to a predetermined position in the axial direction of a rotating first shaft is fixed to a fixing member. And a fixed core having a core body and an exciting coil through which an alternating current is passed and forming a magnetic circuit in cooperation with the insulating magnetic material and the first rotor, and a first shaft, A second rotor attached to the second shaft that rotates relative to the first shaft and disposed between the first rotor and the fixed core, and detects a relative rotation angle between the first and second shafts. In the relative rotation angle detecting device, the first rotor is provided with metal shielding layers at predetermined intervals along a circumferential direction, and the second rotor is formed with shielding teeth at intervals corresponding to the metal shielding layers. ing It was an adult.

Preferably, the insulating magnetic material and the core body are formed of an insulating material in which a thermoplastic resin and a soft magnetic material are mixed, and the content of the soft magnetic material is not less than 10% by volume and not more than 70% by volume. The following is assumed.

[0010]

When the first and second rotors rotate relative to each other, the average magnetic flux density of the magnetic field crossing the shielding teeth of the second rotor fluctuates. As a result, in the first rotor, the magnitude of the eddy current generated in the metal shielding layer varies. A signal processing circuit connected to the exciting coil measures a relative rotation angle between the two rotors by measuring a change in impedance of the exciting coil caused by the eddy current.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a relative rotation angle detecting device according to the present invention will be described below in detail with reference to FIGS. Relative rotation angle detection device (hereinafter, “detection device”
1), as shown in FIG.
It includes a fixed core 12 and a second rotor 13, and detects a relative rotation angle between a first shaft SF1 and a second shaft SF2 (see FIG. 2) that rotate relatively. The detecting device 10 is used, for example, in a case where the rotational torque of a handle shaft of an automobile is detected by transmitting rotational torque from a driving shaft to a driven shaft by a conversion joint (torsion bar), and the like. The rotation angle varies within a range of ± 8 °.

The first rotor 11 is formed in a cylindrical shape, and is attached to a predetermined position in the axial direction of the rotating first shaft SF1, as shown in FIG. In the first rotor 11, as shown in FIG. 1, a flange 11b extending outward in the radial direction is integrally formed on the upper part of a cylindrical shaft 11a with a synthetic resin, and an insulating magnetic member 11c is attached to the outer periphery of the cylindrical shaft 11a. At the same time, a plurality of copper foils 11d serving as a metal shielding layer are adhered to the surface of the insulating magnetic member 11c at predetermined intervals along the circumferential direction, for example, at an interval of 60 ° central angle.

However, the copper foil 11d is made of an insulating magnetic member 11c.
It may be provided inside instead of the surface. The metal shielding layer may be made of a material such as aluminum, silver, iron or the like, in addition to the copper foil 11d, as long as it is a conductor. Further, in theory, the smaller the central angle and the smaller the interval between the metal shielding layers, the larger the number of the shielding layers or the number of teeth, and the amount of change in the total eddy current induced in the members of the detection device. (In proportion to the number of shielding layers or shielding teeth) increases, and the detection sensitivity of the relative rotation angle increases, but the measurable angle range decreases. As described above, the detection device 10 according to the present embodiment converts the plurality of copper
The maximum measurable angle range is about 30
°.

Here, in electromagnetic engineering, the following equation is widely used as a measure of the thickness t (mm) required for the metal shielding layer. t ≧ 1 / (ωκμ) ^1/2 where ω is the angular frequency of the signal, κ is the electric conductivity of the metal shielding layer, and μ is the vacuum magnetic permeability.

Therefore, according to the above formula, for example, the copper foil 1
When the shielding layer is manufactured in 1d, the thickness required to substantially shield the magnetic field of 100 KHz is about 0.158 mm or more. In practice, when the thickness of the copper foil 11d is t = 0.2 mm, the magnetic resistance generated by the copper foil 11d with respect to an alternating magnetic field of 100 KHz is equal to the first rotor 11 and the fixed core 12 described later.
Sufficiently larger than the magnetic resistance due to the radial gap G between That is, due to the shielding effect of the copper foil 11d, the detection device 10 can form an AC magnetic field having a large degree of non-uniform distribution even though it is small.

The fixed core 12 is fixed to a fixed member (not shown) located near the handle shaft with a gap G (see FIG. 4) in the radial direction from the first rotor 11, and FIG.
As shown in the figure, a core body 12a made of an insulating magnetic material,
An exciting coil 12b which forms a magnetic circuit PMG (see FIG. 4) in cooperation with the first rotor 11 is provided. Magnetic circuit P
Since the magnetic flux of MG is formed concentrated as shown in FIG.
When the height of the first rotor 11 in the axial direction is higher than the height of the second rotor 13 in the axial direction, the first rotor 11 and the second rotor 13 may be displaced in the axial direction. Even if there is, fluctuation of the output of the sensor can be suppressed, which is preferable. The exciting coil 12b is connected to a signal processing circuit (not shown) by an electric wire 12c (see FIG. 1) extended to the outside, and an alternating current is passed from the signal processing circuit.

As shown in FIG. 1, the second rotor 13 has a plurality of metal teeth 13b serving as shielding teeth on a ring-shaped main body 13a.
Are uniformly arranged in a ring shape, and each metal tooth 13b has an interval corresponding to each copper foil 11d. Second rotor 13
Is made of, for example, copper, copper alloy, aluminum, aluminum alloy, iron, and iron alloy. As shown in FIG. 1, a plurality of metal teeth 13b are uniformly arranged in a ring shape like copper foil 11d, and each copper foil 11d Is provided in correspondence with. The second rotor 13 can also be configured as follows. That is, a shielding layer having a certain thickness (for example, a copper foil of 0.2 mm or a material of aluminum, silver, iron, or the like) having a certain thickness is formed on the surface or inside of the cylindrical member made of an insulating material in the same number as the copper foil 11d. They are evenly arranged in a ring shape corresponding to the copper foil 11d. The second rotor 13 is adjacent to the first rotor 11 and has a first shaft S
Second shaft SF2 that rotates relative to F1 (see FIG. 2)
The plurality of metal teeth 13b are disposed between the first rotor 11 and the fixed core 12, as shown in FIG.

The detection device 10 configured as described above is
The first rotor 11 is connected to the first shaft SF1 and the second rotor 13
Are attached to the second shaft SF2, respectively.
The fixed core 12 is fixed to the fixing member and assembled. And in the assembled detection device 10,
The magnetic flux due to the alternating current flowing through the exciting coil 12b is shown in FIG.
Flows along the magnetic circuit PMG shown in FIG. Thereby, the first
Since the alternating magnetic field crosses the plurality of copper foils 11d of the rotor 11, an eddy current is induced in the copper foil 11d. At this time, the direction of the AC magnetic field induced by the eddy current is opposite to the direction of the AC magnetic field by the AC current flowing through the exciting coil 12b. As a result, the direction of the magnetic flux due to the AC exciting current of the coil and the direction of the magnetic flux due to the eddy current are reversed in the space of the gap where the shielding layer exists, so that the total magnetic flux density is reduced, and conversely, the shielding layer does not exist. Since the direction of the magnetic flux due to the AC exciting current of the coil is the same in the space of the gap, the total magnetic flux density increases.

Therefore, in the detecting device 10, the first
As shown in FIG. 3, a copper foil 11d exists in a gap G formed between the rotor 11 and the fixed core 12, and a region Asp having a small magnetic flux density and a copper foil 11d do not exist. Are formed alternately in the circumferential direction. As a result, the detection device 10 includes the first rotor 11 and the fixed core 1
2, a non-uniform magnetic field having a central angle of 60 ° in the circumferential direction is formed in the gap G between the two. Here, FIG.
In the figure, the cylindrical shaft 11a of the first rotor 11 is omitted from illustration.

Therefore, the first rotor 11 is connected to the first shaft S
When the rotor rotates relative to the second rotor 13 together with F1, the non-uniform magnetic field also rotates with the first rotor 11 along the circumferential direction. For this reason, in the gap G, the metal teeth 13b formed in the circumferential direction at a central angle of 60 ° traverse the non-uniform magnetic field. At this time, the metal teeth 13b are rotated by the relative rotation between the first rotor 11 and the second rotor 13. The ratio of the area where 13b is located in the area Asp where the magnetic flux density is small and the area where the area 13b is located in the area Ade where the magnetic flux density is large changes, and the amount of the total magnetic flux traversed changes. Changes.

Therefore, in the detecting device 10, the magnitude of the eddy current generated in the metal teeth 13b is different, and the exciting coil 1
The impedance of 2b varies depending on the relative rotation angle between the first rotor 11 and the second rotor 13. Therefore, the detection device 10 can easily detect the relative rotation angle between the first rotor 11 and the second rotor 13 by measuring the impedance by a known method in a signal processing circuit connected to the excitation coil 12b. it can.

Here, the detecting device 10 of the present invention has a structure in which the first rotor 11 rotates with the gap G with respect to the fixed core 12, so that the size of the gap between the constituent members is as follows.
Has a direct effect on manufacturing costs. That is, it is very difficult for the detection device 10 to set the gap G to about several μm,
To achieve such a gap, the manufacturing accuracy of component parts,
Strict demands are placed on the assembly accuracy between the components. In particular, when the detection device 10 of the present invention is used for detecting a rotational torque on a handle shaft of an automobile, it is ideal that the gap G is set to the order of mm in consideration of vibration and the like accompanying the traveling of the automobile.

At this time, the effective magnetic permeability of the magnetic circuit PMG is determined by the relative magnetic permeability of the insulating magnetic member 11c and the core body 12a and the size of the gap G. In particular, when the ratio between the length of the magnetic circuit PMG and the size of the gap G is in the same order as the relative magnetic permeability of the magnetic material, the effective magnetic permeability of the magnetic circuit PMG depends almost entirely on the size of the gap G. The influence of the relative magnetic permeability of the magnetic material becomes very small. For example, as in the case where the length of the magnetic circuit PMG is 100 mm and the gap G is about several mm, the ratio between the length of the magnetic circuit PMG and the gap G is much smaller than the relative permeability of the soft magnetic material. When the gap G is small, the effective magnetic permeability is almost determined by the size of the gap G.

That is, the detecting device 10 includes the insulating magnetic member 11
No matter how large the relative magnetic permeability of c and the core body 12a is, the effective magnetic permeability of the magnetic circuit PMG is almost determined by the size of the gap G. Therefore, the insulating magnetic member 11c and the core body 12a are made of nylon, polypropylene (P
P), polyphenylene sulfide (PPS), ABS resin and other electrically insulating thermoplastic synthetic resins, Ni-
A soft magnetic material powder composed of Zn or Mn-Zn based ferrite is molded from a mixture in which the content of the soft magnetic material is 10 to 70% by volume.

As a result, in the detection device 10 of the present invention, the effective magnetic permeability of the magnetic circuit PMG is slightly smaller than that of the conventional soft magnetic material using ferrite, but the vibration resistance is improved and the manufacturing is easy. The advantages obtained are large, such as cost reduction and mass production. The eddy current that affects the impedance of the exciting coil 12b is:
It is not generated from inside the core material, which is also an insulating material, and is generated only from the metal shielding layer, that is, the copper foil 11d.
A value of 0 provides more linear characteristics of detection sensitivity and detection output.

Next, a second embodiment according to the detection apparatus of the present invention will be described with reference to FIGS. Detection device 15
As shown in FIG. 5, the first rotor 16 and the fixed core 17
And a second rotor 18, which are made of the same material as in the first embodiment, and which are the same as those in the first embodiment.
It is attached to the shaft SF1 and the like.

The first rotor 16 has a copper foil 16b adhered to a circumferential half of the surface of a cylindrical body 16a made of an insulating magnetic material. The fixed core 17 is a fixed core 1 according to the first embodiment.
As in the case of 2, a core body 17a made of an insulating magnetic material and an exciting coil (not shown) are provided. Second rotor 18
As shown in FIG. 6, a half of the cylinder is cut out in the circumferential direction to form a half circumference of the shield teeth 18a formed in the circumferential direction. Attachment opening 18 attached to second shaft (not shown)
c is formed.

The detection device 15 is configured as described above, so that when an alternating current is applied to the exciting coil, the first
As shown in FIG. 5, a copper foil 16b exists in a gap formed between the rotor 16 and the fixed core 17, and a region Asp where the magnetic flux density is small, and the copper foil 16b does not exist and the magnetic flux density is low. A large area Ade is formed equally in the circumferential direction. As a result, the detection device 15 includes the first rotor 16 and the fixed core 17.
A non-uniform magnetic field having a central angle of 180 ° is formed in the circumferential direction in the gap between the above and the rotational angle of 180 ° can be detected. For example, by using an absolute position sensor, etc. If the absolute position of 0 ° is detected, 360
°, that is, the rotation angle up to one rotation can be detected.

Next, a third embodiment according to the detection apparatus of the present invention will be described with reference to FIG. The detection device 20 includes a first rotor 21, a fixed core 22, and a second rotor 23, and a first shaft SF1 and a second shaft SF2 that rotate relative to each other.
The relative rotation angle of is detected. The first rotor 21 is made of an insulating magnetic material, and a plurality of fan-shaped copper foils having a plurality of predetermined central angles are adhered on the disk 21a at predetermined intervals. First
The rotor 21 is attached to the first shaft SF1, as shown.

The fixed core 22 is fixed to a fixed member (not shown) located near the handle shaft with a gap G in the axial direction between the first rotor 21 and the first shaft SF1.
As shown, a core body 22a made of an insulating magnetic material,
An exciting coil 22b forming a magnetic circuit PMG in cooperation with the first rotor 21; The second rotor 23 is made of, for example, copper, copper alloy, aluminum, aluminum alloy,
A plurality of shielding teeth 23a corresponding to the plurality of main bodies 21a of the first rotor 21 are formed radially by cutting out a plurality of sectors having a predetermined central angle from a metal disk such as iron, iron alloy, or silver.
Moreover, you may comprise as follows. That is, fan-shaped metal foils having the same number of predetermined center angles as the fan-shaped copper foil are attached at predetermined intervals on a disk made of plastic or the like having insulating properties, corresponding to the fan-shaped copper foil. Have been. The second rotor 23 is attached to a second shaft SF2 adjacent to the first rotor 21 and relatively rotating with respect to the first shaft SF1,
The plurality of shielding teeth 23a are, as shown in FIG.
And the fixed core 22.

Therefore, the detecting device 20 of the present embodiment is provided in the gap G between the first rotor 21 and the fixed core 22.
A non-uniform magnetic field is formed in the circumferential direction, and the non-uniform magnetic field crosses the plurality of shielding teeth 23a of the second rotor 23, thereby generating an eddy current. The detecting device 20 determines the impedance of the exciting coil 22b due to the change of the eddy current as the first impedance.
By performing the measurement in the same manner as in the first embodiment, the first rotor 2
The relative rotation angle between the first and second rotors 23 can be easily detected.

Further, the detecting device of the present invention comprises the first rotor 2
1, the fixed core 22 and the second rotor 23 are connected to the first shaft S
Since the configuration is such that F1 is overlapped in the axial direction, it is effective in reducing the size in the radial direction. Here, in each of the above embodiments, the first rotors 11, 16, 21 are connected to the first rotor.
The second rotors 13, 18, and 23 were attached to the shaft SF1 and the second shaft SF2, respectively. However, if the second rotor is disposed between the first rotor and the fixed core, the detection device of the present invention can be used as the first rotor 11, 16, 21.
May be attached to the second shaft SF2, and the second rotors 13, 18, and 23 may be attached to the first shaft SF1.

The detecting device of the present invention described above is constituted, for example, as follows, by a sensor unit having a torque sensor for detecting a rotational torque of a steering shaft of an automobile and a steering angle sensor for detecting a rotational angle. It can be applied as That is, the sensor unit 2 shown in FIG.
5 includes a torque detection core 26, a steering angle detection core 27, a magnetic material rotor 28, and a metal rotor 29. The torque detection core 26 and the steering angle detection core 27 are vertically overlapped (axial direction of the handle shaft). I have.

The torque detecting core 26 and the steering angle detecting core 27
Are core bodies 26a, 27 each made of an insulating magnetic material.
a, and exciting coils 26b and 27b forming a magnetic circuit in cooperation with the magnetic material rotor 28. Then, the torque detecting core 26 is attached to the fixing bracket 31 by the steering angle detecting core 27.
Are fixed to the fixing bracket 32, respectively.
Metal spacers 33 are arranged between the seven. here,
The fixing brackets 31 and 32 are arranged near the handle shaft in the automobile.

The magnetic material rotor 28 is formed into a cylindrical shape.
A slit 28a is formed at the center in the central axis direction in the circumferential direction. In the metal rotor 29, a flange 29b extends radially outward from an upper portion of a main body 29a having a smaller diameter than the magnetic material rotor 28, and extends in both up and down directions at the tip of the flange 29b, so that the magnetic material rotor 28 and the torque detecting core 26 or A plurality of shielding teeth 29c arranged between the steering angle detection core 27 are formed.

On the other hand, the sensor unit 35 shown in FIG.
A torque detection core 36, a steering angle detection core 37, a magnetic material rotor 38 and a metal rotor 39 are provided, and the torque detection core 36 and the steering angle detection core 37 are arranged concentrically in the radial direction. The torque detection core 36 and the steering angle detection core 37 are respectively composed of core bodies 36a and 37a made of an insulating magnetic material,
Excitation coils 36b and 37b forming a magnetic circuit in cooperation with the magnetic material rotor 38 are provided. Torque detection core 3
6, a predetermined gap is formed between the metal rotor 38 and the magnetic material rotor 38. The rudder angle detection core 37 has a core body 37a in which a groove 37c for disposing a shielding tooth 39c of the metal rotor 39 described later is formed in the circumferential direction. I have. The torque detection core 36 and the steering angle detection core 37 are housed in a metal shielding case 41.

The magnetic material rotor 38 is formed in a cylindrical shape. The metal rotor 39 has a flange 39b extending radially outward from the main body 39a and extending downward from the flange 39b, and is provided between the magnetic material rotor 38 and the torque detection core 36 or the steering angle detection core 37. A plurality of teeth 39c are formed in the circumferential direction.

Therefore, by appropriately selecting the sensor unit 25 or the sensor unit 35 according to the installation space, the rotation torque and the rotation angle of the handle shaft of the automobile can be detected simultaneously. In the above embodiments, the detection of the relative rotation angle related to the handle shaft of the vehicle has been described. However, the relative rotation angle detection device of the present invention can also be used for, for example, detecting the relative rotation angle of two robot arms that are connected to each other and rotate relatively.

[0039]

According to the first to third aspects of the present invention, it is possible to provide a relative rotation angle detecting device which is small in size, has a linear detection output characteristic, and has high detection sensitivity.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a relative rotation angle detection device of the present invention.

FIG. 2 is a cross-sectional view showing a state where the relative rotation angle detecting device of FIG. 1 is attached to first and second shafts.

FIG. 3 is a plan view of the assembled relative rotation angle detection device.

FIG. 4 is a cross-sectional view illustrating a schematic configuration in which a right half side of the relative rotation angle detection device of FIG. 2 is enlarged.

FIG. 5 is a plan view showing a second embodiment of the relative rotation angle detection device of the present invention.

FIG. 6 is a perspective view of a second rotor used in the detection device of FIG.

FIG. 7 is a sectional view corresponding to FIG. 2, showing a third embodiment of a relative rotation angle detection device of the present invention.

FIG. 8 shows a first applied example of the relative rotation angle detecting device of the present invention, and is a cross-sectional view of a sensor unit cut along a diameter.

FIG. 9 shows a second application example of the relative rotation angle detection device of the present invention, and is a cross-sectional view of a sensor unit cut along a diameter.

FIG. 10 is a plan view of a conventional relative rotation angle detection device.

FIG. 11 is a variation characteristic diagram of a magnetic flux density showing a variation ΔB of a magnetic flux density in a circumferential direction of a gap formed in a conventional relative rotation angle detecting device and a boundary region Δθ of strong and weak in a generated magnetic field distribution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Detector 11 First rotor 11c Insulated magnetic member 11d Copper foil (metal shielding layer) 12 Fixed core 12a Core body 12b Exciting coil 13 Second rotor 13b Metal teeth (shielding teeth) 15 Detector 16 First rotor 16b Copper foil ( 17 fixed core 17a core main body 18 second rotor 18a shielding tooth 20 detecting device 21 first rotor 21a main body 21b copper foil (metal shielding layer) 22 fixed core 22a core main body 22b exciting coil 23 second rotor 23a shielding tooth G gap SF1 First shaft SF2 Second shaft

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kengo Tanaka 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 2F063 AA35 CA34 CA40 DA01 DA19 DD02 EA03 GA08 GA29 GA33 2F077 AA49 FF02 FF31 VV11

Claims (3)

[Claims] A first rotor formed of an insulating magnetic material and fixed to a predetermined position in an axial direction of a rotating first shaft, fixed to a fixing member, an AC current flows through the core body,
A fixed core having an exciting coil cooperating with the insulating magnetic material to form a magnetic circuit, and the first rotor,
A second rotor attached to a second shaft that rotates relative to the first shaft, the second rotor being disposed between the first rotor and the fixed core; the first and second shafts; In the relative rotation angle detecting device for detecting the relative rotation angle of the first, the first rotor is provided with a metal shielding layer at predetermined intervals along a circumferential direction, and the second rotor corresponds to the metal shielding layer A relative rotation angle detecting device, wherein shielding teeth are formed at intervals. 2. The relative rotation angle detecting device according to claim 1, wherein said insulating magnetic material and said core body are formed of an insulating material obtained by mixing a thermoplastic resin and a soft magnetic material. 3. The relative rotation angle detecting device according to claim 2, wherein the content of the soft magnetic material is not less than 10% by volume and not more than 70% by volume.