JP2002357496A - Rotation sensor, and rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation sensor excellent in detection precision, in which a rotor can be molded in a correct form, and in which difference is not generated between effective inductance of two excitation cols. SOLUTION: This rotation sensor is provided with a first rotor 11 having a first conductive layer 11c disposed in the circumferential direction, a fixed core 12 having two excitation coils 12b disposed at a prescribed interval in the rotation axial direction of the first rotor, and core main bodies 12a to contain the excitation coils, and a second rotor 13 having a main body 13a molded of insulation magnetic material in a cylindrical form, and a second conductive layer 13b disposed in two stages on the main body. A high frequency AC current is made to flow to the two excitation coils to detect a relative rotation angle between the first rotor 11 and the second rotor 13 in this rotation sensor 10 and the second rotor 13. The second rotor 13 is molded to have an outer form that is plane-symmetric to a plane perpendicular to a rotation axis Art at a center in the direction of the rotation axis Art.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotation sensor and a rotor used for the rotation sensor.

[0002]

2. Description of the Related Art As a rotation sensor for detecting a torque between two relatively rotating shafts having two rotating bodies (rotor) and a fixed body having an exciting coil, for example, a relative rotation is provided via a torsion bar. There is known a rotation sensor that detects torque on a handle shaft of an automobile to which two rotating shafts are connected and uses the torque for smooth electronic control of a steering device (for example, Japanese Patent Publication No. 21433/1995).
Reference).

In such a rotation sensor, detection accuracy fluctuates due to disturbances such as environmental temperature fluctuations, electromagnetic noise, fluctuations in the oscillating frequency of the oscillating circuit, power supply voltage and assembly errors, and the torque can be accurately detected. In order to avoid this, the above-mentioned disturbance is canceled by using two excitation coils.

[0004]

By the way, the above-mentioned rotation sensor has a plurality of non-magnetic members arranged as upper and lower stages at predetermined intervals on a main body formed into a cylindrical shape from an insulating magnetic material as one rotating body. A rotor provided with a conductor layer is used. The magnetic material used for this rotor is easy to mold even in complicated shapes, and can be mass-produced at low cost in a short time. Plastic magnets mixed with material powder have come to be used.

[0005] When the rotor using such a material is mass-produced using a mold, a punching margin (a punching taper) for the die cutting is required. With such a margin, the outer shape of the formed rotor is not plane-symmetric with respect to a plane perpendicular to the rotation axis at the center in the rotation axis direction.
Therefore, when the rotor is assembled into the rotation sensor,
The gap between the excitation coil and the excitation coil changes depending on the position in the height direction along the rotation axis. If such a change occurs, the rotation sensor has a difference in effective inductance between the two exciting coils, and as a result, there is a problem that the disturbance is not properly canceled and the detection accuracy is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a rotation sensor which can form a rotor having an appropriate shape and which has no difference in effective inductance between two exciting coils and has excellent detection accuracy. The purpose is to provide.

[0007]

In order to achieve the above object, a rotation sensor according to the present invention has a first conductor layer arranged in a circumferential direction, and has a first conductor layer attached to a rotating first shaft. A rotor, two excitation coils arranged at a predetermined interval in a rotation axis direction of the first rotor, and a core body accommodating the excitation coil; A fixed core that is placed and attached to the fixed member, a main body formed into a cylindrical shape from an insulating magnetic material,
A second conductor layer disposed in two stages on the main body, wherein the first conductor is spaced apart from the first rotor by a predetermined distance in the radial direction;
A second rotor connected to a second shaft which is connected to a second shaft via a torsion bar and relatively rotates, and wherein a high-frequency AC current is supplied to the two exciting coils to cause the first and second rotors to rotate. In the rotation sensor for detecting a relative rotation angle with respect to the rotation axis, the second rotor has a configuration in which the outer shape is formed to be plane-symmetric with respect to a plane perpendicular to the rotation axis at the center in the rotation axis direction.

According to another aspect of the present invention, there is provided a rotor including a main body formed into a cylindrical shape from an insulating magnetic material, and a second conductor layer disposed on the main body in two stages. The outer shape is formed to be plane-symmetric with respect to a plane perpendicular to the rotation axis at the center in the rotation axis direction.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rotation sensor and a rotor according to the present invention will be described below. For example, a rotation sensor for detecting torque of a steering shaft transmitted from a driving shaft to a driven shaft via a torsion bar in an automobile. FIG. 1 shows a rotor used in this rotation sensor.
This will be described with reference to FIGS.

As shown in FIG. 1, the rotation sensor 10 includes a first rotor 11, a fixed core 12, and a second rotor 13, and a high-frequency AC current flows through two exciting coils 12b of the fixed core 12, which will be described later. One rotor 11 and second rotor 1
3 is used to detect a torque based on the relative rotation angle. Here, although not shown, the steering shaft has a driving shaft on the steering wheel side connected to a driven shaft on the wheel side via a torsion bar, and the driving shaft is ±
Relative rotation within a range of 8 °.

As shown in FIG. 2, the first rotor 11 is disposed between the second rotor 13 and the fixed core 12, and is attached to the driving shaft. The first rotor 11 is made of a synthetic resin having electrical insulation properties and excellent moldability, and a plurality of blades 1 parallel to the rotation axis Art on the outer periphery of the flange 11a.
1b are uniformly arranged. Each slat 11b
Are formed at intervals corresponding to each of the copper foils 13b described later, and a copper foil 11c is provided on the outer surface.

At this time, the first rotor 11 is
A conductor layer of a certain thickness (for example, a copper foil of 0.2 mm or a material of aluminum, silver, or the like) is applied to the copper foil 13b on the inner surface of the b or the inner surface or the inside of the cylindrical body made of an insulating material. They may be arranged evenly in correspondence. As shown in FIG. 2, the fixed core 12 is disposed with a slight gap of about several mm in the radial direction from the first rotor 11, and is fixed to a fixed member (not shown) located near the steering shaft. . The fixed core 12 includes two core bodies 12a made of an insulating magnetic material, an excitation coil 12b housed in each core body 12a, and a shielding case (hereinafter simply referred to as “case”) 12c housing both core bodies 12a. And The core body 12a is made of an electrically insulating Mn-Z
n-Mg-Zn, Ni-Zn and other sintered materials, and nylon, polypropylene (PP), polyphenylene sulfide (PPS), ABS synthetic resin and other electrically insulating thermoplastic synthetic resins. And Mn-
A soft magnetic material powder made of Zn-based ferrite is formed into a ring shape from an insulating magnetic material in which the soft magnetic material is mixed in an amount of 10 to 70% by volume. Each excitation coil 12b is connected to a signal processing circuit (not shown) by an electric wire 12d (see FIG. 1) extending from the case 12c to the outside, and an alternating current flows from the signal processing circuit. The case 12c is made of a metal such as aluminum or copper having an AC magnetic field shielding property.
It is formed in a ring shape having two concave portions 12e for accommodating each core body 12a.

At this time, as shown in FIG. 2, the fixed core 12 is
Core body 12a and case 12c accommodating 2b
Are arranged in plane symmetry. Also, two excitation coils 12b
The direction of the magnetic circuit formed between the first rotor 11 and the first rotor 11 is reversed by setting the winding direction to be reversed or the direction in which the alternating current flows.

The second rotor 13 is formed in a cylindrical shape from the same insulating magnetic material as the fixed core 12, and is mounted at a predetermined position in the axial direction of the driven shaft which rotates relatively to the driven shaft. The second rotor 13 is shown in FIGS.
As shown in FIG. 4, the rotation axis Art is provided on the outer periphery of the main body 13a.
A plurality of copper foils 13b are arranged at predetermined intervals in the circumferential direction, for example, alternately shifted vertically, at a central angle of 30 °.

At this time, the outer shape of the second rotor 13 is formed to be plane-symmetric with respect to a plane perpendicular to the rotation axis Art in the center of the rotation axis Art shown in FIG. The second rotor 13 having such an outer shape can be mass-produced in an appropriate shape by sintering the ferrite or injection-molding the insulating magnetic material. For example, the second rotor 13
When the insulating magnetic material is injection-molded and mass-produced, as shown in FIG. 5, the molds D1, D2 and the core C
Is formed such that the outer shape is vertically symmetric with respect to the dotted line A so that the outer shape is plane-symmetric with respect to the plane.

Here, in the main body 13a shown in FIG. 5, the punching margin (drawing taper) is extremely emphasized, but the taper angle θ for the punching margin is preferably about 1 degree. FIG.
In the main body 13a shown in FIG. 7, the inner shape is not vertically symmetrical with respect to the dotted line A. This is because the second rotor 13
When assembled in the rotation sensor 10, the excitation coil 12b
It is necessary to make sure that the gap between and does not change depending on the position in the height direction along the rotation axis, but it is not necessary on the inside, and even if such a change does not greatly affect the magnetic flux. It is.

If the outer shape of the main body 13a of the second rotor 13 is formed to be symmetrical with respect to the plane as described above, the same shaped half Hb having a taper angle θ of about 1 degree by the insulating magnetic material. And the two halves Hb may be combined and bonded as shown in FIGS. 6 and 7. Here, the main body 13a is also illustrated in FIGS.

Further, if the second rotor 13 is a conductor layer, a material such as aluminum or silver can be used instead of the copper foil 13b, and these conductor layers including the copper foil 13b are made of insulating magnetic material. It may be embedded inside the material. Furthermore,
When shielding the high-frequency magnetic field, these conductor layers are desirably about 0.1 to 0.5 mm thick in consideration of the magnetic resistance based on the radial gap between the first rotor 11 and the fixed core 12. On the other hand, the number of copper foils 13b theoretically increases as the center angle is reduced and the arrangement interval is reduced, and the amount of change in the total eddy current induced (in proportion to the number of conductor layers) is increased. ) Increases, and the relative rotation angle detection sensitivity increases, but the measurable relative rotation angle range becomes smaller.

The rotation sensor 10 configured as described above
The first rotor 11 is attached to the driving shaft and the second rotor 13 is attached to the driven shaft, and the fixed core 12 is fixed to the fixing member to be assembled to the steering device. And the rotation sensor 10
The torque of the steering shaft transmitted from the driving shaft to the driven shaft via the torsion bar by operating the steering handle is determined based on the relative rotation angle between the first rotor 11 and the second rotor 13. It can be determined based on the relationship between the torque acting on the driven shaft and the relative rotation angle between the two shafts.

At this time, in the rotation sensor 10, the outer shape of the second rotor 13 is formed symmetrically with respect to a plane perpendicular to the rotation axis Art at the center in the direction of the rotation axis Art shown in FIG. For this reason, the rotation sensor 10
Even when the rotor 11 and the second rotor 13 rotate relative to each other, the gap between the exciting coil 12b and the second rotor 13 does not change depending on the position in the height direction along the rotation axis Art. Therefore, the rotation sensor 10 does not cause a difference in the effective inductance of the two exciting coils 12b,
The disturbance is properly canceled, and the detection accuracy does not decrease.

Here, the rotation sensor of the present invention has the same structure as the rotation sensor 10 even if the first rotor 21 and the second rotor 23 are configured as follows, as in the rotation sensor 20 shown in FIG. The goal can be achieved. Here, the rotation sensor 20 differs from the rotation sensor 10 only in the configuration of the first rotor 21 and the second rotor 23, and the configuration of the fixed core is the same as that of the rotation sensor 10. Therefore, in the following description and the drawings used in the description, the rotation sensor 20
For the fixed core 12, the same reference numerals as those of the rotation sensor 10 are used to omit redundant description, and the first rotor 2
The first and second rotors 23 will be described.

The first rotor 21 is disposed between the second rotor 23 and the fixed core 12, and is attached to the driving shaft. In the first rotor 21, a blade 21b parallel to the rotation axis Art is arranged on the outer periphery of the flange 21a using the same synthetic resin as the first rotor 11. The wing plate 21b is
A copper foil 21c is provided on the outer surface. At this time, the first rotor 21 is provided on the inner surface of the wing plate 21b or on the inner surface or inside of the cylindrical body made of an insulating material. And the like) may be arranged corresponding to the copper foil 23b.

The second rotor 23 is formed of the same insulating magnetic material as the fixed core 12 into a cylindrical shape, and is mounted at the same position as the second rotor 13. The second rotor 23 is shown in FIG.
As shown in the figure, the copper foil 13b is provided on the outer periphery of the main body 23a in two stages with the position shifted in the direction of the rotation axis Art and over a half circumference in the circumferential direction. At this time, similarly to the second rotor 13, the second rotor 23 has an outer shape symmetric with respect to a plane perpendicular to the rotation axis Art at the center in the rotation axis Art direction. The second rotor 23 having such an outer shape can be mass-produced in the same manner as the second rotor 13.

Although the above embodiment has been described with respect to the case of a rotation sensor for detecting torque, it is also possible to detect a rotation angle. Further, the rotation sensor of the present invention may be a sensor for determining a relative rotation angle, a rotation angle, and a torque between rotating shafts rotating with each other, such as a robot arm, in addition to the steering shaft of the automobile described in the above embodiment. It can be used for anything.

[0025]

According to the first and second aspects of the present invention, it is possible to form a rotor having an appropriate shape, and to provide a rotation sensor excellent in detection accuracy without a difference in effective inductance between two exciting coils. can do.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a rotation sensor showing an embodiment of a rotation sensor and a rotor according to the present invention.

FIG. 2 is a sectional front view of the rotation sensor of FIG. 1;

FIG. 3 is a plan view of a second rotor used in the rotation sensor of FIG.

FIG. 4 is a cross-sectional view of the second rotor of FIG. 3 taken along line C1-C1.

FIG. 5 is a cross-sectional view showing a state in which the main body of the second rotor is molded using a mold and a core.

FIG. 6 is a sectional view showing another shape of the main body of the second rotor.

FIG. 7 is a sectional view showing still another shape of the main body of the second rotor.

FIG. 8 is an exploded perspective view of a rotation sensor showing another embodiment of the rotation sensor and the rotor of the present invention.

[Explanation of symbols]

 Reference Signs List 10 rotation sensor 11 first rotor 11a flange 11b blade 11c copper foil (first conductor layer) 12 fixed core 12a core body 12b excitation coil 12c shielding case 12e recess 13 second rotor 13a body 13b copper foil (second conductor) Layer) 20 Rotation sensor 21 First rotor 21a Flange 21b Blade 21c Copper foil (first conductor layer) 23 Second rotor 23a Main body 23b Copper foil (second conductor layer) Art Rotation axis C Core D1, D2 Gold Type Hb half

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomotaka Watanabe 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Masahiro Hasegawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Furukawa Electric Co., Ltd. (reference) 2F077 AA21 CC02 FF03 FF13 FF31 VV02 VV11 3D033 CA28 DB05

Claims (2)

[Claims] 1. A first rotor having a first conductor layer arranged in a circumferential direction and attached to a rotating first shaft, arranged at a predetermined interval in a rotation axis direction of the first rotor. A fixed core, which is attached to a fixed member at a radial distance from the first rotor, and is formed into a cylindrical shape from an insulating magnetic material. And a second conductor layer disposed in two stages on the main body, and at a predetermined radial distance from the first rotor, the first shaft is connected to the first shaft via a torsion bar. A second rotor attached to a second shaft that is connected to and relatively rotates;
A rotation sensor that detects a relative rotation angle between the first rotor and the second rotor by passing a high-frequency AC current through the two excitation coils, wherein the second rotor is orthogonal to the rotation axis at the center in the rotation axis direction. A rotation sensor characterized in that an outer shape is formed to be plane-symmetric with respect to a plane. 2. A rotor having a main body formed into a cylindrical shape from an insulating magnetic material, and a second conductor layer disposed in two stages on the main body, wherein the rotor is orthogonal to the rotation axis at the center in the rotation axis direction. A rotor whose outer shape is formed symmetrically with respect to a plane to be formed.