JP4028294B2 - Rotation sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotation sensor.
[0002]
[Prior art]
In a rotation member that detects rotation of a rotating member, such as a shaft, detection of the number of rotations may be required in addition to the rotation angle of the shaft. As such a rotation sensor, Japanese Patent Application No. 2000-288946 proposes a rotation sensor in which a coil member having the same size as that of an intermittent gear (Geneva gear) is arranged opposite to the intermittent gear.
[0003]
[Problems to be solved by the invention]
By the way, since the rotation detection range of the intermittent gear is 180 °, for example, in order to detect the number of rotations of the handle 5 rotation, the intermittent gear must be rotated 36 ° by one rotation of the handle. Ten teeth were required. However, when the number of teeth of the intermittent gear increases as described above, it is difficult to stably rotate due to the rotation structure, and the intermittent gear may be rotated by vibration or the like. As a result, when the rotation sensor is provided in, for example, a steering device, there is a problem that the intermittent gear is likely to rotate due to vibration accompanying traveling, and the risk of erroneously detecting the number of rotations of the steering wheel increases.
[0004]
The present invention has been made in view of the above points, and an object of the present invention is to provide a rotation sensor capable of accurately displaying the rotation speed.
[0005]
[Means for Solving the Problems]
In the present invention, in order to achieve the above object, (I) a rotor having a sensing unit attached to a rotating shaft and changing in width along a circumferential direction, and an AC excitation current flow between the rotor and the rotor A first exciting coil that forms a magnetic circuit; and a first core that is molded from an insulating magnetic material and holds the first exciting coil; A rotation sensor comprising a plurality of sets of fixed cores arranged to face each other at an interval in the axial direction of the shaft,
(II) The one fixing member sandwiching the rotation surface of the sensing unit includes a conductor whose width changes along the rotation direction, and includes a Geneva gear that is rotated by the rotor ,
(III) A second exciting coil, which is formed of an insulating magnetic material, and that holds the second exciting coil on the other fixed member that sandwiches the rotation surface of the sensing unit, and an alternating exciting current flows. Comprising a detection coil for detecting the rotational speed of the rotor ,
(IV) The plurality of sets of fixed cores arranged opposite to each other are arranged at intervals of central angles of 90 degrees along the circumferential direction of the fixed member (rotational circumferential direction of the shaft) .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to a rotation sensor of the present invention will be described in detail with reference to FIGS.
The rotation sensor 1 is attached to a steering shaft and includes a rotor 2, fixed cores 4 and 5, a measuring device 6, a geneva gear 7, and a detection coil 8, as shown in FIGS. 1 and 2A and 2B. The rotor 2 and the fixed cores 4 and 5 are accommodated in the case 10.
[0007]
As shown in FIGS. 2A and 2B, the rotor 2 has a sensing plate 3 made of a conductive material attached to the outer periphery of the inner cylinder 2a. As shown in FIG. 2A, the inner cylinder 2 a is provided with a protrusion 2 b that protrudes outward in the radial direction and engages with a protrusion 7 d described later of the Geneva gear 7. Further, in the upper and lower surfaces of the inner cylinder 2a, concave grooves 2c and 2d are formed in the circumferential direction in which upper case 11 (described later) of the case 10 and inner peripheral edges 11a and 12a of the lower case 12 are engaged. Further, the inner cylinder 2a is provided with a recess 2e through which the teeth 7a of the Geneva gear 7 pass on the Geneva gear 7 side.
[0008]
As shown in FIG. 3, the sensing plate 3 includes a ring-shaped attachment portion 3a attached to the inner cylinder 2a, a sensing portion 3b disposed on the outer side of the attachment portion 3a, and having a width that varies along the circumferential direction. Two connecting portions 3c that connect the portion 3a and the sensing portion 3b are integrally formed. The sensing part 3b has the smallest width at one connection part 3c, the largest width at the other connection part 3c rotated by 180 °, and the radial width changes in accordance with the rotation angle of the rotor 2. And an eddy current having a magnitude corresponding to the width accompanying rotation is induced by an AC magnetic field described later. The rotor 2 is manufactured by pressing a conductive metal such as aluminum, copper, silver, iron, or brass.
[0009]
The fixed core 4 is mounted on a printed circuit board that constitutes the measuring device 6, and is disposed opposite to the fixed core 5 with the sensing plate 3 interposed therebetween, as shown in FIG. 2B. . The fixed core 5 is attached to an upper case 11 described later of the case 10. As shown in FIG. 1, the fixed cores 4 and 5 are arranged to be opposed to each other at four locations at intervals of central angles of 90 ° along the circumferential direction. The fixed cores 4 and 5 include core bodies 4a and 5a made of an insulating magnetic material, excitation coils 4b1 to 4b4 and excitation coils 5b1 to 5b4 held in the core bodies 4a and 5a (see FIG. 3). . The excitation coils 4b1 to 4b4 and the excitation coils 5b1 to 5b4 are connected in series, and are electrically connected to the printed circuit board of the measuring device 6 in the case 10, and an AC excitation current is passed. These excitation coils form an AC magnetic field around the AC excitation current that flows, thereby forming a magnetic circuit.
[0010]
As shown in FIGS. 2A and 2B, the measuring device 6 is fixed to a lower case 12 described later of the case 10. The measuring device 6 is connected to a power source and a signal transmission wire harness via a plurality of electric wires 10 a extending from the case 10 to the outside, and is connected to an external device provided outside the case 10.
As shown in FIG. 4, the measuring device 6 includes a phase shift unit 6c1, a phase shift amount detection unit 6d1, a converter 6e1, a phase shift unit 6c2, and a phase shift amount detection unit between the frequency divider 6b and the measurement unit 6g. 6d2, converter 6e2, phase shift unit 6c3, phase shift amount detection unit 6d3, converter 6e3 and phase shift unit 6c4, phase shift amount detection unit 6d4, and converter 6e4 are connected in parallel.
[0011]
The output signal Sc1 of the converter 6e1 and the output signal Sc2 of the converter 6e2 are differentiated by the differential amplifier 6h1, then amplified and output to the A / D converter of the measuring unit 6g as the voltage signal output Po1, or directly measured. To 6g. The differential amplifier 6h1 is connected to a shift level adjustment unit 6j1 that adjusts the voltage level of the amplified voltage value.
[0012]
Similarly, the output signal Sc3 of the converter 6e3 and the output signal Sc4 of the converter 6e4 are differentiated by the differential amplifier 6h2, amplified, and output to the A / D converter of the measuring unit 6g as the output Po2 of the voltage signal. , Directly output to the measuring unit 6g. The differential amplifier 6h2 is connected to a shift level adjustment unit 6j2 that adjusts the voltage level of the amplified voltage value. Further, the output signal Sc5 of the converter 6e5 is directly output to the measuring unit 6g.
[0013]
The oscillation circuit 6a converts an oscillation signal having a specific frequency into a phase shift unit 6c1 comprising resistors R1 to R4, excitation coils 4b1 to 4b4, excitation coils 5b1 to 5b4 and capacitors C1 to C4 shown in FIG. Output to ~ 6c4. At this time, the phase of the voltage signal at both ends of each of the capacitors C1 to C4 changes due to fluctuations in impedance described later of the exciting coils 4b1 to 4b4 and the exciting coils 5b1 to 5b4. The voltage signals at both ends of the capacitors C1 to C4 are output to the phase shift amount detectors 6d1 to 6d4.
[0014]
Each of the phase shift amount detectors 6d1 to 6d4 detects the phase shift amount of the voltage signal across the capacitors C1 to C4.
Converters 6e1 to 6e4 convert the detected phase shift amounts into corresponding voltage values.
As shown in FIG. 4, the rotation sensor 1 includes, for example, a measurement unit 6g using a one-chip microprocessor or the like, and outputs from two amplified signals Po1 and Po2 and four converters 6e1 to 6e4. Signals Sc1 to Sc4 are input. Then, the measurement unit 6g first arranges the excitation coils 4b1 to 4b4 and the excitation coils 5b1 to 5b4 in the sensing unit 3b of the rotor 2 by comparing the level relationship of the levels of the four output signals Sc1 to Sc4. Determine the position. After that, according to the position, the measuring unit 6g performs appropriate signal processing using the differential signals of the exciting coils 4b1 to 4b4 and the exciting coils 5b1 to 5b4 having excellent linearity, and the processed signal is used as an angle signal to produce a one-chip micro. Output from the processor. In the present embodiment, the angle signal output from the one-chip microprocessor of the measuring unit 6g is a pulse signal having a constant period, and the duty ratio is proportional to the rotation angle of the rotor 2.
[0015]
As shown in FIG. 2A, the Geneva gear 7 is rotatably screwed to the lower surface of an upper case 11 described later of the case 10. As shown in FIG. 5, the Geneva gear 7 has five teeth 7a formed at equal intervals along the circumferential direction, and a screw hole 7b is provided at the center. As shown in FIG. 2A, the Geneva gear 7 is rotatably screwed to the lower surface of the upper case 11 (described later) of the case 10 using a screw hole 7b. The Geneva gear 7 is provided with a conductor layer 7c made of a conductive metal such as aluminum, copper, silver, iron, and brass whose width changes in five steps along the circumferential direction on the lower surface, and the center of the upper surface of each tooth 7a. Is provided with a protrusion 7d (see FIG. 1) extending in the radial direction.
[0016]
As shown in FIG. 2A, the detection coil 8 is installed on the printed circuit board constituting the measuring device 6 on the outer periphery side of the Geneva gear 7, and is held in the core body 8a made of an insulating magnetic material and the core body 8a. And an excitation coil 8b through which an alternating excitation current is passed. The excitation coil 8b of the detection coil 8 is connected to the phase shift unit 6c5 shown in FIG. 4, and the signal passes through the phase detection unit 6d5 and is output as an output signal Sc5 to the measurement unit 6g via the converter 6e5. Then, the measurement unit 6g reads the voltage value, performs appropriate signal processing, and detects the rotational speed of the rotor 2 as described later.
[0017]
The case 10 is a fixed member attached to a vehicle body side member (not shown) located in the vicinity of the rotating steering shaft Sh. Each of the cases 10 is a conductive metal such as aluminum or copper having an AC magnetic field shielding property or the insulation. An upper case 11 and a lower case 12 are formed from a magnetic material in a ring shape.
The upper case 11 is a disk-shaped member which is combined with the lower case 12 to form an annular space for accommodating the rotor 2, the fixed core 4 and the measuring device 6, and is an inner member engaged with the concave groove 2c of the inner cylinder 2a. It has a peripheral edge 11a. The lower case 12 is a disk-shaped member that houses the measuring device 6 on which the fixed core 4 is installed, and has an inner peripheral edge 12a that engages with the concave groove 2d of the inner cylinder 2a.
[0018]
The rotation sensor 1 configured as described above is used with the rotor 2 attached to a steering shaft and the case 10 attached to a vehicle body side member (not shown) in the vicinity of the steering shaft.
In the rotation sensor 1, the width of the sensing unit 3 b is set to be proportional to the rotation angle of the rotor 2. For this reason, the alternating magnetic field induced by the eddy current generated in the sensing unit 3b as the rotor 2 rotates changes the impedance of the excitation coils 4b1 to 4b4 and the excitation coils 5b1 to 5b4. The fluctuation amount of the impedance of the exciting coils 4b1 to 4b4 and the exciting coils 5b1 to 5b4 is proportional to the rotation angle of the rotor 2.
[0019]
Accordingly, the rotation sensor 1 can measure the rotation angle of the rotor 2 by measuring the amount of impedance variation in the excitation coils 4b1 to 4b4 and the excitation coils 5b1 to 5b4.
Here, every time the rotor 2 makes one rotation, the rotation sensor 1 rotates the Geneva gear 7 by 1/5 of 360 °, that is, 72 ° by engaging the protrusion 2b with the protrusion 7d. As a result, the output (V) of the detection coil 8 changes in five steps according to the position of the opposing sensing unit 3b. Therefore, based on these five-stage outputs (V), the rotation sensor 1 can detect the number of rotations of the rotor 2.
[0020]
Therefore, by processing the signal when the rotation angle of the rotor 2 is measured and the signal when the rotation number of the rotor 2 is detected, it is possible to output an angle corresponding to five rotations of the handle.
Thus, in this system, when the rotation sensor 1 is provided in the steering device, the rotation detection range of the Geneva gear 7 is 360 °. Therefore, for example, in order to detect the number of rotations of the handle 5 rotation, the Geneva gear 7 And the number of teeth of the Geneva gear 7 can be as small as five. Therefore, the Geneva gear 7 can be stably rotated due to the rotation structure, and as a result, erroneous detection of the handle rotation speed can be prevented.
[0021]
Further, the Geneva gear 7 is not easily rotated by vibration because the protrusion 2b of the rotor 2 is engaged with each protrusion 7d and the tooth 7a rotates while passing through the recess 2e of the inner cylinder 2a. For this reason, when the rotation sensor 1 is provided in the steering device, the rotation number can be accurately displayed even when there is vibration associated with traveling, and the rotation sensor 1 is also excellent in reliability.
[0022]
In addition, in the conventional Geneva gear rotation number detection coil, it is necessary to provide a conductor on the coil side, but in this method, there is an advantage that the rotation sensor 1 can be easily manufactured because it is not necessary. .
Here, the Geneva gear used in the rotation sensor 1 detects the rotation speed of the rotor 2 based on intermittent rotation and the width of the conductor layer at that time. Therefore, like the Geneva gear 9 shown in FIG. 7, the conductor layer 9c provided outside the screw hole 9b on the lower surface may be formed so that the width continuously changes along the circumferential direction. In this case, the output (V) when the Geneva gear 9 does not rotate intermittently but continuously rotates is as shown in FIG. However, since the Geneva gear 9 rotates intermittently, the output (V) of the detection coil 8 becomes a discrete value corresponding to a point divided into five in the continuous output (V) shown in FIG. .
[0023]
In addition, the detection coil 8 may change the output (V) by changing the thickness of the conductor layer in the Geneva gear or by forming a groove across the width direction in the conductor layer.
In addition, the rotation sensor of the said embodiment demonstrated the case where it used for the steering device of a motor vehicle. However, the rotation sensor of the present invention can be used for any device that can obtain the relative rotation angle, rotation angle, and rotation torque between rotating shafts that rotate with each other, such as a robot arm.
[0024]
【The invention's effect】
According to invention of Claim 1, the rotation sensor which can display a rotation speed correctly can be provided.
[Brief description of the drawings]
FIG. 1 is a plan view of a rotation sensor according to the present invention.
2A and 2B are a cross-sectional view taken along line C1-C1 and a cross-sectional view taken along line C2-C2 of the rotation sensor of FIG.
FIG. 3 is a plan view showing a sensing plate used in the rotation sensor of FIG. 1 together with the arrangement of the first excitation coil.
4 is a circuit diagram of a rotation angle measuring device used in the rotation sensor of FIG. 1. FIG.
FIG. 5 is a bottom view showing the Geneva gear used in the rotation sensor of FIG. 1 together with the arrangement of detection coils.
6 is an output characteristic diagram of a detection coil when the Geneva gear of FIG. 5 is used. FIG.
FIG. 7 is a bottom view showing a modification of the Geneva gear together with the arrangement of detection coils.
FIG. 8 is an output characteristic diagram of a detection coil when the Geneva gear of FIG. 7 is used.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotation sensor 2 Rotor 3 Sensing board 3a Attachment part 3b Sensing part 3c Connection part 4,5 Fixed core 4a, 5a Core main body (1st core)
4b1 to 4b4 exciting coil (first)
5b1 to 5b4 exciting coil (first)
6 measuring device 7 Geneva gear 7a tooth 7b screw hole 7c conductor layer 7d ridge 8 detection coil 8a core body (second core)
8b Excitation coil (second)
10 Case 11 Upper case 12 Lower case

Claims (1)

(I) a rotor having a sensing unit attached to a rotating shaft and having a width that varies along a circumferential direction; and a first excitation coil that forms a magnetic circuit between the rotor and an AC excitation current flowing therethrough A first core formed of an insulating magnetic material and holding the first exciting coil, and is attached to a fixed member and disposed opposite to the sensing portion at an interval in the axial direction of the shaft A rotation sensor comprising a plurality of sets of fixed cores,
(II) The one fixing member sandwiching the rotation surface of the sensing unit includes a conductor whose width changes along the rotation direction, and includes a Geneva gear that is rotated by the rotor ,
(III) A second exciting coil, which is formed of an insulating magnetic material, and that holds the second exciting coil on the other fixed member that sandwiches the rotation surface of the sensing unit, and an alternating exciting current flows. Comprising a detection coil for detecting the rotational speed of the rotor ,
( IV ) The rotation sensor characterized in that the plurality of sets of fixed cores arranged opposite to each other are arranged at intervals of central angles of 90 degrees along the circumferential direction of the fixed member (rotational circumferential direction of the shaft) .

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