JPS63171318A - Rotation detector - Google Patents

Abstract

PURPOSE:To obtain a small size and simple magnetic detecting sensor with excellent speed response by concentrically forming a plurality of magnetic thin film tracks on one surface of a rotating plate connected to a rotating shaft. CONSTITUTION:A plurality of magnetic thin film tracks 3 with a magnetic pole pitches different from one another are concentrically formed on the surface of a rotating plate 2. A magnetic detecting element 7 wherein a high frequency exciting coil 5 and a detecting coil 6 are lap-wound around amorphous alloy thin wires 4 is perpendicularly and oppositely provided to the tracks 3 so that the distal ends of the thin wires 4 approach the tracks 3. As a result, the surface leakage magnetic field of the magnetic poles of the tracks 3 is taken out from the coil 6 for every track 3 as amplitude- modulated high frequency induced voltage by utilizing the magnetic saturation of the thin wires 4. The amplitude-modulated components of the amplitude-modulated high frequency induced voltage are taken out and converted to binary signals in a position detecting circuit 26. The circumferential direction position of the rotating plate 2 is detected by combining the binary signals from the tracks 3. The rotational angle and rotating speed of the rotating plate 2 are detected by counting the binary signals from the specific track 3.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an absolute type rotation detection device that magnetically detects the rotation speed, rotation angle, and angular position used for positioning control in F'A equipment, etc. (commonly known as rotary encoder).

[Conventional technology]

Rotary encoders are mainly used for positioning control in F'A equipment. A rotary encoder optically or magnetically detects the rotation speed and rotation angle of a rotary plate.Functionally, there are two types: an incremental type that detects the relative rotation speed and rotation angle change, and a rotary encoder that detects the relative rotation speed and rotation angle change amount. There is an absolute type that can detect the absolute position in the circumferential direction of the plate. As production automation becomes more widespread, the importance of absolute rotary encoders is increasing due to the need for equipment control and operation during power outages, highly accurate angle control, etc.

The optical type is known to have many slit holes in a rotating plate and detect the light passing through the slit holes with a light receiving element such as an a-si semiconductor. Several tracks of slit holes are provided concentrically in the plate], and the circumferential position of the rotating plate is determined by combining the binary signals of the output signals of the light receiving elements provided corresponding to each track. By processing the slit hole and the light-receiving element with high precision using precision processing technology, the resolution of the rotation angle can be increased.

In the magnetic type, the KS and N poles on the outer circumferential surface of the rotary plate are alternately magnetized, and this polarity change is detected by a magnetic sensor.In the absolute type, multiple pieces with different pitches of magnetized poles are used. The rotating plates are connected parallel to each other around the same rotating shaft, and the polarity change is detected by a Hall element or a magnetoresistive element (semiconductor or ferromagnetic thin film) K provided corresponding to each rotating plate.
As with the optical method, the circumferential position of the rotary plate can be determined by a combination of binary signals. , a rotation detection device with excellent high-speed response can now be obtained.

[Problem that the invention seeks to solve]

For optical absolute rotary encoders, there is a limit to the response frequency due to the followability of the light receiving element.)
Furthermore, there is a problem that the light receiving element is easily affected by the ambient temperature and lacks long-term reliability. On the other hand, in magnetic absolute rotary encoders, Hall elements and semiconductor magnetoresistive elements have the same weakness as light receiving elements in that they are easily affected by ambient temperature, and when magnetic thin film resistance elements are used, high resolution There is a problem in that the axial dimension becomes large due to the need for a special detection method 2 circuit design and the need for a plurality of rotary plates.

An object of the present invention is to obtain a rotation detection device that can magnetically specify a position in the circumferential direction using a single rotary plate, has a small and simple magnetic detection sensor, has excellent speed response, and has little temperature dependence. It is in.

[Means for solving problems]

In order to solve the above problems, according to the present invention, a rotating shaft rotatably supported by a case, a rotating plate fixed to the rotating shaft, and a magnetized pole pitch on the surface of the rotating plate are mutually arranged. A plurality of magnetic thin film tracks formed differently and concentrically, and a plurality of tips of an amorphous alloy wire around which a high frequency excitation coil and a detection coil are wound are arranged perpendicularly close to the surface of the magnetic thin film tracks. The magnetic detection element includes a magnetic detection element, and a position detection circuit that detects the amplitude modulation component of the amplitude modulated high frequency signal outputted from each of the magnetic detection elements and detects the position of the rotating plate based on the binary signal.

[Effect]

A plurality of magnetic thin film tracks having perpendicular magnetic anisotropy are formed concentrically on one surface of one rotating plate connected to a rotating shaft, and each track has a KN pole in the local direction.

By changing the magnetization pattern (magnetized pole pitch) in which S poles are alternately magnetized for each track, the functions of a plurality of rotary plates in a conventional device can be integrated into one rotary plate.

In addition, a magnetic detection element consisting of an amorphous alloy wire whose tip is arranged vertically close to each magnetic thin film track, and a high-frequency excitation coil and a detection coil wound around each other, generates a surface leakage magnetic field from the magnetized pole. is amplitude-modulated using the magnetic saturation of the amorphous alloy thin wire and can be extracted from the detection coil as a large high-frequency induced voltage for each track.The position detection circuit extracts the amplitude modulation component of the amplitude-modulated high-frequency induced voltage. By converting into a digitized signal and combining the binarized signals from each track, the circumferential position of the rotary plate can be determined, and by counting the binarized signals of a specific track, the number of revolutions per rotation angle can be determined. Can be done.

Furthermore, amorphous alloy thin wire has high high frequency magnetic permeability.

It is strong, has low temperature dependence, and has an outer diameter number + μ
Since an m-order magnetic sensor can be formed, polarity changes can be detected at high speed and with high resolution.

〔Example〕

Hereinafter, this invention will be explained based on examples.

FIG. 1 is a sectional view showing an example device. In the figure,
10 is a case of the rotation detection device, 1 is a rotary shaft rotatably supported in the case 10 by a bearing, etc., and 2 is a rotary plate fixed to the rotary shaft, and on one surface of the rotary plate 2. Magnetic thin film tracks 3 consisting of 3A to 3F' having perpendicular magnetic anisotropy and having a predetermined width are deposited concentrically with each other.

Reference numeral 4 is a Co-based amorphous alloy thin wire consisting of 4A, 4B, 4C, .
The detection coil 6 is wound overlappingly to form a magnetic detection element 7, and the supporting member 9 vertically supports the amorphous alloy thin wire 4 so that its tip is close to the surface of the magnetic thin film track 30 with a slight gap therebetween. and is supported on the case 10 side so that each detection element is aligned in the radial direction of the rotating plate. In addition, the high-frequency excitation coils 6 #i are connected in series with each other, and are conductively connected to the oscillator 25K'' through the lead 1l115, and are excited in the same phase by the high-frequency excitation current from the oscillator 25.Furthermore, each of the detection coils 6 has independent leads. It is conductively connected to the detection circuit 26 by #16. 11 is a detection signal lead line.

Figure ta2 is a plan view showing the magnetic thin film track in the embodiment flGc, and in the innermost track 3F, one half round at a time
A pair of north and south poles are magnetized, and in the track 3E, the north and south poles are magnetized so that they are alternately located in the circumferential direction every quarter of a turn, and the same goes for the north and south poles.

It is magnetized so that the pole pitch of the S pole is shortened by -2, and if the number of tracks is n, then the magnetic thin film tracks that can distinguish the circumferential direction of the rotary plate 20 in proportion to the first power of 2 are formed. It can be formed on one rotating plate.

FIG. 3 is a detailed view of the main part of the embodiment device. The magnetic thin film tracks 5A and 3B having perpendicular magnetic anisotropy are each magnetized in the thickness direction as shown by the arrows in the figure. Space leakage magnetic flux corresponding to the polarity of the magnetized pole is generated in the space above the surface. *In order to detect this spatial leakage magnetic flux, the quality alloy thin wires 4A, 4B, etc. are arranged vertically so that their tips face each track with a gap in between, and the high frequency excitation coils 4A, 4B, etc. are connected in series with each other. The six detection coils, 6B, etc. are conductively connected to the oscillator 25 through lead wires IST, and are wound around the high-frequency excitation coil in an overlapping manner through independent lead wires 16A and 16B.
etc., and is conductively connected to the detection circuit.

Co-based amorphous alloy thin A4 has high mechanical rigidity and almost no magnetostriction, so it is possible to wind a thin conducting wire around a thin wire with a diameter of about 50 to 120 μm without affecting the magnetic properties. Another advantage is that the magnetic detection element 7 can be made thin and compact, and the width of the corresponding magnetic thin film track 30 can be less than 1fi, so the magnetic detection element 7 can have more than 10 tracks without increasing the diameter of the rotary plate 2. It is possible to form thin film tracks. In addition, Co-based amorphous alloy thin wires have higher magnetic permeability in the high frequency range than magnetic materials such as permalloy and ferrite, and have excellent sensitivity to magnetic fields, and are more sensitive to ambient temperature than thread elements or magnetoresistive elements. Since the temperature is low, a temperature compensation circuit is not required, thus making the device smaller.

It is strong and can be configured simply. In addition, in order to prevent mutual interference between the magnetic detection elements 7 excited by high frequency,
The outer circumferences of the overlapping coils 5 and 6 are surrounded by a magnetic shield 8.

When the excitation coil 5 is excited at high frequency, the amorphous alloy thin wire 4
A high-frequency magnetic field is generated, and surface leakage magnetic flux from the magnetized pole of the magnetic thin film track 30 is added. If the polarity change of the surface leakage magnetic flux accompanying the rotation of the 0-rotation plate 20 (K) is longer than the period of the high-frequency magnetic flux, it can be detected. A high frequency voltage whose amplitude is modulated by the surface leakage magnetic flux is induced in the coil 6.
Become.

FIGS. 4 to 6 are B-H special line diagrams showing the magnetization state of the amorphous alloy thin wire 4 in the embodiment device, and are shown in a cylindrical shape ignoring the L steresis. Figure 4 shows the magnetization state caused by high-frequency excitation current.
It is assumed that high-frequency magnetization is performed so that the width of change in magnetic flux density is dBIK (indicated by a solid line in the figure), which is slightly lower than s.

FIG. 5 shows the magnetization state when the surface leakage magnetic flux of the magnetized pole matches the positive direction of the high-frequency magnetic field, and FIG. 6 shows the magnetization state when it matches the negative direction. In Fig. 5, the high-frequency magnetic field is hit by -42 points on the positive side due to the surface leakage magnetic field w JP J++
-y? r koji bP Mm translation 1 v'lh soraku ek ^-1b width is reduced to dB. In FIG. 6, the high frequency magnetic field is biased to the negative side (by the surface leakage magnetic field) and saturated to the negative side, and the variation width of the magnetic flux density is reduced to dB.

Figures 7 and 8 are waveform diagrams showing the induced voltage of the detection coil. Figure 7 shows the induced voltage waveform due to only the high-frequency magnetic field K, and Figure 8 shows the amplitude-modulated induced voltage waveform. The high-frequency induced voltage 50 having the peak value VO becomes a high-frequency induced voltage 60 whose amplitude is modulated by an amplitude modulation component 63 shown by a broken line in the figure due to the surface leakage magnetic field. Further, the amplitude modulated wave component 630 period T is shorter on the track 6A side and longer on the track 6F side because the magnetic thin film tracks 3A to 6F have different magnetized pole pitches.

FIG. 9 is a waveform diagram of a binary signal applied to the embodiment device K, in which a modulated wave component 63 of an amplitude-modulated high-frequency induced voltage 60 is shown.
Converting K into a binary signal 260 using a predetermined threshold value
Yoshi, N pole, and S pole are respectively H level and L level (1,
0), it is possible to obtain a digital signal 260 whose period T is the passing time of the rain magnetized pole. Therefore, by combining the digital saving signals 260 from the magnetic thin film tracks 3A to 3F, the position in the circumferential direction of the rotating plate 20 can be determined by n.
It can be specified with a resolution of

In the above-mentioned embodiment, the amorphous alloy thin wire and the high frequency excitation coil wound around the thin amorphous alloy wire are used.

The explanation has been given using an example in which the magnetic detection elements 7 made up of detection coils are arranged in alignment in the radial direction of the rotating plate, but it is also possible to arrange the magnetic detection elements 7 and the magnetized poles of the corresponding tracks 3 to be shifted in the circumferential direction of the track electrification. Alternatively, if the track width is formed by the magnetic detecting element 7, it is possible to eliminate the restriction on the track width, and by forming a large number of magnetic thin film tracks 3 on the rotary plate 2 having a small outer diameter, the resolution of position detection can be improved. can be increased.

〔Effect of the invention〕

As described above, this invention consists of concentrically forming a plurality of magnetic thin film tracks with mutually varying magnetization pole pitches on the surface of one rotary plate, and winding a high-frequency excitation coil and a detection coil around an amorphous alloy thin wire. The magnetic detection elements were arranged perpendicularly to each magnetic thin film track so that the tip of the thin amorphous alloy wire was close to the surface of each track. As a result, the polarity change of the magnetized pole of each magnetic thin film track is amplitude-modulated using the magnetic saturation characteristics of the amorphous alloy thin wire and can be detected as a high-frequency induced voltage, and this voltage can be detected by the detection circuit as a high-frequency induced voltage.
Convert to a digital signal that becomes 1, 0 corresponding to the S pole,
It is possible to provide an amplified magnetic rotation detection device that can specify the circumferential position of the rotary plate by combining the digital signals of each track. In addition, Co-based amorphous alloy thin wires are mechanically strong, have almost no magnetostriction, and have high high-frequency magnetic permeability. The width of the magnetic thin film track facing the magnetic thin film track and the pitch of the magnetized poles can be reduced.
A large number of tracks can be formed on a single rotating plate, compared to conventional magnetic rotation detection devices that use multiple rotating plates.
Therefore, it is possible to provide an absolute type rotation detection device that is small and simple, and has excellent speed responsiveness in rotation angle rotation speed detection and excellent resolution in position detection. Furthermore, since the magnetic sensing element using amorphous alloy thin wire is less affected by ambient temperature, it can eliminate the temperature dependence of conventional devices using Hall elements and magnetoresistive elements, and does not require a correction circuit. Therefore, it is possible to provide a rotation detection device with high reliability and a simplified detection circuit.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the device of the embodiment, Fig. 2 is a plan view showing the magnetic thin film track in the embodiment, Fig. 6 is a schematic side view of the main parts in the embodiment, and Figs. B-H4 showing the magnetization state of the amorphous alloy thin wire in Example! j
7 and 8 are induced voltage waveform diagrams of the detection coil in the embodiment, and FIG. 9 is a binary signal waveform diagram of the detection circuit in the embodiment. 1... Rotating shaft, 2... Rotating plate, 5.5A to 3E...
・Magnetic thin film track, 4, 4A, 4B... Amorphous alloy thin wire, 5... High frequency excitation coil, 6... Detection coil, 7... Magnetic detection element, 8... Magnetic shield, 9・
... Support member, 10... Case, 25... Oscillator,
26...Detection circuit. feet? Kusunoki 112 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1) A rotary shaft rotatably supported by a case, a rotary plate fixed to the rotary shaft, and concentrically formed magnetized poles with different pitches on the surface of the rotary plate. a plurality of magnetic thin film tracks, a plurality of magnetic sensing elements each having a tip of an amorphous alloy wire around which a high frequency excitation coil and a detection coil are wound, arranged vertically close to the surface of the magnetic thin film track; A rotation detecting device comprising: a position detecting circuit that detects amplitude modulated components of amplitude modulated high frequency signals respectively output from magnetic detecting elements and detects the position of the rotary plate based on the binary signals thereof. 2) The rotation detecting device according to claim 1, wherein the magnetic detecting element has a magnetic shield surrounding the magnetic detecting element.