JPH0735572A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To accurately detect a position without suffering any interference on a magnetic detector by forming a bracket and a cover out of a soft magnetic substance for isolating an externally acting leakage flux. CONSTITUTION:A magnetic drum 6 is coupled to one end of a rotary shaft 2 supported on the bearing of a bracket 1, and a magnetic detector 3 is provided so as to oppose the external surface of the drum 6. Also, a signal processing circuit 5 to process output data from the detector 3, the detector 3 and the drum 6 are respectively concealed with the cover 4, and fixed to the bracket 1. In this case, the bracket 1 and the cover 4 are formed out of a soft magnetic substance with high magnetic permeability, for example, mild steel or the like. Thus, the bracket 1 for mounting a magnetic encoder on other equipment isolates a leakage flux flowing therefrom along the direction of the shaft 2, while the cover 4 isolates a leakage flux intruding along the external surface of the bracket 1. As a result, the detector 3 can detect an accurate position without suffering any interference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder, and more particularly to a magnetic encoder used in an environment where a magnetic flux leaks from the outside.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing the structure of a magnetic encoder which has been conventionally used. 8 is a bracket, 2 is a rotary shaft, 3 is a magnetic detector, 10 is a cover, 5 is a signal processing circuit, and 6 Is a magnetic drum, and 7 is a cable for transmitting signals to the outside.

The magnetic encoder shown in FIG. 3 has a rotating shaft 2 rotatably supported by bearings provided on a bracket 8.
A magnetic drum 6 having a thin ferromagnetic material fixed to its outer peripheral surface, and magnetic poles of N and S are magnetized along the circumferential surface at equal intervals on the outer peripheral surface of the ferromagnetic material. The magnetic detector 3 is disposed so as to face the outer peripheral surface with a gap therebetween, the position of the magnetic pole magnetized on the outer periphery of the magnetic drum is converted by the magnetic detector 3 into an electric signal, and the electric signal is processed by the signal processing circuit 5. Is transmitted to the external control device through the cable 7 and is covered with a cover 10 to protect the magnetic drum 6, the magnetic detector 3 and the signal processing circuit 5. And cable 7
The position of the rotary shaft 2 can be known from the signal sent from the device. FIG. 4 is a sectional view showing another embodiment of the magnetic encoder, which is different from the embodiment of FIG. 3 in that the rotary shaft is formed of a hollow shaft, and other parts are the same as those shown in FIG. The embodiment shown in FIG. 4 has a structure suitable for being directly connected to a servo motor, and the rotary shaft of the servo motor is inserted and fixed in the hollow shaft.

[0004]

In the conventional magnetic encoder shown in FIGS. 3 and 4, the bracket 1 and the cover 10 are generally light in weight, easy to process, and excellent in corrosion resistance. For this reason, it was made of a light alloy mainly composed of aluminum. However, when the magnetic encoder is used in a position control device controlled by a servo motor, leakage flux generated by the servo motor penetrates the bracket 8 and the cover 10 formed of a light alloy and interferes with the magnetic detector. There is a problem that an accurate position signal cannot be obtained.

[0005]

In the magnetic encoder according to the present invention, the bracket and the cover are made of a soft magnetic material,
The problem is solved by blocking the leakage magnetic flux acting from the outside with the bracket and the cover so as not to interfere with the magnetic detector 3.

[0006]

[Operation] The leakage magnetic flux acting from the outside is blocked by the bracket and cover made of soft magnetic material with high permeability, and does not interfere with the magnetic detector.

[0007]

1 is a sectional view showing a first embodiment of a magnetic encoder according to the present invention, in which a bracket 1 and a cover 4 are made of a soft magnetic material having a high magnetic permeability, for example, a soft steel or a silicon steel plate. The other features are the same as those of the prior art shown in FIG. Since the bracket 1 is formed thick so as to attach the magnetic encoder to other equipment, it is effective in blocking the leakage magnetic flux from other equipment coming from the direction of the rotation axis, and the cover 4 is made of mild steel or silicon steel plate. It is effective in blocking the leakage magnetic flux which is formed and goes around the outer periphery of the bracket. Further, an embodiment in which the rotary shaft as shown in FIG. 4 is a hollow shaft is also possible.

FIG. 2 is a sectional view showing a second embodiment. The bracket 8 is formed of a light alloy as in FIG. 4 of the prior art, and the end face of the bracket 8 on which the magnetic detector 3 is attached is made of soft steel.
Alternatively, a shield plate 9 made of a silicon steel plate is provided, and the cover 4 is made of mild steel or a silicon steel plate.
Since it is a light alloy, it is lighter in weight than the embodiment formed of mild steel shown in FIG. 1, and the leakage flux coming from the axial direction is blocked by the shield plate 9. In addition, the rotary shaft 2 is shown in FIG.
Although the same hollow shaft as in the case shown in FIG. 1 is shown, it can be applied to an embodiment using a normal rotary shaft as shown in FIG.

[0009]

Since the magnetic encoder according to the present invention has the above-described structure, it blocks the leakage magnetic flux coming from the outside and does not interfere with the magnetic detector, so that the position can be accurately detected.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a first embodiment of a magnetic encoder according to the present invention.

FIG. 2 is a cross-sectional view showing the structure of another embodiment of the magnetic encoder according to the present invention.

FIG. 3 is a sectional view showing the structure of the first embodiment of the magnetic encoder according to the prior art.

FIG. 4 is a cross-sectional view showing the structure of another embodiment of the conventional magnetic encoder.

[Explanation of symbols]

 1: Bracket made of soft magnetic material 2: Rotating shaft 3: Magnetic detector 4: Cover made of soft magnetic material 5: Signal processing circuit 6: Magnetic drum 7: Cable 8: Bracket made of light alloy 9 : Shield plate made of soft magnetic material 10: Cover made of light alloy

Claims (4)

[Claims] 1. A rotary shaft rotatably supported by a bearing provided on a bracket, and a magnetic drum having a thin ferromagnetic material fixed to the outer peripheral surface of a rotary body mounted at one end of the rotary shaft.
A magnetic detector disposed opposite to the outer peripheral surface of the magnetic drum via a gap; and a signal processing circuit for processing the output of the magnetic detector, the signal processing circuit, and the magnetic detector, A magnetic encoder having a structure in which a cover for covering the magnetic drum is fixed to the bracket, wherein the bracket and the cover are made of a soft magnetic material. 2. The bracket is formed of a non-magnetic material, a shield plate formed of a soft magnetic material is provided on an end surface of the bracket facing the magnetic detector, and the cover is formed of a soft magnetic material. Magnetic encoder to do. 3. The magnetic encoder according to claim 1, wherein the rotary shaft is formed by a hollow shaft. 4. The magnetic encoder according to claim 2, wherein the rotary shaft is formed by a hollow shaft.