JP2559884Y2 - Motor with magnetic encoder - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor with a magnetic encoder, and more particularly to a structure for shielding a magnetic noise from a magnetic encoder.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional motor with a magnetic encoder. In FIG. 2, the magnetic encoder E is provided with a bottomed cylindrical shaft holder 3 on the inner peripheral side of the base 1 via bearings 2. This shaft holder 3
The distal end side of the rotating shaft 4 protruding from the motor 15 toward the magnetic encoder E is held in the hole 3a. Also,
At the bottom 3b of the shaft holder 3, there is provided a magnet holder 6 having a magnetized portion 5 on which a magnetic signal is magnetized and recorded attached to the outer periphery. The magnet holder 6 and the magnetized part 5 form a magnetic drum. A magnetic sensor 7 for detecting a magnetic signal recorded by magnetization is closely opposed to the magnetized portion 5. The magnetic sensor 7 is made of, for example, a magnetoresistive element, and is disposed on a sensor holder 8 fixed to the outer periphery of the lower end of the base 1.

A yoke 9 is mounted on the magnet holder 6.
Is held down by the leaf spring 10 and the screw 1
It is fixed via 1,11. These screws 11, 11
Also serves as a means for fixing the magnet holder 6 to the shaft holder 3. A ring-shaped pole magnet 12 is fixed to the inner bottom surface of the yoke 9. Pole magnet 1
A circuit board 13 is disposed on an upper portion of the motor 2, and a pole sensor 14 is disposed on a lower surface of the shaft holder 3 at a position facing the pole magnet 12. The holder 6 and the yoke 9 rotate. The magnetic pole of the pole magnet 12 is detected by the pole sensor 14 by this rotation, so that the magnetic pole of the rotor magnet (not shown) of the motor 15 is detected.

As such a magnetic encoder, there is one shown in Japanese Utility Model Laid-Open No. 3-70319.

[0005]

In the above-mentioned conventional motor with a magnetic encoder, the shaft holder 3 located at the center of the magnetic encoder E has a rotating shaft 4 of a motor 10 formed of a magnetic material such as iron. Is held. For this reason,
Magnetic noise composed of magnetic flux generated from the motor 10 or an electromagnetic brake built in the motor 10 is transmitted through the rotating shaft 4 and jumps into the magnetic sensor 7 in the magnetic encoder E, thereby deteriorating the output characteristics of the magnetic sensor 7. I was In order to prevent the magnetic noise from the motor 15, a magnetic shield plate such as an iron plate must be provided on the end face of the motor 15, which inevitably increases the cost as the number of parts increases and increases the size and size. There is also a problem that the number increases.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object to prevent the arrival of magnetic noise from a motor to a magnetic sensor by a simple means and to stabilize the output characteristics of the magnetic sensor. It is an object of the present invention to provide a magnetic encoder-equipped motor that can be used.

[0007]

Means for Solving the Problems The present invention is directed to a cylindrical body which rotates integrally with a rotating shaft of a motor on which an object to be detected on which a signal is recorded is mounted on an outer periphery, and a tip end of the rotating shaft with respect to the cylindrical body. Provided magnetic body, bearing mounted inside the cylindrical body, and axially extending inside the bearing
A fixed-side bearing cylindrical body made of a magnetic material for holding the bearing, a magnetic sensor attached to the fixed-side bearing cylindrical body so as to face the object to be detected, and a cylindrical shape provided on the outer periphery of the magnetic sensor of and a casing made of a magnetic material, to form a flange portion extending casing side cylinder for the fixed-side bearing, and the cylindrical body for the fixed bearing, and the magnetic body, the upper
The case and the detection object and the magnetic sensor inside,
Enclosed from outside and from above and below, magnetic
A shield is formed .

[0008]

A magnetic body is provided at the tip end of a rotating shaft of a motor, and a fixed-side bearing cylinder body made of a magnetic material that extends in the axial direction and that holds the bearing is provided inside the bearing. For the fixed-side bearing
The object to be detected and the magnetic sensor consist of a cylindrical body, a magnetic body, and a case.
When the motor is surrounded from the inside, outside, and top and bottom , a path is formed for transmitting magnetic noise such as the magnetic flux of the motor, which has transmitted the rotation axis of the motor, from the magnetic material to the flange of the fixed-side bearing cylinder via the case. Is done. As a result, the object to be detected and the magnetic sensor are not affected by noise because they are located inside the path.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a motor with a magnetic encoder according to the present invention will be described below with reference to the drawings. FIG.
, The rotating shaft 21 of the motor 20
It is projected from 0 to reach the magnetic encoder A. The magnetic encoder A includes a cylindrical body 23 that rotates integrally with a rotary shaft 21 of a motor 20 having a detection target 22 on which a signal is recorded on the outer periphery, and a rotary shaft 21 formed by the cylindrical body 23.
, A bearing 25 mounted inside the cylindrical body 23, a fixed-side bearing cylindrical body 26 made of a magnetic material provided inside the bearing 25, A magnetic sensor 27 attached to the side bearing cylindrical body 26 so as to face the detection target 22, and a case 2 made of a cylindrical magnetic material provided on the outer periphery of the magnetic sensor 27.
8 is provided.

The detected object 22 is formed of a cylindrically formed plastic magnet or the like. Magnetic signals are magnetized and recorded at regular intervals in the circumferential direction, and are fitted and fixed to the outer periphery of the cylindrical body 23. The detection object 22 and the cylindrical body 23 form a magnetic drum. A magnetic sensor 27 including a magnetoresistive element or the like is closely opposed to the detection target 22, and detects a magnetic signal of the detection target 22. The magnetic sensor 27 is provided on a sensor holder 30 attached to a flange 26a of a fixed-side bearing cylindrical body 26 by a screw 29.

The fixed-side bearing cylindrical body 26 is formed of a magnetic material such as iron, and has two bearings 25 made of ball bearings on the outer periphery of the cylindrical portion 26b into which the rotary shaft 21 is inserted with a gap provided in the inner hole. Are held side by side in the axial direction.
A cylindrical body 23 is rotatably held on outer rings of the two bearings 25. The upper part of the cylindrical body 23 is formed in a cylindrical shape, the rotary shaft 21 is inserted into the inner hole, and the mounting boss 31 made of a non-magnetic material such as aluminum is fitted on the outer periphery.
2 fixed to the rotating shaft 21.

A substantially dish-shaped magnetic body 24 made of a magnetic material such as iron is attached to an end surface of the mounting boss 31, and a ring-shaped pole magnet 33 is fixed to an inner bottom surface portion. The pole magnet 33 is combined with a pole sensor 34 to detect a magnetic pole position of a rotor (not shown) of the motor 20. Also, the pole magnet 33
A circuit board 35 is disposed on the upper side of the panel, and a pole sensor 36 is disposed on the lower side at a position facing the pole magnet 33. The circuit board 35 and the fixed-side bearing cylindrical body 26
A case 28 made of a cylindrical magnetic material is disposed between the outer periphery of the flange 26 a and the outer periphery of the magnetic sensor 27 . The case 28 is disposed so as to be close to the magnetic body 24 and the flange 26a of the fixed-side bearing cylindrical body 26.

The flange 26 of the fixed-side bearing cylindrical body 26
aA plate spring 37 is attached between the outer peripheral side of the bottom surface and the upper end surface of the motor 20 by screws 38 and 39, and the axis of the motor 20 and the axis of the magnetic encoder A are fixed by the plate spring 37. In the case of eccentricity, misalignment between the two is absorbed. Further, a cover 40 that covers the above-described magnetic encoder A is fitted to the upper end surface of the motor 20, and is fixed by the screws 38 and 41.

In the motor with the magnetic encoder having the above-described configuration, magnetic noise generated from the motor 20 and magnetic noise generated from a magnetic flux or the like built in the motor 20 are transmitted through the rotating shaft 21. The magnetic noise arrives in the magnetic encoder A, and this magnetic noise is first transmitted from the rotating shaft 21 to the magnetic body 24,
Through 8, it is transmitted to the flange of the fixed-side bearing cylindrical body. As a result, a magnetic closed loop is formed, and the magnetic noise disappears. Therefore, the magnetic sensor 27 disposed in this loop
Magnetic noise is prevented from jumping into. Also, even if some sort of magnetic noise tries to jump in from the outside, or if the magnetic flux leaks from the above-described pole magnet 33, the magnetic noise is cut off by the above-described magnetic closed loop, and the jump into the magnetic sensor 27 is also prevented. You.
If the mounting boss 31 is made of a magnetic material, the formation of a magnetic closed loop becomes easier.

[0016]

[Effects of the Invention] As is clear from the above description, the motor with the magnetic encoder of the present invention has a cylindrical body for the fixed bearing.
And the part extending axially inside the bearing and the case side
The fixed side bearing cylindrical body is formed
Object and magnetic sensor inside and outside
Since it is surrounded from the side and from the top and bottom , magnetic noise such as the magnetic flux of the motor that transmits the rotation axis of the motor forms a path from the magnetic material to the flange of the fixed-side bearing cylinder through the case, and as a result In addition, the object to be detected and the magnetic sensor located inside the path surrounded by the path can be prevented from being affected by magnetic noise, and stable output characteristics can be obtained. In addition, it is not necessary to add special magnetic shielding parts, so the number of parts does not increase and the size increases.
No.

[0019]

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a motor with a magnetic encoder according to the present invention.

FIG. 2 is a cross-sectional view showing a conventional motor with a magnetic encoder.

[Explanation of symbols]

 Reference Signs List 20 motor 21 rotating shaft A magnetic encoder 22 object 23 cylindrical body 24 magnetic body 25 bearing 26 fixed-side bearing cylindrical body 26a flange 27 magnetic sensor 28 case

Claims (1)

(57) [Scope of request for utility model registration] A cylindrical body which rotates integrally with a rotation shaft of a motor having a detection object on which a signal is recorded on an outer periphery, a magnetic body provided on a tip side of the rotation shaft with respect to the cylindrical body;
A bearing attached to the inside of the cylindrical body, a fixed-side bearing cylindrical body made of a magnetic material that extends axially inside the bearing and holds the bearing; A magnetic sensor attached to face the object to be detected, and a case made of a cylindrical magnetic material provided on the outer periphery of the magnetic sensor;
A flange portion extending casing side is formed, cylindrical for the fixed-side bearing
Body, the magnetic body, the case and the object to be detected and
Surrounding the magnetic sensor from inside, outside and top and bottom,
Characterized by forming a magnetic shield for the magnetic sensor
Motor with magnetic encoder shall be the.