JPH0550975U - Motor with magnetic encoder - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the arrival of motor noise to the magnetic sensor and stabilize the output characteristics of the magnetic sensor. [Structure] A cylindrical body 23 that rotates integrally with a rotary shaft 21 of a motor 20 to which a detected body 22 having a signal recorded on the outer periphery is attached, and a magnetic body provided on the tip side of the rotary shaft 21 with respect to the cylindrical body 23. 24, a bearing 25 mounted inside the cylindrical body 23, a fixed-side bearing cylindrical body 26 made of a magnetic material disposed inside the bearing 25, and the fixed-side bearing cylindrical body 26 to be detected. A magnetic sensor 27 attached so as to face the body 22 and a case 28 made of a cylindrical magnetic material provided on the outer periphery of the magnetic sensor 27, and a flange extending to the outer peripheral side of the fixed-side bearing cylindrical body 26. The portion 26a is formed, and the case 28 is arranged so as to be at least close to the magnetic body 24 and the collar portion 26a. [Effect] The magnetic sensor can be prevented from being affected by magnetic noise such as magnetic flux transmitted through the rotating shaft of the motor, and stable output characteristics can be obtained.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a motor with a magnetic encoder, and more particularly to a magnetic noise shielding structure for a magnetic encoder.

[0002]

[Prior Art]

 An example of a conventional motor with a magnetic encoder is shown in FIG. 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 and 2. In the hole 3a of the shaft holder 3, the tip end side of the rotary shaft 4 which is projected from the motor 15 toward the magnetic encoder E is held. Further, on the bottom portion 3b of the shaft holder 3, there is provided a magnet holder 6 having a magnetized portion 5 on which magnetic signals are magnetized and recorded and which is attached to the outer periphery. A magnetic drum is formed by the magnet holder 6 and the magnetizing portion 5. A magnetic sensor 7 for detecting a magnetically recorded magnetic signal is closely opposed to the magnetizing section 5. The magnetic sensor 7 is composed of, for example, a magnetic resistance element, and is arranged in a sensor holder 8 fixed to the outer periphery of the lower end of the base 1.

A yoke 9 is fixed to the magnet holder 6 via screws 11 and 11 while being pressed by a leaf spring 10. The screws 11 and 11 also serve as fixing means for 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. A circuit board 13 is arranged above the pole magnets 12, and a pole sensor 14 is arranged on the lower surface in a position facing the pole magnets 12, and receives rotation of the rotation shaft 4 of the motor 15. The shaft holder 3, the magnet holder 6 and the yoke 9 rotate. By this rotation, the magnetic pole of the pole magnet 12 is detected by the pole sensor 14, so that the magnetic pole of the rotor magnet (not shown) of the motor 15 is detected.

An example of such a magnetic encoder is disclosed in Japanese Utility Model Laid-Open No. 3-70319.

[0005]

[Problems to be solved by the device]

 In the conventional motor with a magnetic encoder, the rotary shaft 4 of the motor 10 formed of a magnetic material such as iron is held by the shaft holder 3 located at the center of the magnetic encoder E. For this reason, magnetic noise composed of magnetic flux generated from the motor 10 or an electromagnetic brake incorporated in the motor 10 propagates through the rotary shaft 4 and jumps into the magnetic sensor 7 in the magnetic encoder E, so that the magnetic sensor 7 is driven. The output characteristics were deteriorated. In order to prevent magnetic noise from the motor 15, it is necessary to provide a magnetic shield plate such as an iron plate on the end surface of the motor 15, which inevitably increases the cost as the number of parts increases, and increases the size. Also has the problem of increasing.

The present invention has been made to solve such a problem, and prevents magnetic noise from coming from a motor to a magnetic sensor by a simple means and stabilizes the output characteristic of the magnetic sensor. It is an object of the present invention to provide a motor with a magnetic encoder that can be used.

[0007]

[Means for Solving the Problems]

 The present invention provides a cylindrical body that rotates integrally with a rotation shaft of a motor, in which a detected object having a signal recorded on the outer periphery is attached, a magnetic body provided on the tip side of the rotation shaft with respect to the cylindrical body, and A bearing mounted inside the cylindrical body, a fixed-side bearing cylindrical body made of a magnetic material disposed inside the bearing, and a fixed-side bearing cylindrical body facing the above-mentioned detected body. It has a magnetic sensor to be attached and a case made of a cylindrical magnetic material provided on the outer periphery of the magnetic sensor, and a flange portion extending to the outer peripheral side is formed on the fixed-side bearing cylindrical body, and the case is formed. It is characterized in that it is arranged so as to be at least close to the magnetic body and the collar portion.

[0008]

[Action]

 A magnetic body is provided on the tip side of the motor's rotating shaft, a fixed side bearing cylinder made of magnetic material is placed inside the bearing, and a cylindrical case made of magnetic material is provided on the outer circumference of the magnetic sensor. Is placed so that it is at least close to the magnetic body and the flange of the fixed-side bearing cylinder, the magnetic noise such as the magnetic flux of the motor that has transmitted the motor's rotating shaft will pass from the magnetic body to the fixed side through the case. A path is formed for transmission to the flange of the bearing cylinder. As a result, since the object to be detected and the magnetic sensor are located inside the path, they are not affected by noise.

[0009]

【Example】

 An embodiment of a motor with a magnetic encoder according to the present invention will be described below with reference to the drawings. In FIG. 1, the rotary shaft 21 of the motor 20 is made to project so that its tip end side reaches the magnetic encoder A from the motor 20. The magnetic encoder A is provided with a cylindrical body 23 that rotates integrally with a rotary shaft 21 of a motor 20 to which a detected body 22 having a signal recorded on the outer circumference is attached, and a tip end side of the rotary shaft 21 with respect to the cylindrical body 23. A magnetic body 24, a bearing 25 mounted inside the cylindrical body 23, a fixed-side bearing cylindrical body 26 made of a magnetic material disposed inside the bearing 25, and a fixed-side bearing cylindrical body 26. In addition, the magnetic sensor 27 is attached so as to face the detection target 22, and a case 28 made of a cylindrical magnetic material is provided on the outer circumference of the magnetic sensor 27.

The detected body 22 is made of a plastic magnet or the like formed in a cylindrical shape, and magnetic signals are magnetized and recorded at regular intervals in the circumferential direction, and are fitted and fixed to the outer circumference of the cylindrical body 23. The detected body 22 and the cylindrical body 23 form a magnetic drum. A magnetic sensor 27 including a magnetoresistive element and the like closely faces and opposes the detection target 22, and detects a magnetic signal of the detection target 22. The magnetic sensor 27 is arranged in the sensor holder 30 which is attached to the flange portion 26a of the fixed-side bearing cylindrical body 26 with a screw 29.

The stationary-side bearing cylindrical body 26 is made of a magnetic material such as iron, and the rotating shaft 21 is inserted in the inner hole with a gap between the cylindrical portion 26 b and the outer periphery of the cylindrical portion 26 b. Are held side by side in the axial direction. The cylindrical body 23 is rotatably held by the outer rings of the two bearings 25. The upper part of the cylindrical body 23 is formed in a cylindrical shape, and the rotary shaft 21 is fitted and inserted in the inner hole, and a mounting boss 31 made of a non-magnetic material such as aluminum is fitted on the outer periphery and fixed to the rotary shaft 21 by a screw 32. Has been done.

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

A leaf spring 37 is attached between the outer peripheral side of the bottom surface of the flange portion 26 a of the stationary-side bearing cylindrical body 26 and the upper end surface of the motor 20 with screws 38 and 39. When the shaft center on the motor 20 side and the shaft center on the magnetic encoder A side are eccentric, the misalignment between them is absorbed. Further, the cover 40 that covers the magnetic encoder A described above is fitted to the upper end surface of the motor 20, and is fixed by the screws 38 and 41.

In the motor with a magnetic encoder configured as described above, magnetic noise generated from the motor 20 or magnetic noise generated from a magnetic flux generated from an electromagnetic brake incorporated in the motor 20 is transmitted to the rotating shaft 21. Then, the magnetic noise is transmitted to the magnetic encoder A from the rotary shaft 21 to the magnetic body 24 and then to the flange portion of the stationary side bearing cylindrical body through the case 28. As a result, a magnetic closed loop is formed and magnetic noise disappears. Therefore, magnetic noise is prevented from entering the magnetic sensor 27 arranged in this loop. Further, even if some magnetic noise is attempted to jump in from the outside or magnetic flux leaks from the pole magnet 33, the magnetic noise is blocked by the magnetic closed loop described above and the jump to the magnetic sensor 27 is prevented. It If the mounting boss 31 is made of a magnetic material, it is easier to form the magnetic closed loop.

[0016]

[Effect of the device]

 As is clear from the above description, the motor with a magnetic encoder of the present invention has a case made of a cylindrical magnetic material on the outer periphery of the magnetic sensor, a magnetic body provided on the tip side of the rotating shaft of the motor, and a magnetic material. Since it is placed so as to be at least close to the flange of the fixed-side bearing cylindrical body, the magnetic noise such as the magnetic flux of the motor that transmits the motor's rotating shaft is transmitted from the magnetic body to the fixed-side bearing through the case. A path is formed to reach the flange of the cylindrical body, and as a result, the object to be detected and the magnetic sensor located inside the path can be prevented from being affected by magnetic noise, and stable output characteristics can be obtained. Can be obtained. Further, it is not necessary to add a special magnetic shield component, so that the number of components can be reduced and the size can be reduced.

[0019]

[Brief description of 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]

 20 Motor 21 Rotational Axis A Magnetic Encoder 22 Detected Object 23 Cylindrical Body 24 Magnetic Material 25 Bearing 26 Fixed Side Bearing Cylindrical Body 26a Collar 27 Magnetic Sensor 28 Case

Claims (1)

[Scope of utility model registration request] 1. A cylindrical body that rotates integrally with a rotation shaft of a motor, to which a detected body having a signal recorded on its outer periphery is attached, and a magnetic body provided on the tip side of the rotation shaft with respect to the cylindrical body.
A bearing mounted inside the cylindrical body, a fixed-side bearing cylindrical body made of a magnetic material disposed inside the bearing, and the fixed-side bearing cylindrical body facing the detected body. It has a magnetic sensor to be attached and a case made of a cylindrical magnetic material provided on the outer periphery of the magnetic sensor, and a flange portion extending to the outer peripheral side is formed on the fixed-side bearing cylindrical body, and the case is set to the magnetic field. A motor with a magnetic encoder arranged so as to be at least close to the body and the flange portion.