JPH02297012A - Rotating body position detecting device - Google Patents

Abstract

PURPOSE:To prevent the adhesion of contamination and the generation of rust and to improve the position detecting accuracy by forming a space closed up tightly by a magnetic fluid seal so as to face the surface of a rotating body, and placing a position detecting sensor in this closed space. CONSTITUTION:Magnetic fluid seals 4a, 4b are formed by an annular seal plate 7 consisting of a permanent magnet in which the outside peripheral part is fixed to a casing 2, and a sharp projecting edge part 7a positioned adjacently on the outside peripheral surface of a spindle 1 is formed in the inside peripheral part, and a magnetic fluid 8 interposed between the inside periphery of the seal plate 7 and the outside peripheral surface of the spindle 1. The seal plate 7 is magnetized in the diameter direction, and the seals 4a, 4b are magnetized so that the magnetic poles become opposite to each other in the inside periphery and the outside periphery. Also, by the fluid 8 caught by the projecting edge part 7a in which the magnetic flux density is concentrated, a gap between the spindle 1 and the outside peripheral surface is sealed, and a space 5 becomes a closed space against the external space, therefore, the position detection can be executed with high accuracy extending over a long period of time. As a result, the rotation accuracy of the spindle 1 is maintained high.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotating body position detection device used in controlled magnetic bearings and the like.

BACKGROUND OF THE INVENTION Control type magnetic bearings that actively control the shaft center position using electromagnets are known as a type of high-speed, high-precision bearings.

This controlled magnetic bearing is non-contact and does not require the use of lubricant, so it is suitable for high-speed rotation with low torque and low noise. It can also be used in high vacuum, is free from contamination with lubricant, and has high speed control. It has features such as being able to obtain a rigid bearing, and is suitable for high-speed rotation and can be applied to spindle bearings of processing machines such as milling machines. It is proposed that.

The schematic configuration of the spindle drive device in this milling machine will be explained. In FIG. 3, 11 is a spindle, and an end mill 12 is fitted into one end of the spindle. The spindle 11 is rotatably supported near both ends by magnetic bearings 13a and 13b, and is configured to be driven by a motor 14 disposed in the middle. Furthermore, a magnetic bearing 13a located on one end side of the spindle 11 and a motor 1
A thrust magnetic bearing 15 is disposed between the two.

16a and 16b are sensors arranged at both ends of the spindle 11 to detect the radial position; 17 is the sensor of the spindle 1;
1 is a sensor that detects the position in the axial direction provided at the other end of the shaft. 18a, 18b are magnetic bearings 13a, 13b, 1
This is a rolling bearing that supports the spindle 11 when the spindle 5 does not operate effectively or when the bearing action is unstable such as when starting or stopping.

The sensors 16a and 16b are as shown in FIG. 2 (only 16b is shown in FIG. 2, but 16a is also similar),
It is installed so as to face a detection cylindrical surface 20 formed on a spacer ring 19 externally fitted onto the spindle 11 with an appropriate gap therebetween.

In the above configuration, the spindle 11 is raised by detecting the radial and axial positions of the spindle 11 using the sensors 16a, 16b, and 17, and controlling the magnetic bearings 13a, 13b, and 15 according to the amount of eccentricity. The spindle 11 can be held in a predetermined position with high accuracy, and by rotating the spindle 11 with the motor 14, the end mill 12 can perform highly accurate machining.

Problem to be Solved by the Invention However, in the above configuration, the sensor and the detection surface are arranged in a space that communicates with the outside space, and furthermore, in the case of a milling machine, etc., the environment where the machine is placed is not clean, so the sensor It is easy for dirt to adhere to the detection part of the sensor, and for rust to form on the mirror-finished detection surface, and this dirt and rust can have a significant effect on position detection accuracy, making it difficult to detect accurate position over a long period of time. The problem was that I couldn't do it.

For example, in the spindle of a processing machine that uses magnetic bearings, such as the milling machine mentioned above, the position detection accuracy has a large effect on the processing accuracy, so the position detection accuracy needs to be 0.1 μm or less. Accuracy is greatly affected by dirt and rust.

SUMMARY OF THE INVENTION In view of the above conventional problems, it is an object of the present invention to provide a rotating body position detection device that does not generate dirt or rust on the sensor or detection surface and can provide high position detection accuracy over a long period of time.

Means for Solving the Problems In order to achieve the above object, the present invention disposes a sensor close to the surface of a rotating body to detect a gap between the surface and the rotating body based on a change in the detected gap. A rotating body position detection device for detecting the position of a rotating body is characterized in that a space sealed with a magnetic fluid seal is formed facing the surface of the rotating body, and the sensor is disposed in this sealed space.

Function According to the present invention, the magnetic fluid seal can prevent dirt, moisture, etc. from entering the closed space, and prevent dirt from adhering to the surface of the rotating body, which serves as the sensor and detection surface, and from forming rust. can be prevented, and high position detection accuracy can be maintained over a long period of time. Furthermore, since a magnetic fluid seal is used, the load torque of the rotating body is not affected.

Example An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a spindle 1 is driven to rotate at high speed by a drive means (not shown), and is rotatably supported by a controlled magnetic bearing (not shown). 2 is a casing that accommodates and holds the driving means and the magnetic bearing; 3 is a spindle 1;
This sensor is placed close to the outer peripheral surface of the spindle 1 and detects the gap between the spindle 1 and the outer peripheral surface of the spindle 1, and is attached to the casing 2. The sensor 3 is arranged so that its detection end is located in a space 5 surrounded by the magnetic fluid seals 4a and 4b on both sides, the outer peripheral surface of the spindle 1, and the inner peripheral surface of the casing 2. The outer peripheral surface facing the space 5 is formed into a mirror surface and serves as a detection surface 6.

The magnetic fluid seals 4a and 4b include an annular seal plate 7 made of a permanent magnet whose outer circumferential portion is fixed to the casing 2 and whose inner circumferential portion is formed with a sharp protruding edge 7a located close to the outer circumferential surface of the spindle 1; It is formed of a magnetic fluid 8 interposed between the inner periphery of the annular seal plate 7 and the outer periphery of the spindle 1. The annular seal plate 7 is magnetized in the radial direction so that the magnetic poles of the magnetic fluid seals 4a and 4b are opposite to each other at the inner and outer circumferences.

The magnetic fluid 8 has both fluidity, which is the property of a liquid, and properties as a magnetic material made from an alloy of iron, nickel, ferrite, etc. In this embodiment, magnetite (Feo- 100
Commercially available products are used that are made into microparticles with the diameter of a human being and dispersed in a solvent with the help of a surfactant.

In the above configuration, the spindle 1 is rotatably supported by a magnetic bearing and is rotationally driven by a driving means. At this time, by detecting the change in the gap between the outer peripheral surface of the spindle 1 and the detection surface 6 using the sensor 3, it is possible to detect the minute amount of eccentricity accompanying the rotation of the spindle 1, and the amount of eccentricity can be detected. By controlling the magnetic bearing so that the axis is 0, the axis of the spindle 1 can be held and rotated.

In addition, in the magnetic fluid seals 4a, 4, and b on both sides of the sensor 3, the magnetic fluid 8 captured by the ridge 7a on the inner circumference of the annular seal plate 7 where the magnetic flux density is concentrated is connected to the outer peripheral surface of the spindle 1. Since the gap between them is sealed and the space 5 is a closed space sealed from the outside space, dust and moisture are prevented from entering from the outside space. Therefore, it is possible to reliably prevent dust from adhering to the detection part and the detection surface 6 of the sensor 3, and to prevent rust from forming, and highly accurate position detection is possible for a long period of time.As a result, the rotation accuracy of the spindle 1 can be improved. can be maintained high. Furthermore, since it is sealed with the magnetic fluid 8, it does not affect the load torque or the like.

In the above embodiment, only the case where the position of the spindle 1 in the radial direction is detected has been described, but the present invention can be similarly applied to the case of a sensor that detects the position in the axial direction. Further, in the above embodiment, an example of position detection for controlling a magnetic bearing has been shown, but it goes without saying that the present invention can also be applied to position detection for use in other devices.

Effects of the Invention According to the rotating body position detection device of the present invention, a space sealed with a magnetic fluid seal is formed so as to face the surface of the rotating body as described above, and a sensor is disposed in this sealed space.
The magnetic fluid seal prevents dirt, moisture, etc. from entering the sealed space, preventing dirt from adhering to the detection surface of the sensor and rotating body, and preventing rust from forming. Detection accuracy can be maintained, reliability is improved, and since a magnetic fluid seal is used, load characteristics are not affected.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a rotary body position detection device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional front view of a conventional example, and FIG. 3 is a milling machine as an example to which the rotary body position detection device is applied. FIG. ■・・・Spindle, 3・・・Sensor, 4
a, 4b...Magnetic fluid seal, 5...
Closed space, 6...Detection surface. Agent: Patent attorney Shigetaka Awano (1 person) Figure 1 Figure 2

Claims (1)

[Claims] In a rotating body position detection device that detects the position of the rotating body by placing a sensor close to the surface of the rotating body and detecting the gap between the sensor and this surface, the sensor is placed close to the surface of the rotating body and detects the position of the rotating body based on the change in the detected gap. 1. A rotating body position detecting device, characterized in that a space sealed with a magnetic fluid seal is formed in the rotating body, and the sensor is disposed in the sealed space.