JPH0854020A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To obtain a magnetic bearing device which enables higher speed rotation by arranging a radial displacement sensor and an axial displacement sensor in a superposing manner in at least their one portions in an axial direction of a rotary shaft, and thereby enlarging a load capacity of the bearing. CONSTITUTION:An axial displacement sensor 5b an a radial displacement sensor 4b are arranged superposingly in an axial direction of a shaft 2, so that an arrangement spase for the sensors is saved in an axial direction. The axial measurement of the shaft 2 can be reduced. As a result, characteristic frequency of the shaft 2 is increased, and higher speed rotation is enabled. The axial displacement sensor 5b can be arranged in the vicinity of a radial magnetic bearing device 6 compared to a conventional case, so that detection error of the axial displacement sensor 5b due to the influence of inclination of the shaft 2 is minimized. It is thus possible to perform axial control with higher accuracy. Margin of an axial measurement is utilized for a suctioning area of the magnetic bearing, so that a load capacity of the bearing is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device used for a spindle of a machine tool or the like.

[0002]

2. Description of the Related Art Conventionally, a magnetic bearing device having a structure as shown in FIG. 3 has been used for a spindle of a machine tool which rotates at an extremely high speed. In the figure, the shaft 50 is a rotary shaft, and the shaft end 50
A tool (not shown) or the like is attached to a. The main body 51 includes a ball bearing 52, an axial displacement sensor 53 for detecting the axial displacement of the shaft 50, a radial displacement sensor 54 for detecting the radial displacement of the shaft 50, and the shaft 50 in the radial direction from the shaft end 50a side. Radial magnetic bearing 55 supported by contact, motor 56, radial magnetic bearing 55, radial displacement sensor 5
4, an axial magnetic bearing 57 and a ball bearing 52 that support the shaft 50 in the axial direction without contact are attached.

Usually, the radial displacement sensor and the axial displacement sensor are arranged apart from each other in the axial direction of the shaft 50.

[0004]

Therefore, the installation space for the radial displacement sensor and the axial displacement sensor is
It becomes longer in the axial direction, and along with this, the axial length of the shaft 50 becomes longer. As a result, since the natural frequency of the shaft cannot be increased, it has been impossible to rotate at a very high speed. On the other hand, since the attraction area of the magnetic bearing cannot be increased for the shaft 50 having a limited axial length, the load capacity of the bearing cannot be increased. Therefore, the load capacity of the spindle cannot be increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems and to provide a magnetic bearing device capable of increasing the load capacity of the bearing and rotating at a higher speed.

[0006]

In order to achieve the above object, a magnetic bearing device according to a first aspect of the present invention controls a radial magnetic bearing based on an output of a radial displacement sensor that detects a radial displacement amount of a rotary shaft. In addition, in the magnetic bearing device for controlling the axial magnetic bearing based on the output of the axial displacement sensor that detects the amount of axial displacement of the rotating shaft, the rotating shaft is supported by magnetic force in the radial and axial directions in a non-contact manner. The rotating shaft is provided with a stepped portion constituted by a first surface perpendicular to the axis and a second surface consisting of a circumferential surface having the axis as a center, and the radial displacement sensor includes the second surface. Of the radial displacement sensor and the axial displacement sensor, the axial displacement sensor opposes the first surface, and at least a part of the radial displacement sensor and the axial displacement sensor rotate with respect to the first surface. And it is characterized in that it is arranged so as to overlap in the axial direction.

A magnetic bearing device according to a second aspect of the present invention is the magnetic bearing device according to the first aspect, wherein the radial displacement sensor and the axial displacement sensor share the same circumference about the axis of the rotary shaft. It is characterized in that it is arranged in a state of being.

The magnetic bearing device according to a third aspect of the present invention is the magnetic bearing device according to the second aspect, wherein four radial displacement sensors and four axial displacement sensors are alternately arranged in a circumferential arrangement. The four axial displacement sensors have equivalent temperature dependence characteristics with respect to output, and
Among the axial displacement sensors, a pair of axial displacement sensors that face each other with the axis interposed therebetween are characterized in that they constitute a temperature compensation sensor attached in a state in which displacement detection is avoided. .

[0009]

According to the structure of the invention according to claim 1, the radial displacement sensor and the axial displacement sensor are arranged so that at least a part of each of them overlaps with each other in the axial direction of the rotary shaft, whereby the radial displacement sensor and the axial displacement sensor are axially aligned. It takes up less space in the axial direction than if it were placed at a distance. Therefore, the required length of the rotating shaft can be shortened. As a result, the natural frequency of the rotary shaft can be increased, and high speed rotation can be supported. Further, the load capacity of the bearing can be increased by using the generated dimensional margin in the axial direction as the attraction area of the magnetic bearing. Further, the axial displacement sensor can be brought close to the radial magnetic bearing, and when the rotating shaft is bent or tilted, the error in the detection signal of the axial displacement sensor due to the influence can be reduced.

According to the configuration of the invention according to claim 2,
In addition to the actions described in claim 1, the following actions are exhibited. That is, since the radial displacement sensor and the axial displacement sensor, which are overlapped in the axial direction as described above, are arranged so as to share the same circumference, the sensor mounting space can be integrated. As a result, the mounting space for the sensor can be made compact. It is also possible to configure the sensor and the sensor mounting portion as an integrated unit.

According to the configuration of the invention according to claim 3 above,
In addition to the action described in claim 2, the following action is exhibited. That is, by configuring a part of the axial displacement sensor as a temperature compensating sensor, this temperature compensating sensor is also arranged in the integrated space, which contributes to downsizing of the sensor mounting space. .

[0012]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 is a sectional view showing a schematic configuration of one embodiment of the magnetic bearing device of the present invention. FIG. 2 is a sectional view taken along the line AA in FIG. However, FIG. 1 is B--C--D in FIG.
The cross section along the line is shown. In FIG. 1, reference numeral 1 denotes a main body, which serves as a main shaft of a machine tool and which is inserted through the shaft 2.
A machine frame that accommodates components such as the motor 7 and is used alone or integrally formed with a member such as a housing of a machine tool.

The shaft 2 is rotatably provided and is driven to rotate by a motor 7. A processing tool (not shown) or the like is attached to one shaft end 2a of the shaft 2. A ball bearing 3, a sensor base 12, a radial magnetic bearing 6, a motor 7, a radial magnetic bearing 6, a radial displacement sensor 8, an axial magnetic bearing 9 and a ball bearing 3 are installed around the shaft 2 from the side of the shaft 2a. They are arranged and fixed to the main body 1, respectively. On the sensor base 12, radial displacement sensors 4b and 4c (only 4b is shown in FIG. 1) and axial displacement sensors 5b and 5c (only 5b are shown in FIG. 1) are provided in the axial direction of the shaft 2. It is installed in the same position.

The shaft 2 comprises a two-stage shaft in which the small diameter shafts 2c and 2d are integrally formed coaxially at both ends of the large diameter shaft 2e. A stepped portion 2de is provided between the large diameter shaft 2e and one small diameter shaft 2d. The stepped portion 2de is composed of the circumferential surface of the small diameter shaft 2d and the end surface 2b of the large diameter shaft 2e. Further, a disc-shaped flange portion 2f is formed at a boundary portion between the large diameter shaft 2e and the other small diameter shaft 2c.
The shaft 2 has an axial magnetic bearing 9 and a radial magnetic bearing 6
It is supported in a non-contact manner by the magnetic force of.

Referring to FIG. 2, the radial displacement sensor 4
b, 4c and the axial displacement sensors 5b, 5c are the shaft 2
In a state of sharing the same circumference centered on the axis of, the shafts 2 are alternately arranged around the small-diameter shaft 2d in equal distribution. The sensor base 12 is an annular plate member made of a hard member such as metal, and has radial displacement sensors 4b, 4c on one surface thereof.
Also, the axial displacement sensors 5b and 5c are fixed. Sensor base 12, radial displacement sensors 4b, 4c
The axial displacement sensors 5b and 5c are configured as one unit. Radial displacement sensors 4b, 4
The sensor base 12 is fixed to the main body 1 so that the c and the axial displacement sensors 5b and 5c have a predetermined positional relationship with the shaft 2.

The radial displacement sensors 4b and 4c are inductance type displacement sensors, and four detecting units 4a are installed on the same circumference with their detecting portions 4a facing the circumferential surface of the small diameter shaft 2d. There is. The pair of radial displacement sensors 4b sandwiching the shaft 2 measure the displacement of the shaft 2 in the radial direction (direction of arrow X in FIG. 2) without contact. Similarly, the pair of radial displacement sensors 4c includes a radial direction of the shaft 2 orthogonal to the arrow X direction (see FIG.
The displacement in the direction of arrow Y) is measured.

The axial displacement sensors 5b and 5c are eddy current type ferrite core displacement sensors. The pair of axial displacement sensors 5b sandwiching the shaft 2 is the detection unit 5 of the sensor.
a is provided so as to face the end surface 2b of the stepped portion 2de of the shaft 2, and the axial displacement of the shaft 2 is measured in a non-contact manner. The other pair of axial displacement sensors 5c are attached so that their detection surfaces face the sensor base 12 and do not detect the displacement of the shaft 2. The axial displacement sensor 5c is used as a temperature compensation sensor. That is, the pair of axial displacement sensors 5c that do not detect displacement are affected by the temperature change as in the axial displacement sensor 5b. Therefore, by subtracting the output signals of the pair of axial displacement sensors 5c from the output signals of the pair of axial displacement sensors 5b, the output signals of the pair of axial displacement sensors 5b are corrected with respect to the temperature change.

As with the radial displacement sensors 4b and 4c, four radial displacement sensors 8 are attached to the main body, and detect the radial displacement of the shaft 2. The ball bearing 3 is a so-called touchdown bearing that receives the shaft 2 when the shaft 2 stops. The axial magnetic bearing 9 includes a pair of electromagnets 9a.
And 9b, and the pair is arranged so as to sandwich the flange portion 2f provided on the shaft 2 at a predetermined interval.

The output signals of the axial displacement sensors 5b, 5c, the radial displacement sensors 4b, 4c and the radial displacement sensor 8 are subjected to predetermined signal processing by a control unit (not shown), and the radial direction and the axial direction of the shaft 2 are controlled. Is detected. At this time, the output signal of the axial displacement sensor 5b is corrected with respect to the temperature change. Based on the result, the control unit controls and drives the radial magnetic bearing 6 and the axial magnetic bearing 9 so as to keep the axial and radial positions of the shaft 2 in predetermined states.

In the above embodiment, since the axial displacement sensors 5b and 5c and the radial displacement sensors 4b and 4c are arranged so as to overlap each other in the axial direction of the shaft 2, the installation space of the sensor is axially spaced. Absent. As a result, the axial dimension of the shaft 2 can be shortened. As a result, the natural frequency of the shaft 2 can be increased and higher speed rotation can be achieved. Further, even if the shaft length is the same as the conventional one, the load capacity of the bearing can be increased by using the shortened dimension for increasing the attraction area of the magnetic bearing.

By the way, when the shaft 2 is bent or tilted,
Each part of the shaft 2 is displaced in the axial direction and the radial direction. The displacement detected by the axial displacement sensor 5b includes the displacement due to the inclination and the like, and this portion is an error.
If the axial displacement sensor 5b is arranged away from the radial magnetic bearing 6 which is a support point, the displacement due to the inclination and the like becomes large, so that the error becomes large and the measurement accuracy decreases.

On the other hand, in this embodiment, the axial displacement sensor 5b can be arranged closer to the radial magnetic bearing 6 than in the conventional case, so that the detection error of the axial displacement sensor 5b due to the influence of the inclination of the shaft 2 or the like. Can be made smaller. Therefore, it is possible to control the axial direction with higher accuracy. In addition, the amount of displacement detected by the axial displacement sensor 5b is reduced accordingly, and it is possible to use a sensor having a lower dynamic range.

Further, since the radial displacement sensors 4b and 4c and the axial displacement sensors 5b and 5c, which are axially overlapped with each other as described above, are arranged so as to share the same circumference, the sensor mounting space can be integrated. I was able to. As a result, the sensor and the sensor base 12 are attached to the main body 1
It was able to be configured as an integral unit that can be freely attached to and detached from. Conventionally, each sensor has been individually mounted and worked in a narrow space in the main body 1, so the mounting work has been very troublesome. On the other hand, in this embodiment, the previously assembled unit is incorporated into the main body 1, so that the work of attaching the sensor to the main body 1 can be very simplified. It is also possible to inspect the sensor as a unit before mounting the main body.

Further, since the axial displacement sensor 5c is constructed as a temperature compensating sensor and this temperature compensating sensor is also arranged in the integrated space, it is possible to further contribute to downsizing of the sensor mounting space. Further, since the distances between the axial displacement sensors 5b and 5c and the radial displacement sensors 4b and 4c are made equal, each sensor can be affected by other sensors equally.
Therefore, the above influence can be eliminated by applying a predetermined simple correction to the output of the sensor, for example, by taking the difference between the output signals of the pair of sensors of the same type.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the above embodiments, the axial displacement sensors 5b, 5
Although c is provided only at the shaft end 2a of the shaft 2 on the side where the tool is mounted, it may be provided at both ends of the shaft 2. Further, the shaft may be provided only on the opposite shaft end, not on the side where the tool is mounted, or in the middle of the shaft. If provided at both ends, the effect of the present invention is doubled. Further, the effect of the present invention is not impaired by the mounting position.

Further, the axial displacement sensor 5b, the axial displacement sensor 5c, the radial displacement sensor 4b and the radial displacement sensor 4c are each composed of a pair of two sensors, but the number may be larger or at least. Further, although the radial displacement sensor 8 is composed of four sensors, this number may be more or at least. If it is larger, the detection accuracy can be improved, and if it is smaller, the structure is simple and the cost can be reduced.

Further, in the above embodiment, the above-mentioned two pairs of sensors are arranged so that the direction in which the axial displacement sensors 5b are arranged is orthogonal to the direction in which the axial displacement sensors 5c are arranged, but the present invention is not limited to this. You may arrange | position so that the said alignment direction may intersect at an angle other than 90 degrees. When the axial displacement sensor 5b and the axial displacement sensor 5c as the temperature compensation sensor come close to each other, the temperature change becomes closer, and the compensation accuracy can be further increased.

Further, in the above embodiment, the radial displacement sensors 4b and 4c and the axial displacement sensors 5b and 5c are
Although they are arranged so as to share the same circumference, they do not have to share the same circumference. Further, in the above-mentioned embodiment, the radial displacement sensors 4b and 4c and the axial displacement sensor 5 are used.
b and 5c are sensor bases 1 made of a hard member such as metal.
2, and the sensor and the sensor base 12 were fixed to the main body 1 as an integral unit. In addition, the radial displacement sensors 4b and 4c and the axial displacement sensors 5b and 5c may be integrally molded with resin in a state of being arranged in a predetermined positional relationship. In this case,
The integrally molded resin corresponds to the sensor base 12. This makes it easier to handle as a unit.
Further, the attached sensor does not drop out and the attachment position is not displaced due to vibration, etc., and the reliability of the magnetic bearing device is improved.

Further, in the above embodiment, the sensor base 12
Is a circular plate material, but it may be divided into a plurality of fan-shaped members and fixed to the main body 1. In this case, the unit including the sensor and the sensor base 12 can be easily attached to and detached from the main body 1, and the maintainability of the magnetic bearing device is improved. Further, in the above embodiment, the radial displacement sensors 4b, 4c and 8 are inductance type displacement sensors, and the axial displacement sensors 5b, 5c.
Uses an eddy current type ferrite core displacement sensor, but this is because it is inexpensive and stable and can be used in a magnetic bearing device, and other methods may be used.

In the above embodiment, the same axial displacement sensors 5b and 5c are used, but the axial displacement sensors 5b and 5c may be of other types as long as they have similar output characteristics with respect to temperature. In addition, various design changes can be made without changing the gist of the present invention.

[0031]

According to the invention of claim 1, the radial displacement sensor and the axial displacement sensor are different from the conventional ones.
Does not take up space in the axial direction. Therefore, the required length of the rotating shaft can be shortened. As a result, the natural frequency of the shaft can be increased, and high speed rotation is possible. Further, the load capacity of the bearing can be increased by using the generated dimensional margin in the axial direction as the attraction area of the magnetic bearing. Further, it is possible to reduce the error in the detection signal of the axial displacement sensor due to the influence of the bending and the inclination of the rotary shaft, and it is possible to control the axial direction with high accuracy.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, the mounting space for the radial displacement sensor and the axial displacement sensor can be integrated. It is also possible to configure the sensor and the sensor mounting portion as an integrated unit. According to the invention of claim 3, in addition to the effect of the invention of claim 2, the temperature compensation sensor can also be arranged in the integrated space,
This can contribute to downsizing of the sensor mounting space.

[Brief description of drawings]

FIG. 1 is a sectional side view showing an outline of a magnetic bearing device according to an embodiment of the present invention.

2 is a cross-sectional view taken along arrow A in FIG.

FIG. 3 is a sectional side view showing an outline of a conventional magnetic bearing device.

[Explanation of symbols]

1 Main body 2 Axis (rotating shaft) 4b, 4c Radial displacement sensor 5b Axial displacement sensor 5c Axial displacement sensor provided as a temperature compensation sensor 6 Radial magnetic bearing 9 Axial magnetic bearing 12 Sensor base

Claims (3)

[Claims] Claim: What is claimed is: 1. A radial magnetic bearing is controlled based on the output of a radial displacement sensor that detects the radial displacement of a rotary shaft, and the axial magnetic sensor is axial based on the output of an axial displacement sensor that detects the axial displacement of the rotary shaft. A magnetic bearing device that controls a magnetic bearing and supports a rotating shaft in a radial direction and an axial direction in a non-contact manner by magnetic force, wherein the rotating shaft has a first surface perpendicular to the axis and a circumference about the axis. A stepped portion configured by a second surface made of a surface is provided, the radial displacement sensor faces the second surface, and the axial displacement sensor faces the first surface, A magnetic bearing device, wherein the radial displacement sensor and the axial displacement sensor are arranged such that at least a part of each of the radial displacement sensor and the axial displacement sensor overlap each other in the axial direction of the rotating shaft. . 2. The magnetic bearing device according to claim 1, wherein the radial displacement sensor and the axial displacement sensor are arranged so as to share the same circumference centered on the axis of the rotary shaft. And magnetic bearing device. 3. The magnetic bearing device according to claim 2, wherein each of the radial displacement sensor and the axial displacement sensor is alternately arranged such that four of them are arranged circumferentially evenly, and the four axial displacement sensors output Among the four axial displacement sensors, the pair of axial displacement sensors facing each other with the axis line interposed therebetween are temperature compensating sensors attached while avoiding detection of displacement. A magnetic bearing device characterized by being configured.