JPH04185911A - magnetic bearing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to a magnetic bearing device that supports an annular rotating body made of a magnetic material in a non-contact manner, and particularly relates to a magnetic bearing device that supports a rotating body made of a magnetic material in a non-contact manner. Regarding position control.

B. Prior Art Conventionally, in this type of magnetic bearing "217," there are two methods for controlling the position of the rotating body in the radial direction.

(1) As shown in Fig. 3, one method is to arrange a plurality of electromagnets 2a at equal intervals close to the outer circumference of an annular rotating body l, and to correspond to each electromagnet 2a. The gap sensor 3 detects the distance between the rotating body l and the electromagnet 2a, and the drive current of each magnet 2a is independently controlled based on these detection signals, so that the rotating body 1 is oriented outward in the radial direction. It is designed to attract and support this in a neutral state.

(2) The other method is to arrange a plurality of electromagnets 2b at equal intervals close to the inner circumference of the annular rotating body 1, as shown in FIG. The drive current of each electromagnet 2b is independently controlled using the gap sensor 3 to attract the rotating body 1 radially inward and support it in a neutral state.

C6 Problems to be Solved by the Invention One of the applications of the above-mentioned magnetic bearing device is, for example,
There is a rotating cathode chi-ray tube device used in a tomography device. This rotating cathode X-ray tube device includes, for example, a cathode section in which a filament is attached to an annular rotating body supported by a magnetic bearing device in a vacuum container, and a ring-shaped cathode section fixedly installed opposite to this cathode section. By rotating the rotating body, the target surface is scanned circularly with thermionic electrons emitted from the cathode, and X-rays are emitted from the target 7) toward its center. It is designed to radiate light.

The diameter of the rotating body used in the rotating cathode X-ray tube device is approximately 1 m.
Moreover, the temperature of the rotating body increases from a low temperature state to a considerably high temperature state due to the heat emitted from the filament attached to the rotating body.

When the above-mentioned conventional devices are applied to such a rotating cathode X-ray tube device, the following problems arise.

(1) In the magnetic bearing device shown in Fig. 3, Fig. 5(a)
As shown in , the gap size A between the electromagnet 2a and the rotating body 1 is set to a value suitable for magnetic bearing control in a low temperature state, for example, IIw1.
However, if there is a temperature rise of about 60 to 70°C in the rotating body 1 with a diameter of about 1 m, the distance is set to about 1 m.
As shown in EI (b), the rotating body 1 is about 1 m in the radial direction.
This causes the inconvenience that the rotating body 1 and the electromagnet 2a come into contact with each other due to expansion by about m.

(2) On the other hand, in the magnetic bearing device shown in FIG.
As shown in a), in a low temperature state, the gap between the electromagnet 2b and the rotating body 1 is set to a distance of about 11, which is suitable for magnetic bearing control, but when the temperature of the rotating body 1 increases by 60 to 70°C. Then, as shown in FIG. 4B, the gap C between the rotating body 1, the inner circumferential portion, and the electromagnet 2b increases to about 21, causing a disadvantage that magnetic bearing control becomes difficult.

This invention was made in view of the above circumstances, and even if the temperature of the rotating body increases, the rotating body does not come into contact with the electromagnets around it, and moreover, magnetic bearing control is possible. The purpose of the present invention is to provide a possible magnetic bearing device.

D. Means for Solving the Problem The present invention has the following configuration in order to achieve the above object.

That is, in the magnetic bearing device according to the present invention, the gap between the annular rotating body made of a magnetic material and the inner circumferential portion of the rotating body is a distance that allows the magnetic bearing to control in a low temperature range. , a gap between a plurality of inner peripheral part IIT magnets disposed close to each other along the inner peripheral part of the rotary body and the outer peripheral part of the rotary body in a high temperature range is a distance that allows magnetic bearing control. , a plurality of outer circumferential electromagnets disposed close to each other along the outer circumference of the rotating body, a thermal expansion detecting means for detecting the degree of thermal expansion of the rotating body, and a detection signal from the thermal expansion detecting means. , in a low temperature range, the inner circumference electromagnet is driven, and in a high temperature range, the outer circumference electromagnet is driven! The magnet is equipped with a switching control means for driving the magnet.

E1 action The operation of this invention is as follows.

In a low temperature range where thermal expansion is small, the internal electromagnet is driven by the switching control means, and the rotating body is magnetically bearing controlled by the internal electromagnet.

In addition, in high temperature ranges where thermal expansion is large, the rotating body expands and the gap between the rotating body and the internal electromagnet expands to an extent inappropriate for magnetic bearing control. Since the distance is narrowed to a distance suitable for control, the switching control means switches from the driving state of the internal electromagnet to the driving state of the external electromagnet.

F. Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a magnetic bearing device according to the present invention.

A plurality of outer peripheral portions TM and N stones 2a are arranged at equal intervals close to the outer peripheral portion of the annular rotating body 1 formed of a magnetic material, and are located close to the inner peripheral portion of the rotating body 1. A plurality of inner circumference electromagnets 2b are arranged to face the outer circumference magnets 2a. Gear knob sensors 3 are arranged in parallel to each of the outer circumferential Nm stones 2a, and these gap sensors 3 are used to connect each outer circumferential electromagnet 2a and the rotating body I.
The gap size is being detected. The outer circumferential electromagnets 2a are each independently driven by an electromagnet driving section 4a, and the inner circumferential electromagnets 2b are each independently driven by an electromagnet driving section 4b. The electromagnet drive units 4a and 4b are switching circuits SW.
It is connected to the control unit 5 via. A detection signal from each gap sensor 3 is given to the control section 5 .

The gap size between each electromagnet 2a, 2b and the rotating body 1 is set as follows.

As shown in the second ID (a), a rotating body 1 with a diameter of about 1 m
The inner circumferential electromagnet 2b is installed so that the gap with the rotating body 1 is about 0.5 mm when the is in a low temperature state, and the gap E with the rotating body 1 is about 1°51. The outer peripheral electromagnet 2a is installed so that When such a gap size is set, when the temperature of the rotating body 1 increases by 60 to 70°C, the rotating body 1 thermally expands, and the 211th
As shown in ffl(b), the gap F between the inner electromagnet 2b and the rotating body 1 has expanded to about 1.5 m, and the gap G between the outer electromagnet 2a and the rotating body 1 has increased to about 0. It narrows down to .51.

Next, the operation of the above-described embodiment device will be explained.

The control unit 5 monitors the gap size between the electromagnets 2a, 2b and the rotating body 1 by inputting the detection signals of each gap sensor 3 and calculating the average value of each gap from these detection signals. Specifically, the control unit 5 controls the gap size 1. OL
llm is set as a darkness value, and it is determined whether the gap average value is larger or smaller than this darkness value.

When the average gap value is larger than the threshold (1!!1.0 am, that is, when the rotating body 1 is in a low temperature state, the gap between the outer circumferential electromagnet a and the rotating body) is
However, the gap between the inner peripheral part @ VA stone 2b and the rotating body 1 is in the range of approximately 0.5 to 1.0 am; is a distance suitable for magnetic bearing control.Therefore, the control section 5 sets the switching circuit SW on the electromagnet drive section 4b side, and
It activates the magnet drive section 4b. As a result, the driving current of each inner circumferential Nm stone 2b is independently controlled according to the detection signal of the gear and sensor 3 corresponding to each, so that the rotating body I has an attractive force directed inward in the radial direction. is supported in a neutral state by

On the other hand, when the average gap value is smaller than the dark value of 1.0 mm, that is, when the rotating body 1 is in a high temperature state, the gap between the inner circumferential electromagnet 2b and the rotating body 1 is determined by the inner circumferential electromagnet 2b. In contrast, the gap between the outer peripheral part '&tJff stone 2a and the rotating body I becomes a distance suitable for magnetic bearing control by the outer peripheral part electromagnet 2a. Therefore, the control section 5 sets the switching circuit SW on the electromagnet drive section 4a side, and operates the electromagnet drive section 4a. As a result, the drive current of each inner circumferential electromagnet 2a is independently controlled according to the detection signal of the corresponding gap sensor 3, so that the rotating body 1 is brought into a neutral state by the attraction force directed outward in the radial direction. Supported by

In the above-described embodiment, the gap sensor 3 detects the degree of thermal expansion of the rotating body I, and the outer peripheral part iit magnet 2a
The inner peripheral electromagnet 2b is switched and controlled, but by detecting the temperature rise of the rotating body 1 using a temperature sensor, the degree of thermal expansion of the rotary body 1 is indirectly detected, and the outer peripheral electromagnet 2b is Electromagnet 2a and inner circumference! The magnet 2b may be switched and controlled.

Furthermore, in the above embodiment, four pieces each of the outer peripheral part 141 stones 2a and the four inner peripheral part electromagnets 2b are arranged.
The number of electromagnets installed is not limited.

Furthermore, the gap dimensions between each of the stones 2a, 2b and the rotating body 1 described above are merely examples, and may be set appropriately depending on the size, thermal expansion coefficient, and temperature rise of the rotating body 1. Needless to say.

Effects of the G8 Invention As is clear from the above explanation, according to the magnetic bearing device according to the present invention, a plurality of electromagnets are provided along the inner circumference and the outer circumference of the rotating body, and the inner circumference if the electromagnet rotates. The gap between the outer electromagnet and the rotating body is set to such a size that the inner electromagnet can control the magnetic bearing in a low temperature state, and the gap between the outer electromagnet and the rotating body is such that the outer electromagnet can control the magnetic bearing in a high temperature state. The dimensions are set to enable control, and the inner peripheral electromagnet is driven in a low temperature state where the thermal expansion of the rotating body is small, and the outer peripheral tiff stone is driven in a high temperature state where the thermal expansion of the rotating body is large. Therefore, magnetic bearing control of the rotating body is possible over a wide temperature range, and the inconvenience of the rotating body coming into contact with the electromagnet due to thermal expansion of the rotating body can also be avoided.

[Brief explanation of the drawing]

1 and 2 relate to the explanation of one embodiment of the present invention, FIG. 1 is a block diagram showing a schematic configuration of a magnetic bearing device, and FIG. 2 is a rotating body in a low temperature state and a high temperature state. FIG. 3 is an explanatory diagram of the gap between the magnet and the magnet. 3 to 6 relate to the explanation of conventional examples, FIG. 3 is an explanatory diagram of a magnetic bearing device equipped with an outer peripheral electromagnet, and FIG. 4 is an explanatory diagram of a magnetic bearing device equipped with an inner peripheral part NN stone. , Fig. 5 is an explanatory diagram of the gap between the rotating body and the electromagnet in the magnetic bearing device shown in the third round, and Fig. 6 is an explanatory diagram of the gap between the rotating body and the electromagnet in the magnetic bearing device shown in the fourth round. It is. ■...Rotating body 2a...Outer electromagnet 2b
... Inner peripheral electromagnet 3 ... Camp sensor 4a, 4
b...Electromagnet drive unit 5...Control unit SW...Switching circuit Patent applicant Shimadzu Corporation

Claims (1)

[Claims] (1) An annular rotating body formed of a magnetic material and an inner circumferential portion of the rotating body such that the gap between the inner circumferential portion of the rotating body is a distance that allows magnetic bearing control in a low temperature range. A plurality of inner circumference electromagnets arranged close to each other along the outer circumference of the rotary body are arranged so that the gap between the outer circumference of the rotor and the outer circumference of the rotor is a distance that allows magnetic bearing control in a high temperature range. a plurality of outer peripheral electromagnets arranged close to each other, a thermal expansion detection means for detecting the degree of thermal expansion of the rotary body, and a detection signal from the thermal expansion detection means. A magnetic bearing device comprising switching control means for driving an electromagnet and for driving the outer peripheral electromagnet in a high temperature range.