JPH01219391A - Magnetic bearing unit - 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 Field of the Invention The present invention relates to a magnetic bearing device, and more particularly, to a single-axis controlled four-axis passively stable magnetic bearing device used in, for example, a vacuum spindle.

Conventional technology As a magnetic bearing device used in a vacuum spindle, etc., a 5-degree-of-freedom active control bearing is conventionally used, in which positioning is performed by adjusting the attractive force of an electromagnet in all 5 degrees of freedom, excluding the degree of freedom around the rotation axis of a rotating body. In addition, a three-axis controlled magnetic bearing with a reduced degree of freedom for active control is known (Japanese Unexamined Patent Application Publication No. 1983-1999).
277896). This 3-axis controlled magnetic bearing device uses a permanent magnet and an active axial magnetic bearing to determine its position in the axial direction. Positioning in the radial direction is performed by a passive radial restoring force.

Problems to be Solved by the Invention Although the above three-axis controlled magnetic bearing is cheaper than a five-degree-of-freedom active control magnetic bearing, it still requires magnetic bearings for three axes and their control circuits. , which is quite expensive.

An object of the present invention is to solve the above problems and provide a single-axis controlled four-axis passive stable magnetic bearing device that is cheaper than a three-axis controlled magnetic bearing and that can stably support a rotating body in a completely non-contact state. There is a particular thing.

Means for Solving the Problems A magnetic bearing device according to the present invention includes a permanent magnet type bearing that rotatably supports a rotating body by applying magnetic force in the axial direction of the rotating body, and a permanent magnet type bearing in which the magnetic force exerted on the rotating body is in the opposite direction. an electromagnet that applies a magnetic force to the rotating body; a whirling amount detection means for detecting the amount of whirling of the rotary body in the radial direction; and means for changing the magnetic force of the electromagnet so as to decrease the magnetic force of the electromagnet.

When the whirling amount of the working rotating body increases, the magnetic force of the electromagnet changes, the position of the rotating body changes, and the mutual spacing between the permanent magnet type bearings decreases. Therefore, the magnetic force of the permanent magnet type bearing increases, and the rigidity in the radial direction increases. Therefore, the amount of whirling of the rotating body is reduced, and the rotating body is stably supported and rotated.

Embodiment FIG. 1 shows an example of the mechanical configuration of a magnetic bearing device according to the present invention.

This magnetic bearing device is a 1-axis controlled 4-axis passive stable magnetic bearing device, in which a cylindrical upper housing (2) with open upper and lower ends is mounted on the upper surface of a horizontal disc-shaped base (1).
A short cylindrical lower housing (3) with only its upper end open is fixed to the lower surface of each of the housings (1). Base (1)
In the center of the shaft is a shaft insertion hole (4
) is formed. The upper surface of the base (1) has an inner diameter larger than the shaft insertion hole (4) and an upper housing (2).
) A cylindrical portion (la) having an outer diameter smaller than the inner diameter is formed into a negative body. A circular recess (5) having an inner diameter larger than the shaft insertion hole (4) and the same inner diameter as the lower housing (3) is formed on the lower surface of the base (1).

A horizontal disk-shaped permanent magnet support member (8) is fixed to the upper part of the upper housing (2) via a spacer (7). A cylindrical portion (8
a) are integrally formed.

A horizontal disk-shaped electromagnet support member (9) is fixed to the lower part of the lower housing (3) via a spacer (8) fitted in a recess (5) of the base (1). A sensor mounting hole (lO) is formed in the center of this support member (9), passing through it vertically, and a horizontal disc-shaped sensor mounting member (11) is fitted into the lower part of this hole (lO). It's stopped.

A vertical shaft (12) is inserted vertically through the shaft insertion hole (4) of the base (1) with a gap therebetween.

A cylindrical body (1) located between the spacer (7) in the upper housing (2) and the cylindrical part (la) is attached to the upper part of the shaft (12) that protrudes upward from the cylindrical part (la) of the base (1).
The central disk portion (13a) of 3) is fixed. The shaft (12) protrudes downward from the recess (5) of the base (1).
), a horizontal disk-shaped permanent magnet mounting member (14) and a rotor disk (15) located inside the spacer (8) in the recess (5) are fixed to the lower part of the electromagnet support member (9
) Shaft (12) fitted into sensor mounting hole (10)
A cylindrical target (1B) with the bottom end bound at the bottom end of the
is fixed. Then, the shaft (12) and the above-mentioned parts fixed thereto rotate the rotor (rotating body) (R).
is configured.

An upper permanent magnet type bearing (17) is provided between the permanent magnet support member (6) and the cylindrical body (13) in the upper housing (2). This bearing (17) consists of an annular permanent magnet (17a) fixed to the lower surface of the permanent magnet support member (6) and an annular permanent magnet (17a) fixed to the upper end surface of the cylindrical body (13).
b), and these permanent magnets (17a) (17
b) are placed opposite to each other so as to exert an attractive force on each other. A lower permanent magnet type bearing (18) is also provided between the base (1) and the permanent magnet mounting member (14) fixed to the shaft (12). This bearing (18) is
Consists of an annular permanent magnet (18a) fixed to the lower surface of the recess (5) of the base (1) and an annular permanent magnet (18b) fixed to the upper surface of the permanent magnet mounting member (14). The magnets (18a) and (18b) are opposed to each other so as to exert an attractive force on each other. The rotor (R) is attracted upward by these upper and lower permanent magnet type bearings (17) (1B). The shaft (12) is attached to the electromagnet support member (9) in the lower housing (3).
An electromagnet (19) is provided facing the rotor disk (15) fixed to the rotor (R) and attracting the rotor (R) downward. A motor stator (20) is provided within the cylindrical portion (la) of the base (1), and a corresponding motor rotor (21) is provided on the shaft (12).

The upper end of the shaft (12) is placed within a cylindrical portion (6a) of the permanent magnet support member (6), and an upper protection bearing (22) is provided within this cylindrical portion (8a).

Further, a lower protection bearing (23) is provided in the shaft insertion hole (4) of the base (1). In addition, the rotor (R
) During rotation, a slight gap is created between the upper and lower protective bearings (22) (23) and the shaft (12).

A shaft (1
An axial direction sensor (24) for detecting the position of the rotor (R) in the axial direction (vertical direction) is provided opposite to the target (1B) fixed to the rotor (2). Further, the cylindrical body (13) of the rotor (R) is attached to the peripheral wall of the upper housing (2).
) is provided with a radial sensor (25) facing the outer circumferential surface of the rotor for detecting the amount of whirling in the radial direction.

FIG. 2 shows an example of the electrical configuration of the electromagnet control portion of the magnetic bearing device. The output of the axial direction sensor (24) is converted by the axial position detection circuit (26) into a signal proportional to the axial displacement of the rotor (R), and the output of this detection circuit (26) is sent to the control circuit (27). input. Note that the axial displacement is positive when the rotor (R) rises from the steady state, and negative when the rotor (13) descends from the steady state.The output of the axial position detection circuit (26) is It increases as the rotor (R) rises, and decreases as the rotor (R) descends. −
On the other hand, the output of the radial direction sensor (25) is converted into a signal proportional to the amount of whirling of the rotor (R) by the whirling amount detection circuit (28), and the output of this detection circuit (28) is sent to the control circuit (27). Enter. And the control circuit (27)
The signals from these detection circuits (26) and (28) are processed and a control signal is output to a power amplifier 29) that drives the electromagnet (19).

FIG. 3 shows an example of the control circuit (27). The output of the axial position detection circuit (2B) is converted by a proportional differential element (PIl element (31)) into the sum of an amount proportional to the axial displacement and an amount proportional to the differential value of the axial displacement, and this PIl element The output of 31) passes through an amplifier (32) to an adder (33).
Enter. The output of the axial position detection circuit (26) is also converted by an integral element (l element) (34) into a signal proportional to the integral value of the axial displacement, and this l element (34)
The output of is input to the adjustment element (35). On the other hand, the output of the whirling amount detection circuit (28) is input to the adjustment element (35). The adjustment element (35) is composed of, for example, an adder, which allows the output of the l element (34) and the whirling amount detection circuit (
28), that is, the amount of whirling, are added together and sent to an adder (33). Then, by the adder (83),
The output of the amplifier (32) and the output of the regulating element (35) are summed and sent to the power amplifier (29).

FIG. 4 shows an example of the whirling amount detection circuit (28), and FIG. 5 shows signals of each part thereof. When the rotor (R) whirls around, the radial direction sensor (25) is detected as shown in Fig. 5 (a).
An AC output like this can be obtained.

The output of this sensor (25) is rectified by the absolute value circuit (36) as shown in FIG. 2(b). This output is further smoothed by a low-pass filter (37) to become a DC voltage as shown in FIG. 3(C), and this voltage is proportional to the whirling amount.

A circuit obtained by removing the adjustment element (35) from the control circuit (27),
In other words, the output of the l element (34) is directly sent to the adder (3
The input to 3) is a normal PID control circuit that controls the electromagnet in a magnetic bearing device.

Next, first, the operation of the control circuit (27) excluding the adjustment element (35) will be described.

In this case, the output of the amplifier (32), that is, the signal of the sum of the amount proportional to the axial displacement and the amount proportional to the differential value of the axial displacement, and the output of one element (34), that is, the signal proportional to the integral value of the axial displacement. The signals are summed by an adder (33) and sent to a power amplifier (29).

In steady state, upper and lower permanent magnet type bearings (17) (18
) attracts the rotor (R) upward, and the electromagnet (19) attracts the rotor (R) downward. At this time, the permanent magnets (17a) (17b) of the bearing (17) (1g)
By appropriately selecting the specifications of (18a) and (18b), the upward suction force by the bearings (17) and (18) can be made significantly larger than the weight of the rotor (R), so that the influence of this weight can be ignored. It can be done. A current is constantly passed through the electromagnet (19) to generate a downward attractive force that is equal in magnitude to the upward attractive force of the permanent magnet bearings (17, 18). When the rotating body (R) rises and the output of the axial position detection circuit (2B) increases, the current flowing through the electromagnet (19) increases and the rotating body (R) is lowered.

Conversely, the rotating body (R) descends and the axial position detection circuit (
2B) becomes small (when the output of the electromagnet (19) becomes small, the current flowing through the electromagnet (19) becomes small, and the rotating body (R) is raised.

This maintains the balance of axial forces and enables axial positioning. In addition, permanent magnet type bearing (17) (
18) and the attractive force of the electromagnet (19), it is passively stabilized in the radial direction, and the rotor (R) is supported in a completely non-contact state by uniaxial control that only controls the electromagnet (19). It is possible to rotate.

By the way, in this way, the adjustment element (
In the circuits other than 35), various instability occurs because the radial movement of the rotor (R) is not controlled at all.

However, in the above control circuit (27), the rotor (R)
Since the adjustment element (35) according to the amount of whirl is provided, the amount of whirl of the rotating body (R) can be reduced and the rotating body (R) can be rotated stably, as will be explained next.

The adjustment element (35) changes the output of the I element (34) by the amount of whirl, and as a result, the control circuit (1) changes the current flowing through the electromagnet (19) by the amount of whirl.
7) output is controlled. When the amount of whirling is 0, the output of the I element (34) is sent as is to the adder, and the same control as in the case without the adjustment element (35) described above is performed. When whirling occurs in the rotor (R), the current flowing through the electromagnet (19) decreases by the whirling amount, as described above, so the rotor (R) is raised and the upper and lower permanent magnet type bearings (17 ) (1g) becomes smaller.

As the distance between the permanent magnet bearings (17) (1g) becomes smaller, the attractive force increases accordingly, and as a result, the rotating body (
The rigidity of R) in the radial direction is increased, and the amount of whirling is reduced.

Effects of the Invention According to the magnetic bearing device of the present invention, as described above, since only one electromagnet needs to be controlled, the cost can be lower than that of a three-axis control type magnetic bearing, and moreover, the swing of the rotating body can be reduced. By reducing the amount, it is possible to stably support this in a completely non-contact state.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a magnetic bearing device showing one embodiment of the present invention, FIG. 2 is a block diagram showing an example of the electrical configuration of the electromagnet control portion of the magnetic bearing device, and FIG. 3 is a control circuit diagram. 1
A block diagram showing an example, Fig. 4 is one of the whirling amount detection circuits.
FIG. 5, a block diagram showing an example, is a graph showing signals of each part of the whirling amount detection circuit. (17) (18) --- Permanent magnet type bearing, (17a)
(17b) (18a) (18b)... Annular permanent magnet, (19)... Electromagnet, (25)... Radial direction sensor, (27)... Control circuit, (28)... Runout Rotation amount detection circuit, (R)...rotor (rotating body). Patent applicant: Koyo Seiko Co., Ltd.

Claims (1)

[Claims] A permanent magnet type bearing applies a magnetic force in the axial direction to a rotating body so that it can rotate, an electromagnet applies a magnetic force on the rotating body in the opposite direction to the magnetic force that this bearing exerts on the rotating body, and a permanent magnet bearing applies a magnetic force in the radial direction of the rotating body. whirling amount detection means for detecting the whirling amount of the permanent magnet type bearing; and changing the magnetic force of the electromagnet in order to change the position of the rotating body so that the mutual distance between the permanent magnet type bearings decreases when the whirling amount increases. A magnetic bearing device comprising means.