JP3268322B2 - Inverter control device for magnetic bearing spindle device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control device for a magnetic bearing spindle used in a machine tool, a turbo molecular pump or the like.

[0002]

2. Description of the Related Art In a magnetic bearing spindle device having a magnetic bearing and an induction motor built therein, the rotation of the spindle is controlled by an inverter.

However, when such a magnetic bearing spindle device is compared with a spindle device using a rolling bearing or the like, the bearing rigidity is low in a frequency range where the rotational speed is low. Insufficient, vibration may be large and acceleration may be poor.

For this reason, there has been proposed an inverter control device in which the inverter control output is limited in the entire rotation speed range of the spindle.

[0005]

However, if the inverter control output is limited in the entire rotation speed range of the spindle as described above, the magnetic bearing in the high rotation speed range where the rigidity of the magnetic bearing requires the highest acceleration torque is high. However, the acceleration torque is too small, the acceleration is poor, and the required torque may not be obtained.

An object of the present invention is to solve the above problems,
It is an object of the present invention to provide an inverter control device of a magnetic bearing spindle device which has a small vibration in a low rotation region and a large acceleration torque in a high rotation region.

[0007]

SUMMARY OF THE INVENTION An inverter control device for a magnetic bearing spindle according to the present invention is an inverter control device for a magnetic bearing spindle device for controlling the rotation of a spindle that is non-contactly supported by a magnetic bearing. Low based on the stiffness of the magnetic bearing
It is small in the rev range and gradually increases in the high rev range
And a current limiting circuit for limiting the inverter control output.

In the low rotation range where the rigidity of the magnetic bearing is low, the limit value of the inverter control output is reduced, and in the high rotation range where the rigidity of the magnetic bearing is high, the limit value of the inverter control output is gradually increased.

In the low rotation range where the rigidity of the magnetic bearing is low,
By reducing the limit value of the inverter control output,
Vibration during acceleration can be reduced.

In the high rotation range where the rigidity of the magnetic bearing is high,
By gradually increasing the limit value of the inverter control output, a large acceleration torque can be obtained, and a necessary torque at a high speed, which is the most problematic in practical use, can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an example of an electrical configuration of a main part of a magnetic bearing spindle device.

Although not shown in detail, the spindle device incorporates a magnetic bearing for supporting the spindle in a non-contact manner and an induction motor (high-frequency motor) for rotating and driving the spindle. FIG. 1 shows an induction motor (1) and its inverter control device, and FIG. 2 shows one of the radial magnetic bearings.
The pair of electromagnets (2a) (2b) and their magnetic bearing control device are shown.

The induction motor (1) is of a built-in type, and although not shown, a motor rotor is formed integrally with the spindle (3), and a motor stator is provided around the spindle (3) so as to surround the motor rotor. Is fixedly provided in the housing.

As shown in FIG. 1, the motor (1) is driven to rotate by an inverter (4), and the inverter (4) is controlled by a rotation speed control circuit (5). A rotation sensor (6) for detecting the number of rotations is provided on a portion of the housing around the spindle (3). A current limiting circuit (7) between the rotation sensor (6) and the inverter (4) to limit the control output of the inverter (4) according to the rotation speed of the spindle (3)
Is provided. This circuit (7) has an F / V (frequency /
A voltage) converter (10), an offset circuit (11), a clipping circuit (12), an adder (13), and an offset setting circuit (14).

As shown in FIG. 2, a pair of electromagnets (2a) (2b)
Are arranged symmetrically so as to sandwich the spindle (3) from both sides in the radial direction with a gap, and the power amplifier (16
a) Driven by (16b). A pair of position sensors (15a, 15b) that detect the radial position of the spindle (3) corresponding to the electromagnets (2a, 2b) around the spindle (3)
The outputs of these position sensors (15a) (15b) are input to a displacement detection circuit (17). The displacement detection circuit (17) calculates the difference between the outputs of the two position sensors (15a) and (15b), and further calculates the difference between the calculation result and a fixed reference signal (usually 0), thereby obtaining the spindle. (3) The displacement in the radial direction is detected. The output of the displacement detection circuit (17) is a PID control circuit
(18), and based on the output of the PID control circuit (18),
The electromagnets (2a) and (2b) are controlled by the power amplifiers (16a) and (16b).

One radial magnetic bearing includes a pair of electromagnets arranged in a radial direction and another pair of electromagnets arranged in a radial direction orthogonal to the magnet.
FIG. 2 shows only one pair of the electromagnets (2a) and (2b), and omits the other pair of electromagnets and the magnetic bearing control device. In addition to the radial magnetic bearing, a part of which is shown in FIG. 2, the magnetic bearing spindle device further includes another set of radial magnetic bearings that are axially separated from the radial magnetic bearing, and the spindle (3) is non-axially non-axial. An axial magnetic bearing for contact support is provided, but these are also omitted.

In the spindle device described above, the inverter (4) is controlled by the output from the rotation speed control circuit (5), and the motor (1) is driven to rotate by the inverter (4). At this time, as described later, a current limiting signal Si is output from the current limiting circuit (7) to the inverter (4), whereby the control output of the inverter (4) is limited.

When the spindle (3) rotates, a rotation sensor
From (6), the pulse signal proportional to the rotation speed is converted to the F / V converter (1
0) from the F / V converter (10) to the offset circuit (1
In 1), a voltage signal proportional to the rotation speed is output. The output signal S1 of the F / V converter (10) changes as shown in FIG. In the offset circuit (11), the output signal S1 of the F / V converter (10) is offset in the negative direction, and the output signal S2 is input to the clipping circuit (12). The output signal S2 of the offset circuit (11) changes as shown in FIG.
In the clipping circuit (12), the output signal S2 of the offset circuit (11) is clipped, and the negative part of this signal S2 is set to 0.
V. The output signal S3 of the clipping circuit (12) changes as shown in FIG. The output signal S3 of the clipping circuit (12) is added to the adder (1
Input to one input terminal of 3). On the other hand, a constant positive offset signal is set in the offset setting circuit (14), and is input to the other input terminal of the adder (13). The adder (13) adds the output signal S3 of the clipping circuit (12) and the offset signal from the offset setting circuit (14), and outputs a current limiting signal Si to the inverter (4). The current limiting signal Si changes as shown in FIG.

As is apparent from FIG. 3D, the current limit signal Si is small in the low rotation range and gradually increases in the high rotation range. And, in the whole range of the rotation frequency,
The control output of the inverter (4) is the current limit signal S at that time.
i so that the current limit corresponding to i is not exceeded.
(4) is controlled. As mentioned above, the rigidity of the magnetic bearing is
It is low in the low rotation range and high in the high rotation range. Therefore, by limiting the control output of the inverter (4) based on the rotational speed as described above, the control output of the inverter (4) is limited based on the rigidity of the magnetic bearing. By reducing the limit value of the control output of the inverter (4) in the low rotation range where the rigidity of the magnetic bearing is low,
Although the acceleration torque is reduced, vibration during acceleration can be reduced. Also, in a high rotation range where the rigidity of the magnetic bearing is high, a large acceleration torque can be obtained by increasing the limit value of the inverter control output. For example, in a turbo molecular pump or the like, there is a great merit in a gas load operation in a semiconductor manufacturing apparatus using the same.

[0021]

According to the inverter control device of the magnetic bearing spindle device of the present invention, as described above, the vibration in the low rotation range can be reduced, and the acceleration torque in the high rotation range can be increased.

[Brief description of the drawings]

FIG. 1 is an electric block diagram of a part of an inverter control device of a magnetic bearing spindle device showing an embodiment of the present invention.

FIG. 2 is an electric block diagram of a magnetic bearing portion of the spindle device showing the embodiment of the present invention.

FIG. 3 is a graph showing a change in a signal of each part of the current limiting circuit depending on a rotation frequency.

[Explanation of symbols]

 (1) Induction motor (2a) (2b) Electromagnet (3) Spindle (4) Inverter (7) Current limiting circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16C 32/04 H02K 7/09 H02M 7/00-7/40 H02P 5/408-5/412 H02P 7/628-7 / 632

Claims (1)

(57) [Claims] An inverter control device of a magnetic bearing spindle device for controlling rotation of a spindle non-contact supported by a magnetic bearing, wherein the inverter control device is small in a low rotation range based on a rigidity of a magnetic bearing that changes according to a rotation speed of the spindle. High times
An inverter control device for a magnetic bearing spindle device, comprising a current limiting circuit for limiting an inverter control output so as to gradually increase in a shift range .