Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-07-26
2001-07-10
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
Reexamination Certificate
active
06259178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to initial adjustment circuits and initial adjustment methods of a magnetic bearing apparatus. More specifically, the present invention relates to an initial adjustment circuit and an initial adjustment method used for initially adjusting offset amounts and gains of a plurality of position sensors in a magnetic bearing apparatus used for a vacuum pump for obtaining a high vacuum or the like for magnetically supporting a rotational shaft of a spindle for a turbo molecular pump.
2. Description of the Background Art
FIG. 4
is a view showing a structure of a conventional magnetic bearing spindle. Referring to
FIG. 4
, a magnetic bearing spindle for turbo molecular pump
1
has a rotational shaft
3
provided in a case
2
. Rotational shaft
3
is supported in a non-contact manner in thrust and radial directions by a thrust magnetic bearing
4
and radial magnetic bearings
5
and
6
respectively provided above and below magnetic bearing
4
, and rotationally driven by a driving motor
7
. A position in a radial direction of rotational shaft
3
is detected by radial position sensors
8
and
9
, and a position in a thrust direction is detected by a thrust position sensor
10
. Further, ball bearings for protection
11
and
12
, which support rotational shaft
3
in case of abnormality of radial magnetic bearings
5
and
6
, are arranged above and below rotational shaft
3
.
Detection outputs from position sensors
8
,
9
and
10
are applied to a controller
20
which is externally provided. Controller
20
controls magnetic bearings
4
,
5
and
6
under control of an external system controller
30
. As motor
7
is driven, rotational shaft
3
of magnetic bearing spindle
1
rotates.
In magnetic bearing spindle
1
shown in
FIG. 4
, when offset amounts and sensor gains of the outputs from position sensors
8
,
9
and
10
are different from designed values, rotational shaft
3
is vibrated to be in contact with bearings for protection
11
and
12
, whereby stable rotation is not ensured. To avoid this problem, the offset amounts and gains of position sensors
8
,
9
and
10
must be precisely measured for adjustment.
SUMMARY OF THE INVENTION
Therefore, a main object of the present invention is to provide an initial adjustment circuit and an initial adjustment method capable of automatically adjusting a drift and a gain of each position sensor.
In short, the present invention is an initial adjustment circuit for a magnetic bearing apparatus provided with a magnetic bearing body including a plurality of position sensors for detecting a position of a rotator, a magnetic bearing arranged corresponding to respective position sensor for supporting an axis of a rotator magnetically in a non-contact manner, and a protection bearing for supporting the rotator in case of abnormality of the magnetic bearing. The magnetic bearing is controlled by a control circuit in accordance with detection signals from the plurality of position sensors. The rotator is vibrated to be in contact with the protection bearing by reduction in the gain of the control circuit during initial operation, and a position where the rotator is supported by the corresponding magnetic bearing is adjusted in accordance with outputs from the plurality of position sensors at the time.
Therefore, according to the present invention, the output from the position sensor is detected when the gain of the control system is reduced and the rotator is brought into contact with the protection bearing, and the control system is initially adjusted to obtain a gain corresponding to a position where contact between the rotator and the protection bearing are avoided. Thus, stable rotation is ensured.
In a more preferred embodiment of the present invention, the control circuit reduces the gain to obtain an intermediate value of the vibration by using maximum and minimum values of each sensor output when the offset value of the output from each of the plurality of position sensors is maximum. Then, a difference between the intermediate value of the vibration and 0V of the output from each of the plurality of sensors is obtained, so that the difference is added to or subtracted from the output from the corresponding position sensor.
In a more preferred embodiment, the above mentioned addition or subtraction by the control circuit is performed several times.
In a more preferred embodiment, the magnetic bearing body includes a thrust magnetic bearing for supporting the rotator in the thrust direction and a radial magnetic bearing for magnetically supporting the rotator in the radial direction.
In a more preferred embodiment, the plurality of position sensors include thrust and radial position sensors for respectively detecting displacements of the rotator in the thrust and radial directions. The protection bearings are arranged on one end and the other end sides of the rotator, and the rotator is provided with a motor.
According to another aspect of the present invention, an initial adjustment method of a magnetic bearing apparatus is provided, where the magnetic bearing apparatus is provided with a magnetic bearing body including a plurality of sensors for detecting a position of a rotator, a magnetic bearing arranged corresponding to each of the plurality of sensors for supporting an axis of a rotator in a magnetically non-contact manner, and a protection bearing for supporting the rotator in case of abnormality of the magnetic bearing. In the method, the magnetic bearing is controlled in accordance with detection signals from the plurality of position sensors. Further, the rotator is vibrated to be in contact with the protection bearing by reduction in the gain of the control system during initial operation, and a position where the rotator is supported by the corresponding magnetic bearing is adjusted in accordance with the outputs from the plurality of position sensors at the time.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4643592 (1987-02-01), Lewis et al.
patent: 5093754 (1992-03-01), Kawashima
patent: 5347190 (1994-09-01), Lewis et al.
patent: 5350283 (1994-09-01), Nakazeki et al.
patent: 5453684 (1995-09-01), Nakayama
patent: 5471106 (1995-11-01), Curtis et al.
patent: 5703424 (1997-12-01), Dorman
Ozaki Takayoshi
Suzuki Nobuyuki
McDermott & Will & Emery
NTN Corporation
Tamai Karl
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