JPH02212622A - Magnetic bearing spindle unit - Google Patents

Abstract

PURPOSE:To support a spindle stably by constructing an axial magnetic bearing controller so that it may add the output signal of an axial acceleration sensor to the output signal of a PID control circuit and control electromagnetic number. CONSTITUTION:The output signals of an axial position sensor 13 and spindle axial reference position signals are inputted in a differential amplifier 19 and its output signals are inputted in element P 15, I element 16 and element D 17 respectively, and their output signals are inputted in an adder 20. On the other hand, the output signals of an axial acceleration sensor 14 are inputted in an amplifier 21, and its output signals are inputted in the adder 20. The output signals of the adder 20 are fed to the first electromagnet 9a of an axial bearing 9 through a power amplifier 22 and is fed to the second electromagnet 9b through an inversion amplifier 23. It is thus possible to decrease the lag in the position control of a spindle by means of feed forward control when some axial vibration occurs at the time of cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic bearing spindle unit used in machine tools such as grinders.

In a conventional magnetic bearing spindle unit used in a grinding machine, for example, a spindle is rotated while being supported in a non-contact manner within a case by a radial magnetic bearing and an axial magnetic bearing. Then, the displacement of the spindle in the radial direction is detected by the radial direction position sensor, and the radial magnetic bearing control device controls the radial magnetic bearing by the PID control circuit based on the output signal of this sensor.

Furthermore, the axial displacement of the spindle is detected by an axial position sensor, and the axial magnetic bearing control device controls the axial magnetic bearing by a PID control circuit based on the output signal of this sensor.

Problems to be Solved by the Invention In the case of a magnetic bearing spindle unit used in a grinding machine, a grinding wheel is attached to the tip of the spindle. The spindle unit is attached to a stand or the like, and vibrations (oscillations) of the spindle in the axial direction may be applied to the stand during grinding.

When vibration is applied to the table in the axial direction as described above, the case of the spindle unit also vibrates in the same direction, which should have a large effect on spindle position control. In other words, even if the case vibrates, the spindle is supported by the case in a non-contact state via a magnetic bearing, so the vibration of the case is not immediately transmitted to the spindle, and the position of the spindle relative to the case changes due to the vibration of the case. The position of the spindle is controlled only when a displacement occurs. For this reason, in the conventional axial magnetic bearing control device, there is a delay in controlling the position of the spindle in the axial direction, making the control unstable. Incidentally, if the gain of the differential element of the PID control circuit is increased, this delay can be improved, but noise is likely to be picked up and control becomes unstable.

The above phenomenon also occurred in the radial magnetic bearing control device of the magnetic bearing spindle unit when vibration was applied in the radial direction.

An object of the present invention is to provide a magnetic bearing spindle unit that solves the above problems.

Means for Solving the Problems A magnetic bearing spindle unit according to the first invention includes a case, a radial magnetic bearing and an axial magnetic bearing disposed in the case, and a rotating system supported in a non-contact state by the radial magnetic bearing and the axial magnetic bearing. A radial position sensor detects the radial displacement of the spindle, an axial position sensor detects the axial displacement of the spindle, and an electromagnet of the radial magnetic bearing is controlled based on the output signal of the radial position sensor. A magnetic bearing spindle that is equipped with a radial magnetic bearing control device and an axial magnetic bearing control device that controls an electromagnet of the radial magnetic bearing by a PID control circuit based on an output signal of an axial direction position sensor, and in which the case is moved in the axial direction of the spindle. In the unit, an axial acceleration sensor that detects the axial acceleration of the case is installed on the case or a part that moves in the axial direction of the spindle integrally with the case, and the axial magnetic bearing control device receives the output signal of this acceleration sensor. It is characterized in that it is added to the output signal of the PID control circuit to control the electromagnet of the axial magnetic bearing.

A magnetic bearing spindle unit according to a second invention includes a case, a radial magnetic bearing and an axial magnetic bearing disposed in the case, a spindle supported in a non-contact state by the radial magnetic bearing and the axial magnetic bearing and rotated, and a radial shaft of the spindle. A radial position sensor that detects displacement in the axial direction, an axial position sensor that detects the axial displacement of the spindle, and a radial magnetic bearing that controls the electromagnet of the radial magnetic bearing by a PID control circuit based on the output signal of the radial position sensor. In a magnetic bearing spindle unit that includes a control device and an axial magnetic bearing control device that controls an electromagnet of the axial magnetic bearing based on an output signal of an axial position sensor, and in which the case is moved in the radial direction of the spindle, the case or the case and the axial magnetic bearing control device are provided. A radial acceleration sensor that detects the radial acceleration of the case is provided on the part of the spindle that moves in the radial direction, and the radial magnetic bearing control device converts the output signal of this acceleration sensor into the output signal of the PID control circuit. This feature is characterized in that the electromagnets of the radial magnetic bearing are controlled by addition.

In the case of the first invention, the output signal of the axial direction acceleration sensor is added to the output signal of the PID control circuit of the axial magnetic bearing control device, thereby controlling the axial magnetic bearing. Since the axial magnetic bearing is controlled by acceleration in the axial direction, feedforward control is performed against vibration in the axial direction, which reduces the delay in spindle position control and supports the spindle stably. can.

In the case of the second invention, the output signal of the radial direction acceleration sensor is added to the output signal of the PID control circuit of the radial magnetic bearing control device, and the radial magnetic bearing is thereby controlled. Since the radial magnetic bearing is controlled by acceleration in the radial direction, feedforward control is performed against vibration in the radial direction, which reduces the delay in spindle position control and supports the spindle stably. can.

Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows the mechanical configuration of a magnetic bearing spindle unit used in a grinding machine.

In addition, in the following explanation, the top and bottom of Fig. 1 are assumed to be the top and bottom,
The left side of Figure 1 is the front, and the right side is the rear.

Further, the direction perpendicular to the paper surface of FIG. 1 is defined as the left-right direction.

In Figure 1, the magnetic bearing spindle unit (+,)
The case (2) is fixed to the oscillation base (4) via the mount (3), and the head (4) is placed on the bed (5) so as to be movable back and forth.

The case (2) of the spindle unit (1) has a substantially cylindrical shape and is arranged horizontally so that its center line (axis) is in the front-rear direction. A spindle (6) is arranged on the center line within the case (2).

Two sets of front and rear radial magnetic bearings (7) (8), an axial magnetic bearing (9), and a high-frequency motor stator (10) are provided on the inner surface of the peripheral wall of the case (2), and these allow the spindle clock to be in a non-contact state. is supported and rotated. The front radial magnetic bearing (7) is mounted on the spindle (
A pair of radial electromagnets (7a) (7b) arranged vertically symmetrically with respect to 6), that is, a first radial electromagnet (7
a), a second radial electromagnet (7b), and a pair of radial electromagnets (path shown) arranged symmetrically with respect to the spindle (6). Similarly, the rear radial magnetic bearing (8) includes a pair of radial electromagnets (8a) (8b) arranged vertically symmetrically with respect to the spindle (6), that is, a first radial electromagnet (8a) and a second radial electromagnet ( 8b) and a pair of radial electromagnets (path shown) arranged symmetrically with respect to the spindle (6). The axial magnetic bearing (9) includes a first axial electromagnet (9a) on the front side and a second axial electromagnet (9b) on the rear side.
It consists of. The case (2) also has a spindle (6
) before and after detecting displacement in the vertical direction (radial direction) 2
Set of radial position sensors (upper and lower sensors) (1,,
1, ) (12), two sets of front and rear radial position sensors (left and right sensors) (path shown) for detecting displacement of the spindle (6) in the left-right direction (radial direction) and the spindle (6).
) Axial direction position sensor (axial sensor) that detects displacement in the longitudinal direction (axial direction) (+,,
3) is provided. The front end of the spindle (6) protrudes from the front of the case (2), and a grinding wheel (not shown) is attached to this part.

An axial acceleration sensor (14) is attached to the mounting base (3) to detect acceleration in the axial direction.

The spindle unit (1) is provided with a radial magnetic bearing control device and an axial magnetic bearing control device.

The radial magnetic bearing control device has a vertical sensor (I) (1
2) and the radial magnetic bearings (7) (8) by the PID control circuit based on the output signals of the left and right sensors]
It controls a pair of electromagnets (7a), (7b), (8a), and (8b) and a pair of left and right electromagnets.

The axial magnetic bearing control device uses an axial sensor (1
Axial magnetic bearing (9) based on the output signal of (8)
The electromagnets (9a) and (9b) are controlled, and its outline is shown in FIG.

In Figure 2, the axial magnetic bearing control device consists of P element (proportional element) (15), ■ element (integral element) (1
B) and D element (differential element> PID containing (17)
It is equipped with a control circuit (18). Axial sensor (1
The output signal of 3) and the spindle axial direction position reference signal are input to the differential amplifier (19). The output signal of this differential amplifier (19) is P element (I5), I element (16)
and D element (17), and the output signals of these elements (15) (], [i) (1, 7) are input to the adder (20). On the other hand, the output signal of the axial direction acceleration sensor (14) is input to the amplifier (21), and the output signal of this amplifier (21) is input to the double adder (20). The output signal of the adder (2o) is then sent to the electromagnet (9a) of the axial magnetic bearing (9) via a non-inverting amplifier (power amplifier) (22), and is also sent to the electromagnet (9a) of the axial magnetic bearing (9) via an inverting amplifier (23). It is sent to the second electromagnet (9b).

During grinding, vibrations in the axial direction may be applied to the base (4). In this case, the case (2) of the spindle unit (1) also vibrates in the axial direction via the mount 3) due to the vibration of the base (4), and the acceleration of this vibration is the output signal of the PID control circuit (18). Therefore, feedforward control is performed for the vibration in the axial direction, and the delay in position control of the spindle (6) can be reduced, and the spindle (6) can be stably supported.

Vertical vibrations may be applied to the spindle unit 1-(I). In such a case, as shown by the chain lines in Figure 1, the upper and lower sensors (
1], ) (12), there is a radial acceleration sensor (24) that detects the vertical acceleration of the case (2).
) (25), and upper and lower electromagnets (7a) (7b) (8a) (8b) of the radial magnetic bearings (7) and (8).
The radial direction acceleration sensor (24) (2
5) are added together.

Figure 3 shows the front radial magnetic bearing (7) in such a case.
) shows a radial magnetic bearing control device that controls the upper and lower electromagnets (7a, ) (7b). This radial magnetic bearing control device is similar to the axial magnetic bearing control device shown in Fig. 2, and in Fig. 3, parts corresponding to each element in Fig. 2 are indicated by the same numbers with a subscript r. ing.

In this case as well, since the acceleration of the vertical vibration of the case (2) is added to the output signal of the PID control circuit (18r), feedforward control is performed for the vertical vibration, and the spindle (6 ), it is possible to stably support the spindle (6) by reducing the delay in position control.

Although Fig. 3 shows the radial magnetic bearing control device that controls the upper and lower electromagnets (7a, > (7b) of the front radial magnetic bearing 7), the upper and lower electromagnets of the rear radial magnetic bearing (8>) The radial magnetic bearing control device that controls (8a) (81+) is also similar to this.

Lateral vibrations may also be applied to the spindle unit (1,). In this case as well, radial acceleration sensors are installed in front and behind the case (2) to detect the acceleration in the left and right direction of the case (2), and the left and right electromagnets of the radial magnetic bearings (7) and (8) are controlled. The output signal of the radial acceleration sensor is added to the output signal of the PID control circuit of the radial magnetic bearing control device.

Vibrations may be applied to the spindle unit (1) in both the axial direction and the radial direction. In such a case, both the axial magnetic bearing control device and the radial magnetic bearing control device may be configured as shown in FIGS. 2 and 3.

Effects of the Invention According to the magnetic bearing spindle unit of the present invention, as described above, the delay in position control of the spindle due to vibration can be reduced and the spindle can be stably supported.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a magnetic bearing spindle unit showing one embodiment of the present invention, FIG. 2 is an electrical block diagram showing an axial magnetic bearing control device, and FIG. 3 is an electrical block diagram showing a radial magnetic bearing control device. It is. (1)...Magnetic bearing spindle unit, (2)...
・Case, (3)... Mounting base, (4)... Oscillation base, (6)... Spindle, (7) (8)
...Radial magnetic bearing, (7a) (7b) (8a
) (8b) --- Radial electromagnet, (9) -- Axial magnetic bearing, (9a,) (9b) -- Axial electromagnet, (10) --- High frequency motor stator, (11
) (12)...Radial direction position sensor, (13)
... Axial direction position sensor, (14) ... Axial direction acceleration sensor, (18) (18r) ・=
PID control circuit, (20) (2Or)... adder, (24) (25)... radial direction acceleration sensor. Above] 6

Claims (2)

[Claims] (1) A case, a radial magnetic bearing and an axial magnetic bearing placed in the case, a spindle that is supported in a non-contact state and rotated by the radial magnetic bearing and the axial magnetic bearing, and a radial direction that detects the radial displacement of the spindle. A position sensor, an axial position sensor that detects the axial displacement of the spindle, a radial magnetic bearing control device that controls the electromagnet of the radial magnetic bearing based on the output signal of the radial position sensor, and an output signal of the axial position sensor. In a magnetic bearing spindle unit, which is equipped with an axial magnetic bearing control device that controls the electromagnet of the axial magnetic bearing by a PID control circuit, and in which the case is moved in the axial direction of the spindle, the case or integrally with the case moves in the axial direction of the spindle. An axial acceleration sensor that detects the acceleration of the case in the axial direction is installed in the moving part of the case, and the axial magnetic bearing control device adds the output signal of this acceleration sensor to the output signal of the PID control circuit to control the electromagnet of the axial magnetic bearing. A magnetic bearing spindle unit that controls. (2) A case, a radial magnetic bearing and an axial magnetic bearing placed in the case, a spindle that is supported and rotated in a non-contact state by the radial magnetic bearing and the axial magnetic bearing, and a radial direction that detects the radial displacement of the spindle. A position sensor, an axial position sensor that detects displacement of the spindle in the axial direction, a radial magnetic bearing control device that controls the electromagnet of the radial magnetic bearing by a PID control circuit based on the output signal of the radial position sensor, and an axial position sensor. In a magnetic bearing spindle unit, which is equipped with an axial magnetic bearing control device that controls the electromagnet of the axial magnetic bearing based on the output signal of the axial magnetic bearing, and in which the case is moved in the radial direction of the spindle, the case or integrally with the case moves in the radial direction of the spindle. A radial acceleration sensor that detects acceleration in the radial direction of the case is installed in the moving part of the case, and the radial magnetic bearing control device adds the output signal of this acceleration sensor to the output signal of the PID control circuit to control the electromagnet of the radial magnetic bearing. A magnetic bearing spindle unit that controls.