RU2370344C1 - Spindle - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building, particularly to spindles with built-in motors and magnetic bearings, and can be used incorporated with machine tools, centrifuges and various centrifugal plants. Proposed spindle comprises housing, motor, hollow shaft, unit of magnetic bearings (UMB) and safety bearings running on axle fitted inside the shaft, attached to spindle end face and furnished with damper representing a disk and elastomer ring. UMB is arranged at the hollow shaft output area plugged on the side of operating tool.

EFFECT: simpler design, higher reliability.

5 cl, 5 dwg

Description

Technical field

The invention relates to mechanical engineering, namely to spindles with a built-in electric motor with magnetic bearings on the shaft, and can be used to equip various processing machines, in high-speed centrifuges and other special centrifugal installations (for example, in various material shredders).

State of the art

At present, a number of foreign companies are manufacturing spindles with magnetic shaft bearings, for example, SKF Group (Catalog General Catalog. School edition (Catalog 5000 E - June 2003), pp. 1095, 1103). They contain blocks of active (controlled by signals from the shaft position sensors) magnetic bearings, a built-in electric motor and two safety (used in the event of a magnetic suspension failure) ball bearings mounted with a gap relative to the spindle housing. The magnetic bearing block contains two radial and one axial or two radial-axial (tapered) bearings and requires a complex, cumbersome and expensive electronic control system containing five control channels (two for each radial bearing and one for the axial bearing).

A similar spindle described by the author (Zhuravlev Yu.N. “Active Magnetic Bearings. Theory, Calculation, Application”, Polytechnic, St. Petersburg, 2003, p.22, fig. 2.4, p.24 fig.2.6 -2.7, p. 187 (prototype) [1]) and shown in FIG. 1, which contains a housing 1, an electric motor (stator 2, rotor 3), a magnetic bearing unit (BMP), consisting of two tapered bearings (the first is a stator 5, rotor 6, the second - stator 7, rotor 8), and two safety ball bearings SP1 and SP2 mounted on a shaft with gaps between the outer rings and the housing. If the magnetic bearing fails, the rotating shaft comes into contact with the housing through these bearings, after which it stops, for example, on a free coast.

The disadvantages of the prototype spindle are the complexity of the design and electronic control units, the possibility of destruction due to the rolling phenomenon (p. 187 [1]) upon contact of the housing with safety bearings, the permissible rotation speed of which is naturally lower than the shaft rotation speed in a non-contact magnetic suspension (therefore safety bearings withstand a limited number of emergencies). The main disadvantage of the prototype from the point of view of the consumer is the high cost of magnetic bearings with complex control units, which in practice leads to the fact that they cannot withstand competition with conventional bearings with lubrication, for example, oil mist. The use of magnetic bearings is economically viable in powerful power plants by eliminating the extremely high oil consumption for traditional shaft bearings.

SUMMARY OF THE INVENTION

The objective of the invention is to significantly simplify both the design of the spindle and its electronic components, reducing their number and increasing the reliability of the entire device. The consequence of this is a significant reduction in the cost of the spindle, and, therefore, it becomes available to a wide range of consumers of high-speed drives.

This problem is solved due to the fact that the spindle shaft is hollow, safety bearings are installed between the hollow part of the shaft and the axis fixed to the end of the housing, and the BMP is located in the housing in the area of the output part of the hollow shaft, muffled from the installation side of the working tool. A damping device in the form of a disk and a ring of porous elastomer placed between the disk and the end face of the housing is mounted on the axis. For the ultimate simplification, the BMP is made in the form of a single stator with windings and a rotor. Moreover, in the working gaps on the surfaces of the stator and rotor, a number of ring-shaped recesses corresponding to each other are made. The electronic control system is made in the form of bridge circuits of diametrically opposite stator windings connected in two (along orthogonal axes). In this case, the source of the supply alternating voltage is connected to the first diagonals of the circuits, and the control units to the second ones. To increase the axial stiffness, a third control unit is used, which is connected between the bridge circuits and the power supply source.

List of drawings

The invention is illustrated by drawings.

Figure 1 shows the device spindle prototype.

Figure 2 presents the design of the proposed spindle.

Figure 3 shows in more detail the design of the proposed spindle with a damping device of the axis and BMP in the form of one special stator and rotor.

Figure 4 presents in section a special stator of a magnetic bearing.

Figure 5 shows the electrical diagram of the connection of the stator windings of the magnetic bearing to a power source and control units.

The proposed spindle (figure 2) contains a housing 1, an electric motor consisting of a stator 2 and a rotor 3 mounted on a hollow shaft 4, and two groups of safety bearings (the first 9 in the end face of the spindle, the second 10 in the area of the shaft output). The BMP contains two conical (radial-axial) bearings: the first is the stator 5 and the rotor 6, the second is the stator 7 and the rotor 8. Safety bearings are installed without a gap in the cavity of the shaft 4 on the axis 11. At the output of the shaft there is a plug 12, to which is attached working tool (to simplify the drawing, the windings of the motor stators and magnetic bearings are not shown).

To increase the rigidity of the axis 11 (figure 3), mounted in the rear cover 13 of the spindle (front cover 14), a configuration was used in which the middle part of the axis (without bearings) is made with an increased diameter, the value of which is determined by the diameter of the shaft cavity. At the end of the spindle relative to the cover 13, a damping device is installed, consisting of a disk 15, rigidly fixed to the axis 11, and a ring 15, for example, of a porous elastomer. The BMP is made in the form of one gear stator 17 (stator windings are not shown in FIG. 3) and a rotor 18, on which a series of ring-shaped recesses corresponding to each other are made in the working gap (four in the drawing). Toothed stator BMP (figure 4) contains eight windings 19-26. The diametrically opposite windings 19-23 and 20-24 are included (Fig. 5) in the first bridge circuit for realizing the thrust of the magnetic field along the y axis. Similarly, windings 21-25 and 22-26 are included in the second bridge circuit to implement traction along the orthogonal axis x. A power supply voltage source 27 is connected to the first (input) diagonals of these circuits, electronic control units 28 and 29 are connected to the second (output) diagonals. This BMP design in the form of one stator 17 and rotor 18 with ring-shaped recesses provides axial shaft rigidity without using additional funds. To increase the axial stiffness of the shaft and control its longitudinal displacement, an additional third control unit is used, connected in series between the bridge circuits and the supply voltage source.

The proposed spindle (figure 2) works as follows. The block of ball bearings 9 mounted without a gap between the shaft cavity and the axis 11, provides radial rigidity in the area of the shaft end. The number and dimensions of these bearings are set based on the radial load and the permissible speed of rotation of the bearings. Their diameter can be several times smaller than the diameter of the safety bearings of the prototype and, therefore, satisfies the high working speed of rotation of the spindle shaft, transmitting more power from the engine to the tool due to the almost unlimited outer diameter. The bearing block 10 provides (without BMP enabled) in the area of the shaft exit (installation of the working tool) radial stiffness corresponding to the angular stiffness of axis 11 and sufficient for emergency operation without contact of the components of the rotating shaft with the housing. The damper at the base of the axis 11 (disk 15 and ring 16, figure 3) provides acceleration and stop of the spindle without turning on the BMP when passing through the resonant frequency of rotation of the shaft, determined by its mass and angular stiffness of the axis. The contact of the plug 12 (Fig. 3) with the spherical surface of the free end of the axis 11 prevents excessive axial load. In the operating mode, the BMP is turned on, which creates high static radial and axial stiffnesses of the shaft in the area of the working tool, provides damping of the shaft vibrations, and allows it to be adjusted position and fend off loads caused by tool unbalance.

The proposed principle of spindle construction allows you to create the most simple and reliable design with magnetic bearings, presented in figure 3. BMP, which creates radial and at the same time axial stiffness in the shaft exit zone, is made in the form of a special stator 17 and rotor 18 with a number of radial annular recesses leading to the formation (in a section) of longitudinal tooth zones. The attraction in the magnetic field of the stator of the teeth of the rotor to the teeth of the stator determines the axial stiffness of the shaft, proportional to the number of these teeth, without using an electronic control unit.

The windings 19-26 (figure 4) of the stator 17 with eight radial teeth are connected along the x and y axes in identical bridge circuits (figure 5). When the rotor 18 is displaced, for example, along the y axis, towards the windings 23 and 24, the inductances of these windings increase, and the inductances of the opposite windings 19 and 20 decrease. As a result, a signal proportional to the body displacement appears in the output diagonal of the bridge circuit under consideration connected to an AC voltage source 27. This signal is converted into a power alternating voltage applied to the points of the output diagonal to create a force that counteracts the displacement of the rotor, for example, using control unit 28 (RF Patent No. 2209393, CL G01C 19/00, 2003) where the compensation of the influence of power voltage on the signal the mismatch is realized due to the introduction of negative feedback in the amplifier, taking into account the phase shift with respect to the mismatch signal. It should be noted that in the proposed spindle, the source voltage of the magnetic bearing 27 is the phase voltage of the induction motor.

An even simpler implementation of the control units corresponds to the use of resonant circuits with special passive dampers (RF Patent No. 2193122, class F16C 32/04, class G01C 19/24, 2002), containing integrators that result in high static rigidity of the resonant suspension.

The use of the control unit 30 can significantly increase the natural axial stiffness of the BMP under consideration with a limited number of annular recesses on the stator and rotor.

The proposed spindle with magnetic bearings in comparison with the prototype is much simpler and more reliable. The consequence of this is its relatively low cost, which can lead to the availability of the spindle in high-power high-speed drives.

Claims (5)

1. Spindle containing a housing and an electric motor with a block of magnetic bearings and safety bearings of the shaft, characterized in that the shaft is hollow with damping on the installation side of the working tool, safety bearings are installed in the cavity of the shaft on an axis fixed to the end of the housing, and the block of magnetic bearings placed in the housing in the area of the output part of the hollow shaft. 2. The spindle according to claim 1, characterized in that it is equipped with a damping device in the form of a disk mounted on an axis and a ring made, for example, of an elastomer placed between the disk and the end of the housing. 3. The spindle according to claim 1 or 2, characterized in that the block of magnetic bearings is made in the form of one gear stator and rotor, the surfaces of which on the side of the working gap are made with corresponding annular recesses. 4. The spindle according to claim 3, characterized in that the diametrically opposite stator windings on each of the two orthogonal axes are connected in two bridge circuits, to the first diagonals of which a source of supplying alternating voltage is connected, and to the second - control units. 5. The spindle according to claim 4, characterized in that the bridge circuits are connected to a power source through a third control unit.

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