A radial magnetic levitation bearing

Abstract

The present invention discloses a radial magnetic suspension bearing, which comprises two rotor cores, a bias magnet core yoke and a horizontal axis winding. A permanent magnet is arranged between the two horizontal axis windings. A horizontal axis exciting positive winding and a horizontal axis exciting negative winding are installed between the upper-layer bias magnet core yoke and the rotor core. A vertical axis exciting positive winding and a vertical axis negative winding are installed between the lower-layer vertical axis bias magnet core yoke and the rotor core. That is, the upper and lower horizontal axis rotor cores and vertical axis rotor cores are stacked in a 90-degree rotation. A displacement measurement winding is arranged at the orthogonal position of two horizontal axis magnetic conduction teeth in each layer through a displacement measurement tooth for measuring the displacement of the vertical axis. The present invention has the advantages of small loss, integration of position test and control, high integration degree, accurate position calculation, etc., and also has the advantages of few winding tap numbers and few external IPMs required.

Description

Technical Field

[0001] The present invention belongs to the field of bearings, and particularly relates to a radial magnetic levitation bearing, which is applicable to fields requiring non-contact rotor support. Background Art

[0002] In the engineering structure of a magnetic levitation bearing, it generally includes a displacement test element, an exciting winding, a magnetic conducting core (armature), a rotor core, and a control device, etc. First, the displacement test element measures the position of the rotor and transmits the signal to the control device. Then, after being calculated and power amplified by the control device, a current is output to the exciting winding. Again, after the exciting winding obtains the current, a magnetic field is generated in the magnetic conducting core (armature) and conducted into the rotor core through the air gap. Then, the rotor core is affected by the magnetic field to generate an electromagnetic force and change the movement trajectory, realizing the adjustment of the rotor displacement. Finally, the rotor position is controlled at the center of the air gap to achieve rotor magnetic levitation.

[0003] Magnetic levitation bearings generally adopt a paired armature arrangement. The main advantage of this arrangement is that the relationship between the control current of the exciting winding and the generated electromagnetic force is linear, which is beneficial to control. Its main principle is that one armature is supplied with I0 + Ik current to generate a large attractive force, and the other armature is supplied with I0 - Ik current to generate a small attractive force. Although the relationship between the current I and the electromagnetic force F is non-linear f(I), after adopting the above method, (f(I0 + Ik) + f(I0 - Ik)) / (I0 + Ik - (I0 - Ik)), the above formula is the difference form of the differential of f(I) mathematically and can be approximated as linear. It can be seen that in order to achieve linear control, a bias magnetic field is generated by introducing the current I0. Since this current I0 always exists, it causes fixed losses in the magnetic levitation bearing, makes the bearing heat up, and affects the heat dissipation design and overall layout.

[0004] To radially position the bearing, two pairs of paired armatures must be used and arranged in a cross shape to form two-axis control in the radial direction, called the horizontal axis and the vertical axis, also called the x-axis and the y-axis. The two-axis theoretical axes are at 90 degrees, and the theoretical axes are on the symmetry center line of the magnetic conducting core (armature). Considering that one armature has two teeth and a single axis has two paired teeth, generally, a magnetic levitation bearing has two axes, eight teeth, and four windings, as shown in the figure. In the controller, multiple control interfaces also need to be set separately to generate currents for the four windings. If a switching power supply is used, if each axis is independently controlled, three-bridge-arm IPMs are required, then a radial bearing requires 3 groups of IPMs with a total of 12 bridge arms. Therefore, the multi-winding interface of the traditional structure also makes the main circuit structure of the control device complex.

[0005] In this structure, a general eddy current sensor is usually adopted for the displacement test element, and precise positioning is required for two reasons. First, due to inaccurate positioning, the displacement test element may measure the vibration generated by itself, thus causing the position vibration of the rotor of the control system. Second, inaccurate initial position of the rotor will lead to incorrect calculation method. Therefore, in actual engineering design, a positioning mounting bracket is used, which solves the problem of radial positioning accuracy to a certain extent. However, considering the size space occupied by the mounting bracket, the test axis of the magnetic levitation bearing is inconsistent with the control axis in the axial direction, which will also affect the control calculation.

[0006] Therefore, there is a contradiction in the existing structure of the magnetic levitation bearing that the test point of the displacement test element does not coincide with the control point of the magnetic levitation bearing and the installation accuracy of the displacement test element is not high. Summary of the Invention

[0007] The purpose of the present invention is to overcome the disadvantages of the existing structure, such as large loss, complex structure of the main control loop, inaccurate rotor displacement calculation due to the non - coincidence between the test point of the displacement test element and the control point of the magnetic levitation bearing, etc., and to provide a radial magnetic levitation bearing.

[0008] The technical solution adopted by the present invention to solve its technical problems is as follows: A radial magnetic levitation bearing includes two rotor cores arranged side by side axially, a concentric yoke of the bias magnet core sleeved outside the rotor core, and a horizontal axis winding arranged on the yoke of the bias magnet core. A permanent magnet is arranged between the two horizontal axis windings. Between the upper - layer horizontal axis yoke of the bias magnet core and the rotor core, a horizontal axis exciting positive winding and a horizontal axis exciting negative winding are respectively installed through two symmetric horizontal axis magnetic conduction teeth. When the two horizontal axis exciting windings are connected in series and energized, they generate magnetic fields with the same direction. Between the lower - layer vertical axis yoke of the bias magnet core and the rotor core, a vertical axis exciting positive winding and a vertical axis negative winding are respectively installed through two symmetric horizontal axis magnetic conduction teeth. When the two vertical axis exciting windings are connected in series and energized, they generate magnetic fields with the same direction. The connection line between the horizontal axis exciting positive winding and the horizontal axis exciting negative winding is perpendicular to the connection line between the vertical axis exciting positive winding and the vertical axis negative winding, that is, the upper - layer and lower - layer horizontal axis rotor cores and vertical axis rotor cores are stacked in a 90 - degree rotation. At the orthogonal position of two horizontal axis magnetic conduction teeth in each layer, a displacement measurement winding is arranged through a displacement measurement tooth for measuring the displacement of the vertical axis.

[0009] The radial magnetic suspension bearing described also includes a power supply circuit for a transverse axis excitation positive winding, a transverse axis excitation negative winding, a longitudinal axis excitation positive winding and a longitudinal axis negative winding, a signal power supply circuit for a displacement measurement winding, a displacement resolution module and a displacement control module. The power supply circuit provides an excitation power supply for the excitation winding, and the signal power supply circuit provides an AC power supply for the displacement measurement winding to facilitate measurement. The displacement resolution module measures the inductance of the circuit according to the current response caused by the AC power supply. Since its inductance is related to the displacement, the table lookup relationship between the inductance and the current can be completed by setting at the factory, thereby realizing the displacement resolution. Finally, the displacement control module adjusts and controls the power supply circuit according to the calculated displacement value and the magnetic field suspension force relationship between the permanent magnet and the transverse axis excitation positive winding, the transverse axis excitation negative winding and the longitudinal axis excitation positive winding, so that the excitation winding outputs a correct current value, thereby realizing closed-loop control of the suspension force.

[0010] The radial magnetic bearing, wherein the displacement measuring teeth include longitudinal displacement measuring teeth arranged on the upper transverse axis rotor core and transverse axis displacement measuring teeth arranged on the lower longitudinal axis rotor core, and the displacement measuring windings include longitudinal displacement measuring positive windings and longitudinal displacement measuring negative windings arranged on the longitudinal axis displacement measuring teeth, and transverse axis displacement measuring positive windings and transverse axis displacement measuring negative windings arranged on the transverse axis displacement measuring teeth.

[0011] In the radial magnetic suspension bearing, the winding directions of the transverse axis excitation positive winding and the transverse axis excitation negative winding satisfy that the directions of the magnetic fields generated by the two windings when they are connected in series are the same.

[0012] In the radial magnetic suspension bearing, two transverse-axis magnetic conductive teeth are connected through the bias core yoke to form a full circle.

[0013] The beneficial effects of the present invention are as follows: the radial magnetic bearing of the new structure has the advantages of low loss, integrated position test control, high integration, accurate position solution, etc., and also has the advantages of small number of winding taps and few external IPMs required; among which the high-precision position solution method will provide important support for the advanced algorithms of the control device (such as rotor modal control, unbalance identification and rotor over-critical speed, etc.), and a small number of IPMs and taps reduces system losses and reduces the configuration complexity of peripheral components. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a three-dimensional structural diagram of the present invention;

[0015] Figure 2 It is a front structural schematic diagram of the present invention;

[0016] Figure 3 It is a schematic diagram of the structure of the present invention after being cut apart;

[0017] Figure 4 It is the diagram of the magnetic field direction of the horizontal-axis winding excitation of the present invention;

[0018] Figure 5 It is the diagram of the magnetic field direction of the permanent magnet bias of the present invention;

[0019] Figure 6 It is the developed diagram of the magnetic flux density distribution of the main magnetic field of the present invention;

[0020] Figure 7 It is the developed diagram of the measured magnetic field distribution of the present invention.

[0021] Each reference numeral is: 1 - rotor core, 2 - yoke part of the bias magnet core, 3 - permanent magnet, 4 - horizontal-axis winding, 5 - positive horizontal-axis excitation winding, 6 - negative horizontal-axis excitation winding, 7 - positive longitudinal-axis excitation winding, 8 - negative longitudinal-axis winding, 9 - horizontal-axis magnetic conduction teeth, 10 - displacement measurement teeth, 11 - positive longitudinal-axis displacement measurement winding, 12 - negative longitudinal-axis displacement measurement winding. Specific Embodiments

[0022] To further illustrate the purpose and technical solution of the present invention, the following will further describe the present invention in detail with specific embodiments of the accompanying drawings. The following embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

[0023] Refer to Figure 1 、 Figure 2 and Figure 3As shown in the figure, a radial magnetic suspension bearing disclosed by the present invention includes two rotor cores 1 arranged side by side axially, a bias magnet core yoke 2 sleeved concentrically outside the rotor core 1, and a transverse axis winding 4 arranged on the bias magnet core yoke 2. A permanent magnet 3 is arranged between the two transverse axis windings 4. It also includes a power supply circuit for the transverse axis exciting positive winding 5, the transverse axis exciting negative winding 6, the longitudinal axis exciting positive winding 7 and the longitudinal axis negative winding 8, a signal power supply circuit for the longitudinal axis displacement measuring positive winding 11 and the longitudinal axis displacement measuring negative winding 12, a displacement calculation module and a displacement control module to form a controller. A permanent magnet 3 is arranged between the two transverse axis windings 4. Between the upper transverse axis bias magnet core yoke 2 and the rotor core 1, a transverse axis exciting positive winding 5 and a transverse axis exciting negative winding 6 are respectively installed through two symmetrical transverse axis magnetic conduction teeth 9. When the two transverse axis exciting windings are connected in series and energized, they generate magnetic fields in the same direction. Between the lower longitudinal axis bias magnet core yoke 2 and the rotor core 1, a longitudinal axis exciting positive winding 7 and a longitudinal axis negative winding 8 are respectively installed through two symmetrical transverse axis magnetic conduction teeth 9. When the two longitudinal axis exciting windings are connected in series and energized, they generate magnetic fields in the same direction. The two transverse axis magnetic conduction teeth 9 are connected through the bias magnet core yoke 2 to form a complete circle. The connection line between the transverse axis exciting positive winding 5 and the transverse axis exciting negative winding 6 is perpendicular to the connection line between the longitudinal axis exciting positive winding 7 and the longitudinal axis negative winding 8, that is, the upper and lower transverse axis rotor cores and longitudinal axis rotor cores are stacked in a 90-degree rotation. At the orthogonal position of the two transverse axis magnetic conduction teeth 9 in each layer, a displacement measuring winding is arranged through a displacement measuring tooth 10 for measuring the displacement of the longitudinal axis. The winding directions of the transverse axis exciting positive winding 5 and the transverse axis exciting negative winding 6 satisfy the following relationship: when the two windings are connected in series and energized, they generate magnetic fields in the same direction.

[0024] Wherein the displacement measuring tooth includes a longitudinal axis displacement measuring tooth arranged on the upper layer transverse axis rotor core 1 and a transverse axis displacement measuring tooth arranged on the lower layer longitudinal axis rotor core 1. The displacement measuring winding includes a longitudinal axis displacement measuring positive winding 11 and a longitudinal axis displacement measuring negative winding 12 arranged on the longitudinal axis displacement measuring tooth, and a transverse axis displacement measuring positive winding and a transverse axis displacement measuring negative winding arranged on the transverse axis displacement measuring tooth. The magnetic field direction of the transverse axis winding excitation is as Figure 4 shown, and the magnetic field direction of the permanent magnet bias is as Figure 5 shown.

[0025] Referring to Figure 6 、 Figure 7 shown, when the radial magnetic suspension bearing of the present invention works, in the transverse axis direction, B = B0 + B1, B = B0 - B1, the resultant force ;

[0026] Perform vector synthesis on the x-axis , where B0 is a fixed value, B1 is proportional to the current of the transverse axis winding. By adjusting the current, the magnitude of B1 can be adjusted. At the same time, it can be seen from the formula that the control of the resultant force is also linear.

[0027] Since B0 is excited by a permanent magnet, for the same resultant force F, if the designed B0 is larger, the requirement for B1 can be made smaller, thus reducing the control current loss.

[0028] By designing the initial distance from the displacement measurement tooth 10 to the rotor to ensure that the magnetic flux density Bt for displacement measurement is more than two orders of magnitude smaller than both B0 and B1, the influence on the resultant force is minimized. At the same time, considering that the displacement measurement teeth 10 are arranged in pairs with opposite magnetic field directions, the resultant electromagnetic force generated by itself is zero and will not affect the magnetic force of the magnetic levitation bearing. Moreover, the arrangement of the measurement teeth is also orthogonal to the main magnetic field generated by the permanent magnet excitation and the exciting winding, further reducing the influence on the levitation force during measurement.

[0029] The power supply circuit of the controller of the present invention provides excitation power for the horizontal axis excitation positive winding 5, the horizontal axis excitation negative winding 6, and the vertical axis excitation positive winding 7. The signal power supply circuit provides an AC power supply for the vertical axis displacement measurement positive winding 11 and the vertical axis displacement measurement negative winding 12 for convenient measurement. The displacement calculation module calculates the inductance of the circuit according to the current response caused by the AC power supply. Since its inductance has a certain relationship with the displacement, the look-up relationship between the inductance and the current can be completed through calibration at the factory, thereby realizing the calculation of the displacement. Finally, the displacement control module adjusts and controls the power supply circuit according to the calculated displacement value and the relationship between the magnetic levitation force of the permanent magnet 3 and the exciting winding magnetic field, so that the exciting winding outputs the correct current value to realize the closed-loop control of the levitation force.

[0030] Since the inductance value of the displacement measurement winding is related to the displacement value, the displacement offset can be obtained by measuring the inductance of the displacement measurement winding through an external circuit. The relationship between the displacement and the inductance can be obtained with high precision through the method of experimental test calibration.

[0031] Those skilled in the art can easily understand that the above is only a preferred use case of the present invention and is not used to limit the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A radial magnetic suspension bearing, characterized in that: it includes two rotor cores (1) arranged side by side axially, a bias magnet core yoke portion (2) sleeved outside the rotor core (1), and a transverse axis winding (4) arranged on the bias magnet core yoke portion (2). A permanent magnet (3) is arranged between the two transverse axis windings (4). A transverse axis exciting positive winding (5) and a transverse axis exciting negative winding (6) are respectively installed between the upper bias magnet core yoke portion (2) and the rotor core (1) through two symmetrical transverse axis magnetic conduction teeth (9). A longitudinal axis exciting positive winding (7) and a longitudinal axis negative winding (8) are respectively installed between the lower bias magnet core yoke portion (2) and the rotor core (1) through two symmetrical transverse axis magnetic conduction teeth (9). The connection line of the transverse axis exciting positive winding (5) and the transverse axis exciting negative winding (6) is perpendicular to the connection line of the longitudinal axis exciting positive winding (7) and the longitudinal axis negative winding (8). At the orthogonal position of the two transverse axis magnetic conduction teeth (9) in each layer, a displacement measuring winding is arranged through a displacement measuring tooth (10). The displacement measuring winding includes a longitudinal axis displacement measuring positive winding (11) and a longitudinal axis displacement measuring negative winding (12) arranged on the longitudinal axis displacement measuring tooth, and a transverse axis displacement measuring positive winding and a transverse axis displacement measuring negative winding arranged on the transverse axis displacement measuring tooth; it also includes a controller composed of a power supply circuit for the transverse axis exciting positive winding (5), the transverse axis exciting negative winding (6), the longitudinal axis exciting positive winding (7) and the longitudinal axis negative winding (8), a signal power supply circuit for the displacement measuring winding, a displacement calculation module and a displacement control module. The displacement calculation module calculates the inductance of the circuit according to the current response caused by the AC power supply, completes the look-up table relationship between the inductance and the current, and realizes the calculation of the displacement. The displacement control module adjusts and controls the power supply circuit according to the calculated displacement value and the magnetic field suspension force relationship between the permanent magnet (3) and the transverse axis exciting positive winding (5), the transverse axis exciting negative winding (6) and the longitudinal axis exciting positive winding (7), so as to make the exciting winding output the correct current value and realize the closed-loop control of the suspension force.

2. The radial magnetic suspension bearing according to claim 1, characterized in that the displacement measuring tooth (10) includes a longitudinal axis displacement measuring tooth arranged on the upper rotor core (1) and a transverse axis displacement measuring tooth arranged on the lower rotor core (1).

3. The radial magnetic suspension bearing according to claim 2, characterized in that the winding directions of the transverse axis exciting positive winding (5) and the transverse axis exciting negative winding (6) satisfy that: when the two windings are connected in series, the directions of the magnetic fields generated by energization are the same.

4. The radial magnetic suspension bearing according to claim 3, characterized in that the two transverse axis magnetic conduction teeth (9) are connected through the bias magnet core yoke portion (2) to form a complete circle.

Images