Magnetic bearing falling protection device based on extrusion oil film damping

Abstract

The invention discloses a magnetic bearing falling protection device based on extrusion oil film damping. The magnetic bearing falling protection device comprises a damper base, a damper inner ring, a damper outer ring and a squirrel-cage elastic support. The damper outer ring is located at the top end of the damper base. The damper inner ring is mounted at an outer side port of the magnetic bearing outer ring in an interference fit manner through the squirrel-cage elastic support; the squirrel-cage elastic support is vertically mounted on the inner side of the damper base; an annular oil supply groove is formed in the inner wall of the damper outer ring, and an oil film is formed in the area defined by the outer wall of the damper inner ring, the inner wall of the damper outer ring and the groove wall of the annular oil supply groove. The damper inner ring has elastic damping, and stress is evenly distributed under the load effect so as to resist reverse vortex motion and forward vortex motion of the rotor in the rotating speed decreasing process. Through the damping effect of the oil film in the arch-shaped structure, vibration and noise of a bearing rotor system are reduced, and meanwhile the stability and accuracy of the rotor are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic bearing protection, and in particular relates to a magnetic bearing drop protection device based on squeeze oil film damping. Background Art

[0002] Magnetic bearings (also known as active magnetic bearings or active magnetic bearings) are bearing systems that use electromagnetic fields to support rotating mechanical parts. The basic principle is to use electromagnetic force to suspend and rotate the rotor, without mechanical contact in space, to control the position and stability of the rotor. Unlike traditional mechanical bearings, magnetic bearings have the advantages of no contact, no wear, and long life because they do not require physical contact. The rotor under their control can have a very high operating speed (generally up to 30,000 rad / min).

[0003] However, when the magnetic force of the magnetic bearing suddenly disappears due to control system failure, high temperature environment, external environment collision and other factors, the rotor exits the steady state and falls onto the bearing. The high-speed rotor produces large vibration and impact on the protective shaft, which will cause damage to the magnetic bearing and further cause immeasurable damage to the entire bearing-rotor system.

[0004] A Chinese patent with publication number CN1544821A discloses a protective bearing device suitable for large active electromagnetic bearings, which provides an auxiliary bearing protection device for the system after the electromagnetic bearing system fails. However, the product of this invention has the following problems during use: First, the protection of the bearing is too cumbersome and complicated, which increases the difficulty of installation and maintenance; second, when designing the protective bearing device, the magnitude of various forces in contact between the specific rotor and the bearing and their changing process are not considered, so that the protection effect has room for improvement; third, the protection effect is not good for the resonance damage caused by the violent vibration generated when the rotor fails; fourth, the protective device for the magnetic bearing rotor system has a high loss rate and a short service life. Summary of the invention

[0005] The present invention discloses a magnetic bearing drop protection device based on squeeze film damping. By applying a squeeze film damper, the stability of a rotor magnetic bearing system under fault failure conditions is effectively improved, thereby improving the safety and reliability of the entire system operation.

[0006] A magnetic bearing drop protection device based on squeeze film damping, the device is installed at the support position of the magnetic bearing, and includes a damper base, a damper inner ring, a damper outer ring and a squirrel cage elastic support;

[0007] The cross section of the damper base is L-shaped and is fixed to the fixed support surface by pins; the damper outer ring is located at the top of the damper base; the damper inner ring is installed at the outer port of the magnetic bearing outer ring through a squirrel cage elastic support interference fit; the squirrel cage elastic support is vertically installed on the inner side of the damper base;

[0008] An annular oil supply groove is provided on the inner wall of the damper outer ring, and an oil supply hole connected to the annular oil supply groove is opened on the damper base; the area surrounded by the outer wall of the damper inner ring, the inner wall of the damper outer ring and the groove wall of the annular oil supply groove is used to form an oil film;

[0009] The magnetic bearing is installed on the inner wall of the squirrel cage elastic support to support and stabilize the rotating shaft rotor; the damper inner ring has elastic damping and evenly distributes stress under load to resist reverse vortex and forward vortex that occur in the rotor during speed reduction.

[0010] As a preferred example, the squirrel cage elastic support includes a fastening flange and squirrel cage bars;

[0011] The fastening flange is fixed on the fixed support surface by flange bolts, one end of the squirrel cage bar is connected to the fastening flange, and the other end is connected to the inner ring of the damper.

[0012] As a preferred example, the stiffness of the squirrel cage bar is:

[0013]

[0014] Wherein, n represents the number of cage ribs; E represents the elastic modulus of the material; a represents the cross-sectional height of the cage rib; b represents the cross-sectional width of the cage rib; and c represents the length of the cage rib.

[0015] As a preferred example, the device includes 6 squirrel cage elastic supports, which are evenly distributed on the inner side of the outer ring of the damper, and the diameter of the squirrel cage bars is set to 6 mm.

[0016] As a preferred example, the magnetic bearing includes a stator housing and a stator, the stator includes permanent magnets, magnetic poles and coils; the permanent magnets connect the magnetic poles together, the coils are densely wound around the magnetic poles, and adjacent magnetic poles are evenly distributed around the rotor at a preset angle; the damper inner ring is assembled with the stator through the stator housing.

[0017] As a preferred example, the thickness h of the oil film in the annular oil supply groove is:

[0018]

[0019] Where R b Indicates the radius of the oil film ring; R jrepresents the oil film radius clearance; θ represents the starting angle when the oil film thickness is at the maximum position; e represents the eccentricity between the oil film journal and the oil film ring.

[0020] As a preferred example, a plurality of oil supply holes are provided on the damper base, and the plurality of oil supply holes are evenly distributed on the damper base along the circumferential direction.

[0021] As a preferred example, the diameter of the oil supply hole is set to 4 mm.

[0022] The beneficial effects of the present invention are:

[0023] First, the magnetic bearing drop protection device based on squeeze oil film damping of the present invention reduces the vibration and noise of the bearing rotor system through the damping effect of the oil film in the arch structure when the magnetic bearing system fails and causes the rotor to fall, while improving the stability and accuracy of the rotor and improving the safety and reliability of the entire system operation.

[0024] Secondly, the magnetic bearing drop protection device based on squeeze oil film damping of the present invention has a simple structure and is easy to replace and repair, so it can greatly reduce the maintenance cost and has a wider scope of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a front view of the magnetic bearing drop protection device based on squeeze film damping of the present invention;

[0026] Figure 2 A top view of the magnetic bearing drop protection device based on squeeze film damping of the present invention;

[0027] Figure 3 This is a partial enlarged view of the oil film of the magnetic bearing drop protection device based on squeeze oil film damping of the present invention.

[0028] Figure numerals: 1 represents squirrel cage bar, 2 represents damper base, 3 represents rotor, 4 represents annular oil supply groove, 5 represents damper outer ring, 6 represents oil supply hole, 7 represents permanent magnet, 8 represents coil, 9 represents fastening flange, 10 represents spring support outer ring (damper inner ring), 11 represents magnetic pole, 12 represents coil, and 13 represents oil film. DETAILED DESCRIPTION

[0029] The following examples will enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0030] The present invention discloses a magnetic bearing drop protection device based on squeeze oil film damping, the device is installed at the support position of the magnetic bearing, and comprises a damper base, a damper inner ring, a damper outer ring and a squirrel cage elastic support;

[0031] The cross section of the damper base is L-shaped and is fixed to the fixed support surface by pins; the damper outer ring is located at the top of the damper base; the damper inner ring is installed at the outer port of the magnetic bearing outer ring through a squirrel cage elastic support interference fit; the squirrel cage elastic support is vertically installed on the inner side of the damper base;

[0032] An annular oil supply groove is provided on the inner wall of the damper outer ring, and an oil supply hole connected to the annular oil supply groove is opened on the damper base; the area surrounded by the outer wall of the damper inner ring, the inner wall of the damper outer ring and the groove wall of the annular oil supply groove is used to form an oil film;

[0033] The magnetic bearing is installed on the inner wall of the squirrel cage elastic support to support and stabilize the rotating shaft rotor; the damper inner ring has elastic damping and evenly distributes stress under load to resist reverse vortex and forward vortex that occur in the rotor during speed reduction.

[0034] See also Figure 1 and Figure 2 The magnetic bearing drop protection device (squeeze film damper) includes a damper base 2, a damper inner ring 10, a damper outer ring 5 and a squirrel cage elastic support. A squirrel cage bar 1 is fixedly installed on one side of the damper base 2. The squirrel cage bar 1 is fixed to the fixed support surface through a fastening flange 9 via flange bolts and connected to the stator housing through an elastic support outer ring (damper inner ring) 10, so that the squeeze film damper is firmly installed on the magnetic bearing 8, which is convenient for load transmission and better play the shock absorption effect of the squeeze film damper. An oil supply hole 6 is opened in the damper base 2, and the oil supply hole 6 is connected to the annular groove on the inner wall of the damper outer ring 5. In the present invention, the annular grooves are designed on the left and right sides of the inner wall of the damper outer ring 5 to facilitate the adjustment of the oil film thickness and the oil film squeeze effect. An annular oil supply groove 4 is designed between the oil supply hole 6 and the inner wall of the damper outer ring 5, and is connected to it through the oil supply hole 6, thereby forming a closed oil supply system. The area enclosed by the outer wall of the damper inner ring 10, the inner wall of the damper outer ring 5 and the wall of the oil supply groove 4 is used to form an oil film, which is convenient for the storage of the oil film. The oil supply hole 6 is set on the damper base 2, the purpose of which is to facilitate the timely adjustment of the thickness of the oil film in the annular oil supply groove 4, and to facilitate the change of the flow path of the oil and the working state of the damper, so as to achieve precise control of the damping characteristics, so that the squeeze film damper can provide the required damping effect in response to the load generated by the rotor 3 falling on the magnetic bearing 8 at different masses and different speeds. Figure 3 It is a partial enlarged view of the oil film of the magnetic bearing drop protection device based on squeeze oil film damping of the present invention. Preferably, in order to simplify the manufacturing process, the damper base 2 and the damper outer ring 5 are made in one piece.

[0035] The rotor 3 is mounted on the inner wall of the elastic support through the magnetic bearing 8. The magnetic bearing includes a stator housing and a stator, and the stator includes a permanent magnet, a magnetic pole and a coil. The permanent magnet connects the magnetic poles together. The coils are densely wound on the magnetic poles, with a fixed and uniform angle between adjacent magnetic poles, and are evenly distributed around the rotor. The damper inner ring is assembled with the stator through the stator housing, and the upper and lower end surfaces of the damper inner ring should be flush with the permanent magnet of the magnetic bearing. When the rotor 3 system of the magnetic bearing 8 fails and the rotor 3 falls, the rotor 3 initially whirls in the reverse direction at a high speed and collides with the magnetic bearing 8 initially. The load is transmitted to the squeeze film damper, and the damper inner ring 10 undergoes elastic deformation to absorb the load of the initial back-and-forth collision of the rotor, so that the damper inner ring 10 and the damper outer ring 5 exert pressure on the oil film in the annular oil supply groove 4. Because the rotor collides back and forth, violent vibration occurs, so that the local thickness of the oil film changes. The oil film flows in the annular oil supply groove 4, and the viscosity of the oil film produces a damping force, thereby absorbing the load and mechanical vibration of the magnetic bearing 8 system and dissipating the vibration energy. In the subsequent process, after the intermittent contact between the rotor and the magnetic bearing, the critical speed is reached, and the system resonates. The damper inner ring 10 produces more violent vibrations, which drives the local thickness of the oil film in the annular oil supply groove 4 to change more, and produces a stronger damping force, so that the rotor speed drops, so that the system quickly jumps out of the resonance state.

[0036] Examples

[0037] After testing, it was found that when the rotor falls, the magnetic bearing interacts with the rotor nonlinearly through dry friction, reducing the rotor speed to a safe state, and the maximum radial force under the condition of radial force greater than 0.3 friction coefficient is 296N. In this example, the outer diameter of the damper base is set to 250mm to provide sufficient support area to withstand the impact load force of 296N when the rotor falls and ensure good contact with the fixed support surface. The thickness is set to 20mm to enhance the strength and rigidity of the base to resist the initial collision of the rotor at high speed.

[0038] One side of the squeeze film damper is installed at the support position of the magnetic bearing, and the other side is fixed to the fixed support surface by pins. It is used to mitigate the instability caused by the high-pressure oil film effect, and can effectively resist the radial force of the initial back-and-forth collision of the rotor with the magnetic bearing, reducing the vibration and noise of the bearing-rotor system, while improving the stability and accuracy of the rotor.

[0039] The inner wall of the damper outer ring is designed with an annular oil supply groove. The closed area surrounded by the outer wall of the damper inner ring, the inner wall of the damper outer ring and the wall of the oil supply groove is used to form an oil film to ensure lubrication and damping performance during operation. An oil supply hole is opened on the outside of the damper base to communicate with the annular oil supply groove to control the size of the oil film in the annular oil supply groove, provide lubrication for the damper, and improve the damping effect of the oil film. The inner diameter of the damper inner ring is set to 95mm, so that a certain gap is maintained between the magnetic bearing and the rotor to reduce friction and wear and extend the life of the equipment. Preferably, an annular groove is opened on the inner wall of the damper outer ring, so that the oil supply groove surrounded by the outer wall of the damper inner ring, the inner wall of the damper outer ring and the wall of the oil supply groove presents an annular boss, which can increase the stress area of ​​the oil film, improve the anti-shock absorption effect of the damper, and reduce the radial vibration of the magnetic bearing. The oil supply hole is connected to the annular groove on the inner wall of the outer ring of the damper. The number of oil supply ports is set to 4 and evenly distributed on the inner wall of the outer ring of the damper, which can balance the distribution of the oil film. The diameter of the oil supply hole is set to 4mm. On the one hand, it provides sufficient oil flow to ensure the formation and maintenance of the oil film, avoid the rupture of the oil film under high load, and the air intake is small; on the other hand, the generation of a larger oil supply pressure can eliminate the influence of negative pressure and increase the oil film pressure. When the load impact reaches the maximum, the oil film is in a full oil film state, and the obtained oil film damping is also larger. In the full oil film state, the supporting force of the oil film refers to the following formula:

[0040]

[0041]

[0042] The thickness h of the oil film in the oil supply groove refers to the following formula:

[0043]

[0044] Where R b ——Radius of oil film ring; R j ——Oil film radius clearance; θ——Starting angle when the oil film thickness is maximum; e——Eccentricity between the oil film journal and the oil film ring.

[0045] Preferably, the depth of the oil supply groove is set to 3mm to form the necessary space for the oil film, ensuring that the oil film can effectively absorb the impact when the rotor falls. The width is set to 8mm to ensure smooth oil flow and avoid blockage and rupture of the oil film. If the oil film gap is too small, the damper vibration reduction effect is not obvious enough, and if the oil film gap is too large, the vibration of the rotor system may be aggravated.

[0046] The rotor is installed on the inner wall of the elastic support through a magnetic bearing. The elastic support itself has elastic damping, which evenly distributes stress under load and resists the reverse and forward vortices that occur when the rotor speed decreases, allowing the system to quickly jump out of the resonance state, further improving the stability of the system.

[0047] The calculation formula of the stiffness of the squirrel cage bar is as follows:

[0048]

[0049] Where n is the number of cage ribs; E is the elastic modulus of the material; a is the cross-sectional height of the cage rib; b is the cross-sectional width of the cage rib; c is the length of the cage rib. In practical applications, the corresponding structural parameters can be adjusted according to specific requirements.

[0050] In this example, the diameter of the squirrel cage bar is set to 6 mm to provide the necessary elasticity and strength to ensure that the elastic support can evenly distribute stress under load. The number of squirrel cage bars is set to 6, evenly distributed, to ensure the stability of the elastic support and absorb the load of the initial back-and-forth collision of the rotor.

[0051] After the active magnetic bearing fails, the rotor will lose the support of electromagnetic force. At this time, contact will occur between the rotor and the landing bearing, resulting in friction. The rotor drop simulation model under the common TDB protection bearing was established. Matlab was used to analyze the damage of the rotor drop under the friction coefficient of 0.1, 0.2, and 0.3 with a drop speed of 5000r / min. The results show that when the friction coefficient is 0.1, the time when the speed is reduced to zero is about 3.6s, and the maximum radial contact force is 272N. When the friction coefficient is 0.2, the time when the speed is reduced to zero is about 2.8s, and the maximum radial contact force is 294N; when the friction coefficient is 0.3, the time when the speed is reduced to zero is about 2.2s, and the maximum radial contact force is 296N. At the same time, the rotor drop damage process is obtained: when the vertical rotor is on the TDB, after the axial rebound, the rotor obtains stable support. The friction of the contact surface drives the TDB inner ring to accelerate to the same speed as the rotor. In the radial direction, the rotor enters a rotational motion after the initial collision. The direction of rotation depends on the direction of friction, so the system first enters a backward rotation state, and then has a natural rotation frequency (speed) and a critical speed. The rotor vortex first manifests as a reverse vortex, then as a forward vortex, and finally the vortex speed decreases. At a rotation speed of 5000r / min, the friction coefficient between the rotor and the bearing is changed. After several collisions, the rotor and the bearing will achieve axial stability and enter a stable rotational motion in the radial direction. Shortly after the decline, the inner ring accelerates to the same speed as the rotor. Appearing around 200rad / s, the speed is close to the critical speed of the rotor, and resonance occurs; then the speeds of the two are synchronously decelerated to zero. As the friction coefficient increases, the radial clearance becomes larger and larger, the vibration amplitude becomes more and more obvious, and the time it takes for the speed to be reduced to zero becomes shorter and shorter. Use the following formula to characterize the collision contact force and puncture depth:

[0052]

[0053] The contact stiffness is:

[0054]

[0055] In this example, when the magnetic bearing system fails and the rotor falls, the pressure-resistant oil film damper reduces the vibration and noise of the bearing rotor system through the damping effect of the oil film in the arch structure, while improving the stability and accuracy of the rotor.

[0056] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A magnetic bearing drop protection device based on squeeze film damping, characterized in that: The device is installed at the supporting position of the magnetic bearing, and includes a damper base, a damper inner ring, a damper outer ring and a squirrel cage elastic support; The cross section of the damper base is L-shaped and is fixed to the fixed support surface by pins; the damper outer ring is located at the top of the damper base; the damper inner ring is installed at the outer port of the magnetic bearing outer ring through a squirrel cage elastic support interference fit; the squirrel cage elastic support is vertically installed on the inner side of the damper base; An annular oil supply groove is provided on the inner wall of the damper outer ring, and an oil supply hole connected to the annular oil supply groove is opened on the damper base; the area surrounded by the outer wall of the damper inner ring, the inner wall of the damper outer ring and the groove wall of the annular oil supply groove is used to form an oil film; The magnetic bearing is installed on the inner wall of the squirrel cage elastic support to support and stabilize the rotating shaft rotor; the damper inner ring has elastic damping and evenly distributes stress under load to resist reverse vortex and forward vortex that occur in the rotor during speed reduction.

2. The magnetic bearing drop protection device based on squeeze film damping according to claim 1 is characterized in that: The squirrel cage elastic support comprises a fastening flange and squirrel cage bars; The fastening flange is fixed on the fixed support surface by flange bolts, one end of the squirrel cage bar is connected to the fastening flange, and the other end is connected to the inner ring of the damper.

3. The magnetic bearing drop protection device based on squeeze film damping according to claim 2 is characterized in that: The stiffness of the squirrel cage bar is: Wherein, n represents the number of cage ribs; E represents the elastic modulus of the material; a represents the cross-sectional height of the cage rib; b represents the cross-sectional width of the cage rib; and c represents the length of the cage rib.

4. The magnetic bearing drop protection device based on squeeze film damping according to claim 1 is characterized in that: The device comprises 6 squirrel cage elastic supports, which are evenly distributed on the inner side of the outer ring of the damper, and the diameter of the squirrel cage bars is set to 6 mm.

5. The magnetic bearing drop protection device based on squeeze film damping according to claim 1 is characterized in that: The magnetic bearing includes a stator housing and a stator, and the stator includes permanent magnets, magnetic poles and coils; the permanent magnets connect the magnetic poles together, the coils are densely wound around the magnetic poles, and adjacent magnetic poles are evenly distributed around the rotor at a preset angle; the damper inner ring is assembled with the stator through the stator housing.

6. The magnetic bearing drop protection device based on squeeze film damping according to claim 1 is characterized in that: The thickness h of the oil film in the annular oil supply groove is: Where R b Indicates the radius of the oil film ring; R j represents the oil film radius clearance; θ represents the starting angle when the oil film thickness is at the maximum position; e represents the eccentricity between the oil film journal and the oil film ring.

7. The magnetic bearing drop protection device based on squeeze film damping according to claim 1 is characterized in that: The damper base is provided with a plurality of oil supply holes, and the plurality of oil supply holes are evenly distributed on the damper base along the circumferential direction.

8. The magnetic bearing drop protection device based on squeeze film damping according to claim 1, characterized in that: The oil supply hole diameter is set to 4 mm.

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