Energy storage flywheel with out-of-control protection function

Abstract

The invention discloses an energy storage flywheel with an out-of-control protection function. The upper end and the lower end of a flywheel rotor are each provided with a concave cavity, a radial magnetic bearing assembly comprises a support, a radial magnetic bearing rotor and a radial magnetic bearing stator, and the support penetrates through a top plate and a bottom plate and extends into the corresponding concave cavities; the hydraulic protection bearing assembly comprises a hydraulic control piece and a protection bearing, the hydraulic control piece is installed on the upper end face of the support at the bottom, the protection bearing is installed at the upper end of the hydraulic control piece, and a supporting clamping plate is arranged on the bottom wall of a concave cavity at the end and provided with a clamping groove concaved upwards. The hydraulic control piece is used for controlling the protection bearing to move in the vertical direction so as to be matched with or separated from the clamping groove. The protection bearing of the energy storage flywheel with the out-of-control protection function can actively jack up and support the flywheel rotor at the initial stage of out-of-control of the flywheel rotor, and the flywheel rotor cannot fall off, so that accidental risks in the falling process can be avoided, and meanwhile, the risk that the flywheel rotor falls to impact and damage the protection bearing can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage devices, and in particular, to an energy storage flywheel with an out-of-control protection function. Background Art

[0002] The flywheel energy storage system is an efficient and energy-saving inertial energy storage device. It stores energy by means of a flywheel rotating at a super-high speed, and realizes the mutual conversion of mechanical energy and electrical energy through an electromechanical energy conversion device.

[0003] In the related art, the flywheel rotor may have an accidental out-of-control problem during high-speed rotation. Conventional flywheels usually set mechanical protection bearings to support the flywheel after it gets out of control, playing a protective role. However, the activation of the mechanical protection bearings is passive. Other accidents may occur during the falling process of the out-of-control flywheel. In addition, the falling of the out-of-control flywheel will carry a large potential energy and collide with the mechanical protection bearings, which may cause damage to the protection bearings at the initial stage of contact. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent.

[0005] Therefore, an embodiment of the present invention provides an energy storage flywheel with an out-of-control protection function. The protection bearing of the energy storage flywheel with an out-of-control protection function can actively jack up and support the flywheel rotor at the initial stage of the out-of-control of the flywheel rotor (when there is an axial deviation trend), so that the flywheel rotor will not fall, thereby avoiding accidental risks during the falling process and at the same time avoiding the risk of the flywheel rotor falling and hitting and damaging the protection bearing.

[0006] An energy storage flywheel with an out-of-control protection function according to an embodiment of the present invention includes: a housing; a flywheel rotor disposed within the housing, with concave cavities at both the upper and lower ends of the flywheel rotor; a radial magnetic bearing assembly including a bracket, a radial magnetic bearing rotor, and a radial magnetic bearing stator, where the radial magnetic bearing rotor is installed on the inner circumferential surface of the concave cavity and is arranged in a ring along the circumferential direction of the concave cavity, the bracket passes through the top plate and the bottom plate of the housing respectively and extends into the corresponding concave cavity, and the radial magnetic bearing stator is a plurality of uniformly spaced along the circumferential direction of the bracket; an axial magnetic bearing assembly including an axial magnetic bearing stator and an axial magnetic bearing rotor, where the axial magnetic bearing stator is disposed on the bracket, and the axial magnetic bearing rotor is disposed on the bottom wall of the concave cavity and is opposite to the axial magnetic bearing stator; a hydraulic protection bearing assembly including a hydraulic control member and a protection bearing, where the hydraulic control member is installed on the upper end surface of the bottom bracket, the protection bearing is installed on the upper end of the hydraulic control member, a support clamping plate is provided on the bottom wall of the concave cavity at the lower end of the flywheel rotor, the support clamping plate has a downwardly concave card slot, and the hydraulic control member is used to control the up-and-down movement of the protection bearing to cooperate with or separate from the card slot.

[0007] For the energy storage flywheel with an out-of-control protection function according to an embodiment of the present invention, concave cavities are provided at both the upper and lower ends of the flywheel rotor. The radial magnetic bearing assembly includes a bracket, a radial magnetic bearing rotor, and a radial magnetic bearing stator. The radial magnetic bearing rotor is installed on the inner circumferential surface of the concave cavity and is arranged in a ring along the circumferential direction of the concave cavity. The bracket passes through the top plate and the bottom plate of the housing respectively and extends into the corresponding concave cavity. The radial magnetic bearing stator is a plurality of uniformly spaced along the circumferential direction of the bracket. The hydraulic protection bearing assembly includes a hydraulic control member and a protection bearing. The hydraulic control member is installed on the upper end surface of the bottom bracket, and the protection bearing is installed on the upper end of the hydraulic control member. A support clamping plate is provided on the bottom wall of the concave cavity at the lower end of the flywheel rotor. The support clamping plate has a downwardly concave card slot. The hydraulic control member is used to control the up-and-down movement of the protection bearing to cooperate with or separate from the card slot. Thus, the protection bearing of the present application can actively jack up and support the flywheel rotor at the initial stage of out-of-control of the flywheel rotor (when there is an axial deviation trend), and the flywheel rotor will not fall, thereby avoiding accidental risks during the falling process and also avoiding the risk of damage to the protection bearing caused by the falling impact of the flywheel rotor.

[0008] In some embodiments, an oil passage is provided within the bracket, with one end of the oil passage communicating with an external oil supply device and the other end communicating with the hydraulic control member.

[0009] In some embodiments, an axial sensor is provided on the lower end face of the bracket at the upper end. The energy storage flywheel with runaway protection function further includes a controller, and the controller can control the hydraulic control member to act according to the detection information of the axial sensor.

[0010] In some embodiments, the radial magnetic bearing stator includes a first layer and a second layer arranged axially on the flywheel rotor, and a plurality of the radial magnetic bearing stators in the first layer and a plurality of the radial magnetic bearing stators in the second layer are alternately arranged circumferentially on the flywheel rotor.

[0011] In some embodiments, counterweight rings extending inward are connected to both the top and the bottom of the flywheel rotor. The inner peripheral surface of the concave cavity has a groove, and the counterweight ring is located at the notch of the groove and holds the radial magnetic bearing rotor.

[0012] In some embodiments, the axial magnetic bearing rotor includes an axial permanent magnet magnetic bearing rotor and a disc motor rotor. The axial permanent magnet magnetic bearing rotor is provided on the bottom wall of the concave cavity at the lower end, and the disc motor rotor is provided on the bottom wall of the concave cavity at the upper end. The axial magnetic bearing stator includes an axial permanent magnet magnetic bearing stator and a disc motor stator. The axial magnetic bearing stator is provided on the bracket at the bottom and is opposite to the axial permanent magnet magnetic bearing rotor, and the disc motor stator is provided on the bracket at the top and is opposite to the disc motor rotor.

[0013] In some embodiments, the flywheel rotor includes a hub and an energy storage ring sleeved on the outer periphery of the hub, and the energy storage ring is a multi-layer stacked axially along the hub.

[0014] In some embodiments, the outer peripheral surface of the hub has a plurality of assembly grooves arranged at intervals along its circumferential direction, and the inner peripheral surface of the energy ring has a plurality of adapted assembly protrusions.

[0015] In some embodiments, the outer peripheral surface of the hub has a structure that protrudes in the middle and gradually contracts at both ends in the axial direction of the hub.

[0016] In some embodiments, an elastic support layer is sleeved on the middle protrusion of the hub. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of an energy storage flywheel with runaway protection function according to an embodiment of the present invention.

[0018] Figure 2 is a schematic structural diagram of the radial magnetic bearing stator of an energy storage flywheel with runaway protection function according to an embodiment of the present invention.

[0019] Figure 3It is a schematic diagram of the double-layer arrangement of the radial magnetic bearing stator of the energy storage flywheel with runaway protection function according to an embodiment of the present invention.

[0020] Reference numerals:

[0021] Housing 1, bracket 2, axial sensor 3, radial magnetic bearing stator 4, radial magnetic bearing rotor 5, axial magnetic bearing stator 6, axial magnetic bearing rotor 7, hydraulic control member 8, protection bearing 9, support clamping plate 10, flywheel rotor 11, hub 111, energy storage ring 112, elastic support layer 12, counterweight ring 13, fuel injection device 14. Detailed implementation manners

[0022] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0023] As Figures 1 - 3 shown, the energy storage flywheel with runaway protection function according to an embodiment of the present invention includes a housing 1, a flywheel rotor 11, a radial magnetic bearing assembly, an axial magnetic bearing assembly, and a hydraulic protection bearing 9 assembly.

[0024] Specifically, the flywheel rotor 11 is disposed inside the housing 1. Both the upper and lower ends of the flywheel rotor 11 have concave cavities. The radial magnetic bearing assembly includes a bracket 2, a radial magnetic bearing rotor 5, and a radial magnetic bearing stator 4. The radial magnetic bearing rotor 5 is installed on the inner circumferential surface of the concave cavity and is arranged in a ring shape along the circumferential direction of the concave cavity. The bracket 2 respectively passes through the top plate and the bottom plate of the housing 1 and extends into the corresponding concave cavities. The radial magnetic bearing stator 4 is a plurality of pieces evenly spaced along the circumferential direction of the bracket 2. The axial magnetic bearing assembly includes an axial magnetic bearing stator 6 and an axial magnetic bearing rotor 7. The axial magnetic bearing stator 6 is disposed on the bracket 2. The axial magnetic bearing rotor 7 is disposed on the bottom wall of the concave cavity and is opposite to the axial magnetic bearing stator 6. The hydraulic protection bearing 9 assembly includes a hydraulic control member 8 and a protection bearing 9. The hydraulic control member 8 is installed on the upper end surface of the bottom bracket 2. The protection bearing 9 is installed on the upper end of the hydraulic control member 8. A support clamping plate 10 is provided on the bottom wall of the concave cavity at the lower end of the flywheel rotor 11. The support clamping plate 10 has a downwardly concave card slot. The hydraulic control member 8 is used to control the protection bearing 9 to move in the up and down directions to cooperate with or separate from the card slot.

[0025] It can be understood that when the flywheel rotor 11 gets out of control, the hydraulic control part 8 can jack up the protective bearing 9 upwards. After the protective bearing 9 is engaged with the card slot, it can support the out-of-control flywheel rotor 11 to maintain its rotation and achieve the protective effect. Different from the traditional protective bearing 9, the protective bearing 9 of the present application can actively jack up and support the flywheel rotor 11 at the initial stage of the out-of-control of the flywheel rotor 11 (when there is an axial deviation trend), and the flywheel rotor 11 will not fall, thus avoiding accidental risks during the falling process and at the same time avoiding the risk of the flywheel rotor 11 falling and hitting to damage the protective bearing 9.

[0026] For the energy storage flywheel with out-of-control protection function in the embodiment of the present invention, both the upper and lower ends of the flywheel rotor 11 have concave cavities. The radial magnetic bearing assembly includes a bracket 2, a radial magnetic bearing rotor 5 and a radial magnetic bearing stator 4. The radial magnetic bearing rotor 5 is installed on the inner peripheral surface of the concave cavity and is arranged in a ring along the circumferential direction of the concave cavity. The bracket 2 passes through the top plate and the bottom plate of the housing 1 respectively and extends into the corresponding concave cavities. The radial magnetic bearing stators 4 are multiple and are evenly spaced along the circumferential direction of the bracket 2. The hydraulic protection bearing 9 assembly includes a hydraulic control part 8 and a protective bearing 9. The hydraulic control part 8 is installed on the upper end surface of the bottom bracket 2, and the protective bearing 9 is installed on the upper end of the hydraulic control part 8. A support card plate 10 is provided on the bottom wall of the concave cavity at the lower end of the flywheel rotor 11. The support card plate 10 has a card slot sunken upwards. The hydraulic control part 8 is used to control the up-and-down movement of the protective bearing 9 to cooperate with or separate from the card slot. Thus, the protective bearing 9 of the present application can actively jack up and support the flywheel rotor 11 at the initial stage of the out-of-control of the flywheel rotor 11 (when there is an axial deviation trend), and the flywheel rotor 11 will not fall, thus avoiding accidental risks during the falling process and at the same time avoiding the risk of the flywheel rotor 11 falling and hitting to damage the protective bearing 9.

[0027] Further, an oil passage is provided in the bracket 2. One end of the oil passage communicates with an external oil supply device, and the other end communicates with the hydraulic control part 8. Thus, the oil passage can be used to supply oil to the hydraulic control part 8, eliminating the need to separately set up an oil supply pipeline and optimizing the overall structure of the energy storage flywheel.

[0028] In some embodiments, as Figure 1 shown, an axial sensor 3 is provided on the lower end surface of the upper bracket 2. The energy storage flywheel with out-of-control protection function further includes a controller. The controller can control the action of the hydraulic control part 8 according to the detection information of the axial sensor 3. Thus, the axial sensor 3, the controller and the hydraulic control part 8 can form a control feedback system to realize the intelligent control of the protective bearing 9 to respond and jack up in real time according to the rotation state of the flywheel.

[0029] Specifically, when the axial sensor 3 detects that the flywheel rotor 11 is axially unstable, the controller can determine that the flywheel rotor 11 is about to get out of control at this time, and then send an instruction to the hydraulic control member 8 and control the protective bearing 9 to move upward until it contacts the support clamping plate 10 to support the flywheel rotor 11.

[0030] Further, as Figure 1 and Figure 3 shown, the radial magnetic bearing stator 4 includes a first layer and a second layer arranged axially on the flywheel rotor 11, and a plurality of the radial magnetic bearing stators 4 in the first layer and a plurality of the radial magnetic bearing stators 4 in the second layer are alternately arranged circumferentially on the flywheel rotor 11. Thus, the double-layer radial magnetic bearing stator 4 can provide greater magnetic force support to meet the stability maintenance requirements of the flywheel rotor 11 under high-speed rotation. In addition, the two layers of radial magnetic bearing stators 4 are alternately arranged, which can increase the adjustment freedom and realize multi-angle and multi-direction support for the flywheel rotor 11, with better stability.

[0031] Further, as Figure 1 shown, weight rings 13 extending inward are connected to both the top and bottom of the flywheel rotor 11. The inner peripheral surface of the concave cavity has a groove, and the weight rings 13 are located at the notch of the groove and hold the radial magnetic bearing rotor 5. Thus, holes can be drilled in the weight rings 13 as needed to maintain the dynamic balance of the flywheel rotor 11 without damaging the hub 111 structure of the flywheel rotor 11.

[0032] In some embodiments, as Figure 1 shown, the axial magnetic bearing rotor 7 includes an axial permanent magnetic bearing rotor and a disc motor rotor. The axial permanent magnetic bearing rotor is provided on the bottom wall of the concave cavity at the lower end, and the disc motor rotor is provided on the bottom wall of the concave cavity at the upper end. The axial magnetic bearing stator 6 includes an axial permanent magnetic bearing stator and a disc motor stator. The axial magnetic bearing stator 6 is provided on the bracket 2 at the bottom and is opposite to the axial permanent magnetic bearing rotor, and the disc motor stator is provided on the bracket 2 at the top and is opposite to the disc motor rotor. Thus, the upper disc motor rotor and the disc motor stator form an axially active control magnetic bearing, and the axial permanent magnetic bearing stator and the axial permanent magnetic bearing rotor at the lower end form a radially passive control magnetic bearing. The combination of the two can realize the active adjustment of the magnetic force to meet the balance requirements of the flywheel rotor 11 in different states. Moreover, the disc motor structure has a small volume and occupies little installation space, and the disc motor structure can drive the rotation of the flywheel rotor 11, so there is no need to set up a driving motor externally, further optimizing the structure of the energy storage flywheel.

[0033] Further, as Figure 1As shown, the flywheel rotor 11 includes a hub 111 and an energy storage ring 112 sleeved on the outer periphery of the hub 111. The energy storage ring 112 is a multi-layer structure stacked along the axial direction of the hub 111 to improve the energy density of the energy storage flywheel by using the multi-layer energy storage ring 112.

[0034] Furthermore, the outer peripheral surface of the hub 111 has a plurality of assembly grooves arranged at intervals along its circumferential direction, and the inner peripheral surface of the energy ring has a plurality of adapted assembly protrusions. Specifically, the energy ring can be assembled by sleeving it on one end of the hub 111, and the assembly grooves and the assembly protrusions can play a role in locking and fixing. Preferably, the assembly groove is a T-shaped groove, which can achieve radial anti-disengagement.

[0035] Furthermore, as Figure 1 shown, the outer peripheral surface of the hub 111 has a structure that is convex in the middle and gradually shrinks at both ends in the axial direction of the hub 111. An elastic support layer 12 is sleeved at the middle convex portion of the hub 111. Thus, the outer peripheral surface of the hub 111 has an inclined surface structure that shrinks at both sides and is convex in the middle. When the flywheel rotor 11 rotates at a high speed, the energy storage ring 112 will move along the inclined surface towards the middle part and squeeze the elastic support layer 12 after being stressed. The inner diameter ring surface of the energy storage ring 112 will become larger, which can offset a part of the pulling force on the hub 111, allowing the energy storage ring 112 to bear this part of the force by itself, reducing the influence of the pulling force on the hub 111, ensuring the safety of the hub 111, and also making full use of the material strength of the energy storage ring 112.

[0036] Furthermore, an oil injection device 14 is also provided on the outer peripheral surface of the bracket 2. When the axial sensor 3 detects that the flywheel rotor 11 is out of control, the oil injection device 14 can inject oil towards the end face of the radial magnetic bearing rotor 5 to play a role in lubrication and protection, reducing the contact wear between the radial magnetic bearing stator 4 and the radial magnetic bearing rotor 5.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0038] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0039] In the present invention, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0041] In the present invention, terms such as "an embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0042] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. An energy storage flywheel with a runaway protection function, characterized in that: include: case: A flywheel rotor, the flywheel rotor is arranged in the housing, and the upper and lower ends of the flywheel rotor both have concave cavities; A radial magnetic bearing assembly, the radial magnetic bearing assembly comprising a bracket, a radial magnetic bearing rotor and a radial magnetic bearing stator, the radial magnetic bearing rotor being mounted on the inner circumferential surface of the concave cavity and being arranged in an annular shape along the circumference of the concave cavity, the bracket respectively passing through the top plate and the bottom plate of the shell and extending into the corresponding concave cavity, the radial magnetic bearing stator being a plurality of stators evenly spaced along the circumference of the bracket; An axial magnetic bearing assembly, the axial magnetic bearing assembly comprising an axial magnetic bearing stator and an axial magnetic bearing rotor, the axial magnetic bearing stator being arranged on the bracket, and the axial magnetic bearing rotor being arranged on the bottom wall of the concave cavity and opposite to the axial magnetic bearing stator; A hydraulic protective bearing assembly, the hydraulic protective bearing assembly includes a hydraulic control component and a protective bearing, the hydraulic control component is installed on the upper end surface of the bracket at the bottom, the protective bearing is installed on the upper end of the hydraulic control component, a supporting card plate is provided on the bottom wall of the concave cavity at the lower end of the flywheel rotor, the supporting card plate has an upwardly recessed slot, and the hydraulic control component is used to control the movement of the protective bearing in the up and down directions to cooperate with or separate from the slot.

2. The energy storage flywheel with fail-safe protection function according to claim 1, characterized in that: An oil passage is provided in the bracket, one end of the oil passage is connected to an external oil supply device, and the other end is connected to the hydraulic control component.

3. The energy storage flywheel with fail-safe function according to claim 1, characterized in that: An axial sensor is provided on the lower end surface of the bracket at the upper end. The energy storage flywheel with a fail-safe protection function also includes a controller, and the controller can control the action of the hydraulic control component according to the detection information of the axial sensor.

4. The energy storage flywheel with fail-safe protection function according to claim 1, characterized in that: The radial magnetic bearing stator includes a first layer and a second layer arranged in the axial direction of the flywheel rotor, and the plurality of radial magnetic bearing stators in the first layer and the plurality of radial magnetic bearing stators in the second layer are alternately arranged in the circumferential direction of the flywheel rotor.

5. The energy storage flywheel with fail-safe function according to claim 1, characterized in that: The top and bottom of the flywheel rotor are both connected with a counterweight ring extending inwardly, the inner circumferential surface of the concave cavity is provided with a groove, the counterweight ring is located at the notch of the groove and clamps the radial magnetic bearing rotor.

6. The energy storage flywheel with fail-safe function according to claim 1, characterized in that: The axial magnetic bearing rotor includes an axial permanent magnetic bearing rotor and a disc motor rotor. The axial permanent magnetic bearing rotor is arranged on the bottom wall of the concave cavity at the lower end, and the disc motor rotor is arranged on the bottom wall of the concave cavity at the upper end. The axial magnetic bearing stator includes an axial permanent magnetic bearing stator and a disc motor stator. The axial magnetic bearing stator is arranged on the bracket at the bottom and opposite to the axial permanent magnetic bearing rotor, and the disc motor stator is arranged on the bracket at the top and opposite to the disc motor rotor.

7. The energy storage flywheel with fail-safe protection function according to claim 1, characterized in that: The flywheel rotor comprises a hub and an energy storage ring sleeved on the outer periphery of the hub, and the energy storage ring is a plurality of layers stacked along the axial direction of the hub.

8. The energy storage flywheel with fail-safe protection function according to claim 7, characterized in that: The outer peripheral surface of the hub has a plurality of assembly grooves arranged at intervals along the circumference thereof, and the inner peripheral surface of the energy ring has a plurality of matching assembly protrusions.

9. The energy storage flywheel with fail-safe protection function according to claim 1, characterized in that: The outer peripheral surface of the hub is in a structure in which the middle is convex and the two ends are gradually contracted in the axial direction of the hub.

10. The energy storage flywheel with fail-safe protection function according to claim 9, characterized in that: An elastic supporting layer is sleeved on the middle protrusion of the hub.

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