A porous tilting pad gas thrust bearing with controllable rotational stiffness

Abstract

The present invention discloses a porous tilting pad gas thrust bearing with controllable rotational stiffness, belonging to the technical field of gas bearings; it includes a porous block, a tilting pad, an active control beam and a bearing base, a plurality of tilting pads are provided and evenly spaced in the circumferential direction, each tilting pad and the bearing base are supported and connected by two active control beams, and a porous block with the same outer contour as the tilting pad is bonded and connected to the upper end surface of the tilting pad; the active control beam is composed of an integral bracket, a connecting block, a cylindrical piezoelectric ceramic block, a fastening block and a fastening bolt. The present invention roughly adjusts the rotational stiffness of the active control beam by fastening bolts and fastening blocks, and precisely adjusts the rotational stiffness of the active control beam by cylindrical piezoelectric ceramic blocks, the tilting pad is connected to two active control beam structures, and the rotational stiffness of the tilting pad is adjusted by controlling the stiffness of each active control beam, thereby better regulating the stability characteristics of the bearing and more easily adapting to changes in external loads.

Description

Technical Field

[0001] The invention belongs to the technical field of gas thrust bearings, and in particular relates to a porous tilting pad gas thrust bearing capable of controlling rotational stiffness. Background Art

[0002] As one of the many commonly used gas throttles, the porous throttle has countless pores inside and on the surface, which makes the porous material an excellent throttle. Compared with other throttling methods of dynamic and static pressure gas bearings, it has better bearing capacity, stiffness and uniformity of air film. After the existing porous tilting pad bearing structure is manufactured, its stiffness and damping are fixed values ​​and cannot be adjusted. When the impact external load or the speed is too high, the rotor is prone to vibration, which has a greater impact on the bearing itself and will also cause vortex and oscillation problems, making the rotor unstable.

[0003] The existing solutions are basically based on improving bearing damping to achieve the purpose of improving rotor stability; while there are few methods to reduce bearing vibration from the root by adjusting bearing stiffness. Some existing tilting pad bearings with dampers use squeeze film dampers or some electromagnetic dampers. When using squeeze film, viscous fluid needs to be filled inside, but it is inevitable that oil leakage will cause pollution during operation; the use of electromagnetic dampers can achieve an oil-free working environment, but the need for numerous electromagnetic damping components inevitably increases the cost and complexity of the design.

[0004] For example, the patent application number is CN110686007B, and the invention name is active variable stiffness air bearing based on SMA spring, but it is sensitive to temperature and seriously affected by external temperature. It requires a complete temperature control system, and the structure is complex and the cost is high; for example, the existing document Active metamaterials with broadband controllablestiffness for tunable band gaps and non-reciprocal wavepropagation. The document introduces a method of controlling the rotational stiffness of a beam based on piezoelectric ceramics, but its adjustment range is limited and cannot greatly adjust the stiffness of the beam. In addition, the control method of the above method is basically based on passive control, and still has certain limitations. Its reaction degree and sensitivity limit the application of the above method in high-precision instruments.

[0005] Therefore, there is an urgent need for a bearing structure design that can perform precise adjustment within a large range to expand the use range of the bearing. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art and provide a porous tilting pad gas thrust bearing with controllable rotational stiffness. The main control beam system is composed of an integral bracket, a fastening bolt, a fastening block, a cylindrical piezoelectric ceramic block and a connecting block. The threaded connection structure is used to achieve coarse adjustment of the bearing rotational stiffness, that is, a relatively large adjustment. At the same time, the piezoelectric ceramic sheet is combined to achieve fine adjustment of the bearing rotational stiffness, that is, a small adjustment. The bearing rotational stiffness can be precisely adjusted within a wide range, and the bearing structure design with the ability to adjust the rotational stiffness is simplified.

[0007] To achieve the above object, the present invention adopts the following technical scheme: a porous tilting pad gas thrust bearing with controllable rotational stiffness, comprising a porous block, a tilting pad, an active control beam and a bearing base, wherein a plurality of the tilting pads are provided and are evenly spaced in the circumferential direction, each tilting pad and the bearing base are supported and connected by two active control beams, and the porous block having the same outer contour as the tilting pad is bonded and connected to the upper end surface of the tilting pad;

[0008] The active control beam is composed of an integral bracket, a fastening bolt, a fastening block, a cylindrical piezoelectric ceramic block and a connecting block; the integral bracket is a Chinese-character-shaped internal hollow structure, the centers of the upper and lower end surfaces of the integral bracket are both provided with threaded blind holes and are fixedly connected between the tilting pad and the bearing base by bolts, a blind hole is horizontally provided at one end of the radial inner side of the integral bracket, and a threaded through hole is coaxially provided at the other end to be threadedly matched with the fastening bolt; the connecting block is a cylindrical stepped shape, the small diameter end of which is tightly matched in the blind hole of the integral bracket, and a blind hole is provided in the end face of the large diameter end; the fastening block is a stepped shape, the small diameter is a cylindrical shape, and its end portion is matched and connected in the blind hole of the connecting block, and the large diameter is a hexagonal shape, and a threaded blind hole is provided in the middle of its end face to be threadedly matched with the fastening bolt; the cylindrical piezoelectric ceramic block is a cylindrical sleeve structure, which is matched and sleeved on the small diameter cylinder of the fastening block between the fastening block and the connecting block.

[0009] The radius of the threaded through hole arranged in the radial direction of the integral bracket is the same as the radius of the blind hole, and the radius of the inscribed circle of the large diameter end of the fastening block is twice the radius of the small diameter end.

[0010] The tilting pad is a fan-shaped groove structure, and the porous block is provided with a boss structure that is connected to the fan-shaped groove; two annular pressure-equalizing grooves are provided on the bottom surface of the groove of the tilting pad in the circumferential direction, and an air supply hole connected to the pressure-equalizing groove is provided in the middle of the radial side surface; top countersunk holes are symmetrically provided on both sides of the bottom surface of the groove of the tilting pad, and the top countersunk holes are correspondingly provided with the threaded blind holes at the upper end of the integral bracket and are connected to the top bolts, and the tilting pad is fixedly connected to the active control beam through the top bolts.

[0011] There are three tilting pads, each of which has an angle of 100° to 110°, and the angle between the top countersunk hole and the nearest pad edge is between 10° and 20°.

[0012] The radius of the air supply hole is one third of the thickness of the tilting pad.

[0013] The lower bottom surface of the bearing base is provided with a truncated cone, and four threaded blind holes are evenly distributed along the circumference of the truncated cone, and the bearing base is fixedly connected to the bearing base by bolts; six bottom countersunk holes are distributed on the bearing base located at the outer edge of the truncated cone on the lower bottom surface, and the bottom countersunk holes are correspondingly arranged with the threaded blind holes at the lower end of the integral bracket and are matched and connected with bottom bolts, and the bearing base is fixedly connected to the active control beam by the bottom bolts.

[0014] The included angle between three adjacent bottom countersunk holes is 120°.

[0015] The beneficial effects of the present invention are:

[0016] 1) The present invention adopts an integral bracket, a fastening bolt, a fastening block, a cylindrical piezoelectric ceramic block and a connecting block to form a main control beam system. The system preload is roughly adjusted by the fastening bolts and the fastening block and the cylindrical piezoelectric ceramic block is precisely adjusted. The purpose of changing the rotational stiffness of the tilting pad is achieved by regulating the structure of the two active control beams that cooperate with each other; the stability of the bearing is improved, the application range of the bearing is expanded, the design of the tilting pad porous bearing with a control system is simplified, and the separation structure reduces the difficulty of processing.

[0017] 2) In the bearing structure of the present invention, the force on the integral bracket is roughly adjusted by tightening the bolts and the tightening blocks. When the bolts are pre-tightened, the integral bracket drives the active control beam itself to undergo elastic deformation to increase the stiffness of the active control beam. When the bolts are loosened, the stiffness of the active control beam is reduced. Since a tilting pad is supported by two active control beams, the stiffness of each tilting pad is controlled by the stiffness of the two active control beams. By controlling the bolt pre-tightening force of each active control beam structure respectively, the stiffness of each active control beam is further controlled, thereby achieving rough adjustment of the stiffness of the tilting pad bearing. Similarly, the force on the integral bracket can be precisely adjusted by the cylindrical piezoelectric ceramic block, and then the stiffness of the active control beam can be precisely adjusted to fine-tune the stiffness of the bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an exploded schematic diagram of the tilting pad gas thrust bearing structure of the present invention;

[0019] Figure 2 It is a schematic diagram of the step assembly of the tilting pad gas thrust bearing structure of the present invention;

[0020] Figure 3for Figure 2 A cross-sectional view of

[0021] Figure 4 for Figure 1 Schematic diagram of the structural assembly of the active control beam;

[0022] Figure 5 for Figure 1 Schematic diagram of the structural distribution of the middle tilting pad;

[0023] Figure 6 for Figure 1 Schematic diagram of the bottom bolt distribution of the middle bearing base.

[0024] In the figure, 1-porous block, 2-top bolt, 3-tilt pad, 301-air supply hole, 302-top countersunk hole, 303-pressure equalizing groove, 4-active control beam, 401-integral bracket, 402-fastening bolt, 403-fastening block, 404-cylindrical piezoelectric ceramic block, 405-connecting block, 5-bearing base, 501-threaded blind hole, 502-bottom countersunk hole, 6-bottom bolt. DETAILED DESCRIPTION

[0025] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0026] Example: Figure 1 , 2 As shown in the schematic diagram of the bearing structure, the present invention provides a porous tilting pad gas thrust bearing with controllable rotational stiffness, the bearing comprising a porous block 1, a top bolt 2, a tilting pad 3, an active control beam 4, a bearing base 5 and a bottom bolt 6; the tilting pads 3 are evenly spaced in the circumferential direction, each tilting pad 3 and the bearing base 5 are connected, supported and fixed by two active control beams 4 as bridges, and a porous block 1 with the same outer contour as the tilting pad 3 is glued and connected to the upper end surface of the tilting pad 3, and the porous block 1 is made of graphite block.

[0027] like Figure 4 As shown, the active control beam 4 consists of an integral bracket 401, a fastening bolt 402, a fastening block 403, a cylindrical piezoelectric ceramic block 404 and a connecting block 405; the integral bracket 401 is a Chinese-character-shaped internal hollow structure, and threaded blind holes are opened in the centers of the upper and lower end faces of the axial direction, and the threaded blind hole of the upper end face is fixedly connected to the tilting pad 3 through the top bolt 2, and the threaded blind hole of the lower end face is fixedly connected to the bearing base 5 through the bottom bolt 6; a blind hole is horizontally opened at one end of the radial inner side of the integral bracket 401, and a threaded through hole threadedly connected to the fastening bolt 402 is coaxially opened at the other end, and the radius of the threaded through hole opened in the radial direction is the same as the radius of the blind hole.

[0028] The connecting block 405 is a cylindrical stepped shape, with its small diameter end tightly fitting in the blind hole of the integral bracket 401 and a blind hole opened in the end face of the large diameter end; the fastening block 403 is a stepped shape, with a small diameter being a cylindrical shape and its end portion fittingly connected in the blind hole of the connecting block 405, and a large diameter being a hexagon and a threaded blind hole opened in the middle of its end face for threaded connection with the fastening bolt 402, and the radius of the inscribed circle of the large diameter end of the fastening block 403 is twice the radius of the small diameter end; the cylindrical piezoelectric ceramic block 404 is a cylindrical sleeve structure, which fits and is sleeved on the small diameter cylinder of the fastening block 403 between the fastening block 403 and the connecting block 405.

[0029] like Figure 2 , 3 , 5 and the structural diagram of the tilting pad shown in the figure, the tilting pad 3 is a fan-shaped groove structure, the porous block 1 is provided with a boss structure matched with its fan-shaped groove, the boss of the porous block 1 is matched with and connected in the fan-shaped groove of the tilting pad 3; two annular pressure equalizing grooves 303 with the same width are opened on the bottom surface of the groove of the tilting pad 3 in the circumferential direction, and an air supply hole 301 connected with the pressure equalizing groove 303 is opened in the middle of the radial side surface, top countersunk holes 302 are symmetrically opened on both sides of the bottom surface of the groove of the tilting pad 3, the top countersunk holes 302 are arranged corresponding to the threaded blind holes at the upper end of the integral bracket 401 and matched with the top bolts 2, and the tilting pad 3 is fixedly connected to the active control beam 4 through the top bolts 2.

[0030] Three tilting pads 3 are installed, three corresponding porous blocks 1 are installed, and six active control beams 4 are installed; there is an angle α between two adjacent tilting pads 3 in the circumferential direction, and the range of α is 10°~20°, and α determines the bearing capacity of the bearing; the angle of each tilting pad 3 is 100°~110°, and the sum of the angles occupied by α and the tilting pad 3 is 120°; the corresponding porous blocks 1 also have an angle α, and the porous blocks 1 are equistep-shaped, and the thickness of each layer is the same.

[0031] The radius of the air supply hole 301 is one third of the thickness of the tilting pad 3; the top countersunk hole 302 has an angle β with the pad edge closest to it, and the angle range of β is between 10° and 20°. The top countersunk hole 302 has an angle γ with the center line of the pad, and the sum of α, β and twice γ is 120°; β and γ determine the range of change of the bearing stiffness affected by the active control beam stiffness, and the larger β and γ are, the larger the range of change of the bearing stiffness is; α used in the present invention is 10°, β is 15°, and γ is 40°. Under this parameter, the position of the threaded hole will not affect the adhesion of the porous block, and the bearing can also maintain a high load-bearing capacity. At the same time, its stiffness also has a higher range of variation.

[0032] like Figure 6The bottom bolt distribution diagram of the bearing base is shown, the lower bottom surface of the bearing base 5 is provided with a truncated cone, four threaded blind holes 501 are evenly distributed along the circumference of the truncated cone, and the bearing base 5 is fixedly connected to the bearing base by bolts; six bottom countersunk holes 502 are distributed on the bearing base 5 located at the outer edge of the truncated cone on the lower bottom surface, and the angle between three adjacent bottom countersunk holes 502 is 120°, the bottom countersunk holes 502 and the threaded blind holes at the lower end of the integral bracket 401 are correspondingly arranged and matched with bottom bolts 6, and the bearing base 5 is fixedly connected to the active control beam 4 through the bottom bolts 6.

[0033] Working principle:

[0034] The preload force of the integrated bracket can be roughly adjusted by changing the depth of the thread fit between the fastening bolt and the fastening block. During the rough adjustment, one turn of the thread can increase or decrease the stiffness of the entire active control beam structure by 5%.

[0035] The preload force can also be precisely adjusted through the cylindrical piezoelectric ceramic block to cause elastic deformation of the integral bracket and thus change its stiffness. If a cylindrical piezoelectric ceramic with an outer diameter of 1mm and an inner diameter of 0.5mm is selected, the bearing stiffness can be adjusted by 0.1% when the power-on voltage is 150V.

[0036] In the bearing structure of the present invention, two active control beam structures connect the tilting pad to the bearing base by using top bolts and bottom bolts, and the purpose of changing the rotational stiffness of the tilting pad is achieved by controlling the stiffness of the two active control beam structures.

[0037] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A porous tilting pad gas thrust bearing with controllable rotational stiffness, Features: It comprises a porous block (1), a tilting pad (3), an active control beam (4) and a bearing base (5), wherein a plurality of the tilting pads (3) are arranged and are evenly spaced in the circumferential direction, each tilting pad (3) and the bearing base (5) are supported and connected by two active control beams (4), and the porous block (1) having the same outer contour as the tilting pad (3) is bonded to the upper end surface of the tilting pad (3); The active control beam (4) is composed of an integral bracket (401), a fastening bolt (402), a fastening block (403), a cylindrical piezoelectric ceramic block (404) and a connecting block (405); the integral bracket (401) is a Chinese-shaped internal hollow structure, the centers of the upper and lower end surfaces of the integral bracket (401) are both provided with threaded blind holes and are fixedly connected between the tilting pad (3) and the bearing base (5) by bolts, one end of the radial inner side of the integral bracket (401) is horizontally provided with a blind hole, and the other end is coaxially provided with a threaded through hole threadably connected to the fastening bolt (402); the connecting block (405) is a cylindrical stepped shape, with one end of the small diameter tightly fitting in the blind hole of the integral bracket (401), and a blind hole is arranged in the end face of the large diameter end; the fastening block (403) is a stepped shape, with a small diameter of a cylinder and its end portion fittingly connected in the blind hole of the connecting block (405), and a large diameter of a hexagon and a threaded blind hole threadedly connected to the fastening bolt (402) is arranged in the middle of the end face; the cylindrical piezoelectric ceramic block (404) is a cylindrical sleeve structure, which is fitted and sleeved on the small diameter cylinder of the fastening block (403) between the fastening block (403) and the connecting block (405).

2. A porous tilting pad gas thrust bearing with controllable rotational stiffness according to claim 1, Features: The radius of the threaded through hole provided in the radial direction of the integral bracket (401) is the same as the radius of the blind hole, and the radius of the inscribed circle of the large diameter end of the fastening block (403) is twice the radius of the small diameter end.

3. A porous tilting pad gas thrust bearing with controllable rotational stiffness according to claim 1, Features: The tilting pad (3) is a fan-shaped groove structure, and the porous block (1) is provided with a boss structure that is matched and connected with the fan-shaped groove; two annular pressure equalizing grooves (303) are provided on the bottom surface of the groove of the tilting pad (3) along the circumferential direction, and an air supply hole (301) connected with the pressure equalizing groove (303) is provided in the middle of the radial side surface; top countersunk holes (302) are symmetrically provided on both sides of the bottom surface of the groove of the tilting pad (3); the top countersunk holes (302) and the threaded blind holes at the upper end of the integral bracket (401) are correspondingly provided and matched and connected with top bolts (2); the tilting pad (3) is fixedly connected to the active control beam (4) through the top bolts (2).

4. A porous tilting pad gas thrust bearing with controllable rotational stiffness according to claim 3, Features: Three tilting pads (3) are provided, each tilting pad (3) has an angle of 100° to 110°, and the angle between the top countersunk hole (302) and the pad edge closest thereto is between 10° and 20°.

5. A porous tilting pad gas thrust bearing with controllable rotational stiffness according to claim 3, Features: The radius of the air supply hole (301) is one third of the thickness of the tilting pad (3).

6. A porous tilting pad gas thrust bearing with controllable rotational stiffness according to claim 1, Features: The lower bottom surface of the bearing base (5) is provided with a truncated cone, and four threaded blind holes (501) are evenly distributed along the circumference of the truncated cone, and the bearing base (5) is fixedly connected to the bearing base by bolts; six bottom countersunk holes (502) are distributed on the bearing base (5) at the outer edge of the truncated cone on the lower bottom surface, and the bottom countersunk holes (502) are correspondingly arranged with the threaded blind holes at the lower end of the integral bracket (401) and are matched and connected with bottom bolts (6), and the bearing base (5) is fixedly connected to the active control beam (4) by the bottom bolts (6).

7. A porous tilting pad gas thrust bearing with controllable rotational stiffness according to claim 6, Features: The included angle between three adjacent bottom countersunk holes (502) is 120°.

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