A radial foil bearing

Abstract

The utility model belongs to bearing technical field relates to a radial foil bearing. The utility model, including the bearing seat main body, the coaxial installation of wave foil and top foil has in bearing seat main body, the uniform distribution of several axial extension's guide groove has in the bearing seat main body inner wall along the axial direction, wave foil is equipped with the guide alignment spare that extends and enters into the guide groove one end close to the bearing seat main body inner wall. The utility model in the use process, through the guide groove of bearing seat inner wall and the guide alignment spare cooperation of wave foil, limit the circumferential of wave foil and move, guarantee the coaxial degree of wave foil and top foil, avoid lubricating film gap abnormality, simultaneously the multidirectional elastic support structure of wave foil inside and outside two sides can provide elastic force from two -way, adapt radial multidirectional load, improve the carrying capacity and vibration absorption performance of bearing.

Description

Technical Field

[0001] This utility model belongs to the field of bearing technology and relates to a radial foil bearing. Background Technology

[0002] Radial foil bearings, as a type of non-contact bearing lubricated by gas or liquid, offer advantages such as adaptability to high speeds, high temperatures, and low friction, and are widely used in aerospace, turbomachinery, and precision machine tools. The core structure of existing radial foil bearings typically includes a bearing housing, corrugated foil, and top foil. The corrugated foil acts as an elastic support, providing elastic cushioning for the top foil through its own deformation. The top foil contacts the journal to form a lubricating film, achieving contactless operation. However, existing technologies have the following shortcomings: 1. Poor corrugated foil positioning stability: The lack of a precise guiding structure between the corrugated foil and the bearing housing makes it prone to circumferential movement during high-speed operation or load changes, resulting in uneven contact gap between the top foil and the journal, affecting the stability of the lubrication film; 2. Unidirectional elastic support: Traditional corrugated foils are mostly unidirectional arched structures, which can only provide elastic buffering in one direction, making it difficult to adapt to multi-directional loads (such as radial off-center loads and axial micro-vibrations), and limiting their load-bearing capacity and vibration resistance; 3. Inconvenient disassembly and maintenance: The fixing of the corrugated foil to the bearing housing and the top foil to the bearing housing mostly adopts welding or integrated structure. When components wear or fail, the entire assembly needs to be replaced, resulting in high maintenance costs; 4. Limited top foil performance: The top foil needs to meet both wear resistance and elasticity requirements simultaneously, which is difficult to achieve with a single material, leading to short service life or poor adaptability. Therefore, there is an urgent need to design a radial foil bearing that can overcome the above defects.

[0003] To overcome the shortcomings of existing technologies, people have continuously explored and proposed various solutions. For example, a Chinese patent discloses a radial foil air bearing [application number: 202111545415.3], which includes a bearing sleeve and a thick top foil coaxially installed inside the bearing sleeve. The annular gap between the bearing sleeve and the thick top foil is filled with a metal mesh, which extends circumferentially. The first end of the circumferential direction of the metal mesh is fixedly connected to the bearing sleeve, while the last end of the circumferential direction of the metal mesh is free. However, this solution still has drawbacks in use, such as poor foil positioning stability, unidirectional elastic support, inconvenient disassembly and maintenance, and limited top foil performance. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a radial foil bearing.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A radial foil bearing includes a bearing housing body. A corrugated foil and a top foil are coaxially mounted inside the bearing housing body. A plurality of axially extending guide grooves are evenly distributed along the axial direction on the inner wall of the bearing housing body. A guide alignment member extending into the guide groove is provided at one end of the corrugated foil near the inner wall of the bearing housing body. Multi-directional elastic support structures are provided on the inner and outer sides of the corrugated foil. The inner wall of the bearing housing body and the outer peripheral surface of the top foil respectively abut against the multi-directional elastic support structures. A fixing connector for fixing the corrugated foil is provided between the corrugated foil and the bearing housing body. The fixing connector, the guide alignment member, and the multi-directional elastic support structure are staggered. Detachable auxiliary overlapping members for fixing the top foil are provided at both ends of the bearing housing body.

[0006] In the aforementioned radial foil bearing, the multi-directional elastic support structure includes an inner elastic metal foil and an outer elastic metal foil disposed on the inner and outer sides of the corrugated foil. Both the inner and outer elastic metal foils are arched. The inner elastic metal foil abuts against the outer peripheral surface of the top foil, and the outer elastic metal foil abuts against the inner wall of the bearing housing body.

[0007] In the aforementioned radial foil bearing, an elastic buffer space is formed between the inner elastic metal foil and the top foil, and an elastic buffer space is formed between the outer elastic metal foil and the inner wall of the bearing housing body. The outer elastic metal foil, the guide alignment member, and the fixed connection member are arranged alternately.

[0008] In the aforementioned radial foil bearing, the guide alignment member includes a plurality of guide protrusions disposed on the outer side of the corrugated foil. The guide protrusions extend into the guide groove, and the guide protrusions are alternately arranged with the outer elastic metal foil.

[0009] In the aforementioned radial foil bearing, the fixed connector includes several connecting baffles disposed at both ends of the bearing housing body. The connecting baffles are arranged in a circular array along the axis of the bearing housing body. A connector is provided on the outer side of the corrugated foil, and the connector is connected to the connecting baffles.

[0010] In the aforementioned radial foil bearing, the connecting member includes several connecting inner plates disposed on the outer side of the corrugated foil. The connecting inner plates are provided with positioning holes, and the connecting baffles are provided with positioning holes. The connecting inner plates and the connecting baffles are fixed together by positioning pins.

[0011] In the aforementioned radial foil bearing, the connecting inner plate and the connecting baffle are respectively staggered with the outer elastic metal foil.

[0012] In the aforementioned radial foil bearing, the detachable auxiliary lap joint includes a plurality of lap fixing rods disposed at both ends of the bearing housing body, the lap fixing rods abutting against the two end faces of the top foil.

[0013] In the aforementioned radial foil bearing, the bearing housing body has several rod-body embedded grooves, and the overlapping fixing rod is embedded in the rod-body embedded grooves. The cross-section of the overlapping fixing rod is L-shaped.

[0014] In the aforementioned radial foil bearing, the top foil is composed of an outer wear-resistant layer and an inner elastic substrate. The outer wear-resistant layer is made of polytetrafluoroethylene composite material, and the inner elastic substrate is made of beryllium bronze.

[0015] Compared with existing technologies, the advantages of this utility model are: 1. This utility model uses the guide groove on the inner wall of the bearing housing to cooperate with the guide alignment component of the corrugated foil to restrict the circumferential movement of the corrugated foil, ensure the coaxiality of the corrugated foil and the top foil, and avoid abnormal lubrication film gap. At the same time, the multi-directional elastic support structure on the inner and outer sides of the corrugated foil can provide elastic force from both directions, adapt to radial multi-directional loads, and improve the bearing capacity and vibration absorption performance of the bearing.

[0016] 2. This utility model avoids interference between components by interleaving fixed connectors, guide alignment components and multi-directional elastic support structures, ensuring that each structure functions independently and works collaboratively. In addition, the design of detachable auxiliary overlapping components and fixed connectors allows the top foil and corrugated foil to be disassembled and replaced separately, reducing maintenance costs.

[0017] 3. The composite structure of the top foil in this utility model combines wear resistance and elasticity, extending service life and improving compatibility with journals.

[0018] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0019] Figure 1 This is an assembly diagram of the present invention.

[0020] Figure 2 This is a cross-sectional schematic diagram of the bearing housing body.

[0021] Figure 3 This is a schematic diagram of the cross-section of the corrugated foil.

[0022] Figure 4 This is a cross-sectional diagram of the lapped fixing rod.

[0023] In the figure: 1. Bearing housing body, 2. Corrugated foil, 3. Top foil, 4. Guide groove, 5. Guide alignment component, 6. Multi-directional elastic support structure, 7. Fixed connector, 8. Detachable auxiliary overlap component, 9. Inner elastic metal foil, 10. Outer elastic metal foil, 11. Guide protrusion, 12. Connecting baffle, 13. Connecting inner plate, 14. Overlap fixing rod. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] like Figure 1-4 As shown, a radial foil bearing includes a bearing housing body 1. A corrugated foil 2 and a top foil 3 are coaxially mounted inside the bearing housing body 1. Several axially extending guide grooves 4 are evenly distributed along the axial direction on the inner wall of the bearing housing body 1. A guide alignment member 5 extending into the guide groove 4 is provided at one end of the corrugated foil 2 near the inner wall of the bearing housing body 1. Multi-directional elastic support structures 6 are provided on the inner and outer sides of the corrugated foil 2. The inner wall of the bearing housing body 1 and the outer peripheral surface of the top foil 3 respectively abut against the multi-directional elastic support structures 6. A fixing connector 7 for fixing the corrugated foil 2 is provided between the corrugated foil 2 and the bearing housing body 1. The fixing connector 7, the guide alignment member 5 and the multi-directional elastic support structure 6 are staggered. Detachable auxiliary overlapping members 8 for fixing the top foil 3 are provided at both ends of the bearing housing body 1.

[0026] In this embodiment, the bearing housing body 1 is a hollow cylindrical structure, serving as the basic support component of the bearing. The corrugated foil 2 and top foil 3 are coaxially sleeved inside the bearing housing body 1, with the top foil 3 located on the innermost side, directly contacting the journal. The corrugated foil 2 is located between the top foil 3 and the bearing housing body 1, providing elastic support. Multiple guide grooves 4 (the number adapted to the bearing size) are uniformly machined axially on the inner wall of the bearing housing body 1. A guide alignment component 5 is integrally formed on the side of the corrugated foil 2 closest to the bearing housing body 1. The guide alignment component 5 and the guide groove 4 are clearance-fitted (0.1-0.3 mm), which restricts the circumferential rotation of the corrugated foil 2 while allowing for slight radial deformation. Multi-directional elastic support structures 6 are provided on both the inner and outer sides of the corrugated foil 2. The outer support structure is connected to the inner side of the bearing housing body 1. The inner support structure abuts against the outer circumference of the top foil 3, forming a two-way elastic buffer. The fixed connector 7 is used to fix both ends of the corrugated foil 2 to the bearing housing body 1 to prevent the corrugated foil 2 from moving axially. The fixed connector 7, the guide alignment component 5 and the multi-directional elastic support structure 6 are staggered in the circumferential direction (adjacent components are spaced 30°-60° apart) to avoid mutual obstruction or interference and to ensure that the elastic support structure 6 can deform freely. The bearing housing body 1 is equipped with detachable auxiliary overlapping components 8 at both ends, which abut against the two ends of the top foil 3 from the axial direction to prevent the top foil 3 from moving axially during operation. Through the overall design of "guide positioning + two-way elastic support + staggered layout", the problems of corrugated foil movement and single support direction in traditional bearings are solved, and the synergistic improvement of structural stability and elastic performance is achieved.

[0027] Combination Figure 1-4As shown, the multi-directional elastic support structure 6 includes an inner elastic metal foil 9 and an outer elastic metal foil 10 disposed on the inner and outer sides of the corrugated foil 2. Both the inner elastic metal foil 9 and the outer elastic metal foil 10 are arched. The inner elastic metal foil 9 abuts against the outer peripheral surface of the top foil 3, and the outer elastic metal foil 10 abuts against the inner wall of the bearing seat body 1.

[0028] Specifically, the multi-directional elastic support structure 6 consists of an inner elastic metal foil 9 and an outer elastic metal foil 10. Both are made of 0.1-0.3mm thick spring steel sheets and are stamped into a symmetrical arch shape (arch height 5-10mm). The arch apex of the inner elastic metal foil 9 faces the top foil 3 and abuts against the outer periphery of the top foil 3. The arch apex of the outer elastic metal foil 10 faces the inner wall of the bearing housing body 1 and abuts against the inner wall. When the top foil 3 is subjected to radial load from the journal, the inner elastic metal foil 9 is compressed and deformed, which at the same time drives the corrugated foil 2 to shift outward, so that the outer elastic metal foil 10 contacts and deforms against the inner wall of the bearing housing body 1. The load is offset by the elastic restoring force of the inner and outer foils. The bidirectional arch structure can provide multi-directional elastic buffering. Compared with the traditional unidirectional corrugated foil, the load-bearing capacity is improved and it can absorb the additional torque generated by radial off-center load.

[0029] Combination Figure 1 , Figure 3 As shown, an elastic buffer space is formed between the inner elastic metal foil 9 and the top foil 3, and an elastic buffer space is formed between the outer elastic metal foil 10 and the inner wall of the bearing seat body 1. The outer elastic metal foil 10, the guide alignment member 5 and the fixed connection member 7 are arranged alternately.

[0030] In this embodiment, a 0.5-1mm elastic buffer space is reserved between the inner elastic metal foil 9 and the top foil 3, and a 0.5-1mm elastic buffer space is reserved between the outer elastic metal foil 10 and the inner wall of the bearing housing body 1. When the foil is deformed under load, the buffer space provides deformation allowance to avoid fatigue damage caused by rigid collision. The outer elastic metal foil 10, the guide alignment member 5 and the fixed connection member 7 are alternately distributed in the circumferential direction to ensure that the guide alignment member 5 and the fixed connection member 7 do not block the deformation area of ​​the outer foil. The buffer space extends the fatigue life of the foil, and the staggered layout ensures the independence of the functions of each component.

[0031] The guide alignment member 5 includes a plurality of guide protrusions 11 disposed on the outside of the corrugated foil 2. The guide protrusions 11 extend into the guide groove 4 and are staggered with the outer elastic metal foil 10.

[0032] In this embodiment, the guide alignment member 5 is a guide protrusion 11 integrally stamped on the outer side of the corrugated foil 2. The number of protrusions is the same as that of the guide groove 4. The cross-sectional shape of the protrusion matches that of the guide groove 4 (such as rectangular or trapezoidal), and the length is the same as the axial length of the guide groove 4. After the guide protrusion 11 is embedded in the guide groove 4, the fit gap between the two is controlled at 0.1-0.3mm, which restricts the circumferential rotation of the corrugated foil 2 and allows it to move slightly in the radial direction. The guide protrusion 11 and the outer elastic metal foil 10 are staggered in the circumferential direction (interval of 30°-60°) to avoid the protrusions from hindering the deformation of the outer foil.

[0033] Combination Figure 2 As shown, the fixed connector 7 includes several connecting baffles 12 disposed at both ends of the bearing housing body 1. The several connecting baffles 12 are arranged in a ring array along the axis of the bearing housing body 1. A connector 13 is provided on the outer side of the corrugated foil 2, and the connector 13 is connected to the connecting baffles 12.

[0034] In this embodiment, the fixed connector 7 includes a connecting baffle 12 and a connector 13: the connecting baffle 12 is a metal block distributed in a ring array at both ends of the bearing housing body 1, and is evenly arranged along the axis of the bearing housing body 1; the connector 13 is a protruding structure integrally formed on the outer side of both ends of the corrugated foil 2, which corresponds one-to-one with the connecting baffle 12. During assembly, the connectors 13 at both ends of the corrugated foil 2 are fixed to the connecting baffle 12 of the bearing housing body 1 by bolts or buckles, locking the axial position of the corrugated foil 2, but not restricting its radial elastic deformation. The axial movement of the corrugated foil 2 is prevented by end fixing, and the elastic support function of its middle part is not affected.

[0035] The connector 13 includes several inner connecting plates 14 disposed on the outside of the corrugated foil 2. The inner connecting plates 14 are provided with positioning holes, and the connecting baffle 12 is provided with positioning holes. The inner connecting plates 14 and the connecting baffle 12 are fixed together by positioning pins.

[0036] In this embodiment, the connector 13 is a connecting inner plate 14 extending from the outer side of the corrugated foil 2. The connecting inner plate 14 is machined with positioning holes (3-5mm in diameter), and the connecting baffle 12 is machined with positioning holes of the same size. The two are fixed by positioning pins (interference fit). The positioning pin connection ensures that the relative position of the corrugated foil 2 and the bearing seat body 1 is accurate, and the disassembly and assembly are convenient, making it easy to replace the corrugated foil 2 individually.

[0037] The inner connecting plate 14 and the connecting baffle 12 are respectively staggered with the outer elastic metal foil 10.

[0038] In this embodiment, the connecting inner plate 14 and the connecting baffle 12 are staggered with the outer elastic metal foil 10 in the circumferential direction (i.e., the connecting inner plate 14 does not overlap with the outer foil), so as to avoid the fixed structure from blocking the deformation area of ​​the outer foil.

[0039] Combination Figure 1, Figure 4 As shown, the detachable auxiliary connecting member 8 includes several overlapping fixing rods 15 disposed at both ends of the bearing seat body 1, and the overlapping fixing rods 15 abut against the two end faces of the top foil 3.

[0040] In this embodiment, the detachable auxiliary lap joint 8 is a lap fixing rod 15 installed at both ends of the bearing seat body 1. It is evenly distributed along the circumference. One end of the lap fixing rod 15 is connected to the bearing seat body 1 by a thread, and the other end extends towards the center of the bearing and abuts against the end face of the top foil 3, thereby restricting the movement of the top foil 3 in the axial direction. The detachable design facilitates the installation and replacement of the top foil 3 and solves the problem of difficult maintenance of traditional top foil welding and fixing.

[0041] Combination Figure 1 , Figure 2 As shown, the bearing housing body 1 has several rod-body embedded grooves, and the overlapping fixing rod 15 is embedded in the rod-body embedded grooves. The cross-section of the overlapping fixing rod 15 is L-shaped.

[0042] In this embodiment, the inner walls of both ends of the bearing housing body 1 are machined with rod-embedded grooves (2-3mm deep). The overlapping fixing rod 15 is embedded in the groove, and its cross-section is L-shaped: the short side is embedded in the groove and fixed to the bearing housing body 1, and the long side extends inward to abut the end face of the top foil 3. The L-shaped structure and the embedded groove design prevent the fixing rod from protruding from the inner wall of the bearing housing, avoiding interference with the radial deformation of the corrugated foil 2 or the top foil 3, and making the structure more compact.

[0043] Combination Figure 1 As shown, the top foil 3 is composed of an outer wear-resistant layer and an inner elastic substrate. The outer wear-resistant layer is made of polytetrafluoroethylene composite material, and the inner elastic substrate is made of beryllium bronze.

[0044] In this embodiment, the top foil 3 adopts a composite layer structure: the outer layer is a 0.1-0.2mm thick polytetrafluoroethylene composite material (with graphite or molybdenum disulfide lubricant added), which has a low coefficient of friction and high wear resistance; the inner layer is a 0.2-0.3mm thick beryllium bronze, which has excellent elasticity and fatigue resistance. The two layers are combined into one by rolling process.

[0045] The working principle of this utility model is as follows: When the journal rotates at high speed in the radial foil bearing, an air film (or liquid film) lubrication layer is formed between the top foil 3 and the journal to avoid direct contact. The radial load of the journal is transmitted to the top foil 3 through the lubrication layer. The top foil 3 distributes the load to the inner elastic metal foil 9, causing the inner foil to be deformed under pressure. The deformation of the inner foil causes the corrugated foil 2 to shift outward, causing the outer elastic metal foil 10 to contact and deform with the inner wall of the bearing housing body 1. The elastic restoring force of the inner and outer foils forms a buffer and balance for the load. During operation, the cooperation between the guide protrusion 11 and the guide groove 4 restricts the circumferential movement of the corrugated foil 2, ensuring that the gap between the top foil 3 and the journal is uniform. Fixed connector 7 fixes both ends of corrugated foil 2 to prevent axial displacement; detachable auxiliary overlapping connector 8 fixes top foil 3 from both ends to prevent top foil 3 from moving axially with the journal. The outer wear-resistant layer of top foil 3 reduces friction loss, while the inner elastic substrate ensures that it can adapt to the deformation of corrugated foil 2 and always maintain a stable lubrication gap with the journal. When the load changes, the multi-directional elastic support structure 6 quickly adjusts the elastic force to adapt to load fluctuations through the coordinated deformation of the inner and outer foils, absorbs vibration energy, and ensures stable bearing operation. If top foil 3 or corrugated foil 2 is worn, the positioning pin and overlapping fixing rod 15 can be removed to replace the damaged parts separately, reducing maintenance costs.

[0046] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of this utility model.

[0047] Although this document frequently uses terms such as bearing housing body 1, corrugated foil 2, top foil 3, guide groove 4, guide alignment component 5, multi-directional elastic support structure 6, fixed connector 7, detachable auxiliary overlap component 8, inner elastic metal foil 9, outer elastic metal foil 10, guide protrusion 11, connecting baffle 12, connector 13, connecting inner plate 14, and overlap fixing rod 15, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of this utility model; interpreting them as any additional limitation would contradict the spirit of this utility model.

Claims

1. A radial foil bearing comprising a bearing seat body (1), characterized in that, The bearing housing body (1) is coaxially mounted with a corrugated foil (2) and a top foil (3). The inner wall of the bearing housing body (1) is evenly distributed with several axially extending guide grooves (4). The corrugated foil (2) is provided with a guide alignment member (5) extending into the guide groove (4) at one end near the inner wall of the bearing housing body (1). The corrugated foil (2) is provided with a multi-directional elastic support structure (6) on both the inner and outer sides. The inner wall of the bearing housing body (1) and the outer peripheral surface of the top foil (3) respectively abut against the multi-directional elastic support structure (6). A fixing connector (7) for fixing the corrugated foil (2) is provided between the corrugated foil (2) and the bearing housing body (1). The fixing connector (7), the guide alignment member (5) and the multi-directional elastic support structure (6) are arranged in an alternating manner. The bearing housing body (1) is provided with detachable auxiliary overlapping members (8) for fixing the top foil (3) at both ends.

2. A radial foil bearing according to claim 1, wherein, The multi-directional elastic support structure (6) includes an inner elastic metal foil (9) and an outer elastic metal foil (10) disposed on the inner and outer sides of the corrugated foil (2). Both the inner elastic metal foil (9) and the outer elastic metal foil (10) are arched. The inner elastic metal foil (9) abuts against the outer peripheral surface of the top foil (3), and the outer elastic metal foil (10) abuts against the inner wall of the bearing seat body (1).

3. A radial foil bearing according to claim 2, wherein, An elastic buffer space is formed between the inner elastic metal foil (9) and the top foil (3), and an elastic buffer space is formed between the outer elastic metal foil (10) and the inner wall of the bearing seat body (1). The outer elastic metal foil (10), the guide alignment member (5) and the fixed connection member (7) are arranged alternately.

4. A radial foil bearing according to claim 3, wherein, The guide alignment member (5) includes a plurality of guide protrusions (11) disposed on the outside of the corrugated foil (2). The guide protrusions (11) extend into the guide groove (4) and are staggered with the outer elastic metal foil (10).

5. A radial foil bearing according to claim 4, wherein, The fixed connector (7) includes several connecting baffles (12) disposed at both ends of the bearing seat body (1). The several connecting baffles (12) are arranged in a ring array along the axis of the bearing seat body (1). A connector (13) is provided on the outer side of the corrugated foil (2). The connector (13) is connected to the connecting baffles (12).

6. A radial foil bearing according to claim 5, wherein, The connector (13) includes several connecting inner plates (14) disposed on the outside of the corrugated foil (2). The connecting inner plates (14) are provided with positioning holes, and the connecting baffle (12) is provided with positioning holes. The connecting inner plates (14) and the connecting baffle (12) are fixed together by positioning pins.

7. A radial foil bearing according to claim 6, characterized in that, The connecting inner plate (14) and the connecting baffle (12) are respectively staggered with the outer elastic metal foil (10).

8. A radial foil bearing according to claim 1 wherein, The detachable auxiliary connector (8) includes several overlapping fixing rods (15) disposed at both ends of the bearing seat body (1), and the overlapping fixing rods (15) abut against the two end faces of the top foil (3).

9. A radial foil bearing according to claim 8, wherein, The bearing seat body (1) has several rod-body embedded grooves, and the overlapping fixing rod (15) is embedded in the rod-body embedded grooves. The cross-section of the overlapping fixing rod (15) is L-shaped.

10. A radial foil bearing according to claim 1 wherein, The top foil (3) is composed of an outer wear-resistant layer and an inner elastic substrate. The outer wear-resistant layer is made of polytetrafluoroethylene composite material, and the inner elastic substrate is made of beryllium bronze.

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