A magnetorheological fluid hydraulic bushing for a vehicle suspension and a vehicle suspension system

Abstract

This application relates to the technical field of hydraulic bushings, and in particular to a magnetorheological hydraulic bushing and vehicle suspension system for vehicle suspension, comprising: a shell, an inner tube, a rubber elastomer covering the inner tube and the shell, and a magnetorheological fluid; the hydraulic space includes a first cavity and a second cavity arranged circumferentially along the bushing; the bushing also includes an internal excitation coil, a magnetic tube, a first magnetic block, and a second magnetic block; the magnetic tube is sleeved on the inner tube, and the excitation coil is disposed on the magnetic tube; the first magnetic block and the second magnetic block are connected to the magnetic tube, and a magnetorheological fluid flow channel is defined between their opposing working surfaces; when the excitation coil is energized, the magnetic lines of force generated therefrom pass through the magnetic circuit formed by the magnetic tube, the first magnetic block, and the second magnetic block, and are concentrated through the magnetorheological fluid flow channel. This application reduces the external space occupation, improves the structural integrity and load-bearing capacity of the bushing in the axial direction, and achieves compactness and high performance of the magnetorheological hydraulic bushing.

Description

Technical Field

[0001] This application relates to the technical field of hydraulic bushings, and in particular to a magnetorheological hydraulic bushing for vehicle suspension and a vehicle suspension system. Background Technology

[0002] Hydraulic bushings, as highly efficient vibration isolation components, effectively attenuate and isolate vibrations and impacts transmitted to the vehicle body from excitation sources such as the powertrain and uneven road surfaces through the synergistic effect of their internal rubber elastomer and enclosed fluid. Therefore, they are widely used in vehicle suspension systems. Their core mechanism utilizes the flow damping of fluid within the internal cavities to dissipate energy, thereby optimizing dynamic stiffness and damping characteristics.

[0003] To address the varying suspension performance requirements of vehicles under different driving conditions (such as comfort and sport modes), intelligent adjustable magnetorheological hydraulic bushings have emerged. These bushings incorporate magnetorheological fluid into traditional hydraulic bushings, allowing their rheological properties (such as viscosity and yield stress) to undergo rapid, reversible, and significant changes under the influence of an external magnetic field. In existing technologies, the primary method for achieving magnetic field adjustment is to attach an excitation coil assembly to the outside or periphery of the bushing. This external coil generates a magnetic field that penetrates the bushing wall and acts on the internal magnetorheological fluid channels, thereby achieving active or semi-active control of the bushing's dynamic characteristics.

[0004] However, the aforementioned method of externally mounting the excitation coil has significant drawbacks: First, the external coil and its necessary fixing and protection structures significantly increase the overall external dimensions of the bushing, occupying valuable suspension layout space and hindering the compact and lightweight design of the vehicle chassis system. Second, the installation of the external coil usually requires disrupting or bypassing the rubber main spring outside the bushing, potentially affecting the structural continuity and integrity of the rubber elastomer in the axial and circumferential directions, thereby weakening the bushing's load-bearing capacity and durability. Finally, the external coil and its leads, exposed to complex vehicle operating environments (such as mud, salt spray, high temperatures, and mechanical shock), have a higher risk of short circuits, open circuits, or insulation failures, reducing the reliability and service life of the entire vibration control system. Therefore, a novel magnetorheological hydraulic bushing structure that can overcome these drawbacks is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to propose a magnetorheological hydraulic bushing for vehicle suspension and a vehicle suspension system. By setting the excitation coil in the internal structure of the bushing, the magnetic field adjustment unit is highly integrated with the bushing body, thereby reducing the external space occupation while improving the structural integrity and load-bearing capacity of the bushing in the axial direction, and realizing the compactness and high performance of the magnetorheological hydraulic bushing.

[0006] In a first aspect, this application provides a magnetorheological hydraulic bushing for vehicle suspension, which adopts the following technical solution: A magnetorheological hydraulic bushing for vehicle suspension, comprising: The outer shell, the inner tube, the rubber elastomer covering the space between the inner tube and the outer shell, and the magnetorheological fluid filling the closed hydraulic space formed inside the rubber elastomer; The hydraulic space includes a first cavity and a second cavity arranged circumferentially along the rubber elastomer; It also includes a built-in excitation coil, a magnetic tube, a first magnetic block, and a second magnetic block; the magnetic tube is sleeved on the inner tube, and the excitation coil is disposed on the magnetic tube; the first magnetic block and the second magnetic block are connected to the magnetic tube and extend into the space between the first cavity and the second cavity, and the relative working surfaces of the two define a magnetorheological fluid flow channel so that the first cavity and the second cavity are connected through the magnetorheological fluid flow channel; When the excitation coil is energized, the magnetic lines of force it generates pass through the magnetorheological fluid flow channel via the magnetic circuit formed by the magnetic tube, the first magnetic block, and the second magnetic block.

[0007] By adopting the above technical solution, compared with the traditional external coil solution, the built-in excitation coil significantly reduces the space occupied by the bushing and avoids the decrease in load-bearing capacity caused by the disruption of the continuity of the rubber elastomer. By integrating the magnetic tube, the first magnetic block and the second magnetic block into a specific magnetic circuit structure, a built-in magnetorheological fluid flow channel with a highly concentrated magnetic field is actively constructed between the two circumferentially arranged cavities. First, the excitation coil is directly set on the magnetic tube, which is part of the magnetic circuit, realizing the deep integration of the electromagnetic unit and the bushing body, and providing a stable installation foundation for the coil. Second, the first and second magnetic blocks not only serve as the flow channel walls connecting the cavities, but also act as magnetic poles, efficiently guiding and concentrating the magnetic lines of force on the narrow flow channel cross section. This allows the magnetorheological fluid to be subjected to a high-intensity and large-gradient magnetic field when flowing through it, thereby greatly improving the control efficiency and sensitivity of the liquid rheological properties, and ultimately realizing a wide range and rapid adjustability of the bushing's dynamic stiffness and damping characteristics.

[0008] Optionally, the magnetic tube has a mounting ring groove for mounting the excitation coil.

[0009] By adopting the above technical solution, a mounting ring groove for mounting the excitation coil is formed on the magnetic tube. This structure provides precise radial and axial positioning for the coil, preventing it from shifting during vibration and ensuring the stability of the magnetic field. At the same time, the ring groove allows the coil to be embedded in the surface of the magnetic tube, optimizing the use of internal space and making the overall structure more compact.

[0010] Optionally, the magnetorheological fluid channel is a cuboid or slit-like structure defined by the opposing working surfaces of the first and second magnetic blocks.

[0011] By adopting the above technical solution, the magnetorheological fluid channel is defined as a cuboid or slit-like structure. The regular and elongated channel shape is ensured by the parallel working surfaces of the two magnetic blocks, which makes the magnetic field distribution in the channel more uniform and avoids magnetic dead zones. The uniform magnetic field makes the magnetorheological fluid flowing through it experience consistent forces, improving the linearity and predictability of damping adjustment. The slit-like structure can also generate a higher magnetic field gradient in a specific direction.

[0012] Optionally, several excitation coils are provided and are equally spaced along the axial direction of the inner tube.

[0013] By adopting the above technical solution, several excitation coils are set at equal intervals along the axial direction. The arrangement of multiple coils can generate a stronger or more uniform axial magnetic field. These coils can be controlled independently, in groups, or uniformly, thereby making it possible to achieve gradient distribution or segmented adjustment of magnetic field strength in the axial direction of the bushing, providing the bushing with a more complex and diversified dynamic characteristic adjustment mode.

[0014] Optionally, the magnetic tube, the first magnetic block, and the second magnetic block are all made of soft magnetic material.

[0015] By adopting the above technical solution, the soft magnetic material has high permeability and low coercivity, which can efficiently conduct and concentrate magnetic lines of force to form a closed magnetic circuit with low magnetic resistance. This minimizes the magnetic energy loss in the magnetic circuit, so that the magnetic field energy generated by the excitation coil can act more efficiently on the magnetorheological fluid in the flow channel, thereby improving the energy utilization efficiency and response speed of the entire system.

[0016] Optionally, it further includes a limiting support disposed in the first cavity and the second cavity, the limiting support being used to support the first cavity and the second cavity.

[0017] By adopting the above technical solution, the core function of the limiting support is mechanical support and limiting. When the bushing is under load, it can effectively limit the excessive radial or axial expansion deformation of the hydraulic cavity formed by the rubber elastomer, thereby maintaining the relative stability of the cavity volume and shape. This enhances the overall structural rigidity, load-bearing capacity and fatigue resistance of the bushing, ensuring that the core flow channel structure does not shift under long-term vibration and that the performance remains stable.

[0018] Optionally, the limiting support is a ring structure, and its inner edge is fixed to the inner tube or a component connected to the inner tube.

[0019] By adopting the above technical solution, the limiting support is further defined as a ring structure, with its inner edge fixed to the inner tube or its connector, and its outer edge having a gap with the outer shell. The ring structure provides uniform circumferential support force. When the bushing undergoes radial deformation, the outer shell does not contact the limiting support during the initial stroke. When the radial stroke reaches a certain point, the outer shell contacts the limiting support, limiting the maximum radial displacement of the bushing.

[0020] Secondly, the vehicle suspension system provided in this application adopts the following technical solution: A vehicle suspension system includes the magnetorheological hydraulic bushing.

[0021] By adopting the above technical solution, the application and protection scope of the aforementioned high-performance, intelligently adjustable magnetorheological hydraulic bushing is extended to the entire vehicle suspension system. Suspension systems using this bushing can actively adapt to different road conditions and driving modes, thereby achieving comprehensive performance improvements in ride comfort, handling stability, and noise and vibration control.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. By integrating the excitation coil, magnetic tube, and magnetic block into a built-in magnetic circuit unit and deeply bonding it with the rubber elastomer, the external coil and its additional structure are completely eliminated, significantly reducing the external space occupied by the bushing; avoiding structural damage to the external rubber main spring, maintaining the structural continuity of the bushing, thereby achieving the ultimate compactness of the overall structure and improving the foundation bearing capacity. 2. By utilizing the first and second magnetic blocks connected to the magnetic tube, a narrow magnetorheological fluid flow channel is actively constructed between the two circumferentially arranged hydraulic cavities. This allows the magnetic lines of force generated by the excitation coil to be efficiently guided through a low magnetic reluctance circuit and to penetrate the entire flow channel cross-section in a highly concentrated and uniform manner. This improves the utilization rate and control efficiency of magnetic field energy, making the adjustment of the rheological properties of the magnetorheological fluid more sensitive, rapid, and precise, thereby achieving a wide range of continuously adjustable dynamic stiffness and damping coefficient of the bushing. 3. A limiting support structure is set in the hydraulic cavity. This support can effectively restrain the excessive deformation of the rubber elastomer under heavy load and maintain the stability of the geometry of the cavity and the flow channel. Combined with the environmental protection of the built-in magnetic circuit unit, this design ensures the structural durability, operational reliability and performance consistency of the bushing under complex working conditions and long-term vibration from both mechanical constraints and sealing protection. Attached Figure Description

[0023] Figure 1 This is a diagram illustrating the internal structure of the single-coil magnetorheological hydraulic bushing in an embodiment of this application; Figure 2 This is a cross-sectional view of a single-coil magnetorheological hydraulic bushing in an embodiment of this application; Figure 3 This is a diagram illustrating the internal structure of the dual-coil magnetorheological hydraulic bushing in an embodiment of this application; Figure 4 This is a cross-sectional view of the dual-coil magnetorheological hydraulic bushing in an embodiment of this application.

[0024] Reference numerals in the attached drawings: 1. Rubber elastomer; 2. Inner tube; 3. Magnetic tube; 4. First magnetic block; 5. Second magnetic block; 6. Excitation coil; 8. Limiting support; 9. First cavity; 10. Second cavity; 11. Magnetorheological fluid channel; 12. Outer shell. Detailed Implementation

[0025] The following combination Figures 1 to 4 This application will be described in further detail.

[0026] This embodiment discloses a magnetorheological hydraulic bushing for vehicle suspension.

[0027] Example: Refer to Figures 1 to 4 This invention provides a magnetorheological hydraulic bushing for a vehicle suspension. The bushing is generally cylindrical and, from the outside in, mainly includes an outer shell 12, a rubber elastomer 1, a magnetic circuit assembly, and an inner tube 2. The outer shell 12 is the outermost rigid support structure of the bushing, and the inner tube 2 is the central connecting component of the bushing. The rubber elastomer 1 is enclosed within the annular space between the outer shell 12 and the inner tube 2. The rubber elastomer 1 is vulcanized and bonded to the inner wall of the outer shell 12 and the outer wall of the inner tube 2 to form a single, sealed annular hydraulic space filled with magnetorheological fluid.

[0028] The magnetic circuit assembly includes a magnetic tube 3 sleeved outside the inner tube 2, which can be fixedly connected to the inner tube 2 or integrally formed; the excitation coil 6 is stably mounted on the magnetic tube 3, and on the outer wall of the magnetic tube 3 facing the rubber elastomer 1, a first magnetic block 4 and a second magnetic block 5 are connected at intervals along the circumference of the bushing; the two magnetic blocks extend into the rubber elastomer 1 and are embedded therein, and a narrow gap is reserved between the working surfaces of the first magnetic block 4 and the second magnetic block 5 facing each other, which forms a magnetorheological fluid flow channel 11 connecting the two regions inside the bushing.

[0029] When the bushing is in operation, if an external radial load is applied, a relative displacement will occur between the inner tube 2 and the outer shell 12, squeezing the rubber elastomer 1 and the magnetorheological fluid inside, forcing the magnetorheological fluid to flow between the two regions through the magnetorheological fluid channel 11. At this time, if a current is applied to the excitation coil 6, the coil will generate a magnetic field. The magnetic lines of force are guided through a low magnetic resistance loop formed by the magnetic tube 3, the first magnetic block 4, and the second magnetic block 5, and pass through the magnetorheological fluid channel 11 in a highly concentrated manner. Under the action of a strong magnetic field, the rheological properties (such as apparent viscosity and shear yield stress) of the magnetorheological fluid in the channel will undergo rapid and reversible significant changes, thereby changing the damping force when the liquid flows through the channel, and ultimately achieving real-time and active adjustment of the overall dynamic stiffness and damping characteristics of the bushing.

[0030] The following will elaborate on the specific structure of each of the above components, their positional relationships, and their connections.

[0031] The outer shell 12 is a cylindrical structure made of metal, providing rigid external support and mounting interface for the entire bushing. Its inner wall is firmly bonded to the outer surface of the rubber elastomer 1 through a vulcanization process.

[0032] The inner tube 2 is a cylindrical structure made of metal, located at the geometric center of the bushing, and usually serves as the core load-bearing component connected to the frame or swing arm. The outer wall of the inner tube 2 is tightly fitted and fixed to the inner wall of the magnetic tube 3 or connected by other means (such as key connection or welding) to ensure that the two do not rotate or shift relative to each other when the bushing is working.

[0033] The rubber elastomer 1, as the core flexible element of the bushing, is a thick-walled annular structure formed in one piece through a compression molding and vulcanization process. Its material is oil-resistant and fatigue-resistant rubber. This rubber elastomer 1 is not a simple solid structure; it has a specific hollow internal design to form a hydraulic chamber. Specifically, within the annular body of the rubber elastomer 1 surrounding the inner tube 2 and the magnetic tube 3, two large connecting holes are symmetrically formed along its circumference. These two connecting holes directly penetrate the inner and outer surfaces of the rubber elastomer 1. Simultaneously, at the positions of the first magnetic block 4 and the second magnetic block 5 on the magnetic tube 3, a central hole penetrating its thickness is also provided on the rubber elastomer 1. This hole connects the two large connecting holes on the side closest to the magnetic tube 3. After assembly, the inner wall of the outer shell 12, the outer surface of the magnetic tube 3 (i.e., the area enclosing the magnetic tube 3 and the magnetic blocks), and the walls of the two connecting holes inside the rubber elastomer 1 together form two independent, circumferentially separated, sealed cavities, namely the first cavity 9 and the second cavity. An installation groove is provided on the inner wall of the central hole on the rubber elastomer 1. The installation groove can just accommodate the first magnetic block 4 and the second magnetic block 5. The gap between the magnetic blocks forms the only liquid channel connecting the first cavity 9 and the second cavity - the magnetorheological fluid channel 11. Both cavities and the channel are filled with magnetorheological fluid.

[0034] The magnetic conductor tube 3, as the core framework of the magnetic circuit system, is fixedly sleeved outside the inner tube 2. The magnetic conductor tube 3 is preferably made of a soft magnetic material with high permeability (such as low-carbon steel or silicon steel) to efficiently conduct magnetic lines of force. One or more annular mounting grooves can be machined on the outer circumferential wall of the magnetic conductor tube 3. These grooves are used to precisely accommodate and position the excitation coil 6. The number of excitation coils 6 is selected according to requirements; in this embodiment, a single coil is preferred (see reference). Figure 1 and Figure 2 ) or double coil (refer to) Figure 3 and Figure 4 The coil is tightly wound within the groove. This structure not only prevents the coil from radially or axially shifting during vibration, ensuring the stability of the magnetic field, but also allows the coil to be tightly integrated with the magnetic tube 3, optimizing the internal space layout and making the structure more compact. The coil can be partially or completely embedded in the annular mounting groove; in this embodiment, it is preferably completely embedded in the annular mounting groove.

[0035] The first magnetic block 4 and the second magnetic block 5 are also made of soft magnetic material. They can be firmly connected to the outer wall of the magnetic tube 3 by welding, bonding, or mechanical inlay, and are distributed at a certain angle along the circumference of the magnetic tube 3. The main body of the two magnetic blocks extends outward from the surface of the magnetic tube 3 and passes through the pre-reserved central hole in the rubber elastomer 1. Their ends can approach or contact the inner wall of the outer shell 12. The sides of the first magnetic block 4 and the second magnetic block 5 facing each other are processed into smooth and flat working surfaces. These two working surfaces are strictly parallel, and there is no gap between them. The narrow, uniform gap is maintained, thus forming the magnetorheological fluid flow channel 11. The shape of this flow channel, defined by two parallel planes, is similar to a flat "box" or "slit," and can be compared to a cuboid or slit-shaped channel. In this embodiment, a slit-shaped structure is preferred because it can generate a higher magnetic field gradient in the direction perpendicular to the working surface, thus having a more significant effect on the magnetorheological fluid. The two magnetically conductive blocks not only serve as the physical boundaries of the flow channel, but more importantly, they, together with the magnetically conductive tube 3, constitute a complete magnetic circuit, becoming magnetic poles that guide and concentrate the magnetic field when energized.

[0036] In addition, to enhance the structural stability of the bushing under heavy loads and prevent excessive deformation of the rubber elastomer 1, independent limiting support structures 8 are provided inside the first cavity 9 and the second cavity. These limiting supports 8 can be made of metal or high-strength engineering plastic, and their main body is annular, nested within the cavity. The inner edge of the limiting support 8 is fixed to the outer surface of the inner tube 2 or the magnetic tube 3 by interference fit or bonding; its outer edge is located inside the outer shell 12. When the bushing deforms significantly, the limiting support 8 provides a rigid mechanical stop, effectively limiting excessive expansion of the cavity, thereby protecting the rubber elastomer 1, maintaining the stability of the flow channel geometry, and improving the overall load-bearing capacity and durability of the bushing. When the bushing undergoes radial deformation, the outer shell does not initially contact the limiting support; when the radial travel reaches a certain point, the outer shell contacts the limiting support, limiting the maximum radial displacement of the bushing.

[0037] During vehicle operation, the magnetorheological hydraulic bushing is installed between the control arm of the suspension system and the vehicle body or subframe. When the wheel encounters a bump, the impact force is transmitted to the bushing through the relative movement of the inner tube 2 and the outer shell 12, which is converted into compression of the rubber elastomer 1 and its internal magnetorheological fluid. The magnetorheological fluid is forced to flow from the cavity on the compressed side (e.g., the first cavity 9) through the narrow magnetorheological fluid channel 11 defined by the first magnetic guide block 4 and the second magnetic guide block 5, and enters the cavity on the other side (the second cavity). This flow process generates damping and dissipates vibration energy.

[0038] At this time, based on the vehicle's driving mode (such as comfort or sport) or real-time road conditions, the control system outputs a specific current to the excitation coil 6. The current generates a magnetic field in the coil, and the magnetic lines of force are collected by the magnetic tube 3 and efficiently transmitted to the first magnetic block 4 and the second magnetic block 5. Because the working surfaces of the two magnetic blocks are parallel and the gap is narrow, the magnetic field is highly concentrated and uniformly penetrates the entire flow channel cross-section; under the action of the strong magnetic field, the magnetic particles in the magnetorheological fluid flowing through this area instantly align into chains along the direction of the magnetic lines of force, significantly increasing the shear resistance of the liquid flow, which manifests as a sharp increase in apparent viscosity; by steplessly adjusting the coil current, continuous and precise control of this flow resistance can be achieved, thereby ultimately adjusting the dynamic stiffness and damping coefficient of the bushing.

[0039] In summary, the magnetorheological hydraulic bushing provided in this embodiment of the invention achieves multiple beneficial technical effects by highly integrating the excitation coil 6, the magnetic tube 3, and the magnetic block into a built-in magnetic circuit unit, and innovatively utilizing the magnetic block to construct a narrow flow channel between the circumferential double cavities. Firstly, it completely avoids the space occupation, structural damage, and environmental reliability issues caused by external coils, achieving extreme compactness. Secondly, the unique integrated design of the magnetic circuit and flow channel results in extremely high efficiency in magnetic field generation, guidance, and application, with low energy loss and sensitive and precise control of the magnetorheological fluid. Thirdly, combined with the built-in limiting support 8, it ensures excellent mechanical load-bearing capacity, structural integrity, and long-term reliability of the bushing while achieving intelligent adjustability. Ultimately, the vehicle suspension system using this bushing can intelligently and quickly achieve the optimal balance between ride comfort and handling stability, significantly improving the driving experience.

[0040] This application also discloses a vehicle suspension system, including a magnetorheological hydraulic bushing.

[0041] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A magnetorheological hydraulic bushing for vehicle suspension, characterized in that: include: The outer shell (12), the inner tube (2), the rubber elastomer (1) covering the inner tube (2) and the outer shell (12), and the magnetorheological fluid filling the closed hydraulic space formed inside the rubber elastomer (1); The hydraulic space includes a first cavity (9) and a second cavity arranged circumferentially along the rubber elastomer (1); It also includes a built-in excitation coil (6), a magnetic tube (3), a first magnetic block (4) and a second magnetic block (5); the magnetic tube (3) is sleeved on the inner tube (2), and the excitation coil (6) is disposed on the magnetic tube (3); the first magnetic block (4) and the second magnetic block (5) are connected to the magnetic tube (3) and extend into the space between the first cavity (9) and the second cavity, and the relative working surfaces of the two define a magnetorheological fluid flow channel (11) so that the first cavity (9) and the second cavity are connected through the magnetorheological fluid flow channel (11); When the excitation coil (6) is energized, the magnetic lines of force generated therefrom pass through the magnetic circuit formed by the magnetic tube (3), the first magnetic block (4) and the second magnetic block (5), and are concentrated in the magnetorheological fluid flow channel (11).

2. The magnetorheological hydraulic bushing for vehicle suspension according to claim 1, characterized in that: The magnetic tube (3) has a mounting ring groove for mounting the excitation coil (6).

3. The magnetorheological hydraulic bushing for vehicle suspension according to claim 1, characterized in that: The magnetorheological fluid channel (11) is a cuboid or slit-like structure defined by the opposing working surfaces of the first magnetic block (4) and the second magnetic block (5).

4. The magnetorheological hydraulic bushing for vehicle suspension according to claim 1, characterized in that: Several excitation coils (6) are provided and are equally spaced along the axial direction of the inner tube (2).

5. The magnetorheological hydraulic bushing for vehicle suspension according to claim 1, characterized in that: The magnetic tube (3), the first magnetic block (4) and the second magnetic block (5) are all made of soft magnetic material.

6. The magnetorheological hydraulic bushing for vehicle suspension according to claim 1, characterized in that: It also includes a limiting support (8) disposed in the first cavity (9) and the second cavity, the limiting support (8) being used to support the first cavity (9) and the second cavity.

7. The magnetorheological hydraulic bushing for vehicle suspension according to claim 6, characterized in that: The limiting support (8) is a ring structure, and its inner edge is fixed to the inner tube (2) or a component connected to the inner tube (2).

8. A vehicle suspension system, characterized in that: Includes the magnetorheological hydraulic bushing as described in any one of claims 1-7.

Images