A five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing

Abstract

This invention discloses a five-axis, five-ball, concentrically nested, six-degree-of-freedom ball joint bearing, belonging to the field of ball joint bearings. It aims to solve the technical problem that existing ball joint structures cannot simultaneously satisfy the requirements of multiple rod intersections, spherical shape, and six-degree-of-freedom motion. The invention includes: a core ball head, fixedly connected to a reference shaft along the -Z axis; at least four concentric ball sleeves, sequentially and concentrically nested outside the core ball head, each ball sleeve fixedly connected to a drive shaft; and a through-hole structure, formed on each layer of ball sleeves, for the inner layer shafts to pass through, the through-holes being funnel-shaped and optimized layer by layer. Each layer of ball sleeves can rotate independently around the sphere's center, and through the coordinated extension and retraction of each drive shaft, the core ball head achieves six-degree-of-freedom spatial motion. In a preferred embodiment, the five ball sleeves are respectively connected to the -Z axis and the +Y, +X, -Y, and -X axes. This invention, while maintaining the complete spherical shape, achieves for the first time the simultaneous convergence of five shafts at the same sphere center without interference between their movements. It has advantages such as compact structure, excellent aerodynamic performance, and strong controllability, and can be widely used in fields such as UAV vector thrust mechanisms and parallel robots.

Description

Technical Field

[0001] This invention relates to the field of ball joint bearings, and more specifically to a six-degree-of-freedom ball joint bearing with a five-layer concentric nested ball structure that enables the intersection of five-axis connecting rods. Background Technology

[0002] 2.1 Technological Development Needs and the Objectives of this Invention Ball bearings, as fundamental components for achieving angle compensation and universal joints, are widely used in automobiles, robotics, and construction machinery. In recent years, with the increasing demand for multi-axis collaborative control and compact structures in high-end equipment (such as UAV vector thrust mechanisms and parallel robots), a new technological challenge has emerged: how to achieve the simultaneous convergence of multiple drive shafts (e.g., five) at the same center of the ball while maintaining its spherical shape, and how to enable that center to possess complete six-degree-of-freedom motion capabilities? The essence of this requirement is to encapsulate the entire control core of a multi-bar drive mechanism within a well-shaped, aerodynamically friendly sphere. However, a comprehensive review of existing technologies revealed that no ball joint structure can simultaneously meet the three core requirements of "five-bar intersection," "spherical shape," and "six degrees of freedom."

[0003] 2.2 Existing technical solutions and their core limitations To clearly reveal the shortcomings of existing technologies, we systematically analyze various existing ball joint structures from three dimensions: "number of connecting rods", "normality of shape" and "degree of freedom".

[0004] The first type is the single-point connection ball joint, represented by spherical bearings and rod end spherical bearings. It has only one or two connecting rods, and its shape resembles a ball head and seat, making it relatively regular. It allows for rotation and small-angle swing. Its core limitation is the insufficient number of rods, making it unable to meet the requirements of a five-rod connection.

[0005] The second type is the two-point connection universal joint, represented by the cross-shaft type and the ball-cage type. It is specifically designed for two-shaft transmission, and its shape is mostly an irregular polyhedron, enabling variable-angle power transmission. Its core limitations include its irregular shape (which can easily cause aerodynamic interference in airflow-sensitive applications) and insufficient number of links.

[0006] The third category consists of special configurations, such as parallel mechanisms (three-degree-of-freedom spherical mechanisms) and active ball joints. These typically connect three links, have a radial, convex structure, and are mostly three-degree-of-freedom. Their core limitations include irregular shape, incomplete degrees of freedom, and insufficient number of links (unable to accommodate more than five drive shaft links).

[0007] As can be seen from the above comparison, the existing technology cannot simultaneously meet the objectives of this invention in terms of the three core indicators.

[0008] The specific analysis is as follows: 2.2.1. Single-point connection type ball joint (spherical plain bearing / rod end spherical plain bearing) This type of bearing consists of a ball head and a ball seat, allowing for 360° rotation and ±5° to ±15° oscillation. Rod end spherical plain bearings integrate a single connecting rod. Their advantage is their simple structure, but due to the single-point connection characteristic, they can only connect a maximum of 1-2 connecting rods, making it impossible to meet the requirement of five drive shafts simultaneously converging at the same ball center.

[0009] 2.2.2. Two-point connection universal joint Universal joint series (cross-type, ball-cage type, etc.) are specifically designed for variable-angle power transmission between two shafts. Although the ball-cage type constant velocity universal joint achieves a large angle (up to 42°) through multiple steel balls, its shape is an irregular polyhedron or composite body, and its axial dimension is large. In applications sensitive to airflow, such as rotorcraft, this irregular shape can severely disrupt the flow field, generate turbulence interference, and affect flight stability. In addition, its connecting rods are limited to two.

[0010] 2.2.3. Special configurations (parallel mechanisms and active ball joints) In pursuit of multi-link control, special designs such as three-degree-of-freedom spherical parallel mechanisms have emerged in engineering. These mechanisms connect the platform through three linear drive branches, enabling adjustment of the sphere's center position. However, they typically only provide three degrees of freedom, failing to meet the complete motion requirements of six degrees of freedom (three rotations + three translations). More importantly, these mechanisms generally employ a radial layout, resulting in highly irregular shapes and an inability to accommodate more than five drive shafts.

[0011] 2.3 Overall Contradictions and Unresolved Issues in Existing Technologies The above analysis reveals a long-standing unresolved contradiction in existing technologies: If the goal is to achieve multiple intersecting links (such as in parallel mechanisms), then the spherical shape and the integrity of the degrees of freedom must be sacrificed. If the spherical shape is maintained (such as a spherical bearing), the number of connecting rods is strictly limited to 1 to 2. A compromise solution of series or parallel welding (such as multiple axially nested fisheye bearings) will result in bulky axial dimensions, misalignment of the stress points of each rod, and uncontrolled shape, failing to meet aerodynamic requirements.

[0012] Therefore, when faced with the complex requirement of "five drive shafts converging at the same center of the ball, maintaining the complete shape of the ball, and achieving six degrees of freedom of motion", all existing solutions have obvious defects, and there is still a lack of a ball joint bearing structure that can solve the above three major contradictions at the same time.

[0013] 2.4 Technical problems to be solved Based on the above background, the technical problem to be solved by the present invention is: how to design a ball joint bearing that can enable five or more drive shafts to converge at the same center of the ball while maintaining the shape of the ball, and ensure that the center of the ball has complete six degrees of freedom of motion (three translations + three rotations), while ensuring that the motion of each shaft does not interfere with each other.

[0014] 2.5 Brief Description of the Innovative Idea of ​​this Invention To address the aforementioned problems, this invention breaks away from the conventional mindset of single-point connection or radial layout, proposing a novel "multi-layered concentric sphere nesting" configuration: a core sphere head and at least four concentric sphere sleeves are incorporated, with each sleeve fixedly connected to a drive shaft. Through holes are precisely drilled in each sleeve for the inner shaft to pass through. This design allows each sleeve to rotate independently around the same sphere center, thus achieving multi-rod convergence and six-degree-of-freedom motion without compromising the sphere's shape. The following detailed description of this technical solution will illustrate the specific implementation. Summary of the Invention

[0015] 3.1 Technical problems to be solved This invention aims to solve the following problems existing in multi-link converging ball joint structures: traditional single ball joints cannot meet the motion requirements of five or more links converging at the same center of the ball; the series-connected fisheye bearing scheme leads to misalignment of the force points of each link and axial space congestion; the parallel welding scheme of multiple ball joints has an irregular shape, which is prone to aerodynamic interference in airflow-sensitive applications such as rotorcraft. This invention provides a ball joint bearing that can achieve simultaneous convergence of five-axis links and has six degrees of freedom motion capability while maintaining the shape of the ball.

[0016] 3.2 Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing, characterized in that it comprises: The core ball joint is fixedly connected to a reference shaft along the -Z axis, which serves as the motion reference for the entire mechanism. In a typical configuration of this reference shaft, it is a non-driven static shaft with a fixed length and no telescopic movement.

[0017] At least four concentric spherical sleeves are nested sequentially outside the core spherical head. Each spherical sleeve is a concentric spherical shell structure, and a drive shaft is fixedly connected to each spherical sleeve. A through-hole structure is formed on each layer of the ball sleeve for the inner layer's shaft to pass through. The through-hole is flared in the thickness direction of the ball sleeve, and its opening range is optimized layer by layer according to the radial position of each layer of ball sleeve and the diameter of the shaft. Each of the ball sleeves in each layer can rotate independently around the center of the core ball head. Through the coordinated extension and retraction of each drive shaft, the core ball head is driven to achieve six degrees of freedom in space.

[0018] Preferably, the number of ball sleeves is five, including a first-layer core ball head, a second-layer ball sleeve, a third-layer ball sleeve, a fourth-layer ball sleeve, and a fifth-layer ball sleeve, which are respectively connected to the -z-axis reference shaft and the four drive shafts of the +Y-axis, +X-axis, -Y-axis, and -X-axis.

[0019] Preferably, the strategy for opening the through hole is as follows: in the XY plane, with the center of the ball as the origin and the center line of each shaft as the reference, extend 22.5°~27.5° to the left and right to form a flared mouth with a cone angle of 45°~55°. The cone angle can be adjusted according to the required swing angle (e.g., ±7.5°~±12.5°) and the diameter of the shaft.

[0020] Preferably, a self-lubricating layer is provided between the ball sleeves. The self-lubricating layer is a copper alloy inlaid with graphite material or a PEEK composite material, which is used to reduce the coefficient of friction and compensate for processing errors.

[0021] Preferably, the core ball head is made of titanium alloy substrate with surface hardening coating, and the outer ball sleeve is made of PEEK composite material or aluminum alloy to achieve lightweight design.

[0022] Preferably, for mechanical applications where lightweighting is not required, the core ball joint, each layer of ball sleeves, and the corresponding shaft can all be made of bearing steel.

[0023] 3.3 Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: 1. Achieve five-axis synchronous intersection and six-degree-of-freedom motion. Through a nested structure of five concentric spheres and a through-hole design, it was achieved for the first time that five drive shafts simultaneously converge at the same sphere center, with each shaft moving independently without interference. Verified by REVIT 3D simulation, under the conditions of five shafts with a length of 120mm and a swing angle of ±7.5°, the sphere center can move continuously within a sphere top area of ​​15.8mm radius without any jamming.

[0024] 2. Maintains a spherical shape, resulting in excellent aerodynamic performance. The invention is a regular sphere with a smooth surface and no protruding structures. When applied to the vector thrust mechanism of a rotorcraft, it can minimize airflow disturbance and avoid turbulence.

[0025] 3. Compact structure and high space utilization Compared to the tandem spherical bearing scheme (large axial dimension) and the multi-ball joint parallel welding scheme (radial layout), this invention integrates all the connection points of the five rods inside the ball, significantly reducing both axial and radial dimensions, making it particularly suitable for situations where the space at the shaft head is limited.

[0026] 4. The kinematic model is clear and highly controllable. Each layer of the ball sleeve rotates independently, with a clear kinematic relationship, allowing for precise control through mathematical modeling and real-time calculation. Verification at the most unfavorable point confirms the absence of kinematic singularities.

[0027] 5. Flexible material compatibility to meet diverse application needs. Depending on load requirements and weight limitations, different material combinations such as bearing steel, titanium alloy, aluminum alloy, and PEEK composite materials can be selected to balance strength and lightweight.

[0028] 3.4 Technology Expansion The core concept of this invention lies in using a nested structure of multiple concentric ball sleeves (balls) to allow each layer of ball sleeves (including the core ball head) to independently connect to a shaft, and to achieve interference-free passage of the inner shafts using through holes. This design concept has good scalability and adaptability, allowing for flexible addition or reduction of the number of ball sleeve layers according to the actual number of drive shafts, thereby covering ball joint bearing configurations from three-axis to six-axis and even more shafts. Its expansion directions are described below.

[0029] 3.4.1 Six-axis connecting rod, six-ball concentric nested six-degree-of-freedom ball joint bearing When the application scenario requires that all six drive shafts converge at the same center of the sphere simultaneously (e.g., a six-axis parallel mechanism or a fully driven vector thrust platform), and the sphere's shape and six-degree-of-freedom motion capability must be maintained, the five-axis solution of this invention can be expanded in the following ways: Increased number of layers: The total number of ball sleeves has increased from five layers (core ball head + four layers of sleeves) to six layers (core ball head + five layers of sleeves). The core ball head is connected to one axle, and each of the other five layers of sleeves is connected to one axle, for a total of six axles.

[0030] Axis configuration: The typical configuration is a six-axis full-drive mode, meaning there is one drive axis in each of the six directions in the Cartesian coordinate system: +X, -X, +Y, -Y, +Z, and -Z. All axes in the six-axis scheme are telescopic drive axes. The core ball joint is fixedly connected to the -Z axis, and the sixth-layer ball sleeve (outermost layer) connects to the opposing drive axis (in the +Z axis direction). The remaining axes in the XY plane are the same as in the five-axis linkage scheme, i.e., the second, third, fourth, and fifth-layer ball sleeves connect to the four drive axes corresponding to the +Y, +X, -Y, and -X axes, respectively; thus achieving completely independent control of the six degrees of freedom.

[0031] Further optimization of the through-holes: After adding a layer of ball sleeves, the inner shafts (up to five) need to pass through the outer ball sleeve. The original five-axis scheme's conical angle (45°) and layer-by-layer shaping strategy for the through-holes still apply, but the opening angle and boundary of each layer of through-holes need to be recalculated and optimized based on the diameter of the newly added shafts, their range of motion, and the geometric constraints of adjacent ball sleeves. Generally, by appropriately increasing the conical angle of the flared opening (e.g., from 45° to 50°~55°), the swing range of the six shafts can be increased to ±12.5° without interference.

[0032] Kinematic characteristics: The coordinated extension and retraction of the six drive shafts enables the core ball joint to achieve six degrees of freedom in space. The six-axis full-drive scheme eliminates the motion coupling caused by non-drive reference axes, resulting in a more symmetrical kinematic model and a more direct control algorithm, theoretically enabling higher-precision trajectory tracking.

[0033] It should be noted that the six-axis solution has higher requirements for the design accuracy of the through hole and the machining and assembly of the ball sleeve. However, the "flared mouth + layer-by-layer shaping" technical framework proposed in this invention is fully compatible with this expansion direction and does not require changes to the basic structural principle.

[0034] 3.4.2 Four-axis connecting rod with four concentric nested ball joint bearing When the actual requirement is only the intersection of four drive shafts (such as a planar four-bar linkage or a specific spatial mechanism), one ball sleeve can be removed from the five-axis solution to form a four-layer structure of "core ball head + three-layer ball sleeve". The specific implementation method is as follows: The core ball joint is retained to connect to the Z-axis (which can be either a stationary or drive shaft), and three layers of ball sleeves are nested outside, each connecting to one of the three drive shaft rods, for a total of four shaft rods.

[0035] Typical configuration example: The core ball joint connects to the -Z axis (static axis), the second ball joint connects to the +Y axis, the third ball joint connects to the +X axis, and the fourth ball joint connects to the -Y axis. A missing direction (such as the -X axis) can be compensated for by the coupled motion of other axes, or omitted according to actual degree-of-freedom requirements.

[0036] The through-hole still adopts the "flared opening + layer-by-layer shaping" technical framework, which can meet the requirements of this solution without changing the basic structural principle.

[0037] This solution reduces the number of parts and assembly complexity while maintaining the spherical shape and six-degree-of-freedom motion capability, making it suitable for applications that are more sensitive to cost or weight.

[0038] 3.4.3 Three-axis connecting rod three-ball nested ball hinge bearing Further simplification allows for the construction of a three-layer structure consisting of a "core ball head + two layers of ball sleeves," enabling the convergence of three shafts. A typical application is a simple vector control device. At this point: The core ball joint is connected to a shaft - the Z-axis (which can be set as the reference static shaft or the drive shaft). The second and third layer ball joints are each connected to a drive shaft, namely +Y-axis and +X-axis (these two shafts are perpendicular to each other).

[0039] Because there are only three drive shafts, each shaft is free from opposing shaft constraints. For example, the -Z axis connected by the core ball joint is free from opposing +Z axis constraints, the +Y axis connected by the second ball joint is free from opposing -Y axis constraints, and the +X axis connected by the third ball joint is free from opposing -X axis constraints. Due to the elimination of the geometric constraints of opposing shafts, the space (angle) available for rotation inside the ball joint bearing does not need to be evenly distributed between the two shafts, but is exclusively used by one shaft. Therefore, under the same shaft length and through-hole opening conditions, the available swing angle of each shaft can be doubled (to ±15°, compared to ±7.5° in the five-axis scheme).

[0040] With only three drive shafts, theoretically, a maximum of three degrees of freedom can be independently controlled. If each shaft has a push-pull bidirectional drive capability, precise control of the three translational degrees of freedom of the sphere's center in space can be achieved, while the three rotational degrees of freedom require external constraints or mechanical coupling. Therefore, the three-axis solution is usually used in applications with lower requirements for degrees of freedom (such as three-degree-of-freedom positioning), but it still retains the core advantages of the sphere's shape and concentric intersection.

[0041] The design of through holes is more flexible, and through holes in some layers can even be eliminated (if the inner shaft does not need to pass through the outermost layer), further simplifying the machining process.

[0042] In summary, the technical solution provided by this invention has a clear correspondence between "number of layers - number of shafts - degrees of freedom", as detailed below: For the three-axis, three-ball nested scheme: the total number of ball nest layers is 3, the actual number of shafts is 3, and the number of drive shafts is 2 drives plus 1 stationary shaft or 3 drives. Its six degrees of freedom capability is partial (or six degrees of freedom can be achieved with the help of external constraints). A typical application is a simple pointing mechanism.

[0043] For the four-axis, four-ball nested scheme: the total number of ball nest layers is 4, the actual number of shafts is 4, and the number of drive shafts is 3 drives plus 1 stationary shaft or 4 drives. Its six degrees of freedom capability is partial (or six degrees of freedom can be achieved with the help of external constraints). A typical application is a simple pointing mechanism.

[0044] For the five-axis, five-sphere nested scheme: the total number of sphere nesting layers is 5, the actual number of shafts is 5, and the number of drive shafts is 4 drives plus 1 stationary shaft or 5 drives. Its six-degree-of-freedom capability is a complete six-degree-of-freedom capability, and its typical application is the vector thrust of rotorcraft.

[0045] For the six-axis, six-ball nested scheme: the total number of ball nest layers is 6, the actual number of axes is 6, and the number of driving axes is 6 for full drive. Its six-degree-of-freedom capability is a complete six-degree-of-freedom and symmetrical control. A typical application is a six-axis parallel robot.

[0046] The total number of ball sleeve layers equals the total number of axles, which is also equal to the number of core ball head layers plus the number of outer ball sleeve layers. Each additional ball sleeve layer adds one axle, requiring additional through holes to be drilled in all outer ball sleeve layers for the newly added inner axle, and the flare angle needs to be re-optimized. Conversely, each reduction in ball sleeve layer reduces one axle, and the design margin for the through holes increases accordingly.

[0047] This extension pattern fully demonstrates the technical advantages of the invention's "modular nesting and scalable design," enabling it to flexibly adapt to different working conditions from three-axis to six-axis without changing the core structural principle, providing a unified and complete solution for multi-bar converging ball joint bearings. Attached Figure Description

[0048] The embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the drawings are for illustrative purposes only, and the proportional relationships between the components are not limited to actual manufacturing. Because each layer is only 1 mm thick (1.5 mm for the outermost layer) and is spherical, color drawing is used to clearly distinguish the structure of each layer and its boundaries.

[0049] Figure 1 This is a front 3D view of the "five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball hinge bearing" of the present invention.

[0050] Figure 2 for Figure 1 Top view of the structure shown.

[0051] Figure 3 for Figure 2 The diagram shows a cross-sectional view of the structure obtained by cutting it with a horizontal plane through the center of the circle. The position of each layer of spherical sleeve and its corresponding rod in the XY plane can be clearly seen, as well as the situation of the rod passing through the "through hole".

[0052] Figure 4 for Figure 1 The front view of the structure shown.

[0053] Figure 5 For along Figure 2 The cross-sectional view obtained by cutting the section plane 1-1 shown can clearly show the position of each layer of ball joints and their corresponding rods in the XZ plane, as well as the situation of the rods passing through the "through hole".

[0054] Figure 6 for Figure 1 Side view of the structure shown.

[0055] Figure 7For along Figure 2 The cross-sectional view obtained by cutting the section plane 2-2 shown can clearly show the position of each layer of ball joints and their corresponding rods in the YZ plane, as well as the situation of the rods passing through the "through holes".

[0056] Figure 8 for Figure 1 The diagram shows a three-dimensional top-down view of the structure and its exploded view. The diagram clearly shows the shape and decomposition process of each sphere / sleeve layer, as well as the opening of the "through holes" in each sphere sleeve layer.

[0057] Figure 9 for Figure 1 The structure shown and its exploded view are viewed from the right rearward in three dimensions, allowing a clear view of the shape and decomposition process of each sphere / sleeve layer, as well as the opening of the "through holes" in each sphere sleeve layer.

[0058] Figure 10 for Figure 1 The diagram shows a three-dimensional structural schematic of the motion verification system and its XYZ three-dimensional coordinate system.

[0059] Figure 11 for Figure 10 The diagram shows a two-dimensional structural schematic and a planar coordinate system of the motion verification system.

[0060] Figure 12 For motion verification: In dynamic mode 1, the layout and motion state of the rods and balls in the XY plane; that is: when the five-axis connecting rod and five balls are concentrically nested in a six-degree-of-freedom ball joint bearing (hereinafter referred to as: five-axis ball joint) is subjected to the tension of the +X axis telescopic rod, and moves from the origin (0,0) to the coordinate (15.8,0), the opposite -X axis rod extends by 15.8mm; while the +Y axis and -Y axis rods are forced to move together, that is, swing 7.5°; at this time, the actual Z axis also tilts towards the +X direction and swings 7.5° (assuming that the Z axis rod is the same length as the X and Y axis rods).

[0061] Figure 13 for Figure 12 The diagram shows a two-dimensional structural schematic and a planar coordinate system of the motion verification system.

[0062] Figure 14 for Figure 13 The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane can clearly see the rotation of each layer of ball sleeve and its corresponding rod in the XY plane; among them, the verification point Ax (the most unfavorable point) has no jamming (interference), that is, the cross-sectional verification is successful.

[0063] Figure 15 For along Figure 13 The cross-sectional view obtained by cutting the section 1-1 shown clearly shows the movement state of the Z-axis rod and its core ball head. It can be seen that there is no jamming (interference) phenomenon, that is, the cross-section has been verified.

[0064] Figure 16 for Figure 13 The cross-sectional view obtained by sectioning section 2-2 clearly shows the movement of each layer of ball joint and its shaft in the ZY plane. No jamming (interference) is visible, further verifying that the ball joint operates smoothly within the range of +7.5° to -7.5°. Therefore, this cross-sectional verification is successful. The above three cross-sectional verifications are all successful, confirming that dynamic verification 1 is successful.

[0065] Figure 17 For motion verification: In dynamic mode 2, the layout and motion state of the rods and spheres in the XY plane; that is: when the ball joint is pulled by the -X axis telescopic rod, it moves from the origin (0,0) to the coordinate (-15.8,0), and the opposing +X axis rod extends by 15.8mm; while the +Y axis and -Y axis rods are forced to move together, i.e., swing 7.5°; at this time, the actual Z axis also tilts towards the -X direction and swings 7.5° (assuming that the Z axis rod is the same length as the X and Y axis rods).

[0066] Figure 18 for Figure 17 The diagram shows a two-dimensional structural schematic and a planar coordinate system of the motion verification system.

[0067] Figure 19 for Figure 18 The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane can clearly see the rotation of each layer of ball sleeve and its corresponding rod in the XY plane; among them, the verification point Bx (the most unfavorable point) has no jamming (interference), that is, the cross-sectional verification is successful.

[0068] Figure 20 For along Figure 18 The cross-sectional view obtained by cutting the section 1-1 shown clearly shows the movement state of the Z-axis rod and its core ball head. It can be seen that there is no jamming (interference) phenomenon, that is, the cross-section has been verified.

[0069] Figure 21 for Figure 18 The cross-sectional view obtained by section 2-2 clearly shows the movement of each layer of ball joint and its shaft in the ZY plane. No jamming (interference) is visible, further verifying that the ball joint operates smoothly within the range of +7.5° to -7.5°. Therefore, this cross-sectional verification is successful. The above three cross-sectional verifications are all successful, confirming that dynamic verification 2 is successful.

[0070] Figure 22For motion verification: In dynamic mode 3, the layout and motion state of the rods and spheres in the XY plane; that is: when the ball joint is pulled by the +Y axis telescopic rod, it moves from the origin (0,0) to the coordinate (0,15.8) point, and the opposing -Y axis rod extends by 15.8mm; while the +X axis and -X axis rods are forced to move together, that is, swing 7.5°; at this time, the actual Z axis also tilts in the +Y direction and swings 7.5° (assuming that the Z axis rod is the same length as the X and Y axis rods).

[0071] Figure 23 for Figure 22 The diagram shows a two-dimensional structural schematic and a planar coordinate system of the motion verification system.

[0072] Figure 24 for Figure 23 The cross-sectional view obtained by cutting through the horizontal plane passing through the origin shows the rotation of each layer of ball sleeves and their respective rods; the verification point Cy (the most unfavorable point) did not show any jamming (interference), that is, the cross-section verification is successful.

[0073] Figure 25 For along Figure 23 The cross-sectional view obtained by cutting the section 1-1 shown clearly shows the movement state of the Z-axis rod and its core ball head. It can be seen that there is no jamming (interference) phenomenon, that is, the cross-section has been verified.

[0074] Figure 26 for Figure 23 The cross-sectional view obtained by section 2-2 clearly shows the movement of each layer of ball joint and its shaft in the ZY plane. No jamming (interference) is visible, further verifying that the ball joint operates smoothly within the range of +7.5° to -7.5°. Therefore, this cross-sectional verification is successful. The success of all three cross-sectional verifications confirms that the dynamic verification (Verification 3) is successful.

[0075] Figure 27 For motion verification: In dynamic mode 4, the layout and motion state of the rods and spheres in the XY plane; that is: when the ball joint is pulled by the -Y axis telescopic rod, it moves from the origin (0,0) to the coordinate (0, -15.8) point, and the opposing +Y axis rod extends by 15.8mm; while the +X axis and -X axis rods are forced to move together, that is, swing 7.5°; at this time, the actual Z axis also tilts in the -Y direction and swings 7.5° (assuming that the Z axis rod is the same length as the X and Y axis rods).

[0076] Figure 28 for Figure 27 The diagram shows a two-dimensional structural schematic and a planar coordinate system of the motion verification system.

[0077] Figure 29 for Figure 28The cross-sectional view obtained by cutting through the horizontal plane passing through the origin can be clearly seen in the XY plane, showing the rotation of each layer of ball sleeve and its corresponding rods; among them, the verification point Dy (the most unfavorable point) did not show any jamming (interference), that is, the cross-section verification is successful.

[0078] Figure 30 For along Figure 28 The cross-sectional view obtained by cutting the section 1-1 shown clearly shows the movement state of the Z-axis rod and its core ball head. It can be seen that there is no jamming (interference) phenomenon, that is, the cross-section has been verified.

[0079] Figure 31 for Figure 28 The cross-sectional view obtained by sectioning section 2-2 clearly shows the movement of each layer of ball joint and its shaft in the ZY plane. No jamming (interference) is visible, further verifying that the ball joint operates smoothly within the range of +7.5° to -7.5°. Therefore, this cross-sectional verification is successful. The success of all three cross-sectional verifications confirms that the dynamic verification (section 4) is successful.

[0080] Figure 32 This is a front 3D view of a three-axis connecting rod and three-ball concentric nested ball joint bearing structure.

[0081] Figure 33 for Figure 32 The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane; the position of each layer of ball sleeve and its corresponding rod in the XY plane can be clearly seen in the figure, as well as the situation of the rod passing through the "through hole".

[0082] Figure 34 for Figure 33 The cross-sectional view obtained by cutting along the cutting plane 1-1 shows the position of each layer of ball joints and their corresponding members in the XZ plane, as well as the situation of the members passing through the "through hole".

[0083] Figure 35 for Figure 33 The cross-sectional view obtained by cutting along the cutting plane 2-2 shows the position of each layer of ball joints and their corresponding members in the YZ plane, as well as the situation of the members passing through the "through hole".

[0084] Figure 36 This is a front 3D view of a four-axis connecting rod with four concentric nested ball joint bearings.

[0085] Figure 37 for Figure 36 The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane; the position of each layer of ball sleeve and its corresponding rods can be seen in the figure, as well as the situation of the rods passing through the "through hole".

[0086] Figure 38 for Figure 37The cross-sectional view obtained by cutting along the cutting plane 1-1 shows the position of each layer of ball joints and their corresponding members in the XZ plane, as well as the situation of the members passing through the "through hole".

[0087] Figure 39 for Figure 37 The cross-sectional view obtained by cutting along the cutting plane 2-2 shows the position of each layer of ball joints and their corresponding rods in the YZ plane, as well as the situation of the rods passing through the "through holes".

[0088] Figure 40 This is a front 3D view of a six-axis connecting rod and six-ball concentric nested ball joint bearing structure.

[0089] Figure 41 for Figure 40 The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane; the position of each layer of ball sleeve and its corresponding rods can be seen in the figure, as well as the situation of the rods passing through the "through hole".

[0090] Figure 42 for Figure 41 The cross-sectional view obtained by cutting along the cutting plane 1-1 shows the position of each layer of ball joints and their corresponding members in the XZ plane, as well as the situation of the members passing through the "through hole".

[0091] Figure 43 for Figure 41 The cross-sectional view obtained by cutting along the cutting plane 2-2 shows the position of each layer of ball joints and their corresponding rods in the YZ plane, as well as the situation of the rods passing through the "through holes".

[0092] Figure 44 The ball joint bearing used in a five-axis linkage vector drive system according to Embodiment 1 of the present invention is a stationary axis, meaning it is not driven and does not extend or retract; the -Z axis can carry a load, such as a motor-rotor power system. Each of the +X, -X, +Y, and -Y axes in the XY plane is equipped with a telescopic rod with driving force. Through the "five-axis linkage five-ball concentric nested six-degree-of-freedom ball joint bearing" of the present invention, the stationary axis shaft head is driven, achieving omnidirectional vector thrust.

[0093] Figure 45 The diagram shows a comparison of a five-axis connecting rod with a five-ball concentric nested six-degree-of-freedom ball joint bearing with a "lubricating layer" with each sub-level. Compared with the aforementioned ordinary "five-axis connecting rod with a five-ball concentric nested six-degree-of-freedom ball joint bearing" scheme, there is a "lubricating layer" between the first and second levels, between the second and third levels, between the third and fourth levels, and between the fourth and fifth levels.

[0094] Figure 46 for Figure 45The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane; the position of each layer of ball sleeve and its corresponding rods can be seen in the figure, as well as the situation of the rods passing through the "through hole".

[0095] Figure 47 for Figure 45 The cross-sectional view obtained by cutting along the cutting plane 1-1 shows the position of each layer of ball joints and their corresponding members in the XZ plane, as well as the situation of the members passing through the "through hole".

[0096] Figure 48 for Figure 45 The cross-sectional view obtained by cutting along the cutting plane 2-2 shows the position of each layer of ball joints and their corresponding rods in the YZ plane, as well as the situation of the rods passing through the "through holes".

[0097] Figure 49 In a preferred embodiment of the lubrication layer in Embodiment 2 of the present invention, the lubrication layer is made of brass alloy ball sleeve, which also serves as a "cage". The lubrication layer ball sleeve is uniformly inlaid with stainless steel balls.

[0098] Figure 50 for Figure 49 The cross-sectional view obtained by cutting through the center of the ball with a horizontal plane; the relationship between the lubricating layer and the ball and the "through hole" can be seen in the figure.

[0099] Figure 51 for Figure 50 The cross-sectional view obtained by cutting along the shown section plane 1-1 can clearly show the stainless steel balls embedded in the lubrication layer (cage) in the XZ plane, as well as the rods passing through the "through holes".

[0100] Figure 52 for Figure 50 The cross-sectional view obtained by cutting along the shown section plane 2-2 can clearly show the stainless steel balls embedded in the lubrication layer (cage) in the YZ plane, as well as the rods passing through the "through holes".

[0101] The meanings of the labels in the attached diagram are as follows: 5500: Five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing; 100: First-level ball (core ball) club, 110: First-level ball head, 120: First-level pivot (-Z axis) 200: Second-level ball joint; 210: Second-level ball sleeve; 220: Second-level shaft (+Y axis); 211: Corresponding -Z axis opening (through hole) for the second level. 300: Third-level ball joint; 310: Third-level ball sleeve; 320: Third-level shaft (+X axis); 311: Corresponding -Z axis opening (through hole) for the third level; 312: Corresponding +Y axis opening (through hole) for the third level. 400: Fourth-level ball joint; 410: Fourth-level ball sleeve; 420: Fourth-level shaft (-Y axis); 411: Fourth-level corresponding -Z axis opening (through hole); 412: Fourth-level corresponding +Y axis opening (through hole); 413: Fourth-level corresponding +X axis opening (through hole). 500: Fifth-level ball joint; 510: Fifth-level ball sleeve; 520: Fifth-level shaft (-X-axis); 511: Fifth-level corresponding -Z-axis opening (through hole); 512: Fifth-level corresponding +Y-axis opening (through hole); 513: Fifth-level corresponding +X-axis opening (through hole); 514: Fifth-level corresponding -Y-axis opening (through hole) 6600: Six-axis connecting rod, six-ball concentric nested ball joint bearing; 600: Sixth-level ball joint; 610: Sixth-level ball sleeve; 620: Sixth-level shaft (+Z axis); 611: Sixth-level corresponding -Z axis opening (through hole); 612: Sixth-level corresponding +Y axis opening (through hole); 613: Sixth-level corresponding +X axis opening (through hole); 614: Sixth-level corresponding -Y axis opening (through hole); 615: Sixth-level corresponding -X axis opening (through hole) 9500: A total of nine layers of ball sleeves, five of which are shaft ball sleeves, and four are "lubricating layers". 1200: The "lubricating layer" between the first and second layers in the second embodiment. 2300: The "lubricating layer" between the second and third layers in the second embodiment. 3400: The "lubricating layer" between the third and fourth layers in the second embodiment. 4500: The "lubricating layer" between the fourth and fifth layers in the second embodiment. 4510: Lubricating layer ball sleeve (ball cage, brass alloy optional); 4520: Ball (stainless steel optional); 4511: Lubricating layer -Z-axis opening (through hole); 4512: Lubricating layer +Y-axis opening (through hole); 4513: Lubricating layer +X-axis opening (through hole); 4514: Lubricating layer -Y-axis opening (through hole) Detailed Implementation

[0102] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. The following description is exemplary and not restrictive; modifications and variations can be made by those skilled in the art within the spirit of the present invention.

[0103] 5.1 Example 1 A five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing (5500).

[0104] 5.1.1 Application Scenario Model Figure 44 A five-axis linkage vector drive system is illustrated. In this system, the -Z axis is a stationary axis, i.e., a non-driving reference axis, with a fixed length and no telescopic movement. This stationary axis (-Z axis) can be used to carry loads, such as an electric motor-rotor power system. In the XY plane, a telescopic rod with driving capability is arranged in each of the +X, -X, +Y, and -Y axis directions. Through the five-ball concentric nested six-degree-of-freedom ball joint bearings of the present invention, these telescopic rods cooperate to drive the shaft head of the stationary axis, thereby achieving omnidirectional vector thrust.

[0105] As an example, the parameters are set as follows: the lengths of the telescopic rods along the +X, -X, +Y, and -Y axes, as well as the stationary axis (-Z axis), are all 120mm. With each axis swinging at an angle of ±7.5°, the range of motion of the ball's center (i.e., the reference point for the ball joint's motion) constitutes a sphere with a radius of 120mm. All points within the spherical crown region (top cover area) with a latitude radius of R=15.8mm, as shown in the diagram, can be continuously reached.

[0106] Special note: The issues of telescopic rod drive and motor-rotor power system are not within the scope of this invention and will not be discussed further.

[0107] 5.1.2 Structural Composition The five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing (5500) consists of a first-level core ball head and its shaft (100), four concentrically nested ball sleeves on the core ball head, and shafts (200, 300, 400, 500) for each level. It can be made of materials such as bearing steel, stainless steel, titanium alloy, aluminum alloy, copper alloy, and PEEK engineering plastics. Its structural diagram is shown below. Figures 1 to 7 Its composition process is as follows Figure 8 , Figure 9 (Reverse order of the exploded diagram).

[0108] 5.1.3 Manufacturing Materials In this case, because it is used in an unmanned aerial vehicle (UAV) system, the core ball joint uses a titanium alloy substrate with a surface-hardened coating, while the outer ball sleeve is made of aluminum alloy. The core ball has a diameter of 6mm, and its mounting shaft has a diameter of 3mm.

[0109] The second to fourth level ball sleeves use 1mm thick sleeves, and the fifth level uses 1.5mm thick sleeves; the material is aluminum alloy.

[0110] 5.1.4 Assembly Method 1. Ball sleeve heating assembly: The second to fifth layers of ball sleeves are heated sequentially to a predetermined temperature (e.g., 150℃-200℃) to increase their inner diameter due to thermal expansion. Using a special fixture, the heated ball sleeves are quickly and concentrically fitted onto the inner ball head or ball sleeve, forming a tight interference fit after cooling.

[0111] 2. Shaft installation: After each layer of ball sleeve has cooled, insert the corresponding drive shaft through the preset "through hole" on the outer surface of the ball sleeve; the root of the shaft is provided with a positioning boss, which cooperates with the corresponding positioning hole on the ball sleeve.

[0112] 3. Fixing Method: After positioning, it can be fixed using any of the following methods: a) Laser welding, circumferential welding along the joint between the shaft and the ball sleeve; b) High-strength structural adhesive bonding; c) Radial pin fastening. In this embodiment, laser welding is preferred to ensure connection strength and the integrity of the ball's shape.

[0113] 5.2 Example 2 A five-axis connecting rod with a "lubricating layer," featuring five concentric nested six-degree-of-freedom ball joint bearing, such as... Figure 45 As shown.

[0114] Based on a five-axis connecting rod with a five-ball concentric nested six-degree-of-freedom ball joint bearing, a rolling lubrication assembly (1200) is installed between the first and second stages. This assembly includes a thin-walled spherical ball cage and a plurality of balls uniformly embedded in the cage. The balls form rolling contact with the spherical surfaces of the inner and outer ball sleeves, respectively, converting sliding friction into rolling friction, significantly reducing friction and wear.

[0115] At the same time, a "lubricating layer" (2300) is added between the second and third levels, a "lubricating layer" (3400) is added between the third and fourth levels, and a "lubricating layer" (4500) is added between the fourth and fifth levels.

[0116] Each lubrication layer (1200, 2300, 3400, 4500) has the same structure, including a thin-walled spherical ball retainer and multiple balls evenly embedded thereon. Taking the lubrication layer (4500) between the fourth and fifth levels as an example: multiple balls (4520) are evenly embedded on the ball retainer (4510), and the balls form rolling contact with the spherical surfaces of the inner and outer ball sleeves, respectively, transforming sliding friction into rolling friction, greatly reducing friction and wear.

[0117] The embedded "balls" can also be replaced with other lubricating materials, such as graphite; or even the entire lubricating layer can be replaced by a lubricating material, such as PEEK.

[0118] As a preferred example, the lubrication scheme can also adopt the following scheme: a layered lubrication layer scheme. Taking the "five-axis connecting rod five-ball concentric nested six-degree-of-freedom ball joint bearing" as an example, in the second ball sleeve of the first to third layers of ball sleeves, and in the fourth ball sleeve of the third to fifth layers of ball sleeves, lubricating material (graphite or ball bearings, etc.) is directly and uniformly embedded on the ball sleeves, and the arrangement scheme is similar to that of steel ball bearings.

[0119] 5.3 Example 3 This embodiment provides a six-axis connecting rod six-ball concentric nested ball joint bearing (6600).

[0120] The difference between this and Embodiment 1 (five-axis scheme) is that a sixth-layer ball sleeve (610) is further coaxially nested outside the fifth-layer ball sleeve (510). A sixth drive shaft (620), for example, a drive shaft along the +Z direction, is fixedly connected to the sixth-layer ball sleeve (610). Correspondingly, in addition to having five through holes (611-615) for the -Z axis, +Y axis, +X axis, -Y axis, and -X axis to pass through, the hole-opening strategy on the sixth-layer ball sleeve (610) is the same as that of the five-axis scheme, that is: the hole-opening boundary line of the five-axis scheme continues to the sixth-layer ball sleeve, and the hole is opened according to this boundary line to maintain the smoothness with the boundary of the through hole of the fifth-layer ball hinge.

[0121] By coordinating the extension and retraction of the six drive shafts, fully symmetrical six-degree-of-freedom full drive control can be achieved.

Claims

1. A five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing, characterized in that, include: The core ball joint is fixedly connected to a reference shaft along the -Z axis, which serves as the motion reference for the entire mechanism. At least four concentric spherical sleeves are nested concentrically around the core spherical head. Each spherical sleeve is a concentric spherical shell structure, and a drive shaft is fixedly connected to each spherical sleeve. A through-hole structure is formed on each layer of the ball sleeve for the inner layer's shaft to pass through. The through-hole is flared in the thickness direction of the ball sleeve, and its opening range is optimized layer by layer according to the radial position of each layer of ball sleeve and the diameter of the shaft. Each of the ball sleeves in each layer can rotate independently around the center of the core ball head. Through the coordinated extension and retraction of each drive shaft, the core ball head is driven to achieve six degrees of freedom in space.

2. The five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, The number of ball sleeves is five, including a first core ball head, a second ball sleeve, a third ball sleeve, a fourth ball sleeve, and a fifth ball sleeve.

3. The five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing according to claim 2, characterized in that, The second layer of ball sleeve is fixedly connected to the +Y axis drive shaft, the third layer of ball sleeve is fixedly connected to the +X axis drive shaft, the fourth layer of ball sleeve is fixedly connected to the -Y axis drive shaft, and the fifth layer of ball sleeve is fixedly connected to the -X axis drive shaft.

4. The five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, The flared opening of the through hole extends 22.5° to 27.5° to the left and right in the XY plane with the center of the ball as the origin and the center line of each shaft as the reference, forming a flared opening with a cone angle of 45° to 55°.

5. The five-axis connecting rod, five-ball concentric nested six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, A self-lubricating layer is provided between the ball sleeves.

6. The five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing according to claim 5, characterized in that, The self-lubricating layer is one of copper alloy inlaid with graphite material, PEEK composite material, or a rolling assembly containing balls and a cage.

7. The five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, The core ball head is made of titanium alloy substrate with surface hardening coating, and the outer ball sleeve is made of PEEK composite material or aluminum alloy.

8. The five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, The core ball head, each layer of ball sleeves, and the corresponding shaft are all made of bearing steel.

9. The five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, A sixth ball sleeve is further coaxially nested outside the fifth ball sleeve, and a drive shaft along the +Z direction is fixedly connected to the sixth ball sleeve, forming a six-axis connecting rod and a six-ball concentric nested ball hinge bearing.

10. The five-axis connecting rod, five-ball concentric nested, six-degree-of-freedom ball joint bearing according to claim 1, characterized in that, The number of ball sleeves is three or four, which respectively constitute a ball hinge bearing structure for a three-axis connecting rod or a four-axis connecting rod.

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