A centrifugal clutch for a drone

Abstract

The unmanned aerial vehicle centrifugal clutch provided by the application replaces the traditional bottom plate assembly and spline sleeve riveting shaft welding connection mode through cam matching embedding design, eliminates the radial runout problem caused by welding thermal deformation, thereby reducing the tremor and abnormal sound of the shoe block during work, the bidirectional symmetrical cam groove structure makes the clutch have equal transmission capacity in forward and reverse rotation, without the need for special design for the rotation direction, thereby expanding the working mode of the unmanned aerial vehicle, simplifying the assembly process, avoiding the potential failure points of the welding deformation and riveting process, and helping to improve the production consistency and product yield. The air flow in the working cavity of the clutch is enhanced, the heat diffusion of the friction interface is accelerated, the working temperature of the friction material is reduced, the thermal degradation phenomenon is reduced, and the reliability under high temperature working conditions is improved.

Description

Technical Field

[0001] This application relates to the field of unmanned aerial vehicle (UAV) technology, specifically to a centrifugal clutch for UAVs. Background Technology

[0002] Centrifugal clutches, as key components of the transmission systems of unmanned helicopters and other drones, are primarily used to connect and disconnect the engine from the drive shaft. Their performance directly affects the drone's starting smoothness, transmission efficiency, and component lifespan. These clutches allow the prime mover to start near no-load, load smoothly, reduce engine torsional vibration and shock, extend the lifespan of transmission gears, and prevent overload of the transmission system.

[0003] Currently, the centrifugal clutches commonly used in UAVs mainly include free-block type, radial spring block type (such as tension spring type), and leaf spring block type. Among them, the free-block centrifugal clutch has a simple structure, light weight, and short engagement time, but poor smoothness and is prone to slippage and overheating when not synchronized, making it unsuitable for frequent start-up applications. The radial spring block centrifugal clutch requires overcoming the spring clamping force to achieve contact between the block and the inner wall of the housing. Although its smoothness is better than the free-block type, its transmitted torque is smaller and the engagement time is longer, making it unsuitable for frequent start-up applications as well. Furthermore, the traditional tension spring type, as a type of clutch, has a separate tension spring for each block, and the tension springs work differently, resulting in poor consistency of engagement between the block and the driven part and greater vibration. Although the leaf spring block centrifugal clutch is small in size and light in weight, it has a complex structure, is difficult to manufacture, inconvenient to maintain, and has poor adjustability of the leaf springs.

[0004] In addition, existing centrifugal clutches have other significant drawbacks: First, the friction surfaces continuously generate a large amount of heat during friction operation, and the lack of an effective airflow acceleration mechanism leads to heat accumulation and a sharp rise in temperature, which can easily cause thermal degradation of the friction material, reduce the friction coefficient and torque transmission capacity, and pose a risk of thermal failure. Second, the base plate assembly and spline sleeve are mostly connected by welding, and high temperatures can easily cause thermal deformation of both, especially causing the spline sleeve to produce large radial runout, which in turn leads to increased shoe vibration, resulting in uneven friction, increased wear, abnormal noise, and deterioration of shift smoothness. Third, the shoes are mostly fixed by riveting shafts, which can only rotate in one direction, and the friction surfaces are in contact with the inner cavity of the outer cover during operation. When the speed increases sharply, impact loads are easily generated, affecting the smoothness of transmission and the life of components. Summary of the Invention

[0005] In view of the above problems, the present invention provides a centrifugal clutch for unmanned aerial vehicles (UAVs) that overcomes or at least partially solves the above problems, the technical solution of which is as follows:

[0006] A centrifugal clutch for unmanned aerial vehicles includes a spline sleeve, shoe blocks, a tension spring, and an outer cover. The spline sleeve is connected to the engine input shaft. Multiple shoe blocks are tightened inward by the tension spring. A cam engagement structure with the spline sleeve is formed between the shoe blocks and the spline sleeve, allowing the shoe blocks to slide radially along the cam surface of the spline sleeve under centrifugal force. The friction surface of the shoe blocks is an eccentric arc surface, the center of which is offset from the geometric center of the shoe blocks, and the eccentric direction points towards the axis of the spline sleeve.

[0007] Preferably, the outer side of the spline sleeve is provided with an airflow acceleration mechanism.

[0008] Preferably, the airflow acceleration mechanism is an impeller fixed to the spline sleeve, used to drive the airflow circulation in the clutch cavity when rotating; the impeller is provided with blades.

[0009] Preferably, the spline sleeve is composed of an upper cover plate, a lower cover plate, and an intermediate sleeve, wherein the upper cover plate and the lower cover plate are fixedly connected to the upper and lower ends of the intermediate sleeve, respectively; and blades are provided on the upper cover plate.

[0010] Preferably, the blade is a radial straight blade.

[0011] Preferably, the cam engagement structure includes a cam groove on the outer periphery of the spline sleeve and a protrusion on the inner end of the shoe block, wherein the protrusion is embedded in the cam groove to form a sliding pair.

[0012] Preferably, the cam groove has a bidirectional symmetrical profile, and the shoe can slide radially outward along the cam surface under the action of centrifugal force in both forward and reverse directions.

[0013] Preferably, the hoof block has an arc-shaped groove at its end, and the arc-shaped grooves of multiple hoof blocks are combined to form an annular groove. The tension spring is located in the annular groove and pulls the multiple hoof blocks inward.

[0014] Preferably, the outer cover sidewall is provided with heat dissipation holes; the axial distribution of the heat dissipation holes corresponds to the air inlet end of the blade.

[0015] Beneficial effects

[0016] This invention significantly improves the performance of a UAV centrifugal clutch through structural optimization. The embedded cam design replaces the traditional welded connection between the base plate assembly and the spline sleeve, eliminating radial runout caused by welding thermal deformation and thus reducing vibration and noise during clutch operation. The bidirectional symmetrical cam groove structure enables the clutch to have equal transmission capacity in both forward and reverse directions, eliminating the need for specialized design for the rotation direction and expanding the operational possibilities of the UAV. It also simplifies the assembly process, avoiding potential failure points from welding deformation and riveting, contributing to improved production consistency and product yield. Enhanced airflow within the clutch working chamber accelerates heat dissipation at the friction interface, helping to lower the operating temperature of the friction material, mitigate thermal degradation, and improve reliability under high-temperature conditions. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and provide explanations, but do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 This is a schematic diagram of the centrifugal clutch structure for the UAV of the present invention;

[0019] Figure 2 This is a schematic diagram of the centrifugal clutch of the UAV of the present invention under an explosive state;

[0020] Figure 3 This is a schematic diagram of a UAV centrifugal clutch in an explosive state, according to another embodiment of the present invention.

[0021] Figure 4 A schematic diagram of the spline sleeve, shoe block, and tension spring assembly;

[0022] Figure 5 A cross-sectional view of the spline sleeve, shoe block, and tension spring assembly;

[0023] Figure 6 This is a front view of the clutch cover structure of the present invention.

[0024] Attached icon number

[0025] 1-Spline sleeve; 11-Cam groove; 12-Intermediate sleeve; 13-Upper cover plate; 14-Lower cover plate; 2-Horses; 21-Protrusion; 22-Arc groove; 23-Annular groove; 3-Tension spring; 4-Impeller; 5-Outer cover; 51-Heat dissipation hole; 6-Blade. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 and Figure 2 As shown in the figure, an embodiment of the present invention discloses a centrifugal clutch for a drone, including a spline sleeve 1, shoe blocks 2, a tension spring 3, and an outer cover 5. The spline sleeve 1 is connected to the engine input shaft. Multiple shoe blocks 2 are tightened inward by the tension spring 3. The shoe blocks 2 and the spline sleeve 1 form a cam engagement structure that can transmit power in both directions, so that the shoe blocks 2 slide radially along the cam surface of the spline sleeve 1 under the action of centrifugal force. The friction surface of the shoe blocks 2 is an eccentric arc surface, the center of which is offset from the geometric center of the shoe blocks, and the eccentric direction points to the axis of the spline sleeve 1.

[0028] In practical applications, the inner spline of the spline sleeve 1 is connected to the engine input shaft. Its outer circumferential surface is machined with symmetrically distributed cam grooves. These cam grooves can adopt a wavy or involute profile, and the bidirectional symmetrical design of the grooves ensures consistent forward and reverse transmission. Multiple shoe blocks 2 are used, typically three. The inner end of each shoe block 2 is engaged with the spline sleeve 1 using existing technology, completely eliminating the traditional welding connection method. This fundamentally eliminates the vibration of the shoe blocks 2 caused by welding thermal deformation, especially the radial runout of the spline sleeve 1. Frictional contact is more uniform, significantly reducing abnormal noise and wear, and improving the smoothness of the transmission process. The outer surface of each shoe block 2 is an eccentric arc friction surface, meaning that the center O' of the arc-shaped outer surface of the shoe block 2 deviates from its geometric center O, with the offset direction pointing towards the axis of the spline sleeve 1.

[0029] Specifically, the center of the friction surface of the shoe block 2 is located at one end of a line along the direction of the center of the shoe block friction surface. In the initial engagement phase, the center of the friction surface of the shoe block 2 engages with the outer cover 5 first. As the rotational speed increases, the two ends of the friction surface then engage with the outer cover 5. This structural design provides better stability for the shoe block 2 and the outer cover 5 in the initial engagement phase. After the break-in period, the front and rear ends of the shoe block 2 gradually engage to transmit torque. The friction surface of the shoe block 2 adopts an off-center design, meaning the center is deviated from the geometric center. This allows the middle of the shoe block friction surface to contact the outer cover 5 first in the initial engagement phase, with the two ends gradually engaging fully as the rotational speed increases. This gradual engagement process significantly improves the smoothness of clutch engagement, effectively avoids shock and vibration in the initial engagement phase, and results in more stable torque output.

[0030] In other embodiments, an airflow acceleration mechanism is provided on the outer side of the spline sleeve 1.

[0031] In practical applications, the airflow acceleration mechanism refers to the structure used to accelerate the airflow inside the clutch and remove the heat generated by friction. Specifically, it can be achieved by machining a spiral groove on the outer cylindrical surface of the spline sleeve 1, or by welding or casting an arc-shaped guide vane on the axial end face of the spline sleeve 1, or by opening radial ventilation holes inside the spline sleeve 1.

[0032] In another specific embodiment, the airflow acceleration mechanism is an impeller 4 fixed on the spline sleeve 1, which is used to drive the airflow circulation in the clutch cavity when rotating; the impeller 4 is provided with blades 6.

[0033] In practical applications, the impeller 4 can be bolted or interference-fitted to the spline sleeve 1. The impeller is equipped with blades 6, which can be forward-curved or backward-curved blades using existing technology. The impeller 4 can drive the airflow circulation in the clutch chamber when rotating. Multiple blades 6 are provided.

[0034] Specifically, this invention integrates an impeller 4 to force airflow circulation within the clutch working chamber, and in conjunction with the heat dissipation holes 51 in the outer casing 5, significantly accelerates the diffusion and discharge of heat from the friction interface. This effectively avoids thermal degradation caused by localized high-temperature accumulation in the friction material, maintains a stable coefficient of friction and torque transmission capability, and greatly improves the reliability and service life of the clutch under high-load, long-term operating conditions.

[0035] In another embodiment, such as Figure 3 As shown, the spline sleeve 1 is composed of an upper cover plate 13, a lower cover plate 14 and an intermediate sleeve 12. The upper cover plate 13 and the lower cover plate 14 are fixedly connected to the upper and lower ends of the intermediate sleeve 12, respectively. The upper cover plate 13 is provided with blades 6.

[0036] In practical applications, the spline sleeve 1 can be integrally formed or it can be a separate piece. In this embodiment, the spline sleeve 1 is a separate piece, consisting of an upper cover plate 13, a lower cover plate 14, and an intermediate sleeve 12. The upper cover plate 13 is fixed to the upper end of the intermediate sleeve 12, and the lower cover plate 14 is fixed to the lower end of the intermediate sleeve 12. The fixing method can adopt existing technology, and in this embodiment, a countersunk bolt connection is used. The upper cover plate has multiple blades 6, preferably three groups of four blades each.

[0037] Specifically, the separate spline sleeve facilitates processing and assembly, reducing the processing cost of the clutch of this invention.

[0038] In some more specific implementation schemes, such as Figure 2 and Figure 3 As shown, blade 6 is a radial straight blade. This blade shape ensures that blade 6 functions effectively regardless of whether the clutch rotates in either direction.

[0039] In other implementation schemes, such as Figure 4 and Figure 5 As shown, the cam mating structure includes a cam groove on the outer periphery of the spline sleeve 1 and a protrusion on the inner end of the shoe block 2. The protrusion is embedded in the cam groove to form a sliding pair.

[0040] In practical applications, the spline sleeve cam groove 11 is machined on the outer circumferential surface of the spline sleeve 1, and multiple grooves are evenly distributed along the circumference, corresponding to the number of shoe blocks 2. The shoe block protrusion 21 is located at the inner end of the shoe block 2, and the shoe block protrusion 21 is embedded in the cam groove 11 to form a sliding pair.

[0041] Compared to traditional riveting processes, the cam-fit structure of the shoe block embedded in the spline sleeve, and the spline connection between the spline sleeve and the base plate assembly (with an anti-fretting wear coating), significantly reduce the complexity and difficulty of the manufacturing process. This avoids the risks associated with welding deformation, riveting failure, and other multi-step processes, improving production efficiency and the consistency of the final product quality.

[0042] In some other specific embodiments, the cam groove 11 has a bidirectional symmetrical profile, and the shoe 2 can slide radially outward along the cam surface under the action of centrifugal force in both forward and reverse directions.

[0043] In practical applications, the cam surface is the contact surface between the cam groove 11 and the protrusion 21. The center line of the motor groove 11 is the reference circle, and the forward and reverse contact surfaces of the shoe 2 within the cam groove 11 are completely symmetrical.

[0044] Specifically, when the engine output shaft switches between forward and reverse rotation, the clutch of this invention automatically adapts without mechanical adjustment. The bidirectional symmetrical design of the cam groove 11 and the protrusion 21 allows the shoe 2 to smoothly slide radially outward along the cam surface under centrifugal force, regardless of whether it rotates forward or reverse, effectively engaging with the outer cover 5 to transmit torque. Efficient and stable bidirectional power transmission can be achieved without additional design for a specific direction of rotation.

[0045] In another embodiment, the hoof block 2 has an arc-shaped groove 22 at its end, and the arc-shaped grooves 22 of the multiple hoof blocks 2 are combined to form an annular groove 23. The tension spring 3 is located in the annular groove 23 and pulls the multiple hoof blocks 2 inward.

[0046] In practical applications, when multiple of the shoe blocks 2 are closed, their end arc-shaped grooves 22 combine to form a continuous annular groove 23. The tension spring 3 is placed in the annular groove 23. The tension spring 3 and the annular groove 23 are in an interference fit. The tension spring 3 is circumferentially constrained by the annular groove 23, generating a uniform radial tension. The interference fit ensures that the tension spring 3 remains positioned within the annular groove 23 under the action of centrifugal force.

[0047] Specifically, the upper and lower end faces of the shoe block 2 are provided with the arc-shaped groove 22, that is, when multiple shoes block 2 are closed, two tension springs 3 are placed in the upper and lower annular grooves 23. The double tension springs form a torque to suppress shoe block overturning; at low speed, the upper tension spring mainly tightens, and at high speed, the lower tension spring strengthens the constraint to adapt to changes in centrifugal force gradient.

[0048] In other implementations, such as Figure 6 As shown, the outer casing 5 has heat dissipation holes 51 on its side wall, and the axial distribution of these holes 51 corresponds to the air inlet end of the impeller 4 blades. Specifically, the circulating airflow generated by the rotation of the impeller 4 not only dissipates heat but also continuously blows away wear debris and dust generated by friction from the friction interface and clutch cavity. This reduces abrasive wear, keeps the friction surface clean, and further improves the performance and lifespan of the clutch.

[0049] In practical applications, engine power is input through spline sleeve 1, which drives the connected clutch shoe 2 to rotate. Under centrifugal force, the clutch shoe 2 overcomes the spring force of tension spring 3 and opens outward, pressing against the inner surface of outer cover 5. Torque is transmitted to outer cover 5 through friction, thereby driving the load. As the speed increases, a large amount of heat is generated at the friction interface. When the speed reaches a certain value, the circulating air in the clutch chamber begins to increase. The rotating impeller 4 generates circulating airflow, balancing the temperature of the friction interface and the chamber. Combined with the heat dissipation holes 51 of outer cover 5, some of the heat and wear debris accumulated in the clutch chamber are dissipated. When the speed decreases, the clutch shoe 2 retracts under the action of tension spring 3, disengaging from outer cover 5, and the clutch disengages. This achieves air circulation and material handling within the clutch chamber.

[0050] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0051] It should be understood that the use of terms such as "system," "device," "unit," and / or "module" in this application is merely one method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0052] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0053] In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, in the description of the embodiments of this application, "multiple" refers to two or more.

[0054] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0055] If a flowchart is used in this application, it is used to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0056] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A centrifugal clutch for an unmanned aerial vehicle (UAV), comprising a splined sleeve, shoe blocks, a tension spring, and an outer cover, wherein the splined sleeve is connected to an engine input shaft, and the plurality of shoe blocks are tightened inward by the tension spring, characterized in that: The shoe block and the spline sleeve form a cam engagement structure that allows bidirectional transmission, so that the shoe block slides radially along the cam surface of the spline sleeve under the action of centrifugal force; the friction surface of the shoe block is an eccentric arc surface, the center of which is offset from the geometric center of the shoe block, and the eccentric direction points to the axis of the spline sleeve.

2. The UAV centrifugal clutch according to claim 1, characterized in that, An airflow acceleration mechanism is provided on the outside of the spline sleeve.

3. The UAV centrifugal clutch according to claim 2, characterized in that, The airflow acceleration mechanism is an impeller fixed to the spline sleeve, used to drive the airflow circulation in the clutch chamber when rotating; the impeller is provided with blades.

4. The UAV centrifugal clutch according to claim 1, characterized in that, The spline sleeve consists of an upper cover plate, a lower cover plate, and an intermediate sleeve. The upper cover plate and the lower cover plate are fixedly connected to the upper and lower ends of the intermediate sleeve, respectively. The upper cover plate is provided with blades.

5. The UAV centrifugal clutch according to claim 3 or 4, characterized in that: The blade is a radial straight blade.

6. The UAV centrifugal clutch according to claim 1, characterized in that: The cam mating structure includes a cam groove on the outer periphery of the spline sleeve and a protrusion on the inner end of the shoe block, wherein the protrusion is embedded in the cam groove to form a sliding pair.

7. The UAV centrifugal clutch according to claim 6, characterized in that: The cam groove has a bidirectional symmetrical profile, and the shoe can slide radially outward along the cam surface under the action of centrifugal force in both forward and reverse directions.

8. The UAV centrifugal clutch according to claim 1, characterized in that: The end of the hoof block has an arc-shaped groove, and the arc-shaped grooves of multiple hoof blocks are combined to form an annular groove. The tension spring is located in the annular groove and pulls the multiple hoof blocks inward.

9. The UAV centrifugal clutch according to claim 3 or 4, characterized in that: The outer cover sidewall is provided with heat dissipation holes; the axial distribution of the heat dissipation holes corresponds to the air inlet end of the blade.

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