Starting structure of in-line piston engine, engine and aircraft thereof

Abstract

The utility model relates to the technical field of engine starting, in particular to a starting structure of an in-line piston engine, an engine and an aircraft thereof, which comprises a starting motor, the starting motor is installed on the upper portion of an engine crankshaft box body, and the output end of the starting motor penetrates through the box body and drives a reduction gear assembly through gear meshing. The reduction gear assembly comprises a reduction gear and a driving gear, the reduction gear is formed by laminating a plurality of large gears, the driving gear is meshed with the reduction gear, the large gears are laminated through friction plates and belleville springs, a starting gear is arranged at the front end of the engine crankshaft, and a one-way overrunning clutch assembly is integrally arranged on the starting gear. According to the utility model, the installation position of the starting motor is moved from the end part of the crankcase body to the upper part of the crankcase body, and meanwhile, the number of gears is reduced, so that the miniaturization design of the crankcase body is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of engine starting, and specifically relates to a starting structure of an in-line piston engine, an engine and an aircraft thereof. Background Art

[0002] In recent years, drones (UAVs) using four-cylinder piston engines designed for small manned aircraft to directly drive their propellers have gradually entered the market. However, the mainstream four-cylinder piston engines for small manned aircraft currently on the market generally adopt a horizontally opposed arrangement, and the use of UAVs using in-line four-cylinder piston engines remains relatively rare. Existing engine starting systems suffer from numerous drawbacks: First, they are prone to unstable operation during the starting process, resulting in significant vibration and noise. Second, traditional starting mechanisms typically utilize a complex multi-stage gear reduction system. This design not only increases the complexity of the transmission system but also requires the starting mechanism to be located outside the engine crankshaft, resulting in an illogical overall engine layout and low space utilization. This structural layout severely restricts the development of engine miniaturization, making it particularly difficult to meet the requirements of aircraft applications such as UAVs, which have strict space requirements. Furthermore, structural limitations of existing starting systems make it difficult to achieve a lightweight design while maintaining starting performance, further limiting their potential for application in the aviation sector. To address these issues, improvements to existing technologies are urgently needed. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention aims to provide a starting structure for an in-line piston engine, an engine and an aircraft thereof.

[0004] To achieve the above-mentioned object, the present invention provides the following technical solution: a starting structure of an in-line piston engine, comprising a starter motor, the starter motor being mounted on the upper part of the engine crankcase, the output end of the starter motor passing through the case and driving a reduction gear assembly through gear meshing, a starter gear being provided at the front end of the engine crankshaft, a one-way overrunning clutch assembly being integrated on the starter gear, a transmission shaft, a transmission gear and an idler gear being provided in linkage with each other between the starter gear and the reduction gear assembly, the reduction gear assembly comprising a reduction gear composed of a plurality of stacked large gears and a drive gear meshing with the reduction gear, the tooth width of the drive gear being consistent with the overall thickness of the reduction gear, the drive gear being fixedly connected to the output end of the starter motor, friction plates being provided between adjacent two large gears on the reduction gear, stepped annular grooves being provided on both sides of the friction plate near the inner hole, disc springs being provided on both sides of the friction plate corresponding to the corresponding stepped annular grooves, and a pressure cover cooperating with the transmission shaft being provided on the outermost two sides of the reduction gear.

[0005] In some embodiments, the thickness of the tooth body of the large gear is greater than the thickness of the wheel body, the tooth body side surfaces between adjacent large gears conflict with each other, and the wheel body side walls between adjacent large gears form a gap for accommodating the disc spring and the friction plate.

[0006] In some embodiments, an annular protrusion is provided on one side of the tooth body of the large gear, and an annular groove matching the annular protrusion is provided on the other side. The annular protrusions and annular grooves on the corresponding sides of adjacent large gears are fitted and matched with each other.

[0007] In some embodiments, the reduction gear drives the transmission shaft through a key connection, the transmission shaft drives the transmission gear, the transmission gear is meshed with the idler gear, and the idler gear is meshed with the starting gear.

[0008] In some embodiments, the pressing cover is threadedly connected to the transmission shaft.

[0009] In some embodiments, a fixing hole is provided on the pressing cover, a fixing groove matching the fixing hole is provided at the point where the reduction gear and the pressing cover are pressed, and a fixing pin extending into the fixing groove is provided in the fixing hole.

[0010] In some embodiments, the inner ring of the one-way overrunning clutch assembly cooperates with the front end of the engine crankshaft, and the outer ring of the one-way overrunning clutch assembly is assembled and connected with the starting gear.

[0011] In order to achieve the above-mentioned purpose, the present invention also provides the following technical solution: an engine adopts the above-mentioned starting structure.

[0012] In order to achieve the above-mentioned purpose, the present invention also provides the following technical solution: an aircraft adopting the above-mentioned engine.

[0013] Compared with the existing technology, the beneficial effects of the present invention are: by installing the starter motor on the housing of the engine crankshaft, coordinating the reduction gear assembly with the starting gear of the integrated one-way overrunning clutch assembly, simplifying the transmission structure and optimizing the reduction ratio distribution, solving the problems of complex structure, unreasonable layout and insufficient lightweight of the traditional starting system, and at the same time adopting the matching structure of the laminated reduction gear assembly with the friction plate and disc spring to optimize the gear meshing accuracy and power transmission path, solving the problems of unstable operation, complex structure and low space utilization of the traditional starting mechanism, and having the advantages of simplifying the transmission structure, optimizing the space layout, improving the starting smoothness and realizing lightweight design.

[0014] Details of one or more embodiments of the present application are presented in the following drawings and descriptions to make other features, purposes and advantages of the present application more concise and easy to understand, and the present application is fully described and understood through the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of the utility model;

[0016] Figure 2 It is a side view of the utility model;

[0017] Figure 3 It is a schematic diagram of the reduction gear structure;

[0018] Figure 4 for Figure 3 Cross-sectional view of the middle reduction gear;

[0019] Figure 5 for Figure 3 Exploded cross-sectional view of the reduction gear.

[0020] In the figure: 1. Starter motor; 2. Engine crankshaft; 3. Starter gear; 4. One-way overrunning clutch assembly; 5. Idle gear; 6. Reduction gear; 7. Transmission gear; 8. Transmission shaft; 9. Drive gear; 10. Large gear; 11. Friction plate; 12. Stepped annular groove; 13. Disc spring; 14. Clamping cover; 15. Tooth body; 16. Wheel body; 17. Annular protrusion; 18. Annular groove; 19. Fixing hole; 20. Fixing groove; 21. Fixing pin; 22. Pressure plate. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] In existing technology, four-cylinder piston engines for small manned aircraft are mostly arranged horizontally, but inline four-cylinder piston engines are not yet widely used in drones. Existing engines suffer from severe vibration and excessive noise during startup, and their starting mechanisms are often located outside the crankcase, resulting in a cumbersome overall engine structure. Because power transmission requires multiple gear reduction mechanisms, the excessive number of gears not only increases transmission losses but also consumes a large amount of installation space, making it difficult to meet the compact power system requirements of drones.

[0023] To address these issues, the positioning and transmission structure of the starting mechanism in existing technologies are key constraints. Analysis revealed that relocating the starter motor from the end of the housing to the upper portion of the housing optimizes space utilization, but this requires addressing the issue of a long transmission path. Further research revealed that reducing the number of intermediate gears and adjusting the reduction ratio distribution can shorten the transmission chain while maintaining torque output. Furthermore, integrating a one-way transmission device into the starting gear prevents reverse impact, thereby reducing vibration sources.

[0024] In this regard, Figures 1 to 5 As shown, the present application proposes a starting structure for an in-line piston engine, including a starter motor 1, which is installed on the upper part of the engine crankshaft 2 housing. The output end of the starter motor 1 passes through the housing and drives a reduction gear assembly through gear meshing. A starter gear 3 is provided at the front end of the engine crankshaft 2, and a one-way overrunning clutch assembly 4 is integrated on the starter gear 3. A transmission shaft 8, a transmission gear 7 and an idler gear 5 are provided in linkage between the starter gear 3 and the reduction gear assembly. The reduction gear assembly includes a reduction gear 6 composed of a plurality of stacked large gears 10 and a drive gear 9 meshing with the reduction gear 6. The tooth width of the drive gear 9 is consistent with the overall thickness of the reduction gear 6. The drive gear 9 is fixedly connected to the output end of the starter motor 1. Friction plates 11 are provided between adjacent large gears 10 on the reduction gear 6. Stepped annular grooves 12 are provided on both sides of the friction plate 11 near the inner hole. Disc springs 13 are provided on both sides of the friction plate 11 corresponding to the corresponding stepped annular grooves 12. A clamping cover 14 cooperating with the transmission shaft 8 is provided on the outermost two sides of the reduction gear 6.

[0025] The starter motor 1 is mounted on top of the engine crankcase 2, meaning it is positioned in the top area of ​​the engine crankcase 2. This can be achieved by bolting. This layout utilizes the internal space of the crankcase, avoiding external space occupation, thereby optimizing the overall engine structure. The reduction gear assembly comprises multiple stacked gears 10, meaning multiple gears of varying diameters are stacked axially to form an assembly. Keyways can be used to achieve synchronous rotation. The stacked structure achieves multi-stage reduction within a limited space, reducing the complexity of the transmission system. The tooth width of the drive gear 9 is consistent with the overall thickness of the reduction gear 6, meaning the axial dimension of the drive gear 9 is equal to the total height of the stacked reduction gears 6. This dimensional matching can be achieved through precision machining. This design ensures full contact between the meshing surfaces of the drive gear 9 and the reduction gear 6, improving transmission stability. The friction plates 11 are positioned between adjacent gears 10, meaning an annular friction element is inserted between the stacked gears 10. These elements can be made of a metal-matrix composite material. The friction plates 11 engage disc springs 13 via stepped annular grooves 12 to absorb vibration energy during gear transmission and reduce starting shock. The disc springs 13 are arranged in the stepped annular grooves 12 on both sides of the friction plate 11, which utilize the elastic deformation of the disc springs 13 to provide axial preload. Specifically, they can be installed in a symmetrical distribution. The spring pressure maintains controllable friction between the friction plate 11 and the gear end face, preventing slippage or excessive wear between the gears. The clamping cover 14 is arranged on the outermost side surfaces of the reduction gear 6 and cooperates with the transmission shaft 8. This means that the end cover structure applies axial clamping force to the laminated gear assembly. Specifically, it can be fixed by a threaded connection. The clamping cover 14 constrains the axial displacement of the gear set and ensures the integrity of the laminated structure during transmission. At the same time, to ensure the compression area of ​​the reduction gear at the clamping cover, a pressure plate 22 is provided between the reduction gear and the clamping cover to increase the uniform compression area of ​​the clamping cover on the side of the reduction gear.

[0026] The core innovation of this application lies in integrating the starter motor 1 into the upper portion of the crankcase, combining it with a laminated reduction gear 6 and a friction plate 11-disc spring 13 buffer structure to achieve a high reduction ratio within a limited space while simultaneously utilizing friction damping to suppress starting shock. This design simplifies the traditional multi-stage gear system while improving starting smoothness through axial compression and elastic buffering, meeting the dual requirements of compact layout and low vibration for aircraft engines.

[0027] The working process and principle of the present application are as follows: the starter motor 1 is installed on the upper part of the engine crankshaft 2 housing, and its output end passes through the housing and drives the reduction gear assembly through gear meshing. The reduction gear assembly includes a reduction gear 6 composed of a plurality of stacked large gears 10 and a driving gear 9 meshing with the reduction gear 6. The driving gear 9 is fixedly connected to the output end of the starter motor 1, and its thickness is consistent with the overall thickness of the reduction gear 6 to ensure meshing stability. A friction plate 11 is provided between two adjacent large gears 10 on the reduction gear 6, and step ring grooves 12 are provided on both sides of the friction plate 11 near the inner hole, and disc springs 13 are provided at the corresponding step ring grooves 12. This structural design can compensate for the axial dimension chain error and improve the stability of the transmission system. The outermost sides of the reduction gear 6 are provided with a clamping cover 14 that cooperates with the drive shaft 8 for fixing and adjusting the reduction gear assembly.

[0028] A starting gear 3 is located at the front end of the engine crankshaft 2, and a one-way overrunning clutch assembly 4 is integrated into the starting gear 3. The starting gear 3 and the reduction gear assembly are linked together via a drive shaft 8, a drive gear 7, and an idler gear 5. When the starter motor 1 is operating, power is transmitted to the starting gear 3 through the reduction gear assembly, drive shaft 8, drive gear 7, and idler gear 5, which in turn drives the crankshaft to start the engine. The one-way overrunning clutch assembly 4 prevents the starting system from being reverse-driven while the engine is running.

[0029] This starting structure integrates the starter motor 1 into the crankcase, shortening the power transmission distance and reducing the number of drive chain stages, which helps reduce vibration and noise. The laminated reduction gear 6 structure and friction buffer mechanism optimize the axial load distribution of the gear system, improve meshing accuracy, and further enhance the stability and reliability of the starting system.

[0030] As a preferred embodiment, the solution of this application is specifically implemented as follows:

[0031] The starter motor 1 is mounted on top of the engine crankshaft 2 housing. Its output end passes through the housing and is fixedly connected to the drive gear 9. The drive gear 9 meshes with the reduction gear 6, which is composed of a stack of large gears 10. Friction plates 11 are located between adjacent large gears 10 on the reduction gear 6. Stepped annular grooves 12 are formed on both sides of the friction plates 11 near the inner hole, and disc springs 13 are installed in corresponding grooves 12. The outermost sides of the reduction gear 6 are provided with pressure caps 14 that mate with the drive shaft 8.

[0032] The transmission shaft 8 is connected to the transmission gear 7, the transmission gear 7 is meshed with the idler gear 5, and the idler gear 5 is meshed with the starting gear 3. The starting gear 3 is arranged at the front end of the engine crankshaft 2 and is integrated with the one-way overrunning clutch assembly 4.

[0033] During startup, starter motor 1 rotates drive gear 9, which in turn drives the reduction gear assembly. The reduction gear assembly, via drive shaft 8, drives transmission gear 7, which in turn drives starter gear 3 via idler gear 5, thereby rotating the crankshaft and starting the engine. During this process, the friction plate 11 and disc spring 13 compensate for axial dimensional chain errors and improve transmission system stability. The one-way overrunning clutch assembly 4 prevents the starting system from reverse driving while the engine is running.

[0034] Through the above scheme, the present application integrates the starter motor 1 into the crankcase, reconstructs the gear transmission path, and shortens the power transmission distance. The laminated combined reduction gear 6 structure optimizes the axial load distribution of the gear system and realizes the load-balancing effect of torque transmission. The friction buffer mechanism composed of the stepped ring groove 12 and the disc spring 13 compensates for the axial dimension chain error and improves the meshing accuracy. These designs work together to effectively reduce the vibration and noise during the starting process and improve the stability and reliability of the transmission system. At the same time, since the starting mechanism is arranged on the upper part of the crankcase, the overall structural layout of the engine is improved, the space utilization rate is increased, and it is conducive to the miniaturization design of the engine. In addition, the simplified structure of the optimized starting system helps to achieve a lightweight design and better meet the application requirements of aircraft such as drones that have strict requirements on space size and weight.

[0035] The present application further proposes that the thickness of the tooth body portion 15 of the large gear 10 is greater than the thickness of the wheel body portion 16, the side surfaces of the tooth body portions 15 between adjacent large gears 10 conflict with each other, and the side walls of the wheel body portions 16 between adjacent large gears 10 form a gap for accommodating the disc spring and the friction plate 11.

[0036] Among them, the design that the thickness of the tooth body part 15 is greater than the thickness of the wheel body part 16 enables the tooth body side surfaces of adjacent gears to directly contact each other, and a gap of a specific width is formed between the side walls of the wheel bodies; the side surfaces of the tooth body parts 15 contact each other to form a supporting structure, and the gap in the side walls of the wheel body part 16 is used to accommodate the disc spring and the friction plate 11; the gap width matches the compression stroke of the disc spring and the thickness of the friction plate 11, ensuring that the spring and the friction plate 11 are evenly compressed in the gap.

[0037] Specifically, when the reduction gear 6 is operating, the sides of the tooth bodies 15 of adjacent gears 10 contact each other, limiting axial displacement between the gears and preventing meshing misalignment due to gear deformation. The gap formed by the sidewalls of the wheel body 16 provides installation space for the disc springs and friction plates 11. The spring preload is transmitted to the gear stack via the friction plates 11, maintaining a stable and compressed state for the entire stack. The thickness difference between the tooth body 15 and the wheel body 16 further optimizes the load distribution of the gears. The tooth body 15 bears the meshing transmission force, while the wheel body 16 absorbs vibration energy through the springs and friction plates 11 within the gap, thereby reducing impact and noise during transmission while maintaining the compact layout of the reduction gear assembly.

[0038] As a preferred embodiment, the solution of the present application is specifically implemented as follows: the thickness of the tooth body portion 15 of the large gear 10 is greater than the thickness of the wheel body portion 16. The side surfaces of the tooth body portions 15 between adjacent large gears 10 collide with each other. The side walls of the wheel body portions 16 between adjacent large gears 10 form a gap for accommodating the disc springs and the friction plates 11. Specifically, the thickness of the tooth body portion 15 of the large gear 10 can be 14 mm, and the thickness of the wheel body portion 16 is 6 mm. The side surfaces of the tooth body portions 15 of adjacent large gears 10 are in close contact to form a stable connection. The gap between the side walls of the wheel body portion 16 is 8 mm, which is used to place the disc springs and the friction plates 11. As a result, the disc springs and the friction plates 11 are safely accommodated in the gap to avoid exposure and damage.

[0039] Through the above technical solution, the present application achieves a secure connection between the large gears 10 while providing protective space for the disc springs and friction plates 11. The mutual interference of the tooth bodies 15 enhances the overall strength of the reduction gear 6 and improves transmission reliability. The gap formed by the wheel body 16 effectively accommodates the disc springs and friction plates 11, preventing these components from being exposed to the external environment and extending their service life. Furthermore, this structural design simplifies the assembly process, reduces the number of parts, and lowers production costs.

[0040] The present application further proposes that an annular protrusion 17 is provided on one side of the tooth body portion 15 of the large gear 10, and an annular groove 18 is provided on the other side to cooperate with the annular protrusion 17, and the annular protrusions 17 and the annular grooves 18 on the corresponding sides between adjacent large gears 10 are fitted and matched with each other.

[0041] The annular protrusion 17 is formed on the side of the tooth body 15 by turning, and the annular groove 18 is formed by milling. The difference between the protrusion height and the groove depth is controlled within a range of 0.02-0.05 mm. The clearance fit tolerance between the outer diameter of the annular protrusion 17 and the inner diameter of the groove is H7 / g6, ensuring radial positioning during engagement. The clearance between the wheel body 16 of adjacent gears 10 is adjusted by the depth of engagement between the protrusion and the groove, maintaining a consistent preload force in the disc springs on both sides of the friction plate 11.

[0042] Specifically, during assembly, the annular protrusion 17 engages with the corresponding groove to achieve circumferential positioning of the gears, eliminating axial misalignment on the sides of the tooth body 15. When the reduction gear 6 is subjected to torque, the interlocking structure limits relative rotation between the gears, forming the laminated gear set into a single transmission unit. The friction plate 11 generates axial compressive force under the action of the disc spring. The interlocking surface of the annular protrusion 17 and the groove shares some of the shear stress, preventing the sides of the tooth body 15 from directly bearing the axial load transmitted by the friction plate 11. This structure maintains dynamic balance during high-speed operation of the laminated gears and reduces the transmission of vibration energy caused by gear misalignment to the crankcase.

[0043] As a preferred embodiment, the solution of the present application is specifically implemented as follows: an annular protrusion 17 is provided on one side of the tooth body portion 15 of the large gear 10, and an annular groove 18 that cooperates with the annular protrusion 17 is provided on the other side. The annular protrusion 17 and the annular groove 18 on the corresponding sides of adjacent large gears 10 are fitted together. The annular protrusion 17 can adopt a circular arc or trapezoidal cross-section, and the annular groove 18 can adopt a shape that matches the annular protrusion 17 accordingly. The width of the annular protrusion 17 and the annular groove 18 can be designed to be 2-5 mm, and the depth can be designed to be 1-3 mm. This design can provide positioning and guiding functions when assembling the large gears 10, ensuring precise alignment between adjacent large gears 10.

[0044] Through the above-mentioned technical solution, the present application improves the assembly precision and stability of the reduction gear assembly. The interlocking structure of the annular protrusion 17 and the annular groove 18 enhances the connection strength between adjacent large gears 10, reducing relative displacement and vibration of the gears during high-speed operation. This structural design also simplifies the assembly process of the reduction gear assembly and improves assembly efficiency. As a result, the overall performance and reliability of the engine starting system are improved, and noise and vibration during the starting process are effectively reduced.

[0045] The present application further proposes that the reduction gear 6 drives the transmission shaft 8 through a key connection, the transmission shaft 8 drives the transmission gear 7, the transmission gear 7 is meshed with the idler gear 5, and the idler gear 5 is meshed with the starting gear 3.

[0046] The key connection uses a double-round flat key structure, with a keyway depth of 18%-22% of the shaft diameter. Shaft shoulder positioning structures are set at both ends of the transmission shaft 8, with a shoulder height of 2-3mm. The transmission gear 7 is press-fitted into the middle of the transmission shaft 8 with an interference fit of 0.02-0.05mm. The distance between the axis of the idler gear 5 and the axis of the transmission gear 7 is 2.3-2.5 times the module, and the tooth width of the idler gear 5 is 10%-15% larger than the tooth width of the transmission gear 7. A lubricating oil channel is set in the meshing area between the transmission gear 7 and the idler gear 5. The oil channel diameter is 1.5-2mm and extends along the tooth direction.

[0047] Specifically, when reduction gear 6 rotates, torque is transmitted to drive shaft 8 via a double-headed flat key, with a shoulder structure limiting axial displacement. Drive shaft 8 drives the interference-fitted transmission gear 7 to rotate synchronously, which in turn drives idler gear 5 to achieve secondary reduction. Idler gear 5 compensates for axis spacing errors by increasing its tooth width, and the lubrication channels form a continuous oil film in the meshing area. The keyed connection between drive shaft 8 and reduction gear 6 increases torque transmission efficiency to 92%-95%. The combined effect of the shoulder and interference fit keeps axial play to within 0.1mm. The incremental tooth width of idler gear 5 effectively compensates for manufacturing and assembly errors, increasing the meshing contact area to over 75%. The lubrication channels reduce gear surface temperature by 15-20°C. This transmission chain structure reduces system vibration amplitude by 40%-45% and noise levels by 8-10dB(A).

[0048] As a preferred embodiment, the solution of the present application is specifically implemented as follows: the reduction gear 6 drives the transmission shaft 8 through a key connection, the transmission shaft 8 drives the transmission gear 7, the transmission gear 7 is meshed with the idler gear 5, and the idler gear 5 is meshed with the starting gear 3. Specifically, the inner hole of the reduction gear 6 is provided with a keyway, and the outer surface of the transmission shaft 8 is correspondingly provided with a cam, and the two are keyed to achieve power transmission. One end of the transmission shaft 8 is fixedly connected to the reduction gear 6, and the other end is fixedly connected to the transmission gear 7. An appropriate center distance is set between the transmission gear 7 and the idler gear 5 so that the tooth shapes of the two can mesh correctly. The idler gear 5 and the starting gear 3 also maintain a suitable meshing relationship to ensure that power can be smoothly transmitted to the starting gear 3.

[0049] Through the above technical solution, the present application realizes the effective transmission of power of the starter motor 1. The reduction gear assembly is connected to the transmission shaft 8 through a key connection, which ensures the reliability of power transmission. The meshing arrangement of the transmission gear 7, the idler gear 5 and the starter gear 3 forms a complete transmission chain, so that the power of the starter motor 1 can be smoothly transmitted to the engine crankshaft 2. This transmission structure simplifies the design of the starting system, reduces the transmission links, and improves the transmission efficiency. At the same time, the use of the idler gear 5 as an intermediate transmission component increases the flexibility of the transmission system, facilitates the rational arrangement of various transmission components in a limited space, and is conducive to the miniaturization design of the engine.

[0050] The present application further proposes that the compression cover 14 and the transmission shaft 8 are threadedly connected.

[0051] The threaded connection utilizes a fine-pitch thread design, with the thread rotation direction opposite to that of the drive shaft 8, preventing the threads from loosening during operation. The inner hole of the compression cap 14 is machined with an internal thread, and the corresponding position of the drive shaft 8 is machined with an external thread. The two threads engage to achieve axial compression. Furthermore, an anti-loosening adhesive layer is provided on the mating surface of the threaded connection to enhance the locking effect. For example, the nominal thread diameter is set to 12 mm, the pitch is 1.25 mm, and the effective thread engagement length is no less than 1.2 times the thread diameter.

[0052] Specifically, during assembly, after the reduction gear assembly is keyed to the drive shaft 8, the internally threaded compression cap 14 is screwed into the threaded section of the drive shaft 8. The axial compressive force of the threaded pair presses the friction plates 11 and disc springs 13 on either side of the reduction gear assembly together to create a preset pressure. The axial preload generated by the threaded connection maintains a stable contact state between the laminated reduction gear 6. At the same time, the inverse design of the thread rotation direction and the working direction of the drive shaft 8 creates a self-locking effect during power transmission. This connection method ensures axial positioning accuracy while giving the compression cap 14 both axial fixation and anti-loosening functions, effectively preventing axial movement of the gear assembly under alternating loads and ensuring that the reduction gear 6 and drive gear 9 always maintain precise meshing.

[0053] As a preferred embodiment, the solution of the present application is specifically implemented as follows: a threaded connection is employed between the compression cover 14 and the transmission shaft 8. The inner wall of the compression cover 14 is provided with internal threads, and the outer wall of the transmission shaft 8 is provided with matching external threads. During installation, the compression cover 14 is rotated axially along the transmission shaft 8, so that the internal threads of the compression cover 14 engage with the external threads of the transmission shaft 8. By adjusting the rotational position of the compression cover 14 on the transmission shaft 8, the pressure applied by the compression cover 14 to the reduction gear 6 can be controlled.

[0054] Through the above technical solution, the present application achieves a reliable connection between the clamping cap 14 and the transmission shaft 8, ensuring the stability of the reduction gear assembly. The threaded connection method facilitates adjustment of the clamping force, which helps optimize the performance of the reduction gear assembly. In addition, the threaded connection structure is simple and easy to process and assemble, improving the production efficiency and maintenance convenience of the starting mechanism.

[0055] The present application further proposes that a tightening hole 19 is provided on the pressing cover 14, a tightening groove 20 that cooperates with the tightening hole 19 is provided at the point where the reduction gear 6 and the pressing cover 14 are pressed against each other, and a tightening pin 21 that extends into the tightening groove 20 is provided in the tightening hole 19; the tightening hole 19 and the tightening groove 20 are processed by post-processing. After the reduction gear 6 and the transmission shaft 8 are assembled and tightened by the two pressing covers 14, the tightening hole 19 is processed on the pressing cover 14, and the tightening groove 20 is processed on the reduction gear 6, and finally the limiting is completed by the tightening pin 21.

[0056] Among them, the tightening hole 19 is machined on the surface of the clamping cover 14, and its axial direction is perpendicular to the contact surface between the clamping cover 14 and the reduction gear 6; the tightening groove 20 is opened on the end face of the reduction gear 6, and its shape matches the geometric dimensions of the end of the tightening pin 21. The post-processing treatment method is specifically as follows: after completing the key connection assembly of the transmission shaft 8 and the reduction gear 6, the clamping cover 14 is screwed into the threaded section of the transmission shaft 8 and a preset torque is applied to tighten the reduction gear 6; at this time, the relative position of the clamping cover 14 and the reduction gear 6 is fixed by a positioning fixture, and the tightening hole 19 is machined on the surface of the clamping cover 14 by a drilling process, and the tightening groove 20 is machined at the corresponding position of the reduction gear 6; the tightening pin 21 is pressed into the tightening hole 19 by an interference fit, and the depth of its end embedded in the tightening groove 20 ranges from 1.5 to 2 mm.

[0057] Specifically, during the assembly process, the reduction gear 6 is first mounted to the drive shaft 8 via a keyed connection. Two clamping caps 14 are then screwed in from both ends of the drive shaft 8, applying axial compressive force via threaded connections. When the clamping caps 14 reach the set torque value, the friction plates 11 and disc springs 13 between the large gears 10 of each layer of the reduction gear 6 are compressed. At this point, an axial positioning structure is machined into the contact area between the clamping caps 14 and the reduction gear 6 through a synchronous machining process. The locking pins 21 simultaneously penetrate the mechanical mating surfaces of the clamping caps 14 and the reduction gear 6, forming a three-dimensional spatial limit. This structure effectively prevents the clamping caps 14 from circumferential rotation or axial displacement under vibration conditions, ensuring that the reduction gear 6 stack assembly remains fixed to the drive shaft 8. Post-machining eliminates the impact of cumulative assembly errors on positioning accuracy, ensuring that the axial overlap error between the locking holes 19 and the locking slots 20 is less than 0.05 mm, enabling the limit structure to withstand the periodic impact loads transmitted by the crankshaft during engine startup.

[0058] As a preferred embodiment, the solution of the present application is specifically implemented as follows: a fixing hole 19 is provided on the pressing cover 14, a fixing groove 20 that matches the fixing hole 19 is provided at the point where the reduction gear 6 and the pressing cover 14 are pressed against each other, and a fixing pin 21 that extends into the fixing groove 20 is provided in the fixing hole 19. The fixing hole 19 and the fixing groove 20 are processed by post-processing. After the reduction gear 6 and the transmission shaft 8 are assembled and pressed by the two pressing covers 14, the fixing hole 19 is punched on the pressing cover 14, and the fixing groove 20 is punched on the reduction gear 6. Finally, the limiting is completed by the fixing pin 21. Specifically, the reduction gear 6 can be installed on the transmission shaft 8 first, and then the two pressing covers 14 can be installed on both sides of the reduction gear 6 respectively and pressed and fixed. Next, the fixing hole 19 is drilled on the pressing cover 14, and the fixing groove 20 is processed at the corresponding position on the reduction gear 6. Finally, the fixing pin 21 is inserted into the fixing hole 19 and extends into the fixing groove 20 , thereby achieving position limiting and fixing of the reduction gear 6 .

[0059] Through the above-mentioned technical solution, the present application achieves reliable connection and positioning between the reduction gear 6 and the transmission shaft 8. This reduces relative rotation and axial play between the reduction gear 6 and the transmission shaft 8, improving the stability and reliability of the transmission system. Furthermore, the post-processing method used to manufacture the fixing structure ensures precise alignment of the fixing hole 19 and the fixing groove 20, avoiding assembly errors and improving assembly accuracy and efficiency.

[0060] The present application further proposes that the one-way overrunning clutch assembly 4 is fixed to the front end of the engine crankshaft 2 , and the one-way overrunning clutch assembly 4 is assembled and connected to the starting gear 3 .

[0061] The one-way overrunning clutch assembly 4 is directly fixed to the crankshaft front journal by bolts or an interference fit, and its outer ring and starting gear 3 are circumferentially positioned by splines or flat keys. During assembly, the inner ring of the one-way overrunning clutch assembly 4 and the front end of the crankshaft are heat-fitted to achieve an interference fit, and an axial limit step is provided on the assembly surface of the outer ring and the starting gear 3. The fixed position at the front end of the crankshaft can fully utilize the internal space of the crankcase and avoid external extension structures. As a preferred embodiment, the front end of the crankshaft is machined with a mounting section with a diameter of 30-40 mm, and the inner hole tolerance of the one-way overrunning clutch assembly 4 is controlled to the H7 / k6 fit grade.

[0062] Specifically, when the engine is started, the starter motor 1 drives the transmission shaft 8 through the reduction gear assembly, and transmits power to the starter gear 3 through the transmission gear 7 and the idler gear 5. At this time, the outer ring of the one-way overrunning clutch assembly 4 rotates synchronously with the starter gear 3, and the inner ring drives the crankshaft to rotate through an interference fit. When the engine is started, the crankshaft speed exceeds the speed of the starter gear 3, and the one-way overrunning clutch assembly 4 automatically cuts off the power transmission path. This fixing method allows the starter gear 3 to be directly integrated into the crankshaft rotating axis, eliminating the axial dimensional cumulative error caused by the independent clutch mounting seat in the traditional structure. The assembly connection adopts a step positioning structure to ensure that the coaxiality error between the starter gear 3 and the clutch assembly is less than 0.05mm, thereby reducing the impact vibration during the gear meshing process.

[0063] As a preferred embodiment, the solution of the present application is specifically implemented as follows: A one-way overrunning clutch assembly 4 is fixed to the front end of the engine crankshaft 2. The one-way overrunning clutch assembly 4 is assembled and connected to the starter gear 3. Specifically, the one-way overrunning clutch assembly is a prior art product, such as the roller-type one-way overrunning clutch structure disclosed in Publication No. CN101988547A or the related structure described in the improved design of the roller-type overrunning clutch structure in the Journal of Mechanical Industry, Issue 2, 2005. The one-way overrunning clutch assembly 4 includes an outer ring, an inner ring, a roller, and a spring. The outer ring is fixed inside the starter gear 3, while the inner ring is fixed to the front end of the engine crankshaft 2. The roller and spring are located between the outer and inner rings. When the starter motor 1 drives the starter gear 3 to rotate, the outer ring drives the roller to compress the spring. The roller is stuck in the wedge-shaped space between the outer and inner rings, thereby driving the inner ring and the crankshaft to rotate. When the engine is started and the crankshaft speed exceeds the speed of the starting gear 3, the roller overcomes the spring force under the action of centrifugal force and moves to the wide end of the wedge-shaped space, so that the inner ring and the outer ring are separated, realizing one-way transmission.

[0064] Through the above-mentioned technical solution, the present application achieves the simplification and integration of the engine starting system. The one-way overrunning clutch assembly 4 is directly integrated into the starter gear 3, eliminating additional transmission components and reducing system complexity. Furthermore, because the one-way overrunning clutch assembly 4 is fixed to the front end of the crankshaft, the problem of traditional starting systems requiring external placement of the crankcase is avoided, making the overall engine structure more compact. Furthermore, the one-way transmission mechanism ensures that the starter motor 1 can be disengaged promptly after the engine is started, preventing reverse drag and improving system reliability and service life.

[0065] The present application further proposes an engine, which uses a starting mechanism comprising a starter motor 1, a reduction gear assembly, and a one-way overrunning clutch assembly 4. The starter motor 1 is fixed to the upper portion of the engine crankshaft 2 housing, with its output end passing through the housing and connected to a drive gear 9; the reduction gear assembly is composed of a plurality of stacked large gears 10, with friction plates 11 with stepped annular grooves 12 and disc springs 13 provided between adjacent large gears 10; the transmission shaft 8 transmits the power of the reduction gear 6 to the transmission gear 7 via a key connection, and the transmission gear 7 engages with the starter gear 3 of the integrated one-way overrunning clutch assembly 4 via an idler gear 5; the clamping cover 14 is fixed to both ends of the transmission shaft 8 by threads, and forms an axial limit with the reduction gear 6 via a locking pin 21.

[0066] The output end of the starter motor 1 is rigidly connected to the drive gear 9, whose thickness matches the overall thickness of the laminated reduction gear 6, ensuring axial stability of power transmission. The laminated structure of the reduction gear 6 utilizes friction plates 11 and disc springs 13 to achieve dynamic damping adjustment, suppressing gear meshing shock. The clamping cover 14 is post-processed to form a fixing hole 19 and a fixing groove 20 after assembly, eliminating the effects of cumulative assembly errors on gear coaxiality. The one-way overrunning clutch assembly 4 is directly integrated into the starter gear 3 at the front end of the engine crankshaft 2, eliminating the need for additional mounting structures.

[0067] Specifically, when the starter motor 1 is energized, the drive gear 9 rotates the laminated reduction gear 6. The friction plate 11 and the disc spring 13 generate controllable sliding friction under the action of the gear meshing force, absorbing the instantaneous impact energy of the transmission system. The reduction gear 6 transmits power to the drive shaft 8 through a key connection. After secondary deceleration by the drive gear 7 and the idler gear 5, it drives the starter gear 3 to rotate the engine crankshaft 2. The one-way overrunning clutch assembly 4 automatically cuts off power transmission after the crankshaft reaches a self-sustaining speed. The clamping cover 14 fixes the axial position of the reduction gear 6 through threaded preload, and the locking pin 21 cooperates with the locking groove 20 formed by post-processing to prevent axial movement of the drive shaft 8 under vibration. This structure completely integrates the starting mechanism into the engine crankshaft 2 housing. Through multi-stage dynamic damping and compact meshing design, it minimizes the axial size while ensuring starting torque.

[0068] As a preferred embodiment, the present invention is implemented as follows: A starter motor 1 is fixedly mounted on the upper portion of the engine crankcase. The output shaft of the starter motor 1 extends through the side wall of the crankcase and forms a rigid connection with a drive gear 9. The drive gear 9 meshes with a reduction gear 6, which is composed of three stacked large gears 10. The tooth bodies 15 of adjacent large gears 10 are positioned by annular protrusions 17 on the sides and engage with grooves. A clearance is formed between the gear bodies 16 to accommodate friction plates 11 and disc springs 13. The reduction gear 6 is circumferentially secured to the drive shaft 8 via a flat key. The end of the drive shaft 8 is threadedly secured by a clamping cap 14. Axial positioning is achieved between the clamping cap 14 and the reduction gear 6 by a post-machined locking hole 19 and a locking pin 21. The drive gear 7 at the end of the drive shaft 8 meshes with an idler gear 5, which in turn meshes with the starter gear 3 at the front end of the crankshaft. The starter gear 3 incorporates a one-way overrunning clutch and is secured to the crankshaft via an interference fit.

[0069] Through the above-mentioned technical solution, this application effectively solves the vibration and noise problems caused by the excessively long gear transmission chain in traditional engine starting systems. By integrating the reduction gear assembly and the drive shaft 8 within the crankcase, the overall engine structure is made more compact, significantly improving space utilization. The coordinated design of the laminated reduction gear 6, friction plate 11, and disc spring 13 achieves a smooth transition during the transmission process, avoiding abnormal wear caused by the starting shock. The combined assembly of the clamping cover 14 and the locking pin 21 further ensures the axial stability of the drive shaft 8 under high-speed rotation conditions, thereby meeting the stringent requirements for lightweight and high-reliability engines in aircraft such as drones.

[0070] The present application further proposes an aircraft using an in-line piston engine, which includes a starter motor 1 integrated into a starting mechanism on the upper part of the crankcase, which is linked to the starting gear 3 at the front end of the crankshaft through a reduction gear assembly, wherein the reduction gear 6 adopts a combined structure of a laminated large gear 10 and a friction plate 11, and the clamping cover 14 is axially positioned by a locking pin 21.

[0071] The aircraft's engine compartment is located within the aircraft's fuselage, with propeller mounting ports located at the front. The engine crankshaft (2) maintains its axis parallel to the aircraft's longitudinal axis. The starter motor (1) located above the crankshaft housing (2) is recessed into the overhead space within the aircraft's power compartment. The reduction gear assembly is compactly arranged along the crankshaft's axial direction. The locking pin (21) of the hold-down cover (14) prevents axial displacement of the gear assembly during aircraft maneuvers. The in-line layout shortens the overall engine length, accommodating the limited cross-sectional area of ​​the drone.

[0072] Specifically, during the installation of the aircraft power system, the engine is fixed to the inside of the cabin through a three-point suspension bracket, and the front end of the crankshaft extends to the outside of the cabin to connect to the propeller. The design of embedding the starting mechanism in the upper part of the box reduces the lateral size of the power cabin, leaving lateral space for the fuel system and heat dissipation device. The laminated structure of the reduction gear 6 reduces the radial size while ensuring transmission efficiency, so that the engine width can adapt to the streamlined cabin of the drone. The clamping cover 14 is threadedly connected to the drive shaft 8 and cooperates with the locking pin 21 to ensure that the gear assembly remains stably engaged during the pitch maneuver of the aircraft. The in-line layout of the engine matches the longitudinal space of the drone body, and the power output from the front end of the crankshaft directly drives the propeller, eliminating the transmission steering mechanism required for traditional horizontally opposed engines.

[0073] As a preferred embodiment, the solution of the present application is specifically implemented as follows: the aircraft adopts a four-rotor unmanned aircraft type, and its power system includes an in-line four-cylinder piston engine. The upper part of the engine's crankcase is integrated with a starter motor 1, and the output shaft of the starter motor 1 is connected via a key to drive the reduction gear assembly. The reduction gear assembly is composed of three layers of stacked gears. Friction plates 11 with stepped annular grooves 12 and double-sided disc springs 13 are provided between adjacent gears. The two sides of the gear set are threadedly connected to the transmission shaft 8 through a pressure cap with a tightening hole 19. The end gear of the transmission shaft 8 is meshed with the starting gear 3 at the front end of the crankshaft through the idler gear 5. The starting gear 3 has an integrated one-way overrunning clutch, and the inner ring of the clutch is fixedly connected to the crankshaft via a spline. The engine is installed as a whole in the middle frame of the UAV fuselage. The starting system components are completely built into the upper space of the crankcase, and there are no external transmission components on the outer surface of the case.

[0074] Through the above-mentioned technical solution, this application solves the problems of loose layout and significant vibration transmission caused by the external starting mechanism of traditional horizontally opposed engines. The internal design of the gear assembly shortens the engine's axial dimension. At the same time, the structure of multi-layered gears and friction plates 11 combined with disc springs 13 effectively absorbs the starting impact load and eliminates transmission jitter caused by gear meshing clearance. The direct assembly of the one-way overrunning clutch and the crankshaft avoids the risk of reverse power transmission. The overall structure achieves a compact layout while ensuring starting torque, meeting the stringent requirements of drones for lightweight power systems and space occupancy.

[0075] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

[0076] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A starting structure for an in-line piston engine, comprising a starting motor (1), characterized in that: The starter motor (1) is mounted on the upper part of the engine crankshaft (2) housing. The output end of the starter motor (1) passes through the housing and drives a reduction gear assembly through gear meshing. A starter gear (3) is provided at the front end of the engine crankshaft (2). A one-way overrunning clutch assembly (4) is integrated on the starter gear (3). A transmission shaft (8), a transmission gear (7) and an idler gear (5) are provided in linkage with each other between the starter gear (3) and the reduction gear assembly. The reduction gear assembly includes a reduction gear (6) composed of a plurality of stacked large gears (10) and a driving gear (9) meshed with the reduction gear (6). The tooth width of the driving gear (9) is consistent with the overall thickness of the reduction gear (6). The driving gear (9) is fixedly connected to the output end of the starter motor (1). A friction plate (11) is provided between two adjacent large gears (10) on the reduction gear (6). Both sides of the friction plate (11) are provided with friction plates. A stepped annular groove (12) is provided near the inner hole, and disc springs (13) are provided on both sides of the friction plate (11) corresponding to the corresponding stepped annular grooves (12). A pressing cover (14) is provided on the outermost two sides of the reduction gear (6) for matching with the transmission shaft (8). The thickness of the tooth body (15) of the large gear (10) is greater than the thickness of the wheel body (16). The side surfaces of the tooth body (15) between adjacent large gears (10) contact each other. The side walls of the wheel body (16) between adjacent large gears (10) form a gap for accommodating the disc spring (13) and the friction plate (11). An annular protrusion (17) is provided on one side of the tooth body (15) of the large gear (10), and an annular groove (18) matching with the annular protrusion (17) is provided on the other side. The annular protrusion (17) and the annular groove (18) on the corresponding side surfaces between adjacent large gears (10) are fitted and matched with each other.

2. The starting structure of an in-line piston engine according to claim 1, characterized in that: The reduction gear (6) drives the transmission shaft (8) through a key connection, the transmission shaft (8) drives the transmission gear (7), the transmission gear (7) is meshed with the idler gear (5), and the idler gear (5) is meshed with the starting gear (3).

3. The starting structure of an in-line piston engine according to claim 2, characterized in that: The pressing cover (14) and the transmission shaft (8) are connected by threads.

4. The starting structure of an in-line piston engine according to claim 3, characterized in that: The pressing cover (14) is provided with a fixing hole (19), the position where the reduction gear (6) and the pressing cover (14) are pressed against each other is provided with a fixing groove (20) that matches the fixing hole (19), and the fixing hole (19) is provided with a fixing pin (21) that extends into the fixing groove (20).

5. The starting structure of an in-line piston engine according to claim 1, characterized in that: The inner ring of the one-way overrunning clutch assembly (4) is matched with the front end of the engine crankshaft (2), and the outer ring of the one-way overrunning clutch assembly (4) is assembled and connected with the starting gear (3).

6. An engine, characterized in that: The starting structure according to any one of claims 1 to 5 is adopted.

7. An aircraft, characterized in that: The engine according to claim 6 is used.

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