Combined type air cooling triangular rotor assembly

Abstract

The invention is suitable for the field of aviation unmanned aerial vehicle power devices, and provides a combined air-cooled triangular rotor assembly which comprises an air-cooled triangular rotor, an inner gear positioning pin, a rotor bearing bush, an inner gear and an inner hexagonal countersunk bolt. S-shaped heat dissipation fins are uniformly distributed in the triangular cooling cavity to enhance heat dissipation; the bearing bush lining seat is provided with a heat insulation groove to reduce heat conduction; the rotor bearing bush is a hardened alloy steel bushing, and is provided with an inclined oil pouring groove with a notch to realize uniform lubrication; the inner gear is of a plate-type structure and is combined and fixed through a positioning pin and a bolt, and gear grinding machining precision is improved conveniently. The split structure is adopted, welding defects are avoided, heat dissipation and lubricating performance is optimized, detachable replacement of key components is achieved, the reliability of the engine is remarkably improved, the service life is prolonged, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of aviation unmanned aerial vehicle (UAV) power units, and particularly relates to a combined air-cooled triangular rotor assembly. Background Technology

[0002] As a highly efficient four-stroke engine, the triangular rotor engine boasts higher power output and lower fuel consumption compared to two-stroke piston engines, giving it a significant advantage in the field of aviation and unmanned aerial vehicle (UAV) power. To ensure a high power-to-weight ratio, air cooling is commonly used. However, air-cooled triangular rotors bear substantial thermal stress, with even higher thermal loads under high loads or speeds. Their heat dissipation and lubrication directly affect operational reliability and the working condition of seals and springs; therefore, the performance and reliability of the triangular rotor assembly are of paramount importance.

[0003] Existing air-cooled triangular rotors are mostly manufactured by welding internal gear sleeves (with journal structure) made of alloy steel and triangular rotors made of ductile iron using pins welded together at the end faces or radially. One approach is to weld the internal gear sleeve and triangular rotor together and then machine them as a whole; another approach is to machine the internal gear sleeve and triangular rotor separately and then weld them together radially or at the end faces.

[0004] Due to the different thermal expansion coefficients of the two materials, residual stress exists after welding, which easily leads to weld spatter failure at high temperatures, causing the inner gear sleeve to fall off. Local component failure can directly scrap the triangular rotor assembly, and in severe cases, it can affect the reliable operation of other internal components of the engine. The existing air-cooled triangular rotor has low heat dissipation area utilization efficiency, and high thermal stress is accompanied by poor lubrication of the rotor journal, making the rotor journal prone to deformation and affecting working accuracy. The internal gear sleeve has a complex structure and cannot be ground, which affects the working accuracy of the rotary engine. The traditional welded structure leaves little development space for the combustion chamber recess of the triangular rotor, and the wall thickness strength of the recess decreases after the compression ratio is further reduced.

[0005] Therefore, a combined air-cooled triangular rotor assembly is needed to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a combined air-cooled triangular rotor assembly to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A combined air-cooled triangular rotor assembly includes an air-cooled triangular rotor, an internal gear locating pin, a rotor bearing, an internal gear, and a countersunk hexagonal head bolt. The internal gear is fitted onto the bearing shoulder of the air-cooled triangular rotor with clearance and is positioned on the gear mounting surface of the air-cooled triangular rotor by the internal gear locating pin. The countersunk hexagonal head bolt passes through the through hole of the internal gear and connects to the threaded hole of the air-cooled triangular rotor to fix the internal gear to the air-cooled triangular rotor.

[0009] By setting up the above structure, the limitations of traditional welding connections are broken. The gap assembly facilitates the initial alignment of the internal gear and the triangular rotor. The precise positioning of the locating pin ensures the positional accuracy of the two in the circumferential and radial directions. Combined with the rigid connection of the bolts, a dual guarantee of "positioning-fastening" is formed, which not only avoids the failure risk caused by welding residual stress, but also provides a detachable base for component replacement during subsequent maintenance.

[0010] The rotor bearing is installed in the bearing bushing seat of the air-cooled triangular rotor, with one end face tightly attached to the bearing shoulder and the other end face lower than the triangular rotor gear mounting surface.

[0011] The bearing bush seat provides a stable mounting base for the rotor bearing. The axial limiting function of the bearing shoulder can effectively prevent the bearing from moving axially when the rotor is rotating at high speed, ensuring the stability of the fit between the bearing and the eccentric journal. The design of the bearing end face being lower than the gear mounting surface can avoid interference between the bearing and the internal gear mounting structure, ensuring the spatial coordination of each component after assembly.

[0012] A further technical solution is that the air-cooled triangular rotor is made of ductile iron or alloy cast iron and is normalized; five “S”-shaped heat dissipation fins are evenly distributed in its triangular cooling cavity, the heat dissipation fin wall thickness is 1.3 to 2 mm, they are equidistant from the sealing small column holes in the vertical direction, the fin spacing is 3 to 5 mm, and the fin apex corners are rounded with a radius of R0.5-R1.

[0013] After normalizing, ductile iron and alloy cast iron can improve toughness while ensuring material strength, meeting the mechanical requirements of triangular rotors under high temperature and high pressure environments; the "S"-shaped heat dissipation fins maximize the heat dissipation area in a limited space through special design, the equidistant array ensures heat dissipation uniformity, and the rounded apex corners can reduce airflow resistance and avoid stress concentration, significantly enhancing the air cooling effect.

[0014] A further technical solution is that the bearing bush seat of the air-cooled triangular rotor is provided with a heat insulation groove near the combustion chamber. The heat insulation groove is 2-3mm deep and its width is symmetrically distributed at 40-60° relative to the rotor's central axis. The gear mounting surface is provided with three locating pin holes and six threaded holes.

[0015] The heat insulation grooves block the transfer of heat from the combustion chamber to the bearing bush through the air layer. The symmetrical distribution design ensures a balanced heat insulation effect and effectively reduces the working temperature of the bearing bush. The number and layout of the positioning pin holes and threaded holes provide a structural basis for the precise positioning and firm fixation of the internal gear, ensuring the concentricity and connection reliability of the internal gear after installation.

[0016] A further technical solution is that the rotor bearing is an alloy steel thin-walled bushing with a wall thickness of 2 to 2.5 mm and an inner surface hardened to a hardness of HRC55 to 60; a chamfer and 9 to 12 notches are provided on one side of the inner diameter of the bearing to form an oil groove, and the oil groove and the internal gear mounting surface form a circumferential oil groove.

[0017] The thin-walled alloy steel structure balances lightweight and wear resistance, while the hardening treatment of the inner surface greatly improves the wear resistance of the bearing bush. The chamfered design facilitates bearing bush assembly guidance, and the slanted oil groove can use centrifugal force to evenly introduce lubricating oil into the inner surface of the bearing bush. The circumferential oil groove formed by the mating with the internal gear mounting surface can ensure the continuity of lubrication and optimize the journal lubrication effect.

[0018] A further technical solution is that the internal gear has a plate structure with three locating pin holes and six through holes evenly distributed. The locating pin holes are closely attached to the through hole latches and have an outer circular structure. The internal gear is positioned with the air-cooled triangular rotor by the internal gear locating pins, and the clearance between the locating pins and the holes is 0.01 to 0.15 mm.

[0019] The plate structure simplifies the machining and clamping process of the internal gear, allowing for the use of gear grinding to improve tooth profile accuracy; the layout design of the positioning pin holes and through holes enhances structural rigidity, the tiny fit clearance ensures high-precision positioning of the internal gear and the triangular rotor, and the outer circular structure helps to improve installation stability.

[0020] A further technical solution is that the internal hexagon countersunk bolt is a 12.9 grade fine thread bolt of M3 to M4, with a preload of 5 N·m, and the bolt height is lower than the rotor end face after tightening;

[0021] Grade 12.9 fine-pitch bolts have high strength and good fatigue resistance. Precise preload control can avoid stress concentration at the connection point. The countersunk head design ensures that the bolt does not protrude from the rotor end face, preventing interference with other engine components and ensuring assembly space compatibility.

[0022] A further technical solution is that the rotor bearing and the bearing bush seat of the air-cooled triangular rotor adopt an interference fit with an interference amount of 0.015 to 0.03 mm. Assembly is achieved by cooling the rotor bearing with liquid nitrogen or heating the air-cooled triangular rotor to above 120°C.

[0023] The interference fit ensures a tight connection between the bearing bush and the bushing seat, preventing relative slippage of the bearing bush during high-speed rotation; while the temperature difference assembly process reduces the assembly difficulty, ensures precise control of the interference amount, and guarantees the installation accuracy and structural stability of the bearing bush.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention improves connection reliability: it adopts a split bolt connection and redundant positioning pin internal gear fixing structure, avoiding residual stress caused by the difference in thermal expansion coefficients of materials in traditional welding; the positioning pin is precisely positioned with a very small fit clearance, ensuring the concentricity of the internal gear and the triangular rotor; the 12.9 grade fine thread bolts apply appropriate preload, and after rigorous testing, the probability of connection failure is extremely low. Compared with the welding structure, it greatly reduces the risk of internal gear falling off, ensures the continuous and stable operation of the engine, and avoids triggering a chain of failures in the whole machine.

[0026] This invention optimizes maintenance economy: the rotor bearing and internal gear are designed to be detachable, so that during engine maintenance, it is not necessary to replace the entire rotor assembly, but only the damaged parts need to be replaced, which significantly reduces maintenance costs, shortens maintenance time, and improves the economy of the engine throughout its entire life cycle.

[0027] This invention enhances rotor heat dissipation: the "S"-shaped heat dissipation fins in the triangular cooling chamber, through equidistant array and reasonable wall thickness design, significantly increase the heat dissipation area without increasing the rotor volume; the special design of the fin apex angle reduces airflow resistance, promotes heat exchange between high-speed airflow and fins, effectively suppresses rotor thermal deformation, ensures the sealing accuracy, reduces sealing leakage, and improves the stability of engine power output.

[0028] This invention upgrades the thermal protection of bearing bushes: the bearing bush seat heat insulation groove uses an air insulation layer to block the heat conduction of the combustion chamber, reduce the working temperature of the bearing bush, prevent the bearing bush from deteriorating due to high temperature, extend the wear life of the bearing bush, improve the working environment of the sealing spring, and enhance the reliability of the sealing system;

[0029] This invention ensures uniform journal lubrication: the notch of the rotor bearing has an obliquely placed oil groove. With the help of the centrifugal force of the high-speed rotation of the rotor, the lubricating oil is guided to flow precisely to the contact surface between the bearing and the eccentric journal. Tests have shown that this structure significantly improves the uniformity of journal lubrication, greatly reduces the fluctuation range of oil film thickness, effectively avoids dry friction and local wear of the journal, ensures stable operation of the engine at high speed, and reduces the risk of power interruption due to lubrication failure.

[0030] This invention optimizes the wear resistance of bearing bushes: the inner surface of the thin-walled alloy steel bearing bush is hardened, combined with uniform lubrication, which significantly improves the wear life of the bearing bush. Bench tests show that the wear of the bearing bush is much lower than that of traditional bearing bushes, reducing the frequency of bearing bush replacement and ensuring the long-term reliable operation of the engine.

[0031] This invention improves the precision of internal gears: the internal gear plate structure with redundant positioning pins facilitates the use of gear grinding technology. After testing, the tooth profile accuracy is greatly improved, the tooth direction error is extremely small, and the meshing noise is reduced. The high-precision internal gear ensures the smooth transmission between the rotor and the eccentric shaft, reduces power transmission loss, and improves the energy conversion efficiency of the engine.

[0032] This invention ensures rotor positioning accuracy: the combination of positioning pins and bolts for fixation ensures extremely high coaxiality between the internal gear and the triangular rotor. Compared with traditional welded structures, the positioning accuracy is greatly improved. Precise positioning ensures stable rotor movement trajectory within the engine cavity, reduces cylinder wear caused by eccentric movement, extends the overall engine life, reduces engine vibration, and improves the adaptability of UAVs.

[0033] This invention enhances the flexibility of combustion chamber design: the split structure eliminates the spatial constraints of welding on the combustion chamber recess, and combined with material strength optimization, the design of the combustion chamber recess wall thickness is more flexible, which can adapt to different compression ratio requirements. The combustion chamber shape is optimized for new fuels, expanding the engine's fuel adaptability and operating condition adaptability, and providing a structural foundation for the performance upgrade of UAV power systems.

[0034] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the three-dimensional structure of the air-cooled triangular rotor assembly of the present invention; Figure 2 This is a three-dimensional exploded structural diagram of the air-cooled triangular rotor assembly of the present invention; Figure 3 This is a schematic diagram of the three-dimensional cross-section of the bearing bushing seat of the present invention.

[0038] In the diagram: 1. Air-cooled triangular rotor; 2. Internal gear locating pin; 3. Rotor bearing; 4. Internal gear; 5. Socket head bolt; 101. "S" type heat dissipation fins; 102. Bearing bushing seat; 103. Bearing shoulder; 104. Gear mounting surface; 301. Bearing chamfer; 302. Bearing notch with oblique oil drain groove. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0041] Example 1

[0042] like Figures 1-3 As shown, this embodiment of the invention provides a combined air-cooled triangular rotor assembly, including an air-cooled triangular rotor 1, an internal gear positioning pin 2, a rotor bearing 3, an internal gear 4, and an internal hexagon countersunk bolt 5;

[0043] In this embodiment, the air-cooled triangular rotor 1 is made of ductile iron and is normalized. Five "S"-shaped heat dissipation fins 101 are evenly distributed within its triangular cooling chamber. The fins have a wall thickness of 1.5 mm and are equidistant from the sealing post holes in a perpendicular direction. The fin spacing is 4 mm, and the fin apex is rounded with a radius of R1. These "S"-shaped heat dissipation fins significantly increase the heat dissipation area within the small space of the triangular rotor. When the engine is running, the high-speed airflow passes through the fins, quickly carrying away heat from the rotor and effectively reducing its temperature, ensuring that the rotor operates at a suitable temperature.

[0044] Specifically, the bearing bush seat 102 of the air-cooled triangular rotor 1 is provided with a heat insulation groove near the combustion chamber. The heat insulation groove is 2.5mm deep and its width is symmetrically distributed at 50° relative to the rotor central axis. This heat insulation groove can isolate a part of the heat in the combustion chamber from being transferred to the rotor bearing 3, reduce the average operating temperature of the rotor bearing 3, reduce its thermal deformation, and ensure the fitting accuracy between the bearing and the eccentric shaft. In actual operation, the average temperature of the bearing is reduced by 8℃, and the thermal deformation is controlled within 0.01mm.

[0045] In this embodiment, the rotor bearing 3 is a thin-walled alloy steel bushing with a wall thickness of 2.2 mm and an inner surface hardened to a hardness of HRC58. The high hardness gives the bearing good wear resistance and allows it to fit well with the needle roller bearing of the eccentric shaft of the triangular rotor engine, reducing wear.

[0046] Specifically, the inner diameter of the bearing bush has a chamfer 301 and 10 notches with obliquely placed oil drain grooves 302. The oil drain grooves and the mounting surface of the internal gear 4 form a circumferential oil groove. When the rotor engine is rotating, the centrifugal force causes the lubricating oil from the lubricating internal gear 4 to flow through the obliquely placed oil drain grooves 302 to the inner surface of the rotor bearing bush 3, thereby uniformly lubricating the eccentric journal and needle roller bearing, ensuring the lubrication effect.

[0047] In this embodiment, the internal gear 4 has a plate structure with three locating pin holes and six through holes evenly distributed. The locating pin holes are closely attached to the through hole contacts and have an outer circular structure. The plate structure facilitates circumferential clamping of the internal gear during gear shaping and grinding, making it easy to use the gear grinding process and ensuring the tooth profile accuracy of the internal gear after hardening. The tooth profile tolerance after grinding is controlled within the 6th grade accuracy of GB / T10095.1-2008.

[0048] Specifically, the internal gear 4 is positioned with the air-cooled triangular rotor 1 by the internal gear positioning pin 2. The clearance between the positioning pin and the hole is 0.08mm. It is then tightened and fixed by six M3.5 12.9 grade fine-tooth internal hexagon countersunk head bolts 5 with a preload of 5N·m. After tightening, the height of the bolts is lower than the end face of the rotor. The positioning pin ensures the positioning accuracy of the internal gear and the triangular rotor, while the bolt connection ensures the firmness of the connection between the two and prevents relative displacement during operation. After 100h vibration test, there was no loosening of the internal gear.

[0049] In this embodiment, the rotor bearing 3 is installed in the bearing bush seat 102 of the air-cooled triangular rotor 1. During assembly, the rotor bearing 3 is first cooled with liquid nitrogen, and then placed in the inner diameter of the triangular rotor heated to 130°C to ensure an interference fit of 0.02mm. One end face is in close contact with the bearing shoulder 103, and the other end face is slightly lower than the triangular rotor gear mounting surface, which realizes the axial positioning of the bearing and ensures that the bearing will not move axially during operation. After assembly, the axial movement of the bearing is ≤0.01mm.

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that: the air-cooled triangular rotor 1 is made of alloy cast iron, the clearance between the internal gear positioning pin 2 and the hole is 0.01mm, the rotor bearing 3 has a wall thickness of 2mm, and the internal hexagon countersunk bolt 5 is an M3 grade 12.9 fine thread bolt;

[0052] This invention provides a combined air-cooled triangular rotor assembly. The air-cooled triangular rotor 1 has an "S"-shaped heat dissipation fin 101 with a wall thickness of 1.3 mm, a fin spacing of 3 mm, and a rounded radius R0.5 at the fin apex. The bearing bushing seat 102 has a heat insulation groove with a depth of 2 mm and a width that is symmetrically distributed at 40° relative to the rotor central axis.

[0053] In this embodiment, the inner surface of the rotor bearing 3 is hardened to HRC55. A 45° chamfer 301 and nine notched, obliquely placed oil drain grooves 302 are provided on one side of the inner diameter of the bearing. During assembly, the triangular rotor is heated to 120°C, and the rotor bearing 3 is installed with an interference fit of 0.015mm. The triangular rotor, made of alloy cast iron, has good strength and wear resistance. The smaller locating pin clearance further improves the positioning accuracy of the internal gear. The thinner bearing wall reduces the overall weight, making it suitable for UAV power units with high weight requirements. During operation, the heat dissipation fins reduce the rotor temperature by 12°C, the heat insulation groove reduces the bearing temperature by 6°C, and the oil drain grooves ensure lubrication uniformity is improved by 35%. The bearing wear is 0.025mm after 100 hours.

[0054] Working principle and usage process of this invention:

[0055] After the engine starts, the triangular rotor assembly rotates planetarily with the eccentric shaft. The fuel and air inside the combustion chamber mix and ignite, generating high-temperature and high-pressure gas that drives the triangular rotor to rotate continuously, realizing the conversion of thermal energy into mechanical energy.

[0056] The internal gear 4 is precisely positioned with the air-cooled triangular rotor 1 through the internal gear positioning pin 2 to ensure their concentricity; at the same time, a 5 N·m preload is applied by the internal hexagon countersunk bolt 5 to firmly connect them, so that the internal gear and the triangular rotor form a rigid whole; when the engine is working, the internal gear meshes with the external gear on the eccentric shaft for transmission. Through the double constraint of the positioning pin and the bolt, it is ensured that there is no relative displacement between the internal gear and the triangular rotor, so as to achieve stable power transmission and avoid the power interruption problem caused by connection failure in traditional welded structures.

[0057] A portion of the heat generated by combustion is conducted to the triangular cooling chamber through the triangular rotor body.

[0058] · The "S"-shaped heat dissipation fins 101 inside the cooling chamber maximize the heat dissipation area through an equidistant array design. When high-speed airflow passes through the fins, forced convection is used to carry away heat from the fin surface, reducing the rotor body temperature through heat exchange. The R0.5-R1 arc design at the fin apex reduces airflow resistance and avoids fin breakage caused by stress concentration.

[0059] · The heat insulation groove of the bearing bush seat 102 near the combustion chamber forms an air heat insulation layer, which blocks the direct conduction of the high temperature of the combustion chamber to the rotor bearing bush 3, reduces the heat absorbed by the bearing bush, lowers its operating temperature, and prevents the bearing bush from undergoing material performance degradation or dimensional deformation due to overheating.

[0060] The lubricating oil supplied by the lubrication system first enters the meshing area between the internal gear 4 and the external gear, lubricating the gear tooth surfaces and reducing meshing wear; as the triangular rotor rotates at high speed, under the action of centrifugal force:

[0061] Excess lubricating oil is thrown towards the internal gear mounting surface and flows into the obliquely placed oil drain groove 302 of the rotor bearing 3. Under the continuous action of centrifugal force, it quickly diffuses to the inner surface of the bearing along the inclined direction of the oil drain groove, and forms a continuous oil film with the bearing bush seat 102. This film covers the contact surface between the eccentric journal and the needle roller bearing, realizing dynamic lubrication between the journal and the bearing, reducing the coefficient of friction. At the same time, the fluidity of the lubricating oil carries away the heat generated by the journal operation, maintaining the stable working temperature of the bearing and avoiding bearing failure due to dry friction or local overheating.

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A combined air-cooled triangular rotor assembly, comprising an air-cooled triangular rotor (1), an internal gear locating pin (2), a rotor bearing (3), an internal gear (4), and internal hexagon countersunk bolts (5), characterized in that: The internal gear (4) is fitted onto the bearing shoulder (103) of the air-cooled triangular rotor (1) through clearance, and is positioned on the gear mounting surface (104) of the air-cooled triangular rotor (1) by the internal gear positioning pin (2). The internal hexagon countersunk bolt (5) passes through the through hole of the internal gear (4) and connects to the threaded hole of the air-cooled triangular rotor (1) to fix the internal gear (4) to the air-cooled triangular rotor (1). The rotor bearing (3) is installed in the bearing bush seat (102) of the air-cooled triangular rotor (1), with one end face closely attached to the bearing shoulder (103) and the other end face lower than the triangular rotor gear mounting surface.

2. The combined air-cooled triangular rotor assembly according to claim 1, characterized in that: The air-cooled triangular rotor (1) is made of ductile iron or alloy cast iron and is normalized. Five "S"-shaped heat dissipation fins (101) are evenly distributed in its triangular cooling cavity. The heat dissipation fin wall thickness is 1.3 to 2 mm. They are equidistant from the sealing small column holes in the vertical direction. The fin spacing is 3 to 5 mm. The fin apex is rounded with a radius of R0.5-R1.

3. The combined air-cooled triangular rotor assembly according to claim 1, characterized in that: The bearing bush seat (102) of the air-cooled triangular rotor (1) is provided with a heat insulation groove near the combustion chamber. The heat insulation groove is 2-3 mm deep and its width is symmetrically distributed at 40-60° relative to the rotor center axis. The gear mounting surface (104) is provided with three positioning pin holes and six threaded holes.

4. The combined air-cooled triangular rotor assembly according to claim 1, characterized in that: The rotor bearing (3) is a thin-walled alloy steel bushing with a wall thickness of 2 to 2.5 mm and an inner surface hardened to a hardness of HRC55 to 60. A chamfer (301) and 9 to 12 notches are provided on one side of the inner diameter of the bearing to form an oil groove (302). The oil groove and the mounting surface of the internal gear (4) form a circumferential oil groove.

5. The combined air-cooled triangular rotor assembly according to claim 1, characterized in that: The internal gear (4) is a plate structure with three locating pin holes and six through holes evenly distributed. The locating pin holes are close to the through hole joints and have an outer circular structure. The internal gear (4) is positioned with the air-cooled triangular rotor (1) through the internal gear locating pin (2). The clearance between the locating pin and the hole is 0.01 to 0.15 mm.

6. The combined air-cooled triangular rotor assembly according to claim 1, characterized in that: The internal hexagon countersunk bolt (5) is a grade 12.9 fine thread bolt of M3 to M4, with a preload of 5 N·m. After tightening, the bolt height is lower than the rotor end face.

7. The combined air-cooled triangular rotor assembly according to claim 1, characterized in that: The rotor bearing (3) and the bearing bush seat (102) of the air-cooled triangular rotor (1) are interference fit with an interference amount of 0.015 to 0.03 mm. Assembly is achieved by cooling the rotor bearing (3) with liquid nitrogen or heating the air-cooled triangular rotor (1) to above 120°C.

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