A motorcycle engine

Abstract

This invention belongs to the technical field of motorcycle parts and relates to a motorcycle engine, including a crankcase, a cylinder block, and a cylinder head. The crankcase houses a crankshaft and is filled with engine oil. One end of the crankshaft extends out of the crankcase and is fitted with a fan. The fan is covered by a fan shroud, and the circumferential sidewall of the fan shroud has two independent air outlets: a first outlet connects to the radial extension of the fan shroud to cool the engine oil, and a second outlet connects to a guide shroud to cool the cylinder block and cylinder head. A three-dimensional cooling fin array is provided on the side of the crankcase near the fan shroud. The three-dimensional cooling fin array is located in the airflow path of the radial extension, and its inner side exchanges heat with the engine oil. The cylinder head has guide ribs to divide the cooling airflow and guide it to the intake and exhaust ports respectively. The motorcycle engine provided by this invention can significantly improve cooling uniformity and efficiency, meeting the performance requirements of the engine under high load.

Description

Technical Field

[0001] This invention belongs to the technical field of motorcycle parts and relates to a motorcycle engine. Background Technology

[0002] An air-cooled engine is an engine that uses air as the cooling medium. It has cooling fins cast into the outer walls of the cylinder and cylinder head, and a cooling fan blows air at high speed across the surface of these fins, carrying away the heat dissipated by the engine and cooling it down. Air-cooled engines are a type of engine characterized by their simple structure and light weight. They are easy to maintain and use, highly adaptable to climate changes, quick to start, and do not require a radiator, making them widely used in motorcycles.

[0003] However, traditional air-cooled engines have limited coverage. Chinese invention patent application CN119435189A (publication date: 2025.02.14) discloses an air-cooling system and engine, including an engine block and a cooling system. The cooling system includes a fan assembly, including a fan and a fan shroud with an air outlet I; an air guide shroud for forming a cooling air duct for cooling the engine block, the cooling air duct being connected to the air outlet I; and a flow guide, disposed within the cooling air duct, for forming a branch air duct for diverting and guiding the cooling air to the area near the intake side of the cylinder head spark plug I. The air-cooling system and engine of the present invention, with the air guide shroud connected to the fan shroud, thereby forming a cooling air duct for cooling the cylinder block and cylinder head, can achieve sufficient cooling of the cylinder block and cylinder head. At the same time, by setting the flow guide, the cooling air is guided to the area of ​​the cylinder head spark plug, which can improve the cooling effect on the spark plug, improve the utilization rate of the cooling air, and make the heat dissipation of various engine components uniform, thereby meeting the requirements of engine power, economy and reliability.

[0004] The aforementioned structure directs cooling air to the cylinder block and cylinder head, expanding the coverage of the air-cooled system, especially for cooling the spark plug area. However, the engine oil in the crankcase lacks a cooling structure, resulting in poor cooling performance, and prolonged exposure to high temperatures negatively impacts oil performance. Furthermore, the aforementioned airflow design only directs cooling air to the spark plug area of ​​the cylinder head, lacking cooling structures for other areas. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a motorcycle engine that can significantly improve cooling uniformity and efficiency, meeting the performance requirements of the engine under high loads.

[0006] To solve the above-mentioned technical problems, the objective of this invention is achieved through the following technical solution:

[0007] A motorcycle engine includes a crankcase, a cylinder block, and a cylinder head. The crankcase houses a crankshaft and stores engine oil. One end of the crankshaft extends out of the crankcase and is fitted with a fan. The fan is covered by a fan shroud. Two independent air outlets are provided on the circumferential sidewall of the fan shroud: a first outlet connects to a radial extension of the fan shroud to cool the engine oil, and a second outlet connects to a guide shroud to cool the cylinder block and cylinder head. A three-dimensional cooling fin array is provided on the side of the crankcase near the fan shroud. The three-dimensional cooling fin array is located in the airflow path of the radial extension and its inner side exchanges heat with the engine oil. The radial extension covers the three-dimensional cooling fin array and has an air outlet at the end of the airflow path. Air guide ribs are provided inside the cylinder head to divide the cooling airflow and guide it to the intake and exhaust ports respectively.

[0008] In the aforementioned motorcycle engine, the inner side of the three-dimensional heat dissipation fin array forms a curved heat-conducting surface, and the outer side forms a heat dissipation air guide groove with an arc-shaped bottom. The air outlet is provided in a one-to-one correspondence with the heat dissipation air guide groove, and the cooling airflow from the first air outlet flows along the heat dissipation air guide groove and flows out through the air outlet.

[0009] In the aforementioned motorcycle engine, the three-dimensional cooling fin array is integrally formed with the crankcase and includes several spaced-apart three-dimensional fins. Cooling air ducts are formed between adjacent three-dimensional fins. A concave heat-conducting surface is formed on the inner side of each three-dimensional fin, and a convex heat-conducting surface is formed on the inner side of each cooling air duct. In this invention, the three-dimensional fins differ from traditional sheet-like fins; the three-dimensional fins have a considerable width, sufficient to form a curved heat-conducting surface on the corresponding back side.

[0010] In the aforementioned motorcycle engine, an arc-shaped boss is provided at the bottom of the crankcase on the side away from the cylinder block. The arc-shaped boss has a coverage range of 45°-90° and forms a base structure for a three-dimensional heat dissipation fin array. The heat dissipation air guide groove connects the outer side of the arc-shaped boss and the opposite side of the arc-shaped boss and the crankshaft. The outer side of the arc-shaped boss refers to its axial outer side, and the opposite side of the arc-shaped boss and the crankshaft refers to its radial inner side.

[0011] In the aforementioned motorcycle engine, the air guide gradually converges along the airflow direction and enters the cylinder head through the spark plug. The gaps on both sides of the spark plug form an air intake channel, the gaps on both sides of the air intake port form an air intake side exhaust channel, and the gaps on both sides of the exhaust port form an exhaust side exhaust channel.

[0012] In the aforementioned motorcycle engine, the cylinder head is provided with air guide ribs that guide the cooling airflow from the outside of the air intake and exhaust ports to the inside. The air guide ribs are inclined towards the exhaust port side along the airflow direction. Preferably, the end of the air guide ribs forms an arc-shaped structure that bends towards the exhaust port side.

[0013] In the aforementioned motorcycle engine, the air guide ribs include a first air guide rib, a second air guide rib, and a third air guide rib. The first air guide rib is disposed between the spark plug and the exhaust port, the second air guide rib is disposed between the air intake and the exhaust port, and the third air guide rib is disposed between the air intake and the side cylinder wall. The upper and lower ends of the second and third air guide ribs are respectively integrated with the upper and lower cylinder walls and an air passage gap is left between them and the side cylinder walls.

[0014] In the aforementioned motorcycle engine, the air intake is connected to the main air intake passage of the combustion chamber. An auxiliary air intake passage connected to the main air intake passage is provided on one side of the main air intake passage. The diameter of the auxiliary air intake passage is smaller than that of the main air intake passage. Gas enters the main air intake passage through the auxiliary air intake passage and disturbs the gas in the main air intake passage to enhance tumble flow.

[0015] In the aforementioned motorcycle engine, the intake openings of both the main intake manifold and the auxiliary intake manifold are located on the end face of the intake port. The auxiliary intake manifold is located on the side closer to the combustion chamber. The main intake manifold is inclined towards the combustion chamber and connects to it. The auxiliary intake manifold is arranged radially along the cylinder head and extends through the main intake manifold. The cross-section of the auxiliary intake manifold is a flat structure. Preferably, the long side of the flat structure extends parallel to the main intake manifold. Preferably, the auxiliary intake manifold is located at a position corresponding to the middle of the main intake manifold. Preferably, the auxiliary intake manifold has an irregular variable diameter or curved surface structure.

[0016] In the aforementioned motorcycle engine, the ratio of the cross-sectional area of ​​the main air intake to the auxiliary air intake is 10:1 to 5:1; the connection between the auxiliary air intake and the main air intake is located on the side of the main air intake closer to the combustion chamber.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The motorcycle engine provided by this invention features an independent oil cooling structure. Addressing the problem of insufficient oil cooling within the crankcase, an independent cooling path and a three-dimensional heat dissipation fin array structure are designed. Airflow is guided through the radial extension of the fan shroud's first outlet to cover the three-dimensional heat dissipation fin array on one side of the crankcase. The inner side of this fin array undergoes efficient heat exchange with the oil via a curved heat-conducting surface. The outer airflow flows through the cooling air guide groove and is then discharged through the outlet, carrying away the heat exchanged by the fin array. This effectively reduces the oil temperature, preventing the long-term effects of high temperatures on oil performance and ensuring the reliability of the lubrication system. The unique three-dimensional heat dissipation fin array structure of this invention ensures excellent heat exchange efficiency on both its inner and outer sides.

[0019] 2. The motorcycle engine provided by this invention optimizes the cooling structure of the cylinder head. For cooling the cylinder head and cylinder block, an air guide shroud is connected to the second air outlet of the fan shroud to introduce airflow into the cylinder head. The airflow is then divided by air guide ribs and directed to the spark plug, intake port, and exhaust port areas, ensuring uniform cooling of critical components such as the spark plug, intake port, and exhaust port. This solves the problem of insufficient coverage in traditional air-cooled systems, especially the lack of a cooling structure on the intake side.

[0020] 3. This invention further improves the air intake structure of the engine by adopting a dual-air intake, which increases the intake volume. More importantly, the designed auxiliary air intake, through a small-diameter channel, disturbs the airflow in the main air intake, enhances the tumble effect, and indirectly improves combustion efficiency, thus providing further support for the engine's power and economy. Attached Figure Description

[0021] Figure 1 This is a perspective view of the present invention;

[0022] Figure 2 This is a perspective view of the present invention (with the fan cover and air guide cover removed);

[0023] Figure 3 This is a perspective view of the fan cover and air guide cover of the present invention;

[0024] Figure 4 This is a perspective view of the crankcase of the present invention;

[0025] Figure 5 This is another perspective view of the crankcase of the present invention;

[0026] Figure 6 This is a perspective view of the cylinder head of the present invention;

[0027] Figure 7 This is a cross-sectional view of the cylinder head of the present invention;

[0028] Figure 8 This is another sectional view of the cylinder head of the present invention;

[0029] Reference numerals: 1. Crankcase; 2. Cylinder block; 3. Cylinder head; 4. Crankshaft; 5. Fan; 6. Fan shroud; 7. First air outlet; 8. Radial extension; 9. Second air outlet; 10. Air guide shroud; 11. Three-dimensional heat dissipation fin array; 12. Air outlet; 13. Air guide rib; 14. Air inlet; 15. Exhaust outlet; 16. Heat-conducting surface; 17. Heat dissipation air guide groove; 18. Three-dimensional fins; 19. Concave heat-conducting surface; 20. Convex heat-conducting surface; 21. Arc-shaped boss; 22. Spark plug; 23. First air guide rib; 24. Second air guide rib; 25. Third air guide rib; 26. Combustion chamber; 27. Main intake duct; 28. Auxiliary intake duct. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. See also: Figure 1-8 :

[0031] A motorcycle engine includes a crankcase 1, a cylinder block 2, and a cylinder head 3. The crankcase 1 houses a crankshaft 4 and stores engine oil. One end of the crankshaft 4 extends out of the crankcase 1 and is fitted with a fan 5. The fan 5 is covered by a fan shroud 6. Two independent air outlets are provided on the circumferential sidewall of the fan shroud 6: a first air outlet 7 connects to a radial extension 8 of the fan shroud 6 to cool the engine oil, and a second air outlet 9 connects to a guide shroud 10 to cool the cylinder block 2 and the cylinder head 3. A three-dimensional cooling fin array 11 is provided on the side of the crankcase 1 closest to the fan shroud 6. The three-dimensional cooling fin array 11 is located on the airflow path of the radial extension 8, and its inner side exchanges heat with the engine oil. The radial extension 8 covers the three-dimensional cooling fin array 11 and has an air outlet 12 at the end of the airflow path. Air guide ribs 13 are provided inside the cylinder head 3 to divide the cooling airflow and guide it to the intake port 14 and the exhaust port 15, respectively.

[0032] Referring to the accompanying drawings, the structure of the three-dimensional heat dissipation fin array 11 in this embodiment is as follows: the inner side of the three-dimensional heat dissipation fin array 11 forms a curved heat-conducting surface 16, and the outer side forms a heat dissipation air guide groove 17 with an arc-shaped bottom. The air outlet 12 is arranged in a one-to-one correspondence with the heat dissipation air guide groove 17. The cooling airflow of the first air outlet 7 flows along the heat dissipation air guide groove 17 and flows out through the air outlet 12.

[0033] Furthermore, the three-dimensional heat dissipation fin array 11 is integrally formed with the crankshaft housing 4, including a plurality of spaced three-dimensional fins 18, with heat dissipation air ducts 17 formed between adjacent three-dimensional fins 18, a concave heat-conducting surface 19 formed on the inner side corresponding to the three-dimensional fins 18, and a convex heat-conducting surface 20 formed on the inner side corresponding to the heat dissipation air ducts 17. The concave heat-conducting surface 19 and the convex heat-conducting surface 20 together form a curved heat-conducting surface 16. In this embodiment, the three-dimensional fins 18 are different from traditional sheet-like fins; the three-dimensional fins 18 have a considerable width, sufficient to form a curved heat-conducting surface 16 on the corresponding part of the back side.

[0034] In this embodiment, after the motorcycle engine starts, the crankshaft 4 drives the fan 5 at one end to rotate at high speed. The cooling airflow generated by the fan 5 (where low-temperature external gas enters through the axial air inlet at the end of the fan shroud 6 to form the cooling airflow) is constrained and diverted by the fan shroud 6. Specifically:

[0035] Oil cooling path: Part of the airflow enters the radial extension 8 through the first air outlet 7. This airflow is guided to the surface of the three-dimensional heat dissipation fin array 11 on the side wall of the crankshaft housing 1. The airflow flows along the heat dissipation guide groove 17 formed by adjacent three-dimensional fins 18. The airflow contacts the three-dimensional fins 18 and the heat dissipation guide groove 17 at the same time to exchange heat efficiently. Meanwhile, the curved heat-conducting surface 16 (with a larger heat exchange area) on the inner side of the three-dimensional heat dissipation fin array 11 (facing the inside of the crankshaft housing 1) exchanges heat efficiently with the oil in the housing, absorbing the heat of the oil. The airflow carrying the heat is finally discharged through the air outlet 12 at the end, realizing continuous forced air cooling of the oil.

[0036] Cooling path of cylinder block 2 and cylinder head 3: Another part of the airflow enters the air guide shroud 10 through the second air outlet 9. The air guide shroud 10 guides it to cylinder block 2 and cylinder head 3, and carries away the heat on the surface of cylinder block 2 and cylinder head 3 during the flow. The cooling airflow then flows through the spark plug 22 area of ​​cylinder head 3, cools the spark plug 22 area and enters the interior of cylinder head 3. Guided by the air guide ribs 13, it splits again. Part of it is guided to the exhaust port 15 area and finally flows out, and part of it is guided to the intake port 14 area and finally flows out.

[0037] The specific structure of the aforementioned three-dimensional heat dissipation fin array 11 is as follows: an arc-shaped boss 21 is provided at the bottom of the crankshaft housing 1 on the side away from the cylinder block 2. The arc-shaped boss 21 covers an area of ​​45°-90° and forms the base structure of the three-dimensional heat dissipation fin array 11. The heat dissipation air guide groove 17 connects the outer side of the arc-shaped boss 21 and the opposite surface of the arc-shaped boss 21 to the crankshaft 4. The outer side of the arc-shaped boss 21 refers to its axial outer side, and the opposite surface of the arc-shaped boss 21 to the crankshaft 4 refers to its radial inner side. By setting the arc-shaped boss 21, the axial distance between the three-dimensional fins 18 and the cooling airflow can be extended, significantly enhancing the heat dissipation effect.

[0038] Furthermore, the air guide shroud 10 gradually converges along the airflow direction, which can accelerate and guide the cooling airflow to the cylinder head 3 area, and enter the cylinder head 3 through the spark plug 22. The gaps on both sides of the spark plug 22 form an air intake channel, the gaps on both sides of the air intake port 14 form an air intake side exhaust channel, and the gaps on both sides of the exhaust port 15 form an exhaust side exhaust channel. The above channel design can increase the coverage of the cooling airflow and improve the cooling effect.

[0039] The cylinder head 3 is provided with air guide ribs 13 that guide the cooling airflow from the outside of the air inlet 14 and the exhaust port 15 to the inside. The air guide ribs 13 are inclined towards the exhaust port 15 along the airflow direction; preferably, the ends of the air guide ribs form an arc-shaped structure that bends towards the exhaust port 15. By providing air guide ribs 13, the airflow can be divided and guided to the air inlet 14 and the exhaust port 15 respectively. The inclined structure of the air guide ribs 13 can increase the gas distribution on the exhaust port 15 side.

[0040] The aforementioned air guide ribs 13 include a first air guide rib 23, a second air guide rib 24, and a third air guide rib 25. The first air guide rib 23 is disposed between the spark plug 22 and the exhaust port 15. The second air guide rib 24 is disposed between the intake port 14 and the exhaust port 15. The third air guide rib 25 is disposed between the intake port 14 and the side cylinder wall. The upper and lower ends of the second air guide rib 24 and the third air guide rib 25 are respectively integrated with the upper and lower cylinder walls and a gap is left between them and the side cylinder walls. Both sides of the second air guide rib 24 and the third air guide rib 25 form a partitioned flow channel to obtain a better flow distribution effect.

[0041] This embodiment further improves the intake structure, specifically:

[0042] The aforementioned air intake 14 connects to the main air intake duct 27 of the combustion chamber 26. An auxiliary air intake duct 28, which connects to the main air intake duct 27, is provided on one side of the main air intake duct 27. The diameter of the auxiliary air intake duct 28 is smaller than that of the main air intake duct 27. Gas enters the main air intake duct 27 through the auxiliary air intake duct 28 and disturbs the gas in the main air intake duct 27 to enhance tumble flow. When the engine intake valve is activated, gas mainly enters the combustion chamber 26 through the main air intake duct 27. At the same time, some gas enters through the smaller-diameter auxiliary air intake duct 28. The airflow entering through the auxiliary air intake duct 28 disturbs the mainstream gas in the main air intake duct 27, disrupts the laminar flow state, and significantly enhances the tumble flow intensity of the gas entering the combustion chamber 26, that is, forms a stronger air rotation motion. The enhanced tumble flow promotes the mixing of fuel and air, increases the turbulence intensity in the combustion chamber 26, and thus indirectly improves combustion efficiency and speed.

[0043] The intake openings of the main intake duct 27 and the auxiliary intake duct 28 are both located on the end face of the intake port 14. The auxiliary intake duct 28 is located on the side close to the combustion chamber 26. The main intake duct 27 is inclined towards the combustion chamber 26 and connects to the combustion chamber 26. The auxiliary intake duct 28 is arranged radially along the cylinder head 3 and extends through the main intake duct 27. The cross-section of the auxiliary intake duct 28 is a flat structure. Preferably, the long side of the flat structure extends parallel to the main intake duct 27. Preferably, the auxiliary intake duct 28 is located at the position corresponding to the middle of the main intake duct 27. Preferably, the auxiliary intake duct 28 has an irregular variable diameter or curved surface structure.

[0044] The ratio of the cross-sectional area of ​​the main air intake 27 to the auxiliary air intake 28 is 10:1 to 5:1; the connection between the auxiliary air intake 28 and the main air intake 27 is located on the side of the main air intake 27 near the combustion chamber 26.

[0045] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A motorcycle engine, comprising a crankcase (1), a cylinder block (2), and a cylinder head (3), wherein a crankshaft (4) is disposed within the crankcase (1) and stores engine oil, one end of the crankshaft (4) extends through the crankcase (1) and is fitted with a fan (5), the fan (5) being covered by a fan shroud (6), characterized in that, The fan shroud (6) has two independent air outlets on its circumferential sidewall: the first air outlet (7) connects to the radial extension (8) of the fan shroud (6) to cool the engine oil, and the second air outlet (9) connects to the air guide shroud (10) to cool the cylinder block (2) and cylinder head (3); the crankcase (1) has a three-dimensional heat dissipation fin array (11) on the side near the fan shroud (6), the three-dimensional heat dissipation fin array (11) is located on the airflow path of the radial extension (8) and its inner side exchanges heat with the engine oil, the radial extension (8) covers the three-dimensional heat dissipation fin array (11) and has an air outlet (12) at the end of the airflow path; the cylinder head (3) has air guide ribs (13) inside, which are used to divide the cooling airflow and guide it to the air inlet (14) and the exhaust port (15) respectively. The inner side of the three-dimensional heat dissipation fin array (11) forms a curved heat-conducting surface (16), and the outer side forms a heat dissipation air duct (17) with an arc bottom. The air outlet (12) is provided in a one-to-one correspondence with the heat dissipation air duct (17). The cooling airflow of the first air outlet (7) flows along the heat dissipation air duct (17) and flows out through the air outlet (12). The crankcase (1) has an arc-shaped boss (21) at the bottom of the side away from the cylinder block (2). The arc-shaped boss (21) covers an area of ​​45°-90°. The arc-shaped boss (21) forms the base structure of the three-dimensional heat dissipation fin array (11). The heat dissipation air guide groove (17) connects the outer side of the arc-shaped boss (21) and the opposite side of the arc-shaped boss (21) and the crankshaft (4). The air guide shroud (10) gradually converges along the airflow direction and enters the cylinder head (3) from the spark plug (22) of the cylinder head (3). The gaps on both sides of the spark plug (22) form an air intake channel, the gaps on both sides of the air inlet (14) form an air intake side air outlet channel, and the gaps on both sides of the exhaust port (15) form an exhaust side air outlet channel. The cylinder head (3) is provided with air guide ribs (13) that guide the cooling airflow from the outside of the air inlet (14) and the exhaust port (15) to the inside. The air guide ribs (13) are inclined towards the exhaust port (15) along the airflow direction. The air guide rib (13) includes a first air guide rib (23), a second air guide rib (24) and a third air guide rib (25). The first air guide rib (23) is disposed between the spark plug (22) and the exhaust port (15). The second air guide rib (24) is disposed between the air intake port (14) and the exhaust port (15). The third air guide rib (25) is disposed between the air intake port (14) and the side cylinder wall. The upper and lower ends of the second air guide rib (24) and the third air guide rib (25) are respectively connected to the upper and lower cylinder walls and a gap is left between them and the side cylinder wall.

2. A motorcycle engine according to claim 1, characterized in that, The three-dimensional heat dissipation fin array (11) is integrally formed with the crankcase (1) and includes a number of spaced three-dimensional fins (18). A heat dissipation air guide groove (17) is formed between adjacent three-dimensional fins (18). A concave heat conduction surface (19) is formed on the inner side corresponding to the three-dimensional fins (18), and a convex heat conduction surface (20) is formed on the inner side corresponding to the heat dissipation air guide groove (17).

3. A motorcycle engine according to claim 1, characterized in that, The air inlet (14) is connected to the main air intake (27) of the combustion chamber (26). An auxiliary air intake (28) is provided on one side of the main air intake (27) and is connected to the main air intake (27). The diameter of the auxiliary air intake (28) is smaller than that of the main air intake (27). Gas enters the main air intake (27) through the auxiliary air intake (28) and disturbs the gas in the main air intake (27) to enhance the tumble flow.

4. A motorcycle engine according to claim 3, characterized in that, The intake openings of the main intake passage (27) and the auxiliary intake passage (28) are both located on the end face of the intake port (14). The auxiliary intake passage (28) is located on the side close to the combustion chamber (26). The main intake passage (27) is inclined towards the combustion chamber (26) and connects to the combustion chamber (26). The auxiliary intake passage (28) is arranged radially along the cylinder head (3) and extends through the main intake passage (27). The cross-section of the auxiliary intake passage (28) is a flat structure.

5. A motorcycle engine according to claim 3, characterized in that, The ratio of the cross-sectional area of ​​the main air intake (27) to the auxiliary air intake (28) is 10:1-5:1; the connection between the auxiliary air intake (28) and the main air intake (27) is located on the side of the main air intake (27) near the combustion chamber (26).

Images