Motorcycle engine

Abstract

The motorcycle engine comprises a crankcase, an air cylinder, a cylinder head, an air inlet system and an exhaust system, the cylinder head is located above the air cylinder, the bottom wall of the cylinder head is provided with an air inlet channel and an exhaust channel, the air inlet channel is provided with two air inlets, the exhaust channel is provided with two air outlets, and the cylinder head is provided with a heat dissipation air channel. Air inlets of the heat dissipation air channel are located in the windward side of the cylinder head, and the heat dissipation air channel passes through the space between the two air inlets and the two air outlets. The air inlet system comprises an air inlet cam shaft and two air inlet valves. The air inlet cam shaft is provided with two first cams used for controlling opening and closing of the two air inlet valves correspondingly. The exhaust system comprises an exhaust cam and two exhaust valves, and the exhaust cam shaft is provided with two second cams used for controlling opening and closing of the exhaust valves respectively. According to the motorcycle engine, the structure that double-cam air inlet and double-cam exhaust are combined with cylinder head air cooling can be adopted, the large displacement and the efficient cooling effect of the engine are both considered, and the small size and low cost of the engine can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, in particular to a motorcycle engine. Background Art

[0002] With the continuous improvement of consumer spending levels, the current market for large-displacement engine motorcycles is growing.

[0003] Generally speaking, as the engine displacement increases, the engine thermal load also increases. Currently, most engines are cooled by oil cooling and water cooling to reduce the internal thermal load of the engine.

[0004] However, using existing cooling methods will increase the size of the engine and increase the cost. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a motorcycle engine that utilizes a dual-cam intake and dual-cam exhaust system combined with a cylinder head air-cooled structure, thereby balancing large engine displacement with efficient cooling, thereby ensuring a compact and low-cost engine.

[0006] A motorcycle engine according to an embodiment of the present invention includes: a crankcase, in which the crankshaft is arranged; a cylinder, located above the crankcase, having a combustion chamber; a cylinder head, located above the cylinder, with a bottom wall used to form a top wall of the combustion chamber, having an intake passage and an exhaust passage, the intake passage having two air inlets connected to the combustion chamber, the exhaust passage having two air outlets connected to the combustion chamber, the two air inlets and the two air outlets being circumferentially arranged along a central position of the combustion chamber, the cylinder head being provided with a heat dissipation duct, the air inlet of the heat dissipation duct being located on a windward surface of the cylinder head, and the heat dissipation duct passing between the two air inlets and the two air outlets; An intake system comprising an intake camshaft and two intake valves, wherein the intake valves are used to open and close the intake port, and the intake camshaft is provided with two first cams for controlling the opening and closing of the two intake valves respectively; The exhaust system comprises an exhaust camshaft and two exhaust valves, wherein the exhaust valves are used to open and close the air outlet, and the exhaust camshaft is provided with two second cams respectively used to control the opening and closing of the exhaust valves.

[0007] A motorcycle engine according to an embodiment of the present invention has at least the following beneficial effects: 1. The present invention achieves efficient air cooling and heat dissipation under a four-valve structure by providing two air inlets and two exhaust ports arranged circumferentially along the center of the combustion chamber, in conjunction with a heat dissipation duct passing between the two air inlets and the two air outlets. At the same time, the heat dissipation duct directly acts on the high-temperature area between the four valve channels, using the driving wind pressure to remove heat. Compared with traditional oil-cooling or water-cooling systems, the volume of heat dissipation components can be reduced, reducing manufacturing costs.

[0008] 2. The present invention arranges two first cams on the intake camshaft so that the intake system uses the two first cams on one intake camshaft to simultaneously control the opening and closing of two intake valves, and arranges two second cams on the exhaust camshaft so that the exhaust system uses the two second cams on one exhaust camshaft to simultaneously control the opening and closing of two exhaust valves, thereby achieving the effect of the intake camshaft simultaneously controlling the dual-channel intake and the exhaust camshaft simultaneously controlling the dual-channel exhaust, improving the intake and exhaust efficiency, and being conducive to increasing the engine displacement while maintaining the small size of the engine, thereby reducing the manufacturing cost.

[0009] 3. The present invention adopts a dual-cam intake and dual-cam exhaust combined with a cylinder head air-cooling structure, taking into account both the large displacement of the engine and the efficient cooling effect, which is conducive to ensuring the small size and low cost of the engine.

[0010] According to some embodiments of the present invention, the heat dissipation air duct includes an air inlet section and an air outlet section that are interconnected, the air inlet is arranged in the air inlet section, the air outlet section passes between the two air inlets and the two air outlets, and the air inlet section and the air outlet section are offset.

[0011] According to some embodiments of the present invention, a first heat sink is provided in the heat dissipation duct, and the first heat sink is located at the connection between the air inlet section and the air outlet section.

[0012] According to some embodiments of the present invention, the air inlet of the air inlet section is trumpet-shaped, and the large-diameter end of the air inlet faces outward.

[0013] According to some embodiments of the present invention, the intake camshaft has a first passage running through both ends, and the intake system further includes: a first sprocket engaged with a timing chain of the engine and configured to drive the intake camshaft to rotate; a centrifugal separation disc connected to one end of the intake camshaft, having a separation chamber connected to the first channel, wherein a fan blade is provided in the separation chamber, wherein the centrifugal separation disc rotates to draw the mixed oil and gas into the separation chamber, and the fan blade directs the gas into the first channel and throws the engine oil out of the separation chamber; A vent pipe is connected to an end of the first channel away from the centrifugal separation disk and is used to discharge gas in the first channel.

[0014] According to some embodiments of the present invention, the intake system further includes a connecting seat, which is arranged between the intake camshaft and the breather pipe, and the connecting seat has a first through hole running through both ends of the connecting seat, the end of the intake camshaft away from the centrifugal separation disk is connected to one end of the first through hole, and the breather pipe is connected to the other end of the first through hole, the end of the intake camshaft away from the centrifugal separation disk is provided with a first oil seal, and one end of the breather pipe is provided with a second oil seal, and the first oil seal and the second oil seal are respectively abutted and sealed against the inner circular surfaces at both ends of the first through hole.

[0015] According to some embodiments of the present invention, the first through hole includes a first section, a second section, and a third section arranged in sequence along the axial direction of the first through hole, the first section and the third section are used to install the first oil seal and the second oil seal, respectively, the inner diameter of the second section is larger than the outer diameter of one end of the intake camshaft inserted into the first through hole and the outer diameter of one end of the breather pipe inserted into the first through hole, there is a gap between the end of the intake camshaft and the end of the breather pipe, and the third section forms an oil storage ring groove.

[0016] According to some embodiments of the present invention, the exhaust system further comprises: a second sprocket engaged with a timing chain of the engine and configured to drive the exhaust camshaft to rotate; a ejector pin movably disposed on at least one of the second cams and capable of protruding from and recessing into a base circular surface of the second cam; A swing block is hinged on the second sprocket, and the swing block swings along the hinge center of the swing block and the second sprocket under the action of centrifugal force to drive the ejector pin to be recessed into the base circular surface of the second cam; A spring is used to drive the swing block to reset so that the swing block drives the ejector pin to protrude from the base circular surface of the second cam; One of the swing block and the second sprocket is provided with a first pin, and the other of the swing block and the second sprocket is provided with an arc groove extending circumferentially along the hinge center of the swing block and the second sprocket, and the first pin cooperates with the arc groove to guide and limit.

[0017] According to some embodiments of the present invention, the exhaust system also includes a drive shaft, which is coaxially rotated with the exhaust camshaft and arranged inside the exhaust camshaft. A transmission portion for abutting the ejector pin is provided on the drive shaft, and the swinging of the swing block drives the drive shaft to rotate relative to the exhaust camshaft, so that the drive shaft drives the ejector pin to protrude from the base circular surface of the second cam through the transmission portion.

[0018] According to some embodiments of the present invention, the transmission shaft is provided with a radially extending shift rod, and the swing of the swing block drives the shift rod to swing so that the transmission shaft rotates relative to the exhaust camshaft, and one of the swing block and the shift rod is provided with a transmission pin, and the other of the swing block and the shift rod is provided with a transmission slot for accommodating the transmission pin, and the transmission pin and the transmission slot cooperate for transmission.

[0019] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic structural diagram of a motorcycle engine according to an embodiment of the present invention; Figure 2 for Figure 1 Schematic diagram of the internal structure shown; Figure 3 for Figure 1 A schematic structural diagram of the left crankcase body is shown; Figure 4 for Figure 1 A schematic structural diagram of the right case of the crankcase is shown; Figure 5 for Figure 1 A schematic structural diagram of a crankcase gasket is shown; Figure 6 for Figure 1 The structural diagram of the cylinder head shown; Figure 7 for Figure 6 A schematic structural diagram from another perspective is shown; Figure 8 for Figure 6 Schematic diagram of the windward side of the cylinder head shown; Figure 9 for Figure 8 AA cross-sectional view shown; Figure 10 for Figure 2 The structural diagram of the intake system is shown; Figure 11 for Figure 10 Exploded view of the parts shown; Figure 12 for Figure 10 A front view is shown; Figure 13 for Figure 12 BB cross-sectional view shown; Figure 14 for Figure 2 A schematic diagram of the exhaust system is shown; Figure 15 for Figure 14 A schematic diagram of the structure of the second cam and the ejector pin is shown; Figure 16 for Figure 14 The schematic diagram of the structure of the swing block and the transmission shaft is shown.

[0022] Reference numerals: 100-crankcase, 101-left case, 102-right case, 103-gasket, 104-left labyrinth channel, 105-intake hole, 106-first oil drain hole, 107-right labyrinth channel, 108-second channel, 109-exhaust port, 110-crankshaft, 111-second oil drain hole, 112-air hole, 113-return oil hole, 120-cylinder, 130-combustion chamber, 140-cylinder head, 150-intake channel, 160-exhaust channel, 170-intake port, 180-outlet port, 190-cooling duct, 200-intake camshaft, 210-intake valve, 220-first cam, 230-exhaust camshaft, 240-exhaust valve, 25 0-second cam, 260-air inlet section, 270-air outlet section, 280-first heat sink, 290-air inlet, 300-first sprocket, 310-centrifugal separation disc, 320-separation chamber, 330-first channel, 340-fan blades, 350-ventilation pipe, 360-connecting seat, 370-first through hole, 380-first oil seal, 390-second oil seal, 400-first section, 410-second section, 420-third section, 430-second sprocket, 440-lift pin, 450-throw block, 460-spring, 470-first pin, 480-arc groove, 490-transmission shaft, 500-transmission part, 510-shift lever, 520-transmission pin, 530-transmission slide. DETAILED DESCRIPTION

[0023] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0024] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. If a first or second is mentioned, this is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted, connected, and connected" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0027] The following is combined with Figure 1 -Attached Figure 16 A motorcycle engine according to an embodiment of the present invention is described.

[0028] The present invention is directed to an embodiment of a motorcycle engine.

[0029] Reference Figure 1 and Figure 2 In this embodiment, a motorcycle engine mainly includes a crankcase 100, a cylinder 120, an intake system and an exhaust system.

[0030] Reference Figure 3 、 Figure 4 and Figure 5 Regarding the crankcase 100 , a crankshaft 110 is disposed inside the crankcase 100 .

[0031] Specifically, the left side of the crankshaft 110 is respectively installed with a clutch driving gear, a balance shaft driving gear and a first roller bearing from left to right, and the right side of the crankshaft 110 is respectively installed with a magnetic motor, a starting large gear, a timing small sprocket and a second roller bearing from right to left.

[0032] In some specific embodiments, the crankcase 100 includes a left case body 101, a right case body 102, and a gasket 103 connected between the left case body 101 and the right case body 102. A crankshaft cavity is formed between the left case body 101 and the right case body 102. The side of the left case body 101 facing away from the right case body 102 is used to form a left chamber, and the side of the right case body 102 facing away from the left case body 101 is used to form a right chamber.

[0033] Specifically, the clutch driving gear and the balance shaft driving gear are arranged in the right chamber, the first ball bearing is connected to the right case 102, the magnetic motor and the starting large gear are arranged in the left chamber, the timing small sprocket is arranged in the crankshaft chamber, and the second ball bearing is connected to the left case 101.

[0034] In some specific embodiments, the left case 101 is provided with a left labyrinth channel 104, an air inlet 105 connecting the left chamber and the left labyrinth channel 104, and a first oil drain hole 106 connecting the crankshaft cavity is provided at the bottom of the left labyrinth channel 104. The mixed oil and gas in the crankcase 100 enters the left labyrinth channel 104 from the air inlet 105, and the wall of the left labyrinth channel 104 blocks the oil in the mixed oil and gas from adhering to it and guides it to the first oil drain hole 106 and discharges it into the crankshaft cavity, so as to separate the oil from the mixed oil and gas.

[0035] The present invention utilizes the adhesive properties of engine oil so that the mixed oil and gas can adhere to the wall of the left labyrinth channel 104 during the process of passing through the left labyrinth channel 104. At the same time, the first oil drain hole 106 is set at the bottom of the left labyrinth channel 104, and the gravity properties of the engine oil are utilized to achieve preliminary separation of the engine oil and gas in the mixed oil and gas.

[0036] In some specific embodiments, the left labyrinth channel 104 has a first oil baffle wall arranged obliquely, the air inlet 105 is arranged at one end of the first oil baffle wall inclined upward, and the first oil drain hole 106 is arranged below the end of the first oil baffle wall inclined downward.

[0037] It can be understood that the inclined first oil baffle creates an inclined guide surface, which enhances the inertial separation effect by changing the direction of oil and gas flow. At the same time, the structure of upper air intake and lower oil discharge conforms to the law of gas-liquid movement, using gravity to accelerate the dripping of oil and prevent the separated oil from being sucked into the airflow for the second time.

[0038] Furthermore, a third channel is formed at the bottom of the first oil baffle wall. The third channel is provided with an oil baffle rib, which is used to positively block the mixed oil and gas entering from the air inlet 105 in the extension direction of the third channel.

[0039] It can be understood that the oil baffles form a turbulent field and establish multi-level barriers in the third channel. By making the oil baffles collide head-on with the mixed oil and gas in the flow direction of the mixed oil and gas, the mixed oil and gas is forced to change its motion trajectory, thereby increasing the probability of contact between the engine oil and the wall.

[0040] Furthermore, the air inlet hole 105 is located on the left side wall of the third channel, and the oil baffle protrudes to the right on the left side wall of the third channel. Thus, the right convex oil baffle and the left air inlet hole 105 form a head-on collision structure, so that the oil baffle can collide head-on with the mixed oil and gas in the flow direction of the mixed gas.

[0041] In some specific embodiments, the right box body 102 is provided with a right maze channel 107, the gasket 103 has a second channel 108, the second channel 108 connects the left maze channel 104 and the right maze channel 107, and the top of the right maze channel 107 is provided with an exhaust port 109. The gas after oil and gas separation in the left maze channel 104 flows through the second channel 108 to the right maze channel 107 for secondary oil and gas separation. The exhaust port 109 is used to discharge the exhaust gas after secondary oil and gas separation in the right maze channel 107.

[0042] This embodiment realizes secondary oil and gas separation through the dual labyrinth channel series design of the left labyrinth channel 104 and the right labyrinth channel 107, thereby greatly improving the separation efficiency.

[0043] In addition, this embodiment further separates the engine oil by using the wall of the right labyrinth channel 107 to collide with the gas after entering the right labyrinth channel 107 through the second channel 108 of the gasket 103, which can effectively cope with the high oil-gas mixture volume of large-displacement engines.

[0044] Furthermore, in this embodiment, the exhaust port 109 is arranged at the top of the right labyrinth channel 107, and the separated exhaust gas is discharged through the top exhaust port 109, which has a compact structure and a scientific separation path.

[0045] In some specific embodiments, a second oil drain hole 111 communicating with the crankshaft chamber is provided at the bottom of the right labyrinth channel 107 . The second oil drain hole 111 is used to discharge the engine oil that has undergone secondary oil-gas separation in the right labyrinth channel 107 into the crankshaft chamber.

[0046] It can be understood that the second oil drain hole 111 at the bottom of the right labyrinth channel 107 forms a closed-loop oil drain system at the bottom of the right labyrinth channel 107, ensuring that the oil after secondary separation flows back to the crankshaft chamber in time, avoiding the accumulation of oil in the right labyrinth channel 107 and causing secondary carryover. Thus, the dual oil drain hole design forms a complete oil reflux channel system.

[0047] In some specific embodiments, the left labyrinth passage 104 and the right labyrinth passage 107 are both disposed at the top of the crankshaft chamber, and the gasket 103 is used to isolate the left labyrinth passage 104 from the right labyrinth passage 107 .

[0048] It can be understood that the left labyrinth channel 104 and the right labyrinth channel 107 are concentratedly arranged at the top of the crankshaft chamber, which not only fully utilizes the top space of the crankcase 100, but also allows the mixed oil and gas to naturally enter the left labyrinth channel 104 during the rising process. In addition, the gasket 103 serves as a physical isolation layer to ensure the independence of the two-stage separation and simplify the assembly process.

[0049] In some specific embodiments, the left case 101 has an air hole 112 that passes through the left and right sides. The air hole 112 connects the crankshaft chamber and the left chamber. The air hole 112 allows the mixed oil and gas in the crankshaft chamber to enter the left chamber.

[0050] It can be understood that the air hole 112 establishes a dynamic balance channel between the crankshaft chamber and the left chamber, so that the mixed oil and gas in the crankshaft chamber can enter the left chamber through the air hole 112, and then enter the left labyrinth channel 104 from the left chamber through the air intake hole 105, thereby realizing the exhaust gas discharge from the crankshaft chamber.

[0051] In some specific embodiments, the left case 101 has an oil return hole 113 that passes through the left and right sides. The oil return hole 113 connects the crankshaft chamber and the left chamber, and the oil return hole 113 allows the oil to pass through.

[0052] It can be understood that the oil return hole 113 establishes a dynamic balance channel for the oil between the crankshaft chamber and the left chamber, ensuring that the oil can be supplied to the crankshaft chamber and the right chamber in a timely manner.

[0053] In some specific embodiments, the left case 101 has an air hole 112 and an oil return hole 113 that pass through the left and right sides. The air hole 112 connects the crankshaft chamber and the left chamber, and the oil return hole 113 connects the crankshaft chamber and the left chamber. The air hole 112 and the oil return hole 113 are arranged vertically. The air hole 112 allows the mixed oil and gas in the crankshaft chamber to enter the left chamber, and the oil return hole 113 allows the engine oil to pass through and / or allows the mixed oil and gas in the crankshaft chamber to enter the left chamber.

[0054] It can be understood that the air hole 112 establishes a dynamic balance channel between the crankshaft chamber and the left chamber, so that the mixed oil and gas in the crankshaft chamber can enter the left chamber through the air hole 112, and then enter the left maze channel 104 from the left chamber through the air inlet hole 105, thereby realizing the exhaust gas discharge of the crankshaft chamber. The oil return hole 113 establishes a dynamic balance channel for the engine oil between the crankshaft chamber and the left chamber, ensuring that the engine oil can be supplied to the crankshaft chamber and the right chamber in time. At the same time, the oil return hole 113 can take into account the discharge of the mixed oil and gas in the crankshaft chamber, which is beneficial to speed up the discharge efficiency of the mixed oil and gas in the crankshaft chamber.

[0055] The cylinder 120 is located above the crankcase 100 and has a combustion chamber 130 .

[0056] Specifically, the cylinder 120 includes a cylinder body and a piston. The cylinder body has a piston cavity. The piston slides in the piston cavity. The side of the piston away from the crankcase 100 forms a combustion chamber 130. A connecting rod for transmission is provided between the piston and the crankshaft 110. One end of the connecting rod is hinged to the piston, and the other end of the connecting rod is hinged to the crankshaft 110.

[0057] More specifically, the diameter of the piston is 81.5 mm, the reciprocating stroke of the piston is 66 mm, the center distance between the hinge centers of both ends of the connecting rod is 106.7 mm, and the rotation radius of the crankshaft 110 is 33 mm.

[0058] Reference Figure 6 、 Figure 7 、 Figure 8 and Figure 9 As for the cylinder head 140, the cylinder head 140 is located above the cylinder 120, and the bottom wall of the cylinder head 140 is used to form the top wall of the combustion chamber 130. The cylinder head 140 has an intake channel 150 and an exhaust channel 160. The intake channel 150 has two air intakes 170 connected to the combustion chamber 130, and the exhaust channel 160 has two air outlets 180 connected to the combustion chamber 130. The two air intakes 170 and the two air outlets 180 are arranged circumferentially along the central position of the combustion chamber 130. The cylinder head 140 is provided with a heat dissipation duct 190. The air inlet 290 of the heat dissipation duct 190 is located on the windward side of the cylinder head 140, and the heat dissipation duct 190 passes between the two air intakes 170 and the two air outlets 180.

[0059] This embodiment achieves efficient air cooling and heat dissipation under a four-valve structure by providing two air inlets 170 and two air outlets 180 arranged circumferentially along the central position of the combustion chamber 130, in conjunction with a heat dissipation duct 190 passing between the two air inlets 170 and the two air outlets 180. At the same time, the heat dissipation duct 190 directly acts on the high-temperature area between the four-valve channels, and uses the driving wind pressure to carry away heat. Compared with traditional oil cooling or water cooling systems, it can reduce the volume of heat dissipation components and reduce manufacturing costs.

[0060] In some specific embodiments, the heat dissipation duct 190 includes an air inlet section 260 and an air outlet section 270 that are interconnected, the air inlet 290 is set in the air inlet section 260, the air outlet section 270 passes between the two air inlets 170 and the two air outlets 180, and the air inlet section 260 and the air outlet section 270 are offset.

[0061] It can be understood that the offset setting of the air inlet section 260 and the air outlet section 270 means that the air inlet section 260 and the air outlet section 270 are not parallel. It can be understood that, on the one hand, the air inlet section 260 and the air outlet section 270 are interconnected, so that the cooling airflow entering the air inlet section 260 can all enter the air outlet section 270, avoiding the diversion of the cooling airflow and weakening the cooling effect of the air outlet section 270. On the other hand, the offset design of the air inlet section 260 and the air outlet section 270 forms an airflow bending path, which prolongs the contact time of the cooling airflow with the high-temperature area, which is conducive to improving the heat dissipation effect.

[0062] In some specific embodiments, a first heat sink 280 is provided in the heat dissipation duct 190 , and the first heat sink 280 is located at the connection between the air inlet section 260 and the air outlet section 270 .

[0063] It can be understood that the first heat sink 280 is arranged at the turning point of the heat dissipation duct 190, and the maximum airflow impact effect in this area is utilized to enhance the heat dissipation effect, so that the first heat sink 280 forms a turbulence generator, breaks the boundary layer, improves the heat transfer coefficient, increases the heat dissipation area, and improves the heat dissipation effect.

[0064] Furthermore, the first heat sink 280 is arranged on a side wall of the heat dissipation duct 190 close to the engine combustion chamber 130, so that the first heat sink 280 is arranged on the high-temperature side wall close to the combustion chamber 130, which specifically strengthens the heat dissipation at the heat source, shortens the heat conduction path, and improves the heat dissipation response speed.

[0065] Furthermore, the number of first heat sinks 280 is set to be multiple, and the multiple first heat sinks 280 are arranged along the width direction of the heat dissipation duct 190, so that the parallel structure of multiple first heat sinks 280 forms a heat dissipation array, which increases the heat dissipation area exponentially. At the same time, the multiple first heat sinks 280 are arranged at intervals to form multi-channel air supply, thereby improving the heat transfer coefficient.

[0066] In some specific embodiments, the air inlet section 260 and the air outlet section 270 are perpendicular to each other, so that the heat dissipation duct 190 forms an L-shaped duct structure, which facilitates the arrangement of an efficient heat dissipation path in a limited space.

[0067] In some specific embodiments, the air inlet 290 of the air inlet section 260 is trumpet-shaped, with the large-diameter end of the air inlet 290 facing outward.

[0068] It can be understood that the trumpet-shaped air inlet 290 complies with the principles of fluid mechanics, reduces the inlet flow velocity loss through the gradual expansion structure, and can increase the air intake volume compared to a straight opening. At the same time, the outward expansion design of the large-diameter end effectively captures the driving wind pressure and enhances the forced convection effect.

[0069] In some specific embodiments, the outer peripheral wall of the cylinder head 140 is provided with a second heat sink. Thus, on the one hand, the second heat sink forms an external auxiliary heat dissipation system, which cooperates with the internal cooling air duct to form a composite heat dissipation system. On the other hand, the heat dissipation of the outer peripheral wall improves the cooling effect of the edge area of ​​the cylinder head 140 to avoid local overheating.

[0070] Reference Figure 10 、 Figure 11 、 Figure 12 and Figure 13 As for the intake system, the intake system includes an intake camshaft 200 and two intake valves 210. The intake valves 210 are used to open and close the intake port 170. The intake camshaft 200 is provided with two first cams 220 for controlling the opening and closing of the two intake valves 210 respectively.

[0071] Specifically, the maximum lift of the first cam 220 pushing the intake valve 210 to open and close is 8.4837 mm.

[0072] In some specific embodiments, the intake camshaft 200 has a first passage 330 extending through both ends, and the intake system further includes: The first sprocket 300 is engaged with the timing chain of the engine and is used to drive the intake camshaft 200 to rotate; The centrifugal separation disc 310 is connected to one end of the intake camshaft 200 and has a separation chamber 320. The separation chamber 320 is connected to the first channel 330. The separation chamber 320 is provided with a fan blade 340. The centrifugal separation disc 310 rotates to draw the mixed oil and gas into the separation chamber 320. The fan blade 340 guides the gas into the first channel 330 and ejects the oil from the separation chamber 320. The vent pipe 350 is connected to an end of the first channel 330 away from the centrifugal separation disk 310 and is used to discharge the gas in the first channel 330 .

[0073] In this embodiment, the oil-gas separation function is integrated into the first channel 330 and the centrifugal separation disk 310 inside the intake camshaft 200, and no independent oil-gas separator is required, which greatly saves the internal space of the engine, simplifies the internal structure of the engine, and reduces the manufacturing difficulty and manufacturing cost of the engine. At the same time, the rotational power of the intake camshaft 200 itself is used to drive the centrifugal separation disk 310, and the rotational power of the intake camshaft 200 is fully utilized to achieve low-energy oil-gas separation. In addition, by arranging the fan blades 340 in the separation chamber 320, when the centrifugal separation disk 3 When the fan blades 340 rotate, they can generate suction to draw the mixed oil and gas outside the separation chamber 320 into the separation chamber 320. In the process of the mixed oil and gas passing through the fan blades 340, the oil with its own viscosity and heavy mass will adhere to the fan blades 340 and be thrown out of the separation chamber 320 by the fan blades 340 under the action of centrifugal force as the fan blades 340 rotate. The light mass gas will be sucked by the fan blades 340 through the separation chamber 320 and enter the first channel 330. Therefore, the fan blades 340 and the centrifugal separation disk 310 work together to realize dynamic separation of gas and liquid, ensuring high separation efficiency.

[0074] In some specific embodiments, the intake system also includes a connecting seat 360, which is arranged between the intake camshaft 200 and the ventilation pipe 350. The connecting seat 360 has a first through hole 370 that passes through both ends of the connecting seat 360. The end of the intake camshaft 200 away from the centrifugal separation disk 310 is connected to one end of the first through hole 370, and the ventilation pipe 350 is connected to the other end of the first through hole 370. The end of the intake camshaft 200 away from the centrifugal separation disk 310 is provided with a first oil seal 380, and one end of the ventilation pipe 350 is provided with a second oil seal 390. The first oil seal 380 and the second oil seal 390 are respectively abutted and sealed against the inner circular surfaces at both ends of the first through hole 370.

[0075] It can be understood that the intake camshaft 200 and the breather pipe 350 are connected by using the connecting seat 360, so that the intake camshaft 200 can rotate relative to the connecting seat 360, thereby avoiding the rotation of the intake camshaft 200 interfering with the breather pipe 350. At the same time, the first oil seal 380 and the second oil seal 390 are respectively abutted and sealed against the inner circular surfaces at both ends of the first through hole 370, which can prevent oil and gas leakage at both ends of the first through hole 370.

[0076] Specifically, the first through hole 370 includes a first section 400, a second section 410 and a third section 420 arranged in sequence along the axial direction of the first through hole 370. The first section 400 and the third section 420 are used to install the first oil seal 380 and the second oil seal 390, respectively. The inner diameter of the second section 410 is larger than the outer diameter of one end of the intake camshaft 200 inserted into the first through hole 370 and the outer diameter of one end of the ventilation pipe 350 inserted into the first through hole 370. There is a gap between the end of the intake camshaft 200 and the end of the ventilation pipe 350. The third section 420 forms an oil storage ring groove.

[0077] It can be understood that there is a gap between the end of the intake camshaft 200 and the end of the breather pipe 350, so that the insufficiently separated oil can move along the inner wall of the first through hole 370 to the end of the first through hole 370 away from the centrifugal separation disk 310 and then enter the oil storage ring groove along the gap between the intake camshaft 200 and the breather pipe 350. On the one hand, the oil can be prevented from entering the breather pipe 350. On the other hand, the oil in the oil storage ring groove can achieve lubrication between the first through hole 370 and the intake camshaft 200, thereby reducing the resistance encountered by the intake camshaft 200 during rotation, making the rotation of the intake camshaft 200 smoother.

[0078] In some specific embodiments, the centrifugal separation disc 310 is coaxially connected to the intake camshaft 200 , and the fan blades 340 are arranged radially outside the intake camshaft 200 .

[0079] It can be understood that, on the one hand, the coaxial connection between the centrifugal separation disc 310 and the intake camshaft 200 ensures the smoothness of power transmission and reduces the risk of sealing failure caused by vibration. On the other hand, the radial arrangement of the fan blades 340 can maximize the use of the centrifugal force field and improve the oil-gas separation efficiency.

[0080] Furthermore, the number of the fan blades 340 is set to be multiple, and the multiple fan blades 340 are arranged along the circumferential direction of the intake camshaft 200.

[0081] It can be understood that the multiple blades 340 are evenly distributed circumferentially to form a continuous separation surface, which enhances the airflow disturbance effect, improves the aggregation effect of tiny oil mist particles, and effectively improves the oil separation efficiency.

[0082] In some specific embodiments, the fan blades 340 extend in an arc shape in a direction away from the rotation axis of the centrifugal separation disk 310 .

[0083] It can be understood that the arc-shaped extension of the fan blade 340 optimizes the airflow trajectory, reduces the flow resistance loss, and at the same time, prolongs the residence time of the oil droplets on the fan blade 340, thereby improving the thoroughness of separation.

[0084] In some specific embodiments, the concave arc surface of the blade 340 has a hook portion protruding in a direction away from the rotation axis of the centrifugal separation disk 310 .

[0085] It can be understood that the hook structure forms a local low-pressure area, which enhances the oil droplet capture ability of the fan blade 340.

[0086] In some specific embodiments, the centrifugal separation disc 310 includes a detachably connected disc body and a cover body, a separation chamber 320 is formed between the disc body and the cover body, and one end of the intake camshaft 200 passes through the disc body to connect the first channel 330 to the separation chamber 320.

[0087] It is understandable that the separate structural design of the disc body and the cover body facilitates cleaning of the separation chamber 320 and extends the service life of the centrifugal separation disc 310 .

[0088] Furthermore, the fan blades 340 are fixed on the disc body, so that the disc body fixing the fan blades 340 can ensure dynamic balance accuracy and reduce high-speed rotation vibration.

[0089] In some specific embodiments, the centrifugal separation disc 310 is connected to a sprocket, so that the sprocket and the centrifugal separation disc 310 are linked to each other to shorten the power transmission path and improve energy utilization. At the same time, the sprocket and the centrifugal separation disc 310 are synchronously driven to ensure that the separation speed is accurately matched with the engine operating condition.

[0090] Reference Figure 14 、 Figure 15 and Figure 16 As for the exhaust system, the exhaust system includes an exhaust camshaft 230 and two exhaust valves 240 . The exhaust valve 240 is used to open and close the outlet 180 . The exhaust camshaft 230 is provided with two second cams 250 for controlling the opening and closing of the exhaust valve 240 .

[0091] Specifically, the maximum lift of the second cam 250 pushing the exhaust valve 240 to open and close is 8.1507 mm.

[0092] In some specific embodiments, the exhaust system further comprises: The second sprocket 430 is engaged with the timing chain of the engine and is used to drive the exhaust camshaft 230 to rotate; A push pin 440 is movably disposed on at least one second cam 250 and is capable of protruding from and being recessed into the base circular surface of the second cam 250; The swing block 450 is hinged on the second sprocket 430. Under the action of centrifugal force, the swing block 450 swings along the hinge center between the swing block 450 and the second sprocket 430 to drive the ejector pin 440 to be recessed into the base circular surface of the second cam 250. The spring 460 is used to drive the swing block 450 to reset so that the swing block 450 drives the ejector pin 440 to protrude from the base circular surface of the second cam 250; One of the swing block 450 and the second sprocket 430 is provided with a first pin 470, and the other of the swing block 450 and the second sprocket 430 is provided with an arc groove 480 extending circumferentially along the hinge center of the swing block 450 and the second sprocket 430, and the first pin 470 cooperates with the arc groove 480 to guide and limit.

[0093] In this embodiment, a push pin 440 is movably provided on the exhaust cam. The push pin 440 can protrude and be recessed in the base circular surface of the exhaust cam. It can be understood that when the push pin 440 protrudes from the base circular surface of the exhaust cam and the base circular surface of the exhaust cam abuts against the valve top sleeve, the internal combustion engine is in a compression process. At this time, the push pin 440 can lift the valve top sleeve, thereby realizing a small opening of the exhaust valve 240, releasing the gas pressure in the closed combustion chamber 130 of the original internal combustion engine, achieving the purpose of decompression, and effectively improving the problem of large engine starting resistance and difficulty in starting due to excessive starting cylinder pressure.

[0094] This embodiment provides a swing block 450, which is hinged on the second sprocket 430. Under the action of centrifugal force, the swing block 450 swings along the hinge center of the swing block 450 and the second sprocket 430 to drive the top pin 440 to be recessed into the base circular surface of the exhaust cam. It can be understood that when the engine is started, the second sprocket 430 starts to rotate. When the rotation of the second sprocket 430 reaches a certain speed, that is, when the engine is started and operates normally, the centrifugal force exerted on the swing block 450 can drive the swing block 450 to swing along the hinge center of the swing block 450 and the second sprocket 430, thereby enabling the swing block 450 to drive the top pin 440 to be recessed into the base circular surface of the exhaust cam, so that the decompression effect of the starting decompression mechanism fails when the engine is operating normally, thereby avoiding the starting decompression mechanism from decompressing when the engine is operating normally.

[0095] In this embodiment, a spring 460 is provided, and the spring 460 is used to drive the swing block 450 to reset so that the swing block 450 drives the push pin 440 to protrude from the base circular surface of the exhaust cam. It can be understood that after the engine is shut down, the rotation speed of the second sprocket 430 gradually decreases until it stops rotating, and the centrifugal force exerted on the swing block 450 also gradually decreases until it reaches zero. At this time, the spring 460 can drive the swing block 450 to reset so that the swing block 450 drives the push pin 440 to protrude from the base circular surface of the exhaust cam, thereby enabling the starting decompression mechanism to restore the decompression function after the engine is shut down, and then, when the engine is started next time, the starting decompression mechanism can achieve the decompression effect.

[0096] The present embodiment is achieved by providing a first pin 470 in one of the swing block 450 and the second sprocket 430, and providing an arc groove 480 extending circumferentially along the hinge center of the swing block 450 and the second sprocket 430 in the other one. The first pin 470 and the arc groove 480 cooperate to guide and limit. It can be understood that the cooperation and guidance of the first pin 470 and the arc groove 480 can accurately limit the swing stroke range of the swing block 450, thereby avoiding excessive displacement of the swing block 450 due to centrifugal force, thereby ensuring that the protruding / recessing action of the ejector pin 440 is stable and reliable. At the same time, the cooperation of the arc groove 480 and the first pin 470 can guide the swing path of the swing block 450 and limit the maximum swing stroke of the swing block 450, thereby ensuring the stable position of the ejector pin 440 and ensuring the effect of starting the decompression mechanism. This structure can effectively solve the problem of position fluctuation of the ejector pin 440 caused by the unstable stroke of the traditional swing block 450, and significantly improve the action consistency of the decompression mechanism.

[0097] In some specific embodiments, the exhaust system also includes a drive shaft 490, which is coaxially rotated with the exhaust camshaft 230 and is arranged inside the exhaust camshaft 230. A transmission part 500 is provided on the drive shaft 490 for abutting the ejector pin 440. The swing block 450 drives the drive shaft 490 to rotate relative to the exhaust camshaft 230, so that the drive shaft 490 drives the ejector pin 440 to protrude from the base circular surface of the second cam 250 through the transmission part 500.

[0098] It can be understood that the drive shaft 490 is coaxial with the camshaft to achieve direct power transmission, and the push pin 440 is indirectly driven through the transmission part 500 to convert the swing block 450 into a linear motion of the push pin 440, which not only isolates the impact of the camshaft vibration on the push block 450, but also improves the synchronization of the movement through mechanical linkage.

[0099] Furthermore, the transmission shaft 490 is provided with a radially extending shift rod 510, and the swing of the swing block 450 drives the shift rod 510 to swing so that the transmission shaft 490 rotates relative to the exhaust camshaft 230. One of the swing block 450 and the shift rod 510 is provided with a transmission pin 520, and the other of the swing block 450 and the shift rod 510 is provided with a transmission groove 530 for accommodating the transmission pin 520, and the transmission pin 520 and the transmission groove 530 cooperate for transmission.

[0100] The lever 510 is provided with a plurality of springs, which are provided on the upper and lower sides of the transmission shaft 490, so that the springs 520 and the lower ends of the transmission shaft 490 are provided with a plurality of springs, which are provided on the upper and lower sides of the transmission shaft 490.

[0101] In some specific embodiments, the swing block 450 and the second sprocket 430 are hinged by a first rivet, and the spring 460 is configured as a torsion spring, which is mounted on the first rivet, with one end of the torsion spring connected to the swing block 450 and the other end of the torsion spring connected to the second sprocket 430.

[0102] It can be understood that the structure of using a torsion spring sleeve on the first rivet simplifies the installation space layout of the spring 460, and directly acts between the swing block 450 and the second sprocket 430 through the rotational elastic characteristics of the torsion spring, providing a more stable reset force, while reducing the number of parts and assembly complexity, and improving the reliability of the mechanism.

[0103] In some specific embodiments, the hinge center between the swing block 450 and the second sprocket 430 is parallel to the rotation center of the second sprocket 430 and is not coaxial.

[0104] It can be understood that by setting the hinge center parallel to and not coaxial with the rotation center of the second sprocket 430, the mechanical leverage ratio of the swing block 450 is optimized during swinging, so that it can generate sufficient centrifugal force to trigger the action at a low speed, thereby improving the action sensitivity and response speed.

[0105] In some specific embodiments, the second cam 250 is provided with a first slide groove, one end of which extends outside the base circular surface of the second cam 250 , and the ejector pin 440 slides on the first slide groove to protrude and recess into the base circular surface of the second cam 250 .

[0106] It can be understood that the design of the first sliding groove extending outside the base circular surface provides a clear sliding path guide for the ejector pin 440, thereby avoiding the problem of eccentric wear of the ejector pin 440 due to lateral force.

[0107] In this embodiment, two first cams 220 are set on the intake camshaft 200, so that the intake system uses the two first cams 220 on one intake camshaft 200 to simultaneously control the opening and closing of two intake valves 210, and two second cams 250 are set on the exhaust camshaft 230, so that the exhaust system uses the two second cams 250 on one exhaust camshaft 230 to simultaneously control the opening and closing of two exhaust valves 240, thereby achieving the effect of the intake camshaft 200 simultaneously controlling the dual-channel intake and the exhaust camshaft 230 simultaneously controlling the dual-channel exhaust, improving the intake and exhaust efficiency, and being conducive to increasing the engine displacement while maintaining the small size of the engine, thereby reducing manufacturing costs.

[0108] This embodiment adopts a dual-cam intake and dual-cam exhaust structure in combination with an air-cooled cylinder head 140 , thereby taking into account both the large displacement of the engine and the efficient cooling effect, which is conducive to ensuring the small size and low cost of the engine.

[0109] In some specific embodiments, the intake system and / or exhaust system further includes a valve top sleeve and a valve spring, wherein the valve top sleeve is connected to the end of the intake valve 210 or the exhaust valve 240 away from the combustion chamber 130, the valve top sleeve is used to abut the first cam 220 or the second cam 250, one end of the valve spring abuts the cylinder head 140, and the other end of the valve spring is connected to the valve top sleeve, and the valve spring is used to drive the valve top sleeve to reset so that the intake valve 210 or the exhaust valve 240 is closed.

[0110] Throughout this specification, references to terms such as "one embodiment, some embodiments, exemplary embodiments, examples, specific examples, or some examples" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, illustrative uses of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0111] The terms "first, second, third, fourth," etc., as used in the specification and claims of this application and in the accompanying drawings, where applicable, are used to distinguish similar items and are not necessarily used to describe a particular order or sequential sequence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments described herein can be practiced in an order other than that shown or described herein.

[0112] It should also be noted that in the description of this specification, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0113] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may also include other steps or elements not explicitly listed or inherent to such process, method, product or apparatus.

[0114] Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0115] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. A motorcycle engine, characterized in that: include: A crankcase (100) having a crankshaft (110) disposed therein; A cylinder (120), located above the crankcase (100), having a combustion chamber (130); A cylinder head (140) is located above the cylinder (120), and its bottom wall is used to form the top wall of the combustion chamber (130). The cylinder head (140) has an intake channel (150) and an exhaust channel (160). The intake channel (150) has two intake ports (170) connected to the combustion chamber (130), and the exhaust channel (160) has two exhaust ports (180) connected to the combustion chamber (130). The two intake ports (170) and the two exhaust ports (180) are circumferentially arranged along the center of the combustion chamber (130). The cylinder head (140) is provided with a heat dissipation duct (190). The air inlet (290) of the heat dissipation duct (190) is located on the windward side of the cylinder head (140), and the heat dissipation duct (190) passes between the two intake ports (170) and the two exhaust ports (180). An intake system comprises an intake camshaft (200) and two intake valves (210), wherein the intake valves (210) are used to open and close the intake port (170), and the intake camshaft (200) is provided with two first cams (220) respectively used to control the opening and closing of the two intake valves (210); An exhaust system comprises an exhaust camshaft (230) and two exhaust valves (240), wherein the exhaust valves (240) are used to open and close the air outlet (180), and the exhaust camshaft (230) is provided with two second cams (250) respectively used to control the opening and closing of the exhaust valves (240).

2. A motorcycle engine according to claim 1, characterized in that: The heat dissipation air duct (190) comprises an air inlet section (260) and an air outlet section (270) that are interconnected, the air inlet (290) is arranged in the air inlet section (260), and the air outlet section (270) passes between the two air inlets (170) and the two air outlets (180), and the air inlet section (260) and the air outlet section (270) are offset.

3. A motorcycle engine according to claim 2, characterized in that: A first heat sink (280) is provided in the heat dissipation air duct (190), and the first heat sink (280) is located at the connection between the air inlet section (260) and the air outlet section (270).

4. A motorcycle engine according to claim 2, characterized in that: The air inlet (290) of the air inlet section (260) is trumpet-shaped, with the large-diameter end of the air inlet (290) facing outwards.

5. A motorcycle engine according to claim 1, characterized in that: The intake camshaft (200) has a first channel (330) running through both ends, and the intake system further comprises: A first sprocket (300) is engaged with a timing chain of the engine and is used to drive the intake camshaft (200) to rotate; A centrifugal separation disc (310) is connected to one end of the intake camshaft (200) and has a separation chamber (320). The separation chamber (320) is connected to the first channel (330). A fan blade (340) is provided in the separation chamber (320). The centrifugal separation disc (310) rotates to draw mixed oil and gas into the separation chamber (320). The fan blade (340) guides the gas into the first channel (330) and throws the oil out of the separation chamber (320). A vent pipe (350) is connected to an end of the first channel (330) away from the centrifugal separation disc (310) and is used to discharge gas in the first channel (330).

6. A motorcycle engine according to claim 5, characterized in that: The intake system further comprises a connecting seat (360), the connecting seat (360) being arranged between the intake camshaft (200) and the ventilation pipe (350), the connecting seat (360) having a first through hole (370) penetrating both ends of the connecting seat (360), the end of the intake camshaft (200) away from the centrifugal separation disc (310) being connected to one end of the first through hole (370), the ventilation pipe (350) being connected to the other end of the first through hole (370), the end of the intake camshaft (200) away from the centrifugal separation disc (310) being provided with a first oil seal (380), and the end of the ventilation pipe (350) being provided with a second oil seal (390), the first oil seal (380) and the second oil seal (390) respectively abutting against the inner circular surfaces at both ends of the first through hole (370) for sealing.

7. A motorcycle engine according to claim 6, characterized in that: The first through hole (370) includes a first section (400), a second section (410) and a third section (420) sequentially arranged along the axial direction of the first through hole (370). The first section (400) and the third section (420) are used to install the first oil seal (380) and the second oil seal (390), respectively. The inner diameter of the second section (410) is larger than the outer diameter of one end of the intake camshaft (200) inserted into the first through hole (370) and the outer diameter of one end of the ventilation pipe (350) inserted into the first through hole (370). There is a gap between the end of the intake camshaft (200) and the end of the ventilation pipe (350). The third section (420) forms an oil storage ring groove.

8. A motorcycle engine according to claim 1, characterized in that: The exhaust system further comprises: A second sprocket (430) is engaged with a timing chain of the engine and is used to drive the exhaust camshaft (230) to rotate; a lift pin (440) movably disposed on at least one of the second cams (250) and capable of protruding from and recessing into the base circular surface of the second cam (250); A swing block (450) is hinged on the second sprocket (430), and the swing block (450) swings along the hinge center between the swing block (450) and the second sprocket (430) under the action of centrifugal force to drive the ejector pin (440) to be recessed into the base circular surface of the second cam (250); A spring (460) is used to drive the swing block (450) to reset so that the swing block (450) drives the ejector pin (440) to protrude from the base circular surface of the second cam (250); One of the swing block (450) and the second sprocket (430) is provided with a first pin (470), and the other of the swing block (450) and the second sprocket (430) is provided with an arcuate groove (480) extending circumferentially along the hinge center of the swing block (450) and the second sprocket (430), and the first pin (470) cooperates with the arcuate groove (480) to guide and limit.

9. A motorcycle engine according to claim 8, characterized in that: The exhaust system further comprises a transmission shaft (490), the transmission shaft (490) being coaxially rotatable with the exhaust camshaft (230) and being arranged inside the exhaust camshaft (230), the transmission shaft (490) being provided with a transmission portion (500) for abutting against the ejector pin (440), the swinging block (450) driving the transmission shaft (490) to rotate relative to the exhaust camshaft (230), so that the transmission shaft (490) drives the ejector pin (440) through the transmission portion (500) to protrude from the base circular surface of the second cam (250).

10. A motorcycle engine according to claim 9, characterized in that: The transmission shaft (490) is provided with a radially extending shifting rod (510), and the swinging block (450) drives the shifting rod (510) to swing so that the transmission shaft (490) rotates relative to the exhaust camshaft (230). One of the swinging block (450) and the shifting rod (510) is provided with a transmission pin (520), and the other of the swinging block (450) and the shifting rod (510) is provided with a transmission slot (530) for accommodating the transmission pin (520), and the transmission pin (520) and the transmission slot (530) cooperate for transmission.

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