A water circulation structure for a motorcycle engine

Abstract

The present invention provides a water circulation structure for a motorcycle engine, belonging to the technical field of motorcycles. It solves the technical problems of insufficient compactness of the existing engine water circulation structure and affecting the circulation effect. The water circulation structure of this motorcycle engine includes a reversing housing located on one side of the cylinder block. The reversing housing has a liquid inlet chamber and a liquid outlet chamber separated by a thin wall. The thin wall has a liquid passing port communicating the liquid inlet chamber and the liquid outlet chamber. Both ends of the water circuit are respectively communicated with the liquid inlet chamber and the liquid outlet chamber. The inner wall of the liquid inlet chamber has a liquid inlet for communicating with the cooling water tank, and the inner wall of the liquid outlet chamber has a liquid outlet for communicating with the cooling water tank. The thermostat is located in the liquid outlet chamber, and one end of the thermostat closes the liquid outlet. The other end of the thermostat is arranged towards the liquid passing port. After being heated, the thermostat can close the liquid passing port and open the liquid outlet. The present invention can ensure a sufficient circulating cooling effect while improving the structural compactness.

Description

Technical Field

[0001] The present invention belongs to the technical field of motorcycles and relates to a water circulation structure of a motorcycle engine. Background Art

[0002] Generally, there are two main circulation passages on the engine. When the vehicle is just started in cold condition, in order to make the temperature of the antifreeze reach the ideal working temperature (about 90 °C) as soon as possible, the engine adopts the small circulation mode, and the antifreeze only circulates in the internal water channels of the engine. In this way, since the heat is not easily dissipated, the antifreeze heats up faster. When the antifreeze reaches the ideal working temperature, the engine needs to switch from the small circulation to the large circulation mode, and the component for realizing this switching control generally relies on a thermostat.

[0003] The patent with the authorization announcement number CN206845297U discloses a motorcycle and its engine, including a cylinder head and a cylinder block, and further including a thermostat and a radiator. A cooling channel and a small circulation channel are arranged inside the engine; the cooling channel includes a first channel located in the cylinder block, a second channel located in the cylinder head, a thermostat and a radiator that are connected in sequence; the small circulation channel includes a thermostat and a third channel located in the cylinder block that are connected in sequence.

[0004] Although the above engine can realize the functions of small circulation and large circulation, its overall switching flow path involves narrow one-way flow paths such as the third channel, which occupies more space and is not conducive to circulating cooling. And those of ordinary skill in the art are more likely to consider: a solution such as reducing the volume of the third channel, thereby reducing the amount of coolant retained therein and ensuring the cooling circulation effect. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the present invention provides a water circulation structure of a motorcycle engine. The technical problem to be solved by the present invention is: how to improve the structural compactness of the water circulation structure.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A water circulation structure for a motorcycle engine. The engine includes a cylinder block and a cylinder head. The water circulation structure includes a water pump, a thermostat, and a water passage located inside the engine. The water passage is connected to the water pump. It is characterized in that the water circulation structure further includes a reversing cover shell located on one side of the cylinder block. An inlet chamber and an outlet chamber separated by a thin wall are provided inside the reversing cover shell. A liquid passage opening communicating the inlet chamber and the outlet chamber is provided on the thin wall. Both ends of the water passage are respectively connected to the inlet chamber and the outlet chamber. An inlet port for communicating with the outlet of the cooling water tank is provided on the inner wall of the inlet chamber. An outlet port for communicating with the inlet of the cooling water tank is provided on the inner wall of the outlet chamber. The thermostat is located inside the outlet chamber, and one end of the thermostat closes the outlet port. The other end of the thermostat is arranged towards the liquid passage opening. When the thermostat is heated, it can close the liquid passage opening and open the outlet port.

[0008] In the engine of a motorcycle, the cylinder block and the cylinder head are fixedly connected to form a combustion chamber to do work on the piston. The water pump can pressurize the water liquid in the cooling water passage to make it circulate. The thermostat is an existing component, and a temperature sensing component is provided in the middle section thereof. It is a valve that controls the flow path of the cooling water liquid. The water passage is the coolant passage inside the engine, is connected to the water pump, and the coolant inside it is driven by the water pump to flow and exchange heat. By arranging the thermostat in the outlet chamber of the reversing cover shell, and making the inlet chamber and the outlet chamber respectively connected to both ends of the water passage, and the inlet chamber and the outlet chamber are connected through the liquid passage opening, and an inlet port for connecting with the cooling water tank is provided on the inner wall of the inlet chamber, and an outlet port for connecting with the cooling water tank is provided on the inner wall of the outlet chamber. When the engine is warming up, the water pump drives the coolant in the water passage to flow into the outlet chamber and enter the inlet chamber through the liquid passage opening, and then enter the water passage again to achieve internal circulation. When the coolant temperature is high enough, the thermostat is heated to close the liquid passage opening and open the outlet port. At this time, since the liquid passage opening is closed, the coolant entering the outlet chamber will flow into the cooling water tank from the outlet port and then flow into the inlet chamber through the inlet port to achieve external circulation. In this way, the switching between internal and external circulation is concentrated in the reversing cover shell and realized through opening and closing control. The overall structure is more compact. The coolant at the end where the thermostat is closed is directly introduced into the inlet chamber and can still fully participate during external circulation, improving the structural compactness while avoiding local overheating of the coolant and ensuring a sufficient circulating cooling effect.

[0009] In the above water circulation structure of the motorcycle engine, the water passage includes a cylinder block water jacket located in the cylinder block and a cylinder head water jacket located in the cylinder head. The inlet and outlet of the water pump are respectively communicated with the cylinder block water jacket and the cylinder head water jacket. The cylinder block water jacket is communicated with the liquid inlet chamber, and the cylinder head water jacket is communicated with the liquid outlet chamber. The cylinder block water jacket is a coolant flow chamber arranged around the cylinder block, and the cylinder head water jacket is a coolant flow chamber arranged around the cylinder head. The inlet and outlet of the water pump that drives the coolant flow are respectively communicated with the cylinder block water jacket and the cylinder head water jacket. When the engine is warming up, the coolant usually only needs to circulate several times as a whole to complete. In this way, the high-temperature coolant flowing out of the cylinder head water jacket will first pass through the cylinder block water jacket and then flow to the external water pump, so that the heat can be transferred to the cylinder block that needs to be heated first, reducing heat loss and improving the warm-up efficiency. During the external circulation, the coolant flowing out of the cylinder head water jacket is first cooled by the cooling water tank, and the coolant flowing out of the cylinder block water jacket can be cooled to a certain extent by the external water pump to increase the temperature difference with the cylinder head, which is further conducive to more fully exchanging heat of the coolant and improving the cooling effect, thus improving both the warm-up effect and the circulating cooling effect.

[0010] In the above water circulation structure of the motorcycle engine, the thermostat includes a bracket and a valve core. A ring-shaped valve plate is fixedly connected to the bracket. The outer edge of the ring-shaped valve plate is sealingly matched with the inner edge of the liquid outlet. The valve core closes the inner hole of the ring-shaped valve plate. When the valve core is heated, it can move relative to the bracket toward the side where the liquid passing port is located and open the inner hole of the ring-shaped valve plate. In this way, the valve core can cooperate with the ring-shaped valve plate to close the liquid outlet during warm-up. When the valve core is heated to a certain degree, it can move relative to the bracket to open the inner hole of the ring-shaped valve plate so that the coolant can flow out through the liquid outlet, ensuring the external circulation effect.

[0011] In the above water circulation structure of the motorcycle engine, the reversing cover is arranged on the side wall of the cylinder block and is arranged close to the cylinder head. There is a water passage arranged in the up and down direction in the cylinder block. The cylinder head water jacket is communicated with the liquid outlet chamber through the water passage. In this way, it is avoided that the heat directly transmitted by the relatively high-temperature cylinder head through the reversing cover affects the internal thermostat and causes an early switch to the external circulation, ensuring sufficient warm-up. At the same time, the distance for the coolant in the cylinder head water jacket to flow into the reversing cover is minimized as much as possible, reducing the loss of warm-up heat and ensuring the warm-up efficiency. By connecting the cylinder head water jacket and the liquid outlet chamber through the water passage inside the cylinder block, not only can the reversing cover be prevented from directly contacting the cylinder head and being heated, but also the coolant can exchange heat with the cylinder block when flowing in the water passage, which is conducive to rapid warm-up.

[0012] In the water circulation structure of the above motorcycle engine, the liquid inlet is arranged in a staggered manner with the liquid passing port along the setting direction. The inner wall of the liquid inlet cavity has a groove with an opening facing the side where the cylinder block water jacket is located, and the liquid passing port is located on the inner wall of the groove. In this way, during the outer circulation process, the coolant entering the liquid inlet cavity from the liquid inlet will not cause an external force impact on the thermostat blocked at the liquid passing port, ensuring stable sealing. And during the inner circulation warm-up, the coolant flowing into the liquid inlet cavity from the liquid passing port will not rush into the liquid inlet to exchange heat with the coolant that does not participate in the inner circulation, which is beneficial to ensuring the warm-up efficiency. At the same time, the groove can ensure that after the coolant flows out of the liquid passing port, it can flow towards the side where the cylinder block water jacket is located through the groove, and then smoothly flow into the cylinder block water jacket, reducing heat loss and further ensuring rapid warm-up.

[0013] In the water circulation structure of the above motorcycle engine, the engine further includes an oil cooler. The inner wall of the liquid inlet cavity has a port one, and the inner wall of the liquid outlet cavity has a port two. Both the port one and the port two are communicated with the oil cooler; the port one is located on the bottom surface of the liquid inlet cavity, and the position of the port one is vertically opposite to the position of the groove. In this way, during the inner circulation process, the liquid inlet cavity and the liquid outlet cavity are directly interconnected, and the oil cooler will not affect the warm-up effect. During the outer circulation, the pressure difference between the coolant in the liquid outlet cavity and the coolant in the liquid inlet cavity is relatively large, so that the coolant can enter the oil cooler at the same time to cool the engine oil, that is, while not affecting the warm-up effect, it ensures the engine oil cooling effect; during the outer circulation, the coolant flowing at the port one can directly increase the flow rate of the coolant in the groove, which is beneficial to improving the overall circulation cooling effect of the coolant.

[0014] In the water circulation structure of the above motorcycle engine, the oil cooler and the reversing housing are located on the same side of the engine. This facilitates the oil cooler to directly connect to the reversing housing, reducing the layout difficulty.

[0015] In the water circulation structure of the above motorcycle engine, the reversing housing is detachably connected to the cylinder block. In this way, when there is wear between the movable end of the thermostat and the reversing housing, it can be replaced as a whole, which is beneficial to reducing the maintenance cost.

[0016] In the water circulation structure of the above motorcycle engine, the inner wall of the liquid outlet cavity has a columnar groove, the thermostat is arranged in the columnar groove, and the liquid passing port and the liquid outlet are respectively located on the inner walls at both ends of the columnar groove. The existing thermostat is columnar, so the shape of the thermostat is more suitable for the columnar groove, which is beneficial to evenly arranging the coolant around the thermostat, ensuring the accuracy of the temperature at its temperature-receiving part, and at the same time, it is beneficial to ensuring that the thermostat more accurately controls the opening and closing of the liquid passing port and the liquid outlet.

[0017] In the water circulation structure of the above motorcycle engine, the inner wall of the liquid outlet cavity from the open edge of the columnar groove to the cylinder block is flared. In this way, the coolant flowing from the cylinder head water jacket into the liquid outlet cavity is guided by the flared inner wall, which can increase the coolant pressure and flow rate at this place, making the coolant circulation smoother.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] When the water circulation structure of this motorcycle engine is in the internal circulation, the high-temperature coolant flowing out of the cylinder head water jacket first passes through the cylinder block water jacket and then flows to the externally provided water pump, so that the heat can be transferred to the cylinder block that needs to be heated first, reducing heat loss and improving the warm-up efficiency; in the external circulation, the coolant flowing out of the cylinder head water jacket is first cooled by the cooling water tank, and the coolant flowing out of the cylinder block water jacket can be cooled to a certain extent by the externally provided water pump, which is beneficial to the coolant for more sufficient heat exchange, and can ensure that the coolant at the end closed by the thermostat will not stay in place, enabling all the coolant to participate in the external circulation, avoiding local overheating of the coolant, and ensuring a sufficient circulating cooling effect, that is, improving the warm-up and circulating cooling effects at the same time. Description of the Drawings

[0020] Figure 1 is the three-dimensional structure schematic diagram of this embodiment.

[0021] Figure 2 is the side view structure schematic diagram of this embodiment.

[0022] Figure 3 is Figure 2 the A-A cross-sectional view in

[0023] Figure 4 is Figure 3 the enlarged view of part D in

[0024] Figure 5 is Figure 2 the B-B cross-sectional view in

[0025] Figure 6 is Figure 2 the B-B cross-sectional view in

[0026] Figure 7 is Figure 2 the C-C cross-sectional view in

[0027] Figure 8 is the top view structure schematic diagram of this embodiment.

[0028] Figure 9 is Figure 8 the F-F cross-sectional view in

[0029] Figure 10 is Figure 9 the enlarged view of part G in

[0030] Figure 11 It is a schematic three-dimensional structure diagram of the commutation housing in this embodiment.

[0031] In the figure, 1 is the cylinder block; 11 is the cylinder block water jacket; 12 is the water passage;

[0032] 2 is the cylinder head; 21 is the cylinder head water jacket;

[0033] 3 is the water pump;

[0034] 4 is the thermostat; 41 is the bracket; 42 is the valve core; 43 is the annular valve plate; 44 is the inner hole;

[0035] 5 is the commutation housing; 51 is the thin wall; 511 is the liquid passing port; 52 is the liquid inlet cavity; 521 is the liquid inlet; 522 is the groove; 523 is the port one; 53 is the liquid outlet cavity; 531 is the liquid outlet; 532 is the port two; 533 is the columnar groove;

[0036] 6 is the oil cooler; 7 is the water circuit. Specific embodiments

[0037] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0038] Such as Figure 1-11As shown, in the water circulation structure of this motorcycle engine, the engine includes a cylinder block 1 and a cylinder head 2. The water circulation structure includes a water pump 3, a thermostat 4, and a water passage 7. The water passage 7 includes a cylinder block water jacket 11 located in the cylinder block 1 and a cylinder head water jacket 21 located in the cylinder head 2. The water pump 3 and the thermostat 4 are both existing components. The inlet and outlet of the water pump 3 are respectively connected to the cylinder block water jacket 11 and the cylinder head water jacket 21. The cylinder block water jacket 11 and the cylinder head water jacket 21 are not directly connected but are separated by a gasket (not shown) pressed between the cylinder block 1 and the cylinder head 2. The water circulation structure further includes a reversing cover 5 on one side of the engine. The reversing cover 5 has a liquid inlet chamber 52 and a liquid outlet chamber 53 separated by a thin wall 51. The thin wall 51 has a liquid passage opening 511 connecting the liquid inlet chamber 52 and the liquid outlet chamber 53. The cylinder block water jacket 11 is connected to the liquid inlet chamber 52, and the cylinder head water jacket 21 is connected to the liquid outlet chamber 53. The inner wall of the liquid inlet chamber 52 has a liquid inlet 521, and the inner wall of the liquid outlet chamber 53 has a liquid outlet 531. The thermostat 4 is located in the liquid outlet chamber 53, and one end of the thermostat 4 closes the liquid outlet 531. The other end of the thermostat 4 is arranged towards the liquid passage opening 511. When the thermostat 4 is heated, it can close the liquid passage opening 511 and open the liquid outlet 531.The middle cylinder block 1 and the cylinder head 2 of the motorcycle engine are fixedly connected to form a combustion chamber to do work on the piston. The water pump 3 is an existing component that can pressurize the water liquid in the cooling water path to make it circulate. The thermostat 4 belongs to an existing component, and a temperature sensing component is arranged in the middle section thereof, which is a valve for controlling the flow path of the cooling water liquid. The cylinder block water jacket 11 is a cooling liquid flow chamber arranged around the cylinder block 1, and the cylinder head water jacket 21 is a cooling liquid flow chamber arranged around the cylinder head 2; by arranging the water pump 3 that drives the cooling liquid flow on one side of the engine and the two liquid-connecting ends are respectively communicated with the cylinder block water jacket 11 and the cylinder head water jacket 21, and arranging the thermostat 4 in the liquid outlet chamber 53 of the side reversing cover 5 of the engine, and making the liquid inlet chamber 52 communicate with the cylinder block water jacket 11 in this area, the liquid outlet chamber 53 communicate with the cylinder head water jacket 21 in this area, and the liquid inlet chamber 52 communicate with the liquid outlet chamber 53 through the liquid port 511. The inner wall of the liquid inlet chamber 52 is provided with a liquid inlet 521 for communicating with the water outlet of the cooling water tank, and the inner wall of the liquid outlet chamber 53 is provided with a liquid outlet 531 for communicating with the water outlet of the cooling water tank. When the engine is warming up, the water pump 3 drives the cooling liquid into the cylinder head water jacket 21. After the cooling liquid is heated, it flows out of the cylinder head water jacket 21 and enters the liquid outlet chamber 53. Since the liquid outlet 531 is closed, the cooling liquid will enter the liquid inlet chamber 52 through the liquid passing port 511 on the thin wall 51, and then enter the cylinder block water jacket 11 from the liquid chamber. After the cooling liquid flows out of the cylinder block water jacket 11, it enters the water pump 3 again, forming an internal circulation. At this time, the high-temperature cooling liquid flowing out of the cylinder head water jacket 21 first passes through the cylinder block water jacket 11 and then flows to the externally arranged water pump 3, so that the heat can be transferred to the cylinder block 1 that needs to be heated first, reducing heat loss and improving the warm-up efficiency; when the temperature of the cooling liquid is high enough, the thermostat 4 is heated to close the liquid passing port 511 and open the liquid outlet 531. At this time, since the liquid passing port 511 is closed, the cooling liquid entering the liquid outlet chamber 53 will flow into the cooling water tank from the liquid outlet 531 and then flow into the liquid inlet chamber 52 through the liquid inlet 521, realizing an external circulation. The thermostat 4 includes a bracket 41 and a valve core 42. A ring valve plate 43 is fixedly connected to the bracket 41. The ring valve plate 43 is embedded in the liquid outlet 531 and the outer edge of the ring valve plate 43 is sealed with the inner wall of the liquid outlet 531. The ring valve plate 43 has an inner hole 44. The valve core 42 is a temperature sensing component. During internal circulation, the valve core 42 abuts against the ring valve plate 43 and closes the inner hole 44. During external circulation, the valve core 42 is heated and moves towards the side where the liquid passing port 511 is located, so that the inner hole 44 is opened, realizing the outflow of the cooling liquid from the liquid outlet 531; at this time, the cooling liquid flowing out of the cylinder head water jacket 21 is first cooled by the cooling water tank, and the cooling liquid flowing out of the cylinder block water jacket 11 can be cooled to a certain extent by the externally arranged water pump 3, increasing the temperature difference from the cylinder head 2, which is beneficial to more sufficient heat exchange of the cooling liquid, and can ensure that the cooling liquid at the end closed by the thermostat 4 will not stay in place, so that all the cooling liquid can participate in the external circulation, avoiding local overheating of the cooling liquid and ensuring a sufficient circulating cooling effect, that is, improving the warm-up and circulating cooling effects at the same time. Further, the reversing cover 5 is only connected to the side wall of the cylinder block 1, and the reversing cover 5 is arranged close to the cylinder head 2.This avoids the heat transferred directly through the reversing housing 5 from the cylinder head 2 at a relatively high temperature from affecting the internal thermostat 4 and causing an early switch to the external circulation, ensuring sufficient engine warming-up. At the same time, it tries to minimize the distance for the coolant in the cylinder head water jacket 21 to flow into the reversing housing 5, reducing the loss of engine warming-up heat and ensuring the engine warming-up efficiency. There are two water channels 12 arranged vertically in the cylinder block 1, and the cylinder head water jacket 21 is communicated with the liquid outlet cavity 53 through the water channel 12. In this way, by connecting the cylinder head water jacket 21 and the liquid outlet cavity 53 through the water channel 12 inside the cylinder block 1, it can not only avoid the reversing housing 5 directly contacting and being heated by the cylinder head 2, but also enable the coolant to exchange heat with the cylinder block 1 first when flowing in the water channel 12, which is beneficial for rapid engine warming-up. The inner wall of the liquid outlet cavity 53 has a columnar groove 533, and the thermostat 4 is connected in the columnar groove 533. The liquid passing port 511 and the liquid outlet 531 are respectively located on the inner walls at both ends of the columnar groove 533. The existing thermostat 4 is columnar, so the shape of the thermostat 4 is more adapted to the columnar groove 533, which is beneficial for the coolant to be evenly arranged around the thermostat 4, ensuring the accuracy of the temperature at its temperature-receiving part, and at the same time being beneficial for ensuring that the thermostat 4 more accurately controls the opening and closing of the liquid passing port 511 and the liquid outlet 531. The inner wall of the liquid outlet cavity 53 from the open edge of the columnar groove 533 to the cylinder block 1 is flared. In this way, the coolant flowing from the cylinder head water jacket 21 into the liquid outlet cavity 53 can increase the pressure and flow rate of the coolant at this place under the guiding action of the flared inner wall, making the coolant circulation smoother. The reversing housing 5 is detachably connected to the cylinder block 1. In this way, when there is wear between the extending end of the thermostat 4 and the thin wall 51, it can be replaced as a whole, which is beneficial for reducing the maintenance cost.

[0039] Such as Figure 1-9 , Figure 11As shown, the liquid inlet 521 is arranged in a staggered manner with the liquid passing port 511 along the set direction. The inner wall of the liquid inlet chamber 52 has a groove 522 with an opening facing the side where the cylinder block water jacket 11 is located, and the liquid passing port 511 is located on the inner wall of the groove 522. In this way, during the outer circulation process, the coolant entering the liquid inlet chamber 52 from the liquid inlet 521 will not cause an external force impact on the thermostat 4 blocked at the liquid passing port 511, ensuring stable sealing. And during the inner circulation warm-up, the coolant flowing into the liquid inlet chamber 52 from the liquid passing port 511 will not rush into the liquid inlet 521 to exchange heat with the coolant not participating in the inner circulation, which is beneficial to ensuring the warm-up efficiency. At the same time, the groove 522 can ensure that the coolant flows toward the side where the cylinder block water jacket 11 is located after flowing out of the liquid passing port 511 through the groove 522, and then smoothly flows into the cylinder block water jacket 11, reducing heat loss and further ensuring rapid warm-up. The engine further includes an oil cooler 6. The oil cooler 6 is an existing component. There is a port one 523 on the inner wall of the liquid inlet chamber 52, and a port two 532 on the inner wall of the liquid outlet chamber 53. The port one 523 and the port two 532 are respectively communicated with the outlet and the inlet of the oil cooler 6. In this way, during the inner circulation process, the liquid inlet chamber 52 and the liquid outlet chamber 53 are directly interconnected, and the oil cooler 6 will not affect the warm-up effect. During the outer circulation, the large pressure difference between the coolant in the liquid outlet chamber 53 and the coolant in the liquid inlet chamber 52 can cause the coolant to enter the oil cooler 6 at the same time to cool the engine oil, that is, while not affecting the warm-up effect, it ensures the engine oil cooling effect. The port one 523 is located on the bottom surface of the liquid inlet chamber 52, and the position of the port one 523 is vertically opposite to the position of the groove 522. In this way, during the outer circulation, the coolant flowing at the port one 523 can directly increase the flow rate of the coolant in the groove 522, which is beneficial to improving the overall circulation cooling effect of the coolant. The oil cooler 6 and the reversing housing 5 are located on the same side of the engine. This facilitates the oil cooler 6 to directly take over the pipe from the reversing housing 5 and reduces the layout difficulty.

[0040] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A water circulation structure for a motorcycle engine. The engine includes a cylinder block (1) and a cylinder head (2). The water circulation structure includes a water pump (3), a thermostat (4), and a water passage (7) located within the engine. The water passage (7) is in communication with the water pump (3), and is characterized in that, The water circulation structure further includes a reversing housing (5) located on one side of the cylinder block (1). Inside the reversing housing (5), there is a liquid inlet chamber (52) and a liquid outlet chamber (53) separated by a thin wall (51). The thin wall (51) has a liquid passing port (511) connecting the liquid inlet chamber (52) and the liquid outlet chamber (53). Both ends of the water passage (7) are respectively connected to the liquid inlet chamber (52) and the liquid outlet chamber (53). The inner wall of the liquid inlet chamber (52) has a liquid inlet port (521) for connecting to the water outlet of the cooling water tank. The inner wall of the liquid outlet chamber (53) has a liquid outlet port (531) for connecting to the water inlet of the cooling water tank. The thermostat (4) is located inside the liquid outlet chamber (53), and one end of the thermostat (4) closes the liquid outlet port (531). The other end of the thermostat (4) is arranged towards the liquid passing port (511). When the thermostat (4) is heated, it can close the liquid passing port (511) and open the liquid outlet port (531); the water passage (7) includes a cylinder block water jacket (11) located inside the cylinder block (1) and a cylinder head water jacket (21) located inside the cylinder head (2). The inlet and outlet of the water pump (3) are respectively connected to the cylinder block water jacket (11) and the cylinder head water jacket (21). The cylinder block water jacket (11) is connected to the liquid inlet chamber (52), and the cylinder head water jacket (21) is connected to the liquid outlet chamber (53). The thermostat (4) includes a bracket (41) and a valve core (42). An annular valve plate (43) is fixedly connected to the bracket (41). The outer edge of the annular valve plate (43) is in sealing cooperation with the inner edge of the liquid outlet port (531). The valve core (42) closes the inner hole (44) of the annular valve plate (43). When the valve core (42) is heated, it can move relative to the bracket (41) towards the side where the liquid passing port (511) is located and open the inner hole (44) of the annular valve plate (43).

2. The water circulation structure of the motorcycle engine according to claim 1, characterized in that, The reversing housing (5) is arranged on the side wall of the cylinder block (1), and the reversing housing (5) is arranged close to the cylinder head (2); there is a water passage (12) arranged in the up-down direction inside the cylinder block (1), and the cylinder head water jacket (21) is connected to the liquid outlet chamber (53) through the water passage (12).

3. The water circulation structure of the motorcycle engine according to claim 2, characterized in that, The liquid inlet port (521) is arranged in a staggered manner with the liquid passing port (511) along the setting direction. The inner wall of the liquid inlet chamber (52) has a groove (522) with an open end facing the side where the cylinder block water jacket (11) is located. The liquid passing port (511) is located on the inner wall of the groove (522).

4. The water circulation structure of a motorcycle engine according to claim 3, characterized in that, The engine further includes an oil cooler (6). The inner wall of the liquid inlet chamber (52) has a port one (523), and the inner wall of the liquid outlet chamber (53) has a port two (532). Both the port one (523) and the port two (532) are connected to the oil cooler (6); the port one (523) is located on the bottom surface of the liquid inlet chamber (52), and the position of the port one (523) is vertically opposite to the position of the groove (522).

5. The water circulation structure of the motorcycle engine according to claim 4, characterized in that, The oil cooler (6) and the reversing housing (5) are located on the same side of the engine.

6. The water circulation structure of a motorcycle engine according to claim 1 or 2 or 3 or 4, characterized in that, The commutation housing (5) is detachably connected to the cylinder block (1).

7. The water circulation structure of a motorcycle engine according to claim 1 or 2 or 3 or 4, characterized in that, The inner wall of the liquid outlet cavity (53) has a columnar groove (533), the thermostat (4) is arranged in the columnar groove (533), and the liquid passing port (511) and the liquid outlet (531) are respectively located on the inner walls at both ends of the columnar groove (533).

8. The water circulation structure of the motorcycle engine according to claim 7, characterized in that, The inner wall of the liquid outlet cavity (53) from the open edge of the columnar groove (533) to the cylinder block (1) is in a flared shape.

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