Engine oil return structure

Abstract

The utility model discloses an engine oil return structure, an engine comprises a cylinder body and a crankcase connected with the bottom of the cylinder body, a cylinder head is arranged at the top of the cylinder body, a bottom shell is arranged at the bottom of the crankcase, a crankshaft and a balance shaft are arranged on the crankcase, the engine oil return structure comprises an oil return channel arranged in the engine, and the oil return channel starts from the cylinder head. The oil return channel penetrates through the space between the crankshaft and the balance shaft from the air cylinder body and the crankcase to the bottom shell. The oil return channel is of a built-in structure and has more advantages compared with an existing external oil return structure, arrangement and attachment of parts on the outer surface of the engine can be reduced, the overall structural layout of the engine is more compact and concise, the oil return channel can be prevented from being impacted by external force during maintenance, and therefore the oil return channel is protected more effectively. In addition, the oil return channel penetrates through the space between the crankshaft and the balance shaft, so that the oil return channel can be bent and straightened as much as possible, the length of an oil way is shortened, and the oil return speed is increased.

Description

Technical Field

[0001] The utility model relates to the technical field of motorcycle engines, in particular to an engine oil return structure. Background Art

[0002] When a motorcycle engine is working, it is necessary to continuously lubricate and dissipate heat for the moving parts inside the engine, so an oil circulation system needs to be set up, and the oil return structure is a component of the oil circulation system. The oil return structure of existing motorcycle engines is mostly an external structure, located outside the engine, which not only increases the space occupancy rate of the engine, but also causes the oil return structure to be poorly protected and easily bumped. The utility model patent with announcement number CN212838131U discloses a two-stage oil return pipe installation structure for an engine. The oil return structure in the utility model is in the form of an oil return pipe, which is external to the engine. Although it can reduce the design accuracy and manufacturing accuracy requirements, it still has the above-mentioned problems of high space occupancy rate and poor protection of the oil return structure. Utility Model Content

[0003] The oil return structure of existing motorcycle engines is mostly an external structure, which not only increases the space occupancy rate of the engine, but also leads to poor protection of the oil return structure. In order to overcome these defects, the utility model provides an engine oil return structure, which is conducive to a more compact overall structural layout of the engine and can be better protected.

[0004] The technical solution of the utility model is: an engine oil return structure, the engine includes a cylinder block and a crankcase connected to the bottom of the cylinder block, a cylinder head is provided on the top of the cylinder block, a bottom shell is provided at the bottom of the crankcase, a crankshaft and a balance shaft are provided on the crankcase, and the engine oil return structure includes an oil return channel provided inside the engine, the oil return channel starts from the cylinder head, passes through the cylinder block and the crankcase to the bottom shell, and the oil return channel passes between the crankshaft and the balance shaft. The oil return channel in the utility model is a built-in structure, which is more advantageous than the existing external oil return structure, not only can it reduce the arrangement and attachment of parts on the outer surface of the engine, making the overall structural layout of the engine more compact and simple, but also can prevent the oil return channel from being hit by external forces during maintenance, so that it is more effectively protected. In addition, the cylinder head, cylinder block and crankcase are usually arranged in a spatially tortuous manner rather than in a straight line. The oil return passage passes between the crankshaft and the balance shaft and goes deep into the crankcase rather than being arranged along the surface of the cylinder head, cylinder block and crankcase. This allows the oil return passage to be straightened as much as possible, shortening the length of the oil circuit and thus speeding up the oil return speed.

[0005] Preferably, the oil return passage includes a cylinder head section oil return passage, a cylinder block section oil return passage connected to the cylinder head section oil return passage, and a crankcase section oil return passage connected to the cylinder block section oil return passage. The engine is assembled from independent main components such as the cylinder head, cylinder block and crankcase, which determines that the oil return passage cannot be formed at one time and needs to be set in sections accordingly. Each section is set on the structure of each main engine component and connected accordingly to form a complete oil return passage.

[0006] Preferably, the cylinder head section oil return passage is arranged in the housing of the cylinder head, and the cylinder block section oil return passage is arranged in the housing of the cylinder block. The spatial position between the cylinder head and the cylinder block is relatively small in misalignment, and the cylinder head section oil return passage and the cylinder block section oil return passage are arranged in the housings of the cylinder head and the cylinder block, respectively, and can be connected to form a relatively straight oil path.

[0007] Preferably, a mounting wall plate is provided in the crankcase, the crankshaft and the balance shaft are mounted on the mounting wall plate, and the crankcase oil return passage penetrates the mounting wall plate. The mounting wall plate is an inherent mounting support structure of the crankshaft and the balance shaft in the crankcase, and is made of thick solid material, which is convenient for processing the oil return passage, and is convenient for cutting and straightening, shortening the length of the oil path, and thus accelerating oil return.

[0008] As a preferred embodiment, the bottom end face of the cylinder head is joined with the top end face of the cylinder block, the bottom end face of the cylinder block is joined with the top end face of the crankcase, the end of the oil return passage of the cylinder head section is located on the bottom end face of the cylinder head, the start and end of the oil return passage of the cylinder block section are respectively located on the top end face and the bottom end face of the cylinder block, and the start and end of the oil return passage of the crankcase section are respectively located on the top end face and the bottom end face of the crankcase. The oil return passage sections are butted on the joint surfaces of the main components, which can conveniently realize the connection of short oil circuits and finally form a longer oil circuit.

[0009] Preferably, a sealing gasket is provided between the bottom end surface of the cylinder head and the top end surface of the cylinder body, and between the bottom end surface of the cylinder body and the top end surface of the crankcase. A sealing gasket is provided on the joint surface of the main cylinder component to ensure the sealing of the joint surface.

[0010] Preferably, the crankcase is made of aluminum alloy. The engine operating conditions are relatively harsh, with large vibrations and high temperatures. In addition, the engine also has lightweight design requirements, so the manufacturing material for the engine crankcase must also be carefully selected. Aluminum alloy is light, has strong heat dissipation, and good fuel economy, and is suitable for engines of small motor vehicles.

[0011] As a preferred method, the cylinder head is connected to the cylinder block by bolts, and the crankcase is connected to the cylinder block by bolts. The cylinder head, the cylinder block and the crankcase are assembled by bolting, which is a mature and economical assembly method.

[0012] The beneficial effects of the utility model are:

[0013] Optimize the overall structure of the engine. The oil return channel in the utility model is a built-in structure, which can reduce the arrangement and attachment of parts on the outer surface of the engine, making the overall structure layout of the engine more compact and simple.

[0014] Effectively protect the oil return structure. In the utility model, since the oil return channel is built-in, the oil return channel can be prevented from being impacted by external forces during engine maintenance, so that the oil return channel is more effectively protected.

[0015] Shorten the oil path and speed up the oil return. In the utility model, the oil return path goes deep into the crankcase and passes between the crankshaft and the balance shaft, so that the oil return path can be straightened as much as possible, shortening the length of the oil path, thereby speeding up the oil return speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The utility model is a structural schematic diagram of an engine to which the utility model is applied.

[0017] Figure 2 A sectional view of an engine to which the utility model is applied.

[0018] Figure 3 The utility model is a schematic diagram of a partial disassembled structure of an engine.

[0019] Figure 4 The utility model is applied to the split structure of the crankcase of the engine.

[0020] Figure 5 The figure is a schematic diagram of the internal structure of the lower half of the crankcase in the engine to which the utility model is applied.

[0021] Figure 6 The figure is a schematic diagram of the internal structure of the upper part of the crankcase of the engine to which the utility model is applied.

[0022] Figure 7 The bottom structure schematic diagram of the lower half of the crankcase in the engine to which the utility model is applied is shown.

[0023] Figure 8 The figure is a schematic structural diagram of a cylinder head in an engine to which the utility model is applied.

[0024] In the figure, 1-cylinder block, 2-crankcase, 3-cylinder head, 4-cylinder head section oil return passage, 5-cylinder block section oil return passage, 6-crankcase section oil return passage, 7-mounting wall panel, 8-crankshaft mounting hole, 9-balance shaft mounting hole, 10-bottom shell. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the specific embodiments of the drawings.

[0026] Embodiment 1:

[0027] like Figures 1 to 8 As shown, an engine oil return structure, the engine includes a cylinder block 1, a crankcase 2, a cylinder head 3 and a bottom shell 10, the cylinder block 1, the crankcase 2 and the cylinder head 3 are all made of aluminum alloy, wherein the aluminum alloy grade of the cylinder block 1 is AC8B, the aluminum alloy grade of the crankcase 2 is ADC12, and the aluminum alloy grade of the cylinder head 3 is AC4B. The crankcase 2 is connected to the bottom of the cylinder block 1, the cylinder head 3 is installed on the top of the cylinder block 1, and the bottom shell 10 is installed on the bottom of the crankcase 2. The cylinder head 3 and the cylinder block 1, the crankcase 2 and the cylinder block 1, and the bottom shell 10 and the crankcase 2 are all connected by bolts. A crankshaft and a balance shaft are installed on the crankcase 2. The engine oil return structure includes an oil return channel, which is a built-in oil return channel and is arranged inside the engine. There are two oil return channels, and the paths of the two oil return channels are parallel. The oil return passage starts from the inside of the cylinder head 3, extends through the cylinder block 1 and the crankcase 2 in sequence, and ends at the bottom shell 10, wherein the oil return passage passes between the crankshaft and the balance shaft when passing through the crankcase 2. The oil return passage includes a cylinder head section oil return passage 4, a cylinder block section oil return passage 5, and a crankcase section oil return passage 6. The cylinder block section oil return passage 5 is connected and communicated with the cylinder head section oil return passage 4, and the crankcase section oil return passage 6 is connected and communicated with the cylinder block section oil return passage 5. The cylinder block 1 includes a cylinder block shell and a cylinder block cavity, and the cylinder block cavity is located in the space enclosed by the cylinder block shell; the crankcase 2 includes a crankcase shell and a crankcase cavity, and the crankcase cavity is located in the space enclosed by the crankcase shell; the cylinder head 3 includes a cylinder head shell and a cylinder head cavity, and the cylinder head cavity is located in the space enclosed by the cylinder head shell; the cylinder head section oil return passage 4 is arranged in the shell of the cylinder head 3, and the cylinder block section oil return passage 5 is arranged in the shell of the cylinder block 1. The cylinder head section oil return passage 4, the cylinder body section oil return passage 5 and the crankcase section oil return passage 6 are all formed by drilling.

[0028] The bottom end face of the cylinder head 3 is aligned with the top end face of the cylinder block 1, and the bottom end face of the cylinder block 1 is aligned with the top end face of the crankcase 2. The end of the cylinder head section oil return passage 4 is located on the bottom end face of the cylinder head 3, the beginning and end of the cylinder section oil return passage 5 are located on the top end face and the bottom end face of the cylinder block 1, respectively, and the beginning and end of the crankcase section oil return passage 6 are located on the top end face and the bottom end face of the crankcase 2, respectively. The crankcase 2 is divided into an upper half and a lower half, the upper half has a lower end face formed by milling, and the lower half has an upper end face formed by milling. The upper and lower end faces are correspondingly fitted and then fixed with bolts to complete the splicing of the crankcase 2. Four parallel installation wall panels 7 are arranged in the crankcase 2, and the installation wall panels 7 are also correspondingly divided into upper and lower parts that can be butted and spliced ​​according to the split mode of the crankcase 2. The two outer mounting wall panels 7 are provided with crankshaft mounting holes 8 and balance shaft mounting holes 9, which are used to mount the crankshaft and balance shaft respectively. The two middle mounting wall panels 7 are also provided with crankshaft mounting holes 8. The axes of the crankshaft mounting holes 8 and balance shaft mounting holes 9 are parallel, ensuring that the crankshaft and balance shaft are mounted in parallel on the mounting wall panels 7. The upper half of the crankcase section oil return passage 6 is located in the shell of the crankcase 2, and the lower half of the crankcase section oil return passage 6 penetrates the two middle mounting wall panels 7, and the penetration position is located between the crankshaft mounting holes 8 and the balance shaft mounting holes 9. The terminal outlet of the crankcase section oil return passage 6 is not located on the joint surface of the crankcase 2 and the bottom shell 10, but is located at the junction of the bottom of the mounting wall panel 7 in the lower half of the crankcase and the crankcase shell. There are gaskets between the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1, and between the bottom end face of the cylinder block 1 and the top end face of the crankcase 2. The outer edge of the gasket between the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1 is flush with the outer edge of the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1, and the outer edge of the gasket between the bottom end face of the cylinder block 1 and the top end face of the crankcase 2 is flush with the outer edge of the bottom end face of the cylinder block 1 and the top end face of the crankcase 2. The gasket is made of a composite of multiple layers of polyurethane sheets and the periphery is coated with fluororubber. Through holes are opened on the gasket corresponding to the bolts and oil passages, which does not affect the installation of the bolts and the smooth flow of the oil passage.

[0029] When the engine is working, the lubricating oil in the cavity of the cylinder head 3 flows out of the cylinder head 3 through the cylinder head section oil return passage 4, enters the cylinder block section oil return passage 5 on the joint surface between the cylinder head 3 and the cylinder block 1 and continues to flow downward, enters the crankcase section oil return passage 6 on the joint surface between the cylinder block 1 and the crankcase 2, flows through the upper half of the crankcase section oil return passage 6, enters the lower half of the crankcase section oil return passage 6 on the joint surface between the upper and lower halves of the crankcase 2, passes through the mounting wall panel 7 between the crankshaft and the balance shaft, cuts off the bend to take a straight line through the crankcase 2, and then freely drips into the oil storage cavity of the bottom shell 10. The lubricating oil in the bottom shell 10 is then transported to the cavity of the cylinder head 3 by the action of the oil pump, forming a lubricating oil circulation.

[0030] Embodiment 2:

[0031] like Figures 1 to 6 , Figure 8As shown, an engine oil return structure, the engine includes a cylinder block 1, a crankcase 2, a cylinder head 3 and a bottom shell 10, the cylinder block 1, the crankcase 2 and the cylinder head 3 are all made of aluminum alloy, wherein the aluminum alloy grade of the cylinder block 1 is AC8B, the aluminum alloy grade of the crankcase 2 is ADC12, and the aluminum alloy grade of the cylinder head 3 is AC4B. The crankcase 2 is connected to the bottom of the cylinder block 1, the cylinder head 3 is installed on the top of the cylinder block 1, and the bottom shell 10 is installed on the bottom of the crankcase 2. The cylinder head 3 and the cylinder block 1, the crankcase 2 and the cylinder block 1, and the bottom shell 10 and the crankcase 2 are all connected by bolts. A crankshaft and a balance shaft are installed on the crankcase 2. The engine oil return structure includes an oil return channel, which is a built-in oil return channel and is arranged inside the engine. There are two oil return channels, and the paths of the two oil return channels are parallel. The oil return passage starts from the inside of the cylinder head 3, extends through the cylinder block 1 and the crankcase 2 in sequence, and ends at the bottom shell 10, wherein the oil return passage passes between the crankshaft and the balance shaft when passing through the crankcase 2. The oil return passage includes a cylinder head section oil return passage 4, a cylinder block section oil return passage 5, and a crankcase section oil return passage 6. The cylinder block section oil return passage 5 is connected and communicated with the cylinder head section oil return passage 4, and the crankcase section oil return passage 6 is connected and communicated with the cylinder block section oil return passage 5. The cylinder block 1 includes a cylinder block shell and a cylinder block cavity, and the cylinder block cavity is located in the space enclosed by the cylinder block shell; the crankcase 2 includes a crankcase shell and a crankcase cavity, and the crankcase cavity is located in the space enclosed by the crankcase shell; the cylinder head 3 includes a cylinder head shell and a cylinder head cavity, and the cylinder head cavity is located in the space enclosed by the cylinder head shell; the cylinder head section oil return passage 4 is arranged in the shell of the cylinder head 3, and the cylinder block section oil return passage 5 is arranged in the shell of the cylinder block 1. The cylinder head section oil return passage 4, the cylinder body section oil return passage 5 and the crankcase section oil return passage 6 are all formed by drilling.

[0032] The bottom end face of the cylinder head 3 is aligned with the top end face of the cylinder block 1, and the bottom end face of the cylinder block 1 is aligned with the top end face of the crankcase 2. The end of the cylinder head section oil return passage 4 is located on the bottom end face of the cylinder head 3, the beginning and end of the cylinder section oil return passage 5 are located on the top end face and the bottom end face of the cylinder block 1, respectively, and the beginning and end of the crankcase section oil return passage 6 are located on the top end face and the bottom end face of the crankcase 2, respectively. The crankcase 2 is divided into an upper half and a lower half, the upper half has a lower end face formed by milling, and the lower half has an upper end face formed by milling. The upper and lower end faces are correspondingly fitted and then fixed with bolts to complete the splicing of the crankcase 2. Four parallel installation wall panels 7 are arranged in the crankcase 2, and the installation wall panels 7 are also correspondingly divided into upper and lower parts that can be butted and spliced ​​according to the split mode of the crankcase 2. The two outer mounting wall panels 7 are provided with crankshaft mounting holes 8 and balance shaft mounting holes 9, which are used to mount the crankshaft and balance shaft respectively. The two middle mounting wall panels 7 are also provided with crankshaft mounting holes 8. The axes of the crankshaft mounting holes 8 and balance shaft mounting holes 9 are parallel, ensuring that the crankshaft and balance shaft are mounted in parallel on the mounting wall panels 7. The upper half of the crankcase section oil return passage 6 is located in the shell of the crankcase 2, and the lower half of the crankcase section oil return passage 6 penetrates into the two middle mounting wall panels 7, and the penetration position is located between the crankshaft mounting holes 8 and the balance shaft mounting holes 9. The terminal outlet of the crankcase section oil return passage 6 is not located on the joint surface of the crankcase 2 and the bottom shell 10, but is located at the junction of the bottom of the mounting wall panel 7 in the lower half of the crankcase and the crankcase shell. Different from Example 1, a drainage groove is provided on the inner wall of the crankcase shell at the terminal outlet of the crankcase section oil return passage 6. There are gaskets between the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1, and between the bottom end face of the cylinder block 1 and the top end face of the crankcase 2. The outer edge of the gasket between the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1 is flush with the outer edge of the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1, and the outer edge of the gasket between the bottom end face of the cylinder block 1 and the top end face of the crankcase 2 is flush with the outer edge of the bottom end face of the cylinder block 1 and the top end face of the crankcase 2. The gasket is made of a composite of multiple layers of polyurethane sheets and the periphery is coated with fluororubber. Through holes are opened on the gasket corresponding to the bolts and oil passages, which does not affect the installation of the bolts and the smooth flow of the oil passage.

[0033] When the engine is working, the lubricating oil in the cavity of the cylinder head 3 flows out of the cylinder head 3 through the cylinder head section oil return passage 4, enters the cylinder block section oil return passage 5 on the joint surface between the cylinder head 3 and the cylinder block 1 and continues to flow downward, enters the crankcase section oil return passage 6 on the joint surface between the cylinder block 1 and the crankcase 2, flows through the upper half of the crankcase section oil return passage 6, enters the lower half of the crankcase section oil return passage 6 on the joint surface between the upper and lower halves of the crankcase 2, passes through the mounting wall panel 7 between the crankshaft and the balance shaft, cuts off the bend to take a straight line through the crankcase 2, and then flows along the drainage groove on the inner wall of the crankcase 2 shell to enter the oil storage cavity of the bottom shell 10. The lubricating oil in the bottom shell 10 is then transported to the cavity of the cylinder head 3 under the action of the oil pump, forming a lubricating oil circulation.

[0034] Embodiment 3:

[0035] like Figure 1 , Figure 2 As shown, an engine oil return structure, the engine includes a cylinder block 1, a crankcase 2, a cylinder head 3 and a bottom shell 10, the cylinder block 1, the crankcase 2 and the cylinder head 3 are all made of aluminum alloy, wherein the aluminum alloy grade of the cylinder block 1 is AC8B, the aluminum alloy grade of the crankcase 2 is ADC12, and the aluminum alloy grade of the cylinder head 3 is AC4B. The crankcase 2 is connected to the bottom of the cylinder block 1, the cylinder head 3 is installed on the top of the cylinder block 1, and the bottom shell 10 is installed on the bottom of the crankcase 2. The cylinder head 3 and the cylinder block 1, the crankcase 2 and the cylinder block 1, and the bottom shell 10 and the crankcase 2 are all connected by bolts. A crankshaft and a balance shaft are installed on the crankcase 2. The engine oil return structure includes an oil return channel, which is a built-in oil return channel and is arranged inside the engine. There are three oil return channels, and the paths of the three oil return channels are parallel. The oil return passage starts from the inside of the cylinder head 3, extends through the cylinder block 1 and the crankcase 2 in sequence, and ends at the bottom shell 10, wherein the oil return passage passes between the crankshaft and the balance shaft when passing through the crankcase 2. The oil return passage includes a cylinder head section oil return passage 4, a cylinder block section oil return passage 5, and a crankcase section oil return passage 6. The cylinder block section oil return passage 5 is connected and communicated with the cylinder head section oil return passage 4, and the crankcase section oil return passage 6 is connected and communicated with the cylinder block section oil return passage 5. The cylinder block 1 includes a cylinder block shell and a cylinder block cavity, and the cylinder block cavity is located in the space enclosed by the cylinder block shell; the crankcase 2 includes a crankcase shell and a crankcase cavity, and the crankcase cavity is located in the space enclosed by the crankcase shell; the cylinder head 3 includes a cylinder head shell and a cylinder head cavity, and the cylinder head cavity is located in the space enclosed by the cylinder head shell; the cylinder head section oil return passage 4 is arranged in the shell of the cylinder head 3, and the cylinder block section oil return passage 5 is arranged in the shell of the cylinder block 1. The cylinder head section oil return passage 4, the cylinder body section oil return passage 5 and the crankcase section oil return passage 6 are all formed by drilling.

[0036] The bottom end face of the cylinder head 3 is aligned with the top end face of the cylinder block 1, and the bottom end face of the cylinder block 1 is aligned with the top end face of the crankcase 2. The end of the cylinder head section oil return passage 4 is located on the bottom end face of the cylinder head 3, the beginning and end of the cylinder section oil return passage 5 are respectively located on the top end face and the bottom end face of the cylinder block 1, and the beginning and end of the crankcase section oil return passage 6 are respectively located on the top end face and the bottom end face of the crankcase 2. The crankcase 2 is divided into an upper half and a lower half, the upper half has a lower end face formed by milling, and the lower half has an upper end face formed by milling. The upper and lower end faces are correspondingly fitted and then fixed with bolts to complete the splicing of the crankcase 2. Different from the embodiment 1, five parallel installation wall panels 7 are provided in the crankcase 2, and the installation wall panels 7 are also correspondingly divided into upper and lower parts that can be spliced ​​and spliced ​​according to the split mode of the crankcase 2. The two outer mounting wall panels 7 are provided with crankshaft mounting holes 8 and balance shaft mounting holes 9, which are used to mount the crankshaft and balance shaft respectively. The three middle mounting wall panels 7 are also provided with crankshaft mounting holes 8. The axes of the crankshaft mounting holes 8 and balance shaft mounting holes 9 are parallel, ensuring that the crankshaft and balance shaft are mounted in parallel on the mounting wall panels 7. The upper half of the crankcase section oil return passage 6 is located in the shell of the crankcase 2, and the lower half of the crankcase section oil return passage 6 penetrates into the three middle mounting wall panels 7, and the penetration position is located between the crankshaft mounting holes 8 and the balance shaft mounting holes 9. The terminal outlet of the crankcase section oil return passage 6 is not located on the joint surface of the crankcase 2 and the bottom shell 10, but is located at the junction of the bottom of the mounting wall panel 7 in the lower half of the crankcase and the crankcase shell. There are gaskets between the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1, and between the bottom end face of the cylinder block 1 and the top end face of the crankcase 2. The outer edge of the gasket between the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1 is flush with the outer edge of the bottom end face of the cylinder head 3 and the top end face of the cylinder block 1, and the outer edge of the gasket between the bottom end face of the cylinder block 1 and the top end face of the crankcase 2 is flush with the outer edge of the bottom end face of the cylinder block 1 and the top end face of the crankcase 2. The gasket is made of a composite of multiple layers of polyurethane sheets and the periphery is coated with fluororubber. Through holes are opened on the gasket corresponding to the bolts and oil passages, which does not affect the installation of the bolts and the smooth flow of the oil passage.

[0037] When the engine is working, the lubricating oil in the cavity of the cylinder head 3 flows out of the cylinder head 3 through the cylinder head section oil return passage 4, enters the cylinder block section oil return passage 5 on the joint surface between the cylinder head 3 and the cylinder block 1 and continues to flow downward, enters the crankcase section oil return passage 6 on the joint surface between the cylinder block 1 and the crankcase 2, flows through the upper half of the crankcase section oil return passage 6, enters the lower half of the crankcase section oil return passage 6 on the joint surface between the upper and lower halves of the crankcase 2, passes through the mounting wall panel 7 between the crankshaft and the balance shaft, cuts off the bend to take a straight line through the crankcase 2, and then freely drips into the oil storage cavity of the bottom shell 10. The lubricating oil in the bottom shell 10 is then transported to the cavity of the cylinder head 3 by the action of the oil pump, forming a lubricating oil circulation.

Claims

1. An engine oil return structure, the engine comprising a cylinder block (1) and a crankcase (2) connected to the bottom of the cylinder block (1), a cylinder head (3) being provided at the top of the cylinder block (1), a bottom shell being provided at the bottom of the crankcase (2), a crankshaft and a balance shaft being provided on the crankcase (2), wherein: The invention comprises an oil return passage arranged inside the engine, wherein the oil return passage starts from a cylinder head (3), passes through a cylinder body (1) and a crankcase (2) to a bottom shell, and passes between a crankshaft and a balance shaft.

2. The engine oil return structure according to claim 1, characterized in that: The oil return passage comprises a cylinder head section oil return passage (4), a cylinder block section oil return passage (5) connected to the cylinder head section oil return passage (4), and a crankcase section oil return passage (6) connected to the cylinder block section oil return passage (5).

3. The engine oil return structure according to claim 2, characterized in that: The cylinder head section oil return passage (4) is arranged in the housing of the cylinder head (3), the cylinder body section oil return passage (5) is arranged in the housing of the cylinder body (1), and the crankcase section oil return passage (6) is arranged in the housing of the crankcase (2).

4. The engine oil return structure according to claim 2, characterized in that: A mounting wall plate (7) is provided inside the crankcase (2), the crankshaft and the balance shaft are mounted on the mounting wall plate (7), and the crankcase section oil return passage (6) penetrates into the mounting wall plate (7).

5. The engine oil return structure according to claim 2, characterized in that: The bottom end surface of the cylinder head (3) is joined to the top end surface of the cylinder block (1), the bottom end surface of the cylinder block (1) is joined to the top end surface of the crankcase (2), the end of the cylinder head section oil return passage (4) is located on the bottom end surface of the cylinder head (3), the start and end of the cylinder block section oil return passage (5) are respectively located on the top end surface and the bottom end surface of the cylinder block (1), and the start and end of the crankcase section oil return passage (6) are respectively located on the top end surface and the bottom end surface of the crankcase (2).

6. The engine oil return structure according to claim 5, characterized in that: A sealing gasket is provided between the bottom end surface of the cylinder head (3) and the top end surface of the cylinder body (1), and between the bottom end surface of the cylinder body (1) and the top end surface of the crankcase (2).

7. The engine oil return structure according to claim 1, characterized in that: The crankcase (2) is made of aluminum alloy.

8. The engine oil return structure according to any one of claims 1 to 7, characterized in that: The cylinder head (3) is connected to the cylinder body (1) by bolts, and the crankcase (2) is connected to the cylinder body (1) by bolts.

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