CN117759402A - Oil circuit structure of engine - Google Patents

Abstract

The invention belongs to the technical field of engines, and relates to an oil circuit structure of an engine. In order to solve the problem of the lubricating difference of the existing oil way structure, an oil way structure of an engine is provided, the engine comprises a cylinder head, a cylinder body arranged below the cylinder head, a crankcase arranged below the cylinder body and a fine filter connected to the crankcase, the oil way structure comprises a lubricating oil way arranged on the left side of the engine, an oil outlet of the fine filter is communicated with an oil inlet of the cylinder head through the lubricating oil way, and the oil way structure is characterized by further comprising a crankcase oil way arranged on the right side of the crankcase and communicated with the oil outlet of the fine filter, a tensioner is connected to the cylinder body, a tensioner oil way is arranged in the tensioner, an oil inlet II is arranged on the cylinder head, the crankcase oil way is communicated with an inlet of the tensioner oil way, and an outlet of the tensioner oil way is communicated with the oil inlet II of the cylinder head. The left side and the right side of the cylinder head can be lubricated, and the lubricating effect of the cylinder head is improved.

Description

Oil circuit structure of engine

Technical Field

The invention belongs to the technical field of engines, and relates to an oil circuit structure of an engine.

Background

When the engine is used as a power device for running a motorcycle, lubricating oil is needed to lubricate all parts in the engine to slow down the abrasion of parts, so an oil way system is usually arranged in the engine to lubricate all parts, and the lubricating oil is needed to be pumped from the bottom of a crankcase through an oil pump and then is arranged through all oil ways in the engine to lubricate all parts and then reach a cylinder head to lubricate the cylinder head.

Such as chinese patent application [ grant bulletin number: CN208106518U discloses a lubricating oil way of engine, which comprises a strainer, an oil pump, a pressure reducing valve, an oil filter and a built-in oil way for connecting the above components, wherein the engine oil of the oil pan enters the oil pump after being filtered by the strainer, the oil pump outputs high-pressure oil, the output oil passes through the pressure reducing valve (the pressure reducing valve can ensure that the oil pressure of the lubricating system is not too high to damage the sealing property of the engine sealing element), the engine oil is filtered again by the oil filter and then is output to the parts needing lubrication and cooling through the oil way, the built-in oil way further comprises a cylinder cover bolt hole, and an oil way for the hydraulic tensioner, and the built-in oil way further comprises an oil way for sequentially passing through a right cylinder body, a cylinder cover and a cam shaft seat, and is used for lubricating the cam shaft.

The structure is characterized in that the camshaft seat in the cylinder cover is lubricated by the independent oil way, the hydraulic tensioner is lubricated by the independent oil way, and at the moment, the camshaft is lubricated only through the oil way on the right side, but the camshaft is positioned at the cylinder head part and is positioned at the uppermost end of the engine, so that the camshaft is lubricated only on one side, and the lubrication effect at the cylinder head part is poorer.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and provides an oil circuit structure of an engine, which aims to solve the technical problems that: how to solve the problem of poor lubrication effect of the existing oil way structure.

The aim of the invention can be achieved by the following technical scheme:

the utility model provides an oil circuit structure of engine, engine includes the cylinder end, sets up the cylinder body under the cylinder end, sets up crankcase under the cylinder body and connects the smart filter on the crankcase, this oil circuit structure is including seting up the left lubrication circuit of engine, lubrication circuit is with the oil-out of smart filter and the first intercommunication of oil inlet of cylinder end, its characterized in that, this oil circuit structure is still including seting up the crankcase oil circuit on the crankcase right side and with the oil-out intercommunication of smart filter, be connected with the tensioning ware on the cylinder body, the tensioning ware oil circuit has been seted up in the tensioning ware, seted up oil inlet second on the cylinder end, the import intercommunication of crankcase oil circuit and tensioning ware oil circuit, the export of tensioning ware oil circuit and the second intercommunication of oil inlet of cylinder end.

Working principle: during lubrication, the existing oil pump of the engine rotates to convey engine oil to the fine filter, after the engine oil is subjected to fine filtration by the fine filter, a lubricating oil way is formed in the left side of the engine, at the moment, a part of lubricating oil flowing out of an oil outlet of the fine filter flows into the cylinder head from an oil inlet of the cylinder head through the lubricating oil way, a crankcase oil way is formed in the right side of the crankcase, lubricating oil at the oil outlet of the fine filter flows into the crankcase along the crankcase oil way, parts in the crankcase are lubricated, after lubrication, the lubricating oil flows into the tensioner from an inlet of the tensioner oil way, the tensioner is lubricated, and then flows into two parts of the oil inlet of the cylinder head from an outlet of the tensioner, at the moment, the cylinder head is lubricated by the lubricating oil from the left side and the right side, and the lubricating effects of the parts on the left side and the right side of the cylinder head are approximately the same, and the cylinder head can be lubricated rapidly by adding two parts in the space arrangement, the lubricating efficiency of the cylinder head can be improved by increasing the mode of the lubricating oil inlet of the lubricating oil cylinder head, and the whole lubricating effect of the tensioner is also achieved on the cylinder body.

In the oil path structure of the engine, the cylinder body is provided with the oil inlet channel communicated with the crankcase oil path and the oil outlet channel communicated with the oil inlet II of the cylinder head, the tensioner is vertically arranged on the cylinder body, the inlet of the tensioner oil path is positioned at the upper end of the cylinder body and is communicated with the outlet of the oil inlet channel, and the outlet of the tensioner oil path is positioned at the upper end of the cylinder body and is communicated with the oil outlet channel.

Through the import with the tensioning ware oil circuit all sets up the upper end at the cylinder body with the export for from the lubrication fluid of crankcase need flow into the tensioning ware oil circuit from the upper end of cylinder body in, promoted the lubricated effect to the tensioning ware, and lubricating oil has an effect of gathering in the tensioning ware, thereby makes the lubricating oil that enters into in the cylinder head comparatively smooth and easy, further promotion the lubricated effect to the cylinder head, also made things convenient for the processing of oil circuit in the cylinder body.

In the oil way structure of the engine, the crankcase oil way comprises a first oil way which is vertically arranged and communicated with the oil outlet of the fine filter, and a second oil way which is frontward arranged and communicated with the oil inlet channel, wherein the first oil way is communicated with the second oil way, and one end of the second oil way, which is close to the tensioner, is provided with a flow limiting plug for limiting the flow of oil to the tensioner.

Lubricating oil flowing out of the fine filter can flow into the crankcase through the oil way I and lubricate the crankshaft, lubricating oil after lubrication of the crankshaft flows out of the oil way II into the oil way of the tensioner, and the oil can be collected at the position through the flow limiting plug arranged at one end of the oil way II and flows towards the tensioner at a uniform speed, so that the lubrication effect of the tensioner is good, and the lubrication effect of the oil way structure is improved.

In the oil way structure of the engine, a communication gap is formed between the cylinder body and the crankcase, one end of the oil way II provided with the flow limiting plug is communicated with the communication gap, an annular flow passage communicated with the communication gap is formed by recessing the outer side wall of the crankcase, and the annular flow passage is communicated with one end of the oil inlet passage.

Through the setting of annular runner for the fluid through restriction end cap can be further in annular runner department buffering gathering, and in the stable inflow tensioning ware oil circuit, realized the lubrication effect to tensioning ware stability, promoted the stability of oil circuit structure.

In the oil way structure of the engine, a chain tensioning plate for tensioning the chain is arranged in the cylinder body, an installation through hole communicated with the inner cavity of the cylinder body is formed in the end portion of the cylinder body, a connecting cover for limiting the tensioner in the installation through hole is connected to the cylinder body, one end of the tensioner penetrating through the installation through hole is always propped against the chain tensioning plate, and the tensioner oil way is formed between the connecting cover and the end face of the cylinder body.

Through directly having seted up the installation through-hole at the tip of cylinder body, through with in the tensioning ware embedding installation through-hole, and carry out spacingly to the tensioning ware through the connecting cover, can form the tensioning ware oil circuit between the terminal surface of connecting cover and cylinder body this moment, make the tensioning ware oil circuit flow into in the tensioning ware from between connecting cover and the cylinder body, can realize a small amount of lubrication effect to the tensioning ware, also can make most lubricating oil can directly flow into the oil inlet second of cylinder head through the tensioning ware oil circuit, realized the quick lubrication to the cylinder head, promote the lubrication effect of cylinder head when guaranteeing the lubrication effect to the tensioning ware.

In the oil path structure of the engine, the crankcase comprises a crank oil groove which is formed in an annular shape along the circumferential direction of the crank shaft, the first oil path is communicated with the crank oil groove, and the second oil path is positioned above the crank oil groove and is communicated with the crank oil groove.

Through the setting of the relative position of oil circuit I and oil circuit II for the fluid that flows into in the crankcase from oil circuit I flows the bent axle oil groove earlier, lubricates the back to the bent axle, and the oil circuit I that flows into the tensioning ware oil circuit from bent axle oil groove top again, through the difference in height, makes the bent axle obtain abundant lubrication, thereby can not influence the lubrication effect to the bent axle in the crankcase when providing cylinder end and tensioning ware lubrication.

In the oil circuit structure of the engine, the fine filter is connected to the left side of the crankcase, a transverse oil circuit transversely arranged along the crankcase is arranged in the middle of the crankcase, the middle of the transverse oil circuit is communicated with an oil outlet of the fine filter, the lubricating oil circuit is arranged on the left side of the crankcase, the lower end of the lubricating oil circuit is communicated with the left side of the transverse oil circuit, and the lower end of the crankcase oil circuit is communicated with the right side of the transverse oil circuit.

Through the middle part intercommunication with the oil-out of fine filter and horizontal oil circuit for the velocity of flow of lubricating oil from the fine filter flow direction both sides equals, and makes the intercommunication of lubricating oil circuit and crankcase oil circuit and horizontal oil circuit more convenient, thereby guarantees that the lubrication effect of engine left and right sides is stable.

In the above-mentioned oil circuit structure of engine, the lubricated oil circuit includes the crankcase lubricated oil circuit of vertical setting and the first lubricated oil circuit of cylinder head that sets up forward, the lower extreme of crankcase lubricated oil circuit communicates with the left side of horizontal oil circuit, the upper end and the bent axle oil groove intercommunication of crankcase lubricated oil circuit, the one end and the middle part intercommunication of crankcase lubricated oil circuit of first lubricated oil circuit, the other end and the first intercommunication of oil inlet of cylinder head of first lubricated oil circuit of cylinder head.

Because the cylinder head lubricating oil way is communicated with the middle part of the crankcase lubricating oil way, the lubrication of the cylinder head and the crankshaft is connected in parallel at the moment, so that the lubrication between the crankcase and the cylinder head is not affected mutually at the left side of the engine, and the lubrication efficiency of each part is improved.

In the oil way structure of the engine, the crank case comprises a left crank case and a right crank case, a fine filter oil way connected with an oil outlet of the fine filter is formed between the left crank case and the right crank case, and the lower end of the fine filter oil way is communicated with the middle part of the transverse oil way.

The oil duct of the fine filter is formed by abutting two oppositely arranged end faces of the left crankcase and the right crankcase, so that lubricating oil flowing out of the oil outlet of the fine filter can flow into a transverse oil duct through the lower end of the oil duct of the fine filter, and at the moment, the lower end of the oil duct of the fine filter is also positioned between the left crankcase and the right crankcase, so that the speeds of the lubricating oil flowing into the left crankcase and the lubricating oil flowing into the right crankcase are equal, and the lubrication stability is improved.

Compared with the prior art, the oil circuit structure of the engine has the following advantages:

1. through set up lubrication oil way in the left crankcase and realize the lubrication to left crankcase and cylinder head respectively, be provided with the crankcase oil way in the right crankcase to connect the tensioning ware on the cylinder body, because the tensioning ware also need lubricate when using, consequently accomplish lubricated the back to the bent axle through the crankcase oil way, again with remaining lubricating oil inflow to tensioning ware oil way to the tensioning ware lubrication, the lubrication to the cylinder head is realized in the cylinder head is flowed into to remaining lubricating oil again, thereby realize lubricated the left and right sides of cylinder head, promoted the lubrication effect of cylinder head.

2. Through the setting of oil inlet channel and play oil channel in flow restrictor and the cylinder body for fluid can be slow and stable part flows into in the tensioning ware, lubricates the tensioning ware, and another part flows into in the cylinder head to the lubrication of cylinder head, thereby satisfies tensioning ware a small amount and stable lubrication again, also can realize the multiple spot lubrication to the cylinder head.

Drawings

Fig. 1 is a partial schematic structure of an engine of the present invention.

Fig. 2 is one of the sectional views of the present invention.

Fig. 3 is one of the cross-sectional views of the present invention at the right crankcase.

Fig. 4 is a partial enlarged view at a in fig. 3.

Fig. 5 is a second cross-sectional view of the present invention at the right crankcase.

Fig. 6 is a partial cross-sectional view of the present invention at the right crankcase.

Fig. 7 is one of the sectional views of the present invention at the left crankcase.

Fig. 8 is a second cross-sectional view of the present invention at the left crankcase.

In the figure, 1, a cylinder head; 11. an oil inlet I; 12. an oil inlet II; 2. a cylinder; 21. an oil inlet passage; 22. an oil outlet channel; 23. a chain tensioning plate; 24. mounting through holes; 25. a connection cover; 3. a crankcase; 31. a left crank case; 31a, a lubricating oil path; 31a1, crankcase lubrication oil path; 31a2, cylinder head lubrication oil path; 32. a right crankcase; 32a, crankcase oil passages; 32a1, first oil passage; 32a2, oil passage two; 32b, annular flow channels; 33. a transverse oil path; 34. a crankshaft oil groove; 4. a fine filter; 41. an oil outlet; 5. a tensioner; 51. tensioner oil circuit; 6. a current limiting plug; 7. a communication gap; 8. fine filter oil duct.

Detailed Description

The following are specific embodiments of the present invention and the technical solutions of the present invention will be further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

As shown in fig. 1 to 7, the oil passage structure of the engine comprises a cylinder head 1, a cylinder body 2 arranged below the cylinder head 1 and a crank case 3 arranged below the cylinder body 2, wherein the crank case 3 comprises a crank oil groove 34 which is formed in a ring shape along the circumferential direction of the crank shaft, the crank case 3 comprises a left crank case 31 and a right crank case 32, the left crank case 31 is connected with a fine filter 4, the oil passage structure comprises a lubrication oil passage 31a formed in the left crank case 31, the lubrication oil passage 31a comprises a vertically arranged crank case lubrication oil passage 31a1 and a front arranged cylinder head lubrication oil passage 31a2, the lower end of the crank case lubrication oil passage 31a1 is communicated with the left side of a transverse oil passage 33, the upper end of the crank case lubrication oil passage 31a1 is communicated with the crank oil groove 34 in the left crank case 31, one end of the cylinder head lubrication oil passage 31a2 is communicated with the middle part of the crank case lubrication oil passage 31a1, and the other end of the cylinder head lubrication oil passage 31a2 is communicated with the first oil inlet 11 of the cylinder head 1.

Specifically, as shown in fig. 1-8, a crankcase oil path 32a communicated with the oil outlet 41 of the fine filter 4 is formed on the right crankcase 32, the tensioner 5 is connected to the cylinder body 2, a tensioner oil path 51 is formed in the tensioner 5, the crankcase oil path 32a comprises an oil path I32 a1 vertically arranged and communicated with the oil outlet 41 of the fine filter 4 and an oil path II 32a2 forwardly arranged and communicated with the tensioner oil path 51, the oil path I32 a1 is communicated with the crankshaft oil groove 34, the oil path II 32a2 is positioned above the crankshaft oil groove 34 and communicated with the crankshaft oil groove 34, the cylinder head 1 is provided with an oil inlet II 12, the oil path II 32a2 is communicated with the inlet of the tensioner oil path 51, and the outlet of the tensioner oil path 51 is communicated with the oil inlet II 12 of the cylinder head 1.

As shown in fig. 2-5, an oil inlet channel 21 communicated with a crankcase oil channel 32a and an oil outlet channel 22 communicated with an oil inlet second 12 of the cylinder head 1 are formed on the cylinder body 2, the tensioner 5 is vertically arranged on the cylinder body 2, an inlet of the tensioner oil channel 51 is communicated with the upper end of the oil inlet channel 21, an outlet of the tensioner oil channel 51 is communicated with the upper end of the oil outlet channel 22, a flow limiting plug 6 for limiting oil flowing into the tensioner 5 is arranged at one end of the oil channel second 32a2 close to the tensioner 5, a communication gap 7 is formed between the cylinder body 2 and the right crankcase 32, one end of the oil channel second 32a2 is provided with the flow limiting plug 6 and is communicated with the communication gap 7, an outer side wall of the right crankcase 32 is recessed to form an annular flow channel 32b communicated with the communication gap 7, the annular flow channel 32b is communicated with one end of the oil inlet channel 21, a chain tensioning plate 23 for tensioning a chain is arranged in the cylinder body 2, a mounting through hole 24 communicated with an inner cavity of the cylinder body 2 is formed at one end of the cylinder body 2, a connecting cover 53 limiting the tensioner 5 in the mounting through hole 24 is connected to the cylinder body 2, one end of the tensioner 5 is always abutted against the end face of the tensioning plate 23 of the mounting through the mounting hole 24, and the end face of the tensioner is always abutted against the end cover 53 of the chain tensioning plate 51 is formed between the end face of the tensioner cover and the end face of the tensioner plate and the end plate.

As shown in fig. 2 and 8, the middle parts of the crank cases 3 are provided with transverse oil passages 33 transversely arranged along the crank cases 3, a fine filter oil passage 8 connected with an oil outlet 41 of the fine filter 4 is formed between the left crank case 31 and the right crank case 32, the lower end of the fine filter oil passage 8 is communicated with the middle part of the transverse oil passages 33, the lower end of the lubricating oil passage 31a is communicated with the left side of the transverse oil passages 33, and the lower end of the crank case oil passage 32a is communicated with the right side of the transverse oil passages 33.

Working principle: during lubrication, the engine oil is supplied to the fine filter 4 by rotation of an existing oil pump of the engine, and after the engine oil is fine-filtered by the fine filter 4, the lubricating oil flowing out of the fine filter 4 flows into the left crankcase 31 and the right crankcase 32 through the lateral oil passage 33, respectively.

Left side lubrication: the left crankcase 31 is provided with a lubrication oil path 31a, the lubrication oil path 31a comprises a crankcase lubrication oil path 31a1 and a cylinder head lubrication oil path 31a2, a part of lubricating oil flowing out of an oil outlet 41 of the fine filter 4 flows into a crankshaft oil groove 34 of the left crankcase 31 along the crankcase lubrication oil path 31a1 and lubricates a crankshaft, and the other part of lubricating oil flows into the cylinder head lubrication oil path 31a2 through the middle part of the crankcase lubrication oil path 31a1 and flows into the first oil inlet 11 of the cylinder head 1 from the cylinder head lubrication oil path 31a 2.

Right side lubrication: the right crankcase 32 is provided with a crankcase oil path 32a, lubricating oil at the oil outlet 41 of the fine filter 4 flows into a crankshaft oil groove 32c along the crankcase oil path 32a to lubricate the crankshaft, residual lubricating oil flows into the tensioner 5 from the inlet of the tensioner oil path 51 to lubricate the tensioner 5, and then flows into the second oil inlet 12 of the cylinder head 1 from the outlet of the tensioner 5.

The cylinder head 1 is lubricated by lubricating oil entering the cylinder head 1 from the left side and the right side, and is lubricated respectively from the left side and the right side, so that the lubricating effects of parts on the left side and the right side of the cylinder head 1 are approximately the same, and the cylinder head 1 can realize rapid lubrication of the parts in the cylinder head 1 in space arrangement by adding the oil inlet II 12, the lubricating efficiency of the cylinder head 1 can be improved in a mode of adding a lubricating oil inlet, the cylinder head 1 is lubricated, and the tensioner 5 on the cylinder body 2 is lubricated, so that the lubricating effect of the whole oil circuit structure is improved.

The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.

Claims (9)

1. The utility model provides an oil circuit structure of engine, engine includes cylinder end (1), sets up cylinder body (2) under cylinder end (1), sets up crankcase (3) under cylinder body (2) and connects fine filter (4) on crankcase (3), this oil circuit structure is including seting up on engine left lubrication circuit (31 a), lubrication circuit (31 a) communicates oil-out (41) of fine filter (4) with first oil inlet (11) of cylinder end (1), its characterized in that, this oil circuit structure still includes and sets up crankcase oil circuit (32 a) on crankcase (3) right side and with oil-out (41) of fine filter (4) intercommunication, be connected with tensioning ware (5) on cylinder body (2), set up tensioning ware oil circuit (51) in tensioning ware (5), set up second oil inlet (12) on cylinder end (1), the import intercommunication of crankcase oil circuit (32 a) and tensioning ware oil circuit (51), the export of tensioning ware oil circuit (51) and second oil inlet (12) of cylinder end (1) intercommunication.

2. The oil path structure of the engine according to claim 1, characterized in that an oil inlet channel (21) communicated with a crankcase oil path (32 a) and an oil outlet channel (22) communicated with an oil inlet second (12) of the cylinder head (1) are formed on the cylinder body (2), the tensioner (5) is vertically arranged on the cylinder body (2), an inlet of the tensioner oil path (51) is positioned at the upper end of the cylinder body (2) and is communicated with the oil inlet channel (21), and an outlet of the tensioner oil path (51) is positioned at the upper end of the cylinder body (2) and is communicated with the oil outlet channel (22).

3. The oil passage structure of the engine according to claim 2, characterized in that the crankcase oil passage (32 a) includes an oil passage one (32 a 1) disposed vertically and communicating with an oil outlet (41) of the fine filter (4) and an oil passage two (32 a 2) disposed frontward and communicating with the oil inlet passage (21), the oil passage one (32 a 1) communicates with the oil passage two (32 a 2), and an end of the oil passage two (32 a 2) near the tensioner (5) is provided with a flow restricting plug (6) that restricts flow of oil to the tensioner (5).

4. An oil passage structure of an engine according to claim 3, characterized in that a communication gap (7) is provided between the cylinder block (2) and the crankcase (3), one end of the oil passage two (32 a 2) provided with a flow limiting plug (6) is communicated with the communication gap (7), an annular flow passage (32 b) communicated with the communication gap (7) is formed by an outer side wall depression of the crankcase (3), and the annular flow passage (32 b) is communicated with one end of an oil inlet passage (21).

5. The oil circuit structure of an engine according to any one of claims 1-4, characterized in that a chain tensioning plate (23) for tensioning a chain is arranged in the cylinder body (2), a mounting through hole (24) communicated with an inner cavity of the cylinder body (2) is formed in the end portion of the cylinder body (2), a connecting cover (25) for limiting the tensioner (5) in the mounting through hole (24) is connected to the cylinder body (2), one end of the tensioner (5) penetrating out of the mounting through hole (24) is always abutted against the chain tensioning plate (23), and the tensioner oil circuit (51) is formed between the connecting cover (25) and the end face of the cylinder body (2).

6. The oil passage structure of an engine according to claim 3 or 4, characterized in that the crankcase (3) includes a crank oil groove (32 c) that is open in a circumferential direction of the crankshaft and is annular, the first oil passage (32 a 1) communicates with the crank oil groove (34), and the second oil passage (32 a 2) is located above the crank oil groove (34) and communicates with the crank oil groove (34).

7. The oil path structure of an engine according to claim 6, characterized in that the fine filter (4) is connected to the left side of the crankcase (3), the middle part of the crankcase (3) has a lateral oil path (33) which is laterally provided along the crankcase (3), the middle part of the lateral oil path (33) is communicated with an oil outlet (41) of the fine filter (4), the left side of the crankcase (3) is provided with the above-mentioned lubrication oil path (31 a), the lower end of the lubrication oil path (31 a) is communicated with the left side of the lateral oil path (33), and the lower end of the crankcase oil path (32 a) is communicated with the right side of the lateral oil path (33).

8. The oil passage structure of an engine according to claim 7, characterized in that the lubrication oil passage (31 a) includes a vertically arranged crankcase lubrication oil passage (31 a 1) and a forwardly arranged cylinder head lubrication oil passage (31 a 2), a lower end of the crankcase lubrication oil passage (31 a 1) communicates with a left side of a lateral oil passage (33), an upper end of the crankcase lubrication oil passage (31 a 1) communicates with a crank oil groove (34), one end of the cylinder head lubrication oil passage (31 a 2) communicates with a middle portion of the crankcase lubrication oil passage (31 a 1), and the other end of the cylinder head lubrication oil passage (31 a 2) communicates with an oil inlet one (11) of the cylinder head (1).

9. The oil passage structure of an engine according to claim 7, characterized in that the crankcase (3) includes a left crankcase (31) and a right crankcase (32), a fine filter oil passage (8) connected with an oil outlet (41) of the fine filter (4) is formed between the left crankcase (31) and the right crankcase (32), and a lower end of the fine filter oil passage (8) communicates with a middle portion of the lateral oil passage (33).