JP2009013887A - Engine lubricating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine lubricating device of adopting a dry sump lubricating method, superior in manufacturability and maintainability, and capable of reducing the deterioration in fuel economy performance of an engine. <P>SOLUTION: This engine lubricating device of the dry sump lubricating method has an oil receiving part 155 formed in an engine lower part, a scavenge pump 170 transferring oil in the oil receiving part to an oil tank 165, and a feed pump 180 supplying the oil stored in the oil tank 165 in the engine, and has a crankcase 120 formed so that at least both side parts parallel to the crankshaft axis have an inside wall 123, an outside wall 124 and a space part 125 having a lower part opened between both of these, a first oil pan member 150 installed on an under surface of the inside wall of the crankcase and forming the oil receiving part, and a second oil pan member 160 installed on an under surface of the outside wall of the crankcase and constituting the oil tank together with the space part by covering the first oil pan member from the lower side while having a predetermined distance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine lubrication device, and more particularly to an engine lubrication device employing a dry sump lubrication system.

  In general, a wet sump lubrication system and a dry sump lubrication system are known as engine lubrication systems.

  In the wet sump lubrication method, an oil pan capable of storing the total amount of lubricating oil supplied to the lubricated part of the engine is provided at the bottom of the engine body, and the oil stored in the oil pan is sucked up by an oil pump and covered. This is a system in which each part of the lubrication part is supplied and lubricated. This wet sump lubrication system is used in many commercial vehicles because of its simple structure. However, in order to store a desired amount of lubricating oil, an oil pan having a predetermined depth is required, and there is a power loss due to the engine crankshaft stirring the oil stored in the oil pan. In addition, there is a drawback that the suction failure of the oil pump is likely to occur with the movement of the oil in the oil pan due to the acceleration / deceleration or turning of the vehicle.

  In response to these problems, the dry sump lubrication system was developed especially for racing engines, etc. The dry sump lubrication system was equipped with an oil tank separately from the engine body, and was installed at the bottom of the engine body. The oil in the oil receiving part (dry sump) is sucked up by the scavenge pump and stored in the oil tank, and the oil stored in this oil tank is supplied to each part of the lubricated part by the oil feed pump and lubricated. .

  However, in the dry sump lubrication system as described above, since the engine body and the oil tank are separate, a large space is required around the engine body, and piping connecting the oil receiving part and the oil tank. In addition, both the oil tank and the pipe that connects the engine body are required to be long, and there is a new problem such as an increase in oil loss head and a decrease in oil pressure response due to the oil pump. For this reason, the technique described in Patent Document 1 has been proposed to solve such a problem.

  In Patent Document 1, in an engine that stores oil in an engine in an oil tank and supplies the oil in the oil tank to each part of the engine by an oil main pump, an oil tank is provided on one side of an oil pan. A storage chamber is integrally formed on the other side, an oil passage communicating with the oil tank and the storage chamber is integrally formed on the bottom of the oil pan, and the oil in the oil pan is passed through a scavenging pipe by a scavenge pump. An engine lubrication device that integrates the engine body and oil tank so that the oil is collected in the oil tank, and the oil in the oil tank is supplied from the supply pipe to each part of the engine through the oil passage and the storage chamber. Is described.

  Further, in Patent Document 2, for the purpose of downsizing the dry sump type lubrication device in the same manner as the wet sump type, a pump accommodating portion is provided in a corner of an oil pan covering the lower surface of the crankcase of the engine, and this pump accommodating A lubricating device for an internal combustion engine is disclosed in which an oil tank portion having an upper surface partitioned from a crankcase by a partition wall is formed on a lower surface side of an oil pan adjacent to the portion.

JP-A-6-248927 JP-A-4-246216

  However, in the engine lubrication device described in Patent Document 1, although the engine body and the oil tank are integrated to ensure the space around the engine, the oil tank is provided on one side of the oil pan, A storage chamber is integrally formed on the other side, and an oil passage communicating with the oil tank and the storage chamber is also integrally formed on the bottom of the oil pan, which makes it difficult to secure the required amount of oil, and to manufacture and maintain it. There is a need for further improvement because of its lack of practicality.

  By the way, the main purpose of adopting the dry sump lubrication system is to reduce power loss due to oil mixing resistance of the crankshaft. On the other hand, in the dry sump lubrication system provided with the scavenge pump, power loss for driving the scavenge pump is generated more than in the wet sump lubrication system. In the high-speed rotation region of the engine, the power loss due to oil agitation resistance is greater than the power loss driving the scavenge pump, so the merit of adopting the dry sump lubrication method is great. However, since the oil agitation resistance is relatively small in the low-speed rotation region of the engine, the benefits of the dry sump lubrication system cannot be obtained much, and there is a problem that the fuel efficiency of the engine deteriorates due to power loss driving the scavenge pump.

  SUMMARY OF THE INVENTION An object of the present invention has been made in view of such conventional problems, and is an engine lubrication device that employs a dry sump lubrication system that is excellent in manufacturability and maintainability and that can reduce deterioration in fuel efficiency of the engine. Is to provide.

  An engine lubrication apparatus according to an embodiment of the present invention that solves the above problems includes an oil receiving portion formed in a lower portion of the engine, a scavenge pump that transfers oil in the oil receiving portion to an oil tank, and a storage in the oil tank. A lubrication device for a dry sump lubrication type engine having a feed pump for supplying the oil to be supplied into the engine, and at least both sides parallel to the crankshaft axis are open on the inner wall and the outer wall and the lower part between them. And a first oil pan member attached to a lower surface of the inner wall of the crankcase and forming the oil receiving portion, and the outer wall of the crankcase. The first oil pan member is attached to the lower surface of the housing and covers the first oil pan member from the lower side while having a predetermined distance. Characterized in that it comprises a second oil pan member constituting the oil tank.

  According to this aspect, at least both sides parallel to the crankshaft axis are formed on the lower surface of the inner wall of the crankcase formed with the inner wall and the outer wall, and the space portion opened downward between them. One oil pan member is attached to form an oil receiving portion. Then, the first oil pan member is covered from the lower side while having a predetermined distance, and the second oil pan member is attached to the lower surface of the outer wall of the crankcase, whereby the first oil pan member and An oil tank having a volume between the second oil pan member and a space between the inner and outer walls of the crankcase is configured. Thus, the required oil amount can be ensured with a compact configuration, and the first oil pan member forming the oil receiving portion and the second oil pan member configuring the oil tank can be separately removed. Therefore, an engine lubrication device excellent in manufacturability and maintainability can be obtained.

  Here, it is preferable that a part of the lower end portion of the inner wall on both sides of the crankcase is connected by a bottom wall, and the remaining part forms an opening to which the first oil pan member is attached. .

  According to this form, the rigidity of the crankcase can be maintained at a high level by reducing a part of the lower end portion of the inner wall on both sides of the crankcase with the bottom wall, and the vibration of the engine body can be reduced. .

  A partition wall defining an oil passage is provided between the first oil pan member and the second oil pan member, and a discharge port from the scavenge pump is opened near the start end of the oil passage. Preferably, the oil strainer suction port of the feed pump is opened near the end of the oil passage.

  According to this form, even when bubbles or the like are mixed in the oil by discharging from the scavenge pump, it can be defoamed in the course of the oil flowing from the vicinity of the start end of the oil passage to the vicinity of the end, It is possible to effectively reduce the intake of bubble-mixed oil from the oil strainer suction port of the feed pump that is opened near the terminal end of the oil passage.

  Furthermore, it is preferable that the oil passage is formed in a substantially spiral shape.

  According to this aspect, since the oil passage can be made relatively long in an allowable space, it is possible to secure the oil retention time and promote natural defoaming.

  The oil return system to the oil tank has a first return path that is transferred from the scavenge pump, and a second return path that directly returns the oil supplied into the engine. Is preferred.

  According to this embodiment, the power for driving the scavenge pump can be reduced and the fuel efficiency performance of the engine can be improved compared to the conventional case where the total amount of oil supplied into the engine is returned to the oil tank by the scavenge pump. Can do.

  Here, the second return path is formed in the cylinder block, and is formed in the chain cover so as to open to the space portion in the oil return path from the cylinder head and / or the crankcase. In addition, it is preferable that a communication passage communicating with the oil return passage from the cylinder head is used.

  According to this aspect, in the oil return passage formed in the chain cover from the cylinder head and the communication passage communicating with the oil return passage from the cylinder head formed in the cylinder block, the oil is oiled by gravity. It is possible to return directly to the tank, and the power loss for driving the scavenge pump can be effectively reduced. Therefore, the power loss due to the oil stirring resistance is greater. The power loss that drives the scavenge pump in the low speed rotation range of the engine with relatively small oil stirring resistance while enjoying the benefits of the dry sump lubrication method in the high speed rotation range of the engine. This can improve the fuel efficiency of the engine.

  The discharge capacity of the scavenge pump may be smaller than the discharge capacity of the feed pump.

  According to this embodiment, it is possible to reliably reduce the drive power loss of the scavenge pump and to reduce the cost by the dry sump lubrication method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The engine body 100 according to the present embodiment is configured such that a crankcase 120 is attached to a lower portion of a cylinder block 110 and a cylinder head 130 and a head cover 140 are sequentially coupled to the upper portion of the cylinder block 110. The crankcase 120 includes a front wall 121 and a rear wall 122 that are orthogonal to the crankshaft axis, and part of both side portions (front side) parallel to the crankshaft axis are the inner wall 123 and the outer wall 124 and both of them. And a space 125 that is open at the bottom.

  A flange 123f for attaching a first oil pan member as an oil receiving member, which will be described later, is formed at the lower end portion of the inner wall 123. Similarly, a flange for attaching an oil tank, which will be described later, is formed at the lower end portion of the outer wall 124. 124f is formed. In the present embodiment, on the rear side of the crankcase 120 to which a transmission or the like is attached, both lower ends of the inner walls 123 on both sides of the crankcase 120 are connected together with the rear wall 122 by the bottom wall 127 as an integral structure. The oil receiving portion is formed and the rigidity is ensured. The remaining part of the crankcase 120 excluding the bottom wall 127 forms an opening 129 surrounded by the first oil pan member mounting flange 123f.

  The first oil pan member 150 having a substantially flat bottom surface and a shallow bottom is attached to the lower surface of the flange 123f of the inner wall 123 of the crankcase 120 by a bolt (not shown) or the like via the flange 150f. A receiving portion 155 is formed. The first oil pan member 150, the front wall 121, the rear wall 122, the inner wall 123, and the bottom wall 127 define the inside of a crankcase that houses a rotating body such as the crankshaft 112 and the pair of balance shafts 114. Yes.

  The piston 116 is accommodated in the bore in the cylinder block 110 so as to be able to reciprocate. The connecting rod 118 converts the reciprocating motion of the piston 116 into the rotational motion of the crankshaft 112. In addition, a combustion chamber is formed in the cylinder head 130 and is connected to an intake port and an exhaust port (not shown) of the combustion chamber, respectively, and an intake manifold and an exhaust manifold (both not shown) are connected. The intake port and the exhaust port are opened and closed by an intake valve and an exhaust valve, respectively, and these intake / exhaust valves are driven by an intake / exhaust camshaft (not shown). In the present embodiment, as will be described later, a variable intake valve timing mechanism VVT-i for changing the operation timing of the intake valve is provided, and the operation oil supplied to the variable intake valve timing mechanism VVT-i is switched. An oil control valve OCV is also disposed in the cylinder head 130 and the head cover 140. Reference numeral 119 denotes an oil return passage formed in the cylinder block 110 for returning a part of the oil supplied to the cylinder head 130 to an oil tank 165 described later. Further, a timing chain is wound between a sprocket 117 provided at the extreme end of the crankshaft 112 and a sprocket (not shown) provided on each of the intake / exhaust camshafts described above, and covers these. The chain cover 111 is attached to the cylinder block 110.

  Furthermore, in the engine main body 100 according to the present embodiment, the second oil pan member 160 is also bolted to the lower surface of the flange 124f of the outer wall 124 of the crankcase 120 and the flange 111f of the chain cover 111 via the flange 160f. It is attached with. The second oil pan member 160 is attached in such a manner that it is deeper than the shallow first oil pan member 150 and covers from below while having a predetermined distance including the entire surface. Thus, the oil tank 165 is configured together with the space 125 of the crankcase 120 described above. The oil tank 165 includes a second oil pan member 160 having a substantially flat bottom surface, a space between the flat bottom surface and the lower surface of the first oil pan member 150, a front wall 121 of the crankcase 120, The space between the chain cover 111 and the space 125 between the inner wall 123 and the outer wall 124 on both sides of the crankcase 120 is included as an internal volume, and the axis of the crankshaft 112 of the engine body 100 is included. It is substantially symmetrical with respect to the center plane. In the oil tank 165, the internal volume is determined such that the oil surface OL when the engine is stopped is above the lower surface of the mounting flange 123f of the first oil pan member 150.

  In the present embodiment, a scavenge pump 170 that transfers oil collected in the main oil receiving portion 155 to the oil tank 165 is provided inside the crankcase so as to be driven by one of the pair of balance shafts 114. ing. The feed pump 180 that supplies the oil stored in the oil tank 165 into the engine body 100 is also disposed inside the crankcase so as to be driven by the other of the pair of balance shafts 114.

  The driven gear 113 provided on one of the pair of balance shafts 114 is driven by the drive gear 115 press-fitted into the counterweight of the crankshaft 112. As is well known, the pair of balance shafts are rotated in opposite directions in synchronization with each other by a driven gear (not shown) that meshes with each other.

  The suction port of the scavenge pump 170 is connected to an oil strainer 171 opened close to the upper surface of the first oil pan member 150 forming the main oil receiving portion 155 via the suction pipe 172, and the scavenge pump The discharge port 170 is connected to the discharge pipe 174. An outlet 176 of the discharge pipe 174, in other words, a discharge port 176 from the scavenge pump 170 is opened in the oil tank 165.

  Further, the suction port of the feed pump 180 is connected to an oil strainer 181 that is opened close to the second oil pan member 160 constituting the oil tank 165 via a suction pipe 182. Further, the discharge port of the feed pump 180 is connected to a supply passage for lubrication or hydraulic oil formed in the crankcase 120 or the cylinder block 110, and to a discharge pipe (not shown) communicating with an oil filter (not shown) in this figure. ing. Reference numeral 190 denotes a bottom surface of the oil tank 165, in other words, a partition wall provided upright on the second oil pan member 160, which defines the oil flow path 200 as will be described later.

  Therefore, a configuration relating to the arrangement of the oil flow path 200 defined by the partition wall 190, the discharge port 176 from the scavenge pump 170, and the suction port of the oil strainer 181 of the feed pump 180 will be described with reference to FIG. 3A is a perspective view showing a state before the second oil pan member 160 constituting the lower portion of the oil tank 165 is attached to the crankcase 120 and the chain cover 111, and FIG. FIG. 3 is a perspective view from the lower surface of the oil tank 165.

  In this embodiment, the four corners of the oil tank 165 whose basic shape is substantially rectangular in plan view are curved inward, and a recess 166 for attaching the oil filter 195 is formed evenly. And the partition wall 190 is comprised from four 1st partition walls 190A thru | or 4th partition wall 190D from which the adjacent member cross | intersects substantially at right angles mutually. One end portion of the first partition wall 190A is disposed with a slight gap between the first partition wall 190A and the inner wall of the recess 166, and the end portion of the fourth partition wall 190D and one end portion of the first partition wall 190A In between, the inlet 204 to the central chamber 202 where the oil strainer 181 of the feed pump 180 is disposed is formed. The upper ends of the four first partition walls 190A to 190D abut against the lower surface of the first oil pan member 150 when the second oil pan member 160 is attached to the crankcase 120. Thus, in FIGS. 3A and 3B, a substantially spiral oil flow path 200 is formed with the solid arrow as the main stream line and the above-described central chamber 202 as the downstream end.

  The discharge port 176 from the scavenge pump 170 is arranged on the upstream side of the oil flow path 200, and the discharge direction is indicated by a solid arrow as shown by a white arrow in FIG. The oil flow path 200 is directed in the same direction as the main flow line.

  Next, the general operation of the embodiment configured as described above will be described. During operation of the engine 100, the oil in the oil tank 165 is sucked up by the feed pump 180 through the oil strainer 181, and is supplied to the supply passage formed in the crankcase 120 or the cylinder block 110 through the oil filter 195. The Then, the oil supplied to the lubricated part or the hydraulic operating part is then collected in the oil receiving part 155 inside the crankcase 120 according to the gravity. Further, the oil collected in the oil receiving portion 155 is sucked into the scavenge pump 170 through the oil strainer 171 together with other blow-by gas, and the oil defined by the partition wall 190 standing on the bottom surface of the oil tank 165. The ink is discharged from the discharge port 176 disposed on the upstream side of the flow path 200.

  This discharged oil flows through the oil flow path 200 along the main flow line indicated by the solid arrow, and reaches the central chamber 202 through the inlet 204. Thereafter, the oil is drawn into the feed pump 180 via the oil strainer 181 that is a suction port disposed in the central chamber 202 that is the downstream end of the oil flow path 200, and is again supplied into the engine 100 by the feed pump 180. .

  At this time, when air bubbles are mixed in the oil discharged from the scavenge pump 170, the discharge port 176 from the scavenge pump 170 disposed on the upstream side of the oil flow path 200 and the downstream end of the oil flow path 200 This bubble is effectively degassed when passing through a relatively long path between the oil strainer 181 of the feed pump 180 disposed in The defoamed bubbles gather in the space 125 above the oil level OL in the oil tank 165, and return again to the inside of the crankcase through the communication hole. Thus, it is prevented that the bubble-containing oil discharged from the scavenge pump 170 is directly sucked into the feed pump 180, and it takes a considerable time to pass through the oil passage 200 of a relatively long path. Supply of oil mixed with bubbles by the feed pump 180 is suppressed. Note that a gas-liquid separator 400 may be provided at the discharge port 176 from the scavenge pump 170 as shown in FIG. 4 to promote the defoaming of bubbles mixed in the oil.

  Next, the oil circulation system in the present embodiment will be described with reference to FIG. In the present embodiment, first, oil sucked from the oil tank 165 by the feed pump 180 via the oil strainer 181 is pressure-fed to the main oil hole 210 formed in the cylinder block 110 via the oil filter 195. Is done. As a first supply system, oil is sent from the main oil hole 210 to the cylinder head 130 via a supply passage formed in the cylinder block 110, and the intake / exhaust camshaft journal 220 and the variable intake valve timing mechanism VVT. -I oil control valve OCV230. At the same time, the oil is sent from the main oil hole 210 through the cylinder head 130 to the chain tensioner 240 and also sent to the oil jet 250 formed in the cylinder block 110 and supplied to the timing chain 117 by injection.

  On the other hand, as a second supply system, the oil is sent from the main oil hole 210 to the journal 260 of the crankshaft 112 in the cylinder block 110, and to the crankpin 270 which is a connecting portion with the connecting rod 118 via the journal. Supplied. At the same time, it is sent to the oil jet 280 through the journal 260 of the crankshaft 112 and is supplied to the lower surface of the piston 116 by injection. After the oil sent to the second supply system is used for lubrication of the respective supply points, the oil naturally falls on the bottom wall 127 and the main oil receiving portion 155 at the lower part of the crankcase 120, and finally Is recovered by the main oil receiving portion 155 formed of the first oil pan member 150.

  On the other hand, as a return system of the oil pressure-fed by the feed pump 180 to the oil tank 165 in this manner, the scavenge pump 170 pumps up and transfers the oil from the main oil receiving portion 155 collected as described above. A first return path and a second return path through which oil supplied to the cylinder block 110 or the cylinder head 130 of the engine body 100 is directly returned to the oil tank 165 are provided. The second return path will be described in more detail. In the present embodiment, an oil return passage 300 formed in the chain cover 111 through which the oil supplied to the chain tensioner 240 and the timing chain 117 circulates is described. One of them is configured. The other of the second return paths is an oil return passage 119 formed in the cylinder block 110 for returning the oil from the cylinder head 130 by natural fall, and a crankcase 120 for communicating with the oil return passage 119. The communication path 128 is formed in the upper portion so as to open to the space 125.

  Then, from the main oil hole 210 to the cylinder head 130, the flow rate ratio of the oil returned to the oil tank 165 from the first return path and the second return path is, for example, about 7 to 3. The flow resistance of the first supply system sent to the oil jet 250 and the flow resistance of the second supply system in the cylinder block 110 are set, and the discharge capacities of the feed pump 180 and the scavenge pump 170 are set. Is set. Specifically, the oil supplied to the first supply system is returned to the oil tank 165 by natural fall through the second return path as described above, and the oil supplied to the second supply system is the crankcase. 120 naturally falls on the bottom wall 127 of the lower part of 120 and the main oil receiving part 155 and is collected in the main oil receiving part 155, and finally returned to the oil tank 165 by the scavenge pump 170 via the first return path. The discharge capacity of the scavenge pump 170 is about 70% of the discharge capacity of the feed pump 180. In other words, the rated discharge capacity ratio between the scavenge pump 170 and the feed pump 180 is about 0.7. According to this embodiment, the power for driving the scavenge pump 170 can be reduced as compared with the conventional dry sump system in which the total amount of oil supplied into the engine is returned to the oil tank 165 by the scavenge pump 170. 100 fuel efficiency can be improved.

  Here, in the present embodiment, the second return path is formed in the chain cover 111 so as to open to the space 125 in the oil return passage 300 and / or the crankcase 120 formed from the cylinder head. A communication path 128 is formed in the cylinder block 110 and communicates with the oil return path 119 from the cylinder head 130. As a result, oil can be returned directly to the oil tank 165 by using gravity without using the scavenge pump 170, and the power loss for driving the scavenge pump 170 can be effectively reduced. . Therefore, the power for driving the scavenge pump 170 in the low-speed rotation region of the engine having a relatively small oil stirring resistance while enjoying the advantages of the dry sump lubrication method in the high-speed rotation region of the engine in which the power loss due to the oil stirring resistance is larger. The fuel consumption performance of the engine can be improved by reducing the loss.

  Furthermore, the discharge capacity of the scavenge pump 170 may be smaller than the discharge capacity of the feed pump 180, which is advantageous in terms of cost.

It is a longitudinal cross-sectional schematic diagram which shows embodiment in which the engine lubricating device which concerns on this invention was integrated. 1 is a schematic cross-sectional view showing an embodiment in which a lubricating device for an engine according to the present invention is integrated. In the embodiment of the engine lubricating device according to the present invention, (A) is a perspective view showing a state before the second oil pan member constituting the lower portion of the oil tank is attached, and (B) is an oil It is a perspective view from the lower surface of a tank. It is a block diagram which shows the circulation system of the oil in embodiment of the lubricating apparatus of the engine which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Engine main body 110 Cylinder block 111 Chain cover 112 Crankshaft 113 Driven gear 114 Balance shaft 115 Drive gear 116 Piston 118 Connecting rod 119 Oil return passage 120 Crankcase 121 Front wall 122 Rear wall 123 Inner side wall 124 Outer side wall 125 Space part 127 Bottom wall 129 Opening portion 130 Cylinder head 140 Head cover 150 First oil pan member 155 Main oil receiving portion 160 Second oil pan member 165 Oil tank 170 Scavenge pump 171 Oil strainer 174 Discharge pipe 176 Discharge port 180 Feed pump 181 Oil strainer 190 Partition Wall 200 Oil flow path

Claims (7)

A dry sump lubrication system comprising an oil receiving portion formed at the lower part of the engine, a scavenge pump for transferring oil in the oil receiving portion to an oil tank, and a feed pump for supplying oil stored in the oil tank into the engine. An engine lubrication device,
A crankcase formed such that at least both sides parallel to the crankshaft axis are provided with an inner wall and an outer wall, and a space that is open between both of them.
A first oil pan member attached to the lower surface of the inner wall of the crankcase and forming the oil receiving portion;
A second oil pan member attached to a lower surface of the outer wall of the crankcase and covering the first oil pan member from below while having a predetermined distance and constituting the oil tank together with the space portion; ,
An engine lubrication device comprising:   The lower end portion of the inner side wall on both sides of the crankcase is partially connected by a bottom wall, and the remaining portion forms an opening to which the first oil pan member is attached. Item 2. The engine lubricating device according to Item 1.   A partition wall defining an oil passage is provided between the first oil pan member and the second oil pan member, and a discharge port from the scavenge pump is opened near the start end of the oil passage, 3. The engine lubrication device according to claim 1, wherein an oil strainer suction port of the feed pump is opened near a terminal portion of the oil passage. 4.   4. The engine lubrication device according to claim 3, wherein the oil passage is formed in a substantially spiral shape.   The oil return system to the oil tank has a first return path that is transferred by the scavenge pump, and a second return path that directly returns the oil supplied into the engine. The engine lubrication device according to any one of claims 1 to 4.   The second return path is formed from an oil return passage formed in the chain cover from the cylinder head and / or a cylinder head formed in the crankcase so as to open to the space portion and formed in the cylinder block. The engine lubrication device according to claim 5, comprising a communication passage communicating with the oil return passage.   The engine lubrication device according to any one of claims 1 to 5, wherein a discharge capacity of the scavenge pump is smaller than a discharge capacity of the feed pump.

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