JP2023016515A - Oil passage structure for engine - Google Patents

Abstract

To provide an oil passage structure for an engine capable of suppressing an increase in an oil temperature.SOLUTION: In an oil passage structure for an engine 1, oil stored in an oil pan 30 disposed on the lower side of a cylinder block 3 of an engine body 10 is transported and supplied to lubricated parts 17, 18 by using an oil pump 31 and then is returned to the oil pan 30 for circulation. The oil passage structure includes an oil return passage 22 provided in the engine body 10 to return oil from a cylinder head 4 side of the engine body 10 to the oil pan 30. The oil return passage 22 includes an orifice 50 for temporarily storing oil in a predetermined region 43a of the oil return passage 22 located adjacent to a cooling part 19 of the engine body 10.SELECTED DRAWING: Figure 3

Description

The present invention relates to an oil passage structure for an engine mounted on a vehicle such as an automobile.

Generally, an engine mounted on a vehicle sucks out oil stored in an oil pan provided on the lower side of a cylinder block of the engine by an oil pump, and lubricates parts of the engine (e.g., cylinders, pistons, etc.). , cams, etc.).

The oil supplied to the parts to be lubricated lubricates the parts to be lubricated, receives (absorbs) heat such as frictional heat from the parts to be lubricated, and is returned to the oil pan through the oil return passage provided in the engine body. be

The temperature of the oil supplied to the lubricated portion may rise due to heat received from the lubricated portion depending on the temperature of the lubricated portion. In this case, it is preferable to cool the oil because the viscosity of the oil decreases due to the temperature rise of the oil and the lubricity decreases.

Patent Literature 1 discloses an engine oil return passage structure formed in a cylinder block having cylinders and a cylinder head arranged on the upper surface thereof. The oil return passage includes a head-side return passage and a block-side return passage formed in the cylinder head and the cylinder block and communicating with each other.

The block-side return passage is provided outside a water jacket as a cooling portion that surrounds the cylinders of the cylinder block. A plurality of fins, etc. are provided on the inner side of the water jacket side at the top of the block side return passage, and the cooling water of the water jacket is used to promote the heat dissipation of the oil passing through the oil return passage and suppress the temperature rise of the oil. is configured as

JP 2019-148227 A

When using low-viscosity oil with a lower upper limit temperature than oil with normal viscosity for the purpose of improving fuel efficiency, or when eliminating the oil cooler for the purpose of reducing costs and the number of parts, the temperature rise of the oil itself is minimized. Further suppression is required.

The present invention provides an engine oil passage structure capable of suppressing an oil temperature rise.

The present invention is an engine oil passage structure in which oil stored in an oil pan arranged below a cylinder block of an engine body is transported by an oil pump, supplied to a lubricated part, and then returned to the oil pan for circulation. and
An oil return passage provided in the engine body and for returning oil from the cylinder head side of the engine body to the oil pan,
The oil return passage provides an engine oil passage structure having an orifice for temporarily storing oil in a predetermined region of the oil return passage adjacent to a cooling portion provided in the engine body.

According to the present invention, the oil can be temporarily stored in the predetermined region adjacent to the cooling section when the flow rate of the oil flowing into the predetermined region of the oil return passage is greater than the flow rate of the oil flowing out from the orifice. Therefore, compared with the case where the oil passes through the predetermined area without being stored, the heat dissipation to the oil return passage wall is promoted, and the temperature rise of the oil can be suppressed.

When the oil is stored in the predetermined region of the oil return passage, the predetermined region is filled with oil, so heat dissipation to the oil return passage wall is promoted compared to the case where the oil return passage is partially filled with oil. .

As a result, for example, it is possible to improve fuel efficiency by using low-viscosity oil with a low upper temperature limit, and to reduce costs by eliminating an oil cooler.

Preferably, the orifice is provided below the predetermined area.

According to this configuration, more oil can be stored in the predetermined area than when the orifice is provided in the middle or upper portion of the predetermined area, and more oil heat is radiated to the oil return passage wall. can suppress the temperature rise of the oil.

The oil return passage comprises a first return passage with the orifice and a second return passage,
the first return passage and the second return passage are arranged in parallel with each other,
The first return passage may be located closer to the cooling section than the second return passage.

According to this configuration, the second return passage is provided on the outer wall side of the engine body, which is the side opposite to the cooling portion side of the first return passage in which the oil is temporarily stored. When a heat source such as an exhaust pipe is arranged in the first return passage, it is possible to prevent the oil stored in the first return passage from receiving heat from the outer wall side of the engine body.

The engine body is provided with a water jacket for flowing cooling water from a water pump,
The cooling unit may be composed of the water jacket.

According to this configuration, since the oil return passage is arranged in the predetermined region adjacent to the water jacket, the oil return passage wall is cooled by the cooling water flowing through the water jacket. As a result, the heat dissipation of the oil is promoted, and the temperature rise of the oil can be suppressed.

According to the engine oil passage structure of the present invention, it is possible to suppress the temperature rise of the oil.

1 is a schematic diagram showing the configuration of an engine according to a first embodiment of the present invention; FIG. It is a schematic diagram showing an oil supply passage of the engine concerning a 1st embodiment of the present invention. 1 is a cross-sectional view showing an oil passage of an engine according to a first embodiment of the invention; FIG. FIG. 4 is another cross-sectional view showing the oil passage of the engine according to the first embodiment of the present invention; FIG. 4 is a schematic cross-sectional view of an oil return passage indicated by an arrow V in FIG. 3; FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5; FIG. 4 is a cross-sectional view showing a state in which the amount of oil flowing into the upper return passage is greater than the amount of oil flowing out of the orifice; FIG. 5 is a schematic cross-sectional view of an oil return passage in a second embodiment of the invention; FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8; FIG. 4 is a cross-sectional view showing a state in which the amount of oil flowing into the upper return passage is greater than the amount of oil flowing out of the orifice;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

The oil passage structure of the present invention is applied to the engine 1. As shown in FIG. As shown in FIG. 1, an engine 1 according to an embodiment of the present invention is a so-called transverse type engine 1 which is mounted on a vehicle such as an automobile and has a crankshaft extending in the width direction of the vehicle body. The engine 1 includes an engine body 10 , and the engine body 10 includes a cylinder block 3 in which cylinders 2 are formed, and a cylinder head 4 arranged on the cylinders 2 .

A piston 5 is arranged in the cylinder 2 so as to be able to reciprocate. The piston 5 is connected via a connecting rod 7 to a crankshaft 6 rotatably supported at the bottom of the cylinder block 3 , so that the reciprocating motion of the piston 5 is converted into the rotational motion of the crankshaft 6 .

An intake port 15 and an exhaust port 16 are formed in the cylinder head 4 . Each cylinder 2 is provided with two intake ports 15 and an exhaust port 16, and the two intake ports 15 and exhaust ports 16 are provided separately in the axial direction of the crankshaft 6a orthogonal to the central axis 2a of the cylinder 2. ing.

The cylinder head 4 is provided with an intake valve and an exhaust valve (not shown) for opening and closing the intake port 15 and the exhaust port 16, respectively. The intake valve opens and closes the intake port 15 at a predetermined timing by an intake camshaft 17 drivingly connected to the crankshaft 6 to supply air to the combustion chamber 8 during the intake stroke. The exhaust valve opens and closes the exhaust port 16 at a predetermined timing by an exhaust camshaft 18 drivingly connected to the crankshaft 6, and discharges exhaust gas from the combustion chamber 8 during the exhaust stroke.

A water jacket 19 serving as a cooling portion through which cooling water flows is provided in the cylinder block 3 so as to surround the cylinder 2 on the outer circumference of the cylinder 2 . The water jacket 19 has a closed-loop structure that surrounds the radially outer side of the two rows of cylinders. Water jacket 19 is formed to open upward. The water jacket 19 has a portion that enters between the cylinders 2 .

Portions of the water jacket 19 positioned on both sides across the axial direction of the crankshaft 6a are formed continuously with arcuate portions that partially surround the cylinder 2 . The water jacket 19 is formed with a depth that extends downward from the upper end of the cylinder block 3 to the vicinity above a main gallery 37a, which will be described later.

In this embodiment, the cylinder block 3 includes an upper cylinder block 3a and a lower cylinder block 3b located below the upper cylinder block 3a. An oil pan 30 for storing oil for lubricating parts to be lubricated such as the piston 5, the crankshaft 6, the camshafts 17 and 18 is arranged at the lower end of the cylinder block lower 3b.

In this embodiment, as shown in FIG. 1, the engine 1 is mounted on the vehicle body frame in a state in which the central axis 2a of the cylinder 2 extends in a direction inclined by a predetermined angle θ1, such as 10 degrees, from the vertical direction toward the exhaust side. is supported by and mounted on the vehicle.

As shown in FIGS. 2 to 4, the engine 1 is provided with an oil passage 20 for circulating oil for lubricating the parts to be lubricated (piston 5, crankshaft 6, camshafts 17, 18, etc.). The oil passage 20 has an oil supply passage 21 for supplying oil to the lubricated portion and an oil return passage 22 for returning the oil supplied to the lubricated portion to the oil pan.

The oil supply passage 21 includes an oil pump 31 for sucking up the oil stored in the oil pan 30, an oil filter 32 for filtering the oil discharged from the oil pump 31, and an oil for cooling the oil discharged from the oil pump 31. A cooler 33 and a supply oil passage 35 provided in the engine body 10 are provided.

The supply oil passage 35 includes a first supply oil passage 36 provided on the oil pan 30 side, a second supply oil passage 37 provided in the cylinder block, and a third supply oil passage 38 provided in the cylinder head 4 . , a first communication oil passage 39 that connects the first supply oil passage 36 and the second supply oil passage 37, and a second communication oil passage 40 that connects the second supply oil passage 37 and the third supply oil passage 38. Prepare.

As shown in FIGS. 1 and 2, the oil pump 31 is driven by the crankshaft 6, and the oil discharged from the oil pump 31 flows through the first supply oil passage 36 into the oil filter 32 where it is filtered. After that, it flows into the oil cooler 33 and is cooled. Oil cooled by the oil cooler 33 is supplied to the second supply oil passage 37 of the cylinder block 3 through the first communication oil passage 39 .

As shown in FIGS. 1 to 3, the first supply oil passage 36 includes an oil passage 36a provided in the oil pan 30 and connecting the oil pump 31 and the oil filter 32, and a side surface of the oil pan 30 on the exhaust side. and an oil passage 36b that connects the oil filter 32 and the oil cooler 33, and an oil passage 36c that extends upward from the oil cooler 33 and is connected to a first communication oil passage 39 provided in the cylinder block. Prepare.

As shown in FIGS. 2 and 3, the first communication oil passage 39 is provided in the lower cylinder block 3b, opens to the exhaust side, and extends in the radial direction of the cylinder 2 (the width direction of the engine body 10). an oil passage 39b extending upward from a radially inner end of the oil passage 39a to open the cylinder block lower 3b upward; and an oil provided in the cylinder block upper 3a and communicating with the oil passage 39b and extending upward. path 39c.

The second supply oil passage 37 includes a main gallery 37a to which an oil passage 39c is connected and extending in the direction of the row of cylinders, and a main gallery 37a branched from the main gallery 37a and extending downward toward the crankshaft 6a to supply lubrication to the crankshaft 6. and a plurality of branched oil passages 37b for supplying oil to the parts.

The main gallery 37 a is located near the lower end of the cylinder 2 on the exhaust side of the cylinder block 3 in the width direction of the cylinder block 3 perpendicular to the row direction of the cylinders. A downstream end of each of the plurality of branched oil passages 37 b opens toward the crankshaft 6 a of the cylinder block 3 .

As shown in FIGS. 2 and 4 , the second supply oil passage 37 further includes an oil passage 37 c that branches from one end of the main gallery 37 a and extends in the width direction to communicate with the second communication oil passage 40 . Prepare.

The second communication oil passage 40 is provided in the cylinder block upper 3a and communicates with the oil passage 40a extending upward from the main gallery 37a side end of the oil passage 37c and the oil passage 40a provided in the cylinder head 4. and an oil passage 40b extending upward.

The third supply oil passage 38 includes an oil passage 38a extending from the upper end of the oil passage 40b to both sides in the width direction, a pair of oil passages 38b extending upward from the exhaust side and the intake side of the oil passage 38a, and a cylinder row extending from the oil passage 38b. and a head-side gallery 38c extending in the direction. The head-side gallery 38c includes a plurality of branched oil passages 38d formed to supply oil from the head-side gallery 38c to the cam journals on the intake side and the exhaust side of the camshafts 17 and 18, respectively.

In addition to the configuration described above, the oil supply passage 21 is formed, for example, to supply oil to an oil jet or the like for cooling the piston.

The oil supplied to the parts to be lubricated of the engine 1 through the oil supply oil passage 21 is returned to the oil pan 30 through the oil return passage 22 after cooling and lubricating the parts to be lubricated.

As shown in FIG. 3, the oil return passage 22 includes a plurality of exhaust-side return passages 41 through which the oil supplied to the camshafts 17 and 18, which are lubricated portions, is divided into the exhaust port 16 side and the intake port 15 side. An intake side return passage 45 is provided. The exhaust-side return passage 41 and the intake-side return passage 45 include head-side return passages 42 and 46 provided in the cylinder head 4 and block-side return passages 43 and 47 provided in the cylinder block 3 . Since the exhaust-side return passage 41 and the intake-side return passage 45 have the same configuration, the exhaust-side return passage 41 will be described.

The head-side return passage 42 is formed in a substantially circular shape and extends vertically. A plurality of head-side return passages 42 are provided on the exhaust side of the cylinder head 4 and communicate with the block-side return oil passage 43 . The head-side return passage 42 is arranged between the cylinders 2 at a position offset from each cylinder 2 in the cylinder row direction.

The block-side return passage 43 includes upper-side passages 43a and 43b formed in a substantially circular shape and extending vertically from the upper end to the lower end of the cylinder block upper 3a, and extending downward from the upper end of the cylinder block lower 3b to the oil pan 30. It has an open lower side passage 43f.

The upper return passages 43a and 43b include an upper return passage 43a positioned above the cylinder block upper 3a and a lower return passage 43b positioned below the cylinder block upper 3a.

The upper return passage 43 a is adjacent to the water jacket 19 and provided along the water jacket 19 . The upper return passage 43 a extends from the upper end of the cylinder block 3 to near the lower end of the water jacket 19 . The upper return passage 43 a is formed to have approximately the same depth as the water jacket 19 .

The upper return passage 43a is located between the arcuate portions of the water jacket 19 and outside the portion that enters between the cylinders. The upper return passage 43a is arranged between the cylinders 2 at a position shifted from each cylinder 2 in the cylinder row direction.

The lower return passage 43b is adjacent to the outside of the oil passage 39c of the first communication oil passage 39 of the oil supply passage 21 and is provided along the oil passage 39c. The lower return passage 43b extends from the vicinity of the main gallery 37a to the lower end of the cylinder block upper 3b.

The upper return passage 43a and the lower return passage 43b are offset in the width direction position orthogonal to the cylinder row direction, and the lower return passage 43b is arranged closer to the outer wall side of the engine body 10 than the upper return passage 43a. ing. A radial oil passage 43c is provided between the upper return passage 43a and the lower return passage 43b to allow the upper return passage 43a and the lower return passage 43b to communicate with each other.

The radial oil passage 43c has a substantially circular shape and extends from the outer wall portion of the cylinder block 3 toward the lower side of the water jacket 19 in a direction perpendicular to the upper return passage 43a and the lower return passage 43b. The lower end of the upper return passage 43a communicates with the radial oil passage 43c, and the upper end of the lower return passage 43b communicates with the radial oil passage 43c. They are communicated via a directional oil passage 43c.

The lower side passage 43f extends vertically from the upper end toward the lower end of the cylinder block lower 3b. The lower side passage 43f is formed to communicate with the lower return passage 43b and open to the oil pan 30. As shown in FIG.

When the engine 1 starts operating, the oil pump 31 is driven as the crankshaft 6 rotates. 2, the oil pump 31 sucks the oil stored in the oil pan 30 from the suction port 31a of the oil pump 31, and feeds the sucked oil through the first supply oil passage 36, The lubricant is supplied to the parts to be lubricated in the engine body 10 through the first communication oil passage 39 , the second supply oil passage 37 , the second communication oil passage 40 and the third supply oil passage 38 in order.

The oil supplied to the parts to be lubricated in this way lubricates the parts to be lubricated through the oil supply oil passage 21, and absorbs heat such as frictional heat generated during the operation of the parts to be lubricated. is returned to the oil pan 30 via the

Since the oil flowing into the oil return passage 22 is warmed by absorbing heat such as frictional heat generated during the operation of the lubricated portion, the oil returns to the upper return passage provided adjacent to the water jacket 19. The heat of the oil is dissipated in 43 a to cool the oil, and the oil is returned to the oil pan 30 .

Since the amount of oil supplied to the lubricated parts and flowing into the oil return passage 22 is roughly proportional to the rotation speed of the oil pump 31, when the engine 1 rotates at a low speed below a predetermined rotation speed, the oil returns to the oil return passage 22. The amount of oil flowing into the engine 1 becomes a low oil flow rate state, which is smaller than that at a high engine speed when the engine 1 is at or above a predetermined engine speed.

When the oil flow rate is low, the amount of oil flowing down the upper return passage 43a is small, and the oil flowing down the upper return passage 43a may not come into contact with the inner wall of the upper return passage 43a. is provided with an engine oil passage structure for dissipating the heat of the oil into the upper return passage 43a even at a low oil flow rate by contacting the oil with the wall portion of the upper return passage 43a.

FIG. 5 shows a schematic cross-sectional view of an oil return passage in an embodiment of the invention. As shown in FIG. 5, the block-side return passage 42 is provided with an orifice 50 that restricts the flow of oil and temporarily stores the oil. More specifically, the orifice 50 is provided in the upper return passage 43a, which is a predetermined region having a lower temperature than the head-side return passage 42 and the lower return passage 43b, by being adjacent to the water jacket 19 as a cooling portion.

The orifice 50 is provided near the lower end of the water jacket 19 under the upper return passage 43a. In this embodiment, the orifice 50 is provided in the upper return passage 43a at a boundary with the radial oil passage 43c.

The cylinder-side return passage 43 is provided with a vertical partition wall 44 that vertically partitions the upper return passage 43a and the radial oil passage 43c. , the upper return passage 43a and the radial oil passage 43c are communicated with each other. The upper return passage 43a communicates with the lower return passage 43b via the orifice 50 and the radial oil passage 43c. The orifice 50 is provided along the wall of the upper return passage 43a on the water jacket 19 side.

As shown in FIG. 6, the orifice 50 is formed by an opening having a semicircular cross section. A cross-sectional area S1 of the orifice 50 is set smaller than a cross-sectional area S of the upper return passage 43a. In this embodiment, for example, the channel cross-sectional area S1 of the orifice 50 is set to be about 1/5 of the cross-sectional area S of the upper return passage 43a.

As a result, as shown in FIG. 7, when the flow rate of oil flowing out of the orifice 50 is smaller than the flow rate of oil flowing into the upper return passage 43a, the oil is temporarily stored in the upper return passage 43a. A dwell time will be provided.

With the above configuration, when the flow rate of oil flowing into the upper return passage 43a is greater than the flow rate of oil flowing out of the orifice 50, the oil flows through the upper return passage 43a as a predetermined area adjacent to the water jacket 19 as a cooling portion. can be temporarily stored, the heat dissipation of the oil to the wall of the upper return passage 43a is accelerated and the temperature rise of the oil can be suppressed, compared to the case where the oil passes through the predetermined area without being stored. .

When oil is stored in the upper return passage 43a, the upper return passage 43a is filled with oil. heat dissipation is promoted.

As a result, for example, it is possible to improve fuel efficiency by using low-viscosity oil with a low upper temperature limit, and to reduce costs by eliminating an oil cooler.

Since the orifice 50 is provided in the lower portion of the upper return passage 43a, more oil can be stored in the upper return passage 43a than when the orifice 50 is provided in the middle or upper portion of the upper return passage 43a. As a result, more oil heat is radiated to the wall of the upper return passage 43a, and an increase in oil temperature can be suppressed.

8 to 10 are cross-sectional views of an oil return passage according to a second embodiment of the invention. The oil return passage of the engine according to the second embodiment is the same as the oil return passage of the engine according to the first embodiment, except that the upper return passage is different, so the description of the same configuration will be omitted.

As shown in FIG. 8, the cylinder block 3 according to the second embodiment is formed with an upper return passage 43a adjacent to the water jacket 19 as a cooling portion of the cylinder block 3, as in the first embodiment. .

In this embodiment, the upper return passage 43a consists of a first return passage 44a located on the water jacket 19 side and a second return passage 44b located closer to the outer wall side (exhaust side) of the cylinder block 3 than the first return passage 44a. and In this embodiment, the first return passage 44a and the second return passage 44b are partitioned by providing a dividing wall 44c that divides the upper return passage 43a in the width direction at the center of the upper return passage 43a in the width direction. formed. As shown in FIG. 9, the first return passage 44a and the second return passage 44b have a substantially semicircular cross section. It should be noted that the first return passage and the second return passage are not limited to the above configuration, and are formed by, for example, two cylindrical passages arranged side by side in the radial direction of the cylinder 2 perpendicular to the cylinder row. may be

In this embodiment, as shown in FIG. 8, an orifice 60 is provided in the lower portion of the first return passage 44a, like the upper return passage 43a of the first embodiment. No orifice is provided in the second return passage 44b.

The orifice 60 is configured by an opening that penetrates the vertical partition wall 44 in the vertical direction and communicates the upper return passage 43a and the radial oil passage 43c. The upper return passage 43a communicates with the lower return passage 43b via the orifice 50 and the radial oil passage 43c. The orifice 50 is provided along the wall of the upper return passage 43a on the water jacket 19 side.

As shown in FIG. 9, the orifice 60 is formed by an opening having a semicircular cross section. A cross-sectional area S1 of the orifice 60 is set smaller than a cross-sectional area S of the upper return passage 43a. In this embodiment, for example, the channel cross-sectional area S1 of the orifice 50 is set to be about 1/5 of the cross-sectional area S of the upper return passage 43a. In this embodiment, the dividing wall 44c that separates the first return passage 44a and the second return passage 44b is provided in the center of the upper return passage 43a, so that the passage cross-sectional area S1 of the orifice 50 is equal to that of the first return passage 44b. The cross-sectional area of the passage 44a is about 2/5 of the cross-sectional area S2 of the passage 44a.

As a result, as shown in FIG. 10, when the flow rate of oil flowing out of the orifice 50 is lower than the flow rate of oil flowing into the upper return passage 43a, the oil is temporarily stored in the upper return passage 43a. A residence time is provided to facilitate the dissipation of heat from the oil to the oil return passage wall.

Furthermore, in the second embodiment, since the second return passage 44b is provided between the first return passage 44a and the outer wall of the engine body 10, when the exhaust pipe is arranged on the outer wall side of the engine body 10, As described above, the oil stored in the first return passage 44a can be prevented from receiving heat from the outer wall heated by the heat of the exhaust pipe, and further, the temperature rise of the oil can be suppressed.

The present invention is not limited to the illustrated embodiments, and various improvements and design changes are possible without departing from the gist of the invention.

In the present embodiment, the configuration in which the orifice 50 is provided in each of the plurality of upper return passages 43a has been described, but the configuration is not limited to this, and the orifice 50 is provided in at least one of the plurality of upper return passages 43a. It is good if there is

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to provide an engine oil passage structure capable of suppressing an increase in temperature of oil, so that it may be preferably used in the engine manufacturing industrial field.

1 Engine 3 Cylinder Block 4 Cylinder Head 5 Piston 6 Crankshaft 10 Engine Body 17 Intake Camshaft 18 Exhaust Camshaft 19 Water Jacket 20 Oil Passage 22 Oil Return Passage 30 Oil Pan 31 Oil Pump 43a Upper Return Passage 44a First Return Passage 44b Second return passage 50 Orifice 60 Orifice

Claims (4)

An oil passage structure for an engine in which oil stored in an oil pan arranged below a cylinder block of an engine body is transported by an oil pump, supplied to a lubricated part, and then returned to the oil pan for circulation,
An oil return passage provided in the engine body and for returning oil from the cylinder head side of the engine body to the oil pan,
An oil passage structure for an engine, wherein the oil return passage includes an orifice for temporarily storing oil in a predetermined region of the oil return passage adjacent to a cooling portion provided in the engine body. 2. The engine oil passage structure according to claim 1, wherein said orifice is provided below said predetermined area. The oil return passage comprises a first return passage with the orifice and a second return passage,
the first return passage and the second return passage are arranged in parallel with each other,
3. The engine oil passage structure according to claim 1, wherein the first return passage is located closer to the cooling portion than the second return passage. The engine body is provided with a water jacket for flowing cooling water from a water pump,
4. The engine oil passage structure according to any one of claims 1 to 3, wherein the cooling portion is configured by the water jacket.

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