JP2023032898A - Engine oil passage structure - Google Patents

Abstract

To provide an engine oil passage structure capable of curbing an increase in an oil temperature.SOLUTION: An oil passage structure of an engine 1, for circulating oil stored in an oil pan 30 arranged beneath a cylinder block 3 of an engine body 10 with an oil pump 31 in a manner that transfers and supplies the same to a lubricated section and returns the same to the oil pan 30, comprises a head side oil return passage 42 which is installed on a cylinder head of the engine body 10 and allows the oil to be returned from the cylinder head 4 to the oil pan 30. An inner peripheral surface of the head side oil return passage 42 has a wettability changing section in which wettability with respect to the oil is changed in a flow direction of the head side oil return passage 42 so as to enhance an oil flow on the inner peripheral surface.SELECTED DRAWING: Figure 4

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 under a cylinder block of the engine by an oil pump. It is configured to be supplied to the part to be lubricated.

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

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 a plurality of cylinders and a cylinder head disposed on the upper surface of the cylinder block and forming a combustion chamber together with a piston. . The oil return passage includes a head-side return passage and a block-side return passage that are formed in the cylinder head and the cylinder block, respectively, and communicate with each other.

A water jacket for circulating cooling water for cooling the cylinder is provided on the radially outer side of the cylinder of the cylinder block so as to surround the outer periphery of the cylinder. The block-side return passage is provided outside the water jacket in the cylinder radial direction and extends vertically. A plurality of fins are provided on the inner surface of the block-side return passage on the water jacket side, and the cooling water flowing in the water jacket is used to promote the heat dissipation of the oil passing through the oil return passage, thereby raising the oil. temperature is controlled.

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.

An object of the present invention is to provide an engine oil passage structure capable of suppressing an increase in oil temperature.

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. a head-side oil return passage provided in the cylinder head of the engine body for returning oil from the cylinder head side to the oil pan;
The inner peripheral surface of the head-side oil return passage has a wettability changing portion that changes the wettability with respect to oil in the direction of the flow path of the head-side oil return passage to promote the flow of oil flowing along the inner peripheral surface. To provide an engine oil passage structure having

According to the present invention, the wettability changing portion can change the wettability with respect to oil in the head-side oil return passage in the flow direction of the head-side oil return passage. By moving oil from the upstream side to the downstream side of the head-side oil return passage, the flow of oil flowing toward the downstream side of the head-side oil return passage can be promoted. Retention time can be reduced.

Even when the cylinder head in which the head-side oil return passage is formed is warmed by the exhaust gas, the residence time of the oil in the head-side oil return passage can be reduced, and the oil is prevented from receiving heat from the cylinder head. Oil temperature rise can be reduced.

The wettability changing portion includes a plurality of concave portions formed on the inner peripheral surface of the head-side oil return passage such that the oleophilicity increases from the upstream portion toward the downstream portion of the head-side oil return passage. may

With this configuration, since a plurality of recesses are formed in the inner peripheral surface of the head-side oil return passage in the wettability changing portion, a relatively simple configuration formed by forming a plurality of recesses can improve the lipophilicity of the head-side oil return passage. It is possible to guide the oil to the downstream side of the head-side oil return passage by increasing the height from the upstream side to the downstream side of the passage and moving the oil from the upstream side to the downstream side of the head-side oil return passage. The retention time of oil in the side oil return passage can be reduced.

The cylinder head may be made of a metal material, and the plurality of recesses may be formed to become deeper from an upstream portion toward a downstream portion of the head-side oil return passage.

With this configuration, the plurality of recesses formed on the inner peripheral surface of the head-side oil return passage with a depth extending from the upstream side to the downstream side of the head-side oil return passage increases the lipophilicity of the head-side oil return passage upstream of the head-side oil return passage. from the side to the downstream side.

A layer made of a fluororesin material is provided on the inner peripheral surface of the head-side oil return passage. may be formed shallow.

With this configuration, a plurality of recesses formed on the inner peripheral surface of the head-side oil return passage with shallower depths from the upstream side of the head-side oil return passage toward the downstream side of the head-side oil return passage improve the lipophilicity of the head-side oil return passage upstream of the head-side oil return passage. from the side to the downstream side.

The cylinder head may be made of a metal material, and the plurality of recesses may be formed with a width that increases from an upstream portion toward a downstream portion of the head-side oil return passage.

With this configuration, a plurality of grooves formed on the inner peripheral surface of the head-side oil return passage with a large width from the upstream side to the downstream side of the head-side oil return passage provide lipophilicity to the upstream side of the head-side oil return passage. to the downstream side.

A layer made of a fluororesin material is provided on the inner peripheral surface of the head-side oil return passage, and the plurality of recesses increase in width from the upstream portion toward the downstream portion of the head-side oil return passage. may be formed.

With this configuration, a plurality of concave portions formed on the inner peripheral surface of the head-side oil return passage with a large width from the upstream side to the downstream side of the head-side oil return passage provide lipophilicity to the upstream side of the head-side oil return passage. to the downstream side.

The head-side oil return passage may be provided on the exhaust side of the cylinder head.

With this configuration, even when the engine body forming the head-side oil return passage is warmed by the exhaust gas, it is possible to reduce the retention time of the oil in the head-side oil return passage and prevent the oil from receiving heat from the cylinder head. It is suppressed, and the temperature rise of the oil can be reduced.

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 an embodiment of the invention; FIG. FIG. 2 is a cross-sectional view of the cylinder head taken along line II-II in FIG. 1; FIG. 2 is a cross-sectional view of a cylinder block taken along line III-III in FIG. 1; 1 is a cross-sectional view showing an oil passage of an engine according to an embodiment of the invention; FIG. 1 is a schematic diagram showing an oil supply passage of an engine according to an embodiment of the invention; FIG. FIG. 4 is another cross-sectional view showing the oil passage of the engine according to the embodiment of the present invention; FIG. 5 is a schematic cross-sectional view of a head-side oil return passage indicated by arrow VII in FIG. 4; FIG. 4 is an explanatory diagram for explaining wettability to oil; FIG. 8 is a diagram showing a modification of the head-side oil return passage shown in FIG. 7;

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

An oil passage structure according to an embodiment of the present invention is applied to an 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 vertical type engine 1 that is mounted on a vehicle such as an automobile and has a crankshaft 6a that extends in the front-rear direction. 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 .

The cylinder head 4 is made of a metal material such as an aluminum alloy. 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.

An intake passage (not shown) that supplies air to the combustion chamber 8 is connected to the intake port 15, and an exhaust passage (not shown) that discharges exhaust gas, which is combustion gas, from the combustion chamber 8 is connected to the exhaust port 16. ) is connected. A catalyst device 11 having a catalyst for purifying exhaust gas and an exhaust pipe 12 are connected to the exhaust passage. The catalyst device 11 and the engine 1 are arranged side by side in the width direction of the vehicle body.

Intake valves and exhaust valves for opening and closing the intake port 15 and the exhaust port 16, respectively, are arranged in the upper portion of the cylinder head 4, as indicated by the phantom lines. 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 head-side water jacket 14 through which cooling water circulates is formed inside the cylinder head 4 . A head-side water jacket 14 is provided above the combustion chamber 8 and between the intake port 15 and the exhaust port 16 in the cross section shown in FIG. The head-side water jacket 14 is formed to surround each combustion chamber 8 from above. The cylinder head 4 has a deck surface 4a above the head-side water jacket 14 in the vicinity of the substantially central portion of the cylinder head 4 in the vertical direction.

As shown in FIG. 2, the cylinder head 4 extends in the cylinder direction and has a rectangular shape in plan view. The deck surface 4a is provided with a boss portion 51 for mounting a spark plug (not shown) for each cylinder 2. As shown in FIG. The deck surface 4a is provided with an intake boss portion 52 and an exhaust boss portion 53 on the intake side and the exhaust side, respectively, with the boss portion 51 interposed therebetween. An intake valve is arranged on the intake boss portion 52 , and an exhaust valve is arranged on the exhaust boss portion 53 .

The deck surface 4a is provided with a plurality of head bolt insertion holes 54a for inserting head bolts (not shown) for attaching the cylinder head 4 to the cylinder block 3 so as to surround the cylinder 2 for each cylinder. On the deck surface 4a, head-side return passages 42 and 46, which will be described later, are provided on the side wall of the head bolt insertion hole 54a on the side opposite to the crankshaft.

As shown in FIG. 1, the cylinder head 4 includes an intake-side inclined surface 4b and an exhaust-side inclined surface 4c extending outward and upward from both sides of the deck surface 4a in the width direction orthogonal to the crankshaft, and the deck surface 4a. has a front surface portion 4d and a rear surface portion 4e rising from one end side and the other end side of the crankshaft (see FIG. 2). Concave portions for arranging the intake camshaft 17 and the exhaust camshaft 18 are provided in the front surface portion 4d and the rear surface portion 4e.

As shown in FIG. 1 , the exhaust-side inclined surface 4 c constitutes part of the inner surface of the side wall of the cylinder head 2 and is adjacent to the catalyst device 11 . The temperature of the deck surface 4c is higher than that of the deck surface 4a. A central portion of the deck surface 4a in the width direction is positioned above the head-side water jacket 14, and the central portion of the deck surface 4a is cooled more than both side portions of the deck surface 4a.

As shown in FIG. 3 , on the upper side of the cylinder block 3 , a cylinder-side water jacket 13 as a cooling portion through which cooling water flows is provided so as to surround the cylinder 2 radially outwardly of the cylinder 2 . The cylinder-side water jacket 13 has a closed-loop structure surrounding the radially outer side of the cylinders 2 of the cylinder train. The cylinder-side water jacket 13 is formed to open upward.

Portions of the cylinder-side water jacket 13 located on both sides across the axial direction of the crankshaft 6a include a plurality of arcuate portions 13a that partially surround the cylinders 2 and a plurality of recesses 13b that enter between the cylinders 2. have. In the cylinder-side water jacket 13, arc-shaped portions 13a and recessed portions 13b are alternately and continuously arranged on both sides in the axial direction of the cylinder row. A front end portion 13c and a rear end portion 13c, which connect the arcuate portions 13a and surround the front and rear ends of the cylinder 2, are arranged at the front and rear ends of the cylinder row.

A plurality of screw holes 54b into which head bolts for fixing the cylinder head 4 are screwed are provided on both sides of the cylinder block 3 across the row of cylinders. Each screw hole 54b is arranged outside the concave portion 13b, the front end portion 13c, and the rear end portion 13c of the cylinder-side water jacket 13 in plan view.

As shown in FIG. 4, the cylinder block 3 has an upper cylinder block 3a and a lower cylinder block 3b arranged below the upper cylinder block 3a. It is provided in the area above 3a. The cylinder-side water jacket 13 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, 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, etc., 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. 1 and 4 to 6, the engine 1 includes an oil passage 20 for circulating oil for lubricating the parts to be lubricated (the piston 5, the crankshaft 6, the camshafts 17 and 18, etc.). is provided. 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.

As shown in FIG. 5 , the oil supply passage 21 includes an oil pump 31 that sucks up the oil stored in the oil pan 30 , an oil filter 32 that filters the oil discharged from the oil pump 31 , and an oil filter 32 that filters the oil discharged from the oil pump 31 . and an oil cooler 33 for cooling the oil to be supplied, and a supply oil passage 35 provided in the engine body 10. - 特許庁

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 3, 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. and

As shown in FIGS. 1 and 5, 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, 4, and 5, 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 an exhaust gas from the oil pan 30. The oil passage 36b is provided adjacent to the side surface of the cylinder block 3 and connects the oil filter 32 and the oil cooler 33, and the oil passage 36b extends upward from the oil cooler 33 and is connected to the first communication oil passage 39 provided in the cylinder block 3. and 36c.

As shown in FIGS. 4 and 5, 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. 5 and 6, the second supply oil passage 37 further includes an oil passage 37c that branches from one end of the main gallery 37a 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, so as to supply oil to an oil jet or the like for cooling the piston.

As shown in FIG. 4, the oil supplied to the camshafts 17, 18, which are the parts to be lubricated, of the engine 1 through the oil supply passage 21 is applied to the intake-side and exhaust-side inclined surfaces 4b, 4c of the cylinder head 4 and the deck. The oil is dripped onto the surface 4a (arrow a) and returned to the oil pan 30 through the head-side return passages 42, 46 forming the oil return passage 22 provided on the deck surface 4a.

When the engine 1 is mounted on the vehicle body, the deck surface 4a is inclined with respect to the horizontal surface 2b so that the exhaust side is lower than the intake side. Therefore, the oil dropped onto the deck surface 4a is easily guided to the head-side return passage 42 on the exhaust side.

The oil return passage 22 comprises a plurality of exhaust-side return passages 41 and an intake-side return passage 45 through which the oil supplied to the camshafts 17 and 18, which are lubricated portions, flows divided into the exhaust port 16 side and the intake port 15 side. Prepare. 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 in a plan view 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 passages 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 is formed in a substantially circular shape in a plan view and extends vertically. The block-side return passage 43 includes upper-side return passages 43a and 43b extending vertically from the upper end to the lower end of the cylinder block upper 3a, and lower-side return passages extending downward from the upper end of the cylinder block lower 3b and opening into the oil pan 30. 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 43a is adjacent to the cylinder-side water jacket 13 and provided along the cylinder-side water jacket 13, as shown in FIGS. The upper return passage 43 a extends from the upper end of the cylinder block 3 to near the lower end of the cylinder-side water jacket 13 . The upper return passage 43 a is formed to have approximately the same depth as the cylinder-side water jacket 13 .

The upper return passage 43 a is positioned outside the recess 13 b that enters between the cylinders 2 , between the arc-shaped portions 13 a of the cylinder-side water jacket 13 . The upper return passage 43a is offset between the cylinders 2 in the central axis 2a of each cylinder 2 and 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 3a.

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 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 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 cylinder-side water jacket 13 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 passage 43c, and the upper end of the lower return passage 43b communicates with the radial passage 43c. 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. 5, 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 passage 21, and after absorbing heat such as frictional heat generated during the operation of the parts to be lubricated, flows through the oil return passage 22. 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 when the parts to be lubricated operate, the deck surface 4a provided at a position including the upper side of the head-side water jacket 14 , and the heat of the oil is radiated in the upper return passage 43 a provided adjacent to the cylinder-side water jacket 13 to be cooled and returned to the oil pan 30 .

7 is a cross-sectional view of the head-side return passage shown in FIG. 4. FIG. FIG. 7 shows a schematic cross-sectional view of an oil return passage in an embodiment of the invention. As shown in FIG. 7, the head-side return passage 42 is provided adjacent to the outer wall portion of the engine 1 on the exhaust side. Therefore, the temperature of the oil passing through the head-side return passage 42 is likely to rise due to the heat received from the outer wall portion of the cylinder head 4 by the catalyst device 11 . In contrast, in the present embodiment, by changing the wettability with oil in the flow direction of the head-side return passage 42 so that the oleophilicity increases from the upstream side to the downstream side of the head-side return passage 42, By facilitating the oil flowing through the head-side return passage 42 to flow out from the head-side return passage 42, the temperature rise of the oil in the head-side return passage 42 is suppressed.

As shown in FIG. 7, in the head-side return passage 42, the wettability to oil changes in the flow direction of the head-side return passage 42 so that the lipophilicity increases from the upstream side to the downstream side of the head-side return passage. A wettability changing portion 60 is provided.

The wettability changing portion 60 includes a plurality of groove portions as a plurality of concave portions formed on the inner peripheral surface 42a of the head-side return passage 42 so that the lipophilicity increases from the upstream side to the downstream side of the head-side return passage 42. 61. The plurality of grooves 61 are each formed to extend in the circumferential direction of the head-side return passage 42 over the entire circumferential direction of the head-side return passage 42 , and the plurality of grooves 61 extend from the upstream side to the downstream side of the head-side return passage 42 . are spaced apart from each other.

Each of the plurality of grooves 61 is formed in a U shape having a predetermined width W1 and a predetermined depth D1. The widths W1 of the plurality of grooves 61 are set to be the same, and the depths D1 of the plurality of grooves 61 are set to increase from the upstream side of the head-side return passage 42 toward the downstream side.

In this way, the plurality of grooves 61 are formed such that the depth D1 increases from the upstream side of the head-side return passage 42 toward the downstream side, thereby increasing the lipophilicity from the upstream side of the head-side return passage 42 . It is formed so as to rise toward the downstream side. In FIG. 6, the groove 61 is shown enlarged for easy viewing, but the groove 61 is a fine groove having a width and a depth of several micrometers to several tens of micrometers, for example.

FIG. 8 is an explanatory diagram for explaining wettability to oil. 8A shows a state in which the oil 100 adheres to the wall surface 101, and FIG. 8B shows a state in which the oil 100 enters the groove 102 provided on the wall surface 101. FIG. In FIG. 8, the width of the groove 102 is W, the depth of the groove 102 is D, the opening area of the groove 102 is a1, and the area of the groove 102 is a2.

When the oil 100 transforms from the state shown in FIG. 8A to the state shown in FIG. 8B and the oil 100 creates a new surface, E1 is the energy required. It can be represented by Esurf×(a2−a1). Here, Esurf indicates the surface free energy of the oil 100.

Also, the energy required when the oil 100 transforms from the state shown in FIG. 8B to the state shown in FIG. E2, the energy E2 can be expressed by the following equation: E2=Einterface×a2. Here, Einterface indicates the interfacial interaction energy of the oil 100 .

The lipophilicity, which is the degree of lipophilicity of the oil 100 with respect to the wall surface 101, can be expressed by (E2-E1). When E1<E2, as shown in FIG. The state of penetrating into 102 is stable (lipophilic), and the greater the difference (E2-E1) between the energy E1 and the energy E2, the higher the lipophilicity. In the case of E1>E2, as shown in FIG. 8A, the state in which the oil 100 adheres to the wall surface 101 is stabilized (oil repellency).

The lipophilicity (E2−E1) is expressed as (Einterface−Esurf)×a2+Esurf×a1. When the groove 102 is formed of a metal material satisfying the following formula: Einterface>Esurf, the depth D of the groove 102 is increased. Then, since the area a2 of the groove portion 102 is increased, the degree of lipophilicity is increased and the lipophilicity is enhanced.

On the other hand, when the groove 102 is made of a fluororesin material that satisfies the following equation: Einterface<Esurf, increasing the depth D of the groove 102 increases the area a2 of the groove 102, thereby lowering the lipophilicity. It becomes less lipophilic and more oil-repellent.

Further, when the width W of the groove portion 102 is increased, the difference between the area a2 of the groove portion 102 and the opening area a1 of the groove portion 102 becomes smaller, and the energy E1 becomes smaller. Also when it is formed by

In the head-side return passage 42 shown in FIG. 7 , the plurality of grooves 61 are formed such that the depth D1 increases from the upstream side of the head-side return passage 42 toward the downstream side, and the lipophilicity of the head-side return passage 42 increases. is formed so as to be higher from the upstream side to the downstream side.

In this way, by changing the wettability of the oil so that the lipophilicity increases from the upstream side to the downstream side of the head-side return passage 42, the oil is distributed from the upstream side to the downstream side of the head-side return passage 42. can be moved to guide the oil to the downstream side of the head-side return passage 42, and the retention time of the oil in the head-side return passage 42 can be reduced.

Even when the engine body 10 in which the head-side return passage 42 is formed is warmed by the exhaust gas of the catalyst device 11 or the like, the retention time of the oil in the head-side return passage 42 can be reduced, and the oil can be removed from the engine body 10. Receiving heat is suppressed, and the temperature rise of the oil can be reduced.

In the wettability changing portion 60 , grooves 61 are formed as a plurality of recesses in the inner peripheral surface of the head-side return passage 42 . can be formed.

FIG. 9 is a sectional view showing a modification of the head-side return passage 42 shown in FIG. A layer 42b made of a fluorine resin such as PTFE (polytetrafluoroethylene) is provided on an inner peripheral surface 42a of the head-side return passage 42 shown in FIG. The layer 42b made of fluororesin is formed with a thickness of several hundred μm, for example. The layer 42b made of fluororesin has oil repellency.

Similarly to the head-side return passage 42 shown in FIG. 7, the head-side return passage 42 shown in FIG. is changed in the flow direction of the head-side return passage 42 . On the inner peripheral surface 42c of the fluororesin layer 42b of the head-side return passage 42, a plurality of grooves are formed so that the oil repellency decreases, that is, the lipophilicity increases from the upstream side to the downstream side. A wettability changing portion 70 having a groove portion 71 may be provided.

The plurality of grooves 72 formed in the inner peripheral surface 42c of the layer 42b made of fluororesin are formed so as to extend in the circumferential direction of the head-side return passage 42 over the entire circumferential direction of the head-side return passage 42. The grooves 71 are formed separately from the upper end side of the head-side return passage 42 and the lower end side thereof.

Each of the plurality of grooves 71 is formed in a U shape having a predetermined width W2 and a predetermined depth D2. The widths W2 of the plurality of grooves 71 are set to be the same, and the depths D2 of the plurality of grooves 71 are set to decrease from the upstream side of the head-side return passage 42 toward the downstream side.

The plurality of grooves 71 are formed so that the depth D2 becomes shallower from the upstream side to the downstream side of the head-side return passage 42, so that the oleophilicity is directed from the upstream side to the downstream side of the head-side return passage 42. It is formed so that it becomes high.

In this way, by changing the wettability of the oil so that the lipophilicity increases from the upstream side to the downstream side of the head-side return passage 42, the oil is distributed from the upstream side to the downstream side of the head-side return passage 42. can be moved to guide the oil to the downstream side of the head-side return passage 42, and the retention time of the oil in the head-side return passage 42 can be reduced.

In this embodiment, the plurality of grooves 61 formed in the head-side return passage 42 have the same width W1 and a depth D1 that increases from upstream to downstream of the head-side return passage 42 . However, the width W1 may be increased from the upstream side to the downstream side of the head-side return passage 42 while the depth D1 is set constant.

In this embodiment, in the head-side return passage 42, the plurality of grooves 71 formed in the inner peripheral surface 42c of the layer 42b made of fluororesin have the same width W2 and the depth D2 of the head-side return passage 42. While the depth D2 is set constant, the width W2 of the head-side return passage 42 is formed to be large from the upstream side to the downstream side. good too.

In the present embodiment, the plurality of grooves 61 and 71 are formed to have a U-shaped cross section, but they can also be formed to have other cross-sectional shapes such as a rectangular cross-section and a triangular cross-section. The plurality of grooves 61 and 71 are formed so as to extend in the circumferential direction of the head-side return passage 42 over the entire circumferential direction of the head-side return passage 42 . For example, it may be formed so as to extend in the circumferential direction of the head-side return passage 42 only on the exhaust side.

In this embodiment, the plurality of grooves 61 formed in the head-side return passage 42 have the same width W1 and a depth D1 that increases from upstream to downstream of the head-side return passage 42 . However, in addition to the change in the depth D1, the width W1 may be increased from the upstream side of the head-side return passage 42 toward the downstream side. Thereby, the oleophilicity is further enhanced from the upstream side toward the downstream side of the head-side return passage 42 .

In this embodiment, in the head-side return passage 42, the plurality of grooves 71 formed in the inner peripheral surface 42c of the layer 42b made of fluororesin have the same width W2 and the depth D2 of the head-side return passage 42. However, in addition to the change in the depth D2, the width W2 of the head-side return passage 42 may be increased from the upstream side to the downstream side. good. Thereby, the oleophilicity is further enhanced from the upstream side toward the downstream side of the head-side return passage 42 .

In this embodiment, the plurality of recesses provided in the wettability changing portions 60 and 70 of the head-side return passage 42 are formed by the plurality of grooves 61 and 71, but the plurality of recesses are formed inside the head-side return passage 42. It may be formed by arranging a plurality of dimple rows arranged side by side in the circumferential direction on the peripheral surface in the direction of the flow path. The row of dimples is formed by arranging a plurality of dimples arranged in the circumferential direction, for example, which are circular in plan view and have arcuate cross-sections that are concave radially outward of the head-side return passage 42 . may A plurality of dimples forming a dimple row arranged in the circumferential direction are formed with the same diameter as depth and width. The depth and width diameters of the dimple rows arranged side by side in the flow direction may be set such that the lipophilicity changes in the flow direction, similarly to the plurality of grooves 61 and 71 . As a result, the lipophilicity increases from the upstream side to the downstream side of the head-side return passage 42 .

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.

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 10 engine body 11 exhaust device 20 oil passage 30 oil pan 31 oil pump 42 head side return passage 42a inner peripheral surface 60 wettability changing portion 61 a plurality of grooves (a plurality of recesses)
D1 depth W1 width

Claims (7)

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,
a head-side oil return passage provided in the cylinder head of the engine body for returning oil from the cylinder head side to the oil pan;
The inner peripheral surface of the head-side oil return passage has a wettability changing portion that changes the wettability with respect to oil in the direction of the flow path of the head-side oil return passage to promote the flow of oil flowing along the inner peripheral surface. engine oil passage structure. The wettability changing portion includes a plurality of recesses formed on the inner peripheral surface of the head-side oil return passage so that the oleophilicity increases from the upstream portion toward the downstream portion of the head-side oil return passage. The engine oil passage structure according to claim 1. The cylinder head is made of a metal material,
3. The oil passage structure for an engine according to claim 2, wherein the plurality of recesses are formed to have a greater depth from an upstream portion toward a downstream portion of the head-side oil return passage. A layer made of a fluororesin material is provided on the inner peripheral surface of the head-side oil return passage,
3. The engine oil passage structure according to claim 2, wherein the plurality of recesses are formed to have a shallower depth from an upstream portion toward a downstream portion of the head-side oil return passage. The cylinder head is made of a metal material,
4. The engine oil passage structure according to claim 2 or 3, wherein the plurality of recesses are formed so as to increase in width from the upstream portion toward the downstream portion of the head-side oil return passage. A layer made of a fluororesin material is provided on the inner peripheral surface of the head-side oil return passage,
6. The engine oil passage structure according to claim 2 or 5, wherein the plurality of recesses are formed so as to increase in width from the upstream portion toward the downstream portion of the head-side oil return passage. The engine oil passage structure according to any one of claims 1 to 6, wherein the head-side oil return passage is provided on the exhaust side of the cylinder head.

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