Engine oil cooling structure

Abstract

To effectively cool oil even when a flow rate of the oil is large.SOLUTION: An engine oil cooling structure includes: a return passage 42 having an inlet part 42a on an exhaust side of a middle deck part 4a of a cylinder head 4; a main fin 50 located on an intake side of the inlet part 42a, erected on an upper side of the middle deck part 4a and inclined to one side or the other side in a predetermined direction orthogonal to both of an intake / exhaust direction and a vertical direction toward the exhaust side; and an auxiliary fin 51 located on the exhaust side of the main fin 50 and on the side of inclination of the main fin 50 in the predetermined direction relative to the inlet part 42a and erected on an upper side of the middle deck part 4a. The auxiliary fin 51 is inclined to the inlet part 42a side in the predetermined direction toward the exhaust side.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The technology disclosed herein belongs to the technical field of engine oil cooling structures. [Background technology]

[0002] Conventionally, there has been a trend toward using low-viscosity oil, which has a lower upper temperature limit than oil with normal viscosity, in order to improve engine fuel efficiency. However, low-viscosity oil reduces lubrication, so when low-viscosity oil is used, it is necessary to actively cool the oil.

[0003] In Patent Document 1, a plate having a plurality of heat dissipating protrusions is attached to the deck surface of the cylinder head to cool the oil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-245577 Summary of the Invention [Problem to be solved by the invention]

[0005] After careful consideration, the inventors of the present invention found that an increase in the flow rate of returned oil reduces the oil cooling performance. Further investigation by the inventors revealed that an increase in the oil flow rate causes uneven distribution of oil in the circumferential direction of the return passage, preventing the oil from contacting part of the wall surface of the return passage.

[0006] In addition to situations where the engine load is high, such as when climbing hills, the oil flow rate increases when the oil becomes unevenly distributed inside the cylinder head, such as when driving on an incline or turning. In other words, even when the engine load is not high, the oil cooling performance may decrease, which could lead to poor fuel economy.

[0007] The cooling structure described in Patent Document 1 actively dissipates heat from the deck surface, but a decrease in cooling performance in the return passage is unavoidable. While it is possible to increase the size of the oil cooler, this increases costs and the size of the engine itself. Therefore, there is room for improvement in terms of efficiently cooling the oil, even when the oil flow rate is high.

[0008] The technology disclosed herein has been made in consideration of these points, and its purpose is to enable oil to be cooled efficiently even when the oil flow rate is high. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, a first aspect of the technology disclosed herein is directed to an engine oil cooling structure in which oil stored in an oil pan located below a cylinder block of an engine body is supplied to lubricated parts of a cylinder head by an oil pump, and then returned to the oil pan while being cooled. The engine oil cooling structure includes: an inlet portion on the exhaust side of a middle deck portion of the cylinder head, a return passage for returning oil from the cylinder head to the oil pan; a main fin located on the intake side of the inlet portion, erected above the middle deck portion, and inclined toward the exhaust side to one or the other of a predetermined direction perpendicular to both the intake / exhaust direction and the up-and-down direction; and a secondary fin located on the exhaust side of the main fin with respect to the inlet portion and on the side of the primary fin inclined in the predetermined direction, and erected above the middle deck portion, wherein the secondary fin is inclined toward the exhaust side in the opposite direction to the main fin in the predetermined direction.

[0010] In the first aspect, the primary and secondary fins deflect the oil flow, forming a vortex in the return passage, which allows the oil to flow along the entire wall surface of the return passage, thereby efficiently cooling the oil even when the oil flow rate is high.

[0011] In the second aspect, in the first aspect, the bolt heads of the bolts fastening the cylinder head and the cylinder block are located closer to the intake side than the inlet portion, and the main fins extend at an angle from a position closer to the intake side than the bolt heads toward the exhaust side.

[0012] In the second mode, the oil flow can be deflected by the primary fin before being branched by the bolt head. This allows as much oil as possible to flow along the secondary fin, making it easier for vortexes to form in the return passage. This allows the oil to be cooled efficiently.

[0013] In a third aspect, in the second aspect, the main fin is located on the intake side of the bolt head and on one side or the other side of the center of the bolt head in the specified direction, and the main fin is also inclined toward the bolt head in the specified direction, toward the exhaust side.

[0014] In the third embodiment, the bolt heads can be used in addition to the primary fins to deflect the oil flow, directing as much oil as possible along the secondary fins, which facilitates the formation of vortices in the return passage, allowing for efficient cooling of the oil.

[0015] In a fourth aspect, in the third aspect, engine parts are arranged on both sides of the bolt head in the specified direction, and the main fin is arranged so as to block one of a pair of passages located between the bolt head and the engine part.

[0016] In the fourth aspect, the oil passage is restricted, allowing as much oil as possible to flow along the secondary fins, which makes it easier for vortexes to form in the return passage, allowing the oil to be cooled efficiently.

[0017] In a fifth aspect, in the first aspect, the angle between a line extending in the direction in which the primary fin extends and a line extending in the direction in which the secondary fin extends is 80° to 90° in plan view.

[0018] In the fifth aspect, the oil whose flow has been deflected by the primary fin collides with the secondary fin at a substantially right angle and is deflected back into flow, allowing a large amount of oil to flow efficiently toward the inlet, thereby efficiently cooling the oil.

[0019] A sixth aspect is any one of the first to fifth aspects, wherein the width of the secondary fin is wider on the side closer to the middle deck portion than on the side farther from the middle deck portion.

[0020] In the sixth aspect, the oil near the middle deck is relatively cool because heat is dissipated through the middle deck. By widening the width of the portion of the secondary fins closer to the middle deck, the oil with a relatively low temperature can be made to collide with the secondary fins. When the oil with a relatively low temperature collides with the secondary fins, the oil is stirred in the vertical direction, so the temperature of the oil flowing into the return passage is averaged. This increases the cooling efficiency within the return passage. [Effects of the Invention]

[0021] As described above, according to the technology disclosed herein, oil can be cooled efficiently even when the oil flow rate is high. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view showing an engine body having an engine oil cooling structure according to a first exemplary embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an oil supply passage of the engine. [Figure 3] FIG. 3 is a cross-sectional view showing a return passage of the engine. [Figure 4]FIG. 4 is a view of the middle deck of the cylinder head as seen from above. [Figure 5] FIG. 5 is a plan view showing the periphery of the inlet of the exhaust return passage. [Figure 6] FIG. 6 is a view of the main fin as seen from the intake side. [Figure 7] FIG. 7 is a view of the first sub-fin and the second sub-fin as viewed from the exhaust side. [Figure 8] FIG. 8 is a side view of the first sub-fin. [Figure 9] FIG. 9 is a schematic diagram showing the positional relationship between the primary fin, the first secondary fin, and the second secondary fin. [Figure 10] FIG. 10 is a diagram showing the flow of oil around the inlet portion. [Figure 11] FIG. 11 is a diagram showing the flow of oil around the first sub-fin. [Figure 12] FIG. 12 is a plan view showing the periphery of the inlet of the exhaust return passage in the engine body having the engine oil cooling structure according to the second embodiment. [Figure 13] FIG. 13 is a cross-sectional view taken along a plane corresponding to line XIII-XIII in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] Exemplary embodiments will now be described in detail with reference to the drawings.

[0024] (Embodiment 1) <Overall structure of oil passage> Exemplary embodiments will now be described in detail with reference to the drawings.

[0025] 1 shows an engine body 10 having an oil passage structure according to an embodiment. The engine body 10 is disposed in the engine compartment of an automobile. The engine body 10 includes a cylinder block 3, a cylinder head 4 disposed above the cylinder block 3, and an oil pan 30 disposed below the cylinder block 3.

[0026] The cylinder block 3 has a plurality of (four in this example) cylinders 2. The cylinders 2 are arranged side by side in the direction of the paper surface of FIG. 1 (hereinafter referred to as the cylinder row direction) with their cylinder axes parallel to one another. Pistons 5 are arranged reciprocatingly within the cylinders 2. The pistons 5 are connected via connecting rods 7 to a crankshaft 6, which is rotatably supported at the bottom of the cylinder block 3. The reciprocating motion of the pistons 5 within the cylinders 2 causes the crankshaft 6 to rotate. A combustion chamber 8 is formed by the upper surfaces of the pistons 5, the cylinders 2, and part of the cylinder head 4.

[0027] A block-side water jacket 11 through which cooling water flows is provided in the cylinder block 3. The block-side water jacket 11 is provided on the outer periphery of the cylinder 2 so as to surround the cylinder 2 and communicate with the cylinders in the cylinder row direction.

[0028] The cylinder head 4 is divided into upper and lower sections by a middle deck section 4a, and has intake ports 15 and exhaust ports 16 below the middle deck section 4a. Two intake ports 15 and two exhaust ports 16 are provided for each cylinder 2. The middle deck section 4a is formed so as to be horizontal when the engine body 10 is placed in the engine room.

[0029] The cylinder head 4 is provided with an intake valve 15a for opening and closing the intake port 15, and an exhaust valve 16a for opening and closing the exhaust port 16. The cylinder head 4 also is provided with an intake camshaft 17 for opening and closing the intake valve 15a, and an exhaust camshaft 18 for opening and closing the exhaust valve 16a. The intake camshaft 17 and the exhaust camshaft 18 are each drivingly connected to the crankshaft 6. As a result, the intake valve 15a and the exhaust valve 16a open and close the intake port 15 and the exhaust port 16, respectively, in accordance with the rotation of the crankshaft 6.

[0030] The cylinder head 4 is provided with a head-side water jacket 19 (see FIG. 3 ) through which cooling water flows. The head-side water jacket 19 is formed in a portion between the intake port 15 and the exhaust port 16 and communicates in the cylinder row direction. The head-side water jacket 19 communicates with the block-side water jacket 11, and cooling water flows into the head-side water jacket 19 from the block-side water jacket 11. The head-side water jacket 19 constitutes a cooling section of the engine body 10.

[0031] The oil pan 30 stores oil for lubricating the parts to be lubricated, such as the piston 5, the crankshaft 6, the intake camshaft 17, and the exhaust camshaft 18.

[0032] In this embodiment 1, the engine body 10 is disposed in the engine compartment, supported by the vehicle body frame, with the cylinder 2 arranged to extend in a direction inclined toward the exhaust side, as shown in FIG.

[0033] 2 and 3, the engine body is provided with an oil passage that circulates oil that lubricates the parts to be lubricated (piston 5, crankshaft 6, intake camshaft 17, exhaust camshaft 18, etc.) within the engine body 10. The oil passage has an oil supply passage 21 that supplies oil to the parts to be lubricated, and a return passage 22 that returns the oil that has been supplied to the parts to be lubricated to the oil pan.

[0034] The oil supply passage 21 includes an oil pump 31 that draws up oil stored in an oil pan 30, an oil filter 32 that filters the oil discharged from the oil pump 31, and an oil supply passage 35 provided in the engine body 10.

[0035] 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, a third supply oil passage 38 provided in the cylinder head 4, a first communicating oil passage 39 connecting the first supply oil passage 36 and the second supply oil passage 37, and a second communicating oil passage 40 connecting the second supply oil passage 37 and the third supply oil passage 38.

[0036] As shown in FIG. 2, the first oil supply passage 36 is an oil passage that is provided in the oil pan 30 and connects the oil pump 31 and the oil filter 32.

[0037] As shown in FIG. 2, the first communication oil passage 39 extends upward from the oil filter 32 within the cylinder block 3, extends in a width direction perpendicular to both the vertical direction and the cylinder row direction, and then extends upward again.

[0038] The second oil supply passage 37 includes a main gallery 37a connected to the first communication oil passage 39 and extending in the cylinder row direction, a plurality of branch oil passages 37b branching from the main gallery 37a and extending downward to supply oil to lubricated parts of the crankshaft 6, and an oil passage 37c branching from one end of the main gallery 37a, extending in the width direction, and communicating with the second communication oil passage 40. The main gallery 37a is located on the exhaust side of the cylinder block 3 in the width direction perpendicular to the cylinder row direction of the cylinder block 3, near the lower end of the cylinder 2.

[0039] The second communication oil passage 40 extends upward from the end of the oil passage 37c on the main gallery 37a side. The second communication oil passage 40 has a lower portion provided in the cylinder block 3 and an upper portion provided in the cylinder head 4.

[0040] The third oil supply passage 38 includes an oil passage 38a extending from the upper end of the second communication oil passage 40 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 head-side gallery 38c extending from the oil passage 38b in the cylinder row 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 of the intake camshaft 17 and the exhaust camshaft 18, etc.

[0041] Although not shown in the drawings, the oil supply passage 21 is configured to supply oil to an oil jet for cooling a piston, for example, in addition to the above-mentioned configuration.

[0042] The oil supplied to the lubricated parts of the engine body 10 cools and lubricates the lubricated parts, and then passes through the return passage 22 and returns to the oil pan 30.

[0043] 3 and 4, the return passage 22 includes multiple (four in this example) exhaust-side return passages 41 through which oil supplied to the intake camshaft 17 and the exhaust camshaft 18, which are lubricated parts, flows toward the exhaust port 16, and one intake-side return passage 42 toward the intake port 15. Because the configuration of the intake-side return passage 42 is the same as the configuration of the exhaust-side return passage 41, the following will describe the exhaust-side return passage 41 in detail, and a detailed description of the intake-side return passage 42 will be omitted. In the following description, the intake port 15 side in the intake / exhaust direction will be simply referred to as the intake side, and the exhaust port 16 side in the intake / exhaust direction will be simply referred to as the exhaust side.

[0044] The exhaust-side return passage 41 is formed by dividing it into the cylinder block 3 and the cylinder head 4. Within the cylinder head 4, the exhaust-side return passage 41 is formed in a substantially circular cross section and extends in the vertical direction. The exhaust-side return passage 41 is disposed between each cylinder 2 at a position offset from each cylinder 2 in the cylinder row direction. Specifically, the exhaust-side return passage 41 is disposed adjacent to each exhaust port 16.

[0045] An inlet portion 41a of the exhaust-side return passage 41 is provided in the middle deck portion 4a of the cylinder head 4. The exhaust-side return passage 41 is disposed adjacent to a bolt hole 61 into which a connecting bolt that connects the cylinder head 4 and the cylinder block 3 is fastened. The inlet portion 41a of the exhaust-side return passage 41 is formed at a position lower than the upper end of the bolt hole 61.

[0046] The exhaust return passage 41 is formed in a substantially circular shape within the cylinder block 3 and extends from the upper end to the lower end of the cylinder block 3. The lower end of the exhaust return passage 41 opens into the oil pan 30.

[0047] When the engine starts operating, the oil pump 31 is driven in response to the rotation of the crankshaft 6. Then, as shown by the arrow in Figure 2, the oil pump 31 draws in oil stored in the oil pan 30 and supplies the drawn-in oil to parts to be lubricated in the engine body 10 via the first oil supply passage 36, the first communication oil passage 39, the second oil supply passage 37, the second communication oil passage 40, and the third oil supply passage 38 in that order.

[0048] The oil supplied to the parts to be lubricated lubricates the parts through the oil supply passage 21 and absorbs heat, such as frictional heat, generated when the parts to be lubricated operate. The oil supplied to the cylinder head 4 is stored in the cylinder head 4 and flows into the return passage 22 via the middle deck portion 4a. The oil is then returned to the oil pan 30 through the return passage 22.

[0049] <Entrance area surrounding structure> In recent years, there has been a trend toward using low-viscosity oil, which has a lower upper limit temperature than oil with normal viscosity, in order to improve engine fuel efficiency. When using low-viscosity oil, it is necessary to actively cool the oil to prevent a decrease in lubrication. However, the inventors of the present application found that when the flow rate of oil flowing into the exhaust-side return passage 41 increases, the oil becomes uneven in the circumferential direction of the exhaust-side return passage 41, causing the oil to not come into contact with part of the wall surface of the exhaust-side return passage 41. When the oil no longer comes into contact with the wall surface of the exhaust-side return passage 41, it becomes difficult for the oil to dissipate heat, thereby reducing the oil cooling effect.

[0050] Therefore, in the first embodiment, the flow of oil is deflected in the middle deck section 4a to generate a vortex in the exhaust return passage 41, causing the oil to come into contact with the wall surface of the exhaust return passage 41. The structure for generating the vortex will be described in detail below.

[0051] FIG. 5 shows an enlarged view of the inlet portion 41a and its surroundings of the exhaust-side return passage 41. A primary fin 50, a first sub-fin 51, and a second sub-fin 52 are arranged around the inlet portion 41a. A bolt head 62 of a connecting bolt is located closer to the intake side than the inlet portion 41a. A washer 63 with a larger diameter than the bolt head 62 is located between the bolt head 62 and the middle deck portion 4a. Exhaust valves 16a are arranged on both sides of the bolt head 62 in a predetermined direction perpendicular to both the intake / exhaust direction and the up-down direction. The exhaust valves 16a are an example of an engine part.

[0052] The main fins 50 are located closer to the intake side than the inlet portion. As shown in Fig. 6, the main fins 50 are rectangular. The main fins 50 are erected above the middle deck portion 4a. The main fins 50 are inclined toward the first side in a predetermined direction toward the exhaust side.

[0053] The primary fin 50 is located on the intake side of the bolt head 62. The primary fin 50 extends at an angle from a position on the intake side of the bolt head 62 toward the exhaust side. The primary fin 50 is located on a second side in the predetermined direction, opposite the first side, from the center of the bolt head 62 in the predetermined direction. Therefore, the primary fin 50 is inclined toward the bolt head 62 in the predetermined direction, toward the exhaust side.

[0054] 5 and 6, the bolt head 62 and the exhaust valve 16a form passages on a first side and a second side in a predetermined direction relative to the bolt head 62. The main fin 50 is disposed so as to close the passage located on the second side of the pair of passages.

[0055] The main fins 50 are made of metal. The main fins 50 are made of a metal with high thermal conductivity, such as aluminum or copper. The main fins 50 may be formed integrally with the middle deck portion 4a, or may be fixed to the middle deck portion 4a by welding or the like.

[0056] The first sub-fin 51 is located on the exhaust side of the main fin 50 and on a first side in the predetermined direction relative to the inlet section 41a. In other words, the first sub-fin 51 is located on the side where the main fin 50 is inclined in the predetermined direction. The first sub-fin 51 is erected above the middle deck section 4a. The first sub-fin 51 is inclined to a second side in the predetermined direction toward the exhaust side. In other words, the first sub-fin 51 is inclined toward the inlet section 41a in the predetermined direction toward the exhaust side. The exhaust side end of the first sub-fin 51 is located closer to the intake side than the exhaust side end of the inlet section 41a.

[0057] 7 and 8, the width of the first sub-fin 51 is wider on the side closer to the middle deck section 4a (lower side) than on the side farther from the middle deck section 4a (upper side). The width of the upper end of the first sub-fin 51 is less than half the width of the lower end of the first sub-fin 51. The first sub-fin 51 has a first inclined portion 51a in the upper exhaust side portion that is inclined downward toward the exhaust side.

[0058] The first sub-fins 51 are made of metal. The first sub-fins 51 are made of a metal with high thermal conductivity, such as aluminum or copper. The first sub-fins 51 may be formed integrally with the middle deck portion 4a, or may be fixed to the middle deck portion 4a by welding or the like.

[0059] The second sub-fin 52 is located on the exhaust side of the main fin 50 and on the second side in the predetermined direction relative to the inlet section 41a. The second sub-fin 52 is erected above the middle deck section 4a. The second sub-fin 52 is inclined toward the first side in the predetermined direction toward the intake side. In other words, the second sub-fin 52 is inclined toward the inlet section 41a in the predetermined direction toward the intake side. The intake side end of the second sub-fin 52 is located closer to the exhaust side than the intake side end of the inlet section 41a. The second sub-fin 52 is parallel to the first sub-fin 51.

[0060] The second sub fin 52 has the same structure as the first sub fin 51. The second sub fin 52 has, at the upper portion on the intake side, a second inclined portion 52a that is inclined downward toward the intake side.

[0061] The second sub-fins 52 are made of metal. The second sub-fins 52 are made of a metal with high thermal conductivity, such as aluminum or copper. The second sub-fins 52 may be formed integrally with the middle deck portion 4a, or may be fixed to the middle deck portion 4a by welding or the like.

[0062] FIG. 9 shows a schematic diagram of the positional relationship between the inlet portion 41a, the primary fin 50, the first secondary fin 51, the second secondary fin 52, the bolt head 62, and the washer 63.

[0063] A straight line L1 extending in the direction in which the main fin 50 extends along the exhaust side surface of the main fin 50 comes into contact with the washer 63.

[0064] In a plan view, the angle α1 between a straight line L1 extending in the extension direction of the primary fin 50 and a straight line L2 extending in the extension direction of the first sub fin 51 is 80° to 90°. Since the second sub fin 52 is parallel to the first sub fin 51, in a plan view, the angle α2 between the straight line L1 extending in the extension direction of the primary fin 50 and a straight line L3 extending in the extension direction of the second sub fin 52 is the same as the angle α1.

[0065] The angle β of the first sub fin 51 on the acute angle side with respect to the predetermined direction is 15° to 60°. Because the second sub fin 52 is parallel to the first sub fin 51, the angle of the first sub fin 51 on the acute angle side with respect to the predetermined direction is also 15° to 60°. The angle of the primary fin 50 on the acute angle side with respect to the predetermined direction is (90° - β).

[0066] In the intake / exhaust direction, the first sub fin 51 overlaps with the inlet portion 41a by more than half, and the second sub fin 52 overlaps with the inlet portion 41a by more than half in the intake / exhaust direction.

[0067] A straight line L2 extending in the direction in which the first sub-fin 51 extends does not pass through the inlet portion 41a. Also, a straight line L3 extending in the direction in which the second sub-fin 52 extends does not pass through the inlet portion 41a.

[0068] 4, each inlet portion 41a is provided with a main fin 50 and a first sub-fin 51. A second sub-fin 52 is also provided at each of the three inlet portions 41a except for the inlet portion 41a provided at the end on the first side in the predetermined direction.

[0069] 10 shows the flow of oil around the inlet portion 41a. Oil flowing from the intake side toward the exhaust side is deflected toward the exhaust side and the first side in the predetermined direction by the main fins 50. The oil flows along the main fins 50, bolt heads 62, and washers 63 toward the exhaust side and the first side in the predetermined direction.

[0070] Next, the oil collides with the first sub-fin 51. As shown in FIG. 11, when the oil collides with the first sub-fin 51, the oil below the first inclined portion 51a (below the dashed line in FIG. 11) is deflected along the first sub-fin 51 toward the exhaust side and the second side in the predetermined direction, and a portion of the oil moves upward. On the other hand, the oil above the first inclined portion 51a (above the dashed line in FIG. 11) continues to flow without colliding with the first sub-fin 51. This difference in flow causes the oil to be agitated around the first inclined portion 51a. The oil below the first inclined portion 51a is in contact with the middle deck portion 4a, and therefore has a relatively low temperature. Therefore, the oil is agitated, and the oil temperature is uniformed.

[0071] The oil deflected by the first sub-fin 51 toward the exhaust side and the second side in the predetermined direction flows toward the inlet 41a along the wall surface of the cylinder head 4. The oil that reaches the inlet 41a flows into the inlet 41a from the exhaust-side edge of the inlet 41a along the circumferential direction of the edge. This causes the oil to flow while forming a vortex inside the exhaust-side return passage 41.

[0072] Oil flowing from the first side to the second side in a predetermined direction also collides with the first sub-fin 51. The oil is deflected by the first sub-fin 51 so that it flows along the wall surface of the cylinder head 4. The oil then flows into the inlet portion 41a from the exhaust-side edge of the inlet portion 41a, along the circumferential direction of the edge.

[0073] Because the primary fin 50 blocks the passage between the bolt head 62 and the exhaust valve 16a on the second side in the predetermined direction, almost no oil flows from the exhaust side toward the second sub-fin 52. However, some oil flows from the second side in the predetermined direction toward the first side, and this oil collides with the second sub-fin 52. The oil that collides with the second sub-fin 52 is deflected along the second sub-fin 52 toward the intake side and the first side in the predetermined direction. The oil deflected by the second sub-fin 52 then flows into the inlet portion 41a from the intake-side edge of the inlet portion 41a, circumferentially around the edge. The oil that flows along the first sub-fin 51 and into the inlet portion 41a flows toward the first side in the predetermined direction in the intake-side portion of the inlet portion 41a. Therefore, the oil that flows along the second sub-fin 52 flows along a vortex in the exhaust-side return passage 41 without impeding the flow of oil in the inlet portion 41a. Furthermore, at the position of the second sub-fin 52, as with the first sub-fin 51, the oil below the second inclined portion 52a and the oil above the second inclined portion 52a are mixed near the second inclined portion 52a, thereby making the oil temperature uniform.

[0074] In this way, a vortex flow is formed in the exhaust-side return passage 41, flowing along the wall surface of the exhaust-side return passage 41. The formation of the vortex flow keeps the oil in contact with the wall surface of the exhaust-side return passage 41 for as long as possible. This allows the oil to be cooled efficiently even if a large amount of oil flows into the exhaust-side return passage 41.

[0075] Effects of the First Embodiment As described above, the first embodiment includes the primary fin 50, which is located closer to the intake side than the inlet 41a of the exhaust-side return passage 41 and stands upright relative to the middle deck 4a. The primary fin 50 is inclined toward the exhaust side in a first direction perpendicular to both the intake / exhaust direction and the up-down direction. The first sub-fin 51 is located closer to the exhaust side than the primary fin 50 and on the side (first side) where the primary fin 50 is inclined in the predetermined direction relative to the inlet 41a. The first sub-fin 51 is inclined toward the inlet 41a in the predetermined direction toward the exhaust side. The primary fin 50 and the first sub-fin 51 deflect the oil flow, thereby forming a vortex in the exhaust-side return passage 41. This allows the oil to flow along the entire wall surface of the exhaust-side return passage 41, thereby efficiently cooling the oil even when the oil flow rate is high. Furthermore, by forming a vortex, the oil can be kept in contact with the wall surface of the exhaust return passage 41 for as long as possible, compared to when the oil is simply made to flow along the exhaust return passage 41. This also makes it possible to cool the oil efficiently.

[0076] In the first embodiment, the bolt heads 62 of the connecting bolts that fasten the cylinder head 4 and the cylinder block 3 are located closer to the intake side than the inlet portion 41a, and the primary fins 50 extend at an angle from a position closer to the intake side than the bolt heads 62 toward the exhaust side. This allows the primary fins 50 to deflect the oil flow before it is branched by the bolt heads 62. As a result, as much oil as possible can flow along the first sub-fins 51, making it easier to form vortexes in the exhaust-side return passage 41. This allows the oil to be cooled efficiently.

[0077] In the first embodiment, the primary fin 50 is located on the intake side of the bolt head 62 and on the second side of the center of the bolt head in the predetermined direction, and the primary fin 50 is also inclined toward the bolt head 62 in the predetermined direction, toward the exhaust side. This makes it possible to deflect the oil flow using the bolt head 62 in addition to the primary fin 50, and to direct as much oil as possible along the first secondary fin 51. As a result, vortices are more likely to form in the exhaust-side return passage 41, allowing the oil to be cooled efficiently.

[0078] In the first embodiment, exhaust valves 16a are disposed on both sides of the bolt head 62 in a predetermined direction, and the primary fin 50 is disposed so as to block the second of a pair of passages located between the bolt head 62 and the exhaust valve 16a in the predetermined direction. Because the oil passage is restricted, as much oil as possible can flow along the first secondary fin 51. This makes it easier for a vortex to form in the exhaust-side return passage 41, allowing the oil to be cooled efficiently.

[0079] In the first embodiment, in a plan view, the angle between a line extending in the extension direction of the primary fin 50 and a line extending in the extension direction of the first sub fin 51 is 80° to 90°. As a result, the oil whose flow is deflected by the primary fin 50 collides with the first sub fin 51 at a substantially right angle and is deflected to flow. As a result, a large amount of oil can be efficiently flowed toward the inlet portion 41a, and the oil can be efficiently cooled.

[0080] In this first embodiment, the width of the first sub-fin 51 is wider on the side closer to the middle deck section 4a than on the side farther from the middle deck section 4a. That is, the oil closer to the middle deck section 4a has a relatively low temperature because heat is dissipated through the middle deck section 4a. By widening the width of the portion of the first sub-fin 51 closer to the middle deck section 4a, the relatively low-temperature oil can be made to collide with the first sub-fin 51. When the relatively low-temperature oil collides with the first sub-fin 51, the oil is agitated in the vertical direction, and the temperature of the oil flowing into the exhaust-side return passage 41 is equalized. This improves the cooling efficiency within the exhaust-side return passage 41.

[0081] In the first embodiment, the straight line extending toward the exhaust side along the exhaust side surface of the primary fin 50 contacts the washer 63. This allows the oil deflected by the primary fin 50 to flow smoothly along the washer 63, allowing the oil to flow efficiently to the first secondary fin 51.

[0082] In the first embodiment, the straight line L2 extending in the extension direction of the first sub-fin 51 does not pass through the inlet portion 41a. This makes it possible to prevent as much as possible the oil deflected by the first sub-fin 51 from flowing into the inlet portion 41a along the radial direction of the inlet portion 41a. As a result, a vortex is easily formed in the exhaust-side return passage 41, and the cooling efficiency in the exhaust-side return passage 41 can be improved.

[0083] In the first embodiment, the exhaust-side end of the first sub-fin 51 is located closer to the intake side than the exhaust-side end of the inlet portion 41a, and the first sub-fin 51 overlaps with at least half of the inlet portion 41a in the intake / exhaust direction. This allows oil deflected along the first sub-fin 51 to flow into the inlet portion 41a from the edge of the inlet portion 41a on the exhaust side and the first side in the predetermined direction, along the circumferential direction of the edge. As a result, vortices are easily formed in the exhaust-side return passage 41, and the cooling efficiency in the exhaust-side return passage 41 can be improved.

[0084] The angle β of the first sub-fin 51 on the acute angle side relative to the predetermined direction is 15° to 60°. That is, if the angle β is too small, the oil flows along the predetermined direction and is likely to flow into the inlet portion 41a in a radial direction of the inlet portion 41a. On the other hand, if the angle β is too large, the oil flows along the intake / exhaust direction, thereby eliminating the effect of providing the first sub-fin 51. By setting the angle β to 15° to 60°, the first sub-fin 51 can deflect the oil so that it flows along the circumferential direction of the edge of the inlet portion 41a.

[0085] In the first embodiment, a second sub-fin 52 is provided on the opposite side of the inlet portion 41a from the first sub-fin 51 in the predetermined direction. The second sub-fin 52 is inclined toward the first side in the predetermined direction toward the intake side. This allows the second sub-fin 52 to deflect oil flowing toward the first side in the predetermined direction toward the intake side and the first side in the predetermined direction. By deflecting the oil with the second sub-fin 52, the oil can flow into the inlet portion 41a from the intake-side edge of the inlet portion 41a along the circumferential direction of the edge. The oil that flows along the first sub-fin 51 and into the inlet portion 41a flows toward the first side in the predetermined direction in the intake-side portion of the inlet portion 41a. Therefore, the oil that flows along the second sub-fin 52 flows along a vortex in the exhaust-side return passage 41 without impeding the flow of oil in the inlet portion 41a. This improves the cooling efficiency in the exhaust-side return passage 41.

[0086] In the first embodiment, the intake-side end of the second sub-fin 52 is located closer to the exhaust side than the intake-side end of the inlet portion 41a, and the second sub-fin 52 overlaps with at least half of the inlet portion 41a in the intake / exhaust direction. This allows oil deflected along the second sub-fin 52 to flow into the inlet portion 41a from the edge of the inlet portion 41a on the exhaust side and in the second direction along the circumferential direction of the edge. As a result, vortices are easily formed in the exhaust-side return passage 41, and the cooling efficiency in the exhaust-side return passage 41 can be improved.

[0087] The acute angle of the second sub fins 52 relative to the predetermined direction is 15° to 60°. By setting the angle of the second sub fins 52 to 15° to 60°, the second sub fins 52 can deflect the oil so that it flows along the circumferential direction of the edge of the inlet portion 41a.

[0088] In the first embodiment, the primary fin 50, the first sub fin 51, and the second sub fin 52 are made of a metal with high thermal conductivity, which allows the primary fin 50, the first sub fin 51, and the second sub fin 52 to dissipate heat from the oil, thereby efficiently cooling the oil.

[0089] (Embodiment 2) Hereinafter, the second embodiment will be described in detail with reference to the drawings. In the following description, parts common to the first embodiment will be given the same reference numerals and detailed description thereof will be omitted.

[0090] In the second embodiment, the configuration of the primary fin 250 differs from that of the first embodiment. Specifically, as shown in Fig. 12, the primary fin 250 is disposed so as to overlap with the bolt head 62 in a plan view. The primary fin 250 passes through the center of the bolt head 62 and extends toward the exhaust side, inclining toward a first side in a predetermined direction.

[0091] As shown in Figure 13, the primary fin 250 has an engaging portion 250a that engages with a recess 62a formed in the bolt head 62. The recess 62a is the portion that engages with a tool. A straight line extending along the primary fin 250 intersects with the first secondary fin 51. An inclined portion 250b that slopes downward is provided on the upper portion of the primary fin 250 on the exhaust side.

[0092] The primary fin 250 is integral with a cap 253 that covers the periphery of the bolt head 62. When the cap 253 is fitted onto the bolt head 62, the primary fin 250 is installed on the cylinder head 4 at the same time.

[0093] The main fin 250 and the cap 253 are made of a metal with high thermal conductivity, such as aluminum or copper.

[0094] The configurations of the first sub fin 51 and the second sub fin 52 are the same as those in the first embodiment described above.

[0095] In the second embodiment as well, oil flowing from the intake side to the exhaust side can be deflected by the main fin 250 toward the exhaust side and the first side in the predetermined direction. The oil deflected by the main fin 250 is then deflected by the first sub-fin 51 and flows from the exhaust-side edge of the inlet portion 41a into the inlet portion 41a along the circumferential direction of the edge. This forms a vortex in the exhaust-side return passage 41, thereby improving the cooling efficiency in the exhaust-side return passage 41.

[0096] In the second embodiment, the primary fins 250 are integrally formed with the caps 253, and are installed in the cylinder head 4 at the same time that the caps 253 are fitted onto the bolt heads 62. This makes it easy to install the primary fins 250.

[0097] (Other embodiments) The technology disclosed herein is not limited to the above-described embodiments, and can be substituted within the scope of the claims.

[0098] In the above-described first and second embodiments, the primary fin 50, the first sub-fin 51, and the second sub-fin 52 are provided only around the inlet portion 41a of the exhaust-side return passage 41. However, the present invention is not limited to this, and the primary fin, the first sub-fin, and the second sub-fin may also be provided around the inlet portion of the intake-side return passage 42 so as to generate a vortex flow in the intake-side return passage 42.

[0099] In the above-described first and second embodiments, the second sub-fins 52 are provided, but the second sub-fins 52 may be omitted.

[0100] In the first and second embodiments described above, the primary fins 50, 250 are inclined toward the first side in the predetermined direction toward the exhaust side. However, the primary fins 50, 250 may be inclined toward the second side in the predetermined direction toward the exhaust side. In this case, the first sub-fin 51 is located on the second side in the predetermined direction with respect to the inlet portion 41a and is inclined toward the first side in the predetermined direction toward the exhaust side. Furthermore, the inclination direction and inclination angle of the primary fin 50, the first sub-fin 51, and the second sub-fin 52 may differ for each exhaust-side return passage 41.

[0101] In the above-described first embodiment, the primary fin 50 is located on the second side in the predetermined direction of the center of the bolt head 62. However, the present invention is not limited to this, and the primary fin 50 may overlap with the center of the bolt head 62 in the predetermined direction as long as the center of the primary fin 50 in the predetermined direction coincides with the center of the bolt head 62 in the predetermined direction or is located on the second side in the predetermined direction of the center of the bolt head 62.

[0102] In the first embodiment described above, the primary fin 50 is disposed so as to block one of a pair of passages located between the bolt head 62 and the exhaust valve 16a. However, the present invention is not limited to this, and the primary fin 50 does not necessarily have to block the passage.

[0103] The above-described embodiments are merely examples and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations that fall within the scope of the claims equivalents are within the scope of the present disclosure. [Industrial Applicability]

[0104] The technology disclosed herein is useful as an engine oil cooling structure. [Explanation of symbols]

[0105] 3 Cylinder block 4. Cylinder head 4a Middle Deck 10 Engine body 30 Oil pan 31 Oil pump 41 Exhaust return passage 41a Entrance 50 Main fin 51 1st secondary fin 61 Bolt head 250 Main fin L1 straight line L2 straight line α1 angle

Claims

1. An engine oil cooling structure for supplying oil stored in an oil pan disposed below a cylinder block of an engine body by an oil pump to a lubricated part of a cylinder head and then returning the oil to the oil pan while cooling it, a return passage having an inlet on the exhaust side of a middle deck portion of the cylinder head for returning oil from the cylinder head to the oil pan; a main fin located closer to the intake side than the inlet portion, erected above the middle deck portion, and inclined toward the exhaust side to one side or the other of a predetermined direction perpendicular to both the intake / exhaust direction and the up-and-down direction; a secondary fin positioned on the exhaust side of the main fin and on the inclined side of the main fin in the predetermined direction with respect to the inlet portion, the secondary fin being erected above the middle deck portion, The secondary fin is inclined toward the inlet portion in the predetermined direction toward the exhaust side.

2. 2. The engine oil cooling structure according to claim 1, a bolt head for fastening the cylinder head and the cylinder block is located closer to the intake side than the inlet portion; The main fin extends obliquely from a position closer to the intake side than the bolt head toward the exhaust side.

3. 3. The engine oil cooling structure according to claim 2, the main fin is located on the intake side of the bolt head and on the one side or the other side of the center of the bolt head in the predetermined direction, The main fin is also inclined toward the bolt head side in the predetermined direction toward the exhaust side.

4. 4. The engine oil cooling structure according to claim 3, engine parts are disposed on both sides of the bolt head in the predetermined direction, The engine oil cooling structure, wherein the main fin is arranged so as to block one of a pair of passages located between the bolt head and the engine component.

5. 2. The engine oil cooling structure according to claim 1, In a plan view, an angle between a line extending in the direction in which the primary fin extends and a line extending in the direction in which the secondary fin extends is 80° to 90°.

6. The engine oil cooling structure according to any one of claims 1 to 5, The engine oil cooling structure has a width of the secondary fins that is wider on the side closer to the middle deck portion than on the side farther from the middle deck portion.

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