Engine oil cooling structure

Abstract

To provide an oil cooling structure for an engine capable of suppressing rise in an oil temperature.SOLUTION: There is provided an oil cooling structure for an engine, in which, oil stored in an oil pan 30 disposed below a cylinder block 3 of an engine body 10, after supplied to parts 17 and 18 to be lubricated by being transferred with help of an oil pump 31, returns to the oil pan 30 and circulates, comprising a cylinder head recess 4A that is disposed on a cylinder head 4 of the engine body 10, and on which the oil after lubricating the parts 17 and 18 to be lubricated is dripped. The cylinder head recess 4A comprises agitation mechanisms 60 and 70 that are disposed in a location including a portion above a cooling part 14 for cooling the cylinder head 4, and by using rotation of cam shafts 17 and 18 rotatably mounted on the cylinder head 4, agitate the oil stored in the cylinder head recess 4A.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to an oil cooling structure for an engine mounted on a vehicle such as an automobile.

Background Art

[0002] An engine mounted on a vehicle is generally configured such that oil stored in an oil pan provided below a cylinder block of the engine is sucked out by an oil pump and supplied to lubricated parts of the engine (e.g., cylinders, pistons, camshafts, etc.).

[0003] The oil supplied to lubricated parts such as a camshaft provided above the engine drips onto a cylinder head that is disposed on the upper surface of the cylinder block and forms a combustion chamber together with a piston, and returns to the oil pan through an oil return passage provided in the cylinder head and the cylinder block.

[0004] The oil supplied to the lubricated parts may be heated by the lubricated parts and its temperature may rise depending on the temperature of the lubricated parts. 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 deteriorates.

[0005] Generally, a cylinder head includes a combustion chamber, intake ports and exhaust ports that open into the combustion chamber, and a water jacket as a cooling part through which cooling water for cooling the combustion chamber flows. The cylinder head is provided with a cylinder head recess that includes a bottom surface extending in the width direction (intake side and exhaust side) orthogonal to the crankshaft above the water jacket, and inclined surfaces that incline outward in the width direction upward from both ends of the bottom surface. A camshaft or the like is disposed at the upper end of the cylinder head, and the oil supplied to the lubricated parts such as the camshaft drips onto the bottom surface of the cylinder head recess.

[0006] Patent Document 1 discloses an engine with a cylinder head structure that promotes heat exchange between oil dripping onto the bottom surface and cooling water, by providing a plurality of fins protruding upward from the bottom surface on the bottom surface located above the water jacket, with the aim of promoting oil cooling. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-44118 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] When using low-viscosity oil with a lower upper temperature limit than conventional oils to improve fuel efficiency, or when eliminating oil coolers to reduce costs and the number of parts, there is an even greater need to suppress the temperature rise of the oil itself.

[0009] The present invention aims to provide an engine oil cooling structure capable of suppressing the rise in oil temperature. [Means for solving the problem]

[0010] The present invention relates to an engine oil cooling structure in which oil stored in an oil pan located below the cylinder block of the engine body is transported by an oil pump to a lubricated part, and then returned to the oil pan for circulation, and further comprises a cylinder head recess provided in the cylinder head of the engine body, from which the oil that has lubricated the lubricated part is dripped, and the cylinder head recess is a cooling part that cools the cylinder head Directly above The system includes a stirring mechanism that is located in a position including the cylinder head and utilizes the rotation of a camshaft rotatably mounted to the cylinder head to agitate the oil accumulated in the cylinder head recess. The camshafts are provided in multiple locations, and in a plan view, the multiple camshafts are arranged side by side in a width direction perpendicular to the crankshaft, and the cylinder head recess is located directly above the combustion chamber partitioned by the cylinder block, the cylinder head, and the piston, and below the region between the multiple camshafts in the width direction. To provide an engine oil cooling structure.

[0011] According to the present invention, the oil accumulated in the cylinder head recess is agitated by the agitation mechanism, which promotes the cooling of the oil accumulated in the cylinder head recess compared to when the oil is not agitated, thereby suppressing the rise in oil temperature. As a result, the reliability of the engine can be improved.

[0012] The bottom surface of the cylinder head recess is located near the cooling section, so the oil accumulated in the cylinder head recess tends to become cooler due to heat exchange between the oil near the bottom surface and the bottom surface itself. On the other hand, the oil located on the upper side, opposite the cooling section, tends to become hotter than the oil near the bottom surface.

[0013] In contrast, when a stirring mechanism mixes the low-temperature oil near the bottom with the high-temperature oil above, the oil temperature near the bottom rises above the oil temperature before mixing the low-temperature and high-temperature oils. This increases the temperature difference between the bottom and the oil near the bottom, promoting heat exchange between the bottom and the oil near the bottom compared to a case where only the oil near the bottom is cooled and maintains a temperature close to the bottom temperature.

[0014] Therefore, the overall oil temperature of the oil accumulated in the cylinder head recess is lowered, and the temperature rise of the oil when it flows from the cylinder head recess into the return passage is suppressed.

[0015] It is preferable that the engine is equipped with a disconnection mechanism that connects the stirring mechanism to the camshaft when the engine enters an operating state where the oil temperature exceeds a predetermined temperature.

[0016] With this configuration, the agitation mechanism can be activated only when oil cooling is necessary, thus suppressing the rise in oil temperature while minimizing the increase in mechanical resistance that may occur when the agitation mechanism is activated. Due to the properties of oil, viscosity decreases at high temperatures, causing seizure in the lubricated parts, so it is necessary to suppress the rise in oil temperature. To address this, the agitation mechanism can be activated when the oil temperature exceeds a predetermined temperature during operation, or when the engine is running at high speeds where the oil is prone to becoming hot, thereby promoting oil cooling. The operation of the agitation mechanism may also be determined by the relationship between the engine load and rotational speed at which the oil temperature exceeds a predetermined temperature.

[0017] The stirring mechanism may be provided only on the intake side of the engine, with the intake side and exhaust side being the other side, centered on the crankshaft of the engine.

[0018] With this configuration, the oil on the intake side tends to be cooler than the exhaust side, and the temperature difference with the bottom surface of the cylinder head recess tends to be closer. By agitating the oil on the intake side, the cooling of the oil accumulated in the cylinder head recess is promoted, and the rise in oil temperature is suppressed.

[0019] The stirring mechanism may be provided only on the exhaust side of the engine, with the intake side and the exhaust side being the other side, centered on the crankshaft of the engine.

[0020] With this configuration, the oil dripping from the exhaust side of the cylinder head recess is agitated by the agitation mechanism, which prevents it from directly flowing into, for example, the return passage provided on the exhaust side. Compared to the case where the oil dripping from the lubricated part directly flows into the return passage, the oil can be cooled by the cooling unit, thus suppressing the rise in oil temperature.

[0021] The stirring mechanism may rotate to guide the oil accumulated in the cylinder head recess towards the intake side.

[0022] According to this configuration, by guiding the oil accumulated in the cylinder head recess to the intake side, which is at a lower temperature than the exhaust side, the oil can be cooled by the cooling unit compared to the case where the oil only passes through the exhaust side and flows into the return passage, so that the temperature rise of the oil is suppressed.

[0023] The stirring mechanism may include a drive gear provided on the rotation axis of the camshaft, a driven gear driven by the drive gear, and a stirring member disposed on the rotation axis of the driven gear and having a plurality of fins radially extending outward from the center of the rotation axis.

[0024] According to this configuration, by utilizing the rotation of the camshaft, the stirring of the oil by the stirring member can be realized, so there is no need to provide a rotation mechanism for the stirring mechanism, and while suppressing an increase in the number of parts and an increase in the assembly man-hours, the cooling of the oil can be promoted. The stirring mechanism can be arranged in a limited area within the cylinder head recess.

[0025] It is preferable that the outer ends of the plurality of fins extend to near the bottom surface of the cylinder head recess.

[0026] According to this configuration, the plurality of fins can mix the lower-temperature oil near the bottom surface of the cylinder head recess and the upper high-temperature oil, so that the cooling of the oil is more effectively promoted.

[0027] The cylinder head recess preferably extends in the cylinder bank direction of the engine, and a plurality of the stirring members are preferably arranged in the cylinder bank direction.

[0028] According to this configuration, the plurality of stirring members can easily mix the entire oil accumulated in the cylinder head recess over a wide range. Since the area for promoting heat exchange in the cylinder head recess can be increased, the cooling of the oil is more effectively promoted.

[0029] The cylinder head is provided with a water jacket through which cooling water from a water pump flows. The cooling unit may be composed of the water jacket.

[0030] In this configuration, since the cylinder head recess is positioned adjacent to the water jacket, the bottom surface of the cylinder head recess can be cooled by the cooling water flowing through the water jacket. This promotes heat dissipation from the oil and suppresses the rise in oil temperature.

[0031] According to the engine oil cooling structure of the present invention, it is possible to suppress the rise in oil temperature. [Brief explanation of the drawing]

[0032] [Figure 1] This is a schematic diagram showing the configuration of an engine according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view of the cylinder head along the line II-II in Figure 1. [Figure 3] This is a cross-sectional view of the cylinder block along the line III-III in Figure 1. [Figure 4] This is a cross-sectional view showing the engine oil passage along the IV-IV line in Figure 2. [Figure 5] This is a schematic diagram showing the oil supply passage of an engine according to an embodiment of the present invention. [Figure 6] This is a cross-sectional view showing an analytical model of the temperature distribution of oil flowing through a pipeline. [Figure 7] This graph shows the temperature of the oil flowing near the inner wall surface W of the pipeline and the temperature of the oil flowing through the center of the pipeline. [Figure 8] This is an explanatory diagram of the analytical model for the oil mixture accumulated in the recess of the cylinder head. [Figure 9] This graph shows the oil temperature near the bottom and the average temperature of the entire oil accumulated in the cylinder head recess, both when the oil accumulated in the recess is not mixed and when it is mixed. [Figure 10] This is a plan view of the stirring mechanism and cylinder head as seen from arrow X in Figure 1. [Figure 11] Figure 10 shows a cross-sectional view of the stirring mechanism and cylinder head along the line XI-XI. [Figure 12] This is a schematic cross-sectional view showing the disconnection mechanism of the oil cooling structure in a disassembled state. [Figure 13] This is a schematic cross-sectional view showing the state in which the disconnection mechanism of the oil cooling structure is fastened. [Figure 14] This diagram illustrates the oil flow when the stirring mechanism in Figure 11 is in operation. [Figure 15] This figure shows a modified example of the stirring mechanism shown in Figure 11. [Modes for carrying out the invention]

[0033] Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0034] The oil cooling structure according to an embodiment of the present invention is applied to an engine 1. As shown in Figure 1, the engine 1 according to an embodiment of the present invention is mounted on a vehicle such as an automobile and is a so-called longitudinally mounted engine 1 in which the crankshaft 6a extends in the front-rear direction. The engine 1 comprises an engine body 10, the engine body 10 comprising a cylinder block 3 in which cylinders 2 are formed and a cylinder head 4 disposed on the cylinders 2. The cylinder block 3 and cylinder head 4 are formed of a metal material such as an aluminum alloy.

[0035] A piston 5 is positioned within the cylinder 2 so as to be able to reciprocate. The piston 5 is connected via a connecting rod 7 to a crankshaft 6, which is 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.

[0036] The cylinder head 4 has intake ports 15 and exhaust ports 16. Each cylinder 2 is provided with two intake ports 15 and two exhaust ports 16, and the two intake ports 15 and two exhaust ports 16 are spaced apart in the axial direction of the crankshaft 6a, which is perpendicular to the central axis 2a of the cylinder 2.

[0037] 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. A catalytic converter 11 equipped with a catalyst for purifying exhaust gas, and an exhaust pipe 12 are connected to the exhaust passage. The catalytic converter 11 and the engine 1 are arranged side by side in the width direction of the vehicle body.

[0038] As shown by the dashed lines, intake valves and exhaust valves are provided at the top of the cylinder head 4 to open and close the intake port 15 and exhaust port 16, respectively. The intake valve opens and closes the intake port 15 at predetermined timings by an intake camshaft 17 driven by the crankshaft 6, supplying air to the combustion chamber 8 during the intake stroke. The exhaust valve opens and closes the exhaust port 16 at predetermined timings by an exhaust camshaft 18 driven by the crankshaft 6, discharging exhaust gas from the combustion chamber 8 during the exhaust stroke.

[0039] Inside the cylinder head 4, a head-side water jacket 14 is formed, which serves as a cooling section through which cooling water circulates to cool the cylinder head 4, particularly the combustion chamber 8. The head-side water jacket 14 is located above the combustion chamber 8, and in the cross-section shown in Figure 1, it is located between the intake port 15 and the exhaust port 16. The head-side water jacket 14 is located above each combustion chamber 8 and is formed to surround a boss portion 51 (see Figure 2) for mounting a spark plug (not shown). In this embodiment, since the spark plug is located at the center of the cylinder 2 along the central axis 2a of the cylinder 2, the central part of the head-side water jacket 14 in the width direction perpendicular to the crankshaft 6a is located near the central axis 2a of the cylinder 2.

[0040] As shown in Figure 1, the cylinder head 4 is provided with a cylinder head recess 4A into which oil drips after lubrication of lubricated parts such as the camshafts 17 and 18 located at the upper end of the cylinder head 4. The cylinder head recess 4A is located approximately in the center of the vertical direction of the cylinder head 4, above the head-side water jacket 14, and has a bottom surface 4a that extends in the width direction perpendicular to the crankshaft 6a, and inclined surfaces 4b and 4c that slope upward toward the outside in the width direction from both ends of the bottom surface 4a. The bottom surface 4a constitutes the upper surface of the head-side water jacket 14.

[0041] The widthwise center of the bottom surface 4a is positioned to roughly coincide with the central axis 2a of the cylinder 2. Therefore, the widthwise center of the bottom surface 4a and the widthwise center of the head-side water jacket 14 roughly coincide in the widthwise direction. The inclined surfaces 4b and 4c consist of an intake-side inclined surface 4b located on one side of the widthwise direction of the bottom surface 4a and an exhaust-side inclined surface 4c located on the other side of the widthwise direction, with the crankshaft 6a in between.

[0042] The exhaust-side inclined surface 4c slopes upward toward the catalytic converter 11 from the end of the bottom surface 4a on the catalytic converter 11 side. The exhaust-side inclined surface 4c forms part of the inner surface of the side wall of the cylinder head 4 and, being located on the exhaust side, becomes hotter than the bottom surface 4a due to the exhaust gas. In addition, since the catalytic converter 11 is located adjacent to the outer side of the exhaust-side inclined surface 4c in the width direction, the exhaust gas from the catalytic converter 11 tends to make the exhaust-side inclined surface 4c even hotter.

[0043] Since the bottom surface 4a is positioned above the head-side water jacket 14, it is at a lower temperature than the exhaust-side inclined surface 4c. Furthermore, as mentioned above, the center of the bottom surface 4a in the width direction roughly coincides with the center of the head-side water jacket 14 in the width direction, so the center of the bottom surface 4a is cooled compared to the sides of the bottom surface 4a in the width direction.

[0044] The cylinder head recess 4A is closed at one end and the other end in the direction of the crankshaft 6a by a front portion 4d and a rear portion 4e that rise from the one end and the other end of the crankshaft 6a on the bottom surface 4a (see Figure 2). The front portion 4d and the rear portion 4e are provided with recesses for arranging the intake camshaft 17 and the exhaust camshaft 18.

[0045] As shown in Figure 2, the cylinder head 4 extends in the direction of the cylinders and has a rectangular shape in plan view. The bottom surface 4a is provided with a boss portion 51 for mounting a spark plug (not shown) for each cylinder 2. On the bottom surface 4a, an intake boss portion 52 and an exhaust boss portion 53 are provided on the intake side and exhaust side, respectively, flanking the boss portion 51. An intake valve is located in the intake boss portion 52, and an exhaust valve is located in the exhaust boss portion 53.

[0046] The bottom surface 4a has multiple head bolt insertion holes 54a, each surrounding the cylinder 2, through which head bolts (not shown) for attaching the cylinder head 4 to the cylinder block 3 are inserted. The bottom surface 4a also has head-side return passages 42 and 46, described later, on the side wall opposite the crankshaft to the head bolt insertion holes 54a.

[0047] As shown in Figure 3, a cylinder-side water jacket 13, which serves as a cooling section through which cooling water flows, is provided on the upper side of the cylinder block 3, surrounding the cylinder 2 radially outward. The cylinder-side water jacket 13 has a closed-loop structure that surrounds the radially outward side of the cylinder 2 in the cylinder row. The cylinder-side water jacket 13 is formed to open upward.

[0048] The cylinder-side water jacket 13, located on both sides of the crankshaft 6a axis, has multiple arc-shaped portions 13a that partially surround the cylinder 2 and multiple recesses 13b that extend inward between the cylinders 2. In the cylinder-side water jacket 13, the arc-shaped portions 13a and recesses 13b are arranged alternately on both sides of the cylinder row in the axial direction. At the front and rear ends of the cylinder row, front end portions 13c and rear end portions 13c are provided, respectively, which connect the arc-shaped portions 13a and surround the front and rear ends of the cylinders 2.

[0049] Multiple screw holes 54b are provided on both sides of the cylinder row of the cylinder block 3 for screwing in head bolts to secure the cylinder head 4. In a plan view, each screw hole 54b is located outside the recess 13b, the front end 13c, and the rear end 13c of the cylinder-side water jacket 13.

[0050] In this embodiment, an oil pan 30 is located at the lower end of the cylinder block 3 to store oil for lubricating the parts to be lubricated, such as the piston 5, crankshaft 6, and camshafts 17 and 18.

[0051] In this embodiment, the engine 1 is mounted on the vehicle and supported by the vehicle frame, with the central axis 2a of the cylinder 2 positioned to extend in a direction inclined toward the exhaust side at a predetermined angle θ1, such as 10 degrees, from the vertical, as shown in Figure 1.

[0052] As shown in Figures 1, 4, and 5, the engine 1 is equipped with an oil passage 20 that circulates oil within the engine 1 to lubricate the lubricated parts (piston 5, crankshaft 6, camshafts 17, 18, etc.), and constitutes part of the oil cooling structure. The oil passage 20 has an oil supply passage 21 that supplies oil to the lubricated parts and an oil return passage 22 that returns the oil supplied to the lubricated parts back to the oil pan.

[0053] As shown in Figure 5, the oil supply passage 21 includes an oil pump 31 that draws up oil stored in the oil pan 30, an oil filter 32 that filters the oil discharged from the oil pump 31, an oil cooler 33 that cools the oil discharged from the oil pump 31, and an oil supply passage 35 provided in the engine body 10.

[0054] 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, a third supply oil passage 38 provided in the cylinder head 4, a first connecting oil passage 39 that connects the first supply oil passage 36 and the second supply oil passage 37, and a second connecting oil passage 40 that connects the second supply oil passage 37 and the third supply oil passage 38.

[0055] As shown in Figures 1 and 5, the oil pump 31 is driven by the crankshaft 6. The oil discharged from the oil pump 31 flows through the first supply oil passage 36 to the oil filter 32 for filtration, and then flows into the oil cooler 33 for cooling. The oil cooled in the oil cooler 33 is supplied to the second supply oil passage 37 of the cylinder block 3 through the first connecting oil passage 39.

[0056] As shown in Figures 1, 4, and 5, the first supply oil passage 36 includes an oil passage 36a located within the oil pan 30 and connecting the oil pump 31 and the oil filter 32, an oil passage 36b located adjacent to the exhaust side of the oil pan 30 and connecting the oil filter 32 and the oil cooler 33, and an oil passage 36c extending upward from the oil cooler 33 and connected to the first communication oil passage 39 located in the cylinder block 3.

[0057] As shown in Figures 4 and 5, the first connecting oil passage 39 is provided in the cylinder block 3 and includes an oil passage 39a that opens to the exhaust side and extends radially in the direction of the cylinder 2 (width direction of the engine body 10), and an oil passage 39b that extends upward from the radially inner end of the oil passage 39a.

[0058] The second oil supply passage 37 includes a main gallery 37a to which the oil passage 39c is connected and which extends in the direction of the cylinder row, and a plurality of branch oil passages 37b that branch off from the main gallery 37a and extend downward toward the crankshaft 6a to supply oil to the lubricated part of the crankshaft 6.

[0059] 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, and is situated near the lower end of the cylinder 2. The downstream end of each of the multiple branch oil passages 37b opens toward the crankshaft 6a of the cylinder block 3.

[0060] As shown in Figure 5, the second supply oil passage 37 further includes an oil passage 37c that branches off from one end of the main gallery 37a, extends in the width direction, and communicates with the second connecting oil passage 40.

[0061] The second connecting oil passage 40 includes an oil passage 40a provided in the cylinder block 3 and extending upward from the end of the oil passage 37c on the main gallery 37a side, and an oil passage 40b provided in the cylinder head 4 that communicates with oil passage 40a and extends upward.

[0062] 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 intake side of the oil passage 38a, and a head-side gallery 38c extending from the oil passage 38b in the direction of the cylinder row. 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 intake side and exhaust side cam journals of the camshafts 17 and 18, respectively.

[0063] In addition to the above-described configuration, the oil supply passage 21 is also formed to supply oil to, for example, an oil jet for cooling the piston.

[0064] As shown in Figure 4, the oil supplied to the camshafts 17 and 18, which are the lubricated parts of the engine 1, via the oil supply passage 21 drips onto the intake and exhaust inclined surfaces 4b and 4c and the bottom surface 4a of the cylinder head 4 (arrow a), and is returned to the oil pan 30 through the head-side return passages 42 and 46 that constitute the oil return passage 22 provided on the bottom surface 4a.

[0065] When engine 1 is mounted on the vehicle body, the bottom surface 4a is inclined with respect to the horizontal plane 2b such that the exhaust side is lower than the intake side. Therefore, oil that drips onto the bottom surface 4a is easily guided to the exhaust side head-side return passage 42.

[0066] The oil return passage 22 comprises a plurality of exhaust-side return passages 41 and intake-side return passages 45 through which the oil supplied to the camshafts 17 and 18, which are lubricated parts, flows to the exhaust port 16 side and the intake port 15 side. The exhaust-side return passages 41 and intake-side return passages 45 are formed to communicate with return passages 43 and 47 provided in the cylinder block 3 and to open into the oil pan 30.

[0067] When engine 1 is started, the oil pump 31 is driven in conjunction with the rotation of the crankshaft 6. As shown by the arrows in Figure 5, the oil pump 31 draws oil stored in the oil pan 30 through its suction port 31a and supplies the drawn-in oil to the lubricated parts of the engine body 10 via the first supply oil passage 36, the first connecting oil passage 39, the second supply oil passage 37, the second connecting oil passage 40, and the third supply oil passage 38 in sequence.

[0068] The oil supplied to the lubricated part in this manner lubricates the part via the oil supply passage 21, absorbs heat such as frictional heat generated during the operation of the lubricated part, and is then returned to the oil pan 30 via the oil return passage 22.

[0069] 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 part. Therefore, the oil is cooled by dissipating heat at the bottom surface 4a, which is located above the head-side water jacket 14, and at the return passage 43, which is located adjacent to the cylinder-side water jacket 13, before being returned to the oil pan 30.

[0070] As mentioned above, the exhaust-side inclined surface 4c forms part of the inner surface of the side wall of the engine body 10 and is located on the exhaust side, so it becomes hotter than the bottom surface 4a due to the exhaust gas. For this reason, the oil that flows from the exhaust-side inclined surface 4c to the bottom surface 4a is easily heated up by the heat absorbed from the exhaust-side inclined surface 4c. The oil accumulated in the cylinder head recess 4A is cooled by heat exchange with the bottom surface 4a, which is cooled by the cooling water flowing through the water jacket 14, and then flows out into the exhaust-side return passage 41.

[0071] Here, with reference to Figures 6 and 7, the cooling of the oil 100 by heat exchange between the cooled inner wall surface W of the pipeline and the oil 100 flowing through the pipeline will be explained. Figure 6 shows an analytical model of the oil temperature behavior of the oil 100 flowing through the pipeline: (a) a cross-sectional view along the flow direction, and (b) a cross-sectional view perpendicular to the flow direction along the VI-VI line in Figure 6(a). Figure 7 is a graph comparing the temperature T1 of the oil 101 flowing near the inner wall surface W of the pipeline and the temperature T2 of the oil 102 flowing through the center of the pipeline.

[0072] In the analysis model, the temperature T1 of the oil 101 flowing near the inner wall W of the pipeline and the temperature T2 of the oil 102 flowing through the center of the pipeline were calculated by simulation, assuming that the wall temperature Twall of the inner wall W of the pipeline W was 80 degrees and the temperature Toil of the oil 100 flowing into the pipeline at the inlet was 120 degrees.

[0073] According to the simulation results shown in Figure 7, the temperature T1 of oil 101 near the inner wall surface W of the pipe (a layer 0.5 mm from the inner wall surface W) decreases, while the temperature Toli2 of oil 102 in the center of the pipe (for example, a layer 1 mm from the center of the pipe) does not decrease.

[0074] The amount of heat dissipated Q is given by Q = hS(T1-Twall), where h is the heat transfer coefficient of the oil, S is the inner wall area of ​​the pipe, T1 is the oil temperature near the wall, and Twall is the wall temperature. Therefore, since the amount of heat dissipated Q is proportional to the temperature difference between the oil temperature T1 and the inner wall surface Twall of the pipe, if the oil 101 near the inner wall surface W of the pipe is cooled and the temperature difference with the inner wall surface W becomes small, heat exchange between the oil 101 and the inner wall surface W becomes less likely.

[0075] The phenomenon described above can also occur between the oil accumulated in the cylinder head recess 4A of this embodiment and the bottom surface 4a. Specifically, as schematically shown in Figure 8, the oil 110 that drips into and accumulates in the cylinder head recess 4A flows over the bottom surface 4a from the intake side to the exhaust side and flows out to the return passage 41 side. Therefore, only the oil 111 near the bottom surface 4a exchanges heat with the oil accumulated in the cylinder head recess 4A, and the oil 111~120 accumulated on the upper side of the cylinder head recess 4A flows out to the return passage 41 side without the oil temperature decreasing, thus not promoting a decrease in the overall oil temperature.

[0076] In contrast, to increase the amount of heat dissipated Q by maintaining or increasing the temperature difference between the temperature Twall of the bottom surface 4a and the temperature T11 of the oil 111 near the bottom surface 4a, this embodiment has stirring mechanisms 60 and 70 that mix the oil 111 near the bottom surface 4a with the oil 111 to 120 on the upper side (opposite side of the bottom surface 4a) of the cylinder head recess 4A, as shown by the arrows in Figure 8. The stirring mechanisms 60 and 70 constitute part of the oil cooling structure.

[0077] Figure 8 is an explanatory diagram of the analytical model for the mixing of oil accumulated in the cylinder head recess. Figure 9 is a graph showing the oil temperature near the bottom and the average temperature of the entire oil accumulated in the cylinder head recess, both when the oil accumulated in the cylinder head recess is not mixed and when it is mixed.

[0078] In the analysis model shown in Figure 8, the oil accumulated in the cylinder head recess 4A is divided into 10 layers vertically, and the temperature of the first layer 111, which is the bottom layer in contact with the bottom surface 4a of the cylinder head recess 4A, and the temperature of the oil in the entire cylinder head recess 4A were calculated for each oil mixing state. The oil mixing state was compared between the oil temperature T3 near the bottom surface 4a and the total oil temperature T30 in the cylinder head recess 4A when no oil is mixed, and the oil temperature T4 near the bottom surface 4a and the total oil temperature T40 in the cylinder head recess 4A when the oil from the first layer 111 to the fourth layer 114 is mixed. Here, the oil temperatures T3 and T4 near the bottom surface 4a are the temperatures of the first layer 111 shown in Figure 8. In the analysis model, the wall temperature Twall of the bottom surface 4a was set to 80 degrees, and the temperature T0 at the inlet (intake side) of the oil 110 flowing into the cylinder head recess 4A was set to 120 degrees.

[0079] Figure 9 shows the oil temperature T3 near the bottom surface 4a and the total oil temperature T30 in the cylinder head recess 4A when the first layer of oil 111 near the bottom surface 4a and the second and subsequent layers of oil 112-120 are not mixed, as shown by dashed lines. The oil temperature T4 near the bottom surface 4a and the total oil temperature T40 in the cylinder head recess 4A when the first layer of oil 111 to the fourth layer of oil 114 near the bottom surface 4a are mixed are shown by solid lines.

[0080] According to the simulation results shown in Figure 9, the oil temperature T4 near the bottom surface 4a in the mixed state showed less of a temperature decrease compared to the oil temperature T3 near the bottom surface 4a in the unmixed state. However, the overall oil temperature T40 in the mixed state was lower than the overall oil temperature T30 in the unmixed state.

[0081] As shown by the arrows in Figure 9, compared to the oil temperature T3 near the bottom surface 4a in the unmixed state, the temperature difference ΔT between the oil temperature T4 near the bottom surface 4a and the bottom surface 4a is increased in the mixed state. Therefore, heat exchange between the oil and the bottom surface 4a is promoted, and the amount of heat dissipated by the oil Q can be increased.

[0082] Next, the configuration of the stirring mechanisms 60 and 70 will be explained with reference to Figures 10 to 14.

[0083] As shown in Figures 10 and 11, an exhaust-side stirring mechanism 60 is provided on the exhaust side of the cylinder head recess 4A, and an intake-side stirring mechanism 70 is provided on the intake side of the cylinder head recess 4A. The exhaust-side stirring mechanism 60 and the intake-side stirring mechanism 70 are rotated using the rotation of the exhaust camshaft 18 and the intake camshaft 17, respectively.

[0084] As shown in Figure 11, the intake camshaft 17 and exhaust camshaft 18 drive the intake valve 15a and exhaust valve 16a to open and close by oscillating the rocker arms 17c and 18c at predetermined timings. One end of the rocker arms 17c and 18c abuts against the upper ends of the intake valve 15a and exhaust valve 16a from above, respectively. The other ends of the rocker arms 17c and 18c are abutted from below by lash adjusters 17d and 18d for adjusting the valve clearance of the intake valve 15a and exhaust valve 16a.

[0085] As shown in Figure 10, the intake camshaft 17 and exhaust camshaft 18 extend in the direction of the cylinder row and are rotatably supported by a plurality of bearing portions 17a and 18a provided on the cylinder head 4. The intake camshaft 17 and exhaust camshaft 18 have a plurality of cams 17b and 18b formed on them. The plurality of cams 17b and 18b, rocker arms 17c and 18c, and lash adjusters 17d and 18d are arranged at predetermined intervals in the direction of the cylinder row to correspond to each cylinder.

[0086] As shown in Figure 11, the exhaust-side stirring mechanism 60 and the intake-side stirring mechanism 70 each have drive gears 61, 71, intermediate gears 62, 72, driven gears 63, 73, rotating shafts (second rotating shafts) 64, 74, stirring members 65, 75, disconnection mechanisms 66, 76, and hydraulic supply units 67, 77, respectively. Since the exhaust-side stirring mechanism 60 and the intake-side stirring mechanism 70 have similar configurations, only the exhaust-side stirring mechanism 60 will be described.

[0087] As shown in Figure 10, the drive gear 61 is integrally mounted on the rotation axis (first rotation axis) 18e of the exhaust camshaft 18. The drive gear 61 is located at one end of the exhaust camshaft 18 in the cylinder direction. As shown in Figure 11, the drive gear 61 rotates clockwise (right-hand rotation in Figure 11) along with the rotation of the exhaust camshaft 18. An intermediate gear 62 meshes with the drive gear 61.

[0088] The intermediate gear 62 is positioned below the drive gear 61 (on the bottom surface 4a side of the cylinder head recess 4A) and inward in the cylinder radial direction. The intermediate gear 62 is rotatably supported by, for example, multiple bearing parts provided on the cylinder head 4. The intermediate gear 62 rotates counterclockwise (leftward in Figure 11) in conjunction with the rotation of the drive gear 61. The driven gear 63 meshes with the intermediate gear 62.

[0089] The driven gear 63 is positioned below (towards the bottom surface 4a) and inward in the cylinder radial direction compared to the intermediate gear 62. In the width direction of the cylinder head 4, the driven gear 63 is located between one end and the other end of the rocker arm 18c. In other words, the driven gear 63 is positioned between the exhaust valve 16a and the lash adjuster 18d. The driven gear 63 is rotatably supported, for example, by a plurality of bearing parts provided on the cylinder head 4. The driven gear 63 rotates clockwise via the intermediate gear 62 in conjunction with the rotation of the drive gear 61. The rotation shaft 63a of the driven gear 63 is provided with a disconnection mechanism 66 that switches between a state in which the rotation of the driven gear 63 is transmitted to the rotation shaft 64 of the stirring member 65 and a state in which it is not transmitted.

[0090] As shown in Figure 12, the disconnection mechanism 66 comprises a drum 66a, a hub 66b, a drum-side friction plate 66c, a hub-side friction plate 66d, a piston 66e, a hydraulic chamber 66h, and a return spring 66i. The drum 66a is cylindrical, and the rotating shaft 63a of the driven gear 63 is fixed to its bottom. The drum 66a rotates integrally with the rotating shaft 63a. The hub 66b is positioned opposite the drum 66a on the radially inward side. The hub 66b is fixed to the outer circumference of the rotating shaft 64 of the stirring member 65, which is arranged coaxially with the rotating shaft 63a. The hub 66b rotates integrally with the rotating shaft 64.

[0091] A drum-side friction plate 66c is spline-fitted to the drum 66a so as to be slidable in the axial direction, and a hub-side friction plate 66d is spline-fitted to the hub 66b so as to be slidable in the axial direction. The drum-side friction plate 66c and the hub-side friction plate 66d are arranged alternately in the axial direction.

[0092] The piston 66e is positioned on the driven gear 63 side in the axial direction of the drum-side friction plate 66c and the hub-side friction plate 66d. By moving in the axial direction, the piston 66e presses against the drum-side friction plate 66c and the hub-side friction plate 66d, thereby fastening the drum-side friction plate 66c and the hub-side friction plate 66d together. The piston 66e has a disc portion 66f that forms a hydraulic chamber and a pressing portion 66g that presses against the drum-side friction plate 66c and the hub-side friction plate 66d.

[0093] A hydraulic chamber 66h is provided on the driven gear 63 side in the axial direction of the piston 66e. The hydraulic chamber 66h is provided so as to be continuous with the hollow portion 63b provided on the inner circumference of the rotating shaft 63a. Hydraulic oil is supplied to and discharged from the hydraulic supply unit 67 into the hydraulic chamber 66h. The supply and discharge of hydraulic oil to and from the hydraulic chamber 66h by the disconnection mechanism 66 is controlled by a control unit such as an ECU (Engine Control Unit). When the oil temperature exceeds a predetermined value, a signal is output to the hydraulic supply unit 67 to supply hydraulic oil to the hydraulic chamber 66h. When the oil temperature falls below the predetermined value, the hydraulic oil in the hydraulic chamber 66h is drained.

[0094] At the radial center of the drum 66a is a drum shaft portion 66j, which has a drum shaft hollow portion 66k that is continuous with the hollow portion 63b of the rotating shaft 63a. The hydraulic pressure supplied from the hydraulic supply unit 67 is supplied to the hydraulic chamber 66h via the rotating shaft hollow portion 63b and the drum shaft hollow portion 66k.

[0095] A spring receiving portion 66m is provided on the outer circumference of the drum shaft portion 66j, projecting radially outward. A return spring 66i is mounted on the outer circumference of the drum shaft portion 66j to bias the piston 66e in the release direction. The return spring 66i is positioned between the spring receiving portion 66m and the disc portion 66f of the piston 66e.

[0096] As shown in Figure 13, when the disconnection mechanism 66 is connected, hydraulic pressure is supplied from the hydraulic supply unit 67 to the hydraulic chamber 66h, causing the piston 66e to press against the drum-side friction plate 66c and the hub-side friction plate 66d, fastening the drum 66a and the hub 66b together, and transmitting the rotation of the driven gear 63 to the rotating shaft 64. On the other hand, as shown in Figure 12, when the disconnection mechanism 66 is disconnected, the supply of hydraulic pressure from the hydraulic supply unit 67 to the hydraulic chamber 66h is stopped, the oil in the hydraulic chamber 66h is drained, the disc portion 66f of the piston 66e is pushed back towards the driven gear 63 by the biasing force of the return spring 66i, and the drum-side friction plate 66c and the hub-side friction plate 66d are released.

[0097] The disconnection mechanism 66 maintains a disconnected state as shown in Figure 12 when the oil temperature is below a predetermined temperature. When the oil temperature rises above the predetermined temperature and an operating condition requiring oil cooling is detected, for example, a signal is sent from the control unit to the hydraulic supply unit 67, and hydraulic pressure is supplied to the hydraulic chamber 66h, causing the rotation shafts 64 and 74 of the agitation members 65 and 75 to rotate in conjunction with the rotation of the camshafts 17 and 18. In this embodiment, an operating condition requiring oil cooling is when the oil temperature detected by a temperature sensor, for example, placed in the oil pan, reaches a high temperature of a predetermined temperature (e.g., 100 to 120 degrees Celsius) or higher. Alternatively, an operating condition requiring oil cooling may occur when the engine speed exceeds a predetermined speed, or when the engine torque reaches a high load of a predetermined value or higher. The operation of the agitation mechanisms 60 and 70 may be determined by the relationship between the engine load and speed (e.g., high load and high rotation). The predetermined rotational speed, predetermined torque value, and engine load and rotational speed may be, for example, values ​​corresponding to operating conditions where the oil temperature is above a predetermined temperature.

[0098] As shown in Figure 10, the rotating shaft 64 is positioned to coincide with the rotating shaft 63a of the driven gear 63. The rotating shaft 64 extends in the cylinder direction and is rotatably supported via a plurality of bearings provided on the cylinder head 4. The rotating shaft 64 is arranged parallel to the intake camshaft 17 and the exhaust camshaft 18. A plurality of stirring members 65 are arranged on the rotating shaft 64. The plurality of stirring members 65 are arranged in a line at predetermined intervals in the cylinder row direction, with their positions in the cylinder direction differing from those of the plurality of cams 17b and 18b. In plan view, the plurality of stirring members 65 are provided in a portion corresponding to the water jacket 14 located below the bottom surface 4a of the cylinder head recess 4A.

[0099] As shown in Figures 11 and 12, each stirring member 65 comprises a cylindrical base portion 65a fixed to the rotating shaft 64 in a non-rotatable manner, and a plurality of fins 65b extending radially outward from the outer circumference of the base portion 65a. Referring to Figure 14, the fins 65b are formed of, for example, resin. The fins 65b extend radially outward from the center side of the rotating shaft 64. The fins 65b are curved to bulge outward toward the exhaust side. In this embodiment, since the stirring member 65 rotates clockwise, the fins 65b are curved to bulge outward toward the rear side in the direction of rotation. The outer ends of the fins 65b extend to the vicinity of the bottom surface 4a of the cylinder head recess 4A (for example, the first layer 111 in Figure 8).

[0100] The engine oil cooling structure according to the above embodiment provides the following effects.

[0101] As shown in Figure 14, the agitation mechanisms 60 and 70 agitate the oil accumulated in the cylinder head recess 4A, which promotes the cooling of the oil accumulated in the cylinder head recess 4A compared to when the oil is not agitated, thereby suppressing the rise in oil temperature. As a result, the reliability of the engine can be improved.

[0102] Since the bottom surface 4a of the cylinder head recess 4A is located near the water jacket 14, the oil accumulated in the cylinder head recess 4A is prone to becoming cold due to heat exchange between the oil near the bottom surface 4a and the bottom surface 4a. On the other hand, the oil located on the upper side opposite the water jacket 14 is prone to becoming hotter than the oil near the bottom surface 4a.

[0103] In contrast, when the stirring mechanisms 60 and 70 mix the low-temperature oil near the bottom surface 4a with the high-temperature oil on the upper side, the simulation results shown in Figure 9 above indicate that the oil temperature near the bottom surface 4a rises above the oil temperature before mixing the low-temperature and high-temperature oils. This increases the temperature difference ΔT between the bottom surface 4a and the oil near the bottom surface 4a, promoting heat exchange between the bottom surface 4a and the oil near the bottom surface 4a compared to the case where only the oil near the bottom surface 4a is cooled and maintains a temperature close to that of the bottom surface 4a.

[0104] Therefore, the overall oil temperature of the oil accumulated in the cylinder head recess 4A is lowered, and the rise in oil temperature when it flows from the cylinder head recess 4A into the return passage 42 is suppressed.

[0105] The disconnection and reconnection mechanisms 66 and 76 activate the agitation mechanisms 60 and 70 when the engine oil temperature exceeds a predetermined temperature during operation. This suppresses the rise in oil temperature while minimizing the increase in mechanical resistance that may occur when the agitation mechanisms are activated. In other words, the agitation mechanisms can be activated only when oil cooling is necessary. Due to the properties of oil, viscosity decreases at high temperatures, causing seizure in the lubricated parts, so it is necessary to suppress the rise in oil temperature. To address this, the agitation mechanisms are activated when the oil temperature exceeds a predetermined temperature during operation, or when the engine is running at high speeds where the oil is prone to becoming hot, thereby promoting oil cooling. The operation of the agitation mechanisms may also be determined by the relationship between the engine load and rotational speed at which the oil temperature exceeds a predetermined temperature.

[0106] As shown by the arrows in Figure 14, when the camshafts 17 and 18 rotate clockwise, the drive gear 61, which is mounted on the rotation axis of the camshafts 17 and 18, rotates clockwise, the intermediate gear 62 that meshes with the drive gear 61 rotates counterclockwise, the driven gear 63 that meshes with the intermediate gear 62 rotates clockwise, and the rotating shaft 64 and stirring members 65 and 75, which are connected to the driven gear 63 by the disconnection mechanism 66, rotate clockwise together with the driven gear 63.

[0107] As a result, the oil accumulated in the cylinder head recess 4A is guided from the intake side to the exhaust side by the agitator 65 on the exhaust side and the agitator 75 on the intake side. This flow coincides with the flow of oil accumulated in the cylinder head recess 4A out into the return passage 42 on the exhaust side from the intake side, thus preventing the agitator structures 60 and 70 from obstructing the flow of oil in the cylinder head recess 4A.

[0108] Since the exhaust-side stirring mechanism 60 is provided on the exhaust side, centered on the engine's crankshaft 6a, as shown in Figure 14, the oil dripping onto the exhaust side of the cylinder head recess 4A is stirred by the exhaust-side stirring mechanism 60, thereby preventing it from directly flowing into the return passage 42 provided on the exhaust side. Furthermore, compared to the case where oil dripping from the lubricated part directly flows into the return passage 42, the oil can be cooled by the cooling unit 14, thus suppressing the rise in oil temperature.

[0109] Since the intake agitation mechanism 70 is provided on one intake side, centered around the engine's crankshaft 6a, it can agitate the oil on the intake side, which tends to be cooler than the exhaust side and where the temperature difference with the bottom surface 4a of the cylinder head recess 4A is closer. This promotes the cooling of the oil accumulated in the cylinder head recess 4A.

[0110] The stirring mechanisms 60 and 70 can achieve oil agitation by the stirring members 65 and 75 by utilizing the rotation of the camshafts 17 and 18. Therefore, there is no need to provide a separate rotating mechanism for the stirring mechanism, which promotes oil cooling while suppressing an increase in the number of parts and assembly man-hours. The stirring mechanisms 60 and 70 can be easily positioned in the limited area within the cylinder head recess.

[0111] As shown in Figure 14, since the outer ends of the multiple fins 65b and 75b extend to the vicinity of the bottom surface 4a of the cylinder head recess 4A, the multiple fins 65b and 75b can mix the cooler oil near the bottom surface 4a of the cylinder head recess 4A with the hotter oil above, thereby more effectively promoting oil cooling.

[0112] As shown in Figure 10, since the stirring members 60 and 70 are arranged in multiple locations in the direction of the cylinder row, the entire oil accumulated in the cylinder head recess 4A is easily mixed over a wide area. This increases the area over which heat exchange is promoted in the cylinder head recess 4A, thereby promoting oil cooling more effectively.

[0113] Since the cylinder head recess 4A is located adjacent to the water jacket 14, the bottom surface 4a of the cylinder head recess 4A can be cooled by the cooling water flowing through the water jacket 14.

[0114] In the above-described embodiment, the stirring mechanisms 60 and 70 are configured to guide the oil accumulated in the cylinder head recess 4A to the exhaust side. However, as shown in Figure 15, the stirring mechanisms 60 and 70 may also be configured to guide the oil accumulated in the cylinder head recess 4A to the intake side.

[0115] More specifically, in the stirring mechanisms 60 and 70 shown in Figure 15, the rotation of the drive gears 61 and 71, which rotate together with the camshafts 17 and 18, is transmitted to the driven gears 63 and 73 without passing through the intermediate gears 62 and 72. When the driven gears 63 and 73 are rotated counterclockwise, the rotating shaft 64 and stirring members 65 and 75, which are connected to the driven gears 63 by the disconnection mechanism 66, rotate counterclockwise together with the driven gears 63.

[0116] As a result, the oil accumulated in the cylinder head recess 4A is guided from the exhaust side to the intake side by the agitator 65 on the exhaust side. The oil guided to the intake side flows from the exhaust side to the intake side by the agitator 75 on the intake side and flows out into the return passage 42. Consequently, by guiding the oil accumulated in the cylinder head recess 4A to the intake side, which is cooler than the exhaust side, the oil can be cooled by the cooling unit 14 compared to when the oil passes only through the exhaust side and flows into the return passage 42, thus suppressing the rise in oil temperature.

[0117] In the above-described embodiment, a configuration was described in which the stirring mechanism includes an intake-side stirring mechanism 70 and an exhaust-side stirring mechanism 60. However, the stirring mechanism may also consist of only one of the intake-side stirring mechanism 70 and the exhaust-side stirring mechanism 60.

[0118] The present invention is not limited to the embodiments described herein, and various improvements and design modifications are possible without departing from the spirit of the invention. [Industrial applicability]

[0119] As described above, the present invention provides an engine oil cooling structure that can suppress the rise in oil temperature, and therefore has the potential to be suitably used in the engine manufacturing industry. [Explanation of Symbols]

[0120] 1 Engine 10 Engine body 3 Cylinder block 4 Cylinder head 4A Cylinder head recess 4a Bottom 4c slope 6a Crank axle 11 Exhaust system 14. Head-side water jacket (cooling section) 17. Intake side camshaft (camshaft) 17e Rotation axis (first rotation axis) 18. Exhaust side camshaft (camshaft) 18e Rotation axis (first rotation axis) 20 Oil passages 30 oil pans 31 Oil pump 60. Exhaust side stirring mechanism (stirring mechanism) 61 Drive gear 63 Driven gear 64. Rotation axis (2nd rotation axis) 65 Stirring member 65b fins 66 Disconnection mechanism 70. Intake-side stirring mechanism (stirring mechanism) 76 Disconnection mechanism

Claims

1. An engine oil cooling structure in which oil stored in an oil pan located below the cylinder block of the engine body is transported by an oil pump to the parts to be lubricated, and then returned to the oil pan for circulation, The cylinder head of the engine body is provided with a cylinder head recess from which oil that has been used to lubricate the lubricated part is dripped, The cylinder head recess is provided in a position that includes directly above the cooling section for cooling the cylinder head. The system includes a stirring mechanism that utilizes the rotation of a camshaft rotatably mounted to the cylinder head to agitate the oil accumulated in the recess of the cylinder head, Multiple camshafts are provided, The aforementioned multiple camshafts are arranged in a line in the width direction perpendicular to the crankshaft in a plan view. The cylinder head recess is located directly above the combustion chamber partitioned by the cylinder block, the cylinder head, and the piston, and below the region between the widthwise sections of the plurality of camshafts. Engine oil cooling structure.

2. The engine is equipped with a disconnection mechanism that connects the stirring mechanism to the camshaft when the engine enters an operating state where the oil temperature exceeds a predetermined temperature. The engine oil cooling structure according to claim 1.

3. The stirring mechanism is located on the intake side of the engine, with the crankshaft as the center, and is provided only on the exhaust side of the engine, with one side being the intake side and the other the exhaust side. The engine oil cooling structure according to claim 1.

4. The stirring mechanism is located around the crankshaft of the engine, and is provided only on the exhaust side of the intake side and the exhaust side of the other side. The engine oil cooling structure according to claim 1.

5. The stirring mechanism rotates to guide the oil accumulated in the cylinder head recess towards the intake side. The engine oil cooling structure according to claim 1.

6. The stirring mechanism is, A drive gear provided on the first rotation axis of the camshaft, A driven gear driven by the aforementioned drive gear, The system includes a stirring member disposed on the second rotation axis of the driven gear and having a plurality of fins extending radially outward from the center of the second rotation axis. The engine oil cooling structure according to claim 1.

7. The aforementioned plurality of fins have outer ends that extend to near the bottom surface of the cylinder head recess. The engine oil cooling structure according to claim 6.

8. The cylinder head recess extends in the direction of the cylinder row of the engine, Multiple stirring members are arranged in the direction of the cylinder row. The engine oil cooling structure according to claim 6.

9. The cylinder head is provided with a water jacket through which cooling water from the water pump flows. The cooling unit is composed of the water jacket. The engine oil cooling structure according to claim 1.

10. An engine oil cooling structure comprising an oil pump that transports oil stored in an oil pan located below the cylinder block of the engine body to a part to be lubricated, and then returns the oil to the oil pan for circulation, The cylinder head of the engine body is provided with a cylinder head recess from which oil that has been used to lubricate the lubricated part is dripped, The cylinder head recess is provided in a position that includes above the cooling section for cooling the cylinder head. The system includes a stirring mechanism that utilizes the rotation of a camshaft rotatably mounted to the cylinder head to agitate the oil accumulated in the recess of the cylinder head, The engine is equipped with a disconnection mechanism that connects the stirring mechanism to the camshaft when the engine enters an operating state where the oil temperature exceeds a predetermined temperature. Engine oil cooling structure.

11. An engine oil cooling structure comprising an oil pump that transports oil stored in an oil pan located below the cylinder block of the engine body to a part to be lubricated, and then returns the oil to the oil pan for circulation, The cylinder head of the engine body is provided with a cylinder head recess from which oil that has been used to lubricate the lubricated part is dripped, The cylinder head recess is provided in a position that includes above the cooling section for cooling the cylinder head. The system includes a stirring mechanism that utilizes the rotation of a camshaft rotatably mounted to the cylinder head to agitate the oil accumulated in the recess of the cylinder head, The stirring mechanism is, A drive gear provided on the first rotation axis of the camshaft, A driven gear driven by the aforementioned drive gear, The system includes a stirring member disposed on the second rotation axis of the driven gear and having a plurality of fins extending radially outward from the center of the second rotation axis. Engine oil cooling structure.

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