Engine oil passage structure

Abstract

To efficiently cool the oil without making the oil return passage excessively large. [Solution] The engine 1 comprises a cylinder block 10, a cylinder head 20, an oil pan 30, and a gasket 80. In the oil return passage 50 that returns the oil L that lubricates the lubricated part A of the cylinder head to the oil pan via the cylinder head and cylinder block, the block passage 60 has a larger cross-sectional area S than the head passage 70. The block surface 90 of the cylinder block facing the cylinder head and the head surface 100 of the cylinder head facing the cylinder block are joined to each other via a gasket. The head surface includes a sealing surface 101 that overlaps the block surface via the gasket, and a non-sealing surface 102 that is located on the oil return passage side of the sealing surface and does not overlap the block surface. The non-sealing surface is provided with a first small contact angle portion E1 having a contact angle θ smaller than that of the sealing surface.

Description

Technical Field

[0001] The present disclosure relates to an oil passage structure of an engine.

Background Art

[0002] Generally, an engine is formed with an oil return passage as an oil passage structure. The oil return passage is for returning the oil that has lubricated the lubricated portion of the cylinder head to the oil pan through the cylinder head and the cylinder block. [[ID=1##]]

[0003] The engine according to Patent Document 1 includes a cylinder head provided with a plurality of oil return passages, and a cylinder block provided with an oil return space disposed below the cylinder head and where the oil return passages of the cylinder head merge so as to face the water jacket. In this engine, among the open ends on the cylinder block side of the oil return passages of the cylinder head, the side facing the water jacket is shaped to be closer to the water jacket.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to efficiently cool the oil after lubricating the lubricated portion of the cylinder head, it is important to increase the contact area of the oil flowing through the oil return passage with respect to the cylinder block. A simple method to achieve this is to increase the passage cross - sectional area of the return passage on the cylinder block side.

[0006] However, there are numerous obstructions around the oil return passage on the cylinder block side. Also, the space between the cylinder block and the cylinder head is sealed by a gasket. Simply increasing the cross-sectional area of ​​the oil return passage on the cylinder block side may cause interference with the surrounding obstructions or reduce the sealing performance due to the decrease in the sealing area provided by the gasket.

[0007] In other words, the method of efficiently cooling the oil by excessively increasing the cross-sectional area of ​​the oil return passage on the cylinder block side is difficult from a layout perspective.

[0008] The purpose of this disclosure is to efficiently cool the oil without making the oil return passage on the cylinder block side excessively large. [Means for solving the problem]

[0009] The oil passage structure of the engine according to this disclosure comprises a cylinder block in which a cylinder housing a piston is formed, a cylinder head that together with the cylinder and the piston forms a combustion chamber, an oil pan for storing oil, and a sheet-like gasket that seals the space between the cylinder block and the cylinder head. The cylinder head and the cylinder block are formed with an oil return passage for returning the oil that has lubricated the lubricated portion of the cylinder head back to the oil pan via the cylinder head and the cylinder block. The oil return passage comprises a block passage formed in the cylinder block and a head passage formed in the cylinder head. The block passage has a larger cross-sectional area than the head passage. The block surface of the cylinder block facing the cylinder head and the head surface of the cylinder head facing the cylinder block are joined to each other via the gasket. The head surface includes a sealing surface that overlaps the block surface via the gasket and a non-sealing surface that is located on the oil return passage side of the sealing surface and does not overlap the block surface. The non-sealing surface is provided with a first small contact angle portion having a smaller contact angle than the sealing surface.

[0010] In the oil return passage, the block passage formed in the cylinder block has a larger cross-sectional area than the head passage formed in the cylinder head. The head surface of the cylinder head includes a sealing surface that overlaps the block surface of the cylinder block via a gasket, and a non-sealing surface that is located on the oil return passage side of the sealing surface and does not overlap the block surface of the cylinder block. The non-sealing surface is provided with a first small contact angle portion that has a smaller contact angle than the sealing surface. Because the first small contact angle portion provided on the non-sealing surface has a small contact angle, its wettability is improved.

[0011] After lubricating the lubricated parts of the cylinder head, the oil flows into the head passages of the cylinder head and then into the block passages of the cylinder block. As the oil flows from the head passages into the block passages, it wets and spreads along the first small contact angle provided on the non-sealing surface of the cylinder head surface.

[0012] The oil, which spreads along the first small contact angle, is more likely to come into contact with the passage walls of the block passages in the cylinder block. This increases the contact area between the oil flowing through the block passages and the cylinder block. This allows for efficient cooling of the oil after it has lubricated the lubricated parts of the cylinder head.

[0013] This allows for efficient cooling of the oil without excessively enlarging the block passage, which is the oil return passage on the cylinder block side.

[0014] In one embodiment of the engine oil passage structure, the gasket includes a sealing portion disposed between the sealing surface and the block surface and a non-sealing portion disposed on the non-sealing surface, and the first small contact angle portion is formed by the surface of the non-sealing portion of the gasket that is located on the cylinder block side.

[0015] The first small contact angle can be easily constructed by using a gasket.

[0016] In one embodiment of the engine oil passage structure, the gasket is provided with an opening for the oil return passage, and the edge of the opening is provided with a second small contact angle portion having a smaller contact angle than the sealing surface.

[0017] The oil is more easily wetting and spreading to the second small contact angle located at the edge of the gasket opening. From the second small contact angle located at the edge of the gasket opening, the oil is more easily guided to the first small contact angle located on the non-sealing surface of the gasket (on the cylinder block side).

[0018] In the oil passage structure of the engine according to one embodiment, the surface roughness of the first small contact angle portion is greater than that of the sealing surface.

[0019] By adjusting the surface roughness of the first small contact angle portion, the contact angle of the first small contact angle portion can be easily adjusted.

[0020] In the oil passage structure of the engine according to one embodiment, the contact angle of the first small contact angle portion is 3° or less.

[0021] By making the contact angle of the first small contact angle portion equal to or less than a predetermined value, the wettability of the first small contact angle portion can be further improved.

Advantages of the Invention

[0022] According to the present disclosure, oil can be efficiently cooled without excessively enlarging the oil return passage on the cylinder block side.

Brief Description of the Drawings

[0023] [Figure 1] FIG. 1 shows a cross-sectional view of the engine according to the first embodiment taken along line I-I of FIG. 3. [Figure 2] FIG. 2 shows a cross-sectional view of the engine according to the first embodiment taken along line II-II of FIG. 3. [Figure 3] FIG. 3 shows a cross-sectional view of the engine according to the first embodiment taken along line III-III of FIGS. 1 and 2. [Figure 4] FIG. 4 schematically shows an oil supply passage according to the first embodiment. [Figure 5] FIG. 5 shows an enlarged view of part V of FIG. 2 of an oil return passage according to the first embodiment. [Figure 6] FIG. 6 shows a view of the gasket according to the first embodiment as seen in the direction of arrow along line VI of FIG. 5. [Figure 7] FIG. 7 shows a graph of the relationship between surface roughness and contact angle according to the first embodiment. [Figure 8]Figure 8 is a diagram corresponding to Figure 5 according to the second embodiment, and shows an enlarged view of the oil return passage. [Figure 9] Figure 9 is a diagram corresponding to Figure 5 according to the third embodiment, and shows an enlarged view of the oil return passage. [Modes for carrying out the invention]

[0024] Embodiments of the present disclosure will be described in detail below with reference to the drawings. The following description of preferred embodiments is illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses in any way.

[0025] <First Embodiment> The oil passage structure of the engine 1 according to the first embodiment will be described.

[0026] (engine) Figure 1 shows a cross-sectional view of engine 1 along line II in Figure 3. Figure 2 shows a cross-sectional view of engine 1 along line II-II in Figure 3. Figure 3 shows a cross-sectional view of engine 1 along line III-III in Figures 1 and 2.

[0027] Engine 1 is mounted in the vehicle. As shown in Figures 1-3, engine 1 comprises a cylinder block 10, a cylinder head 20, an oil pan 30, and a gasket 80. The oil passage structure of engine 1 includes an oil supply passage 40 and an oil return passage 50.

[0028] As shown in Figure 1, the cylinder block 10 has a plurality of cylinders 11 formed therein. The cylinders 11 are cylindrical and extend in the vertical direction. The plurality of cylinders 11 are arranged in a row in the cylinder row direction. The vertical direction may be straight with respect to the vertical direction or diagonally with respect to the vertical direction (in this example, it is diagonally extended). The cylinder row direction intersects the vertical direction. The cylinder row direction extends in the horizontal direction.

[0029] The cylinder 11 houses the piston 12. The piston 12 is columnar and extends vertically coaxially with the cylinder 11. The piston 12 reciprocates vertically within the cylinder 11.

[0030] A crank chamber 13 is formed below the cylinder 11 (piston 12) in the cylinder block 10. A crankshaft 14 is located in the crank chamber 13. The crankshaft 14 extends in the direction of the cylinder row and is rotatably supported relative to the cylinder block 10.

[0031] The piston 12 and the crankshaft 14 are connected by a connecting rod 15. When the piston 12 reciprocates within the cylinder 11, the crankshaft 14 rotates.

[0032] As shown in Figures 2 and 3, the cylinder block 10 is provided with a block-side jacket 16. Cooling water (coolant) flows through the block-side jacket 16. The block-side jacket 16 extends in the direction of the cylinder row. The block-side jacket 16 is provided on both outer sides of the cylinders 11 in the width direction (hereinafter simply referred to as the "width direction") perpendicular to the direction of the cylinder row. The block-side jacket 16 collectively surrounds the outer circumference of multiple cylinders 11.

[0033] As shown in Figure 1, the cylinder head 20 is located on the upper part of the cylinder block 10. The cylinder head 20 is positioned on the upper side of the cylinder block 10. The cylinder head 20, together with the cylinder 11 and the piston 12, forms the combustion chamber 21. The combustion chamber 21 is formed above the piston 12. The combustion chamber 21 is formed by the cylinder 11, the piston 12 and the cylinder head 20.

[0034] The cylinder head 20 is divided into upper and lower sections by a middle deck 20a. The middle deck 20a extends horizontally.

[0035] In the cylinder head 20, intake ports 22 and exhaust ports 23 are provided below the middle deck 20a. For example, two intake ports 22 and two exhaust ports 23 are provided for each cylinder 11. In the width direction, the intake ports 22 are located on one side of the combustion chamber 21 (hereinafter sometimes referred to as the "intake side"), and the exhaust ports 23 are located on the other side of the combustion chamber 21 (hereinafter sometimes referred to as the "exhaust side"). Intake air is drawn from the intake pipe into the combustion chamber 21 through the intake ports 22. Exhaust gas is discharged from the combustion chamber 21 into the exhaust pipe through the exhaust ports 23.

[0036] The cylinder head 20 is provided with an intake valve 24 and an exhaust valve 25. The intake valve 24 opens and closes the intake port 22. The exhaust valve 25 opens and closes the exhaust port 23.

[0037] The cylinder head 20 is equipped with an intake camshaft 26 and an exhaust camshaft 27. The intake camshaft 26 drives the intake valve 24. The exhaust camshaft 27 drives the exhaust valve 25. The intake camshaft 26 and the exhaust camshaft 27 are connected to the crankshaft 14. When the crankshaft 14 rotates, the intake camshaft 26 and the exhaust camshaft 27 are driven at a predetermined timing, causing the intake valve 24 and the exhaust valve 25 to open and close the intake port 22 and the exhaust port 23.

[0038] As shown in Figures 1 and 2, the cylinder head 20 is provided with a head-side jacket 28. Cooling water (coolant) flows through the head-side jacket 28. The head-side jacket 28 is formed between the intake port 22 and the exhaust port 23 and above the combustion chamber 21. The head-side jacket 28 extends in the direction of the cylinder row so as to correspond to the block-side jacket 16.

[0039] As shown in Figure 2, the block-side jacket 16 and the head-side jacket 28 are in communication with each other. Cooling water flows between the block-side jacket 16 and the head-side jacket 28.

[0040] As shown in Figure 1, the oil pan 30 is located at the bottom of the cylinder block 10. The oil pan 30 is positioned on the underside of the cylinder block 10. The oil pan 30 is box-shaped with an open top. The oil pan 30 stores oil L.

[0041] The gasket 80, the oil supply passage 40, and the oil return passage 50 will be described later.

[0042] (oil) The cylinder 11, piston 12, crankshaft 14, intake camshaft 26, and exhaust camshaft 27 constitute the lubricated part A of the engine 1. The oil L is there to lubricate the lubricated part A of the engine 1. The cylinder 11, piston 12, and crankshaft 14 constitute the block-side lubricated part A1, which is the lubricated part A of the cylinder block 10. The intake camshaft 26 and exhaust camshaft 27 constitute the head-side lubricated part A2, which is the lubricated part A of the cylinder head 20.

[0043] (Oil supply passage) Figure 4 shows a schematic diagram of the oil supply passage 40. The oil supply passage 40 supplies oil L to the lubricated part A. The oil supply passage 40 is provided in the cylinder block 10, the cylinder head 20, and the oil pan 30.

[0044] The oil supply passage 40 includes an oil pump 41, an oil filter 42, an oil cooler 43, a pan-side supply oil passage 44, a block-side supply oil passage 45, a head-side supply oil passage 46, a first connecting passage 47, and a second connecting passage 48.

[0045] The oil pump 41 is located inside the oil pan 30 (see Figure 1) and draws up the oil L stored in the oil pan 30. The oil filter 42 is located outside the oil pan 30 (specifically, on the exhaust side in the width direction relative to the oil pan 30, see Figure 1) and filters the oil L discharged from the oil pump 41. The oil cooler 43 is located outside the oil pan 30 (specifically, on the exhaust side in the width direction relative to the oil pan 30, see Figure 1) and cools the oil L discharged from the oil pump 41.

[0046] The pan-side supply oil passage 44 is located inside the oil pan 30 and on the outer wall of the oil pan 30. The pan-side supply oil passage 44 includes an oil passage connecting the oil pump 41 and the oil filter 42, and an oil passage connecting the oil filter 42 and the oil cooler 43.

[0047] The block-side supply oil passage 45 is located in the cylinder block 10. The block-side supply oil passage 45 includes a main gallery 45a, a number of branch oil passages 45b, and connecting oil passages 45c.

[0048] The main gallery 45a extends from the cylinder block 10 in the direction of the cylinder row. The main gallery 45a is positioned on the exhaust side in the width direction of the cylinder 11 and near the lower end of the cylinder 11 (see Figure 1).

[0049] The branched oil passages 45b branch off from the main gallery 45a and extend downward. Multiple branched oil passages 45b are arranged in a row with spacing in the direction of the cylinder row. Each branched oil passage 45b corresponds to each cylinder 11. The lower end of each branched oil passage 45b communicates with the bearing section 13a (see Figure 2) for supporting the crankshaft 14 in the crank chamber 13. The oil L that flows from the branched oil passage 45b to the bearing section 13a lubricates the crankshaft 14 (and the bearing section 13a).

[0050] The connecting oil passage 45c branches off from one end of the main gallery 45a in the cylinder row direction and extends to the intake side in the width direction.

[0051] The head-side supply oil passage 46 is located in the cylinder head 20. The head-side supply oil passage 46 has a head-side first oil passage 46a, two head-side second oil passages 46b, a head-side gallery 46c, and a plurality of head-side branch oil passages 46d.

[0052] The head-side first oil passage 46a extends in the width direction. The head-side second oil passage 46b branches off from the head-side first oil passage 46a and extends upward. The two head-side second oil passages 46b are spaced apart in the width direction, with one provided on the intake side and one on the exhaust side.

[0053] The head-side gallery 46c is connected to the head-side second oil passage 46b midway and extends in the direction of the cylinder row.

[0054] The head-side branch oil passages 46d branch off from the head-side gallery 46c and extend downward. Multiple head-side branch oil passages 46d are arranged in a row with spacing between them in the direction of the cylinder row. Each head-side branch oil passage 46d corresponds to each cylinder 11. The intake-side head-side branch oil passage 46d communicates with the bearing portion for supporting the intake camshaft 26. The exhaust-side head-side branch oil passage 46d communicates with the bearing portion for supporting the exhaust camshaft 27. The oil L that flows out from the head-side branch oil passages 46d to each bearing portion lubricates the intake camshaft 26 (and its bearing portion) and the exhaust camshaft 27 (and its bearing portion).

[0055] The first connecting passage 47 extends in the vertical direction. The first connecting passage 47 connects the pan-side supply oil passage 44 and the main gallery 45a of the block-side supply oil passage 45, and also connects the two. The second connecting passage 48 extends in the vertical direction. The second connecting passage 48 connects the connecting oil passage 45c of the block-side supply oil passage 45 and the head-side first oil passage 46a of the head-side supply oil passage 46, and also connects the two.

[0056] Although not shown in the diagram, the oil supply passage 40 further includes an oil passage that supplies oil L to an oil jet or the like for lubricating and cooling the piston 12 (and cylinder 11).

[0057] (Oil return passage) As shown in Figure 2, the oil return passage 50 is formed in the cylinder head 20 and the cylinder block 10. The oil return passage 50 is there to return the oil L that has lubricated the head-side lubricated parts A2 (intake camshaft 26 and exhaust camshaft 27) of the cylinder head 20 to the oil pan 30 via the cylinder head 20 and the cylinder block 10.

[0058] As shown in Figures 2 and 3, there are multiple oil return passages 50, corresponding to multiple cylinders 11. The multiple oil return passages 50 are arranged in a line in the direction of the cylinder row. The oil return passages 50 extend in the vertical direction.

[0059] The oil return passages 50 are provided one on the intake side and one on the exhaust side, between two adjacent cylinders 11 in the cylinder direction, and outside the cylinder row direction of the cylinders 11 located at both ends of the cylinder row direction.

[0060] The intake side oil return passage 50 and the exhaust side oil return passage 50 are located on the outer sides of the cylinder 11 in the width direction. The oil return passage 50 is located further out in the width direction than the block side jacket 16 and the head side jacket 28. The oil return passage 50 is located close to the block side jacket 16 and the head side jacket 28.

[0061] Here, the cylinder block 10 and the cylinder head 20 are connected by bolts (not shown). The cylinder block 10 is provided with block-side bolt holes 17 for passing the bolts through. The cylinder head 20 is provided with head-side bolt holes 29 for passing the bolts through.

[0062] The oil return passage 50 is located outside the width direction of the block-side bolt holes 17 and the head-side bolt holes 29. The oil return passage 50 is located near the block-side bolt holes 17 and the head-side bolt holes 29.

[0063] Figure 5 shows the oil return passage 50 as an enlarged view of section V in Figure 2. As shown in Figures 2, 3 and 5, the oil return passage 50 includes a block passage 60 and a head passage 70.

[0064] The block passage 60 is formed in the cylinder block 10. The block passage 60 extends in the vertical direction. When viewed in the vertical direction, the cross-section of the block passage 60 includes one large circle and two smaller circles connected to the outer circumference of the large circle. Although not shown, the lower end of the block passage 60 communicates with the oil pan 30. A block passage wall 61 is formed on the inner circumference of the block passage 60.

[0065] The head passage 70 is formed in the cylinder head 20. The head passage 70 extends in the vertical direction. The cross-section of the head passage 70 is approximately circular when viewed in the vertical direction. Although not shown, the upper end of the head passage 70 communicates with the head-side lubricated portion A2 of the cylinder head 20. A head passage wall 71 is formed on the inner circumference of the head passage 70.

[0066] After lubricating the head-side lubricated portion A2 of the cylinder head 20, the oil L first flows into the head passage 70 of the oil return passage 50, then into the block passage 60 of the oil return passage 50, and finally returns to the oil pan 30. Since the oil return passage 50 extends vertically, the oil L falls from above to below due to gravity.

[0067] The block passage 60 has a larger cross-sectional area S than the head passage 70. The cross-sectional area S is the area of ​​the cross section perpendicular to the flow direction of the oil return passage 50. The block passage cross-sectional area S1 of the block passage 60 is larger than the head passage cross-sectional area S2 of the head passage 70. A step G is formed between the block passage wall 61 of the block passage 60 and the head passage wall 71 of the head passage 70.

[0068] As shown in Figure 5, the cylinder block 10 has a block surface 90. The block surface 90 is the upper surface facing upwards. The cylinder head 20 has a head surface 100. The head surface 100 is the lower surface facing downwards.

[0069] The block surface 90 of the cylinder block 10 faces the cylinder head 20. The head surface 100 of the cylinder head 20 faces the cylinder block 10. The cylinder head 20 side is the upper side. The cylinder block 10 side is the lower side.

[0070] The upper end of the block passage 60 is provided on the block surface 90. The lower end of the head passage 70 is provided on the head surface 100. As described above, in the oil return passage 50, a step G is formed between the block passage wall 61 of the block passage 60 and the head passage wall 71 of the head passage 70. Correspondingly, the head surface 100 protrudes toward the oil return passage 50 side relative to the block surface 90. Here, the oil return passage 50 side means the side closer to the oil return passage 50. In the example in Figure 5, the oil return passage 50 side is the right side of Figure 5.

[0071] As mentioned above, the cylinder head 20 tends to get hotter than the cylinder block 10 because of the presence of the combustion chamber 21. Conversely, the cylinder block 10 tends to get colder than the cylinder head 20.

[0072] Therefore, in order to efficiently cool the oil L after it has lubricated the head-side lubricated parts A2 of the cylinder head 20 (intake camshaft 26 and exhaust camshaft 27), it is important to increase the contact area of ​​the oil L flowing through the oil return passage 50 with the cylinder block 10. Specifically, increasing the cross-sectional area S of the block passage 60 (which is the oil return passage 50 on the cylinder block 10 side) is effective in efficiently cooling the oil L.

[0073] However, there are numerous obstructions around the block passage 60 (for example, the block-side jacket 16 and the block-side bolt holes 17). Also, the space between the cylinder block 10 and the cylinder head 20 is sealed by a gasket 80. If the passage cross-sectional area S of the block passage 60 is simply increased, there is a risk of interference with the surrounding obstructions or a decrease in sealing performance due to the reduction in the sealing area provided by the gasket 80.

[0074] In other words, the method of efficiently cooling the oil L by excessively increasing the cross-sectional area of ​​the block passage 60 is difficult from a layout standpoint.

[0075] In this embodiment, by implementing the improvements described later, it is possible to efficiently cool the oil L without making the block passage 60 (which is the oil return passage 50 on the cylinder block 10 side) excessively large.

[0076] (gasket) Figure 6 shows the gasket 80 in a view along line VI in Figure 5. As shown in Figures 5 and 6, the gasket 80 is in sheet form. The gasket 80 has its thickness in the vertical direction and extends horizontally. The gasket 80 is positioned between the cylinder block 10 and the cylinder head 20. The gasket 80 provides a liquid-tight seal between the cylinder block 10 and the cylinder head 20.

[0077] Specifically, the gasket 80 is interposed between the block surface 90 of the cylinder block 10 and the head surface 100 of the cylinder head 20. The block surface 90 of the cylinder block 10 and the head surface 100 of the cylinder head 20 are joined to each other via the gasket 80.

[0078] The gasket 80 is positioned over the entire head surface 100. Here, the head surface 100 protrudes toward the oil return passage 50 relative to the block surface 90. Therefore, the gasket 80 protrudes toward the oil return passage 50 relative to the block surface 90.

[0079] As shown in Figures 5 and 6, the head surface 100 includes a sealing surface 101 and a non-sealing surface 102. The sealing surface 101 overlaps the block surface 90 (viewed vertically) via the gasket 80. The sealing function of the gasket 80 is performed on the sealing surface 101.

[0080] The non-sealing surface 102 is located on the oil return passage 50 side of the sealing surface 101. The non-sealing surface 102 does not overlap with the block surface 90 (when viewed in the vertical direction). The sealing function of the gasket 80 is not performed on the non-sealing surface 102.

[0081] As shown in Figures 5 and 6, the gasket 80 includes a sealing portion 81 and a non-sealing portion 82. The gasket 80 includes an upper surface 80a facing upward and a lower surface 80b facing downward. The upper surface 80a is the surface of the gasket 80 that is located on the cylinder head 20 side. The lower surface 80b is the surface of the gasket 80 that is located on the cylinder block 10 side.

[0082] The sealing portion 81 of the gasket 80 is positioned between the sealing surface 101 of the head surface 100 and the block surface 90. The upper surface 80a of the sealing portion 81 of the gasket 80 faces the sealing surface 101 of the head surface 100. The lower surface 80b of the sealing portion 81 of the gasket 80 faces the block surface 90.

[0083] In the gasket 80, the non-seal portion 82 is positioned on the oil return passage 50 side of the seal portion 81. The non-seal portion 82 of the gasket 80 is positioned on the non-seal surface 102 of the head surface 100. The non-seal portion 82 of the gasket 80 is not positioned on the block surface 90. The upper surface 80a of the non-seal portion 82 of the gasket 80 faces the non-seal surface 102 of the head surface 100. The lower surface 80b of the non-seal portion 82 of the gasket 80 does not face the block surface 90.

[0084] As shown in Figures 5 and 6, the gasket 80 is provided with an opening 83. The opening 83 penetrates the gasket 80 in the vertical direction (thickness direction). The opening 83 is there for the oil return passage 50 to pass through.

[0085] The opening 83 is approximately circular when viewed in the vertical direction. The shape and size of the opening 83 correspond to the head passage 70 and are the same as the cross-section of the head passage 70. The edge 83a of the opening 83 extends along the head passage wall 71 of the head passage 70. The edge 83a constitutes the inner circumference of the opening 83.

[0086] (Surface roughness and contact angle) Figure 7 shows the relationship between surface roughness R and contact angle θ in a graph. Surface roughness R represents the degree of unevenness of a solid surface. A smaller surface roughness R indicates a smoother surface, while a larger surface roughness R indicates a rougher surface. Examples of surface roughness R include arithmetic mean roughness Ra, maximum height roughness Rz, and ten-point mean roughness RzJIS. The unit of surface roughness R is, for example, [μm]. In this example, arithmetic mean roughness Ra is used as the surface roughness R. Surface roughness R can be measured using a known surface roughness measuring instrument.

[0087] The contact angle θ is the angle between a solid surface and a liquid, and is an index for evaluating the wettability between a solid surface and a liquid. Wettability is the ease with which a liquid adheres to a solid surface. A smaller contact angle θ indicates better wettability, meaning the liquid adheres more easily to the solid surface. A larger contact angle θ indicates poorer wettability, meaning the liquid does not adhere as easily to the solid surface. The contact angle θ can be measured using a known contact angle measuring instrument. Alternatively, the contact angle θ may be measured by actually dropping a liquid droplet onto a solid surface and observing the result.

[0088] When a solid surface is hydrophilic with a small contact angle θ (θ < 90°), the contact angle θ decreases as the surface roughness R increases, and conversely, the contact angle θ increases as the surface roughness R decreases. Also, the contact angle θ is smaller when the oil temperature L is high (e.g., 110°C) than when the oil temperature L is low (e.g., 45°C).

[0089] Generally, sealing surfaces have a small surface roughness R (large contact angle θ). Specifically, for example, a sealing surface has an arithmetic mean roughness Ra of about 1.6 and a corresponding contact angle θ of about 10°.

[0090] (First small contact angle and second small contact angle) As shown in Figure 5, the surface roughness R of the sealing surface 101 of the head surface 100 is small. The contact angle θ of the sealing surface 101 of the head surface 100 is large. Specifically, the arithmetic mean roughness Ra of the sealing surface 101 of the head surface 100 is about 1.6, and the corresponding contact angle θ is about 10°.

[0091] On the head surface 100, the non-sealing surface 102 is adjacent to the sealing surface 101. Therefore, from the viewpoint of processing efficiency, the surface roughness R (contact angle θ) of the non-sealing surface 102 is the same as the surface roughness R (contact angle θ) of the sealing surface 101. The surface roughness R of the non-sealing surface 102 on the head surface 100 is small. The contact angle θ of the non-sealing surface 102 on the head surface 100 is large. Specifically, on the non-sealing surface 102 of the head surface 100, the arithmetic mean roughness Ra is about 1.6, and the corresponding contact angle θ is about 10°.

[0092] The surface roughness R of block surface 90 is small. The contact angle θ of block surface 90 is large. Specifically, the arithmetic mean roughness Ra of block surface 90 is about 1.6, and the corresponding contact angle θ is about 10°.

[0093] The sealing portion 81 of the gasket 80 is positioned between the sealing surface 101 of the head surface 100 and the block surface 90. The upper surface 80a and lower surface 80b of the sealing portion 81 of the gasket 80 have a small surface roughness R and a large contact angle θ. Specifically, the arithmetic mean roughness Ra is about 1.6 and the corresponding contact angle θ is about 10°.

[0094] The non-seal portion 82 of the gasket 80 is positioned on the non-seal surface 102 of the head surface 100. Here, the lower surface 80b of the gasket 80 is the surface of the gasket 80 that is positioned on the cylinder block 10 side. The lower surface 80b of the non-seal portion 82 of the gasket 80 does not face the block surface 90 of the cylinder block 10.

[0095] A first small contact angle E1 is provided on the non-sealing surface 102 of the head surface 100. The first small contact angle E1 is formed by the lower surface 80b of the non-sealing portion 82 of the gasket 80, which is located on the cylinder block 10 side.

[0096] The first small contact angle E1 (the lower surface 80b located on the cylinder block 10 side of the non-seal portion 82 of the gasket 80) has a surface roughness R greater than the sealing surface 101 of the head surface 100. The first surface roughness R1 of the first small contact angle E1 is greater than the sealing surface roughness R0 of the sealing surface 101. The first surface roughness R1 of the first small contact angle E1 is preferably 10 or more in terms of arithmetic mean roughness Ra, and more preferably 100 or more.

[0097] The first small contact angle portion E1 (the lower surface 80b located on the cylinder block 10 side of the non-seal portion 82 of the gasket 80) has a contact angle θ smaller than the sealing surface 101 of the head surface 100. The first contact angle θ1 of the first small contact angle portion E1 is smaller than the sealing contact angle θ0 of the sealing surface 101. The first contact angle θ1 of the first small contact angle portion E1 is preferably 3° or less, and more preferably 1° or less.

[0098] Furthermore, the upper surface 80a of the non-seal portion 82 of the gasket 80 may have a small surface roughness R (a large contact angle θ), similar to the upper surface 80a and lower surface 80b of the seal portion 81, or conversely, it may have a large surface roughness R (a small contact angle θ), similar to the first small contact angle portion E1 (lower surface 80b of the non-seal portion 82).

[0099] As shown in Figures 5 and 6, the gasket 80 is provided with an opening 83. The opening 83 is for the oil return passage 50 to pass through. The edge 83a of the opening 83 of the gasket 80 extends along the head passage wall 71 of the head passage 70. The edge 83a constitutes the inner circumference of the opening 83.

[0100] A second small contact angle E2 is provided at the edge 83a of the opening 83 of the gasket 80. The second small contact angle E2 (edge ​​83a of the opening 83 of the gasket 80) has a surface roughness R greater than the sealing surface 101 of the head surface 100. The second surface roughness R2 of the second small contact angle E2 is greater than the sealing surface roughness R0 of the sealing surface 101. The second surface roughness R2 of the second small contact angle E2 may be the same as or different from the first surface roughness R1 of the first small contact angle E1. The second surface roughness R2 of the second small contact angle E2 is preferably 10 or more in terms of arithmetic mean roughness Ra, and more preferably 100 or more.

[0101] The second small contact angle portion E2 (the edge 83a of the opening 83 of the gasket 80) has a smaller contact angle θ than the sealing surface 101 of the head surface 100. The second contact angle θ2 of the second small contact angle portion E2 is smaller than the sealing contact angle θ0 of the sealing surface 101. The second contact angle θ2 of the second small contact angle portion E2 may be the same as or different from the first contact angle θ1 of the first small contact angle portion E1. The second contact angle θ2 of the second small contact angle portion E2 is preferably 3° or less, and more preferably 1° or less.

[0102] As shown in Figure 7, when the oil temperature of oil L is high (for example, 110°C), the contact angle θ becomes approximately 3° or less when the surface roughness R is approximately 10 or more. Although not shown in the figure, regardless of the oil temperature of oil L, the contact angle θ becomes approximately 1° or less when the surface roughness R is approximately 100 or more.

[0103] In this example, the block surface 90 of the cylinder block 10, the head surface 100 of the cylinder head 20, and the gasket 80 are all made of metal.

[0104] Methods to increase the surface roughness R of the first small contact angle E1 (the lower surface 80b located on the cylinder block 10 side of the non-sealing portion 82 of the gasket 80) and the second small contact angle E2 (the edge 83a of the opening 83 of the gasket 80) include, for example, sandblasting or surface roughening with a file.

[0105] For the first small contact angle E1 and the second small contact angle E2, the surface roughness R is deliberately made larger (the contact angle θ is deliberately made smaller).

[0106] The non-sealing portion 82 of the gasket 80 is deliberately present, even though it does not perform a sealing function, in order to provide a first small contact angle E1 on its lower surface 80b.

[0107] (Effects and Benefits) In the oil return passage 50, the block passage 60 formed in the cylinder block 10 has a larger cross-sectional area S than the head passage 70 formed in the cylinder head 20. The head surface 100 of the cylinder head 20 includes a sealing surface 101 that overlaps with the block surface 90 of the cylinder block 10 via a gasket 80, and a non-sealing surface 102 that is located on the oil return passage 50 side of the sealing surface 101 and does not overlap with the block surface 90 of the cylinder block 10.

[0108] The non-sealing surface 102 is provided with a first small contact angle portion E1, which has a smaller contact angle θ than the sealing surface 101. Because the first small contact angle portion E1 on the non-sealing surface 102 has a small contact angle θ, its wettability is improved.

[0109] After lubricating the head-side lubricated portion A2 of the cylinder head 20, the oil L flows into the head passage 70 of the cylinder head 20 and then into the block passage 60 of the cylinder block 10. As the oil L flows from the head passage 70 into the block passage 60, the oil L spreads and wets along the first small contact angle E1 provided on the non-sealing surface 102 of the head surface 100 of the cylinder head 20.

[0110] The oil L, which spreads along the first small contact angle E1, is more likely to come into contact with the block passage wall 61 of the block passage 60 of the cylinder block 10. In particular, the oil L is more likely to come into contact with the upper end of the block passage wall 61 of the block passage 60 (near the step G between the block passage wall 61 and the head passage wall 71).

[0111] The contact area of ​​the oil L flowing through the block passage 60 with the cylinder block 10 can be increased. Furthermore, the residence time of the oil L in the block passage 60 of the cylinder block 10 can be increased. Cooling water flows through the block-side jacket 16 of the cylinder block 10. Also, the cylinder block 10 tends to become colder than the cylinder head 20, where the combustion chamber 21 is located.

[0112] By increasing the contact area of ​​the oil L flowing through the block passage 60 with the cylinder block 10, the oil L can be cooled efficiently after lubricating the head-side lubricated portion A2 of the cylinder head 20.

[0113] The oil L can be efficiently cooled without making the block passage 60 (which is the oil return passage 50 on the cylinder block 10 side) excessively large.

[0114] Furthermore, the opening end of the block passage 60 on the block surface 90 does not need to be enlarged in diameter to guide the oil L.

[0115] Since the block passage 60 does not need to be made excessively large, interference between the block passage 60 and surrounding objects (for example, the block-side jacket 16 or the block-side bolt holes 17) can be suppressed.

[0116] Furthermore, since the block passage 60 does not need to be made excessively large, the decrease in sealing performance due to the reduction in the sealing area by the gasket 80 can be suppressed.

[0117] The first small contact angle E1 is formed by the lower surface 80b of the gasket 80, which is located on the cylinder block 10 side of the non-seal portion 82. The first small contact angle E1 can be easily formed by using the gasket 80. In particular, the formation of the first small contact angle E1 is easier compared to the case where the first small contact angle E1 is directly formed on the non-seal surface 102 of the head surface 100 (third embodiment).

[0118] A second small contact angle portion E2 is provided on the edge 83a of the opening 83 of the gasket 80, where the contact angle θ is smaller than that of the sealing surface 101 of the head surface 100. Oil L can easily wet and spread to the second small contact angle portion E2 provided on the edge 83a of the opening 83 of the gasket 80. Oil L can easily be guided from the second small contact angle portion E2 provided on the edge 83a of the opening 83 of the gasket 80 to the first small contact angle portion E1 provided on the lower surface 80b (located on the cylinder block 10 side) of the non-seal portion 82 of the gasket 80.

[0119] The contact angle θ of the first small contact angle E1 can be easily adjusted by adjusting the surface roughness R of the first small contact angle E1. The same applies to the second small contact angle E2.

[0120] By setting the contact angle θ of the first small contact angle portion E1 to a predetermined value or less (for example, preferably 3° or less, and more preferably 1° or less), the wettability of the first small contact angle portion E1 can be further improved. The same applies to the second small contact angle portion E2.

[0121] In particular, by making the contact angle θ of the first small contact angle portion E1 3° or less, the amount of heat dissipated from the oil L to the cylinder block 10 can be reduced by about 20% compared to the normal case (contact angle θ = 10°).

[0122] Applying the oil passage structure of the engine 1 according to this embodiment is particularly effective when the upper limit temperature of the oil L is low or when the oil L has low viscosity.

[0123] <Second Embodiment> The oil passage structure of the engine 1 according to the second embodiment will now be described. In the following description, components similar to those in the above embodiment will be denoted by the same reference numerals, and detailed descriptions will be omitted. Figure 8 is a diagram corresponding to Figure 5, and shows an enlarged view of the oil return passage 50.

[0124] The non-sealing surface 102 of the head surface 100 and the lower surface 80b of the non-sealing portion 82 of the gasket 80 are inclined with respect to the flow direction (vertical direction) of the oil L. The head passage 70 widens in diameter as it moves downstream (downward) in the flow direction of the oil L.

[0125] The other configurations are the same as in the first embodiment.

[0126] <Third Embodiment> The oil passage structure of the engine 1 according to the third embodiment will now be described. In the following description, components similar to those in the above embodiment will be denoted by the same reference numerals, and detailed descriptions will be omitted. Figure 9 is a diagram corresponding to Figure 5, and shows an enlarged view of the oil return passage 50.

[0127] The gasket 80 is positioned only on the sealing surface 101 of the head surface 100. The gasket 80 includes only the sealing portion 81. The gasket 80 does not include the non-sealing portion 82. The first small contact angle E1 is directly formed on the non-sealing surface 102 of the head surface 100.

[0128] The first small contact angle portion E1 directly provided on the non-sealing surface 102 has a smaller contact angle θ than the sealing surface 101. For example, the first small contact angle portion E1 directly provided on the non-sealing surface 102 has a larger surface roughness R than the sealing surface 101.

[0129] The other configurations are the same as in the first embodiment.

[0130] <Other Embodiments> Although this disclosure has been described above with reference to preferred embodiments, this description is not limiting, and various modifications, substitutions, or combinations are, of course, possible.

[0131] In the above embodiments, the contact angle θ of the first small contact angle E1 was adjusted by adjusting the surface roughness R of the first small contact angle E1, but the invention is not limited to this. In the first and second embodiments, the contact angle θ of the first small contact angle E1 may be adjusted by performing oxidation treatment or coating (e.g., lipophilic fluorine coating) on ​​the lower surface 80b (located on the cylinder block 10 side) of the non-seal portion 82 of the gasket 80, and in the third embodiment, on the non-seal surface 102. Furthermore, in the first and second embodiments, the contact angle θ of the first small contact angle E1 may be adjusted by using a different material for the gasket 80 than the material for the head surface 100 of the cylinder head 20. The same applies to the second small contact angle E2.

[0132] The oil return passage 50 may have a simple shape in which a large-diameter block passage 60 and a small-diameter head passage 70 are connected concentrically to each other. [Industrial applicability]

[0133] This disclosure is extremely useful and has high industrial applicability because it can be applied to engine oil passage structures. [Explanation of symbols]

[0134] L Oil A Lubricated part S Passage cross-sectional area R Surface roughness θ contact angle E1 1st small contact angle part E2 2nd small contact angle part 1 Engine 10 Cylinder Block 11 cylinders 12 pistons 20 Cylinder head 21 Combustion chamber 30 oil pans 50 Oil return passage 60 Block Passage 70 Headway 80 Gasket 80b Bottom surface (side) 81 Seal part 82 Non-sealed portion 83 Aperture 83a Edge 90 Block surface 100 Head surface 101 Sealing surface 102 Non-sealing surface

Claims

1. A cylinder block in which a cylinder housing a piston is formed, A cylinder head that, together with the cylinder and the piston, forms a combustion chamber, An oil pan for storing oil, The cylinder includes a sheet-like gasket that seals the space between the cylinder block and the cylinder head, The cylinder head and the cylinder block are provided with an oil return passage for returning the oil that has lubricated the lubricated portion of the cylinder head back to the oil pan via the cylinder head and the cylinder block. The aforementioned oil return passage is Block passage formed in the cylinder block, The cylinder head has a head passage formed therein, The aforementioned block passage has a larger cross-sectional area than the aforementioned head passage. The block surface of the cylinder block facing the cylinder head and the head surface of the cylinder head facing the cylinder block are joined to each other via the gasket. The head surface is The sealing surface overlaps the block surface via the gasket, It includes a non-sealing surface that is located on the oil return passage side of the sealing surface and does not overlap the block surface, An engine oil passage structure wherein the non-sealing surface is provided with a first small contact angle portion having a smaller contact angle than the sealing surface.

2. The gasket includes a sealing portion disposed between the sealing surface and the block surface, and a non-sealing portion disposed on the non-sealing surface. The oil passage structure for an engine according to claim 1, wherein the first small contact angle portion is formed by a surface of the gasket located on the cylinder block side in the non-seal portion.

3. The gasket is provided with an opening for the oil return passage to pass through. The engine oil passage structure according to claim 2, wherein the edge of the opening is provided with a second small contact angle portion having a smaller contact angle than the sealing surface.

4. The oil passage structure for an engine according to any one of claims 1 to 3, wherein the first small contact angle portion has a greater surface roughness than the sealing surface.

5. The oil passage structure for an engine according to any one of claims 1 to 3, wherein the contact angle of the first small contact angle portion is 3° or less.

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