Cylinder head of an internal combustion engine

Abstract

To provide a cylinder head for an internal combustion engine having an aggregated exhaust port, which can improve the circulation property of oil by allowing oil introduced into a dynamic valve chamber to easily flow to an oil return hole.SOLUTION: In a cylinder head 4, an upper wall 19a of an exhaust upper-side water jacket 19 is inclined so that a distance between a lower face 4f of the cylinder head 4 and itself increases as it goes toward an oil return hole 4c from sides of combustion chamber ceiling walls 8A, 8B, 8C in a fore-and-aft direction L2 intersecting with a cylinder row direction L1. The cylinder head 4 has a recess 23 which is formed by recessing the upper wall 19a of the exhaust upper-side water jacket 19 downward, and the recess 23 has a bottom face 23a which is substantially parallel with the lower face 4f of the cylinder head 4 and into which the oil return hole 4c is open. The bottom face 23a extends to the sides of the combustion chamber ceiling walls 8A, 8B, 8C from the oil return hole 4c.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a cylinder head of an internal combustion engine.

Background Art

[0002] There is known a cylinder head of an internal combustion engine having an oil return hole for discharging oil introduced into a valve chamber from the valve chamber (see Patent Document 1).

[0003] This cylinder head includes a collective exhaust port formed by integrally collecting exhaust ports extending from a plurality of combustion chambers arranged along a cylinder row in an exhaust collecting portion formed inside the cylinder head, and an oil dropping passage is formed in a region surrounded by a pair of exhaust ports extending from adjacent combustion chambers and the exhaust collecting portion.

[0004] Thereby, it becomes possible to form an oil passage without interfering with the collective exhaust port on the exhaust side of the cylinder head.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the above-described collective exhaust port, in order to smoothly flow the exhaust gas, there is known one in which the cross-sectional area of the exhaust passage is enlarged upward as it goes downstream along the flow direction of the exhaust gas.

[0007] In a manifold exhaust port with such a configuration, the upper wall of the manifold exhaust port and the upper wall of the water jacket located above the manifold exhaust port become upward-sloping surfaces that rise from the combustion chamber side towards the upper end of the oil return hole. As a result, it may become difficult for oil to flow from the combustion chamber side into the oil return hole, which may worsen the oil circulation.

[0008] This invention has been made in view of the circumstances described above, and aims to provide a cylinder head for an internal combustion engine having a collective exhaust port that can improve oil circulation by facilitating the flow of oil introduced into the valve chamber into the oil return hole. [Means for solving the problem]

[0009] The present invention relates to a cylinder head of an internal combustion engine, comprising: a plurality of combustion chamber ceiling walls arranged along the cylinder row direction and constituting a part of each of a plurality of combustion chambers; a valve train chamber located above the combustion chamber ceiling walls and housing a valve train mechanism for driving intake valves and exhaust valves; a collective exhaust port having a plurality of exhaust ports communicating with each of the plurality of combustion chambers and an exhaust manifold that brings together the plurality of exhaust ports; an exhaust upper water jacket covering the upper part of the collective exhaust port; a partition wall located in the region surrounded by the plurality of exhaust ports and the exhaust manifold, separating adjacent exhaust ports; and an oil return hole located in the partition wall, the upper end of which opens into the valve train chamber, wherein the upper wall of the exhaust upper water jacket is inclined such that the distance from the lower surface of the cylinder head increases as it moves from the combustion chamber ceiling wall side toward the oil return hole in a direction intersecting the cylinder row direction, and the upper wall of the exhaust upper water jacket has a recess that is recessed downward, the recess is substantially parallel to the lower surface of the cylinder head and has a bottom surface through which the oil return hole opens. The aforementioned bottom surface is It is located below the upper wall of the exhaust upper water jacket, and, In a direction intersecting the cylinder row direction, extending from the oil return hole towards the combustion chamber ceiling wall. Furthermore, the recess bulges inward from the combustion chamber ceiling wall side in a direction intersecting the cylinder row direction, with its end entering the exhaust upper water jacket. Yes, they are. [Effects of the Invention]

[0010] As described above, according to the present invention, in a cylinder head of an internal combustion engine having a collective exhaust port, the oil introduced into the valve chamber can be made to flow more easily into the oil return hole, thereby improving the circulation of the oil. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a longitudinal cross-sectional view (corresponding to the view in direction II in Figure 2) of an internal combustion engine equipped with a cylinder head according to one embodiment of the present invention. [Figure 2] Figure 2 is a plan view of a cylinder head according to one embodiment of the present invention. [Figure 3] Figure 3 is a side view (front side view) of the exhaust side of a cylinder head according to one embodiment of the present invention. [Figure 4] Figure 4 is a cross-sectional view taken along the IV-IV line in Figure 3. [Figure 5] Figure 5 is a cross-sectional view taken along the VV direction arrow in Figure 2. [Figure 6] Figure 6 is a cross-sectional view taken along the VI-VI line in Figure 5. [Modes for carrying out the invention]

[0012] A cylinder head of an internal combustion engine according to one embodiment of the present invention includes a plurality of combustion chamber ceiling walls arranged along the cylinder row direction and constituting a part of each of a plurality of combustion chambers, a valve train chamber located above the combustion chamber ceiling walls and housing a valve train mechanism that drives intake valves and exhaust valves, and a collective exhaust port having a plurality of exhaust ports that communicate with each of the plurality of combustion chambers and an exhaust manifold that brings together the plurality of exhaust ports. A cylinder head for an internal combustion engine having an exhaust upper water jacket covering the upper part of a manifold exhaust port, a partition wall arranged in a region surrounded by a plurality of exhaust ports and an exhaust manifold, separating adjacent exhaust ports, and an oil return hole arranged in the partition wall, the upper end of which opens into a valve chamber, wherein the upper wall of the exhaust upper water jacket is inclined such that the distance from the lower surface of the cylinder head increases as it moves from the combustion chamber ceiling wall side toward the oil return hole in a direction intersecting the cylinder row direction, and the upper wall of the exhaust upper water jacket has a recess that is recessed downward, the recess is substantially parallel to the lower surface of the cylinder head and has a bottom surface through which the oil return hole opens, and the bottom surface extends from the oil return hole toward the combustion chamber ceiling wall side in a direction intersecting the cylinder row direction.

[0013] As a result, the cylinder head of an internal combustion engine according to one embodiment of the present invention, in a cylinder head of an internal combustion engine having a collective exhaust port, can facilitate the flow of oil introduced into the valve chamber into the oil return hole, thereby improving the circulation of oil. [Examples]

[0014] Hereinafter, a cylinder head of an internal combustion engine according to one embodiment of the present invention will be described with reference to the drawings. Figures 1 to 6 show the cylinder head of an internal combustion engine according to one embodiment of the present invention. In Figures 1 to 6, the up, down, front, rear, left, and right directions are based on the internal combustion engine installed in the vehicle, with the front-rear direction of the vehicle being the front-rear direction, the left-right direction of the vehicle being the left-right direction, and the up and down direction of the vehicle (the height direction of the vehicle) being the up and down direction.

[0015] First, let me explain the structure. In Figure 1, an engine 2, which is an internal combustion engine, is installed in the engine compartment 1A of vehicle 1.

[0016] The engine 2 includes a cylinder block 3, a cylinder head 4 provided on the upper part of the cylinder block 3, a cylinder head cover 5 provided on the upper part of the cylinder head 4, and an oil pan (not shown) provided on the lower part of the cylinder block 3.

[0017] As shown in FIG. 2, the cylinder block 3 is provided with cylinders 3A, 3B, and 3C, and the cylinders 3A, 3B, and 3C are arranged side by side in the left - right direction of the vehicle 1. The arrangement direction (left - right direction) of the cylinders 3A, 3B, and 3C is referred to as the cylinder row direction L1.

[0018] The engine 2 of the present embodiment is a horizontally - mounted three - cylinder engine in which three cylinders 3A, 3B, and 3C are arranged side by side in the left - right direction (see FIG. 4), and the cylinder axis S is installed with an inclination to the front side with respect to the vertical direction.

[0019] Pistons 3D are respectively accommodated in the cylinders 3A, 3B, and 3C (only the piston of the cylinder 3B is shown in FIG. 1), and the pistons 3D are connected to a crankshaft (not shown) via connecting rods (not shown). The pistons 3D reciprocate in the cylinders to rotate the crankshaft via the connecting rods.

[0020] As shown in FIG. 2, the cylinder head 4 has a right - hand side wall 4A, a left - hand side wall 4B facing the right - hand side wall 4A in the left - right direction, a front wall 4C connecting the right - hand side wall 4A and the left - hand side wall 4B, and a rear wall 4D connecting the right - hand side wall 4A and the left - hand side wall 4B and facing the front wall 4C in the front - rear direction L2 orthogonal to the cylinder row direction L1.

[0021] As shown in FIG. 4, intake ports 6a, 6b, and 6c are provided in the cylinder head 4. The intake ports 6a, 6b, and 6c communicate with the cylinders 3A, 3B, and 3C respectively, and introduce the intake air into the cylinders 3A, 3B, and 3C.

[0022] The cylinder head 4 is provided with a manifold exhaust port 7. The manifold exhaust port 7 has three pairs of exhaust ports 7a, 7b, and 7c and an exhaust manifold section 7A.

[0023] The exhaust ports 7a, 7b, and 7c are connected to cylinders 3A, 3B, and 3C, respectively, and the exhaust manifold 7A collects and combines the downstream ends of the exhaust ports 7a, 7b, and 7c.

[0024] The exhaust gases discharged from cylinders 3A, 3B, and 3C to their respective exhaust ports 7a, 7b, and 7c are collected in the exhaust manifold 7A.

[0025] An exhaust gas outlet 7d is provided at the downstream end of the exhaust manifold 7A, and the exhaust gas collected in the exhaust manifold 7A is discharged from the exhaust gas outlet 7d to a catalytic converter (not shown).

[0026] Specifically, as shown in Figure 3, an exhaust flange 4F is provided on the front wall 4C of the cylinder head 4, and the upstream opening end of the catalytic converter is connected to the exhaust flange 4F. An exhaust gas outlet 7d opens inside the exhaust flange 4F, and the exhaust manifold 7A communicates with the upstream opening end of the catalytic converter through the exhaust gas outlet 7d.

[0027] Note that "downstream" refers to the direction downstream of the exhaust gas flow, and "upstream" refers to the direction upstream of the exhaust gas flow. The exhaust manifold 7A is located downstream of the exhaust ports 7a, 7b, and 7c, while the exhaust ports 7a, 7b, and 7c are located upstream of the exhaust manifold 7A.

[0028] As shown in Figure 1, the engine 2 is provided with three combustion chambers 8 (one shown in the figure), and the combustion chambers 8 are arranged along the cylinder row direction L1.

[0029] The combustion chamber 8 is the space enclosed by the combustion chamber ceiling walls 8A, 8B, and 8C (see Figures 2 and 4) formed at the bottom of the cylinder head 4, the cylinders 3A, 3B, and 3C, and the upper surface of the piston 3D, and is the area where the fuel-air mixture is burned. Thus, the combustion chamber ceiling walls 8A, 8B, and 8C of the cylinder head 4 constitute a part of the combustion chamber 8.

[0030] As shown in Figures 1 and 2, the cylinder head 4 is provided with three spark plug insertion walls 4G, which extend upward from the combustion chamber ceiling walls 8A, 8B, and 8C. Spark plug insertion holes 4g are formed in the spark plug insertion walls 4G, and spark plugs (not shown) are inserted through the spark plug insertion holes 4g.

[0031] The spark plug has an electrode (not shown) facing the combustion chamber 8, and the electrode ignites the air-fuel mixture introduced into the combustion chamber 8.

[0032] As shown in Figure 1, a valve train chamber 9 is provided above the combustion chamber 8. The valve train chamber 9 is a space enclosed by the cylinder head 4 and the cylinder head cover 5, and houses an intake valve 10, an exhaust valve 11, and a valve train mechanism 12 that drives the intake valve 10 and the exhaust valve 11.

[0033] Each combustion chamber 8 is provided with one pair of intake valves 10 and exhaust valves 11, and the cylinder head 4 is equipped with six intake valves 10 and six exhaust valves 11. In other words, each cylinder head 4 is equipped with three pairs of intake valves 10 and exhaust valves 11.

[0034] The intake valve 10 and the exhaust valve 11 each have valve stems 10A and 11A, and valve heads 10B and 11B provided at the lower ends of the valve stems 10A and 11A, respectively.

[0035] The valve stems 10A and 11A are housed in the valve chamber 9. Valve stem 10A is inclined rearward with respect to the cylinder shaft S, and valve stem 11A is inclined forward with respect to the cylinder shaft S. In this embodiment, valve stem 11A constitutes the valve stem.

[0036] As shown in Figure 2, above the combustion chamber ceiling walls 8A, 8B, and 8C, the bottom wall 9A of the valve train chamber 9 is provided with multiple pairs of intake valve guide bosses 13 and exhaust valve guide bosses 14 (see Figure 2).

[0037] A pair of intake valve guide bosses 13 and exhaust valve guide bosses 14 are provided for each combustion chamber 8. As shown in Figure 6, the pair of exhaust valve guide bosses 14 are arranged with gaps 31a, 31b, and 31c in the cylinder row direction L1.

[0038] In this embodiment, a total of six exhaust valve guide bosses 14 are provided, with one pair provided for each combustion chamber 8 (for each combustion chamber ceiling wall 8A, 8B, 8C).

[0039] A pair of intake valve guide bosses 13 are also arranged with a gap in the cylinder row direction L1, but they are not shown in Figure 6.

[0040] The valve stems 10A and 11A are slidably supported by the intake valve guide boss portion 13 and the exhaust valve guide boss portion 14, respectively.

[0041] In other words, the valve stem 10A is provided on the intake valve guide boss portion 13 so that the valve head 10B can open and close the intake ports 6a, 6b, and 6c, and the valve stem 11A is provided on the exhaust valve guide boss portion 14 so that the valve head 11B can open and close the exhaust ports 7a, 7b, and 7c.

[0042] As shown in Figure 1, the valve train 12 includes an intake camshaft 15, an intake cam 15A, an intake side rocker arm 16, an exhaust camshaft 17, an exhaust cam 17A, and an exhaust side rocker arm 18.

[0043] The intake camshaft 15 and the exhaust camshaft 17 are rotatably supported by a cam housing (not shown) and a cylinder head 4, and extend parallel to each other in the left-right direction.

[0044] The intake cam 15A is fixed to the intake cam shaft 15 so as to rotate integrally with the intake cam shaft 15, and is provided for each intake valve 10. The exhaust cam 17A is fixed to the exhaust cam shaft 17 so as to rotate integrally with the exhaust cam shaft 17, and is provided for each exhaust valve 11.

[0045] The intake side rocker arm 16 is in contact with the intake cam 15A at its center in the direction of extension. One end of the intake side rocker arm 16 in the direction of extension abuts against the upper end of the intake cam shaft 15, and the other end of the intake side rocker arm 16 in the direction of extension abuts against a hydraulic lash adjuster (HLA) (not shown).

[0046] As the intake cam 15A rotates, the intake cam 15A pivots on the HLA and causes the intake side rocker arm 16 to swing, causing the intake valve 10 to slide vertically, supported by the intake valve guide boss 13, to open and close the intake ports 6a, 6b, and 6c.

[0047] The exhaust side rocker arm 18 is in contact with the exhaust cam 17A at its center in the direction of extension. One end of the exhaust side rocker arm 18 in the direction of extension is in contact with the upper end of the exhaust cam shaft 17, and the other end of the exhaust side rocker arm 18 in the direction of extension is in contact with an HLA (not shown).

[0048] As the exhaust cam 17A rotates, the exhaust cam 17A pivots on the HLA and causes the exhaust side rocker arm 18 to swing, and the exhaust valve 11 slides vertically supported by the exhaust valve guide boss 14 to open and close the exhaust ports 7a, 7b, and 7c.

[0049] As shown in Figures 1 and 5, the cylinder head 4 is provided with an upper exhaust water jacket 19, a lower exhaust water jacket 20, and a combustion chamber side water jacket 21.

[0050] The upper exhaust water jacket 19 covers the upper part of the collective exhaust port 7 and extends in the vehicle width direction so as to be aligned with the six exhaust valve guide bosses 14 in the front-rear direction L2 (see Figure 6).

[0051] The lower exhaust water jacket 20 covers the area below the collective exhaust port 7 and faces the upper exhaust water jacket 19 across the collective exhaust port 7. The combustion chamber side water jacket 21 covers the upper part of the combustion chamber ceiling walls 8A, 8B, and 8C so as to be located above the three combustion chambers 8.

[0052] Cooling water is introduced into these water jackets 19, 20, and 21 from cooling water passages (not shown) provided in the cylinder block 3.

[0053] Cooling water is introduced into the cooling water passages of the cylinder block 3 from a water pump (not shown), and the cooling water that has cooled cylinders 3A, 3B, and 3C of the cylinder block 3 is introduced into water jackets 19, 20, and 21 from the cooling water passages of the cylinder block 3.

[0054] The water jackets 19, 20, and 21 cool the high-temperature areas of the cylinder head 4, such as the exhaust manifold port 7 and the combustion chamber ceiling walls 8A, 8B, and 8C.

[0055] As shown in Figure 1, the upper wall 7e of the collective exhaust port 7 and the upper wall 19a of the exhaust upper water jacket 19 are inclined such that the distance from the lower surface 4f of the cylinder head 4 increases as you move from the combustion chamber ceiling wall 8B (including combustion chamber ceiling walls 8A and 8B) towards the front wall 4C in the longitudinal direction L2, which is a direction that intersects (is perpendicular to) the cylinder row direction L1.

[0056] As shown in Figure 1, in this embodiment, the collective exhaust port 7 has a passage cross-sectional area that gradually expands upward as it moves downstream from the combustion chamber 8 along the direction of exhaust gas flow. This allows exhaust gas to flow smoothly from the exhaust ports 7a, 7b, and 7c through the exhaust manifold 7A to the exhaust gas outlet 7d.

[0057] The upper wall 19a of the exhaust upper water jacket 19 constitutes part of the bottom wall 9A of the valve train chamber 9. In the top view of Figure 2, the wall portion surrounded by the right wall 4A, left wall 4B, front wall 4C, and rear wall 4D is the bottom wall 9A of the valve train chamber 9. In other words, the bottom wall 9A of the valve train chamber 9 includes the upper wall 19a of the exhaust upper water jacket 19.

[0058] As shown in Figure 4, the cylinder head 4 is provided with partition walls 4H and 4I. Partition wall 4H is located in the area surrounded by the exhaust ports 7a and 7b and the exhaust manifold 7A, and separates the adjacent exhaust port 7a from exhaust port 7b.

[0059] The partition wall 4I is located in the area surrounded by the exhaust ports 7b and 7c and the exhaust manifold 7A, and separates the adjacent exhaust port 7b and exhaust port 7c.

[0060] In Figure 4, the exhaust manifold 7A is composed of a region enclosed by the front end 4h of the partition wall 4H, the front end 4i of the partition wall 4I, and the exhaust gas outlet 7d. The exhaust port 7a extends from a pair of exhaust ports that communicate with the cylinder 3A and are opened and closed by the exhaust valve 11 to the exhaust manifold 7A.

[0061] Exhaust port 7b communicates with cylinder 3B and extends from a pair of exhaust ports, which are opened and closed by the exhaust valve 11, to the exhaust manifold 7A. Exhaust port 7c communicates with cylinder 3C and extends from a pair of exhaust ports, which are opened and closed by the exhaust valve 11, to the exhaust manifold 7A.

[0062] The cylinder head 4 is provided with oil return holes 4a, 4b, and 4c. The oil return holes 4a and 4b are provided in the bottom wall 9A of the valve chamber 9 so as to penetrate the bottom wall 9A of the valve chamber 9, and their upper ends open into the valve chamber 9.

[0063] The oil return hole 4c is provided in the partition wall 4I so as to penetrate the partition wall 4I in the vertical direction, and the upper end 4u of the oil return hole 4c opens into the valve chamber 9 (see Figure 5).

[0064] The lower ends of the oil return holes 4a, 4b, and 4c communicate with an oil passage (not shown) provided in the cylinder block 3, and the oil passage of the cylinder block 3 communicates with the oil pan. In other words, the valve chamber 9 and the oil pan are in communication via the oil return holes 4a, 4b, and 4c and the oil passage.

[0065] Oil is supplied to lubrication points such as the contact surface between the intake cam 15A and the intake side rocker arm 16, and the contact surface between the exhaust cam 17A and the exhaust side rocker arm 18, through the intake camshaft 15 and the exhaust camshaft 17.

[0066] The oil that has lubricated these lubrication points falls onto the bottom wall 9A of the valve chamber 9, and then returns to the oil pan through the oil passages of the cylinder block 3 via the oil return holes 4a, 4b, and 4c.

[0067] In other words, the oil stored in the oil pan is returned to the oil pan after being used by the oil pump to lubricate the lubrication parts, and the oil circulates inside the engine 2.

[0068] As shown in Figure 4, head bolt insertion holes 4d and 4e are provided in the bottom wall 9A of the valve chamber 9. The head bolt insertion hole 4d is provided in the bottom wall 9A so as to sandwich the intake ports 6a, 6b, and 6c in the left-right direction and penetrates the bottom wall 9A.

[0069] The head bolt insertion holes 4e are provided in the bottom wall 9A and partition walls 4H and 4I so as to sandwich the exhaust ports 7a, 7b, and 7c in the left-right direction, and penetrate the bottom wall 9A and partition walls 4H and 4I.

[0070] Head bolts 22 are inserted through head bolt insertion holes 4d and 4e (see Figures 4 and 5), and the head bolts 22 fasten the cylinder head 4 to the cylinder block 3.

[0071] Specifically, as shown in Figure 5, the head bolt 22 is inserted from above through the head bolt insertion holes 4d and 4e, and the lower part of the threaded portion 22A is fastened to the cylinder block 3. The head portion 22B of the head bolt 22 is located in the valve chamber 9.

[0072] As shown in Figure 4, the head bolt insertion hole 4e is located on the combustion chamber ceiling wall 8A, 8B, 8C side in the front-to-back direction L2 than the oil return hole 4c. In other words, the oil return hole 4c is located on the opposite side of the combustion chamber ceiling wall 8A, 8B, 8C from the head bolt insertion hole 4e in the front-to-back direction L2.

[0073] In the cylinder head 4 of this embodiment, the upper wall 19a of the exhaust upper water jacket 19 is inclined such that the distance from the lower surface 4f of the cylinder head 4 increases as it moves in the front-rear direction L2 from the combustion chamber ceiling walls 8A, 8B, and 8C towards the oil return hole 4c.

[0074] Therefore, oil that has fallen onto the bottom wall 9A of the valve train chamber 9 is less likely to flow from the combustion chamber ceiling walls 8A, 8B, and 8C to the oil return hole 4c.

[0075] To address this issue, the cylinder head 4 of this embodiment is provided with a recess 23 to facilitate the flow of oil from the combustion chamber ceiling walls 8A, 8B, and 8C to the oil return hole 4c.

[0076] As shown in Figures 5 and 6, the cylinder head 4 has a recess 23 formed by recessing the upper wall 19a of the exhaust upper water jacket 19 downwards.

[0077] The recess 23 has a bottom surface 23a located below the upper wall 19a of the exhaust upper water jacket 19, and bulges inward into the exhaust upper water jacket 19 from the combustion chamber ceiling walls 8A, 8B, and 8C in the longitudinal direction L2 which intersects the cylinder row direction L1 (see Figure 6). In other words, the front end of the recess 23 is embedded in the exhaust upper water jacket 19 in the longitudinal direction L2.

[0078] The bottom surface 23a of the recess 23 is formed approximately parallel to the lower surface 4f of the cylinder head 4, and an oil return hole 4c is opened in the bottom surface 23a. The lower surface 4f of the cylinder head 4 is formed as a flat surface.

[0079] The bottom surface 23a of the recess 23 and the upper wall 19a of the exhaust upper water jacket 19 are connected by an inclined surface 23c, and the oil return hole 4c is located on the side of the inclined surface 23c.

[0080] The bottom surface 23a of the recess 23 extends in the front-rear direction L2 from the oil return hole 4c towards the combustion chamber ceiling walls 8A, 8B, and 8C. Head bolt insertion holes 4e are provided on the side of the combustion chamber ceiling walls 8A, 8B, and 8C relative to the oil return hole 4c, and the bottom surface 23a of the recess 23 extends from the vicinity of the head bolt insertion holes 4e towards the vicinity of the oil return hole 4c.

[0081] A connecting portion 23b is formed on the bottom surface 23a of the recess 23, and the connecting portion 23b extends from the bottom surface 23a to a gap 31b located adjacent to the recess 23.

[0082] Specifically, the exhaust valve guide boss portions 14 are arranged in three pairs in the left-right direction, corresponding to the combustion chamber ceiling walls 8A, 8B, and 8C. The connecting portion 23b is located in the center in the left-right direction and connects the gap 31b between the recess 23 and the adjacent exhaust valve guide boss portion 14 with the bottom surface 23a of the recess 23.

[0083] Next, the effect of the cylinder head 4 of engine 2 in this embodiment will be explained. The cylinder head 4 of this embodiment is arranged along the cylinder row direction L1 and comprises combustion chamber ceiling walls 8A, 8B, and 8C that each constitute a part of the combustion chamber 8, a valve train chamber 9 located above the combustion chamber ceiling walls 8A, 8B, and 8C and housing a valve train mechanism 12 that drives the intake valve 10 and exhaust valve 11, and a collective exhaust port 7 having exhaust ports 7a, 7b, and 7c that communicate with the multiple combustion chambers 8 and an exhaust manifold 7A that brings together the exhaust ports 7a, 7b, and 7c.

[0084] Furthermore, the cylinder head 4 has an exhaust upper water jacket 19 that covers the upper part of the collective exhaust port 7, partition walls 4H and 4I located in the region surrounded by the exhaust ports 7a, 7b, and 7c and the exhaust manifold 7A, separating adjacent exhaust ports 7a, 7b, and 7c, and an oil return hole 4c located in the partition wall 4I, the upper end 4u of which opens into the valve chamber 9.

[0085] In addition, the upper wall 19a of the exhaust upper water jacket 19 is inclined such that the distance from the lower surface 4f of the cylinder head 4 increases as it moves from the combustion chamber ceiling walls 8A, 8B, and 8C towards the oil return hole 4c in the longitudinal direction L2 which intersects the cylinder row direction L1.

[0086] As a result, the upper wall 19a of the exhaust upper water jacket 19 has an oil return hole 4c positioned above the combustion chamber ceiling walls 8A, 8B, and 8C, making it difficult for lubricating oil introduced into the valve train chamber 9 to flow from the combustion chamber ceiling walls 8A, 8B, and 8C to the oil return hole 4c.

[0087] According to the cylinder head 4 of this embodiment, the upper wall 19a of the exhaust upper water jacket 19 has a recess 23 that is recessed downwards. The recess 23 is substantially parallel to the lower surface 4f of the cylinder head 4 and has a bottom surface 23a through which the oil return hole 4c opens. The bottom surface 23a extends in the front-rear direction L2 from the oil return hole 4c toward the combustion chamber ceiling walls 8A, 8B, and 8C.

[0088] As a result, as shown in Figure 6, the oil introduced into the valve train chamber 9 can be smoothly flowed into the oil return hole 4c from the combustion chamber ceiling walls 8A, 8B, and 8C through the recess 23 (see oil O1). Therefore, the oil introduced into the valve train chamber 9 can be actively returned to the oil pan from the cylinder head 4 through the oil return hole 4c and the oil passage of the cylinder block 3.

[0089] In this way, in a cylinder head 4 having a collective exhaust port 7, the oil introduced into the valve chamber 9 can be easily allowed to flow into the oil return hole 4c, thereby improving oil circulation.

[0090] Furthermore, as shown in Figure 6, the oil introduced into the valve train chamber 9 can be guided from the exhaust upper water jacket 19 side, which is located forward from the combustion chamber ceiling walls 8A, 8B, and 8C, towards the recess 23, into the recess 23, and then into the oil return hole 4c (see oil O2).

[0091] Furthermore, according to the cylinder head 4 of this embodiment, head bolt insertion holes 4d and 4e are formed in the partition wall 4I through which head bolts 22 for fastening the cylinder head 4 to the cylinder block 3 are inserted. The head bolt insertion holes 4e are located in the front-rear direction L2 on the side of the combustion chamber ceiling walls 8A, 8B, and 8C that is closer to the oil return hole 4c.

[0092] In addition, the bottom surface 23a extends from the vicinity of the head bolt insertion hole 4e to the vicinity of the oil return hole 4c.

[0093] This allows the oil, after being introduced into the valve chamber 9, to flow into the area around the head bolt insertion hole 4e without being obstructed by the head portion 22B of the head bolt 22, and into the oil return hole 4c.

[0094] In other words, oil O1 (see Figure 6) that flows from the combustion chamber ceiling walls 8B and 8C to the area around the head bolt insertion hole 4e can be allowed to flow from the combustion chamber ceiling walls 8B and 8C to the oil return hole 4c through the area around the head portion 22B of the head bolt 22.

[0095] As a result, the oil introduced into the valve chamber 9 can be more easily drawn into the oil return hole 4c, thereby more effectively improving oil circulation.

[0096] Furthermore, according to the cylinder head 4 of this embodiment, a pair of exhaust valves 11 are arranged for each combustion chamber 8 to open and close the exhaust ports 7a, 7b, and 7c, and multiple pairs of exhaust valve guide bosses 14 are arranged on the bottom wall 9A of the valve train chamber 9, each supporting the valve stem 11A of the pair of exhaust valves 11, with gaps 31a, 31b, and 31c in the cylinder row direction L1.

[0097] The bottom surface 23a of the recess 23 has a connecting portion 23b, which connects the gap 31b between the recess 23 and the adjacent exhaust valve guide boss portion 14 with the bottom surface 23a of the recess 23.

[0098] This allows oil O3 (see Figure 6) that has passed through the gap 31b between the pair of exhaust valve guide bosses 14 from the combustion chamber ceiling wall 8B to be introduced into the oil return hole 4c.

[0099] In other words, the bottom surface 23a of the recess 23 can be connected to the combustion chamber ceiling walls 8A, 8B, and 8C through the gap 31b between the pair of exhaust valve guide bosses 14 by the connecting portion 23b, making it easier for the oil introduced into the valve train chamber 9 to flow into the oil return hole 4c from the combustion chamber ceiling walls 8A, 8B, and 8C, thereby more effectively improving oil circulation.

[0100] In addition, by limiting the recess 23 and the connecting portion 23b to the extent necessary for recovering lubricating oil, it is possible to prevent the exhaust upper water jacket 19 from shrinking excessively and reducing the volume of the collective exhaust port 7.

[0101] Therefore, it is possible to more effectively improve oil circulation while preventing a decrease in the cooling performance of the collective exhaust port 7 by the upper exhaust water jacket 19.

[0102] Furthermore, the remaining oil introduced into the valve chamber 9 is returned to the oil pan through the oil passages of the cylinder block 3 via the oil return holes 4a and 4c.

[0103] In Figure 6, the arrows indicating the oil flow, labeled O1, O2 and O2, O3, represent the oil flowing continuously across the bottom surface 23a of the recess 23, corresponding to oil O1, oil O2, and oil O3, respectively.

[0104] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of symbols]

[0105] 2...Engine (internal combustion engine), 3...Cylinder block, 4c...Oil return hole, 4e...Head bolt insertion hole, 4f...Bottom surface (bottom surface of cylinder head), 4I...Partition wall, 4u...Top end (top end of oil return hole), 7...Exhaust manifold port, 7A...Exhaust manifold section, 7a,7b,7c...Exhaust ports, 8...Combustion chamber, 8A,8B,8C...Combustion chamber ceiling wall, 9...Valve train chamber, 9A...Bottom wall (bottom wall of valve train chamber), 10... Intake valve, 11...Exhaust valve, 11A...Valve stem, 12...Valve train, 14...Exhaust valve guide boss, 19...Exhaust upper water jacket, 19a...Upper wall (upper wall of exhaust upper water jacket), 22...Head bolt, 23...Recess, 23a...Bottom surface (bottom surface of recess), 23b...Connecting part, 31a, 31b, 31c...Gap, L1...Cylinder row direction, L2...Front-rear direction (direction intersecting the cylinder row direction)

Claims

1. Multiple combustion chamber ceiling walls are arranged along the direction of the cylinder row and constitute part of each of the multiple combustion chambers, A valve train chamber is located above the ceiling wall of the combustion chamber and houses a valve train mechanism that drives the intake valve and the exhaust valve, A collective exhaust port having a plurality of exhaust ports communicating with each of the plurality of combustion chambers and an exhaust manifold that brings together the plurality of exhaust ports, An exhaust upper water jacket covering the upper part of the aforementioned collective exhaust port, A partition wall is provided in the area surrounded by the plurality of exhaust ports and the exhaust manifold, and separates adjacent exhaust ports. A cylinder head of an internal combustion engine having an oil return hole positioned in the partition wall, the upper end of which opens into the valve chamber, The upper wall of the exhaust upper water jacket is inclined such that the distance from the lower surface of the cylinder head increases as it moves from the combustion chamber ceiling wall towards the oil return hole in a direction intersecting the cylinder row direction. The upper wall of the exhaust upper water jacket has a recess that is indented downwards, The recess is substantially parallel to the lower surface of the cylinder head and has a bottom surface through which the oil return hole opens. The bottom surface is located below the upper wall of the exhaust upper water jacket and extends from the oil return hole toward the combustion chamber ceiling wall in a direction intersecting the cylinder row direction. The cylinder head of an internal combustion engine is characterized in that the end of the recess is inserted into the exhaust upper water jacket in a direction intersecting the cylinder row direction.

2. The partition wall has head bolt insertion holes through which head bolts for fastening the cylinder head to the cylinder block are inserted. The head bolt insertion holes are positioned on the combustion chamber ceiling wall side of the oil return holes in a direction intersecting the cylinder row direction. The cylinder head of an internal combustion engine according to claim 1, characterized in that the bottom surface of the recess extends from the vicinity of the head bolt insertion hole to the vicinity of the oil return hole.

3. The exhaust valves are arranged in pairs for each combustion chamber to open and close the exhaust port, Multiple pairs of exhaust valve guide bosses, each supporting the valve stem of the exhaust valve, are arranged on the bottom wall of the valve chamber with gaps between them in the direction of the cylinder row. The bottom surface of the recess has a connecting portion, The cylinder head of an internal combustion engine according to claim 1 or 2, characterized in that the connecting portion connects one of the gaps located adjacent to the recess with the bottom surface of the recess.

Images