Cylinder head structure for internal combustion engine

Abstract

In an internal combustion engine transversely mounted on a vehicle, an intake camshaft (5) is located at a lower position than an exhaust camshaft (6), and an appropriate gap can be obtained between a hood (L) and a cam holder (2). The exhaust-side hydraulic lash adjuster (37) is located further inward in the width direction than the center line (M2) of the exhaust valve than the center line (M2) of the exhaust valve. The intake-side hydraulic lash adjuster (36) is positioned further outward in the width direction than the center line (M1) of the intake valve than the cylinder head (1). An oil source pressure passage (45) is disposed in the center of the cylinder head (1) in the width direction and communicates with the oil reservoir (46). Oil is supplied to the lash adjuster (36) on the intake side via a cam holder internal passage (42) passing through the inside of the cam holder (2).

Description

Technical Field

[0001] The present invention relates to a cylinder head structure of an internal combustion engine, which has hydraulic lash adjusters for an intake valve and an exhaust valve, respectively. Background Art

[0002] Regarding the valve operating mechanisms of the intake valve and the exhaust valve of an internal combustion engine, it is known to have hydraulic lash adjusters for automatically adjusting the valve clearance to 0. Regarding the structure in which the cylinder head has such a hydraulic lash adjuster, the dimension in the width direction of the cylinder head tends to increase.

[0003] On the other hand, Patent Document 1 discloses the following structure. That is, regarding an internal combustion engine mounted in a transverse attitude on a vehicle, the exhaust side camshaft located at a position closer to the front of the vehicle is arranged at a position relatively lower than the intake side camshaft located at a position closer to the rear of the vehicle in a manner corresponding to the inclination of the engine hood.

[0004] An object of the present invention is to provide a more appropriate arrangement of hydraulic lash adjusters in the case where the height positions of the two camshafts are different as described above.

[0005] Patent Document 1: Japanese Patent Laid-Open No. 10-54242 Summary of the Invention

[0006] The present invention is a cylinder head structure of an internal combustion engine, which has:

[0007] A cylinder head;

[0008] A first camshaft and a second camshaft, one of which is for an intake valve and the other is for an exhaust valve;

[0009] A first hydraulic lash adjuster provided corresponding to the first camshaft; and

[0010] A second hydraulic lash adjuster provided corresponding to the second camshaft,

[0011] As the height position along the cylinder block center axis, the first camshaft is arranged at a lower position than the second camshaft,

[0012] The second hydraulic lash adjuster is located inside the internal combustion engine in the width direction compared with the center line of the valve stem of the corresponding intake valve or exhaust valve inclined with respect to the cylinder block center axis,

[0013] The first hydraulic lash adjuster is located outside the internal combustion engine in the width direction compared with the center line of the valve stem of the corresponding intake valve or exhaust valve.

[0014] If the hydraulic lash adjuster is disposed on the outer side in the width direction of the internal combustion engine as compared with the center line of the valve stem of the intake valve or the exhaust valve, the outer edge of the cylinder head extends outward in the width direction of the internal combustion engine by adding the hydraulic lash adjuster itself, ensuring the structure required for assembling the hydraulic lash adjuster, forming an oil passage for supplying oil, etc. On the other hand, if the hydraulic lash adjuster is to be disposed on the inner side in the width direction of the internal combustion engine with respect to both the intake side and the exhaust side, i.e., closer to the center line of the valve stem of the intake valve or the exhaust valve, the width direction dimension of the cylinder head will instead increase in order to ensure the space for both.

[0015] In the present invention, the second hydraulic lash adjuster corresponding to the second camshaft at a relatively high position is located on the inner side in the width direction of the internal combustion engine as compared with the valve stem center line, and the first hydraulic lash adjuster corresponding to the first camshaft at a relatively low position is located on the outer side in the width direction of the internal combustion engine as compared with the valve stem center line. Therefore, on the side of the second camshaft at a relatively high position, the outward extension of the outer edge of the cylinder head is small, and thus the influence on the clearance with the engine hood when mounted on the vehicle is small. On the side of the first camshaft at a relatively low position, the outer edge of the cylinder head extends outward, but this part is at a relatively low position, so the influence on the vehicle mountability is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a front view of a cylinder head having a cam bracket.

[0017] Figure 2 is a top view of the cam bracket.

[0018] Figure 3 is a sectional view of a cylinder head having a cam bracket.

[0019] Figure 4 is an explanatory view showing the layout of the oil passage.

[0020] Figure 5 is an explanatory view of the valve actuating mechanism. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. Figure 1 is a front view showing the cylinder head 1 of the internal combustion engine according to the present invention together with the cam bracket 2. The cylinder head 1 is integrally cast using a metal material such as aluminum alloy and is mounted on the upper surface of the cylinder block 3. The internal combustion engine of the embodiment is a spark ignition type internal combustion engine with three in-line cylinders, i.e., a so-called gasoline internal combustion engine, and is mounted on the front part of the vehicle in a so-called transverse attitude. In the vehicle-mounted state, the center axis of the cylinder block is substantially vertical, and therefore, Figure 1 substantially corresponds to the attitude in the vehicle-mounted state.

[0022] In addition, the internal combustion engine of the embodiment has a roof-shaped combustion chamber, that is, a spark plug and a fuel injection valve are provided at the center of the combustion chamber, and a pair of intake valves and a pair of exhaust valves are provided for each cylinder.

[0023] The cylinder head 1 has an intake camshaft 5 for the intake valve and an exhaust camshaft 6 for the exhaust valve. The cam bracket 2 is configured in a shape of a cover that covers the upper surface opening of the cylinder head 1, and is joined and fixed to the upper surface of the cylinder head 1 via an appropriate sealing member such as a liquid gasket. The cam bracket 2 has an intake-side camshaft bearing portion 11 and an exhaust-side camshaft bearing portion 12 that are approximately semicircular and face downward, and between the cam brackets 13 and 14 that are relatively mounted on the camshaft bearing portions 11 and 12, the intake camshaft 5 and the exhaust camshaft 6 are respectively supported so as to be rotatable.

[0024] As Figure 1 shown, as the height position along the cylinder block center axis, the intake camshaft 5 is arranged at a relatively lower position compared to the exhaust camshaft 6. Correspondingly, the height position of the upper edge portion of the cam bracket 2 that covers the upper sides of the camshafts 5 and 6 is also lower on the intake camshaft 5 side than on the exhaust camshaft 6 side. The internal combustion engine of one embodiment is mounted in the engine compartment at the front of the vehicle with the intake camshaft 5 side facing the front of the vehicle and the exhaust camshaft 6 side facing the rear of the vehicle. Therefore, the gaps between the engine hood (shown by the virtual line L) of the vehicle that is inclined in such a way that the front end is at a lower position are appropriate on both the intake camshaft 5 side and the exhaust camshaft 6 side.

[0025] As Figure 2 shown, the cam bracket 2 of one embodiment has a stepped structure, that is, two camshaft accommodating portions 21 and 22 that extend longitudinally in the cylinder bank direction are connected to each other at an inter-cylinder position. At three positions corresponding to the cylinder positions in the cylinder bank direction, relatively large injection valve openings 23 are respectively provided between the two camshaft accommodating portions 21 and 22. In addition, on the exhaust camshaft 6 side (camshaft accommodating portion 22 side) closer than the injection valve opening 23, the insertion holes 24 for the spark plugs are respectively formed in a cylindrical shape. The cam bracket 2 is integrally cast using a metal material such as aluminum alloy.

[0026] Figure 3 is a cross-sectional view of the cylinder head 1 and the cam bracket 2 shown by cutting along a cross-section passing through the centers of the intake valve and the exhaust valve Figure 1 shown. As described above, it has a roof-shaped combustion chamber 31 that connects the intake port 32 and the exhaust port 33. In Figure 3 , the illustration of the valve actuating mechanism is omitted, and it is known to those skilled in the art that cylindrical rod guides are respectively installed in the rod guide mounting holes 34 and 35, and the lift valve type intake side and exhaust valves are assembled together with valve springs.

[0027] Figure 5 Yes means Figure 3 A schematic illustration of the valve mechanism not shown in the figure shows that a rocker arm 101 supported at one end by the hydraulic clearance adjuster 36 swings due to the cam action of the intake camshaft 5 to open and close the intake valve 103. Similarly, a rocker arm 102 supported at one end by the hydraulic clearance adjuster 37 swings due to the cam action of the exhaust camshaft 6 to open and close the exhaust valve 104. 105 represents a fuel injection valve, and 106 represents a spark plug. The hydraulic clearance adjuster itself is a well-known structure, so its detailed description is omitted, but it is formed into a structure that is approximately cylindrical, and is stretched by an internal spring in such a way that the valve clearance becomes 0, and the reaction force when the valve is lifted is borne by the engine oil that fills the interior. In addition, Figure 5 This is an explanatory diagram of the mechanism and does not show the exact configuration of each part.

[0028] exist Figure 3 In the figure, line M1 represents the center line of the valve stem of the intake valve, and line M2 represents the center line of the valve stem of the exhaust valve. The intake valve center line M1 and the exhaust valve center line M2 are inclined relative to the cylinder center axis in a substantially symmetrical manner. Figure 3 As shown, the intake valve center line M1 is closer to the center O1 of the intake camshaft 5 in the width direction of the cylinder head 1 ( Figure 3 On the other hand, the exhaust valve center line M2 passes from the outside in the width direction of the cylinder head 1 compared to the center O2 of the exhaust camshaft 6. In addition, the "width direction of the internal combustion engine" in the technical solution has the same meaning as the "width direction of the cylinder head 1" described above, which is a direction that is orthogonal to the central axis of the cylinder block and to the cylinder row direction.

[0029] Hydraulic lash adjusters 36 and 37 are provided for the intake valve and the exhaust valve, respectively. The hydraulic lash adjusters 36 and 37 are mounted in cylindrical lash adjuster mounting holes 38 and 39 provided in the cylinder head 1 and are supplied with hydraulic pressure.

[0030] The hydraulic lash adjuster 36 on the intake side is located outside the cylinder head 1 in the width direction compared to the intake valve center line M1, and in the illustrated example, is arranged at a position substantially directly below the intake camshaft 5. The hydraulic lash adjuster 37 on the exhaust side is located inside the cylinder head 1 in the width direction compared to the exhaust valve center line M2 (in other words, between the center line M2 and the center line M1), and in the illustrated example, is provided at a relatively higher position than the intake side hydraulic lash adjuster 36.

[0031] Regarding the entire cylinder head 1 of the series-connected three cylinders, there are six intake-side hydraulic lash adjusters 36 and six exhaust-side hydraulic lash adjusters 37. The lash adjuster mounting holes 38 and 39 communicate with the lash adjuster oil passages 41 and 42 extending in the cylinder row direction, respectively. The lash adjuster oil passages 41 and 42 are formed by drilling, for example, in the cylinder row direction, and the ends of the lash adjuster oil passages 41 and 42 depicted in Figure 1 are closed by plugs.

[0032] Figure 4 To show the oil passages existing inside the cylinder head 1 and the cam bracket 2, the oil passages are shown in a perspective view along the cylinder row direction. Most of the above-mentioned oil passages other than the lash adjuster oil passages 41 and 42 are formed in the front end portions of the cylinder head 1 and the cam bracket 2 ( Figure 2 the lower side portion in ). In addition, similar to the lash adjuster oil passages 41 and 42, the above-mentioned oil passages are constituted by a combination of linear drilling processes, and the unnecessary open ends are closed by plugs.

[0033] At approximately the center in the width direction of the cylinder head 1, in other words, at a position between the intake camshaft 5 and the exhaust camshaft 6 when viewed in the cylinder block axial direction, an oil source pressure passage 45 extending in the vertical direction is formed. The lower end portion of the oil source pressure passage 45 communicates with a main oil passage (not shown) of the cylinder block 3. Therefore, the engine oil pressurized by the oil pump is supplied to the oil source pressure passage 45.

[0034] The upper end of the oil source pressure passage 45 opens on the lower surface of an oil storage portion 46 formed in the upper part of the cylinder head 1. The oil storage portion 46 is formed as a bathtub-shaped recess at a position between the intake camshaft 5 and the exhaust camshaft 6 and on the joint surface with respect to the cam bracket 2, and is formed as a closed space covered by the lower surface of the cam bracket 2. The joint surface 47 between the cylinder head 1 and the cam bracket 2 around the oil storage portion 46 is sealed by an appropriate sealing member such as the above-mentioned liquid gasket.

[0035] The side surface 46a on the exhaust camshaft 6 side of the oil storage portion 46 is formed as an inclined surface as Figure 4 shown, and one end of the exhaust-side oil passage 51 opens at the center of the side surface 46a. The exhaust-side oil passage 51 is formed as a straight line inclined at about 40 to 50° with respect to the joint surface 47 (in other words, the upper surface of the cylinder head 1), and the front end communicates with the exhaust-side lash adjuster oil passage 42. That is, the engine oil is supplied to the exhaust-side lash adjuster mounting hole 39 from the oil storage portion 46 via the exhaust-side oil passage 51 and the lash adjuster oil passage 42.

[0036] On the other hand, in the cam bracket 2, as a part of the oil passage from the oil storage portion 46 to the hydraulic lash adjuster 36 on the intake side, a cam bracket internal passage 52 formed by connecting a plurality of straight sections is formed so as to pass through the inside of the cam bracket 2. The cam bracket internal passage 52 is composed of the following parts: a straight section 52a that extends obliquely upward from the oil storage portion 46; a straight section 52b that extends parallel to the joint surface 47 above the intake camshaft 5; and a straight section 52c that extends downward more on the outer side in the cylinder head 1 width direction than the intake camshaft 5. That is, the cam bracket internal passage 52 has an inlet portion 52d that faces the oil storage portion 46 between the two camshafts 5 and 6, and an outlet portion 52e that faces the upper surface of the cylinder head 1 outside the two camshafts 5 and 6. In addition, in the middle portion of the straight section 52c that extends parallel to the joint surface 47, a camshaft lubricating oil passage 56 that branches off from the cam bracket internal passage 52 and reaches the intake side camshaft bearing portion 11 for the intake camshaft 5 is formed. The shaft neck portion of the intake camshaft 5 is lubricated by the engine oil flowing through the camshaft lubricating oil passage 56.

[0037] An intake side oil passage 53 is formed on the cylinder head 1 side so as to be connected to the outlet portion 52e of the cam bracket internal passage 52. The intake side oil passage 53 has a straight section 53a that extends in the vertical direction, and a straight section 53b that extends obliquely downward from the outer peripheral portion of the cylinder head 1. The front end of the straight section 53b communicates with the oil passage 41 for the lash adjuster on the intake side. In addition, the periphery of the connection portion between the two is still sealed by the sealing member of the joint surface 47 between the cylinder head 1 and the cam bracket 2. Therefore, engine oil is supplied to the intake side lash adjuster mounting hole 38 from the oil storage portion 46 via the cam bracket internal passage 52, the intake side oil passage 53, and the oil passage 41 for the lash adjuster.

[0038] Thus, in the above-described embodiment, the intake camshaft 5 is in a relatively lower position than the exhaust camshaft 6. Correspondingly, the shape of the upper surface of the cam bracket 2 is formed in a shape that descends downward on the intake camshaft 5 side. Therefore, as Figure 1 shown, the clearance with the engine hood (virtual line L) lowered on the vehicle front side can be appropriately ensured. In other words, the height of the engine hood can be set lower.

[0039] Here, the hydraulic lash adjuster 37 on the exhaust side corresponding to the exhaust camshaft 6 at a relatively high position is closer to the inner side in the width direction of the cylinder head 1 than the exhaust valve center line M2. Correspondingly, the outer edge position on the exhaust side of the cylinder head 1 is close to the inner side. In other words, the degree of protrusion of the outer edge position on the exhaust side toward the outer side in the width direction is reduced. Thus, the mountability to the vehicle is good. Assuming that if the upper part of the cylinder head 1 and the rear side part of the cam bracket 2 on the vehicle side protrude rearward of the vehicle, the mountability to the vehicle deteriorates. As a result, it is difficult to reduce the height of the engine hood.

[0040] On the other hand, the hydraulic lash adjuster 36 on the intake side corresponding to the intake camshaft 5 at a relatively low position is on the outer side in the width direction of the cylinder head 1 compared with the intake valve center line M1. Therefore, interference in the layout with the exhaust side hydraulic lash adjuster 37 located on the inner side in the width direction of the cylinder head 1 is avoided. Thus, if the hydraulic lash adjuster 36 is on the outer side in the width direction of the cylinder head 1 compared with the intake valve center line M1, there is a tendency that the outer edge position on the intake side of the cylinder head 1 is close to the outer side. Even if it is in a lower position and the outer edge position on the intake side of the cylinder head 1 is close to the outer side, the influence on the relationship with the engine hood (virtual line L) is small and it does not become a factor restricting the height of the engine hood.

[0041] In other words, under the limitation that either of the two hydraulic lash adjusters 36 and 37 is arranged close to the outer side, if the configuration of the above embodiment in which the exhaust side hydraulic lash adjuster 37 is on the inner side and the intake side hydraulic lash adjuster 36 is close to the outer side, and the configuration in which, conversely, the exhaust side hydraulic lash adjuster 37 is close to the outer side and the intake side hydraulic lash adjuster 36 is arranged on the inner side (this is taken as a reference example) are compared, the configuration of the embodiment is advantageous for further reducing the height of the engine hood. That is, it is assumed that the overall width of the cylinder head 1 is equal in the embodiment and the reference example, and if it is assumed that the mounting position to the vehicle is specified based on the outer edge on the exhaust side of the cylinder head 1 (i.e., the outer edge close to the rear of the vehicle) in any case, the intake camshaft 5 and the exhaust camshaft 6 of the embodiment are located closer to the rear of the vehicle compared with the reference example. Therefore, correspondingly, the height of the front part of the cam bracket 2 close to the vehicle is reduced, which is advantageous for reducing the height of the engine hood. In the reference example, the exhaust camshaft 6 at a higher position is arranged closer to the front of the vehicle compared with the embodiment. Correspondingly, the clearance obtained between the cam bracket 2 and the engine hood is reduced.

[0042] In addition, in the above-described embodiment, the supply of oil to the hydraulic lash adjuster 36 on the intake side configured to be close to the outside is performed through the internal passage 52 of the cam bracket. Therefore, compared with the case where the entire required oil passage is formed inside the cylinder head 1, the layout of the oil passage becomes easier, and it is possible to avoid interference with other components when arranging the oil passage. For example, although the intake valve is disposed between the oil source pressure passage 45 and the lash adjuster mounting hole 38 on the intake side, by providing the internal passage 52 of the cam bracket inside the cam bracket 2, interference with the intake valve can be avoided and the oil passage can be arranged. Further, since the internal passage 52 of the cam bracket crosses above the intake camshaft 5, there is no need to form an oil passage on the cylinder head 1 side that crosses below the camshaft 5 at a lower position.

[0043] The hydraulic lash adjuster 37 on the exhaust side is located between the exhaust valve and the oil source pressure passage 45. Therefore, by linearly providing the exhaust side oil passage 51 from the oil storage portion 46 at the center as described above, a simple structure is formed.

[0044] Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and various modifications can be made. For example, in the above-described embodiment, the structure may be such that the cam bracket 2 has a stepped shape, and the camshafts 5 and 6 are rotatably supported on the lower surface side of the cam bracket 2 via the cam brackets 13 and 14, and the camshaft bearing portions are provided on the upper surface of the cylinder head 1, and the camshafts 5 and 6 are supported between the cam brackets mounted on the cylinder head 1. Further, in the above-described embodiment, the "first camshaft" in the technical solution is the intake camshaft 5, and the "second camshaft" is the exhaust camshaft 6. Conversely, the "first camshaft" at a relatively lower position is the exhaust camshaft, and the "second camshaft" at a relatively higher position is the intake camshaft.

Claims

1. A cylinder head structure of an internal combustion engine, comprising: A cylinder head; A first camshaft and a second camshaft, one of which is for an intake valve and the other is for an exhaust valve; A first hydraulic lash adjuster disposed corresponding to the first camshaft; and A second hydraulic lash adjuster disposed corresponding to the second camshaft, In the cylinder head structure of the internal combustion engine, As the height position along the cylinder block center axis, the first camshaft is disposed at a lower position than the second camshaft, The second hydraulic lash adjuster is located inside the internal combustion engine in the width direction compared to the center line of the valve stem of the corresponding intake valve or exhaust valve that is inclined with respect to the cylinder block center axis, The first hydraulic lash adjuster is located outside the internal combustion engine in the width direction compared to the center line of the valve stem of the corresponding intake valve or exhaust valve.

2. The cylinder head structure of an internal combustion engine according to claim 1, Wherein, The cylinder head structure further has a cam bracket that is fixed to the upper part of the cylinder head to support the two camshafts, When observed in the cylinder block axial direction, the oil source pressure passage inside the cylinder head is located between the first camshaft and the second camshaft, A part of the oil passage from the oil source pressure passage to the first lash adjuster passes through the inside of the cam bracket as an internal passage of the cam bracket.

3. The cylinder head structure of an internal combustion engine according to claim 2, Wherein, The cylinder head structure has a camshaft lubricating oil passage that branches from the internal passage of the cam bracket inside the cam bracket and reaches the bearing portion of the first camshaft.

4. The cylinder head structure of an internal combustion engine according to claim 1, Wherein, The internal combustion engine is mounted on the front part of the vehicle in a transverse attitude with the first camshaft closer to the front of the vehicle than the second camshaft.

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