Cylinder head structure of internal combustion engine

Abstract

Air-intake-side and air-discharge-side hydraulic lash adjusters (36, 37) are provided to a cylinder head (1) in an internal combustion engine. An oil original-pressure passage (45) is positioned at a width-direction central section of the cylinder head (1), the oil original-pressure passage (45) communicating with an oil reservoir part (46). A cam carrier internal passage (52) that passes through the interior of a cam carrier (2) is provided to the air-intake-side lash adjuster (36). Oil is supplied from the oil reservoir part (46) to a lash-adjuster mounting hole (38) via the cam carrier internal passage (52) and an air-intake-side oil passage (53).

Description

Cylinder head structure of an internal combustion engine

[0001] The present invention relates to a cylinder head structure for an internal combustion engine equipped with a hydraulic lash adjuster, and more particularly to an improvement in the layout of an oil passage that supplies oil to the lash adjuster.

[0002] Hydraulic lash adjusters are known for automatically adjusting valve clearance to 0 in the valve trains of intake and exhaust valves in internal combustion engines. In configurations where this hydraulic lash adjuster is provided in the cylinder head, an oil passage is generally required to guide oil supplied from the cylinder block to the hydraulic lash adjuster.

[0003] Patent Document 1 discloses a configuration in which an oil reservoir covered by a cam cap member is formed between the intake camshaft and exhaust camshaft of the cylinder head, and an oil passage is formed from the bottom of this oil reservoir to a hydraulic lash adjuster.

[0004] As disclosed in Patent Document 1, conventionally, the entire oil passage for a hydraulic lash adjuster is formed inside the cylinder head, for example, by drilling, which limits design freedom and can make it difficult to position the oil passage due to interference with other components.

[0005] Japanese Utility Model Application Laid-Open Publication No. 5-1807

[0006] This invention relates to a cylinder head structure for 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 for an exhaust valve; a hydraulic lash adjuster arranged in the cylinder head corresponding to at least the first camshaft; and a cam carrier fixed to an upper part of the cylinder head and supporting at least the first camshaft, wherein, when viewed in the direction of the cylinder axis, an oil source pressure passage inside the cylinder head is located between the first camshaft and the second camshaft, and a part of the oil passage from this oil source pressure passage to the hydraulic lash adjuster passes through the inside of the cam carrier as an internal passage of the cam carrier.

[0007] Pressurized oil is supplied from the cylinder block to the oil source pressure passage inside the cylinder head, and from there it is sent to the hydraulic lash adjuster via an oil passage. Part of this oil passage passes through the inside of the cam carrier. This means that there are fewer restrictions on the placement of the oil passage due to interference with other parts on the cylinder head side.

[0008] Furthermore, the cam carrier is located relatively high in the internal combustion engine and the vertical distance to the lash adjuster is long, so oil is retained even if the internal combustion engine has been left unused for an extended period of time, ensuring that oil is supplied to the lash adjuster from the early stages of the next start-up.

[0009] 1 is a front view of a cylinder head equipped with a cam carrier; a plan view of the cam carrier; a cross-sectional view of a cylinder head equipped with a cam carrier; an explanatory diagram showing the layout of oil passages; a top view of the cylinder head; and an explanatory diagram of a valve mechanism.

[0010] An embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a front view showing a cylinder head 1 of an internal combustion engine according to the present invention together with a cam carrier 2. The cylinder head 1 is integrally cast from a metal material, such as an aluminum alloy, and is attached to the upper surface of a cylinder block 3. The internal combustion engine of the embodiment is an in-line three-cylinder spark-ignition internal combustion engine, a so-called gasoline engine, and is mounted in a so-called transverse position at the front of a vehicle. When mounted on a vehicle, the center axis of the cylinder is generally vertical, and therefore FIG. 1 generally corresponds to the position when mounted on a vehicle.

[0011] The internal combustion engine of the embodiment has a pent roof type combustion chamber with a spark plug and a fuel injection valve in the center of the combustion chamber, and each cylinder is provided with a pair of intake valves and a pair of exhaust valves.

[0012] Cylinder head 1 is equipped with an intake camshaft 5 for the intake valves and an exhaust camshaft 6 for the exhaust valves. Cam carrier 2 is configured like a cover that covers the top opening of cylinder head 1 and is joined and fixed to the top surface of cylinder head 1 via an appropriate sealing member such as a liquid gasket. Cam carrier 2 has intake-side camshaft bearing portion 11 and exhaust-side camshaft bearing portion 12, each of which is roughly semicircular facing downward, and rotatably supports intake camshaft 5 and exhaust camshaft 6 between itself and cam brackets 13 and 14, which are attached opposite camshaft bearing portions 11 and 12.

[0013] As shown in Figure 1, the intake camshaft 5 is positioned at a relatively lower height along the cylinder center axis than the exhaust camshaft 6. Correspondingly, the height of the upper edge of the cam carrier 2 covering the camshafts 5, 6 is also configured so that the height of the upper edge of the cam carrier 2 on the intake camshaft 5 side is lower than that of the exhaust camshaft 6 side. In one embodiment, the internal combustion engine is mounted in an 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 clearance between the engine hood (shown by imaginary line L) of the vehicle, which is tilted so that its front end is positioned low, is appropriate on both the intake camshaft 5 side and the exhaust camshaft 6 side.

[0014] As shown in Figure 2, the cam carrier 2 in one embodiment has a ladder-like configuration in which two camshaft housings 21, 22, each elongated in the cylinder row direction, are connected to each other at a position between the cylinders. Relatively large injection valve openings 23 are provided between the two camshaft housings 21, 22 at three locations corresponding to the cylinder positions in the cylinder row direction. Furthermore, cylindrical plug holes 24 for inserting spark plugs are formed closer to the exhaust camshaft 6 (camshaft housing 22) than the injection valve openings 23. The cam carrier 2 is integrally cast from a metal material, such as an aluminum alloy.

[0015] Figure 3 is a cross-sectional view of the cylinder head 1 and cam carrier 2 shown in Figure 1, taken along a plane passing through the centers of the intake and exhaust valves. As mentioned above, the cylinder has a pent roof type combustion chamber 31, to which an intake port 32 and an exhaust port 33 are connected. Although the valve train is not shown in Figure 3, as is well known to those skilled in the art, cylindrical stem guides are attached to stem guide mounting holes 34, 35, respectively, and poppet valve type intake and exhaust valves are assembled together with valve springs.

[0016] FIG. 6 is an explanatory diagram showing an outline of the valve train mechanism not shown in FIG. 3 . A rocker arm 101, one end of which is supported by the hydraulic lash adjuster 36, swings due to the cam action of the intake camshaft 5, opening and closing an intake valve 103. Similarly, a rocker arm 102, one end of which is supported by the hydraulic lash adjuster 37, swings due to the cam action of the exhaust camshaft 6, opening and closing an exhaust valve 104. Reference numeral 105 denotes a fuel injection valve, and 106 denotes a spark plug. The hydraulic lash adjuster itself is a well-known structure, so a detailed description thereof will be omitted. However, it has a generally cylindrical shape, extends to zero valve clearance by an internal spring, and supports the reaction force during valve lift with oil filled inside. Note that FIG. 6 is an explanatory diagram of the mechanism and does not show the precise layout of each part.

[0017] In Figure 3, line M1 indicates the center line of the intake valve stem, and line M2 indicates the center line of the exhaust valve stem. As shown in Figure 3, the intake valve center line M1 passes inside the center O1 of the intake camshaft 5 in the width direction of the cylinder head 1 (left and right direction in Figure 3). On the other hand, the exhaust valve center line M2 passes outside the center O2 of the exhaust camshaft 6 in the width direction of the cylinder head 1.

[0018] The intake valve and exhaust valve are provided with hydraulic lash adjusters 36, 37, respectively. These hydraulic lash adjusters 36, 37 are fitted into cylindrical lash adjuster mounting holes 38, 39 provided in the cylinder head 1 and receive hydraulic pressure.

[0019] The intake-side hydraulic lash adjuster 36 is located outside the intake valve center line M1 in the width direction of the cylinder head 1, and in the illustrated example, is located approximately directly below the intake camshaft 5. The exhaust-side hydraulic lash adjuster 37 is located inside the exhaust valve center line M2 in the width direction of the cylinder head 1, and in the illustrated example, is provided at a relatively higher position than the intake-side hydraulic lash adjuster 36.

[0020] The in-line three-cylinder cylinder head 1 is equipped with six intake-side hydraulic lash adjusters 36 and six exhaust-side hydraulic lash adjusters 37. The lash adjuster mounting holes 38, 39 are connected to lash adjuster oil galleries 41, 42, respectively, which extend in the cylinder row direction. The lash adjuster oil galleries 41, 42 are formed, for example, by drilling along the cylinder row direction, and the ends of the lash adjuster oil galleries 41, 42 shown in FIG. 1 are closed with plugs.

[0021] Next, the configuration of the oil passages, which are an essential part of the present invention, will be described with reference to Figure 4. Figure 4 shows the oil passages in a see-through manner along the cylinder row direction in order to show the oil passages present inside the cylinder head 1 and the cam carrier 2. Most of these oil passages, except for the lash adjuster oil galleries 41, 42, are formed in the front end portions (lower portions in Figure 2) of the cylinder head 1 and the cam carrier 2. Like the lash adjuster oil galleries 41, 42, these oil passages are formed by a combination of linear drilling, with unnecessary open ends blocked by plugs.

[0022] An oil source pressure passage 45 extending in the vertical direction is formed in 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 axial direction. The lower end of this oil source pressure passage 45 communicates with a main oil gallery (not shown) of the cylinder block 3. Therefore, oil pressurized by the oil pump is supplied to this oil source pressure passage 45.

[0023] The upper end of the oil source pressure passage 45 opens to the underside of an oil reservoir 46 formed in the upper part of the cylinder head 1. The oil reservoir 46 is formed as a bathtub-shaped recess in the joint surface with the cam carrier 2, at a position between the intake camshaft 5 and the exhaust camshaft 6 (see FIG. 5), and is formed as a closed space by being covered by the underside of the cam carrier 2. The joint surface 47 between the cylinder head 1 and the cam carrier 2 around the oil reservoir 46 is sealed with an appropriate sealing member such as the liquid gasket mentioned above.

[0024] 4, a side surface 46a of the oil reservoir 46 facing the exhaust camshaft 6 is formed as an inclined surface, and one end of an exhaust-side oil passage 51 opens in the center of this side surface 46a. The exhaust-side oil passage 51 is formed in a straight line inclined, for example, at an angle of approximately 40 to 50 degrees with respect to the joint surface 47 (in other words, the top surface of the cylinder head 1), and its tip communicates with the exhaust-side lash adjuster oil gallery 42. In other words, oil is supplied to the exhaust-side lash adjuster mounting hole 39 from the oil reservoir 46 via the exhaust-side oil passage 51 and the lash adjuster oil gallery 42.

[0025] Meanwhile, a cam carrier internal passage 52 made up of multiple connected straight sections is formed in the cam carrier 2 as part of the oil passage leading from the oil reservoir 46 to the intake-side hydraulic lash adjuster 36. The cam carrier internal passage 52 is made up of a straight section 52a extending diagonally upward from the oil reservoir 46, a straight section 52b extending parallel to the joint surface 47 above the intake camshaft 5, and a straight section 52c extending downward on the outer side of the intake camshaft 5 in the width direction of the cylinder head 1. In other words, the cam carrier internal passage 52 has an inlet section 52d facing the oil reservoir 46 between the two camshafts 5, 6, and an outlet section 52e facing the top surface of the cylinder head 1 outside the two camshafts 5, 6. A camshaft lubricating oil passage 56 is formed in the middle of the straight section 52c extending parallel to the joint surface 47. The camshaft lubricating oil passage 56 branches off from the cam carrier internal passage 52 and reaches the intake-side camshaft bearing 11 for the intake camshaft 5. The journal portion of the intake camshaft 5 is lubricated by the oil flowing through the camshaft lubricating oil passage 56.

[0026] An intake-side oil passage 53 is formed on the cylinder head 1 side so as to connect to the outlet 52e of the cam carrier internal passage 52. The intake-side oil passage 53 has a straight section 53a extending vertically and a straight section 53b extending diagonally downward from the outer periphery of the cylinder head 1. The tip of the straight section 53b communicates with the intake-side lash adjuster oil gallery 41. The periphery of the connection between the two is also sealed by a seal member at the joint surface 47 between the cylinder head 1 and the cam carrier 2. Figure 5 shows the upper end opening of the intake-side oil passage 53 (straight section 53a). Therefore, oil is supplied to the intake-side lash adjuster mounting hole 38 from the oil reservoir 46 via the cam carrier internal passage 52, the intake-side oil passage 53, and the lash adjuster oil gallery 41.

[0027] As described above, in the above embodiment, oil is supplied from the oil reservoir 46 to the intake-side lash adjuster mounting hole 38 through the cam carrier internal passage 52. This simplifies the layout of the oil passages compared to forming all of the necessary oil passages inside the cylinder head 1, and allows the oil passages to be located without interfering with other components. For example, an intake valve is located between the oil source pressure passage 45 and the intake-side lash adjuster mounting hole 38 (see FIG. 6 ). However, by providing the cam carrier internal passage 52 inside the cam carrier 2, the oil passage can be located without interfering with the intake valve. Furthermore, because the cam carrier internal passage 52 crosses above the intake camshaft 5, it is not necessary to form an oil passage on the cylinder head 1 side that crosses below the camshaft 5.

[0028] Furthermore, the cam carrier internal passage 52 is located higher than the hydraulic lash adjusters 36, 37 and forms a relatively long path leading to the hydraulic lash adjusters 36, 37. This contributes to oil retention while the internal combustion engine is stopped, improving oil retention even when the internal combustion engine has been left unused for an extended period of time. As a result, when the internal combustion engine is started after being left unused, oil is quickly supplied to the hydraulic lash adjusters 36, 37, preventing oil shortage and air intake.

[0029] Because the exhaust-side hydraulic lash adjuster 37 is located between the exhaust valve and the oil source pressure passage 45, providing the exhaust-side oil passage 51 in a straight line from the central oil reservoir 46 as described above results in a simple structure. For the exhaust-side hydraulic lash adjuster 37, there is no passage with an oil retention function that passes through the inside of the cam carrier 2, but oil is retained by the oil reservoir 46, thereby preventing oil shortage and air intake. Therefore, the intake-side hydraulic lash adjuster 36 and the exhaust-side hydraulic lash adjuster 37 each have separate portions with an oil retention function, which reliably prevents oil shortage in each.

[0030] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, the cam carrier is not limited to the ladder-shaped configuration as in the above embodiment, and may be any configuration having at least one camshaft bearing portion. Furthermore, the camshaft may be rotatably supported between the cylinder head 1 and the cam carrier.

Claims

1. 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 in the cylinder head corresponding to the first camshaft, a second hydraulic lash adjuster disposed in the cylinder head corresponding to the second camshaft, and a cam carrier fixed to the upper part of the cylinder head and supporting at least the first camshaft, A cylinder head structure of an internal combustion engine comprising: the first hydraulic lash adjuster is located outside the width direction of the internal combustion engine with respect to the center line of the valve stem of the corresponding intake valve or exhaust valve, the second hydraulic lash adjuster is located between the center line of the valve stem of the intake valve and the center line of the valve stem of the exhaust valve as a position in the width direction of the internal combustion engine, when viewed in the cylinder axis direction, an 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 hydraulic lash adjuster passes through the inside of the cam carrier as an internal passage of the cam carrier, the oil source pressure passage extends vertically inside the cylinder head and is connected to the internal passage of the cam carrier at the joint surface between the cylinder head and the cam carrier, when viewed in the cylinder axis direction, the internal passage of the cam carrier crosses above the first camshaft and is connected to an internal oil passage of the cylinder head for the first hydraulic lash adjuster, the second hydraulic lash adjuster is connected to the oil source pressure passage via an internal oil passage of the cylinder head for the second hydraulic lash adjuster without passing through the cam carrier, A cylinder head structure of an internal combustion engine.

2. (Deleted)

3. having an oil gallery for lash adjusters extending along the cylinder bank direction inside the cylinder head, the oil gallery for lash adjusters is connected between the internal passage of the cam carrier and the first hydraulic lash adjuster, The cylinder head structure of the internal combustion engine according to Claim 1.

4. comprising a camshaft lubricating oil passage that branches from the internal passage of the cam carrier inside the cam carrier and reaches the camshaft bearing portion, The cylinder head structure of the internal combustion engine according to Claim 1.

5. The oil supply passage has an oil reservoir formed so as to have an enlarged volume at the joint surface between the cylinder head and the cam carrier. The internal oil passage in the cylinder head for the second hydraulic lash adjuster communicates with the oil reservoir. The cylinder head structure of an internal combustion engine according to claim 1.