Cylinder head structure of an internal combustion engine

Abstract

According to the present invention, in an internal combustion engine mounted transversely in a vehicle, an intake camshaft (5) is at a lower position than an exhaust camshaft (6) so that appropriate clearance is provided between an engine hood (L) and a cam carrier (2). An exhaust-side hydraulic lash adjuster (37) is inward from the centerline (M2) of an exhaust valve in the width direction of a cylinder head (1). An intake-side hydraulic lash adjuster (36) is outward from the centerline (M1) of an intake valve in the width direction of the cylinder head (1). An oil source pressure passage (45) is disposed in a center portion in the width direction of the cylinder head (1) and is connected to an oil reservoir (46). Oil is supplied to the intake-side hydraulic lash adjuster (36) through a cam carrier internal passage (52) that passes internally through the cam carrier (2).

Description

Technical Field

[0001] The present invention relates to a cylinder head structure of an internal combustion engine provided with hydraulic lash adjusters for each of an intake valve and an exhaust valve.

Background Art

[0002] In a valve operating mechanism of an intake valve or an exhaust valve of an internal combustion engine, a hydraulic lash adjuster is known for automatically adjusting the valve clearance to zero. In a configuration in which this hydraulic lash adjuster is provided in a cylinder head, the width dimension of the cylinder head tends to increase.

[0003] On the other hand, Patent Document 1 discloses a configuration in which, in an internal combustion engine mounted in a horizontal posture in a vehicle, an exhaust side camshaft located closer to the front of the vehicle is arranged at a position relatively lower than an intake side camshaft located closer to the rear of the vehicle so as to correspond to the inclination of an engine hood.

[0004] An object of the present invention is to provide a more appropriate arrangement of hydraulic lash adjusters when the height positions of two camshafts are different in this way.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] The present invention is 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 provided corresponding to the first camshaft, a second hydraulic lash adjuster provided corresponding to the second camshaft, A cylinder head structure for an internal combustion engine, comprising: In terms of height along the cylinder's central axis, the first camshaft is positioned lower than the second camshaft. The second hydraulic lash adjuster described above is located inward in the width direction of the internal combustion engine from the center line of the corresponding intake valve or exhaust valve stem, which is inclined with respect to the cylinder's central axis. The first hydraulic lash adjuster described above is located outside the width direction of the internal combustion engine relative to the centerline of the valve stem of the corresponding intake or exhaust valve.

[0007] If the hydraulic lash adjusters are positioned outside the width of the internal combustion engine beyond the centerline of the intake or exhaust valve stem, the outer edge of the cylinder head will protrude outward in the width direction of the internal combustion engine due to the addition of the hydraulic lash adjusters themselves, the securing of the structure necessary to incorporate the hydraulic lash adjusters, and the formation of oil passages for oil supply. On the other hand, if the hydraulic lash adjusters on both the intake and exhaust sides are to be positioned inside the width of the internal combustion engine beyond the centerline of the intake or exhaust valve stem, the width dimension of the cylinder head will actually increase in order to secure space for both.

[0008] In this invention, the second hydraulic lash adjuster corresponding to the second camshaft, which is located in a relatively high position, is located inward in the width direction of the internal combustion engine relative to the valve stem centerline, while the first hydraulic lash adjuster corresponding to the first camshaft, which is located in a relatively low position, is located outward in the width direction of the internal combustion engine relative to the valve stem centerline. Therefore, on the side of the second camshaft, which is located in a relatively high position, the outward protrusion of the outer edge of the cylinder head is small, and thus the impact on the clearance between the engine and the engine hood when mounted in a vehicle is small. On the side of the first camshaft, which is located in a relatively low position, the outer edge of the cylinder head protrudes outward, but because this part is in a relatively low position, the impact on vehicle mountability is small. [Brief explanation of the drawing]

[0009] [Figure 1] Front view of a cylinder head with a cam carrier. [Figure 2] Plan view of the cam carrier. [Figure 3] Cross-sectional view of a cylinder head equipped with a cam carrier. [Figure 4] An explanatory diagram showing the layout of the oil passages. [Figure 5] Diagram illustrating the valve train mechanism. [Modes for carrying out the invention]

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

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

[0012] The cylinder head 1 includes an intake camshaft 5 for the intake valve and an exhaust camshaft 6 for the exhaust valve. The cam carrier 2 is configured as a cover that covers the upper opening of the cylinder head 1 and is joined and fixed to the upper surface of the cylinder head 1 via a suitable sealing member such as a liquid gasket. The cam carrier 2 has an intake-side camshaft bearing portion 11 and an exhaust-side camshaft bearing portion 12 that are approximately semicircular in shape and extend downwards, and rotatably supports the intake camshaft 5 and exhaust camshaft 6, respectively, between these camshaft bearing portions 11 and 12 and cam brackets 13 and 14 that are mounted opposite to them.

[0013] As shown in Figure 1, the intake camshaft 5 is positioned relatively lower than the exhaust camshaft 6 in terms of height along the cylinder's central axis. Correspondingly, the height of the upper edge portion of the cam carrier 2 covering the top of each camshaft 5 and 6 is also configured so that the intake camshaft 5 side is lower than the exhaust camshaft 6 side. In one embodiment, the internal combustion engine is mounted in the engine compartment at the front of the vehicle with the intake camshaft 5 side at the front of the vehicle and the exhaust camshaft 6 side at the rear of the vehicle. Therefore, the clearance between the engine and the vehicle's engine hood (shown by the dashed line L), which is inclined so that the front end is at a lower position, is appropriate for both the intake camshaft 5 side and the exhaust camshaft 6 side.

[0014] As shown in Figure 2, the cam carrier 2 of one embodiment has a ladder-like structure in which two elongated camshaft housings 21 and 22 extending in the direction of the cylinder row are connected to each other at the inter-cylinder positions. At three locations corresponding to the cylinder positions in the direction of the cylinder row, relatively large injection valve openings 23 are provided between the two camshaft housings 21 and 22. In addition, cylindrical plug holes 24 for inserting spark plugs are formed on the exhaust camshaft 6 side (camshaft housing 22 side) of the injection valve openings 23. The cam carrier 2 is integrally cast using 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, cut along a cross-section passing through the centers of the intake and exhaust valves. As mentioned above, it has a pent-roof type combustion chamber 31, to which the intake port 32 and exhaust port 33 are connected. In Figure 3, the valve train is not shown, but as is well known to those skilled in the art, cylindrical stem guides are attached to the stem guide mounting holes 34 and 35, respectively, and poppet valve type intake and exhaust valves are assembled together with valve springs.

[0016] FIG. 5 is an explanatory diagram showing an outline of a valve operating mechanism not shown in FIG. 3. A rocker arm 101 supported at one end by a hydraulic lash adjuster 36 swings by the cam action of an intake camshaft 5 to open and close an intake valve 103. Similarly, a rocker arm 102 supported at one end by a hydraulic lash adjuster 37 swings by the cam action of an exhaust camshaft 6 to open and close an exhaust valve 104. 105 indicates a fuel injection valve and 106 indicates a spark plug. Since the hydraulic lash adjuster itself has a known configuration, its detailed description is omitted. It has a substantially cylindrical shape and extends by an internal spring so that the valve clearance becomes zero, and is configured to be supported by oil filling the inside against the reaction force during valve lift. Note that FIG. 5 is an explanatory diagram of the mechanism and does not show the exact arrangement of each part.

[0017] In FIG. 3, line M1 indicates the center line of the valve stem of the intake valve, and line M2 indicates the center line of the valve stem of the exhaust valve. These intake valve center line M1 and exhaust valve center line M2 are inclined with respect to the cylinder center axis so as to form a substantially symmetric shape. As shown in FIG. 3, the intake valve center line M1 passes inside in the width direction of the cylinder head 1 (the left-right direction in FIG. 3) from the center O1 of the intake camshaft 5. On the other hand, the exhaust valve center line M2 passes outside in the width direction of the cylinder head 1 from the center O2 of the exhaust camshaft 6. Note that the "width direction of the internal combustion engine" in the claims is synonymous with the above "width direction of the cylinder head 1", and is a direction orthogonal to the cylinder center axis and orthogonal to the cylinder bank direction.

[0018] Hydraulic lash adjusters 36 and 37 are provided for each of the intake valve and the exhaust valve. These hydraulic lash adjusters 36 and 37 are loaded into cylindrical lash adjuster mounting holes 38 and 39 provided in the cylinder head 1 and receive hydraulic supply.

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

[0020] The entire cylinder head 1 of the in-line three-cylinder engine includes six intake-side hydraulic lash adjusters 36 and six exhaust-side hydraulic lash adjusters 37. The lash adjuster mounting holes 38, 39 communicate with the oil galleries 41, 42 for the lash adjusters that extend in the cylinder bank direction, respectively. The oil galleries 41, 42 for the lash adjusters are, for example, drilled along the cylinder bank direction, and the ends of the oil galleries 41, 42 for the lash adjusters depicted in FIG. 1 are closed by plugs.

[0021] FIG. 4 shows the oil passages in a perspective view along the cylinder bank direction in order to show the oil passages existing inside the cylinder head 1 and the cam carrier 2. Most of these oil passages other than the oil galleries 41, 42 for the lash adjusters are formed at the front end portion (the lower portion in FIG. 2) of the cylinder head 1 and the cam carrier 2. Note that, similar to the oil galleries 41, 42 for the lash adjusters, these oil passages are constituted by a combination of linear drilling processes, and unnecessary open ends are closed by plugs.

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

[0023] The upper end of the oil pressure passage 45 opens to the lower surface of the oil reservoir 46 formed on the upper part of the cylinder head 1. The oil reservoir 46 is formed as a bathtub-shaped recess at the joint surface with the cam carrier 2, at a position between the intake camshaft 5 and the exhaust camshaft 6, and is covered by the lower surface of the cam carrier 2, forming a closed space. The joint surface 47 between the cylinder head 1 and the cam carrier 2 around the oil reservoir 46 is sealed by a suitable sealing member such as the liquid gasket described above.

[0024] As shown in Figure 4, the side surface 46a of the oil reservoir 46 on the exhaust camshaft 6 side is formed as an inclined surface, and one end of the 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 at, for example, about 40 to 50° with respect to the joint surface 47 (in other words, the upper 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] On the other hand, the cam carrier 2 has an internal cam carrier passage 52 formed by connecting multiple straight sections so as to pass through the inside of the cam carrier 2, as part of the oil passage from the oil reservoir 46 to the intake-side hydraulic lash adjuster 36. The internal cam carrier passage 52 consists 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 outward in the width direction of the cylinder head 1 from the intake camshaft 5. In other words, the internal cam carrier passage 52 has an inlet 52d facing the oil reservoir 46 between the two camshafts 5 and 6, and an outlet 52e facing the upper surface of the cylinder head 1 outside the two camshafts 5 and 6. Furthermore, in the middle of the straight section 52c that extends parallel to the joint surface 47, a camshaft lubrication oil passage 56 is formed, branching off from the cam carrier internal passage 52 and leading to the intake side camshaft bearing section 11 for the intake camshaft 5. The journal portion of the intake camshaft 5 is lubricated by the oil flowing through this camshaft lubrication 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 portion 52e of the cam carrier internal passage 52 described above. The intake-side oil passage 53 has a straight section 53a extending in the vertical direction and a straight section 53b extending diagonally downward from the outer circumference of the cylinder head 1. The tip of the straight section 53b communicates with the intake-side lash adjuster oil gallery 41. The area around the connection between the two is sealed by a sealing member at the joint surface 47 between the cylinder head 1 and the cam carrier 2. 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] Thus, in the above embodiment, the intake camshaft 5 is positioned relatively lower than the exhaust camshaft 6, and correspondingly the shape of the upper surface of the cam carrier 2 slopes downward on the intake camshaft 5 side. As shown in Figure 1, this allows for adequate clearance between the cam carrier and the engine hood (dummy line L), which is lower at the front of the vehicle. In other words, it becomes possible to set the height of the engine hood lower.

[0028] Here, the exhaust-side hydraulic lash adjuster 37, which corresponds to the relatively high exhaust camshaft 6, is located inward in the width direction of the cylinder head 1 compared to the exhaust valve centerline M2, and the exhaust-side outer edge of the cylinder head 1 is positioned further inward. In other words, the outward protrusion of the exhaust-side outer edge in the width direction is reduced. This improves the ease of mounting on the vehicle. If the upper part of the cylinder head 1 or the rear part of the cam carrier 2 protrudes towards the rear of the vehicle, the ease of mounting on the vehicle will worsen, and as a result it will be difficult to lower the height of the engine hood.

[0029] On the other hand, the intake-side hydraulic lash adjuster 36, which corresponds to the intake camshaft 5 located in a relatively low position, is located outside the width direction of the cylinder head 1 relative to the intake valve centerline M1, thus avoiding layout interference with the exhaust-side hydraulic lash adjuster 37, which is located inside the width direction of the cylinder head 1. When the hydraulic lash adjuster 36 is located outside the width direction of the cylinder head 1 relative to the intake valve centerline M1 in this way, the position of the outer edge of the intake side of the cylinder head 1 tends to be further outward. However, even if the position of the outer edge of the intake side of the cylinder head 1 is further outward at this relatively low position, it has little effect on the relationship with the engine hood (imaginary line L) and does not become a factor that limits the height of the engine hood.

[0030] In other words, given the constraint that one of the two hydraulic lash adjusters 36 and 37 is positioned towards the outside, comparing the configuration of the above embodiment, where the exhaust-side hydraulic lash adjuster 37 is positioned inward and the intake-side hydraulic lash adjuster 36 is positioned towards the outside, with the opposite configuration, where the exhaust-side hydraulic lash adjuster 37 is positioned towards the outside and the intake-side hydraulic lash adjuster 36 is positioned inward (this is considered a reference example), the configuration of the embodiment is more advantageous in lowering the height of the engine hood. That is, assuming that the overall width of the cylinder head 1 is the same in the embodiment and the reference example, and further assuming that in both cases the mounting position on the vehicle is determined based on the outer edge of the exhaust side of the cylinder head 1 (i.e., the outer edge closer to the rear of the vehicle), the intake camshaft 5 and exhaust camshaft 6 are positioned closer to the rear of the vehicle in the embodiment compared to the reference example. Therefore, correspondingly, the height of the portion of the cam carrier 2 closer to the front of the vehicle is lower, which is advantageous in lowering the height of the engine hood. In the reference example, the exhaust camshaft 6, which is located at a high position, is positioned closer to the front of the vehicle compared to the embodiment, which reduces the clearance between the cam carrier 2 and the engine hood.

[0031] Furthermore, in the above embodiment, oil is supplied to the intake-side hydraulic lash adjuster 36, which is positioned towards the outside, through the cam carrier internal passage 52. Therefore, compared to the case where all the necessary oil passages are formed inside the cylinder head 1, the layout of the oil passages becomes easier, and the oil passages can be provided while avoiding interference with other parts. For example, an intake valve is interposed between the oil source pressure passage 45 and the intake-side lash adjuster mounting hole 38, but by providing the cam carrier internal passage 52 inside the cam carrier 2, it is possible to lay out the oil passages while avoiding interference with the intake valve. Moreover, since the cam carrier internal passage 52 crosses above the intake camshaft 5, it is unnecessary to form an oil passage on the cylinder head 1 side that crosses below the camshaft 5, which is located at a relatively low position.

[0032] Since the exhaust-side hydraulic lash adjuster 37 is located between the exhaust valve and the oil source pressure passage 45, a simple structure can be achieved by providing the exhaust-side oil passage 51 in a straight line from the central oil reservoir 46 as described above.

[0033] 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, in the above embodiment, a ladder-shaped cam carrier 2 is provided, and camshafts 5 and 6 are rotatably supported on the lower surface side of the cam carrier 2 via cam brackets 13 and 14. However, the cylinder head 1 may have a camshaft bearing portion on its upper surface, and the camshafts 5 and 6 may be supported between the camshaft bearing portion and a cam bracket attached to the cylinder head 1. Also, in the above embodiment, the "first camshaft" in the claim is the intake camshaft 5 and the "second camshaft" is the exhaust camshaft 6. However, conversely, the "first camshaft" located in a relatively lower position may be the exhaust camshaft, and the "second camshaft" located in a relatively higher position may be the intake camshaft.

Claims

1. Cylinder head and, A first camshaft and a second camshaft, one of which is for the intake valve and the other for the exhaust valve, A first hydraulic lash adjuster is provided corresponding to the first camshaft, A second hydraulic lash adjuster is provided in accordance with the second camshaft, A cylinder head structure for an internal combustion engine, comprising: In terms of height along the cylinder's central axis, the first camshaft is positioned lower than the second camshaft. The second hydraulic lash adjuster described above is located inward in the width direction of the internal combustion engine from the center line of the corresponding intake valve or exhaust valve stem, which is inclined with respect to the cylinder's central axis. The first hydraulic lash adjuster described above is located outside the width direction of the internal combustion engine, relative to the centerline of the valve stem of the corresponding intake or exhaust valve. This internal combustion engine is mounted transversely at the front of the vehicle, with the first camshaft positioned further forward than the second camshaft. Cylinder head structure of an internal combustion engine.

2. It further includes a cam carrier fixed to the top of the cylinder head to support the two camshafts mentioned above, When viewed in the direction of the cylinder axis, the oil pressure passage inside the cylinder head is located between the first camshaft and the second camshaft. A portion of the oil passage from this oil pressure passage to the first lash adjuster passes through the inside of the cam carrier as an internal passage of the cam carrier. The cylinder head structure for an internal combustion engine according to claim 1.

3. The above-mentioned cam carrier is provided with a camshaft lubrication oil passage that branches off from the internal passage of the cam carrier and reaches the bearing portion of the first camshaft. The cylinder head structure for an internal combustion engine according to claim 2.

4. A cylinder head and A first camshaft and a second camshaft, one of which is for the intake valve and the other for the exhaust valve, A first hydraulic lash adjuster is provided corresponding to the first camshaft, A second hydraulic lash adjuster is provided in accordance with the second camshaft, A cylinder head structure for an internal combustion engine, comprising: In terms of height along the cylinder's central axis, the first camshaft is positioned lower than the second camshaft. The second hydraulic lash adjuster described above is located inward in the width direction of the internal combustion engine from the center line of the corresponding intake valve or exhaust valve stem, which is inclined with respect to the cylinder's central axis. The first hydraulic lash adjuster described above is located outside the width direction of the internal combustion engine, relative to the centerline of the valve stem of the corresponding intake or exhaust valve. It further includes a cam carrier fixed to the top of the cylinder head to support the two camshafts mentioned above, When viewed in the direction of the cylinder axis, the oil pressure passage inside the cylinder head is located between the first camshaft and the second camshaft. A portion of the oil passage from this oil pressure passage to the first lash adjuster passes through the inside of the cam carrier as an internal passage of the cam carrier. Cylinder head structure of an internal combustion engine.

5. The cam carrier is provided with a camshaft lubrication oil passage that branches off from the internal passage of the cam carrier and reaches the bearing portion of the first camshaft. The cylinder head structure for an internal combustion engine according to claim 4.

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