Cylinder head structure for internal combustion engine

Abstract

A cylinder head (1) of an internal combustion engine is provided with intake-side and exhaust-side hydraulic lash adjusters (36, 37). 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). The air intake side lash adjuster (36) is provided with a cam holder internal passage (52) passing through the inside of the cam holder (2), and oil is supplied to the lash adjuster mounting hole (38) from the oil reservoir (46) via the cam holder internal passage (52) and the air intake side oil passage (53).

Description

Technical Field

[0001] The present invention relates to a cylinder head structure of an internal combustion engine having a hydraulic lash adjuster, and particularly to an improvement in the layout of an oil passage for supplying oil to the lash adjuster. Background Art

[0002] Regarding the valve operating mechanism of the intake valve and exhaust valve of an internal combustion engine, a hydraulic lash adjuster is known for automatically adjusting the valve clearance to 0. Regarding a structure in which the cylinder head has the hydraulic lash adjuster, an oil passage for guiding the oil supplied from the cylinder block side to the hydraulic lash adjuster is generally required.

[0003] Patent Document 1 discloses the following structure: an oil accumulation portion covered by a cam cover member is formed between the intake camshaft and the exhaust camshaft of the cylinder head, and an oil passage is formed from the lower portion of the oil accumulation portion to the hydraulic lash adjuster.

[0004] As disclosed in this Patent Document 1, currently, the entire oil passage for the hydraulic lash adjuster is formed inside the cylinder head, for example, by drilling. Therefore, the degree of design freedom is sometimes low, and it is difficult to arrange the oil passage due to interference with other components.

[0005] Patent Document 1: Japanese Utility Model Laid-Open No. 5-1807 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 the intake valve and the other is for the exhaust valve;

[0009] A hydraulic lash adjuster disposed at least corresponding to the first camshaft in the cylinder head; and

[0010] A cam bracket fixed to the upper part of the cylinder head and supporting at least the first camshaft,

[0011] When viewed in the cylinder block axial direction, an oil source pressure passage inside the cylinder head is located between the first camshaft and the second camshaft,

[0012] A part of the oil passage from the oil source pressure passage to the hydraulic lash adjuster passes through the inside of the cam bracket as an internal passage of the cam bracket.

[0013] The pressurized engine oil is supplied from the side of the cylinder block to the oil source pressure passage inside the cylinder head and is delivered from here to the hydraulic lash adjuster via an oil passage. A part of this oil passage passes through the inside of the cam bracket. Therefore, the restriction on the layout of the oil passage caused by interference with other components on the cylinder head side is reduced.

[0014] Moreover, the cam bracket is located at a relatively high position in the vertical direction of the internal combustion engine, and the distance in the vertical direction to the lash adjuster is also large. Therefore, the engine oil can be retained even when the internal combustion engine is left standing for a long time. Thus, the lash adjuster can be reliably supplied with engine oil at the initial stage of the next startup. Description of the Drawings

[0015] Figure 1 is a front view of a cylinder head having a cam bracket.

[0016] Figure 2 is a top view of the cam bracket.

[0017] Figure 3 is a sectional view of a cylinder head having a cam bracket.

[0018] Figure 4 is an explanatory diagram showing the layout of the oil passage.

[0019] Figure 5 is a top view of the cylinder head.

[0020] Figure 6 is an explanatory diagram of the valve actuating mechanism. Detailed Description of the Invention

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to 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 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. Therefore, Figure 1 it 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 intake valves and an exhaust camshaft 6 for exhaust valves. The cam bracket 2 is configured in a hood shape 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 disposed 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 respective camshafts 5 and 6 is also lower on the intake camshaft 5 side than on the exhaust camshaft 6 side. An 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 the following 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, insertion holes 24 for 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 Figure 1 along a section passing through the centers of the intake valve and the exhaust valve. 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 this, the illustration of the valve operating mechanism is omitted, and as is known to those skilled in the art, cylindrical rod guides are respectively mounted in the rod guide mounting holes 34 and 35, and lift valve type intake-side and exhaust valves are assembled together with valve springs.

[0027] Figure 6 is a view showing Figure 3A schematic explanatory diagram of a dynamic valve mechanism not shown in the figure. One end of a rocker arm 101 supported by a hydraulic lash adjuster 36 swings due to the cam action of an intake camshaft 5 to open and close an intake valve 103. Similarly, one end of a rocker arm 102 supported by a hydraulic lash adjuster 37 swings due to the cam action of an exhaust camshaft 6 to open and close an exhaust valve 104. 105 represents a fuel injection valve, and 106 represents a spark plug. Since the hydraulic lash adjuster itself is a well-known structure, its detailed description is omitted, but it is formed in the following structure, that is, it is approximately cylindrical, and is extended by an internal spring so that the valve clearance becomes zero, and the reaction force during valve lift is borne by the engine oil filled inside. In addition, Figure 6 is an explanatory diagram of the mechanism, and the exact configuration of each part is not shown.

[0028] In Figure 3 , a line M1 represents the center line of the valve stem of the intake valve, and a line M2 represents the center line of the valve stem of the exhaust valve. As Figure 3 shown, compared with the center O1 of the intake camshaft 5, the intake valve center line M1 passes through from the inside in the width direction ( Figure 3 the left and right directions) of the cylinder head 1. On the other hand, compared with the center O2 of the exhaust camshaft 6, the exhaust valve center line M2 passes through from the outside in the width direction of the cylinder head 1.

[0029] Hydraulic lash adjusters 36 and 37 are respectively provided for the intake valve and the exhaust valve. The above-mentioned hydraulic lash adjusters 36 and 37 are filled in cylindrical lash adjuster mounting holes 38 and 39 provided in the cylinder head 1 and receive hydraulic supply.

[0030] The intake-side hydraulic lash adjuster 36 is located outside the width direction of the cylinder head 1 compared with the intake valve center line M1. In the illustrated example, it is arranged 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 compared with the exhaust valve center line M2. In the illustrated example, it is provided at a position relatively higher than the intake-side hydraulic lash adjuster 36.

[0031] Regarding the entire cylinder head 1 of the in-line 3 cylinders, there are 6 intake-side hydraulic lash adjusters 36 and 6 exhaust-side hydraulic lash adjusters 37. The lash adjuster mounting holes 38 and 39 are respectively communicated with lash adjuster oil passages 41 and 42 extending in the cylinder row direction. 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] Next, with reference to Figure 4 the structure of the oil passage, which is the main part of the present invention, will be described. Figure 4The oil passages existing inside the cylinder head 1 and the cam bracket 2 are shown in a perspective view along the cylinder row direction to represent the oil passages. Most of the above-mentioned oil passages other than the oil passages 41 and 42 for the clearance adjuster are formed in the front end portions of the cylinder head 1 and the cam bracket 2 ( Figure 2 the lower side portion in the figure). In addition, similar to the oil passages 41 and 42 for the clearance adjuster, the above-mentioned oil passages are constituted by a combination of linear drilling processes, and the unnecessary open end portions are closed by plugs.

[0033] An oil source pressure passage 45 extending in the vertical direction is formed at approximately the center in the width direction of the cylinder head 1, that is, at a position between the intake camshaft 5 and the exhaust camshaft 6 when viewed in the cylinder block axial direction. 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 portion 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 (refer to Figure 5 ), and is covered by the lower surface of the cam bracket 2 to form a closed space. 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 portion of the side surface 46a. The exhaust side oil passage 51 is formed as a linear shape inclined at approximately 40 to 50° with respect to the joint surface 47 (that is, the upper surface of the cylinder head 1), and the front end communicates with the oil passage 42 for the clearance adjuster on the exhaust side. That is, the engine oil is supplied to the clearance adjuster mounting hole 39 on the exhaust side from the oil storage portion 46 via the exhaust side oil passage 51 and the oil passage 42 for the clearance adjuster.

[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 clearance adjuster 36 on the intake side, a cam bracket internal passage 52 formed by connecting a plurality of linear sections and passing through the inside of the cam bracket 2 is formed. The cam bracket internal passage 52 is composed of the following parts: a linear section 52a that extends obliquely upward from the oil storage portion 46; a linear section 52b that extends parallel to the joint surface 47 above the intake camshaft 5; and a linear section 52c that extends downward more on the outer side in the width direction of the cylinder head 1 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 linear 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 oil flowing through the camshaft lubricating oil passage 56 lubricates the journal portion of the intake camshaft 5.

[0037] An intake side oil passage 53 is formed on the cylinder head 1 side in a manner connected to the outlet portion 52e of the cam bracket internal passage 52. The intake side oil passage 53 has a linear section 53a that extends in the vertical direction; and a linear section 53b that extends obliquely downward from the outer peripheral portion of the cylinder head 1. The front end of the linear section 53b communicates with the oil passage 41 for the clearance 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. In Figure 5 the upper end opening of the intake side oil passage 53 (linear section 53a) is shown. Therefore, oil is supplied to the intake side clearance 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 clearance adjuster.

[0038] In this way, in the above embodiment, the supply of oil from the oil storage portion 46 to the intake side clearance adjuster mounting hole 38 is carried out through the cam bracket internal passage 52. 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 the interference with other components can be avoided when setting the oil passage. For example, the intake valve is located between the oil source pressure passage 45 and the intake side clearance adjuster mounting hole 38 (refer to Figure 6 ), but by arranging the cam bracket internal passage 52 inside the cam bracket 2, the interference with the intake valve can be avoided and the oil passage can be laid out. And since the cam bracket internal passage 52 crosses above the intake camshaft 5, there is no need to form an oil passage that crosses below the camshaft 5 on the cylinder head 1 side.

[0039] In addition, the internal passage 52 of the cam bracket forms a path that is at a higher position than the hydraulic lash adjusters 36, 37 and extends for a relatively long distance up to the hydraulic lash adjusters 36, 37. Therefore, it helps to retain engine oil during the period when the internal combustion engine is stopped. For example, it improves the oil retention performance when the internal combustion engine is left idle for a long time. Thus, when the internal combustion engine is started after being left idle, engine oil is quickly supplied to the hydraulic lash adjusters 36, 37, suppressing the interruption of engine oil and the inhalation of air.

[0040] The hydraulic lash adjuster 37 on the exhaust side is located between the exhaust valve and the oil source pressure passage 45. Therefore, by arranging the exhaust side oil passage 51 linearly from the oil storage portion 46 at the central portion as described above, a simple structure is formed. There is no passage with an oil retention function passing through the inside of the cam bracket 2 for the exhaust side hydraulic lash adjuster 37, but the engine oil is retained by the oil storage portion 46, thus suppressing the interruption of engine oil and the inhalation of air. Therefore, there are parts with an oil retention function for the intake side hydraulic lash adjuster 36 and the exhaust side hydraulic lash adjuster 37 respectively, reliably suppressing the interruption of engine oil.

[0041] One embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment and various modifications can be made. For example, the cam bracket is not limited to the stepped structure as in the above embodiment, and it suffices to have at least one camshaft bearing portion. In addition, it can be a structure in which the camshaft is rotatably supported between the cylinder head 1 and the cam bracket.

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 the intake valve and the other is for the exhaust valve; A hydraulic lash adjuster disposed at least corresponding to the first camshaft in the cylinder head; and A cam bracket fixed to the upper part of the cylinder head and supporting at least the first camshaft, In this cylinder head structure of the internal combustion engine, When viewed 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 this oil source pressure passage to the above-mentioned hydraulic lash adjuster passes through the inside of the above-mentioned cam bracket as an internal passage of the cam bracket.

2. The cylinder head structure of the internal combustion engine according to claim 1, Wherein, When viewed in the cylinder block axial direction, the internal passage of the above-mentioned cam bracket extends from the inlet part between the two camshafts across the upper part of the first camshaft and extends to the outlet part outside the two camshafts.

3. The cylinder head structure of the internal combustion engine according to claim 2, Wherein, There is an oil passage for the lash adjuster extending in the cylinder row direction inside the cylinder head, The above-mentioned oil passage for the lash adjuster is connected between the above-mentioned outlet part of the internal passage of the cam bracket and the above-mentioned hydraulic lash adjuster.

4. The cylinder head structure of the internal combustion engine according to claim 2, Wherein, There is a camshaft lubricating oil passage that branches from the internal passage of the above-mentioned cam bracket inside the above-mentioned cam bracket and reaches the camshaft bearing part.

5. The cylinder head structure of the internal combustion engine according to claim 1, Wherein, The above-mentioned oil source pressure passage has an oil storage part formed in such a way that the volume expands at the joint surface of the cylinder head and the cam bracket, A second hydraulic lash adjuster disposed at least corresponding to the second camshaft in the cylinder head is communicated with the above-mentioned oil storage part via a second oil passage.

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