JP3583563B2 - Engine cylinder head - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cylinder head of a double overhead camshaft type engine.
[0002]
[Prior art]
Conventionally, a double overhead camshaft (DOHC) type four-stroke engine that drives an intake valve and an exhaust valve via a rocker arm is known. The DOHC engine has an advantage that a degree of freedom in setting a valve (valve) included angle, which is an angle formed between an intake valve and an exhaust valve, is large.
[0003]
The cylinder head of this engine has two overhead camshafts, one for intake and one for exhaust, and a plurality of rocker arms for intake and exhaust, which operate by transmitting the movement of the cam accompanying the rotation of each overhead camshaft. It has been incorporated. Each rocker arm is rotatably attached to two rocker shafts separately for intake and exhaust. A rocker arm mounted on the rocker shaft has its working end facing outside the two rocker shafts. The upper end of the intake valve or the exhaust valve is in contact with the lower surface of the working end. The intake valve and the exhaust valve oppose each other so that the upper end is inclined outward to form a V-shape, and each rocker shaft is fixed to a partition wall formed in a cylinder head corresponding to the cylinder.
[0004]
The partition is provided side by side on both sides of the bore, and both rocker shafts are fixedly supported in parallel substantially parallel to the partition. In the case of a multi-cylinder, the cylinder head is divided for each cylinder by a partition. In a room partitioned by the partition, a plug mounting portion to which a spark plug is mounted is formed substantially at the center of the bore. A combustion chamber is formed below the plug mounting portion.
[0005]
A water jacket serving as a cooling water passage is formed around the plug mounting portion and at the upper part of the periphery of the combustion chamber. The water jacket surrounds the plug mounting portion along the outer shape of the spark plug, and is formed on the periphery of the combustion chamber along the upper shape of the combustion chamber. The spark plug and the combustion chamber can be cooled by the cooling water flowing through the water jacket.
[0006]
Two partition walls on both sides for partitioning each cylinder gap separates at its center, respectively (corresponding to the gap 15 a of the embodiment of FIG. 3) are formed. This gap is provided with substantially the same width over the entire area in the vertical direction at the center of each partition wall to which each rocker shaft is fixed. At the base of each of the separated partition walls (below the center between the two rocker shafts), which is the bottom of the gap, there is formed an after-mentioned sand removal opening communicating with the water jacket. The opening is open in a direction along both partition walls, and the opening surface is substantially parallel to the bore surface. That is, the opening surface is substantially parallel to a plane including the two rocker axes, and the axial direction of the opening is substantially perpendicular to the plane including the rocker axes.
[0007]
The cylinder head is manufactured by, for example, a shell mold casting method. In this case, the water jacket is formed as a space after the shell core is extracted. When forming the water jacket, the shape of the water jacket is taken into consideration so as not to waste meat around the opening in order to reduce the weight of the entire cylinder head. The shell core is formed by sintering and hardening a molding sand made of sand mixed with a thermosetting resin. The shell core is extracted after molding, and a cavity of a water jacket is formed inside the casting. The removal of the sand is performed from the above-mentioned opening. The opening after removing the shell core is closed by the plug. The plug is attached, for example, by screwing a screw formed on the outer peripheral portion of the plug into a screw formed on the inner peripheral surface of the opening to seal the opening.
[0008]
The threading of the opening and the work of attaching and detaching such a plug are performed by inserting a tool from above and perpendicular to the opening surface. Therefore, a space having a width corresponding to at least the diameter of the opening is required above the opening.
[0009]
[Problems to be solved by the invention]
By the way, in the DOHC engine, since the degree of freedom of setting the valve pinch angle is large, it is demanded to make the valve pinch angle as small as possible. By reducing the valve pinching angle, it is possible to form a combustion chamber having a high thermal efficiency with a high compression ratio, and to make the intake passage straight so that the flow of intake and exhaust can be made smooth.
[0010]
However, the above-mentioned conventional DOHC engine is structurally restricted from having a small valve pinch angle. In order to reduce the valve pinch angle, the distance between the two rocker shafts must be reduced, but this distance cannot be shorter than the above-described gaps at the center of each partition. That is, since the axial direction of the opening is substantially perpendicular to the plane including the rocker shaft, at least a space having a width corresponding to the diameter of the opening is required above the opening, and the opening for extracting the molding sand is required. Therefore, the distance between the two rocker shafts could not be made shorter than the diameter of the shaft, and the valve pinching angle could not be further reduced.
[0011]
In addition, if the water jacket is shaped so as to actively cool the spark plug, which is a heat source, the structure becomes complicated to match the spark plug having a complicated outer shape, and wasteful meat increases. easy.
[0012]
Furthermore, since the combustion chamber is provided below the water jacket, the lower portion of the water jacket must be formed so as to avoid components related to the combustion chamber, and becomes narrow. If the ceiling area of the water jacket is larger than the lower area, much of the cooling water will flow to the ceiling, and only a part of the cooling water will be in the lower part of the combustion chamber or ignition plug where you want to cool. Only flows. Therefore, the ignition plug cannot be sufficiently cooled.
[0013]
The present invention has been made in view of the above circumstances, it is possible to reduce the distance between the two rocker shafts without being limited by the diameter of the sand removal opening, to reduce the valve pinching angle, It is an object of the present invention to provide a cylinder head of an engine provided with a water jacket capable of actively cooling a spark plug in a shape that does not have unnecessary meat.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a water jacket through which cooling water flows around an ignition plug, and the rotation of two camshafts for intake and exhaust disposed above the cylinder head is transmitted. A plurality of rocker arms that are operated when the rocker arms are mounted, and the water jacket is formed below the supporter that supports the two rocker shafts for intake and exhaust, in which the rocker arms are attached, in parallel between the two rocker shafts. A sand vent opening for casting sand is provided , and a partition wall integral with the cylinder head is formed on both sides of the bore, the partition wall has a gap at the center thereof, and legs of the partition wall are formed on both sides of the gap. is, said sand抜開opening in the bottom of the gap is formed, said rocker shaft in a cylinder head of an engine is supported by the partition wall, the axis of the sand抜開port, the two rocker Axis inclined to the plane containing the (axial center) at which the vertical and in the camshaft and in a cross section parallel legs of said partition wall, projecting into the gap side at the top of the gap, the overhanging portion of the partition wall And the rocker shaft is supported on the cylinder head of the engine.
[0015]
According to the above configuration, since the axis of the sand extraction opening is oblique, insertion of a tool or the like into the sand extraction opening is not limited to the partition just above the sand extraction opening, and can be inserted from an oblique direction, and a gap corresponding to the diameter of the opening is formed. There is no need to provide it at the center of the partition. Accordingly, the two rocker shafts supported by the partition can be brought closer to the center. Thus, the distance between the two rocker shafts can be shortened without being limited by the diameter of the opening, and the valve pinching angle can be reduced, and the angle decreases toward the spark plug in accordance with the inclination of the sand extraction opening. By forming the water jacket having a ceiling surface, the cooling water can be made to flow toward the combustion chamber and the lower portion where the ignition portion of the ignition plug is located.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
In a preferred embodiment , a spark plug is attached at a substantially central position of the bore, and a ceiling surface of the water jacket is inclined so as to decrease toward the spark plug and reduce a cross section of the flow path. It is characterized by:
[0017]
With this configuration, the water jacket is formed so that the spark plug can be actively cooled in a shape that does not cause waste meat, and the cooling water flowing through the water jacket is supplied to the ignition portion of the combustion chamber and the ignition plug. It can flow down to a certain lower side.
[0018]
Further, in a preferred embodiment, an opening surface of the sand extraction opening and a ceiling surface of the water jacket are substantially parallel to each other.
[0019]
With this configuration, the peripheral portion of the sand extraction opening can be formed with the same thickness without adding unnecessary meat.
[0020]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory plan view showing the inside of a cylinder head of an engine according to one embodiment of the present invention. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. 1, and FIG. 4 is a sectional view taken along line CC of FIG. FIG. 5 is a cross-sectional view taken along line DD of FIG.
[0021]
As shown in FIGS. 1 to 5, a cylinder head 1 of the engine is installed above a cylinder 2 and forms a combustion chamber 3 between the cylinder head 1 and a piston (not shown). FIG. 1 shows a middle cylinder 2 of three cylinders 2 arranged in a line. This engine is a double overhead camshaft (DOHC) type four-stroke engine that drives an intake valve and an exhaust valve via a rocker arm.
[0022]
As shown in FIG. 1, two overhead camshafts 4 and 5 for exhaust and intake and movements of cams 4 a and 5 a accompanying rotation of each of the overhead camshafts 4 and 5 are transmitted to the cylinder head 1. Four rocker arms 6, 7, 8, 9 for the exhaust and the intake, which are operated by being operated, are incorporated. Each of the rocker arms 6, 7, 8, 9 is divided into two, each of which is an exhaust rocker arm 6, 7 and an intake rocker arm 8, 9, and is rotatably attached to two rocker shafts 10, 11. .
[0023]
As shown in FIG. 4, each of the rocker arms 6, 7, 8, 9 attached to the rocker shafts 10, 11 has respective working ends 7a, 9a (the others are not shown) having two rocker shafts 10, 9, respectively. 11 outside. The upper end of the exhaust valve 12 or the intake valve 13 is in contact with the lower surfaces of the working ends 7a and 9a. The exhaust valve 12 and the intake valve 13 face each other so that the upper end is inclined outward to form a V-shape. Each rocker shaft 10, 11 is provided with a partition 14 formed on the cylinder head 1 corresponding to the cylinder 2. (See FIG. 3). In the case of a multi-cylinder, the cylinder head 1 is partitioned by a partition 14 into each cylinder.
[0024]
The partition walls 14 are arranged substantially parallel to both sides of the bore. The two rocker shafts 10 and 11 fixed to the partition wall 14 are supported in parallel substantially in parallel, and a plane including the axis of the two rocker shafts 10 and 11 is a mating surface with the block on the bottom surface of the head. It is substantially parallel to the bore surface. As shown in FIG. 3, the partition wall 14 has a portal shape in which the upper ends of two legs 15 that are spaced apart and juxtaposed are connected. A shaft mounting portion 16 for mounting the rocker shafts 10 and 11 is formed on an upper portion of each leg 15. The shaft mounting portions 16 bulge so as to approach each other, and the space between the shaft mounting portions 16 is narrower than the space between the leg portions 15. At the base of the partition 14, which is the bottom of the gap 15a formed between the legs 15, 15, there is formed a sand removal opening 21 for removing casting sand that communicates with a water jacket 20, which will be described later.
[0025]
As shown in FIGS. 1 and 2, in a room partitioned by the partition wall 14, a plug mounting portion 18 to which a spark plug is mounted is formed substantially at the center of the bore. The combustion chamber 3 is formed below the plug mounting portion 18. A water jacket 20 is formed around the plug mounting portion 18 and above the peripheral edge of the combustion chamber 3 as a cooling water passage.
[0026]
The water jacket 20 is stretched around the inside of the cylinder head 1 so that cooling water flows around the heat source requiring cooling such as the spark plug 17 and the combustion chamber 3. The water jacket 20 extends along the outer shape of the spark plug 17 and the plug mounting portion 18. And is formed on the periphery of the combustion chamber 3 along the upper shape of the combustion chamber 3. The cooling water flowing through the water jacket 20 flows and circulates in the water jacket 20 in a certain direction, for example, from the front to the rear in the traveling direction of the engine (see the arrow in FIG. 5). The heat sources such as the spark plug 17 and the combustion chamber 3 can be constantly cooled by the circulating cooling water. The ceiling surface 20a of the water jacket 20 is inclined so as to decrease toward the spark plug 17, and the cross section of the flow path through which the cooling water flows decreases toward the spark plug 17 (see FIG. 5). That is, since the ceiling surface 20a has an inclined surface that decreases toward the spark plug 17, the cooling water flows at a low position of the cylinder head 1 near the spark plug 17, and the ignition portion 17a at the lower end of the spark plug 17 and the combustion chamber 17 It will pass through a part close to 3. Further, since the cross section of the flow path decreases toward the spark plug 17, the flow rate of the cooling water around the spark plug 17 increases.
[0027]
Therefore, the cooling water flowing through the water jacket 20 can be provided with directivity toward the combustion chamber 3 and the spark plug 17, so that the combustion chamber 3 and the spark plug 17 can be actively cooled. In addition, the flow rate of the cooling water is increased around the ignition plug 17 requiring a large cooling amount, so that the cooling efficiency is improved and a sufficient cooling effect is obtained.
[0028]
As shown in FIGS. 3 and 5, the sand removal opening 21 formed at the base of the partition wall 14 is opened in the ceiling surface 20 a of the water jacket 20, and the opening axis L of the sand removal opening 21 is two. It is inclined with respect to a plane including the rocker shafts 10 and 11 (a plane including the axis). Therefore, the opening surface of the sand removal opening 21 is inclined with respect to the plane, that is, the bore surface (head bottom surface). In the case of this embodiment, the opening axis L is inclined along the flow direction of the cooling water, and the inclination direction and the angle of the opening axis L coincide with the ceiling surface 20 a of the water jacket 20. In this case, the extension line M indicating the outer diameter of the sand removal opening 21 does not hang on the plug mounting portion 18 to which the ignition plug 17 is mounted.
[0029]
Further, as shown in FIG. 5, the shaft mounting portion 16 of the partition wall 14 can be formed in a range not extending over the extension line M. In other words, if the area indicated by the extension line M is secured as a space, the threading of the sand removal opening 21 and the attaching / detaching operation of the plug to be described later can be performed without any trouble. The distance between 16 and 16 can be set arbitrarily.
[0030]
Therefore, the distance between the two shaft mounting portions 16 can be made as close as possible without being limited by the diameter of the sand removal opening 21. That is, as shown in FIG. 3, both rocker shafts 10 and 11 can be brought closer to each other by bringing both shaft mounting portions 16 and 16 closer to each other. As shown in FIG. The inclination of the exhaust valve 12 and the intake valve 13 abutting on the lower surfaces of the working ends 7a, 9a of the rocker arm 9 can be further raised. As a result, the valve pinching angle α, which is the angle formed between the exhaust valve 12 and the intake valve 13, can be further reduced.
[0031]
Also, as shown in FIG. 5, since the opening direction of the sand extraction opening 21 and the inclination direction and the angle of the ceiling surface 20a of the water jacket 20 match, the opening surface of the sand extraction opening 21 and the ceiling surface of the water jacket 20. 20a are substantially parallel. Therefore, the periphery of the sand removal opening 21 has a uniform thickness, and no wasteful wall is formed around the sand removal opening 21, so that the weight of the entire cylinder head 1 can be reduced.
[0032]
As shown in FIGS. 1 to 3, journals 22 are respectively mounted on the upper ends of the partition walls 14. By means of the journal 22, the two overhead camshafts 4, 5 arranged for the exhaust and the intake arranged above the cylinder head 1 are rotatably positioned and fixed. Each journal 22 is fixed to the cylinder head 1 via a journal fixing member 23 placed thereon.
[0033]
The journal fixing member 23 is fixed to the cylinder head 1 by a journal bolt 24 screwed to the cylinder head 1. The bolts 24 are provided two by two corresponding to the overhead camshafts 4 and 5. Two journal bolts 24 are arranged on one journal fixing member 23 such that one journal bolt 24 is located on each side of the overhead camshafts 4 and 5. The journal bolts 24 located inside the overhead camshafts 4 and 5 have their tips reaching the rocker shafts 10 and 11 (see FIG. 3), and fix the rocker shafts 10 and 11 so that they cannot rotate.
[0034]
As shown in FIG. 3, an oil hole 25 for passing lubricating oil is formed in the axis of the overhead camshafts 4 and 5. Similar oil holes 26 are also formed in the shaft centers of the rocker shafts 10 and 11, and lubricated to the oil holes 26 through an oil passage 27 provided in communication with the journal fixing member 23, the journal 22 and the partition 14. Oil is supplied.
[0035]
As shown in FIG. 3, the cylinder head 1 is screwed to a cylinder block (not shown) by a head bolt 28a (see FIG. 1) attached to the head bolt attachment portion 28, and is integrated with the cylinder block. As shown in FIG. 1, the head bolts 28a are arranged so that the circumference of each cylinder 2 can be fixed with four bolts. By integrating the cylinder head 1 and the cylinder block, a combustion chamber 3 is formed above the bore.
[0036]
As shown in FIG. 4, the combustion chamber 3 is provided with an exhaust port 29 and an intake port 30. The exhaust port 29 communicates with the exhaust passage 31 and is opened and closed by the exhaust valve 12. The intake port 30 communicates with the intake passage 32 and is opened and closed by the intake valve 13. The exhaust valve 12 and the intake valve 13 are mounted on the cylinder head 1 via a valve guide 33, respectively, and the operating ends 7a, 9a of the exhaust rocker arm 7 and the intake rocker arm 9 via a valve cotter 34 at the upper end of the valve. Is in contact with the lower surface of. A valve spring 35 is mounted above the exhaust valve 12 and the intake valve 13. Due to the urging force of the valve spring 35, the exhaust valve 12 and the intake valve 13 are always lifted to the valve upper end side, and close the exhaust port 29 and the intake port 30, respectively.
[0037]
A valve seat 36 is attached to the exhaust port 29 and the intake port 30, and when the valve is closed, the exhaust valve 12 and the intake valve 13 are in close contact with the valve seat 36, thereby sealing the exhaust port 29 and the intake port 30.
[0038]
The exhaust valve 12 that closes the exhaust port 29 and the intake valve 13 that closes the intake port 30 rotate the exhaust port 29 and the intake port 30 by the rotation of the overhead camshafts 4 and 5 connected to the crankshaft by a chain. Open at a predetermined valve timing synchronized with. That is, when each of the overhead camshafts 4 and 5 is rotated and the cams 4a and 5a push down the exhaust rocker arm 7 and the intake rocker arm 9, each of the pushed exhaust rocker arm 7 and the intake rocker arm 9 is pushed down. The operating ends 7a and 9a push down the exhaust valve 12 and the intake valve 13 against the urging force of the valve spring 35. The depressed exhaust valve 12 and intake valve 13 move below the exhaust port 29 and the intake port 30, and the exhaust port 29 and the intake port 30 are opened.
[0039]
The cylinder head 1 is manufactured by, for example, a shell mold casting method in which a cavity is formed by combining upper and lower molds and a molten metal is poured into the cavity. At this time, the water jacket 20, which is a cavity in the cylinder head, is formed by disposing a shell core in a mold. The shell core is formed by firing and hardening molding sand made of sand mixed with a thermosetting resin, and is extracted after casting.
[0040]
The casting sand is removed from the sand removal opening 21. After the cylinder head 1 is removed from the mold, the sand removal opening 21 is formed by using a not-shown drilling tool. The drilling tool is operated toward the bottom of the space between the two legs 15 which is the base of the partition wall 14 from a direction inclined with respect to the two legs 15 so as not to cover the shaft mounting portion 16 (see FIG. 5). Therefore, the sand removal opening 21 is in a state where the opening axis L is inclined with respect to the plane including the rocker shafts 10 and 11. The sand removal opening 21 after the shell core has been removed is closed by the plug 37 as shown in FIG. The plug 37 is, for example, screwed to a screw formed on the inner peripheral surface of the sand extraction opening 21 with a screw formed on the outer peripheral portion of the plug 37 to seal the sand extraction opening 21. It is attached.
[0041]
After forming the sand removal opening 21 and attaching the plug 37 in this way, the rocker shafts 10 and 11 are attached to the partition wall 14.
[0042]
【The invention's effect】
As described above, according to the cylinder head of the engine according to the present invention, the axis of the sand removal opening for removing casting sand is inclined with respect to the plane including the rocker shaft, so that it is limited to the diameter of the opening. Therefore, the distance between the two rocker shafts can be reduced, and the valve pinching angle can be reduced. Therefore, it is possible to select a desired optimum sandwich angle to improve the engine operation characteristics.
[0043]
In addition, the water jacket can be actively cooled in a shape that does not have useless flesh by inclining the ceiling surface so as to decrease toward the spark plug and reduce the cross section of the flow path. The cooling water flowing in the water jacket can flow at a high flow rate toward the lower side where the ignition portion of the combustion chamber and the ignition plug is located. Therefore, it is possible to intensively cool the high-temperature portion to increase the cooling efficiency, maintain stable combustion, and maintain good operation performance.
[0044]
Furthermore, if the opening surface of the sand extraction opening and the ceiling surface of the water jacket are made substantially parallel, the peripheral portion of the sand extraction opening can be formed with the same thickness without unnecessary waste. With the effect described above, waste meat can be efficiently removed, and the engine weight can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory plan view showing the inside of a cylinder head of an engine according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along the line AA of FIG. 1;
FIG. 3 is a sectional view taken along the line BB of FIG. 1;
FIG. 4 is a sectional view taken along the line CC of FIG. 1;
FIG. 5 is a sectional view taken along line DD of FIG. 1;
[Explanation of symbols]
1: cylinder head, 2: cylinder, 3: combustion chamber,
4, 5: overhead camshaft, 4a, 5a: cam,
6, 7: rocker arm for exhaust, 8, 9: rocker arm for intake,
10, 11: rocker shaft, 12: exhaust valve, 13: intake valve, 14: partition wall,
16: shaft mounting part, 17: spark plug, 20: water jacket,
20a: ceiling surface, 21: sand opening, L: shaft, M: extension, α: valve pinching angle.

Claims (3)

It has a water jacket through which cooling water flows around the spark plug, and has a plurality of rocker arms that operate by transmitting rotations of two camshafts for intake and exhaust disposed at the top of the cylinder head, respectively. Below the two rocker shafts of the supporter, which supports the two rocker shafts for intake and exhaust, to which the rocker arms are attached, a sand removal opening of the molding sand forming the water jacket is provided ,
Partition walls integral with the cylinder head are formed on both sides of the bore,
The partition has a gap at its center, and legs of the partition are formed on both sides of the gap,
The sand vent opening is formed at the bottom of the gap,
In the cylinder head of the engine supported by the partition wall ,
The axis of the sand extraction opening is inclined in a section perpendicular to the plane including the two rocker axes and in a section parallel to the cam axis ,
The leg portion of the partition wall projects toward the gap side above the gap,
The cylinder head of the engine , wherein the rocker shaft is supported by the partition wall at the protruding portion . A spark plug is attached at a substantially central position of the bore,
The engine cylinder head according to claim 1, wherein a ceiling surface of the water jacket is inclined so as to decrease toward the spark plug and reduce a cross section of the flow path. 3. The engine cylinder head according to claim 2, wherein an opening surface of the sand extraction opening and a ceiling surface of the water jacket are substantially parallel.

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