JP3591278B2 - Cylinder head structure - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cylinder head structure of an engine.
[0002]
[Prior art]
FIG. 5 is a plan view of a cylinder head of a four-valve center nozzle type diesel engine. As shown in the figure, a block portion b for supporting a valve tappet and a seating portion c on which the head of a cylinder head bolt is seated are provided for each cylinder in the cylinder head main body a.
[0003]
In each block portion b, guide holes d of four valve tappets per cylinder are recessed with respect to the top surface e (shown by oblique lines in the figure) of the cylinder head body a, and the fuel is provided at the center thereof. The receiving hole f of the injection nozzle is recessed. A cylindrical valve tappet is accommodated in the guide hole d so as to be movable in the valve axis direction. The valve tappet has an upper surface in contact with the cam ridge of the camshaft, a lower surface in contact with the top of the valve shaft of each intake / exhaust valve, and opens and closes each valve by pushing down the valve shaft in accordance with the rotation of the camshaft. is there.
[0004]
A bolt hole g into which the cylinder head bolt is inserted is formed in each seat c. A cylinder head bolt is inserted into the bolt hole g from the top surface e side of the cylinder head body a, the bolt shaft portion is screwed into the screw hole of the cylinder body, and the bolt head is inserted into the seating surface h of the seating portion c. Be seated. The cylinder head body a is fastened to the cylinder body by the head bolt.
[0005]
[Problems to be solved by the invention]
The seating surface h of the cylinder head bolt is flush with the top surface e of the head body a so as to be connected to the top surface i of the block portion b, and surrounds the block b of each cylinder. A plurality (six per cylinder in the illustrated example) are arranged at predetermined intervals in the direction.
[0006]
For this reason, when the head bolt is inserted into the bolt hole g of each seating surface h and fastened to the cylinder body, and the bolt's axial force acts to push down the seating surface h via the bolt head, each seating surface h is surrounded. A radially outward tensile force F as shown by an arrow in FIG. Further, since the cylinder head main body a receiving the in-cylinder combustion pressure of each cylinder is pressed through the bolt head and the seating surface h, a tensile force F is similarly generated on the top surface i of the block portion b. .
[0007]
The tensile force F is concentrated on the top surface i of the block portion b and on a portion having a very shallow depth from the top surface i. When a tensile force F is generated for each cylinder on the top surface i of the block portion b, the tensile force F concentrates on a portion j (the thinnest portion) that partitions between the guide hole d and the accommodation hole f. And a crack k may be formed on the top surface of the part. Such cracks k are particularly likely to occur when the cylinder head body is made of aluminum for weight reduction.
[0008]
SUMMARY OF THE INVENTION An object of the present invention, which has been made in view of the above circumstances, is to provide a cylinder head structure that can suppress a crack generated due to a tensile force generated on a top surface of a block portion.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a cylinder head structure according to the present invention is provided with a block portion for supporting a valve tappet on a top surface of a cylinder head body , and a head of a cylinder head bolt is seated so as to surround the block portion. A cylinder head structure provided with a seating portion , wherein the block portion is formed so that the top surface thereof is at the same height as the top surface of the cylinder head body, and the seating portion has a height of the seating surface thereof. The block is formed separately in the height direction so as to be lower than the top surface of the block portion, and a notch is provided in a wall connecting the top surface of the block portion and the seating surface of the seating portion. .
[0010]
According to the present invention, the force acting so that the bolt head of the cylinder head bolt pushes down the seating surface is transmitted to the top surface of the block portion via the wall in which a part of the force transmission path is removed by the notch. Therefore, it hardly acts on the top surface of the block portion. Therefore, it is difficult for a tensile force to be generated on the top surface of the block portion, and cracks are suppressed.
[0013]
According to the present invention, even if the cylinder head main body is made of an aluminum base material having low mechanical strength, the force acting to push down the seating surface does not act on the top surface of the block portion or becomes difficult. Therefore, the crack can be suppressed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 is a partial perspective view of a cylinder head according to the present embodiment, FIG. 2 is a plan view of the cylinder head, and FIG. 3 is a sectional view taken along line III-III of FIG.
[0016]
As shown in the figure, the cylinder head main body 1 is formed in a substantially rectangular parallelepiped shape using aluminum as a base material, and its top surface 2 (shown by oblique lines in FIGS. 1 and 2) has a flat planar shape. The cylinder head main body 1 is provided with a block portion 3 for supporting a valve tappet and a seating portion 4 on which the head of a cylinder head bolt is seated for each cylinder.
[0017]
Each block 3 is formed such that its top surface 5 is at the same height as the top surface 2 of the cylinder head body 1. Guide holes 6 for four valve tappets per cylinder are recessed in the top surface 5 of each block portion 3. A cylindrical valve tappet is accommodated in each guide hole 6 so as to be movable in the valve axis direction.
[0018]
The valve tappet has an upper surface in contact with the cam ridge of the camshaft, a lower surface in contact with the top of the valve shaft of each intake / exhaust valve, and opens and closes each valve by pushing down the valve shaft in accordance with the rotation of the camshaft. is there. In FIG. 3, reference numeral 7 denotes a hole for inserting and supporting the valve shaft of the intake valve, 8 denotes a hole for inserting and supporting the valve shaft of the exhaust valve, 9 denotes an intake port, and 10 denotes an exhaust port.
[0019]
The top surface 5 of each block portion 3 is provided with a receiving hole 11 for the fuel injection nozzle, which is located at the center of the four guide holes 6. That is, the present engine is a direct injection type 4-valve center nozzle diesel engine. The present invention can be applied to a four-valve gasoline engine in which a spark plug is attached to the accommodation hole 11.
[0020]
On the other hand, a plurality of seat portions 4 are provided at predetermined intervals in the circumferential direction of each cylinder bore so as to surround the block portion 3 of each cylinder. Each seating portion 4 is formed separately in the height direction so that the height of the seating surface 12 is lower than the top surface 5 of the block portion 3 (that is, the top surface 2 of the cylinder head body 1). ing.
[0021]
As shown in FIGS. 1 and 2, a cutout portion 14 is formed in a wall 13 connecting a height difference between the seating surface 12 of the seating portion 4 and the top surface 5 of the block portion 3. When the axial force (pressing force) of the head bolt acting on the seating surface 12 is transmitted to the top surface 5 of the block portion 3 via the wall 13, the notch portion 14 has a transmission path area corresponding to the notch portion 14. It has the function of reducing transmission and reducing transmission power.
[0022]
Each seating portion 4 is provided with a head bolt hole 15. In each head bolt hole 15, a head bolt is inserted from the top surface 2 side of the cylinder head body 1, a bolt screw portion thereof is screwed into a screw hole of the cylinder body, and a bolt head is inserted into the seating surface 12 of the head body 1. To sit down. Thereby, the cylinder head main body 1 is fastened to the cylinder body.
[0023]
The operation of the present embodiment having the above configuration will be described.
[0024]
According to the present embodiment, as described above (see the section “Problems to be Solved by the Invention” and FIG. 5), the force (the bolt shaft) that acts so that the bolt head of the cylinder head bolt pushes down the seating surface 12. The pressing force due to the force or the like is transmitted to the top surface 5 of the block portion 3 through the wall 13 from which a part of the force transmission path has been deleted by the notch portion 14. On the top surface 5 of the lens.
[0025]
As a result, a tensile force F (see FIG. 5) based on the above-mentioned force is less likely to be generated on the top surface 5 of the block portion 3, and cracks due to the tensile force are suppressed. That is, according to the present embodiment, as shown in FIG. 5, the crack k generated in the portions j and 16 that partition between the guide holes d and 6 and the accommodation holes f and 11, which has been a problem in the related art, is suppressed. Even when the cylinder head body 1 is made of aluminum having a low mechanical strength as in the present embodiment, the force acting to push down the seating surface 12 is exerted on the top surface 5 of the block portion 3. Can be exerted without regret.
[0026]
Further, in the present embodiment, the notch 18 is formed in the portion 17 separating the guide holes 6 of the top surface 5 of the block portion 3 so as to surround the accommodation hole 11. Even if a slight tensile force F is generated in 5, the tensile force F is divided by the notch groove 18 and does not act on the portion 16 around the housing hole 11 where cracks are likely to occur. Therefore, in the present embodiment, the crack can be reliably prevented in combination with the effect of the notch groove 18.
[0027]
FIG. 4 shows another cylinder head structure that can prevent the occurrence of cracks due to the tensile force F.
[0028]
In this cylinder head structure , the top surface 5 of the block portion 3 and the seating surface 12 of the seating portion 4 are completely separated from each other when viewed from above. That is, the lower portions of the block portion 3 and the seating portion 4 are integrally attached to the cylinder head body 1 by casting or the like, and the top surface 5 and the seating surface 12 are completely separated. . In this cylinder head structure , the seating surface 12 of the seat portion 4 is lower than the top surface 5 of the block portion 3, but they may have the same height.
[0029]
Also in such a cylinder head structure , the force that the bolt head of the cylinder head bolt acts to push down the seating surface 12 is generated because the seating surface 12 is separated from the top surface 5 of the block portion 3. It no longer acts on surface 5. Therefore, similarly to the above-described embodiment of the present invention , a tensile force based on the above-described force is not generated on the top surface 5 of the block portion 3, and a crack due to the tensile force is prevented.
[0030]
Incidentally, an embodiment of the present invention described above, but since the series 4-cylinder engine block part 3 is kicked four set in series, the present invention is not limited thereto. In the case of a two-valve, three-valve, five-valve engine or the like instead of a four-valve engine as in the illustrated example, two, three, and five guide holes 6 are recessed, respectively. Further, six seats 4 are provided for each cylinder, and two of the adjacent cylinders have a common bolt hole 15, but the present invention is not limited to this.
[0031]
【The invention's effect】
As described above, according to the cylinder head structure of the present invention, the seating surface of the seating portion is formed in the height direction so as to be lower than the top surface of the block portion. Since the notch is provided in the wall connecting the seating surface of the block portion, the force acting to push down the seating surface by the cylinder head bolt is less likely to act on the top surface of the block portion, and the above force is applied to the top surface of the block portion. Is suppressed, and a crack due to the tensile force can be prevented.
[Brief description of the drawings]
FIG. 1 is a partial perspective view showing a cylinder head according to an embodiment of the present invention.
FIG. 2 is a plan view of the cylinder head.
FIG. 3 is a sectional view taken along line III-III of FIG. 2;
FIG. 4 is a plan view of a cylinder head that can prevent occurrence of cracks.
FIG. 5 is a plan view of a cylinder head showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder head main body 3 Block part 4 Seating part 5 Top surface 12 Seating surface 13 Wall 14 Notch

Claims (2)

On the top surface of the cylinder head main body , a block portion for supporting the valve tappet is provided, and a cylinder head structure provided with a seating portion on which the head of the cylinder head bolt is seated so as to surround the block portion ,
The block portion is formed such that the top surface thereof is at the same height as the top surface of the cylinder head body, and the seating portion is formed so that the height of the seating surface is lower than the top surface of the block portion. A cylinder head structure which is formed separately in the vertical direction and has a notch provided in a wall connecting the top surface of the block portion and the seating surface of the seating portion . The cylinder head structure according to claim 1 , wherein the cylinder head body is made of an aluminum base material .

Images