JPH0515554Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a cylinder head structure for a pre-chamber engine.

(Prior art) In recent years, in pre-chamber type engines, a water jacket has been installed around the entire circumference of the pre-chamber, which is recessed from the lower surface of the cylinder head, in order to improve the cooling performance of the engine. has been attempted (for example, see Japanese Utility Model Application No. 60-54720).

However, in a pre-chamber type engine equipped with a cylinder head with a water jacket formed all around the pre-chamber, the sealing performance at the mating surface of the engine head and cylinder block is poor due to the following reasons. The inventor of the present application discovered the problem that the

That is, when the cylinder head is fastened and fixed to the upper surface of the cylinder block, the auxiliary chamber is arranged to straddle the cylinder bore in the radial direction, as disclosed in the above-mentioned known example. Therefore, in order to maintain a high level of sealing performance at the mating surface of the cylinder head and cylinder block over the entire circumference of the cylinder bore, it is natural that the above-mentioned auxiliary chamber forming part should be treated as well as other parts. A predetermined pressure force must be applied to the gasket by the tightening force of the head bolt.

However, when the cylinder head is fastened to the cylinder block side with a head bolt in such a case where a water jacket is formed all around the auxiliary chamber, (a) the area where the auxiliary chamber is formed obstructs the load transmission to the surrounding area; (b) The water jacket needs to have as large a passage area as possible in order to ensure cooling capacity, but it is also necessary to have a head bolt boss with a head bolt insertion hole. The height of the seat surface from the bottom surface of the cylinder head must be as low as possible from the perspective of preventing the bolt axial force from attenuating.For this reason, the ceiling wall of the water jacket is usually placed above the seat surface of the head bolt boss. As shown in FIG. When the cylinder head 49 and the cylinder block 50 are fastened together, a part of the axial force of the head bolt 54 is transmitted through a long detour transmission path (i.e., an axial Most of the force is transmitted as a bending drag force of the ceiling wall 55 through a transmission path with a large force drop. For this reason, compared to the case where the axial force of the head bolt 54 is transmitted linearly to the lower surface of the cylinder head as a direct compression force, the axial force transmission efficiency is lower, and a sufficient gasket pressing force cannot be obtained, resulting in The sealing performance at the mating surfaces of the cylinder head and cylinder block deteriorates at this portion where the auxiliary chamber 52 is formed.

(Purpose of the invention) The present invention is an attempt to solve the problems pointed out in the section of the prior art described above, and involves forming a water jacket around the sub-chamber, and inserting the water jacket into the sub-chamber. In a pre-chamber type engine equipped with a cylinder head with a head bolt boss provided on the side of the engine, it is possible to achieve both improved sealing performance at the mating surface of the cylinder head and cylinder block and improved engine cooling performance. The purpose is to propose a cylinder head structure.

(Means for Achieving the Object) The present invention, as a means for achieving the above object, surrounds the sub-chamber with a water jacket formed around it, and connects the sub-chamber with the water jacket in between. In a pre-chamber type engine in which head bolt bosses with head bolt insertion holes are formed at positions close to each other, the height of the ceiling wall of the water jacket is set so that the height of the ceiling wall of the water jacket is on the side of the head bolt boss with respect to the pre-chamber. The part located closer to the center of the cylinder is located lower than the part located closer to the center of the cylinder with respect to the sub-chamber, and is also located lower than the seat surface of the head bolt boss. On the lower surface side of the water jacket ceiling wall located between the boss and the water jacket, there is a straight line extending between the side wall of the sub-chamber and the head bolt boss and connecting the center of the sub-chamber and the center of the head bolt boss. It has a protrusion extending along it.

(Function) In the present invention, by the above-mentioned means, (1) the ceiling wall of the water jacket is set higher in the area near the center of the cylinder where the heat load is relatively higher than in the subchamber, thereby ensuring a large cooling water passage area; On the other hand, in the area with relatively low heat load located closer to the head bolt boss than the auxiliary chamber, the ceiling wall of the water jacket is set low and the cooling water passage area is narrowed, so the heat load around the auxiliary chamber is reduced. (2) The ceiling wall of the portion of the water jacket located closer to the head bolt boss than the subchamber is located at a lower level than the seat surface of the head bolt boss, and By forming a protrusion on the lower surface of the wall that extends along a straight line connecting the center of the auxiliary chamber and the center of the head bolt boss, the height of the ceiling wall is locally lowered at the protrusion. , the tightening axial force of the head bolt is in a state where it passes through the ceiling wall from the seat surface of the head bolt boss to the lower surface of the cylinder head in the shortest distance and as close to a straight line as possible (i.e., a state where the decrease in axial force is small) (3) The protrusion formed on the lower surface of the ceiling wall spanning between the side wall of the auxiliary chamber and the head bolt boss is the main axial force transmission path. The ribs act as reinforcing ribs for the ceiling wall in the ceiling wall, increasing the rigidity of the portion, thereby further promoting the transmission of axial force through the bending resistance of the ceiling wall.

(Embodiment) Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. 1 to 4.

1 and 2 show the main parts of a cylinder head 1 of an automobile pre-chamber engine equipped with a cylinder head structure according to an embodiment of the present invention, and in FIG. 1, reference numeral 2 indicates a cylinder block. It is.

Cylinder bore 2 on the lower surface 1a of the cylinder head 1 and in the tightened state to the cylinder block 2.
At a position corresponding to 0, a subchamber 3 is recessed upward from the lower surface 1a. Further, a water jacket 4 is formed around the auxiliary chamber 3, and the auxiliary chamber 3 is in contact with the water jacket 4 through its side wall 11 over its entire circumference.

Furthermore, a head bolt boss 6 is formed on the side of the auxiliary chamber 3 with the water jacket 4 interposed therebetween. The head bolt boss 6 has a head bolt insertion hole 7 in its axial center for mounting the head bolt 5, and its upper end surface serves as a seating surface 17 for the head bolt 5. Therefore, the cylinder head 1 is connected to the head bolt boss 6.
It is fastened and fixed to the cylinder block 2 side by a head bolt 5 provided at the side, and a gasket 9 interposed between the two ensures sealing of the mating surface.

Furthermore, in this embodiment, by applying the present invention, the shape of the water jacket 4 and the shape of the head bolt boss 6 are set as shown below, thereby improving the cooling performance of the engine and improving the cooling performance of the cylinder head 1 and the cylinder block 2. This is intended to improve the sealing performance at the mating surface. Hereinafter, this specific configuration will be explained using FIGS. 3 and 4 in addition to FIGS. 1 and 2.

As shown in FIGS. 1 and 2, the water jacket 4 is formed continuously from a position near the head bolt boss 6 toward the center of the cylinder.
In this case, in this embodiment, the passage area of the water jacket 4 is set depending on the heat load around the auxiliary chamber 3. Specifically, as shown in FIGS. 1 to 4, the water jacket 4 is placed between a relatively high heat load area, that is, a central area 4a located closer to the center of the cylinder than the subchamber 3, and a relatively high heat load area. It is divided into two areas: a part with a low load, that is, an outer peripheral part 4b located closer to the head bolt boss 6 than the subchamber 3. In the central portion 4a, the height of the ceiling wall 14 of the water jacket 4 is increased to ensure a large passage area, while in the outer peripheral portion 4b, the ceiling wall 14 of the water jacket 4 is raised.
4 is lower than that of the central portion 4a to reduce the passage area to a relatively small size. Therefore, the surroundings of the auxiliary chamber 3 are cooled under optimal conditions corresponding to the magnitude of the heat load.

On the other hand, the outer peripheral side portion 4b of the water jacket 4
Between the ceiling wall 14 of the water jacket 4 and the seat surface 17 of the head bolt boss 6, as shown in FIGS.
The outer peripheral side portion 4b is the seat surface 1 of the head bolt boss 6.
7, and the height of the lower surface 14a of the ceiling wall 14 is set near the line connecting the central part of the auxiliary chamber 3 and the central part of the head bolt boss 6 (that is, the height of the lower surface 14a of the ceiling wall 14 is The shortest path of the axial force transmission path from the seat surface 17 of the boss 6 to the mouth edge of the auxiliary chamber 3) is locally lowered, and the peripheral wall of the auxiliary chamber 3 is connected from the head bolt boss 6 to this portion. A protruding ridge portion 15 is formed that extends in a ridge shape toward the 11 side (see the portion shown by the chain line in FIG. 2).

With such a configuration, first of all, among the transmission paths of the fastening axial force by the head bolt 5 applied to the seat surface 17 of the head bolt boss 6 to the lower surface 1a of the cylinder head, the transmission path is transmitted through the ceiling wall 14. However, in the portion formed by the protrusion 15, as shown by the solid arrow in FIG. 3, and in the vicinity of the protrusion 15, as shown by the broken line arrow, in the case of the conventional example (see FIG. 2), The path is closer to a straight line from the seat surface 17 of the head bolt boss 6 to the vicinity of the mouth edge of the auxiliary chamber 3 on the lower surface 1a of the cylinder, and this tendency is particularly strong in the area where the ridge 15 is formed, and the transmitted coat color is the shortest. It becomes the distance. As a result,
Since the tightening axial force of the head bolt 5 is more efficiently transmitted as compressive force to the cylinder lower surface 1a side while minimizing power loss, a higher level of gasket pressing force can be obtained and its sealing performance can be improved. You will be forced to improve.

Secondly, since the protruding portion 15 also functions as a reinforcing rib for the ceiling wall 14, the protruding portion 15 increases the rigidity of the portion of the ceiling wall 14 that serves as the main axial force transmission path. As a result, of the axial force of the head bolt 5, the axial force that is transmitted as a bending drag force of the ceiling wall 14 is efficiently transmitted by the increased rigidity of the ceiling wall 14, and can contribute to an increase in the gasket pressing force. Become.

In this way, by setting the correlation between the ceiling wall 14 of the water jacket 4 and the head bolt boss 6 as in this embodiment, and by forming the protrusion 15 in the shortest axial force transmission path, the auxiliary chamber 3 can be improved. It is possible to improve the sealing performance at the mating surface of the cylinder head and cylinder block while maintaining the effect of improving cooling performance due to the provision of the water jacket 4 around the cylinder head.

(Effects of the invention) The cylinder head structure of the sub-chamber type engine of the present invention surrounds the sub-chamber with a water jacket formed around it, and at a position close to and facing the sub-chamber with the water jacket in between. In a subchamber type engine having a head bolt boss provided with a head bolt insertion hole, the height of the ceiling wall of the water jacket is determined by the portion located on the head bolt boss side with respect to the subchamber. It is set to be located lower than the part located closer to the center of the cylinder with respect to the auxiliary chamber, and also lower than the seat surface of the head bolt boss, and between the auxiliary chamber and the head bolt boss. A protrusion extending along a straight line connecting the center of the sub-chamber and the center of the head bolt boss and extending between the side wall of the sub-chamber and the head bolt boss on the lower surface side of the water jacket ceiling wall where the water jacket is located. It is characterized by the formation of

Therefore, according to the cylinder head structure of the pre-chamber type engine of the present invention, the ceiling wall of the water jacket is set high in the area near the center of the cylinder where the heat load is relatively high compared to the pre-chamber, and a large cooling water passage area is created. On the other hand, in the area with relatively low heat load located closer to the head bolt boss than the auxiliary chamber, the ceiling wall of the water jacket is set low and the cooling water passage area is narrowed, so the cooling water passage area is reduced depending on the heat load. (2) The ceiling wall of the portion of the water jacket located closer to the head bolt boss than the pre-chamber is lowered from the seat surface of the head bolt boss. In addition, by forming a protrusion extending along a straight line connecting the center of the auxiliary chamber and the center of the head bolt boss on the lower surface side of the ceiling wall, the height of the ceiling wall is lowered at the protrusion part. Since the height is locally lowered, the tightening axial force of the head bolt is applied in the shortest distance from the seat surface of the head bolt boss to the lower surface of the cylinder head through the ceiling wall, in a state as close to a straight line as possible. In other words, most of the axial force is transmitted as compressive force, and as a result, a larger gasket pressing force can be secured, and the seal at the mating surface of the cylinder head and cylinder block can be secured accordingly. (3) The protrusion formed on the lower surface of the ceiling wall spanning between the side wall of the auxiliary chamber and the head bolt boss is a reinforcing rib on the ceiling wall in the area that becomes the main axial force transmission path. Since the rigidity in this part is increased, the transmission of axial force via the bending resistance of the ceiling wall is further promoted, which can contribute to improving the sealing performance at the mating surface of the cylinder head and cylinder block. Practical effects such as these can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part of a cylinder head of a subchamber type engine according to an embodiment of the present invention, and FIG.
Fig. 3 is a longitudinal sectional view of Fig. 2, Fig. 4 is a longitudinal sectional view of Fig. 2, and Fig. 5 is a longitudinal sectional view of Fig. 2.
The figure is a vertical cross-sectional view of the main part of a cylinder head of a conventional structure. 1...Cylinder head, 2...Cylinder block, 3...Subchamber, 4...Water jacket, 5
... Head bolt, 6... Head bolt boss, 7
... Head bolt insertion hole, 14 ... Ceiling wall, 17
...Seating surface, 20...Cylinder bore.

Claims (1)

[Scope of utility model registration request] An auxiliary chamber type in which a auxiliary chamber is surrounded by a water jacket formed around the auxiliary chamber, and a head bolt boss having a head bolt insertion hole is formed at a position close to and facing the auxiliary chamber with the water jacket in between. In the engine, the height of the ceiling wall of the water jacket is such that the part located on the head bolt boss side with respect to the sub-chamber is lower than the part located closer to the center of the cylinder with respect to the sub-chamber. Moreover, while the head bolt boss is set to be located at a lower level than the seat surface of the head bolt boss, the side wall of the auxiliary chamber is located on the lower surface side of the water jacket ceiling wall located between the auxiliary chamber and the head bolt boss. 1. A cylinder head structure for a pre-chamber type engine, characterized in that a protrusion is formed spanning between the pre-chamber and the head bolt boss and extending along a straight line connecting the center of the pre-chamber and the center of the head bolt boss.