JPH0244019Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an improvement of a cylinder head in a diesel engine equipped with a pre-combustion chamber.

[Conventional technology]

The area between the valves in the cylinder head becomes high temperature and is affected by thermal expansion in the intake valve seat and the exhaust valve seat, so there is a risk of cracks occurring in the area between the valves, especially in the pre-combustion chamber. In the case of cylinder heads in diesel engines with
Since the cracks reach the inter-valve portion through the thick portion between the pre-combustion chamber and both valve seats, there is an even greater possibility that cracks will occur in the inter-valve portion.

Therefore, as prior art, Japanese Utility Model Application Publication No. 51-68941 etc. form cooling water passages in the thick part of the cylinder head between both valve seats and the pre-combustion chamber and in the part between the valves. It is proposed to forcibly cool the thick part between the combustion chamber and the pre-combustion chamber and the part between the valves.

[Problem that the invention attempts to solve]

However, the pre-combustion chamber in a diesel engine is
It is necessary to maintain a certain high temperature in order to promote the vaporization of the fuel injected into the fuel. Nevertheless, as in the prior art, forced cooling of the thick part between both valve seats and the pre-combustion chamber and the part between the valves by the cooling water passage provided in the said part is not effective for pre-combustion. There is a risk of excessive cooling of the cylinder head, and forming a cooling water passage in the thick wall between the valve seats and the pre-combustion chamber and in the area between the valves would significantly complicate the structure of the cylinder head. It will become. Furthermore, when such a cooling water passage is provided, the temperature difference between the part facing the inside of the cooling water passage and the other part (for example, the part in contact with the combustion chamber) increases, and this large temperature Differences can cause cracks.

The present invention provides a diesel engine in which the cylinder head is equipped with a valve seat for an intake valve, a valve seat for an exhaust valve, and a precombustion chamber, in which an area surrounded by both valve seats and the precombustion chamber is provided. The above-mentioned drawbacks are solved by actively cooling the combustion chamber with air taken into the combustion chamber.

[Means for solving problems]

For this reason, the present invention provides a diesel engine in which a valve seat for an intake valve, a valve seat for an exhaust valve, and a pre-combustion chamber are provided in a cylinder head. A concave portion extending toward a region surrounded by the valve seats and the pre-combustion chamber is formed, and the outer periphery of the intake valve seated on the valve seat is formed in the concave portion around the intake valve seat. The structure includes a land portion that surrounds the area except for the area corresponding to the area.

[Functions and effects of the idea]

With this configuration, when the intake valve is slightly away from the valve seat both at the beginning of opening and immediately before closing during the intake stroke to the combustion chamber, the intake air flowing into the combustion chamber from the intake port Since the outer periphery of the intake valve is surrounded by a land except for the part corresponding to the recess on the lower surface of the cylinder head, almost all of the air is blown out from the recess at a considerable flow velocity. , and this concave portion extends to a region of the lower surface of the cylinder head surrounded by the intake valve seat, the exhaust valve seat, and the precombustion chamber, so that both valve seats and the precombustion chamber are connected to each other. The area surrounded by the recess is cooled by the intake air jetted out from the recess.

In other words, according to the present invention, the area of the lower surface of the cylinder head surrounded by both valve seats and the pre-combustion chamber can be cooled by low-temperature intake air. It is possible to reduce thermal expansion in the area between the pre-combustion chamber and the valve seat between the two valve seats, and also to reduce the transfer of heat from the pre-combustion chamber to the valve area. This cooling is done by intake air, which does not cause the same temperature difference as in the case of cooling water as in the prior art, so it is possible to reduce the thermal influence of the pre-combustion chamber on the area between the valves. This makes it possible to synergistically reduce the occurrence of cracks in the intervalve portion.

Moreover, since the present invention cools the lower surface of the cylinder head in the area surrounded by both valve seats and the pre-combustion chamber by the intake air into the combustion chamber, it is better than the prior art. Unlike forced cooling with cooling water, the precombustion chamber does not become overcooled, and the precombustion chamber can be maintained at a high temperature while reducing the occurrence of cracks in the area between the valves. Since it is only necessary to form a recess and a land in the cylinder head, the structure of the cylinder head does not become complicated.

〔Example〕

The present invention will be explained below with reference to the drawings of the embodiments. In the drawings, reference numeral 1 designates a cylinder head, in which an intake port 2 and an exhaust port 3 are adjacent to each other with a valve gap 4 between them. In addition, a swirl chamber type pre-combustion chamber 5 is formed adjacent to both the ports 2 and 3.

A valve seat 7 for the intake valve 6 is located at the opening of the intake port 2 to the lower surface 1a of the cylinder head, and a valve seat 9 for the exhaust valve 8 is located at the opening of the exhaust port 3 to the lower surface of the cylinder head 1a. The lower surfaces of both valve seats 7 and 9 are fitted into the cylinder head at an appropriate depth H recessed from the lower surface 1a of the cylinder head, and nozzle holes 11 are provided in the lower surface 1a of the cylinder head at the location of the pre-combustion chamber 5. cap 1 having
0 is fitted (in this case, both valve seats 7,
9 and the base 10 may be cast into the cylinder head at the same time when the cylinder head is cast).

In the figure, reference numeral 12 is a recess formed in the lower surface 1a of the cylinder head A. The intake valve seat 7 is provided so as to extend toward the enclosed area, and is provided around the intake valve seat 7 to surround the outer periphery of the intake valve 6 seated on the valve seat 7 except for the portion corresponding to the recess 12. Land portion 13 designed to
It is formed by forming.

In this way, on the lower surface 1a of the cylinder head 1,
A concave portion 12 is formed extending from the intake valve seat 7 toward the area surrounded by both valve seats 7 and 9 and the precombustion chamber 5. By providing the land portion 13 that surrounds the outer periphery of the intake valve 6 seated on the valve seat 7 except for the portion corresponding to the recessed portion 12, the intake valve 6 is shaped as shown by the solid line in FIG. When the valve is slightly away from the valve seat 7 both when it begins to open and just before it closes, almost all of the intake air flowing into the combustion chamber from the intake port 2 is shown in FIGS. 2 and 3. Since it is ejected from the recess 12 as shown by arrow A, both valve seats 7 and 9 and the pre-combustion chamber 5 are ejected from the lower surface 1a of the cylinder head.
The area surrounded by is the recess 1 as described above.
It can be cooled by the intake air blown out from 2.

Incidentally, in the above embodiment, the recess 12 was formed into a groove shape, but instead of forming the recess into a groove shape, as shown in FIG.
It may be formed into a conical recess 12a having a'.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the main part of the cylinder head, and the line shown in FIG.
FIG. 2 is a bottom view of FIG. 1, FIG. 3 is a cross-sectional view of FIG. 2, and FIG. 4 is a bottom view of a second embodiment of the present invention. 1...Cylinder head, 1a...Bottom surface of cylinder head, 2...Intake port, 3...Exhaust port,
4... Part between valves, 5... Pre-combustion chamber, 6... Intake valve, 7... Valve seat for intake valve, 8... Exhaust valve, 9
... Valve seat for exhaust valve, 10 ... Base, 11 ...
Nozzle hole, 12... recess, 13... land part.

Claims (1)

[Scope of utility model registration request] In a diesel engine in which a valve seat for an intake valve, a valve seat for an exhaust valve, and a pre-combustion chamber are provided in a cylinder head, the bottom surface of the cylinder head is provided with a valve seat for an intake valve, a valve seat for an exhaust valve, and a pre-combustion chamber. A recess is formed around the intake valve seat, and the outer periphery of the intake valve seated on the valve seat, excluding the portion corresponding to the recess, is formed around the intake valve seat. 1. A cylinder head for a diesel engine with a pre-combustion chamber, characterized in that a land portion surrounding the cylinder head is provided.