JPH04166648A - Aluminum-alloy-made cylinder head for diesel engine - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a high-temperature corrosion part by forming a linear cooling water passage in a partition wall between intake and exhaust ports, and engaging a cathode member, composed of a corrosion-resistant metal material electric-potentially noble to aluminum, with the passage. CONSTITUTION:A set of a water jacket 14 is formed in an aluminum-alloy-made cylinder head 1, a cooling water passage 16, communicated with the water jacket 14, is formed on the lower surface of the cylinder head 1 through in a partition wall 15 between intake and exhaust ports 4 and 5, and also another cooling water passage 18 is connected to the cooling water passage 16. In this case, cathode members 17a and 17b, formed in a C-form or cruciform cross section, are pushedly engaged with the combustion chamber wall 3 side, which is thermally severest and in which boiling is apt to occur, of the cooling water passage 16. These cathode members 17a and 17b are composed of corrosion resistant metal materials such as stainless or zirconium, etc., and the corrosion of aluminum can be prevented due to the discharge of hydrogen (H<+>) by these materials on a cathode surface.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an aluminum alloy cylinder head for a diesel engine, and in particular, a corrosion-resistant member is provided in a high-temperature corrosion area of the aluminum alloy cylinder head to improve its corrosion resistance. This invention relates to an aluminum alloy cylinder head for diesel engines.

[Prior Art] Most of the cylinder heads of swirl combustion chamber type or pre-combustion chamber type diesel engines are formed with holes for passing cooling water between intake and exhaust valve seats.

The main purpose of cooling is to maintain the parts of the cylinder head that become hot due to combustion at an appropriate temperature, reduce thermal fatigue of the cylinder head material, prevent thermal cracks, and ensure its durability. However, in regions such as Europe where water containing a lot of corrosive ions, especially chlorine ions, must be used as engine cooling water, corrosion occurs in the cooling water passages, especially on the high temperature side of the aluminum base metal cylinder head. pitting corrosion)
This may occur, and in some cases, water leakage may result in engine damage. This corrosion of aluminum is
Environmental conditions (water, LLC properties, flow rate, temperature), material conditions (
However, depending on the constraints of local natural and market conditions as well as technical and economic conditions, it can be dealt with using water, LLC properties, and material composition. Things have become extremely difficult. Therefore, as a normal countermeasure on the engine side, the wall thickness of the thermally severe parts (*corrosion-prone parts) is increased toward the water jacket side to reduce the temperature of the high-temperature corrosion part and activate the corrosion reaction. A method of protecting the cooling water passage from corrosion by press-fitting a pipe made of corrosion-resistant metal material such as stainless steel into the cooling water passage.
No. 5-4330) has been requested.

[Problem to be solved by the invention] However, in the former case, it is difficult to design a well-balanced wall thickness due to corrosion concerns, so it is not possible to sufficiently reduce the temperature on the underside of the cylinder head and around the combustion chamber. Especially in high-output engines such as those with turbochargers, there have been cases where we have been forced to abandon commercialization due to difficulties in maintaining this balance.

In addition, the latter was made of 411, which could not radiate heat directly to the cooling water, so it was insufficient in terms of cooling performance.

A first object of the present invention is to provide an electrically corrosion-protective member on the inner surface of the cooling water passage so as to allow heat to be radiated directly from the cylinder head to the cooling water without interfering with the flow of the cooling water. It is equipped with an aluminum alloy cylinder head for diesel engines.

A second object of the present invention is to cool an aluminum alloy cylinder head for a diesel engine by raising the wall thickness of the partition wall between the intake and exhaust ports on the pre-combustion chamber side toward the water jacket side to form a thick wall portion. To provide an aluminum alloy cylinder head for a diesel engine which prevents pitting corrosion in high-temperature corrosion parts of a combustion chamber wall while improving performance.

[Means for Solving the Problems] The first invention forms a linear cooling water passage in the partition between the intake and exhaust ports by communicating with the water jacket,
A cathode member formed into a C-shaped or cross-shaped cross section from a corrosion-resistant metal material that is potentially nobler than aluminum is integrally fitted into the high-temperature corrosion portion of the passage.

In the second invention, the partition wall on the pre-combustion chamber side between the intake and exhaust ports is raised toward the water jacket side to form a thick wall portion,
A cathode member formed of a corrosion-resistant metal material that is more noble in potential than aluminum near the thick portion is sprayed and buried in the water jacket.

[Function] In the first invention, the cathode member formed into a C-shaped or cross-shaped cross section has a portion that directly contacts the inner surface of the cooling water passage and a portion that opens the inner surface of the cooling water passage to the cooling water. As a result, the partition wall between the intake and exhaust ports that partitions the cooling water passage, especially the high-temperature corrosion part side, is directly and indirectly cooled by the cooling water. For this reason, conventional
-4330), the entire inner surface of the cooling water passage is separated from the cooling water by a 11 tl pipe made of corrosion-resistant metal.
In contrast to the structure that indirectly cools the partition wall, heat is effectively removed from the partition wall, and the cooling performance is greatly improved and the heat load is reduced. Moreover, since the cathode member is formed into a C-shaped or cross-shaped cross section, it also functions as a member for improving the rigidity of the partition wall. The cathode member causes hydrogen (H+) discharge to occur on the cathode surface, and exhibits #j phagocytosis, which passivates the aluminum alloy by using the cylinder head including the cooling water passage as an anode.

In the second invention, the cathode member is embedded in the thick part on the side of the pre-combustion chamber, thereby reducing the inner wall thickness of the thick part to substantially improve cooling performance and reduce the thermal load on the partition wall. Also, similar to the first invention, the vl of the thick part! The cathode surface exerts a cutting action to prevent pitting corrosion of the combustion chamber wall and the aluminum alloy in its vicinity without impairing J properties.

[Embodiment] A preferred embodiment of the present invention will be described below based on the accompanying drawings.

(Example 1) FIG. 1 shows a cross section of an aluminum alloy cylinder head for a diesel engine according to the present invention, FIG. 2 shows a cross section taken along the line n-n in FIG. 1, and FIG. A cross section taken along the line ■-■ is shown.

As shown in the figure, the cylinder head 1 includes a combustion chamber wall 3 forming a swirl combustion chamber 2 as a pre-combustion chamber, a pipe wall 6 and a pipe wall 7 forming an intake port 4 and an exhaust port 5, respectively. - A series of water jackets 14 are formed by hollowing out the other parts except for the valve guide cylinder parts 10° 11 which slidably house the exhaust valves 8 and 9, the injector housing part 12, and the globe lug housing part 13. ing. On the lower surface of the cylinder head 1, a hole corresponding to the area between the intake port 4 and the exhaust port 5 is bored from one side wall side thereof, and the hole is inserted through the partition wall 15 between the intake port 4 and the exhaust port 5, and the water jacket 14 A cooling water passage 16 is formed so as to open so as to face the lower outer surface of the combustion chamber W3 facing the combustion chamber W3. stop.

Another cooling water passage 18 bored from the cylinder 171'J1 side is connected to the cooling water passage 16 of the lever. 1
Reference numeral 9a is a plug member for closing the other end of the cooling water passage 16, and is provided in a screwed manner 15 to the other end of the cooling water passage 16.

An object of the present invention is to prevent corrosion (pitting corrosion) of the corroded parts of the cooling water passage 16, particularly the high temperature corrosion part, so as not to impede the cooling performance of the cooling water passage 16.

Therefore, in the present invention, as shown in FIG. 1 and FIG. 2, the cooling water passage 16 is provided with a C-shaped or cross-shaped cross section on the side of the combustion chamber wall 3 which is most thermally severe and where boiling is likely to occur. The cathode members 17a and 17b formed in the respective parts are fitted together by press-fitting. However, the slit of the cathode member 17a having a C-shaped cross section is provided so as to face the lower cylinder side. Also, these cathode members 17a.

17b is made of a corrosion-resistant metal material such as stainless steel or zirconia laminate, which is good for aluminum cladding.

Next, the operation of this embodiment will be explained.

The cathode member 17a having a C-shaped cross section or the cathode member 17b having a cross-shaped cross section respectively opens a part of the inner surface of the cooling water passage 16 to the cooling water, and allows the cooling water to be efficiently filtered without obstructing the flow of the cooling water. Therefore, the cooling performance of the partition wall 15, which has been a problem in the past, is improved, and thermal fatigue of the partition wall 15 is reduced. In addition, these cathode members 17
a.

17b causes hydrogen (H+) discharge to occur on the cathode surface rather than at the boundary between aluminum and the protective oxide film, thereby eliminating destruction of the oxide film and preventing corrosion of aluminum. The cathode members 17a, 17h are also electrically contacted (bonded) with aluminum to create a cathode portion and passivate the aluminum alloy.

Therefore, the vicinity of the inner surface of the cooling water passage 16, including the high-temperature corrosion portion, is protected from corrosion (pitting corrosion).

(Embodiment 2) In this embodiment, the intake/exhaust port 4.
5 to 15 to cool the cooling water passage F#
116 is not formed, but the partition wall 15 on the swirl combustion chamber 2 side is raised toward the water jacket 14 side to form the thick wall portion 19. A cathode member 17c made of a corrosion-resistant metal material such as stainless steel or zirconium is embedded in the thick portion 19 on the water jacket 14 side by casting with its upper surface exposed. This cathode member 1.7c is formed with a cross section that is continuous with the lower side of the combustion chamber wall 3, which is a high-temperature corrosion part, and the outer surface of the thick part 19, and forms a part of the wall surface of the water jacket 14. .

Therefore, in this embodiment, by embedding the cathode member 17e in the thick wall portion 19, the cathode member 17e is buried in the thick wall portion 19. The wall thickness of the partition wall 9 can be reduced to a thickness suitable for cooling performance without impairing the rigidity of the partition wall 9, ensuring good cooling performance, and the thermal load on the partition wall 15 can be reduced. Then, as in the first embodiment, the thick portion 19 is
Also, pitting corrosion in the vicinity of the combustion chamber wall 3 is prevented.

Note that in cases where the heat load on the cylinder head 1 becomes considerably high due to an increase in engine output, such as when a turbo supercharger is adopted, the cathode member having the C-shaped or cross-shaped cross section of the first embodiment may be added to the structure of the second embodiment. Of course, it is also possible to form the cooling water passage 16 into which 17a or 17b is press-fitted. Further, the cathode member 17b is not limited to a cross section, and the cross section of the cooling water passage 1
It is also possible to have four or more ribs in the radial direction that contact the inner surface of 6 as much as possible.

[Effects of the Invention J] As is clear from the above explanation, according to the present invention, cooling water can be used directly to prevent the stiffness of high-temperature corroded parts such as the partition wall between the intake and exhaust ports and the vicinity thereof including the combustion chamber wall. It exhibits an excellent effect of being able to prevent corrosion (pitting corrosion) of these high-temperature corrosion parts while enabling indirect cooling.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a preferred embodiment of an aluminum alloy cylinder head for a diesel engine according to the present invention;
Figure 2 is a sectional view taken along the line ■-■ in Figure 1, and Figure 3 is a cross-sectional view taken along the line ■ in Figure 1.
4 is a sectional view showing a second embodiment of the present invention. In the figure, 1 is a cylinder head, 4 is an intake port, 5 is an exhaust port, 14 is a water jacket, 15 is a partition, 16
is a cooling water passage, 17a. 17b and 17c are cathode members.

Claims (1)

[Claims] 1. A linear cooling water passage is formed in the partition wall between the intake and exhaust ports to communicate with the water jacket, and the passage has:
C from a corrosion-resistant metal material that is potentially nobler than aluminum
An aluminum alloy cylinder head for diesel engines that has a cathode member formed into a cross-shaped or cross-shaped cross section that is integrally fitted. 2. The preheating combustion chamber side of the partition between the intake and exhaust ports is raised toward the water jacket side to form a thick wall, and the area including the thick wall is made of a corrosion-resistant metal material that is more noble in potential than aluminum. An aluminum alloy cylinder head for a diesel engine, characterized in that a formed cathode member is exposed and buried within a water jacket.