JPH02196117A - Cylinder head - Google Patents

Abstract

PURPOSE:To enhance the extent of deposition efficiency to a cylinder head in a clad seat layer by forming a plastic deformation layer in a base metal surface layer at the underside of the clad seat layer formed in a part equivalent to a valve seat of the cylinder head. CONSTITUTION:A port part 2 is formed in a cylinder head body 1, and this port part 2 is opened to a recess 3 at the side of a combustion chamber. Likewise, a valve seat surface 5, with which a valve 4 comes into contact, is formed in an opening end of the port part 2. In addition, the valve seat surface 5 is partitioned off by a clad seat layer 6 padded by laser cladding. In the above constitution, a plastic deformation layer 7 plastically deformed by a mill roller or the like is formed in a base metal surface layer at the underside (side of the cylinder head 1) of the clad seat layer 6. With this constitution, a defect 8 such as a pinhole or the like so far existing in the cylinder head body 1 (base metal part) is brought to nothing in substance at a part of the plastic deformation layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a cylinder head used in an internal combustion engine such as an automobile engine, and particularly relates to a cylinder head in which a seat portion is formed by laser cladding in a portion corresponding to a valve seat. be.

BACKGROUND OF THE INVENTION Aluminum alloys are often used for cylinder heads of internal combustion engines in view of weight reduction and formability. On the other hand, pulp repeatedly collides with the valve seat part of the cylinder head for receiving the intake valve and exhaust valve in J3 during operation of the internal combustion engine, and the valve seat part is affected by the heat generated by the explosion of the air-fuel mixture in the combustion chamber. Exposure to harsh temperature conditions. Therefore, in conventional aluminum alloy cylinder heads, in order to prevent the valve seat from blowing through due to abrasion or melting damage, or from sagging due to pulp collision, and to suppress the expansion and expansion of the valve seat due to heat, Usually, a recess is formed in the valve seat portion of the cylinder head body by counterboring, and a ring-shaped valve seat made of cast iron or iron-based sintered material is press-fitted into the recess.

However, as mentioned above, in the conventional cylinder head where the valve seat is press-fitted, a gap is created between the valve seat and the cylinder head body, and this gap acts as an air heat layer. There is a problem in that the conduction of heat is inhibited, causing the valve seat to reach a high temperature during operation of the internal combustion engine, and as a result, various properties such as wear resistance of the valve seat deteriorate.

In addition, as mentioned above, heat conduction from the valve seat to the cylinder head body is inhibited, so the cooling performance of the cylinder head is forced to decline, making it difficult to improve the performance of the internal combustion engine. be.

Recently, as shown in Japanese Patent Application Laid-open No. 62-150014, for example, a copper alloy with excellent heat resistance, wear resistance, and corrosion resistance is applied to the valve seat portion of the cylinder head body using a laser or other method. Alternatively, as shown in JP-A No. 62-150015, the valve seat portion of the cylinder head is clad with a hard material such as stellite using a laser, and the valve seat is formed by these overlays W (cladding layer). A cylinder head has been proposed. The valve seat formed by the laser cladding layer is welded to the material (base material) of the cylinder head body or alloyed at the interface with the base material, so the valve seat is Heat conduction to the cylinder head body is good, which reduces the thermal load on the valve seat and valves and improves durability, and improves cooling efficiency, which improves the power performance of the internal combustion engine. can be achieved.

Problems to be Solved by the Invention As mentioned above, in a valve seat formed with a built-up layer using laser cladding, heat conduction to the cylinder head body is much better compared to a valve seat formed by press-fitting. Cooling performance and durability are also improved, but
The reality is that in some cases, the results were still far from satisfactory. In other words, in order to provide sufficiently good heat conduction, sufficient cooling performance, and sufficient durability, the overlay layer that makes up the valve seat must have few defects, especially at the interface between the overlay layer and the base material. It is desirable for the overlay to be completely welded to the base material without any defects, but it is extremely difficult to completely eliminate defects even when laser cladding is applied, and the overlay is completely welded to the base material by laser cladding. The reality is that it is inevitable that there will be some unwelded parts between the base metal and the base metal.

The present invention was made against the background of the above circumstances, and in a cylinder head in which a valve seat portion is formed with a built-up layer formed by laser cladding, the welding zone of the built-up layer (clad sheet layer) to the cylinder head body is increased. The object of the present invention is to provide a cylinder head that has even better heat conduction to the cylinder head body.

Means for Solving the Problems The present inventors conducted various experiments and investigations into the causes of defects in the valve seat portion formed with a built-up layer formed by laser cladding, that is, the clad seat layer, and found that the cylinder head body on which laser cladding is applied If there are many defects such as pinholes in the surface layer of the (base material), there will be many defects at the interface between the clad sheet layer and the base material or inside the clad sheet layer, and the welding rate of the clad sheet layer to the base material will decrease. I found that it was lower. In order to eliminate defects in the surface layer of the base material, the inventors discovered that it is effective to plastically deform the surface layer of the base material using a rolling roll or the like, leading to the present invention.

Therefore, the present invention is characterized in that in a cylinder head in which a clad sheet layer formed by laser cladding is formed in a portion corresponding to a valve seat, a plastic deformation layer is formed in a base material surface layer below the clad sheet layer. That is.

Function: If the surface layer of the part of the cylinder head body where the clad sheet layer is to be formed, that is, the surface layer of the base material that is to be the underside of the clad sheet layer, is plastically deformed in advance by rolling with a rolling roll, etc. Defects such as pinholes that existed in the surface layer are crushed, and there are no pit defects. In this way, the sheet part (clad sheet layer) is formed by laser cladding on the surface layer of the base material, which has no defects.
By forming the clad sheet layer, the defects at the interface between the clad sheet layer and the base material will be significantly reduced, the welding rate of the clad sheet layer to the base material will be significantly increased to a value close to 100%, and the defects inside the clad sheet layer will also be reduced. In other words, if there are many defects such as pinholes in the surface layer of the base material, the interface between the clad sheet layer and the base material and the clad sheet portion may be damaged due to gas generation from the defects in the surface layer of the base material during cladding. There is a risk that defects such as pinholes may occur frequently inside, but if you eliminate defects such as pinholes in the surface layer of the base material in advance as described above, the clad sheet caused by defects on the surface layer of the base material can be eliminated. Defects at the interface between the layer and the base material and inside the clad sheet layer can be reduced. Therefore, in the cylinder head of the present invention in which a plastic deformation layer is formed on the surface layer of the base material below the clad sheet layer, there are fewer defects at the interface between the clad sheet layer and the base material and inside the clad sheet layer. The welding rate of the clad sheet layer to the material is also high. Therefore, heat conduction from the clad sheet layer to the base material is also extremely good.

Embodiment FIGS. 1 and 2 show essential parts of an embodiment of a cylinder head to which the present invention is applied.

In FIG. 1, a cylinder head main body 1 is formed with a boat portion 2 constituting an intake boat or an exhaust boat, and this boat portion 2 opens into a combustion chamber side recess 3. A valve seat surface 5 is formed at the open end of the boat portion 2, with which the pulp 4 constituting the intake valve or the exhaust valve comes into close contact. This valve seam i-face 5 is defined by a clad sheet layer 6 built up with laser cladding, and the lower side of the clad sheet protection 6 (
The surface layer of the base material on the cylinder head main body 1 side) is a plastically deformed layer 7 that is plastically deformed by a rolling roll or the like.

In such a cylinder head, as shown in detail in FIG. Therefore, there are almost no defects at the interface 9 between the clad sheet layer 6 and the base material or inside the clad sheet layer 1 and layer 6, and the welding rate of the clad sheet layer 1 and layer 6 at the interface 9 is also remarkable. It is expensive.

Here, as the material (base material) of the cylinder head body 1, a He2 alloy is normally used. Further, as the clad material of the clad sheet layer 6, the cylinder head body 1
The specific type of metal does not matter as long as it can be overlaid on the base material and has good wear resistance, heat resistance, corrosion resistance, and thermal conductivity, but for example, 15.0wt%Ni13wt%l" e
, 1. Copper alloy with composition consisting of Owt%P1 and balance substantially consisting of Qu, or 20.0wt%Ni, 4.5
wt%F e, t, wt%P, remainder substantially C
Copper alloy with a component composition consisting of u, further 25.0 wt%
Ni, 2.5wt%Fe, 1. It is desirable to use a Cu-Ni-4e alloy such as a copper alloy with hvt%P1 and the balance being Cu.

Further, specific examples of this invention will be described.

The part where the clad sheet layer of the cylinder head made of aluminum alloy (JIS AC2C) is to be formed is rolled 30 times using an O-roll with a roll width of 8.0M while applying a load of 150ONy, and the roll is deformed to 1 it.
After forming the (plastic deformation layer), N is used as the cladding material.
i 20wt%, Fe8.0wt%, 31.5wt%,
Laser cladding was performed using a copper alloy with a composition of 3.0 wt% i and the balance Qu, and the thickness was 0.8 m.
.

A clad sheet layer was formed. The laser cladding conditions at this time were: laser output 4.5~, scanning speed 800u/
City. Note that the thickness of the plastically deformed layer is approximately 0.5#.

A cross-sectional photograph of the Tararad sheet layer A4 thus formed is shown in FIG. In Figure 3, the white part at the top is the Talarado sheet layer, the gray part at the bottom is the base material (cylinder head body), the slightly dark part in the middle is the plastic deformation layer, and the black dotted part. are defects such as pinholes.

As shown in Figure 3, defects such as pinholes remain in the base material below the plastic deformation layer, but the defects in the plastic deformation layer have disappeared, so the clad sheet layer and base metal There were no defects at the interface with the cladding sheet or in the cladding sheet 1 layer, indicating that the cladding sheet layer was sufficiently welded to the base material.

On the other hand, for comparison, the following is a cross-sectional photograph of a comparative amount of clad sheet layer formed by cladding the copper alloy with copper alloy under the same conditions as above without rolling the area where the clad sheet layer is to be formed. Shown in Figure 4. In this case, it can be seen that defects in the base material cause defects at the interface between the clad sheet layer and the base material or inside the clad sheet layer.

Furthermore, in order to confirm the effects of this invention, the following experiment was conducted.

That is, first, the thickness of the plastic deformation layer under the clad sheet layer by rolling is varied, and the average number of defects occurring at the interface between the clad sheet layer and the base material and inside the clad sheet layer (specifically, the maximum The relationship between the number of pinholes with a diameter of 0.2 mm or more and the thickness of the plastically deformed layer was investigated.

The results are shown in FIG. Note that the materials of the base material and cladding material, and the cladding conditions are the same as in the previous case.

From FIG. 5, it can be seen that as the thickness of the plastically deformed layer increases, the number of defects decreases. The thickness of the plastic deformation layer is 0.1.
However, although the effect of reducing defects was poor, a sufficient effect was obtained for 0.2 times or more, and in particular, the occurrence of defects could be almost completely suppressed for 0.5 times or more.

Next, the welding rate of the clad sheet layer to the base material was investigated by varying the thickness of the plastically deformed layer by rolling.

The results are shown in FIG. The materials of the base material and cladding material and the cladding conditions were the same as in the previous case. In addition, the welding rate (%) was as follows.

From Figure 6, the welding rate increases as the thickness of the plastically deformed layer increases, and when the thickness of the plastically deformed layer is zero, the welding rate is approximately 9.
5%, whereas the thickness of the plastic deformation layer is 0.111#I
It can be seen that the welding rate reached 99.0% at 0.2 days, and 99.5% at 0.2 days.

Therefore, if the results in FIG. 5 and the results in FIG. 6 are considered together, the thickness of the plastically deformed layer is 0.1. Although the above is effective, in order to obtain a sufficiently high quality clad sheet layer, it is desirable to set the time to 0.2 seconds or more, and in particular, if it is 0.5 seconds or more, it is difficult to obtain an extremely high quality clad sheet layer. can. Although there is no particular limit to the thickness of the plastically deformed layer, it is usually 1.5. , or less.

Furthermore, the thickness of the plastically deformed layer due to rolling is Os (no plastic deformation due to rolling), 0.1. , O, S, and each cylinder head is 1600ccD.
We applied this to an OHC engine and conducted a continuous high-speed durability test using an actual engine. The materials of the base material and cladding material and the cladding conditions were the same as in the previous case, and the operating conditions were a rotational speed of 6,800 to 7,300 rpm and a full load. The amount of wear on the clad sheet layer was investigated based on the amount of pulp sinking before and after this running test, and the results are shown in FIG.

From FIG. 7, it can be seen that the case where the plastic deformation layer is formed by rolling (plastic deformation layer thickness 0.
1s, 0.5a), it can be seen that the amount of wear of the clad sheet layer is reduced and its durability is improved. This is because, as described in the experimental results in Figure 6, the welding rate of the clad sheet layer increases by forming a plastic deformation layer, which results in better heat conduction to the base material and This is thought to be due to a decrease in heat load.

Effects of the Invention In the cylinder head of the present invention, by forming a plastic deformation layer on the surface layer of the base material below the clad layer, defects at the interface between the clad sheet layer and the base material and inside the clad layer are significantly reduced. As a result, the welding rate of the clad sheet layer becomes significantly higher, making it possible to significantly improve heat conduction to the base material, and as a result, it is possible to further improve the power performance and durability of the engine. It has become possible.

In other words, the heat conduction from the clad sheet layer to the base material has improved as described above, which improves cooling performance and improves the knock limit of the engine, which in turn makes it possible to improve torque and horsepower. The fuel efficiency of the engine can be improved, and the heat load on the clad sheet layer during operation is reduced due to improved heat conduction, which reduces the amount of wear on the clad sheet layer and improves durability. Ta.

Furthermore, in manufacturing the cylinder head of this invention, a high-quality clad sheet layer can be obtained simply by forming the plastic deformation layer as described above, so the burden of quality control during the manufacturing of the cylinder head body can be reduced compared to the conventional method. Therefore, it is possible to reduce the cost required for manufacturing and inspecting the cylinder head body.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the main parts of the cylinder head of one embodiment of this light beam, and FIG. 2 is an enlarged cross-sectional view of part (2) in FIG.
FIG. 3 is a photograph of the metal cross-sectional structure near the clad sheet layer in a cylinder head according to an embodiment of the present invention (magnification: 10
Figure 4 is a photograph of the metal cross-sectional structure near the clad sheet layer in a comparative cylinder head that did not form a plastic deformation layer (magnification = 10x). Figure 5 is the thickness of the plastic deformation layer and the clad sheet layer. Figure 6 is a graph showing the relationship between the thickness of the plastic deformation layer and the welding rate of the clad sheet layer, and Figure 7 is a graph showing the amount of clad sheet wear in the actual machine durability test. be. 1... Cylinder head body (base material), 6... Clad sheet layer, 7... Plastic deformation layer.

Claims (1)

[Scope of Claims] In a cylinder head in which a clad sheet layer formed by laser cladding is formed in a portion corresponding to a valve seat, a plastic deformation layer is formed in a base material surface layer below the clad sheet layer. Characteristic cylinder head.