JPS62611A - Steel valve for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the abrasion resistance of the contact surface with a locker arm by forming a composite layer in matrix form into which ceramics particles are dispersed, at the top edge of the valve stem of an intake/exhaust valve for an engine. CONSTITUTION:In an exhaust valve 1 for engine which is made of steel, a composite layer 9 is formed onto the contact part with a locker arm at the upper edge part. Said composite layer 9 is made of the heat-resisting steel 7 in matrix form into which TiC particles 8 are dispersed. Said TiC particle is obtained by adding the aqueous solution of polyvinyl alcohol in 5% as bonding agent into TiC powder having an average particle size of 80mu and arranging said TiC powder into a layer form having a thickness of about 1mm except the peripheral edge part having a width of about 1.0mm at the edge surface of the valve and then drying said layer after the heating at about 110 deg.C in the atmosphere for 20min and then melting said layer in argon gas by a laser gun.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to internal combustion IIA valves, and more particularly to valves manufactured by Jll incorporated in the intake and exhaust systems of internal combustion engines.

Problems to be solved by conventional technology and inventions As the performance of internal combustion engines increases, the usage conditions for intake and exhaust valves are becoming increasingly strict. High wear resistance is increasingly required.

In order to meet these demands, the valve is made of austenitic heat-resistant steel with excellent heat resistance, and since austenitic heat-resistant steel does not have quench hardening ability, a chip of martensitic heat-resistant steel is welded to the tip of the stem. Conventionally, the tip of the stem is then hardened by quenching. However, in such valves, it is not always possible to ensure sufficient wear resistance, and the manufacturing process is difficult. There are problems in that it is complicated and expensive.

In addition, in order to meet the above-mentioned requirements, it has been conventionally practiced to form the valve from heat-resistant steel of the J■S standard S U +- series, and to deposit a CO alloy on the tip of the stem. However, even such valves do not necessarily have satisfactory wear resistance, and acetylene flame is generally used as a heat source in their manufacture, and the wear resistance is far greater than that of the expensive Go gold alloy. A large amount of metal is deposited on the valve, and two-thirds or more of the metal deposit is removed by polishing, which results in a problem that the valve is expensive. Furthermore, since all of the above-mentioned valves have a structure in which a chip or a metal plate is integrally bonded to the tip of the stem of the valve material, there is a problem that the impact resistance is not necessarily sufficient.

In view of the above-mentioned problems with conventional steel valves for internal combustion engines, the present invention aims to improve the wear resistance of the abutment surface of the valve stem tip with the rocker arm and the balance resistance of the valve stem tip. The purpose of the present invention is to provide a low-mounted steel valve for internal combustion engines.

Means for Solving the Problems According to the present invention, the above object is achieved by having a contact surface with the rocker arm at the tip of the stem, and the contact surface being a composite material in which ceramic particles are dispersed in a steel matrix. This is achieved by a steel valve for internal combustion engines defined in layers.

Effects and Effects of the Invention According to the present invention, the contact surface of the stem tip with the rocker arm is defined by a composite layer in which ceramic particles are dispersed in steel as a matrix, so that the conventional valve as described above is not The wear resistance of the contact surface with the rocker arm can be made much higher than that of the rocker arm.

Further, in the composite layer of the steel valve for internal combustion engines of the present invention, ceramic powder is arranged on the end face of the stem tip of the steel valve raw material, and the ceramic powder and the surface of the stem tip are heated by a high-density energy source, especially a laser. The steel valve for internal combustion engines of the present invention is more efficient than conventional valves, as described above, because the steel valve for internal combustion engines of the present invention may be formed by locally heating and melting the ceramic powder and dispersing it within the surface of the stem tip. It can be easily manufactured, and the integrity of the composite layer at the tip of the stem and the pulp material is far superior to the integrity of the tip or fillet part and the pulp material in conventional valves. Therefore, the impact resistance of the stem tip is also far superior.

Furthermore, according to the invention, the composite layer defining the abutment surface with the rocker arm may be formed as described above, and its depth may be equal to the depth of the abutment surface that occurs during the use of the valve. Compared to conventional valves such as those mentioned above, the diameter of the ceramic particles dispersed in the composite layer can be small, on the order of a few millimeters, which corresponds substantially to the wear. A low-mounted steel valve for an internal combustion engine can be obtained.

The ceramic particles in the internal combustion engine and utility steel pulp of the present invention include oxide ceramic particles such as aluminum oxide, magnesium oxide, silicon oxide, and titanium oxide, and carbides such as titanium carbide, tantalum carbide, molybdenum carbide, and chromium carbide. It may be any of nitride-based ceramic particles such as titanium nitride, zirconium nitride, silicon nitride, etc., or it may be a mixture of these two IIJX particles. According to the results of experimental research, in order to ensure sufficient wear resistance of the contact surface with the rocker arm and reduce the cost of the valve, it is necessary to increase the amount of helical particles in the composite layer. The volume fraction is preferably 20 to 95%, particularly 45 to 85%.

Also, according to the results of experimental research conducted by the inventors of the present application,
If the size of the ceramic particles dispersed in the steel matrix is too small, it is difficult to sufficiently improve the wear resistance of the contact surface with the rocker arm, and if the size of the ceramic particles is too large. When the valve is used, problems such as ceramic particles falling off the surface of the composite layer tend to occur. According to another detailed feature of the invention, therefore, the average particle size of the ceramic particles is between 0.1 and 190μ, in particular between 1.0 and 30μ.

Also, according to the results of experimental research conducted by the inventors of the present application,
If the area ratio of the portion defined by the ceramic particle dispersed composite layer of the contact surface with the rocker arm is too small, it is difficult to sufficiently improve the wear resistance of the contact surface. According to yet another detailed feature of the invention, 50% or more of the contact surface with the rocker arm is defined by the ceramic particle dispersed composite layer.

Furthermore, according to the results of experimental research conducted by the inventors of the present application,
If the depth of the center of the composite layer is too small, it will not be able to cover the amount of wear on the contact surface that occurs during the use of the valve, and if the depth of the center of the composite layer is too large, According to yet another detailed feature of the invention, the depth of the central part of the composite layer is 0.1. ~2,011. Preferably 0.2-0.5I1m
It is said that

Note that when the steel valve for internal combustion engines of the present invention is manufactured using a high-density energy source such as a laser as described above, the surface portion or the entire ceramic powder is melted, and unmelted ceramic is left in the matrix. The remaining or molten ceramic crystallizes in the matrix, so that the ceramic is finely dispersed in the matrix, but a part of the molten ceramic is solidly dissolved in the steel as a matrix, thus The ceramic dissolved in the matrix also improves the wear resistance of the contact surface with the rocker arm. Furthermore, when the steel pulp for internal combustion engines of the present invention is produced by the method described above, when the entire end surface of the stem tip of the valve material is melted, mra sagging occurs in places, so the rocker arm and It is preferable that the area ratio of the portion of the contact surface defined by the composite layer be suppressed to 90% or less. Further, the steel constituting the steel valve for an internal combustion engine of the present invention may be any heat-resistant steel such as austenitic heat-resistant steel or martensitic heat-resistant steel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

X11 FIG. 1 is a front view showing an embodiment of the steel valve for internal combustion IA+ according to the present invention, and FIG. 2 is a large-scale longitudinal sectional view showing the main part of the embodiment shown in FIG. 1. In these figures, reference numeral 1 indicates a steel valve for an internal combustion engine made of heat-resistant steel (J [S standard S U H36). The valve 1 includes a cap section 2 that opens and closes an intake boat or an exhaust boat of an internal combustion engine (not shown), and a stem 4 that is formed integrally with the cap section and extends along an axis 3. The stem 4 has a contact surface 6 with a rocker arm (not shown) on an end surface 5 of its tip 4a. As shown in detail in FIG. 2, the abutment surface 6 in the illustrated embodiment is
It is defined by a composite layer 9 in which TiC particles 8 are dispersed in heat-resistant steel 7 as a matrix.

The steel valve for an internal combustion engine shown in FIGS. 1 and 2 was manufactured as follows. First, as shown in Fig. 3, it is made of heat-resistant steel (JIS standard S U l-136) and has substantially the same shape and dimensions as the internal combustion engine opening steel valve shown in Figs. 1 and 2. A valve rough material 10 was prepared. Next, TiC powder with an average particle size of 80 μm was prepared, and the Ti
A 5% aqueous solution of polyvinyl alcohol as a binder was added to the C powder to form a paste that was more viscous than water and less viscous than clay. Next, valve rough material 1
The paste is placed in a layer with a thickness of about 111-m on the end face 11 of the tip 10a of the paste, excluding the periphery with a width of about 1.011 m, and heated in the atmosphere at about 110° C. for 20 minutes. The TiC powder layer 12 was thereby formed on the end surface 11 as shown in FIG.

Next, as shown in FIG. 4, argon as a shielding gas is emitted from the tip of the laser gun 13, thereby shielding the molten part of the end face 11 with argon, and the laser 14 is applied to the TiC1tf) terminal layer 12. irradiate,
As a result, the TiC powder and the end surface 11 are locally heated under the conditions shown in Table 1 below to partially melt the tip 10a, thereby dispersing the TiC powder in the molten layer,
As shown in FIG. 5, a composite layer 15 was formed in which TiC particles 8 were dispersed in heat-resistant steel 7 as a matrix. Next, the surface of the composite layer 15 is perpendicular to the axis 3 by 0.2
~Q, 4+em grinding was performed to obtain a steel valve for an internal combustion engine as shown in FIGS. 1 and 2.

Table Laser output 3kW Laser irradiation time: 0.8sec Laser beam diameter: 6.511 Argon flow ffi: 80Q/1n The diameter of the tip 4a of the stem 4 of the valve manufactured as described above is 8.0I
I11, and the diameter d of the composite layer 9 is 7. Qia+, and the depth t of composite 119 was 1.21. Also complex 1
The average particle diameter and volume fraction of the TiC particles in 19 are 3.0μ and 55%, respectively, and the hardness of the contact surface 6 is HV.
-600 to 1100.

In order to evaluate the wear resistance of the contact surface with the rocker arm of the valve manufactured as described above, the load was 20 kg, the rotor rotation speed was 104, and the sliding speed Q was 3 m/SeO.

Surface hardness Hv = approx. 500 under the condition of sliding distance 1001W
A wear test was conducted using 1 mm cast iron as the mating material, and the wear ff1 (wear length mm) of the contact surface was measured. In addition, for comparison purposes, martensitic heat-resistant steel (JIS standard 5
Regarding a valve in which a tip made of UH11) was welded and the tip was hardened by induction hardening (Comparative Example 1), and a conventional valve in which Stellite alloy was deposited on the end face of the stem tip of the valve raw material (Comparative Example 2). A wear test was also conducted under the same conditions. The results of these wear tests are shown in FIG.

From FIG. 6, the amount of wear on the contact surface of the steel valve for internal combustion engines in Example 1 is about 1/8 and about 1/3 of the amount of wear in Comparative Examples 1 and 2, respectively. It can be seen that the abrasion resistance of the contact surface of the valve of Example 1 is significantly superior to that of any of the valves of Comparative Examples.

In addition, in order to evaluate the integrity of the composite H9 of the valve of the example and the part made only of heat-resistant steel, and the integrity of the chip or fillet part of the valve of the comparative example and the part made only of heat-resistant steel, an impact load of 40 kg was applied. /l1l12) Impact load loading time 0.3
When repeated impact tests were conducted under the conditions of a sec1 load cycle of 1 x 107 nicles, in the valves of Comparative Examples 1 and 2, there were signs that the chip and the stellite alloy fill-in part were separated from the part made only of heat-resistant steel. Whereas it was seen
No such signs were observed in the valve of Example 1.

Further, FIG. 7 is an optical micrograph showing the metal structure of a cross section along the axis of the central part of the composite layer 9 of the bulb manufactured as described above, but not shown at 400 times magnification. In the figure, the white island-like part is T
These are iC particles, and the gray area is the heat-resistant steel part as a matrix. From FIG. 7, it can be seen that relatively fine and relatively uniformly sized TiC particles are uniformly dispersed in the matrix, and defects such as pores are not generated at all.

The above implementation was carried out except that instead of IL and TiC powder, a mixed powder of TiC powder with an average particle size of 80μ and At 203 powder with an average particle size of 60μ mixed in a weight ratio of 1:1 was used. A valve was manufactured in the same manner and under the same conditions as in Example 1. The contact surface of the stem tip of the valve thus manufactured with the rocker arm was subjected to an ultra-thread wear test under the same conditions as in Example 1. The results of this wear test are shown in FIG. 8 together with the results of the wear test of Example 1.

The average particle diameters of the TiC particles and Al2O3 particles in the composite layer were 3.0 .mu. and 2.5 .mu., respectively, and the volume fractions of these particles were both 30%.

From FIGS. 6 and 8, the amount of wear on the contact surface of the valve of this example with the rocker arm is approximately 1/10 of the amount of wear in Comparative Examples 1 and 2, respectively. Therefore, the wear resistance of the contact surface of the valve of this example is about 1/4 that of Comparative Examples 1 and 2.
You can see that it is far superior to any other valve.

Further, when the valve of this example was subjected to repeated impact tests under the same conditions as in Example 1, no signs of peeling of the composite layer from the portion made only of heat-resistant steel were observed.

Example 3 Example 3 except that a mixed powder in which 7-i3N4 powder with an average particle size of 50 μm and TaC powder with an average particle size of 80 μm were mixed in a 3=1 multilayer structure was used instead of TiC powder. 1
A valve was manufactured in the same manner and under the same conditions as in the case of . The thus manufactured valve was subjected to an ultra-thread wear test under the same conditions as in Example 1. The results of this wear test are shown in FIG. Furthermore, Ti3N4 in the composite layer
The average particle diameters of particles and 180 particles are 1.0μ and 3μ, respectively.
．． 5μ, and the volume fraction of these particles is 30% each.
, 10%.

6 and 8, the amount of wear on the abutment surface of the valve of this example with the rocker arm is slightly larger than that of Examples 1 and 2 described above, but the amount of wear in Comparative Examples 1 and 2 is Therefore, it can be seen that the wear resistance of the valve contact surface of this example is also far superior to that of Comparative Examples 1 and 2.

Further, when the valve of this example was subjected to repeated impact tests under the same conditions as in Example 1, no signs of peeling of the composite layer from the portion made only of heat-resistant steel were observed.

11 Ratio of the area of the composite layer to the area of the end surface of the tip of the nine-pointed stem (
In order to examine how the wear fit (wear length) of the contact surface with the rocker arm changes depending on the composite area ratio (hereinafter referred to as composite area ratio), the same procedure and conditions as in Example 1 were carried out. A composite layer made of heat-resistant steel in which particles with an average particle size of 3.0μ are dispersed at a volume ratio of 60% is formed on the end face of the tip of the pulp rough material, and the contact surface of each valve is the same as in Example 1. An ultra-high-pressure wear test was conducted under the following conditions. In this case, the composite area ratio is 90%, 80%, 60%, 50%, 40%, 2
Wear tests were conducted on six types of valves set at 0%. The results of this wear test are shown in Figure 9. In Fig. 9, the imaginary line indicates the rocker arm of a conventional valve filled with Stellite alloy.

The wear ff1 (wear length l-) of the contact surface is shown.

As shown in Figure 9, the amount of wear on the contact surface with the rocker arm is smaller than that of conventional valves with stellite alloy overlay when the composite area ratio is 45% or more, preferably 50% or more. It turns out that.

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art that

[Brief explanation of drawings]

FIG. 1 is a front view showing one embodiment of the steel pulp for internal combustion engines according to the present invention, FIG. 2 is an enlarged longitudinal cross-sectional view of a main part of the embodiment shown in FIG. 1, and FIG. Figures 5 to 5 are the first
FIG. 6 is a process diagram showing the manufacturing process of the valve of the embodiment shown in FIG. A graph showing the test results, FIG. 7, shows the metal structure of a cross section along the central axis of the composite layer of the bulb of Example 1.
Optical micrograph shown at 00x magnification, Figure 8 shows Examples 1 to 3.
Figure 9 is a graph showing the results of wear tests conducted on the abutment surface between the tip of the valve stem and the rocker arm. It is a graph showing the results of a wear test conducted on the contact surface. 1... Steel valve for internal combustion engine, 2... Umbrella part, 3...
・Axis line, 4... Stem, 4a... Tip, 5... End face, 6... Contact surface, 7... Heat resistant steel, 8... TiC
Particles, 9...composite layer. 10... Valve rough material, 10a... Tip, 11...
End face. 12... TiC powder powder layer, 13... laser gun,
14...Laser, 15...Composite layer patent Applicant: Toyota Motor Corporation representative
Patent attorney Masa Akashi
Takeshi Figure 1 Figure 6 Comparative Example 1 Comparative Example 2 Example 1 Figure 7 Combined surface area ratio (%)

Claims (5)

[Claims] (1) The tip of the stem has a contact surface with the rocker arm,
A steel valve for internal combustion engines whose contact surface is defined by a composite layer of ceramic particles dispersed in a steel matrix. (2) The steel valve for internal combustion engines according to claim 1, wherein the volume percentage of the ceramic particles in the composite layer is 20 to 92%. valve. (3) In the steel valve for an internal combustion engine according to claim 1 or 2, the ceramic particles have an average particle size of 0.
A steel valve for an internal combustion engine, characterized in that it has a diameter of 5 to 190μ. (4) In the steel valve for an internal combustion engine according to any one of claims 1 to 3, 50% or more of the contact surface is defined by the composite layer. A steel valve for internal combustion engines featuring: (5) The steel valve for an internal combustion engine according to any one of claims 1 to 4, characterized in that the depth of the central portion of the composite layer is 0.1 to 2.0 mm. Steel valves for internal combustion engines.