Patent Application
20080022962
The objects and advantages of the invention will become understood from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings in which like numerals designate like elements, and in which:
Next, embodiments of the present invention will be described.
An internal combustion piston used as an object to be treated of the present invention is not particularly limited as long as it is used in internal combustion engines. For example, any type of piston, such as a piston for a gasoline engine or a piston for a diesel engine, may be used.
The internal combustion piston used as an object to be treated is a piston produced by casting and forging of an aluminum-silicon alloy.
As for the internal combustion pistons described above, the entire surface may be used as an object to be treated; however, it is not always necessary to use the entire surface of the internal combustion piston as an object to be treated, and treatment according to the method of the present invention may be performed on only a part of the surface.
When the treatment according to the method of the present invention is performed on only a part of the surface of the internal combustion piston, the surface treatment according to the method of the present invention is preferably performed on at least one of the following portions:
Portion where flaws, such as cold shuts, are generated on a surface during casting
Portion where the stress is high, and strength is required
Portion at which weight saving is required
Casting surface of a product
Portion which requires abrasion resistance and heat resistance
Top surface (portion with which fuel and/or exhaust gas is brought into contact) of a piston when a photocatalytic function is imparted thereto
The injection powders used for injection are powders which contain an element for improving the mechanical strength of the alloy comprising the internal combustion piston when being diffused and penetrated in the alloy (hereinafter, referred to as a “reinforcing element” in the present invention”).
In the method for surface treatment of the present invention, in which the material for the internal combustion piston is an aluminum alloy, examples of the reinforcing element contained in the injection powders includes Fe, Mn, Zn, Ti, C, Si, Ni, Cr, W, Cu, Sn, and Zr. In consideration of the properties to be imparted to the internal combustion piston, one or more of the above elements may be contained in the injection powders.
When it is attempted to impart a photocatalytic function to the modified surface layer, an element exhibiting a photocatalytic function by oxidation is selected as the reinforcing element, or injection powders containing an element exhibiting a photocatalytic function by oxidation (referred to as a “photocatalytic element” in the present invention), besides the reinforcing element, are used.
Representative elements exhibiting a photocatalytic function by oxidation include, for example, Ti, Sn, Zn, Zr, and W, and one or more of the above elements may be contained in the injection powders.
Furthermore, when the photocatalytic function is imparted to the modified surface layer to be formed, the photocatalytic function can be improved when approximately 0.1 wt % to 10 wt % of a noble metal element (such as Pt, Pd, Ag, or Au) is included with respect to the photocatalytic element. In order to support the noble metal, for example, injection powders containing the above photocatalytic element and the noble metal element may be used, or the above noble element may be applied to the piston having a modified surface layer by injecting different injection powders containing the above noble metal element.
As one example, the relationship between the element contained in the injection powders and the effect obtained when the element is diffused and penetrated in the surface of the object to be treated is shown in the following Table 1.
When improvement in mechanical strength and impartment of the photocatalytic function are to be performed by a single blasting treatment, injection powders containing both the reinforcing element and the photocatalytic element may be used, or injection powders containing an element, such as Ti, Sn, Zn, Zr, or W, having properties of improving the mechanical strength of the piston alloy and properties of exhibiting a photocatalytic function by oxidation may be used. In addition, injection powders containing the reinforcing element and injection powders containing the photocatalytic element may be mixed together or may be injected separately.
In addition, after a modified surface layer is formed to obtain higher strength by injecting injection powders containing iron (Fe), nickel (Ni), copper (Cu), chromium (Cr), manganese (Mn), silicon (Si), or carbon (C) as a reinforcing element, which has no photocatalytic function by oxidation or has a small effect even when the photocatalytic function is obtained, by injecting injection powders containing titanium (Ti), tin (Sn), zinc (Zn), zirconium (Zr), tungsten (W), or the like as a photocatalytic element on the above modified surface layer, the photocatalytic function may be imparted thereto.
For example, when the reinforcing element and the photocatalytic element are each a metal, the injection powders described above may be formed of a pure metal of the element or may be formed of an alloy containing the metal.
The average particle diameters of the injection powders to be used is within a range from 20 μm to 400 μm. The reason the particle diameter of the injection powders is limited to the above range is that, when the particle diameter of the injection powders is less than 20 μm or more than 400 μm, even when the injection powders are brought to be collided with the surface of an internal combustion piston by injecting, the element in the injection powders cannot be diffused and penetrated in the piston surface.
The reason why the element in the injection powders cannot be diffused and penetrated in the piston surface when the injection powder having a diameter beyond the above range is not clearly understood. However, it is through that, when the particle diameter is less than 20 μm, since the mass is excessively small, sufficient heat generation necessary at the collided portion cannot be obtained, and when the particle diameter is more than 400 μm, since a predetermined injection rate cannot be obtained, or heat generated in collision is widely diffused, in both cases, a local increase in temperature necessary for modification elements in the injection powders to be diffused and penetrated cannot be obtained.
Unlike the invention disclosed in Japanese Patent KOKAI (LOPI) No. H5-86443 described as a related art in which the injection powders are mixed with other injection powders, such as shots (such as steel balls having a particle diameter of 400 μm) for shot blasting, the injection powders described above are separately injected.
The injection powders described above are injected on the above internal combustion piston used as an object to be treated at an injection speed of 80 m/s or more or an injection pressure of 0.3 MPa or more, and at an arc height amount of 0.1 N or more.
Various known blast machines and shot peening devices may be used as the device for this injection.
In addition, a direct pressure type, a suction type, and other injecting types may be used as the injection device; however, in this embodiment, as one example, the injection device of the direct pressure type is used.
The propellant used for injection is compressed gas, and as one example of the compressed gas, compressed air or compressed nitrogen may be used.
For example, in the direct pressure type, after injected abrasives in the form of powder and dust are separated in a recovery tank, the dust is sent to a dust collector provided with an exhaust fan via a duct, and the abrasive falls in the recovery tank and is stored at a lower portion thereof. At the lower portion of the recovery tank, a pressurized tank is provided with a dump valve interposed therebetween, and when there is no longer any abrasive in the pressurized tank, the dump valve is lowered, so that the powdered abrasive in the recovery tank is supplied to the pressurized tank. When the powder is supplied to the pressurized tank, since compressed gas is fed into this tank, and at the same time, the dump valve is closed, the pressure inside the tank is increased, and as a result, the powder is pushed out from a supply port provided at the bottom of the tank. For example, compressed nitrogen gas contained in a compressed gas cylinder is supplied to the supply port as compressed gas separately used as a reactive injection gas, and the powder is transported to a nozzle via a hose, so that the powder is injected from a nozzle tip together with the above gas at high velocity.
In a suction-type blast machine, when compressed gas used as a reactive injection gas is injected inside an injection nozzle for suction via a hose communicating with a compressed gas supply source, the inside of the nozzle has a negative pressure, then the powders in the tank is sucked into the nozzle via a hose used for abrasive due to the negative pressure, then injected from the nozzle tip.
In addition, instead of the above compressed air or compressed nitrogen, compressed low-temperature nitrogen gas may also be used, and when nitrogen gas is used as such, low-temperature gas, such as nitrogen gas passing through a cooling medium, or nitrogen gas at a temperature of 0° C. or less obtained by vaporizing liquid nitrogen, may be used as the low-temperature nitrogen gas. In this embodiment, nitrogen, which can be obtained at a reasonable cost by removing oxygen from liquid air, or in particular, vaporized gas of liquid nitrogen, from which gas at a low temperature of 0° C. or less can be easily obtained by vaporization, is used.
By the blasting treatment, a mixed fluid comprising the injection powders and nitrogen gas can be injected on the piston surface, and a nitride compound formed by a chemical reaction of the nitrogen gas with the injection powders and a piston having a nitrogen reactive component, such as aluminum, silicon, or iron, can be diffused and penetrated in the surface of the piston. In addition, even when dust is generated, for example, by injection of injection powders and collision between the injection powders and the piston, the probability of dust explosion and the like can be reduced.
As described above, when the injection powders are brought to be collided with the surface of the internal combustion piston, serving as an object to be treated, by injecting at an injection speed of 80 m/s or more or at an injection pressure of 0.3 MPa or more, the velocity of the injection powders is changed before and after the collision with the surface.
In consideration of the law of conservation of energy, a part of the energy corresponding to this change in velocity at collision as a grinding force on the piston surface, and hence surface oxides, such as oxides at cold shuts and the like generated in casting, are removed.
In addition, the other part of the energy generated at collision deforms collided portions of a surface of the metal product, and thermal energy is generated by internal friction caused by this deformation.
By repeated local heating and cooling of the piston surface by this thermal energy, minute surface flaws, such as cold shuts described above, generated on the piston surface are repaired. In addition, an alloy component in the vicinity of the surface of the piston is recrystallized thereby fine-grained.
Furthermore, besides the local temperature increase on the piston surface caused by the above thermal energy, a temperature increase similar to that described above also occurs in the injection powders, and an element in the injection powders thus heated undergoes adsorption on the piston surface which is locally heated, so that the element, in a fine-grained state, is diffused and penetrated in the piston surface.
As described above, in the internal combustion piston treated by the surface treatment method according to the present invention, the minute surface flaws, such as cold shuts, generated on the surface are repaired, and in addition, the element in the injection powders is diffused and penetrated in the piston from the surface thereof to a depth of approximately 20 μm and is dispersed in a fine-grained state among the alloy elements of the alloy comprising the piston, so that a modified surface layer is formed which has a uniformly fine-grained metal microstructure containing the above elements.
Since the surface flaws are repaired and regenerated as described above, stress concentration at the surface flaw portions does not occur, and since the modified surface layer is formed on the treated surface, an increase in strength of the internal combustion piston is realized.
In addition, in general, it has been known that in a cast aluminum alloy, iron makes a compound such as Al—Fe—Si coarser and degrades the toughness and corrosion resistance thereof, however, concomitant with the formation of the fine-grained microstructure described above, the abrasion resistance and the high-temperature strength are improved. In addition, in a copper alloy, Ni forms Al—Cu—Ni, and the high-temperature strength is improved.
When low-temperature nitrogen gas is used as compressed gas, by supplying nitrogen as compressed gas using a nitrogen bottle as a compressed gas supply source, injection powders are pressure-fed together with nitrogen to an injection nozzle and are then injected to the piston, which is placed in a cabinet.
For example, injection powders to be pressure-fed by low-temperature nitrogen gas at a pressure of 0.6 MPa and a temperature of 0° C. are appropriately mixed therewith and are then injected from a nozzle to the piston surface at a pressure of 0.6 MPa, a compressed gas temperature of 0° C., and a injection distance of 200 mm.
As described above, during a surface strengthening heat treatment by shot peening, since the piston surface is rapidly cooled to room temperature, surface strengthening, such as improvement in hardness and the effects of preventing aging deformation and secular deformation, can also be performed on the piston, which is a non-ferrous metal and has a low recrystallization temperature. In addition, when the low-temperature compressed gas is injected together with injection powders to the piston surface which is heated to a high temperature, such as the recrystallization temperature or more, by injecting the injection powders, a local surface area of the metal product injected with this nitrogen gas is rapidly cooled from the high temperature, such as the recrystallization temperature or more, due to collision with the injected injection powders to room temperature or less, and the microstructure of the metal product at the surface portion thereof is preferably fine-grained, so that the mechanical strength can be increased, and the aging deformation and/or the secular deformation can be prevented. That is, in the embodiment of the present invention, because of the low temperature of the nitrogen gas, since the metal is not liable to be deformed, and sliding between grain boundaries is not liable to occur, energy generated by the collision with the injection powders is not absorbed, and the temperature at the surface becomes high; hence, as a result, by rapid heating and rapid cooling, the microstructure can be fine-grained and can have a higher density.
When the injection powders contain a nitrogen reactive component, such as Cr or Mo, besides Al, the piston surface is nitrided. In particular, when silicon nitride is formed on the piston surface by reaction of nitride gas with silicon, which is a piston alloy element, or more particularly, when silicon nitride is formed by reaction of nitrogen gas with silicon at a high concentration, the microstructure is uniformly fine-grained.
It is known that silicon nitride, a non-oxide ceramic, is a heat resistant structural material having a high-temperature strength, superior high-temperature corrosion resistance, and high abrasion resistance, and in a high temperature region in which the piston of the present invention is used, significant improvement in strength can be obtained.
When injection of the injection powders is performed not only for improving mechanical strength of the piston but also for imparting a photocatalytic function to the formed modified surface layer, injection powders containing a photocatalytic element as well as the above-described reinforcing element may be used, or injection powders containing an element, such as Ti, Sn, Zn, Zr, or W, which functions as a reinforcing element as well as a photocatalytic element, may also be used. Furthermore, a mixture of injection powders containing a reinforcing element and injection powders containing a photocatalytic element may be injected on a piston used for engines.
In addition, before or after the injection powders containing a reinforcing element are injected on the internal combustion piston used as an object to be treated, the injection powders containing a photocatalytic element may be injected. Furthermore, for example, the injection powders containing a reinforcing element and the injection powders containing a photocatalytic element may be simultaneously injected by using two blast machines.
When the photocatalytic element contained in injection powders is diffused and penetrated in the piston surface as described above, it is oxidized by reaction, for example, with oxygen in the compressed air used for injection or oxygen in ambient air and is then diffused and penetrated in the vicinity of the piston surface.
The oxidation state of the photocatalytic element is not uniform in the modified surface layer to be formed but has a structure in which bonding with oxygen is reduced from the surface of the modified layer to the inside of the modified layer.
The modified layer containing the photocatalytic element bonded with oxygen in an unstable state as described above exhibits a photocatalytic function without UV irradiation, even at room temperature.
Next, experimental examples of surface treatment by the method according to the present invention will be described.
By performing surface treatment of the method according to the present invention, it is confirmed whether surface flaws of an internal combustion piston can be repaired, and whether a modified surface layer can be formed from the surface thereof to a predetermined depth.
By using materials shown in Table 4 below, injection powders were injected on an Al—Si composition (internal combustion piston) shown in Table 2 under the treatment conditions shown in Table 3.
After a dye was applied to the surface of the piston for a gasoline engine used as an object to be tested, the dye was removed by washing, and the color development of the dye remaining in flaws (recesses of cold shuts) on the piston surface was confirmed, thus performing a dye penetrant test for checking the presence of the flaws on the piston surface.
As shown in
In addition, according to the observation results of the state of the piston surface before and after the surface treatment of the present invention using SEM images, although numerous flaws (cold shuts) were observed on the untreated piston surface, as shown in
After the method for surface treatment according to the present invention was performed, a modified surface portion of the piston was cut out, and a cross-section thereof was observed. The result observed by a metallurgical microscope is shown in
In all the results described above, it was confirmed that the modified surface layer was formed at a surface layer portion from the surface of the piston to a depth of approximately 20 μm.
As is apparent from
As shown in
In the case in which a mixed fluid is injected by using compressed nitrogen gas, when the piston is made of a metal material always containing Al, which is a nitrogen reactive component, and also containing Si, Cr, Ti. or the like, and when the injection powders are made of a metal similar thereto, a nitride layer, such as Si3N4, TiN, VN, AlN, or CrN, is formed on the piston surface by diffusion and penetration, and at the same time, a nitride is also generated in a surface coat formed by the injected injection powders. When the piston surface is the same as described above, and the injection powders are made, for example, of a ceramic having no nitrogen reactive component, a nitride is formed only on the piston surface. When the piston and the injection powders both have nitrogen reactive components, nitrides are formed on the piston surface and the coat. In particular, silicon nitride has superior high-temperature corrosion resistance and high-temperature strength as a heat-resistant structural material and, in addition, forms a modified layer having superior abrasion resistance.
In addition, also in the following case, film formation can be performed by injection of injection powders. That is, when the piston is made of a metal material containing Ti, Al, Cr, or the like or a mixture of the above metal and a ceramic, and when the injection powders are formed of the same material as that for the piston material, nitrides are formed on both the piston and the coat.
That is, when only the piston contains a nitride reactive component, a nitride is formed on the piston surface.
As shown in
By performing the surface treatment method according to the present invention, it is confirmed whether the fatigue strength and the tensile strength of a metal product used as an object to be treated are improved.
The test method and test conditions were as follows.
The shape and the size of test pieces used for the fatigue test and those for the tensile strength test are shown in
The fatigue test was performed for a test piece treated by the surface treatment method according to the present invention (example) and an untreated test piece (comparative example) in a treatment region shown by an arrow in
The injection powders and injecting method used for the surface modification of the example were the same as shown in Table 3, and the injection powders were injected for 30 seconds while the test piece shown in
For the test piece treated by the surface treatment method according to the present invention, as described above, and the untreated test piece, measurement of the fatigue strength was performed at room temperature (25° C.) and a high temperature (250° C.) respectively.
The tensile test was performed for a test piece treated by the surface treatment method according to the present invention in a treatment region shown by an arrow in
The injection powders and injection fluid used for the surface modification of the example were the same as shown in Table 3, and the injection powders were injected for 30 seconds while the test piece shown in
For the test piece treated by the surface treatment method according to the present invention, as described above, and the untreated test piece, measurement of the tensile strength was performed at room temperature (25° C.) and a high temperature (250° C.) respectively.
According to the results of the above fatigue test, it was confirmed that the test piece treated by the surface treatment of the present invention was improved with respect to that of the untreated test piece by 12% at room temperature and by 11% at a high temperature, in terms of the amplitude stress (number of amplitude cycles: 108·−3σ value) (see
This indicates that the strength in a high temperature region in which the piston is to be used is improved by 10% or more.
According to the results of the above tensile test, it was confirmed that the test piece treated by the surface treatment of the present invention was improved with respect to that of the untreated test piece by 4% at room temperature and by 7% at a high temperature, in terms of the tensile strength (−3σ value) (see
The component distribution of a modified layer obtained by injecting high-speed tool steel powders using nitrogen gas was as follows.
It is confirmed whether a modified surface layer formed by injecting injection powders containing an element exhibiting a photocatalytic function by oxidation exhibits a fuel modification effect without UV irradiation and in a room-temperature atmosphere.
Injection powders containing titanium, tin, or zinc, i.e., the reinforcing element described above as well as an element exhibiting a photocatalytic function by oxidation, were injected on a top surface of the internal combustion piston shown in Table 6, so that a modified surface layer was formed.
The injection powders used in this experiment were the same as shown in Table 7, and the treatment was performed under the conditions shown in Table 8.
Results Using Titanium-Based Injection Powders
Surface analysis of a cross-sectional portion obtained by cutting the piston for a gasoline engine injected with the above titanium-based injection powders was performed by SEM-EDX, and the results are shown in
From the above analytical results, it was confirmed that a uniformly fine-grained modified surface layer was formed by diffusion and penetration of the titanium component from a surface of the piston (Al) to the inside.
This modified surface layer had a composition in which an Si component in an aluminum base material was also present in a fine-grained state (
From the analytical results by SEM-EDX, it was confirmed that an oxidation state was formed since oxygen was detected in the modified surface layer formed by diffusion and penetration of the titanium elements. Specifically, it was confirmed that titanium oxide, which is a known photocatalytic material, was generated. It was also confirmed that in the oxidation state of this modified surface layer, the oxide concentration gradually decreased from the surface thereof to the inside (
Results Using Tin-Based Injection Powders
Surface analysis of a cross-sectional portion obtained by cutting the piston for a gasoline engine injected with the above titanium-based injection powders was performed by SEM-EDX, and the results are shown in
From the above analytical results, a coat including the tin component was formed on the piston surface, and the formation of a uniformly fine-grained modified surface layer was confirmed.
This modified surface layer had a microstructure in which aluminum and silicon components in the piston, which were base materials, were uniformly distributed in a fine-grained state.
Furthermore, from the analytical results by SEM-EDX, it was confirmed that an oxidation state was formed since oxygen was detected in the modified surface layer. Specifically, it was confirmed that tin oxide, which is a known photocatalytic material, was generated. It was also confirmed that in the oxidation state of this modified surface layer, the oxide concentration gradually decreased from the surface thereof to the inside (
Results Using Zinc-Based Injection Powders
Surface analysis of a cross-sectional portion obtained by cutting the piston for a gasoline engine injected with the above zinc-based injection powders was performed by SEM-EDX, and the results are shown in
From the above analytical results, it was confirmed that a uniformly fine-grained modified surface layer was formed by diffusion and penetration of the zinc component from the piston (Al) surface to the inside.
This modified surface layer had a composition in which an Si component in an aluminum base material was also present in a fine-grained state.
From the analytical results by SEM-EDX, it was confirmed that an oxidation state was formed since oxygen was detected in the modified surface layer. Specifically, it was confirmed that zinc oxide, which is a known photocatalytic material, was generated. It was also confirmed that in the oxidation state of this modified surface layer, the oxide concentration gradually decreased from the surface thereof to the inside (
Of the pistons for gasoline engines each having the modified surface layer thus formed, a fuel (light oil) was brought into contact with the pistons obtained by injecting the titanium-based injection powders and the tin-based injection powders in a dark place at room temperature, and component analysis was then performed by pyrolysis GC-MS measurement.
As a comparative example, a fuel was brought into contact with an internal combustion piston which was similar to that described above and which had a modified surface layer formed by injecting injection powders made of high-speed tool steel having an average particle diameter of 50 μm, and component analysis was then performed by pyrolysis GC-MS measurement. In addition, GC-MS measurement was also performed for untreated light oil, and the results were compared with each other.
A graph of the pyrolysis GC-MS measurement results obtained from the light oil sample of the comparative example which was brought into contact with the piston modified the surface by injecting injection powders made of high-speed tool steel containing iron (Fe) as a reinforcing element showed a waveform which is not changed from that of a graph of the pyrolysis GC-MS measurement results obtained from the untreated light oil sample; hence, it was confirmed that modification of the fuel did not occur, or even if modification did occur, the degree thereof was very low.
On the other hand, as for the light oil samples brought into contact with the pistons each having an unstable compound layer in which the oxygen bonding amount decreased from the surface to the inside, the compound layers being formed by injecting injection powders containing titanium (Ti) and tin (Sn), each of which is an element exhibiting a photocatalytic function by oxidation, it was found from the results of the change in pyrolytic behavior, that chain aliphatic hydrocarbons, which are primary light oil components, were decomposed, hence, it was confirmed that decomposition of light oil was facilitated.
In the graphs showing the pyrolysis GC-MS measurement results, in general, C13 to C25 are aliphatic hydrocarbons, which are primary components of light oil, and the aliphatic hydrocarbons periodically observed from C13 to the right side in the graph are constituent elements originally contained in the light oil.
In the pyrolysis analyzer used for this measurement, because of the features of this analyzer, the temperature was increased to 700° C. for a very short time of 1 second or less, and pyrolyzed and evaporated components were introduced into an instant analysis line; hence, although heating was performed in the air, complete combustion could not be performed.
Peaks around the hydrocarbons (C13 to C25) and low molecular weight components observed from the hydrocarbon of C13 to the left side in the graph are pyrolyzed products from light oil. Hence, the pyrolytic properties can be confirmed from the differences between pyrolyzed products (1) to (7) shown in the figures.
Since the graph of the pyrolysis GC-MS measurement result obtained from the light oil sample which was brought into contact with the piston treated by injecting injection powders containing tin, shown in
When pyrolysis of light oil is facilitated, combustion is facilitated, and the molecular weights of hydrocarbons used as an agent for reducing NOx is increased. Hence, it is apparent that the change described above contributes to improvement in combustion (reduction in CO2 exhaust amount) and reduction in NOx exhaust amount.
In addition, since a flame propagation speed (combustion inside the cylinder) is improved by improvement in pyrolytic properties, ignition lag in a high rotation speed region is prevented, and knocking is also reduced. Furthermore, an effect of decreasing the combustion chamber temperature and of increasing the torque in a high rotation speed region is also obtained.
Accordingly, with the piston treated by the surface treatment described above, besides the improvement in fuel consumption due to modification of the fuel, the amount of exhaust CO2 gas is reduced by complete combustion or a state close thereto. In addition, since the temperature inside the combustion chamber is decreased, the generation of NOx is reduced, so that the amount of exhaust gas is reduced.
Furthermore, since the fuel modification as described above is performed when the piston having a modified surface layer formed by the method according to the present invention is brought into contact with the fuel in a dark place at room temperature, irradiation of light and high-temperature conditions are not required for the fuel modification, hence, the fuel modification can be performed even at a starting stage of the engine, when the temperature of the piston is not increased, so that improvement in combustion properties and reduction in generation of CO2 gas, NOx, and the like can be expected immediately after the engine is started, by virtue of the fuel modification.
After pistons having modified surface layers formed on the top surfaces by injecting injection powders containing titanium (Ti) or tin (Sn) and untreated pistons were both fitted in an inline four-cylinder engine, the engine was operated for 20 hours, and the exhaust gas temperature and the carbon adhesion on the top surface were observed.
In this example, the untreated pistons were fitted in second and fourth cylinders, a piston injected with powdered titanium was fitted in the first cylinder, and a piston injected with powdered tin was fitted in the third cylinder.
The engine used in the experiment and other experiment conditions are shown in Table 9.
Carbon Adhesion State
The results of carbon adhesion to the pistons are shown in Table 10.
Exhaust-Gas Temperature
According to the measurement results of temperatures (average value for 60 seconds) of exhaust gas discharged from the cylinders, although the exhaust-gas temperatures of the second and fourth cylinders fitted with the untreated pistons were approximately 670° C., it was confirmed that the exhaust-gas temperature of the first cylinder fitted with the piston treated by injecting injection powders containing powdered tin and that of the third cylinder fitted with the piston treated by injecting injection powders containing powdered titanium were lower by approximately 20° C. (approximately 3% lower when the exhaust-gas temperature from the cylinder fitted with the untreated piston is defined as 100) (see
Discussion of Experimental Results
From the experimental results described above, with the piston having a modified surface layer formed by the method according to the present invention, it is believed that, since the combustion properties in the cylinder were improved because of the fuel modification using the photocatalytic function of the modified surface layer, the generation of carbon itself is reduced, or even if carbon is generated, it is decomposed by the photocatalytic function. Hence, degradation in fuel consumption caused by the change in volume does not occur, and it is confirmed that improvement in combustion efficiency can be stably obtained for a long period of time.
In addition, the reason for the decrease in exhaust-gas temperature from the cylinder in which the piston having a modified surface layer formed by the method according to the present invention is fitted is believed to be because fuel in the cylinder is completely combusted or is combusted in a state close to complete combustion because of fuel modification due to the photocatalytic function, no afterburning occurs in an exhaust pipe, and as a result, the exhaust-gas temperature is decreased.
According to the results described above, when using the piston having a modified surface layer in the top surface thereof formed by the method of the present invention to have a photocatalytic function, the combustion in the cylinder can be performed in a complete combustion state or in a state close thereto, and hence the fuel consumption is improved, and the amount of fuel can be reduced. In addition, concomitant therewith, reduction in exhaust amount of CO2 gas, decrease in combustion temperature, and reducing of generation of NOx due to an increase in molecular weight of hydrocarbons used as a reducing agent for NOx by fuel modification can be expected.
Thus the broadest claims that follow are not directed to a machine that is configured in a specific way. Instead, the broadest claims are intended to protect the heart or essence of this breakthrough invention. This invention is clearly new and useful. Moreover, it was not obvious to those of ordinary skill in the art at the time it was made, in view of the prior art when considered as a whole.
Moreover, in view of the revolutionary nature of this invention, it is clearly a pioneering invention. As such, the claims that follow are entitled to very broad interpretation so as to protect the heart of this invention, as a matter of law.
It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
Additionally although individual features may be included in different claims, these may possibly be advantageously combined and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In further addition singular references do not exclude a plurality. Thus references to “a”, “an”, “first”, “second” etc. do not preclude a plurality.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-206947 | Jul 2006 | JP | national |
| 2007-166713 | Jun 2007 | JP | national |
