Patent Application
20090241654
The present invention relates to a thermal gas flowmeter, and an exhaust gas recirculation system using the thermal gas flowmeter.
In order to measure the flow rate of gas to be measured for a long time, the certain accuracy is desired to be maintained over the long time in operation. When the gas to be measured contains various components and material, however, it is difficult to maintain the accurate measurement for the long time. Measurement of the flow rate of an exhaust gas in an exhaust gas recirculation system of an internal combustion engine will be described below as-one example.
The exhaust gas recirculation (hereinafter referred to as an “EGR”) system is a system for returning an exhaust gas discharged from the internal combustion engine, such as a vehicle, to an intake side. The system is designed to mix a CO2 gas component with a small ratio of specific heat contained in the exhaust gas with intake air, thereby decreasing the combustion temperature to reduce the amount of nitrogen oxide NOx of the exhaust gas. In order to reduce the amount of nitrogen oxide NOx, it is necessary to control the amount of EGR with high accuracy. In a gasoline engine, for example, when the flow rate of recirculated exhaust gas is not controlled accurately, there poses a problem that a desired torque output is not obtained, or an air fuel ratio is not controlled appropriately. Further, for example, in a diesel engine, the excessive amount of EGR leads to an increase in amount of soot (particulate molecule, which is hereinafter referred to as a “PM”) of the exhaust gas. The amount of EGR needs to be controlled with high accuracy so as to reduce occurrence of PM while decreasing the amount of NOx.
The present EGR system performs indirect control which involves estimating the amount of EGR based on information on the intake side, for example, information about an air flow sensor for measuring the amount of air on the intake side, and about the degree of opening of a throttle. However, in order to satisfy emission regulations more strictly required domestically and internationally in the future, it is necessary to develop a gas flowmeter for directly measuring the EGR amount.
It has been reported in development of the gas flowmeter for directly measuring the flow rate of EGR that PMs contained in the exhaust gas adhere to the surface of a measuring element to reduce the accuracy of measurement. On the other hand, JP-A-2007-101426 (Patent Document 1) discloses means for preventing the adhesion of PM by heating an element.
In the case of exhaust gas, the exhaust gas can have different properties, including compositions, depending on the state of the internal combustion engine, which may result in different polluted states of the element. For example, when the temperature of exhaust gas is equal to or higher than a dew-point temperature, the PM is a main component of pollution. For the exhaust gas temperature below the dew-point temperature, pollution may be caused due to condensed water contained in the exhaust gas.
Thus, it is an object of the invention to provide a flow rate measuring element, and a flowmeter which can maintain the necessary accuracy of measurement of the exhaust gas even with different components and even in the case where the causes for pollution of the measuring element of the flowmeter are different.
Further, it is another object of the invention to provide an exhaust gas recirculation system for a vehicle which controls the flow rate of recirculated gas with high accuracy.
According to one aspect of the invention, a thermal gas flowmeter is provided which includes a heating resistor disposed in a flow of gas to be measured, and an external circuit electrically connected to the heating resistor for outputting a signal according to a flow rate of the gas to be measured. The gas flowmeter is adapted to measure the flow rate of the gas from the amount of heat taken from the heating resistor.
The thermal gas flowmeter includes a heating portion constructed of an electrically insulating base, the heating resistor formed at the base, and a protective layer formed over the base and the heating resistor; the external circuit for outputting a signal according to the flow rate of the gas to be measured obtained from the heating portion; and a lead for electrically connecting the heating portion with the external circuit. The heating resistor is disposed in the flow of the gas to be measured, and thus the mass flow rate of the gas can be detected from a value of current flowing through the heating resistor. The external circuit is electrically connected to the heating resistor, and outputs the signal according to the flow rate of the gas to be measured, which signal is obtained through the heating resistor, to an engine controller or the like.
In order to prevent adhesion of PM and the like to the flowmeter, the heating resistor of the flowmeter is heated. The heating temperature at that time is preferably equal to or higher than a vapor film formation temperature at which a vapor film can be formed around the flowmeter, or equal to or higher than 600° C. Further, the heating resistor is controlled to be heated at a temperature Twsn or more represented by the following formula:
Twsn=TL+(314−TL)/(1+β1/2)
β=λWCWρW/λLCLρL
where TL is a temperature of droplet,
λL is a thermal conductivity of water,
CL is a specific heat of water,
ρL is a density of water,
λW is a thermal conductivity of a coat material,
CW is a specific heat of the coat material, and
ρW is a density of the coat material.
The heating of the heating resistor is effective, in particular, when the temperature of the gas to be measured is equal to or lower than a dew-point temperature. In application to the EGR system or the like of the internal combustion engine, the heating resistor can be heated at a temperature equal to or higher than the vapor film forming temperature for forming the vapor film when the temperature of exhaust gas is lower than the dew-point temperature, or when the flow rate of exhaust gas is measured on the rear stage side of an exhaust gas cooler.
Even when the temperature of the gas to be measured is higher than the dew-point temperature, the heating resistor is preferably heated at a temperature of 350° C. or more because of the possibility of adhesion of PM. The heating resistor is heated at a temperature equal to or higher than the vapor film forming temperature for forming the vapor film when the temperature of the gas to be measured is equal to or lower than the dew-point temperature. When the temperature of the gas to be measured reaches a predetermined temperature equal to or higher than the dew-point temperature, the measurement of flow rate can be continued at the same temperature, but may be performed by decreasing the temperature of the heating resistor down to 350° C.
In order to heat the heating resistor at such a temperature, the protective layer needs to have a heatproof temperature equal to or higher than the heating temperature of the heating resistor. The transition point of glass of the protective layer may be preferably a temperature equal to or higher than 650° C. The protective layer may preferably include a composition containing 30 to 60% by weight of SiO2, and an oxide selected from the group consisting of at least Al2O3, an alkaline earth oxide, ZrO2, and a rare earth oxide, specifically, 5 to 20% by weight of Al2O3, 25 to 50% by weight of alkaline earth oxide, 1 to 15% by weight of ZrO2, and 0 to 20% by weight of rare earth oxide in terms of oxide. The thermal expansion coefficient of the glass is determined taking into consideration thermal expansion coefficients of the insulating base and metal to be preferably 50 to 80×10−7/° C.
The thermal gas flowmeter is suitable for use in an exhaust gas recirculation system for recirculating exhaust gas back to the intake side. The thermal gas flowmeter is disposed in a pipe for recirculating the exhaust gas from the exhaust side back to the intake side, and the flow rate of the recirculated exhaust gas is measured, while a flow rate adjustment valve can be controlled by a flow rate adjustment valve controller for adjusting the amount of exhaust gas recirculated back to the intake side using information about the flow rate.
A cooler for cooling the exhaust gas recirculated in the pipe is provided in the exhaust gas recirculation system. The thermal gas flowmeter can measure the temperature of the recirculated exhaust gas. Furthermore, the gas flowmeters can be provided on the upstream and downstream sides of the cooler.
When the thermal gas flowmeter is provided in the exhaust gas recirculation system, in order to avoid the adhesion of PM or the like to the flowmeter, the exhaust gas cannot be recirculated until the heating element is controlled to be heated at a temperature equal to or higher than the vapor film forming temperature for forming the vapor film, or the heating element can be controlled to be heated at a temperature equal to or higher than the vapor film forming temperature for forming the vapor film before the engine is operated.
Accordingly, the invention can provide the flow rate measuring element and the flowmeter which can maintain the necessary accuracy of measurement, and thus can control the flow rate of EGR using the flowmeter with high accuracy.
The above and other objects, features and advantages-of the present invention will become apparent from the following description taken in connection with the accompanying drawings, in which:
Now, a gas flowmeter will be described below in detail.
The gas flowmeter includes a heating resistor, a controller for controlling heat generation of the heating resistor, and an external circuit for outputting a signal according to the flow rate of gas to be measured. The gas flowmeter is disposed in a flow path for the gas to be measured, and detects the mass flow rate of the gas based on a change in electric resistance of the heating resistor.
The heating resistor includes a heating portion and a lead for electrically connecting the heating portion to the controller. The heating portion has a metal resistor formed on a base having electric insulation (electrically insulating base), and a coating layer for protecting the surface of the metal resistor. The end of the metal resistor is electrically connected to the lead by welding or the like.
An exhaust gas recirculation system is a system for recirculating the exhaust gas of the internal combustion engine back to the intake side. The flow rate of fluid recirculated from the exhaust side back to the intake side needs to be adjusted under control of a flow rate adjustment valve. The gas flowmeter is disposed in a pipe or the like for recirculation to measure the flow rate of gas. Based on the amount measured, the flow rate of exhaust gas recirculated back to the intake side is controlled.
The exhaust gas recirculation system can be provided with a cooler for cooling the recirculated exhaust gas. In the exhaust gas recirculation system including the cooler, the PM components and the like in the exhaust gas are solidified to adhere to the cooler when cooling the exhaust gas by the cooler, thus causing clogging of the cooler, resulting in a decreased flow rate. Thus, the flow rates of exhaust gas before and after the cooler are respectively measured to enable measurement of the degree of clogging.
The set position of the gas flowmeter 7 can be any other position on the exhaust side, but needs to be positioned taking into consideration a heatproof temperature of a member used in the flowmeter. A seal member or the like of a control circuit of the flowmeter includes, in use, a resin member which may be degraded due to a high-temperature exhaust gas. Thus, the flowmeter having low heat resistance and formed of resin or the like may be preferably set on the downstream side (intake side) of the EGR cooler 15. In particular, the optimum set position of the gas flowmeter 7 is provided on the upstream side of the EGR valve as well as on the downstream side (intake side) of the EGR cooler 15 as shown in
Provision of a plurality of flow meters can measure the flow rates of the gas from the respective devices, including the cooler, and the valve, thereby enabling observation or the like of the result of control of each device.
The flowmeter using silica glass of the invention has excellent heat resistance as compared to a conventional flowmeter for an air flow sensor using lead glass. Thus, application of the flowmeter of the invention to measurement of the flow rate on the intake side can prevent the adhesion of pollution material contained in the gas on the intake side by heating the flowmeter at high temperature, thereby effectively improving the accuracy of measurement of the flow rate of the gas on the intake side.
The flow rate measuring element can include the electrically insulating base 5 made of insulating inorganic material, such as alumina, or quartz, or a metal material having an insulating inorganic material formed on its surface. The electrically insulating base 5 can have any one of a columnar shape, a flat plate shape, and a multangular shape, in addition to the cylindrical shape shown in
The lead 2, and the metal resistor 4 in use can contain noble metal, such as platinum, iridium, rhodium, palladium, gold, and silver. Alternatively, alloy material, including an alloy of the above noble metal and non-noble metal, such as nickel or cobalt, may be used. Otherwise, a material having a noble metal formed on a surface of a non-noble metal material can be used.
The lead 2 is made of the above material, and has a section in a circular shape, an ellipsoidal shape, a flat plate shape, or a multangular shape, and preferably in the circular or ellipsoidal shape. When the leads 2 are inserted into both ends of the electrically insulating base 5, the sectional dimension of the lead 2 is smaller than the inner diameter of the electrically insulating base 5.
The metal resistor 4 is disposed on the surface of the electrically insulating base. The metal resistor 4 is formed by winding a wire rod around the surface of the electrically insulating base, or formed as a wiring film on a surface of the electrically insulating base. Methods for forming the wiring film can include in use a physical vapor deposition method (PDV), a chemical vapor deposition method (CVD), and plating.
In forming the metal resistor using a wire rod, the material and diameter of the wire rod, and the length of the winding, a tensile force applied to the wire rod in winding, and the like are adjusted such that a resistance value of the resistor is a predetermined value. The diameter of the wire rod is preferably in a range of 0.1 to 100 μm, and more preferably 1 to 50 μm.
In forming the metal resistor in the form of film, the shape of the resistor can be formed in a shape appropriate for the shape of the electrically insulating base, for example, in a spiral shape or a meandering shape. The resistance of the resistor is adjusted to the predetermined value by the material, shape, and thickness of the formed film. The thickness of the film may be preferably in a range of 0.1 to 100 μm according to the forming method, material, and shape of the film.
The metal resistor does not need to be provided in direct contact with the electrically insulating base. An intermediate layer, such as a stress relaxation layer or a reaction inhibiting layer, may be formed between the electrically insulating base and the metal resistor. Such an intermediate layer can be formed not only in the case of employing the wiring film, but also in the case of employing the wire rod in the same way. The connection member 6 is made of glass, or a mixture of ceramics, such as alumina, or zirconia, and glass, in use. Such glass or ceramics is mixed with solvent, such as terpineol, screen oil, or butyl carbitol, to form a paste. The paste is applied to the leads and/or electrically insulating base, and then calcined, which can connect the leads to the electrically insulating base. Glass materials include, for example, amorphous or crystalline borosilicate glass, alumina-silicate glass, and alumina-borosilicate glass. Ceramics include, for example, alumina, zirconia, silicon nitride, and silicon carbide. The viscosity of the paste can be adjusted by the amount of solvent, or binder, such as ethylcellulose.
The flow rate measuring element is used for measuring the flow rate of the intake gas or exhaust gas. In particular, in setting the measuring element in the exhaust gas, various kinds of materials, including PMs contained in the exhaust gas, exhaust condensed water, and metal components eluted by the exhaust condensed water may adhere to the surface of the element, which leads to degradation of the accuracy of measurement. In order to prevent the adhesion of such materials, it is necessary to energize and heat the element thereby to prevent the adhesion of the materials to the element.
The protective coat is made of inorganic material, in particular, glass material, in use. The glass material can be combined with ceramic or metal if necessary. The protective coat can be formed by adding organic solvent, such as terpineol, or butyl carbitol, to pulverized inorganic material to make a paste, and by applying and burning the paste. The viscosity of the paste can be adjusted by the amount of solvent, or binder to be mixed. The binder is, for example, ethylcellulose. The grain size of glass pulverized in making the paste is preferably equal to or less than 200 μm, and more preferably equal to or less than 100 μm. For the grain size larger than 200 μm, the glass is not sufficiently softened in calcining, thus forming irregularities in the-protective coat after calcination. When the protective coat is made using glass, the temperature of calcination is preferably equal to or less than 1300° C. The calcination at a temperature higher than 1300° C. degrades the strength of the lead or metal resistor, thus resulting in a high possibility of disconnection or breakage. The thickness of the protective coat is preferably in a range of 0.5 to 500 μm. The protective coat having the thickness below 0.5 μm cannot sufficiently coat the metal resistor. The protective coat having the thickness larger than 500 μm results in reduced sensitivity of measurement.
When the protective coat is made of glass material, the heating of the protective coat at a temperature of 600° C. or more can prevent the pollution depending on the temperature of the droplet. Thus, the heating element is preferably heated at a temperature of 600° C. or more. In order to set the above heating temperature, the transition point of the glass material needs to be equal to or more than 650° C. The transition point of the glass material is preferably equal to or more than 700° C.
The thermal expansion coefficient of the glass forming the protective coat needs to be 50 to 80×10−7/° C. from a viewpoint of the relationship among the electrically insulating base, the metal resistor, and the lead, and more preferably 55 to 70×10−7/20 C. For example, when alumina is used as the insulating base, the thermal expansion coefficient of the base is about 73×10−7/° C. The glass material coating the insulating base has a thermal expansion coefficient slightly smaller than that of the base so as to give a compression stress. Thus, the thermal expansion coefficient of the glass material is preferably about 60×10−7/° C.
The composition of the glass used in the protective coat will be described below.
The amount of SiO2 is preferably not less than 30% by weight nor more than 60% by weight, and more preferably equal to or more than 40% by weight. This is because the transition point of the glass becomes lower than 650° C. when the amount of SiO2 is less than 30% by weight, and the calcination temperature becomes higher than 1300° C. when the amount of SiO2 is more than 60% by weight.
Al2O3 has an effect of increasing the transition point of glass, and thus the amount of Al2O3 is preferably not less than 5% by weight nor more than 20% by weight. This is because the effect of increasing the transition point is not exhibited when the amount of the Al2O3 is less than 5% by weight, and the calcination temperature becomes higher than 1300° C. when the amount of the Al2O3 is more than 20% by weight.
Alkaline earth oxides have an effect of decreasing the high-temperature viscosity of the glass, while increasing the thermal expansion coefficient of the glass, and thus the amount of the alkaline earth oxide is preferably not less than 25% by weight nor more than 50% by weight. This is because the effect of improving the thermal expansion coefficient is not exhibited when the amount of alkaline earth oxide is less than 25% by weight, and the thermal expansion coefficient becomes larger than 80×10−7° C. when the amount of alkaline earth oxide is more than 50% by weight.
ZrO2 has an effect of improving corrosion resistance of the glass, and thus the amount of ZrO2 is preferably not less than 1% by weight nor more than 15% by weight. This is because the effect of improving the corrosion resistance is not exhibited when the amount of ZrO2 is below 1% by weight, and the thermal expansion coefficient of the glass becomes larger than 80×10−7° C. when the amount of ZrO2 is more than 15% by weight.
Addition of a rare earth oxide has effects of increasing the transition point of the glass, and of increasing the thermal expansion coefficient thereof. The amount of the rare earth oxide is preferably equal to or less than 20% by weight, and more preferably equal to or less than 10% by weight. This is because the thermal expansion coefficient becomes larger than 80×10−7° C. when the amount of the rare earth oxide is more than 20% by weight.
B2O3, ZnO, or the like can be added to the glass, if necessary. B2O3 is effective for improving the high-temperature viscosity of the glass. When the amount of B2O3 is more than 10% by weight, the transition point of the glass becomes lower than 650° C., which is not preferable. ZnO is effective for improving the corrosion resistance. Thus, when the amount of ZnO is more than 5% by weight, the transition point of the glass becomes lower than 650° C., which is not preferable.
The protective coat can also be made, in use, of ceramic stable in a high-temperature exhaust gas atmosphere, such as alumina oxide, zirconia oxide, silicon carbide, silicon nitride, or mullite, in addition to the glass if necessary. Such ceramic can be formed as the protective coat by a flame spraying process, a sputtering process, or a sol-gel process.
The protective coat layer of the flow rate measuring element is formed by using glass. First, a method for making glass to be used as the protective layer of the flow rate measuring element will be specifically described below.
A certain amount of raw material powder was measured and introduced into a platinum crucible, mixed, and then heated and dissolved in an electric oven at a temperature of 1000 to 1600° C. depending on the composition. After the raw material was sufficiently melted, a platinum stirring blade was inserted into a glass melt, and the glass melt was stirred with the blade for about forty minutes. After removing the stirring blade, the material was allowed to stand still for twenty minutes. The glass melt was flown into a jig made of black lead, and quenched to obtain each glass block of about 100 g in weight. Thereafter, each glass was heated again, and gradually cooled at a cooling rate of 1 to 2° C./minute to perform a straightening process.
A test piece having a size of 4×4×15 mm was cut out of the obtained glass block, and a thermal expansion coefficient and a transition point of the piece were measured. The thus-obtained glass block was pulverized, and the pulverized powder was mixed with organic solvent to manufacture a glass paste. The glass paste was applied to the element 1 without the protective coat, and then calcined. The calcination temperature of the test piece was determined.
Table 1 shows examples of glass compositions. The compositions of glasses of Examples 1 to 11 were manufactured by changing the amount of SiO2. The compositions of glasses of Examples 12 to 18 were manufactured by changing the amount of Al2O3. The compositions of glasses of Examples 19 to 26 were manufactured by changing the amount of alkaline earth oxide. The compositions of glasses of Examples 27 to 31 were manufactured by changing the amount of ZrO2. The compositions of glasses of Examples 32 to 37 were manufactured by changing the amount of Gd2O3.
The glass having a transition point higher than 650° C., a temperature for forming the protective coat of 1300° C. or less, and a thermal expansion coefficient of 50 to 80×10−7/° C. is appropriate for the protective coat material. Taking into consideration these conditions, as shown in Table 1, glass appropriate for the protective coat material was manufactured to contain 30 to 60% by weight of SiO2, 5 to 20% by weight of Al2O3, 25 to 50% by weight of alkaline earth oxide, 1 to 15% by weight of ZrO2, and 0 to 20% by weight of rare earth oxide. The glass obtained had the transition point higher than 650° C., the temperature for forming the protective coat of 1300° C. or less, and the thermal expansion coefficient of 50 to 80×10−7/° C.
: Examples
: Composition (wt.)
: Properties
: Alkaline earth element in total
: Thermal expansion coefficient
: Transition point
: Calcination temperature
Next, the composition of glass having the optimum thermal expansion coefficient was examined. The composition of the glass of Example 15 shown in Table 1 was changed to confirm the relationship between the thermal expansion coefficient of the glass and the weight ratio of each oxide component to SiO2. The results are shown in
Next, the composition of glass suitable for use as a glass paste was examined.
In forming the protective coat layer using the above-mentioned glass material, the glass material was pulverized, and then mixed with solvent and the like to make a glass past. The glass paste was applied and calcined to form the protective coat. As shown in
The glass powder pulverized and sized at 150 μm or less was converted into a glass pellet having a diameter of 10 mm and a height of 5 mm using a hand press or the like. The glass pellet was put on an Al2O3 plate and heated at a temperature of 1100° C. for one hour in atmosphere. An area of wettability spread of the glass after heating was calculated, and the area rate (spread rate) of the heated glass to the glass pellet was calculated using the area of the glass pellet as a reference. The glass having the spread rate larger than 1.3 was able to form a good protective coat. However, the glass having the spread rate below 1.3 makes the thickness of the coat ununiform, and thus was not able to form the good protective coat.
At the heating temperature higher than 1100° C., the weight ratio of each component having the spread rate below 1.3 to SiO2 is increased as compared to the case of the heating temperature at 1100° C. A rate in increase of weight ratio is 0.2 to 0.5/100° C.
The element is used in exhaust gas, and thus the protective coat is required to have corrosion resistance to an acid atmosphere. Thus, 0.5 mL of hydrochloric acid, 1.4 mL of nitric acid, 7.3 mL of sulfuric, acid, 1 mL of formic acid, 8.3 mL of acetic acid, 5.5 mL of formalin, 2000 mg of sodium nitrite, and 1500 mg of sodium sulfite were mixed in 1 L of pure water, and heated to 80° C. to make simulated exhaust gas condensed water (PH=1, 30 cc). Then, the corrosion resistance of each glass material was evaluated using the thus-obtained simulated condensed water.
Specifically, samples of the glass materials formed to have a size of 4 mm×4 mm×15 mm by changing the ratio of each component of the glass of Example 28 shown in Table 1 were immersed in the simulated exhaust gas condensed water, and then the changes in formland weight of the samples were measured.
As shown in
A flow rate measuring element shown in
The EGR cooler was disposed in the exhaust gas recirculation system, and the flowmeters having the protective coat formed of silica glass were on the front and rear stages thereof. The temperature of exhaust gas on the front stage was about 200° C., and the temperature of exhaust gas on the rear stage was about 80° C. During one day, the internal combustion engine was operated taking into consideration actual operating conditions. The element of the flowmeter has the structure shown in
The reason for adhesion of metal is that condensed water provided by cooling steam contained in the exhaust gas by a cooler corrodes the piping to cause metal to be deposited on the flowmeter on the rear side. When the flowmeter is disposed on the rear side of the cooler (when the exhaust gas temperature is 80° C. below the dew-point temperature), metal components eluted from the. piping by the condensed water adhere to the surface of the heating element at the heating temperature of 350° C., whereas no matter adheres thereto at 600° C. When the flowmeter is disposed on the front side of the cooler (when the exhaust gas temperature is 200° C. above the dew-point temperature), no matter adheres to the surface in heating the heating element at a temperature of 600° C.
A vapor film layer is formed on the surface of the flowmeter by water or moisture in exhaust gas by heating the thermal gas flowmeter at a predetermined temperature or higher when the exhaust gas temperature is equal to or less than the dew-point temperature, which prevents the adhesion of components, such as metal.
An example of the EGR system using the flow rate measuring element will be described below.
In a conventional example, the EGR amount is controlled by the indirect type system which is designed to estimate the amount of EGR based on information from the air flow sensor 11 and about the opening degree of the electrically controlled throttle 12. In this example described above, the sensor is provided to achieve the optimal amount of circulation of the exhaust gas, so that the amount of NOx is a tenth part of that in the conventional method, and also that the amount of PM is a fiftieth part of that in the conventional method under the same traveling conditions (states).
In order to reduce the adhesion matter onto the flowmeter, the EGR system is also effective which is designed to heat the flow rate measuring element before driving, and to recirculate the exhaust gas after the predetermined temperature is reached. The same effect is also obtained by heating the flow rate measuring element before driving an internal combustion engine, such as an engine.
Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-085180 | Mar 2008 | JP | national |
