Water purification system assembly method

Abstract

To provide a purification device assembly method capable of suppressing a noble metal use amount of a catalyst while satisfying an exhaust standard.SOLUTION: A purification device assembly method for assembling an exhaust purification device 21 for purifying exhaust gas from an engine 10 into a vehicle, comprises: grading each exhaust purification device 21 that is a candidate for assembly into a vehicle according to an amount of precious metal; identifying a catalyst grade from among catalyst grades B, A, and S that allows the vehicle to satisfy a predetermined exhaust gas standard, according to exhaust gas performance of the engine 10; when there are two or more catalyst grades that satisfy the exhaust gas standard, selecting one catalyst grade with a relatively lower amount of precious metal; and mounting the exhaust purification device 21 corresponding to the selected catalyst grade in an exhaust passage 5 of the engine 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for assembling a purification device. Background Art

[0002] Patent Document 1 proposes a method for assembling an exhaust gas purification device, in which the exhaust gas temperature of each internal combustion engine carried into a factory and the activation temperature of each catalyst are respectively measured, and a combination thereof is determined so as to obtain desired exhaust gas purification performance in accordance with the exhaust gas temperature and activation temperature of each internal combustion engine. Prior Art Literature Patent Literature

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2014-20335 Summary of the Invention Problems to be Solved by the Invention

[0004] It is desired to reduce the amount of noble metal used for an exhaust catalyst while satisfying the exhaust emission standards for vehicles. However, Patent Document 1 merely presents a method for manufacturing an exhaust purification device by combining catalysts exhibiting appropriate activation temperatures according to the exhaust temperature of each internal combustion engine. Therefore, realization of a new method for reducing the amount of noble metal used in manufacturing an exhaust purification device is desired.

[0005] Accordingly, an object of the present invention is to provide a method for assembling a purification device that can suppress the amount of noble metal used in a catalyst while satisfying exhaust emission standards. Means for Solving the Problems

[0006] According to one aspect of the present invention, there is provided a purification device assembling method for assembling an exhaust purification device for purifying engine exhaust gas to a vehicle. In this purification device assembling method, each exhaust purification device that is a candidate for assembly to a vehicle is graded according to the respective amount of noble metal,The exhaust gas performance of each engine is ranked according to the concentration of harmful components in the gas discharged into the exhaust passages of multiple engines and before it flows into the exhaust purification device. Engine exhaust gas performance rank Accordingly, a catalyst grade capable of meeting the vehicle's specified exhaust gas standards is identified from among the various catalyst grades. If there are two or more catalyst grades that meet the exhaust gas standards, one catalyst grade with a relatively low amount of precious metals is selected, and the exhaust purification device corresponding to the selected catalyst grade is installed in the engine's exhaust passage. [Effects of the Invention]

[0007] According to the present invention, a method for assembling a purification device is provided that can suppress the amount of precious metals used in the catalyst while meeting exhaust gas standards. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows the peripheral configuration of an engine to which the purification device assembly method according to the first embodiment of the present invention is applied. [Figure 2] Figure 2 is a flowchart illustrating a method for assembling a purification device according to one embodiment. [Figure 3] Figure 3 shows an example of exhaust gas performance rankings. [Figure 4] Figure 4 shows a table that associates information on whether or not each exhaust gas performance rank, each catalyst grade, and combinations thereof meet the exhaust gas standards. [Figure 5] Figure 5 is a graph showing the relationship between vehicle mileage, exhaust gas performance, and each standard value. [Figure 6] Figure 6 shows the main components of an engine exhaust system to which the purification device assembly method according to the second embodiment is applied. [Figure 7] Figure 7 is a flowchart illustrating the method for assembling the purification device according to the second embodiment. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described below with reference to the drawings.

[0010] [First Embodiment] (Overall engine configuration) Figure 1 shows the engine surrounding the exhaust gas purification device according to this embodiment. As shown in the figure, the engine 10 is formed by a cylinder block 1A and a cylinder head 1B, and the cylinder is formed as a space surrounded by the cylinder block 1A and the cylinder head 1B. In Figure 1, for simplification, only one cylinder of the engine 10 is shown, but the number of cylinders is not limited to one and may be multiple.

[0011] A piston 2 is inserted into the cylinder block 1A so as to be able to reciprocate up and down along the cylinder central axis Ax, and the piston 2 is connected to a crankshaft (not shown) via a connecting rod 3. The reciprocating motion of the piston 2 is transmitted to the crankshaft via the connecting rod 3 and converted into rotational motion of the crankshaft.

[0012] The cylinder head 1B has a lower surface that defines the combustion chamber Ch. The combustion chamber Ch is formed as a space surrounded by the lower surface of the cylinder head 1B and the crown surface 2a of the piston 2. The cylinder head 1B has a pair of intake passages 4 on one side of the cylinder central axis Ax and a pair of exhaust passages 5 on the other side, which serve as passages that connect the combustion chamber Ch to the outside of the engine 10. An intake valve 8 is positioned in the port portion (intake port) 4a of the intake passage 4, and an exhaust valve 9 is positioned in the port portion (exhaust port) 5a of the exhaust passage 5. Air taken in from outside the engine 10 into the intake passage 4 is drawn into the cylinder when the intake valve 8 is open, and exhaust gas after combustion is discharged into the exhaust passage 5 when the exhaust valve 9 is open.

[0013] The intake passage 4 is equipped with an electronically controlled throttle device 41 that controls the flow rate of air drawn into the cylinder through the intake passage 4.

[0014] In the cylinder head 1B, an ignition plug 7 is further provided along the cylinder central axis Ax between the intake port 4a and the exhaust port 5a, and a fuel injection valve (injector 6) is disposed upstream of the intake valve 8 in the intake port 4a.

[0015] A catalytic converter 21 and a muffler 23 are disposed in the exhaust passage 5.

[0016] The catalytic converter 21 is disposed at a position downstream of the exhaust port 5a of the engine 10 and upstream of the muffler 23. In particular, the catalytic converter 21 is a device for removing harmful components such as nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas of the engine 10, and is provided with an exhaust catalyst (three-way catalyst) formed by supporting a catalyst material containing noble metals (such as platinum, rhodium, and palladium) on a predetermined carrier material.

[0017] Therefore, the exhaust gas from the engine 10 is purified by the catalytic converter 21 and discharged to the outside of the vehicle through the muffler 23.

[0018] In the present embodiment, there is provided a purification device assembling method for assembling a catalytic converter 21 having an appropriate amount of noble metal into the exhaust passage 5 of the engine 10. Details thereof will be described below.

[0019] (Purification Device Assembling Method) Figure 2 is a flowchart illustrating the purification device assembling method according to the present embodiment. In particular, in the manufacturing method shown in Figure 2, for a plurality of engines 10 carried into a factory, a catalytic converter 21 having an appropriate amount of noble metal is selected, and the catalytic converter 21 is attached to the exhaust passage 5 of the engine 10.

[0020] As shown in the drawing, first, in step S110, an exhaust gas performance distribution representing variation in exhaust gas performance of each engine 10 carried into the factory is investigated, and exhaust gas performance rank information is created by ranking the exhaust gas performance distribution according to the level of exhaust gas performance.

[0021] In this embodiment, the exhaust gas performance of the engine 10 is indicated by the concentration (content) of harmful components such as NOx in the gas (exhaust gas of the engine 10) discharged from the combustion chamber Ch into the exhaust passage 5 and before flowing into the catalytic converter 21. In other words, the exhaust gas performance is determined according to the exhaust gas characteristics corresponding to individual differences in the engine 10, and not depending on the characteristics of the exhaust purification device (catalytic converter 21).

[0022] Here, even if each engine 10 has the same design specifications, variations in exhaust gas performance occur due to individual differences in the components of each engine 10. In this embodiment, the variation in exhaust gas performance of each engine 10 is investigated in advance to determine the exhaust gas performance distribution, and the exhaust gas performance is ranked and recorded based on this distribution.

[0023] The exhaust gas performance distribution can be obtained by individually measuring the exhaust gas performance of each engine 10. However, in this embodiment, from the viewpoint of reducing the workload associated with measuring individual exhaust gas performance, the exhaust gas performance distribution is determined by referring to variation information of the engine 10 components that correlate with exhaust gas performance. This information includes, for example, individual differences in the fuel pump that pressurizes fuel into the combustion chamber Ch of the engine 10 and individual differences in the injectors 6 that spray fuel. In particular, variations in output characteristics corresponding to individual differences in fuel pumps and variations in spray characteristics (spray diameter and penetration variations) corresponding to individual differences in injectors 6 are strongly correlated with variations in exhaust gas performance. Therefore, the exhaust gas performance distribution can be suitably estimated by referring to these. Furthermore, information regarding the individual differences of the fuel pump and injectors 6 may be stored in advance for purposes such as understanding the output performance of the engine 10. Therefore, by extracting and using information suitable for estimating exhaust gas performance from the stored information, the work of determining the exhaust gas performance distribution can be further simplified.

[0024] Furthermore, from the viewpoint of determining the exhaust gas performance distribution with greater accuracy, it is preferable to refer to the shape variations in the intake port 4a, which affect the combustion quality, in addition to the individual differences of the fuel pump and the injector 6 mentioned above.

[0025] Then, the exhaust gas performance distribution obtained is divided into stages according to the level of exhaust gas performance to define the exhaust gas performance rank.

[0026] Figure 3 shows an example of an exhaust gas performance distribution. In Figure 3, it is assumed that the exhaust gas performance distribution exhibits a nearly normal distribution when the vertical axis represents the number of engines 10 and the horizontal axis represents the exhaust gas performance. As shown in the figure, in this embodiment, the exhaust gas performance distribution is divided into three stages, I to III, in order from the lowest exhaust gas performance (highest concentration of harmful components), and these are defined as exhaust gas performance ranks.

[0027] Returning to Figure 2, in step S120, a single catalyst grade is assigned to each exhaust gas performance rank I to III and recorded.

[0028] Specifically, first, each catalytic converter 21 prepared as a candidate for installation in the vehicle is graded according to its precious metal content. More precisely, each catalytic converter 21 is assigned a catalyst grade, starting with B, A, and S, in descending order of precious metal content, and this is recorded.

[0029] Furthermore, for each exhaust gas performance rank I to III, one or more catalyst grades are identified that will enable the vehicle to meet the prescribed exhaust gas standards. More specifically, first, when the catalytic converter 21 is actually installed in the exhaust passage 5 of the engine 10 of each exhaust gas performance rank I to III, a catalyst grade is identified that will result in the vehicle's exhaust gas concentration (the concentration of harmful components in the gas released outside the vehicle via the muffler 23) being below a prescribed standard value stipulated by laws, regulations, or various guidelines.

[0030] Furthermore, if only one catalyst grade that meets the exhaust gas standards can be identified for a given exhaust gas performance rank, that identified catalyst grade is associated with that exhaust gas performance rank. On the other hand, if two or more catalyst grades that meet the exhaust gas standards can be identified for a given exhaust gas performance rank, one catalyst grade that is more preferable from the perspective of reducing the amount of precious metals is selected, and that selected catalyst grade is associated with that exhaust gas performance rank.

[0031] Figure 4 shows a table that associates information on whether or not each exhaust gas performance rank (I-III), catalyst grade (B, A, S), and combinations thereof meets the exhaust gas standards.

[0032] In the example shown in Figure 4, for exhaust gas performance rank I (the lowest exhaust gas performance rank), only catalyst grade S, which has the highest amount of precious metals, meets the exhaust gas standards. For exhaust gas performance rank II (the rank with intermediate exhaust gas performance), catalyst grade A, which has an intermediate amount of precious metals, and catalyst grade S, which has the highest amount of precious metals, meet the exhaust gas standards. Furthermore, for exhaust gas performance rank III (the highest exhaust gas performance rank), all catalyst grades B, A, and S meet the exhaust gas standards.

[0033] Therefore, from the perspective of meeting exhaust gas standards, catalyst grade S is specified for exhaust gas performance rank I, catalyst grades A and S are specified for exhaust gas performance rank II, and catalyst grades B, A, and S are specified for exhaust gas performance rank III.

[0034] If we focus solely on achieving exhaust gas standards, it is preferable to always select catalyst grade S with the highest amount of precious metals, regardless of the variation in exhaust gas performance among the engines 10. However, in this case, it is anticipated that the amount of precious metals used will be excessive for the purpose of achieving this, leading to increased manufacturing costs. Therefore, in this embodiment, a more appropriate catalyst grade is assigned to each exhaust gas performance rank I to III so as to reduce the amount of precious metals used while still meeting the exhaust gas standards.

[0035] More specifically, for exhaust gas performance rank II, catalyst grade A, which has a relatively low amount of precious metals, will be assigned from among catalyst grades A and S that can meet the exhaust gas standards. For exhaust gas performance rank III, either catalyst grade A or B, which has a relatively low amount of precious metals, will be assigned from among catalyst grades B, A, and S that can meet the exhaust gas standards.

[0036] In particular, from the viewpoint of ensuring that the amount of precious metals used is necessary and sufficient, if there are three or more catalyst grades that can meet the exhaust gas standards for a given exhaust gas performance rank, it is preferable to assign the catalyst grade with the smallest amount of precious metals to that grade. For this reason, for exhaust gas performance rank III, catalyst grade B, which has the smallest amount of precious metals among catalyst grades B, A, and S that can meet the exhaust gas standards, is assigned.

[0037] Therefore, in this embodiment, as shown by the shading in Figure 4, catalyst grade S is associated with exhaust gas performance rank I, catalyst grade A with exhaust gas performance rank II, and catalyst grade B with exhaust gas performance rank III.

[0038] In step S130, the exhaust gas performance rank of the engine 10 in the vehicle to which the catalytic converter 21 is to be installed is determined. Specifically, by referring to information on the components of the engine 10, it is determined which of the exhaust gas performance ranks I to III the engine 10 belongs to. Alternatively, the exhaust gas performance of the target engine 10 may be directly measured, and the corresponding exhaust gas performance rank may be determined from the obtained measured value.

[0039] In step S140, based on the exhaust gas performance rank of the engine 10 identified in step S130, a catalyst grade corresponding to that exhaust gas performance rank is selected by referring to the information recorded in step S120.

[0040] Then, in step S160, the catalytic converter 21 of the selected catalytic grade is installed in the exhaust passage 5 of the engine 10.

[0041] The effects of installing the catalytic converter 21, selected using the above method, into a vehicle will be explained.

[0042] Figure 5 is a graph showing the relationship between vehicle mileage, vehicle exhaust gas concentration, and the standard value set for said exhaust gas concentration. The first standard value shown in the figure is assumed to be the target exhaust gas concentration standard value for a new vehicle (mileage below a specified value). The second standard value is assumed to be the regulated exhaust gas concentration limit that must be met regardless of mileage, as stipulated by laws and regulations.

[0043] In particular, Figure 5(A) shows the relationship between the vehicle's exhaust gas concentration and the first and second reference values ​​when a catalytic converter 21 of catalyst grade S is installed, regardless of the exhaust gas performance rank of the engine 10.

[0044] In this case, even in vehicles equipped with engine 10 that falls under any of the exhaust gas performance ranks I to III, the exhaust gas concentration is below both the first and second standard values ​​(meeting the exhaust gas standards). On the other hand, in exhaust gas performance ranks II or III, there is a certain surplus between the vehicle's exhaust gas concentration and each standard value. This surplus corresponds to an excess amount of precious metals.

[0045] On the other hand, Figure 5(B) shows the relationship between the exhaust gas concentration of the vehicle and the first and second reference values ​​when a catalytic converter 21 of the catalyst grade selected by the method shown in Figure 2 is installed.

[0046] In this case, a catalytic converter 21 with catalyst grade S is installed in a vehicle equipped with an engine 10 of exhaust gas performance rank I, while a catalytic converter 21 with catalyst grade A is installed in vehicles of exhaust gas performance rank II, and a catalytic converter 21 with catalyst grade S is installed in vehicles of exhaust gas performance rank III. Even with this installation configuration, the exhaust gas concentration of the vehicle can be reduced to below the respective standard values. Therefore, by adopting the purification device installation method according to this embodiment, it is possible to reduce the amount of precious metals while meeting exhaust gas standards, thereby reducing manufacturing costs.

[0047] As can be seen from Figure 4, in this embodiment, in a vehicle equipped with an engine 10 corresponding to exhaust gas performance rank II, a reduction in the amount of precious metals can be obtained by installing a catalytic converter 21 with a catalyst grade A, one grade lower than the highest catalyst grade S. Furthermore, in a vehicle equipped with an engine 10 corresponding to exhaust gas performance rank III, a greater reduction in the amount of precious metals can be obtained by installing a catalytic converter 21 with a catalyst grade B, two grades lower than the highest catalyst grade S. Therefore, although the average amount of precious metals reduced per vehicle depends on the characteristics of the exhaust gas performance distribution (standard deviation, etc.) of each engine 10, a certain reduction in the amount of precious metals can be obtained as long as there is a certain number of engines 10 belonging to exhaust gas performance rank II or III.

[0048] The effects and benefits of the purification system assembly method described above will be summarized below.

[0049] According to this embodiment, a method for assembling an exhaust gas purification device (catalytic converter 21) for purifying the exhaust gas of the engine 10 into a vehicle is provided.

[0050] In this purification device assembly method, each catalytic converter 21 that is a candidate for installation in the vehicle is graded according to the amount of precious metals it contains, and a catalytic converter grade B, A, and S is selected from among the catalytic converter grades B, A, and S that will allow the vehicle to meet the specified exhaust gas standards, and if there are two or more catalytic converter grades that meet the exhaust gas standards, one catalytic converter grade with a relatively small amount of precious metals is selected, and the catalytic converter 21 corresponding to the selected catalytic converter grade is installed in the exhaust passage 5 of the engine 10.

[0051] This allows for the selection of a catalyst grade with a lower amount of precious metals from a pre-prepared set of catalyst grades, within the range that meets exhaust gas standards according to the exhaust gas performance of the engine 10. By installing the selected catalyst grade's catalytic converter 21 in the exhaust passage 5, the vehicle's exhaust gas standards can be met while reducing the amount of precious metals used.

[0052] Furthermore, in this embodiment, an exhaust gas performance distribution representing the variation in exhaust gas performance among multiple engines 10 is obtained, and this exhaust gas performance distribution is divided into stages according to the level of exhaust gas performance and ranked, and one catalyst grade to be selected is pre-associated and recorded for each exhaust gas performance rank I to III. Then, by referring to the correspondence between one catalyst grade and each exhaust gas performance rank I to III, one catalyst grade is selected from the exhaust gas performance of one engine 10.

[0053] This makes it easier to select the appropriate catalyst grade according to the exhaust gas performance rank of the engine 10 in the vehicle to which the catalytic converter 21 is to be installed, thereby improving production efficiency.

[0054] Furthermore, the exhaust gas performance distribution is determined by referring to variation information of the engine 10 components that correlate with exhaust gas performance.

[0055] This makes it possible to determine the exhaust gas performance distribution from variation information of each component without directly measuring the exhaust gas performance of each engine 10 individually. Therefore, the work of measuring the exhaust gas performance of each engine 10 can be omitted, further improving production efficiency.

[0056] In particular, the variation information of the above-mentioned components includes individual differences in the fuel pump that pressurizes fuel into the combustion chamber Ch of the engine 10, individual differences in the injector 6 that sprays fuel, and variations in the shape of the intake port 4a provided in the cylinder head 1B of the engine 10.

[0057] This allows for more accurate determination of the exhaust gas performance distribution by referencing the individual differences (variations in characteristics) of the fuel pump and injector 6, which are particularly strongly correlated with exhaust gas performance, as information on variations in the components. Furthermore, by referring to the variations in the shape of the intake port 4a, which affects the combustion properties, in conjunction with these factors, the exhaust gas performance distribution can be determined with even greater accuracy.

[0058] [Second Embodiment] Figure 6 shows the main components of an engine exhaust system to which the purification device assembly method of this embodiment is applied. In this embodiment, the exhaust passage 5 is provided with a manifold direct catalytic converter 22 located directly below the exhaust manifold (not shown), and a so-called underfloor catalytic converter (catalytic converter 21 to be assembled) located downstream of the manifold direct catalytic converter 22 and under the vehicle floor.

[0059] Furthermore, in this embodiment, upstream connection part 21a and downstream connection part 21b for attaching and detaching the catalytic converter 21 are provided upstream and downstream of the catalytic converter 21's position in the exhaust passage 5.

[0060] The following describes the method for assembling the purification device according to this embodiment. As a prerequisite, similar to the first embodiment, each catalytic converter 21 that is a candidate for installation in the vehicle is pre-graded according to its respective precious metal content.

[0061] Figure 7 is a flowchart illustrating the method for assembling the purification device according to this embodiment.

[0062] First, a catalytic converter 21 corresponding to a standard catalyst grade (hereinafter also referred to as "first catalytic converter 21-1") is installed in the vehicle, and the exhaust gas performance of the engine 10 in the vehicle is measured (S210 and S220). The exhaust gas concentration can be measured using a known exhaust gas measuring instrument.

[0063] Next, the measured exhaust gas concentration is compared with a predetermined judgment value (S230), and the first catalytic converter 21-1 is replaced with a catalytic converter 21 of a different catalytic grade (hereinafter also referred to as "second catalytic converter 21-2") according to the comparison result. This judgment value is a value determined from the standpoint of determining whether the vehicle meets the exhaust gas standards, and can be determined, for example, based on the first standard value in the first embodiment.

[0064] If the measured exhaust gas concentration exceeds the threshold value, the first catalytic converter 21-1 is replaced with a second catalytic converter 21-2 of a higher catalytic grade (No. S230 and S260). More specifically, the first catalytic converter 21-1 is removed via the upstream connection part 21a and the downstream connection part 21b, and the second catalytic converter 21-2 is installed.

[0065] On the other hand, if the measured exhaust gas concentration is below the judgment value, it is further determined whether the difference between the measured value and the judgment value is within a predetermined range (S240). This predetermined range is determined to an appropriate value based on the surplus (≒ excess precious metal amount) relative to the standard value of exhaust gas concentration as explained in Figure 5.

[0066] Then, if the difference between the measured value and the judged value is not within a predetermined range (Yes in S240), the first catalytic converter 21-1 is replaced with the second catalytic converter 21-2, which has a lower catalytic grade. More specifically, the first catalytic converter 21-1 is removed via the upstream connection part 21a and the downstream connection part 21b, and the second catalytic converter 21-2 is installed.

[0067] This allows the first catalytic converter 21-1 to be replaced with a second catalytic converter 21-2 of a more appropriate catalyst grade, depending on the measurement results of the exhaust gas concentration of the vehicle to which the first catalytic converter 21-1 is installed. In particular, even if the measured value of the exhaust gas concentration is below the judgment value, if the difference between the measured value and the judgment value does not fall within a predetermined range, the catalytic converter 21 will be replaced with one that contains less precious metal, thus minimizing the amount of precious metal used.

[0068] The effects and benefits of the purification system assembly method described above will be summarized below.

[0069] According to this embodiment, a method for assembling an exhaust gas purification device (catalytic converter 21) for purifying the exhaust gas of the engine 10 into a vehicle is provided.

[0070] In this purification device assembly method, each catalytic converter 21 that is a candidate for installation in the vehicle is graded according to the amount of precious metals it contains. A first exhaust purification device (first catalytic converter 21-1) corresponding to one catalytic grade is installed in the vehicle, and the exhaust gas concentration of the vehicle is measured. Based on the comparison result between the measured exhaust gas concentration and a judgment value determined according to the exhaust gas standards that the vehicle must meet, the first catalytic converter 21-1 is replaced with a second exhaust purification device (second catalytic converter 21-2) of a different catalytic grade.

[0071] This allows the second catalytic converter 21-2, which has a more appropriate catalyst grade, to be replaced with the first catalytic converter 21-1 in a vehicle based on the actual measurement results of the exhaust gas concentration. Therefore, the amount of precious metal in the catalytic converter 21 that is ultimately installed in the vehicle can be determined from the actual measurement results of the exhaust gas concentration, thus more reliably achieving both the achievement of exhaust gas standards and the reduction of precious metal content.

[0072] Furthermore, in this embodiment, upstream connection part 21a and downstream connection part 21b are provided upstream and downstream of the catalytic converter 21's position in the exhaust passage 5 of the engine 10, respectively, for attaching and detaching the catalytic converter 21. The exchange between the first catalytic converter 21-1 and the second catalytic converter 21-2 is then performed via the upstream connection part 21a and the downstream connection part 21b.

[0073] As a result, even after the first catalytic converter 21-1 has been installed in the vehicle, it can be easily replaced with the second catalytic converter 21-2.

[0074] Although embodiments of the present invention have been described above, the configurations described in the above embodiments represent only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0075] For example, the specific configurations of the exhaust gas performance rank and catalyst grade described in the above embodiment are merely examples and can be modified in various ways depending on the situation. In particular, the number of each exhaust gas performance rank and each catalyst grade can be changed as appropriate. Furthermore, regarding the variation information of the components of the engine 10 used to determine the exhaust gas performance distribution, instead of the individual differences of the fuel pump, the individual differences of the injector 6, and the shape variations in the intake port 4a described above, variation information of other components that correlate with exhaust gas performance may be used together with these. [Explanation of symbols]

[0076] 5. Exhaust passage 6 Injectors 10 Engines 21 Catalytic Converter 21a Upstream connection 21b Downstream connection

Claims

1. A method for installing an exhaust gas purification device into a vehicle to purify engine exhaust gases, Each exhaust purification device that is a candidate for installation in the aforementioned vehicle is graded according to the amount of precious metals it contains. The exhaust gas performance of each engine is ranked according to the concentration of harmful components in the gas discharged into the exhaust passages of multiple engines and before it flows into the exhaust gas purification device. Depending on the exhaust gas performance rank of the engine, a catalyst grade is identified from among the catalyst grades that allows the vehicle to meet the predetermined exhaust gas standards. If there are two or more catalyst grades that meet the exhaust gas standards, the catalyst grade with a relatively low amount of precious metals shall be selected. The exhaust gas purification device corresponding to the selected catalyst grade is installed in the exhaust passage of the engine. Method for assembling a water purification system.

2. A method for assembling a purification device according to claim 1, The exhaust gas performance distribution representing the variation in exhaust gas performance among multiple engines is determined, and the exhaust gas performance distribution is divided into stages according to the level of exhaust gas performance and ranked accordingly. One catalyst grade to be selected for each exhaust gas performance rank is recorded in advance, Referencing the correspondence between each exhaust gas performance rank and one of the catalyst grades, one catalyst grade is selected based on the exhaust gas performance of one of the engines. Method for assembling a water purification system.

3. A method for assembling a purification device according to claim 1, The engine's exhaust gas performance is ranked by referring to variation information of the engine's components that correlate with the exhaust gas performance. How to assemble a water purification system.

4. A method for assembling a purification device according to claim 3, The aforementioned variation information includes individual differences in fuel pumps that pressurize fuel into the combustion chamber of the engine, individual differences in injectors that spray the fuel, and variations in the shape of intake ports provided in the cylinder head of the engine. How to assemble a water purification system.

5. A method for installing an exhaust gas purification device into a vehicle to purify engine exhaust gases, Each exhaust purification device that is a candidate for installation in the aforementioned vehicle is graded according to the amount of precious metals it contains. A first exhaust gas purification device corresponding to a first catalyst grade is installed in the vehicle, and the exhaust gas concentration of the vehicle is measured. Based on the comparison result between the measured exhaust gas concentration and the determination value determined according to the exhaust gas standards that the vehicle must meet, the first exhaust gas purification device is replaced with a second exhaust gas purification device of a different catalyst grade. How to assemble a water purification system.

6. A method for assembling a purification device according to claim 5, Upstream and downstream connection parts for attaching and detaching the exhaust purification device are provided, respectively, upstream and downstream of the location of the exhaust purification device in the exhaust passage of the engine. The replacement of the first exhaust gas purification device and the second exhaust gas purification device is performed via the upstream connection and the downstream connection. How to assemble a water purification system.

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