JP3922011B2 - Exhaust pipe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the structure of an exhaust pipe of an internal combustion engine.
[0002]
[Prior art]
In recent years, in an internal combustion engine mounted on an automobile or the like, before the exhaust discharged from the internal combustion engine is released into the atmosphere, carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide ( NOx) and other toxic gas components are required to be purified or removed to improve exhaust missions. One of the means to improve these exhaust missions is to purify harmful gases contained in the exhaust by an exhaust purification catalyst. Techniques to do this have been proposed.
[0003]
As exhaust purification catalysts, a wide variety of exhaust purification catalysts such as three-way catalysts, storage reduction type NOx catalysts, selective reduction type NOx catalysts, oxidation catalysts, or exhaust purification catalysts obtained by appropriately combining these exhaust purification catalysts have been developed. Has been.
[0004]
In the NOx storage reduction catalyst, as an exhaust purification function, when the oxygen concentration of the exhaust gas flowing into the NOx storage reduction catalyst is high, the NOx in the exhaust gas is absorbed, and the oxygen concentration of the exhaust gas flowing in decreases. When the reducing agent is present in the exhaust gas, it is a catalyst that reduces the absorbed NOx to nitrogen while releasing it.
[0005]
However, in this NOx storage reduction catalyst, when sulfur oxide (SOx) is present in the exhaust gas to be purified, this SOx also has a characteristic of absorbing (NOx poisoning) in the same manner as NOx.
[0006]
The SOx absorbed in the NOx storage reduction catalyst forms a sulfate on the catalyst, and this sulfate cannot be reduced in the process of absorbing and reducing NOx, reducing the NOx absorption capacity of the NOx storage reduction catalyst. It was a thing.
[0007]
Therefore, in order to remove this SOx, for example, the atmospheric temperature of the NOx storage reduction catalyst is raised to a high temperature of about 500 to 700 ° C., and the fuel is added to the exhaust gas flowing into the NOx storage reduction catalyst to reduce the air-fuel ratio. make low. Then, HC in the fuel, CO contained in the exhaust gas, and sulfate are reacted and reduced and removed, and the NOx storage reduction catalyst can be recovered (SOx poisoning recovery).
[0008]
In order to form a state in which the fuel / air ratio is lowered by adding fuel to the exhaust gas, the exhaust gas discharged from some cylinders of the internal combustion engine is set to a high air / fuel ratio and discharged from other cylinders. There is a method in which the exhaust gas is brought into a low air-fuel ratio state, these exhaust gases are collected and flowed into a catalyst, fuel and oxygen are reacted to increase the catalyst temperature, and SOx poisoning recovery is performed.
[0009]
Further, the NOx storage reduction catalyst becomes large in order to improve the purification capacity when the exhaust amount of the internal combustion engine increases, but this is divided due to the problem of its mounting ability, and a plurality of catalysts are used. The purification capacity of the catalyst may be improved.
[0010]
Further, from the viewpoint of mountability, for example, in order to avoid interference with the propeller shaft, a plurality of, for example, two catalysts may be provided at a position (offset position) deviated from the central axis of the exhaust passage in front of the catalyst. is there.
[0011]
[Problems to be solved by the invention]
As described above, it is possible to improve the exhaust purification capability while solving the problem of securing the mounting space by dividing the exhaust purification catalyst with the increase in the exhaust amount of the internal combustion engine. As a result, the structure of the exhaust passage through which the exhaust to be purified flows was complicated.
[0012]
At the time of SOx poisoning recovery, on the upstream side, the exhaust in a state where the exhaust having a high air-fuel ratio and the exhaust having a low air-fuel ratio are mixed so as to have a uniform air-fuel ratio is divided into the respective exhausts. It is necessary to flow into the purification catalyst. If these exhausts having different air-fuel ratios are not sufficiently mixed before the catalyst inflows, the SOx poisoning recovery of one catalyst is delayed due to the different air-fuel ratios of the respective catalysts. Further, in some cases, sufficient SOx poisoning recovery may not be possible because the atmosphere of one catalyst does not reach the air-fuel ratio required for SOx poisoning recovery.
[0013]
Further, when a plurality of exhaust purification catalysts are provided, a bent portion is inevitably formed in the exhaust passage. When exhaust flows directly through the bent portion, the amount of exhaust flowing into each catalyst is different, and as a result, the time required for SOx poisoning recovery in each catalyst is different.
[0014]
These problems are not limited to NOx storage reduction catalysts, but are particulate filters that capture, reduce, and remove particulates in exhaust gas, for example, in diesel engines, and exhaust fuel as an additive during oxidative combustion. The same problem occurs when supplying the particulate filter from the upstream side of the passage.
[0015]
The present invention has been made in view of the above problems. In an exhaust pipe in which an exhaust purification catalyst is divided and an exhaust passage is bent, exhaust of substantially uniform components is introduced to a plurality of exhaust purification catalysts so as not to be biased. It is an object of the present invention to provide an exhaust pipe that can be used.
[0016]
[Means for Solving the Problems]
In the present invention, the following means are employed in order to solve the above-mentioned problems.
That is, an exhaust collecting portion for collecting a plurality of exhaust passages of an exhaust pipe connected to a plurality of exhaust ports of an internal combustion engine into a single exhaust passage, a linear exhaust passage connected downstream of the exhaust collecting portion, An exhaust pipe having a plurality of branched exhaust passages provided downstream of the linear exhaust passage, wherein a first exhaust pipe is provided in the exhaust pipe from the collection position of the exhaust collecting portion to the linear exhaust passage. And a second partition plate that is provided from the linear exhaust passage to the exhaust passage branch position and is not continuous with the first partition plate, and is located at the second end with respect to the end of the first partition plate. The exhaust pipe is characterized in that the starting end of the partition plate 2 is in a twisted position.
[0017]
In this exhaust pipe, the exhausts having different air-fuel ratios collected at the exhaust collecting part merge together via the first partition plate installed at the collecting position of the exhaust collecting part and are collected in one exhaust passage. Next, in the linear portion of the exhaust passage, the first partition plate and the twisted position, preferably the second partition plate provided at a position rotated by 90 ° in the axial direction with respect to the first partition plate, The exhaust gas merged by the first partition plate can be diverted so that the air-fuel ratio becomes equal to the branched exhaust passage.
[0018]
An exhaust gas purification device is provided in the branched exhaust passage, and the exhaust gas inflow surface area of the purification device for exhaust gas is increased to improve the exhaust gas purification capability.
[0019]
Further, the second partition plate divides the exhaust passage equally so that the flow rates of the exhaust gas flowing through the branched exhaust passages are equalized.
[0020]
The first partition plate and the second partition plate may be provided with through holes that communicate between the exhaust passages divided by the first partition plate and the second partition plate, respectively. This is because by making a hole in the partition plate, the friction coefficient of the partition plate surface is made larger than the inner surface of other pipes, and a part that becomes a partial resistance is provided in the exhaust flow, thereby generating turbulent flow in the exhaust flow. And the mixing of the exhaust by flowing into the other exhaust passage through the through hole due to the pressure difference of each exhaust passing through the partition plate is promoted. As a result, exhausts having different air-fuel ratios collected from the branch pipes of the exhaust collecting part are mixed inside the pipes.
[0021]
In the second invention,
As means for causing the exhaust gas to uniformly flow into the exhaust gas purification device, an exhaust collecting portion for collecting the exhaust passages of the exhaust pipe connected to the exhaust port of the internal combustion engine into a single exhaust passage, and a downstream portion connected to the exhaust collecting portion. An exhaust pipe comprising a straight exhaust passage, an enlarged exhaust passage provided downstream of the straight exhaust passage and having an enlarged cross-sectional area, and a plurality of exhaust purification devices provided in parallel with the enlarged exhaust passage. A bent exhaust passage is interposed between the linear exhaust passage and the enlarged exhaust passage so that the exhaust flows from the oblique direction into the enlarged exhaust passage having the exhaust purification device from the downstream side of the straight exhaust passage, The exhaust pipe is characterized in that the central axis in the flow direction intersects with the central axis in the flow direction of the enlarged exhaust passage upstream from the branch position of the enlarged exhaust passage.
[0022]
This exhaust pipe is similar to the exhaust pipe in the configuration up to the linear exhaust passage, but the rear configuration is different from the linear exhaust passage, and the exhaust gas is collected at the exhaust collecting portion and passes through the linear exhaust passage. Later, it flows into the bent exhaust passage. The radius of curvature of the bent exhaust passage is reduced, and the angle formed between the enlarged exhaust passage and the central axis of the catalyst that forms the bent exhaust passage to the branch position is set to 80 ° to 90 °. As a result, the exhaust gas is mixed with the bent exhaust passage by generating stagnation that becomes load resistance in the exhaust, and the enlarged exhaust passage formed downstream of the bent exhaust passage is obliquely directed to the branch position of each passage having the exhaust purification device. To flow from. When inflowing from this oblique direction, the exhaust flow path center axis of the expanded exhaust passage intersects the exhaust flow purification center axis of the exhaust purification device upstream from the expanded exhaust path branch position, so that the exhaust installed on the incident side Exhaust does not concentrate on the purification device, and it is possible to allow the exhaust to flow evenly into the parallel exhaust purification devices.
[0023]
Further, the axial projection of the cross section of the straight exhaust passage does not directly overlap with the exhaust inflow surface of the exhaust purification device, and the exhaust purification device is connected to the exhaust purification device via the bent exhaust passage and the enlarged exhaust passage from the downstream of the straight exhaust passage. The pipe diameter to the exhaust inflow surface was increased stepwise.
[0024]
In order to prevent the exhaust gas flowing through the straight exhaust passage from flowing directly into the exhaust inflow surface of the exhaust gas purification device, a bent exhaust passage is provided after flowing through the straight exhaust passage, and then flows into the exhaust inflow surface. And the exhaust passage diameter is increased stepwise in order to allow the exhaust flow whose direction of flow has been changed by the resistance of the bent exhaust passage and whose flow velocity is slow to flow uniformly into the exhaust inflow surface larger than the exhaust passage diameter. This is because the pressure in the entire passage is made uniform to flow into the exhaust purification device.
[0025]
As described above, according to the present invention, the exhaust flowing in the exhaust pipe can be uniformly dispersed and mixed.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Hereinafter, specific embodiments of an exhaust pipe constituting an exhaust passage of an internal combustion engine according to the present invention will be described with reference to the drawings.
[0027]
FIG. 1 is a diagram showing a schematic configuration from an exhaust pipe constituting an exhaust system of an internal combustion engine according to the present invention and from a combustion chamber to an exhaust port of the internal combustion engine. An internal combustion engine 1 shown in FIG. 1 is a four-cycle water-cooled gasoline engine having six cylinders. An ignition plug 3 is attached to the internal combustion engine 1 so as to face the combustion chambers 2a to 2f of each cylinder.
[0028]
An intake branch pipe 11 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 11 communicates with the combustion chambers 2a to 2f of each cylinder via an intake port (not shown). The intake branch pipe 11 is connected to a surge tank 12, and the surge tank 12 is connected to an air cleaner box 13 through an intake pipe.
[0029]
The intake pipe is provided with a throttle valve 14 for adjusting the flow rate of intake air flowing through the intake pipe in conjunction with an accelerator pedal (not shown). A throttle position sensor 31 that outputs an electrical signal corresponding to the opening degree is attached to the throttle valve 14, and the opening degree is detected.
[0030]
A fuel injection valve 4 for injecting fuel toward the intake port of each cylinder is attached to each branch pipe 11a to 11f of the intake branch pipe 11. The fuel injection valve 4 communicates with a fuel distribution pipe 5, and the fuel distribution pipe 5 communicates with a fuel pump (not shown). The fuel discharged from the fuel pump is supplied to the fuel distribution pipe 5 and then distributed from the fuel distribution pipe 5 to each fuel injection valve 4.
[0031]
These fuel injection valves 4 are connected to a drive circuit 32 through electrical wiring. When drive power is applied from the drive circuit 32 to the fuel injection valve 4, the valves are opened to inject fuel. It is like that.
[0032]
On the other hand, the internal combustion engine 1 is connected to an exhaust collecting pipe 22 in which exhaust branch pipes 21 communicating with an exhaust port (not shown) are connected, and a catalyst for purifying harmful substances in the exhaust is provided downstream thereof. Exhaust pipes are joined.
[0033]
As shown in FIG. 2, the installation location of the catalyst mechanism and the configuration of the exhaust path include exhaust branch pipes 21a to 21c corresponding to the combustion chambers 2a to 2c and exhaust branch pipes 21d to 21f corresponding to the combustion chambers 2d to 2f, respectively. After the assembly, the first catalysts 23a and 23b are provided.
[0034]
After passing through the first catalysts 23a and 23b, the exhaust branch pipes 21a to 21f merge to form one straight exhaust pipe 24, branching into two at the end of the straight portion of the straight pipe 24, Second catalysts 25a and 25b are provided in the branched exhaust passage.
[0035]
The exhaust pipes merge again behind the second catalysts 25a and 25b to form one exhaust pipe, and a third catalyst 26 is disposed in the exhaust passage. A muffler 27 is connected to the rear portion of the third catalyst 26.
[0036]
The first catalyst 23a, 23b and the second catalyst 25a, 25b are, for example, a ceramic carrier made of cordierite formed in a lattice shape having a plurality of through holes along the exhaust flow direction, and the ceramic carrier. And a catalyst layer coated on the surface. The catalyst layer has porous alumina (AL ₂ O _Three ) Function as a NOx absorbent, for example, alkali metals such as potassium (K), sodium (Na), lithium (Li), cesium (Cs), barium (Ba), calcium (Ca), etc. A rare earth such as an alkaline earth metal or yttrium (Y) and a noble metal such as platinum (Pt) functioning as an oxidation catalyst (noble metal catalyst) are supported, and the NOx catalyst is configured.
[0037]
Such a NOx catalyst absorbs NOx in a state where the oxygen concentration in the exhaust gas is high, and in a state where the oxygen concentration in the exhaust gas is low (HC, CO, etc. exist in the exhaust gas), the noble metal catalyst is composed of these HC and CO. By promoting the oxidation reaction, a redox reaction using NOx as an oxidizing component and HC or CO as a reducing component occurs between the two. That is, HC and CO are HO and CO ₂ NOx is oxidized to N ₂ Reduced to
[0038]
However, when exhaust gas containing sulfur oxide (SOx) in its components flows into the NOx catalyst, it is absorbed by the NOx catalyst in the same process as the process of absorbing NOx (SOx poisoning state). The absorbed SOx cannot be reduced in the step of reducing NOx, and as a result, the NOx absorption capacity of the NOx catalyst is reduced, and the purification capacity of the NOx catalyst is reduced.
[0039]
The first catalysts 23a and 23b serve to quickly purify harmful substances in the exhaust gas at a low temperature immediately after the internal combustion engine is started. Therefore, it is provided as close as possible to the exhaust port so that the exhaust gas is taken into the exhaust passage at a position where the temperature does not decrease, and the amount of heat is reduced so that the catalyst bed temperature can be purified as quickly as possible. Raise to.
[0040]
On the other hand, the second catalyst 25a, 25b has a larger precursor and larger NOx absorption capacity, so that the exhaust atmosphere becomes a high oxygen concentration over a long period of time or SOx flows in. Even when the SOx poisoning state is approaching, it is possible to prevent NOx from being absorbed into the atmosphere by absorbing NOx.
[0041]
The third catalyst 26 includes, for example, a ceramic carrier made of cordierite formed in a lattice shape having a plurality of through holes along the exhaust flow direction, and a catalyst layer coated on the surface of the ceramic carrier. Porous alumina with a catalyst layer having many pores (AL ₂ O _Three ) Is supported by a platinum-rhodium (Pt-Rh) or palladium-rhodium (Pd-Rh) noble metal catalyst material.
[0042]
The third catalyst 26 configured as described above is activated when the temperature is equal to or higher than a predetermined temperature. When the air-fuel ratio of the exhaust flowing into the catalyst body is close to a desired air-fuel ratio, the HC and CO contained in the exhaust are exhausted. O _Three React with H ₂ O and CO ₂ At the same time, NOx in the exhaust reacts with HC and CO in the exhaust to produce H ₂ O, CO ₂ , N ₂ To reduce.
[0043]
The third catalyst 26 configured as described above is disposed downstream of the second catalysts 25a and 25b, thereby purifying the exhaust gas that has not been purified by the second catalysts 25a and 25b, thereby It plays a role in minimizing harmful gas components discharged into the water.
[0044]
Further, downstream of the second catalysts 25a and 25b, there is a NOx sensor 33 that outputs a detection signal that continuously changes in accordance with the NOx concentration in the exhaust gas.
[0045]
On the other hand, the internal combustion engine 1 includes a timing rotor attached to an end portion of a crankshaft (not shown) and an electromagnetic pickup attached to a cylinder block of the internal combustion engine 1 each time the crankshaft rotates by a predetermined angle. A crank angle sensor 34 that outputs a pulse signal is attached.
[0046]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 80 for controlling the internal combustion engine 1. Various sensors such as a NOx sensor 33, a throttle position sensor 31, and a crank angle sensor 34 are connected to the ECU 80 via electric wiring, and output signals of the sensors are input to the ECU 80.
[0047]
Further, the ECU 80 is connected to the ignition plug 3, the drive circuit 32, and the like via electric wiring, and can control the ignition plug 3, the drive circuit 32, and the like using the output signal values of the various sensors described above as parameters. is there.
[0048]
As shown in FIG. 3, the ECU 80 includes a central processing unit (CPU) 81, a read only memory (ROM) 82, a random access memory (RAM) 83, a backup RAM 84 in which stored information is not erased even after the operation is stopped, and a timer counter 85. , An external input circuit 86 including an A / D converter, and an external output circuit 87 are provided with a logical operation circuit configured by being connected by a bidirectional bus 88.
[0049]
The ECU 80 inputs the detection signals of the various sensors through an external input circuit, and in the CPU 81 provided in the ECU 80 based on these signals, from the program stored in the ROM 82, the fuel injection of the internal combustion engine 1 and the like. In addition to executing the basic control, various controls related to the operating state of the internal combustion engine 1 such as a fuel injection supply amount control, an ignition control, and an intake air amount control are performed.
[0050]
Next, the structure of the exhaust pipe which is the gist of the present invention will be described.
[0051]
First, SOx poisoning due to SOx in the exhaust occurs in the second catalysts 25a and 25b, which are NOx catalysts, so that the NOx components in the exhaust pass through the second catalysts 25a and 25b and are discharged downstream. become. This is detected by the NOx sensor 33 downstream of the second catalyst 25a, 25b, and when the NOx concentration in the exhaust gas is equal to or higher than the predetermined value, the CPU 81 is the SOx poisoning recovery means according to the program stored in the ROM 82. The fuel addition control to the catalyst is executed. With this control, fuel is injected by the fuel injection valve as usual in the combustion chambers 2a to 2c of the internal combustion engine 1, and fuel ignition is performed by the spark plug 3, but only fuel injection is performed in the combustion chambers 2d to 2f. There is no fuel ignition.
[0052]
As a result, unburned fuel is generated in the combustion chambers 2d to 2f, so that the exhaust is in an excess fuel state that is a reducing agent. Further, the combustion chambers 2a to 2c are in a lean fuel state because normal combustion is performed. Therefore, the exhaust branch pipes 21a to 21c and the exhaust branch pipes 21d to 21f have different air-fuel ratios, and these different air-fuel ratio exhaust gases are uniformly mixed to flow into the SOx poisoned catalyst to increase the catalyst bed temperature. At the same time, the SOx component is reduced with the fuel as the reducing agent.
[0053]
As shown in FIG. 2, the exhaust passage collects the exhaust branch pipes 21a to 21c and 21d to 21f in the exhaust collecting pipes 22a and 22b, respectively, and first catalysts 23a and 23b are provided in the exhaust passages thereafter. At the rear of the first catalysts 23a and 23b, the two exhaust passages are joined at the junction 41 as shown in FIG. After merging, the single exhaust passage becomes a straight pipe 24, a branch portion 42 is provided downstream of the straight pipe 24, and two branch exhaust passages are formed again from the branch portion 42. The two exhaust passages are provided with second catalysts 25a and 25b, respectively, after which the exhaust passages merge again to form one exhaust passage, and an exhaust passage through the third catalyst 26 and the muffler 27 is provided. Composed.
[0054]
As shown in FIG. 4A, the junction 41 is provided with a partition plate 28a at the center of the junction 41. The partition plate 28a has a large number of through holes 43 as shown in FIG. 4A. It has been. Through the through holes 43, the flow of exhaust gas flowing from the exhaust collecting pipes 23a and 23b is disturbed to generate turbulent flow, and exhaust gases having different concentrations are stirred and circulated.
[0055]
In addition, a partition plate 28b is provided at a branching position 42 where the straight pipe 24 ends so as to be in a twisted position perpendicular to the partition plate 28a. As shown in FIG. 4B, by providing the partition plate 28b in the linear portion, it is possible to flow the same amount of exhaust gas to each catalyst. Further, by providing the partition plate 28b at a twisted position rotated 90 ° in the axial direction with respect to the partition plate 28a at the merge position 41, the exhaust gas stirred at the merge point can flow evenly in each passage. It becomes.
[0056]
Further, by providing the partition plate 28b with a through hole 43 similar to the partition plate 28a, the exhaust gas can be stirred and circulated even at the branch position 42.
[0057]
The exhaust passage divided by the branching portion 42 behind the straight pipe 24 has a crank shape so that the flowing exhaust does not flow directly from the straight pipe 24 into the second catalysts 25a and 25b, and as the catalyst position approaches, Increase the pipe diameter. This configuration is for generating exhaust resistance by making the piping into a crank shape. By gradually widening the exhaust passage receiving the resistance, the exhaust diffuses into the passage, resulting in a cross-section of the piping. It is possible to allow uniform exhaust to flow into a larger catalyst cross section.
[0058]
The third catalyst 26 is provided after the exhaust passages merge again behind the second catalysts 25a and 25b. The third catalyst 26 purifies untreated NOx and the like remaining in the exhaust, and the exhaust is released to the outside air through the muffler 27.
[0059]
With the above-described configuration, it is possible to cause almost the same amount of exhaust gas to flow into the second catalysts 25a and 25b provided side by side, and the exhaust gas that has flown into the second catalyst 25a and 25b also becomes a substantially uniform component. As a result, the temperature raising step of the NOx catalyst performed for SOx poisoning recovery can be performed simultaneously by the second catalysts 25a and 25b, and the fuel used as the SOx reducing agent for SOx poisoning recovery is also the second. They can be added to the catalysts 25a and 25b so as to have the same amount. Further, when exhaust gas flows into the second catalyst 25a, 25b, the exhaust gas flows into the respective exhaust inflow surfaces 29 almost uniformly, so that SOx poisoning recovery in each catalyst can be performed almost evenly.
[0060]
(Embodiment 2)
Next, a second embodiment will be described. In this embodiment, since the structure from the tip of the exhaust pipe to the straight pipe 24 is the same as that of the first embodiment, description thereof will be omitted, and the structure after the straight pipe 24 will be described. Here, the exhaust passages constituting the second catalysts 25a and 25b are configured such that a branch point is provided immediately before the exhaust inflow surfaces 29a and b as shown in FIG.
[0061]
In this configuration, as shown in FIG. 5B, the central axis of the cone-shaped pipe 30 serving as an expanded exhaust passage that configures the central axis 46 of the catalyst arranged in parallel and the straight line of the pipe to the inflow surface of each catalyst. 45 so that the angle formed by θ is 80 ° to 90 °, directly from the straight pipe 24 to the exhaust inflow surfaces 29a, b of the second catalysts 25a, 25b provided downstream of the cone-shaped pipe 30. Prevent exhaust from entering. As a result, the load resistance of the exhaust flow between the straight pipe 24 and the second catalyst 25a, 25b is increased. Further, the catalyst is installed so that the exhaust gas flowing through the cone-shaped pipe 30 flows obliquely into the branch position of the pipe having the catalyst. Further, by installing the respective exhaust passages so that the central axis 45 of the cone-shaped pipe 30 intersects the central axis 46 of the second catalyst 25a, 25b on the upstream side of the branch position 42, the catalyst on the outside in the incident direction The cross-sectional projected area of the cone-shaped pipe 30 with respect to a certain second catalyst 25b is increased.
[0062]
Thus, if the cross-sectional projected area of the cone-shaped pipe 30 with respect to the second catalyst 25b is increased, it becomes possible to increase the flow rate of exhaust gas flowing into the second catalyst 25b on the outer side in the incident direction.
[0063]
On the other hand, the second catalyst 25a disposed on the inner side in the incident direction has a bent exhaust passage shape upstream of the second catalyst 25a, and the second catalyst 25a has a bent exhaust passage. Since it is installed on the outer peripheral side, the speed of the exhaust flowing into the exhaust inflow surface 29a is increased, the exhaust pressure is increased, and the exhaust flow rate per unit area of the projection such as the cross section of the cone-shaped pipe 30 corresponding to the exhaust inflow surface 29a. Becomes larger.
[0064]
Therefore, although the corresponding cross-sectional radiation area of the cone-shaped pipe 30 is small, the corresponding projection area of the second catalyst 25a inside the incident direction where the exhaust flow rate is high and the exhaust pressure is high and the cone-shaped pipe 30 is large. Since there is the second catalyst 25b outside the incident direction where the exhaust flow rate is low and the exhaust pressure is low, the cone shape, the intersection position between the central axis 45 of the cone-shaped pipe and the catalyst central axis 46, and the angle formed by these are adjusted. By doing so, it becomes possible to allow the exhaust gas flow rate of substantially the same amount to flow into both of the second catalysts 25a and 25b, and it becomes possible to perform temperature reduction of each NOx catalyst similarly from SOx poisoning. Further, as in the first embodiment, by gradually increasing the pipe diameter to the exhaust inflow surfaces 29a, b, the drift to the second catalysts 25a, 25b is eliminated, and the flow distribution of the exhaust inflow surfaces 29a, b is uniform. It is also possible to make it. Therefore, also in the present embodiment, SOx poisoning recovery can be performed almost evenly in the second catalysts 25a and 25b as in the first embodiment.
[0065]
As described above, according to the configurations of the first and second embodiments, exhausts having different air-fuel ratios are mixed to obtain exhausts having a uniform air-fuel ratio, and substantially equal amounts of exhaust gas are distributed to the exhaust passage having a plurality of catalysts. Is possible. Further, in the first embodiment, by providing the through hole 43, reducing the pulsation in the merging portion 41 and reducing the exhaust pipe emission sound can be exemplified as a secondary action.
[0066]
In addition, in the first embodiment, a configuration only in the upstream of the straight pipe 24 in FIG. 1, that is, the partition plate 28a is installed in the junction 41, and the through hole 43 is provided in the partition plate 28a. Even if it is a structure, the exhaust_gas | exhaustion of the different density | concentration which flows into an exhaust gas collection pipe can be mixed in the confluence | merging part 41, a single catalyst is provided in the downstream, and it is equal with respect to the exhaust inflow surface of this catalyst It is also possible to introduce exhaust gas mixed so as to have an air-fuel ratio.
On the other hand, if the exhaust gas having a uniform air-fuel ratio has already flowed upstream of the straight pipe 24 in FIG. 1, it is evenly distributed to the second catalysts 25 a and 25 b only by the exhaust pipe configuration downstream of the straight pipe 24. Exhaust gas can be introduced.
[0067]
In the above configuration, the SOx poisoning recovery is particularly described in the gasoline engine and the catalyst attached thereto. However, the present invention is not limited to this. For example, soot discharged from the diesel engine and the diesel engine, particulate matter such as SOF, etc. Even in a filter-like exhaust gas purification device that purifies a substance, it is possible to purify exhaust gas with a configuration similar to that of the first and second embodiments. That is, regardless of the type of the internal combustion engine and the type of the exhaust purification device, by adopting the configuration of the present invention, substantially uniform exhaust gas is allowed to flow into the exhaust purification devices provided in the plurality of exhaust passages so as not to be biased. It becomes possible to purify the exhaust gas almost uniformly by the exhaust gas purification device.
[0068]
【The invention's effect】
According to the present invention, when an exhaust gas having different air-fuel ratios flows into one exhaust pipe, the exhaust gas having a substantially uniform air-fuel ratio is gathered so that the exhaust gas has a substantially uniform air-fuel ratio. Can be distributed to the rear exhaust passage. Therefore, it is possible to evenly recover the SOx poisoning of a plurality of exhaust purification catalysts by allowing exhaust gas to flow evenly into the exhaust purification catalyst installed in the exhaust passage.
[0069]
In this way, when there are exhaust purification apparatuses installed in the plurality of exhaust passages, they form a similar exhaust purification environment, so that a specific exhaust purification apparatus is not burdened. That is, since it is possible to perform the same exhaust gas purification using the same exhaust gas purification device, only one of the exhaust gas purification devices does not deteriorate at an early stage.
[Brief description of the drawings]
FIG. 1 is a concept showing a gasoline engine and its exhaust passage according to a first embodiment.
Plan view.
FIG. 2 is a side view of an exhaust passage according to the first embodiment.
FIG. 3 is a conceptual diagram of a configuration around an ECU according to the embodiment.
FIG. 4A is a plan cross-sectional view in a straight portion exhaust passage according to the embodiment;
(B) Side surface sectional drawing in a linear part exhaust passage based on the embodiment.
FIG. 5A is a cross-sectional perspective view of an exhaust passage having a second catalyst according to the second embodiment.
(B) Sectional drawing of the exhaust passage which has a 2nd catalyst based on the embodiment.
[Explanation of symbols]
1 Internal combustion engine
2a-2f Combustion chamber
3 Spark plug
4 Fuel injection valve
5 Fuel distribution pipe
11a-11f Intake branch pipe
12 Surge tank
13 Air cleaner box
14 Throttle valve
21a-21f Exhaust branch pipe
22a, 22b Exhaust collecting pipe
23a, 23b first catalyst
24 Straight piping
25a, 25b Second catalyst
26 Third catalyst
27 Muffler
28a, 28b Partition plate
29 Exhaust inflow surface
30 Cone-shaped piping
31 Throttle position sensor
32 Drive circuit
33 sensors
34 Crank angle sensor
41 Junction position
42 Branch position
43 Through hole
44 Center axis
45 Center axis
46 Central axis of catalyst
80 Electronic control unit (ECU)
81 Central processing unit (CPU)
82 Read-only memory (ROM)
83 Random access memory (RAM)
84 Backup RAM
85 Timer counter
86 External input circuit
87 External output circuit
88 bidirectional bus

Claims (6)

An exhaust collecting portion for collecting a plurality of exhaust passages of an exhaust pipe connected to a plurality of exhaust ports of an internal combustion engine into a single exhaust passage, a straight exhaust passage connected downstream of the exhaust collecting portion, and the linear shape An exhaust pipe comprising a plurality of branched exhaust passages provided downstream of the exhaust passage,
In this exhaust pipe, a first partition plate provided from the collecting position of the exhaust collecting portion to the linear exhaust passage,
A second partition plate that is provided from the straight exhaust passage to the exhaust passage branch position and is not continuous with the first partition plate;
An exhaust pipe characterized in that the start end of the second partition plate is in a twisted position with respect to the end of the first partition plate. The exhaust pipe according to claim 1, wherein an exhaust gas purification device is provided in the branched exhaust passage. The exhaust pipe according to claim 1 or 2, wherein the first and second partition plates equally divide the exhaust passage. The first partition plate and the second partition plate each have a through hole that allows the exhaust passages divided by the first partition plate and the second partition plate to communicate with each other. The exhaust pipe according to any one of the above. An exhaust collecting pipe for collecting the exhaust passages of the exhaust pipe connected to the exhaust port of the internal combustion engine into a single exhaust passage, a straight exhaust passage connected downstream of the exhaust collecting pipe, and a downstream of the straight exhaust passage An exhaust pipe having an enlarged exhaust passage having an enlarged cross-sectional area and a plurality of exhaust purification devices provided in parallel with the enlarged exhaust passage,
A bent exhaust passage is interposed between the linear exhaust passage and the enlarged exhaust passage so that exhaust flows from the oblique direction into the enlarged exhaust passage having the exhaust purification device from the downstream side of the straight exhaust passage;
An exhaust pipe characterized in that the flow direction central axis of the exhaust passage intersects with the flow direction central axis of the enlarged exhaust passage upstream from the enlarged exhaust passage branch position. The axial projection of the cross section of the straight exhaust passage and the exhaust inflow surface of the exhaust purification device do not overlap directly, and the exhaust inflow of the exhaust purification device passes through the bent exhaust passage and the enlarged exhaust passage from the downstream of the straight exhaust passage. 6. The exhaust pipe according to claim 5, wherein the pipe diameter to the surface increases stepwise.

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