JP3159131B2 - Exhaust gas purification device with exhaust gas circulation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device provided with an exhaust gas circulation device.

[0002]

2. Description of the Related Art Nitrogen oxides emitted from an internal combustion engine (hereinafter referred to as nitrogen oxides)
Bottom, NO_XExhaust gas purification devices for purifying
You. For example, Japanese Patent Application Laid-Open No. 6-74022 discloses NO_XTo
NO to purify_XAnd hydrocarbons (hereinafter HC)
NO adsorbed on the catalyst surface_XAnd activate HC,
Activated NO_XNO by reacting
_XNO to purify_XSelective reduction catalyst (hereinafter referred to as NO_Xcatalyst)
And the NO_XAn HC supply valve for supplying HC to the catalyst
An exhaust purification device is disclosed.

[0003] Also, NO _X generated in an internal combustion engine
The amount increases as the flame propagation speed during combustion increases. Further, the NO _X generation amount increases as the combustion temperature during combustion increases. On the other hand, since the inert gas slows down the flame propagation during combustion, the flame propagation speed during combustion decreases as the amount of inert gas in the intake air increases. Further, since the inert gas absorbs heat during combustion, the combustion temperature during combustion decreases as the amount of inert gas in the intake air increases. Therefore, Japanese Unexamined Patent Publication No.
In the exhaust gas purification apparatus disclosed in Japanese Patent Publication No. 022, an exhaust gas containing CO ₂ and H ₂ O, which are inert gases, is introduced into intake air to reduce the flame propagation speed during combustion and to perform combustion during combustion. By lowering the temperature, the N
The production of O _X is suppressed.

[0004]

In the above-mentioned known exhaust gas purifying apparatus, an exhaust passage for taking in the exhaust gas to be introduced into the intake air and an exhaust passage for supplying the HC are separated, and the exhaust gas is supplied to the intake air. HC is prevented from being mixed into the intake air together with the exhaust gas at the time of introduction. However, the exhaust pressure in the exhaust passage to which HC is supplied may be higher than the exhaust pressure in the exhaust passage for taking in exhaust gas. At this time, HC flows into the exhaust passage for taking in the exhaust gas and is introduced into the intake air together with the exhaust gas. Therefore, an object of the present invention is to prevent HC supplied for purification from being introduced into intake air.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems
According to the present invention, a plurality of cylinders that sequentially execute an expansion stroke
And an exhaust branch pipe is connected to each cylinder.
At the downstream side, connect to a common exhaust passage,
NOx in exhaust gas can be purified by reducing agent
Exhaust of an internal combustion engine having a NOx catalyst disposed in the exhaust passage
In the purification device, a predetermined one of the exhaust branch pipes is used.
Expansion stroke or exhaust in a cylinder connected to the exhaust branch
The predetermined exhaust branch when a stroke is being performed
And the predetermined exhaust branch pipe is connected.
To the cylinder where the exhaust stroke is executed after the exhaust stroke of the
Introduce exhaust gas into the intake system only from the connected exhaust branch
You. That is, the exhaust gas is separate from the exhaust branch pipe to which the reducing agent is supplied.
Exhaust gas is introduced into the intake system from the branch pipe,
The exhaust stroke of the cylinder connected to the exhaust branch pipe is
Line in the cylinder to which the exhaust branch pipe to which air is supplied is connected
It is executed after the step.

[0006]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment. In FIG. 1, 1 is the engine body,
1, # 2, # 3, and # 4 are first cylinders, second cylinders, third cylinders, and fourth cylinders 2a, 2b, 2c, and 2d formed in the engine body 1, respectively. # 4, a first fuel injection valve, a second fuel injection valve, a third fuel injection valve and a fourth fuel injection valve for supplying fuel for engine combustion and fuel for exhaust gas purification, The passage 4 is an intake manifold connected to the intake passage 3. An intake pressure sensor 5 for detecting an intake air pressure for calculating an intake air amount is attached to the intake manifold 4. Further, the internal combustion engine of the present embodiment includes a crank angle sensor 6 for detecting a crank angle. Note that fuel is supplied to each of the fuel injection valves 2a to 2d from a fuel chamber or a pressure accumulating chamber (not shown) common to the fuel injection valves 2a to 2d. Fuel pressurized to a predetermined pressure is temporarily stored in the fuel chamber. In this embodiment, the first cylinder # 1, the third cylinder # 3, the fourth cylinder # 4, and the first cylinder # 1.
It is ignited in order. In this embodiment, the intake system is an intake passage or an intake manifold.

The first cylinder # 1, the second cylinder # 2, the third cylinder #
A first exhaust branch pipe 7a, a second exhaust branch pipe 7b, a third exhaust branch pipe 7c, and a fourth exhaust branch pipe 7d are respectively connected to the third and fourth cylinders # 4. The first exhaust branch pipe 7a, the second exhaust branch pipe 7b, and the fourth exhaust branch pipe 7d are joined at an upstream junction 8 on the downstream side of the engine body 1, and the collecting pipe 9
Connected to. The collecting pipe 9 and the third exhaust branch pipe 7c are joined at a downstream junction 10 further downstream of the upstream junction 8. In this specification, “upstream” and “downstream” are terms used in a direction along the flow of exhaust gas.

[0008] The internal combustion engine of the present embodiment includes a supercharger 11 for supercharging intake air in order to increase the amount of air taken in. The supercharger 11 includes an intake-side turbine wheel 11 a disposed in the intake passage 3 on the upstream side of the intake manifold 4.
And an exhaust-side turbine wheel 11b disposed in the exhaust passage 20 on the downstream side of the downstream-side merging section 10. Since the exhaust-side turbine wheel 11b is arranged at a position where the exhaust gas discharged from each of the cylinders # 1 to # 4 merges, the supercharging effect of the supercharger can be maintained to the maximum.

The intake side turbine wheel 11a and the exhaust side turbine wheel 11b are connected to each other by one shaft 11c. The exhaust-side turbine wheel 11b receives and rotates the exhaust gas from a direction parallel to the rotation surface of the exhaust-side turbine wheel 11b, and discharges the exhaust gas in a direction perpendicular to the rotation surface. On the other hand, the intake-side turbine wheel 11a is rotated with the rotation of the exhaust-side turbine wheel 11b, draws air from a direction perpendicular to the rotation surface of the intake-side turbine wheel 11a, and directs the air in a direction parallel to the rotation surface. To send out the intake air.

An exhaust gas purifying catalyst 12 for purifying nitrogen oxides (hereinafter, NO _x ) discharged from the internal combustion engine is disposed in an exhaust passage 20 downstream of the exhaust turbine wheel 11b. The exhaust purification catalyst 12 of the present embodiment is provided with NO _X
And hydrocarbons (hereinafter, HC) are adsorbed on the catalyst surface and NO
_X and HC, and the activated NO _X and HC
_The NO _X selective reducing catalyst for purifying NO _X by reacting bets (hereinafter, NO _X catalyst) is. NO _X catalyst 12
Performs a NO _X purification action in a predetermined catalyst temperature range. The upstream end portion of the NO _X catalyst 12 is arranged upstream temperature sensor 13 for detecting a temperature of said upstream end portion, N
The downstream end portion of the O _X catalyst 12 downstream temperature sensor 14 for detecting the temperature of the downstream side portion is disposed.

An exhaust circulation pipe 15 for introducing exhaust gas into the intake air is connected to the fourth exhaust branch pipe 7d. The other end of the exhaust circulation pipe 15 is connected to the intake manifold 4. The exhaust circulation pipe 15 is provided with an exhaust circulation valve 16 for controlling whether or not exhaust gas is introduced into the intake air.
The exhaust circulation valve 16 is connected to a suction pump 18 and the atmosphere via a three-way valve 17. The exhaust circulation valve 16 is controlled to open and close according to the operating state of the engine. When the three-way valve 17 allows the exhaust circulation valve 16 to communicate with the atmosphere, atmospheric pressure is applied to the interior of the exhaust circulation valve 16 and the exhaust circulation valve 16 is closed. On the other hand, the exhaust circulation valve 16 and the suction pump 18 are controlled by the three-way valve 17.
Are communicated with each other, a negative pressure is applied to the exhaust circulation valve 16 and the exhaust circulation valve 16 is opened. As a result, exhaust gas is introduced into the intake air. The NO _X amount generated in the internal combustion engine increases as the flame propagation speed during combustion increases. Further, the NO _X generation amount increases as the combustion temperature during combustion increases. On the other hand, since the inert gas slows down the flame propagation during combustion, the flame propagation speed during combustion decreases as the amount of inert gas in the intake air increases. Further, since the inert gas absorbs heat during combustion, the combustion temperature during combustion decreases as the amount of inert gas in the intake air increases. Therefore, when the exhaust gas containing CO ₂ or H ₂ O, which is an inert gas, is introduced into the intake air, the flame propagation speed during combustion decreases, and the combustion temperature during combustion is suppressed. The generation of NO _X accompanying combustion is suppressed.

In FIG. 1, a control unit (ECU) 40 is composed of a digital computer, and is connected to a CPU (microprocessor) 4 via a bidirectional bus 41.
2, a ROM (read-on memory) 43, a RAM (random access memory) 44, a B-RAM (backup random access memory) 45, an input port 46, an output port 47, and a clock generator 48. Output voltages of the intake pressure sensor 5, the upstream temperature sensor 13, and the downstream temperature sensor 14 are input to the input port 46 via the corresponding AD converters 49, respectively. The output voltage of the crank angle sensor 6 is directly input to the input port 46. On the other hand, the output port 47 is connected to each of the fuel injection valves 2a to 2d and the three-way valve 17 via the corresponding drive circuit 50.
Connected to.

FIG. 2 is a view showing the engine body 1 of the present embodiment. In FIG. 2, reference numeral 21 denotes a piston arranged in a cylinder 22, 23 denotes an intake port connected to the intake manifold 4, 24 denotes an intake valve arranged in the intake port 23, and 25 denotes a connection to the exhaust branch pipes 7a to 7d. The exhaust port 26 is an exhaust valve arranged in the exhaust port 25. 2a to 2d are the first to fourth fuel injection valves of FIG. 1, and 40 is the control unit (ECU) of FIG.

Next, the operation of this embodiment will be described. In the present embodiment, in the compression stroke of the third cylinder # 3, the third cylinder # 3
In addition to the combustion HC supplied into the third cylinder, the third cylinder # 3
During the expansion stroke or the exhaust stroke, the third cylinder # 3 injects HC for purifying exhaust gas (hereinafter, purifying HC).
In the present embodiment, as shown in FIG.
The exhaust stroke is performed in the order of the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2. That is, in this embodiment, the exhaust circulation pipe 1
The fourth cylinder corresponding to the fourth exhaust branch pipe 7d to which the fifth cylinder 5 is connected.
Third cylinder # 3 where the exhaust stroke is performed immediately before the exhaust stroke of # 4
In the expansion stroke or exhaust stroke, the HC for purification is supplied to the third cylinder # 3.

In the exhaust stroke of each of the cylinders # 1 to # 4, the exhaust valve 26 is opened over an angle greater than 180 ° of the crank angle. Therefore, the exhaust pressure in each of the cylinders # 1 to # 4 is as shown in FIG. That is, the exhaust stroke of the fourth cylinder # 4 is started before the exhaust stroke of the third cylinder # 3 is completed. For this reason, as shown in FIG. 4C, when the purifying HC supplied from the third fuel injection valve 2c is caused to reach the downstream merging section 10 in the expansion stroke or the exhaust stroke of the third cylinder # 3. The pressure in the fourth exhaust branch pipe 7d and the inside of the collecting pipe 9 are increased. That is, in the present embodiment, while the pressure in the exhaust branch pipe to which the exhaust circulation pipe is connected is increased, the purifying HC supplied in other cylinders is connected to the exhaust branch pipe to which the exhaust circulation pipe is connected. Purification HC is supplied at the timing when the HC reaches the junction.

Therefore, when the exhaust gas in the fourth exhaust branch pipe 7d is introduced into the intake air via the exhaust circulation pipe 15 according to the engine operating condition, the purification HC in the third exhaust branch pipe 7c is removed. It is prevented from being introduced into the intake air through the collecting pipe 9, the fourth exhaust branch pipe 7d and the exhaust circulation pipe 15. Therefore purifying HC in the third exhaust branch pipe 7c is reliably allowed reaching the NO _X catalyst 12. NO in exhaust gas
_X is purified in the NO _X catalyst 12 by the reducing action of the supplied purification HC. Further, since the exhaust gas is prevented from flowing from the third exhaust branch pipe 7c to the collecting pipe 9, the exhaust gas exhaust performance from the first cylinder # 1, the second cylinder # 2, and the fourth cylinder # 4 is maintained high. Is done.

Further, as described above, the third exhaust branch pipe 7c is joined with the collecting pipe 9 and the fourth exhaust branch pipe 7d at the downstream junction 10 downstream of the upstream junction 8. Therefore, the third cylinder # 3 is connected to the exhaust circulation pipe 15 via the third exhaust branch pipe 7c, the collecting pipe 9, and the fourth exhaust branch pipe 7d.
From the first cylinder # 1 to the exhaust circulation pipe 15 via the first exhaust branch pipe 7a and the fourth exhaust branch pipe 7d.
Is longer than the distance from the second cylinder # 2 to the opening 27 of the exhaust circulation pipe 15 via the second exhaust branch pipe 7a and the fourth exhaust branch pipe 7d. Therefore, assuming that the purifying HC is supplied to the first cylinder # 1 or the second cylinder # 2, the purifying HC supplied to the third cylinder # 3 is supplied to the first cylinder # 1 or the second cylinder # 2. It is difficult to reach the opening 27 of the exhaust circulation pipe 15 as compared with the purification HC supplied in 2.

Further, since the third exhaust branch pipe 7c and the collecting pipe 9 are gathered in parallel at the downstream merging section 10, exhaust gas may flow from the third exhaust branch pipe 7c to the collecting pipe 9. Thus, the performance of discharging exhaust gas from the first cylinder # 1, the second cylinder # 2, and the fourth cylinder # 4 is maintained at a high level. The purifying H supplied from the third fuel injection valve 2c.
The C amount is calculated based on the NO _X amount estimated from the outputs of the intake pressure sensor 5 and the crank angle sensor 6 and the NO _X catalyst temperature estimated from the outputs of the upstream temperature sensor 13 and the downstream temperature sensor 14.

Next, the control of the supply of HC for purification according to this embodiment will be described in detail with reference to the flowchart of FIG. In step S110, the supply amount of purification HC to be supplied from the third fuel injection valve 2c is calculated. The purification HC supply amount is calculated based on the outputs of the intake pressure sensor 5, the crank angle sensor 6, the upstream temperature sensor 13, and the downstream temperature sensor 14, as described above.

Next, the routine proceeds to step S112, where the current crank angle A is a predetermined angle A3 (A = A3).
Is determined. Note that the predetermined angle A3 is an angle in the expansion stroke or the exhaust stroke of the third cylinder # 3, and the purifying HC is supplied from the third fuel injection valve 2c to the third cylinder # 3.
3 is the angle at which injection is to be made. Step S112
If it is determined in step S1 that A = A3, step S1
Proceeding to 14, the third fuel injection valve 2c is operated, and step S
The amount of purification HC calculated at 110 is supplied to the third cylinder
3 and the process ends. On the other hand, step S112
If it is determined that A is not equal to A3, the process ends.

Note that the third exhaust branch pipe of the present embodiment is an exhaust branch pipe to which a reducing agent is supplied, the collecting pipe of the present embodiment is a remaining exhaust branch pipe, and the HC for purification of the present embodiment is a reducing agent. In addition, the exhaust circulation pipe of the present embodiment corresponds to an exhaust circulation device, and the fuel injection valve of the present embodiment corresponds to a reducing agent supply unit. Further, the purifying HC attached to the third exhaust branch pipe as the reducing agent supply means.
A supply valve may be used. Further, in order to further increase the pressure in the collecting pipe when the purifying HC reaches the downstream merging section, the opening of the collecting pipe in the downstream merging section can be reduced.

In this embodiment, the purifying HC is supplied only to the third cylinder # 3 regardless of whether the exhaust gas circulation valve 16 is opened or closed. However, when the exhaust gas circulation valve 16 is opened, the exhaust gas circulation pipe is opened. A cylinder in which an exhaust stroke is performed subsequent to the exhaust stroke of the fourth cylinder # 4 to which the exhaust cylinder 15 is connected. In this embodiment, the third cylinder # 3 is selected to supply the purifying HC, and the exhaust circulation valve 16 is closed. The first to fourth cylinders # 1 to # 4
May be supplied with HC for purification.

[0023]

According to the present invention, exhaust gas to which a reducing agent is supplied is provided.
Exhaust gas is introduced into the intake system from an exhaust branch pipe separate from the branch pipe
The exhaust branch for exhaust circulation is connected to the cylinder.
The exhaust branch is connected to the exhaust branch to which the reducing agent is supplied.
This is executed after the exhaust stroke in the cylinder. For this reason reduction
Immediately after the chemical reaches the junction of the exhaust branch,
Exhaust gas flows out of the exhaust branch pipe. Therefore reducing agent
Contained exhaust gas flows into this exhaust circulation exhaust branch
Never. This causes the reducing agent to flow into the intake system
Is prevented.

[Brief description of the drawings]

FIG. 1 is a view showing an exhaust gas purifying apparatus for an internal combustion engine according to an embodiment.

FIG. 2 is a sectional view of an engine main body of the internal combustion engine according to the embodiment.

FIG. 3 is a flowchart showing the supply of HC for purification according to the embodiment.

FIG. 4 is a diagram for explaining the operation of the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine body 7a ... First exhaust branch pipe 7b ... Second exhaust branch pipe 7c ... Third exhaust branch pipe 7d ... Fourth exhaust branch pipe 9 ... Collecting pipe 11 ... Supercharger 11a ... Intake side turbine wheel 11b ... Exhaust side turbine wheel 12 ... NO _X catalyst 15 ... exhaust circulation pipe 16 ... exhaust recirculation valve 17 ... three-way valve 20 ... exhaust passage

Continuation of front page (72) Inventor Hiroshi Akita 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-6-74022 (JP, A) JP-A-8-121149 (JP, A) JP-A-9-112251 (JP, A) JP-A-6-117228 (JP, A) JP-A-8-200045 (JP, A) Japanese Utility Model Laid-Open No. 59-62219 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) F01N 3/08-3/38 F01N 9/00-11/00 F02D 41/00-41/40 F02D 43/00-45/00 F02M 25/07

Claims (1)

(57) [Claims] A plurality of cylinders for sequentially performing an expansion stroke are provided.
Exhaust cylinders are connected to each cylinder, and these exhaust
And connect to a common exhaust passage for reduction
N that can purify NOx in exhaust gas
Exhaust gas purification of an internal combustion engine having an Ox catalyst disposed in the exhaust passage
In the apparatus, a predetermined exhaust gas among the exhaust branch pipes is provided.
Expansion stroke or exhaust stroke in a cylinder connected to a branch pipe
Return to the predetermined exhaust branch when
The base agent is supplied, and the predetermined exhaust branch is connected.
Connected to the cylinder where the exhaust stroke is executed after the exhaust stroke of the cylinder
Exhaust gas is introduced into the intake system only from the exhaust branch
An exhaust gas purifying apparatus for an internal combustion engine, comprising: