JPH0711940A - Exhaust gas purifying device of engine - Google Patents

Abstract

PURPOSE:To expedite warming-up of a catalyst with a simple structure without using any exhaust gas control valve by collecting exhaust gas in a local place of a catalytic converter so as to increase its temperature, and quickening activation of the catalyst under a low-temperature condition of the catalytic converter at the time of warming up an engine, etc. CONSTITUTION:A movable valve system 12 is driven and controlled based on a detection signal from a water temperature sensor 14 by a control unit 13. Only many second exhaust valves 2, 4, 6, 8, are respectively opened for their operation at the warming-up time when a cooling water temperature after starting an engine 11 is lower than specified value. Exhaust gas from many cylinders is passed through many second exhaust passages 32, 34, 36, 38, and fed to a high-density catalytic carrier part 26 arranged inside a low- density catalytic carrier part 27, in the central part of a catalytic converter 20 and then a temperature increase in the catalyst is expedited. On the other hand, many first exhaust valves 1, 3, 5, 7 are openly/closely operated after the warming-up time when the cooling water temperature is increased beyond the specified value, and then exhaust gas is spread and flowed in all ranges of the catalytic converter 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device for promoting warm-up of a catalytic converter installed in an exhaust pipe of an engine.

[0002]

2. Description of the Related Art In a catalytic converter used as a countermeasure for air pollution of automobiles, etc., it takes a certain amount of time for the catalyst to rise above its activation temperature after a cold start of the engine, during which exhaust gas is exhausted through the catalyst. There is a problem that the gas purifying action cannot be sufficiently obtained.

As a countermeasure against this, when the temperature of the exhaust gas is lower than a predetermined value, an exhaust gas control valve for collecting the exhaust gas at one place at the inlet of the catalytic converter is provided in the middle of the exhaust pipe to collect the exhaust gas. There is one that promotes the temperature rise of the catalyst at the site (see Japanese Utility Model Laid-Open No. 61-97517).

[0004]

However, in such a conventional device, the heat capacity of the exhaust gas control valve itself is large, which hinders the catalyst from being warmed up, and causes the exhaust pipe to reach a relatively high temperature. Since it is necessary to provide a butterfly type exhaust gas control valve on the way, there is a problem that the structure becomes complicated in order to secure sufficient durability.

In view of the above conventional problems, the present invention aims to provide an exhaust gas purifying device which promotes warm-up of the catalytic converter by eliminating the exhaust gas control valve provided in the middle of the exhaust pipe. And

[0006]

The invention according to claim 1 is
In an exhaust gas purifying apparatus for an engine in which a catalytic converter is provided in the middle of an exhaust pipe, first and second exhaust passages communicating with one cylinder and having their respective downstream ends extending to an inlet portion of the catalytic converter. A first and a second exhaust valve for opening and closing the first and second exhaust passages in synchronism with engine rotation; a variable valve mechanism for varying a valve lift amount or a valve opening period of the first exhaust valve; A means for detecting the operating state, and a control means for stopping the valve opening operation of the first exhaust valve via the variable valve mechanism in the operating state where the temperature of the catalyst is low, or for reducing the valve lift amount or the valve opening period. Equipped with.

According to a second aspect of the present invention, the catalytic converter is provided with a high-density catalyst carrier part and a low-density catalyst carrier part having different surface areas per unit volume, and the downstream end of the second exhaust passage is provided in the high-density catalyst carrier part. The downstream end of the first exhaust passage is opposed to the low-density catalyst carrier portion.

[0008]

According to the first aspect of the present invention, the valve opening operation of the first exhaust valve is stopped or the valve lift is reduced through the variable valve mechanism in an operating state where the temperature of the catalyst is low such as during warm-up. The exhaust gas from each cylinder locally flows into the catalytic converter through the second exhaust passage. Emissions can be reduced by promoting the temperature rise of the catalytic converter in the portion where the exhaust gas is collected and shortening the time during which the catalyst rises above its activation temperature.

In an operating state in which the temperature of the catalyst has risen sufficiently,
By opening the first exhaust valve via the variable valve mechanism, the exhaust gas is dispersed and flows through the first and second exhaust passages in the entire area of the catalytic converter.
The conversion efficiency by the catalyst can be increased and the emission can be reduced.

In the second aspect of the present invention, in an operating state in which the temperature of the catalyst is low, the exhaust gas from each cylinder passes through the second exhaust passage and is collected in the dense catalyst carrier portion, where the exhaust gas is collected. By increasing the surface area of the catalyst, the conversion action of the catalyst promotes the temperature rise of the catalytic converter, and the time taken for the catalyst to rise above its activation temperature is shortened to reduce emissions.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a catalytic converter 20 is installed in the exhaust pipe of the engine 11. While the exhaust gas from the engine 11 passes through the catalytic converter 20, the oxidation reaction of HC and CO contained in the exhaust gas is promoted through the catalyst, and the reduction reaction of NOx is promoted.

The four-cylinder engine 11 has two intake valves 9 and two exhaust valves 1 to 8 in each cylinder. By opening and closing each intake valve 9 in synchronization with engine rotation, the intake pipe 1
Intake air is introduced into each cylinder through the intake port 9 and the intake port 18. By opening and closing each of the exhaust valves 1 to 8 in synchronization with engine rotation, exhaust gas discharged from each cylinder is introduced into the catalytic converter 20 through the exhaust port 16 and the exhaust manifold (exhaust pipe) 30.

The engine 11 is provided with a variable valve mechanism 12 for varying the valve lift amount and the valve opening period of one of the first exhaust valves 1, 3, 5, 7 in each cylinder, depending on the engine operating condition. A control unit 13 for controlling the operation of the variable valve mechanism 12 is provided.

As the variable valve mechanism 12, a known mechanism capable of switching between a state in which the exhaust valve is opened / closed and a state in which the exhaust valve is stopped in synchronization with the rotational movement of a cam of a cam shaft (not shown) may be used. .

The control unit 13 is the engine 1
1, the signal TW from the water temperature sensor 14 that detects the temperature of the cooling water circulating through the engine 1 is input, and as shown in FIG.
When the cooling water temperature TW reaches a predetermined value T ₁ after the start-up of 1, the first exhaust valves 1, 3, 3 are connected via the variable valve mechanism 12.
The first exhaust valves 1, 3, 5, 7 are opened via the variable valve mechanism 12 after the valve opening operation of the valves 5, 7 is stopped and the cooling water temperature TW rises above the predetermined value T ₁ after warming up. Activate. In addition,
When the engine is warmed up, the control unit 13 may slightly lift the first exhaust valves 1, 3, 5, 7 via the variable valve mechanism 12 to reduce the valve lift amount and the valve opening period.

The exhaust manifold 30 includes exhaust valves 1-8.
The first and second exhaust passages 31 to 38 are provided so as to communicate with the respective cylinders via the and the downstream ends thereof extend to the inlet portion 21 of the catalytic converter 20. Thereby, each exhaust valve 1-8
The exhaust gas discharged from each cylinder via the first and second exhaust passages 31 to 38 is independently guided to the inlet portion 21 of the catalytic converter 20 without being mixed with each other.

The second exhaust passages 32, 34, 36, 38 are arranged so as to face the central portion 24 of the catalytic converter 20, and the first exhaust passages 31, 33, 35, 37 are provided in the outer peripheral portion of the catalytic converter 20, respectively. It is arranged so as to face 25.

As shown in FIGS. 2 and 3, the exhaust manifold 30 has four flange portions 40 joined to the engine body, one flange portion 45 joined to the casing 22 of the catalytic converter 20, and both flange portions. It has four branch portions 41 to 44 connecting 40 and 45.

The branch portions 41 to 44 are partitioned into the first and second exhaust passages 31 to 38 via a partition wall 46. The downstream end of each partition wall 46 has a second exhaust passage 3 as shown in FIG.
2, 34, 36, 38 face the central portion 24 of the catalytic converter 20, and the first exhaust passage 31,
33, 35, and 37 are arranged so as to face the outer peripheral portion 25 of the catalytic converter 20, respectively.

In FIG. 5, 28 is a catalytic converter 20.
The casing 22 has a flange portion for the exhaust manifold 30, and reference numeral 29 denotes a flange portion for an exhaust pipe (not shown).

As shown in FIG. 6, in the catalytic converter 20, a cylindrical partition wall 23 is concentrically formed inside a cylindrical casing 22, and by this partition wall 23, the second exhaust passage 3 is formed.
Central part 24 where 2, 34, 36 and 38 face each other
Then, the first exhaust passages 31, 33, 35 and 37 are partitioned by the outer peripheral portion 25 facing each other.

A high-density catalyst carrier portion 26 and a low-density catalyst carrier portion 27 having different surface areas per unit volume are housed in the central portion 24 and the outer peripheral portion 25 of the catalytic converter 20, respectively.
That is, the high-density catalyst carrier portion 26 interposed in the central portion 24
Is from the low-density catalyst carrier portion 27 interposed in the outer peripheral portion 25,
Formed with a small grid. As a result, the amount of catalyst supported in the central portion 24 is larger than that in the outer peripheral portion 25.

In FIG. 5, 28 is the casing 2
2 is a flange portion for the exhaust manifold 30, and 29 is a flange portion for an exhaust pipe (not shown).

With the above construction, the operation will be described below.

When the cooling water temperature TW is lower than the predetermined value T ₁ after the engine 11 is started, the opening operation of the first exhaust valves 1, 3, 5, 7 is stopped via the variable valve mechanism 12. Accordingly, there is no flow of exhaust gas in the first exhaust passages 31, 33, 35, 37, and the second exhaust valves 2, 4, 6, 8 are opened, so that the exhaust gas from each cylinder is exhausted to the second exhaust gas. It flows into the central portion 24 of the catalytic converter 20 through the passages 32, 34, 36 and 38, respectively. In this way, the exhaust gas is collected in the central portion 24 of the catalytic converter 20, thereby promoting the temperature rise of the catalyst provided in the central portion 24 and shortening the time required for the catalyst to rise above its activation temperature. The exhaust gas can be sufficiently purified through the catalyst from the early stage of warming up, and the emission can be reduced.

In this way, the dense catalyst carrier portion 26 is provided in the central portion 24 of the catalytic converter 20 where the exhaust gas is collected.
Since the surface area of the catalyst is large in the portion where the exhaust gas is collected, the temperature rise of the catalytic converter can be promoted by the conversion action of the catalyst, and the time required for the catalyst to rise above its activation temperature can be shortened. .

Further, since the high density catalyst carrier portion 26 is arranged inside the low catalyst carrier portion 27, the casing 2
The heat release to the outside air is suppressed via 2 and the temperature rise of the catalyst is promoted.

After the temperature of the cooling water TW has risen above the predetermined value T ₁ , the first exhaust valve 1, through the variable valve mechanism 12 after warming up.
When the valves 3, 5, 7 are opened, they flow into the outer peripheral portion 25 of the catalytic converter 20 through the first exhaust passages 31, 33, 35, 37, respectively. Second exhaust valve 2, 4,
The valves 6 and 8 are also opened and closed successively to flow into the central portion 24 of the catalytic converter 20 through the second exhaust passages 32, 34, 36 and 38, respectively. In this manner, the exhaust gas is dispersed and flows over the entire area of the catalytic converter 20, so that the conversion efficiency by the catalyst is increased and the emission is reduced.

Next, in another embodiment shown in FIG. 8, each branch portion 71 to 74 of the exhaust manifold 60 is connected in parallel to the catalytic converter 50 having an elliptical cross section. It should be noted that the same reference numerals are used for the portions corresponding to those in FIG.

As shown in FIG. 10, the catalytic converter 40
The four flat partition walls 53 are arranged in parallel with each other inside the cylindrical casing 52 having an elliptical cross section. Each partition 53
High-density catalyst carrier portions 56 formed by a small lattice and low-density catalyst carrier portions 57 formed by a large lattice are alternately arranged in a flow path partitioned by.

The branch portions 71 to 74 are partitioned into the first and second exhaust passages 61 to 68 via the partition walls 76. Each partition 76 is arranged so as to face each partition 53 of the catalytic converter 50. Each second exhaust passage 62, 64, 66, 6
8 face the high-density catalyst carrier portion 56 formed by the small lattice of the catalytic converter 50, and each first exhaust passage 6
1, 63, 65 and 67 are arranged so as to face the low density catalyst carrier portion 57 formed by the large lattice of the catalytic converter 50.

In FIG. 8, 78 is the exhaust manifold 6.
0 is a flange portion for the engine body, and each branch portion 71 to 74 is a casing 52 of the catalytic converter 50.
Are integrated and connected to.

With the above construction, the operation will be described below.

When the cooling water temperature TW is lower than the predetermined value T ₁ after the engine 11 is started, the opening operation of the first exhaust valves 1, 3, 5, 7 is stopped via the variable valve mechanism 12. Therefore, there is no flow of exhaust gas in the first exhaust passages 61, 63, 65, 67, and the second exhaust valves 2, 4, 6, 8 are opened, so that the exhaust gas from each cylinder is exhausted to the second exhaust gas. It passes through the passages 62, 64, 66 and 68, respectively, and flows into the dense catalyst carrier portion 56 formed by the small lattice of the catalytic converter 50. In this way, the high-density catalyst carrier portion 56
The exhaust gas is collected in the high density catalyst carrier part 5
6 promotes the temperature rise of the catalyst, shortens the time required for the catalyst to rise above its activation temperature, and obtains a sufficient exhaust gas purification action through the catalyst early in the warm-up period, It can be reduced.

After warming up when the cooling water temperature TW has risen above the predetermined value T ₁ , the first exhaust valve 1,
By opening the valves 3, 5, 7 through the first exhaust passages 61, 63, 65, 67, respectively, they flow into the low-density catalyst carrier portion 57 formed of a large lattice of the catalytic converter 50, and The two exhaust valves 2, 4, 6, 8 are also continuously opened / closed, so that the second exhaust passages 62, 6
They flow into the low-density catalyst carrier portion 57 through 4, 66 and 68, respectively. In this way, the exhaust gas is dispersed and flows over the entire area of the catalytic converter 50, so that the conversion efficiency by the catalyst can be increased and the emission can be reduced.

Regarding the variable valve mechanism, it is possible to change the valve opening amount of the first exhaust valve to a completely stopped state, and to change the valve lift amount or the valve opening period to a known value. The above mechanism may be used.

[0038]

As described above, according to the first aspect of the present invention, the first and second exhaust passages, which communicate with one cylinder and whose downstream ends are extended to the inlet of the catalytic converter, are provided.
First and second exhaust valves that open and close the first and second exhaust passages in synchronization with engine rotation, a variable valve mechanism that varies the valve lift amount or opening period of the first exhaust valve, and engine operation A means for detecting the state, and a control means for stopping the valve opening operation of the first exhaust valve via the variable valve mechanism in the operating state where the temperature of the catalyst is low, or for reducing the valve lift amount or the valve opening period. Therefore, in an operating state where the temperature of the catalytic converter is low, such as when the engine is warmed up, exhaust gas is collected locally in the catalytic converter to accelerate the temperature rise of the catalytic converter and accelerate the activation of the catalyst. As a result, the exhaust gas control valve provided in the middle of the exhaust pipe can be eliminated, and the structure of the exhaust system can be simplified, thereby improving the durability. Further, the heat capacity of the exhaust gas control valve itself can prevent the catalyst from being warmed up late.

According to a second aspect of the present invention, the catalytic converter includes a high-density catalyst carrier part and a low-density catalyst carrier part having different surface areas per unit volume, and the high-density catalyst carrier part has a downstream end of the second exhaust passage. Since the downstream end of the first exhaust passage is opposed to the low-density catalyst carrier portion, the surface area of the catalyst is increased in a portion where exhaust gas is collected in an operating state where the temperature of the catalyst is low such as during warm-up. As a result, the temperature rise of the catalytic converter can be promoted by the conversion action of the catalyst, and the time required for the catalyst to rise above its activation temperature can be further shortened.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exhaust gas purification device showing an embodiment of the present invention.

FIG. 2 is a plan view of an exhaust manifold of the same.

FIG. 3 is a side view of the same exhaust manifold.

FIG. 4 is a plan view of the downstream end of the exhaust manifold.

FIG. 5 is a side view of the same catalytic converter.

FIG. 6 is a sectional view taken along line AA of FIG.

FIG. 7 is a diagram similarly showing operating conditions for stopping the opening / closing operation of the first exhaust valve.

FIG. 8 is a side view of an exhaust manifold and the like showing another embodiment.

FIG. 9 is a plan view of the downstream end of the exhaust manifold.

FIG. 10 is a sectional view of the same catalytic converter.

[Explanation of symbols]

 1 1st exhaust valve 2 2nd exhaust valve 3 1st exhaust valve 4 2nd exhaust valve 5 1st exhaust valve 6 2nd exhaust valve 7 1st exhaust valve 8 2nd exhaust valve 11 Engine 12 Variable valve mechanism 13 Control unit 14 Water Temperature Sensor 20 Catalytic Converter 21 Inlet 26 Highly Dense Catalyst Carrier 27 Low Density Catalyst Carrier 31 First Exhaust Passage 32 Second Exhaust Passage 33 First Exhaust Passage 34 Second Exhaust Passage 35 First Exhaust Passage 36 Second Exhaust Passage 37 First Exhaust Passage 38 Second Exhaust Passage

Claims (2)

[Claims] 1. An exhaust gas purifying apparatus for an engine, wherein a catalytic converter is provided in the middle of an exhaust pipe, and a first cylinder is connected to one cylinder and each downstream end thereof is extended to an inlet section of the catalytic converter. A second exhaust passage, first and second exhaust valves that open and close the first and second exhaust passages in synchronization with engine rotation, and a variable valve that varies the valve lift amount or opening period of the first exhaust valve. Mechanism, means for detecting the operating state of the engine, and stop the valve opening operation of the first exhaust valve via the variable valve mechanism to the operating state where the temperature of the catalyst is low, or set the valve lift amount or the valve opening period. An exhaust gas purifying apparatus for an engine, comprising: a control means for reducing the size. 2. The catalytic converter includes a high-density catalyst carrier part and a low-density catalyst carrier part having different surface areas per unit volume, and the low-density catalyst carrier part faces the downstream end of the second exhaust passage. The exhaust gas purifying apparatus for an engine according to claim 1, wherein a downstream end of the first exhaust passage faces the carrier portion.