JPH06193490A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the exhaust gas purifying function at the time of starting an internal combustion engine by detecting a temperature of catalyst for purifying exhaust gas, and by controlling fuel and air in an intake air system so as to make fuel excessive in comparison with that of a stoichiometric air-fuel ratio when the detected value is lower than a set value. CONSTITUTION:An internal combustion engine 1 comprises an air volume adjusting valve 8 and a fuel injection valve 9 which are incorporated in an intake air system 4. Meanwhile, a precatalyst 2 and a main catalyst 3 are arranged in an exhaust system 4. Further, a secondary air supply pipe 6 incorporating a fuel supply pump 5 is laid upstream of the main catalyst 3. Moreover, a temperature sensor 7 for detecting a temperature of exhaust gas is located downstream of the main catalyst 3. Further, a temperature detected by the sensor 7 is lower than a set value, the air volume adjusting valve 8 and the fuel injection valve 9 is controlled so as to make fuel excessive in comparison with that of a stoichiometric air-fuel ratio by means of a control device 10. Accordingly, the temperature of the main catalyst is raised rapidly up to its activation temperature during a start of the internal combustion engine 1, thereby it is possible to enhance the exhaust purifying function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly, it effectively purifies harmful components in exhaust gas discharged at the start of the engine by means of a purification catalyst installed in the exhaust system of the internal combustion engine. The present invention relates to a control device for an internal combustion engine. The present invention particularly relates to a fuel supply amount control device for an internal combustion engine.

[0002]

2. Description of the Related Art Exhaust gas discharged from an internal combustion engine is
It contains harmful components such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). These harmful components not only adversely affect the human body as air pollutants but also hinder the growth of plants. Therefore, in order to reduce the amount of these harmful components contained in the exhaust gas of the internal combustion engine, an exhaust gas purifying catalyst such as a three-way catalyst is provided in the exhaust system of the internal combustion engine to purify the exhaust gas of the internal combustion engine. Research is being actively conducted.

By installing an exhaust gas purifying catalyst in the exhaust system of an internal combustion engine, the amount of harmful components in the exhaust gas can be reduced, but the exhaust gas purifying performance is exhibited by the catalyst being active. This is after heating to the temperature shown. Until the temperature of the catalyst reaches the temperature at which it is active, the exhaust gas purification performance is extremely poor, and harmful components are almost not purified and are released into the atmosphere.

The temperature at which the exhaust gas purifying catalyst is active varies depending on the components of the catalyst, but is usually 250 to 400 ° C. as described in JP-A-54-16018.

On the other hand, it takes about 2 minutes or more until the temperature of the exhaust gas rises to the above-mentioned temperature of 250 to 400 ° C. after the engine is started. 3-5 in one theory
There is a theory that it takes time, and it is described in JP-A-54-79319.

Therefore, in an internal combustion engine exhaust gas purification system for purifying harmful components in engine exhaust gas by providing a purification catalyst in the engine exhaust system, the number of times from when the engine is started until the catalyst is heated to the activation temperature by the exhaust gas. An important issue is how to effectively remove harmful components in the exhaust gas discharged in a minute.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an internal combustion engine exhaust gas purification system having an exhaust gas purification catalyst in an engine exhaust system, in which the temperature of the exhaust gas purification catalyst is raised to a catalyst activation temperature immediately after the engine is started. It is an object of the present invention to provide an internal combustion engine control device configured to perform the above.

[0008]

The present invention is a control device for an internal combustion engine in which a fuel injection valve and an air amount adjusting valve are installed in an intake system and an exhaust gas purifying catalyst is installed in an exhaust system. The temperature of the exhaust gas purifying catalyst installed in the exhaust system is input, and when the value is lower than a set value, the fuel injection valve and the air amount adjusting valve of the intake system are set so that the fuel exceeds the stoichiometric air-fuel ratio. Is provided with a means for controlling.

As the set value of the temperature of the exhaust gas purifying catalyst, the temperature at which the catalyst is active is set. When the temperature of the exhaust gas purifying catalyst in the engine exhaust system is lower than the activation temperature, the amount of fuel is increased so that the fuel exceeds the stoichiometric air-fuel ratio, or the amount of air is reduced to reduce the components of the exhaust gas. The temperature of the catalyst can be rapidly increased by changing the temperature.

Explaining this point in detail, the components of the engine exhaust gas change depending on the air-fuel ratio, and when the engine is operated with a fuel excess of the stoichiometric air-fuel ratio, a large amount of carbon monoxide is generated and hydrocarbons are also relatively generated. It will occur a lot. Of particular note is the fact that carbon monoxide is now included in the range of a few percent to a dozen percent, well above the concentration of hydrocarbons.

When the engine is operated at a stoichiometric air-fuel ratio, that is, A / F (A is air weight, F is fuel weight), the amount of nitrogen oxides is the highest, followed by the amount of hydrocarbons. Carbon monoxide is less than 1%.

Carbon monoxide is burned at much lower temperatures than hydrocarbons. Therefore, if an excess amount of fuel is supplied to the engine intake system in excess of the stoichiometric air-fuel ratio, catalytic combustion can be carried out even if the temperature of the exhaust gas is low, and the temperature of the catalyst can be raised by the heat generated thereby.

Further, when the engine is operated in a fuel excess of the stoichiometric air-fuel ratio, a considerably large amount of hydrocarbon is also generated, and the calorific value of this hydrocarbon per unit weight is the calorific value of carbon monoxide. It is as large as 5 times. Therefore, if the air-fuel ratio of the engine intake system is set to be in excess of the stoichiometric air-fuel ratio, the catalytic combustion of carbon monoxide is followed by the catalytic combustion of hydrocarbons to rapidly raise the temperature of the catalyst. Will be able to.

As a result, even if the engine is started, the catalyst temperature can be rapidly raised to effectively remove harmful components in the exhaust gas.

The internal combustion engine control apparatus of the present invention comprises means for inputting the temperature of the exhaust gas purification catalyst installed in the exhaust system and comparing it with a set value, and when the temperature of the exhaust gas purification catalyst is lower than the set value. Further, there may be provided a means for generating a signal so that the fuel is in excess of the stoichiometric air-fuel ratio, and a control means for opening / closing the fuel injection valve and the air amount adjusting valve of the intake system based on the signal.

Further, means for inputting the temperature of the exhaust gas purifying catalyst installed in the exhaust system, means for storing the temperature set value of the exhaust gas purifying catalyst, catalyst temperature of the input means and temperature of the storage means Means for comparing a set value, means for generating a signal so that the fuel temperature exceeds the stoichiometric air-fuel ratio when the catalyst temperature of the input means is lower than the temperature set value, and the intake system based on the signal The fuel injection valve and the control means for opening and closing the air amount adjusting valve can be provided.

Here, when the temperature of the exhaust gas purifying catalyst is lower than the set value, the fuel injection of the intake system is made so that the air-fuel ratio A / F (A is air weight, F is fuel weight) becomes 13 or less and 10 or more. It is desirable to open and close the valve and the air amount adjusting valve.

Further, when the temperature of the exhaust gas purifying catalyst installed in the exhaust system is higher than the set value, the fuel injection valve and the air amount adjusting valve of the intake system are opened and closed so as to be at or near the stoichiometric air-fuel ratio. Is desirable.

Any of these controls can be performed using a microcomputer.

The present invention is also applicable to an internal combustion engine having a fuel injection valve and an air amount adjusting valve in an intake system and a combustion catalyst and a three-way exhaust gas purifying main catalyst in an exhaust system. In this case, it is desirable to install the combustion catalyst before the three-way main catalyst, and by making the fuel excess of the stoichiometric air-fuel ratio, the combustion catalyst effectively functions and its combustion heat causes the exhaust gas purification catalyst. Can be quickly heated.

The present invention is directed to an internal combustion engine having a fuel injection valve and an air amount adjusting valve in an intake system, a combustion catalyst and an exhaust gas purifying catalyst in an exhaust system, and an air supply means before the combustion catalyst. Can also be When the engine is operated with a fuel excess of the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is low, and thus oxygen deficiency may occur when catalytically burning carbon monoxide and hydrocarbons in the exhaust gas. Oxygen deficiency can be eliminated by supplying air to the exhaust system when operating the engine with an excess of fuel compared to the stoichiometric air-fuel ratio. Such control of the air amount can also be performed by the control device of the present invention.

[0022]

The internal combustion engine exhaust gas purification system of the present invention has an air amount adjusting valve such as a fuel injection valve and a throttle valve in the intake system of the engine, and a pre-catalyst consisting of a combustion catalyst and an exhaust gas purification main catalyst in the exhaust system. And means for detecting the temperature of the exhaust gas purifying main catalyst, and from the stoichiometric air-fuel ratio during the period from when the engine is started until the detected temperature of the exhaust gas purifying main catalyst reaches a temperature at which it is active. A control means (control box) for driving the fuel injection valve and the air amount adjusting valve to open and close so as to cause excess fuel is provided.

From the time when the engine is started until the temperature of the exhaust gas purifying main catalyst reaches a temperature at which it is active, the fuel is in excess of the stoichiometric air-fuel ratio, and the temperature of the exhaust gas purifying main catalyst is at a temperature at which it is active. If so, it is desirable to drive the fuel injection valve and the air amount adjusting valve to open and close so that the stoichiometric air-fuel ratio or an air-fuel ratio in the vicinity thereof is obtained.

As described above, the air-fuel ratio A / F (A is air weight, F is fuel weight) in the excessive fuel state is 13 or less, 1
It is desirable to set it to 0 or more, and it is particularly desirable to excessively supply the fuel under the condition that the CO concentration of the engine exhaust gas is 3% or more and 14% or less. In carrying out the present invention, for example, an exhaust gas purifying main catalyst is provided under the floor of an automobile,
It is desirable to provide a pre-catalyst consisting of a combustion catalyst as close to the engine as possible. The temperature of engine exhaust gas decreases as it flows through the exhaust gas flow path. By providing the precatalyst at a position as close as possible to the engine, it is possible to guide the exhaust gas to the catalyst before the temperature of the exhaust gas decreases. Further, by using the combustion catalyst as the pre-catalyst, the oxidizing activity of CO and HC can be increased.

It is desirable to provide a means for adding an oxidizer such as air in the exhaust gas flow passage on the upstream side of the front catalyst.

Oxygen in the exhaust gas produced by burning under the excessive fuel condition is generally low in concentration. Therefore, by adding an oxygen-containing gas such as air to the front stage of the front catalyst, CO and HC in the front catalyst are effectively burned.

The amount of air (oxygen) added is preferably equivalent to or slightly more than the theoretical oxygen consumption of exhaust gas. In this case, combustion in the front catalyst and exhaust gas purification in the main catalyst can both be performed satisfactorily.

As the pre-catalyst, it is desirable to use a combustion catalyst that is active in both CO oxidation and HC oxidation. Specifically, as a catalytically active component, Group VIII, Ib of the periodic table is used.
It is desirable to use at least one metal or oxide selected from the group consisting of rare earth metals, zinc and tin.

Exhaust gas purifying main catalysts are CO and HC
It is desirable to use a three-way catalyst that is active in both oxidation and NOx reduction.

A so-called ceramic honeycomb of cordierite, mullite, aluminum titanate or the like is used as a support for the precatalyst, and the above-mentioned catalytically active component is supported on this, or silica, alumina, titania is added to the ceramic honeycomb as a support. A porous carrier such as
Further, it is desirable to carry the above-mentioned catalytically active component.

In the exhaust gas purification system of the present invention, it is essential that the heat generated by the catalytic combustion of the precatalyst be effectively used to rapidly heat and activate the precatalyst itself. This can be achieved by reducing the heat transfer coefficient of the catalyst carrier or support and increasing the temperature gradient between the catalyst and the carrier or support. The ceramics described above have a small heat transfer coefficient and effectively function to rapidly raise the temperature of the catalyst.

As a support for the precatalyst, a honeycomb of a conductive metal or alloy such as stainless steel can be used.

Rapid heating of the catalyst can also be achieved by reducing the specific heat of the catalyst support or support. By using a honeycomb made of metal such as stainless steel as a support for the catalyst, the specific heat of the material itself can be reduced and the material can be thinned, resulting in a smaller heat capacity and a faster temperature rise. Becomes

It is also desirable to energize the precatalyst to heat it.

The temperature of the precatalyst can be accelerated by heating the metal catalyst carrier or support with Joule heat. Further, the temperature can be increased by energizing the pre-catalyst at the start of temperature increase to accelerate the ignition of CO.

According to the present invention, in an operating method of an internal combustion engine, in which fuel and air having a stoichiometric air-fuel ratio are supplied to drive the engine and exhaust gas is purified by an exhaust gas purifying catalyst, from the time of starting the engine. An operating method is realized in which the engine is driven in a fuel excess of the stoichiometric air-fuel ratio at least until the temperature of the exhaust gas purifying catalyst rises to a temperature at which it activates.

Further, the engine is started in a state where the fuel is in excess of the stoichiometric air-fuel ratio, the exhaust gas is catalytically burned by the combustion catalyst and then sent to the exhaust gas purification catalyst, and the temperature of the exhaust gas purification catalyst shows activity. When the temperature rises to a temperature, an internal combustion engine exhaust gas purification system is realized in which excessive fuel supply is stopped and the exhaust gas is directly sent to the exhaust gas purification catalyst without passing through the combustion catalyst.

The internal combustion vehicle according to the present invention is provided with an exhaust gas purifying catalyst in the exhaust gas passage of the engine, and the temperature of the exhaust gas rises to the activation temperature of the exhaust gas purifying catalyst after the engine is started. A means for supplying fuel to the engine in excess of the stoichiometric air-fuel ratio, and a combustion catalyst for catalytically burning the exhaust gas discharged by driving the engine in the excessive fuel state is provided in the exhaust gas flow path. It is provided on the upstream side of the exhaust gas purification catalyst.

The present invention is suitable for use in an automobile driven by gasoline or light oil. In the exhaust gas purifying system of the present invention, the exhaust gas flow passage from the engine to the exhaust gas purifying main catalyst can be provided with a bypass flow passage, and the bypass flow passage can be provided with a pre-catalyst made of a combustion catalyst.

If the pre-catalyst functions for a short time (about 2 minutes) immediately after starting, it becomes essentially unnecessary thereafter. Even after it becomes unnecessary, circulating the exhaust gas unnecessarily increases the pressure loss. Further, exposing the pre-catalyst to a high temperature for a long time brings a cause of catalyst deterioration. A bypass is provided in the exhaust gas flow path from the engine to the main catalyst, and a pre-catalyst is provided in the bypass to burn excess fuel only while the main catalyst does not reach the operating temperature immediately after engine startup, and the exhaust gas is bypassed. These problems can be eliminated by introducing the precatalyst to the main catalyst.

It is also desirable to provide a dehumidifying means, preferably a cooling dehumidifier, in the exhaust gas passage between the engine and the front catalyst. When the temperature of the precatalyst is equal to or lower than the dew point of the exhaust gas, it is desirable to dehumidify the exhaust gas by the dehumidifying means, cool and dehumidify the temperature to, for example, equal to or lower than the precatalyst temperature, and then supply the precatalyst.

The engine exhaust gas usually contains a large amount of water vapor. When the exhaust gas containing water vapor is supplied to the pre-catalyst and the pre-catalyst temperature is low, to be precise, when the temperature of the pre-catalyst is below the dew point of the exhaust gas, the water in the exhaust gas condenses on the catalyst or in the catalyst pores. . This phenomenon not only deteriorates the performance of the catalyst, but also causes deterioration of the catalyst, and also increases pressure loss. Furthermore, once condensation occurs, latent heat of vaporization is required to evaporate it, so 100 ° C
A large amount of heat is required to raise the temperature above, and thus it may take time. Dehumidifying exhaust gas, for example by cooling to a temperature equal to or lower than the precatalyst temperature,
By supplying it to the pre-catalyst after that, it is possible to prevent the condensation of water vapor in the pre-catalyst part and to avoid the troubles associated therewith. In an exhaust gas purification system in which a bypass flow path is provided in the exhaust gas flow path from the engine to the main catalyst and a combustion catalyst is installed, an exhaust gas dehumidifying means is installed in the bypass flow path, and the temperature of the front catalyst is below the dew point of the combustion exhaust gas. In this case, it is preferable to dehumidify the exhaust gas by the dehumidifying means of the bypass and then guide the exhaust gas to the main catalyst, and directly guide the exhaust gas to the front catalyst when the temperature of the precatalyst is equal to or higher than the dew point of the exhaust gas.

If the precatalyst temperature is equal to or higher than the dew point of exhaust gas, the possibility of water condensation disappears. Dehumidifying the exhaust gas in this state is an unnecessary operation. Therefore, a bypass is provided in the exhaust gas flow path from the engine to the main catalyst, an exhaust gas dehumidifying means is provided in the bypass, and the exhaust gas is dehumidified by the bypass dehumidifying means when the temperature of the front catalyst is below the dew point of the exhaust gas. By guiding the exhaust gas to the catalyst and directly to the front catalyst when the temperature of the precatalyst is equal to or higher than the dew point of the exhaust gas, it is possible to remove water condensation in the precatalyst and its accompanying obstacles without unnecessary dehumidification.

An example in which an engine is supplied with fuel in excess of the stoichiometric air-fuel ratio is shown in JP-A-61-58912. However, no consideration is given to measures against exhaust gas when the engine is started.

[0045]

EXAMPLES The present invention will be described in detail below with reference to specific examples. However, the present invention is not limited to the following examples.

FIG. 1 is a schematic diagram of an internal combustion engine exhaust gas purification system according to an embodiment of the present invention. A front catalyst 2 and a main catalyst 3 are provided in an exhaust gas passage 11 of the engine 1. An air amount adjusting valve (throttle valve) 8 and a fuel injection valve 9 are attached to an intake pipe 4 of the engine 1. The degree of opening / closing of the air amount adjusting valve 8 and the fuel injection valve 9 is controlled by a control device (control box) 10. A secondary air supply pipe 6 for supplying air is provided in the exhaust gas flow path 11 before the front catalyst 2, and the secondary air supply pipe 6 is provided.
An air pump 5 is provided in the. A temperature sensor 7 is provided after the main catalyst 3 to detect the temperature of the exhaust gas. The temperature detected here is input to the control box 10, and the control box 10
Then, such a temperature is compared with a set value to determine whether to continue or stop the excess fuel operation.

FIG. 5 shows a specific configuration of the control box (control device) in the embodiment shown in FIG. Main catalyst 3
The signal from the temperature detection sensor 7 provided in the unit is exchanged by the input circuit into a form suitable for comparison with the next catalyst temperature set value, and then sent to the comparison unit, and the catalyst set temperature stored in advance in the storage unit. Compared to. When the temperature of the main catalyst 3 is lower than the set value, a signal for adjusting the fuel injection valve 9 and the throttle valve 8 so that the signal generating means is richer in fuel than the theoretical air-fuel ratio, and a signal for turning on the air pump 5 are given. Occur. This signal is converted into a form suitable for each output destination in the output circuit and transmitted to the fuel injection valve 9, the throttle valve 8 and the air pump 5.

Similarly, when the temperature of the main catalyst is higher than the set value, the fuel injection valve 9 and the throttle valve 8 are controlled by the signal generating means so that the stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio is obtained.
Is generated and a signal for turning off the air pump is generated, and this signal is converted into a form suitable for each output destination in the output circuit and transmitted to the fuel injection valve 9, the throttle valve 8 and the air pump.

FIG. 2 shows the relationship between the air-fuel ratio and the composition of exhaust gas in a gasoline engine.

FIG. 3 is a schematic diagram showing another example of the internal combustion engine exhaust gas purification system according to the present invention. A bypass flow passage 20 is provided in the engine exhaust gas flow passage 11, and a front catalyst 2 is provided in this bypass flow passage. Further, a valve 12 and a valve 21 are provided to switch the flow of exhaust gas. The temperature sensor 7 detects the temperature of the exhaust gas at the outlet of the main catalyst and inputs a temperature signal to the control box 10. When the temperature is below the operating temperature of the main catalyst, the valve 21 is closed and the valve 12 is opened to remove the exhaust gas. It guides to the pre-catalyst 2 of the bypass passage 20, and at the same time, controls the air amount adjusting valve 8 and the fuel injection valve 9 to burn excess fuel. Further, when the temperature is equal to or higher than the operating temperature of the main catalyst, the valve 21 is opened and the valve 12 is closed to guide the exhaust gas directly to the main catalyst 3, and at the same time, the air amount adjusting valve 8 and the fuel injection valve 9 are controlled to theoretically operate. Combustion is performed under an air-fuel ratio or conditions close to it. A signal for opening and closing the valves 12 and 21 is also output from the control box 10.

FIG. 4 is a schematic view of an internal combustion engine exhaust gas purification system according to another embodiment of the present invention. A bypass passage 20 is provided in the engine exhaust gas passage 11, and a dehumidifier 15 is provided in the bypass passage 20.
Further, valves 13 and 14 are provided to switch the flow of exhaust gas. A temperature sensor 16 is provided in the front catalyst 2.
Was set up. When the temperature of the pre-catalyst is below the dew point of the combustion exhaust gas, the exhaust gas is dehumidified by the dehumidifier 15 of the bypass passage 20 and then led to the main catalyst. When the temperature of the pre-catalyst is above the dew point of the combustion exhaust gas, the exhaust gas is directly fed. Lead to pre-catalyst. The control box 10 can also be used to open and close the valves 13 and 14. For example, by inputting the temperature detection value of the temperature sensor 16 and storing it in advance and comparing it with the dew point of the combustion exhaust gas, the valve 13
An opening / closing signal of the valve 14 can be output.

Example 1 In the pre-catalyst 2, a ceramic (cordierite) honeycomb having a volume of 1 liter and an opening ratio of 76% was coated with alumina, and palladium (Pd) was added to 0.5 wt% (hereinafter referred to as wt%). .) Is used for the main catalyst 3, and a catalyst having Pt, Pd and Rh supported on a ceramic honeycomb of the same material and the same structure having a volume of 2 liters is used.
The gasoline engine exhaust gas was distributed to these series. The air-fuel ratio (A / F) was set to 12, and the exhaust gas of CO7 volume% (hereinafter referred to as vol%) and HC 0.35 vol% obtained by burning the fuel in excess of the stoichiometric air-fuel ratio and flow rate of 1000 liters / min. When led to the pre-catalyst 2 at, the pre-catalyst outlet temperature reached 300 ° C. after 63 seconds, and the outlet temperature of the main catalyst 7 reached 300 ° C. after 135 seconds.

Comparative Example 1 CO obtained by burning at an air-fuel ratio of 14.5 close to the theoretical air-fuel ratio
When exhaust gas of 0.9 vol% and HC 0.2 vol% was led to the pre-catalyst 2 at a flow rate of 1000 liter / min, the pre-catalyst outlet temperature reached 300 ° C. after 87 seconds and the main catalyst 3 outlet temperature was 170 seconds. Later reached 300 ° C.

Example 2 When 380 liters / minute of air was added before the precatalyst to the exhaust gas produced under the same pre-catalyst and main catalyst as in Example 1 and the same combustion conditions (A / F = 12), The catalyst outlet temperature reached 300 ° C after 40 seconds and the main catalyst outlet temperature reached 300 ° C after 87 seconds.

Example 3 Under the same conditions as in Example 2, various catalysts were used as the precatalyst and the time required to reach the precatalyst outlet temperature of 300 ° C. was measured, and the results shown in Table 1 were obtained. A ceramic honeycomb was used as a support for the pre-catalyst, which was coated with alumina.
The catalytically active component shown in was loaded.

[0056]

[Table 1]

Example 4 Pd and Pt as precatalysts supported on various porous carriers and supports under the same conditions as in Example 2,
The time required to reach the precatalyst outlet temperature of 300 ° C. was measured and the results shown in Table 2 were obtained.

[0058]

[Table 2]

Example 5 As a pre-catalyst, 0.5 W of Pd was added to a honeycomb having a porosity of 90% and made of a ferritic stainless steel plate having a thickness of 0.05 mm.
When the catalyst temperature rising rate was measured under the same conditions as in Example 2 using the catalyst loaded with t%, the outlet temperature of the front catalyst reached 300 ° C in 36 seconds, and the outlet temperature of the main catalyst reached 300 ° C in 83 seconds. .

Example 6 3k was added to the catalyst under the same conditions and conditions as in Example 5.
When DC power of W was passed, the outlet temperature of the front catalyst reached 300 ° C in 28 seconds and the outlet temperature of the main catalyst reached 300 ° C in 62 seconds.
Reached

[0061]

As described above, according to the present invention, it is possible to purify unburned fuel components and partial combustion components discharged immediately after the engine of the internal combustion engine is started. In particular, the pre-catalyst was installed to start the engine with a fuel excess of the stoichiometric air-fuel ratio, and the exhaust gas was oxidized before the pre-catalyst to rapidly raise the temperature of the pre-catalyst. The main catalyst can be rapidly raised to the activation temperature. As a result, the exhaust gas purification performance of the internal combustion engine at the beginning of engine startup can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an exhaust gas purification system for an internal combustion engine of the present invention.

FIG. 2 is a graph showing a relationship between an air-fuel ratio and an exhaust gas composition in a gasoline engine.

FIG. 3 is a schematic view showing another embodiment of the internal combustion engine exhaust gas purification system of the present invention.

FIG. 4 is a schematic diagram showing another embodiment of the internal combustion engine exhaust gas purification system of the present invention.

5 is a specific configuration diagram of a control box in the embodiment of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Front catalyst, 3 ... Main catalyst, 8 ... Air amount adjustment valve, 9 ... Fuel injection valve, 10 ... Control device, 11 ... Exhaust gas passage, 20 ... Bypass passage.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Noriko Watanabe 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Toshio Ogawa 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Hiroshi Miyadera 1-1-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Atago Samurai Katsuta City, Ibaraki Prefecture 2520, Takaba, Oji Inside Automotive Equipment Division, Hitachi, Ltd.

Claims (8)

[Claims] 1. A control device for an internal combustion engine having a fuel injection valve and an air amount adjusting valve installed in an intake system and an exhaust gas purification catalyst installed in an exhaust system, the exhaust gas purification catalyst being installed in the exhaust system. And a means for controlling the fuel injection valve and the air amount adjusting valve of the intake system such that the temperature of the intake air is input and the value is lower than the set value so that the fuel exceeds the stoichiometric air-fuel ratio. Control device for internal combustion engine. 2. A control device for an internal combustion engine, wherein a fuel injection valve and an air amount adjusting valve are installed in an intake system and an exhaust gas purifying catalyst is installed in an exhaust system, and the exhaust gas purifying catalyst is installed in the exhaust system. Means for inputting the temperature of the exhaust gas and comparing it with a set value, and means for generating a signal to make the fuel excess of the stoichiometric air-fuel ratio when the temperature of the exhaust gas purification catalyst is lower than the set value, and based on the signal. A control device for an internal combustion engine, comprising: a fuel injection valve of the intake system; and control means for driving the air amount adjusting valve to open and close. 3. A control device for an internal combustion engine having a fuel injection valve and an air amount adjusting valve in an intake system and an exhaust gas purifying catalyst in an exhaust system, the temperature of an exhaust gas purifying catalyst installed in the exhaust system. Inputting means, means for storing the temperature set value of the exhaust gas purifying catalyst, means for comparing the catalyst temperature of the input means with the temperature set value of the storage means, and the catalyst temperature of the input means A means for generating a signal so that the fuel exceeds the stoichiometric air-fuel ratio when the temperature is lower than the set temperature value, and a control means for opening / closing the fuel injection valve and the air amount adjusting valve of the intake system based on the signal. A control device for an internal combustion engine, comprising: 4. The air-fuel ratio A / F (A is air weight, F is fuel weight) is 13 or less and 10 or more when the temperature of the exhaust gas purifying catalyst is lower than a set value. A control device for an internal combustion engine, further comprising means for opening and closing the fuel injection valve and the air amount adjusting valve of the intake system. 5. The fuel injection system according to claim 2, wherein when the temperature of the exhaust gas purifying catalyst installed in the exhaust system is higher than a set value, the stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio is obtained. A control device for an internal combustion engine, comprising: means for opening and closing a valve and an air amount adjusting valve. 6. A control device for an internal combustion engine having a fuel injection valve and an air amount adjusting valve in an intake system, and a combustion catalyst and a three-way exhaust gas purifying main catalyst in an exhaust system, wherein the exhaust gas purifying main A means is provided for comparing the temperature of the catalyst with a set value and opening and closing the fuel injection valve and the air amount adjusting valve of the intake system so that when the value is lower than the set value, the fuel exceeds the stoichiometric air-fuel ratio. A control device for an internal combustion engine, characterized in that 7. An intake system having a fuel injection valve and an air amount adjusting valve, a combustion catalyst in the front stage of the exhaust system, and a three-way exhaust gas purifying main catalyst in the rear stage, and air in the front stage of the combustion catalyst. A control device for an internal combustion engine having a supply means, wherein when the temperature of the exhaust gas purifying main catalyst is input and the value is lower than a set value, the fuel exceeds the stoichiometric air-fuel ratio and air is supplied from the air supply means. And a means for turning on and off the air supply means by driving to open and close the fuel injection valve and the air amount adjusting valve of the intake system based on the signal. Control device for internal combustion engine. 8. A method of controlling an internal combustion engine in which a fuel injection valve and an air amount adjusting valve are installed in an intake system and an exhaust gas purification catalyst is installed in an exhaust system, the exhaust gas purification catalyst being installed in the exhaust system. Is input, and the fuel injection valve and the air amount adjusting valve of the intake system are controlled so that when the value is lower than a set value, the fuel exceeds the stoichiometric air-fuel ratio. Internal combustion engine control method.