JPH05321646A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To obtain an exhaust emission control device to purify exhaust gas in an efficient manner even when an internal combustion engine is started in the cooled condition. CONSTITUTION:The upper reaches of a catalyst converter 13 interposed in an exhaust passage 12 are provided with an adsorbing means 16 adsorb the harmful matters such as hydrocarbon(HC) in the exhaust gas when the engine is started in the cooled condition, a temperature sensor 17 to measure the gas temperature in the exhaust gas, and a secondary air supplying passage 19 which is provided upstream from the adsorbing means 16 and purges the air inside the adsorbing means 16 by introducing the secondary air into the exhaust gap passage 12.

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 apparatus which efficiently purifies exhaust gas even when the internal combustion engine is cold started.

[0002]

2. Description of the Related Art Combustion gas (hereinafter referred to as exhaust gas) emitted from an internal combustion engine that uses fossil fuels such as gasoline and light oil contains harmful substances such as hydrocarbons and nitrogen oxides. However, there are various problems in releasing this exhaust gas as it is into the atmosphere.

In view of the above, an exhaust gas purifying apparatus using a three-way catalyst that renders these harmful substances harmless by promoting purification by burning hydrocarbons and reducing nitrogen oxides is proposed. It is well known that it has been developed and put into practical use. In other words, the catalytic converter carrying the three-way catalyst is installed in the middle of the exhaust gas passage of the internal combustion engine so that these harmful substances become harmless while passing through the catalytic converter and are released into the atmosphere. There is.

However, the three-way catalyst of the conventional catalytic converter has an extreme difference in catalytic ability for promoting the oxidation-reduction reaction of harmful substances depending on the temperature thereof, and carbonization occurs in an inactive state after cold start of the engine. The purification of hydrogen could not be promoted sufficiently.

Therefore, a secondary catalytic converter carrying an oxidation catalyst is incorporated in the exhaust passage upstream of a catalytic converter carrying a three-way catalyst (hereinafter referred to as the main catalytic converter). When the three-way catalyst is inactive, an exhaust gas purification device will be developed that electrically heats this auxiliary catalytic converter to activate the oxidation catalyst and accelerate the purification of hydrocarbons. It has arrived.

FIG. 2 shows the concept of an exhaust gas purifying apparatus incorporating such an auxiliary catalytic converter. As shown in the figure, a sub-catalyst converter 3 carrying an oxidation catalyst is provided in the exhaust passage 2 upstream of the catalytic converter 1 carrying a three-way catalyst. A power source 5 is connected via a catalyst switch 4 which is interlocked with the operation of an ignition key switch. That is, when the engine 6 is cold started, the catalyst switch 4 is turned on, the current from the power source 5 flows to the auxiliary catalytic converter 3, and the oxidation catalyst of the auxiliary catalytic converter 3 is heated to the activation temperature. When the hydrocarbons contained in the exhaust gas flowing in the exhaust passage 2 are actually started and purified, and the three-way catalyst of the main catalytic converter 1 reaches the activation temperature, the catalyst switch 4 is turned off and the auxiliary switch 4 is turned off. The power supply to the catalytic converter 3 is stopped.

Therefore, as a carrier for carrying the oxidation catalyst of the auxiliary catalytic converter 3 which is electrically heated by the power source 5, a metal-based carrier such as a heat-resistant alloy of iron-chromium-aluminum is mainly adopted. There is.

[0008]

In the exhaust gas purifying apparatus shown in FIG. 2 which uses an oxidation catalyst and a three-way catalyst, the auxiliary catalyst converter 3 carrying the oxidation catalyst is heated when the engine 6 is started in the cold state. It is necessary to use a heating method that utilizes the heat generated by the electric resistance of the carrier carrying the oxidation catalyst.

Therefore, as a method for activating the oxidation catalyst of the auxiliary catalytic converter 3 within a short time, a method of lowering the electric resistance value of the carrier carrying the oxidation catalyst or increasing the supply voltage to the auxiliary catalytic converter 3 Besides, a method of increasing the supply voltage to the sub-catalyst converter 3 and increasing the electric resistance value of the carrier carrying the oxidation catalyst can be considered.

However, in the case of the method of lowering the electric resistance value of the carrier carrying the oxidation catalyst or raising the supply voltage to the auxiliary catalytic converter 3, a very large current flows in the auxiliary catalytic converter 3, so that the capacity The need arises to use a significantly larger power supply 5.

On the other hand, in the case of the method of increasing the supply voltage to the auxiliary catalytic converter 3 and increasing the electric resistance value of the carrier carrying the oxidation catalyst, the capacity of the power source 5 is not changed so much and the oxidation catalyst is efficiently used for a short time. Conventional iron-chromium-
Aluminum-based heat-resistant alloys, etc., do not have a very high electric resistance value, so the absolute amount of heat generation is small and the power source 5 with a very large capacity is inevitably used, or some kind of device is applied to the structure of the carrier itself. It is necessary to have a characteristic and to lengthen the length of the carrier along the direction in which the current flows (hereinafter referred to as the current path length of the carrier), and the auxiliary catalytic converter 3 becomes large accordingly. There is a risk.

It is possible to use a metal material having a high electric resistance value as the carrier, but there is no substitute for the current carrier material in terms of material cost and workability, and the current carrier material is used as it is. I have no choice.

An object of the present invention is to provide an exhaust gas purifying apparatus capable of efficiently purifying harmful substances such as hydrocarbons at the time of cold start without increasing the capacity of a power source or replacing conventional carrier materials. And

[0014]

An exhaust gas purifying apparatus according to the present invention removes combustion gas from an exhaust passage upstream of a catalytic converter provided in the exhaust passage of combustion gas of an internal combustion engine. Adsorbing means for adsorbing, a temperature sensor provided upstream of the adsorbing means for measuring the gas temperature of the combustion gas, and a secondary air communicating with the exhaust passage upstream of the adsorbing means. And secondary air supply means for supplying.

[0015]

After the engine is started in the cold state, the adsorbing means adsorbs harmful substances such as hydrocarbons (HC) discharged until the catalyst reaches the activation temperature. Then, after confirming that the temperature of the combustion gas has reached a predetermined temperature by a temperature sensor, secondary air is introduced from the secondary air supply means to purge the inside of the adsorption means, and the adsorbed hydrocarbon (HC) and the like. Sends the harmful substances of to the catalytic converter for purification.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an exhaust gas purifying apparatus for an internal combustion engine according to this embodiment.

In the exhaust gas purifying apparatus of this embodiment,
Adsorption means for adsorbing harmful substances such as hydrocarbons (HC) in exhaust gas in the cold state, a temperature sensor for measuring the gas temperature of the exhaust gas, and an upstream side of the catalytic converter interposed in the exhaust passage, A secondary air supply unit is provided upstream of the adsorption unit to introduce secondary air into the exhaust gas passage to purge the inside of the adsorption unit.

That is, as shown in FIG. 1, an exhaust passage 12 is connected to an exhaust port 11 of an engine 10, and a catalytic converter 13 carrying a three-way catalyst is provided in the middle thereof.
And a silencer 14 are respectively interposed.

On the upstream side of the exhaust passage 12 in which the catalytic converter 13 is inserted, an adsorbing means 16 having a high-performance adsorbing member 15 such as zeolite is interposed. Further, a temperature sensor 17 for measuring the gas temperature of the exhaust gas is attached on the upstream side of the adsorbing means 16, and the temperature sensor 17 has an electronic control unit for receiving a detection signal output from the temperature sensor 17. (Hereafter, "ECU"
18) is connected.

A secondary air supply passage 19 for supplying secondary air into the passage is connected to the exhaust passage 12 on the upstream side of the adsorbing means 16.

On the other hand, the air cleaner 20 is connected to an intake port 23 of the engine 10 by an intake pipe 21 via a surge tank 22, and a throttle valve 24 is provided in the middle of the intake pipe 21.

In addition to the air cleaner 20 which sucks the primary air from the air cleaner 20 and introduces it into the combustion chamber 25 of the engine 10 through the intake pipe 21, an air cleaner 26 which sucks secondary air is provided. The air cleaner 26 includes a switching valve 27 and a reed valve 28.
Is connected to the exhaust passage 12 via a secondary air supply passage 19 having The switching valve 27 is the ECU 18
Is controlled to be turned on and off by a predetermined condition so that the secondary air can be supplied to the exhaust passage 12 under a predetermined condition, and the reed valve 28 is opened by a negative pressure on the exhaust passage 12 side.

The primary air sucked from the air cleaner 20 is supplied to the intake port 23 of the engine 10 via the intake pipe 21 and the surge tank 22, while the injector 30 injects a predetermined amount of gasoline from the fuel tank. Then, a mixture of air and gasoline is supplied to the combustion chamber 25. Then, the air-fuel mixture is compressed in the combustion chamber 25 by the vertical movement of the piston 31, and the spark plug 32 generates a spark, which explodes and expands to operate the engine 10.

Hydrocarbon (HC) which is a harmful substance in the exhaust gas generated when the engine 10 is cold started.
Are adsorbed by the adsorption means 16 having the high-performance adsorption member 15. That is, harmful substances such as hydrocarbons (HC) in the exhaust gas generated until the three-way catalyst of the catalytic converter 13 reaches the activation temperature are temporarily adsorbed by the adsorbing member 15 of the adsorbing means 16.

As described above, when the engine 10 is cold-started, the high-performance adsorbing member 15, such as zeolite, which adsorbs a large amount of hydrocarbon (HC) contained in the exhaust gas, reaches a certain temperature after the exhaust temperature reaches a certain temperature. Secondary air is introduced from the secondary air supply passage 19 to be purged, and hydrocarbon (HC) is sent to the catalytic converter 13 carrying a three-way catalyst or the like for purification.

That is, when the temperature of the exhaust gas reaches a temperature at which the three-way catalyst of the catalytic converter 13 is activated by the temperature sensor 17 attached to the exhaust passage 12, for example, 300 ° C., a detection signal is sent to the ECU 18 and the secondary air is sent. The switching valve 27 of the supply means is opened, the secondary air from the air cleaner 26 is supplied into the exhaust passage 12, and the supply means 1
6 is purged, and the adsorption member is regenerated. For example, when the exhaust gas is 300 ° C., the purging time may be about 300 seconds, and the purging is controlled by using a control means such as a timer.

By the introduction of this secondary air, the adsorption means 16
The hydrocarbons (HC) that have been purged inside and sent to the catalytic converter 13 are purified by the activating action of the catalyst of the three-way catalyst that is at a high temperature here.

As described above, at the time of cold start of the engine in which the three-way catalyst of the catalytic converter 13 is inactive, the adsorbing means 16 having the high-performance adsorbing member 15 such as zeolite is provided to remove harmful hydrocarbons (HC). After adsorbing, the exhaust gas reaches a temperature at which the three-way catalyst works, for example, around 300 ° C., and then secondary air is supplied for a predetermined time using a timer or the like to purge the inside of the adsorbing means and refresh by combustion. At the same time, it becomes possible to purify hydrocarbons (HC), and it becomes possible to purify hydrocarbons (HC) even immediately after the engine is started in a cold state.

[0030]

As described above with reference to the embodiments, the exhaust gas purifying apparatus according to the present invention removes harmful substances which cannot be completely purified by the catalytic converter generated during the inactive state of the catalytic converter at the cold start. After adsorbing by the adsorbing means having a high-performance adsorbing member, and after reaching a predetermined activation temperature, secondary air is supplied to purge and refresh, so that harmful substances are always removed even during cold start, and exhaust gas Will be rendered harmless.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an exhaust gas purification device according to this embodiment.

FIG. 2 is a conceptual diagram of a conventional exhaust gas purification device.

[Explanation of symbols]

 10 Engine 11 Exhaust Port 12 Exhaust Passage 13 Catalytic Converter 15 Adsorption Member 16 Adsorption Means 17 Temperature Sensor 18 Electronic Control Unit (ECU) 19 Secondary Air Supply Passage 26 Air Cleaner 27 Switching Valve 28 Reed Valve

Claims (1)

[Claims] 1. An adsorption means for adsorbing combustion gas, which is interposed in the exhaust passage upstream of a catalytic converter, which is interposed in the exhaust passage of combustion gas of an internal combustion engine, and an upstream side of the adsorption means. A temperature sensor for measuring the gas temperature of the combustion gas, and a secondary air supply unit communicating with an exhaust passage upstream of the adsorption unit and supplying secondary air into the exhaust passage. Exhaust gas purification device characterized by.