JPH05321648A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To efficiently purify the harmful matters even when the engine is started in a cooled condition by adsorbing the harmful matters in the exhaust gas by an adsorbing means when the engine is started in a cooled condition, and purifying the harmful matters by a catalyst unit and a catalyst converter when the exhaust gas temperature reaches the specified activation temperature. CONSTITUTION:Switching control of a switching valve 51 is executed by an ECU 18 when an engine 10 is started in a cooled condition. That means, a bypass passage 16B of an adsorbing means 16 is closed while an adsorbing passage 16A is opened, and the harmful matters such as hydrocarbon in the exhaust gas are temporarily adsorbed to this adsorbing member 16. Confirmation that the exhaust gas temperature reaches the catalyst activation temperature is made by detecting the exhaust gas temperature by using the respective sensors 17A, 17B above and below the catalyst unit 53. Then, the exhaust gas is supplied to a catalyst unit 53 and purified. An adsorbing member 15 is reactivated by supplying the secondary air from the secondary air supplying passage 19 to the exhaust gas passage 12. In addition, the harmful matters adsorbed to the adsorbing member 15 are supplied to the catalyst converter 13 and purified.

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. 5 shows the concept of an exhaust gas purifying apparatus incorporating such a sub-catalyst 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. 5, 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 cold started. 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 is installed in the exhaust passage upstream of a catalytic converter installed in the exhaust passage for combustion gas of an internal combustion engine, and the combustion is performed. Purification means having an adsorption passage having an adsorption member for adsorbing gas and a catalyst passage having a catalyst for purifying exhaust gas, and a combustion gas for adsorbing combustion gas to either the adsorption passage or the catalyst passage provided on the inlet side of the purification means. A switching valve for guiding, a temperature sensor provided at each of an inlet portion and an outlet portion of the catalyst passage for measuring a gas passage temperature of the combustion gas, and a secondary air communicating with the exhaust passage and supplying secondary air into the exhaust passage. A secondary air supply means is provided, and a small amount of combustion gas is constantly flowed through the catalyst passage side in the purification means to measure the gas passage temperature by the temperature sensor and control the switching valve. To.

[0015]

After the engine has started cold, until the catalyst reaches its activation temperature, harmful substances such as hydrocarbons (HC) discharged are adsorbed by the adsorbing member of the purifying means. At that time, since a small amount of combustion gas is constantly flowing in the catalyst passage, when the activation temperature of the catalyst is reached, the catalytic action works and reaction heat is generated. This reaction temperature is measured by a temperature sensor on the outlet side of the catalyst passage, and after confirming that the temperature difference with the inlet side has reached a predetermined temperature difference, secondary air is introduced from the secondary air supply means to carry out the adsorption. The inside of the means is purged, and adsorbed harmful substances such as hydrocarbons (HC) are sent to the catalytic converter for purification. After that, the adsorption passage is closed by using the switching valve to guide the combustion gas to the catalyst passage in the purifying unit to prevent the adsorption member from being deteriorated due to the exhaust heat and purify the combustion gas by the catalytic action in the catalyst passage.

[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,
A catalyst having an adsorption passage for adsorbing harmful substances such as hydrocarbons (HC) in exhaust gas in a cold state and a catalyst for purifying the exhaust gas upstream of the catalytic converter interposed in the exhaust passage. A purifying means having a passage, a switching valve provided on the inlet side of the purifying means for guiding the exhaust gas to the adsorption passage or the catalyst passage, and a temperature for measuring the gas passage temperature of the exhaust gas near the inlet and the outlet of the catalyst passage. A sensor and a secondary air supply unit that is provided on the upstream side of the adsorption unit to introduce secondary air into the exhaust passage to purge the inside of the adsorption unit are provided.

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.

The inside of the exhaust passage 12 is divided into two in the longitudinal direction of the passage to have two passages 16A and 16B.
The purifying means 16 is interposed between the adsorbing passage and the other adsorbing passage, and the other is the adsorbing passage having a catalyst unit 53 carrying a catalyst for purifying the exhaust gas. Further, a switching valve 51 is provided on the inlet side of the purifying means 16, and a drive command is issued from an electronic control unit (ECU) 18 to an actuator 52, and the switching valve 51 is switched by driving the actuator 52. The gas G is guided to either of the passages 16A and 16B.

Further, temperature sensors 17A and 17B for measuring the gas temperature of each exhaust gas G are attached near the inlet and the outlet of the catalyst passage 16B, and the temperature sensors 17A and 17B are concerned with the temperature sensors 17A and 17B. Temperature sensor 17
An electronic control unit (hereinafter referred to as "ECU") 18 that receives the detection signal output from A and 17B 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.

Thus, 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 at the cold start of the engine 10 is
It is adsorbed by the adsorption member 15 in the adsorption passage 16A.
That is, the hydrocarbon (H) in the exhaust gas generated until the three-way catalyst of the catalytic converter 13 reaches the activation temperature.
A harmful substance such as C) is temporarily adsorbed by the adsorbing member 15.

In the present embodiment, when hydrocarbon (HC) is adsorbed by the adsorbing member 15 and the catalyst passage 16B side is closed by the switching valve 51, a small amount of exhaust gas is constantly discharged as shown in FIG. The valve body of the switching valve 51 is shortened so that the gas G flows, and the gas passing temperature of the exhaust gas G during the operation of the engine 10 can be measured by using the temperature sensors 17A and 17B. In addition, a small amount of exhaust gas G
The control valve 51 controls the switching valve 51 to flow
May be in a slightly open state.

By measuring the exhaust gas temperature on the upstream side and the downstream side of the catalyst unit 53, it can be confirmed that the temperature at which the catalyst is activated has been reached. That is, when, for example, the oxidation catalyst carried on the catalyst unit 53 reaches the activation temperature, the catalytic action starts, and the reaction temperature of the catalyst unit 53 causes the temperature measured by the temperature sensor 17B on the downstream side of the catalyst unit 53 to be measured on the upstream side. The temperature becomes higher than the measured temperature of 17A, and a temperature difference (for example, 30 ° C to 50 ° C) occurs.

By detecting the temperature difference of the gas passage temperature with the EUC 18, the catalyst of the catalyst unit 52 provided in the adsorbing means 16 reaches the activation temperature, and the hydrocarbon (H
It is confirmed that the state of C) has been reached.

Therefore, after detecting the temperature difference of the passing gas temperature, as shown in FIG. 3, the switching valve 51 is switched to purify by the catalyst unit 53, and the adsorption passage 16A is completely closed to remove the adsorption member 15. Prevents thermal deterioration due to high exhaust gas temperature.

The hydrocarbons (H
In C), when the switching valve 51 is in a neutral state before being fully closed, a detection signal is sent to the ECU 18, the switching valve 27 of the secondary air supply means is opened, and the air cleaner 26 is opened.
Secondary air is supplied to the exhaust passage 12 through the secondary air supply passage 19, the adsorption passage 16A of the supply means 16 is purged, and the adsorption member 15 is regenerated. For example, when the exhaust gas temperature is 300 ° C., this 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 passage 16
The hydrocarbons (HC) that have purged the inside of A and are 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. After performing this purge,
The passage switching valve 51 is operated by the ECU 18 to close the inlet of the adsorption passage 16A so that the exhaust gas flows to the catalyst passage 16B side. After that, the exhaust gas can be efficiently purified by using the catalytic action in the catalytic unit 52 and the catalytic converter 13 together.

In the above-described embodiment, the catalyst passage 16B of the purifying means 16 serves as means for measuring the activation temperature of the catalyst.
By adjusting the switching valve 51 that closes the exhaust gas G, the exhaust gas G is always allowed to flow little by little, and the passing gas temperature on the upstream side and the downstream side of the catalyst unit 53 is measured by the temperature sensor 17.
Although the measurement was performed using A and 17B, FIG. 4 shows a different means for introducing the exhaust gas G into the catalyst passage 16B at all times little by little.

That is, a bypass which communicates with the catalyst passage 16B of the purifying means 16 having the adsorption passage 16A and the catalyst passage 16B which are provided in the exhaust passage 12 and which communicates with the inlet side of the catalyst passage 16B and the exhaust passage 12, respectively. By providing the passage 54, the exhaust gas G is always introduced into the catalyst passage 16B. Therefore, in the present embodiment, the switching valve 51 has only to perform the operation of fully opening or fully closing the adsorption passage 16A or the catalyst passage 16B.

In the embodiment described above, the adsorption member 15 was purged when the switching valve 51 was in the neutral state. However, the passage switching valve 51 is operated to close the adsorption passage side and the catalyst passage 16B side. Exhaust gas is flown into the adsorbing passage 16B, and then, when the catalytic converter 13 is sufficiently activated, secondary air is introduced from a secondary air supply passage provided near the inlet on the adsorbing passage 16A side, and the inside of the adsorbing passage 16B is introduced. Of the hydrocarbon (H
C) may be sent to the catalytic converter 13 for purification.

As described above, during the cold start of the engine in which the three-way catalyst of the catalytic converter is inactive, harmful hydrocarbons (HC) are adsorbed in the adsorption passage 16A having the high-performance adsorption member 15 such as zeolite. After confirming that the temperature of the exhaust gas has reached the temperature at which the catalyst works by detecting the temperature difference between the front and rear of the catalyst unit 53, secondary air is supplied to purge the inside of the adsorbing means and refresh by combustion. It becomes possible to purify hydrocarbons (HC), and it becomes possible to purify hydrocarbons (HC) even immediately after a cold start of the engine.

Further, the catalyst passage 16 provided in the adsorption means 16
Since the exhaust gas is pre-purified by the catalyst unit 52 in B and is purified again by the catalytic converter 13 which is the main catalyst, the purification efficiency of the exhaust gas is significantly improved. Further, since the adsorption passage 16A is closed when purifying with the catalyst unit 53, deterioration of the adsorption member due to heat can be prevented, and exhaust gas can be purified stably over a long period of time. It will be possible.

[0038]

As described above with reference to the embodiments, the exhaust gas purifying apparatus according to the present invention uses the adsorbing means having the high-performance adsorbing member for adsorbing harmful substances generated during the inactive state of the catalytic converter at the time of cold start. After adsorbing and detecting the temperature difference of the exhaust gas in the catalyst passage and activating the catalyst to reach a predetermined activation difference, switch the switching valve to clean the inside of the catalyst passage and supply secondary air. Since it is purged and refreshed, harmful substances are always removed even during cold start, and exhaust gas is 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 schematic diagram of an exhaust gas purification device according to this embodiment.

FIG. 3 is a schematic diagram of an exhaust gas purification device according to this embodiment.

FIG. 4 is a schematic view of an exhaust gas purification device according to another embodiment.

FIG. 5 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 16A Adsorption Passage 16B Bypass Passage 17 Temperature Sensor 18 Electronic Control Unit (ECU) 19 Secondary Air Supply Passage 26 Air Cleaner 27 Switching Valve 28 Reed Valve 51 Passage Switching Valve 52 Actuator 53 Catalyst unit 54 Bypass passage G Exhaust gas

Claims (1)

[Claims] 1. An adsorption passage having an adsorbing member for adsorbing the combustion gas, the adsorption passage being provided in the exhaust passage upstream of a catalytic converter provided in the exhaust passage of the combustion gas of the internal combustion engine, and the exhaust gas. Purifying means having a catalyst passage having a catalyst for purifying the exhaust gas, a switching valve provided on the inlet side of the purifying means for guiding combustion gas to either the adsorption passage or the catalyst passage, and the inlet and outlet of the catalyst passage. A temperature sensor for measuring the gas passage temperature of the combustion gas, and a secondary air supply means communicating with the exhaust passage and supplying secondary air into the exhaust passage. An exhaust gas purifying device characterized in that the temperature sensor measures the gas passage temperature while controlling the switching valve while constantly flowing a small amount of combustion gas to the catalyst passage side.