JP2001027115A - Catalyst converter and exhaust emission control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform full exhaust emission control with small electric power even before a main catalyst part is activated. SOLUTION: When a controller 20 judges that a main catalyst part 11 is before being activated on the basis of an exhaust gas temperature, a selector switch 18 is turned to ON to have a sub-catalyst part 13 energized, and a selector valve 19 is operated to close a second inflow passage R2. Thereby, the sub-catalyst part 13 itself becomes a heating element for getting a high temperature to reach a catalyst activation temperature, and exhaust gas flows only into a first inflow passage R1. Consequently, as in the exhaust gas, its injurious ingredients are fully removed by having the gas passed through the activated sub-catalyst part 13, there is no problem even if the main catalyst part 11 is not activated. As a cross section of the sub-catalyst part 13 is smaller than that of the main catalyst part 11, electric power required for heating and activating the sub-catalyst part 13 may be small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalytic converter for purifying exhaust gas discharged from a vehicle engine and a method for purifying exhaust gas.

[0002]

2. Description of the Related Art Conventionally, in order to purify exhaust gas discharged from a vehicle engine, a catalytic converter is provided in an exhaust gas path of the vehicle engine. An exhaust gas purifying catalyst such as a three-way catalyst (hereinafter simply referred to as a catalyst) used in this catalytic converter does not sufficiently exhibit a purifying action unless its temperature is raised to a predetermined activation temperature or higher. For this reason, for example, in the catalytic converter described in Japanese Utility Model Application Laid-Open No. 63-67609, as shown in FIG.
When the main catalyst unit 111 has not reached the activation temperature, such as immediately after the start of a vehicle engine, the metal monolith catalyst 113 is activated by energizing and heating the metal monolith catalyst 113. The temperature of the main catalyst unit 111 is also increased.

[0003]

However, the catalytic converter shown in FIG. 3 is designed to have a larger cross-sectional area than a general exhaust pipe in consideration of the exhaust resistance when passing through the catalyst. Unless large power is supplied to the catalyst 113, there is a problem that the metal monolith catalyst 113 and the main catalyst unit 111 cannot be heated to an activation temperature or higher.

The present invention has been made in view of the above problems, and provides a catalytic converter and an exhaust gas purifying method that can sufficiently purify exhaust gas with a small amount of electric power even before the main catalyst section is activated. With the goal.

[0005]

Means for Solving the Problems and Effects of the Invention In order to solve the above problems, a catalytic converter according to the present invention comprises a main catalyst section provided in an exhaust gas path of a vehicle engine and an upstream side of the main catalyst section. A partition section for dividing an exhaust gas inflow path to the main catalyst section into two, a first and a second inflow path, a sub-catalyst section provided in the first inflow path, and heating of the sub-catalyst section when energized A heating unit, a switching valve for opening or closing the second inflow passage, and a second valve for energizing the heating unit and closing the second inflow passage by the switching valve before the main catalyst unit is activated. A controller that sets the state to 1 and sets the state to a second state in which the switching valve opens the second inflow path without energizing the heating unit after the main catalyst unit is activated. And

In the catalytic converter according to the present invention, the controller sets the first state before the main catalyst section is activated. Before the main catalyst section is activated, for example, during a cold start of the vehicle engine, even if the exhaust gas passes through the main catalyst section, harmful components in the exhaust gas (for example, C
O, HC, NOx) are not sufficiently removed. For this reason, in such a case, the sub-catalyst section is heated and activated by energizing the heating section, and the second valve is switched by the switching valve.
The setting is made such that the exhaust gas passes only through the first inflow channel by closing the inflow channel. At this time, the exhaust gas is sufficiently removed of harmful components by passing through the activated sub-catalyst section, in other words, is purified before passing through the main catalyst section. Therefore, even if the main catalyst section is not activated, the exhaust gas flows out of the catalytic converter in a state where harmful components have been sufficiently removed. Further, since the first inflow path is one of two parts of the exhaust gas inflow path into the main catalyst section, the cross-sectional area of the sub-catalyst section is smaller than the cross-sectional area of the main catalyst section, and the heat capacity of the sub-catalyst section is small. Is smaller than the heat capacity of the main catalyst portion. Therefore, the power required to heat and activate the sub-catalyst is smaller than the power required to heat and activate the main catalyst.

[0007] On the other hand, the controller sets the second state after the main catalyst section is activated. In this case, it is set so that the exhaust gas passes through both the first and second inflow paths by opening the second inflow path by the switching valve without energizing the heating unit. At this time, the exhaust gas flows out of the catalytic converter in a state where harmful components have been sufficiently removed by passing through the activated main catalyst portion. Also,
Since the exhaust gas flows into both the first and second inflow paths, the exhaust resistance is reduced, and the rise in back pressure is suppressed.

As described above, according to the catalytic converter of the present invention, even before the main catalyst section is activated, the sub-catalyst section having a smaller sectional area than the main catalyst section is activated by heating. At the same time, the exhaust gas is caused to flow only into the first inflow path in which the sub-catalyst section is provided, so that the exhaust gas can be sufficiently purified with a small amount of electric power. Further, after the main catalyst section is activated, exhaust gas is caused to flow into both the first and second inflow paths, so that exhaust resistance is reduced and back pressure rise is suppressed.

Here, in the catalytic converter of the present invention, the controller sets the first state when the exhaust gas temperature is lower than a predetermined temperature or when the main catalyst portion is lower than a predetermined activation temperature, When the temperature is equal to or higher than a predetermined temperature or when the temperature of the main catalyst unit is equal to or higher than a predetermined activation temperature, the second state may be set.
Since the activation of the main catalyst portion largely depends on the exhaust gas temperature, it is preferable to determine whether the main catalyst portion is activated based on the exhaust gas temperature. For example, a temperature detection unit is provided upstream of the main catalyst unit,
You may be comprised so that it may be determined whether the main catalyst part is activated based on the signal output from this temperature detection means. It is also preferable to directly detect the temperature of the main catalyst unit to determine whether the main catalyst unit is activated. For example, temperature detection means capable of detecting the internal temperature of the main catalyst unit may be provided, and it may be configured to determine whether the main catalyst unit is activated based on a signal output from the temperature detection unit. Good.

[0010] In the catalytic converter of the present invention,
The sub-catalyst unit may be configured to function as a heating element when energized, and also to function as the heating unit. In this case, since the heating unit does not need to be provided separately from the sub-catalyst unit, the installation space does not increase, and heating can be performed more efficiently than when the heating unit is provided separately. As such a sub-catalyst, for example, a catalyst in which a catalyst is supported on a conductive catalyst carrier, specifically, a metal monolith catalyst (see Japanese Utility Model Application Laid-Open No. 63-67609) or a conductive silicon carbide-based honeycomb catalyst ( 49-124412
Reference).

Next, the exhaust gas purifying method of the present invention includes a main catalyst section provided in an exhaust gas path of a vehicle engine and an exhaust gas inflow path to the main catalyst section upstream of the main catalyst section. A partition part for dividing into two of the second inflow channel,
A method of purifying exhaust gas by a catalytic converter having a sub-catalyst provided in the first inflow passage, wherein the sub-catalyst is heated and the first is heated before the main catalyst is activated. After the main catalyst section is activated, the heating of the sub-catalyst section is stopped and both the first and second inflow paths are opened.

According to this exhaust gas purifying method, similarly to the above-described catalytic converter, even before the main catalyst section is activated, the sub-catalyst section having a smaller sectional area than the main catalyst section is heated to be activated. At the same time, the exhaust gas is caused to flow only into the first inflow passage in which the sub-catalyst section is provided, so that the exhaust gas can be sufficiently purified with a small amount of electric power. Further, after the main catalyst section is activated, exhaust gas is caused to flow into both the first and second inflow paths, so that exhaust resistance is reduced and back pressure rise is suppressed.

Note that whether to open only the first inflow path or both the first and second inflow paths may employ, for example, a switching valve that opens or closes the second inflow path.
At this time, when the second inflow path is closed by the switching valve, only the first inflow path is opened, and when the second inflow path is opened, both the first and second inflow paths are opened. Become. As this switching valve, for example, an electrically operated switching valve may be used, but in addition, a shape memory alloy switching valve may be used, or a pressure operated valve operated by pressure may be used. When using a shape memory alloy switching valve,
When the exhaust gas temperature is lower than the predetermined temperature (that is, before activation of the main catalyst unit), the first inflow path is closed, and when the exhaust gas temperature is higher than the predetermined temperature (that is, after activation of the main catalyst unit), the first inflow path is opened. . When a pressure-operated valve is used, the first inflow passage is closed when the exhaust gas pressure is lower than a predetermined pressure (that is, before activation of the main catalyst unit), and when the exhaust gas pressure is higher than the predetermined pressure (that is, after activation of the main catalyst unit). The first inflow path is set to be opened.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory diagram of the catalytic converter of the present embodiment. The catalytic converter 10
It is provided in the exhaust gas path of the vehicle engine 2. This catalytic converter 10 mainly includes a main catalytic unit 11,
It includes a partition section 12, a sub-catalyst section 13, a switching valve 19, and a controller 20.

The main catalyst section 11 is a well-known monolithic catalyst, and is disposed inside the metal cylinder 6 forming a part of the exhaust gas path of the vehicle engine 2. The metal tube 6 is disposed between an upstream exhaust pipe 4 connected to the vehicle engine 2 and a downstream exhaust pipe 8 connected to a muffler (not shown). It is formed to be large. The reason why the cross-sectional area of the metal cylinder 6 is increased in this way is to improve the air permeability when the exhaust gas passes through the main catalyst unit 11.

The partition section 12 is a metal plate member that partitions an exhaust gas inflow path into the main catalyst section 11 into two, first and second inflow paths R1 and R2, on the upstream side of the main catalyst section 11. The sub-catalyst unit 13 is an electrically heated catalyst disposed in the first inflow passage R1, and here is a metal monolith catalyst that acts as a heating element when energized. The sub-catalyst unit 13 includes a center electrode 14, a monolith carrier 15 having a plurality of passages formed in the exhaust gas flow direction by winding a corrugated metal bed around the center electrode 14, and a monolith carrier 15. And a catalyst (not shown) carried in the plurality of passages. The sub-catalyst unit 13 is connected to the vehicle battery 17 so as to be energized. That is, the center electrode 14 of the sub catalyst unit 13 is
The metal cylinder 6 connected to one of the electrodes and in contact with the outermost shell of the monolith carrier 15 is connected to the other electrode of the vehicle battery 17 via the changeover switch 18. The center electrode 14 is exposed to the outside of the metal tube 6 while maintaining an insulating state so as not to be electrically short-circuited with the metal tube 6.

The switching valve 19 is an electromagnetic valve that opens or closes the second inflow path R2, and its operating position is switched by the controller 20. The temperature detection sensor 21 is installed upstream of the main catalyst unit 11 and outputs a detection signal to the controller 20.

The controller 20 includes a well-known C (not shown).
A PU, a ROM, a RAM, a clock, and the like, and are connected so that a detection signal from the temperature detection sensor 21 can be input;
The operation of the changeover switch 18 and the changeover valve 19 is connected so as to be controllable. Next, the operation of the catalytic converter of the present embodiment will be described. The controller 20 determines whether or not the main catalyst unit 11 is activated based on a detection signal from the temperature detection sensor 21, and operates the changeover switch 18 and the changeover valve 19 according to the result of the determination. This point will be described in detail.

After the ignition key of the vehicle (not shown) is turned on, the controller 20 reads the catalyst control program from a ROM (not shown) in the controller 20 at predetermined timings, and temporarily stores the data in a RAM (not shown) in the controller 20. Is stored, and processing is performed according to the flowchart of FIG.

First, based on a detection signal from the temperature detection sensor 21, it is determined whether or not the exhaust gas temperature is equal to or higher than a predetermined temperature (S10). Here, the predetermined temperature is the temperature detection sensor 21
The correlation between the temperature of the exhaust gas when passing through the filter and the degree of activity of the main catalyst unit 11 is empirically determined in advance, and the temperature of the exhaust gas when the main catalyst unit 11 is sufficiently activated is determined based on the correlation. The temperature is determined as a predetermined temperature. If the exhaust gas temperature is lower than the predetermined temperature in S10 (NO in S10), the first state setting flag of the RAM (not shown) in the controller 20 is set to "1" or "0".
Is determined (S11). The first state setting flag is a flag that is set to “1” when the changeover switch 18 and the changeover valve 19 are in the first state, and is set to “0” when the changeover switch 18 and the changeover valve 19 are in the second state. If the first state setting flag is “0”, the changeover switch 18 and the changeover valve 19 are set to the first state.
The state is set (S12), the first state setting flag is set to "1" (S13), and the process ends. On the other hand, if the first state setting flag is “1” in S11, the changeover switch 18 and the changeover valve 19 are already in the first state, and thus this processing is ended as it is.

The negative determination in S10 means that the exhaust gas temperature is lower than the predetermined temperature before the main catalyst unit 11 is activated. Even if the exhaust gas passes through the main catalyst unit 11, the exhaust gas is not sufficiently purified. If the changeover switch 18 and the changeover valve 19 are not in the first state, the state is set to the first state, and if the state is the first state, the state is maintained. Here, the first state refers to a state in which the changeover switch 18 is turned on to energize the sub-catalyst unit 13, and the changeover valve 19 is operated to close the second inflow path R2. As a result, the sub-catalyst section 13 itself becomes a heating element and rises in temperature to reach the activation temperature of the catalyst, and the exhaust gas flows only into the first inflow path R1. As a result, the harmful components of the exhaust gas are sufficiently removed by passing through the activated sub-catalyst unit 13. In other words, the exhaust gas is purified before passing through the main catalyst unit 11. Therefore, even if the main catalyst unit 11 is not activated, the exhaust gas flows out of the catalytic converter in a state where harmful components have been sufficiently removed. Further, since the first inflow path R1 is one of the two sections of the exhaust gas inflow path to the main catalyst section 11, the cross-sectional area of the sub-catalyst section 13 is smaller than the cross-sectional area of the main catalyst section 11, and The heat capacity of the catalyst unit 13 is smaller than the heat capacity of the main catalyst unit 11. Therefore, the power required to heat and activate the sub-catalyst unit 13 is smaller than the power required to heat and activate the main catalyst unit 11.

On the other hand, if the exhaust gas temperature is equal to or higher than the predetermined temperature in S10 (YES in S10), it is determined whether the first state setting flag is "1" or "0" (S14), and the first state setting flag is set to "1". ", The changeover switch 18 and the changeover valve 1
9 is changed from the first state to the second state (S15), the first state setting flag is set to "0" (S16), and this processing ends. On the other hand, if the first state setting flag is “0” in S14, the changeover switch 18 and the changeover valve 19 are already in the second state, and thus this process is terminated.

The affirmative determination in S10 means that the exhaust gas temperature is equal to or higher than the predetermined temperature, the main catalyst section 11 has already been activated, and the exhaust gas is purified when passing through the main catalyst section 11. 18 and switching valve 1
If 9 is not the second state, it is set to the second state, and if it is the second state, it is maintained. Here, the second state means that the changeover switch 18 is turned off to stop energizing the sub-catalyst unit 13, and the changeover valve 19 is operated to operate the second inflow passage R2.
Means to release As a result, the exhaust gas flows out of the catalytic converter 10 in a state where the harmful components have been sufficiently removed by passing through the activated main catalyst portion 11. Further, since the exhaust gas flows into both the first and second inflow paths R1 and R2, the exhaust resistance is reduced as compared with the case where the exhaust gas flows only into the first inflow path R1, and the back pressure rise is suppressed.

As described in detail above, according to the catalytic converter 10 of the present embodiment, the following effects can be obtained. Even before the main catalyst section 11 is activated, the sub-catalyst section 13 having a smaller sectional area than the main catalyst section 11 is heated and activated, and only the first inflow path R1 in which the sub-catalyst section 13 is installed is provided. Since the exhaust gas flows into the exhaust gas, it is possible to sufficiently purify the exhaust gas even with a small amount of electric power. After the main catalyst unit 11 is activated, the first and second inflow paths R
Since exhaust gas flows into both R1 and R2, exhaust resistance is reduced, and back pressure rise is suppressed. The controller 20 sets the first state when the exhaust gas temperature is lower than the predetermined temperature, and sets the controller 20 to the second state when the exhaust gas temperature is equal to or higher than the predetermined temperature. Since the activation of the main catalyst unit 11 largely depends on the exhaust gas temperature, it is possible to accurately determine whether or not the main catalyst unit 11 is activated based on the exhaust gas temperature. The sub-catalyst section 13 functions as a heating element when energized, and also functions as a heating section. Therefore, it is not necessary to provide a heating section such as a heater as a separate body from the sub-catalyst section 13 and the installation space is large. First, heating can be performed more efficiently than when the heating unit is provided separately.

It should be noted that the embodiments of the present invention are not limited to the above-mentioned embodiments at all, and it goes without saying that various forms can be adopted as long as they fall within the technical scope of the present invention. For example, in the above-described embodiment, a so-called metal monolith catalyst is used as the sub-catalyst unit 13, but a catalyst in which a catalyst is supported on a silicon carbide ceramic honeycomb carrier having conductivity may be used. The effects (1) to (3) of the embodiment are obtained. Alternatively, a non-conductive monolithic catalyst may be used as the sub-catalyst, and a heater as a heating unit may be provided near the sub-catalyst, and this heater may be connected to the battery and the changeover switch. In this case, it is necessary to separate the sub-catalyst section and the heating section, but since the sub-catalyst section has a smaller heat capacity than the main catalyst section, the main catalyst section 11
An effect is obtained that the exhaust gas can be sufficiently purified with a small amount of electric power even before the gas is activated. Note that the main catalyst unit and the sub catalyst unit are not limited to the monolithic catalyst, but may be, for example, a pellet catalyst.

Although the switching valve 19 is operated by the controller 20 in the above embodiment, the second inflow passage R2 is closed when the exhaust gas temperature is lower than a predetermined temperature (before the activation of the main catalyst section 11). When the temperature is equal to or higher than a predetermined temperature (after activation of the main catalyst unit 11), a switching valve made of a shape memory alloy that opens the second inflow path R2 may be used, or the exhaust gas pressure is lower than the predetermined pressure (the activation of the main catalyst unit 11). A pressure-operated valve that closes the second inflow passage R2 before (before), and opens the second inflow passage R2 when the pressure is equal to or higher than a predetermined pressure (after activation of the main catalyst unit 11).

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a catalytic converter of the present embodiment.

FIG. 2 is a flowchart illustrating a process of a controller.

FIG. 3 is a schematic explanatory view of a conventional catalytic converter.

[Explanation of symbols]

2 ... vehicle engine, 4 ... upstream exhaust pipe, 6 ...
Metal tube, 8 Downstream exhaust pipe, 10 Catalytic converter, 11 Main catalyst unit, 12 Partition unit, 13 Sub-catalyst unit, 14 Central electrode, Fifteen
... Monolith carrier, 17 ... Vehicle battery, 18.
..Changeover switch, 19 ... Switching valve, 20 ... Controller, 21 ... Temperature detection sensor, R1 ... First
Inflow channel, R2... Second inflow channel.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/28 B01D 53/36 ZABB F-term (Reference) 3G091 AA02 AB01 AB03 BA03 BA23 BA24 BA25 CA04 CA13 DA01 DA02 DA03 DB10 EA17 EA32 FA02 FA04 FB02 FC04 FC07 GA01 GA06 GA19 GB01X GB01Z GB10X GB17X HA38 HA47 4D048 AA06 AA13 AA18 AB01 AB02 AB03 CC25 CC26 CC32 CC43 DA02 DA06

Claims (4)

[Claims] 1. A main catalyst section provided in an exhaust gas path of a vehicle engine, and an exhaust gas inflow path to the main catalyst section upstream of the main catalyst section is divided into a first and a second inflow path. A partition, a sub-catalyst provided in the first inflow passage, a heating unit that heats the sub-catalyst when energized, a switching valve that opens or closes the second inflow passage, and the main catalyst Before the unit is activated, the heating unit is energized and the switching valve is set to a first state in which the second inflow path is closed. After the main catalyst unit is activated, the heating unit is energized. A controller for setting the second state in which the second inflow path is opened by the switching valve without using the switching valve. 2. The controller sets the first state when the exhaust gas temperature is lower than a predetermined temperature or when the main catalyst unit is lower than a predetermined activation temperature, and when the exhaust gas temperature is higher than a predetermined temperature, or The catalytic converter according to claim 1, wherein the second state is set when the temperature of the main catalyst section is equal to or higher than a predetermined activation temperature. 3. The catalytic converter according to claim 1, wherein the sub-catalyst functions as a heating element when energized, and also functions as the heating unit. 4. A main catalyst section provided in an exhaust gas path of a vehicle engine, and an exhaust gas inflow path to the main catalyst section at an upstream side of the main catalyst section is divided into a first and a second inflow path. A method for purifying exhaust gas by a catalytic converter having a partition portion and a sub-catalyst portion provided in the first inflow path, wherein the sub-catalyst portion is heated before the main catalyst portion is activated. At the same time, only the first inflow path is opened, and after the main catalyst section is activated, the heating of the sub-catalyst section is stopped and both the first and second inflow paths are opened. Exhaust gas purification method.