JPH04175417A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a high NOx purifying rat irrespective of the degree of a catalyst bed temperature or exhaust temperature by detecting the catalyst bed temperature of a catalyst for reducing nitrogen oxide under the presence of carbon oxide in the oxidized atmosphere or the exhaust temperature to supply the carbon oxide upstream of the catalyst according to the result of the detection. CONSTITUTION:An exhaust path 2 of an internal combustion engine 1 is provided with a lean NOx catalyst 3. Then, a HC supply means 5 is provided upstream of the lean Nox catalyst 3. The HC supply means 5 is provided with a change-over valve 7 to supply any kind of HC from a plurality of kinds of HC supply sources 6a, 6b having different boiling points. Further are provided a change-over valve driving device 8 for driving the change-over valve 7, a flow controlling valve 9 for controlling the flow of the selected kind of HC and a flow controlling valve driving device 10 for driving the flow controlling valve 9. An exhaust temperature sensor 4 for detecting the exhaust temperature is provided right upstream of the lean NOx catalyst 3 to input the output to a control unit (ECU) 11. The ECU controls the supply of HC through the respective drive devices 8, 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust purification device in which a zeolite-based catalyst that reduces NOx in the presence of HC in an oxidizing atmosphere is installed in the exhaust system of a lean-burn internal combustion engine. .

[Conventional technology]

A so-called lean NOx catalyst, which is made of zeolite supporting a transition metal or a noble metal and reduces Now in exhaust gas in an oxidizing atmosphere in the presence of HC, is known (for example, JP-A-1-130735). .

Lean NOx catalyst requires HC to reduce NOx, so in order to achieve good NOx purification effect, lean NOx catalyst is required to reduce NOx.
It is also known to provide an HC supply device upstream of the Ox catalyst (for example, Japanese Patent Application Laid-Open No. 63-283727).
For example, in a diesel engine, since there is little HC in the exhaust, it is desirable to add diHC.

[Problem to be solved by the invention]

However, conventionally, only a certain type of HC is uniformly supplied upstream of the lean NOx catalyst, so a high NOx purification rate may not be obtained depending on the type of HC and the temperature of the lean NOx catalyst.

For example, in a region where the exhaust gas temperature is low (below 400° C.), if the injected HC is high boiling point HC, the NOx purification rate will not improve.

Conversely, in a region where the exhaust temperature is high, if the injected HC is low boiling point HC, the active species generated by partial oxidation of HC will be immediately oxidized to COt, resulting in NOx
Purification rate decreases.

An object of the present invention is to provide an exhaust purification device for an internal combustion engine that can exhibit a high NOx purification rate regardless of whether the catalyst bed temperature or exhaust gas temperature is in a relatively high or relatively low range. do.

[Means to solve the problem]

The above object is achieved by the following exhaust gas purification device for an internal combustion engine according to the present invention. That is, in an exhaust purification device for an internal combustion engine that is installed in the exhaust system of an internal combustion engine and is equipped with a catalyst that reduces nitrogen oxides in an oxidizing atmosphere and in the presence of hydrocarbons, it is installed separately from the engine. , a hydrocarbon supply source that supplies hydrocarbons to the engine; a temperature detection means for detecting a catalyst bed temperature of the catalyst or an exhaust temperature; and a temperature detection means that detects a high catalyst bed temperature or exhaust temperature. When detected, the hydrocarbons from the hydrocarbon supply source are supplied upstream of the catalyst so that the hydrocarbons contain a large amount of high-boiling point hydrocarbons, and the catalyst bed temperature or exhaust temperature is low. and a hydrocarbon supply means for supplying hydrocarbons from the hydrocarbon supply source upstream of the catalyst in such a manner that the hydrocarbons contain a large amount of low-boiling point hydrocarbons. Exhaust purification device for internal combustion engines.

[Effect]

In the exhaust gas purification device for an internal combustion engine according to the present invention, when the catalyst bed temperature or the exhaust temperature is high, hydrocarbons are supplied so as to contain a large amount of high boiling point hydrocarbons, but the high boiling point hydrocarbons are HC on NOx catalyst → active species → Co,
The conversion rate of co, is slow, and the time that active species exist is long (
Since the active species and NOx react with each other, the NOx purification rate improves. Furthermore, when the catalyst bed temperature or exhaust temperature is low, hydrocarbons are supplied so that they contain a large amount of low-boiling point hydrocarbons, but low-boiling point hydrocarbons are oxidized relatively quickly on the lean NOx catalyst. , even at relatively low temperatures.
Partial oxidation of hydrocarbons generates active species, resulting in NOx
Purification rate improves. In this way, a high NOx purification rate can be obtained on both the low temperature side and the high temperature side, and the temperature range in which a high NOx purification rate can be obtained is expanded.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an exhaust purification device for an internal combustion engine according to the present invention will be described below with reference to the drawings.

First example 1 to 4 relate to a first embodiment of the present invention.

As shown in FIG. 1, the first embodiment is an internal combustion engine equipped with a catalyst 3 that is installed in an exhaust system 2 of an internal combustion engine l and that reduces nitrogen oxides in an oxidizing atmosphere and in the presence of hydrocarbons. In the exhaust purification device, hydrocarbon supply sources 5a and 6b, which are provided separately from the engine 1 and supply a plurality of types of hydrocarbons with different boiling points to the engine, and a catalyst bed temperature of the catalyst 3; A temperature detection means 4 detects the exhaust gas temperature, and when the temperature detection means 4 detects that the catalyst bed temperature or the exhaust temperature is high, the hydrocarbon supply sources 6a, 6b
Among the hydrocarbons from the catalyst, high boiling point hydrocarbons are supplied upstream of the catalyst so that they are contained in a larger amount than low boiling point hydrocarbons, and when it is detected that the catalyst bed temperature or exhaust temperature is low,
Among the hydrocarbons from the hydrocarbon supply source, low boiling point hydrocarbons are supplied in a higher amount than high boiling point hydrocarbons (including a hydrocarbon supply means 5 for supplying the hydrocarbons upstream of the catalyst). Become.

The first embodiment will be described in more detail with reference to FIGS. 1 to 4. However, hereinafter, the catalyst 3 will be referred to as a lean NOx catalyst, and the hydrocarbon will be referred to as HC.

The exhaust passage 2 of the internal combustion engine 1 is provided with a catalytic converter containing a lean NOx catalyst 3.

Here, the lean NOx catalyst is made of zeolite on which transition metals or noble metals are supported, and in an oxidizing atmosphere, HC
It is a catalyst that reduces NOx in exhaust gas in the presence of NOx.

An HC supply means 5 is provided upstream of the lean NOx catalyst 3, and the HC supply means 5 supplies a plurality of types of H having different boiling points.
C supply f! It has a switching valve 7 that switches to supply any type of HC from 16a, 6b, . . . .

l(C supply means 5 further includes a switching valve driving device 8 that drives the switching valve 7, a flow control valve 9 that controls the flow rate of the selected type of HC, and a flow control valve that drives the flow control valve 9. It has a drive device 10.

The HC sources 6a and 6b include a low boiling point HC source 6a and a high boiling point HC source 6b. Low-boiling HC consists of hydrocarbons with a carbon number of 5 or less, and high-boiling HC consists of hydrocarbons with a carbon number of 6 or more.

Immediately upstream of the lean NOx catalyst 3, an exhaust temperature sensor 4 is installed as a temperature detection means that detects and outputs gas salts entering the lean NOx catalyst 3. The temperature detection means may be a temperature sensor that detects the catalyst bed temperature of the lean NC3x catalyst 3. In short, it may be any sensor that can detect the catalyst temperature or a temperature correlated thereto (for example, exhaust temperature). The output of the exhaust temperature sensor 4 as a means is input to an engine control unit (ECU) 11.

The ECU II controls the switching of the switching valve drive device 8, controls the drive of the flow rate control valve drive device 10, and thus constitutes an HC supply means control means that controls the supply of HC.

ECLIII consists of a microcomputer, an input/output interface, and a central processor unit (
(CPU), read-only memory (ROM), and random access memory (RAM). Exhaust temperature sensor 4
The output signal is input to the input interface, converted into a digital signal via an analog/digital converter, temporarily stored in RAM, and read out to the CPU when necessary for use in calculations. Signals of engine rotational speed Ne and torque T are also input to the ECU II.

The ECU II stores the program shown in FIG. 2 in its ROM, and this calculation routine is read out by the CPU and executed at regular time intervals. In FIG. 2, in step 101, the catalyst temperature or exhaust temperature TEX, engine rotational speed Ne, and torque T are read.

Subsequently, in step 1G2, the catalyst temperature or exhaust temperature T
EX is at a predetermined temperature TEXO (for example,
400℃) or less, and if it is less than TEXO, proceed to step 103, and if it exceeds TEXO, proceed to step 1.
In step 103, the switching valve 7 is switched to the low boiling point H.
A signal for switching to the C supply side is sent to the switching valve drive device 8, and a low boiling point HC supply execution process is performed. On the other hand, step 104
Now, a signal for switching the switching valve 7 to the high boiling point HC supply side is sent to the switching valve driving device 8, and a high boiling point HC supply execution process is performed.

Proceeding to step 105 from steps 103 and 104, the flow rate of the supplied HC is controlled, that is, step 105
Then, calculate the state of the exhaust gas (exhaust gas amount, Hcs degree) from the engine rotation speed Ne and torque T, find the required amount of HC to be injected, and set the target opening degree of the flow control valve to supply the required amount of HC. demand. Next, proceed to step 106,
A command signal for setting the opening degree of the flow rate control valve 9 to the target opening degree determined in step 105 is sent to the flow rate control valve driving device 1o, and the opening degree control execution process for the flow rate control valve 9 is performed. Then move on to the next step and finish.

Next, the operation of the first embodiment will be explained.

First, the NOx purification mechanism of the lean NOx catalyst 3 is as follows.
It is estimated that the situation will be as shown in FIG.

In other words, most of the HC in the exhaust gas is directly (completely) oxidized to CO8 and HxO, but some is partially oxidized to active species (estimated to be Co-like).
A part of this active species reacts with NOx to reduce NOx,
Purify. The remainder of the active species is oxidized to CO1co, - For boat fishing, at high temperatures (e.g., 500°C or higher), most of the HC is completely oxidized and becomes COx, HzO.
, the rate of partial oxidation decreases and the amount of active species decreases, and even if active species are formed, the rate of oxidation to co and cot increases, reducing the amount of active species used for reaction with NOx. Since the amount decreases, the N0w purification rate decreases. Also, at low temperatures (approximately 350'C or below), lean NO
As the activity of the x catalyst itself decreases, the NOx purification rate also decreases. Therefore, the NOx purification rate-temperature characteristic has a peak at a certain temperature between 350°C and 500'e. The temperature at which this peak appears depends on the type of HC.

Figure 3 shows the NOx purification rate characteristics of low boiling point HC and high boiling point HC.
The NOx purification rate characteristics of the present invention and the NOx purification rate characteristics of the present invention are shown. In other words, in the case of low boiling point HC, the molecules are small and oxidation (partial oxidation) proceeds quickly, so it is
Active species are generated even at low temperatures (below 00°C), and complete oxidation occurs at temperatures above 400°C, and no active species remain. Therefore, the peak showing a high NOx purification rate, as shown in curve A in Figure 3, Appears on the side (below 400℃). On the other hand, in the case of high boiling point HC, the molecules are thick and HC - active species amount CO, CO
The reaction of □ is also slow, and even in the high temperature range (above 400°C), a considerable amount of active species remains, and these react with NOx, so the peak showing a high NOx purification rate is as shown in curve B in Figure 3. In the present invention, the switching valve 7 is switched to the low boiling point HC side in the low temperature range (400°C or lower), and the switching valve 7 is switched to the high boiling point H side in the high temperature range (400°C or higher).
Since it is used by switching to the C side, the NOx purification rate characteristics in the present invention are as shown by curve C in Fig. 3.
The envelope curves are curves A and B, and a high NOx purification rate can be exhibited on both the low temperature side and the high temperature side. In other words, in the present invention, the region (mountain portion) in which a high NOx purification rate can be exhibited has been expanded to a wider temperature range.

According to the first embodiment, a plurality of types of HC with different boiling points
is selectively supplied upstream of the lean NOx catalyst, and depending on the catalyst temperature of the lean NOx catalyst or the exhaust temperature, low boiling point HC is supplied at low temperatures and high boiling point HC at high temperatures. It is possible to make the lean NOx catalyst exhibit a high NO purification rate on both the high temperature side and the high temperature side. Therefore, the temperature range in which a high NOx purification rate can be exhibited is expanded.

Second example 5 to 9 relate to a second embodiment of the present invention.

However, FIGS. 3 and 4 also apply to the second embodiment.

As shown in FIGS. 5 and 6, the second embodiment includes a catalyst 23 that is installed in the exhaust system 22 of an internal combustion engine 21 and reduces nitrogen oxides in an oxidizing atmosphere in the presence of hydrocarbons. In the exhaust gas purification device for an internal combustion engine, a hydrocarbon supply source 26, which is provided separately from the engine 21 and supplies hydrocarbons to the engine, and a catalyst bed temperature of the catalyst or an exhaust temperature are detected. Temperature detection means 201 and 202, and when the temperature detection means detects that the catalyst bed temperature or the exhaust temperature is high, the hydrocarbons from the hydrocarbon supply source 26 are transferred to the intake system 24 of the internal combustion engine and the exhaust system. 22, and when it is detected that the catalyst bed 2 temperature or the exhaust gas temperature is low, the hydrocarbons from the hydrocarbon supply source 26 are supplied to the exhaust system 22 of the internal combustion engine in a larger amount than to the intake system 24. It consists of an exhaust gas purification device for an internal combustion engine provided with a hydrocarbon supply means 25.

The second embodiment will be described in more detail with reference to FIGS. 5 to 9, and FIGS. 3 and 4. However, in the following, the catalyst 23 is a lean NOx catalyst, and the hydrocarbon is H
It is written as C.

In the second embodiment, as shown in FIG. 5, a catalytic converter containing a lean NOx catalyst 23 is provided in the exhaust passage 22 of the internal combustion engine 21.

HC is supplied to the exhaust system 22 and intake system 24 upstream of the lean NOx catalyst 23 by an HC supply means at a variable supply ratio. The HC supply means 25 supplies H from the HC supply source 26.
C is introduced into the exhaust system 22 and intake system 24 upstream of the lean NOx catalyst 23.
The HC control valve 29, the first HC control valve driving device 30 that drives the first HC control valve 28, and the second HC@
Second HC control valve drive device 3 that drives the control valve 29
1. Here, the HC supplied from the HC supply source 26 is IC having 6 or more carbon atoms per molecule (m of CmHn is 6 or more), and is, for example, light oil. The first HC control valve drive device 30 and the second HC control valve drive device 31 are connected to the first HCIIi11 control valve 28 and the second HC control valve 28 so as to exhibit the relationship shown in FIGS. 7 and 8, for example.
Control valve 29 is actuated. Therefore, lean N.

The amount of HC supplied to the exhaust system 22 upstream of the X catalyst 23 and the HC supply ratio supplied to the intake system 24 are variable. Such variable supply ratio also includes selective supply such as turning one side ON and the other OFF. First HC control valve 28, second HC control valve 29
also serves as a flow rate control valve that controls the flow rate of HC. 1st H
The C control valve drive device 30 and the second MCl4 control pulp drive device 31 are connected to an engine control unit (EC
Its operation is controlled by instructions from U) 32.

Therefore, ECU32 is more precisely ECU32
A part of the program stored in the Hc supply means 25
This constitutes an HC supply means control means for controlling the HC supply means. ECU3
2, signals of the engine rotational speed Ne and ) torque T are also input.

The ECU 32 stores the program shown in FIG. 6 in its ROM, and this calculation routine is read out by the cPU and executed at regular time intervals. - In FIG. 6, in step 201, the engine rotational speed (Nes) and torque T are read.

Subsequently, in step 202, the catalyst temperature or exhaust gas temperature TEX is calculated from the map of FIG. 9 of the engine rotational speed Ne, torque T, and exhaust temperature (temperature correlated with the catalyst temperature).

For the exhaust gas temperature, an exhaust temperature sensor may be provided immediately upstream of the lean NOx catalyst 23, and its output may be used.

Subsequently, in step 203, the catalyst temperature or exhaust temperature T
EX is at a predetermined temperature TEXO (for example,
400℃) or less, and if it is less than TEXo, proceed to step 204, and if it exceeds TEXO, proceed to step 2.
Proceed to 05.

In step 204, the opening degree of the first HC control valve 28 is increased, and the opening degree of the second HCMm valve 29 is decreased, so that the amount of HC supplied to the intake system 24 is equal to the amount of HC supplied to the exhaust system 22.
Change the supply ratio so that it is greater than the amount of C, and 24.
In order to control the flow rate of the HC amount to 22 to the required HC amount, a command signal is output to the drive devices 30 and 31 to perform valve opening/closing execution processing.

Further, in step 205, the opening degree of the first HC control valve 28 is made small, and the opening degree of the second HC control valve 29 is made large, so that the amount of HC supplied to the exhaust system 22 is supplied to the intake system 24. A command signal is output to the drive device 30.31 to execute pulp opening/closing by changing the supply ratio so that it is larger than the amount and controlling the flow rate of HC amount to each prefecture 22.24 to the required HC amount. In the above, step 20
3.204.205 constitutes HC supply means control means.

From steps 204 and 205, the process proceeds to the next step and ends the calculation.

Next, the operation of the second embodiment will be explained.

In the second embodiment, in a low temperature range (for example, 400° C. or lower), a larger amount of high boiling point HC is injected into the intake system 24 than into the exhaust system 22, and some of it is decomposed by combustion in the combustion chamber.
It is partially oxidized to HC with a small number of carbon atoms (C50),
Since it flows to the lean NOx catalyst 23, the same effect can be achieved as if low boiling point HC were injected immediately upstream of the lean NOx catalyst 23. That is, in the low temperature range, characteristics similar to the characteristics of the curve in FIG. 3 are obtained. On the other hand, the high temperature range (
For example, at temperatures above 400°C, high boiling point HC is
2 is injected more than the intake system 24, and the lean NOx catalyst 2
3 reacts slowly and produces large amounts of active species. Therefore, in the high temperature range, the characteristics of curve B in FIG. 3 are obtained. As a result, the NOx purification rate characteristic of the present invention becomes an envelope curve of curves A and B, as shown by curve C in FIG. Become. Stated another way, in the present invention, a high N
This means that the region (mountain portion) in which the Ox purification rate can be shown has been expanded to a wider temperature range.

According to the second embodiment, the HC supplied by the HC supply means is supplied to the intake system in a larger amount than the exhaust system in a low temperature range, and in a high temperature range in a larger amount to the exhaust system than the intake system. The supplied HC is decomposed in the combustion chamber and becomes low boiling point HC.
The HC supplied to the exhaust system flows directly to the lean NOW catalyst, which can generate a large amount of active species on both the low and high temperature sides, giving the lean NOX catalyst a high NO purification rate. can be shown. Therefore, the temperature range in which a high NOx purification rate can be exhibited is expanded.

3rd to 5th embodiments The third to fifth embodiments are installed in the exhaust system 42.62.82 of an internal combustion engine 41.61.81, in an oxidizing atmosphere and in the presence of hydrocarbons. Catalyst for reducing nitrogen oxides43.
In an exhaust purification device for an internal combustion engine equipped with 63.83,
A hydrocarbon supply source 46, 66, 86, which is provided separately from the above engine and supplies high boiling point hydrocarbons to the above engine, and which decomposes the high boiling point hydrocarbons from the hydrocarbon supply source into low boiling point hydrocarbons. Hydrocarbon decomposition means 47.6 supplied to the above engine
7.87, temperature detection means 44.64.84 for detecting the catalyst bed temperature of the catalyst or the exhaust gas temperature, and when the temperature detection means detects that the catalyst bed temperature or the exhaust gas temperature is high. , high boiling point hydrocarbons from the hydrocarbon supply source are supplied upstream of the catalyst so that they are contained in a larger amount than low boiling point hydrocarbons from the hydrocarbon decomposition means, and it is detected that the catalyst bed temperature or exhaust temperature is low. an internal combustion engine provided with hydrocarbon supply means 45.65.85 for supplying low-boiling hydrocarbons from the hydrocarbon cracking means in a greater amount than high-boiling hydrocarbons from the hydrocarbon supply source; The system consists of an exhaust gas purification system.

Each embodiment will be explained in more detail as follows. However, in the following description, the catalyst 43.63.83 will be referred to as a lean NOx catalyst, and the hydrocarbon will be referred to as HC.

Third Embodiment FIGS. 10 to 14 relate to the third embodiment, and FIGS.
The figure also applies to the third embodiment. In the third embodiment, as shown in FIG. 1O, the exhaust passage 42 of the internal combustion engine 41 is
A lean N0w catalyst 43 is provided.

Upstream of the lean NOx catalyst 43, HC is supplied from an HC supply source 46 by an HC supply means 45. An exhaust temperature sensor 44 is provided downstream of the lean NOx catalyst 43 to detect exhaust temperature.

The HC of the HC supply source 46 includes HC with a high flash point.

That is, HCl or fuel such as light oil or gasoline having a relatively high boiling point is used, and a mixed gas with air or nitrogen is used to obtain an appropriate concentration (for example, 20%).

The HC supply means 45 includes an HC control well 48 and its actuator 49 for controlling the amount of HC supplied.

The actuator 49 increases the valve opening as the engine speed Ne increases and as the torque T increases (first
(see FIGS. 2 and 13), the actuator 49 is controlled to open and close according to commands from an engine control computer (ECU) 52.

An HC decomposition means 47 is provided in the HC supply passage of the HC supply means 45 downstream from the HC control well 48 . This HC decomposition means 47 includes, for example, H-type mordenite, Y-type mordenite,
Decomposition of zeolite systems such as type zeolite and H type ZSM-5,
A partial oxidation catalyst 50 is loaded. The catalyst 50 is also heated by a heater 51. The heater voltage of the heater 51 becomes smaller as the exhaust gas temperature TEX at the catalyst outlet becomes higher (see FIG. 14), and the degree of heating is controlled by the engine control computer 52.

The engine control computer 52 is composed of a microcomputer, and stores a program as shown in FIG. 11 in a ROM, and this program is called by the CPU to execute calculations.

First, in step 301, the catalyst bed temperature or exhaust temperature TE
Read X, engine speed Ne, and torque T.

Next, the process proceeds to step 302, where the engine rotation speed N
e. The opening degree of the HC control well 48 is determined from the torque T in Fig. 12.
Step 303 calculates based on the one-dimensional map shown in FIG. 13, and sets HC@@valve opening to the calculated value
At this point, the actuator 49 executes the Hc control valve opening control process.

Next, the process proceeds to step 304, where the target voltage of the heater 51 is calculated from the catalyst bed temperature and exhaust temperature TEX based on a one-dimensional map as shown in FIG. 14, and the calculated voltage is obtained. In step 305, heater voltage control is executed.

Next, the operation of the third embodiment will be explained.

The catalyst bed temperature or exhaust temperature TEX is low (for example, 4
(00°C or lower), the heater voltage is increased, and the decomposition catalyst 50 promotes the decomposition of the relatively high boiling point IC from the HC supply source 46, converting it into HC containing a large amount of olefinic HC having 3 to 6 carbon atoms. It is supplied upstream of the lean NOx catalyst 43. Therefore, it matches the characteristics shown in FIG. 3, and a good NOx purification rate can be obtained regardless of the low temperature range.

Conversely, when the catalyst bed temperature or the exhaust TEX is high (for example, 400° C. or higher), the heater voltage is lowered to suppress the decomposition of HC by the decomposition catalyst 50, resulting in a state containing a large amount of HC with a relatively large number of carbon atoms. HC from the HC supply source 46 is supplied upstream of the lean NOx catalyst 43. Most of HC with a small number of carbon atoms is directly oxidized when the exhaust temperature is high and is not effectively used for NOx reduction, but when the exhaust temperature is high, it is supplied in the form of HC with a large number of carbon atoms. It is partially oxidized and generates a large amount of active species, meeting B in FIG. 3, and a good NOx purification rate can be obtained regardless of the high temperature range. (Thus, as shown in C in FIG. 3, a good NOx purification rate can be obtained in both the low temperature range and the high temperature range.

According to the third embodiment, the HC decomposition means 47 is provided, and when the catalyst bed temperature and the exhaust gas temperature are low, the HC decomposition by the HC decomposition means 47 is promoted and the HC is converted into low carbon number HC. In the high catalyst bed temperature and exhaust temperature range, HC
Since the decomposition of HC by the decomposition means 47 is suppressed to make HC with a high carbon number and the HC is supplied upstream of the lean NOx catalyst, it is possible to obtain a good NOx purification rate in both the low temperature range and the high temperature range.

Fourth Embodiment FIGS. 15 to 17 relate to the fourth embodiment, and FIGS.
12 and 13 are also applied to the fourth embodiment.

In the fourth embodiment, as shown in FIG. 15, a lean NOx catalyst 63 is provided in an exhaust passage 62 of an internal combustion engine 61. Upstream of the lean NOx catalyst 63, HC is supplied from an HC supply source 66 by an HC supply means 65. Further, downstream of the lean NOx catalyst 63, an exhaust temperature sensor 64 is provided to detect exhaust temperature.

The 1 liter 166 HC of HC supplied contains HCl with a relatively high boiling point.
For example, light oil is used. H from HC source 66
The C supply passage has a parallel path in the middle, and an HC decomposition catalyst 67 as HC decomposition means is provided in the - side of the passage. As the HC decomposition catalyst 67, H type mordenite, Y
Decomposition of zeolite systems such as type zeolite and H type ZSM-5,
A partial oxidation catalyst is used.

The HC supply means 65 supplies HC from the HC supply source 66 to the upstream side of the lean NOx catalyst 63.
It has an HC control valve 70 and its actuator 71 for controlling the C flow rate, and a switching pulp 68 and its actuator 69 provided at the branch point of the parallel path. As shown in FIGS. 12 and 13, the actuator 71 increases the opening degree of the HCIIIJm valve 70 as the engine speed Ne increases and as the torque T increases. Furthermore, the higher the exhaust gas temperature, the smaller the actuator 69 opens the switching pulp 70 on the decomposition catalyst side. The actuators 69 and 71 are actuated by commands from the engine control computer (ECU) 72.

The engine control computer 72 consists of a microcomputer, and stores a program shown in FIG. 16 in a ROM. This program is called by the CPU to perform calculations.

First, in step 401, the catalyst bed temperature or exhaust temperature TE
Read X, engine rotational performance Ne,) lux T.

Next, the process proceeds to step 402, where the engine rotation speed N
e % Adjust the opening degree of the HC control valve 7o from Flux T to the first
Figures 2 and 13! It is calculated based on the dimensional map, and in step 403, the actuator 71 performs execution processing of HCI control valve opening control so that the HC control valve opening becomes equal to the calculated value.

Next, proceeding to step 404, the opening degree of the switching pulp 68 on the decomposition catalyst side is determined based on the catalyst bed temperature or exhaust temperature TEX.
Calculate based on a one-dimensional map as shown in Figure 17,
In step 405, the opening degree control of the switching pulp 68 is executed so that the calculated opening degree is achieved. Then return.

Next, the operation of the fourth embodiment will be explained.

The catalyst bed temperature or exhaust temperature TEX is low (for example, 4
00°C), the opening degree of the switching pulp 68 on the decomposition catalyst side is increased, and the decomposition catalyst 67 decomposes relatively high boiling point HC from the HC source 66 to produce olefinic H having 3 to 6 carbon atoms.
Lean NOx catalyst 63 with a high C content
supply upstream. Therefore, it matches the characteristics of A in FIG. 3, and a high NOx purification rate can be obtained regardless of the low temperature range.

Conversely, when the catalyst bed temperature or exhaust gas temperature TEX is high (for example, 400°C or higher), the switching pulp 68 is opened to a large degree on the side opposite to the decomposition catalyst, and most of the HC from the HC source 66 is decomposed. The NOx catalyst 63 is supplied upstream of the lean NOx catalyst 63 without being affected. Therefore, H with a relatively large number of carbon atoms
C is supplied upstream of the lean NOx catalyst 63, and reaches the lean NOx catalyst 63 without being completely oxidized.
There, it is partially oxidized to generate active species. Therefore, the characteristic B in FIG. 3 occurs, and a high NOx purification rate can be obtained regardless of the high temperature range. Thus, as shown in Figure 3C,
A good NOx purification rate can be obtained in both low temperature and high temperature ranges.

According to the fourth embodiment, the HC decomposition means 67 is provided, and the switching HAL PRO 8 is also provided, and in the low catalyst bed temperature and exhaust temperature range, the switching valve 68 is switched to allow more flow to the HC decomposition catalyst 67 side, and the low carbon number HC is supplied upstream of the lean NOx catalyst 63 so as to contain a large amount of HC, and when the catalyst bed temperature and exhaust temperature are in the high temperature range, the switching valve 68 is switched to flow 11 times the amount opposite to the HC decomposition catalyst 67. Since HC is supplied upstream of the lean NOx catalyst 63 by containing a large amount of HC, good N
The effect of increasing the Ox purification rate is obtained.

Fifth Embodiment FIGS. 18 to 23 relate to the fifth embodiment, and FIGS.
The figure also applies to the fifth embodiment. In the fifth embodiment, as shown in FIG.
A lean NOx catalyst 83 is provided.

Upstream of the lean NOx catalyst 83, HC is supplied from an HC supply source 86 by an HC supply means 85. Further, an exhaust temperature sensor 84 is provided downstream of the lean NOx catalyst 83, and an exhaust pressure sensor 93 is provided upstream thereof.

As the HC of the HC supply source 66, HCl having a relatively high boiling point, for example, light fuel oil is used. The HC supply means 85 includes a micro pump 88 that pumps light oil and a pipe 94 (
It has a nozzle (FIG. 19) 94 that injects air into the pipe 94 (FIG. 19), and an air pump 89 that sends air to be mixed with the light oil injected into the pipe 94.

In the middle of the HC supply path of the HC supply means 85, there is an HC decomposition catalyst 87 as an HC decomposition means for decomposing and partially oxidizing HC.
is provided. This HC decomposition catalyst 87 is preferably loaded into a pipe 94.

As shown in FIG. 19, a light oil supply conduit is wound around the outer periphery of the pipe 94, and a heater 91 is installed to heat the conduit. The voltage of the heater 91 is made variable by the slider 90.

Light oil supply amount by micro pump 88, air pump 89
The amount of air supplied by the engine control computer 92 and the heater voltage by the slider 90 can be controlled by the engine control computer 92. The engine control computer 92 consists of a microcomputer, and the program shown in FIG. 20 is stored in its ROM, and is called by the CPU.
The operation is executed.

As shown in FIG. 20, the calculation routine first reads in step 501 the catalyst bed temperature or exhaust temperature TEx1, engine rotational speed Ne, accelerator opening T1, and exhaust pressure PM.

Next, in step 502, the necessary HC injection amount is calculated from Ne%T, and the light hydraulic pressure of the micro pump 88 is adjusted so that the required HC injection amount is injected into the pipe 94 through the nozzle 95. Calculate quantities. Further, in step 504, the air pump output is calculated from the PM so that the mixture of HC and air can be injected into the exhaust pipe against the exhaust pressure. Subsequently, in step 505, HC and air supply execution processing is performed.

Through the above steps, the mixture of HC and air becomes lean NO.
1 in FIG. The optimum heater voltage is calculated based on the dimensional map, and then in step 507, the slider 9
0 optimizes the voltage of the heater 91. and return.

Next, the operation of the fifth embodiment will be explained.

The catalyst bed temperature or exhaust temperature TEX is low (for example, 4
(00℃ or below), the heater 9 is
1 is increased to promote the HC decomposition action in the HC decomposition catalyst 87 and supply HC to the upstream side of the lean NOx catalyst 83 in a state containing a large amount of olefinic HC having 3 to 6 carbon atoms. Therefore, as shown in A in FIG. 3, a high NOx purification rate can be obtained regardless of the low temperature range.

Conversely, when the catalyst bed temperature or exhaust temperature TEX is high (for example, 400°C or higher), the voltage of the heater 91 is reduced by the slide duck 90, the HC decomposition effect is suppressed by the HC decomposition catalyst 87, and HC with a relatively high carbon number is HC is supplied upstream of the lean Nox catalyst. Therefore, as shown in B in Figure 3, regardless of the high temperature range, high NOx
Purification rate can be obtained. In this way, as shown in FIG. 3C, a high N0W purification rate can be obtained in both the low temperature range and the high temperature range.

According to the fifth embodiment, the HC decomposition means 87 is provided, and the HC decomposition rate can be changed by changing the voltage of the heater 91. When the catalyst bed temperature and exhaust temperature are in the low temperature range, the heater voltage is increased to reduce the HC decomposition rate. H by increasing the carbon number HC
C is supplied upstream of the lean NOx catalyst 83, and when the catalyst bed temperature and exhaust temperature are in the high temperature range, the heater voltage is lowered to contain a large amount of high carbon number HC and HC is supplied upstream of the lean NOx catalyst 83. However, even in high temperature ranges, high N
The effect of increasing the OX purification rate is obtained.

〔Effect of the invention〕

According to the present invention, when the catalyst bed temperature or exhaust temperature is low,
Hydrocarbons are supplied upstream of the lean NOx catalyst so that they contain a large amount of low-boiling point hydrocarbons, and when the catalyst bed temperature or exhaust temperature is high, the hydrocarbons are supplied to the lean NOx catalyst by containing a large amount of high-boiling point hydrocarbons. Since it is supplied upstream of the NOx catalyst, a high NOx purification rate can be obtained in both low temperature and high temperature ranges.

In addition, hydrocarbons from a hydrocarbon supply source can be used blindly, and effects such as reducing HC consumption, reducing HC emissions, and eliminating the need to control exhaust temperature can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an exhaust purification device for an internal combustion engine according to the first embodiment of the present invention, Fig. 2 is a flowchart of the C supply control calculation routine (stored in EC1J in Fig. 1), and Fig. 3 is a flowchart of the C supply control calculation routine. Lean NOx catalyst bed temperature (or exhaust temperature) - NO
x purification rate characteristic diagram, Fig. 4 is a block diagram showing the NOx purification mechanism of the lean NOx catalyst, Fig. 5 is a system diagram of the exhaust purification device for an internal combustion engine according to the second embodiment of the present invention, and Fig. 6 is the Figure 5 is a flowchart of the HCC supply control calculation routine stored in the ECU, Figure 7 is an exhaust temperature vs. first HC control valve opening characteristic diagram, Figure 8 is an exhaust temperature vs. second HCIlii valve opening characteristic diagram, and Figure 9 is a diagram of the exhaust temperature vs. second HC control valve opening characteristic diagram. FIG. 10 is a system diagram of an exhaust gas purification device for an internal combustion engine according to the third embodiment of the present invention, and FIG. m @ 11 calculation routine flowchart, Figure 12 is engine rotation speed - HCf [11 valve opening characteristic diagram, Figure 13 is torque - HC @ valve opening characteristic diagram, Figure 14 is exhaust temperature (catalyst output gas Figure 15 is a system diagram of an exhaust purification device for an internal combustion engine according to the fourth embodiment of the present invention, and Figure 16 is a HC supply control calculation stored in the ECU of the device in Figure 15. 17 is a flowchart of the routine, FIG. 17 is a characteristic diagram of exhaust temperature (catalyst output gas temperature) and opening degree on the decomposition catalyst side of the switching valve, and FIG. , Figure 19 is an enlarged view of the vicinity of the HC decomposition catalyst of the apparatus shown in Figure 18, and Figure 20 is an enlarged view of the HC stored in the ECtJ of the apparatus shown in Figure 18.
Flowchart of the supply control calculation routine, Figure 21 is a fuel injection amount vs. micro pump pumping amount characteristic diagram, Figure 22 is an exhaust pressure car air pump output characteristic diagram, and Figure 23 is an exhaust temperature (catalyst output gas temperature) vs. heater voltage characteristic diagram. Figure, is. 1.21.41.61.81... Internal combustion engine 2.
22.42.62.82...Exhaust passage 3.23
．． 43.63.83...Lean NOx catalyst 4.
24.44.64.84...Temperature detection means (for example, exhaust temperature sensor) 5.25.45.65.85...HC supply means 6.26.46.66.86 ...HC supply source 1
1.32.52.72.92... Engine control computer (ECU) 47.67.87... HC decomposition catalyst Figure 2 Figure 3 @, :lt, Temperature or: Death Exhaust temperature TEX'C - - → - Fig. 4 Fig. 15 Exhaust gas temperature TEX beak -) - Fig. 18 Fig. 19 Near - □ Fig. 20

Claims (1)

[Claims] 1. An exhaust gas purification device for an internal combustion engine, which is provided in the exhaust system of the internal combustion engine and is equipped with a catalyst that reduces nitrogen oxides in an oxidizing atmosphere and in the presence of hydrocarbons. is provided separately, and includes a hydrocarbon supply source that supplies hydrocarbons to the engine, a temperature detection means for detecting the catalyst bed temperature of the catalyst or the exhaust temperature, and a temperature detection means that detects the catalyst bed temperature, Alternatively, when it is detected that the exhaust gas temperature is high, hydrocarbons from the hydrocarbon supply source are supplied upstream of the catalyst in such a manner that the hydrocarbons contain a large amount of high boiling point hydrocarbons, and the catalyst bed temperature or and a hydrocarbon supply means for supplying hydrocarbons from the hydrocarbon supply source to the upstream side of the catalyst in such a manner that the hydrocarbons contain a large amount of low boiling point hydrocarbons when the exhaust gas temperature is detected to be low. An exhaust purification device for an internal combustion engine, characterized by: 2. In an exhaust purification device for an internal combustion engine, which is installed in the exhaust system of an internal combustion engine and is equipped with a catalyst that reduces nitrogen oxides in an oxidizing atmosphere and in the presence of hydrocarbons, the device is installed separately from the engine. , a hydrocarbon supply source that supplies a plurality of types of hydrocarbons with different boiling points to the engine, a temperature detection means for detecting the catalyst bed temperature of the catalyst or the exhaust temperature, and the temperature detection means detects the catalyst bed temperature, Alternatively, when the exhaust gas temperature is detected to be high, high boiling point hydrocarbons from the hydrocarbon supply source are supplied upstream of the catalyst so as to contain more high boiling point hydrocarbons than low boiling point hydrocarbons, and the catalyst bed temperature is increased. Or,
and hydrocarbon supply means for supplying hydrocarbons upstream of the catalyst so that low boiling point hydrocarbons among the hydrocarbons from the hydrocarbon supply source are contained in a larger amount than high boiling point hydrocarbons when the exhaust gas temperature is detected to be low. An exhaust purification device for an internal combustion engine, characterized by: 3. In an exhaust gas purification device for an internal combustion engine, which is installed in the exhaust system of an internal combustion engine and is equipped with a catalyst that reduces nitrogen oxides in an oxidizing atmosphere and in the presence of hydrocarbons, the device is installed separately from the engine. , a hydrocarbon supply source that supplies hydrocarbons to the engine; a temperature detection means for detecting a catalyst bed temperature of the catalyst or an exhaust temperature; and a temperature detection means that detects a high catalyst bed temperature or exhaust temperature. When it is detected that the catalyst bed temperature or the exhaust gas temperature is low, the hydrocarbons from the hydrocarbon supply source are supplied to the intake system of the internal combustion engine in a larger amount than the exhaust system. 1. An exhaust gas purification device for an internal combustion engine, comprising a hydrocarbon supply means for supplying more hydrocarbons from a source to an exhaust system of the internal combustion engine than to an intake system. 4. In an exhaust gas purification device for an internal combustion engine, which is installed in the exhaust system of an internal combustion engine and is equipped with a catalyst that reduces nitrogen oxides in an oxidizing atmosphere and in the presence of hydrocarbons, the device is installed separately from the engine. , a hydrocarbon supply source that supplies high-boiling hydrocarbons to the engine, a hydrocarbon decomposition means that decomposes the high-boiling hydrocarbons from the hydrocarbon supply source into low-boiling hydrocarbons and supplies them to the engine, and the catalyst. temperature detection means for detecting the catalyst bed temperature or exhaust temperature; and when the temperature detection means detects that the catalyst bed temperature or exhaust temperature is high, high boiling point hydrocarbons from the hydrocarbon supply source is supplied upstream of the catalyst so that it contains more low-boiling point hydrocarbons than the low-boiling point hydrocarbons from the hydrocarbon decomposition means, and when it is detected that the catalyst bed temperature or exhaust temperature is low, the low-boiling point hydrocarbons from the hydrocarbon decomposition means are 1. An exhaust purification device for an internal combustion engine, comprising: hydrocarbon supply means for supplying boiling point hydrocarbons in a larger amount than high boiling point hydrocarbons from the hydrocarbon supply source.