JPH1061429A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control toxic component such as NOx and particulate with high efficiency by suppressing the worsening of derivability, fuel consumption, and emission. SOLUTION: A degree of opening of an intake throttle valve 13 and an exhaust circulation control valve 16 is controlled in accordance with high or low temperature of catalyst temperature and exhaust temperature at an inlet of catalyst and an operation condition of a vehicle to control in such a manner that temperature of catalyst of an exhaust emission control device for internal combustion engine is within a specific scope of temperature which is suitable for the action of catalyst at all times. For example, when exhaust temperature becomes higher than catalyst temperature at the time of acceleration of the vehicle, the intake throttle valve 13 is closed slightly and the exhaust circulation control valve 16 is opened slightly to such extent that its operation is not obstructed to raise catalyst temperature speedily. When exhaust temperature drops below catalyst temperature during idling in a condition in which the vehicle is decelerated and stops, the intake throttle valve 13 is closed greatly and the exhaust circulation control valve 16 is opened greatly to keep catalyst temperature and prepare so that high control efficiency is obtained immediately at the time of next acceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust purification system for an internal combustion engine which purifies harmful components such as NOx and particulates contained in exhaust gas of the internal combustion engine.

[0002]

2. Description of the Related Art A catalyst is installed in an exhaust pipe to purify NOx exhausted from an internal combustion engine such as a diesel engine. In this case, the NOx purification rate by the catalyst is shown in FIG.
As shown in the figure, a predetermined temperature range (for example, 200 to 400
(° C.).

However, since the exhaust gas temperature of the engine greatly changes depending on the operating condition thereof, that is, the operating condition of the vehicle, it is impossible to maintain the catalyst temperature at which a high NOx purification rate can be obtained for a long time. Therefore, there is a problem that there is a time when the NOx purification rate decreases depending on the operation state. Therefore, Japanese Patent Application Laid-Open No. 4-224221
In the publication, the catalyst outlet temperature (exhaust gas temperature at the catalyst outlet) is detected, and when it is lower than a predetermined temperature range, an excess air ratio is reduced by controlling an intake throttle valve and the like, so that the temperature becomes higher than the predetermined temperature range. If it is high, a method of increasing the excess air ratio is described. That is, when the catalyst outlet temperature is low, the exhaust throttle temperature is raised by closing the intake throttle valve to reduce the excess air in the cylinder, and conversely, when the catalyst temperature is high, the intake throttle valve is opened to open the cylinder. The exhaust gas temperature is lowered by increasing the excess air, and the catalyst temperature is controlled so as to be within a range in which a high NOx purification rate can be obtained even when the operation state changes.

[0004] However, this method has a problem that the NOx purification rate does not improve much in an actual running state in which acceleration and deceleration are repeated. For example, in a traveling pattern frequently occurring when traveling in an urban area as shown in FIG. 3, a change in the catalyst outlet temperature is greatly delayed with respect to a change in the traveling state (constant speed, deceleration, stop, acceleration) due to the heat capacity of the catalyst. In contrast,
When the above control is performed by detecting only the catalyst outlet temperature, the intake throttle valve is closed only in the range of A (from the middle of acceleration to a constant speed) in FIG. 3 where the detected temperature is out of the temperature range suitable for NOx purification. It will be. However, the catalyst temperature changes gradually due to heat capacity even when the intake throttle valve is closed, so that the catalyst temperature rises significantly in the range B (at the time of constant speed running) in FIG. For this reason, the control effect does not appear at the time of acceleration when the load on the engine is large and the amount of NOx emission is large, and NOx can be reduced only at a constant speed with a small load on the engine and originally low NOx emission. (See FIG. 3C). Therefore, there is a problem that the NOx purification rate cannot be significantly improved depending on the related art.

Further, since control is performed by detecting only the temperature, for example, in the example shown in FIG. 3, when the temperature is low, the intake throttle valve is closed even when the vehicle is accelerating. However, if the intake air is forcibly throttled during acceleration without considering the driving state of the vehicle, the combustion state of the engine deteriorates and the output decreases, resulting in drastic deterioration of drivability. Further, if the fuel injection amount is increased to make up for this, the fuel efficiency will be greatly deteriorated. On the other hand, if the operation amount of the intake throttle valve is reduced in order to suppress the deterioration of drivability and fuel efficiency, there is a problem that the amount of increase and decrease of the catalyst temperature is reduced, and the effect of the control is reduced.

Furthermore, even when the temperature of the exhaust gas or the catalyst is extremely low, such as immediately after the start of the engine, the intake air is throttled.
There is also a problem that a large amount of particulates, CO, and HC are discharged without being purified by the catalyst, and the emission is greatly deteriorated.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to control the temperature of a catalyst so as to be within a temperature range suitable for the operation of the catalyst while suppressing deterioration in drivability, fuel efficiency, and emission. NOx with high efficiency
It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine that can purify harmful components such as gas and particulates.

[0008]

According to the first aspect of the present invention, the passing flow rate correcting means is arranged such that the exhaust gas temperature (hereinafter, referred to as Tg) at the inlet of the exhaust purifying means is higher than the temperature of the exhaust purifying means (hereinafter, Tc). Is too low, a signal is given to the intake throttle valve and the exhaust gas recirculation control valve to reduce the flow rate of the exhaust gas (hereinafter referred to as the “flow rate”) passing through the catalyst. To prevent Conversely, when Tg> Tc, a large amount of high-temperature exhaust gas is introduced into the exhaust gas purifying means, and the temperature of the exhaust gas purifying means is quickly raised to control the temperature to be suitable for exhaust gas purification. This makes it possible to significantly improve exhaust gas purification performance.

According to the second aspect of the invention, in addition to the first aspect, the flow rate of the exhaust gas passing through the exhaust gas purifying means is controlled by the intake throttle valve and the exhaust gas recirculation control valve in accordance with the operation state of the vehicle. That is, when Tg <Tc, and when the vehicle is decelerating and idling, the decrease correction amount of the passing flow rate is increased. This is because the influence on drivability and fuel efficiency is small, so that the flow rate is reduced as much as possible to keep the exhaust gas purifying means warm, and to quickly raise the temperature of the exhaust gas purifying means during the subsequent acceleration. On the other hand, at the time of vehicle acceleration, the decrease correction amount of the passing flow rate is reduced. This is because reducing the flow rate forcibly has a large effect on drivability and fuel economy.Therefore, reducing the reduction amount and reducing excess air in the cylinder raises the temperature of the exhaust gas, and the exhaust gas purifying means more quickly. In order to raise the temperature. As a result, it is possible to achieve both improvement in exhaust purification performance by raising the temperature of the exhaust purification means and suppression of deterioration in fuel efficiency and drivability.

According to the third aspect of the present invention, since the temperature of the exhaust gas purification means is estimated from the exhaust gas temperatures before and after the exhaust gas purification means, a sensor for detecting the temperature of the exhaust gas purification means must be provided directly inside the exhaust gas purification means. Absent. Therefore, the same effect as in the above case can be obtained while simplifying the configuration of the exhaust gas purifying unit.

According to the fourth aspect of the present invention, the exhaust gas purifying means uses a NOx reduction catalyst, an oxidation catalyst, a trap filter, or a combination of a plurality of these. When a NOx reduction catalyst is used in the invention of claim 1 or 2, a high NOx purification rate can be obtained by controlling the catalyst temperature within a predetermined temperature range. In the case of an oxidation catalyst, exhaust gas can be purified with high efficiency by setting the catalyst at an activation temperature or higher. In a trap filter for collecting particulates, by raising the temperature of the filter to a high temperature, the collected particulates can be incinerated to regenerate the filter.

According to the fifth aspect of the present invention, Tg and Tc
The intake air amount and the exhaust gas recirculation amount are controlled independently by changing the opening of the intake throttle valve and the exhaust gas recirculation control valve in accordance with the size of the vehicle and the operating state of the vehicle. That is, when Tg <Tc and the vehicle is decelerated and idling, the exhaust gas recirculation amount is increased,
The exhaust gas purifying means is kept warm by reducing the passing flow rate as much as possible. On the other hand, at the time of vehicle acceleration, the inflow of low-temperature fresh air is suppressed to such an extent that drivability and fuel efficiency are not affected, and the high-temperature exhaust gas is recirculated to raise the temperature of the exhaust purification means. At this time, the amount of decrease in the flow rate of exhaust gas and the amount of decrease in excess air in the cylinder are independently controlled to effectively prevent a decrease in the temperature of the exhaust gas purifying means.

On the other hand, when Tg> Tc, the passing flow rate is increased. However, when the vehicle is accelerated, the excess air in the cylinder is reduced so as not to affect drivability and fuel efficiency, and the temperature of the exhaust gas is increased. The exhaust gas is recirculated to raise the temperature of the exhaust gas purifying means. At this time, the opening degree of the exhaust gas recirculation control valve is reduced to prevent the exhaust air recirculation amount from increasing by an amount corresponding to the decrease in the intake air amount, thereby preventing the effect of the excess air reduction from being lost.

As a result, it is possible to achieve both improvement in exhaust gas purification performance by raising the temperature of the exhaust gas purification means and suppression of deterioration in fuel efficiency and drivability. According to the invention of claim 6, the same effect as that of the exhaust gas purification apparatus of claim 2 can be obtained by using the waste gate valve of the supercharger as the passage flow rate changing means. Further, in the present invention, when the temperature of the exhaust gas purifying means is lower than the set value and when the vehicle is not accelerating, the supercharging amount is reduced to prevent the exhaust gas purifying means from being cooled by a large amount of low-temperature exhaust gas. Thereby, the temperature of the exhaust gas purifying means can be more quickly raised at the time of subsequent acceleration, so that the exhaust gas can be efficiently purified.

According to the present invention, when the temperature of the exhaust gas purifying means is lower or higher than a predetermined value, the operation of decreasing the passing flow rate is stopped. Thus, by performing unreasonable control in a state where the temperature largely deviates from the temperature suitable for the operation of the exhaust gas purifying means, it is possible to avoid drastic deterioration in drivability, fuel efficiency and emission.

According to the present invention, when the output of the internal combustion engine detected by the operating state detecting means is large, the operation of decreasing the flow rate of exhaust gas is stopped. That is,
If the operation of decreasing the passing flow rate is excessively performed, drivability such as acceleration performance deteriorates. Therefore, when the output of the engine is larger than a predetermined value, the control is stopped. When the output of the engine is large, the exhaust gas temperature is high. Therefore, even if the exhaust gas flow rate is not reduced, the temperature of the exhaust gas purifying means quickly rises, and the purification performance hardly decreases.

The present invention is an exhaust gas purifying apparatus for an internal combustion engine having the above features.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment in which the present invention is applied to a diesel engine will be described with reference to FIGS. 1 and 4 to 6. As shown in FIG. 1, the exhaust gas purifying apparatus 10 includes an intake throttle valve 13 (flow rate changing means) in an intake pipe 12 (intake passage) of a diesel engine 11 and an intake pipe 12 and an exhaust pipe 14 (exhaust passage). An exhaust gas recirculation control valve 16 (passing flow rate changing means) in an exhaust gas recirculation pipe 15 connecting
In the exhaust pipe 14, there is provided a catalytic converter 17 (exhaust gas purifying means) and an ECU (control unit) 18 (passing flow rate correcting means) for controlling the opening degree of the intake throttle valve 13 and the exhaust gas recirculation control valve 16.

The intake throttle valve 13 is a butterfly type valve whose opening degree is changed using an electric motor such as a step motor or a DC motor or a negative pressure. Exhaust gas recirculation control valve 16
As shown in FIG. 4, for example, the diaphragm chamber 161 normally communicates with the atmosphere, and the spring 162
The passage of the exhaust gas recirculation pipe 15 is closed by the force of
When a voltage is applied to the solenoid valve 19 in accordance with a command from the CU 18, communication between the diaphragm chamber 161 and the atmosphere is cut off, and the negative pressure of the vacuum pump 20 is introduced into the diaphragm chamber 161, whereby the exhaust gas recirculation pipe 15 is closed. The passage is opened and the exhaust gas is recirculated to the intake pipe 12. At this time, by changing the duty ratio of the voltage pulse applied to the solenoid valve 19, the pressure in the diaphragm chamber 161 is adjusted to change the opening of the exhaust gas recirculation control valve 16. The catalytic converter 17 supports a catalyst such as Cu-zeolite or Pt-zeolite, which can reduce and purify NOx even in an oxygen-excess atmosphere such as diesel exhaust, on a carrier such as ceramic or metal.

The ECU 18 includes a rotation speed sensor 3 in the input circuit.
0, a load sensor 31, an exhaust temperature sensor 32, a catalyst temperature sensor 33, and a vehicle speed sensor 34 are connected, and an electromagnetic valve 19 for opening and closing the intake throttle valve 13 and the exhaust gas recirculation control valve 16 is electrically connected to the output circuit. Then, the engine speed, the engine load, the exhaust temperature, the catalyst temperature and the vehicle speed detected by those sensors are compared with the patterns previously input to the memory, and the intake throttle valve 13 and the solenoid valve 19, that is, the exhaust gas recirculation control valve 16 is opened and closed.

A rotational speed sensor 30 is disposed on a crankshaft or a fuel injection pump to detect an engine rotational speed Ne. A load sensor 31 is disposed on an accelerator pedal or a fuel injection pump to detect an accelerator opening Th and a temperature sensor. 32 is disposed in the exhaust pipe 14 upstream of the catalytic converter 17 to detect an exhaust gas temperature Tg, and a temperature sensor 33 is disposed in the catalytic converter 17 and
c, and the vehicle speed sensor 34 is disposed on a transmission shaft (not shown) to detect the vehicle speed V1. (Operating State Detecting Means) In the exhaust gas purification device configured as described above, usually, the ECU is controlled in advance according to the engine speed, the engine load, and the like.
The exhaust gas recirculation control is performed in accordance with the pattern input to the internal memory. As a result, N discharged from the engine
Ox is reduced. Then, under predetermined conditions, the opening control of the intake throttle valve and the exhaust gas recirculation control valve for raising the temperature of the catalyst is performed to improve the NOx purification rate by the catalyst.

Next, the operation of the exhaust gas purifying apparatus will be described with reference to a flowchart shown in FIG. In this flowchart, a portion for controlling the intake throttle valve 13 and the exhaust gas recirculation control valve 16 in response to the signal from each sensor as described above is shown. First, in S (step) 101,
The signals from the rotation speed sensor 30, the load sensor 31, the temperature sensors 32 and 33, and the vehicle speed sensor 34 are read. S1
In 02, it is determined whether or not the read catalyst temperature Tc is between the low temperature set value T1 (for example, a value between 50 and 100 ° C.) and the high temperature set value T2 (for example, a value between 300 and 500 ° C.). I do. If Tc <T1, the control such as closing the intake throttle valve only deteriorates the fuel efficiency and does not activate the catalyst, and the harmful components in the exhaust gas increased by the control are purified by the catalyst. The process proceeds to S103, and the exhaust gas recirculation amount control (intake throttle valve opening A0, recirculation control valve opening B) is performed according to the pattern stored in the memory in the ECU 18 in the same manner as before.
0), and the process returns to S101. If Tc> T2, the catalyst temperature is too high, and NOx
Since the purification rate does not improve, the process similarly proceeds to S103. Then, the exhaust gas recirculation amount control is performed as in the related art, and the process returns to S101.

On the other hand, in the determination of S102, the catalyst temperature T
When c is between T1 and T2, the process proceeds to S104, and the accelerator opening Th is set to a set value Th0 (for example, the opening 40 to 60).
%). In the case of Th> Th0, since the engine load is large due to rapid acceleration or the like and the exhaust gas temperature is high, the catalyst temperature quickly rises without specially raising the temperature. Therefore, the process proceeds to S103 in order to avoid deterioration in drivability and fuel efficiency due to the control, and returns to S101 after performing the same exhaust gas recirculation control as before. On the other hand, Th
In the case of <Th0, the process proceeds to S105, and the acceleration a is calculated from the currently read vehicle speed V1 and the previously read vehicle speed V0.

Next, the program proceeds to S106, in which it is determined whether the exhaust gas temperature Tg read in S101 is lower than the catalyst temperature Tc. If Tg <Tc, proceed to S107,
It is determined whether the acceleration a calculated in S105 is positive or negative.
If the value of a is positive, the vehicle is accelerating, and the process proceeds to S108, in which the intake throttle valve is closed so small that there is no effect on drivability and fuel consumption (opening A1), and the inflow of low-temperature fresh air is suppressed. (For example, a value between 20 and 40% of the intake reduction rate)
At the same time, the exhaust gas recirculation control valve is opened slightly (opening B1),
Recirculate high-temperature exhaust gas (for example, an exhaust gas recirculation rate of 10 to 30).
% Of the catalyst). That is, by independently controlling the flow rate of the catalyst and the amount of air in the cylinder, a decrease in the temperature of the catalyst is effectively prevented. Then, the process returns to S101 again to repeat the processing.

If the value of a is negative in the determination of S107, the vehicle is decelerating and the influence on drivability and fuel efficiency is small, so the process proceeds to S109, and the intake throttle valve is largely closed (openings A2, A2 <A1). ), The exhaust gas recirculation control valve is greatly opened (opening degree B2, B2> B1) to suppress the inflow of low-temperature fresh air, increase the amount of exhaust gas recirculation, and reduce the flow rate of exhaust gas passing through the catalyst as much as possible ( For example, a value between the intake reduction rate 50-80%, the exhaust recirculation rate 50
(Value between） 80%) to keep the catalyst warm. Then, the process returns to S101.

If a is 0 in S107, it is determined in S110 whether the vehicle speed V1 is 0. If V1 is 0, the vehicle is stopped and the engine is idling.
Go to 109. If V1 is not 0, the vehicle is traveling at a constant speed, and the process proceeds to S103, where the intake throttle valve opening is set to A0 and the exhaust gas recirculation control valve opening is set to B0, and the same exhaust gas recirculation control as in the past is performed. That is, since the amount of NOx emission is small during traveling at a constant speed, priority is given to suppression of deterioration of fuel efficiency, and excessive control is avoided.

If Tg> Tc in the determination of S106, the process proceeds to S111, where the acceleration a calculated in S105
Is determined to be positive. If the value of a is positive and the vehicle is accelerating, the process proceeds to S112, where the intake throttle valve is closed small enough to have no effect on drivability and fuel efficiency (openings A3, A
0>A3> A1), the exhaust air temperature is raised by reducing the excess air in the cylinder (for example, a value between 10 and 30% of the intake reduction rate). At the same time, the exhaust gas recirculation control valve is opened slightly (opening degree B3, B3 <B
1) Recirculate high-temperature exhaust gas (for example, an exhaust gas recirculation rate of 5 to 2)
Value between 0%).

In this case, the exhaust gas recirculation control valve opening B is used to prevent the exhaust gas recirculation amount from increasing due to the decrease in the intake air amount by reducing the intake air and losing the effect of the excess air reduction.
Set 3 small. That is, in addition to increasing the flow rate through the catalyst, the purpose is to further raise the exhaust gas temperature and raise the temperature of the catalyst more quickly. If the value of a is not positive, that is, if the vehicle is decelerating or stopping, S10
Then, the process proceeds to 3, and the opening degree of the intake throttle valve is set to A0, and the opening degree of the exhaust gas recirculation control valve is set to B0. That is, priority is given to suppressing fuel consumption deterioration.

The above processing is repeatedly executed, for example, once a second. The effect of the first embodiment will be described with reference to a time chart shown in FIG. FIG. 6 shows an example in which the present invention is applied to a traveling pattern (same as the example in FIG. 3) that frequently occurs when traveling in an urban area. Here, T1 <Tc <T2
And Th <Th0.

In the case where the exhaust gas temperature Tg <catalyst temperature Tc is satisfied, the intake throttle valve is greatly closed and the exhaust gas recirculation control valve is greatly opened to increase the amount of exhaust gas recirculation in D during deceleration and stop of the vehicle. As a result, the catalyst temperature is maintained at a high temperature without substantially decreasing, and the catalyst can purify NOx from the beginning with high efficiency at the next acceleration.

At E in FIG. 6 at the start of acceleration, the intake throttle valve is closed so small as to have no effect on drivability and fuel economy, and the inflow of low-temperature fresh air is suppressed, and the exhaust gas recirculation control valve is opened slightly. The catalyst is heated by recirculating the hot exhaust. As a result, it is possible to prevent a low-temperature exhaust gas from flowing into the catalyst at the start of acceleration and to reduce the catalyst temperature, and to maintain the catalyst temperature within a temperature range where the NOx purification rate is high. At G in FIG. 6 where the vehicle is traveling at a constant speed, the same exhaust gas recirculation control as in the related art is performed.

In the case where the exhaust gas temperature Tg> catalyst temperature Tc is satisfied, in FIG. 6F during acceleration of the vehicle, the exhaust throttle is heated by closing the intake throttle valve small to reduce excess air in the cylinder. At the same time, the exhaust gas recirculation control valve is opened small to recirculate high-temperature exhaust gas. That is, the temperature of the catalyst is raised more quickly by increasing the flow rate of the catalyst and further raising the exhaust gas temperature. In other constant speed running states, the conventional exhaust gas recirculation amount control is performed.

With this control, it is possible to maintain the catalyst temperature in a range where the NOx purification rate is high, while suppressing deterioration in drivability and fuel efficiency. Therefore,
Since the catalyst is activated from the beginning even during acceleration when the NOx emission from the engine increases, the NOx purification rate can be greatly improved (see H in FIG. 6). As apparent from the above description, according to the first embodiment of the present invention, the drivability and fuel efficiency of a diesel engine in which the exhaust gas temperature is often lower than the temperature suitable for NOx purification by the catalyst during normal running are often high. NOx can be efficiently purified by the catalyst by quickly raising the catalyst temperature after suppressing the deterioration of NOx. Second Embodiment In the first embodiment, the temperature inside the catalytic converter 17 is detected by the temperature sensor 33 (FIG. 1).
On the other hand, the exhaust gas purifying apparatus 101 of the second embodiment is characterized in that the temperature sensor 331 is installed in the exhaust pipe 14 downstream of the catalytic converter 17 as shown in FIG.

That is, instead of directly measuring the catalyst temperature Tc used for control, the exhaust gas temperature Tg1
And the catalyst temperature Tc is estimated from the exhaust gas temperature Tg2 on the downstream side of the catalyst. This eliminates the need to mount a temperature sensor in the catalytic converter 17, thereby simplifying the structure of the catalyst. Other configurations are the same as in the first embodiment.

Next, the operation of the exhaust gas purifying apparatus 101 according to the second embodiment will be described with reference to the flowchart shown in FIG.
Hereinafter, only different portions from the flowchart of the first embodiment shown in FIG. 5 will be described. In FIG. 5, in S (step) 101, signals from the rotation speed sensor 30, the load sensor 31, the temperature sensors 32 and 33, and the vehicle speed sensor 34 are read. In FIG. 8, the temperature sensor 331 is used instead of the temperature sensor 33 in S1011. Read the signal of

In step S1012, the catalyst temperature Tc is determined from the exhaust gas temperature Tg1 on the upstream side of the catalyst and the exhaust gas temperature Tg2 on the downstream side of the catalyst. This is calculated by a map or a calculation formula stored in a memory in the ECU 18 in advance. The map is determined experimentally. Further, this calculation formula is calculated based on the exhaust temperatures Tg1 and Tg2 before and after the catalyst, for example, Tc = p × Tg1 + q × Tg2 (p and q are coefficients obtained from experiments). After that, the process proceeds to S102. The following processing is the same as that of the first embodiment, and the second embodiment has the same effects as the first embodiment. (Third Embodiment) In this embodiment, instead of carrying a NOx catalyst on the catalytic converter 17 in the first embodiment, for example, Pt, P
It is characterized in that an oxidation catalyst such as d or Rh is supported, and the other configuration is the same as that of the first embodiment shown in FIG.

In the third embodiment, as in the first embodiment, control is performed according to the flowchart shown in FIG. Therefore, only the portions different from the first embodiment will be described. In the first embodiment, in S102, when the catalyst temperature Tc> the set value T2, the temperature increase control is stopped. This is because, as shown in FIG. 2, if the temperature of the catalyst is too high, the NOx purification rate of the catalyst decreases.
This temperature T2 was a value between 300 and 500 ° C., for example. On the other hand, the higher the temperature of the oxidation catalyst used in this example, the higher the purification performance. Therefore, the high-temperature set value T2 at which the control is stopped is determined in view of the durability of the catalyst and the suppression of sulfate generation. This is for example 400-600
Value between ° C. Others are the same as the first embodiment.

According to the third embodiment, the deterioration of drivability and fuel efficiency is suppressed, and the catalyst temperature is quickly raised, so that the catalyst can efficiently purify HC and CO. . (Fourth Embodiment) In this embodiment, instead of carrying the NOx catalyst on the catalytic converter 17 in the second embodiment, for example, Pt, which oxidizes and purifies HC and CO in the exhaust gas in the same manner as the third embodiment. It is characterized in that an oxidation catalyst such as Pd or Rh is supported, but is different from the third embodiment in that other configurations are the same as those of the first embodiment shown in FIG. Other configurations in the fourth embodiment are the same as those in the second embodiment shown in FIG. Therefore, the flowchart showing the operation of the apparatus is the same as that in FIG. 8 described in the description of the second embodiment. In the fourth embodiment, the configuration of the catalyst is simplified, and
The same effects as in the embodiment can be obtained. (Fifth Embodiment) FIG. 9 shows the overall configuration of a fifth embodiment of the present invention.

The exhaust gas purifying apparatus 102 of this embodiment is different from the first embodiment shown in FIG. 1 in that a trap filter 171 is provided instead of the catalytic converter 17, and a pressure sensor 35 is provided upstream of the trap filter 171. It is characterized in that it is added in the exhaust pipe 14. The trap filter 171 has a large number of channels formed by a honeycomb lattice made of a porous material such as ceramics, and the inlets and the outlets of the channels are alternately plugged with a sealing material.
A washcoat layer of, for example, alumina is provided on the surface thereof, and a noble metal such as Pt or Pd or a base metal catalyst such as Cu is carried thereon, and the burning temperature of particulates (fine particles mainly composed of carbon in exhaust gas) during filter regeneration. Is decreasing.

In the exhaust gas purifying apparatus thus configured, if particulates accumulate on the trap filter 171, clogging occurs, so that the pressure of exhaust gas detected by the pressure sensor 35 increases. This pressure sensor 35
The ECU 18 calculates the amount m of particulates accumulated in the trap filter 171 based on the output of the rotation speed sensor 30 and the output of the load sensor 31.

The deposition amount m is equal to the set value m0 at which the regeneration process by burning and removing the particulates is required.
Only when it exceeds (for example, 10 g), control for raising the temperature of the filter is performed. Next, the operation of the exhaust gas purifying apparatus 102 according to the fifth embodiment will be described with reference to the flowchart shown in FIG. Hereinafter, only portions different from the flowchart in the case of the first embodiment shown in FIG. 5 will be described. In the fifth embodiment, in S1013, the rotation speed sensor 30, the load sensor 31, the temperature sensors 32 and 33, the vehicle speed sensor 3
4. Read the signal from the pressure sensor 35. And S
At 1014, based on these signals, the ECU 18
Thus, the amount m of particulate accumulated in the trap filter 171 is calculated. Next, the process proceeds to S1015, where the particulate matter accumulation amount m is compared with a set value m0 of the accumulation amount at which the particulates need to be removed by combustion (regeneration). If m <m0, there is no need for filter regeneration, so S
Proceeding to 103, the same exhaust gas recirculation control as in the past is performed.

In the fifth embodiment, the catalyst is carried on the trap filter to reduce the combustion temperature of the particulates. Therefore, during high-speed running with high exhaust gas temperature, the particulates trapped on the trap filter burn naturally. . However, during traffic congestion with low exhaust temperature, the particulates on the trap filter accumulate without burning and exceed the set value m0. In that case, the process proceeds to S1021, where the temperature Tf of the trap filter detected by the temperature sensor 33 is compared with predetermined values T1 and T2. Thereafter, the temperature rise control is performed as in the case of the first embodiment (FIG. 5), and the trap filter 171 is regenerated by burning the particulates on the trap filter.

According to the fifth embodiment, it is possible to quickly raise the temperature of the trap filter 171 and regenerate the trap filter while suppressing deterioration in drivability and fuel efficiency. Particulates can be efficiently removed. (Sixth Embodiment) As shown in FIG. 11, the exhaust gas purification apparatus 103 of the sixth embodiment is the same as the exhaust gas purification apparatus 1 of the fifth embodiment described above.
02, the temperature inside the trap filter 171 is detected by the temperature sensor 33 (see FIG. 9).
A temperature sensor 33 for a similar trap filter 171
1 to the exhaust pipe 1 downstream of the trap filter 171.
4 is characterized in that it is installed in the inside of the device.

The operation of the exhaust gas purifying apparatus 103 of the sixth embodiment is shown in the flowchart of FIG. 12, but only the parts different from those of the fifth embodiment shown in FIG. 10 will be described. In the sixth embodiment, a temperature sensor for directly detecting the temperature of the trap filter 171 is not provided.
If m> m0 in the determination of S1015, the process proceeds to S1016, and the trap filter temperature Tf is indirectly obtained from the exhaust gas temperature Tg1 on the upstream side of the trap filter and the exhaust gas temperature Tg2 on the downstream side of the trap filter. Then, the process proceeds to S1021. Other processes are the same as those of the fifth embodiment shown in FIG.

According to the sixth embodiment, the same effect as that of the fifth embodiment can be obtained while simplifying the configuration of the trap filter. (Seventh Embodiment) In the first embodiment, the intake throttle valve 13 is used as means for changing the amount of exhaust gas passing through the NOx catalyst.
The exhaust gas purification apparatus 104 of this embodiment shown in FIG. 13 is characterized in that a wastegate valve 50 of a supercharger (turbocharger) is used, while the exhaust gas recirculation control valve 16 is used. Hereinafter, only the portions different from the first embodiment will be described.

The exhaust pipe 14 is provided with an exhaust turbine 51 and a bypass pipe 52 connecting the upstream side and the downstream side thereof. A waste gate valve 50 is provided in the middle of the bypass pipe 52. The exhaust turbine 51 is connected to the intake turbine 5 in the intake pipe 12.
3 and a shaft 54. The waste gate valve 50 normally connects the diaphragm chamber 501 to the atmosphere and closes the passage of the bypass pipe 52 by the force of the spring 502 as shown in FIG. 14, for example.
, The communication between the diaphragm chamber 501 and the atmosphere is cut off, the negative pressure of the vacuum pump 20 is introduced into the diaphragm chamber 502, and the exhaust passage is opened by opening the passage of the bypass pipe 52. At this time, the opening degree of the waste gate valve 50 is changed by changing the pressure in the diaphragm chamber 502 by changing the duty ratio of the voltage pulse applied to the solenoid valve 19. Further, a pressure sensor 55 is provided in the intake pipe 12 on the downstream side of the intake turbine 53, and usually, a waste gate valve 5 is provided to protect the engine when the output of the pressure sensor 55 exceeds a set value.
Open 0 (CO is the valve opening by the same control as the conventional one).

The operation of the exhaust emission control device 104 of the seventh embodiment is shown in the flowchart of FIG. In the first embodiment, S103, S108, S109, S11 shown in FIG.
2, the opening degrees of the intake throttle valve and the exhaust gas recirculation control valve are determined, whereas in this example, S1031, S1081, S1
In 091, S1121, the opening of the waste gate valve is determined. At this time, the valve opening degree is C3 <C1 <C
2, for example, at the valve opening C1, the intake reduction rate is 20
In the value between ４０40% and the valve opening C2, the intake reduction rate is 4
A value between 0 and 60%, a value with a valve opening degree C3 between 10 and 30% of the intake reduction rate, and the like. Others are the same as in the first embodiment.

The case where only the waste gate valve 50 of the supercharger is used as the passage flow rate changing means has been described above, but it goes without saying that it may be combined with the above-described intake throttle valve or exhaust gas recirculation control valve. . Further, in addition to the NOx catalyst, an oxidation catalyst or a trap filter may be used as the exhaust gas purifying means.

Further, instead of directly detecting the temperature of the exhaust gas purifying means, the temperatures of the exhaust gas on the upstream side and the downstream side of the exhaust gas purifying means may be detected and calculated based on them. (Eighth Embodiment) In the present embodiment, similarly to the seventh embodiment, control is performed in accordance with the flowchart shown in FIG. 16 in the configuration of the exhaust gas purification device 104 shown in FIG. Hereinafter, only portions different from the seventh embodiment will be described.

In the eighth embodiment, after each signal is read in S101, the acceleration a is calculated in S1051, and in S1021, the catalyst temperature Tc is set to the low temperature set value T1.
It is determined whether it is greater than or equal to. If Tc <T1, the process proceeds to S1023, and it is determined whether the acceleration a obtained in S1051 is positive. And if a ≦ 0, S1
024, the waste gate valve opening is set to C4 (C
4> C2).

That is, if normal control is performed when the catalyst temperature is extremely low and the vehicle is not accelerating, the pressure detected by the pressure sensor 55 does not exceed a predetermined value in most cases. As the turbine 53 rotates, excess air is introduced into the cylinder of the engine. As a result, since a large amount of low-temperature exhaust gas passes through the catalyst, the catalyst is cooled, and activation of the catalyst becomes difficult.

Therefore, in this example, such a state is detected,
In step S1024, the waste air is reduced by, for example, fully opening the waste gate valve, and the catalyst is activated by increasing the exhaust gas temperature. However, if this control is performed during acceleration, the effect of supercharging may be lost and drivability may be degraded.
If a> 0 in 3, the flow advances to S1031, and the same control as in the related art is performed. At the time of acceleration, the exhaust gas temperature is high, so that the catalyst can be activated at an early stage by the same control as in the past. On the other hand, if Tc> T1 in S1021, S1
Proceeding to 022, control is performed in the same manner as in the seventh embodiment.

The case where only the waste gate valve of the supercharger is used as the means for changing the flow rate of exhaust gas has been described above, but it goes without saying that the exhaust gate may be combined with the above-described intake throttle valve or exhaust gas recirculation control valve. No. For example, exhaust purifying means interposed in an exhaust passage, passing flow rate changing means for changing a flow rate of exhaust gas passing through the exhaust purifying means, and exhaust temperature detecting means for detecting an exhaust gas temperature at an inlet of the exhaust purifying means. Means, temperature detection means of the exhaust purification means for detecting or estimating the temperature of the exhaust purification means,
Temperature comparing means for comparing the output of the exhaust gas temperature detecting means with the output of the temperature detecting means of the exhaust gas purifying means; and the temperature of the exhaust gas at the inlet of the exhaust gas purifying means based on the output of the temperature comparing means. When the temperature of the exhaust gas purification means is higher than that, the flow rate of exhaust gas passing through the exhaust gas purification means is reduced, and when the temperature of the exhaust gas purification means is lower than the temperature of exhaust gas at the inlet of the exhaust gas purification means, The following effects are obtained by providing the passage flow rate correction means for giving a signal to the passage flow rate change means so as to increase the flow rate of the exhaust gas passing through the exhaust gas purification means. That is, when the exhaust gas temperature (hereinafter, referred to as Tg) at the inlet of the exhaust gas purifying means is lower than the temperature (hereinafter, referred to as Tc) of the exhaust gas purifying means, the flow rate of the exhaust gas passing through the catalyst (hereinafter referred to as the flow rate) is reduced,
Exhaust gas purifying means is prevented from being cooled by passing a large amount of low-temperature exhaust gas. Conversely, when Tg> Tc, a large amount of high-temperature exhaust gas is introduced into the exhaust gas purifying means, and the temperature of the exhaust gas purifying means is quickly raised to control the temperature to be suitable for exhaust gas purification. This makes it possible to significantly improve exhaust gas purification performance.

Further, an oxidation catalyst or a trap filter may be used as the exhaust gas purifying means in addition to the NOx catalyst. Further, instead of directly detecting the temperature of the exhaust gas purifying means, the temperature of the exhaust gas on the upstream side and the downstream side of the exhaust gas purifying means may be detected and calculated based on them.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an exhaust gas purification device as a first embodiment of the present invention.

FIG. 2 is a graph showing a change in a NOx purification rate by a catalyst with temperature.

FIG. 3 is a time chart of a traveling pattern for explaining a problem of the related art.

FIG. 4 is a conceptual cross-sectional view showing an enlarged part of the exhaust gas purification device of the first embodiment.

FIG. 5 is a flowchart showing the operation of the exhaust gas purifying apparatus of the first embodiment.

FIG. 6 is a time chart of a traveling pattern for explaining the effect of the first embodiment.

FIG. 7 is an overall configuration diagram showing an exhaust gas purification apparatus as a second embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the exhaust gas purification device of the second embodiment.

FIG. 9 is an overall configuration diagram showing an exhaust gas purification apparatus as a fifth embodiment of the present invention.

FIG. 10 is a flowchart showing the operation of the exhaust gas purification apparatus of the fifth embodiment.

FIG. 11 is an overall configuration diagram showing an exhaust emission control device as a sixth embodiment of the present invention.

FIG. 12 is a flowchart showing the operation of the exhaust emission control device of the sixth embodiment.

FIG. 13 is an overall configuration diagram showing an exhaust emission control device as a seventh embodiment of the present invention.

FIG. 14 is a conceptual cross-sectional view showing a part of an exhaust emission control device according to a seventh embodiment in an enlarged manner.

FIG. 15 is a flowchart showing the operation of the exhaust emission control device of the seventh embodiment.

FIG. 16 is a flowchart showing the operation of the exhaust emission control device according to the eighth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Diesel engine 12 Intake pipe 13 Intake throttle valve 14 Exhaust pipe 15 Exhaust recirculation pipe 16 Exhaust recirculation control valve 17 Catalytic converter 18 Control unit (ECU) 19 Solenoid valve 20 Vacuum pump 30 Speed sensor 31 Load sensor 32 33 ... Temperature sensor 34 Vehicle speed sensor 35 pressure sensor 50 wastegate valve 51 exhaust turbine 52 bypass pipe 53 intake turbine 55 pressure sensor 171 trap filter 331 temperature sensor

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F02D 9/02 ZAB F02D 9/02 ZABS 41/02 310 41/02 310E 43/00 ZAB 43/00 ZAB 301 301K 301T 301N 45/00 ZAB 45/00 ZAB 301 301F 310 310R 360 360C F02M 25/07 ZAB F02M 25/07 ZAB 550 550K 550J 550R Inside DENSO Corporation

Claims (8)

[Claims] An exhaust purification device disposed in an exhaust passage; an intake throttle valve disposed in an intake passage; and an exhaust gas recirculation control valve for controlling an amount of exhaust gas recirculated from the exhaust passage to the intake passage. Having a flow rate changing means for changing a flow rate of the exhaust gas passing through the exhaust gas purifying means; an exhaust temperature detecting means for detecting an exhaust gas temperature at an inlet of the exhaust gas purifying means; and detecting a temperature of the exhaust gas purifying means. Or, a temperature detecting means of the exhaust gas purifying means for estimating, a temperature comparing means for comparing an output of the exhaust gas temperature detecting means with an output of the temperature detecting means of the exhaust gas purifying means, and an output of the temperature comparing means. When the temperature of the exhaust gas purifying means is higher than the temperature of the exhaust gas at the inlet of the exhaust gas purifying means, the flow rate of the exhaust gas passing through the exhaust gas purifying means is reduced, and the temperature of the exhaust gas at the inlet of the exhaust gas purifying means is reduced. Than When the temperature of the exhaust gas purifying means is low, a flow rate correction for giving a signal to the intake throttle valve and the exhaust gas recirculation control valve of the flow rate changing means so as to increase the flow rate of the exhaust gas passing through the exhaust gas purifying means. And an exhaust purification device for an internal combustion engine. 2. The vehicle according to claim 1, further comprising an operating state detecting unit configured to detect an operating state of the vehicle, wherein the passing flow rate correcting unit is configured to detect an operating state of the exhaust purifying unit based on outputs of the temperature comparing unit and the operating state detecting unit. While the temperature of the exhaust gas purifying means is higher than the exhaust gas temperature at the inlet, when the operating state detecting means detects that the vehicle is decelerating or idling,
The opening degree of the intake throttle valve is reduced and the opening degree of the exhaust flow rate control valve is increased to increase the correction amount for decreasing the exhaust flow rate passing through the exhaust purification means. When it is detected that the time has elapsed, the opening degree of the intake throttle valve is increased, and the opening degree of the exhaust gas recirculation control valve is decreased, so that the decrease correction amount of the exhaust flow rate passing through the exhaust gas purifying means is reduced. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein: 3. The exhaust gas temperature detecting means includes means for detecting exhaust gas temperatures at an inlet and an outlet of the exhaust gas purifying means. The temperature detecting means of the exhaust gas purifying means includes an output of the exhaust gas temperature detecting means. 3. A temperature estimating means for estimating the temperature of the exhaust gas purifying means on the basis of the exhaust gas temperatures at the inlet and outlet of the exhaust gas purifying means.
An exhaust gas purification apparatus for an internal combustion engine according to any one of the above. 4. The exhaust gas purifying device according to claim 1, further comprising a NOx reduction catalyst, an oxidation catalyst, a trap filter, or a combination of a plurality of these. An exhaust purification device for an internal combustion engine according to any one of the above. 5. The temperature of the exhaust gas purifying means is higher than the exhaust gas temperature at the inlet of the exhaust gas purifying means based on the outputs of the temperature comparing means and the operating state detecting means. In the case, when the vehicle is accelerating, the opening degree of the intake throttle valve is set to A1, the opening degree of the exhaust gas recirculation control valve is set to B1, and the opening degree of the intake throttle valve is set to A2 (A2 <A2) during deceleration and idling of the vehicle. A1), and the opening degree of the exhaust gas recirculation control valve is set to B2 (B2>
B1), the opening degree of the intake throttle valve is set to A3 (A3> A1) when the vehicle is accelerating while the temperature of the exhaust purification unit is lower than the exhaust gas temperature at the inlet of the exhaust purification unit;
The opening degree of the exhaust gas recirculation control valve is B3 (B3 <B1), and the intake throttle valve and the exhaust gas recirculation control valve are configured to independently change the intake air amount and the exhaust gas recirculation amount according to the driving state of the vehicle. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the opening degree of the exhaust gas is controlled. 6. The passing flow rate changing means has a waste gate valve of a supercharging device, and the passing flow rate correcting means is configured to output the exhaust gas based on outputs of the temperature comparing means and the operating state detecting means. In the case where the temperature of the exhaust gas purifying means is higher than the exhaust gas temperature at the inlet of the purifying means, the valve opening of the waste gate valve is set to C1 during vehicle acceleration, and the valve opening is set to C2 (C2>) during vehicle deceleration and idling. C
In the case where the temperature of the exhaust gas purification unit is lower than the exhaust gas temperature at the inlet of the exhaust gas purification unit, the valve opening is set to C3 (C3 <C1) during vehicle acceleration, and the temperature of the exhaust gas purification unit is set to 1). 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the valve opening degree is set to C4 (C4> C2) when the temperature is lower than the predetermined value T1 and the vehicle is not accelerating. An exhaust gas purification device for an internal combustion engine. 7. The passing flow rate correcting means, when the temperature of the exhaust gas purifying means is lower than a predetermined value T1 or higher than a second predetermined value T2 (T1 <T2). The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the operation of reducing the flow rate of the exhaust gas passing therethrough is stopped. 8. When the output of the internal combustion engine detected by the operating state detecting means is larger than a predetermined value, the passing flow rate correcting means stops the operation of decreasing the exhaust flow rate passing through the exhaust purifying means. 3. The method according to claim 2, wherein
An exhaust gas purification apparatus for an internal combustion engine according to any one of claims 7 to 7.