JP2000186541A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the whole of an exhaust emission control device at a desired temperature and improve purifying rate of the exhaust purifying device to prevent deterioration of exhaust emission by providing a means for intermittently introducing combustion gas of a combustion heater into an exhaust system on the upstream of an exhaust emission purifying catalyst. SOLUTION: An internal combustion engine 1 is provided with a combustion heater 14. A combustion gas exhaust passage 17 of the heater 14 is connected to an exhaust pipe 7 on the upstream of an exhaust emission purifying catalyst 8 of the internal combustion engine 1, and a solenoid valve 70 for opening and closing a passage is provided in the midway of the passage. An ECU 21 determines the operating condition of the engine 1 according to an output signal value of each kind of sensors to execute exhaust emission purifying control. The combustion gas discharged by the heater 14 is intermittently supplied to the exhaust pipe 7 by opening and closing the solenoid valve 70, so that the mixed gas of combustion gas and exhaust and only the exhaust gas are alternately let flow into a selective reducing type lean NOx catalyst 8. Therefore, the temperature of the whole of the catalyst is uniformly raised without an excessive temperature rise of a part of the catalyst so as to improve the purifying rate of NOx.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to an exhaust gas purifying apparatus for an internal combustion engine having a combustion type heater.

[0002]

2. Description of the Related Art In recent years, in an internal combustion engine such as a diesel engine which generates relatively little heat, a combustion type heater is additionally provided for the purpose of improving the performance of an indoor heating device at the time of a cold start and promoting warm-up of the internal combustion engine. A technology to do this has been proposed.

The above-described combustion type heater has a combustion chamber independent of the internal combustion engine and a water passage formed so as to surround the combustion chamber. The water passage in the heater and the cooling water passage in the internal combustion engine are a cooling water introduction passage that guides cooling water from the cooling water passage of the internal combustion engine to the water passage in the heater, and a cooling water that guides cooling water from the water passage in the heater to the cooling water passage of the internal combustion engine. They are connected by a discharge passage. In the middle of the cooling water discharge passage, a heater core of the heating device is provided.

[0004] The combustion type heater configured as described above burns a part of the fuel of the internal combustion engine in the combustion chamber at the time of cold start of the internal combustion engine and the like, and supplies the cooling water for the internal combustion engine to the cooling water introduction passage. To the water channel inside the heater. In this case, heat generated by the combustion in the combustion chamber is transmitted to the water passage in the heater, and the temperature of the cooling water flowing through the water passage in the heater is raised. The cooling water (warm water) whose temperature has been raised in this manner is discharged from the water passage in the heater to the cooling water discharge passage, and returned to the cooling water passage of the internal combustion engine via the heater core. When the hot water passes through the heater core, part of the heat of the hot water is transmitted to the heating air in the heater core, and the heating air is heated.

According to the above-described combustion type heater, the temperature of the engine cooling water or the heating air can be raised at an early stage at the time of a cold start or the like, so that warm-up is promoted and heating performance is improved. Becomes possible.

In the combustion type heater, combustion is performed by using a part of the fuel for the internal combustion engine. Therefore, the combustion gas discharged from the combustion type heater contains the same harmful gas component as the exhaust gas of the internal combustion engine. Therefore, it is necessary to release the harmful gas components after purifying them.

In response to such a demand, Japanese Patent Laid-Open Publication No.
No. 819 discloses a "heating apparatus for a vehicle equipped with a combustion heater". This heating device is provided with a discharge port of a heater exhaust pipe for discharging gas burned in the combustion type heater upstream of an exhaust gas purification device of an exhaust pipe of an internal combustion engine, so that the combustion exhausted from the combustion type heater is provided. The gas is introduced into an exhaust gas purification device for an internal combustion engine, and the exhaust gas purification device for an internal combustion engine purifies harmful gas components in the combustion gas.

[0008]

As an exhaust purifying apparatus for an internal combustion engine [0005] is, and NO _X catalyst for reducing and purification of NO _X in the exhaust gas under predetermined conditions, particulate matter such as soot contained in the exhaust gas ( DPF (Dies) to capture Particulate Matter PM
el Particulate Filter) is known.

[0009] NO The _X catalyst, the NO _X as the reducing agent hydrocarbon (HC) in the state condition of the exhaust gas flowing into the catalyst is present and HC in the oxygen-excess state nitrogen (N _2), water ( H ₂ O), a selective reduction type lean NO _X catalyst that reduces to carbon dioxide (CO ₂ ) or the like, or stores NO _X in exhaust gas when the air-fuel ratio of exhaust gas flowing into the catalyst is lean, and stores NO _X in exhaust gas. with oxygen concentration emits NO _X which has been occluded when lowered, absorbing the released NO _X is reacted with HC and carbon monoxide (CO) or the like of the reducing agent to reduce and purification in N ₂ or the like reducing type lean NO _X catalyst and the like are known.

On the other hand, the DPF is formed of a porous ceramic or the like, and the PM contained in the exhaust gas when the exhaust gas passes through the hole is used.
When the inflow exhaust gas is lean and the exhaust gas temperature is high (for example, 500 ° C. to 700 ° C.), the trapped PM is burned, or a catalyst is carried on the surface of the exhaust passage in the DPF, and It is known that a reducing agent such as HC reacts with oxygen, and the trapped PM is burned by reaction heat generated at that time.

Since the above-described NO _X catalyst or DPF is activated when it is in a predetermined temperature range, the temperature of the NO _X catalyst, DPF, etc. must be adjusted to a certain level in order to reliably purify harmful gas components in the exhaust gas. Temperature range. In particular, small calorific value as a diesel engine, NO _X catalyst and the DPF exhaust gas temperature is provided in the exhaust system of the lower engine
It is difficult to raise the temperature to a predetermined temperature range at the time of a cold start or the like, and even after the temperature is raised, there is a possibility that the temperature is lowered to a temperature lower than the predetermined temperature range by low-temperature exhaust.

On the other hand, a high-temperature combustion gas discharged from a combustion heater is purified by an exhaust gas purification apparatus such as a "heating apparatus for a vehicle equipped with a combustion heater" described in Japanese Patent Application Laid-Open No. 60-78819. Although a method of introducing the gas into the upstream exhaust system is conceivable, if the combustion gas of the combustion heater is continuously supplied to the upstream of the exhaust gas purification device, the heat of the combustion gas is mainly transmitted to the vicinity of the exhaust gas inlet of the exhaust gas purification device, There is a possibility that the temperature near the exhaust gas inlet becomes excessively high.

For example, when a selective reduction type lean NO _X catalyst having a limited temperature range in which NO _X can be purified (catalyst purification window) is used as an exhaust gas purification device, the combustion gas of the combustion type heater is continuously discharged. When supplied to the selective reduction type lean NO _X catalyst, the temperature of the inlet portion of the selective reduction type lean NO _X catalyst will exceed the upper limit of the catalyst purification window, the purification performance of the selective reduction type lean NO _X catalyst Will drop.

Further, when the combustion gas of the combustion heater is continuously added to the exhaust gas purification device and the combustion gas is in a rich atmosphere, the oxygen concentration in the exhaust gas purification device is reduced and the oxidation of harmful gas components is reduced. Since the reaction is not sufficiently performed, the inside of the exhaust gas purification device may be poisoned by harmful gas components, and the purification performance of the exhaust gas purification device may be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and in an internal combustion engine provided with a combustion heater, the entire exhaust gas purifying apparatus utilizes combustion gas discharged from the combustion heater. To achieve a desired temperature of the exhaust gas, improve a purification rate of the exhaust gas purification device, and prevent deterioration of the exhaust emission.

[0016]

The present invention employs the following means to solve the above-mentioned problems. That is, a first exhaust gas purifying apparatus according to the present invention includes a combustion heater for increasing the temperature of related elements of an internal combustion engine, and an exhaust gas purification catalyst provided in an exhaust system of the internal combustion engine for purifying harmful gas components in exhaust gas. And combustion gas supply means for intermittently introducing the gas combusted by the combustion heater into an exhaust system upstream of the exhaust purification catalyst.

In the exhaust gas purification device configured as described above,
The combustion gas supply means intermittently supplies the gas burned by the combustion heater to an exhaust system upstream of the exhaust purification catalyst. In this case, in the exhaust system upstream of the exhaust purification catalyst, the supply and stop of the combustion gas are repeated. Then, the exhaust gas mixed with the combustion gas and only the exhaust gas alternately flow into the exhaust purification catalyst.

The temperature of the exhaust gas mixed with the combustion gas is higher than that of the exhaust gas alone. When such a mixed gas flows into the exhaust gas purification catalyst, for example, heat of the mixed gas is transferred to the vicinity of the exhaust gas inlet of the exhaust gas purification catalyst, or hydrocarbons and carbon monoxide contained in the combustion gas are purified. The reaction heat generated when reacting with oxygen on the catalyst raises the temperature near the exhaust inlet.

Thereafter, when the supply of the combustion gas is stopped,
Only exhaust gas flows into the exhaust purification catalyst. Since the temperature of only the exhaust gas is lower than the above-described mixed gas, the temperature near the exhaust gas inlet does not rise due to excessive heat. Further, heat near the exhaust inlet is transmitted to other parts on the exhaust purification catalyst,
The temperature of other parts of the exhaust purification catalyst rises.

If the vicinity of the exhaust gas inlet has already reached the activation temperature, the harmful gas component in the exhaust gas reacts with the catalyst near the exhaust gas inlet, and the reaction heat at that time is also transmitted to other parts. Therefore, the temperature rise of other parts is promoted.

Subsequently, when the supply of the combustion gas is restarted,
The mixed gas of combustion gas and exhaust gas flows into the exhaust purification catalyst,
The temperature near the exhaust gas inlet rises again. By repeating the supply and the stop of the combustion gas in this way, the temperature of the entire exhaust purification catalyst rises substantially uniformly without a part of the exhaust purification catalyst rising excessively.

In the exhaust gas purifying catalyst described above, when a catalyst temperature is within a predetermined temperature range and hydrocarbons are present when the inflowing exhaust gas is in a lean atmosphere, a selective reduction for reducing and purifying nitrogen oxides in the exhaust gas. An example is a type lean NO _X catalyst. This is because if the temperature of a part of the selective reduction type lean NO _X catalyst becomes higher than the predetermined temperature range, it becomes impossible to purify the NO _X in the exhaust at that part, so that the temperature of the entire selective reduction type NO _X catalyst is substantially reduced. This is because it is necessary to keep it uniform.

Next, a second exhaust gas purifying apparatus according to the present invention comprises: a combustion type heater for raising the temperature of related elements of an internal combustion engine;
An exhaust gas purification unit provided in an exhaust system of the internal combustion engine for purifying harmful gas components in exhaust gas; a temperature distribution detection unit for detecting a temperature distribution of the exhaust gas purification unit; and the exhaust gas purification unit by the temperature distribution detection unit And a combustion gas supply means for supplying gas burned by the combustion-type heater to the portion having a temperature lower than the predetermined temperature when a portion having a temperature lower than the predetermined temperature is detected. .

In the exhaust gas purifying apparatus configured as described above,
The temperature distribution detecting means detects a temperature distribution of the exhaust gas purifying means. At this time, when the temperature distribution detecting means detects a portion having a temperature lower than the predetermined temperature in the exhaust gas purifying means, the combustion gas supply means supplies the gas having a temperature lower than the predetermined temperature with the combustion gas discharged from the combustion heater.

In this case, the heat of the combustion gas is transmitted to a portion of the exhaust gas purification device which is lower than a predetermined temperature, or hydrocarbons, carbon monoxide and the like contained in the combustion gas react with oxygen on the exhaust gas purification means. Due to the heat of reaction
The temperature of the site increases.

As a result, in the exhaust gas purifying apparatus of the present invention, since the combustion gas is supplied only to a portion of the exhaust gas purifying means where the temperature is low, in other words, only the portion that needs to be heated, the other portions are excessively heated. Therefore, the entire exhaust gas purifying means can be maintained at an appropriate temperature substantially uniformly.

An example of the exhaust gas purifying means is an exhaust gas purifying catalyst divided into a plurality of parts. In this case, the temperature distribution detecting means detects the catalyst bed temperature of each exhaust gas purifying catalyst, and the combustion gas supply means detects when the temperature distribution detecting means detects the exhaust gas purifying catalyst whose catalyst bed temperature is lower than the predetermined temperature. The combustion gas of the combustion type heater may be supplied to the exhaust gas purification catalyst having a temperature lower than the predetermined temperature.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings.

<First Embodiment> A first embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification device according to the present embodiment is applied. The internal combustion engine 1 shown in FIG. 1 is a multi-cylinder water-cooled diesel engine.

An intake branch pipe 2 is connected to the internal combustion engine 1.
Each branch pipe of the intake branch pipe 2 communicates with a combustion chamber of each cylinder via an intake port (not shown). The intake branch pipe 2 is
The intake pipe 3 is connected to an air cleaner box 4 in which an air filter is provided.

In the intake system configured as described above, fresh air flowing into the air cleaner box 4 is removed by an air filter to remove dust and dirt, and then guided to the intake branch pipe 2 through the intake pipe 3 to be taken into the intake branch. The fuel is distributed to the combustion chamber of each cylinder through each branch pipe of the pipe 2.

On the other hand, an exhaust branch 6 is connected to the internal combustion engine 1, and each branch of the exhaust branch 6 communicates with a combustion chamber of each cylinder via an exhaust port (not shown). The exhaust branch pipe 6 is connected to an exhaust pipe 7, and the exhaust pipe 7 is connected downstream to a muffler (not shown).

In the middle of the exhaust pipe 7, an exhaust purification catalyst 8
Is arranged. The exhaust purification catalyst 8 includes a selective reduction type lean NO _X catalyst, an occlusion reduction type lean NO _X catalyst,
Alternatively, a DPG supporting an oxidation catalyst or the like can be exemplified, but in the present embodiment, the selective reduction type lean NO _X
A description will be given using a catalyst as an example.

[0035] The selective reduction type lean NO _X catalyst 8, when the catalyst bed temperature is within a predetermined temperature range (catalytic purification window), the air-fuel ratio of the exhaust gas flowing into the selective reduction type lean NO _X catalyst 8 Lean atmosphere and hydrocarbon HC
Is a catalyst that reduces or decomposes NO _X in exhaust gas under the presence of, for example, C
Examples thereof include those in which a transition metal such as u is supported by ion exchange, and those in which a noble metal is supported on a support made of zeolite or alumina.

In the exhaust system configured as described above, the air-fuel mixture burned in the combustion chamber of each cylinder is guided to the exhaust pipe 7 through each branch pipe of the exhaust branch pipe 6, and is provided with a selective reduction type lean NO _X catalyst. 8
Flow into At this time, if the catalyst bed temperature of the selective reduction type lean NO _X catalyst 8 is in the catalyst purification window, the air-fuel ratio of the inflowing exhaust gas is lean, and HC is present in the exhaust gas, the selective reduction is performed. Part of the HC is partially oxidized to form active species in the type lean NO _X catalyst 8, and the active species reacts with NO _X in the exhaust gas to convert NO _X into N ₂ , H ₂ O, CO 2
Reduce to ₂ mag.

Next, the internal combustion engine 1 is provided with one fuel injection valve 10 for each cylinder. Each fuel injection valve 1
Numeral 0 is attached so that the injection hole faces the combustion chamber of each cylinder so that fuel can be directly injected into the combustion chamber. The fuel injection valve 10 communicates with a pressure accumulation chamber (common rail) 12 via a fuel distribution pipe 11, and the common rail 1
Numeral 2 communicates with a fuel pump (not shown) via a fuel passage 13.

In the fuel injection system configured as described above, the fuel discharged from the fuel pump is supplied to the common rail 12 through the fuel passage 13 and accumulated in the common rail 12 to a predetermined pressure. It is applied to the fuel injection valve 10 via the distribution pipe 11. When the fuel injection valve 10 is opened, the accumulated fuel is injected into the combustion chamber, and mixes with the fresh air supplied to the combustion chamber via the above-described intake system to form an air-fuel mixture.

The internal combustion engine 1 includes a combustion heater 14.
Is attached. The combustion heater 14 is connected to an intake introduction passage 15 and a combustion gas discharge passage 17. The intake passage 15 is connected to the intake pipe 3. An air pump 16 for feeding a part of the intake air flowing through the intake pipe 3 to the combustion type heater 14 is provided in the middle of the intake introduction passage 15.

On the other hand, the combustion gas discharge passage 17 is connected to the exhaust pipe 7 upstream of the selective reduction type lean NO _X catalyst 8. An electromagnetic valve 70 for opening and closing a flow path in the combustion gas discharge passage 17 is provided in the middle of the combustion gas discharge passage 17.

Subsequently, the combustion type heater 14 has a cooling water introduction passage 18 for guiding the cooling water of the internal combustion engine 1 to the combustion type heater 14, and the cooling water heated in the combustion type heater 14 to the internal combustion engine 1. The leading cooling water discharge passage 19 is connected.

Further, a fuel introduction passage 20 is connected to the combustion type heater 14, and the fuel introduction passage 20 is connected to the above-described fuel passage 13. Thereby, the fuel passage 1
3 can be supplied to the combustion heater 14.

Here, a specific configuration of the combustion heater 14 will be described with reference to FIG. Combustion heater 14
Communicates with a not-shown water jacket of the internal combustion engine 1 via a cooling water introduction passage 18 and a cooling water discharge passage 19, and inside the combustion type heater 14, for flowing cooling water from the water jacket. A heater internal cooling water passage 14a is formed.

The heater internal cooling water passage 14a is arranged so as to circulate around a combustion chamber 14d formed inside the combustion type heater 14, and the cooling water flowing through the heater internal cooling water passage 14a is discharged from the combustion chamber 14d. The temperature rises due to the heat. This will be described sequentially.

The combustion chamber 14d includes a combustion tube 14b as a combustion source for generating a flame, and a cylindrical partition wall 14c that covers the combustion tube 14b to prevent the flame from leaking to the outside. Thus, the combustion cylinder 14b is
By covering with c, the combustion chamber 14d is defined in the partition wall 14c. The partition wall 14c is covered by an outer wall 43a of the combustion chamber main body 43 of the combustion type heater 14. An annular gap is provided between the partition wall 14c and the outer wall 43a, and this gap functions as the above-described heater internal cooling water passage 14a.

The combustion type heater 14 has an air supply port 14d.
₁ and an exhaust outlet 14d ₂ and is formed, these air supply ports 14d ₁ and an exhaust outlet 14d ₂ is communicated with the combustion chamber 14d. Wherein the air supply port 14d ₁ is connected to the intake introduction passage 15 described above, the combustion gas discharge passageway 17 described above is connected to the exhaust outlet 14d _2.

[0047] Then, the combustion heater 14, a cooling water inlet 14a ₁ and the cooling water outlet 14a ₂ are formed, these cooling water inlet 14a ₁ and the cooling water outlet 14a ₂ and said heater It communicates with the internal cooling water passage 14a. Wherein the cooling water inlet 14a ₁ is connected a cooling water introducing passageway 18 described above, the cooling water discharge passage 19 is connected to said cooling water outlet 14a ₂ described above.

The above-mentioned fuel introduction passage 20 is connected to the above-mentioned combustion cylinder 14b, so that a part of the fuel discharged from the fuel pump is supplied to the combustion cylinder 14b. Further, a vaporizing glow plug (not shown) for vaporizing the fuel supplied through the fuel introduction passage 20 and an ignition glow plug (not shown) for igniting the vaporized fuel are provided in the combustion cylinder 14b. It is decorated. The vaporizing glow plug and the ignition glow plug may be shared by a single glow plug.

[0049] In the thus configured combustion heater 14, with flowing from intake air passage 15 to the air supply port 14d ₁ intake air is introduced into the combustion chamber 14d, which is supplied to the combustion cylinder 14b with the fuel introducing passage 20 The fuel is vaporized by the vaporizing glow plug. Then, the intake air and the vaporized fuel are mixed to form an air-fuel mixture, and the air-fuel mixture is ignited by an ignition glow plug in the combustion chamber 14d and burns.

The combusted in the combustion chamber 14d gas is introduced from the combustion chamber 14d to the exhaust outlet 14d _2, and then is discharged from the exhaust outlet 14d ₂ into the combustion gas discharge passage 17. The combustion gas discharged to the combustion gas discharge passage 17 reaches the solenoid valve 70 through the combustion gas discharge passage 17. At that time, if the solenoid valve 70 is open, the combustion gas is:
It is guided to the exhaust pipe 7 upstream of the selective reduction type lean NO _X catalyst 8.

The combustion gas introduced into the exhaust pipe 7 flows into the selective reduction type lean NO _X catalyst 8 while being mixed with the exhaust gas flowing from the upstream of the exhaust pipe 7. The heat which the combustion gas has is transmitted to the selective reduction type lean NO _X catalyst 8, a catalyst bed temperature of the selective reduction type lean NO _X catalyst 8 increases. At this time, if the catalyst bed temperature of the selective reduction type lean NO _X catalyst 8 is already in the catalyst purification window and sufficient oxygen is present in the mixed gas of the combustion gas and the exhaust gas, the oxygen is contained in the combustion gas. The HC is partially oxidized to form active species, and the active species reacts with NO _x in the exhaust gas to convert NO _x into N ₂ and H ₂ .
Reduce to ₂ O, CO _2, etc.

In the combustion type heater 14, the combustion chamber 14
Heat generated by the combustion in d is transmitted to the cooling water flowing in the heater internal cooling water passage 14a through the partition wall 14c, and the temperature of the cooling water is raised.

Returning to FIG. 1, the internal combustion engine 1 includes an electronic control unit (ECU) for controlling the engine.
ol Unit) 21 is also provided. The ECU 21 includes a CPU, a ROM,
It comprises a RAM, an input interface circuit, an output interface circuit and the like. Various sensors are connected to the input interface circuit via electric wiring, and the output interface circuit is connected to the fuel injection valve 1.
0, combustion type heater 14, air pump 16, and solenoid valve 7
0 is connected via electric wiring.

The various sensors described above operate in conjunction with an air flow meter 5 attached to the intake pipe 3, a crank position sensor 22 and a water temperature sensor 23 attached to the internal combustion engine 1, and an accelerator pedal or accelerator pedal (not shown). An accelerator position sensor 24 attached to an accelerator lever or the like can be exemplified.

The air flow meter 5 is a sensor that outputs an electric signal corresponding to the mass of the intake air flowing through the intake pipe 3. The crank position sensor 22 is a sensor that outputs a pulse signal each time a crankshaft (not shown) of the internal combustion engine 1 rotates by a predetermined angle. The water temperature sensor 23 is a sensor that outputs an electric signal corresponding to the temperature of the cooling water flowing through the water jacket of the internal combustion engine 1. The accelerator position sensor 24 is a sensor that outputs an electric signal corresponding to the operation amount of the accelerator pedal.

The ECU 21 determines the operating state of the internal combustion engine 1 based on the output signal values of the various sensors as described above, and performs fuel injection control and combustion type heater control based on the determination result. Exhaust gas purification control is executed.

Hereinafter, the exhaust gas purification control according to this embodiment will be described. The exhaust gas purification control according to the present embodiment
This is realized by the ECU 21 executing an exhaust gas purification control routine as shown in FIG. The exhaust gas purification control routine is a routine executed by the ECU 21 at predetermined time intervals (for example, every time the crank position sensor 22 outputs a pulse signal).

In the exhaust gas purification control routine, the ECU 2
First, in S301, it is determined whether or not the combustion type heater 14 is in an operating state. If it is determined in step S301 that the combustion type heater 14 is operating, the ECU 21
Proceeds to S302, and determines whether the electromagnetic valve 70 is in the open state.

If it is determined in step S302 that the solenoid valve 70 is in the open state, that is, if it is determined that the combustion gas of the combustion heater 14 is being supplied to the exhaust pipe 7, the ECU 21 proceeds to step S303. Go to ECU2
The counter is configured by a register or the like provided in the counter 1 and counts a valve opening time of the solenoid valve 70 (hereinafter, referred to as a valve opening time measurement counter), and increments the value.

Subsequently, the ECU 21 proceeds to S304,
The value of the incremented opening time measuring counter at the S303 it is determined whether a predetermined time above T _1.

If the ECU 21 determines in step S304 that the value of the valve opening time measurement counter is less than the predetermined time T ₁ , the ECU 21 temporarily terminates the execution of this routine, and stops the execution of this routine. If it is determined to be above T ₁ proceeds to S305.

In step S305, the ECU 21 closes the solenoid valve 70 so that the combustion gas from the combustion heater 14 is not supplied to the exhaust pipe 7. Next, the ECU 21 executes S
Proceeding to 306, the valve opening time measurement counter is reset, and the execution of this routine is temporarily ended.

If it is determined in S302 that the solenoid valve 70 is in the closed state, that is, if it is determined that the combustion gas of the combustion heater 14 is not being supplied to the exhaust pipe 7, the ECU 21 determines , Proceed to S307,
The value of a counter (hereinafter, referred to as a valve closing time measurement counter) configured by a register or the like provided in the ECU 21 and measuring the valve closing time of the solenoid valve 70 is incremented.

In step S308, the ECU 21 executes the processing in step S30.
Incremented value of the valve closing time measuring counter 7 is discriminated whether a predetermined time T ₂ or more. ECU 21
In the S308 the value of the closing time measurement counter once terminates execution of this routine If it is determined that the ₂ less than the predetermined time T in, the value of the closing time measurement counter of the predetermined time T ₂ or more If it is determined that there is, the process proceeds to S309.

In step S309, the ECU 21 opens the solenoid valve 70 so that the combustion gas from the combustion heater 14 is supplied to the exhaust pipe 7. Next, the ECU 21 executes S
Proceeding to 310, the valve closing time measurement counter is reset, and the execution of this routine is temporarily terminated.

On the other hand, if it is determined in step S301 that the combustion type heater 14 is not operating, the ECU 21
Goes to S311 to close the solenoid valve 70, and then to S311.
In step 12, the valve opening time measurement counter and the valve closing time measurement counter are reset, and the execution of this routine is temporarily terminated.

As described above, when the ECU 21 executes the exhaust gas purification control routine, the state in which the combustion gas discharged from the combustion type heater 14 is supplied to the exhaust pipe 7 for a predetermined time T ₁ and the time when the predetermined time T ₂ The state in which the combustion gas is not supplied to the exhaust pipe 7 is alternately repeated, and the combustion gas of the combustion heater 14 is intermittently supplied to the exhaust pipe 7, thereby realizing the combustion gas supply means according to the present invention.

[0068] The predetermined time T _1, T ₂ described above may be a fixed value, the temperature or the like is discharged from the catalyst bed temperature and selective reduction type lean NO _X catalyst 8 of the selective reduction lean NO _X catalyst 8 exhaust May be a variable value changed as a parameter.

In the above-described embodiment, since the combustion gas discharged from the combustion heater 14 is intermittently supplied to the exhaust pipe 7, only the mixed gas of the combustion gas and the exhaust gas and the exhaust gas are selectively reduced. It flows into the type lean NO _X catalyst 8.

The mixed gas of the combustion gas and the exhaust gas is of a selective reduction type.
Lean NO_XWhen flowing into the catalyst 8, the fuel in the mixed gas
The heat of the burning gas is selectively reduced lean NO_XMain exhaust of catalyst 8
It is transmitted to the vicinity of the inlet, and the selective reduction type lean NO_XCatalyst 8
The temperature in the vicinity of the exhaust inflow port rises. Then the combustion gas
Supply is stopped and only exhaust is selective reduction type lean NO _X
When flowing into the catalyst 8, the selective reduction type lean NO_XCatalyst 8
Heat near the exhaust inlet is transmitted to the exhaust outlet side,
The temperature near the exhaust inlet decreases. And of the combustion gas
Supply resumed and mixed gas of combustion gas and exhaust gas was selectively returned
Original type lean NO_XWhen flowing into the catalyst 8, the heat of the combustion gas is
The temperature is transmitted to the vicinity of the exhaust inlet, and the temperature near the exhaust inlet is restored.
And rise.

When the supply and stop of the combustion gas are alternately repeated as described above, the temperature of the selective reduction type lean NO _X catalyst 8 does not rise excessively, and the selective reduction type lean NO _X
The temperature of the entire _X catalyst 8 rises substantially uniformly.

As a result, the selective reduction type lean NO _X catalyst 8
It is excessively heated and there is no departing from the catalyst purification window a part of, since it is possible to raise the temperature of the entire selective reduction type lean NO _X catalyst 8 to the catalytic purification window, selective reduction type lean NO _X catalyst 8 total becomes the NO _X in the exhaust gas can be reduced and purified, the purification rate of the NO _X is improved.

[0073] Also, the intermittent supply of the combustion gas, the catalyst bed temperature of the selective reduction type lean NO _X catalyst repeating the cooling and heating, when the supply of the combustion gas is cooled is stopped catalyst bed temperature Unburned HC in exhaust gas is selectively reduced lean NO
_X is adsorbed by the _X catalyst, and thereafter, when the combustion gas is supplied and the catalyst bed temperature rises, it is possible to reduce and purify NO _X in the exhaust gas by using the previously adsorbed HC as a reducing agent, _X purification rate is further improved.

<Second Embodiment> A second embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to FIGS. Here, a configuration different from that of the above-described first embodiment will be described, and a description of a similar configuration will be omitted.

FIG. 4 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust emission control device according to the present embodiment is applied. In the present embodiment, the selective reduction type lean NO _X catalysts 8a and 8b divided into two parts are arranged in series in the middle of the exhaust pipe 7 (hereinafter, the selective reduction type lean NO _X located on the upstream side).
The catalyst 8a is referred to as a first selective reduction type lean NO _X catalyst 8a, and a selective reduction type lean NO _X catalyst 8b located on the downstream side.
Is referred to as a second selective reduction type lean NO _X catalyst 8b).
These first and second selective reduction type lean NO _X catalysts 8
a and 8b realize an exhaust gas purifying means according to the present invention.

[0076] The first selective reduction type lean NO _X catalyst 8a, the first catalyst temperature sensor 80 for outputting an electric signal corresponding to the catalyst bed temperature of the first selective reduction type lean NO _X catalyst 8a is attached And the second selective reduction type lean NO _X
The catalyst 8b, the second catalyst temperature sensor 81 is attached to output an electric signal corresponding to the catalyst bed temperature of the second selective reduction type lean NO _X catalyst 8b.

The first and second catalyst temperature sensors 8
Numerals 0 and 81 are connected to the ECU 21 via electric wires, respectively, and output signals of the first and second catalyst temperature sensors 80 and 81 are input to the ECU 21.

On the other hand, a combustion gas discharge passage 17 is connected to the combustion type heater 14, and this combustion gas discharge passage 17
It is connected to a three-way switching valve 71. The three-way switching valve 71 is connected to two combustion gas passages 72 and 73.

[0079] One of the combustion gas passages 72 in the two combustion gas passage 72, 73 described above is connected to a first selective reduction type lean NO _X catalyst 8a upstream of the exhaust pipe 7, the other combustion gas passage 73 is connected to the exhaust pipe 7 located between the first selective reduction type lean NO _X catalyst 8a and the second selective reduction type lean NO _X catalyst 8b (hereinafter, the combustion gas passage 72 is connected to the first , And the combustion gas passage 73 is referred to as a second combustion gas passage 73).

The three-way switching valve 71 is connected to the ECU 21 via electric wiring, and connects the first combustion gas passage 71 and the second combustion gas passage 72 in response to a control signal output from the ECU 21. Close either one. That is, the three-way switching valve 71 is configured to control the combustion gas discharge passage 17 and the first combustion gas passage 7 in accordance with a control signal from the ECU 21.
2 and the conduction of the combustion gas discharge passage 17 and the second combustion gas passage 73 are switched.

Next, the exhaust gas purification control according to the present embodiment will be described. The exhaust gas purification control according to the present embodiment
This is realized by the CU 21 executing an exhaust gas purification control routine as shown in FIG. This exhaust gas purification control routine is a routine that is repeatedly executed at predetermined time intervals.

In the exhaust gas purification routine, the ECU 21
First, in S501, it is determined whether or not the combustion type heater 14 is operating. If it is determined in step S501 that the combustion heater 14 is in the non-operation state, the ECU 21
Terminates the execution of this routine once.

On the other hand, if it is determined in step S501 that the combustion type heater 14 is operating, the ECU 21
Proceeds to S502, the output signal of the first catalyst temperature sensor 80 (the catalyst bed temperature of the first selective reduction type lean NO _X catalyst 8a) TEMP ₁ and the output signal of the second catalyst temperature sensor 81 (the second (Catalyst bed temperature of the selective reduction type lean NO _X catalyst 8b)
Enter TEMP ₂ .

[0084] Subsequently, whether ECU21, in S503, the catalyst bed temperature TEMP ₁ of the first selective reduction type lean NO _X catalyst 8a is higher than the catalyst bed temperature TEMP ₂ of the second selective reduction type lean NO _X catalyst 8b It is determined whether or not.

If it is determined in S503 that the catalyst bed temperature TEMP ₁ of the first selective reduction type lean NO _X catalyst 8a is higher than the catalyst bed temperature TEMP _{2 of} the second selective reduction type lean NO _X catalyst 8b, the ECU 21 Proceeds to S504, controls the three-way switching valve 71 to make the combustion gas discharge passage 17 and the second combustion gas passage 73 conductive, and once ends the execution of this routine.

[0086] In this case, the combustion gas discharged from the combustion heater 14, a first selective reduction type lean NO _X catalyst 8a
When guided to the exhaust pipe 7 which is located between the second selective reduction type lean NO _X catalyst 8b, the first selective reduction type lean NO _X
It mixes with the exhaust gas discharged from the catalyst 8a to form a mixed gas.

The mixed gas flows into the second selective reduction type lean NO _X catalyst 8 b through the exhaust pipe 7. And
Heat of the combustion gas contained in the mixed gas is transmitted to the second selective reduction type lean NO _X catalyst 8b, the catalyst bed temperature of the second selective reduction type lean NO _X catalyst 8b is increased.

According to such an exhaust gas purification control, the first selective reduction type lean NO _X catalyst 8a is in an active state and the second selective reduction type lean NO _X catalyst 8b is in an inactive state. The first selective reduction type lean NO _X catalyst 8
Since only the catalyst bed temperature of the second selective reduction type lean NO _X catalyst 8b can be increased without excessively increasing the catalyst bed temperature of the first selective reduction type lean NO _X catalyst 8b, while keeping within the scope of the purification window of the second selective reduction type lean NO _X catalyst 8b can cause the bed temperature of up to a range of catalyst purification window.

The first and second selective reduction type lean N
O _X catalyst 8a, the 8b the internal combustion engine 1 is accelerating operation when the non-activated state, first is the selective reduction type lean NO _X catalyst 8a rapidly heated positioned on the upstream side by the high temperature and a large amount of exhaust However, it takes some time until the second selective reduction type lean NO _X catalyst 8b located on the downstream side is activated. Therefore, until the second selective reduction type lean NO _X catalyst 8b is activated will process the NO _X in the exhaust only the first selective reduction type lean NO _X catalyst 8a. For accelerating the high load operation of such during operation of _the amount of NO _X in the exhaust gas is increased, only the first selective reduction type lean NO _X catalyst 8a is not completely process all NO _X.

In such a case, by performing the above-described exhaust gas purification control and supplying the combustion gas of the fuel-type heater 14 to the second selective reduction type lean NO _X catalyst 8b,
Since the temperature of the second selective reduction lean NO _X catalyst 8b can be quickly raised and activated, a large amount of NO _X contained in the exhaust gas can be reliably processed.

Here, returning to the exhaust gas purification control routine of FIG. 5, in S503, the second selective reduction type lean NO
_When the ECU 21 determines that the catalyst bed temperature TEMP ₂ of the _X catalyst 8b is higher than the catalyst bed temperature TEMP _{1 of} the first selective reduction type lean NO _X catalyst 8a, the ECU 21 proceeds to S505 and connects the combustion gas discharge passage 17 and the first Then, the three-way switching valve 71 is controlled so as to establish communication with the combustion gas passage 73, and the execution of this routine ends.

[0092] In this case, the combustion gas discharged from the combustion heater 14, a first selective reduction type lean NO _X catalyst 8a
The mixture is guided to the exhaust pipe 7 upstream and mixed with the exhaust gas flowing from the upstream of the exhaust pipe 7 to form a mixed gas.

The mixed gas flows into the first selective reduction type lean NO _X catalyst 8 a through the exhaust pipe 7. And
Heat of the combustion gas contained in the mixed gas is transmitted to the first selective reduction type lean NO _X catalyst 8a, the catalyst bed temperature of the first selective reduction type lean NO _X catalyst 8a increases.

According to such exhaust gas purification control, for example, when the second selective reduction type lean NO _X catalyst 8b is in the active state and the first selective reduction type lean NO _X catalyst 8a is in the inactive state, etc. Then, the second selective reduction type lean NO _X catalyst 8
b without excessively raising the catalyst bed temperature of, for the catalyst bed temperature of the first selective reduction type lean NO _X catalyst 8a can be raised, the second selective reduction type lean NO _X catalyst 8
b the first selective reduction type lean NO _X catalyst 8a while keeping within the scope of the catalyst purification window can cause the bed temperature of up to a range of catalyst purification window.

[0095] As described above, according to this embodiment, it is possible to supply hot combustion gases only at the site to increase the catalyst bed temperature in the selective reduction type lean NO _X catalyst, previously catalyst purification without excessively raising the temperature of the portion that was heated to the range of the window, only the portion to be heated to can be raised to within the range of catalytic purification window, selective reduction type lean NO _X catalyst whole NO _X
The purification rate can be improved.

In the present embodiment, an example has been described in which the catalyst bed temperature is raised by transferring the heat of the combustion gas to a catalyst lower than the catalyst purification window, but the catalyst bed temperature is reduced to oxygen monoxide (CO). If the temperature is in a temperature range where hydrocarbons and hydrocarbons (HC) can be oxidized, the combustion type heater is controlled so as to increase the CO concentration or HC concentration in the combustion gas, and CO or H 2
C may be reacted (burned) with oxygen, and the heat of the reaction generated at that time may increase the catalyst bed temperature.

In the first and second embodiments described above, only when the combustion type heater is operating for the purpose of improving the heating performance and the warming-up performance, the combustion discharged from the combustion type heater is performed. Although the example using gas has been described, even if it is not necessary to operate the combustion heater for the purpose of improving the heating performance and warm-up performance, when it is necessary to raise the temperature of the catalyst, the combustion heater is required. Activate the
Combustion gas from a combustion type heater may be used.

[0098]

According to the first exhaust gas purification apparatus of the present invention,
Since the supply and non-supply of the combustion gas to the exhaust purification catalyst are alternately repeated, the temperature of the entire exhaust purification catalyst rises substantially uniformly without a part of the exhaust purification catalyst rising excessively. As a result, the entire exhaust purification catalyst is uniformly activated, and it is possible to reliably purify harmful gas components in exhaust gas.

In the second exhaust gas purifying apparatus according to the present invention, the gas burned by the combustion heater is supplied only to a portion of the exhaust gas purifying means which is lower than a predetermined temperature. Without excessively raising the temperature, it is possible to raise only the temperature below a predetermined temperature,
The entire exhaust gas purifying means can be uniformly heated. As a result, the entire exhaust gas purifying means is uniformly activated, and it is possible to reliably purify harmful gas components in the exhaust gas.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification device for an internal combustion engine according to a first embodiment is applied;

FIG. 2 is a diagram showing an internal configuration of a combustion heater.

FIG. 3 is a flowchart illustrating an exhaust gas purification control routine according to the first embodiment;

FIG. 4 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification device for an internal combustion engine according to a second embodiment is applied;

FIG. 5 is a flowchart illustrating an exhaust gas purification control routine according to a second embodiment;

[Description of Signs] 1 ... Internal combustion engine 2 ... Intake branch pipe 3 ... Intake pipe 6 ... Exhaust branch pipe 7 ... Exhaust pipe 8a ... First selective reduction type lean NO _X catalyst 8b ... second selective reduction type lean NO _X catalyst 9 ... exhaust gas temperature sensor 14 ... combustion heater 15 ... intake air introduction passage 16 .. the air pump 17 .. combustion gas discharge passageway 20 ... fuel introducing passage 21 ··· ECU 70 ··· Solenoid valve 71 ··· Three-way switching valve 72 ··· First combustion gas passage 73 ··· Second combustion gas passage 80 ··· First catalyst temperature sensor 81 ··· Second catalyst temperature sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 3G091 AA02 AA18 AA28 AB02 AB05 AB06 BA03 BA14 BA32 CA02 CA13 CB02 CB08 DA03 DB06 DB10 EA01 EA05 EA07 EA07 EA16 EA18 EA30 EA31 FA02 FA04 FA14 FA16 FA17 FB02 FB10 FC07 GB01 GB01 GB01 GB01 GB01 GB01 GB01 GB01 GB01 HA39 HA42

Claims (4)

[Claims] 1. A combustion heater for increasing the temperature of a related element of an internal combustion engine; an exhaust purification catalyst provided in an exhaust system of the internal combustion engine for purifying harmful gas components in exhaust gas; Combustion gas supply means for intermittently introducing the exhaust gas into an exhaust system upstream of the exhaust gas purification means;
An exhaust gas purification device for an internal combustion engine, comprising: 2. The exhaust gas purifying catalyst according to claim 1, wherein said exhaust gas purifying catalyst is within a predetermined temperature range and said hydrocarbon is present when said inflowing exhaust gas is in a lean atmosphere, and selectively reduces and purifies nitrogen oxides in said exhaust gas. an exhaust purification system of an internal combustion engine according to claim 1, characterized in that a type lean NO _X catalyst. 3. A combustion heater for raising the temperature of a related element of the internal combustion engine, an exhaust purification unit provided in an exhaust system of the internal combustion engine for purifying harmful gas components in exhaust gas, and a temperature distribution of the exhaust purification unit. A temperature distribution detecting means for detecting the temperature of the gas, and when the temperature distribution detecting means detects a portion having a temperature lower than a predetermined temperature in the exhaust gas purification means, supplying the gas burned by the combustion heater to the portion having a temperature lower than the predetermined temperature. Exhaust gas purifying apparatus for an internal combustion engine, comprising: 4. The exhaust gas purifying means comprises a plurality of divided exhaust gas purifying catalysts; the temperature distribution detecting means detects a catalyst bed temperature of each exhaust gas purifying catalyst; 4. The exhaust gas purifying apparatus according to claim 3, wherein when the distribution detecting means detects an exhaust gas purifying catalyst having a catalyst bed temperature lower than a predetermined temperature, the combustion gas of the combustion heater is supplied to the exhaust gas purifying catalyst having a temperature lower than the predetermined temperature. Exhaust purification device for internal combustion engine.