JP2001115883A - Exhaust gas temperature raising device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the arts of efficiently raising exhaust gas temperature without worsening exhaust emission when the exhaust gas temperature needs raising. SOLUTION: An exhaust gas temperature raising device for an internal combustion engine comprises a valve control means to control an exhaust throttle valve, situated in an exhaust passage, such that the valve is approximately fully closed when an unburnt fuel component discharged from the internal combustion engine is reduced, a main fuel injection control means to increase a main fuel amount injected from a fuel injection valve when the exhaust throttle valve is controlled to an approximately fully closed state, an auxiliary fuel injection control means to secondarily inject fuel through a fuel injection valve after main fuel is injected by the main fuel injection control means, and a PM removing means to be situated in the exhaust passage and remove particulates contained in exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for increasing the temperature of exhaust gas discharged from an internal combustion engine mounted on an automobile or the like, and more particularly to a technique for increasing the temperature of exhaust gas without deteriorating the emission of exhaust gas. .

[0002]

2. Description of the Related Art In an internal combustion engine mounted on an automobile or the like, it is required that harmful gas components contained in exhaust gas discharged from the internal combustion engine be purified and then released to the atmosphere.
In response to such demands, there has been proposed a technique in which an exhaust purification catalyst is disposed in an exhaust passage of an internal combustion engine, and a harmful gas component contained in exhaust gas is purified by the exhaust purification catalyst.

[0003] Since the exhaust gas purifying catalyst is generally activated when the temperature is equal to or higher than a predetermined temperature and can purify harmful gas components in the exhaust gas, the exhaust gas purifying catalyst is used as in the case where the internal combustion engine is cold started. When the temperature of the catalyst is lower than the predetermined temperature, it becomes impossible to sufficiently purify harmful gas components in exhaust gas.

[0004] In order to solve such a problem, an exhaust gas heating device as described in Japanese Patent Application Laid-Open No. 10-212995 has been proposed. When the internal combustion engine is in a warm-up operation state after a cold start, for example, the exhaust gas heating device described in this publication adds to the normal fuel injection (main fuel injection) used for combustion of the internal combustion engine, By performing secondary fuel injection (auxiliary fuel injection) during the expansion stroke of each cylinder, the sub-injected fuel is burned, and the in-cylinder gas temperature when the exhaust valve is opened, in other words, the exhaust temperature is increased. Thus, early activation of the exhaust purification catalyst is intended.

[0005]

However, when the internal combustion engine is in a warm-up operation state after a cold start, the temperature in the cylinder is low and the main fuel is hard to completely burn. A very large amount of unburned fuel components will remain. When the sub-fuel injection is performed in such a situation where the remaining amount of the unburned fuel component is large, the unburned fuel component burns using the sub-fuel as an ignition source, but the sub-fuel temperature is low due to the low ambient temperature in the cylinder. The fuel and the unburned fuel component may not completely burn, and a large amount of particulate matter (PM: Particulate Matter) typified by soot and unburned fuel component may be generated.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a technique for efficiently increasing the temperature of exhaust gas without deteriorating exhaust emission.

[0007]

The present invention employs the following means in order to solve the above-mentioned problems. That is,
An exhaust temperature raising apparatus for an internal combustion engine according to the present invention includes an exhaust throttle valve provided in an exhaust passage of the internal combustion engine to adjust a flow rate of exhaust flowing through the exhaust passage, and injects fuel directly into a cylinder of the internal combustion engine. A fuel injection valve, valve control means for controlling the exhaust throttle valve to be almost fully closed when an unburned fuel component discharged from the internal combustion engine is to be reduced, and the exhaust throttle valve is controlled to be almost fully closed. Main fuel injection control means for increasing the amount of main fuel injected from the fuel injection valve, and auxiliary fuel for injecting fuel from the fuel injection valve after the main fuel injection by the main fuel injection control means The fuel cell system further includes: an injection control unit; and a PM removing unit provided in the exhaust passage for removing particulate matter contained in exhaust gas flowing through the exhaust passage.

[0008] In the exhaust gas heating device configured as described above,
The valve control means makes the opening of the exhaust throttle valve almost fully closed at a time when the amount of the unburned fuel component discharged from the internal combustion engine should be reduced. In response, the main fuel injection control means controls the fuel injection valve to increase the injection amount of the main fuel, and the sub fuel injection control means controls the fuel injection valve to inject the sub fuel after the main fuel is injected. I do.

In this case, the pressure and temperature of exhaust gas rise from the exhaust passage upstream of the exhaust throttle valve into the cylinder of the internal combustion engine due to the synergistic effect of the exhaust throttle valve which is almost fully closed and an increase in the injection amount of the main fuel. At the same time, the flow rate of the exhaust gas decreases, so that the unburned fuel component and the auxiliary fuel, which are the unburned main fuel, burn for a long time at a high temperature, and the remaining amount of the unburned fuel component decreases. Further, particulate matter such as soot contained in the exhaust gas is removed from the exhaust gas by the PM removing means disposed in the exhaust passage, and is not released into the atmosphere.

Here, the timing for reducing the amount of unburned fuel components discharged from the internal combustion engine is as follows: when the internal combustion engine is in a warm-up operation state after a cold start, and when the outside air temperature is low, Is in a low load operation state, and the like.

In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, the auxiliary fuel injection control means executes the injection of the auxiliary fuel at a time when the amount of the unburned fuel component discharged from the internal combustion engine is minimized. Is preferred.

In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, a PM trap which physically adsorbs particulate matter contained in exhaust gas can be exemplified as the PM removing means. In this case, it is necessary to regenerate the PM trap before the adsorption capacity of the PM trap is saturated. In such a case, the valve control means controls the exhaust throttle valve to be almost fully closed, and the main fuel injection control means performs the operation. The fuel injection valve is controlled to increase the injection amount of the main fuel, and the auxiliary fuel injection control means controls the fuel injection valve to execute the injection of the auxiliary fuel, thereby increasing the temperature of the exhaust gas passing through the PM trap. What should I do?

[0013] In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, the PM removing means is preferably arranged in an exhaust passage upstream of the exhaust throttle valve. This is because when the exhaust throttle valve is almost fully closed, the exhaust flow velocity is lower in the exhaust passage upstream of the exhaust throttle valve than in the exhaust passage downstream of the exhaust throttle valve, and the high-temperature exhaust gas stays. This is because the PM removing means is exposed to high-temperature exhaust gas for a long period of time to improve the particulate matter regeneration efficiency.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of an exhaust gas heating device for an internal combustion engine according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas heating apparatus according to the present invention is applied. The internal combustion engine 1 shown in FIG. 1 is a four-cycle in-cylinder injection type internal combustion engine including a plurality of cylinders 21 and a fuel injection valve 32 for directly injecting fuel into each cylinder 21.

The internal combustion engine 1 includes a cylinder block 1b in which a plurality of cylinders 21 and a cooling water passage 1c are formed, and a cylinder head 1a fixed on an upper portion of the cylinder block 1b.

A crankshaft 23 as an engine output shaft is rotatably supported on the cylinder block 1b.
The crankshaft 23 is connected to a piston 22 slidably mounted in each cylinder 21.

Above the piston 22, a piston 2
2 and a combustion chamber 24 surrounded by the wall surface of the cylinder head 1a. An ignition plug 25 is attached to the cylinder head 1a so as to face the combustion chamber 24.
An igniter 25 a for applying a drive current to the ignition plug 25 is connected to the ignition plug 25.

Open ends of two intake ports 26 and two exhaust ports 27 are formed in the cylinder head 1a so as to face the combustion chamber 24, and the injection holes thereof face the combustion chamber 24. A fuel injection valve 32 is attached.

Each open end of the intake port 26 is opened and closed by an intake valve 28 supported on the cylinder head 1a so as to be movable forward and backward.
The intake camshaft 30 is rotatably supported by the cylinder head 1a and is driven forward and backward.

Each open end of the exhaust port 27 is opened and closed by an exhaust valve 29 supported on the cylinder head 1a so as to be movable forward and backward. These exhaust valves 29 are rotatably supported on the cylinder head 1a. The exhaust side camshaft 31 is driven forward and backward.

The intake camshaft 30 and the exhaust camshaft 31 are connected to the crankshaft 23 via a timing belt (not shown), and the rotational torque of the crankshaft 23 is reduced via the timing belt. The power is transmitted to the exhaust-side camshaft 31.

Two intake ports 2 communicating with each cylinder 21
6 is connected to the cylinder head 1.
a straight port having a flow path formed linearly from the open end formed on the outer wall to the open end facing the combustion chamber 24, and the other intake port 26 is formed from the open end of the outer wall of the cylinder head 1a. A helical port having a flow path formed to swirl in a plane perpendicular to the axial direction of the cylinder 21 toward the open end of the combustion chamber 24 is formed.

Each intake port 26 communicates with each branch pipe of an intake branch pipe 33 attached to the cylinder head 1a. A branch pipe communicating with a straight port of the two intake ports 26 corresponding to each cylinder 21 is provided with a swirl control valve 37 for adjusting a flow rate in the branch pipe. The swirl control valve 37 includes a stepper motor or the like, an actuator 37a for opening and closing the swirl control valve 37 according to the magnitude of the applied current, and a swirl control valve 3
And an SCV position sensor 37b that outputs an electric signal corresponding to the opening degree of No. 7.

The intake branch pipe 33 is connected to a surge tank 34. The surge tank 34 is connected to an air cleaner box 36 via an intake pipe 35. The intake pipe 35 is provided with a throttle valve 39 for adjusting the flow rate of fresh air flowing in the intake pipe 35.

The throttle valve 39 includes a stepper motor or the like, and an actuator 40 for opening and closing the throttle valve 39 according to the magnitude of the applied current, and outputs an electric signal corresponding to the opening degree of the throttle valve 39. And a throttle position sensor 41 to be mounted.

Further, the throttle valve 39 is provided with an accelerator lever (not shown) which rotates in conjunction with an accelerator pedal 42. The accelerator lever is provided with a rotational position of the accelerator lever (the amount of depression of the accelerator pedal 42). An accelerator position sensor 43 that outputs an electric signal corresponding to ()) is attached.

The intake pipe 3 upstream of the throttle valve 39
Reference numeral 5 denotes an air flow meter 4 which outputs an electric signal corresponding to the mass of fresh air flowing through the intake pipe 35 (mass of intake air).
4 is attached.

On the other hand, each exhaust port 27 of the internal combustion engine 1
Communicates with the branch pipes of the exhaust branch pipe 45 attached to the cylinder head 1a. The exhaust branch pipe 45 is connected to an exhaust pipe 47 via an exhaust purification catalyst 46, and the exhaust pipe 47 is connected downstream to a muffler (not shown).

The exhaust purification catalyst 46 is a P-type catalyst according to the present invention.
This implements M removing means, for example, as shown in FIGS.
As shown in the figure, the first flow path 46a in which the upstream end is opened and the downstream end is closed, and the second flow path in which the upstream end is closed and the downstream end is opened This is a wall-throw type exhaust purification catalyst comprising a porous carrier having the passages 46b arranged in a honeycomb shape and a catalyst layer formed on the surface of the carrier.

Examples of the support include porous ceramics and zeolites, and examples of the catalyst layer include platinum-rhodium (Pt-Rh) on the surface of porous alumina (Al ₂ O ₃ ). ) -Based or palladium-rhodium (Pd-Rh) -based noble metal catalyst, or potassium (K), sodium (Na),
At least one selected from an alkali metal such as lithium (Li) or cesium (Cs), an alkaline earth such as barium (Ba) or calcium (Ca), and a rare earth such as lanthanum (La) or yttrium (Y). And
Those made of a noble metal such as platinum (Pt) can be exemplified.

In the exhaust gas purifying catalyst 46 configured as described above, the exhaust gas flowing into the exhaust gas purifying catalyst 46 is first guided to the first flow path 46a, and then passes through the pores on the wall surface of the carrier to the second flow path 46a. It flows to 46b and is discharged from the second flow path 46b to the exhaust pipe 47 downstream. When the exhaust passes through the wall of the carrier,
The particulate matter such as soot and unburned fuel components contained in the exhaust gas is collected, and the harmful gas components contained in the exhaust gas are purified by the catalyst layer. Therefore, the exhaust purification catalyst 46
It has both the function of a filter for trapping particulate matter in exhaust gas and the function of a catalyst for purifying harmful gas components in exhaust gas.

Returning to FIG. 1, an oxygen sensor (O 2 sensor) 48 for outputting an electric signal corresponding to the concentration of oxygen contained in the exhaust gas flowing through the exhaust branch pipe 45 is attached to the exhaust branch pipe 45. Have been.

In the middle of the exhaust pipe 47, the exhaust pipe 47
An exhaust throttle valve 49 for adjusting the flow rate of exhaust flowing through the inside is provided. The exhaust throttle valve 49 includes a stepper motor or the like, and the exhaust throttle valve 4 according to the magnitude of the applied current.
An actuator 50 that drives the opening and closing of the actuator 9 is mounted.

The internal combustion engine 1 includes a crankshaft 2
3, a crank position sensor 51 including a timing rotor 51a attached to an end of the engine 3 and an electromagnetic pickup 51b attached to a cylinder block 1b near the timing rotor 51a, and a cooling water passage 1c formed inside the internal combustion engine 1. A water temperature sensor 52 attached to the cylinder block 1b to detect the temperature of the cooling water is provided.

An electronic control unit (ECU) 20 for controlling the operating state of the internal combustion engine 1 is also provided in the internal combustion engine 1 thus configured.

Various sensors such as an SCV position sensor 37b, a throttle position sensor 41, an accelerator position sensor 43, an air flow meter 44, an oxygen sensor 48, a crank position sensor 51, and a water temperature sensor 52 are connected to the ECU 20 via electric wiring. The ECU 20 is connected so that the output signal of each sensor is input to the ECU 20.

The ECU 20 includes an igniter 25a,
The fuel injection valve 32, the actuator 37a, the actuator 40, the actuator 50, and the like are connected via electric wiring. The ECU 20 uses the output signal values of the various sensors as parameters as igniters 25a, the fuel injection valve 32, the actuator 37a, Actuator 40,
The actuator 50 can be controlled.

For example, the ECU 20 determines the operating state of the internal combustion engine 1 using output signal values of the crank position sensor 51, the accelerator position sensor 43, the air flow meter 44, and the like as parameters. The internal combustion engine 1
Is determined to be in the low load operation range, the ECU 20 transmits a control signal to the actuator 37a to reduce the opening of the swirl control valve 37 to realize stratified combustion of the internal combustion engine 1. The control signal is transmitted to the actuator 40 to make the throttle valve 39 substantially fully open, and a drive current is applied to the fuel injection valve 32 during the compression stroke of each cylinder 21 to perform the compression stroke injection.

In this case, the combustion chamber 24 of each cylinder 21 has
During the intake stroke, fresh air is mainly introduced from the swirl port 7b, and a strong swirling flow (swirl flow) is generated. In the subsequent compression stroke, the fuel injected from the fuel injection valve 32 swirls inside the combustion chamber 24 according to the swirl flow, and moves to the vicinity of the spark plug 25 at a predetermined timing. At this time, the inside of the combustion chamber 24 is in a so-called stratified state in which the vicinity of the ignition plug 25 becomes a combustible air-fuel mixture layer and the other areas become air layers. Then, the ECU 20 drives the igniter 25a to ignite the spark plug 25 at the above-mentioned predetermined time. As a result,
The mixture in the combustion chamber 24 (including a combustible mixture and an air layer) burns using the combustible mixture in the vicinity of the ignition plug 25 as an ignition source.

The fuel injection amount during the stratified charge combustion operation is determined using the accelerator opening and the engine speed as parameters. That is, the ECU 20 determines the fuel injection amount (fuel injection time) using a stratified combustion fuel injection control map indicating the relationship between the output signal value of the accelerator position sensor 43 (accelerator opening), the engine speed, and the fuel injection amount. decide.

When the ECU 20 determines that the operation state of the internal combustion engine 1 is in the medium load operation region, the ECU 20 transmits a control signal to the actuator 37a to realize the homogeneous lean combustion by the lean air-fuel mixture, thereby controlling the swirl control. The opening degree of the valve 37 is reduced, and a drive current is applied to the fuel injection valve 32 during the intake stroke of each cylinder 21 to perform the intake stroke injection. In this case, a lean mixture in which fresh air and fuel are homogeneously mixed is formed over substantially the entire area of the combustion chamber 24 of each cylinder 21, and homogeneous lean combustion is realized.

When the ECU 20 determines that the operation state of the internal combustion engine 1 is in the high load operation range, the ECU 20 transmits a control signal to the actuator 37a in order to realize homogeneous combustion with the air-fuel mixture near the stoichiometric air-fuel ratio. The swirl control valve 37 is fully opened to transmit a control signal to the actuator 40 so that the throttle valve 39 has an opening corresponding to the depression amount of the accelerator pedal 42 (the output signal value of the accelerator position sensor 43). During the intake stroke 21, a drive current is applied to the fuel injection valve 32 to perform the intake stroke injection. In this case, a mixture with a stoichiometric air-fuel ratio in which fresh air and fuel are homogeneously mixed is formed over substantially the entire area of the combustion chamber 24 of each cylinder 21, and homogeneous combustion is realized.

When the ECU 20 shifts from the stratified combustion control to the homogeneous combustion control, or when shifting from the homogeneous combustion control to the stratified combustion control, the ECU 20 controls the compression stroke of each cylinder 21 in order to prevent the torque fluctuation of the internal combustion engine 1. The driving current is applied to the fuel injection valve 32 in two times, that is, during the intake stroke and during the intake stroke. In this case, in the combustion chamber 24 of each cylinder 21, a combustible mixture layer is formed in the vicinity of the ignition plug 25, and a lean mixture layer is formed in other regions, so-called weak stratified combustion is realized. .

When the ECU 20 determines that the operating state of the internal combustion engine 1 is in the idling operation range, the ECU 20 secures an intake air amount necessary for converging the actual engine speed to the target idle speed. The so-called idle speed control (I) for controlling the opening of the throttle valve 39
SC).

Next, the ECU 20 executes the exhaust gas heating control when the amount of unburned fuel components (unburned HC) to be discharged into the atmosphere is to be reduced. In the exhaust gas temperature raising control, the ECU 20
An exhaust gas temperature rise control routine as shown in FIG. 4 is executed. This exhaust gas temperature raising control routine is executed by the R
This is a routine stored in advance in the OM or the like, and is a routine repeatedly executed at predetermined time intervals (for example, every time the crank position sensor 51 outputs a pulse signal).

In the exhaust gas temperature raising control routine, the ECU 20
First, in S401, it is determined whether or not it is time to reduce the unburned fuel component (unburned HC) discharged from the internal combustion engine 1.

The timing for reducing the unburned HC discharged from the internal combustion engine 1 is, for example, when the internal combustion engine 1 is in a warm-up operation state after a cold start or when the internal combustion engine 1 is in a low load operation state. As in a certain case, the temperature of the combustion chamber 24 of the internal combustion engine 1 is low, and the exhaust purification catalyst 46 is in an inactive state.

This is because when the temperature in the combustion chamber 24 of the internal combustion engine 1 is low, the combustion state of the air-fuel mixture tends to be unstable in the combustion chamber 24 and the air-fuel mixture is hard to completely burn. If the exhaust purification catalyst 46 is in an inactive state at that time, the unburned HC contained in the exhaust gas is not sufficiently purified by the exhaust purification catalyst 46 and is discharged into the atmosphere. It will be released.

If it is determined in S401 that it is not time to reduce the unburned HC discharged from the internal combustion engine 1, the ECU 20 once terminates the execution of this routine. On the other hand, if it is determined in S401 that it is time to reduce the unburned HC discharged from the internal combustion engine 1, the ECU 20 proceeds to S402 and starts execution of the exhaust gas temperature raising process.

In the exhaust gas temperature raising process, the ECU 20 controls the actuator 50 so that the exhaust throttle valve 49 is almost fully closed. In this case, the inside of the exhaust port 27 and the exhaust branch 45
Inside, and in the exhaust pipe 47 upstream of the exhaust throttle valve 49, the exhaust pressure increases. When the exhaust pressure increases in this manner, the pressure of the exhaust gas discharged from the combustion chamber 24 to the exhaust port 27 does not decrease, and the temperature of the exhaust gas is accordingly suppressed from decreasing. Further, when the exhaust throttle valve 49 is almost fully closed, the flow velocity of exhaust gas in the exhaust passage from the exhaust port 27 to the exhaust throttle valve 49 decreases.

As a result, the exhaust gas discharged from the combustion chamber 24 stays at a high temperature in the exhaust passage upstream of the exhaust throttle valve 49 for a long period of time. The fuel HC will be oxidized.

By the way, even when the exhaust throttle valve 49 is almost fully closed, if the temperature of the exhaust gas at the time when the exhaust gas is discharged from the combustion chamber 24 to the exhaust port 27 is excessively low, or if the exhaust gas discharged from the combustion chamber 24 is If the amount of unburned HC contained in is too large, the oxidation reaction of unburned HC may not be performed sufficiently.

Therefore, in the exhaust gas temperature raising process according to the present embodiment, the ECU 20 controls the exhaust throttle valve 49 to a substantially fully closed state, and in addition to the main fuel injection that contributes to the engine output, The fuel injection valve 32 is controlled so as to perform the secondary injection of injecting the fuel at a predetermined time.

In this case, in the combustion chamber 24, unburned HC, which is the unburned main fuel, is burned using the auxiliary fuel as an ignition source. At that time, since the injection of the auxiliary fuel is performed at a high temperature immediately after the main fuel is burned, the auxiliary fuel is almost completely burned, and the amount of unburned HC generated by the injection of the auxiliary fuel is extremely small. Become.

Further, as described above, the auxiliary fuel is supplied to the combustion chamber 24.
When it is burned in the combustion chamber, the combustion heat of the auxiliary fuel and the combustion heat of the unburned HC are generated in addition to the combustion heat of the main fuel, and the temperature of the burned gas in the combustion chamber 24 is further increased. .

As a result, from the combustion chamber 24 to the exhaust port 27
The temperature of the exhaust gas discharged to the exhaust gas becomes sufficiently high, the amount of unburned HC remaining in the exhaust gas is reduced, and the amount of unburned HC remaining in the exhaust gas in the exhaust passage upstream of the exhaust throttle valve 49 is reduced. Almost everything becomes oxidized. Further, in this embodiment, since the exhaust purification catalyst 46 is disposed in the exhaust passage upstream of the exhaust throttle valve 49, when the exhaust temperature is increased as described above, the exhaust purification catalyst 46 is As a result, the activation of the exhaust purification catalyst 46 is promoted.

Regarding the injection timing of the auxiliary fuel, the timing at which the temperature of the exhaust gas discharged from the combustion chamber 24 to the exhaust port 27 is sufficiently high and the amount of unburned HC remaining in the exhaust gas becomes the smallest is experimentally determined in advance. It is preferable to determine

For example, when the internal combustion engine 1 illustrated in the present embodiment is in a warm-up operation state after a cold start, as shown in FIG. When the injection of the auxiliary fuel is performed at about 60 ° after the ignition, the unburned HC amount discharged from the combustion chamber 24 to the exhaust port 27 becomes the smallest, and the combustion chamber 2
Since the temperature of the exhaust gas discharged from the exhaust port 4 to the exhaust port 27 becomes sufficiently high, the ECU 20 executes the auxiliary fuel injection control at around 60 ° after the top dead center in the expansion stroke of each cylinder 21 by the crankshaft 23. Good.

When the exhaust throttle valve 49 is almost fully closed and the exhaust pressure rises, the exhaust pressure acts on the internal combustion engine 1 as a back pressure, so that the output of the internal combustion engine 1 decreases. On the other hand, in the present embodiment, the ECU 20
When the exhaust throttle valve 49 is controlled to be almost fully closed, the main fuel injection amount is increased so that the output of the internal combustion engine 1 matches the output when the exhaust throttle valve 49 is fully open. .

In the example shown in FIG. 5, when the injection of the auxiliary fuel is performed at a time when the amount of unburned HC discharged from the combustion chamber 24 is minimized, a large amount of particulate matter such as soot is generated. However, in the exhaust gas temperature raising device according to the present embodiment, since the wall-through type exhaust purification catalyst 46 is provided in the exhaust passage of the internal combustion engine 1, the particulate matter contained in the exhaust gas is It is removed by the exhaust purification catalyst 46 and is not released into the atmosphere.

Here, returning to the exhaust gas temperature raising control routine of FIG. 4, the ECU 20 executes the processing of S402 as described above, and then proceeds to S403 to determine whether or not the exhaust purification catalyst 46 has been activated.

As a method of determining whether or not the exhaust gas purifying catalyst 46 has been activated, the exhaust gas purifying catalyst 46 may be estimated from the execution time of the exhaust gas temperature raising process. May be determined based on the output signal value.

If it is determined in step S402 that the exhaust purification catalyst 46 has not been activated, the ECU 20 proceeds to step S402.
Returning to S402, the execution of the exhaust gas temperature raising process is continued. On the other hand, if it is determined in S402 that the exhaust purification catalyst 46 has been activated, the ECU 20 proceeds to S404, ends the execution of the exhaust gas temperature raising process, and once ends the execution of this routine.

As described above, the valve control means, the main fuel injection control means, and the sub fuel injection control means according to the present invention are realized by the ECU 20 executing the exhaust gas temperature raising control routine. Therefore, according to the exhaust gas temperature raising apparatus for an internal combustion engine according to the present embodiment, the internal combustion engine 1 is in a warm-up operation state after a cold start, or when the internal combustion engine 1 is in a low load operation state. When the amount of unburned HC discharged from the internal combustion engine 1 needs to be reduced,
In addition, the amount of particulate matter can be reduced, and the exhaust purification catalyst 46 can be activated early.

In the present embodiment, the particulate matter generated in a relatively large amount in the exhaust gas temperature raising control is removed by the exhaust purification catalyst 4.
6, it is necessary to regenerate the exhaust purification catalyst 46 before the particulate matter adsorption capacity of the exhaust purification catalyst 46 is saturated.

Therefore, in this embodiment, the ECU 20
Has been designed to regenerate the adsorption capacity of the exhaust purification catalyst 46 according to an exhaust purification catalyst regeneration control routine as shown in FIG. The exhaust gas purification catalyst regeneration control routine is executed by the ECU 20 using the R
This routine is stored in the OM in advance and is executed by the ECU 20 at predetermined time intervals (for example, the crank position sensor 5).
1 is a routine that is repeatedly executed each time a pulse signal is output.

In the exhaust purification catalyst regeneration control routine, EC
U20 first determines in S601 whether or not it is time to regenerate the adsorption capacity of the exhaust purification catalyst 46. As this determination method, for example, the amount of particulate matter adsorbed on the exhaust purification catalyst 46 is estimated using the operation history of the internal combustion engine 1 as a parameter, and the estimated value and the amount of particulate matter adsorbable by the exhaust purification catalyst 46 are determined. A method of comparing with a maximum value (maximum adsorption amount) and judging that it is time to regenerate the adsorption capacity of the exhaust purification catalyst 46 when the estimated value is equal to or larger than the maximum adsorption amount can be exemplified.

If it is determined in S601 that it is not time to regenerate the adsorption capacity of the exhaust purification catalyst 46,
The ECU 20 once ends the execution of this routine. On the other hand, if it is determined in S601 that it is time to regenerate the adsorption capacity of the exhaust purification catalyst 46, the ECU 20
Proceeds to S602, and executes an exhaust purification catalyst regeneration process.

Here, in order to remove the particulate matter adsorbed on the exhaust purification catalyst 46, the temperature of the atmosphere in the exhaust purification catalyst 46 is raised to about 500 ° C. or more and the atmosphere is made oxygen-excessive. What is necessary is just to oxidize (burn) the state substance.

Accordingly, the ECU 20 increases the temperature of the exhaust gas flowing into the exhaust gas purification catalyst 46 by executing the same process as the exhaust gas temperature raising process in the exhaust gas temperature raising control for a predetermined time in the exhaust gas purification catalyst regeneration process. As a result, the particulate matter adsorbed on the exhaust purification catalyst 46 is oxidized.

When the processing in S602 is completed, E
The CU 20 once ends the execution of this routine. Thus, the temperature of the exhaust gas discharged from the internal combustion engine 1 can be increased by the ECU 20 executing the exhaust gas purification catalyst regeneration control routine. At this time, the exhaust purification catalyst 46
Is disposed in the exhaust passage upstream of the exhaust throttle valve 49, so that the particulate matter adsorbed by the exhaust purification catalyst 46 is exposed to the high-temperature exhaust gas remaining in the exhaust passage upstream of the exhaust throttle valve 49 for a long time. , And will be oxidized efficiently.

When the exhaust purification catalyst is used mainly in a lean atmosphere, such as when the internal combustion engine 1 is a diesel engine or a lean burn type internal combustion engine, the exhaust purification catalyst is poisoned by oxygen. Since the activation capacity tends to decrease, in such a case, when regenerating the exhaust purification catalyst, once the exhaust purification catalyst is once exposed to the stoichiometric air-fuel ratio or exhaust gas in a rich atmosphere to eliminate oxygen poisoning, It is preferable to perform the exhaust gas temperature raising process as described above.

[0074]

In the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, the opening of the exhaust throttle valve is set to a substantially fully closed state at the time when the unburned fuel component discharged from the internal combustion engine is to be reduced. , Because the injection of the secondary fuel is performed after the injection of the main fuel,
From the exhaust passage upstream of the exhaust throttle valve to the inside of the cylinder of the internal combustion engine, the pressure and temperature of the exhaust increase and the flow velocity of the exhaust decreases. As a result, the unburned fuel component remaining as unburned main fuel and the auxiliary fuel burn at high temperature for a long time, and the amount of unburned fuel component remaining in the exhaust gas is reduced.
At that time, since particulate matter such as soot contained in the exhaust gas is removed by the PM removing means provided in the exhaust passage, it is not released into the atmosphere.

Therefore, according to the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, the unburned fuel component is reliably reduced at the time when the unburned fuel component discharged from the internal combustion engine is to be reduced, and the particulate matter is reduced. It is also possible to prevent substances from being released into the atmosphere.

Further, in the exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention, when the PM trap is used as the PM removing means, when the adsorption capacity of the PM trap is regenerated, the opening degree of the exhaust throttle valve becomes almost full. In addition to the closed state, the secondary fuel is injected after the main fuel is injected, so that the temperature of the exhaust gas flowing into the PM trap increases, and as a result, the particulate matter adsorbed in the PM trap is burned and removed. Is done.

At this time, if the PM trap is arranged in the exhaust passage upstream of the exhaust throttle valve, the PM trap is exposed to high-temperature exhaust gas remaining in the exhaust passage upstream of the exhaust throttle valve for a long time. In addition, it is possible to improve the regeneration efficiency of the PM trap.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas heating device for an internal combustion engine according to the present invention is applied;

FIG. 2 is a diagram (1) showing an internal configuration of an exhaust purification catalyst.

FIG. 3 is a diagram (2) showing an internal configuration of an exhaust purification catalyst.

FIG. 4 is a flowchart showing an exhaust gas temperature rise control routine.

FIG. 5 shows timing of auxiliary fuel injection, particulate matter, and unburned HC.
Showing the relationship with the amount of emissions

FIG. 6 is a flowchart showing an exhaust purification catalyst regeneration control routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 21 ... Cylinder 24 ... Combustion chamber 27 ... Exhaust port 29 ... Exhaust valve 32 ... Fuel injection valve 45 ... Exhaust branch pipe 46 ... Exhaust purification Catalyst 47 ・ ・ ・ Exhaust pipe 49 ・ ・ ・ Exhaust throttle valve 50 ・ ・ ・ Actuator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takamitsu Asanuma 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Shunsuke 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F Terms (reference) 3G090 AA01 AA03 BA01 CA01 CB02 CB04 CB25 DA14 DB02 EA01 3G091 AA12 AA18 AA24 AB01 AB13 BA02 BA15 CA18 CB02 CB03 DA02 DC03 EA05 EA07 EA16 EA34 FA04 FA12 FA13 FA14 FB11 GB10 GB07 GB07 GB07 GB07 GBX GB06 GB07 GBX HA37 3G301 HA02 HA04 HA16 HA17 JA21 JA24 JA26 KA05 KA07 KA08 KA09 LA00 LA03 LA05 LB04 LC04 MA11 MA19 MA23 MA26 MA27 NB14 ND02 NE01 NE13 NE14 NE15 PA01Z PA11Z PD00Z PD03A PE03Z PE04Z PE08Z PF03Z

Claims (4)

[Claims] An exhaust throttle valve provided in an exhaust passage of the internal combustion engine for adjusting a flow rate of exhaust flowing through the exhaust passage; a fuel injection valve for injecting fuel directly into a cylinder of the internal combustion engine; Valve control means for controlling the exhaust throttle valve to be almost fully closed when the unburned fuel component discharged from the fuel injection valve is to be reduced; and when the exhaust throttle valve is controlled to be almost fully closed, the fuel injection valve Main fuel injection control means for increasing the amount of main fuel injected from the main fuel injection control means, after the main fuel injection by the main fuel injection control means, sub-fuel injection control means for injecting fuel secondary from the fuel injection valve, An exhaust gas heating device for an internal combustion engine, comprising: a PM removing unit provided in the exhaust passage, for removing particulate matter contained in exhaust flowing through the exhaust passage. 2. The fuel injection control device according to claim 1, wherein the auxiliary fuel injection control means executes the injection of the auxiliary fuel at a time when an amount of the unburned fuel component discharged from the internal combustion engine is minimized.
The exhaust gas temperature raising device for an internal combustion engine according to claim 1. 3. The PM removal means is a PM trap for physically adsorbing particulate matter contained in exhaust gas. When regenerating the PM trap, the valve control means substantially closes the exhaust throttle valve. Fully closed, the main fuel injection control means controls the fuel injection valve to increase the injection amount of the main fuel, and the auxiliary fuel injection control means controls the fuel injection valve to execute the injection of the auxiliary fuel. The exhaust gas temperature raising device for an internal combustion engine according to claim 1, wherein the device is controlled. 4. The exhaust gas temperature raising device for an internal combustion engine according to claim 1, wherein said PM removing means is provided in an exhaust passage upstream of said exhaust throttle valve.