JPH11141329A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly activate catalyst and improve exhaust emission control performance by providing a heat accumulating member for covering the exhaust purifying catalyst and a heat insulating member for covering the heat accumulating member and the exhaust purifying catalyst and by controlling an engine operating state in such a way as raising the catalyst temperature, when the catalyst temperature is lower than the activating temperature of the exhaust purifying catalyst. SOLUTION: An exhaust purifying catalyst device has a triple structure of an inner cylinder 31, an intermediate cylinder 32, and an outer cylinder 33 and exhaust purifying catalyst 34 is loaded in the inner cylinder 31. A heat accumulating material 35 containing lithium chloride as a base material is loaded between the intermediate cylinder 32 and the inner cylinder 31 and a space 36 inside the outer cylinder 33 is set to a vacuum state, and hydrogen storage alloy 37 which stores hydrogen at a temperature lower than a prescribed temperature and emits the hydrogen at the prescribed temperature or more is arranged in a part of the vacuum layer 36. When a CPU judges that the temperature of the catalyst 34 of the catalyst device is lower than the activation temperature from the output signal of a temperature sensor 30 in a catalyst outlet side is starting an engine, the catalyst is made to warm up such as by delay-compensating the ignition time so as to be activated quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for purifying exhaust gas discharged from an internal combustion engine of an automobile or the like, and more particularly, to an exhaust purification device provided with an exhaust purification catalyst covered with a heat storage material.

[0002]

An internal combustion engine such as an automobile, the harmful components in the exhaust gas discharged, for example, carbon monoxide (CO), nitrogen oxides (NO _X), and atmospheric components such as hydrocarbons (HC) In order to purify the exhaust gas before it is released to the exhaust gas, an exhaust purification catalyst carrying a noble metal such as platinum or palladium as a catalyst is provided.

[0003] The exhaust gas purifying catalyst reacts, for example, HC and CO contained in the exhaust gas with oxygen O ₂ in the exhaust gas to oxidize it into H ₂ O and CO ₂ , and at the same time, releases NO in the exhaust gas.
_X reacts with HC and CO in the exhaust gas to produce H ₂ O, CO
_2, is reduced to N _2.

Incidentally, the exhaust purification catalyst is in an inactive state when the temperature is lower than a predetermined temperature, such as when the internal combustion engine is started cold, so that the exhaust gas purifying catalyst cannot completely remove harmful components in the exhaust gas.
There is a problem that the exhaust emission deteriorates.

To solve such a problem, SAE Tech
natural Paper # 961134, # 9504
09, # 941998 and the like are known.

The above-mentioned catalyst device comprises an inner cylinder containing an exhaust purification catalyst, a heat storage member covering the inner cylinder, an outer cylinder covering the inner cylinder and the heat storage member, the inner cylinder, the heat storage member and the outer cylinder. And a hydrogen storage alloy disposed in the vacuum space, wherein during operation of the internal combustion engine, hydrogen is released from the hydrogen storage alloy to place the vacuum space in a non-vacuum state. By transmitting the heat of the exhaust purification catalyst to the outer cylinder via hydrogen, excessive temperature rise of the exhaust purification catalyst is suppressed, and after the operation of the internal combustion engine is stopped, the hydrogen is stored in the hydrogen storage alloy. By setting the vacuum space to a vacuum state, heat radiation from the exhaust gas purification catalyst and the heat storage member is cut off by the vacuum space, and the activated state of the exhaust gas purification catalyst is maintained until the next start of the engine. Exhaust emission deterioration at start It is intended to prevent.

[0007]

By the way, even with the above-described catalyst device, the exhaust purification catalyst may be used when the engine is stopped for a long period of time or when the low load operation is continuously performed. May drop below the activation temperature. When the internal combustion engine is started or the internal combustion engine is operated in such a state, the exhaust purification catalyst receives the heat of the exhaust gas, but the heat is absorbed by the heat storage member, so that the exhaust purification catalyst itself is activated. There is a problem that it takes time to raise the temperature to the activation temperature, and the exhaust emission during that time deteriorates.

The present invention has been made in view of the above-mentioned problems, and in an exhaust gas purifying apparatus having a function of keeping the temperature of an exhaust gas purifying catalyst, when the temperature of the exhaust gas purifying catalyst falls below an activation temperature, the exhaust gas is exhausted. It is an object of the present invention to provide a technique for activating a purification catalyst at an early stage and prevent deterioration of exhaust emission.

[0009]

The present invention employs the following means in order to solve the above-mentioned problems. That is,
The present invention provides an exhaust purification catalyst provided in an exhaust passage of an internal combustion engine, a heat storage member covering the exhaust purification catalyst, and the heat storage member and the exhaust purification catalyst so as to block heat radiation from the heat storage member and the exhaust purification catalyst. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a heat insulating member that covers the catalyst; wherein a catalyst temperature detecting means for detecting a temperature of the exhaust gas purifying catalyst, and a catalyst temperature detected by the catalyst temperature detecting means activates the exhaust gas purifying catalyst. Engine operating state control means for controlling an operating state of the internal combustion engine to raise the temperature of the exhaust purification catalyst when the temperature is lower than the temperature.

[0010] In the exhaust gas purification device thus configured,
If the catalyst temperature detected by the catalyst temperature detection means is lower than the activation temperature of the exhaust purification catalyst, the engine operation state control means controls the operation state of the internal combustion engine to increase the temperature of the exhaust purification catalyst. In this case, the temperature of the exhaust purification catalyst quickly rises to reach the activation temperature.

Further, the exhaust gas purifying apparatus may further include a prohibition means for prohibiting the control by the engine operation state control means when the catalyst temperature detected by the catalyst temperature detection means is equal to or higher than a predetermined temperature. In this case, since the temperature rise of the exhaust purification catalyst is suppressed, the temperature of the exhaust purification catalyst does not excessively rise.

[0012] The present invention may be applied to an exhaust gas purifying apparatus provided with at least one of a heat storage member and a heat insulating member. In short, the present invention is to keep the temperature of the exhaust gas purifying catalyst higher than the activation temperature. The exhaust gas purification device may have any configuration as long as it has a function.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of an internal combustion engine to which an exhaust emission control device according to the present invention is applied and an intake / exhaust system thereof. The internal combustion engine shown in FIG. 1 is a four-cycle multi-cylinder internal combustion engine 1. The internal combustion engine 1 includes a plurality of cylinders 2
Are formed, and a cylinder head 1b fixed to an upper portion of the cylinder block 1a.

Each cylinder 2 of the cylinder block 1a is provided with an axially slidable piston 3 which is connected to a crankshaft 4 which is an engine output shaft. Above the piston 3, a combustion chamber 5 surrounded by the top surface of the piston 3 and the cylinder head 1b is formed.

An ignition plug 6 is attached to the cylinder head 1b so as to face the combustion chamber 5, and the open ends of the intake port 7 and the exhaust port 8 are formed so as to face the combustion chamber 5. Further, the cylinder head 1b includes:
An intake valve 9 and an exhaust valve 10 for opening and closing the open ends of the intake and exhaust ports 7 and 8 are supported to be able to move forward and backward, and an intake camshaft 11 and an exhaust camshaft for driving the intake and exhaust valves 9 and 10 to open and close. 12 are rotatably supported.

The intake camshaft 11 and the exhaust camshaft 12 are connected to the crankshaft 4 via a timing belt (not shown).
The rotational force of the crankshaft 4 is transmitted to the intake camshaft 11 and the exhaust camshaft 12 via the timing belt.

The internal combustion engine 1 has a crank position sensor 13 comprising a timing rotor 13a attached to the end of the crankshaft 4 and an electromagnetic pickup 13b attached to the cylinder block 1a.
Is provided.

Further, the cylinder block 1a includes:
A water temperature sensor 14 that outputs an electric signal corresponding to the temperature of the cooling water flowing in the cooling water flow path 1c formed in the cylinder block 1a is attached.

Next, the intake port 7 communicates with an intake branch pipe 16 attached to the cylinder head 1b, and the intake branch pipe 16 is connected to a surge tank 17. The surge tank 17 is connected to an air cleaner box 19 via an intake pipe 18.

The intake pipe 18 is provided with a throttle valve 20 for opening and closing an intake passage in the intake pipe 18 in conjunction with an accelerator pedal (not shown).
At 0, a throttle position sensor 21 that outputs an electric signal corresponding to the opening of the throttle valve 20 is attached.

The intake pipe 1 upstream of the throttle valve 20
8, an air flow meter 2 for outputting an electric signal corresponding to the mass of fresh air flowing through the intake pipe 18 (mass of intake air);
2 is attached.

Subsequently, a bypass pipe 23 for bypassing the throttle valve 20 is connected to the intake pipe 18.
An idle speed control valve (ISCV) 24 for adjusting the flow rate of fresh air flowing in the bypass pipe 23 is attached to the bypass pipe 23.

Further, a fuel injection valve 25 is attached to the intake branch pipe 16 such that its injection hole faces the intake port 7. The fuel injection valve 25 is connected to a drive circuit 38, opens when a drive current from the drive circuit 38 is applied, and injects fuel toward the intake port 7.

Next, the exhaust port 8 communicates with an exhaust branch pipe 26 attached to the cylinder head 1b, and the exhaust branch pipe 26 is connected to an exhaust pipe 27. Then
The exhaust pipe 27 is connected to a muffler (not shown). A catalyst device 28 is provided in the middle of the exhaust pipe 27, and an electric signal corresponding to the air-fuel ratio of the exhaust gas flowing through the exhaust pipe 27 is output to the exhaust pipe 27 upstream of the catalyst device 28. An air-fuel ratio sensor 29 is attached.

Here, as shown in FIGS. 2 and 3, the catalyst device 28 has a triple structure including an inner cylinder 31, an intermediate cylinder 32, and an outer cylinder 33. Activated above the temperature, carbon monoxide (CO), nitrogen oxides (NO _x ), and hydrocarbons (H) in exhaust gas passing through the inner cylinder 31
An exhaust purification catalyst 34 for purifying C) and the like is loaded.

In a space surrounded by the intermediate cylinder 32 and the inner cylinder 31, a heat storage material 35 based on lithium chloride, sodium chloride or the like is loaded. The heat storage material 35 and the intermediate cylinder 32 realize a heat storage member according to the present invention.

A space 36 surrounded by the outer cylinder 33, the intermediate cylinder 32, and the inner cylinder 31 is formed to be in a vacuum state (hereinafter, the space 36 is referred to as a vacuum layer 36). The vacuum layer 36 and the outer cylinder 33 realize a heat insulating member according to the present invention.

Subsequently, a hydrogen storage alloy 37 that absorbs hydrogen at a temperature lower than a predetermined temperature and releases hydrogen at a temperature equal to or higher than the predetermined temperature is disposed in a part of the vacuum layer 36. The location of the hydrogen storage alloy 37 is set so that the temperature of the hydrogen storage alloy 37 is substantially the same as the temperature of the exhaust purification catalyst 34.
A neighborhood of 4 is preferred.

A temperature sensor 3 for outputting an electric signal corresponding to the temperature of the exhaust gas purifying catalyst 34 is provided in the inner cylinder 31.
0 is attached. This temperature sensor 30 implements the catalyst temperature detecting means according to the present invention.

As a method for detecting the temperature of the exhaust gas purification catalyst 34, a method may be used in which a temperature sensor for detecting the temperature of the heat storage material 35 is provided and the detected value of the temperature sensor is used as a substitute for the catalyst temperature. A method of indirect prediction based on the air amount, the engine speed, the outside temperature, or the like may be used.

In the catalyst device 28 configured as described above,
When the internal combustion engine 1 is operating, the exhaust purification catalyst 34 and the heat storage material 35 receive heat of the exhaust gas and rise in temperature. When the temperature of the exhaust purification catalyst 34 becomes equal to or higher than a predetermined temperature,
Correspondingly, the hydrogen storage alloy 37 also rises in temperature to a predetermined temperature or higher, and releases hydrogen. At this time, hydrogen released from the hydrogen storage alloy 37 floats in the vacuum layer 36,
The vacuum layer 36 is in a non-vacuum state.

As a result, the heat storage material 35 and the exhaust purification catalyst 34
Is transmitted to the outer cylinder 33 via hydrogen, and excessive temperature rise of the exhaust purification catalyst 34 and the heat storage material 35 is suppressed. on the other hand,
For example, after the operation of the internal combustion engine 1 is stopped, the exhaust purification catalyst 3
When the temperature of the heat storage material 4 and the temperature of the heat storage material 35 fall below the predetermined temperature, the temperature of the hydrogen storage alloy 37 also falls below the predetermined temperature, so that hydrogen floating in the vacuum layer 36 is stored in the hydrogen storage alloy 37, The vacuum layer 36 is in a vacuum state.

As a result, the heat storage material 35 and the exhaust purification catalyst 34
Is blocked by the vacuum layer 36,
Since the exhaust purification catalyst 34 receives the heat of the heat storage material 35, the temperature of the exhaust purification catalyst 34 does not easily fall below the activation temperature. Then, the temperature of the exhaust purification catalyst 34 is maintained at or above the activation temperature for a longer period than in the conventional catalyst system.

Returning to FIG. 1, various sensors such as the crank position sensor 13, the water temperature sensor 14, the throttle position sensor 21, the air flow meter 22, the air-fuel ratio sensor 29, and the temperature sensor 30 are electrically operated. Electronic control unit (Electronic Control Unit: ECU) for engine control via wiring
15 and the output signal of each sensor is
To be entered.

Then, the ECU 15 determines the operating state of the internal combustion engine 1 using the output signals from the various sensors as parameters, and according to the operating state, determines whether the ignition plug 6
Various controls of the ISCV 24 or the drive circuit 38 and the like are performed, and a catalyst early activation control which is the gist of the present invention is performed.

Here, as shown in FIG. 4, the ECU 15 is connected to a CP which is interconnected by a bidirectional bus 39.
U40, a ROM 41, a RAM 42, an input port 43, and an output port 44.
A / D converter (A / D) 45 connected to the

The input port 43 receives signals from the throttle position sensor 21 and the crank position sensor 13 and sends these signals to the CPU 40 or R
Transmit to AM42. Further, the input port 43
Signals from the air flow meter 22, the air-fuel ratio sensor 29, the temperature sensor 30, and the water temperature sensor 14 are input via the A / D converter 45, and these signals are transmitted to the CPU 40 or the RAM 42.

The output port 44 outputs a control signal from the CPU 40 to the ignition plug 6, the ISCV 24, or the drive circuit 38. The ROM 41 includes a fuel injection amount control routine for determining a fuel injection amount, a fuel injection timing control routine for determining a fuel injection timing, an ignition timing control routine for determining an ignition timing, and an ISCV 24.
An application program such as an ISCV control routine for determining a target opening of the engine or an early activation routine for controlling an engine operation state to activate the exhaust purification catalyst 34 at an early stage, and various control maps.

The control map includes, for example, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, and a fuel injection timing control showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection timing. There are a map, an ignition timing control map showing the relationship between the operating state of the internal combustion engine 1 and the ignition timing, an ISCV control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the ISCV 24, and the like.

Subsequently, the RAM 42 stores the output signals from the respective sensors, the calculation results of the CPU 40, and the like. The calculation result is, for example, an engine speed calculated from an output signal of the crank position sensor 13. The output signal from each sensor, the calculation result of the CPU 40, and the like are rewritten to the latest data every time the crank position sensor 13 outputs a signal.

Further, the RAM 42 has an early activation flag for discriminating whether it is necessary to activate the exhaust purification catalyst 34 at an early stage or has already been activated. An area for storing various flags such as “completed: 0” is set.

Next, the CPU 40 reads the ROM 41
Operates in accordance with the application program stored in the CPU, determines the operating state of the internal combustion engine 1 from the output signal of each sensor, and determines the fuel injection amount,
The fuel injection timing, ignition timing, ISCV opening, and the like are calculated.
Then, the CPU 40 determines the drive circuit 3 according to the calculated fuel injection amount, fuel injection timing, ignition timing, and ISCV opening.
8. Control the ignition plug 6 and the ISCV 24.

When the internal combustion engine 1 is started, the CPU 40 receives the output signal of the temperature sensor 30 and determines whether or not the exhaust purification catalyst 34 is activated. And
When it is determined that the exhaust purification catalyst 34 is in the inactive state, the CPU 40 controls the operating state of the internal combustion engine 1 to activate the exhaust purification catalyst 34 early.

More specifically, the CPU 40 corrects the ignition timing determined based on the ignition timing control routine so as to be delayed. In this case, since the combustion timing of the air-fuel mixture in each cylinder 2 is delayed, the temperature in the combustion chamber 5 when the exhaust valve 10 is opened increases, and the temperature of the exhaust gas from the combustion chamber 5 also increases. As a result, high-temperature exhaust gas passes through the exhaust purification catalyst 34, and the exhaust purification catalyst 34
Is heated by the high-temperature exhaust gas and quickly rises to the activation temperature.

As described above, the CPU 40 realizes the engine operating state control means according to the present invention by executing the application program in the ROM 41.

The operation and effect of this embodiment will be described below. When an ON signal of an ignition switch (not shown) is input at the time of starting the internal combustion engine 1, the CPU 40 executes an early activation routine as shown in FIG. In this early activation routine, the CPU 40
First, in S501, it is determined whether or not the internal combustion engine 1 is in a starting state. As this determination method, for example, a method of determining whether or not a starter switch (not shown) is on and the engine speed is equal to or lower than a predetermined speed can be exemplified.

If it is determined in step S501 that the internal combustion engine 1 is not in the starting state, the CPU 40 proceeds to step S510.
To "0" in the early activation flag storage area of the RAM 42.
Write.

On the other hand, if it is determined in S501 that the internal combustion engine 1 is in the starting state, the process proceeds to S502, where the output signal of the temperature sensor 30 (the temperature of the exhaust gas purifying catalyst 34) is input. Then, the CPU 40 determines in S503 that
It is determined whether or not the temperature of the exhaust purification catalyst 34 is lower than the activation temperature.

In step S503, the exhaust purification catalyst 3
4 is determined to be equal to or higher than the activation temperature,
The PU 40 proceeds to S509, writes “0” in the early activation flag storage area of the RAM 42, and ends the execution of this routine.

The CPU 40 executes a fuel injection amount control routine, a fuel injection timing control routine,
The drive circuit 38 and the ignition plug 6 are controlled based on the fuel injection amount, fuel injection timing, and ignition timing determined by executing the ignition timing control routine.

As described above, if the exhaust gas purifying catalyst 34 is maintained at the activation temperature or higher by the heat storage material 35 and the vacuum layer 36, the deterioration of the exhaust emission at the time of starting the engine is prevented, and the conventional method is employed. Since there is no need to perform warm-up control such as warm-up, deterioration of the fuel consumption rate due to warm-up or the like is suppressed.

On the other hand, if it is determined in S503 that the temperature of the exhaust purification catalyst 34 is lower than the activation temperature, the CPU 40 proceeds to S504 and writes “1” in the early activation flag storage area of the RAM 42.

Then, S510 or S50 is executed.
The CPU 40 that has completed the processing of step 4 proceeds to S505, reads the engine speed, the output signal (mass of intake air) of the air flow meter 22, or the output signal of the throttle position sensor 21 and the like stored in the RAM 42, and reads the internal combustion engine. It is determined whether the first load is in the low load area.
As this determination method, for example, a method of determining whether the intake air amount is less than the predetermined amount and the engine speed is less than the predetermined speed can be exemplified.

If it is determined in step S505 that the load on the internal combustion engine 1 is in the low load range, the CPU 40 proceeds to step S505.
Proceeding to 506, it is determined whether "1" is stored in the early activation flag storage area of the RAM 42.

If it is determined in step S506 that "1" is stored in the early activation flag storage area of the RAM 42, the CPU 40 proceeds to step S507 and outputs the output signal of the temperature sensor 30 (exhaust gas purification catalyst) stored in the RAM 42. 3
4), and then in S508, it is determined again whether the temperature of the exhaust purification catalyst 34 is higher than the activation temperature. This is because the CPU 40 determines in steps S503 to S5.
This is a process for preventing unnecessary execution of the catalyst warm-up process when the temperature of the exhaust purification catalyst 34 rises to the activation temperature or higher during the execution of the process 07.

In step S508, the exhaust purification catalyst 3
4 is determined to be higher than the activation temperature, the CP
U40 proceeds to S509, writes “0” in the early activation flag storage area of the RAM 42, and ends the execution of this routine.

In this case, the CPU 40 controls the drive circuit 38 and the ignition plug 6 according to the fuel injection amount control routine, the fuel injection timing control routine, and the ignition timing control routine of the ROM 41 without performing the catalyst warm-up processing.

On the other hand, if it is determined in step S508 that the temperature of the exhaust purification catalyst 34 is lower than the activation temperature, the CPU 40 proceeds to step S511, and the CPU 40 proceeds to step S511.
A so-called catalyst warm-up process for controlling the operating state of the internal combustion engine 1 in order to activate the catalyst early is executed.

In the catalyst warm-up process, the CPU 40 corrects the ignition timing determined by executing the ignition timing control routine so as to be delayed for a predetermined period, and controls the ignition plug 6 according to the corrected ignition timing.

When the catalyst warm-up process is executed, the combustion timing of the air-fuel mixture in each cylinder 2 is delayed, so that the exhaust valve 1
The temperature in the combustion chamber 5 at the time of opening the valve becomes higher than when the catalyst warm-up process is not performed. Therefore, the temperature of the exhaust gas discharged from the combustion chamber 5 becomes higher than when the catalyst warm-up process is not performed, and high-temperature exhaust gas flows into the exhaust purification catalyst 34. As a result, the exhaust purification catalyst 34 receives a large amount of heat from the exhaust gas, and reaches the activation temperature early.

If it is determined in step S505 that the load of the internal combustion engine 1 is not in the low load range, the CPU 40
The exhaust gas amount is larger than the low load region and the exhaust gas temperature is higher than the low load region. Therefore, it is considered that the exhaust purification catalyst 34 can be quickly activated without performing the catalyst warm-up process. The execution of the routine ends.

If it is determined in step S506 that "0" is stored in the early activation flag storage area of the RAM 42, the CPU 40 does not perform the catalyst warm-up process.
The execution of this routine ends.

As described above, according to the present embodiment, as in the case where the operation stop state of the internal combustion engine 1 is continued for a long time, the state in which the temperature of the exhaust purification catalyst 34 falls below the activation temperature. When the internal combustion engine 1 is started, the exhaust purification catalyst 3 is controlled to control the operating state of the internal combustion engine 1 so as to increase the temperature of the exhaust gas flowing into the exhaust purification catalyst 34.
4 can be quickly activated to prevent deterioration of exhaust emission.

Incidentally, in addition to the case where the stop state of the internal combustion engine 1 continues for a long time, the case where the idle state continues for a long time after the start of the internal combustion engine 1, Even when the low-load operation is continued for a long time, such as when the vehicle continues to run, the temperature of the exhaust gas purification catalyst 34 may fall below the activation temperature.

Therefore, the CPU 40 may perform the catalyst warm-up process as needed, not only when the internal combustion engine 1 is started. At that time, the CPU 40 repeatedly executes an early activation routine as shown in FIG. 6 every predetermined time.

In the early activation routine, the CPU 40
Is the temperature sensor 3 stored in the RAM 42 in S601.
An output signal value of 0 (temperature of the exhaust purification catalyst 34) is input. Subsequently, in S602, the CPU 40 determines whether or not the catalyst temperature has exceeded a predetermined temperature. The predetermined temperature is an upper limit of the catalyst temperature.

If it is determined in step S602 that the catalyst temperature has exceeded the upper limit, the CPU 40 proceeds to step S612.
Then, if the catalyst warm-up process is being executed at that time, the execution is stopped. As described above, the CPU 40 implements the prohibition unit according to the present invention.

Subsequently, the CPU 40 proceeds to S613,
“1” is written to the inhibition flag storage area set in the RAM 42. The prohibition flag is a flag for identifying whether or not the warm-up process of the exhaust purification catalyst 34 should be prohibited, and is “1” when the temperature of the exhaust purification catalyst 34 exceeds the upper limit.
Is set, and “0” is set when the temperature of the exhaust purification catalyst 34 is equal to or lower than the upper limit value.

If it is determined in S602 that the catalyst temperature is equal to or lower than the upper limit value, the CPU 40 proceeds to S6.
03, "0" is stored in the prohibition flag storage area of the RAM 42.
Then, in S604, it is determined whether or not the catalyst temperature is lower than the activation temperature.

If the CPU 40 determines in step S604 that the catalyst temperature is lower than the activation temperature, the CPU 40 proceeds to step S604.
Proceeding to 605, "1" is written into the early activation flag storage area of the RAM 42. On the other hand, if it is determined that the catalyst temperature is equal to or higher than the activation temperature, the flow proceeds to S614 and the RAM 4
"1" is written to the early activation flag storage area of No. 2.

The CPU 40 that has completed the processing of S605, S613, or S614.
Proceeds to S606, inputs the engine speed, the output signal value of the air flow meter 22 (intake air amount), the output signal value of the throttle position sensor 21 (throttle opening), and the like stored in the RAM 42, and It is determined whether the load is in a low load state.

If it is determined in step S606 that the load on the internal combustion engine 1 is not in the low load region, the CPU 40 determines that the exhaust gas amount is higher than in the low load region and the exhaust gas temperature is higher than in the low load region. Even if the catalyst warm-up process is not performed, it is considered that the exhaust purification catalyst 34 can be activated at an early stage, and the execution of this routine ends.

On the other hand, if it is determined in S606 that the load of the internal combustion engine 1 is in a low load state, the CPU 40
Proceeds to S607, and determines whether or not “0” is stored in the prohibition flag storage area of the RAM.

If it is determined in step S607 that "0" is stored in the inhibition flag storage area of the RAM 42, the CPU 40 proceeds to step S608, and determines whether "1" is stored in the early activation flag storage area of the RAM 42. It is determined whether or not.

If it is determined in step S608 that "1" is stored in the early activation flag storage area of the RAM 42, the CPU 40 proceeds to step S609 and outputs the output signal value of the temperature sensor 30 (exhaust gas purification) stored in the RAM 42. Then, in S611, it is determined whether or not the catalyst temperature is lower than the activation temperature.

If it is determined in S611 that the catalyst temperature is lower than the activation temperature, the CPU 40
Proceeding to 612, the warm-up process of the exhaust purification catalyst 34 is executed. In this case, the CPU 40 corrects the ignition timing determined by the ignition timing control routine so as to be delayed for a predetermined period in order to increase the temperature of the exhaust gas flowing into the exhaust purification catalyst 34, and switches the ignition plug 6 according to the corrected ignition timing. Control.

When the ignition timing is delayed for a predetermined period in this manner, the temperature of the exhaust gas flowing into the exhaust purification catalyst 34 increases, so that the exhaust purification catalyst 34 receives a large amount of heat from the exhaust gas and quickly activates the activation temperature. Heat up to As a result, deterioration of exhaust emission is suppressed.

If it is determined in step S608 that "0" is stored in the early activation flag storage area of the RAM 42, the CPU 40 terminates the execution of this routine without executing the catalyst warm-up process.

When it is determined in step S607 that "1" is stored in the prohibition flag storage area of the RAM 42, or in step S611, the exhaust purification catalyst 3
4 is determined to be equal to or higher than the activation temperature,
The PU 40 proceeds to S615, writes “0” in the early activation flag storage area of the RAM 42, and ends the execution of this routine without executing the catalyst warm-up process.

According to the above-described early activation routine, even when the temperature of the exhaust purification catalyst 34 falls below the activation temperature after the start of the internal combustion engine 1, the temperature of the exhaust gas flowing into the exhaust purification catalyst 34 is increased. Since the catalyst warm-up process is performed, the exhaust purification catalyst 34 can be quickly activated, and deterioration of exhaust emission can be suppressed.

In the embodiment described above, the exhaust gas purification is performed.
As a method for early activation of the catalyst 34, the ignition timing is delayed.
Although the method of raising the exhaust gas temperature by
The air-fuel ratio when flowing into the device 28 becomes the stoichiometric air-fuel ratio, and
Unburned HC, unburned CO, and O _TwoExhaust gas containing a large amount of
A mixture that is burned in at least some of the cylinders to produce
Air-fuel ratio becomes an excess fuel atmosphere (rich atmosphere), and
The air-fuel ratio of the air-fuel mixture burned in some other cylinders
Controls the amount of combustion injection to create a surplus atmosphere (lean atmosphere)
You may make it.

In this case, since the exhaust gas flowing into the exhaust purification catalyst 34 contains a large amount of unburned HC, unburned CO, and O ₂ , the unburned HC and unburned CO
Reaction and with O _2, the reaction between HC and CO and NO _X is promoted, heating rate of the exhaust gas purifying catalyst 34 is increased by these reaction heat.

As another method for activating the exhaust purification catalyst 34 at an early stage, the air-fuel ratio when flowing into the catalyst device 28 becomes the stoichiometric air-fuel ratio, and the unburned HC, unburned CO, and O ₂ are removed. In order to generate a large amount of exhaust gas, the amount of combustion injected is controlled so that the air-fuel ratio of the air-fuel mixture burned in at least some of the cylinders becomes a fuel-rich atmosphere (rich atmosphere). Control may be performed such that secondary air is mixed therein.

Also in this case, since the exhaust gas flowing into the exhaust purification catalyst 34 contains a large amount of unburned HC, unburned CO, and O ₂ , the unburned HC and unburned C
The reaction between O and O ₂ and the reaction between HC and CO and NO _X are promoted, and the heat of these reactions improves the rate of temperature rise of the exhaust purification catalyst 34.

Further, as another method for activating the exhaust purification catalyst 34 early, a variable valve timing mechanism for changing the opening / closing timing of the exhaust valve 10 is attached to the internal combustion engine 1 so that the temperature of the exhaust purification catalyst 34 is activated. When the temperature is lower than the temperature, the variable valve timing mechanism may be controlled so that the valve opening timing of the exhaust valve 10 is advanced by a predetermined period.

In this case, in each cylinder 2, the exhaust valve 10 is opened immediately after the combustion of the air-fuel mixture.
The temperature of the exhaust gas discharged from the exhaust gas becomes high, and high-temperature exhaust gas flows into the exhaust purification catalyst 34. As a result, the exhaust purification catalyst 34 receives a large amount of heat from the exhaust gas, and reaches the activation temperature early.

As another method for activating the exhaust purification catalyst 34 at an early stage, the above-described methods may be combined. For example, at the beginning of the catalyst warm-up process,
By performing the ignition timing retarding process and the exhaust valve opening timing advance process, the temperature of the exhaust gas flowing into the exhaust purification catalyst 34 is increased, and after a predetermined time has elapsed from the start of the catalyst warm-up process, the above-described process is performed. In addition to the processing, the fuel injection amount (and the amount of secondary air) may be controlled to generate exhaust gas containing a large amount of unburned HC, unburned CO, and O ₂ .

That is, when the entire exhaust purification catalyst 34 is in an inactive state, the temperature of the exhaust gas flowing into the exhaust purification catalyst 34 is increased to increase the temperature of the exhaust purification catalyst 34, thereby increasing the temperature of the exhaust purification catalyst 34. After the section is activated, the exhaust gas purification catalyst 34 may be activated early by using both the increase in the exhaust gas temperature and the promotion of the reaction in the exhaust gas purification catalyst 34.

At this time, the predetermined time may be a fixed value set in advance or a variable value determined according to the catalyst temperature at the start of the catalyst warm-up process. Further, instead of the predetermined time, an integrated intake air amount from the start of the catalyst warm-up process may be used.

[0090]

According to the present invention, there is provided an exhaust gas purifying catalyst provided in an exhaust passage of an internal combustion engine, a heat storage member covering the exhaust gas purifying catalyst, and an exhaust gas including a heat insulating member covering the exhaust gas purifying catalyst and the heat storage member. In the purification device, when the temperature of the exhaust purification catalyst is lower than the activation temperature, the internal combustion engine is controlled so as to increase the temperature of the exhaust purification catalyst. , And deterioration of exhaust emission is suppressed.

[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 according to the present invention is applied and an intake / exhaust system thereof.

FIG. 2 is a longitudinal sectional view showing a configuration of a catalyst device.

FIG. 3 is a cross-sectional view of the catalyst device shown in FIG.

FIG. 4 is a diagram showing an internal configuration of an ECU.

FIG. 5 is a flowchart showing an early activation routine.

FIG. 6 is a flowchart illustrating an early activation routine according to another embodiment.

[Description of Signs] 1 ... Internal combustion engine 6 ... Spark plug 8 ... Exhaust port 10 ... Exhaust valve 15 ... ECU 25 ... Fuel injection valve 26 ... Exhaust branch pipe 27 ... Exhaust pipe 28・ ・ Catalyst device 30 ・ ・ Temperature sensor 31 ・ ・ Inner cylinder 32 ・ ・ Intermediate cylinder 33 ・ ・ Outer cylinder 34 ・ ・ Exhaust purification catalyst 35 ・ ・ Heat storage material 36 ・ ・ Vacuum layer 38 ・ ・ Drive circuit 40 ・ ・ CPU 41 ..ROM 42..RAM

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 ZAB F02D 45/00 ZAB 360 360C (72) Inventor Koichi Hoshi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Koichi Takeuchi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (2)

[Claims] 1. An exhaust purification catalyst provided in an exhaust passage of an internal combustion engine, a heat storage member covering the exhaust purification catalyst, and the heat storage member and the exhaust purification catalyst for cutting off heat radiation from the heat storage member and the exhaust purification catalyst. An exhaust purification device for an internal combustion engine, comprising: a heat insulating member covering the exhaust gas purification catalyst; and a catalyst temperature detection unit that detects a temperature of the exhaust purification catalyst; and a temperature detected by the catalyst temperature detection unit activates the exhaust purification catalyst. An engine operating state control means for controlling an operating state of the internal combustion engine so as to raise the temperature of the exhaust purification catalyst when the temperature is lower than the temperature; 2. The internal combustion engine according to claim 1, further comprising prohibiting means for prohibiting control by said engine operating state control means when the temperature detected by said catalyst temperature detecting means is equal to or higher than a predetermined temperature. Engine exhaust purification device.