JPH06185350A - Warm-up control method in exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve a purification ratio of exhaust gas and suppress unnecessary deterioration of fuel consumption performance by properly performing controlling against various factors for lowering a catalyst temperature without excessively increasing the catalyst temperature. CONSTITUTION:A catalytic converter 18 is arranged on the way of an exhaust passage 12. An injector 17 and an igniter 21 are electrically connected to an ECU 51, while the respective driving timings are controlled by the operation of the ECU 51. The ECU 51, does not immediately perform delay-angle control of an ignition timing even under a low-load constant running. It performs delay- angle control when a catalyst temperature estimation counting value is lowered to be a specified value, for increasing the temperature of the catalytic converter 18. The delay-angle control is delayed, so that the catalyst temperature is prevented from exceeding an allowable limit value and further excessively increasing during the delay time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 which raises the temperature of a catalyst for purifying exhaust gas from the internal combustion engine. The present invention relates to a warm-up control method.

[0002]

2. Description of the Related Art Conventionally, when a vehicle equipped with a catalyst for purifying exhaust gas continues to run in a steady state under a light load, it is known that exhaust gas energy is insufficient and the temperature of the catalyst decreases. ing. Then, when the catalyst temperature is lowered, the catalyst is less likely to be activated, which causes a problem that the purification rate of the exhaust gas is lowered.

Therefore, as a measure for solving the above problems, for example, a technique proposed in Japanese Patent Laid-Open No. 61-72876 is known. In this technique, the ignition timing is retarded when the light load steady running state of the vehicle continues. The retard angle increases the amount of unburned components in the exhaust gas, and the unburned components are reburned in the catalytic converter containing the catalyst. Therefore, the catalyst temperature rises and the reduction of the exhaust gas purification rate is prevented.

[0004]

However, until just before shifting to light-load steady running, high-load running may continue for a long time, and the temperature of the catalyst may be sufficiently high. On the other hand, in the above conventional technique, the ignition timing is simply uniformly retarded at the stage when the operating state shifts to light load steady running. Therefore, even if the temperature of the catalyst is sufficiently high, if the retard control is uniformly performed, the temperature of the catalyst may be excessively increased. In addition, such a retard control may unnecessarily deteriorate fuel efficiency.

Further, in the above-mentioned prior art, since the ignition timing is controlled to be retarded only in the light load steady running state, it is possible to prevent other factors such as a fuel cut and the like from causing a decrease in the catalyst temperature. Had not considered any measures. That is, although the catalyst temperature decreases even when the fuel cut is performed, it is impossible to execute the retard control because the fuel injection is not performed during the fuel cut. As a result, there is still a problem that the purification rate of exhaust gas is lowered.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a warm-up control method for an exhaust gas purification apparatus for increasing the temperature of a catalyst for purifying exhaust gas from an internal combustion engine, For various factors that lower the catalyst temperature, control the catalyst temperature to an appropriate value without excessively raising it to improve the purification rate of exhaust gas and suppress unnecessary deterioration of fuel efficiency. Another object of the present invention is to provide a warm-up control method in an exhaust gas purification apparatus for an internal combustion engine that can achieve the above.

[0007]

In order to achieve the above object, in the present invention, the operating state of an internal combustion engine is detected, and the present operating state purifies exhaust gas from the internal combustion engine based on the detection result. A method for warming-up control in an exhaust gas purification apparatus for an internal combustion engine, comprising: determining whether or not an operating state in which the temperature of the catalyst is lowered to raise the temperature of the catalyst is determined based on the result of the determination. When it is judged that the operating state where the catalyst temperature has dropped is started based on the detection result of the engine operating state, the history of the operating state up to immediately before the catalyst temperature drop has been recognized based on the determination result. In addition, the gist is a warm-up control method in an exhaust gas purification apparatus for an internal combustion engine, which is characterized by delaying an increase in the temperature of the catalyst according to the recognition of the history.

[0008]

According to the above construction, whether or not the present operating state is the operating state in which the temperature of the catalyst for purifying exhaust gas from the internal combustion engine is lowered based on the detection result of the operating state of the internal combustion engine. Is determined. Then, when it is determined that the operating state that causes the temperature decrease of the catalyst has started, the history of the operating state up to immediately before that is recognized based on the determination result, and the temperature of the catalyst is changed according to the recognition of the history. Rise is delayed.

Therefore, even when the operating state in which the temperature of the catalyst is lowered is started, the history of the operating state up to immediately before that is recognized. Then, based on the recognition of the history, if the temperature of the catalyst is still sufficiently high, the rise of the temperature of the catalyst is delayed. Therefore, since the temperature of the catalyst does not rise during the delay, the temperature does not become abnormally high.

Further, since the catalyst temperature is not controlled on the basis of the factor that causes the temperature decrease of the catalyst but is controlled after the start of the operating state in which the temperature decrease of the catalyst is caused, the temperature decrease of the catalyst is suppressed. There is no particular limitation on the factors that come and the temperature of the catalyst can be raised after the start of the operating state and after the delay time has elapsed.

[0011]

【Example】

(First Embodiment) A first embodiment embodying a warm-up control method in an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a schematic configuration diagram showing an engine control device in this embodiment. An engine 1 as an internal combustion engine mounted on an automobile has a plurality of cylinders, and a cylinder block 2 constituting the engine 1 has cylinder bores 3 for the number of cylinders. A cylinder head 4 is attached to the upper side of the cylinder block 2 so as to close each cylinder bore 3. A piston 5 is provided in each cylinder bore 3 so as to be vertically movable, and the piston 5 is connected to a crankshaft (not shown) via a connecting rod 6. Inside the cylinder bore 3, a space surrounded by the piston 5 and the cylinder head 4 is a combustion chamber 7. Further, the lubricating oil in an oil pan (not shown) is supplied to each part such as the cylinder bore 3 and the connecting rod 6 when the engine 1 is operating.

The cylinder head 4 is provided with spark plugs 8 corresponding to the respective combustion chambers 7. Also,
The cylinder head 4 is provided with an intake port 9 and an exhaust port 10 that communicate with each combustion chamber 7, and an intake passage 11 and an exhaust passage 12 are connected to each of these ports 9 and 10, respectively. In addition, intake port 9
Further, an intake valve 13 and an exhaust valve 14 for opening and closing are provided at the respective open ends of the exhaust port 10 that communicate with the combustion chamber 7. The intake valve 13 and the exhaust valve 14 are adapted to be opened and closed in conjunction with the rotation of the crankshaft by a valve operating device including a camshaft (not shown). The opening / closing timing of each of the valves 13 and 14 is opened / closed in synchronization with the rotation of the crankshaft. That is, each of the valves 13 and 14 is adapted to be opened and closed at a predetermined timing in synchronization with a series of strokes of an intake stroke, a compression stroke, an explosion / expansion stroke and an exhaust stroke.

An air cleaner 1 is provided on the inlet side of the intake passage 11.
5 are provided. In addition, in the middle of the intake passage 11,
A surge tank 16 is provided to smooth the pulsation of air passing through the passage 11. Further, on the downstream side of the surge tank 16, injectors 17 for fuel injection are provided near the intake port 9 for each cylinder. Fuel of a predetermined pressure is supplied to these injectors 17 from a fuel tank (not shown) by a fuel pump. On the other hand, on the outlet side of the exhaust passage 12, a catalytic converter 18 including a three-way catalyst for purifying exhaust gas is provided.

The engine 1 has an air cleaner 15
The outside air taken in from is introduced through the intake passage 11 including the surge tank 16. Further, the fuel is injected from each injector 17 at the same time as the introduction of the outside air, so that the mixture of the outside air and the fuel is taken into the combustion chamber 7 in synchronization with the opening of the intake valve 13 in the intake stroke. Further, the air-fuel mixture taken into the combustion chamber 7 is ignited by the spark plug 8, so that the air-fuel mixture explodes and burns to provide the engine 1 with a driving force. Then, the exhaust gas after the explosion / combustion is guided to the exhaust passage 12 in synchronization with the opening of the exhaust valve 14 in the exhaust stroke, and is discharged from the exhaust passage 12 to the outside through the catalytic converter 18 and the like.

On the upstream side of the surge tank 16, there is provided a throttle valve 19 which opens and closes in conjunction with the operation of an accelerator pedal (not shown). Then, by opening and closing the throttle valve 19, the intake amount of outside air into the intake passage 11, that is, the intake air amount Q is adjusted. A throttle sensor 31 for detecting the opening of the valve 19, that is, the throttle opening TA is provided near the throttle valve 19. This throttle sensor 31 outputs a signal of the throttle opening TA and
Only when the throttle valve 19 is in the fully closed position, the idle signal is output by the so-called idle contact which is turned on. An air flow meter 32 that detects the intake air amount Q into the intake passage 11 is provided downstream of the air cleaner 15. In addition, the temperature of the air taken into the intake passage 11, that is, the intake air temperature TH, is provided between the air cleaner 15 and the air flow meter 32.
An intake air temperature sensor 33 that detects A is provided.

Further, in the middle of the exhaust passage 12, an oxygen sensor 34 for detecting the oxygen concentration OX in the exhaust, that is, for detecting the exhaust air-fuel ratio in the exhaust passage 12 is provided. Further, the cylinder block 2 is provided with a water temperature sensor 35 that detects the temperature of the cooling water of the engine 1, that is, the cooling water temperature THW.

The ignition signal distributed by the distributor 20 is applied to the ignition plug 8 for each cylinder. The distributor 20 is for distributing the high voltage output from the igniter 21 to each spark plug 8 in synchronization with the rotation of the crankshaft, that is, the crank angle. The ignition timing of each spark plug 8 is determined by the high voltage output timing from the igniter 21.

The distributor 20 incorporates a rotor (not shown) that rotates in association with the rotation of the crankshaft. Then, the distributor 20
A rotation speed sensor 36 for detecting the rotation speed of the engine 1, that is, the engine rotation speed NE from the rotation of the rotor is provided. Similarly, the distributor 20 is provided with a cylinder discrimination sensor 37 that detects a crank angle reference signal of the engine 1 at a predetermined rate according to the rotation of the rotor. In this embodiment, the crankshaft rotates twice for a series of strokes in the engine 1, and the rotation speed sensor 36 detects the crank angle at a rate of 30 ° CA per pulse. The cylinder discrimination sensor 37 detects the crank angle at a rate of 360 ° CA per pulse.

In addition, in the intake passage 11 of this embodiment,
A bypass passage 22 that bypasses the throttle valve 19 and connects the upstream side and the downstream side of the valve 19 to each other is provided. A well-known linear solenoid type idle speed control valve (ISCV) 23 is provided in the middle of the bypass passage 22. And IS
The bypass passage 22 is opened and closed by driving and controlling the CV 23 based on a predetermined control signal. The ISCV 23 is operated to stabilize the idling of the engine 1 when the throttle valve 19 is fully closed. Therefore, when the engine 1 is idling, the opening of the ISCV 23 and its valve opening time are controlled, that is, I
By performing the SC control, the amount of air flowing through the bypass passage 22 is adjusted, and the amount Q of intake air into the combustion chamber 7 is adjusted. Further, the torque of the engine 1 is also adjusted by the above adjustment.

Each injector 17, igniter 21, and ISCV 23 are electronic control units (hereinafter simply referred to as "EC
U ”) 51, and their drive timing is controlled by the operation of the ECU 51. The ECU 51 includes the above-described throttle sensor 31, air flow meter 32, intake air temperature sensor 33, and oxygen sensor 3.
4, a water temperature sensor 35, a rotation speed sensor 36, and a cylinder discrimination sensor 37 are connected to each other. And the ECU 5
Reference numeral 1 denotes ignition timing control of the engine 1, fuel injection amount control and I
In order to control the SC control and the like, the injectors 17, the igniter 21, and the ISCV 23 are preferably driven and controlled based on the output signals from the sensors 31, 33 to 37 and the air flow meter 32.

Here, the electrical configuration of the ECU 51 will be described with reference to the block diagram of FIG. The ECU 51 includes a central processing unit (CPU) 52, a read-only memory (ROM) 53 that stores a predetermined control program and the like in advance, and a random access memory (R) that temporarily stores calculation results of the CPU 52 and the like.
AM) 54, a backup RAM 55 for storing the stored data, a timer counter 56, and the like. The ECU 51 is configured as a theoretical operation circuit in which these units are connected to the external input circuit 57, the external output circuit 58, etc. by a bus 59. In this embodiment, the ROM 53 has a "retard angle amount calculation routine" described later.
Control programs such as the above and various maps are stored in advance. Further, in this embodiment, the timer counter 56
Outputs an interrupt signal every predetermined time and simultaneously performs a plurality of counting operations.

The external input circuit 57 includes the above-mentioned throttle sensor 31, air flow meter 32, and intake air temperature sensor 3.
3, oxygen sensor 34, water temperature sensor 35, rotation speed sensor 3
6, the cylinder discrimination sensor 37, etc. are connected to each other. Further, the external output circuit 58 includes the injectors 1
7, the igniter 21 and the ISCV 23 are connected to each other.

Then, the CPU 52 reads the respective signals from the sensors 31, 33 to 37 and the air flow meter 32, which are input via the external input circuit 57, as input values. Further, the CPU 51 suitably drives and controls each injector 17, the igniter 21, and the ISCV 23 based on the read input values.

Next, the processing operation for controlling the ignition timing in the engine control device configured as described above will be described with reference to FIGS. The flowcharts shown in FIGS. 3 and 4 show the ignition timing by controlling the drive timing of the igniter 21 when performing warm-up control of the catalytic converter 18 by performing light load steady running among the processes executed by the ECU 51. This shows a "retardation amount calculation routine" for delaying the operation, which is executed by a regular interrupt every predetermined time. Since the amount of exhaust gas discharged from the engine 1 is drastically reduced by the light-load steady running, the catalyst temperature THC of the catalytic converter 18 generally decreases.

When the processing shifts to this routine, first, at step 101, the engine speed N is detected based on the detection signals from the speed sensor 36 and the air flow meter 32.
E, the intake air amount QN per one rotation (a value obtained by dividing the intake air amount Q per minute by the engine speed NE), etc. are read.

Next, at step 102, the light load steady running flag FKEI is read. The light load steady running flag FKEI is set by a separate routine, and is set to "1" when the light load steady running is performed, and otherwise, that is, the medium / high load running is performed. When it is performed, it is set to "0".

In the following step 103, it is determined whether or not the light load steady running flag FKEI read in this routine is "1". When the light load steady running flag FKEI is not "1", it is determined that light load steady running is not currently performed. That is,
It is determined that the current operating state is not at least the operating state in which the catalyst temperature THC is reduced by the light load steady running, and the routine proceeds to step 104.

In step 104, a count-up value CUP for counting up the catalyst temperature estimated count value CSKEI is calculated. Here, the catalyst temperature estimation count value CSKEI is a parameter for estimating the catalyst temperature THC. Also, this count value CSK
When the EI becomes "A" or less, it is presumed that the temperature of the catalyst has dropped to the temperature (warning temperature) that requires warming up. Furthermore, this count value CSK
When the EI becomes "A-10" or less, the temperature of the catalyst rises to some extent, and it is presumed that there is no need to raise the temperature of the catalyst for a while (these will be described later). ). The count-up value CUP in this processing is calculated based on the engine speed NE, the intake air amount QN per rotation, and the like described above with reference to a map (not shown).

In step 105, the catalyst temperature estimation count upper limit value CMAX which is the upper limit of the catalyst temperature estimation count value CSKEI is calculated. Similar to the count-up value CUP, the catalyst temperature estimation count upper limit value CMAX in this process is calculated based on the engine speed NE, the intake air amount QN per rotation, and the like with reference to a map (not shown). However, the above count-up value CUP
Also, the catalyst temperature estimation count upper limit value CMAX is set to a larger value as the engine 1 has a higher rotation speed and a higher load.

Next, at step 106, the present estimated catalyst temperature count value CSKEI is the upper limit value CMA.
It is determined whether or not it is larger than X. Then, when the estimated catalyst temperature count value CSKEI is not larger than the upper limit value CMAX, in step 107, the counted up value CUP calculated in this routine is added to the estimated catalyst temperature count value CSKEI. Then, that value is newly set as the catalyst temperature estimated count value CSKEI.

Next, at step 108, the ignition timing retard amount ARTD is set to "0", and the subsequent processing is once terminated. On the other hand, when the catalyst temperature estimated count value CSKEI is larger than the upper limit value CMAX in step 106, the process proceeds to step 109. Then, in step 109, a countdown value CDOWN for counting down the catalyst temperature estimated count value CSKEI is calculated. The countdown value CDOWN in this process is also the above-mentioned countup value CU.
Similar to P, it is calculated by referring to a map (not shown) based on the engine speed NE, the intake air amount QN per rotation, and the like.

Then, in the following step 110, the countdown value CDOWN calculated in this routine is subtracted from the catalyst temperature estimated count value CSKEI, and the value is newly set as the catalyst temperature estimated count value CSKEI. That is, when the light load steady running is not performed, the catalyst temperature estimated count value CSKEI is converged to the upper limit value CMAX (however, the upper limit value CMAX is obtained by the processing of step 107 or step 110).
Fluctuates). Then, the routine proceeds to step 108, where the ignition timing retard amount ARTD is set to "0", and the subsequent processing is once terminated.

The operating conditions in the above series of processing are as follows:
This corresponds to the state up to immediately before time t1 in the timing chart of FIG. That is, light load steady running is not performed until immediately before time t1, so the light load steady running flag FKEI is set to "0". Then, if the catalyst temperature estimated count value CSKEI is larger than the upper limit value CMAX, the count-up value CUP is added to the catalyst temperature estimated count value CSKEI. Although not shown, the catalyst temperature estimated count value CSKEI is the upper limit value CMA.
If it is not larger than X, the catalyst temperature estimated count value C
The countdown value CDOWN is subtracted from SKEI. Further, since the retard amount ARTD is "0", the retard control is not executed.

When the light load steady running flag FKEI is "1" in step 103, it is determined that the light load steady running is currently being performed. That is, it is determined that the current operating state is at least the operating state in which the catalyst temperature THC is lowered by the light load steady running, and the routine proceeds to step 111. In step 111, a countdown value CDOWN for counting down the catalyst temperature estimated count value CSKEI is calculated. Countdown value CDOWN in this process
Also, engine speed NE, intake air amount Q per rotation
It is calculated by referring to a map (not shown) based on N and the like.
However, in this embodiment, the above map is different from the map for calculating the countdown value CDOWN when the light load steady running is not performed.

Next, at step 112, the countdown value CDOWN calculated in this routine is subtracted from the current catalyst temperature estimated count value CSKEI, and the value is newly set as the catalyst temperature estimated count value CSKEI.

In the following step 113, the catalyst temperature estimation count value CSKEI is set to a predetermined value "A".
Is greater than or equal to. When the catalyst temperature estimated count value CSKEI is larger than “A”,
Although the vehicle is currently traveling at a light load, it is assumed that the temperature of the catalyst has not dropped to the caution temperature and is still sufficiently high from the history of the operating conditions up to that point, and the subsequent processing is temporarily terminated.

The operation state and the like in these series of processes are shown in the timing chart of FIG. 5 from time t1 to time t2.
It corresponds to the state up to immediately before. That is, from the time t1 to immediately before the time t2, since the light load steady running is being performed, the light load steady running flag FKEI is set to "1". Then, the catalyst temperature THC is lowered by continuing the light load steady running, and the catalyst temperature estimated count value CSKEI is further counted down. However, at this time, the estimated catalyst temperature count value CSKEI is still larger than “A”. Therefore, although the catalyst temperature THC is currently decreasing, the retard angle amount ARTD is set to "0" and the retard angle control is not executed because it has not yet decreased to the lower limit allowable value.

Further, in step 113, when the estimated catalyst temperature value CSKEI is not larger than "A", as a result of continued light load steady running, the catalyst temperature T
Since HC has decreased and it is necessary to raise the catalyst temperature THC, the routine proceeds to step 114.

In step 114, it is judged whether or not the catalyst temperature estimated count value CSKEI is larger than a predetermined value "A-10" which is "10" smaller than the predetermined value "A". Then, the catalyst temperature estimated count value CS
When KEI is larger than "A-10", that is, the catalyst temperature estimated count value CSKEI is "A-10" to "A".
If it is within the range of, the maximum retard amount ARTDMAX is executed in step 115 to execute the retard control thereafter.
To calculate. Maximum retard amount ARTDMA in this process
X is also calculated by referring to a map (not shown) based on the engine speed NE, the intake air amount QN per rotation, and the like.

Next, at step 116, the retard amount ARTD is the maximum retard amount AR calculated in this routine.
It is determined whether TDMAX or more. And the retard amount AR
If TD is not greater than the maximum retard amount ARTDMAX,
Control goes to step 117.

At step 117, a predetermined value α which is set in advance is added to the current retard amount ARTD, and the value is newly set as the retard amount ARTD. The retard amount ARTD set in this routine is used as a control amount used for retard control in a separate routine.

After that, the routine proceeds to step 118, where ISCV2 is determined based on the retard amount ARTD, engine speed NE, etc.
The opening degree increase amount ISCUP of 3 is calculated. Then, the opening increase amount ISCUP calculated in this routine is used as a control amount used for ISC control in a separate routine. Then, the subsequent processing is temporarily terminated.

The operation state and the like in these series of processes are shown in the timing chart of FIG. 5 from time t2 to time t3.
It corresponds to the state up to immediately before. That is, from the time t2 to immediately before the time t3, since the light load steady running is performed, the light load steady running flag FKEI is set to "1". At this time, the catalyst temperature estimated count value CSKEI is already smaller than “A”. Since the catalyst temperature estimated count value CSKEI is smaller than "A" and larger than "A-10", the catalyst temperature THC has fallen to a temperature that needs to be raised at this time. It is recognized that the temperature is decreasing further. Therefore, the retard amount ARTD
Is controlled to be increased, and the retard control is executed based on the value. In other words, while the light load steady running is already performed at the time t1, the retard control is delayed until the time t2 in this embodiment. The execution of the retard control increases the amount of unburned components in the exhaust gas and reburns the unburned components in the catalytic converter 18. Therefore, the catalyst temperature THC of the catalytic converter 18 is suppressed from falling below the allowable lower limit value, and the catalyst temperature THC gradually rises as the retard angle control is further executed. On the other hand, since the retard control is delayed, the catalyst temperature THC surely decreases to the temperature that needs to be raised when the delay control is performed. For this reason, the catalyst temperature THC does not suddenly exceed the allowable upper limit value when the execution of the retard control is started.

Further, in the conventional case, as shown by the dashed line in FIG. 2, the engine torque drastically decreases with the start of execution of the retard control, but in this embodiment, the retard amount ARTD. , ISCV2 based on engine speed NE, etc.
The opening degree increase amount ISCUP of 3 is calculated. Therefore, as indicated by the solid line in the figure, the decrease in the engine torque is suppressed by the opening control of the ISCV 23.

On the other hand, in step 116, the retard amount A
When the RTD is equal to or larger than the maximum retard amount ARTDMAX, the above-described processing of step 118 is executed, and the subsequent processing is temporarily ended. That is, the retard amount ARTD is held at the maximum retard amount ARTDMAX or a value close thereto.

The operating state and the like in this series of processing correspond to the state and the like from time t3 to immediately before time t4 in the timing chart of FIG. That is, from the time t3 to immediately before the time t4, since the light load steady running is performed, the light load steady running flag FKEI is set to "1". At this time, the catalyst temperature estimated count value CSKEI is smaller than “A”, as described above,
The retard control is executed while the retard amount ARTD is held at the maximum retard amount ARTDMAX or a value close thereto. The execution of this retard control further raises the catalyst temperature THC.

Also at this time, the opening increase amount ISCUP of the ISCV 23 is calculated and the opening control of the ISCV 23 is performed, so that the decrease in the engine torque is suppressed.
Now, in step 114, when the catalyst temperature estimated count value CSKEI is smaller than the predetermined value "A-10", the process proceeds to step 119. This step 11
In 9, it is determined whether the retard angle amount ARTD is larger than "0", that is, whether the retard angle amount ARTD is not "0". When it is determined that the retard amount ARTD is larger than "0" (that is, not "0"), the process proceeds to step 120.

In step 120, a predetermined value β (β <α in this embodiment) is subtracted from the current retard amount ARTD, and the value is newly set as the retard amount ARTD. The retard amount ARTD set in this routine is used as a control amount used for retard control in a separate routine. Then, step 1 above
The process of 18 is executed, and the subsequent processes are once ended.

The operation state and the like in these series of processes are shown in the timing chart of FIG. 5 from time t4 to time t5.
It corresponds to the state up to immediately before. That is, from the time t4 to immediately before the time t5, since the light load steady running is performed, the light load steady running flag FKEI is set to "1". At this time, the catalyst temperature estimated count value CSKEI is already smaller than "A-10". Then, the catalyst temperature estimated count value CSKEI is "A
Since it is smaller than "-10", it is recognized that the catalyst temperature THC has risen to a certain value at this point. Therefore, as a process for canceling the retard angle control later, the retard angle amount ARTD is gradually decreased, and the retard angle control is executed based on the decreasing retard angle amount ARTD. Is the catalyst temperature THC of the catalytic converter 18 extremely gradually decreased by the execution of the retard control?
Or it is held at a nearly constant value (sometimes it rises very gradually). Therefore,
The catalyst temperature THC does not exceed the allowable upper limit value due to execution (continuation) of the retard control.

Also at this time, the opening increase amount ISCUP of the ISCV 23 is calculated and the opening control of the ISCV 23 is performed, so that the reduction of the engine torque is suppressed.
On the other hand, when it is determined in step 119 that the retard amount ARTD is not larger than "0" (that is, "0"), the retard control for raising the catalyst temperature THC to some extent is completed. Step 121 as a thing
Move to.

In step 121, the catalyst temperature estimated count value CSKEI is set to a predetermined value CTEI.
Set as. However, it is assumed that this predetermined value CTEI is larger than the above-mentioned predetermined value "A". Then, the subsequent processing is temporarily terminated.

The operating state and the like in these series of processes correspond to the state and the like at time t5 in the timing chart of FIG. That is, at time t5, since the light load steady running is being performed, the light load steady running flag FKEI is performed.
Is set to "1". At this time, the retard amount ARTD is already "0", and the retard control is completed. Therefore, the catalyst temperature estimation count value CSKEI is set to a predetermined value CTEI larger than "A", assuming that there is no need to perform the retard control for a while to raise the catalyst temperature THC.

Then, for example, when this light load steady running state is continued, from the time t6 when the catalyst temperature estimated count value CSKEI becomes less than or equal to the predetermined value "A" after a while t
Immediately before 7, the same processing as from time t2 to t3, that is, the processing from step 113 to step 118 is performed. As a result, the catalyst temperature THC is controlled to increase by performing the retard control again, and the IS
Since the opening degree control of the CV 23 is performed, the reduction of the engine torque is suppressed.

After that, for example, at time t7, when the light load steady running is stopped, that is, when the running state shifts to the medium / high load running state, the same processing as immediately before the time t1 is performed. Is done.

As described above, according to the warm-up control method of this embodiment, even if the light-load steady running is performed and the running condition that causes the decrease of the catalyst temperature THC is reached, it is delayed immediately. The angle control is not executed. That is,
Only when the catalyst temperature estimated count value CSKEI becomes smaller than “A” does the catalyst temperature THC appear at the present time.
It has been recognized that the temperature has dropped to a temperature that needs to be raised, and that the temperature is decreasing. Then, the retard control is executed based on the recognition. Therefore, the retard angle control suppresses the catalyst temperature THC of the catalytic converter 18 from falling below the allowable lower limit value. Then, the catalyst temperature THC can be raised by further execution of the retard control.

Along with this, the retard control is delayed until the catalyst temperature estimated count value CSKEI becomes "A", so that the catalyst temperature THC does not rise during the delay. Furthermore, the catalyst temperature estimated count value CSKE
When I does not become larger than "A-10", the retard amount ARTD is made small so as to suppress the rapid increase in the catalyst temperature THC. Therefore, the catalyst temperature THC
Does not exceed the allowable upper limit value and excessively rises, and the catalyst temperature THC can be controlled to an appropriate value,
As a result, the purification rate of exhaust gas can be improved. Further, it is possible to suppress unnecessary deterioration of fuel consumption due to excessive increase of the catalyst temperature THC.

Further, in the conventional case, as shown by the chain double-dashed line in FIG. 5, the engine torque is drastically reduced with the start of execution of the retard control, but in this embodiment, the retard amount is increased. The opening degree increase amount ISCUP is calculated based on the ARTD, the engine speed NE, etc., and based on the calculated value, the ISCV2
The opening degree of 3 is controlled. Therefore, as shown by the solid line in the figure, it is possible to suppress a decrease in engine torque. As a result, since the engine torque does not decrease, drivability can be improved.

(Second Embodiment) Next, a second embodiment embodying a warm-up control method in an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described in detail with reference to FIGS. In this embodiment, the same members as those in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted. Differences will be mainly described.

As shown in FIG. 6, in this embodiment, the catalyst 24 with an electric heater is provided on the upstream side of the catalytic converter 18 in the middle of the exhaust passage 12, which is different from the first embodiment. It's very different. The catalyst 24 with an electric heater has an electric heater integrated with the catalyst. When the engine 1 is cold started,
When the heater switch 25 interposed between the battery power source VB and the catalyst with electric heater 24 is turned on, the electric heater is energized and heated. By this heating, the catalyst temperature THC rises, the activation of the catalyst itself is accelerated, and the purification of the exhaust gas is further accelerated.

In this embodiment, in addition to the injector 17, the igniter 21 and the ISCV 23 described above,
The heater switch 25 is electrically connected to the ECU 51, and the drive timing of each is controlled by the operation of the ECU 51. That is, the ECU 51, based on the output signals from the air flow meter 32 and the sensors 31, 33 to 37, the injector 17, the igniter 21, and I.
The SCV 23 and the heater switch 25 are preferably controlled.

Next, the warm-up control processing executed by the above-mentioned ECU 51 will be described according to the flowcharts of FIGS. 7 and 8 and with reference to the timing chart of FIG.
The flowcharts shown in FIGS. 7 and 8 control the energization time and the like of the catalyst with electric heater 24 by controlling the energization time to the catalyst with electric heater 24 when the light load steady running is performed among the processes executed by the ECU 51. This shows a "catalyst control routine with an electric heater" for performing warm-up control, which is executed by a regular interrupt every predetermined time.

When the processing shifts to this routine, first in steps 201 to 207, the same processing as steps 101 to 107 in the first embodiment is performed.

Then, in step 208, the heater switch 25 is turned "off", and the subsequent processing is temporarily terminated. Further, with respect to the processing of step 209 and step 210, the same processing as the processing of step 109 and step 110 in the first embodiment is performed. That is, the count-up value CUP or the count-down value CDOWN
Is calculated, and the catalyst temperature estimated count value CSKEI is converged to the upper limit value CMAX.

The operating conditions in the above series of processing are as follows:
This corresponds to the state up to immediately before time t11 in the timing chart of FIG. That is, light load steady running is not performed until immediately before time t11, so the light load steady running flag FKEI is set to "0". Then, if the catalyst temperature estimated count value CSKEI is larger than the upper limit value CMAX, the count-up value CUP is added to the catalyst temperature estimated count value CSKEI. Although not shown, the catalyst temperature estimated count value CSKEI is the upper limit value C.
If it is not larger than MAX, the countdown value CDOWN is subtracted from the catalyst temperature estimated count value CSKEI. Further, at this time, since the light load steady running is not performed, the catalyst temperature THC does not decrease, and therefore, it is not necessary to energize the catalyst with electric heater 24, and the heater switch 25
Remains off.

When the light load steady running flag FKEI is "1" in step 203, it is determined that the light load steady running is being performed, and step 211 is executed.
Move to. In step 211 and the next step 212, the same processing as step 111 and step 112 of the first embodiment is performed. That is, the countdown value CDOWN when the light load steady running is performed, the countdown value CDOWN is subtracted from the current catalyst temperature estimation count value CSKEI, and the value is newly set as the catalyst temperature estimation count value CSKEI. To do.

In the following step 213, it is determined whether or not the catalyst temperature estimated count value CSKEI is larger than a predetermined value "C". When the estimated catalyst temperature count value CSKEI is larger than "C", the vehicle is currently in light-load steady running, but the temperature of the catalyst has not decreased to the caution temperature from the history of operating conditions up to that point. However, the processing is terminated once, assuming that it is still sufficiently high.

The operation state and the like in the series of processes are shown from time t11 to time t in the timing chart of FIG.
It corresponds to the state up to immediately before 12. That is, time t
From 11 to immediately before time t12, since the light load steady running is performed, the light load steady running flag FKE
I is set to "1". Then, the catalyst temperature THC is reduced by continuing the light load steady running, and the catalyst temperature estimated count value CSKEI is further counted down. However, at this time, the estimated catalyst temperature count value CSKEI is still larger than “C”. Therefore, although the catalyst temperature THC is currently decreasing, it is assumed that the temperature has not yet decreased to the caution temperature, the heater switch 25 is kept "off", and the energization control of the catalyst with electric heater 24 is not executed.

If the catalyst temperature estimated count value CSKEI is not greater than "C" in step 213, the light temperature steady running is continued, and as a result, the catalyst temperature T
Assuming that the HC has become lower than the caution temperature,
Go to step 214. In step 214, it is determined whether or not the catalyst temperature estimated count value CSKEI is larger than "D" which is a predetermined value smaller than the above-mentioned predetermined value "C". Then, the catalyst temperature estimated count value CS
When KEI is larger than "D", that is, when the catalyst temperature estimated count value CSKEI is within the range of "D" to "C", step 2 is executed to execute the energization control thereafter.
At 15, the heater switch 25 is turned on.
By this "on" operation, the heater of the catalyst 24 with an electric heater is energized to raise the temperature of the catalyst.

The operation state and the like in the series of processes are shown from time t12 to time t in the timing chart of FIG.
This corresponds to the state up to immediately before 13. That is, time t
From 12 to immediately before time t13, since the light load steady running is performed, the light load steady running flag FKE
I is set to "1". At this time, the catalyst temperature estimated count value CSKEI is already smaller than “C”. Since the catalyst temperature estimated count value CSKEI is smaller than "C" and larger than "D", the catalyst temperature THC has dropped to the caution temperature that requires heating at the present time. It is recognized that the temperature is decreasing. Therefore, the "on" operation of the heater switch 25 is continued, and the catalyst 24 with an electric heater is heated. In other words, while the light load steady running is already performed at the time t11, the energization control is delayed until the time t12 in this embodiment. The execution of this energization control increases the amount of unburned components in the exhaust gas and reburns the unburned components in the catalyst 24 with an electric heater. Therefore, the catalyst temperature TH of the catalyst with electric heater 24
It is suppressed that C becomes equal to or less than the allowable lower limit value, and the catalyst temperature THC gradually rises by further execution of the energization control. On the other hand, since energization control is delayed,
When the energization control is performed, the catalyst temperature THC is surely lowered to the caution temperature or lower. Therefore, unlike the prior art as shown by the chain line in FIG. 2, the catalyst temperature THC does not exceed the allowable upper limit value with the start of execution of the energization control.

If the catalyst temperature estimated count value CSKEI is not greater than "D" in step 214, the process proceeds to step 216. This step 21
At 6, it is determined whether the catalyst temperature estimated count value CSKEI is "0". If it is determined that the catalyst temperature estimated count value CSKEI is not "0", it is determined that the catalyst temperature estimated count value CSKEI is equal to or less than "D" but still greater than "0" (step 218).
Move to. Then, in step 218, the heater switch 25 is turned off, and the subsequent processing is temporarily terminated.

The operation state and the like in the series of processes are shown from time t14 to time t in the timing chart of FIG.
This corresponds to the state up to immediately before 15. That is, time t
From 14 to immediately before time t15, since the light load steady running is performed, the light load steady running flag FKE is executed.
I is set to "1". At this time, the catalyst temperature estimated count value CSKEI is already smaller than “D”. Since the catalyst temperature estimated count value CSKEI is smaller than “D”, it is recognized that the catalyst temperature THC has risen to a certain value at this point in time. Therefore, the heater switch 25 is once turned off. With this “off” operation, the catalyst temperature THC of the catalyst 24 with an electric heater gradually decreases. Therefore,
The catalyst temperature THC does not exceed the allowable upper limit value due to the execution (continuation) of the energization control.

On the other hand, when it is determined in step 216 that the catalyst temperature estimated count value CSKEI is "0", it is determined that the energization control for raising the catalyst temperature THC to some extent has been completed, and the process proceeds to step 217. To do.

In step 217, the catalyst temperature estimated count value CSKEI is set to a predetermined value CTEI.
Set as. However, it is assumed that this predetermined value CTEI is larger than the above-mentioned predetermined value "C". Then, in step 218, the heater switch 25 is maintained in the "off" state, and the subsequent processing is temporarily terminated.

The operating state and the like in these series of processes correspond to the state and the like at time t4 in the timing chart of FIG. That is, at the time t4, since the light load steady running is performed, the light load steady running flag FKEI is performed.
Is set to "1". At this time, the catalyst temperature estimated count value CSKEI is "0", the energization control has been completed, and the catalyst temperature THC has risen to some extent. Therefore, the catalyst temperature estimation count value CSKEI is set to a predetermined value CTEI larger than "C", assuming that there is no need to perform the retard control for a while to raise the catalyst temperature THC.

Then, for example, when this light load steady running state is continued, immediately before the time t15 to t16 when the catalyst temperature estimation count value CSKEI becomes the predetermined value "C" or less after a while, the time t12 to t13. The same processing as the above, that is, step 213 to step 215
The processing up to is performed. As a result, the catalyst temperature THC is controlled to rise by performing the energization control again.

Thereafter, for example, at time t6, when the light load steady running is stopped, that is, when the running state shifts to the medium / high load running state, the same processing as immediately before the time t1 is performed. Is done.

As described above, according to the warm-up control method of this embodiment, even if the light-load steady running is carried out and the running condition that causes the decrease of the catalyst temperature THC is reached, it is delayed immediately. The angle control is not executed. That is,
Only when the catalyst temperature estimated count value CSKEI becomes smaller than “C” does the catalyst temperature THC appear at the present time.
The temperature has fallen below the caution temperature that requires heating, and it is recognized that the temperature is decreasing. Then, the retard control is executed based on the recognition. Therefore, also in this embodiment, the same effect as that of the first embodiment can be obtained.

The present invention is not limited to the above-described embodiments, but can be implemented as follows by appropriately modifying a part of the configuration without departing from the spirit of the invention. (1) In the first and second embodiments, whether or not the light load steady running is performed is used as the determination condition of whether or not it is in the operating state in which the catalyst temperature is lowered. When performing the energization control in (1), for example, whether the fuel cut is performed or not may be used as the determination condition. Further, it may be possible to make a determination by combining these factors that cause a decrease in the catalyst temperature (light load steady running and fuel cut). Furthermore, the determination may be made by combining other factors that cause a decrease in the catalyst temperature. From the above, the present invention is not controlled based on the factor that causes the temperature decrease of the catalyst, but is controlled after the start of the operating state that causes the temperature decrease of the catalyst. The factors that come are not particularly limited. Therefore, whatever the cause, the temperature of the catalyst can be raised after the start of the operating state in which the temperature of the catalyst is lowered and after the lapse of the delay time.

(2) In the first embodiment, the retard amount ART
Although both D and the retard angle are controlled, it is also possible to control only the retard time with the retard amount ARTD being constant when performing the retard control.

(3) In the second embodiment, the energization amount supplied to the catalyst 24 with an electric heater is set to be constant and the energization time is controlled. A current control circuit (not shown) may be provided between the heater switch 25 and the ECU 51 to control the current control circuit to adjust the amount of current supplied from the battery power source VB to the catalyst with electric heater 24. . With such a configuration, it is possible to control the energization time and the energization amount.

(4) In the first embodiment, ISCV23
The opening degree increase amount ISCUP is calculated and the opening degree of the ISCV 23 is controlled based on the opening degree increase amount ISCUP to suppress the decrease in the engine torque, but such control may not be performed. Further, the torque control of the second embodiment may be incorporated.

[0083]

As described in detail above, according to the present invention, in the warm-up control method of the exhaust gas purification device for raising the temperature of the catalyst for purifying the exhaust gas from the internal combustion engine,
When it is determined that the operating state in which the temperature of the catalyst is lowered has started, the history of the operating state up to immediately before the temperature of the catalyst is lowered is recognized based on the result of the determination, and the history is recognized. The temperature rise of the catalyst was delayed. Therefore, even with respect to various factors that lower the catalyst temperature, the exhaust gas purification rate can be improved by controlling the catalyst temperature to an appropriate value without excessively increasing it, and unnecessary fuel consumption can be improved. It has an excellent effect that deterioration can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an exhaust emission control device for an engine mounted on a vehicle in a first embodiment embodying the present invention.

FIG. 2 is a block diagram showing an electrical configuration of an ECU in the first embodiment.

FIG. 3 is a flowchart showing a processing operation of a “retard angle amount calculation routine” executed by the ECU in the first embodiment.

FIG. 4 is a flowchart showing a processing operation of a “retard angle amount calculation routine” executed by the ECU in the first embodiment.

FIG. 5 is a timing chart for explaining an operating state and the like that change with time in the first embodiment.

FIG. 6 is a schematic configuration diagram showing an engine exhaust gas purification apparatus mounted on a vehicle in a second embodiment embodying the present invention.

FIG. 7 is a flowchart showing a processing operation of an “electric heater-attached catalyst control routine” executed by an ECU in the second embodiment.

FIG. 8 is a flowchart showing a processing operation of an “electric heater-attached catalyst control routine” executed by an ECU in the second embodiment.

FIG. 9 is a timing chart illustrating an operating state and the like that change with time in the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 18 ... Catalytic converter, 24 ... Catalyst with an electric heater, 51 ... ECU.

Claims (1)

[Claims] 1. An operating state of an internal combustion engine is detected, and whether the present operating state is an operating state in which the temperature of a catalyst for purifying exhaust gas from the internal combustion engine is lowered based on the detection result. It is a method of warm-up control in an exhaust gas purification apparatus for an internal combustion engine, which determines whether or not the temperature of the catalyst is increased based on the result of the detection of the operating state of the internal combustion engine. When it is determined that the operating state in which the temperature drops is started, the history of the operating state up to immediately before the temperature in the catalyst is lowered is recognized based on the determination result, and the catalyst is detected according to the recognition of the history. Warm-up control method in an exhaust gas purification apparatus for an internal combustion engine, characterized in that the temperature rise of the engine is delayed.