JPH0726948A - Air leading device inside exhaust pipe for internal combustion engine - Google Patents

Abstract

PURPOSE:To activate a catalyst in an earlier stage, and reduce an exhaust gas amount furthermore. CONSTITUTION:Air led into an exhaust pipe is heated by a heater 22 at the time of engine starting so as to increase the amount of heat transmitted to the catalyst. While heating air is led, the ignition timing of an internal combustion engine 1 is delay-controlled by an engine controller 23 so as to raise an exhaust gas temperature, so that the amount of heat transmitted to the catalyst is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for introducing air into an exhaust pipe of an internal combustion engine, which introduces air into the exhaust pipe of the internal combustion engine and activates a catalyst for purifying exhaust gas.

[0002]

2. Description of the Related Art Conventionally, for purifying exhaust gas from an internal combustion engine,
A catalyst may be provided in the exhaust pipe, but the catalyst temperature is low and the purification efficiency is low immediately after the internal combustion engine is started. For this reason, air is introduced upstream of the catalyst in the exhaust pipe, and HC and C in the catalyst are introduced.
It has been conventionally performed to accelerate the temperature rise of the catalyst and enhance the purification efficiency by promoting the oxidation of O and the like.

FIG. 12 is a block diagram showing an example of a conventional air introducing device in an exhaust pipe. In the figure, the internal combustion engine 1 is
An intake pipe 2 for introducing air and an exhaust pipe 3 for discharging harmful exhaust gas generated by combustion to the atmosphere are connected. An air cleaner 4 for removing dust in the atmosphere is provided at an upstream portion of the intake pipe 2. An air flow sensor 5 for measuring the amount of air taken into the internal combustion engine 1 is provided downstream of the air cleaner 4. Further, a throttle valve 6 for adjusting the amount of air taken into the internal combustion engine 1 is provided downstream of the air flow sensor 5.

A catalyst accommodating portion 7 accommodating a catalyst for purifying exhaust gas by a chemical reaction is provided in the middle of the exhaust pipe 3. An air introduction pipe 8 is connected between the air flow sensor 4 downstream of the intake pipe 2 and the catalyst housing portion 7 upstream of the exhaust pipe 3. An air pump 9 for forcibly sending air to the exhaust pipe 3 and a check valve 10 for preventing exhaust gas from returning to the intake pipe 2 through the air introduction pipe 8 in the middle of the air introduction pipe 8. Is provided.

The exhaust pipe 3 is provided with an air-fuel ratio sensor 11 for detecting the oxygen concentration contained in the exhaust gas. In addition, in the internal combustion engine 1, an injector 12 for injecting fuel sent from a fuel pump (not shown) toward an intake valve (not shown) in a mist state to supply fuel is provided for each cylinder. It is provided. Further, the internal combustion engine 1 is provided with a crank angle sensor 13 that detects the engine speed.

Air flow sensor 5, air-fuel ratio sensor 11,
An engine controller 14 is connected to each injector 12 and crank angle sensor 13. The engine controller 14 controls each injector 12 according to the output of each sensor 5, 11, 13. The ignition coil 15 ignites an ignition plug (not shown) for igniting the fuel injected from the injector 12. The energizing signal to the ignition coil 15 is controlled by the igniter 16,
The igniter 16 is controlled by the engine controller 14.

Next, the operation will be described. A part of the air purified by passing through the air cleaner 4 is part of the air pump 9
Is forcibly sucked into the air introduction pipe 8 by the check valve 10
It is introduced into the exhaust pipe 3 upstream of the catalyst storage portion 7 via the. The air introduced into the exhaust pipe 3 is mixed with the exhaust gas discharged from the internal combustion engine 1 and flows into the catalyst housing portion 7. In the catalyst storage portion 7, harmful components such as HC and CO in the exhaust gas are converted into H ₂ O, CO _{2 and the} like by an oxidation reaction, and the exhaust gas is purified by this.

The injector 12 is controlled by the engine controller 14, and the amount of fuel injected at this time is determined mainly by the output of the air flow sensor 5 and the engine speed. The above engine speed is determined by the crank angle sensor 1
3 is calculated from the output signal. The calculated fuel amount is adjusted according to the output of the air-fuel ratio sensor 11, etc., and the corrected fuel amount is determined by this, and the injector 12 is driven.

The ignition timing is controlled by energizing the ignition coil 15. The igniter 16 that controls the energization of the ignition coil 15 is controlled by the engine controller 14 according to the output of the air flow sensor 5 and the engine speed. Further, the introduction of air into the exhaust pipe 3 by the air pump 9 is started when the internal combustion engine 1 is started, and
It is always done until is stopped.

[0010]

In the conventional exhaust pipe air introducing device configured as described above, the catalyst is activated earlier than in the case without the exhaust pipe air introducing device, and the exhaust gas purification efficiency is increased faster. Therefore, the amount of exhaust gas discharged can be reduced. However, due to increasing environmental problems in recent years, exhaust gas regulations have become stricter, as seen in, for example, exhaust gas regulations in California, USA. The amount is not enough, and there is a problem that the amount of exhaust gas needs to be further reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the air in the exhaust pipe of an internal combustion engine capable of activating the catalyst earlier and further reducing the exhaust gas amount. The purpose is to obtain an introduction device.

[0012]

According to a first aspect of the present invention, there is provided an air introducing device for an exhaust pipe of an internal combustion engine, wherein air introduced into the exhaust pipe is heated by a heating means, and while heated air is being introduced. The ignition timing control means retards the ignition timing of the internal combustion engine at least during a part of the time.

In the exhaust pipe air introducing device for an internal combustion engine according to the second aspect of the present invention, the air introduced into the exhaust pipe is heated by the heating means, and at least a part of the time during which the heated air is being introduced. In addition, the ignition timing control means intermittently retards the ignition timing of the internal combustion engine.

In the exhaust pipe air introducing device for an internal combustion engine according to the third aspect of the present invention, the air introduced into the exhaust pipe is heated by the heating means, and at least a part of the time during which the heated air is introduced. In addition, the ignition timing control means retards the ignition timing of the internal combustion engine, and terminates the ignition timing retard control before the introduction of the heated air is stopped.

[0015]

According to the first aspect of the present invention, the temperature of the exhaust gas from the internal combustion engine is raised by introducing heated air into the exhaust pipe to raise the catalyst temperature and controlling the ignition timing with a retard angle. Increase catalyst temperature further.

According to the second aspect of the present invention, the retarding control is performed intermittently, so that the torque reduction is reduced and the drivability is suppressed from being deteriorated as compared with the case where the all-cylinder retarding control is performed.

According to the third aspect of the present invention, the retardation control is ended before the activation of the catalyst is sufficient, so that the deterioration of drivability due to the torque decrease is suppressed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. 1 is a configuration diagram showing an air introducing device in an exhaust pipe of an internal combustion engine according to an embodiment of the present invention.
The same or corresponding parts as those in 2 are designated by the same reference numerals and the description thereof is omitted. In the figure, a control valve 21 for controlling whether or not to introduce air into the exhaust pipe 3 is provided between the air pump 9 of the air introduction pipe 8 and the check valve 10. A heater 22 is provided between the control valve 21 and the check valve 10 as a heating means for heating the air introduced into the exhaust pipe 3.

These control valve 21 and heater 22
Is an engine controller 23 which is an ignition timing control means.
It is connected to the. The engine controller 23 includes an air flow sensor 5, an air-fuel ratio sensor 11,
The injectors 12, the crank angle sensor 13, the igniter 16, etc. are connected to control the amount of fuel injected from the injectors 12, the injection timing, the ignition timing, the presence or absence of air introduction, and the control of the heater 22. Be seen. The air pump 9 of the first embodiment is a mechanical air pump that discharges air according to the engine speed. The introduction of the outside air may be performed without the air cleaner 4 separately from the intake pipe 2.

Next, the operation will be described. 2 is shown in FIG.
6 is a timing chart for explaining a method of introducing heated air into the exhaust pipe 3 in the apparatus of FIG. First,
The engine speed is calculated from the output signal from the crank angle sensor 13, and the engine speed is set to a predetermined value (for example, 500
r / min) is exceeded to determine whether or not the engine is started. Then, the control valve 21 is opened and the heater 22 is energized for a predetermined time T from the time when the start is determined.

By controlling the above operation by the engine controller 23, the heated air is introduced into the exhaust pipe 3 and the catalyst is heated during the time T after the start. FIG. 3 is a relationship diagram showing a change in the catalyst temperature at the time of starting the engine. By heating the introduced air with the heater 22, the catalyst temperature rises quickly.

In FIG. 3, 300 ° C. is shown as an example of the catalyst activation temperature. The above predetermined time T may be set to a time at which the catalyst activity is sufficiently completed. Further, since the air pump 9 is mechanically moving, the introduction of air into the exhaust pipe 3 is stopped by closing the control valve 21 after the lapse of time T. By such an operation, the introduction of air into the exhaust pipe 3 is controlled.

Next, FIG. 4 is a timing chart for explaining the ignition timing control method. In the figure, the signal from the crank angle sensor 13 is BTDC (B
eforeTopDeadCenter) Get down at 5 ° (5 ° before top dead center). Using this signal, 180 ° CA (Crank
The engine speed is calculated from the cycle between Angles.

BTDC 75 ° (signal rising)
From this, the igniter energization start time T _in and the igniter energization end time T _spark are controlled. That is, after the rising signal of BTDC 75 ° is input and the time T _{in has} elapsed, the igniter 1
6 is energized, and after the time T _spark , the igniter 16 is de-energized. The ignition coil 15 is energized / de-energized in synchronism with energization / de-energization of the igniter 16, and a spark plug is ignited when the ignition coil 15 is de-energized.

Next, FIG. 5 is a flow chart for explaining a method of controlling the igniter 16 by the engine controller 23. First, in order to calculate the basic ignition timing according to a predetermined operating state, the engine speed and the intake air amount are sequentially read (steps S1 and S2). Then, based on these pieces of information, a predetermined basic ignition timing is read and determined (step S3).

Subsequently, it is determined whether or not the control valve 21 is open, that is, whether or not air is introduced into the exhaust pipe 3 (step S4). Here, if the control valve 21 is in the closed state, the air is not introduced, so the ignition timing is made the same as the basic ignition timing (step S5). If the control valve 21 is in the open state, air is being introduced, so the ignition timing is set to the retard side from the basic ignition timing by a predetermined angle A, that is, the basic ignition timing -A (step S6). Through the above processing, the timing (angle) at which ignition should be performed is determined.

After that, the ignition timing (angle) is converted into the ignition timing (step S7). For example, in the case of a 4-cylinder 4-cycle engine, this ignition timing is ignition timing (sec) = {[75 ° −ignition timing (° C
A)] / 180 °} × 30 / engine speed Ne (rp
m.).

Then, based on the calculated ignition timing, the igniter energization start timing T _in and the igniter energization end timing T
_spark is calculated (step S8). Where T _spark
Is a predetermined value, ignition timing = T _in + T
_{Since it is spark} , T _in is calculated by T _in = ignition timing−T _spark . By the above processing, the time required for ignition timing control is calculated.

Next, FIG. 6 is a flow chart for explaining the driving method of the igniter 16. Igniter 16
The actual driving of is carried out using an interrupt process as shown in FIG. That is, first, it is determined whether or not the igniter 16 is in the energized state (step S9). Then, if the igniter 16 is not in the energized state, BTDC 75 ° to T _in
After a lapse of time, the igniter 16 is energized (step S1
0). If the igniter 16 is in the energized state, the igniter 16 is de-energized T _spark time after the start of energization (step S11). It should be noted that such an interrupt process is executed at a predetermined timing (for example, every time BTDC 75 ° and igniter energization start).

As described above, the ignition timing control is as shown in FIG.
6 is performed, the ignition timing is retarded while the air is being introduced into the exhaust pipe 3 by this process. Further, as shown in FIG. 7, the temperature of the exhaust gas discharged from the internal combustion engine 1 to the exhaust pipe 3 rises by performing the above retard control, so that the temperature of the exhaust gas to the catalyst is higher than that when the retard control is not performed. Heat transfer is increased. Therefore, due to the synergistic effect of the introduction of the heated air and the rise in the exhaust gas temperature due to the retard control, the catalyst temperature is activated earlier, as shown in FIG. 3, and the exhaust gas purification efficiency by the catalyst becomes higher. The amount of exhaust gas emission is reduced.

Example 2. In the first embodiment, the ignition timing retard control is performed for all cylinders.
When the all-cylinder retard control is performed, the drivability is deteriorated due to the torque reduction due to the ignition retard. In order to suppress such deterioration of drivability, in the second embodiment,
A counter is provided to intermittently execute ignition retard at predetermined intervals.

FIG. 8 is a timing chart for explaining the ignition timing control method according to the second embodiment of the invention. First, it is determined by a flag whether heated air is introduced into the exhaust pipe 3, and when the flag is set, it is determined that the condition for retarding ignition in the introduced state of heated air is satisfied. Further, the ignition timing β when the heated air is not introduced and the retarded ignition timing α when the heated air is introduced are obtained respectively.

In the case of the retarded angle of all cylinders as in the first embodiment, the ignition timing shown by the broken line is obtained. On the other hand, in the second embodiment, a counter that counts up each ignition is provided, and this counter has the first value Nn (3 in FIG. 8).
The ignition timing is changed until the ignition timing β is exceeded, and the ignition timing is changed until the second value Nr (5 times in FIG. 8) is exceeded. That is, the ignition timing is intermittently retarded. This intermittent retard control is performed for all cylinders, for example, and a certain ignition timing is used to retard only one cylinder, and the next ignition timing is used to retard only another cylinder. To be

Next, FIG. 9 is a flow chart for explaining the ignition timing control method of the second embodiment.
The difference from FIG. 5 is that the process of calculating the ignition timing from the ignition timing and the process of calculating the igniter energization start / end timing from the ignition timing have been moved to the interrupt process, and that flag setting has been added. Is.

In the figure, first, similarly to FIG. 5, the engine speed and the intake air amount are sequentially read (step S1,
S2), the basic ignition timing is determined (step S3). Then, it is determined whether the control valve 21 is open (step S4). If the control valve 21 is open, the above flag is set (step S21),
The ignition timing is set to α, that is, the basic ignition timing-A (step S6). If the control valve 21 is closed, the flag is cleared (step S22), and the ignition timing is set to β, that is, the same as the basic ignition timing (step S5).

FIG. 10 is a flow chart for explaining the driving method of the igniter 16. The interrupt process for driving the igniter 16 occurs at the timing of BTDC 75 ° and the timing of starting energization, and the igniter energization start / end is controlled at each timing.

In the figure, first, it is judged whether or not the interrupt is at the timing of BTDC 75 ° (step S23). If the interrupt is other than BTDC 75 °, the above-mentioned T
_{Since spar k} has already been calculated, the termination of energization of the igniter is controlled (step S33). On the other hand, BTDC 75 °
If it is the interrupt of, it is determined whether or not the flag is set (step S24).

At this time, if the flag is not set, the heated air is not introduced, so after setting the counter to 0 (step S25), the ignition timing is calculated at the ignition timing β (step S26). If the flag is set, it is necessary to intermittently retard the ignition as described above, so it is determined whether the counter exceeds Nn (step S27). If the counter does not exceed Nn, the ignition timing is calculated at the ignition timing β (step S28), and then the counter is incremented to count the number of ignitions (step S29).

If the counter exceeds Nn, it is continuously determined whether or not the counter exceeds Nr (step S30). If the counter exceeds Nr, the retard control may be ended, so the counter is set to 0.
After that (step S31), the ignition timing is calculated with the ignition timing β (step S28), and the counter is incremented (step S29).

If the counter does not exceed Nr, the ignition timing is calculated by the ignition timing α, that is, the ignition delay angle (step S32), and then the counter is incremented (step S29). In this way, the ignition timings for the case where there is no Nn times retard and the cases where there is (Nr-Nn) times retard are calculated. In this way, after calculating the ignition timing and incrementing the counter,
An igniter energization start timing T _in and an igniter energization end timing T _spark are calculated from the ignition timing (step S33). Then, the igniter 16 is driven by performing the same processing as that of FIG. 6 based on these calculation results.

As described above, by intermittently retarding the ignition timing, the efficiency of exhaust gas purification by the catalyst is increased, the exhaust gas emission amount is reduced, and the deterioration of drivability is suppressed.

Example 3. Next, FIG. 11 is a timing chart for explaining an ignition timing control method according to an embodiment of the present invention. As described above, the drivability is deteriorated by the method of the first embodiment, so in the third embodiment, the ignition retard control is ended before the introduction of the heated air is stopped.

That is, in the first embodiment, as shown by the broken line in FIG. 11, the ignition timing is retarded during the time T during which the heated air is introduced, but in the third embodiment, the ignition timing is controlled. The timing for stopping the introduction of the heated air and the timing for ending the retard control are separated by setting the delay control time of Ts (<T). Note that Ts is a preset time, and after Ts is a time when the difference in the catalyst temperature rise due to the presence or absence of ignition retard control is small.

Also by such a method, the efficiency of purifying the exhaust gas by the catalyst is increased, the exhaust gas emission amount is reduced, and the deterioration of drivability is suppressed.

[0045]

As described above, in the exhaust pipe air introducing apparatus for an internal combustion engine according to the first aspect of the present invention, the air introduced into the exhaust pipe is heated by the heating means, and while the heated air is being introduced. During at least a part of the time, the ignition timing control means retards the ignition timing of the internal combustion engine, so that the synergistic effect of the introduction of heated air and the rise in the exhaust gas temperature due to the retard control causes a catalyst The effect that the exhaust gas can be activated earlier and the amount of exhaust gas can be further reduced is obtained.

Further, in the exhaust pipe air introduction device for an internal combustion engine according to the second aspect of the invention, the ignition timing of the internal combustion engine is intermittently retarded, so that the catalyst is activated earlier and the exhaust gas amount is increased. It is possible to suppress the deterioration of drivability due to the torque reduction while further reducing the above.

Further, in the exhaust pipe air introducing device for the internal combustion engine according to the third aspect of the present invention, the retard control of the ignition timing is finished before the introduction of the heated air is stopped, so that the catalyst is activated earlier. Therefore, it is possible to suppress the deterioration of drivability due to the torque reduction while further reducing the exhaust gas amount.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an air introducing device in an exhaust pipe of an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining a method of introducing heated air into the exhaust pipe in the apparatus of FIG.

FIG. 3 is a relationship diagram showing a change in catalyst temperature when the engine is started.

FIG. 4 is a timing chart for explaining a method of controlling ignition timing of the device of FIG.

5 is a flow chart for explaining a method of controlling an igniter by the engine controller of FIG.

6 is a flowchart for explaining a driving method of the igniter of FIG.

FIG. 7 is a relationship diagram showing a difference in exhaust gas temperature due to a difference in ignition timing.

FIG. 8 is a timing chart for explaining an ignition timing control method according to an embodiment of the present invention.

9 is a flow chart for explaining the ignition timing control method of FIG.

10 is a flow chart for explaining a method of driving an igniter during ignition timing control of FIG.

FIG. 11 is a timing chart for explaining an ignition timing control method according to an embodiment of the present invention.

FIG. 12 is a configuration diagram showing an example of a conventional exhaust pipe air introduction device for an internal combustion engine.

[Explanation of symbols]

 1 Internal Combustion Engine 3 Exhaust Pipe 22 Heater (Heating Means) 23 Engine Controller (Ignition Timing Control Means)

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area F02P 5/15

Claims (3)

[Claims] 1. A heating means for heating the introduced air in an exhaust pipe air introduction device of an internal combustion engine for introducing air into the exhaust pipe of the internal combustion engine to activate a catalyst provided in an exhaust path of the internal combustion engine. And an ignition timing control means for retarding the ignition timing of the internal combustion engine during at least a part of the time during which the heated air is being introduced. In-pipe air introduction device. 2. A heating means for heating the introduced air in an exhaust pipe air introduction device for an internal combustion engine, which introduces air into the exhaust pipe of the internal combustion engine for activating a catalyst provided in an exhaust passage of the internal combustion engine. And an ignition timing control means for intermittently retarding the ignition timing of the internal combustion engine during at least a part of the time during which the heated air is being introduced. Air introduction device in the exhaust pipe of the engine. 3. A heating means for heating air to be introduced in an exhaust pipe air introduction device for an internal combustion engine, which introduces air into the exhaust pipe of the internal combustion engine for activating a catalyst provided in an exhaust passage of the internal combustion engine. And retarding the ignition timing of the internal combustion engine during at least a part of the time during which the heated air is being introduced, and retarding the ignition timing before the introduction of the heated air is stopped. An exhaust pipe air introduction device for an internal combustion engine, comprising: ignition timing control means for ending control.