JP3203036B2 - Engine emission control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas control apparatus for an engine, and more particularly, to an exhaust gas control apparatus for adjusting the exhaust pressure of the engine in accordance with the operating condition, thereby reducing the emission of unburned components and improving the exhaust gas purification performance. The present invention relates to an engine emission control device.

[0002]

2. Description of the Related Art Conventionally, a control valve for increasing or decreasing the cross-sectional area of an exhaust passage of an engine is provided in the middle of the exhaust passage, and the opening degree of the control valve is adjusted so that the engine can be started or the exhaust gas can be purified. There is known a technique for improving the image quality. For example, according to Japanese Patent Application Laid-Open No. 2-64236, when the engine is started, the opening degree of a control valve provided in the exhaust pipe on the downstream side of the muffler is reduced to reduce the cross-sectional area of the exhaust pipe, thereby reducing the height of the engine. The starting pressure is increased to improve the flammability, thereby improving the starting failure.

On the other hand, for example, according to Japanese Utility Model Laid-Open Publication No. 55-9894, in an engine in which a low-load intake passage and a high-load intake passage are each independently opened to a combustion chamber, an exhaust passage is provided. On the way, an on-off valve that is controlled to open and close based on the negative pressure difference of the intake air in both intake passages is provided.When the on-off valve is idling, the exhaust pressure of the engine is raised to the fully closed state to improve exhaust reburning performance. In the low and medium load operation range, the on-off valve is opened at a predetermined opening to ensure a balance between output performance and exhaust reburning performance, and the emission of unburned components is low in the low and medium load operation ranges. In the high load operation range, the on-off valve is fully opened,
There is disclosed an exhaust gas purifying device configured to suppress an increase in exhaust pressure and improve output to thereby appropriately perform exhaust reburning in accordance with an operation state of an engine.

[0004]

When an on-off valve is provided in the middle of an exhaust passage and the exhaust pressure is adjusted by the on-off valve as in the prior art described above, the engine is started when a large amount of unburned components is discharged. Immediately at the time of cooling, by increasing the exhaust pressure, the emission of unburned components will be suppressed, but if the exhaust pressure is increased during high load and high rotation where high output is required, This has an adverse effect on the flammability of the engine, resulting in a decrease in output performance and a decrease in traveling performance. As described above, the exhaust pressure at which both the reduction of the unburned components and the prevention of the decrease in the traveling performance fluctuates according to the operating state. How to control the opening of the on-off valve has been an issue.

SUMMARY OF THE INVENTION Accordingly, the present invention provides an engine exhaust control system configured to reduce the emission of unburned components by adjusting the exhaust pressure of the engine in accordance with the operating condition. By controlling the exhaust pressure more precisely and improving its controllability, it is possible to effectively reduce the emission of unburned components and to suppress the adverse effect on traveling performance as much as possible, An object of the present invention is to achieve both reduction of components and prevention of decrease in running performance.

[0006]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized in that it is configured as follows.

First, the invention according to claim 1 of the present application (hereinafter referred to as “the invention”)
) Referred to as the first invention, the exhaust control device of an engine so as to reduce the emission of unburned components by adjusting the exhaust pressure of the engine according to operating conditions, the engine
Operating state detecting means for detecting the operating state of the
A predetermined period after the engine is started based on the signal from the detection means
A period determining means for determining whether or not the inside of the engine is cold; an exhaust pressure adjusting means arranged in the exhaust passage to adjust the pressure of exhaust gas; and an exhaust pressure adjusting device arranged in the exhaust passage upstream of the exhaust pressure adjusting means. A catalytic converter for purifying unburned components in the exhaust gas whose pressure has been adjusted by the exhaust pressure adjusting means , and detecting a pressure of the exhaust gas adjusted by the exhaust pressure adjusting means and upstream of the adjusting means; Exhaust pressure detecting means and the above-mentioned period determination
It is a cold time within a predetermined period after starting the engine by means
And when it is determined, and the actual exhaust pressure detected by said exhaust pressure detecting means, comparing the exhaust pressure of the target set in advance as the exhaust gas pressure increases, the actual exhaust pressure target Control means for feedback-controlling the operation of the exhaust pressure adjusting means so as to converge to the exhaust pressure.

[0008]

Further, the invention according to claim 2 of the present application (hereinafter referred to as “the invention”)
The second invention is a control according to the first invention, wherein when the exhaust pressure detected by the exhaust pressure detecting means is higher than a predetermined value, the control means inhibits the feedback control of the exhaust pressure adjusting means by the control means. Prohibition means is provided.

[0010] Furthermore, the invention according to claim 3 of the present application (hereinafter, referred to as third invention), in the first invention, sets a target value of the exhaust pressure in accordance with the operating state detected by the operating condition detecting means target value setting hand stage is provided with a control means compares the actual exhaust pressure detected by the exhaust pressure detecting means and a target value set by the target value setting means, target the actual exhaust pressure The operation of the exhaust pressure adjusting means is feedback-controlled so as to converge to a value.

[0011]

Further, the invention according to claim 4 of the present application (hereinafter referred to as the invention)
Similar to the first aspect, the fourth aspect of the present invention relates to an exhaust control apparatus for an engine in which the exhaust pressure of the engine is adjusted according to the operating state to reduce the emission of unburned components. Unburned component discharge state detecting means for detecting a state in which unburned components are discharged to the exhaust passage,
Exhaust pressure adjusting means for adjusting the pressure of exhaust gas when a state in which unburned components are discharged is detected by the detecting means; and a bypass passage communicating an exhaust passage on the upstream and downstream sides of the exhaust pressure adjusting means. A bypass passage opening / closing means for opening / closing the bypass passage; an exhaust pressure detecting means for detecting an exhaust pressure of an exhaust passage on an upstream side of the exhaust pressure adjusting means;
The actual exhaust pressure detected by the exhaust pressure detecting means is compared with a preset target exhaust pressure, and the operation of the bypass passage opening / closing means is fed back so that the actual exhaust pressure converges to the target exhaust pressure. And control means for controlling.

Further, the invention according to claim 5 of the present application (hereinafter, referred to as a fifth invention) is characterized in that, in the first invention, a temperature detecting means for detecting temperatures before and after the catalytic converter, and a temperature detecting means for detecting the temperature before and after the catalytic converter. Active state determining means for determining the active state of the catalytic converter based on the detected temperature difference; and when the active state of the catalytic converter is determined by the determining means, feedback control of the exhaust pressure adjusting means by the control means is prohibited. And a control prohibiting means for performing the control.

[0014]

According to the first aspect of the present invention, the control means can achieve both reduction of unburned components and prevention of reduction in traveling performance.
The operation of the exhaust pressure adjusting means is feedback-controlled so that the actual exhaust pressure converges to a preset target exhaust pressure, whereby the actual exhaust pressure is more precisely controlled and its controllability is improved. Is improved, and it is possible to achieve both the reduction of the unburned component and the prevention of the decrease in the traveling performance in accordance with the driving state.

Further, regardless of the degree of deterioration of the exhaust pressure adjusting means or the operating characteristics of an actuator for driving the exhaust pressure adjusting means, feedback control is performed so that the actual exhaust pressure always becomes the target exhaust pressure. As a result, the controllability is further improved.

[0016] Further, the cooling device within a predetermined period after the engine is started.
At the time , the operation of the exhaust pressure control means is feedback-controlled by the control means so that the actual exhaust pressure becomes the target exhaust pressure, whereby, particularly when the engine is cold when the emission of unburned components becomes remarkable. The purification performance of unburned components is further improved.

By the way, for example, in a high-load and high-speed operation region where a high output is required, the actual exhaust pressure rises. When operated, the responsiveness of the operation of the adjusting means is deteriorated, and the exhaust fluctuation becomes remarkable,
Although the amount of air charged fluctuates and adversely affects the flammability of the engine, causing a problem such as a decrease in traveling performance, according to the second invention, the exhaust pressure is detected by the exhaust pressure detecting means. When the actual exhaust pressure is high, the feedback control of the exhaust pressure adjusting means is prohibited by the control prohibiting means, whereby the operation of the exhaust pressure adjusting means is performed in a high-load high-speed operation region or the like. The adverse effect of the control is prevented.

In particular, according to the third aspect of the present invention, the target value setting means sets an optimum target value of the exhaust pressure according to the operating state, and adjusts the exhaust pressure so that the actual exhaust pressure converges to the target value. Since the operation of the means is feedback-controlled, the controllability of the exhaust pressure control for achieving both the reduction of the unburned component and the prevention of the decrease in the traveling performance is further improved.

[0019]

Further, according to the fourth aspect of the present invention, a bypass passage opening / closing means for opening / closing the bypass passage is provided in a bypass passage communicating the exhaust passage on the upstream side and the downstream side of the exhaust pressure adjusting means. The exhaust pressure of the bypass passage is feedback-controlled, so that the driving force for driving the bypass passage opening / closing unit is reduced as compared with the case where the exhaust pressure adjustment unit provided in the exhaust passage is controlled, and the exhaust pressure is reduced. Since the actuator for driving the opening / closing means can be reduced in size, the bypass passage opening / closing means can be controlled with a small driving force, and the responsiveness of the operation is improved, and the controllability is improved. Will do.

According to the fifth aspect , the temperature difference between the front and rear of the catalytic converter provided in the exhaust passage is detected by the temperature detecting means, and the active state of the catalytic converter is determined by the active state determining means based on the temperature difference. After the catalytic converter is activated, the feedback control of the exhaust pressure adjusting means is prohibited by the control prohibiting means, whereby the catalytic converter can clean the unburned component satisfactorily. Unnecessary operation of the exhaust pressure adjusting means after the state is attained is suppressed. As a result, the exhaust pressure adjusting means is controlled to the minimum necessary, and the adverse effect on the traveling performance due to the control of the exhaust pressure adjusting means can be suppressed as much as possible, and the control reliability is improved. Will do.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of an exhaust control system for an engine according to the present invention. As shown, an intake passage 2 and an exhaust passage 3 are connected to a cylinder head 1a of an engine 1, respectively. At the same time, in the intake passage 2,
An air flow meter 4 and a surge tank 5 are provided from the upstream side. The exhaust passage 3 is provided with a first catalyst converter 6 and a second catalyst converter 7 from the upstream side, respectively. Components (HC, CO) in exhaust gas discharged to the environment
Is oxidized or NOx is reduced to purify the exhaust gas.

In the present embodiment, a shutter valve 8 for opening and closing the passage 3 is provided in the exhaust passage 3 downstream of the second catalyst converter 7 so as to be openable and closable. A bypass passage 9 that connects the upstream and downstream exhaust passages 3 is formed, and a bypass valve 10 that opens and closes the passage 9 is provided in the bypass passage 9 to be openable and closable.

On the other hand, a vacuum chamber 13 is connected to the surge tank 5 via an intake negative pressure introducing passage 12 in which a check valve 11 is interposed. 14 and second negative pressure passage 1
The diaphragm-type first and second actuators 16 and 17 are connected to each other via the reference numeral 5. The first actuator 16 and a rotary arm 8a provided integrally with the shutter valve 8 are connected by a link 18, and a rotary arm provided integrally with the second actuator 17 and the bypass valve 10. 10a are connected by a link 19.

Further, in the middle of the first negative pressure passage 14,
The first actuator 16 has the vacuum chamber 13
Before the engine 1 is started, atmospheric pressure is introduced into the first actuator 16 through the solenoid valve 20, and the shutter valve 8 is actuated by the actuator 16. Is kept fully open, and the engine 1
Is started, the solenoid valve 20 is switched, and the intake negative pressure is introduced into the first actuator 16 via the solenoid valve 20, whereby the first actuator 16 operates against the coil spring 16a. Thus, the shutter valve 8 is driven to a fully closed state.

In the second negative pressure passage 15, a duty solenoid valve 21 for applying a negative pressure of intake air from the vacuum chamber 13 to the second actuator 17 is provided.
Before the engine 1 is started, the atmospheric pressure is introduced into the second actuator 17 via the duty solenoid valve 21, and the bypass valve 10 is maintained in a fully closed state by the actuator 17. After the engine 1 is started, the duty solenoid valve 21 is driven to
The negative pressure of the intake air is introduced into the second actuator 17 via the second actuator 17, whereby the second actuator 17 operates against the coil spring 17 a, and the opening of the bypass valve 10 is adjusted. Has become.

Further, the second catalyst converter 7
A pressure sensor 23 is connected to the exhaust passage 3 on the downstream side through a communication passage 22.
The exhaust pressure in the exhaust passage 3 on the downstream side of the catalyst converter 7 is detected.

The shutter valve 8 allows an appropriate amount of exhaust gas to flow even when the shutter valve 8 is fully closed.

Although not shown, an air cleaner is connected to the intake passage 2 upstream of the air flow meter 4 and a silencer is connected to the exhaust passage 3 downstream of the shutter valve 8. ing.

In addition to the above configuration, in the present embodiment, a signal indicating the amount of intake air from the air flow meter 4, a signal indicating the exhaust pressure from the pressure sensor 23, and an engine speed from the rotation sensor 24 The control unit 26 is provided with a signal indicating the number of the engine and a signal indicating the engine cooling water temperature from the water temperature sensor 25. The control unit 26 is provided with a signal indicating the intake air amount, in other words, the engine load. A fuel injection valve (not shown) provided in the cylinder head 1a calculates an intake air amount per cycle based on the engine speed and a signal indicating the engine speed, so that the fuel injection amount is in accordance with the engine load. )) And set the fuel injection time,
The air flow meter 4 and the sensors 23, 24, 2
The operation of the shutter valve 8 or the bypass valve 10 is controlled based on the signal from the shutter valve 5 so that the target exhaust pressure becomes a target exhaust pressure corresponding to the operation state of the engine.

Next, the main control operation of the exhaust pressure by the control unit 26 will be described with reference to the flowchart shown in FIG. 2. First, at step S1, the air flow meter 4 and the sensors 23, 24 , 25, and at step S2, the engine speed N and the fuel injection time T corresponding to the engine load are determined based on the input signals.
n, the actual exhaust pressure Pe in the exhaust passage 3 upstream of the shutter valve 8 and the engine coolant temperature Wt are calculated. Next, at step S3, the engine cooling water temperature W
It is determined whether or not the engine 1 has just been started based on the time t. When it is determined that the engine 1 has been started, that is, immediately after the start, in step S4, the actual exhaust pressure Pe becomes
It is determined whether or not the value is greater than a predetermined value Pe ′, and when the determination is NO, that is, the actual exhaust pressure Pe is determined.
Is smaller than the predetermined value Pe ', step S5
Then, the control time T is calculated from a control map showing the relationship between the engine water temperature Wt and the control time T for controlling the operation of the shutter valve 8 shown in FIG. Then, after setting the flag F to 1 in step S6, it is determined in step S7 whether or not the time is within the control time T from the start of the engine.
When the determination is YES, that is, when it is within the control time T, in step S8, the solenoid valve 2
The exhaust pressure is increased by closing the shutter valve 8 provided in the exhaust passage 3 by energizing the solenoid valve 20 and introducing the intake negative pressure to the first actuator 16 via the solenoid valve 20.

When NO is determined in step S3 or YES is determined in step S4, the control is not performed on the shutter valve 8 and the flag F is set to 0 in step S9. I do. Also, if the determination in step S7 is NO, the control for the shutter valve 8 is not performed and the flag F is set to 0 in step S9, and the routine returns.

In this manner, immediately after the start of the engine 1, as shown in FIG. 5, the shutter valve 8 is fully closed until a predetermined control time T elapses after the start, whereby In particular, when the engine is cold immediately after the start, in which the emission of unburned components becomes remarkable, the exhaust passage 3 is narrowed and the exhaust pressure rises, so that the emission of unburned components is reduced. Further, since the shutter valve 8 is fully closed and the exhaust pressure is increased, the temperature in the exhaust passage 3 rises,
As a result, the reburnability of the exhaust gas is improved, and the first,
The second catalyst converters 6, 7 can be activated at an early stage, and the purification performance of exhaust gas is improved.

When the actual exhaust pressure Pe is higher than a predetermined value Pe ', that is, when the first and second catalyst converters 6 and 7 are clogged, or the actual exhaust pressure Pe is some other cause. When Pe becomes abnormally high, or when, for example, the actual exhaust pressure Pe is high in a high-load high-rotation operation state where high output is required, the shutter valve 8 is opened without being controlled. As a result, when the actual exhaust pressure Pe is higher than the predetermined value Pe ', the adverse effect of controlling the shutter valve 8 in the closing direction is prevented.

Next, the control operation of the exhaust pressure performed in parallel with the main control operation will be described with reference to the flowchart shown in FIG.
First, at step S10, it is determined whether the fuel injection time Tn corresponding to the engine load is equal to or less than a predetermined value Tna and the engine speed N is equal to or less than a predetermined value na. judge. That is, it is determined whether or not the operating state of the engine is in an operating state other than the high-load and high-rotation region indicated by hatching in FIG.
That is, if it is out of the high-load high-rotation region, step S11
When the flag F set during the main control operation is 1
Is determined, and when it is determined that the flag F is 1, in step S12, a target exhaust pressure Peo according to the operating state is obtained. In this case, as shown in FIG. 7, a target exhaust pressure Peo is determined from a control map in which a target exhaust pressure Peo is set in advance according to the engine speed N and a fuel injection time Tn corresponding to the engine load.
Ask for.

Next, in step S13, the control unit 26 calculates a deviation ΔP by subtracting the actual exhaust pressure Pe from the target exhaust pressure Peo. In step S14, the opening degree of the bypass valve 10 according to the deviation ΔP is calculated. Solenoid 2 for adjusting pressure
The energization time t for 1 is calculated. In this case, as shown in FIG. 8, the energization time t is calculated from a control map in which the energization time t is set in advance according to the deviation ΔP, and the energization time t is calculated when the deviation ΔP indicates a negative value. That is, it is set to be longer as the actual exhaust pressure Pe is higher than the target exhaust pressure Peo, and when the deviation ΔP is larger than a predetermined value, the duty solenoid 2
The duty ratio serving as a reference for controlling 1 is set to a maximum value. Then, in step S15, it is determined whether or not it is the control timing. If YES, the duty solenoid valve 21 is energized in step S16 to control the duty of the duty solenoid valve 21, thereby adjusting the opening of the bypass valve 10. Thus, the operation of the bypass valve 10 is feedback-controlled so that the actual exhaust pressure Pe converges to the target exhaust pressure Peo.

When NO is determined in step S10, that is, in the high-load and high-speed rotation region indicated by hatching in FIG. 6, the duty solenoid 2 is turned on in step S17.
The energization time t for 1 is set to the maximum value, and the bypass valve 10 is fully opened. When the determination is NO in step S11, the process returns without executing the control for the bypass valve 10.

As described above, in an operation state other than the high load / high rotation region, as shown in FIG. 5, the unburned components are reduced and the running performance is prevented from being reduced together with the shutter valve 8 within a predetermined control time T. The operation of the bypass valve 10 is feedback-controlled so that the actual exhaust pressure Pe converges to a preset target exhaust pressure Peo so that the actual exhaust pressure P Pe is more precisely controlled, and the controllability is improved, so that it is possible to achieve both reduction of unburned components and prevention of decrease in running performance according to the operating state.

Also, regardless of the assembly error of the bypass valve 10, the amount of carbon attached to the valve 10, or the operating characteristics of the second actuator 17, the actual exhaust pressure Pe is always equal to the target exhaust pressure Peo. As a result, the controllability of the operation of the bypass valve 10 is further improved by feedback control.

Further, in a high-load and high-speed region where high output is required, the bypass valve 10 is fully opened,
The rise of the actual exhaust pressure Pe is suppressed to a minimum, and the bypass valve 10 is controlled in a high-load high-speed operation region where the exhaust pressure rises, as in the case where the opening degree of the bypass valve 10 is controlled. The responsiveness of the operation of the valve 10 is degraded, the fluctuation of exhaust becomes remarkable, and the amount of air charged fluctuates to adversely affect the combustion performance of the engine.

In the high-load high-speed operation state where the actual exhaust pressure Pe increases, in other words, the exhaust passages 3 upstream and downstream of the shutter valve 8 connected to the bypass passage 9.
In the operation state in which the temperature difference is large, the bypass valve 10 is fully opened, so that the temperature difference is reduced, thereby suppressing the thermal deformation or thermal fatigue of the shutter valve 8 or the bypass valve 10. Will be done.

In particular, in the first embodiment, a bypass valve 9 that opens and closes the bypass passage 9 is provided in a bypass passage 9 that connects the exhaust passage 3 on the upstream side and the downstream side of the shutter valve 8. Since the actual exhaust pressure Pe is feedback-controlled by the valve 10, the drive for driving the bypass valve 10 is smaller than when the operation of the shutter valve 8 provided in the exhaust passage 3 is feedback-controlled. The force can be reduced, and the second actuator 17 for driving the valve 10 can be reduced in size, so that the bypass valve 10 can be controlled with a small driving force, and the operation of the bypass valve 10 can be reduced. The response is improved, and the controllability is improved.

In the first embodiment, the target exhaust pressure Peo set according to the operating state of the engine is set.
A case has been described in which the operation of the bypass valve 10 is feedback-controlled so that the actual exhaust pressure Pe converges. However, the feedback control of the opening of the shutter valve 8 allows the actual exhaust pressure Peo to be reduced to the target exhaust pressure Peo. Needless to say, the present invention also includes a concept of converging the exhaust pressure Pe.

FIG. 9 shows a second embodiment of an engine exhaust control apparatus according to the present invention. As shown, an intake passage 32 and an exhaust passage 33 are connected to a cylinder head 31a of an engine 31, respectively. In the intake passage 32, an air flow meter 34 and a surge tank 35 are provided from the upstream side.
3, the first catalyst converter 36 and the second catalyst converter 37 are provided from the upstream side, respectively, as in the first embodiment.

Further, the second catalyst converter 3
A shutter valve 38 that opens and closes the passage 33 is provided in the exhaust passage 33 downstream of the shutter 7 and a bypass passage 39 that connects the exhaust passage 33 upstream and downstream of the shutter valve 38 is formed. In the bypass passage 39, a bypass valve 40 for opening and closing the passage 39 is provided to be openable and closable. The surge tank 35 is connected to the vacuum chamber 4 via an intake negative pressure introducing passage 42 in which a check valve 41 is interposed.
The first and second diaphragm type actuators 46 and 47 are connected to the chamber 43 via a first negative pressure passage 44 and a second negative pressure passage 45, respectively. A rotating arm 38a provided integrally with the first actuator 46 and the shutter valve 38
Are connected by a link 48, and the second
An actuator 47 and a rotary arm 40 a provided integrally with the bypass valve 40 are connected by a link 49.

In the middle of the first negative pressure passage 44, there is provided a solenoid valve 50 for applying a negative pressure of the intake air from the vacuum chamber 43 to the first actuator 46. Before the start of the engine 31, the solenoid valve 50 is provided. Atmospheric pressure is introduced into the first actuator 46 through the valve 50, and the shutter 46 is maintained in the fully open state by the actuator 46, and the engine 31
Is started, the solenoid valve 50 is switched, and the intake negative pressure is introduced into the first actuator 46 via the solenoid valve 50, whereby the first actuator 46 operates against the coil spring 46a. Thus, the shutter valve 38 is driven to a fully closed state.

In the second negative pressure passage 45, a duty solenoid valve 51 for applying a negative pressure of intake air from the vacuum chamber 43 to the second actuator 47 is provided.
Is provided, and before the engine 31 is started,
Atmospheric pressure is introduced to the second actuator 47 via the duty solenoid valve 51,
As a result, the bypass valve 40 is maintained in the fully closed state, and after the engine 31 is started, the duty solenoid valve 51 is driven, and the intake negative pressure is introduced into the second actuator 47 via the solenoid valve 51, Accordingly, the second actuator 47 operates against the coil spring 47a, and the opening of the bypass valve 40 is adjusted.

Further, the second catalyst converter 3
7, a pressure sensor 53 is connected via a communication passage 52 to the exhaust passage 33, and the exhaust passage 3 downstream of the second catalyst converter 37 is connected by the pressure sensor 53.
The exhaust pressure in the pump 3 is detected.

The shutter valve 38 allows an appropriate amount of exhaust gas to flow even when the shutter valve 38 is fully closed, as in the first embodiment.

In addition to the above configuration, in the second embodiment, a signal indicating the amount of intake air from the air flow meter 34, a signal indicating the exhaust pressure from the pressure sensor 53, A signal indicating the engine speed, a signal indicating the engine cooling water temperature from the water temperature sensor 55, and the exhaust passages 33 provided on the upstream and downstream sides of the second catalyst converter 37, respectively, and flow through the exhaust passages 33. Signals from the temperature sensors 56a and 56b for detecting the temperature of the exhaust gas are provided in the exhaust passages 33 on the upstream and downstream sides of the second catalyst converter 37, respectively. Each O ₂ temperature sensor 57 for detecting oxygen concentration
a and 57b are provided. The control unit 58 is provided based on a signal indicating the intake air amount, in other words, a signal indicating the engine load and the engine speed. The amount of intake air per cycle is calculated, and the cylinder head 31a is adjusted so that the fuel injection amount is in accordance with the engine load.
A fuel injection valve (not shown) provided therein sets a fuel injection time, and sets a target according to the operating state of the engine 31 based on signals from the air flow meter 34 and the sensors 53 to 57a and 57b. The operation of the shutter valve 38 or the bypass valve 40 is controlled so that the exhaust pressure is obtained.

Next, the control unit 58
FIG. 10 is a flowchart showing the main control operation of the exhaust pressure.
Explaining based on the chart, this control unit
First, in step S20, the air flow
Data 34 and each of the sensors 53 to 57a and 57b.
Is input, and in step S21, each of the input signals
Based on the engine speed N and the fuel
Injection time Tn, upstream of the shutter valve 8
The actual exhaust pressure Pe in the exhaust passage 33 and the engine
The cooling water temperature Wt is calculated. Next, in step S22,
Is detected by each of the temperature sensors 56a and 56b.
Exhaust gas temperature before and after the second catalyst converter 37
T₁, T _TwoAre calculated, and in step S23, the second key
Exhaust temperature T after passing through catalyst converter 37_Two
Before passing through the second catalyst converter 37
Exhaust temperature T₁Is subtracted to calculate the temperature difference ΔT
After that, in step S24, the deterioration degree determination described in detail later
Control, and then, in step S25, the temperature difference ΔT
Changes the activation state of the second catalyst converter 37
Predetermined reference judgment temperature as a reference for judgment
It is determined whether it is higher than Ta. And when NO,
That is, the second catalyst converter 37 is still active.
For this, the catalyst converter
Oxidation is not sufficiently performed within 37, and the temperature difference ΔT is small.
If not, in step S26, the same as in the first embodiment is performed.
As shown in FIG. 4, the engine water temperature Wt and the shutter
6 shows a relationship with a control time T for controlling the operation of the valve 38.
The control time T is calculated from the control map. And step
In step S27, after setting the flag F to 1,
S28 Whether the time is within the control time T from the start of the engine
Is determined, that is, when the determination is YES, that is, within the control time T
In step S29, the solenoid valve
Power to the valve 50 and the first
By introducing the intake negative pressure to the actuator 46,
The shutter valve 38 provided in the exhaust passage 33 is fully closed.
The exhaust pressure is increased by the state.

When the determination in step S25 is YES, that is, when the second catalyst converter 37 is already activated, the oxidizing action is sufficiently performed in the catalyst converter 37. If the temperature difference ΔT is large, the control is not performed on the shutter valve 38, the flag F is set to 0 in step S30, and the routine returns. Is not performed, the flag F is set to 0 in step S30, and the routine returns. Also, in the second embodiment,
The control operation shown in FIG. 3 is configured to be executed in parallel with the main control.

Here, the control operation of the deterioration degree judging control executed during the main control operation will be described with reference to the flowchart shown in FIG. 11. First, at step S31, the control unit 58 first controls each O ₂ sensor. The signals from 57a and 57b are input, and then, in step S32, the output waveforms of the electric signals from the O ₂ sensors 57a and 57b are compared. In this case, when the degree of deterioration of the second catalyst converter 37 is large, the output waveforms of the electric signals from the two O ₂ sensors 57a and 57b greatly differ, and the second catalyst converter 3
7 is small, the two O ₂ sensors 57
It is generally known that the output waveforms of the electric signals from the signals a and 57b do not differ so much, and it is possible to determine the degree of deterioration of the second catalyst converter 37 based on this characteristic. In step S33, the output waveforms of the electric signals from the two O ₂ sensors 57a and 57b are compared based on the above characteristics, and when the determination is YES, that is, when the waveform difference is large and the second catalyst converter 3
When it is determined that the degree of deterioration of No. 7 is large, in step S34, the reference determination temperature Ta is corrected in a direction to be reduced according to the degree of deterioration based on the control map shown in FIG. This is because, as the degree of deterioration of the second catalyst converter 37 progresses, the second catalyst converter 3
The oxidation effect in the exhaust gas 7 decreases, and the exhaust gas temperature T ₁ before passing through the second catalyst converter 37 and the exhaust gas temperature T ₂ after passing through the second catalyst converter 37.
In view of this tendency, the reference determination temperature Ta is corrected so that the activation state of the second catalyst converter 37 can be determined satisfactorily in consideration of this tendency.

In this manner, immediately after the start of the engine 31, as in the first embodiment, the shutter valve 38 is fully closed until a predetermined control time T has elapsed after the start, and the unburned fuel is discharged. When the engine is cold immediately after the start, in which the emission of components is remarkable, the exhaust passage 33 is narrowed to increase the exhaust pressure, thereby reducing the emission of unburned components. Further, the shutter valve 38 is fully closed and the exhaust pressure is increased, so that the temperature in the exhaust passage 33 rises.
The reburnability of the exhaust is improved, and the first and second catalyst converters 36 and 37 can be activated at an early stage, so that the purification efficiency of the exhaust is improved.

In particular, according to the second embodiment, the temperature difference ΔT before and after the second catalyst converter 37 provided in the exhaust passage 33 is detected by each of the temperature sensors 56a and 56b, and based on this temperature difference ΔT. Thus, the activation state of the second catalyst converter 37 is determined, and after the second catalyst converter 37 is activated,
Control of the shutter valve 38 and the bypass valve 4
The feedback control of 0 is not performed, so that the unnecessary operation of the shutter valve 38 and the bypass valve 40 after the contact second catalyst converter 37 is in an active state in which the unburned component can be satisfactorily purified can be prevented. Will be suppressed. As a result, the exhaust pressure is controlled to a necessary minimum, so that the adverse effect on the traveling performance caused by the exhaust pressure can be suppressed as much as possible, and the reliability of the control is improved.

[0057]

As described above, according to the first aspect of the present invention, the actual exhaust pressure is set to a predetermined target exhaust pressure so as to achieve both reduction of unburned components and prevention of decrease in running performance. The operation of the exhaust pressure adjusting means is feedback-controlled so as to converge, whereby the actual exhaust pressure is more precisely controlled and its controllability is improved, and the actual exhaust pressure is improved according to the operating state. It is possible to achieve both the reduction of the unburned component and the prevention of the decrease in the traveling performance, and at the same time, irrespective of the degree of deterioration of the exhaust pressure adjusting means or the operating characteristics of the actuator for driving the exhaust pressure adjusting means. By performing feedback control so that the actual exhaust gas has the target exhaust pressure, the controllability is further improved.

Further, the cooling machine within a predetermined period after the engine is started.
At the time , the operation of the exhaust pressure control means is feedback-controlled so that the actual exhaust pressure becomes the target exhaust pressure, whereby, particularly when the engine is cold, the emission of the unburned components becomes significant. Purification performance is further improved.

Further, according to the second invention, when the actual exhaust pressure detected by the exhaust pressure detecting means is high, the feedback control of the exhaust pressure adjusting means is inhibited by the control inhibiting means. Accordingly, it is possible to prevent an adverse effect caused by controlling the operation of the exhaust pressure adjusting means in a high-load high-rotation operation region where the actual exhaust pressure increases.

In particular, according to the third aspect , the target value setting means sets the optimum target value of the exhaust pressure according to the operating condition, and adjusts the exhaust pressure so that the actual exhaust pressure converges to the target value. Since the operation of the means is feedback-controlled, the controllability of the exhaust pressure control for achieving both the reduction of the unburned components and the prevention of the decrease in the traveling performance is further improved.

[0061]

Further, according to the fourth aspect of the present invention, the actual exhaust pressure is controlled by the bypass passage opening / closing means provided in the bypass passage communicating the exhaust passage on the upstream side and the downstream side of the exhaust pressure adjusting means for opening / closing the bypass passage. Is controlled in a feedback manner, so that the driving force for driving the bypass passage opening / closing means is reduced as compared with the case where the exhaust pressure adjusting means provided in the exhaust passage is controlled, and the opening / closing means is Since the actuator for driving can be reduced in size, the bypass passage opening / closing means can be controlled with a small driving force, and the responsiveness and controllability of the operation are improved.

According to the fifth aspect , the temperature detecting means detects a temperature difference between before and after the catalytic converter provided in the exhaust passage, and based on the temperature difference, the active state determining means determines the active state of the catalytic converter. After the catalytic converter is activated, the feedback control of the exhaust pressure adjusting means is prohibited by the control prohibiting means, whereby the catalytic converter can clean the unburned component satisfactorily. Unnecessary operation of the exhaust pressure adjusting means after the state is attained is suppressed. As a result, the exhaust pressure adjusting means is controlled to the minimum necessary, and the adverse effect on the traveling performance due to the control of the exhaust pressure adjusting means can be suppressed as much as possible, and the control reliability is improved. Will do.

[Brief description of the drawings]

FIG. 1 is an overall system diagram of an engine exhaust control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating an exhaust pressure control operation immediately after the engine is started.

FIG. 3 is a flowchart illustrating an exhaust pressure control operation according to an operation state.

FIG. 4 is a control map showing a relationship between an engine cooling water temperature and a shutter valve control time.

FIG. 5 is a time chart showing an operation state of a shutter valve and a bypass valve.

FIG. 6 is a graph showing a control region by the exhaust control device.

FIG. 7 is a control map showing a target exhaust pressure set based on a relationship between an engine speed and a fuel injection time.

FIG. 8 is a control map showing a relationship between a deviation of an actual exhaust pressure from a target exhaust pressure and an energizing time to a bypass valve.

FIG. 9 is an overall system diagram of an engine exhaust control device according to a second embodiment.

FIG. 10 is a flowchart showing a main control operation of exhaust pressure control by the exhaust control device of the second embodiment.

FIG. 11 is a flowchart showing a deterioration degree determination control operation during a main control operation.

FIG. 12 is a graph showing the relationship between the deterioration degree of the catalyst converter used for the deterioration degree determination control and the reference determination temperature.

[Explanation of symbols]

 1, 31 Engine 3, 33 Exhaust passage 7, 37 Second catalyst converter 8, 38 Shutter valve 9, 39 Bypass passage 10, 40 Bypass valve 16, 46 First actuator 17, 47 Second actuator 20, 50 Solenoid valve 21 , 51 Duty solenoid valve 23, 53 Pressure sensor 26, 58 Control unit 56a, 56b Temperature sensor

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F01N 3/28 301 F01N 3/28 301B (56) References JP-A-1-208514 (JP, A) Jpn. (JP, U) Japanese Utility Model 3-10021 (JP, U) Japanese Utility Model 1-1115826 (JP, U) Japanese Utility Model 3-21533 (JP, U) Japanese Utility Model 4-111540 (JP, U) 58) Fields surveyed (Int.Cl. ⁷ , DB name) F02D 9/00-11/10 F02D 41/00-41/40

Claims (5)

(57) [Claims] 1. A exhaust gas control apparatus of an engine so as to reduce the emission of unburned components by adjusting the exhaust pressure of the engine according to operating conditions, operation of the engine
Operating state detecting means for detecting a state;
Within a predetermined period after starting the engine based on the signal from the
A period determining means for determining whether or not the engine is cold; an exhaust pressure adjusting means arranged in the exhaust passage for adjusting exhaust pressure; and an exhaust pressure arranged in an exhaust passage upstream of the exhaust pressure adjusting means. a catalytic converter pressure to purify the unburned components in the adjusted exhaust gas by adjusting means, which is adjusted by the exhaust pressure adjusting means, and the exhaust pressure detecting means for detecting the pressure of the exhaust gas upstream from the adjustment means, the Period judge
When the engine is cold within a predetermined period after starting the engine,
When it is determined, the actual exhaust pressure detected by the exhaust pressure detecting means is compared with a target exhaust pressure set in advance so that the exhaust pressure increases, and the actual exhaust pressure is compared with the target exhaust pressure. Control means for feedback-controlling the operation of the exhaust pressure adjusting means so as to converge to the pressure. 2. Exhaust gas detected by exhaust pressure detecting means.
When the pressure is higher than a predetermined value, the control
Prohibits feedback control of exhaust pressure adjustment means by step
Control prohibiting means is provided.
The exhaust control device for an engine according to claim 1. 3. The operating state detected by the operating state detecting means.
Target value setting means for setting the target value of the exhaust pressure according to
The control means is provided to be detected by the exhaust pressure detecting means.
Set by the actual exhaust pressure and the target value setting means.
The actual exhaust pressure to the target value.
Feedback the operation of the exhaust pressure adjustment means so that
The engine according to claim 1, wherein the engine is controlled.
Exhaust control device. 4. The exhaust pressure of the engine is changed according to the operating condition.
Adjust to reduce emission of unburned components
An exhaust control device for the engine,
Unburned fuel that detects the state where unburned components are discharged into the exhaust passage
And the unburned component is discharged by the detecting means.
Exhaust pressure to adjust the exhaust pressure when the
Air pressure adjusting means, and upstream and downstream of the exhaust pressure adjusting means
A bypass passage communicating the exhaust passage with the
A bypass passage opening / closing means for opening / closing the passage, and the exhaust pressure
Detecting the exhaust pressure of the exhaust passage upstream of the adjusting means;
Exhaust pressure detecting means, and detecting by the exhaust pressure detecting means
Set actual exhaust pressure and preset target exhaust pressure
And converge the actual exhaust pressure to the target exhaust pressure.
Feed the operation of the bypass passage opening / closing means
Control means for performing back control is provided.
Engine exhaust control device. 5. A method for detecting temperatures before and after a catalytic converter.
Temperature detecting means, and a temperature detected by the temperature detecting means
Determine the activation state of the catalytic converter based on the difference
Activation state determining means, and the catalytic converter
When the activation state of the data is determined,
Control prohibition for prohibiting feedback control of pressure adjustment means
And means are provided.
On-board engine exhaust control device.