JP3313752B2 - 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 control system for an engine, and more particularly to an exhaust control system for an engine in which the exhaust pressure of the engine is adjusted to reduce the emission of unburned components.

[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 passage cross-sectional area of the exhaust pipe, thereby reducing the engine exhaust. 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]

As described above, when the exhaust pressure is adjusted by an on-off valve provided in the exhaust passage to reduce the discharge of unburned components, the exhaust pressure is increased. However, if the exhaust pressure is increased during high-load high-speed rotation requiring high output, for example, the combustion performance of the engine is adversely affected, and the output of unburned components is reduced. The performance will be reduced, and the running performance will be deteriorated. As described above, it is difficult to control the exhaust pressure so that the reduction of the unburned components and the prevention of the decrease in the traveling performance can be achieved at the same time. For this reason, simply adjusting the exhaust pressure can reduce the discharge of the unburned components. It could not be reduced effectively.

Accordingly, the present invention provides an engine emission control device configured to reduce the emission of unburned components by adjusting the exhaust pressure of the engine, thereby more effectively reducing the emission of the unburned components. The purpose is to:

[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”)
A first aspect of the present invention relates to an exhaust control system for an engine in which the exhaust back pressure of the engine is adjusted to reduce the emission of the unburned components. Unburned component discharge state detecting means for detecting, exhaust pressure adjusting means for adjusting the pressure of exhaust gas in a rising direction when the state of unburned component discharge is detected by the detecting means, and exhaust gas pressure by the adjusting means There intake when being adjusted, intake by variably adjusting the opening and closing timing of the exhaust valve, opening and closing timing control means for increasing the overlapping amount of the valve opening period of the exhaust valve, exhaust pressure
If the force is greater than the preset pressure,
Increased the amount of overlap during the valve opening period
And means for not performing the operation.

The invention according to claim 2 of the present application (hereinafter referred to as “the invention”)
The second invention) is a valve closing timing for delaying the closing timing of the exhaust valve when the exhaust pressure is adjusted in the upward direction by the exhaust pressure adjusting means, instead of the opening / closing timing control means in the first invention. Adjustment means is provided , and exhaust
When the pressure is higher than a preset pressure, the exhaust valve
Means for preventing execution of delaying the valve closing timing .

Further, the invention according to claim 3 of the present application (hereinafter referred to as “the invention”)
A third aspect of the present invention is directed to valve opening timing adjustment that advances the valve opening timing of the intake valve when the exhaust pressure is adjusted by the exhaust pressure adjusting means in place of the opening / closing timing control means in the first aspect. Means , together with the exhaust pressure
Is larger than a preset pressure, the intake valve is opened.
A feature is provided in which means for preventing the valve timing from being advanced is provided .

Further, the invention according to claim 4 of the present application (hereinafter referred to as “the invention”)
According to a fourth aspect of the present invention, in the same manner as in the first aspect of the invention, in the engine exhaust control device configured to reduce the emission of unburned components by adjusting the back pressure of the engine, the operating state of the engine is detected. Operating state detecting means, period determining means for determining whether or not the engine is within a predetermined period after engine start based on a signal from the detecting means, and determining that the engine is within a predetermined period after engine starting by the determining means Exhaust pressure adjusting means for adjusting the exhaust pressure in a rising direction when the exhaust pressure is adjusted, and variably adjusting the opening / closing timing of the exhaust valve when the exhaust pressure is adjusted by the adjusting means. Open / close timing control means to increase the amount of overlap during the valve opening period, and exhaust pressure is preset
If the pressure is higher than the specified pressure, the intake and exhaust valves are open
Hands that do not increase the amount of overlap
A step is provided.

[0011]

According to the first to fourth aspects of the present invention, when the state in which the unburned component is discharged to the exhaust passage of the engine is detected by the unburned component discharge state detecting means, the exhaust pressure is increased by the exhaust pressure adjusting means. And the exhaust pressure is increased, thereby reducing the discharge of unburned components from the exhaust passage.

Further, by increasing the exhaust pressure,
As the temperature in the exhaust passage increases, the re-combustibility of the exhaust gas improves, and the catalytic converter provided in the exhaust passage can be activated at an early stage. It will be further improved.

In particular, according to the first aspect of the invention, when the exhaust pressure is adjusted in the upward direction by the exhaust pressure adjusting means, the opening / closing timing control means controls the amount of overlap between the intake and exhaust valve opening periods. As a result, the amount of overlap between the end of the exhaust stroke near the top dead center of the piston and the beginning of the intake stroke increases, and the unburned fuel pushed out toward the exhaust passage at the end of the exhaust stroke The components flow back into the cylinder again, and at the end of the exhaust process, unburned components pushed out to the exhaust passage side are blown back to the intake passage side, and the unburned components are reburned in the subsequent combustion process. Will be. As a result, the unburned components are reduced, and the emission of the unburned components can be further reduced in addition to the effect obtained by increasing the exhaust pressure as described above.

According to the second aspect of the present invention, the valve closing timing of the exhaust valve is delayed, so that the amount of overlap between the opening periods of the two valves from the opening of the intake valve to the closing of the exhaust valve, ie, the amount of overlap. The amount of overlap between the end of the exhaust stroke and the beginning of the intake stroke near the top dead center of the piston increases, and the unburned components once pushed out to the exhaust passage side at the end of the exhaust stroke again enter the cylinder. Backflow, this unburned component will be reburned in the subsequent combustion process,
Since the unburned components are reduced, the emission of unburned components can be further reduced in addition to the effect of increasing the exhaust pressure as described above.

Further, according to the third aspect of the invention, the opening timing of the intake valve is advanced, so that the amount of overlap between the opening periods of the two valves from the opening of the intake valve to the closing of the exhaust valve, that is, The amount of overlap between the end of the exhaust stroke and the beginning of the intake stroke near the top dead center of the piston will increase, and the unburned components pushed out to the exhaust passage at the end of the exhaust stroke will be blown back to the intake passage, This unburned component will be reburned in the subsequent combustion step, and the unburned component will be reduced. In addition to the effect of increasing the exhaust pressure as described above, the unburned component is further reduced. Emissions can be reduced.

[0016] In particular, according to the fourth aspect, the exhaust pressure is adjusted by the exhaust pressure adjusting means within a predetermined period after the engine is started, and the exhaust pressure is increased. When the exhaust gas pressure is adjusted by the exhaust pressure adjusting means while the purifying performance of the unburned components at the time of the engine cold immediately after the start, in which the emission of the fuel component becomes remarkable, is further improved. Since the overlap amount of the intake and exhaust valves during the valve opening period is increased by the means, the unburned fuel is further increased in combination with the effect of increasing the exhaust pressure by the exhaust pressure adjusting means as in the first invention. It is possible to reduce the emission of components.

According to the fourth aspect of the present invention, when a predetermined period has elapsed after the start of the engine, the exhaust pressure is not adjusted by the exhaust pressure adjusting means.
In a high-load, high-rotation region or the like where high output is required, an adverse effect on traveling performance, which may be caused by increasing exhaust pressure, is suppressed.

[0018]

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

FIG. 1 shows an embodiment of an engine exhaust control apparatus according to the present invention. As shown in FIG. 1, a piston 3 is fitted in a cylinder 2a formed in a cylinder block 2 of the engine 1. A combustion chamber 5 is formed by the inner wall surface of the cylinder block 2, the upper surface of the piston 3, and the lower surface of the cylinder head 4 mounted above the cylinder block 2. And the exhaust passage 7 are connected to each other,
An intake valve 10 and an exhaust valve 1 that open and close intake and exhaust ports 8 and 9 that are communicated with these intake and exhaust passages 6 and 7.
1 is provided. Then, in the intake passage 6,
Air flow meter 12 and surge tank 1 from upstream
3 are provided. A first catalyst converter 14 and a second catalyst converter 15 are provided in the exhaust passage 7 from the upstream side, respectively. The first and second catalyst converters 14 and 15 provide an exhaust passage 7. The unburned components (HC, CO) in the exhaust gas discharged to the exhaust gas are oxidized or NOx is reduced to purify the exhaust gas.

In the present embodiment, a shutter valve 16 for opening and closing the passage 7 is provided in the exhaust passage 7 downstream of the second catalyst converter 15 so as to be openable and closable. A bypass passage 17 that connects the upstream and downstream exhaust passages 7 is formed, and a bypass valve 18 that opens and closes the passage 17 is provided in the bypass passage 17 so as to be openable and closable.

On the other hand, a vacuum chamber 21 is connected to the surge tank 13 via an intake negative pressure introducing passage 20 in which a check valve 19 is interposed. Diaphragm-type first and second actuators 24 and 25 are connected to each other via a second pressure passage 22 and a second negative pressure passage 23, respectively. The first actuator 24 and the rotary arm 16a provided integrally with the shutter valve 16 are connected by a link 26, and the rotary actuator provided integrally with the second actuator 25 and the bypass valve 18 18a are connected by a link 27.

Further, in the middle of the first negative pressure passage 22,
The first actuator 24 has the vacuum chamber 21
Before the engine 1 is started, atmospheric pressure is introduced into the first actuator 24 through the solenoid valve 28, and the shutter valve 16 is actuated by the actuator 24. Is maintained in the fully opened state, and after the engine 1 is started, the solenoid valve 28 is switched to introduce the intake negative pressure to the first actuator 24 via the solenoid valve 28, whereby the first
The actuator 24 operates against the coil spring 24a, so that the shutter valve 16 is driven to a fully closed state.

In the second negative pressure passage 23, a duty solenoid valve 29 for applying a negative pressure from the vacuum chamber 21 to the second actuator 25 is provided.
Before the engine 1 is started, atmospheric pressure is introduced to the second actuator 25 via the duty solenoid valve 29, and the bypass valve 18 is maintained in a fully closed state by the actuator 25. After the engine 1 is started, the duty solenoid valve 29 is driven and the solenoid valve 29
The intake negative pressure is introduced into the second actuator 25 via the second actuator 25, whereby the second actuator 25 operates against the coil spring 25a, so that the opening of the bypass valve 18 is adjusted. Has become.

The shutter valve 16 allows an appropriate amount of exhaust gas to flow even when the shutter valve 16 is fully closed.

Although not shown, an air cleaner is connected to the intake passage 6 upstream of the air flow meter 12 and a silencer is connected to the exhaust passage 7 downstream of the shutter valve 16. ing.

In this embodiment, a valve mechanism 30 for opening and closing the intake and exhaust valves 10 and 11 is provided in the cylinder head 4. The valve mechanism 30 is disposed above the cylinder head 4 and is driven by a crankshaft (not shown).
1b and suction and exhaust cams 32a and 32b provided on these camshafts 31a and 31b, and each tappet 33,
33 is in contact with the suction and exhaust cams 32a, 32b,
The rotation of these cams 32a, 32b causes the intake and exhaust valves 10, 11 at a predetermined time against a valve spring (not shown) which biases the intake and exhaust valves 10, 11 in the closing direction. The opening operation is performed.

Further, an opening / closing timing control means 3 for variably adjusting the opening / closing timing of the intake and exhaust valves 10 and 11.
4 is provided.
Are the intake and exhaust cams 32 for the camshafts 31a and 31b.
The opening and closing timings of the intake and exhaust valves 10 and 11 can be variably adjusted by changing the mounting phase of the a and 32b.

On the other hand, the second catalyst converter 1
A pressure sensor 36 is connected to the exhaust passage 7 on the downstream side of 5 through a communication passage 35, and the pressure sensor 36 detects the exhaust pressure in the exhaust passage 7 on the downstream side of the second catalyst converter 15. It has become so.

In addition to the above configuration, in the present embodiment, a signal indicating the amount of intake air from the air flow meter 12, a signal indicating the exhaust pressure from the pressure sensor 36, and an engine speed from the rotation sensor 37 A control unit 39 to which a signal indicating the number of the engine and a signal indicating the engine cooling water temperature from the water temperature sensor 38 are provided. The control unit 39 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 4 so as to calculate an intake air amount per cycle based on the engine speed and a signal indicating the engine speed, so as to obtain a fuel injection amount corresponding to the engine load. ), The air flow meter 12 and the sensors 36, 37, 3
The operation of the shutter valve 16 or the bypass valve 18 is controlled in accordance with the operation state of the engine 1 based on the signal from the controller 8 to adjust the exhaust pressure in the exhaust passage 7.

The control unit 39 includes:
During the control of the shutter valve 16 or the bypass valve 18, the opening / closing timing of the intake and exhaust valves 10, 11 is variably adjusted by controlling the opening / closing timing control means 34.

Next, the main control operation of the exhaust pressure by the control unit 39 will be described with reference to the flowchart shown in FIG. 2. First, in step S1, the air flow meter 12 and the sensors 36 and 37 are set. , 38, 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 and the engine coolant temperature Wt in the exhaust passage 7 on the upstream side of the shutter valve 16 are calculated. Next, in step S3, it is determined whether or not the engine 1 has just been started based on the engine cooling water temperature Wt. When the determination is YES, that is, when the engine 1 has just been started, the actual exhaust pressure is determined in step S4. Pe is
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
The engine water temperature Wt and the shutter valve 16 shown in FIG.
The control time T is calculated from a control map showing the relationship with the control time T for controlling the operation of the control. Then, in step S6,
After setting the flag F to 1, in step S7, it is determined whether or not it is within the control time T from the start of the engine. If determined to be YES, that is, if it is within the control time T, step S8 is performed. In the above, the solenoid valve 28 is energized, and the first
By introducing the intake negative pressure to the actuator 24,
The exhaust pressure is increased by closing the shutter valve 16 provided in the exhaust passage 7.

When NO is determined in step S3 or YES is determined in step S4, the control for the shutter valve 16 is not performed, the flag F is set to 0 in step S9, and the routine returns. I do.
Also, if the determination in step S7 is NO, the control for the shutter valve 8 is not performed and the process proceeds to step S9.
To set the flag F to 0 and return.

In this manner, immediately after the start of the engine 1, as shown in FIG. 5, the shutter valve 16 is fully closed until a predetermined control time T has elapsed since the start, whereby the shutter 1 is closed. In particular, when the engine is cold immediately after the start, in which the emission of unburned components becomes remarkable, the exhaust passage 7 is narrowed and the exhaust pressure rises, so that the emission of unburned components is reduced. Further, the exhaust pressure is increased by setting the shutter valve 16 to the fully closed state, so that the temperature in the exhaust passage 7 increases, thereby improving the re-combustibility of the exhaust gas. The second catalyst converters 14 and 15 can be activated at an early stage, and the exhaust gas purification efficiency is improved.

When the actual exhaust pressure Pe is higher than a predetermined value Pe ', ie, when the first and second catalyst converters 14 and 15 are clogged, or due to some other cause, the actual exhaust pressure Pe' is increased. 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 16 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 16 in the closing direction is prevented.

Next, the control operation of the exhaust pressure executed in parallel with the main control operation will be described with reference to the flowchart shown in FIG.
9. First, in 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 39 calculates the 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 18 according to the deviation ΔP is calculated. Solenoid 2 for adjusting pressure
9 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
9 is set to the maximum value. Then, in step S15, it is determined whether or not it is the control timing. If YES, the duty solenoid valve 29 is energized in step S16 to control the duty of the duty solenoid valve 21, thereby adjusting the opening of the bypass valve 18. Thus, the operation of the bypass valve 18 is feedback-controlled so that the actual exhaust pressure Pe converges to the target exhaust pressure Peo.

When it is determined NO in step S10, that is, in the high-load and high-rotation region indicated by hatching in FIG. 6, the duty solenoid 2 is turned on in step S17.
9 is set to the maximum value, and the bypass valve 18 is fully opened. If NO is determined in step S11, the process returns without executing the control on the bypass valve 18.

As described above, in the operation state other than the high load / high rotation range, as shown in FIG.
At the same time, within a predetermined control time T, the actual exhaust pressure Pe is converged to a preset target exhaust pressure Peo so that both reduction of unburned components and prevention of decrease in traveling performance can be achieved. The operation of the bypass valve 18 is feedback-controlled, whereby the actual exhaust pressure Pe is more precisely controlled and its controllability is improved, and the unburned component is reduced according to the operation state. And prevention of a decrease in running performance can be achieved.

Also, regardless of the assembly error of the bypass valve 18, the amount of carbon attached to the valve 18, or the operating characteristics of the second actuator 25, the actual exhaust pressure Pe is always equal to the target exhaust pressure Peo. As described above, the feedback control of the operation of the bypass valve 18 further improves the controllability.

Further, in a high-load and high-speed region where high output is required, the bypass valve 18 is fully opened,
The rise of the actual exhaust pressure Pe is suppressed to a minimum, and the bypass valve 18 is controlled in a high-load high-speed operation region where the exhaust pressure is increased, as in the case where the opening degree of the bypass valve 18 is controlled. As a result, the responsiveness of the operation of the valve 18 is deteriorated, the fluctuation of the exhaust gas becomes remarkable, and the air filling amount fluctuates to adversely affect the combustibility of the engine. If a predetermined control time T has elapsed after the start of the engine 1, the shutter valve 16 or the bypass valve 18
The exhaust pressure is not adjusted by the above-described method, thereby suppressing the adverse effect on the traveling performance that may be caused by increasing the exhaust pressure in a high-load and high-speed region where high output is required.

Particularly, in this embodiment, a bypass valve 17 for opening and closing the bypass passage 17 is provided in a bypass passage 17 communicating the exhaust passage 7 on the upstream side and the downstream side of the shutter valve 16. As a result, the actual exhaust pressure Pe is feedback-controlled, so that the shutter valve 1
6, the driving force for driving the bypass valve 18 is reduced, and the size of the second actuator 25 for driving the valve 18 can be reduced. Thus, the bypass valve 18 can be controlled with a small driving force, and the responsiveness of the operation is improved, and the controllability is improved.

In this embodiment, the feedback control of the operation of the bypass valve 18 is performed so that the actual exhaust pressure Pe converges to the target exhaust pressure Peo set according to the operating state of the engine. As described above, it is needless to say that the present invention includes a concept that the actual exhaust pressure Pe is converged to the target exhaust pressure Peo by feedback-controlling the opening degree of the shutter valve.

Next, the intake and exhaust valves 10, which are executed in parallel with the exhaust pressure control, which is a characteristic part of the present embodiment, are described.
The control operation for variably adjusting the opening / closing timing of No. 11 is shown in FIG.
The control unit 39 will be described with reference to the flowchart shown in FIG. 3. First, in step S20, the control unit 39 sets the flag F
Is determined to be 1 or not, and when YES is determined, that is, the flag F is set to 1 and the shutter valve 1
6 or the operation of the bypass valve 18 is controlled, the operation of the intake valve 10 is controlled by the opening / closing timing control means in step S21.
Is executed to advance the valve opening timing of the exhaust valve 11 or to delay the valve closing timing of the exhaust valve 11.

Then, as shown in FIG.
When the closing timing of the exhaust valve 11 is delayed from the normal state shown by the solid line a, as shown by the dotted line a ', with respect to the normal opening and closing operation of the exhaust valve 11 and the intake valve 10 shown by Then, the overlap amount V 'in the open period of the two valves from when the intake valve 10 is opened to when the exhaust valve 11 is closed is larger than the overlap amount V in the normal state. That is, the amount of overlap between the end of the exhaust stroke near the top dead center of the piston 3 and the beginning of the intake stroke increases, and the unburned components once pushed out to the exhaust passage side at the end of the exhaust stroke are again reduced. Cylinder 2a
This unburned component is recombusted in the subsequent combustion process, so that the unburned component is reduced. In addition to the effect of increasing the exhaust pressure as described above, Emission of unburned components can be further reduced.

As shown in FIG. 11, in contrast to the normal opening / closing operation of the exhaust valve 11 and the intake valve 10 indicated by solid lines a and b, the opening of the intake valve 10 is indicated by the dashed line b '. When the valve timing is advanced from the normal state shown by the solid line B, the overlap amount V 'of the open period of the two valves from when the intake valve 10 is opened to when the exhaust valve 11 is closed is reduced. It will be larger than the overlap amount V. That is, the amount of overlap between the end of the exhaust stroke near the top dead center of the piston 3 and the beginning of the intake stroke increases, and the unburned components that are pushed out to the exhaust passage side at the end of the exhaust stroke increase. Is blown back to the side, and this unburned component will be reburned in the subsequent combustion process, and the unburned component will be reduced,
As described above, the emission of unburned components can be further reduced in addition to the effect of increasing the exhaust pressure.

The control for delaying the closing timing of the exhaust valve 11 and the control for accelerating the opening timing of the intake valve 10 may be executed simultaneously.

[0047]

As described above, according to the first to fourth aspects of the present invention, when it is detected that the unburned components are discharged into the exhaust passage of the engine, the exhaust pressure is increased by the exhaust pressure adjusting means. As a result, the discharge of unburned components from the exhaust passage can be reduced, and the exhaust pressure is increased, so that the temperature in the exhaust passage rises and the reburnability of the exhaust is improved. In addition, the catalytic converter provided in the exhaust passage can be activated at an early stage, and the exhaust gas purification performance can be further improved.

In particular, according to the first aspect of the invention, when the exhaust pressure is adjusted by the exhaust pressure adjusting means, the opening / closing timing control means increases the amount of overlap between the intake and exhaust valve opening periods. The amount of overlap between the end of the exhaust stroke and the beginning of the intake stroke near the top dead center increases, and the unburned components pushed out toward the exhaust passage at the end of the exhaust stroke flow back into the cylinder again. At the end of the exhaust process, unburned components pushed out to the exhaust passage side are blown back to the intake passage side, and the unburned components are reburned in the subsequent combustion process. As a result, the unburned components are reduced, and the emission of the unburned components can be further reduced in addition to the effect obtained by increasing the exhaust pressure as described above.

According to the second aspect of the present invention, the valve closing timing of the exhaust valve is delayed, so that the amount of overlap between the opening periods of the two valves from the opening of the intake valve to the closing of the exhaust valve, that is, The amount of overlap between the end of the exhaust stroke and the beginning of the intake stroke near the top dead center of the piston increases, and the unburned components once pushed out to the exhaust passage side at the end of the exhaust stroke again enter the cylinder. Backflow, this unburned component will be reburned in the subsequent combustion process,
Since the unburned components are reduced, the emission of unburned components can be further reduced in addition to the effect of increasing the exhaust pressure as described above.

Further, according to the third aspect of the present invention, the opening timing of the intake valve is advanced, so that the amount of overlap between the opening periods of the two valves from the opening of the intake valve to the closing of the exhaust valve, that is, The amount of overlap between the end of the exhaust stroke and the beginning of the intake stroke near the top dead center of the piston will increase, and the unburned components pushed out to the exhaust passage at the end of the exhaust stroke will be blown back to the intake passage, This unburned component will be reburned in the subsequent combustion step, and the unburned component will be reduced. In addition to the effect of increasing the exhaust pressure as described above, the unburned component is further reduced. Emissions can be reduced.

In particular, according to the fourth aspect, the exhaust pressure is adjusted by the exhaust pressure adjusting means within a predetermined period after the start of the engine, and the exhaust pressure is increased. When the exhaust gas pressure is adjusted by the exhaust pressure adjusting means while the purifying performance of the unburned components at the time of the engine cold immediately after the start, in which the emission of the fuel component becomes remarkable, is further improved. Since the overlap amount of the intake and exhaust valves during the valve opening period is increased by the means, the unburned fuel is further increased in combination with the effect of increasing the exhaust pressure by the exhaust pressure adjusting means as in the first invention. It can reduce the emission of components.

Further, according to the fourth aspect of the present invention, when a predetermined period has elapsed after the start of the engine, the exhaust pressure is not adjusted by the exhaust pressure adjusting means. An adverse effect on running performance, which is a concern due to an increase in exhaust pressure in a high load rotation region or the like, is suppressed.

[Brief description of the drawings]

FIG. 1 is an overall system diagram of an engine exhaust control device according to 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 a flowchart showing an intake / exhaust valve opening / closing control operation executed by the control unit in parallel with the main control operation.

FIG. 10 is a valve lift diagram showing opening and closing timings of intake and exhaust valves.

FIG. 11 is a valve lift diagram showing opening and closing timings of intake and exhaust valves.

[Explanation of symbols]

 Reference Signs List 1 engine 7 exhaust passage 10 intake valve 11 exhaust valve 12 air flow meter 16 shutter valve 17 bypass passage 18 bypass valve 24 first actuator 25 second actuator 28 solenoid valve 29 duty solenoid valve 34 opening / closing timing control means 36 pressure sensor 37 rotation sensor 38 Water temperature sensor 39 control unit

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Claims (4)

(57) [Claims] An exhaust control device for an engine, wherein the exhaust pressure of an engine is reduced by adjusting the exhaust pressure of the engine, wherein a state in which the unburned component is discharged to an exhaust passage of the engine is detected. Unburned component discharge state detecting means, exhaust pressure adjusting means for adjusting the pressure of exhaust gas in an ascending direction when the detecting means detects a state in which unburned components are discharged, and adjusting the exhaust gas pressure by the adjusting means. intake when being adjusted, intake by variably adjusting the opening and closing timing of the exhaust valve, opening and closing timing control means for increasing the overlapping amount of the valve opening period of the exhaust valve, the exhaust gas pressure pre
If the pressure is higher than the set pressure, open the intake and exhaust valves.
Increase the amount of overlap in the valve period
Exhaust control device for an engine, characterized in that no means are provided. 2. An exhaust control system for an engine, wherein the exhaust pressure of the engine is reduced by adjusting the exhaust pressure of the engine, wherein a state in which the unburned component is discharged to an exhaust passage of the engine is detected. Unburned component discharge state detecting means, exhaust pressure adjusting means for adjusting the pressure of exhaust gas in an ascending direction when the detecting means detects a state in which unburned components are discharged, and adjusting the exhaust gas pressure by the adjusting means. Valve closing timing adjusting means for delaying the closing timing of the exhaust valve when being adjusted, and when the exhaust pressure is higher than a preset pressure
Does not delay the closing timing of the exhaust valve.
Exhaust control device for an engine, characterized in that the have means. 3. An exhaust control system for an engine, wherein the exhaust pressure of the engine is reduced by adjusting the exhaust pressure of the engine, wherein a state in which the unburned components are discharged to an exhaust passage of the engine is detected. Unburned component discharge state detecting means, exhaust pressure adjusting means for adjusting the pressure of exhaust gas in an ascending direction when the detecting means detects a state in which unburned components are discharged, and adjusting the exhaust gas pressure by the adjusting means. Valve opening timing adjusting means for accelerating the opening timing of the intake valve when being adjusted, and when the exhaust pressure is higher than a preset pressure,
An engine exhaust control device, comprising: means for preventing the opening timing of the intake valve from being advanced . 4. An exhaust control system for an engine configured to reduce the discharge of unburned components by adjusting the exhaust pressure of the engine, comprising: operating state detecting means for detecting an operating state of the engine; A period determining means for determining whether or not the engine is within a predetermined period after the engine is started based on a signal from the means; and Exhaust pressure adjusting means for adjusting in the ascending direction, and overlapping of the intake and exhaust valve opening periods by variably adjusting the opening and closing timing of the intake and exhaust valves when the exhaust pressure is adjusted by the adjusting means. Opening / closing timing control means for increasing the amount, and when the exhaust pressure is higher than a preset pressure
Increases the amount of overlap during the opening period of the intake and exhaust valves
And means for preventing the engine from being executed .