JP3513948B2 - Engine exhaust purification 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 engine exhaust gas purification apparatus having an exhaust pressure increasing mechanism for suppressing discharge of unburned components of fuel by increasing exhaust pressure after starting the engine. is there.

[0002]

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 5-231195, an exhaust shutter valve is provided in an exhaust passage of an engine, and an exhaust purification catalyst is not sufficiently activated when the engine is started. An exhaust pressure increasing mechanism for increasing the exhaust gas exhaust pressure by narrowing the opening of the exhaust shutter valve is provided, and at the end of the exhaust stroke, the unburned component of the fuel scraped up by the piston increases the exhaust pressure. There is known an engine exhaust gas purification device configured to suppress the discharge of the unburned components to the outside by pushing back to the combustion chamber side accordingly.

Further, the above exhaust gas purifying apparatus increases the amount of overlap between the intake valve and the exhaust valve when the exhaust pressure increasing mechanism is operated, so that the unburned components in the exhaust gas are introduced into the exhaust passage at the end of the exhaust stroke. The so-called internal EGR amount is increased to reburn the unburned components.

[0004]

As described above, when the internal EGR amount is increased by increasing the overlap amount between the intake valve and the exhaust valve when the exhaust pressure increasing mechanism is operated, the exhaust gas is increased. By re-combusting the unburned components in the interior, it has an advantage that the emission amount of the unburned components can be effectively reduced, but on the other hand, the combustibility of the engine may be extremely lowered with the increase of the internal EGR amount. There was an unavoidable problem.

The present invention has been made to solve the above problems, and is an exhaust emission control system for an engine capable of suppressing the discharge of unburned components of fuel without lowering the combustibility of the engine. Is intended to provide.

[0006]

The invention according to claim 1 is
When the exhaust gas purification catalyst is in the inactive state, the engine
Of an engine equipped with an exhaust pressure increasing mechanism that suppresses the discharge of unburned components of fuel by increasing the exhaust pressure for a predetermined time from the time when it is determined that the engine is in the starting state. A device, wherein when the exhaust pressure increasing mechanism is operated,
By delaying the opening timing and closing timing of the intake valve <br /> to reduce the overlap time between the intake valve and the exhaust valve.
A timing control means that control the, the back pressure increase mechanism
During operation, the intake air amount is increased to increase the intake air amount supplied to the combustion chamber.
The measuring means is provided.

[0007] The invention according to claim 2, in the exhaust purification apparatus according to claim 1, wherein the engine, during operation of the exhaust pressure increasing mechanism
The secondary air is supplied to the exhaust port .

According to a third aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the first aspect, the temperature of the engine cooling water is increased.
If the value is high, the operating time of the exhaust pressure raising mechanism will be shortened.
Change the operating time of the exhaust pressure increasing mechanism according to the cooling water temperature
It is set so that

[0009]

According to the invention described in claim 1, the exhaust pressure is increased by the exhaust pressure increasing mechanism after the engine is started, so that the discharge of the unburned component from the exhaust passage is suppressed and the exhaust pressure is increased. The internal EG is reduced by reducing the overlap time between the intake valve and the exhaust valve when rising.
The increase of R is suppressed and the combustion stability is improved. In addition, the temperature of the exhaust gas purification catalyst should be adjusted after the engine is started.
Exhaust pressure rises when exhaust pressure is low
Discharge of unburned components from the exhaust passage
Will be suppressed. Then, when the exhaust pressure rises,
The intake valve and exhaust gas are delayed by delaying the opening time of the air valve.
The overlap period with the valve decreases and the internal EGR increases.
It is suppressed, and the intake valve closing timing is delayed when the exhaust pressure rises.
This reduces the effective compression ratio of the engine.
Combustion becomes slow and the exhaust gas temperature rises
The activation of the oxidization catalyst is promoted. In addition, exhaust pressure
During the exhaust pressure rise control when the raising mechanism is activated, the intake bar
Intake air is supplied to the combustion chamber through the ipas passage, etc.
Due to the execution of the exhaust pressure increase control, etc.
The decrease in engine output is compensated for and the decrease in engine output is prevented.
Will be stopped.

According to the invention described in claim 2, the exhaust pressure is increased.
Exhaust port by the secondary air supply mechanism when the lifting mechanism operates
Since secondary air is supplied to the
The exhaust temperature is raised by actively burning the secondary air.
By raising the temperature, it promotes activation of the exhaust purification catalyst.
It becomes possible to do.

According to the invention described in claim 3, the engine is
The temperature of the cooling water in the engine is high and the engine is in a heated state.
If the time required to activate the exhaust purification catalyst is short,
If possible, the operating time of the exhaust pressure raising mechanism is short.
The exhaust throttle control is executed more than necessary because it is set.
And the temperature of the exhaust purification catalyst becomes excessively high, and
It will be prevented from worsening .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an engine exhaust gas purification apparatus according to the present invention. In the cylinder head 1 of this engine, an intake port 2 for supplying air into the combustion chamber,
An exhaust port 3 for discharging exhaust gas after combustion is formed,
An intake valve 4 and an exhaust valve 5 are provided in the intake port 2 and the exhaust port 3, and an intake passage 6 and an exhaust passage 7 are connected to the intake port 2 and the exhaust port 3.

The intake passage 6 is provided with a fuel injection valve 8 and a throttle valve 9, and an intake bypass passage 10 for bypassing the installation portion of the throttle valve 9. The intake bypass passage 10 is provided with a control valve 11 that controls the amount of air supplied to the combustion chamber of the engine by adjusting the opening area of the intake bypass passage 10.

Further, the exhaust passage 7 is provided with a secondary air supply mechanism 12 for supplying secondary air to the exhaust port 3, a pre-catalyst 13 having a small capacity, and a main catalyzer 14 having a large capacity. . In addition, the main cat 1
4, an HC adsorbent tank 15 is installed on the upstream side, and an exhaust pressure increasing mechanism 16 for increasing exhaust pressure is installed on the downstream side of the main catalyzer 14.

[0015] The secondary air supply system 12 includes an air pump 17, and a air jet nozzle 18, during operation of the back pressure increase mechanism 16, the air pump 1 7 according to a control signal output from the controller 19 In the operating state, the secondary air is blown from the air injection nozzle 18 to the exhaust port 3.

The precatalyst 13 is a three-way catalyst for purifying CO, HC and NOx, and the main catalyzer 14 is an oxidizing catalyst for mainly oxidizing C0 and HC. In addition, the HC adsorbent tank 15 contains HC
Zeolite or the like that adsorbs is disposed.

The exhaust pressure raising mechanism 16 has an exhaust shutter valve 20 provided in the exhaust passage 7, a diaphragm type actuator 21, and an intake negative pressure from a vacuum source (VAC) 22 such as a vacuum pump. And a solenoid valve 23 for displacing the exhaust shutter valve 20 to the exhaust throttle position.

Then, in response to a control signal output from the controller 19 after the engine is started, which will be described later, the solenoid valve 23 is kept in the ON state for a predetermined time, the intake negative pressure is introduced into the actuator 21 and the exhaust shutter valve 20. Is displaced to the exhaust throttle position to reduce the opening area of the exhaust passage 7 and increase the exhaust pressure.

The cylinder head 1 has a valve operating mechanism 24 for the exhaust valve 5 and an operating phase of a cam shaft and a cam pulley provided in the valve operating mechanism 24. An exhaust timing adjusting mechanism 26 having a control valve 27 for adjusting the opening / closing timing of the valve and an ignition plug 28 are provided.

As shown in FIG. 2, the controller 19 starts the engine in response to the detection signals from the starter detecting means 29 for detecting the operating state of the starter of the engine and the rotation speed detecting means 30 for detecting the engine speed. The pre-catalyst 1 is determined by determining whether or not the time set by a timer 32, which will be described later, has elapsed after the engine is started and the start determination means 31 that determines whether the pre-catalyst 1 is in the state.
3 and the main catalyzer 14 are active determining means 3 for determining whether or not the main catalytic converter 14 and the main cater 14 are in an inactive state below a preset reference temperature
3 and 3 are provided.

In addition, the controller 19 controls the exhaust shutter valve 20 of the exhaust pressure increasing mechanism 16 to the exhaust throttle position for a predetermined time after the engine is started according to the output signals of the start determining means 31 and the activation determining means 33. Of the exhaust pressure control means 34 for displacing the control valve 11 of the intake bypass passage 10 to the open position
And the secondary air control means 36 for operating the air pump 17 of the secondary air supply mechanism 12 to supply the secondary air to the exhaust port 3, and the exhaust timing adjusting mechanism 26 for opening the exhaust valve 5. Timing control means 37 for advancing the timing and the valve closing timing as compared with the normal time is provided.

The control operation of the engine exhaust gas purification apparatus constructed as described above will be described with reference to the flow chart shown in FIG. When the above control operation starts, first in step S1, after initialization,
In step S2, it is determined whether the engine is in the starting state based on the operating state of the starter and the engine speed.

If YES is determined in the above step S2, it is determined in step S3 whether an engine stall has occurred, and if YES is determined, the process returns. If it is confirmed in step S3 that no engine stall has occurred, then in step S4,
It is determined whether or not the flag A indicating that the timer 32 has been set is set to 1.

If NO in step S4, the flag A is set to 1 in step S5, and then in step S6, the timer 32 corresponding to the engine cooling water temperature is set from the table shown in FIG. The time is read and the timer 32 is set. This timer 32
The set time is set to the maximum value when the cooling water temperature of the engine is equal to or lower than the reference value W, and gradually decreases as the cooling water temperature becomes higher than the reference value W.

Next, in step S7, it is determined whether or not the timer 32 has timed out. If NO is determined, in step S8, the solenoid 23 of the exhaust pressure increasing mechanism 16 is turned on to release the exhaust pressure. In addition to executing the rising control, in step S9, the exhaust timing adjusting mechanism 26 is operated to execute timing control that advances the opening timing and closing timing of the exhaust valve 5.

Further, in step S10, intake air amount increase control is performed to open the control valve 11 of the intake bypass passage 10, and in step S11, the air pump 17 of the secondary air supply mechanism 12 is operated to activate the secondary air. To supply. Then, when YES is determined in the above step S7 and it is confirmed that the timer 32 has timed out, the timer 32 is reset in step S12.

Next, in step S13, the solenoid 23 of the exhaust pressure increasing mechanism 16 is turned off to stop the exhaust pressure increasing control, and in step S13,
At 14, the exhaust timing adjusting mechanism 26 is operated to stop the above timing control, and the opening timing and closing timing of the exhaust valve 5 are returned to normal timing.

In step S15, the control valve 11 of the intake bypass passage 10 is closed to stop the intake air amount increasing control, and in step S16, the air pump 17 of the secondary air supply mechanism 12 is stopped to stop the secondary air. Return after stopping the air supply.

As described above, since the exhaust shutter valve 20 is displaced to the exhaust throttle position by turning on the solenoid 23 of the exhaust pressure increasing mechanism 16 for a predetermined time after the engine is started, the pre-catalyst 13 and the main catalyzer 14 are arranged. The exhaust gas exhaust pressure is increased until the exhaust purification catalyst consisting of is activated, and the unburned component of the fuel scraped up by the piston at the end of the exhaust stroke is increased in accordance with the increase in the exhaust pressure. By pushing it back to, it is possible to suppress the discharge of unburned components.

When the exhaust pressure increasing mechanism 16 is operated,
By operating the exhaust timing adjusting mechanism 26, the opening timing and the closing timing of the exhaust valve 5 are displaced from the state shown by the solid line in FIG. 5 to the state shown by the broken line so as to accelerate the opening and closing timing of the exhaust valve 5. Since it is configured, the overlap time t between the intake valve 4 and the exhaust valve 5 becomes shorter than that in the normal time.

Therefore, when the exhaust pressure increasing mechanism 16 operates, the internal EGR amount which tends to increase can be suppressed in accordance with the shortening of the overlap time, and the combustion stability can be improved. Then, the synergistic action of the combustion stability improving action and the exhaust pressure increasing action can more effectively suppress the discharge of unburned components.

Further, as the opening timing of the exhaust valve 5 is advanced as described above, the gas is discharged in the middle of the expansion stroke, so the temperature of the exhaust gas discharged to the exhaust passage 7 rises and the precatalyst 13 is exhausted. Also, the activation of the exhaust purification catalyst composed of the main catalyst 14 is promoted.

When the exhaust pressure increasing mechanism 16 is operated,
Since the control valve 11 of the intake bypass passage 10 is opened to increase the amount of intake air supplied to the intake port 2, the pumping loss is increased by executing the exhaust throttle control, and the exhaust valve 5 is opened. A stable engine output can be obtained by compensating for the decrease in engine output due to the decrease in work amount due to the earlier timing.

In order to more effectively promote the activation of the exhaust purification catalyst, the intake air is supplied from the intake bypass passage 10 to the intake port 2 to execute the intake air amount increase control, and at the same time, the cylinder head is operated. The ignition retard control for retarding the ignition timing of the spark plug 28 provided in No. 1 is executed to raise the exhaust gas temperature, or the air-fuel ratio of the air-fuel mixture supplied to the intake port 2 is periodically increased or decreased to reduce CO It is desirable to configure the dither control to promote the oxidation of

In the above embodiment, the exhaust pressure raising mechanism 16
Since the air pump 17 of the secondary air supply mechanism 12 is operated to supply the secondary air to the exhaust port 3 during the operation of, the unburned components in the exhaust gas are actively burned by the secondary air. By increasing the exhaust temperature, activation of the exhaust purification catalyst can be promoted.

Further, as described above, the operating time of the exhaust pressure increasing mechanism 16 after the engine is started, that is, the timer 32.
According to the configuration in which the set time is changed according to the cooling water temperature of the engine, the operating time of the exhaust pressure increasing mechanism 16 can be suppressed to the necessary minimum. That is,
When it is considered that the time required to activate the exhaust purification catalyst is short because the engine coolant temperature is high and the engine is in a heated state, the operating time of the exhaust pressure increasing mechanism 16 is set to be short. Therefore, it is possible to prevent the exhaust throttle control from being executed more than necessary and the temperature of the exhaust purification catalyst from becoming excessively high, and the fuel consumption from being deteriorated.

Further, as shown in the above embodiment, when the HC adsorbent layer 15 is installed on the upstream side of the main catalyzer 14 and the exhaust shutter valve 20, the exhaust throttle control by the exhaust shutter valve 20 is executed. As a result, the residence time of the exhaust gas in the exhaust passage 7 can be lengthened, so that the HC component can be effectively collected by the HC adsorbent layer 15. Further, the HC component collected in the HC adsorbent layer 15 before the activation of the main cata 14 can be purified by the main cata 14 after the activation of the main cata 14.

In the above embodiment, the example in which the overlap time t between the intake valve 4 and the exhaust valve 5 is shortened by advancing the opening timing and closing timing of the exhaust valve 5 has been described. As shown in FIG. 6, the intake valve provided with a control valve 41 for adjusting the opening / closing timing of the intake valve 4 by changing the operation phase of the cam shaft and the cam pulley provided in the valve mechanism 39 of the intake valve 4. The timing adjustment mechanism 40 may be provided.

When the exhaust pressure increasing mechanism 16 is operated, the opening and closing timings of the intake valve 4 are displaced from the normal state shown by the solid line in FIG. 7 as shown by the broken line to open and close the intake valve. The overlap time t between the intake valve 4 and the exhaust valve 5 may be shortened by delaying the timing.

When the overlap time t between the intake valve 4 and the exhaust valve 5 is shortened by delaying the opening timing of the intake valve 4 as described above, the operation of the exhaust pressure increasing mechanism 16 is performed. Sometimes the internal EGR amount, which tends to increase due to the rise in exhaust pressure, is set to the overlap time t
It can be suppressed according to the shortening of, and the combustion stability can be improved.

Further, by delaying the closing timing of the intake valve 4, the effective compression ratio of the engine is lowered, combustion becomes slow, and the exhaust gas temperature rises. Therefore, the exhaust gas composed of the pre-catalyst 13 and the main catalyzer 14 is exhausted. The activation of the purification catalyst can be effectively promoted.

When the closing timing of the intake valve 4 is delayed as described above, the amount of intake air supplied to the combustion chamber decreases and the engine output tends to decrease. By controlling the opening / closing timing of the valve 4 and simultaneously increasing the amount of intake air supplied to the intake port 2 by opening the control valve 11 of the intake bypass passage 10, it is possible to suppress the decrease in the engine output.
It

In the above embodiment, the valve operating mechanism 26 for the exhaust valve 5 is used.
Alternatively, by changing the operating phase of the cam shaft and the cam pulley provided in the valve mechanism 39 of the intake valve 4,
An example in which both the opening timing and the closing timing of the exhaust valve 5 or the intake valve 4 are adjusted has been described. However, a plurality of types of cams are provided in the valve operating mechanisms 26 and 39, and the cam to be used is changed. By so doing, the opening timing of the exhaust valve 5 can be advanced without changing the opening timing of the exhaust valve 5, or the opening timing of the intake valve 4 can be delayed without changing the closing timing of the intake valve 4. The overlap time t between the exhaust valve 4 and the exhaust valve 5 may be shortened.

[0044]

As described above, according to the first aspect of the invention, the exhaust pressure increasing mechanism is actuated after the engine is started to increase the exhaust gas exhaust pressure, so that the piston is scratched at the end of the exhaust stroke. In an engine exhaust gas purification device configured to push back the unburned component of the raised fuel to the combustion chamber side to suppress the discharge of the unburned component, an intake valve and an exhaust valve are provided when the exhaust pressure increasing mechanism is operated. Since the overlap time of is configured to be shorter than the normal time,
The internal EGR amount, which tends to increase during the exhaust throttle control, can be suppressed according to the shortening of the overlap time to improve the combustion stability. This combustion stability improving action and the increase in the exhaust pressure can be achieved. Due to the synergistic action with the action, it is possible to effectively suppress the discharge of unburned components.

Further, by delaying the opening timing of the intake valves, since that is configured to reduce the overlap time of the intake and exhaust valves, due to the fact that when the exhaust throttle control, the exhaust gas pressure rises The internal EGR amount, which tends to increase, is suppressed according to the shortening of the overlap time to improve the combustion stability, and by delaying the closing timing of the intake valve, the effective compression ratio of the engine is improved. Since the exhaust gas temperature is increased by lowering the combustion speed to make combustion slow, there is an advantage that the activation of the exhaust purification catalyst can be effectively promoted.

Moreover, since the intake amount supplied to the combustion chamber is increased during the exhaust throttle control, the pumping loss is increased and the exhaust valve opening timing is accelerated by executing the exhaust throttle control. As a result, the engine output can be stabilized by compensating for the decrease in the work amount and the decrease in the engine output due to the delay in the intake valve closing timing and the decrease in the intake amount.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an exhaust gas purification apparatus for an engine according to the present invention.

FIG. 2 is a block diagram showing a configuration of a controller.

FIG. 3 is a flowchart showing a control operation of the exhaust emission control device.

FIG. 4 is a graph showing the relationship between engine coolant temperature and timer set time.

FIG. 5 is a time chart showing a first example of opening / closing timings of an intake valve and an exhaust valve.

FIG. 6 is an overall configuration diagram showing another embodiment of the exhaust emission control system for an engine according to the present invention.

FIG. 7 is a time chart showing a second example of opening / closing timings of an intake valve and an exhaust valve.

[Explanation of symbols]

4 intake valve 5 exhaust valve 9 Throttle valve 10 Intake bypass passage 11 Control valve 16 Exhaust pressure increasing mechanism 35 Intake amount increasing means 37,40 Timing control means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02D 43/00 F02D 43/00 301T 301Z (72) Inventor Triangular Law 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation (56) Reference JP-A-5-231195 (JP, A) JP-A-5-86989 (JP, A) JP-A-3-271515 (JP, A) JP-A-5-214970 (JP, A) JP-A-5-215001 (JP, A) JP-A-60-145429 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 9 / 04,13 / 02 F02D 41/00 -41/40 F02D 43/00-45/00

Claims (3)

(57) [Claims] 1. When the exhaust gas purifying catalyst is in an inactive state
If it is determined that the engine is in the starting state,
An exhaust gas purification apparatus for an engine, comprising an exhaust pressure increasing mechanism for suppressing discharge of unburned components of fuel by increasing exhaust pressure for a predetermined period of time, the intake air purifying device being operated when the exhaust pressure increasing mechanism is operated. Delay the valve opening and closing times
And control Gosuru timing control means so as to reduce the overlap time between the intake and exhaust valves whereby, the
The amount of intake air supplied to the combustion chamber during operation of the exhaust pressure increasing mechanism
An exhaust emission control device for an engine, comprising: an intake amount increasing means for increasing the amount . 2. Secondary air is exhausted when the exhaust pressure increasing mechanism is operated.
The engine exhaust gas purification apparatus according to claim 1, wherein the exhaust gas purification apparatus is supplied to a port . 3. When the cooling water temperature of the engine is high, it is discharged.
Exhaust pressure increasing mechanism to shorten the operating time of the pressure increasing mechanism
Set so that the operating time of is changed according to the cooling water temperature
Engine exhaust purification device according to claim 1, characterized in that the.