JPH09228826A - Emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent torque change from generating by EGR change in association with switching of a valve for switching conditions in which exhaust gas make flow to a catalyst side or exhaust gas make flow to a bypass passage side, in the emission control device of an internal combustion engine. SOLUTION: A device is provided with an exhaust switching valve 4 for switching a flow passage of an exhaust gas into an upstream catalyst 2 side for exhaust emission control and a bypass passage 22 side alternatively, an EGR passage 101 for refluxing the exhaust gas to an intake passage 103, and a control unit 5 formed in such a constitution that a timing for opening an exhaust valve is variably controlled, the bypass passage 22 is opened by the exhaust switching valve 4 when exhaust gas is refluxed, the bypass passage 22 is closed by the exhaust switching valve 4 when the catalyst 2 side is closed so as to expedite the opening timing of an exhaust valve more than a time when the catalyst 2 side is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, which includes a catalytic converter installed downstream of an exhaust manifold as an exhaust gas purification apparatus for an internal combustion engine, and an exhaust passage bypassing the catalytic converter. Regarding improvement.

[0002]

2. Description of the Related Art A conventional exhaust emission control system for an internal combustion engine is shown in FIG. This is because a three-way catalyst 04 that can purify HC, CO, and NOx is provided in the exhaust passage 02 of the internal combustion engine 01, and the air-fuel ratio of the exhaust gas is determined from the signal of an oxygen sensor 07 provided in the exhaust passage 02. This is a system for controlling the exhaust gas with a stoichiometric control and purifying the exhaust gas with the catalyst 04. Further, in order to further improve the purification rate, it is conceived to mount the catalyst 03 at a position closer to the internal combustion engine 01, that is, on the downstream side of the exhaust manifold 02a. It was
Further, due to the expansion of the region for controlling the air-fuel ratio to stoichiometrically due to the recent demands for exhaust gas regulation, the exhaust gas temperature rises and the catalyst 3 cannot withstand. Therefore, when the exhaust gas temperature is high, the switching valve 0
It has been devised that the exhaust gas is caused to flow into the bypass passage 05 by means of No. 6 (see JP-A-57-210116, etc.).

[0003]

However, in the conventional exhaust gas purifying apparatus for an internal combustion engine, since the exhaust pressure changes when the bypass valve (switching valve 06) is switched, the internal combustion engine provided with the exhaust gas recirculation (EGR) device. In the engine, EGR
There is a problem that a change occurs and a torque change occurs. The present invention focuses on a torque change in an exhaust purification system of an internal combustion engine, and an object thereof is to solve the above-mentioned problems by switching the valve timing by the variable valve operating device simultaneously with the switching of the bypass valve.

[0004]

[Means for Solving the Problems] In order to achieve the above object, in an exhaust gas purification apparatus for an internal combustion engine according to claim 1, a catalyst located in an exhaust passage, and a bypass passage for bypassing the catalyst and flowing exhaust gas. A valve capable of selectively opening and closing the bypass passage and the catalyst passage, exhaust gas recirculation means for recirculating exhaust gas to the intake passage, and exhaust valve opening timing control means for variably controlling the opening timing of the exhaust valve. During exhaust gas recirculation, when the switching valve opens the bypass passage and closes the exhaust passage in which the catalyst is inserted, the switching valve closes the bypass passage and opens the exhaust passage in which the catalyst is inserted. And a means for making the exhaust valve open earlier than when it is operating. Further, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 2, a catalyst located in the exhaust passage, a bypass passage for bypassing the catalyst and flowing exhaust gas, and a valve capable of switching the bypass passage and the catalyst passage. , Exhaust gas recirculation means for recirculating exhaust gas to the intake passage, intake valve opening timing control means for variably controlling the opening timing of the intake valve, and during exhaust gas recirculation,
When the switching valve opens the bypass passage and closes the exhaust passage in which the catalyst is interposed, the switching valve closes the bypass passage and opens the exhaust passage in which the catalyst is inserted. A means for accelerating the opening time of the intake valve is provided.
In the exhaust gas purification apparatus for an internal combustion engine according to claim 1, the exhaust valve opening timing control means is composed of means for changing the phase of a cam shaft that drives the exhaust valve to open and close and a cam pulley that drives the cam shaft to rotate. (Claim 3) Further, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 2, the intake valve opening timing control means comprises means for changing a phase between a cam shaft for opening and closing the intake valve and a cam pulley for rotationally driving the cam shaft. (Claim 4) Further, in the exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, when the exhaust gas temperature is low, the switching valve closes the bypass passage and opens the exhaust passage in which the catalyst is interposed, and the exhaust gas temperature increases. When the temperature is high, the switching valve may be provided with means for opening the bypass passage and closing the exhaust passage in which the catalyst is interposed (claim 5).

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention. First, the configuration will be described. An exhaust purification upstream catalyst (three-way catalyst) 2 is installed in an exhaust passage 21 on a downstream side of an exhaust manifold 1a installed in an engine 1, and an exhaust purification downstream catalyst 3 is also provided downstream thereof. Is installed. A bypass passage 22 that bypasses the exhaust purification upstream catalyst (three-way catalyst) 2 is provided in the exhaust passage 21, and the exhaust gas flow is selectively supplied to the exhaust purification upstream catalyst (three-way catalyst) 2 and the bypass passage 22. An exhaust switching valve 4 for switching to is provided and controlled by the control unit 5.

The variable valve is controlled by the same control unit 5. Here, an example of the variable valve operating device will be described with reference to FIGS. As shown in FIG. 3, the cylinder head 10 of the engine 1 has an intake port 20 for introducing intake air into the combustion chamber 190, an exhaust port 30 for discharging exhaust gas from the combustion chamber 190, and the like. An intake valve 120 that opens and closes the intake port 20 and an exhaust valve 130 that opens and closes the exhaust port 30 are provided. The intake / exhaust valves 120, 130 are slidably supported on the cylinder head 10 via a valve guide 50. A retainer 60 is fitted on the stems of the intake / exhaust valves 120 and 130, and a coiled valve spring 70 is interposed between the retainer 60 and the cylinder head 10. The intake / exhaust valves 120, 130 are pulled up by the urging force of the valve spring 70, and are seated on the respective valve seats 80. Intake / exhaust camshafts 150 and 160 are provided on the cylinder head 10. The intake / exhaust camshafts 150, 160 are provided with two intake / exhaust valves 120, 130 on the Y-shaped rocker arm 11.
Intake / exhaust cams 220 and 230 that are opened and closed via 0 are formed, respectively. Each rocker arm 110 has its base end swingably supported via the pivot 100, and has a cam follower portion 250 for slidingly contacting the intake / exhaust cams 220 and 230 in the middle of each rocker arm 110, and the tip end of each rocker arm 110 sucks / sucks. The stems of the exhaust valves 120 and 130 are slidably contacted via shims. Each pivot 100 is supported by the cylinder head 10 via a hydraulic lash adjuster 240.
The hydraulic lash adjuster 240 receives the hydraulic pressure sent from an oil pump (not shown) via the oil gallery 270 and presses the cam follower part 250 of the rocker arm 110 against the intake / exhaust cams 220 and 230 to keep the valve clearance at zero. . Intake and exhaust cams 220, 2
The sliding contact of the 30 with the intake / exhaust valve 12
It has a base circle portion 271 for seating 0, 130 on each valve seat 80, and a cam crest portion 260 for lifting the intake / exhaust valves 120, 130 from each valve seat 80 by sliding contact therewith.

As shown in FIG. 2, the intake camshaft 15
A valve timing adjusting mechanism 700 that changes the rotational phase difference between 0 and the exhaust camshaft 160 is provided. The valve timing adjusting mechanism 700 is provided between the exhaust camshaft 160 and the cam pulley 71, and changes the phase angle between the exhaust camshaft 160 and the cam pulley 71 according to operating conditions to change the opening / closing timing of the exhaust valve 130. Rotational force from a crankshaft (not shown) is transmitted to the cam pulley 71 via the timing belt 66. At the end of the exhaust cam shaft 160, a cylindrical inner housing 65 is fastened via a bolt 64. A cylindrical outer housing 63 that is rotatably fitted to the outer circumference of the inner housing 65 is provided.
A cam pulley 71 is formed integrally with the roller 3. A ring-shaped helical gear 73 is interposed between the inner housing 65 and the outer housing 63. Helical splines are formed on the inner and outer circumferences of the helical gear 73, and each helical spline meshes with the outer circumference of the inner housing 65 and the inner circumference of the outer housing 63 so that the helical gear 73 moves axially against the return spring 74. Accordingly, the inner housing 65 rotates relative to the outer housing 63, and the phase angle of the intake camshaft 150 with respect to the cam pulley 71 in the rotation direction changes. A hydraulic chamber 75 is defined between the inner housing 65, the outer housing 63, and the helical gear 73. When the hydraulic pressure introduced into the hydraulic chamber 75 rises above a predetermined value, the helical gear 73 moves from the initial position to the right in the figure against the return spring 74, so that the exhaust camshaft 160 causes the exhaust valve 130 to move. It is designed to rotate in the direction of advancing the opening and closing timing of.

As a result, when the helical cam gear 73 is in the initial position, as shown by the dotted line in FIG. 4, the opening and closing timing of the exhaust valve 130 is delayed, and when the helical gear 73 is displaced to the maximum, the opening and closing characteristics are delayed. As indicated by the solid line, the opening / closing characteristic is such that the opening / closing timing of the exhaust valve 130 is advanced. In addition,
The opening / closing characteristics of the intake valve 120 are also shown.

The hydraulic chamber 75 has a shaft hole 78 formed inside the exhaust cam shaft 160, an oil gallery 59 formed in the cylinder head 10, and a main gallery 5 formed in the cylinder block 68 to form an oil supply passage.
The hydraulic pressure discharged from the oil pump 500 is introduced via the control valve 8. The exhaust camshaft 160 is used as a valve switching control valve.
An electromagnetic switching valve 79 that is controlled to open and close according to the engine operating conditions is provided at the other end of the. The electromagnetic switching valve 79 opens the shaft hole 78 when not energized to reduce the hydraulic pressure introduced to the hydraulic chamber 75 as shown in the figure, and closes the shaft hole 78 when energized to close the hydraulic chamber 75.
It is designed to increase the hydraulic pressure introduced to the.

As the control means of the valve timing adjusting mechanism 700, the control unit 5 for controlling the energization of the electromagnetic switching valve 79 is provided.

Next, the operation will be described. In FIG.
Is an EGR passage, one end of which communicates with the exhaust passage 21 and the other end of which communicates with the intake passage 103 installed in the engine 1, and an EGR control valve 105 is interposed midway. EG
The R control valve 105 is controlled to be opened and closed by the control unit 5 depending on the operating state. A temperature sensor 107 measures the temperature of the exhaust gas in the exhaust passage 21.

Exhaust gas temperature is at a certain temperature (eg 700
Up to (° C.), the exhaust purification upstream catalyst 2 does not deteriorate so much, so the exhaust switching valve 4 is driven to flow to the exhaust purification upstream catalyst 2. At this time, the bypass passage 22 side of the exhaust gas switching valve 4 is closed. Here, if the exhaust gas temperature rises (for example, 900 ° C.) due to some action, the control unit 5 senses the exhaust gas temperature measured by the temperature sensor 107, and the exhaust switching valve 4
To close the exhaust purification upstream catalyst 2 side and open the bypass passage 22. At this time, conventionally, the exhaust pressure is reduced and EG
The R ratio changed and a torque step was generated, which adversely affected the drivability. Therefore, by driving the exhaust switching valve 4 simultaneously with opening and closing (EVO) of the exhaust valve 130 by the variable valve operating device, the exhaust pressure is raised to prevent the EGR rate from fluctuating, and the exhaust temperature is raised to increase the temperature under the floor. The deterioration of drivability is prevented by accelerating the activity of the catalyst.

Incidentally, the change in valve timing at this time is shown in FIG. 4 as described above. A flowchart at this time is shown in FIG. That is, the exhaust switching valve 4
Is switched from the state in which the exhaust purification upstream catalyst 2 side is opened to the side in which the bypass passage 22 side is opened, the flow is from step S1 to S2 to S3, and the electromagnetic switching valve is opened to the side to early open the EVO. 79 is driven, and conversely, when the exhaust gas switching valve 4 is switched from the state in which the exhaust gas purification upstream catalyst 2 side is closed to the side in which the exhaust gas purification upstream catalyst 2 side is opened, the steps S1 → S4 → S5 are performed. Flowing, E
The electromagnetic switching valve 79 is driven to the side that opens the VO late, and the electromagnetic switching valve 79 is not driven otherwise.

FIG. 6 shows a second embodiment. Changing the valve timing that is switched at the same time as driving the exhaust switching valve 4 is performed by opening and closing the intake valve 120 (IVO).
Even if the speed is increased, the same effect as that of the first embodiment can be obtained. This is to supplement the EGR rate lowered by the change in exhaust pressure with the internal EGR by increasing the overlap.

[0015]

As described above, according to the present invention, by switching the opening / closing timing of the exhaust valve or the intake valve at the same time as switching the bypass passage,
The effect of preventing deterioration of drivability is obtained.

[Brief description of drawings]

FIG. 1 is an overall view showing an exhaust emission control device for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a structure of a main part of the first embodiment.

FIG. 3 is a cross-sectional view showing a structure of a main part of the first embodiment.

FIG. 4 is an explanatory diagram of changes in valve timing according to the first embodiment.

FIG. 5 is a flowchart showing a control flow of the first embodiment.

FIG. 6 is an explanatory diagram of changes in valve timing according to the second embodiment.

FIG. 7 is an overall view showing a conventional example.

[Explanation of symbols]

 1 Engine 2 Upstream Catalyst for Exhaust Gas Purification 21 Exhaust Passage 22 Bypass Passage 4 Exhaust Switching Valve 5 Control Unit (Exhaust Valve Opening Timing Control Unit) 101 EGR Passage 105 EGR Control Valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location F02M 25/07 F02M 25/07 B (72) Inventor Koji Ishihara 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Within Nissan Motor Co., Ltd.

Claims (5)

[Claims] 1. A catalyst located in an exhaust passage, a bypass passage for bypassing the catalyst and flowing exhaust gas, a valve capable of selectively opening and closing the bypass passage and the catalyst passage, and exhaust gas intake Exhaust gas recirculation means that recirculates to the passage, exhaust valve opening timing control means that variably controls the opening timing of the exhaust valve, and during exhaust gas recirculation, the switching valve opens the bypass passage and closes the exhaust passage in which the catalyst is interposed. The switching valve closes the bypass passage when the exhaust valve is open, and the exhaust valve is opened earlier than when the exhaust passage in which the catalyst is inserted is opened. Exhaust gas purification device for internal combustion engine. 2. A catalyst located in the exhaust passage, a bypass passage for bypassing the catalyst and flowing exhaust gas, a valve capable of switching between the bypass passage and the catalyst passage, and exhaust gas for returning exhaust gas to the intake passage. Recirculation means, intake valve opening timing control means for variably controlling the opening timing of the intake valve, and when the switching valve opens the bypass passage and closes the exhaust passage in which the catalyst is interposed during exhaust gas recirculation. Exhaust gas purification of an internal combustion engine, characterized in that the switching valve closes the bypass passage and opens the intake valve earlier than when the exhaust passage in which the catalyst is inserted is opened. apparatus. 3. The internal combustion engine according to claim 1, wherein the exhaust valve opening timing control means comprises means for changing the phase of a cam shaft for opening / closing the exhaust valve and a cam pulley for rotationally driving the cam shaft. Exhaust purification device. 4. The internal combustion engine according to claim 2, wherein the intake valve opening timing control means comprises means for changing the phase of a cam shaft for opening / closing the intake valve and a cam pulley for rotationally driving the cam shaft. Exhaust purification device. 5. When the exhaust gas temperature is low, the switching valve closes the bypass passage to open the exhaust passage in which the catalyst is interposed, and when the exhaust gas temperature is high, the switching valve opens the bypass passage to open the catalyst. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising means for closing an exhaust passage interposed therein.