JPH08144789A - Exhaust emission control device - Google Patents

Abstract

PURPOSE: To prevent exhaust gas from flowing into a first low temperature active type catalytic converter when the temperature of an engine and a second high temperature active type catalytic converter is high enough. CONSTITUTION: When a temperature measuring means (temperature sensor) 31 detects that the temperature of a second catalytic converter 19 is below a designated value, a second catalytic converter thermometer circuit 32, and a solenoid valve operating circuit 28 of a control circuit 27 are operated to turn on a solenoid valve 22. Thus, an actuator 20 is operated, so that a valve element 11 of a by-pass pipe 16 in an exhaust control valve 3 is opened, and a valve element 10 of a main exhaust pipe 15 is closed to circulate exhaust gas through a first low temperature active type catalytic converter 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention allows the exhaust gas discharged from an internal combustion engine to be selectively passed through two passages depending on the temperature condition of a catalyst to suppress the emission of harmful substances contained in the exhaust gas. The present invention relates to an exhaust gas purification control device.

[0002]

2. Description of the Related Art In a conventional gasoline engine, one catalytic converter provided in the middle of an exhaust pipe purifies harmful substances contained in exhaust gas.

Many recent gasoline engines have adopted a lean burn system in order to improve fuel economy. Since the exhaust temperature of such an engine is lower than that of a normal engine, when the exhaust gas is purified by one catalytic converter provided in the middle of the exhaust pipe as described above, the reaction temperature of the catalyst is reduced. It takes a long time to reach the target, and there is a problem that the purification performance of harmful substances deteriorates especially at idling immediately after engine start and at light load operation.

In order to deal with this problem, the exhaust system is provided with two catalytic converters of a low temperature activated type and a high temperature activated type, and each of these catalytic converters has an exhaust control valve having two passages to selectively exhaust the exhaust gas. Attempts have been made to improve the exhaust gas purification performance by sending in.

That is, when the temperature of the exhaust gas is low and the temperature of the high temperature active catalytic converter is still low immediately after the engine is started, etc., the exhaust gas is circulated through the low temperature active catalytic converter provided near the exhaust manifold. Let
On the contrary, when the high-temperature activated catalytic converter is sufficiently warmed up, the exhaust gas to the low-temperature activated catalytic converter is shut off, and the exhaust control valve is set so that the exhaust gas flows through the high-temperature activated catalytic converter. Have control.

[0006]

As described above, in order to control the exhaust control valve, the valve element on the low-temperature active catalytic converter side must be opened immediately after the engine is started, and the valve for the high-temperature active catalytic converter must be opened. It is necessary to control an appropriate actuator so as to close the valve body. However, if such a control system is simply used, the temperature of the engine and the high temperature activation type catalytic converter is sufficiently high, such as when the engine is temporarily stopped after high-speed operation and restarted after a short time, Even when the exhaust gas is purified without any trouble, the high-temperature exhaust gas flows through the low-temperature activated catalytic converter. In such a case, the active substance in the low-temperature activation type catalytic converter is exposed to the high-temperature exhaust gas, so that the deterioration thereof is rapid and the exhaust gas purification performance is deteriorated.

Further, since it is expected that the valve body of the exhaust control valve will thermally expand and smooth operation will not be performed, the clearance between the valve body and the body in which it is housed is taken into account in anticipation of thermal expansion. It is necessary to take measures such as increasing the value in advance. However, in this case, the hermeticity of the valve element is impaired, and the amount of exhaust gas leaked when the valve is closed increases.

The present invention has been made to solve the above problems, and when the temperature of the engine and the high temperature active catalytic converter is sufficiently high, the low temperature active catalytic converter is provided even immediately after the engine is started. It is an object of the present invention to provide an exhaust gas purification control device that prevents exhaust gas from flowing into the exhaust gas, thereby preventing deterioration of a catalyst and improving exhaust gas purification performance.

[0009]

SUMMARY OF THE INVENTION According to the present invention, the above object is to provide valve bodies which are connected to an exhaust manifold of an engine and which are arranged in two passages in a body. An exhaust control valve configured to selectively allow exhaust gas to flow through the two exhaust pipes by opening and closing the other valve body so as to close the other passage when the valve is open.
An actuator that drives an exhaust control valve, a low-temperature activated first catalytic converter provided on the exhaust upstream side of one of the exhaust pipes, and a downstream side of the first catalytic converter,
In addition, a high temperature active type second catalytic converter provided at an appropriate position of a collecting pipe that joins the two exhaust pipes, a temperature measuring means for detecting the temperature of the second catalytic converter, and an ignition key being turned on, The temperature measuring means is the second
By detecting that the catalytic converter is at a predetermined temperature or lower, the actuator is actuated, one valve body of the exhaust control valve is opened, and exhaust gas is circulated through the exhaust pipe on the side where the first catalytic converter is provided. And let
And a control circuit adapted to close the other valve body.

[0010]

Only when the temperature measuring means detects that the temperature of the second catalytic converter is equal to or lower than the predetermined temperature, the actuator is operated by the control circuit to open one of the exhaust control valves to open the first catalytic converter. Since the exhaust gas is circulated through the converter, the high temperature exhaust gas does not flow into the first catalytic converter when the temperatures of the engine and the second catalytic converter are high.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of the entire exhaust system to which the present invention is applied. (1) is a gasoline engine, and (2) is a bifurcated lower end (downward in the figure) (the direction below refers to the drawing). It is an exhaust manifold branched into. Exhaust manifold
An exhaust control valve (3) is attached to the lower end of (2).

As shown in detail in FIGS. 2 and 3, the exhaust control valve (3) has a large size 2 and a small size 2 which are parallel to each other in the body (4).
One passage (5) (6) is formed, and each passage (5) (6) communicates with each branch pipe of the exhaust manifold (2). In this embodiment, the large diameter passage (5) is the main passage and the small diameter passage (6) is the auxiliary passage.

At the center of the body (4), there are both passages (5) and (6).
A shaft hole (7) facing in a direction orthogonal to the
Two valve shafts (8) and (9), which are coaxial with each other, are mounted on the bearing (7).
It is rotatably supported by (7a). Double valve shaft (8)
(9) is a groove (8a) provided in one of the opposite ends of the body (4) in the middle portion of the body (4), and a protrusion (9a) provided on the other valve shaft (9) They are connected by fitting.

Each passage (5) is provided in the middle of the two valve shafts (8) and (9).
The elliptical disk-shaped valve body (10) (11) that opens and closes (6) is attached to the bolt (1
It is fixed by 2). Both valve bodies (10) (11)
As shown in FIG. 3, when one valve body (10) fully opens the passage (5), the other valve body (11) fully closes the passage (6) (see FIG.
(Indicated by solid lines and broken lines in Fig. 4), when one valve body (10) fully closes the passage (5), the other valve body (11) fully opens the passage (6) (shown by an imaginary line in Fig. 4). The state is fixed so as to have a phase relationship like that. (13) is a closing member for closing the shaft hole (7) at the left end of the body (4).

A drive lever (14) for connecting to an actuator to be described later is screwed to the protruding end of the valve shaft (9) protruding rightward from the shaft hole (7). The main exhaust pipe (15) is connected to the downstream end of the passage (5) in the exhaust control valve (3), and the main exhaust pipe (15) is connected to the downstream end of the passage (6) at the lower end. A bypass pipe (16) which joins with the pipe (15) is connected, and a low temperature activated first catalytic converter (17) is attached to an intermediate portion thereof.

A collecting pipe (18) is connected to the confluence of the main exhaust pipe (15) and the bypass pipe (16), and in the middle of the downstream side thereof,
A high temperature activated second catalytic converter (19) is attached. The exhaust gas that has passed through the second catalytic converter (19) is discharged to the outside through a silencer (not shown).

A drive rod (20a) of a negative pressure type actuator (20) is connected to a drive lever (14) of the exhaust control valve (3), and only when a negative pressure acts on the actuator (20).
The drive rod (20a) is pulled and the drive lever (14) is rotated to fully open the normally closed valve body (11) and fully close the normally open valve body (10).

The actuator (20) is connected to the solenoid valve (22) via the tube (21), and the solenoid valve (22) is connected to the negative pressure tank (24) via the tube (23). There is. The negative pressure tank (24) is connected via a tube (25) and a check valve (26) to a negative pressure generation source, for example, a vacuum pump or an intake pipe (not shown) driven by the engine (1). Therefore, even after the engine (1) is stopped, the depressurized state is maintained for a predetermined time. Solenoid valve (22)
Is electrically connected to the solenoid valve actuation circuit (28) in the control circuit (27), and is actuated by a signal emitted thereby.

(29) is an ignition key, which is a control circuit (2
It is electrically connected to the ignition key on / off detection circuit (30) in (7). When the ignition key (29) is on, that is, when the engine (1) is in operation,
A signal is sent from the ignition key on / off detection circuit (30) to the solenoid valve actuation circuit (28).

Reference numeral (31) is a temperature sensor attached to the second catalytic converter (19) and is electrically connected to the second catalytic converter temperature detecting circuit (32) in the control circuit (27). The second catalytic converter temperature detecting circuit (32) sends a signal to the solenoid valve operating circuit (28) when the temperature of the second catalytic converter (19) is lower than a predetermined temperature (eg, 500 ° C.), that is, lower than the reaction temperature of the catalyst. It is supposed to be emitted.

Next, the operation of the above embodiment will be described with reference to the flowchart shown in FIG. In order to make it easier to understand the open / closed state of each valve body (10) (11) in the exhaust control valve (3), the exhaust control valve (3) shown in FIG. The seen valve bodies (10) (11) are shown for convenience.

First, the ignition key (29) is turned on (step S1) to start the engine (1). At this time, the second catalytic converter (19) has a predetermined temperature (for example, 500 ° C).
If the following (step S2), turn on the ignition key
The solenoid valve actuation circuit (28) operates based on the signals generated by the off detection circuit (30) and the second catalytic converter temperature detection circuit (32), and the solenoid valve (22) is actuated to the valve opening side (step S
3).

When the solenoid valve (22) is activated, the negative pressure tank (24)
Negative pressure acts on the actuator (20), and the piston rod (20a) is pulled (step S4). As a result, the drive lever (14) is rotated, the valve body (10) on the main passage side of the exhaust control valve (3) is closed, and the valve body on the auxiliary passage side is closed.
Open (11) (step S5).

As described above, when the actuator (20) is inoperative, such as when the engine (1) is stopped, the valve body (not shown) is urged by the return spring (not shown) in the actuator (20). 10) is open and the valve body (11) is closed.

When the valve body (11) side is opened, the exhaust gas flows into the bypass pipe (16) side and the low temperature activated first type
The catalytic converter (17) purifies harmful substances (for example, HC and CO) contained in the exhaust gas having a relatively low temperature, for example, immediately after the engine is started.

Engine (1) and second catalytic converter (19)
Is gradually warmed up and the temperature at which the catalytic reaction is possible
When (Step S6) is reached, the solenoid valve control circuit
(22) is closed (step S7), and the actuator (20) becomes inoperative (step S8). Then, the valve body (10) is opened and the valve body (11) side is closed (step S
9). As a result, exhaust gas flows into the main exhaust pipe (15) side,
The harmful substances (for example, HC, CO, NOx) contained in the exhaust gas having a relatively high temperature are purified by the second catalytic converter (19).

When the second catalytic converter (19) does not reach the predetermined temperature (step S6), the solenoid valve (22) is kept in the open state (step S2), so that the valve body (10). Closed, valve body
(11) is maintained in the valve open state (step S5).

Whether the ignition key (29) is off,
Alternatively, when the temperature of the second catalytic converter (19) is higher than the predetermined temperature (steps S1 and S2), the solenoid valve operating circuit (28) does not work, so the solenoid valve (22) does not operate (step S7) and the valve body ( The valve body (11) closes as the 10) opens.

As described above, in the above-mentioned embodiment, the valve body (11) is opened and the exhaust gas is discharged to the first catalytic converter (17) side only when the second catalytic converter (19) is at a predetermined temperature or lower. Other than that, since the valve body (11) is closed, the engine is temporarily stopped immediately after high-speed operation,
When the temperature of the engine is sufficiently high and the temperature of the exhaust gas discharged from it is also high, such as when restarted after a short time, the hot exhaust gas flows into the first catalytic converter (17). Is blocked. As a result, deterioration of the exhaust gas purification performance due to deterioration of the first catalytic converter (17) is prevented, and durability is significantly improved.

Further, since the heat load on the valve body (11) which is opened and closed at a relatively low temperature is reduced, its thermal expansion can be minimized, and therefore the valve body (11) and the passage (6) ) And the valve body (11)
It is possible to increase the degree of airtightness and reduce the leakage amount of exhaust gas into the bypass pipe (16).

The present invention is not limited to the above embodiment. For example, the valve state when the engine is stopped in the above-described embodiment may be such that the valve body (11) is opened and the valve body (10) is closed. In this case, when the temperature of the second catalytic converter (19) is lower than a predetermined temperature, the actuator (20) is inoperative, and when the temperature is higher than the predetermined temperature, the actuator (20) is operated to close the valve body (11) and close the valve body.
Open (10). With this configuration, for example, when the engine is stopped immediately after high-speed operation and restarted after a short time, the high temperature gas temporarily flows into the first catalytic converter (17).
In order to prevent this, for example, an interlock circuit is added to the solenoid valve actuation circuit (28) in the control circuit, and the residual negative pressure in the negative pressure tank (24) causes the second catalytic converter (19) to operate. Temperature sensor (31) is below a certain temperature (for example below 500 ℃)
The actuator (20) may be operated until it is detected.

Further, the actuator (20) may be a compressed air type (for example, an air cylinder), an electromagnetic type cylinder, an electric type or the like instead of the negative pressure type. When using the compressed air type, the negative pressure tank (24) may be a compression tank and may be connected to an air pump or the like driven by an engine. Also,
When using an electromagnetic cylinder or an electric type, instead of the solenoid valve operating circuit (28) in the control circuit (27), an operating circuit that directly turns on and off the electromagnetic cylinder or a forward / reverse control of an electric drive motor It is sufficient to provide an operating circuit that operates.

The negative pressure tank (24) is not always necessary,
The solenoid valve (22) may be directly connected to a vacuum pump or an intake pipe driven by the engine. In the embodiment, each valve body (1
0) (11) is operated by one actuator (20), but each valve body (10) is operated by two actuators.
(11) may be operated independently.

[0034]

According to the present invention, the valve body on the side of the low temperature activated first catalytic converter is opened only when the temperature of the high temperature activated second catalytic converter is lower than the predetermined temperature. The hot exhaust gas when the temperature of the two-catalytic converter is sufficiently high is prevented from flowing into the first catalytic converter. As a result, the deterioration of the first catalytic converter is prevented, and the exhaust gas purification performance is maintained for a long period of time. Further, since the heat load on the valve body on the side of the first catalytic converter can be reduced and the thermal expansion thereof can be suppressed, the gap between the valve body and the passage in which it is housed can be set small in advance, and when the valve is closed. The tightness is increased and the leakage of exhaust gas is minimized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire exhaust system showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional plan view taken along the line II-II in FIG.

3 is a vertical cross-sectional side view taken along the line III-III in FIG.

FIG. 4 is a flowchart illustrating the operation of the present invention.

[Explanation of symbols]

 (1) Engine (2) Exhaust manifold (3) Exhaust control valve (4) Body (5) (6) Passage (7) Shaft hole (7a) Bearing (8) (9) Valve shaft (8a) Groove (9a) Projection piece (10) (11) Valve body (12) Bolt (13) Closure member (14) Drive lever (15) Main exhaust pipe (16) Bypass pipe (exhaust pipe) (17) First catalytic converter (18) Assembly Tube (19) Second catalytic converter (20) Actuator (20a) Drive rod (21) (23) (25) Tube (22) Solenoid valve (24) Negative pressure tank (26) Check valve (27) Control circuit (28) ) Solenoid valve actuation circuit (29) Ignition key (30) Ignition key on / off detection circuit (31) Temperature sensor (32) Second catalytic converter temperature detection circuit

Claims (1)

[Claims] 1. A valve body connected to an exhaust manifold of an engine and arranged in two passages in a body, wherein when one valve body opens one passage, the other valve body opens the other. An exhaust control valve that allows the exhaust gas to selectively flow through the two exhaust pipes by closing and opening the passage, an actuator that drives the exhaust control valve, and an exhaust upstream of one of the exhaust pipes. A low temperature active type first catalytic converter provided on a side, and a high temperature active type second catalytic converter provided on a downstream side of the first catalytic converter and at an appropriate position of a collecting pipe that joins both the exhaust pipes, A temperature measuring unit that detects the temperature of the two-catalyst converter and a temperature measuring unit that detects that the second catalytic converter is at a predetermined temperature or lower in a state in which the ignition key is turned on. , Operating the actuator to open one valve body of the exhaust control valve to allow exhaust gas to flow through the exhaust pipe provided with the first catalytic converter and to close the other valve body. And a control circuit for controlling the exhaust gas.