JP2003247414A - Method of operating catalyst dividing type exhaust gas cleaning apparatus of internal combustion engine for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve more the overall operating performance of an exhaust gas cleaning apparatus in which the same exhaust gas cleaning catalyst is divided into an upstream catalyst converter and a downstream catalyst converter which are arranged in series along an exhaust gas discharging path, in the case where the former operates at a relatively high temperature and the latter operates at a relatively low temperature. <P>SOLUTION: There are provided a bypass passage for bypassing the upstream catalyst converter and a flowing path switching valve. When the operating state of the internal combustion engine is such that the exhaust gas can be made to bypass the upstream catalyst converter from the viewpoint of cleaning of the exhaust gas (or particularly when a temperature of the upstream catalyst is high), the exhaust gas is made to bypass the upstream catalyst converter so as to be led to the downstream catalyst converter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an exhaust gas purifying apparatus for an internal combustion engine for a vehicle, and more specifically, the same exhaust gas purifying catalyst is provided upstream along an exhaust gas exhaust path of the internal combustion engine. The present invention relates to a method for operating an exhaust gas purification device for a vehicle internal combustion engine, which is provided separately for a catalytic converter and a downstream catalytic converter.

[0002]

2. Description of the Related Art In an exhaust system of an internal combustion engine of a vehicle such as an automobile, an oxidation catalyst that helps burn unburned components such as CO and HC in exhaust gas into harmless CO ₂ and H ₂ O, A NOx purification catalyst (lean NOx catalyst) that reduces and purifies NOx in the presence of HC in an oxidizing atmosphere, and oxidizes CO and HC and reduces NOx at the same time to make them harmless CO ₂ , H ₂ It is known to provide a three-way catalyst or the like for converting into O and N ₂ . Although these catalysts are used alone, it is also known to use a NOx purification catalyst and a three-way catalyst in series combination in this order as described in, for example, JP-A-5-312031.

On the other hand, in a vehicle equipped with a vehicle operation control device using a computer in recent years, in order to improve fuel efficiency of an internal combustion engine, for example, when the throttle valve is fully closed and the engine speed is equal to or higher than a predetermined value (that is, When it is determined that fuel supply is unnecessary during vehicle deceleration, "fuel cut (F / F /
C) ”is performed. During fuel cut operation,
The air-fuel ratio of the exhaust gas becomes a lean state containing oxygen. The exhaust gas purification catalyst is generally deteriorated by oxygen and its durability is reduced. In view of this point, the above-mentioned JP-A-5-312
In the 031 publication, a bypass passage that bypasses the NOx purification catalyst is provided in order to avoid deterioration of the NOx purification catalyst due to the fuel cut operation, and when the fuel cut operation is performed, exhaust gas is guided through the bypass passage. It is described that the exhaust gas bypasses the NOx purification catalyst. Regarding the problem of deterioration of the exhaust gas purification catalyst due to fuel cut operation, it is special to prohibit fuel cut when the catalyst is at a high temperature, even under operating conditions where fuel cut operation should be performed. It is described in Japanese Unexamined Patent Publication No. 2001-59444.

[0004]

In the case of an internal combustion engine for a vehicle, the same exhaust gas purifying catalyst, for example, a three-way catalyst, is installed in the exhaust system because of the space available for installing a catalytic converter. A part of a predetermined amount of catalyst is stored in a catalytic converter arranged in an engine compartment of a vehicle, and the remaining catalyst is separately stored in a catalytic converter arranged under the floor of the vehicle. In this way, when a certain amount of catalyst is separated along the flow of exhaust gas and placed in different temperature environments so that the engine room and the underfloor are separately arranged in series,
There is a considerable difference in operating temperature between the catalyst in the upstream catalytic converter and the catalyst in the downstream catalytic converter.

Generally, the exhaust gas purifying catalyst has a higher activity until the operating temperature reaches around 800 ° C. as the operating temperature rises and the exhaust gas purifying performance is improved. When the temperature rises, the particle growth occurs due to the fusion of the catalyst particles, and the surface area of the catalyst decreases correspondingly, so that the function of the catalyst deteriorates. Therefore, when the catalytic activity is high and the catalyst purifies the exhaust gas with higher performance, it means that the catalyst has spent its life at the same time. Also, oxygen accelerates its degradation when the catalyst is hot. Therefore, for upstream catalytic converters that operate at high temperatures, take measures to avoid them in advance, especially when there is a risk of overheating, and if there is an opportunity to prevent the catalyst from operating, operate it. It is considered preferable to loosen or take a break.

Further, since the exhaust gas purifying catalyst can exhibit its function only when the temperature thereof is above a certain level, when the exhaust gas purifying catalyst is provided at a position where it is easily subjected to a cooling action from the outside, Attention must be paid to maintaining the temperature. Therefore, it is considered preferable that the downstream catalytic converter arranged under the floor be subjected to a treatment for increasing its operating temperature when there is an opportunity.

According to the present invention, a predetermined amount of the same exhaust gas purifying catalyst is provided separately in an upstream catalytic converter that operates at a relatively high temperature and a downstream catalytic converter that operates at a relatively low temperature. In view of the above situation in the case where they are arranged in series along the exhaust system of an internal combustion engine, it is an object to further improve the overall operation performance of the exhaust gas purifying apparatus for an internal combustion engine for a vehicle having such a basic configuration. There is.

[0008]

In order to solve the above problems, the present invention provides an identical exhaust gas purifying catalyst for an upstream catalytic converter and a downstream catalytic converter along an exhaust gas exhaust path of an internal combustion engine. According to the operating method of the exhaust gas purifying device for a vehicle internal combustion engine provided separately, the operating state of the internal combustion engine is such that even if the exhaust gas bypasses the upstream side catalytic converter, there is no problem in purifying the exhaust gas. The present invention proposes a method of operating an exhaust gas purifying apparatus for an internal combustion engine for a vehicle, characterized by bypassing the upstream catalytic converter and guiding exhaust gas to the downstream catalytic converter.

In the method for operating the exhaust gas purifying apparatus for an internal combustion engine for a vehicle as described above, the exhaust gas purifying catalyst is a catalyst for purifying unburned components in the exhaust gas, and the upstream side catalytic converter is added to the exhaust gas. The operating state of the internal combustion engine that does not interfere with exhaust gas purification even if bypassed is the operating state of the internal combustion engine in which the engine speed is equal to or higher than a predetermined value and the throttle opening is equal to or lower than a predetermined value, a fuel cut operation, or a fuel. It may be a cut execution delay operation.
Even if the internal combustion engine is in an operating state in which exhaust gas can bypass the upstream catalytic converter and purification of the exhaust gas does not interfere, the bypass of the upstream catalytic converter is such that the catalyst temperature in the upstream catalytic converter is May be performed except when it is not equal to or more than a predetermined value that accelerates the deterioration of. Further, the fuel cut operation or the fuel cut execution delay operation is performed when the catalyst temperature of the upstream side catalytic converter is high such that the temperature is equal to or higher than a predetermined value.
It may include what is performed in order to obtain an operating state of the internal combustion engine that does not interfere with exhaust gas purification even if the exhaust gas bypasses the upstream catalytic converter.

In the method of operating the exhaust gas purifying apparatus for an internal combustion engine for a vehicle as described above, the upstream side catalytic converter is arranged in the engine room of the vehicle and the downstream side catalytic converter is arranged under the floor of the vehicle. Well, and the catalyst may be a three-way catalyst.

Further, in carrying out the method for operating the exhaust gas purifying apparatus for an internal combustion engine for a vehicle as described above, the oxygen in the exhaust gas at the outlet of the upstream catalytic converter during operation of the internal combustion engine without bypassing the upstream catalytic converter Since the concentration does not change according to the rotation cycle of the internal combustion engine,
Malfunction of the means for bypassing the upstream catalytic converter to the exhaust gas may be detected.

In implementing the method of operating the exhaust gas purifying apparatus for an internal combustion engine for a vehicle as described above, the exhaust gas passes through the upstream catalytic converter when the exhaust gas bypasses the upstream catalytic converter in the fuel cut operation state. By detecting the presence of the flow of oxygen, malfunction of the means for bypassing the upstream catalytic converter to the exhaust gas may be detected.

[0013]

In the case of an exhaust gas purifying apparatus for an internal combustion engine for a vehicle, in which the same exhaust gas purifying catalyst is separately provided along the exhaust gas exhaust path into an upstream catalytic converter and a downstream catalytic converter. The catalyst in the upstream catalytic converter is close to the internal combustion engine, and by introducing high-temperature exhaust gas, it always exhibits a high activity at a relatively high temperature and operates at a high operating rate. In order to improve the performance, it is preferable to reduce the operating rate of the exhaust gas as long as it is permissible as long as the required exhaust gas purification is not impaired. However, during normal engine operation, in order to purify the exhaust gas to a predetermined degree of purification, the catalyst must always be operated at a corresponding operating rate.

Therefore, if the operating state of the internal combustion engine is sufficient for bypassing the exhaust gas through the upstream catalytic converter for purification of the exhaust gas at that time, then the exhaust gas is exhausted at the upstream catalyst. If you try to bypass this without guiding it to the converter, during that time,
The operating rate of the catalyst in the upstream catalytic converter is slowed down, the temperature also drops during that time, metabolism under the surface of the catalyst also progresses, and it recovers before the surface fatigue progresses irreversibly, thereby improving the durability of the catalyst. You can improve your sex.

On the other hand, in the downstream side catalytic converter,
Normally, exhaust gas whose temperature has dropped considerably after passing through the upstream catalytic converter is supplied, and the operating temperature tends to be insufficient, so if exhaust gas is supplied by bypassing the upstream catalytic converter, During that time, the operating temperature can be raised, which is a good opportunity for the catalyst of the downstream catalytic converter to improve the exhaust gas purification performance. Further, from the viewpoint of exhaust gas purification degree, even if the upstream side catalytic converter is bypassed, exhaust gas purification degree is not lost at all by bypassing the upstream side catalytic converter, and the downstream side is not lost. The exhaust gas purification performance of the side catalytic converter is compensated for by the increase in temperature.

The exhaust gas purifying catalyst is a catalyst for purifying unburned components in the exhaust gas, and the exhaust gas purifying catalyst is divided into an upstream catalytic converter and a downstream catalytic converter along the exhaust gas discharge path of the internal combustion engine. When the internal combustion engine is provided, the operating state of the internal combustion engine, in which the exhaust gas bypasses the upstream catalytic converter, may be sufficient for exhaust gas purification, when the internal combustion engine is generally operated at a low load and at a high speed. This operating state can be determined by setting appropriate threshold values for the engine speed and the throttle opening, and determining whether the engine speed is equal to or higher than a predetermined value and the throttle opening is equal to or lower than a predetermined value.

In the internal combustion engine for a vehicle, a fuel cut operation is known and is performed, but in the fuel cut operation, the engine speed is usually a predetermined value or more and the throttle is fully closed. The fuel cut operation is one of the operating states in which the engine speed is equal to or higher than the predetermined value and the throttle opening is equal to or lower than the predetermined value. Also, when performing fuel cut, if the throttle opening is returned to zero and the fuel supply is stopped at the same time, a large deceleration shock will occur, and there will be rattling in returning the throttle opening sensor to the zero position. When dealing with the things that may be involved, when performing the fuel cut,
There may be a fuel cut execution delay in which the fuel supply is stopped after a delay of 0.2 to 0.5 seconds from the time when the throttle opening is set to zero. This is one of the operating states in which the engine speed is equal to or higher than the predetermined value and the throttle opening is equal to or lower than the predetermined value.

However, when the internal combustion engine is in an operating state in which there is no problem in purifying the exhaust gas even if the internal combustion engine bypasses the exhaust gas to the upstream catalytic converter, it means that the exhaust gas bypasses the upstream catalytic converter. Does not necessarily mean that the exhaust gas bypasses the upstream catalytic converter if it is in such an operating state. That is, even if the internal combustion engine is in an operating state in which there is no problem in purifying the exhaust gas even if the upstream catalytic converter is bypassed to the exhaust gas,
For example, when it is determined that the catalyst temperature in the upstream catalytic converter is not high enough to cause early deterioration of the catalyst, and it is determined that exhaust gas does not bypass the upstream catalytic converter, bypassing is performed. You don't have to know it.

On the other hand, the fuel cut is usually performed when the vehicle is decelerated when the engine speed is equal to or higher than a predetermined value and the throttle is fully closed. However, the catalyst temperature in the upstream side catalytic converter is predetermined. When it rises above the value, it may be carried out in order to create an operating state of the internal combustion engine that does not interfere with exhaust gas purification even if the exhaust gas bypasses the upstream catalytic converter. This is easily possible at any time, especially in hybrid vehicles.

When the upstream catalytic converter is arranged in the engine room of the vehicle and the downstream catalytic converter is arranged under the floor of the vehicle, the operating temperature of the catalyst in the upstream catalytic converter is considerably high. Since the operating temperature of the catalyst in the downstream catalytic converter becomes considerably low, the upstream catalytic converter is sometimes bypassed and the exhaust gas is transferred to the downstream catalytic converter by taking the opportunity allowed in the exhaust gas purification degree as described above. Direct introduction is effective in terms of temperature control for both the upstream and downstream catalytic converters.

Further, in the method for operating the exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to the present invention, the same exhaust gas purifying catalyst is divided into an upstream side catalytic converter and a downstream side catalytic converter along the exhaust gas discharge path. It is effective when provided, and particularly when the catalyst is a catalyst for purifying unburned components contained in the exhaust gas of an internal combustion engine, the effect is particularly exerted, and the catalyst is a three-way catalyst. In this case, the invention can be carried out without being bothered by arranging the converter for the reduction catalyst required for removing NOx in the unburned component purification catalyst.

When means for bypassing the upstream catalytic converter is provided, when the upstream catalytic converter is bypassed due to malfunction of the bypass means during operation of the internal combustion engine in which the upstream catalytic converter is not bypassed, exhaust gas purification However, because of the fact that the oxygen concentration in the exhaust gas at the outlet of the upstream side catalytic converter does not change in accordance with the rotation cycle of the internal combustion engine, malfunction of the bypass means may occur. If it is designed to be detected, it is possible to promptly deal with a malfunction of bypass operation when the bypass means should not be bypassed.

Further, when the upstream catalytic converter is shut off in the fuel cut operation state and the exhaust gas bypasses the upstream catalytic converter, if there is an oxygen flow through the upstream catalytic converter, it can be detected. With this configuration, when a malfunction in which bypass is not performed occurs when the bypass means should not be bypassed, it is possible to quickly deal with it and prevent the effect of the present invention from being lost. it can.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An exhaust gas purifying apparatus for an internal combustion engine to which the present invention is applied is an internal combustion engine controlled by an electronic engine operation control unit (ECU) 1 shown diagrammatically in FIG. It is applied to an exhaust system 3 of an engine (hereinafter, referred to as an engine for simplicity in the embodiments) 2. The engine 2 may be any internal combustion engine known in the art mounted on a vehicle, such as an automobile, for example, an in-line multi-cylinder 4-stroke cycle reciprocating gasoline engine.

The engine 2 has a combustion chamber (not shown) bounded by a plurality of pistons and cylinders therein.
Air is sucked into the combustion chamber through the throttle valve 4, the surge tank 5, and the intake manifold 6. Throttle valve 4
The opening degree of is controlled in conjunction with the accelerator pedal depressed by the driver of the vehicle to control the amount of air taken into the combustion chamber. In parallel with the throttle valve, an idle adjustment passage for controlling the intake air amount during idle operation, an idle rotation speed control valve and the like (not shown) may be provided. A fuel injection device 7 is provided in the intake manifold 6, and the fuel sent from a fuel supply pump (not shown) is controlled under the control of the ECU so as to be suitable for the operating condition required of the engine. It is sprayed into the air sucked into the combustion chamber in a large amount. The mixture of fuel and air sucked into the combustion chamber of each cylinder is explosively combusted in an explosive stroke to drive a piston and rotate a crankshaft (not shown) connected to the piston, In the exhaust stroke of each cylinder, the exhaust gas is discharged to the exhaust manifold 8. An upstream side catalytic converter 9 and a downstream side catalytic converter 10 are connected in series to the exhaust manifold 8, and the exhaust gas is always purified through these two catalytic converters and then discharged to the outside air. The upstream catalytic converter 9 and the downstream catalytic converter 10 may be loaded with a three-way catalyst.

The ECU 1 is capable of controlling each part of the engine to execute fuel injection control, ignition timing control, etc. so as to achieve appropriate operation of the engine according to the operating state of the engine. It may be a well-known microcomputer control device, such as a CPU,
It includes components well known to those skilled in the art, such as ROM and RAM. To the ECU, in order to detect the operating state of the engine, an intake air amount sensor, an intake pressure sensor, an intake air temperature sensor, etc. (not shown) relating to the intake air, and a throttle valve are provided to detect the opening thereof. A throttle opening sensor 11, a temperature sensor (not shown) for engine cooling water, a crank angle sensor 12 for detecting the rotation of the crankshaft, a mixture provided in the exhaust manifold 8 and burned by residual oxygen in the exhaust gas. The outputs from the O ₂ sensor 13a for detecting the air-fuel ratio of the air, the O ₂ sensor 13b for detecting whether or not the operation of the bypass switching means, which will be described later, are normally performed, are respectively connected to appropriate interfaces. Entered through. Then, the ECU transmits a control signal for operating the fuel injection device 7, the ignition device (not shown) and the like to each part via an appropriate drive circuit based on the signals from these sensors. (Detailed configurations and operations of the above engine and ECU are well known to those skilled in the art, and are described in, for example, Japanese Patent Laid-Open No. 2001-59444.)

The upstream and downstream catalytic converters 9 and 10 which are the subject of the present invention preferably have a built-in three-way catalyst, but they may be simple oxidation catalysts.
It is also possible to separately provide the NOx purification catalyst in the upstream side and downstream side catalytic converters and apply the present invention, but in that case, in general, it is also large for the unburned portion purification catalyst. The need for a converter complicates converter placement and can be impractical. As shown in FIG. 1, the upstream catalytic converter 9 is provided with bypass means 14 for bypassing the exhaust gas. The bypass means 14 includes a bypass passage 15 that connects the exhaust manifold 8 and the inlet of the downstream catalytic converter 10 in parallel with the upstream catalytic converter 9, and a flow passage switching valve 16.
6 operates in the manner described below by a control signal transmitted from the ECU via an appropriate interface, and switches the flow of exhaust gas between the upstream catalytic converter 9 and the bypass passage 15. In the figure, the flow path switching valve is provided at the confluence of the outlet of the upstream catalytic converter and the bypass passage, but may be provided at the branch of the inlet of the upstream catalytic converter and the bypass passage. .

As an example, the ECU controls the flow path switching valve 16 to exhaust gas into the upstream side catalytic converter 9 when any one of the following conditions is satisfied during engine operation.
Issue a command to bypass. (A) When the engine speed is above a predetermined value and the throttle opening is below a predetermined value. (B) During fuel cut control. (C) The fuel cut control is being delayed.

FIG. 2 is a flow chart showing the operation in the case of the above (A). When an ignition switch (not shown) of the vehicle is closed and the vehicle starts to operate, the ECU controls the crank angle sensor 12 and the throttle opening sensor 1 in the example of FIG.
Based on the engine speed and throttle opening obtained from 1, it is determined in step 10 whether the engine speed is equal to or higher than a predetermined value. If the engine speed is equal to or higher than the predetermined value, in step 20, It is determined whether the throttle opening is less than or equal to a predetermined value. If either answer is YES, the control proceeds to step 30, and a control signal is issued to the flow path switching valve 16 to close the upstream side catalytic converter and open the bypass passage. If the determination is NO in either step 10 or 20, the control proceeds to step 40, and the flow path switching valve 16 is issued a control signal for opening the upstream catalytic converter and closing the bypass passage. After proceeding to step 30 or step 40,
The control is returned to the original state, and the control is repeated again from step 10 according to the flowchart while rereading the data.

FIG. 2a is a flowchart in which step 25 is added to the flowchart of FIG. In this embodiment, even when it is determined in step 10 that the engine speed is equal to or higher than the predetermined value, and when it is determined in step 20 that the throttle opening is equal to or lower than the predetermined value, in step 25. It is determined whether or not the catalyst temperature of the upstream side catalytic converter is equal to or higher than a predetermined value which accelerates the deterioration thereof, and if the answer is yes, the control proceeds to step 30 so that the bypass is executed. Has become.

FIG. 3 is a flowchart showing the operations in the cases (B) and (C).
In this case, in step 110, it is determined whether the engine is in the fuel cut (F / C) control. The fuel cut control of the engine is a control performed by the ECU separately from the control of the present invention. In the example of FIG. 1, the engine rotation obtained from the crank angle sensor 12 and the throttle opening sensor 11 is the same as in the case of (A). When the engine speed is higher than a predetermined value based on the number and throttle opening, the accelerator pedal is released and the throttle opening becomes zero, and the engine does not stop even if the fuel supply is stopped. The control is such that the fuel supply is temporarily stopped. If the answer is yes, control proceeds to step 130 and the flow path switching valve 16 is switched to close the upstream catalytic converter 9 and open the bypass passage 15.

If the answer to step 110 is NO, the control proceeds to step 120, where it is determined whether the fuel cut control execution is being delayed. The fuel cut delay is a control that delays the start of the temporary stop of fuel supply by the fuel cut control by about 0.2 to 0.5 seconds. This is to avoid a large deceleration shock if the fuel supply is cut off immediately after the throttle opening is returned to zero as described above, and in some cases, the throttle opening sensor returns to the zero position. This is to avoid the influence of rattling. If the answer to step 120 is YES during the fuel cut control execution delay, the control also proceeds to step 130, and the passage switching valve 16 is switched to close the upstream side catalytic converter and open the bypass passage.

As described above, the bypass control of the upstream side catalytic converter is started during the fuel cut control execution delay, so that the engine operating condition causes a problem in achieving exhaust gas purification without using the upstream side catalytic converter. By making full use of the period in which the exhausted state is lost, it is possible to suspend the operation of the upstream catalytic converter and at the same time improve the warm-up of the downstream catalytic converter. In addition, step 12
When the answer to 0 is also no, the control proceeds to step 140, and the normal operation for operating the upstream catalytic converter is performed.

FIG. 3a is an addition of step 125 to the flowchart of FIG. In this embodiment, even when it is determined in step 110 that the fuel cut control is being executed and when it is determined in step 20 that the fuel cut control execution delay is being executed, the routine proceeds to step 125. Then, it is judged whether or not the catalyst temperature of the upstream side catalytic converter is equal to or higher than a predetermined value which accelerates its deterioration. If the answer is yes, the control proceeds to step 130, and the bypass is executed. It is like this.

The delay of the fuel cut control or the fuel cut control associated therewith is determined by the control judgment of the ECU based on the driving state of the vehicle, as is generally done, for example, when the driver releases the accelerator pedal and opens the throttle. It may be performed when the vehicle decelerates when the engine speed becomes a relatively high value equal to or higher than a predetermined value when the degree becomes zero, but as one embodiment of the present invention, the catalyst temperature of the upstream side catalytic converter 9 is In order to create an operating state of the internal combustion engine that does not interfere with exhaust gas purification even if the exhaust gas bypasses the upstream catalytic converter when it rises above a predetermined value that may cause deterioration due to an unfavorable degree. May be done. FIG. 4 is a flowchart showing the control that the ECU performs in such a case.

In step 210 of FIG. 4, it is determined whether or not the catalyst temperature of the upstream side catalytic converter is equal to or higher than the above predetermined value. And when the answer is yes,
The control proceeds to step 220, where a fuel cut control command is issued. The fuel cut control command based on the upstream catalyst temperature is canceled in step 230 when the answer to step 210 is NO, that is, when the upstream catalyst temperature falls below the predetermined value.

In any of the bypass switching control of FIG. 2 or FIG. 2a or FIG. 3 or FIG. 3a, the flow path switching valve 16 processes the two outputs from the ECU 1 by the AND circuit or the OR circuit. May be operated by
That is, in the case of the control according to the flowchart of FIG. 2 or FIG. 2a, the output of the terminal 17a of the ECU is turned on when the engine speed is equal to or higher than a predetermined value as shown in FIG. So that the output of the terminal 17b of the
When the ND circuit 18 processes and the output is turned on, the flow passage switching valve 16 shuts off the upstream side catalytic converter 9 to open the bypass passage 15, and when the AND circuit has no output, the oil passage switching valve 16 It is sufficient to open the upstream catalytic converter and close the bypass passage 15 as usual.

Similarly, in the case of the control according to the flowchart of FIG. 3 or 3a, the output of the terminal 19a of the ECU is turned on while the fuel cut control is being executed as shown in FIG. 6, and the fuel cut control execution delay is being executed. At this time, the output of the terminal 19b of the ECU is turned on, the output signals of these terminals are processed by the OR circuit 20, and when the output is turned on, the flow path switching valve 16 shuts off the upstream side catalytic converter 9. To open the bypass passage 15, and when there is no output in the OR circuit, the oil passage switching valve 1
As for 6, the upstream side catalytic converter may be opened as usual and the bypass passage 15 may be closed.

Further, as shown in FIG. 1, an O ₂ sensor 13b is provided near the downstream end of the upstream side catalytic converter 9.
By providing the bypass means 14, in particular, the failure diagnosis of the flow path switching valve 16 (on-board diagnosis: O
BD) can be performed. That is, during normal operation of the internal combustion engine, when the flow path switching valve 16 closes the bypass 15 and the upstream side catalytic converter is open, the detected value of the oxygen concentration by the O ₂ sensor 13b is the value of the engine. It should change according to the rotation speed. On the other hand, during the fuel cut, while the upstream catalytic converter 9 is shut off and the exhaust gas is bypassed, no exhaust gas flow should occur in the upstream catalytic converter.
The O ₂ sensor 13b should not detect oxygen. Therefore, if any of these is violated, it indicates that the flow path switching valve 16 is not switched according to the control, and it is estimated that the flow path switching valve 16 has a malfunction such as a stick.

FIG. 7 shows an embodiment of a flow chart for executing the above-mentioned bypass means OBD. When the OBD according to the flowchart shown in the figure is started, it is determined in step 310 whether the bypass is closed and the upstream catalytic converter is in an operating state in which it should be opened based on the data read each time. When the answer is yes, the control proceeds to step 320, where it is judged if the detected value of the oxygen concentration by the O ₂ sensor 13b has changed corresponding to the engine speed. On the other hand, step 310
If the answer is no, that is, if the bypass is executed and the upstream catalytic converter is closed, the control proceeds to step 330, where it is judged whether or not the O ₂ sensor 13b detects oxygen. It If the answer in step 320 is yes, or if the answer in step 330 is no,
Since it may be determined that the bypass means is operating normally, control proceeds to step 340 and the alarm lamp remains off. On the other hand, if the answer to step 320 is NO or the answer to step 330 is YES, it is presumed that the flow path switching valve 16 has malfunctioned, such as a stick. Proceeding to 350, the alarm lamp 21 (FIG. 1) is turned on.

Although the present invention has been described above with reference to some preferred embodiments, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the present invention. It will be apparent to those skilled in the art.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an exhaust system of an internal combustion engine of a vehicle such as an automobile to which the present invention is applied and an exhaust gas purification device provided therein.

FIG. 2 is a flowchart showing one embodiment of bypass control of the present invention for the exhaust gas purification device of FIG.

FIG. 2a is a flowchart showing an embodiment in which a part of the embodiment of FIG. 2 is modified.

FIG. 3 is a flowchart showing another embodiment of the bypass control of the present invention for the exhaust gas purification device of FIG.

FIG. 3a is a flowchart showing an embodiment in which a part of the embodiment of FIG. 3 is modified.

FIG. 4 is a flowchart showing an embodiment in which the fuel cut control of FIG. 3 or 3a is commanded based on the catalyst temperature of the upstream catalytic converter.

5 is a schematic diagram showing one embodiment of an electronic circuit that executes the bypass control of FIG.

FIG. 6 is a schematic diagram showing an embodiment of an electronic circuit that executes the bypass control of FIG.

7 is a flowchart showing one embodiment of a failure diagnosis routine for detecting an abnormality of the flow path switching valve in the exhaust gas purification device of FIG.

[Explanation of symbols]

1 ... ECU 2 ... Engine 3 ... Exhaust system 4 ... Throttle valve 5 ... Surge tank 6 ... Intake manifold 7 ... Fuel injection device 8 ... Exhaust manifold 9 ... Upstream catalytic converter 10 ... Downstream catalytic converter 11 ... Throttle opening sensor 12 ... crank angle sensor 13a, 13b ... O ₂ sensor 14 ... bypass means 15 ... bypass passage 17a, 17b ... terminal 18 ... the AND circuit 19a, 19b ... terminal 20 ... OR circuit 21 ... alarm lamp

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) F01N 3/20 F01N 3/20 U B01D 53/86 3/28 301B F01N 3/28 301 F02D 41/04 301A F02D 41/04 301 330M 330 B01D 53/36 Z F term (reference) 3G091 AA02 AA14 AA17 AA28 AB02 AB03 BA03 BA04 BA07 BA08 BA14 BA15 BA19 BA21 CA12 CA13 CB02 CB08 DA01 DA02 DA07 DB10 DC01 EA01 EA05 EA06 EA07 EA15 EA16 EA31 EA34 FA05 HA08 HA36 HA37 HA42 HB03 3G301 HA01 JA25 JA26 JA33 JB02 JB09 KA26 LA01 LB01 MA01 MA11 NA08 ND01 NE01 NE06 NE13 NE15 PA01B PA01Z PA07B PA07Z PA10B PA10Z PA12B PA12Z PA16A01 PE01 PE08 A8ZB16A01B01A16A01B25A16B01A16A16B16A16B16A8A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A6A4A6A4A6A4A4A4A6A4A0A4A6A0A6A0A4A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0A0O2 CC26 CC32

Claims (10)

[Claims] 1. An operation of an exhaust gas purifying device for an internal combustion engine for a vehicle, wherein the same exhaust gas purifying catalyst is provided separately for an upstream side catalytic converter and a downstream side catalytic converter along an exhaust gas exhaust path of the internal combustion engine. In the method, when the operating state of the internal combustion engine is in a state in which the internal combustion engine bypasses the upstream side catalytic converter into exhaust gas and the internal combustion engine can bypass the upstream side catalytic converter into exhaust gas, A method of operating an exhaust gas purifying apparatus for an internal combustion engine for a vehicle, characterized in that exhaust gas is guided to the downstream catalytic converter by bypassing the upstream catalytic converter. 2. The operation of an internal combustion engine, wherein the exhaust gas purifying catalyst is a catalyst for purifying unburned components in exhaust gas, and even if the exhaust gas bypasses the upstream side catalytic converter, there is no problem in purifying exhaust gas. The state is an operating state in which the engine speed is equal to or higher than a predetermined value and the throttle opening is equal to or lower than a predetermined value, and the operation of the exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to claim 1. Method. 3. The operation of an internal combustion engine, wherein the exhaust gas purifying catalyst is a catalyst for purifying unburned components in the exhaust gas, and even if the exhaust gas bypasses the upstream catalytic converter, there is no problem in purifying the exhaust gas. The operating method of the exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to claim 1 or 2, wherein the state includes a fuel cut operating state. 4. The operation of an internal combustion engine, wherein the exhaust gas purifying catalyst is a catalyst for purifying unburned components in exhaust gas, and even if the exhaust gas bypasses the upstream side catalytic converter, there is no problem in purifying exhaust gas. The state includes a fuel cut execution delay operation state.
9. An operating method of an exhaust gas purifying apparatus for a vehicle internal combustion engine according to any one of 1. 5. When the catalyst temperature of the upstream side catalytic converter is not higher than a predetermined value in the operating state of the internal combustion engine in which the exhaust gas can bypass the upstream side catalytic converter for purification of the exhaust gas. Except for the above, the method for operating the exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to claim 2, 3 or 4, wherein exhaust gas bypasses the upstream catalytic converter. 6. The operation of an internal combustion engine, wherein the exhaust gas purifying catalyst is a catalyst for purifying unburned components in the exhaust gas, and even if the exhaust gas bypasses the upstream side catalytic converter, there is no problem in purifying the exhaust gas. The exhaust gas purification of the internal combustion engine for a vehicle according to claim 3 or 4, wherein the state includes an operating state brought about by performing fuel cut when the catalyst temperature of the upstream side catalytic converter is equal to or higher than a predetermined value. How to operate the device. 7. The vehicle according to claim 1, wherein the upstream catalytic converter is arranged in an engine compartment of the vehicle, and the downstream catalytic converter is arranged under the floor of the vehicle. For operating an exhaust gas purifying apparatus for a commercial internal combustion engine. 8. The method for operating an exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to claim 1, wherein the catalyst is a three-way catalyst. 9. When the internal combustion engine that does not bypass the upstream side catalytic converter is operating, the oxygen concentration in the exhaust gas at the outlet of the upstream side catalytic converter does not change in accordance with the rotation cycle of the internal combustion engine. 9. The method for operating an exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to claim 1, further comprising detecting a malfunction of a unit that causes gas to bypass the upstream side catalytic converter. 10. When the exhaust gas bypasses the upstream side catalytic converter in a fuel cut operation state, it is detected that there is a flow of oxygen through the upstream side catalytic converter to detect the presence of the oxygen in the exhaust gas. 7. The method for operating an exhaust gas purifying apparatus for an internal combustion engine for a vehicle according to claim 3, 4 or 6, further comprising detecting a malfunction of means for bypassing the side catalytic converter.