JP2003301718A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To early activate an exhaust gas purifying catalyst in an engine for arranging the exhaust gas purifying catalyst in a downstream part of an exhaust passage. <P>SOLUTION: The engine is formed by arranging the exhaust gas purifying catalyst 13 in the downstream part of the exhaust passage 3 separate from an aggregation part of an exhaust manifold, and has a secondary air supply means 14 for supplying secondary air to an upstream part of the exhaust passage 3, and has a light-OFF control means 24 for setting the air-fuel ratio in a combustion chamber richer than the theoretical air-fuel ratio at cold starting time of the engine, and controlling so as to early activate the exhaust gas purifying catalyst 13 by supplying the secondary air to the exhaust passage 3, and is constituted so as to put a state in a control state of a first mode for raising an exhaust gas temperature in the upstream part of the exhaust passage 3 in the initial stage of this light-OFF control and a control state of a second mode for raising the exhaust gas temperature in the downstream side of the exhaust passage 3 thereafter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device in which an exhaust gas purifying catalyst is arranged in a downstream portion of an exhaust passage separated from a collecting portion of an exhaust manifold.

[0002]

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 9-100724, it is installed in an intake system of an engine.
A supercharger that supercharges intake air by being driven from at least one of a crankshaft and an exhaust system recovery turbine via a transmission mechanism, a catalyst device arranged in the exhaust system, and a part of the transmission mechanism. And a transmission that drives the supercharger by changing the transmitted power to control the gear ratio of the transmission according to the catalyst temperature detected by the catalyst temperature detection means by the control means. There is known an engine supercharger control device configured to increase or decrease the rotation of the supercharger in association with a change in the gear ratio of the machine. This supercharger control device, when the temperature of the cooling water of the engine is not higher than a predetermined value and is not warmed up, when the temperature of the exhaust gas purifying catalyst arranged in the exhaust passage is below the activation temperature, , The speed ratio of the transmission is set to the deceleration side to activate the exhaust gas purification catalyst early, and then the speed ratio of the transmission is set to the maximum speed-increasing side to accelerate engine warm-up. Is configured to.

[0003]

As described in the above publication, when the engine is not warmed up and the gear ratio of the transmission is set to the deceleration side to suppress the action of the supercharger, Since heat radiation of the catalyst due to excessive intake and exhaust amounts is suppressed, activation of the exhaust gas purification catalyst can be promoted to some extent. However, in the engine in which the exhaust gas purifying catalyst is provided in the downstream portion of the exhaust passage, it takes a considerable time to raise the temperature of the exhaust passage upstream of the installation portion of the exhaust gas purifying catalyst. However, there is a problem in that it is difficult to activate the exhaust gas purifying catalyst in an early stage.

In view of such circumstances, the present invention provides an engine control device capable of activating an exhaust gas purification catalyst in an engine in which the exhaust gas purification catalyst is provided at a downstream portion of an exhaust passage. To do.

[0005]

The invention according to claim 1 is
An exhaust gas purifying catalyst is disposed in a downstream portion of an exhaust passage away from a collecting portion of an exhaust manifold, and an engine including a secondary air supply unit that supplies secondary air to an upstream portion of the exhaust passage is At cold start, the air-fuel ratio in the combustion chamber is set to be richer than the stoichiometric air-fuel ratio, and secondary air is supplied to the exhaust passage to control the exhaust gas purification catalyst so that it is activated early. The exhaust gas purifying catalyst is provided with a control means, which is in a first mode control state in which the temperature of the exhaust gas is increased in the upstream portion of the exhaust passage at the initial stage of the light-off control, and after that, the exhaust gas purifying catalyst located in the downstream portion of the exhaust passage The control mode is the second mode in which the exhaust gas temperature is raised in the vicinity.

According to the above construction, in the initial stage of the light-off control such as when the engine is started, the upstream portion of the exhaust passage is heated as the control state of the first mode, and then the control state of the second mode is entered. By effectively heating the downstream portion of the exhaust passage, the exhaust gas purifying catalyst can be activated early by effectively utilizing the thermal energy of the exhaust gas.

According to a second aspect of the present invention, in the engine control device according to the first aspect, in the control state of the first mode, the ignition timing of the air-fuel mixture is retarded by a predetermined amount from the compression top dead center. In addition to the first timing, in the second mode control state, the ignition timing of the air-fuel mixture is set to the second timing that is advanced after the compression top dead center with respect to the first timing.

With the above arrangement, the ignition timing of the air-fuel mixture is set to the first timing which is retarded by a predetermined amount from the compression top dead center in the initial stage of the light-off control, so that the upstream side of the exhaust passage is The portion is effectively heated, and thereafter, is set to the second timing which is advanced by a predetermined amount from the first timing, whereby the control state of the second mode is entered and the downstream portion of the exhaust passage is set. Is effectively heated, and the exhaust gas purification catalyst is activated early.

According to a third aspect of the present invention, in the engine control device according to the second aspect, the ignition timing of the air-fuel mixture is set to the first timing when the control state of the first mode is changed to the control state of the second mode. From the second to the second period all at once.

According to the above configuration, when the control state of the first mode executed at the initial stage of the light-off control is changed to the control state of the second mode executed thereafter, the ignition timing of the air-fuel mixture is set to the first timing. By switching from the second period to the second period all at once, thermal energy is effectively used to heat the downstream portion of the exhaust passage, which effectively prevents deterioration of fuel efficiency and promotes activation of the exhaust gas purification catalyst. Will be done.

According to a fourth aspect of the present invention, in the engine control device according to the second or third aspect, the fuel is divided into a plurality of injections during the light-off control, and the latter injection timing is set to before the ignition. It is set in the compression stroke.

According to the above arrangement, during the light-off control,
By sufficiently securing the retard amount of the ignition timing with respect to the compression top dead center, the light-off control is effectively executed.

According to a fifth aspect of the present invention, in the engine control device according to the first aspect, first secondary air supply means for supplying secondary air to the upstream portion of the exhaust passage, and the first secondary air supply means. A second secondary air supply means for supplying secondary air to the downstream side of the secondary air supply portion by the supply means, and in the second mode control state, the second secondary air supply means The amount of secondary air supplied from the first secondary air supply means is reduced, and the amount of secondary air supplied from the second secondary air supply means is increased.

According to the above construction, in the initial stage of the light-off control, with the air-fuel ratio in the combustion chamber being set to be richer than the stoichiometric air-fuel ratio, the first secondary air supply means is sufficient for the upstream portion of the exhaust passage. By supplying a sufficient amount of secondary air, the temperature of the upstream portion is sufficiently raised, and then the control mode of the second mode is entered to supply the secondary air amount from the second secondary air supply means. Is increased, the downstream portion of the exhaust passage is effectively heated, and the exhaust gas purification catalyst can be activated early.

The invention according to claim 6 is the above claims 1 to 5.
In the engine control device described in any one of the above ones, the turbine driving the blower of the turbocharger is arranged upstream of the installation portion of the exhaust gas purification catalyst.

According to the above configuration, during the light-off control,
Since the exhaust gas and the secondary air are effectively mixed by the stirring action of the turbine, the above-mentioned heating action is promoted by promoting the oxidation of unburned components in the exhaust gas.

The invention according to claim 7 is the above-mentioned claims 1 to 6.
In the engine control device according to any one of items 1 to 5, the exhaust passages connected to a pair of cylinders whose exhaust strokes are not adjacent to each other are joined together, and a joining passage extending from a joining portion of another cylinder downstream of the joining portion. And an exhaust manifold configured so as to join the two.

According to the above configuration, the effect of preventing the reduction of the intake air amount by preventing the exhaust interference and the effect of activating the exhaust gas purifying catalyst by executing the light-off control can be obtained at the same time. .

The invention according to claim 8 is the above-mentioned claims 1 to 7.
In the engine control device according to any one of items 1 to 3, the secondary air is supplied from the secondary air supply means during the light-off control, so that the oxygen concentration in the exhaust passage is in the combustion state of the stoichiometric air-fuel ratio. The supply amount of the secondary air is set so as to have a value higher than the oxygen concentration of the exhaust gas led to the exhaust passage.

According to the above configuration, during the light-off control,
A sufficient amount of secondary air is ensured for the exhaust gas to oxidize the unburned components therein, and the activation of the exhaust gas purification catalyst is effectively promoted.

The invention according to claim 9 is the above-mentioned claim 1-8.
In the engine control device described in any one of (1) to (4), the stop time of the light-off control is set to the activation time point of the exhaust gas purifying catalyst before the engine is warmed up.

According to the above construction, after the exhaust gas purifying catalyst is activated by executing the light-off control,
Since the light-off control is stopped before the engine is warmed up, it is possible to prevent the light-off control from being executed for a long period of time as necessary.

The invention according to claim 10 is the above-mentioned claim 1
In the engine control device described in any one of 9 above, when the sulfur poisoning of the exhaust gas purifying catalyst is eliminated while the engine is warm, the control mode of the second mode is set.

According to the above construction, when sulfur poisoning occurs in the exhaust gas purifying catalyst, the secondary air is supplied to the exhaust passage and is positioned in the downstream portion of the exhaust passage in the control state of the second mode. By raising the exhaust gas temperature in the vicinity of the exhaust gas purifying catalyst, the sulfur poisoning is eliminated quickly and effectively, and the purifying function of the exhaust gas purifying catalyst is restored.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an engine control device according to the present invention. This engine control device includes an intake passage 2 and an exhaust passage 3 connected to an engine body 1 of a cylinder injection type gasoline engine mounted in an automobile, and an ignition provided at the top of a combustion chamber of the engine body 1. It has a plug 4 and a fuel injection valve 5 for directly injecting fuel into the combustion chamber.

A surge tank 6 is provided in the intake passage 2, and a throttle valve 7 is provided upstream of the surge tank 6. The throttle valve 7 is driven by an electric actuator 9 that operates according to a control signal output from an engine control unit (ECU) 8 to adjust the amount of intake air introduced into the combustion chamber of the engine body 1. Is configured to.

On the downstream side of the surge tank 6, an intake shutter valve 1 that opens and closes an intake passage 2 to form a swirl.
Intake valve 2 which is provided with 0 and opens and closes the intake port
a is provided, and the valve operating mechanism of the intake valve 2a is provided with a valve timing adjusting mechanism 2b for adjusting the opening / closing timing of the intake valve 2a.

The intake shutter valve 10 is disposed on the second passage side of the intake passage 2 which is branched into the first passage and the second passage, and the second passage is closed to close the combustion chamber from the first passage side. It is configured to generate swirl by increasing the flow velocity of intake air supplied to the. Instead of the shutter valve 10, a tumble valve for generating a tumble flow in the combustion chamber may be provided in the intake passage 2.

In the exhaust passage 3, an exhaust valve 3a for opening and closing the exhaust port and O ₂ for detecting the oxygen concentration in the exhaust gas.
A sensor 11 and a turbine 12 for driving a blower (not shown) of a turbocharger arranged in the intake passage 3 are arranged. Further, in the downstream portion of the exhaust passage 3 which is separated from the collecting portion of the exhaust manifold by a predetermined distance, a conventionally known three-way catalyst 13a for purifying all of HC, CO and NOx in the exhaust gas, and an HC in the exhaust gas are provided. An exhaust gas purification catalyst 13 that is an HC adsorption catalyst 13b that adsorbs and purifies the exhaust gas is disposed.

In order to prevent exhaust interference, the exhaust manifold joins the exhaust passages 3 respectively connected to a pair of cylinders whose exhaust strokes are not adjacent to each other, and at the downstream side of this joining portion, to another cylinder. It is configured as a so-called dual type in which a merging passage extending from a merging portion of the connected exhaust passages 3 is joined. For example, as shown in FIG. 2, the first cylinder 1a to the fourth cylinder 1d are arranged in series 4
In the cylinder engine, when the ignition order is set from the first cylinder 1a to the third cylinder 1c, the fourth cylinder 1d, and the second cylinder 1b, the exhaust passage 30 connected to the first cylinder 1a
a and the exhaust passage 30b connected to the second cylinder 1b are joined to form a merging portion 31, and an exhaust passage 30c connected to the third cylinder 1c and an exhaust passage 30d connected to the fourth cylinder 1d. To form a merging portion 32, and the merging passage 3 is formed in a downstream portion of the merging portions 31 and 32.
3, 34 are designed to join each other.

Further, the upstream portion of the exhaust passage 3 and the intake passage 2 which are separated from the installation portion of the exhaust gas purifying catalyst 13 by a predetermined distance are connected by a secondary air supply passage 14a. The on-off valve 14b provided on the way constitutes a secondary air supply means 14 for supplying secondary air, that is, fresh air having a large amount of oxygen, to the upstream portion of the exhaust passage 3.

The engine has various types such as an air flow sensor 16 for detecting the amount of intake air passing through the intake passage 2, a crank angle sensor 17 for detecting the engine speed, an accelerator opening sensor 18, an engine water temperature sensor 19 and the like. Sensors are provided, and these detection signals are input to the engine control unit (ECU) 8.

The engine control unit 8 has an operating state determining means 2 for determining the operating state of the engine.
0, the fuel injection control means 21 for controlling the fuel injection amount and the injection timing, the ignition timing control means 22 for controlling the ignition timing of the air-fuel mixture by the spark plug 4, and the opening degree of the throttle valve 7. An intake amount control means 23 for outputting a control signal to the actuator 9 to control the amount of intake air introduced into the combustion chamber, and a control for early activating the exhaust gas purification catalyst 13 at the cold start of the engine are executed. The light-off control means 24 is provided.

Based on the detected value of the engine speed detected by the crank angle sensor 17 and the detected value of the engine load detected by the accelerator opening sensor 18, the operating state discriminating means 20 determines the engine as shown in FIG. It is configured to determine whether it is in the low-load low-rotation stratified combustion region A or in the high-load high-rotation uniform combustion region B, and output the determination data to the fuel injection control means 21 and the like. .

Further, the operating state judging means 20 estimates the temperature state of the exhaust gas purifying catalyst 13 according to the detection signal of the engine water temperature sensor 19 so that the exhaust gas purifying catalyst 13 has a low temperature below the activation temperature. It is configured to determine whether or not the engine is in a state and whether or not the engine is in a non-warm state. The temperature state of the exhaust gas purifying catalyst 13 is determined based on the detected value of the engine water temperature detecting means 15 and the elapsed time from the engine start time, or the temperature of the exhaust gas purifying catalyst 13 is directly detected. By doing so, the temperature state may be determined.

The fuel injection control means 21 operates in the operating regions A and B of the engine determined by the operating condition determination means 20.
And based on the accelerator opening detected by the accelerator opening sensor 16 that detects the accelerator opening and the engine speed detected by the crank angle sensor 17,
The target torque of the engine is read from a preset map, and the target fuel injection amount is read from the preset map based on the target torque and the actual intake air amount detected by the air flow sensor 7, and the target fuel is read. The control signal corresponding to the injection amount is output to the fuel injection valve 5.

Further, the fuel injection control means 21 is configured to control the fuel injection timing in accordance with the engine operating regions A and B determined by the operating state determination means 20. That is, when the engine is warm and in the low-load low-speed stratified charge combustion region A shown in FIG. 3, the fuel injection control means 21 performs control to inject fuel in the compression stroke to perform stratified charge combustion. When in the high-load, high-rotation uniform combustion region B, the fuel injection control means 21 is configured to execute the control for injecting fuel in the intake stroke to perform uniform combustion.

The ignition timing control means 22 controls the ignition timing according to the operating state of the engine. Basically, the ignition timing control means 22 controls the ignition timing to MBT (timing at which the output and the fuel consumption amount are the best). Is configured. Then, at the time of executing the light-off control described later, the ignition timing of the air-fuel mixture is set to the compression top dead center T during the control of the first mode in the initial stage.
The time is set to a first timing that is retarded by a predetermined amount from DC, and when the second mode is controlled in the latter stage of the light-off control, a timing that is advanced from the first timing after the compression top dead center TDC. It is supposed to be set.

Further, the exhaust gas purifying catalyst 13 is in the activated state in the operation state judging means 20, and the engine coolant temperature is lower than a predetermined value, that is, the engine is not warmed up. If it is confirmed, the ignition timing of the air-fuel mixture is set to a timing slightly retarded from the MBT, so that the engine warm-up is promoted.

The intake air amount control means 23 outputs a control signal according to the operating state of the engine to the actuator 9 of the throttle valve 7 so that when the engine is in the low load, low rotation stratified charge combustion region A. , Increase the throttle opening to increase the amount of intake air introduced into the combustion chamber,
When the engine is in the uniform combustion region B of high load and high rotation, the throttle opening is narrowed to reduce the amount of intake air introduced into the combustion chamber.

Further, at the time of executing the light-off control, which will be described later, a control signal for reducing the opening degree of the throttle valve 7 is output from the intake air amount control means 23 to the actuator 9 of the throttle valve 7, so that the combustion chamber is driven. The intake air amount introduced is reduced so that the air-fuel ratio A / F in the combustion chamber is set to be slightly richer than the stoichiometric air-fuel ratio, for example, the air-fuel ratio A / F is set to about 12.

The light-off control means 25 executes control for early activation of the exhaust gas purifying catalyst 13 when the engine is cold started, and more specifically, as described above. In addition, the intake air amount control means 23 sets the air-fuel ratio in the combustion chamber to be slightly richer than the stoichiometric air-fuel ratio, supplies the secondary air to the exhaust passage 3 via the secondary air supply means 14, and the spark plug. By retarding the ignition timing of the air-fuel mixture by 4 by a predetermined amount from the normal time, the temperature of the exhaust gas in the exhaust passage 3 is increased. The amount of the secondary air supplied during the execution of the light-off control is such that the secondary air is supplied so that the oxygen concentration in the exhaust passage 3 is from the combustion chamber of the engine to the exhaust passage in the combustion state of the stoichiometric air-fuel ratio. Three
It is set to a value higher than the oxygen concentration of the exhaust gas discharged to, for example, a value corresponding to the oxygen concentration when burned with the air-fuel ratio A / F in the combustion chamber set to about 16.

At the initial stage of the light-off control, the control mode of the first mode in which the exhaust gas temperature is increased in the upstream portion of the exhaust passage 3 is set, and thereafter the exhaust gas purification located in the downstream portion of the exhaust passage 3 is performed. The control mode is switched by changing the ignition timing of the air-fuel mixture according to the execution stage of the light-off control so that the control mode is the second mode in which the exhaust gas temperature is raised in the vicinity of the catalyst 13. It is configured.

That is, in the control state of the first mode, the ignition timing of the air-fuel mixture is delayed by a predetermined amount from the compression top dead center TDC, for example, the crank angle CA after the compression top dead center. By setting the timing at about 15 °, the combustion of the air-fuel mixture is approaching the expansion stroke, and the amount of heat discharged from the combustion chamber is significantly increased. Then, by supplying the secondary air from the secondary air supply means 14 to the upstream portion of the exhaust passage 3, immediately after the exhaust gas is led to the exhaust passage 3, the HC and the like contained in the exhaust gas are discharged. I try to oxidize unburned components. As a result, the exhaust gas temperature in the upstream portion of the exhaust passage 3 is effectively increased, and the upstream portion of the exhaust passage 3 is actively heated.

When the temperature of the upstream portion of the exhaust passage 3 rises to a predetermined value after a lapse of a predetermined time from the start of the control of the first mode, the control state of the second mode is entered, and the mixture is ignited. When the timing is set to a second timing after the compression top dead center and advanced from the first timing, for example, a crank angle CA after the compression top dead center is set to about 11 °, the fuel is discharged from the combustion chamber. In addition to suppressing an increase in heat quantity, premature oxidation of the unburned component is suppressed. As a result,
The unburned components in the exhaust gas are oxidized in the vicinity of the installation portion of the exhaust gas purification catalyst 13, and the heat of reaction thereof positively raises the temperature of the exhaust gas in this portion. The activation of 13 will be promoted.

Next, when the exhaust gas purifying catalyst 13 is activated before the engine is warmed up, the control in the second mode is stopped to end the light-off control, and the engine warm-up is promoted. When the engine warm-up is completed after shifting to the warm-up promoting control state, the control state shifts to the normal control state, that is, the control state of the stratified combustion mode or the uniform combustion mode.

Further, during the light-off control, the fuel is injected into the combustion chamber from the fuel injection valve 5 in a plurality of divided injections, and the latter injection timing, for example, the second injection when the divided injections are performed in two divided injections. Is configured to be set to the compression stroke before ignition.

Further, the light-off control means 24 is
When the engine is warm, the second mode control state is set in order to eliminate sulfur poisoning of the exhaust gas purification catalyst 13. That is, when the engine operating state is continued for a predetermined time, sulfur adheres to the NOx adsorbent provided in the NOx adsorbing catalyst 13b, and sulfur poisoning that deteriorates the NOx adsorbing performance occurs. When it is confirmed, the light-off control in the second mode is executed. As a result, the unburned components in the exhaust gas are oxidized in the vicinity of the installation portion of the exhaust gas purification catalyst 13 and the NOx adsorbent of the NOx adsorption catalyst 13b is heated, so that the sulfur poisoning is eliminated. It will be.

The control operation executed in the engine control unit will be described with reference to the flow chart shown in FIG. When the control operation is started, first, the operating state determination means 20 determines whether or not the catalyst temperature is in a low temperature state below the activation temperature (step S1). If YES is determined in this step S1, Then, it is determined whether or not it is in the initial stage of the light-off control before a predetermined time has elapsed since the light-off control was started (step S2).

When it is determined YES in step S2 and it is confirmed that the light-off control is in the initial stage, the light-off control in the first mode is executed (step S2).
3), the air-fuel ratio in the combustion chamber is set to be slightly richer than the theoretical air-fuel ratio, and secondary air is supplied to the exhaust passage 3,
Moreover, by setting the ignition timing of the air-fuel mixture to the first timing, the exhaust gas temperature in the upstream portion of the exhaust passage 3 is raised.

On the other hand, it is determined that the predetermined time has elapsed from the time when the determination at step S2 is NO and the light-off control is started, that is, the temperature of the upstream portion of the exhaust passage 3 is sufficiently increased. If it is confirmed that the second mode light-off control is performed (step S4), the air-fuel ratio in the combustion chamber is set to the stoichiometric air-fuel ratio to be slightly rich, and the secondary air is supplied to the exhaust passage 3. Supply,
Further, by setting the ignition timing of the air-fuel mixture to the second timing after the top dead center, the exhaust gas temperature in the vicinity of the exhaust gas purification catalyst 13 located downstream of the exhaust gas is raised and the exhaust gas purification is performed. The activation of the catalyst 13 is promoted.

If it is determined NO in step S1 and it is confirmed that the exhaust gas purifying catalyst 13 is in the activated state, it is determined whether the engine is warmed up (step S5). YE in this step S5
When it is determined to be S and it is confirmed that the engine is in a non-warm state, the warm-up promotion control is executed to retard the ignition timing of the air-fuel mixture slightly from the MBT (step S).
6).

When it is determined NO in step S5 and it is confirmed that the engine is in the warm-up state, it is determined whether or not the sulfur poisoning should be eliminated, that is, it is time to execute S-regeneration. If NO is determined (step S7), the normal combustion control corresponding to the operating state of the engine, that is, the control of the stratified combustion mode or the uniform combustion mode is executed (step S8).

If it is determined YES in step S7 and it is confirmed that the sulfur poisoning should be eliminated, the process proceeds to step S4 to execute the light-off control in the second mode. The exhaust gas temperature in the vicinity of the exhaust gas purifying catalyst 13 located downstream of the exhaust passage 3 is raised to eliminate the sulfur poisoning.

By executing the above control, FIG.
As shown in, from the engine start time t1 to the time t2 when a predetermined time elapses, the ignition timing of the air-fuel mixture is the first time.
The time (15 ° CA after the compression top dead center TDC) is set, and then the second time (the compression top dead center TDC is set.
It is set at the later time of 11 ° CA). Then, from the time t3 when the exhaust gas purifying catalyst 13 is activated to the time t4 when the engine is warmed up, the ignition timing is set to MB.
It is set to a warm-up promotion period that is slightly retarded from T.

Next, at the time t4 when the engine is warmed up, the ignition timing is set to MBT, and the stratified combustion region A
Is set at a timing advanced from the compression top dead center TDC, and is set at a timing delayed from it in the uniform combustion region B. Further, the ignition timing of the air-fuel mixture is the second timing (11 ° CA after the compression top dead center TDC) for a predetermined time at the time t5 when the time to execute the S regeneration control for eliminating the sulfur poisoning has arrived. Period) will be set.

As described above, the exhaust gas purifying catalyst 13 is disposed downstream of the exhaust passage 3 away from the collecting portion of the exhaust manifold, and the secondary air is supplied to the upstream portion of the exhaust passage 3. In the engine provided with the supply means 14, when the engine is cold started, the air-fuel ratio in the combustion chamber is set to be richer than the stoichiometric air-fuel ratio, and the exhaust gas purifying catalyst is supplied by supplying secondary air to the exhaust passage 3. 1
3 has a light-off control means 24 for controlling the activation of the exhaust gas 3 at an early stage. At the initial stage of the light-off control, the exhaust gas temperature is raised in the upstream portion of the exhaust passage 3, and the first mode is controlled. After that, the control is performed in the second mode in which the exhaust gas temperature is raised in the vicinity of the exhaust gas purifying catalyst 13 located in the downstream portion of the exhaust passage 3, so that the thermal energy of the exhaust gas is effectively used. The exhaust gas purifying catalyst 1 provided downstream of the exhaust passage 3
There is an advantage that 3 can be activated early.

That is, in the initial state of the light-off control which is performed immediately after the engine is started, for example, the first mode in which the ignition timing of the air-fuel mixture is retarded by a predetermined amount from the compression top dead center as the control state of the first mode. By setting the timing, the temperature of the exhaust gas is increased in the upstream portion of the exhaust passage 3 to effectively heat the upstream portion of the exhaust passage 3, and then the control state of the second mode is entered to perform mixing. Since the ignition timing of the air is set to the second timing which is advanced from the first timing after the compression top dead center, the unburned components led to the exhaust passage 3 are heated to the high temperature as described above. The thermal energy in the upstream portion of the exhaust passage 3 and the secondary air supplied from the secondary air supply means 14 are used to oxidize the exhaust gas in the vicinity of the exhaust gas purifying catalyst 13, so that the exhaust gas in this portion is oxidized. Raise the temperature It is possible to heat the exhaust gas purifying catalyst 13 efficiently.

Therefore, as described above, the exhaust passage 3 extending to the installation portion of the exhaust gas purifying catalyst 13 is long, and in an engine requiring a large amount of heat energy to heat the entire exhaust passage 3, the exhaust passage 3 The exhaust gas purifying catalyst 13 is activated at an early stage to perform its purifying function without causing a problem such as an increase in heat energy loss and deterioration in fuel consumption, as in the case where the whole is heated. It can be used effectively.

By executing the light-off control, the upstream portion of the exhaust passage 3 to which the secondary air is supplied and the downstream portion of the exhaust passage 3 located near the upstream side of the exhaust gas purifying catalyst 13 are An experiment was conducted to verify how the temperature changes, and the data shown in FIG. 6 were obtained. From this data, the first timing is set at the time when the ignition timing of the air-fuel mixture is retarded by 15 ° CA from the compression top dead center, and the retard angle is set to the maximum value within the range in which combustion stability can be maintained. It has been confirmed that by setting the above, the upstream portion of the exhaust passage 3 can be intensively heated and the temperature thereof can be effectively increased. Then, when the retard amount of the ignition timing is gradually reduced, the downstream portion of the exhaust passage 3 is set at the time when the retard amount of the ignition timing is set to a predetermined value (the timing of 11 ° CA in the above experimental example). It has been confirmed that the temperature at can be significantly increased.

There is a significant difference in the temperature in the downstream portion of the exhaust passage 3 between when the retard amount of the ignition timing is set to 11 ° CA and when it is set to 13 ° CA. The heating point of the exhaust passage 3 changes according to the amount, and when the retard amount is set to 13 ° CA, the intermediate portion of the exhaust passage 3 is effectively heated, while it changes to 11 ° CA. It is considered that, if set, the downstream portion of the exhaust passage 3 (near the installation portion of the exhaust gas purification catalyst 13) is effectively heated. Therefore, when the control state of the first mode is changed to the control state of the second mode, the ignition timing of the air-fuel mixture is switched from the first timing to the second timing at once, so that the deterioration of the combustibility is more effectively prevented. At the same time, there is an advantage that the exhaust gas purifying catalyst 13 can be activated early and its purifying function can be sufficiently exerted.

Further, in the above embodiment, during the light-off control, the fuel is divided into a plurality of times and injected, and the latter injection timing is set to the compression stroke before ignition. There is an advantage that the above-mentioned light-off control can be effectively executed while ensuring the combustion stability in the above condition, and sufficiently ensuring the retard amount of the ignition timing relative to the compression top dead center.

Further, as shown in the above embodiment, when the turbine 12 for driving the blower of the turbocharger is arranged upstream of the exhaust gas purifying catalyst 13, the turbine 12 agitates during the light-off control. Due to the action, the exhaust gas flowing in the exhaust passage 3 and the secondary air are effectively agitated, so that there is an advantage that the oxidation of unburned components in the exhaust gas can be effectively promoted.

As described above, the exhaust passages 30 are respectively connected to the pair of cylinders 1a and 1b whose exhaust strokes are not adjacent to each other.
In the engine provided with the exhaust manifold 30 configured to join the a and 30b and join the merging passage 34 extending from the merging portion 32 of the other cylinders 1c and 1d on the downstream side of the merging portion 31, By preventing the intake resistance from increasing due to the occurrence of, it is possible to secure a sufficient intake air amount and increase the engine output. Then, the exhaust gas purifying catalyst 1 from the combustion chamber
Since the exhaust passage 3 up to the installation portion of 3 is long and a large amount of heat energy is required to heat the whole, the effect obtained by adopting the above configuration is remarkably obtained.

Further, in the above embodiment, the secondary air is supplied from the secondary air supply means 14, so that the oxygen concentration in the exhaust passage 3 is changed from the combustion chamber to the exhaust passage 3 in the combustion state of the stoichiometric air-fuel ratio. Since the supply amount of the secondary air is set so that it becomes a value higher than the oxygen concentration of the derived exhaust gas, it is necessary to secure a sufficient amount of oxygen required to oxidize the unburned components in the exhaust gas. As a result, the exhaust gas purification catalyst 13 can be effectively heated and activated early.

Further, when the stop time of the light-off control is set to the activation time point of the exhaust gas purifying catalyst 13 before the engine is warmed up as described above, the exhaust gas purifying catalyst 13 is activated early. It is possible to effectively prevent deterioration of fuel consumption due to the above-mentioned light-off control being executed for an unnecessarily long period of time without impairing the function of activating.

Further, in the above embodiment, even when the engine is warm, when the sulfur poisoning of the exhaust gas purifying catalyst is eliminated, the air-fuel ratio in the combustion chamber is increased by setting the second mode control state. The exhaust gas temperature is set to be richer than the stoichiometric air-fuel ratio, and the exhaust gas temperature is increased near the exhaust gas purifying catalyst 13 located downstream of the exhaust passage 3 while supplying secondary air to the exhaust passage 3. Therefore, the sulfur poisoning is eliminated quickly and effectively, and the exhaust gas purifying catalyst 1
The purification function of 3 can be restored.

It is to be noted that, instead of the above-described embodiment configured to switch the first mode and the second mode of the light-off control by changing the ignition timing of the air-fuel mixture as described above, FIG. 7 is shown. As described above, the first secondary air supply means 14 for supplying the secondary air to the upstream portion of the exhaust passage 3 and the downstream side of the secondary air supply portion by the first secondary air supply means 14, for example, the exhaust gas. A second secondary air supply means 15 including a secondary air passage 15a for supplying secondary air and an opening / closing valve 15b is provided on the upstream side in the vicinity of the installation portion of the purification catalyst 13, and in the control state of the second mode, The secondary air amount supplied from the first secondary air supply means 14 is reduced and the secondary air amount supplied from the second secondary air supply means 15 is increased as compared with the control state of the 1 mode. You may comprise.

In the case of the above construction, in the initial stage of the light-off control, the air-fuel ratio in the combustion chamber is set to be richer than the stoichiometric air-fuel ratio, and the first secondary air supply means 14 to the exhaust passage 3 are set. By supplying a large amount of secondary air to the upstream portion of the above, the temperature of this upstream portion is sufficiently raised, and then the control state of the second mode is entered and the secondary air is supplied from the second secondary air supply means 15. By increasing the amount of secondary air, the downstream portion of the exhaust passage 3 can be effectively heated and the exhaust gas purification catalyst 13 can be activated early.

[0070]

As described above, according to the present invention, the exhaust gas purifying catalyst is arranged in the downstream portion of the exhaust passage separated from the collecting portion of the exhaust manifold, and the secondary air is provided in the upstream portion of the exhaust passage. In an engine provided with a secondary air supply means for supplying, when the engine is cold-started, the air-fuel ratio in the combustion chamber is set to be richer than the stoichiometric air-fuel ratio, and the exhaust air is supplied by supplying secondary air to the exhaust passage. It has a light-off control means for controlling so as to activate the gas purification catalyst early, and at the beginning of this light-off control, a control mode of the first mode for raising the exhaust gas temperature in the upstream portion of the exhaust passage is provided, and After that, the control is performed in the second mode in which the exhaust gas temperature is raised in the vicinity of the exhaust gas purifying catalyst located in the downstream portion of the exhaust passage. Without causing problems, by effectively utilizing the thermal energy of the exhaust gas, by early activation of the exhaust gas purifying catalyst, there is an advantage that it is possible to effectively perform its cleaning function.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of an engine control device according to the present invention.

FIG. 2 is an explanatory diagram showing a specific configuration of an exhaust manifold.

FIG. 3 is a graph showing a combustion region of an engine.

FIG. 4 is a flowchart showing a control operation by the engine control device.

FIG. 5 is a time chart showing a control operation by the control device of the engine.

FIG. 6 is a graph showing a correspondence relationship between the ignition timing of the air-fuel mixture and the temperature of the exhaust passage.

FIG. 7 is an explanatory diagram showing another embodiment of the engine control device according to the present invention.

[Explanation of symbols] 3 exhaust passage 12 turbine 13 Exhaust gas purification catalyst 14 (First) Secondary Air Supply Means 15 Second secondary air supply means 24 Light-off control means 30 exhaust manifold

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/24 F01N 3/24 GR T F02D 41/06 305 F02D 41/06 305 330 330A 335 335Z 41 / 34 41/34 H 43/00 301 43/00 301B 301E 301J 301T F02P 5/15 F02P 5/15 E (72) Inventor Junichi Taga No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture (Reference) 3G022 AA07 CA02 DA02 DA05 GA05 GA06 GA08 3G084 AA03 BA05 BA08 BA09 BA13 BA15 BA17 BA21 BA24 BA25 CA01 CA02 CA03 CA04 DA10 EA04 EA11 EB08 EC01 EC03 FA07 FA10 FA20 FA29 FA33 FA38 BA03 BA02 BA03 BA03 BA03 BA03 BA02 BA03 BA03 BA03 BA03 DA02 DB10 FA02 FA04 FB02 FC02 FC07 3G301 HA01 HA04 HA06 HA11 HA16 HA17 JA21 KA01 KA02 KA08 KA09 K A23 LA03 LA05 LB04 LC01 LC03 MA01 MA11 MA18 NA08 NB03 NB13 NC02 NE01 NE06 NE13 PA01Z PD02Z PE01Z PE03Z PE08Z PF03Z

Claims (10)

[Claims] 1. An exhaust gas purifying catalyst is disposed downstream of an exhaust passage away from a collection portion of an exhaust manifold, and secondary air supply means is provided for supplying secondary air to an upstream portion of the exhaust passage. In the engine, when the engine is cold started, the air-fuel ratio in the combustion chamber is set to be richer than the stoichiometric air-fuel ratio, and secondary air is supplied to the exhaust passage so that the exhaust gas purification catalyst is activated early. And a light-off control means for controlling the temperature of the exhaust passage at the beginning of the light-off control so that the temperature of the exhaust gas is increased in the upstream portion of the exhaust passage, and thereafter, the light-off control unit is positioned downstream of the exhaust passage. A control device for an engine, which is in a control mode of a second mode for raising an exhaust gas temperature in the vicinity of an exhaust gas purifying catalyst. 2. In the control state of the first mode, the ignition timing of the air-fuel mixture is set to a first timing which is retarded by a predetermined amount from the compression top dead center, and in the control state of the second mode, the air-fuel mixture is set. 2. The engine control device according to claim 1, wherein the ignition timing of the engine is set to a second timing that is advanced after the compression top dead center with respect to the first timing. 3. The engine according to claim 2, wherein the ignition timing of the air-fuel mixture is switched from the first timing to the second timing at a stroke when the control state of the first mode is changed to the control state of the second mode. Control device. 4. The fuel is divided into a plurality of times for injection during the light-off control, and the latter injection timing is set to a compression stroke before ignition.
The engine control device described. 5. A first secondary air supply means for supplying secondary air to the upstream part of the exhaust passage, and a secondary air downstream of the secondary air supply part by the first secondary air supply means. And a second secondary air supply means for supplying the second secondary air supply means for reducing the amount of secondary air supplied from the first secondary air supply means in the second mode control state as compared with the first mode control state. The control device for the engine according to claim 1, wherein the amount of secondary air supplied from the second secondary air supply means is increased. 6. The engine control device according to claim 1, wherein the turbine driving the blower of the turbocharger is arranged upstream of the exhaust gas purification catalyst installation portion. 7. An exhaust passage connected to a pair of cylinders whose exhaust strokes are not adjacent to each other is joined together, and a joining passage extending from a joining portion of another cylinder is joined downstream of this joining portion. The engine control device according to any one of claims 1 to 6, further comprising an exhaust manifold. 8. The oxygen concentration in the exhaust passage is led from the combustion chamber to the exhaust passage in a combustion state of the stoichiometric air-fuel ratio by supplying the secondary air from the secondary air supply means during the light-off control. The engine control device according to any one of claims 1 to 7, wherein the supply amount of the secondary air is set so as to have a value higher than the oxygen concentration of the exhaust gas. 9. The engine according to claim 1, wherein the stop timing of the light-off control is set to an activation time point of the exhaust gas purifying catalyst before the engine is warmed up. Control device. 10. The control mode of the second mode is set when the sulfur poisoning of the exhaust gas purifying catalyst is eliminated while the engine is warm. Engine control unit.