JP3064755B2 - V-type engine exhaust purification system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device for a V-type engine.

[0002]

2. Description of the Related Art A conventional exhaust gas purifying apparatus for a V-type engine is disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 63-79448. That is, two cylinder banks and two exhaust systems are provided, and a first catalytic converter is provided in each of the exhaust systems, and the air-fuel ratio of the combustion air-fuel mixture formed by the fuel supply device is determined according to a signal from the air-fuel ratio sensor. In a V-type engine capable of feedback control, one main air-fuel ratio sensor is provided in one of the exhaust systems upstream of the first catalytic converter, and each exhaust system is connected to one collecting pipe downstream of the first catalytic converter. merging is, the second catalytic converter is provided, a configuration in which upstream of the second catalytic converter providing one auxiliary air-fuel ratio sensor to the collecting pipe to the collecting pipe,
The air-fuel ratio of the two cylinder banks is feedback-controlled by the main air-fuel ratio sensor, and the average air-fuel ratio of the exhaust gas flowing into the second catalytic converter is corrected by the auxiliary air-fuel ratio sensor.

Accordingly, even when the air-fuel ratio shifts to the rich side or the lean side due to the deterioration of the main air-fuel ratio sensor, it is possible to prevent the deterioration of the emission by the correction from the auxiliary air-fuel ratio sensor. On the other hand, there is a type in which two cylinder banks and two exhaust systems are provided, and catalytic converters having different capacities are provided in the exhaust systems from the respective cylinder banks (see Japanese Utility Model Laid-Open No. 63-102922).

That is, when a V-type engine is mounted in an FF layout, it may not be possible to install a catalytic converter that generates a large amount of heat in the rear cylinder bank due to installation space or heat damage. In this case, a catalytic converter having a small capacity may be installed in the rear cylinder bank at the time of FF layout of the V-type engine in which heat damage is a problem.

[0005]

Here, in such a conventional exhaust gas purifying apparatus for a V-type engine in which a catalytic converter having a different capacity is provided in an exhaust system from each cylinder bank, a first catalyst is used. With one main air-fuel ratio sensor provided in either exhaust system upstream of the converter,
The air-fuel ratio of both cylinder banks is uniformly feedback-controlled.

By the way, when the first catalytic converters having different capacities are provided in the exhaust system of each cylinder bank,
Due to the difference in the capacity of the first catalytic converter, engine
Or different required value of fuel increase during down cold, also
The required air-fuel ratio of each first catalytic converter after the engine is warmed up and the first catalytic converter is activated may be different. However, in the prior art, since the air-fuel ratio of both cylinder banks is uniformly controlled by feedback, the cylinder banks during the engine cold operation are not controlled.
Neither the fuel increase for each time nor the feedback control to the required air-fuel ratio of each first catalytic converter after the engine is warmed up is performed, so that the conversion efficiency of each catalytic converter is increased and the catalytic converter is used more effectively. And there is a risk that exhaust emissions will deteriorate.

Further, since it is difficult to properly judge the deterioration, in order to prevent the deterioration of the exhaust emission, the maintenance of the catalytic converter must be carried out at an early stage.
There is a risk that administrative costs will rise. The present invention has been made in view of such a conventional situation. In an exhaust purification device for a V-type engine in which catalyst converters having different capacities are provided in exhaust pipes from respective cylinder banks, the capacity difference of the catalyst converters is described. By performing control in consideration of
By controlling the optimum air-fuel ratio in each cylinder bank, provided by increasing the conversion efficiency of each of the catalytic converter, the exhaust gas purifying apparatus for a V-type engine that makes it possible to use each of the catalytic converter more effectively It is intended to be.

[0008]

For this purpose, the present invention relates to claim 1.
In the present invention, the exhaust pipe of each cylinder bank has a different capacity.
Exhaust gas purifier for V-type engine provided with respective catalytic converters
At least upstream of at least one catalytic converter
Installed air-fuel ratio sensor and detect engine operating conditions
Operating condition detecting means, and the operating condition detecting means
When it is detected that the engine has been warmed up,
Based on the signal from the air-fuel ratio sensor and the control constant,
Calculate the air-fuel ratio feedback correction coefficient for each bank,
Using this air-fuel ratio feedback correction coefficient, the cylinder
Air-fuel ratio feedback control of air-fuel ratio for each tank
Feedback control means and a small catalytic converter
The average air-fuel ratio of the
Before shifting to a leaner side than the average air-fuel ratio of the bank
Control constants that determine the control constants for each cylinder bank
And a step.

In the invention according to claim 2, the cylinder is
Catalytic converters with different capacities are installed in the exhaust pipe of each bank.
In the exhaust purification device for a V-type engine provided,
Operating condition detecting means for detecting the operating conditions of the
Detecting that the engine is in a cold state
The fuel increase correction coefficient during cold operation for each cylinder bank
To increase the fuel for each cylinder bank using
Stage and syringe with large catalytic converter
The fuel increase of Dubank is equal to the fuel increase of the other cylinder bank
The cooling-time fuel increase correction coefficient is
Means for determining a fuel increase correction coefficient for each of the Linda banks;
The configuration was provided with.

[0010]

SUMMARY OF] With the configuration according to claim 1, the engine is warmed up
When it is detected that a complete state, the cylinder bank-specific air-fuel ratio feedback control means is determined by the control constant determining means the air-fuel ratio of each of said cylinder banks
Feedback control using the control constants of
The exhaust gas flowing into catalytic converters having different capacities provided in the exhaust pipe of each cylinder bank is controlled for each bank so as to be in an exhaust state at the time of stoichiometric air-fuel ratio combustion. Therefore, the exhaust gas in the exhaust state corresponding to the required air-fuel ratio of each catalytic converter flows into each catalytic converter.

In particular, the control constant determining means controls the control constant so that the air-fuel ratio of the cylinder bank provided with the small-capacity catalytic converter is shifted to a leaner side than the air-fuel ratio of the other cylinder bank. I will decide
Thus, the air-fuel ratio feedback control means controls the air-fuel ratio of the cylinder bank provided with the small-capacity catalytic converter to be leaner than the air-fuel ratio of the other cylinder bank.

Here, after the warm-up, despite the fact that the same amount of heat flows in each exhaust system, the temperature of the catalytic converter having a large capacity becomes low because the heat radiation area is larger than that of the catalytic converter having a small capacity. . Here, since the required air-fuel ratio becomes rich when the temperature of the catalytic converter becomes low, the air-fuel ratio of the cylinder bank provided with the small-capacity catalytic converter whose temperature becomes relatively high is set to the other cylinder bank. By controlling the air-fuel ratio leaner than the air-fuel ratio, the exhaust gas having the air-fuel ratio that matches the required air-fuel ratio is introduced.

According to the second aspect of the present invention, the engine
When it detects a cold condition,
The fuel increase is performed every time, while the fuel increase correction coefficient
Since the amount of fuel increase in the cylinder bank provided with the large-capacity catalytic converter is made smaller than the amount of fuel increase in the other cylinder bank, the amount of fuel increase to the large-capacity catalyst takes time to reach the activation temperature. Is suppressed, and the amount of fuel is increased in the catalytic converter having a small capacity that quickly reaches the activation temperature, and the amount of fuel is increased in accordance with the catalyst capacity, thereby reducing exhaust emissions.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a system diagram of a first embodiment of the present invention. The V-type multi-cylinder engine 1 is placed horizontally, and one cylinder bank 2 (this is called a front cylinder bank) and another cylinder bank 3 (this is called a rear cylinder bank) Exhaust pipes 4 and 5 (referred to as front exhaust pipe 4 and rear exhaust pipe 5) are provided. The front exhaust pipe 4 and the rear exhaust pipe 5 join together,
One collective exhaust pipe 10 is provided.

A catalyst 6 made of a three-way catalyst (referred to as a front pre-catalyst) is provided in the middle of the front exhaust pipe 4, and a catalyst made of the three-way catalyst is provided in the middle of the rear exhaust pipe 5. 7 (this is called a rear pre-catalyst),
Further, the combined exhaust pipe 10 after the merging is provided with a catalyst 19 (also referred to as an underfloor catalyst) also composed of a three-way catalyst. Here, fuel is supplied to the front cylinder bank 2 and the rear cylinder bank 3 by fuel injection valves 12 and 13 provided in an intake manifold 11.
The fuel injections 12 and 13 are controlled by a control unit 14 with a built-in microcomputer.

More specifically, a basic fuel injection amount Tp is calculated from an intake air flow rate Q detected based on a signal from the air flow meter 21 and an engine speed N calculated based on a signal from the crank angle sensor 22. = K × Q / N (K is a constant), and this is corrected by various correction coefficients COEF and the air-fuel ratio feedback correction coefficient α.
Calculates a final fuel injection amount Ti = Tp × COEF × α, a driving pulse signal having a pulse width corresponding to the Ti et
Fuel injection valve 1 at a predetermined timing synchronized with engine rotation.
By outputting to 2 and 13, fuel injection is performed.

Here, in the air-fuel ratio feedback control (λ control), the air-fuel ratio is determined to be rich or lean based on a signal from an air-fuel ratio sensor provided in the exhaust system, and the stoichiometric air-fuel ratio is determined based on this. (Stoichiometric) control by setting the air-fuel ratio feedback correction coefficient α by proportional integral control. The various correction coefficients COEF include a post-start increase correction coefficient K _AS and an air-fuel ratio correction coefficient K _MR as shown in the following equations. When performing post-start increase or lean control instead of λ control, the air-fuel ratio Feedback correction coefficient α
Is fixed, and the post-start increase correction coefficient K _AS and the air-fuel ratio correction coefficient K _MR are appropriately set.

COEF = 1 + K _AS + K _MR +... Here, as the configuration according to the present invention, in the first embodiment,
Front cylinder bank 2, Rear cylinder bank 3
In order to enable independent air-fuel ratio feedback control for each, the front-side precatalyst 6 and the rear-side precatalyst 7
A front-side air-fuel ratio sensor 8 and a rear-side air-fuel ratio sensor 9 are provided immediately upstream of the control unit.
Enter in 14.

Further, the control unit 14 determines whether the engine 1 is in a cold state or a warm-up completed state.
Water temperature sensor to determine based on engine coolant temperature
The cooling water temperature Tw detection signal from 23 is also input. Next, an air-fuel ratio control routine by the control unit 14 will be described with reference to the drawings.

Here, the air-fuel ratio feedback correction coefficient α for the air-fuel ratio feedback control includes a proportional component P and an integral component I.
For example, as for the P component, if the P component when the signal of the air-fuel ratio sensor changes from lean to rich is P _R , and the P component when the signal from rich to lean changes is P _L , P _L and P _R are determined from a map of the engine speed N and a basic fuel injection amount T _P described later.

Here, as shown in FIG. 2, when P _L = P _R , the average air-fuel ratio is set to the stoichiometric air-fuel ratio (see a), and P _L
<(See b) the average air-fuel ratio to lean when the P _R,
When P _R <P _L , it is possible to shift the average air-fuel ratio richly (see c). After warming up,
Despite the same amount of heat flowing through each exhaust system, the front-side pre-catalyst 6 has a larger heat radiation area than the rear-side pre-catalyst 7 and is further cooled by receiving traveling wind, as shown in FIG. The temperature is lower than that of the rear precatalyst 7.

[0022] Here, in the case where the catalyst is cold, the air-fuel ratio of the exhaust flowing into the catalyst, HC, the relationship between the residual rate of such NO _X, is a relationship as shown in FIG. 4, when the temperature of the catalyst is changed, the most efficient air-fuel ratio of the exhaust gas purifying the HC and NO _X etc., come changes as shown in FIG. 5 by the temperature of the catalyst. That is, as is apparent from FIG. 5, the required air-fuel ratio of the front-side pre-catalyst 6 having a relatively low catalyst temperature is higher than that of the rear-side pre-catalyst 7 having a relatively high catalyst temperature. Becomes

In the first embodiment, the front-side cylinder bank 2 determines rich / lean of the air-fuel ratio based on a signal from the front-side air-fuel ratio sensor 8, and performs proportional integral control (PI control) based on the determination. ) Determines the proportional constants (P _FR , P _FL ) of the air-fuel ratio feedback control,
Further, the air-fuel ratio feedback control of the front-side cylinder bank 2 is performed using the proportional constants (P _FR , P _FL ).

On the other hand, the rear cylinder bank 3 determines rich / lean air-fuel ratio based on a signal from the rear air-fuel ratio sensor 9 and, based on this, air-fuel ratio feedback performed by proportional integral control (PI control). control proportional constant (P _RR, P _RL) defines, further the proportional constant (P _RR, P
_RL ) to perform air-fuel ratio feedback control of the rear cylinder bank 3.

Therefore, after the engine is warmed up, as shown in FIG.
_FR- P _FL is calculated by subtracting the difference P for the rear cylinder bank 3 from P.
Is made smaller than the _RR -P _RL, the front-side average air-fuel ratio is controlled to be richer than the rear side average air-fuel ratio. Here, the air-fuel ratio feedback correction coefficient setting routine will be described with reference to the flowcharts of FIGS.

FIGS. 7 and 8 show a routine for setting an air-fuel ratio feedback correction coefficient by the front-side air-fuel ratio sensor 8 or the rear-side air-fuel ratio sensor 9, which is executed in rotation for each cylinder bank. 7 and 8
In the description of the first embodiment, only the front side air-fuel ratio sensor 8 or the rear side air-fuel ratio sensor 9 is different. Steps having the same function are denoted by the same step numbers and are described. A description of the rear cylinder bank 3 will not be given.

In step 1 (denoted as S1 in the figure), it is determined whether or not an operating condition (abbreviated as F / B control area in the figure) for performing feedback control of the air-fuel ratio for the front air-fuel ratio sensor 8 is concerned. Is determined. For example, the cooling water temperature T
When w is equal to or less than a predetermined value, at start-up, immediately after start-up, during fuel increase for warm-up, when the output signal of the front-side air-fuel ratio sensor 8 has never been inverted, or during fuel cut, It is assumed that the operating condition is not such that the feedback control of the fuel ratio is performed.

If the above operating conditions are satisfied, the routine proceeds to step 2. If the above operating conditions are not satisfied, the routine proceeds to step 15, where the air-fuel ratio feedback correction coefficient α is clamped to a fixed reference value (α = 1), the feedback control is stopped, and this routine is terminated.
The air-fuel ratio feedback correction coefficient α set by the air-fuel ratio feedback correction coefficient setting routine is an example of a proportional integration operation in which the control center is 1.0 and α periodically changes as shown in FIG. According to this operation, one cycle is composed of the following four cases (1) to (4). That is, (1) When the air-fuel ratio is inverted from lean to rich, the air-fuel ratio is changed stepwise toward the lean side by a proportional amount (P _FR , P _RR ).

(2) Thereafter, the integral (I
_R ) Gradually change to lean side. (3) If the air-fuel ratio changes from rich to lean,
The _ratio is changed to the rich side by a proportional amount (P _FL , P _RL ) in a stepwise manner. (4) After that, it gradually changes to the rich side by the integral ( _IL ) during which the lean operation is continued. That is.

First, in the steps (2), (3) and (9), the output value of the air-fuel ratio sensor and the reference level (corresponding to the sensor output value with respect to the stoichiometric air-fuel ratio) are determined. The comparison is made in combination with the comparison of the size with the comparison with the comparison of the size previously performed. RL in step 3 and step 9 are flags storing the results of the previous magnitude comparison. RL = R means that the previous time was rich, and RL = L means that the last time was lean. As a result, the process proceeds to steps 2, 3, and 4 when the state is reversed from rich to lean. Similarly, the process proceeds to steps 2, 3, and 7 when it is rich continuation, and the process proceeds to steps 2, 9, and 10 when it is reversed from lean to rich. Proceed if it is a lean continuation. Immediately after the magnitude comparison is inverted, the flag is changed to the inverted value in step 4 or 10, respectively.

Thus, when the four cases are divided,
Step 5, Step 7, Step 11, or Step
In step 13, proportional components (P _FR , P _RR and P _FL , P
_RL) and integral amount (I _R and I _L) is calculated, and (P _FR -
P _FL ) <(P _RR −P _RL ), and the feedback correction coefficient α is calculated in step 6, step 8, step 12 or step 14 using these proportional components and integral components.
Is calculated.

[0032] When referred to in correspondence with the (1) to (4) in the case of (1) α = α-P FR, α = α-P RR (2) when α = α-I _R the case α = α + I _L in the case of (3) α = α + P FL, α = α + P RL (4). Here, the meaning of these equations is α
Is read out, and a value obtained by adding and subtracting the feedback correction amount to this value is stored as α again.

That is, the routine described above functions as the control constant determining means and the air-fuel ratio feedback control means .

A fuel injection pulse Ti is determined from α thus obtained in accordance with a fuel injection pulse determination routine shown in FIG. That is, in step 41, the air flow meter
Based on the engine speed N calculated on the basis of a signal from the intake air flow rate Q and the crank angle sensor 22 detected by 21, the basic fuel injection quantity T _P corresponding to the intake air amount per unit rotation by: Calculate.

T _P = K × Q / N (K is a constant) In step 42, various correction coefficients COEF are set based on the cooling water temperature Tw and the like detected by the water temperature sensor 23 . In step 43, the air-fuel ratio feedback correction coefficient α set by the feedback correction coefficient setting routine
Read.

In step 44, a voltage correction amount T _S is set based on the battery voltage value. This is for correcting a change in the injection flow rate of the fuel injection valves 12 and 13 due to the battery voltage fluctuation. In step 45, a final fuel injection quantity (fuel supply quantity) T _I is calculated according to the following equation.

T _I = T _P × COEF × α + T _{S At} step 46, the calculated fuel injection valve T _I is set in an output register. As a result, a predetermined engine
Becomes Gin rotation synchronization of the fuel injection timing, fuel injection is performed a drive pulse signal having a pulse width of the calculated fuel injection amount T _I is given to the fuel injection valve 12, 13.

Accordingly, the air-fuel ratio control corresponding to the required air-fuel ratio for each of the front cylinder bank 2 and the rear cylinder bank 3 can be performed by the above control, and the front pre-catalyst 6 and the rear pre-catalyst 7 can be controlled. Each conversion efficiency can be improved. Next, a second embodiment according to the present invention will be described.

FIG. 10 is a system diagram of the second embodiment of the present invention. The same components as those of the system diagram of the first embodiment shown in FIG. Is omitted. Here, as a configuration according to the present invention, in the second embodiment, only the front-side air-fuel ratio sensor 8 is provided immediately upstream of the front-side pre-catalyst 6, and these signals are input to the control unit 14 so that the Independent air-fuel ratio feedback control is performed for each of the side cylinder banks 2 and the rear cylinder banks 3.

In the second embodiment, the front-side cylinder bank 2 and the rear-side cylinder bank 3 judge whether the air-fuel ratio is rich or lean based on a signal from the front-side air-fuel ratio sensor 8. Proportional integral control (P
I control) to determine the proportional constants (P _FR , P _FL ) and the proportional constants (P _RR , P _RL ) of the air-fuel ratio feedback control, and further determine the proportional constants (P _FR , P _FL ) and the proportional constants (P P
_RR , P _RL ) to perform air-fuel ratio feedback control of the front cylinder bank 2 and the rear cylinder bank 3.

[0041] Also in the second embodiment, after the engine warmed up, as shown in FIG. 6, the difference P _FR -P _FL of P content according to the front cylinder bank 2, according to the rear cylinder bank 3 is made smaller than the difference between P _RR -P _RL of P content, the front side average air-fuel ratio is controlled to be richer than the rear side average air-fuel ratio. Therefore, also in the second embodiment, the air-fuel ratio control corresponding to the required air-fuel ratio for each of the front cylinder bank 2 and the rear cylinder bank 3 can be performed, and the front pre-catalyst 6 and the rear pre-catalyst 7 can be controlled. The respective conversion efficiencies can be improved, and in the second embodiment, since only the front air-fuel ratio sensor 8 is provided, the cost merit increases.

Next, a third embodiment of the present invention will be described. still,
The system configuration of the third embodiment of the present invention is the same as the system diagram of the first embodiment shown in FIG.
Description is omitted. In this embodiment, in order to ensure the operability of the engine in the cold state, when it is detected that the engine 1 is in the cold state based on the output from the water temperature sensor 23, the front cylinder bank 2 and the rear cylinder bank In all three, the amount of fuel is increased.

Here, the fuel increase control according to the third embodiment is performed by a fuel increase routine as shown in FIG. That is, in step 51, it is determined whether or not the engine 1 is at the start. Then, if it is determined that the _engine is at the start, in step 52, a cold-time fuel increase correction coefficient K _TwCOLD as shown in FIG. 11 is read in accordance with the cooling water temperature Tw.

In step 53, the fuel injection pulse Ti for each bank is determined as described above. Here, as shown in FIG. 11, the cold-time fuel increase correction coefficient K _TwCOLD is set such that the front-side increase is smaller than the rear-side increase.
This is because the rear-side pre-catalyst 7 has a smaller capacity than the front-side pre-catalyst 6 and reaches the activation temperature sooner.
Purification performance can be obtained earlier than the front-side precatalyst 6, and when the catalyst becomes active, the HC purification rate can be obtained to some extent even in a rich atmosphere. HC
And so on to reduce exhaust emissions.

Further, since the rear-side increase is larger than the front-side increase and the rear-side cylinder bank 3 is maintained in a rich state, the stability of the engine at the time of cold operation can be improved. It is possible to improve the performance.

[0046]

As described above, according to the first aspect,
According to that invention, different capacity in an exhaust pipe for each cylinder bank
Purification of V-type engine equipped with different catalytic converters
The engine is fully warmed up.
When detected, the signal from the air-fuel ratio sensor and the control constant
Air-fuel ratio feedback correction for each cylinder bank based on
Calculate the coefficient and use this air-fuel ratio feedback correction coefficient.
Feedback control of the air-fuel ratio for each cylinder bank.
On the other hand, a series with a small capacity catalytic converter
The average air-fuel ratio of one cylinder bank is the average of the other cylinder bank.
The above control constant is shifted so as to shift leaner than the air-fuel ratio.
Larger capacity due to the configuration determined for each cylinder bank
Therefore, at low temperatures, the catalytic converter that requires a rich air-fuel ratio
Data and the capacity is small, so it is relatively
The feedback control to the required air-fuel ratio is reliably performed for the catalytic converter whose lean ratio is
Exhaust gas with an air-fuel ratio that meets the required air-fuel ratio is introduced into the barter
As a result, the conversion efficiency of each catalytic converter is increased, so that the catalytic converter can be used more effectively, and there is an effect that the exhaust emission is improved.

According to the second aspect of the invention, the cylinder bar
Catalytic converters with different capacities are installed in the exhaust pipe of each tank.
In an exhaust purification system for a girder V engine, the engine
When it detects a cold condition,
Using the fuel increase correction coefficient during cold
While increasing fuel, a large capacity catalytic converter was installed.
The fuel increase of the displaced cylinder bank
So that the fuel increase during cold
The amount correction coefficient is set for each cylinder bank.
In, for small catalytic converter capacity to reach early activation temperature will be much fuel is increased, with it together with the exhaust gas is purified by the catalytic converter with improved early purification performance, consuming time to reach the activation temperature An increase in the amount of fuel to the catalytic converter having a large capacity is suppressed, and there is an effect that it is possible to reduce the emission of exhaust gas such as HC.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an overall configuration according to a first embodiment and a third embodiment of the present invention.

FIG. 2 is a characteristic diagram of an air-fuel ratio feedback correction coefficient according to the first embodiment;

FIG. 3 is a characteristic diagram of catalyst temperature according to the first embodiment.

FIG. 4 is a characteristic diagram of a catalyst at normal temperature.

FIG. 5 is a characteristic diagram showing a change in characteristics according to catalyst temperature.

FIG. 6 is a characteristic diagram of an air-fuel ratio feedback correction coefficient according to the first embodiment;

FIG. 7 is a flowchart of a front-side air-fuel ratio feedback correction coefficient setting routine according to the first embodiment;

FIG. 8 is a flowchart of a rear air-fuel ratio feedback correction coefficient setting routine according to the first embodiment;

FIG. 9 is a flowchart of a fuel injection pulse determination routine according to the first embodiment.

FIG. 10 is a system configuration diagram showing an overall configuration according to a second embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a relationship between a fuel increase correction coefficient and a water temperature.

FIG. 12 is a flowchart of a fuel increase routine at the time of cold start according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine 2 front side cylinder bank 3 rear side cylinder bank 4 front side exhaust pipe 5 rear side exhaust pipe 6 front side precatalyst 7 rear side precatalyst 8 front side air-fuel ratio sensor 9 rear side air-fuel ratio sensor 10 collective exhaust pipe 14 control Unit 21 Air flow meter 22 Crank angle sensor 23 Water temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/14 310 F01N 3/24 ZAB F01N 3/28 301 F02B 75/22

Claims (2)

(57) [Claims] An exhaust pipe of each cylinder bank has a different capacity.
Exhaust gas purifier for V-type engine provided with respective catalytic converters
In location, the air-fuel which is installed upstream of at least one of the catalytic converter
A ratio sensor, operating condition detecting means for detecting an operating condition of the engine , and an operating condition detecting means for detecting that the engine has been warmed up.
Signal from the air-fuel ratio sensor
Air-fuel ratio for each cylinder bank based on
Calculate the feedback correction coefficient and calculate the air-fuel ratio feedback.
The air-fuel ratio for each cylinder bank using the
Cylinder van provided with air-fuel ratio feedback control means for feedback control and a small capacity catalytic converter
The average air-fuel ratio of the other cylinder bank is
The control constant is set to cylinder
Exhaust purification system for a V-type engine, characterized in that it comprises a control constant determining means for determining for each bank, a. 2. The exhaust pipe of each cylinder bank has a different capacity.
Exhaust gas purifier for V-type engine provided with respective catalytic converters
In location, the operating condition detecting means for detecting the operating condition of the engine, the engine by the operating condition detecting means is in a cold state
Is detected, the fuel increase during cold
Perform fuel increase for each cylinder bank using the amount correction coefficient
Cylinder van provided with fuel increasing means and large capacity catalytic converter
The fuel increase of the other cylinder bank is greater than that of the other cylinder bank.
The cooling-time fuel increase correction coefficient is
An exhaust gas purifying apparatus for a V-type engine, comprising: a fuel increase correction coefficient determining means determined for each bank .