JPH0463214B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an air-fuel ratio control device for a parallel engine such as a parallel 6 cylinder, parallel 8 cylinder, or parallel 12 cylinder gas engine.

<Prior Art> Conventionally, for multi-cylinder in-line engines, such as in-line gas engines, air-fuel ratio control devices have already been used as a measure to purify exhaust gas.

This air-fuel ratio control device installs a lambda-type oxygen sensor on the upstream side of a three-way catalyst installed in the middle of a single collective exhaust pipe, feeds back the output of the oxygen sensor, and controls intake air on the intake side. The amount of fuel supplied to the three-way catalyst is increased or decreased, thereby controlling the oxygen concentration at the inlet of the three-way catalyst to be maintained at a constant value.

By the way, in a parallel engine with multiple cylinders, each parallel bank has a fuel supply path and an exhaust path, and there are two intake and exhaust paths. When a fuel ratio control device is applied, differences in the dimensions and operating performance of each part in both paths may cause variations in the air-fuel ratio between parallel banks, resulting in a decrease in overall fuel efficiency and output horsepower. There is.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned problems in parallel engines, and aims to eliminate variations in air-fuel ratio between parallel banks of the engine and improve overall efficiency of exhaust gas purification. At the same time, the purpose is to stabilize the combustion state.

<Structure of the Invention> In order to achieve the above object, the present invention has the following features:
As clearly shown in the functional block diagram in the figure, the oxygen sensor c on the collecting side is installed in the single collecting exhaust pipe b where the exhaust gas from the parallel banks a ₁ and a ₂ of engine a join together, and the oxygen sensor c in parallel with each bank a Fuel adjustment means _{d 1 for} increasing and decreasing the amount of fuel supplied to intake air on the intake side of 1 and a ₂ , respectively;
d ₁ and a required drive signal based on the detection signal of the oxygen sensor c on the collection side to each of the parallel banks a ₁ and a ₂
calculation means e for the fuel adjustment means d ₁ and d ₂ of _the bank, and bank-side oxygen sensors g ₁ and g ₂ provided in the collective exhaust pipes f ₁ and f ₂ of the parallel banks a 1 and a ₂ , respectively. , sampling means h ₁ and h ₂ sample the detection signals of the oxygen sensors g ₁ and g ₂ on each bank side at a constant cycle, and the detection signals sampled by the sampling means h ₁ and h ₂ are compared with each other. Comparison means i and the calculation means e calculate a correction output for finely adjusting the fuel supply amount in at least one fuel adjustment means d ₁ (d ₂ ) in response to the comparison output of the comparison means i.
This is an air-fuel ratio control device for a parallel engine.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 2 is a configuration diagram of an air-fuel ratio control device for a parallel type gas engine, which is an embodiment of the present invention. each parallel bank, 4,
5 is a bank intake pipe that supplies air-fuel mixture to each of the parallel banks 2 and 3; 6 and 7 are each of the parallel banks 2 and 3;
This is the bank-side collective exhaust pipe that sends out the exhaust air.

Mixers 8 and 9 are disposed upstream of each bank intake pipe 4 and 5, respectively, and each mixer 8 and 9 has gas supply pipes 10 and 11 and air supply pipes 12 and 13.
are connected. 14 and 15 are each mixer 8,
Each gas bypass pipe 14, 15 is provided with a gas regulating valve 18, which is driven by a direct drive type step motor 16, 17, as a fuel regulating means. , 19 are provided. Reference numeral 20 is a regulator, 2
1 and 22 are governors for each bank intake pipe 4 and 5.

On the other hand, the bank-side collective exhaust pipes 6 and 7 merge into a single collective exhaust pipe 23. Lambda-type oxygen sensors 24 and 25 are installed on each bank side and in the middle of the collective exhaust pipes 6 and 7, respectively, and a three-way catalyst 26 is provided in the single collective exhaust pipe 23,
A gathering side oxygen sensor 27 is attached to the upstream side of the three-way catalyst 26.

Reference numeral 28 is a control unit, which controls each oxygen sensor 2.
Input interface 29 for inputting lean/rich signals which are the detection signals of 4, 25 and 27.
and a microcomputer 30 that performs predetermined arithmetic processing based on the detection signal to create a drive signal to each step motor 16, 17, and a microcomputer 30 that generates a drive signal to each step motor 16, 17, and transmits the drive signal created by the microcomputer 30 to each step motor 16, 17. 17, and functionally includes the calculation means e, sampling means h ₁ , h ₂ , comparison means i, and correction output means j shown in FIG.

Next, the operation of the above configuration will be explained based on the time chart of FIG.

Assuming that the air-fuel ratio in a single collective exhaust pipe 23 changes in a cycle as shown in FIG. 3A, correspondingly, the detection signal of the oxygen sensor 27 on the collective side changes as shown in FIG. It changes with a slight time difference.

The microcomputer 30 controls the regulating valves 18 and 19, which are combustion regulating means, in each parallel bank 2 and 3 in a predetermined control pattern based on this detection signal.
Controls the opening degree. C and E in the figure show the opening degrees of the regulating valves 18 and 19 of the respective bank intake pipes 4 and 5.
Both regulating valves 18 and 19 basically open and close in the same opening and closing pattern, and are switched open and closed each time the detection signal of the oxygen sensor 27 on the collecting side switches between lean and rich.

Here, Sd ₁ and Sd ₂ are the opening reduction amount of the regulating valves 18 and 19, Su ₁ and Su ₂ are the opening increase amount, Cd ₁ and Cd ₂ are the opening reduction slope, and Cu ₁ and Cu ₂ are the opening degree. It is an increasing slope.

In this case, if the air-fuel ratio is not balanced between banks 2 and 3, the lean/rich ratio of the detection signal of one bank 2 and the lean/rich ratio of the detection signal of the other bank 3 will be different. The percentages should be quite different. Here, as shown in FIGS. 3D and 3F, the detection signal of the oxygen sensor 24 of one bank 2 is a long signal in a rich state, and the detection signal of the oxygen sensor 25 of the other bank 3 is a signal in a lean state. It's a long signal.

The microcomputer 30 samples the detection signals of the oxygen sensors 24 and 25 on each bank side using sampling pulses of a constant period as shown in FIG. 3G. As a result, the rich portion of the detection signal of each oxygen sensor 24, 25 is sampled, as shown in FIG. The number of sampled rich state signals is then counted to measure the period during which each detection signal is in the rich state. Furthermore, the microcomputer 30 compares the number of rich states of both detection signals and corrects the opening/closing amounts of the regulating valves 18 and 19 so that the detection signals of both the oxygen sensors 24 and 25 match each other.

In other words, if one of the oxygen sensors 24 and 25 is used as a reference, the adjustment valve of the other oxygen sensor 25 will change depending on the number of times of refilling of the other oxygen sensor 25 relative to the number of times of refilling of the one oxygen sensor 24. The opening reduction amount Sd ₂ or the opening increase amount Su ₂ in step 19 is adjusted.

Of course, if the other oxygen sensor 25 is used as a reference, the opening decrease amount Sd ₁ or the opening increase amount Su ₁ of one regulating valve 18 may be adjusted depending on the number of rich states of the one oxygen sensor 24. Just adjust it.

In this way, the oxygen sensors 24, 2 on both banks
The gas supply amount in one parallel bank 2, 3 is corrected with respect to the gas supply amount in the other parallel bank 3, 2 until the number of rich states of 5 match each other. By this, each parallel bank 2, 3
This eliminates variations in air-fuel ratio control.

In this embodiment, the number of rich state detection signals of each bank side is compared with each other, but it is also possible to sample a lean state signal and compare the number of times.

<Effects of the Invention> As described above, according to the present invention, there are differences in the dimensions and operating performance of each part in the intake and exhaust paths of each parallel bank, so that variations in air-fuel ratio occur between each parallel bank. Even if something happens, the amount of fuel supplied in one bank is corrected to the amount of fuel supplied in the other bank, which eliminates variations in air-fuel ratio control in each bank, so overall The efficiency of exhaust gas purification is improved, the combustion state is stabilized, and it is possible to reduce fuel consumption and increase output.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.
FIG. 2 is a block diagram of one embodiment, and FIG. 3 is a time chart showing the operation of this embodiment. 1... Gas engine, 2, 3... Parallel bank, 4,
5... Bank intake pipe, 6, 7... Bank side collective exhaust pipe, 16, 17... Step motor, 18,
19...Gas adjustment valve (fuel adjustment means), 23...
Single collective exhaust pipe, 24, 25...Oxygen sensor on the bank side, 27...Oxygen sensor on the collective side, 28...
...control section.

Claims (1)

[Claims] 1. An oxygen sensor on the collective side installed in a single collective exhaust pipe where the exhaust gas from each parallel bank of the engine joins together, and a fuel adjustment means for increasing or decreasing the amount of fuel supplied to the intake air on the intake side of each parallel bank. , a calculation means for applying a required drive signal to the fuel adjustment means of each of the parallel banks based on a detection signal of the oxygen sensor on the collective side; and an oxygen sensor on the bank side provided in the collective exhaust pipe of each of the parallel banks. and,
sampling means for sampling the detection signals of the oxygen sensors on each bank at a constant cycle; comparison means for comparing the detection signals sampled by the respective sampling means; An air-fuel ratio control device for a parallel engine, comprising: correction output means for providing a correction output for finely adjusting the fuel supply amount in one of the fuel adjustment means to the calculation means.