JPS61138840A - Air-fuel ratio controller for gas engine - Google Patents

Abstract

PURPOSE:To check a gas pressure variation in a bypass pipe as well as to improve a degree of control accuracy, by branching off the bypass pipe from a main feeding pipe line for gas fuel to a mixer and installing an air-fuel ratio control valve, while installing each pressure-regulating valve in the main feeding pipe line and the bypass pipe. CONSTITUTION:A bypass pipe 8 is branched off from a main feeding pipe line 6 for gas fuel to a mixer 4, and an air-fuel ratio control valve 10 is installed in this bypass pipe 8. And, a main pressure-regulating valve 7 is installed in the main feeding pipe line situated more at the upstream side or the downstream side than a spot where the bypass pipe 8 is branched off, while a bypass pressure-regulating valve 9 is installed in the bypass pipe 8. A control unit 16 opens or closes the air-fuel ratio control valve 10 to feed the additional gas supply calculated on the basis of each signal out of an oxygen sensor 13, a governor 14 and a suction pressure sensor 15. At this time, these pressure- regulating valves 7 and 9 also operate, keeping gas pressure inside the bypass pipe 8 almost constant, thus control accuracy in the air-fuel ratio control valve 10 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an air-fuel ratio control device for a gas engine, and more particularly to a structure of a gas fuel supply path portion in which an air-fuel ratio control valve is provided.

<Prior Art> Generally, an air-fuel ratio control device for a gas engine uses a three-way catalyst 120 interposed in the middle of an exhaust pipe 30, as shown in the block diagram of FIG.
And, the oxygen sensor 1 attached to the inlet side of this catalyst 120
3o, a microcomputer 16o which is a control section,
The microcomputer 16o is equipped with an air-fuel ratio control valve 10o installed in the middle of the gas fuel supply pipe, and the microcomputer 16o operates based on the oxygen detection signal, the rotation detection signal from the governor 14°, and the load detection signal from the intake pressure sensor 15o of the mixer 4o. calculates the additional gas supply amount, and in response to the command, air-fuel ratio control valve 1
By opening and closing 0o, the ratio of the gas supply amount to the intake air is adjusted, and the oxygen concentration at the inlet of the catalyst is maintained at a constant value.

By the way, in this type of conventional air-fuel ratio control device, the air-fuel ratio control valve 10o is installed in a bypass supply pipe 8o branched from the main gas fuel supply pipe 60, and is located upstream from the point where the bypass supply pipe 8o branches. A pressure regulating valve 70 is provided in the main supply pipe 60 on the side, and the mixer 4
The pressure difference between the gas pressure at 0 and the intake air pressure is kept constant, but in reality, if the gas supply amount increases or decreases depending on the operating conditions, the differential pressure will change depending on the increase or decrease in the gas supply amount. There is a slight fluctuation of 1". When the differential pressure fluctuates in this way, the gas flow rate naturally changes, and the flow m in the bypass supply pipe 80 also changes, so the air-fuel ratio control valve IOo must be kept at a constant opening. However, as the gas flow M changes, the adjustment m by the air-fuel ratio control valve 10o deviates from the required value, resulting in a disadvantage that the control performance deteriorates.

In addition, in all conventional gas engines, the gas pressure is set to a certain constant pressure by the pressure regulating valve 70, but the same gas pressure regulated by the pressure regulating valve 7o is also applied to the bypass supply pipe 8o. This bypass supply pipe 8
It is necessary to provide an air-fuel ratio control valve 10o that can additionally supply the required amount of gas at a predetermined set pressure.

In other words, in a small gas engine with a small gas supply amount, it is only necessary to supply a small amount of additional gas at a predetermined set pressure, so it is better to use a small air-fuel ratio control valve or to adjust the gas supply amount. In a large gas engine with a large capacity, a large amount of gas must be additionally supplied at a predetermined set pressure, so a large air-fuel ratio control valve with a large capacity must be used. In this way, in the conventional air-fuel ratio control device, it is necessary to use the air-fuel ratio control valve 10o with a capacity and capacity corresponding to the amount of gas to be added through the bypass supply pipe, and the air-fuel ratio control valve 10o has a different capacity depending on the type of gas engine. It is necessary to prepare an air-fuel ratio control valve, which is disadvantageous in manufacturing and increases costs.

Furthermore, as mentioned above, the air-fuel ratio control valve must have a capacity and capacity that corresponds to the amount of gas to be added through the bypass supply pipe under a predetermined set pressure. Since the types of valves 100 are limited, the amount of additional gas supplied and the capacity and capacity of the air-fuel ratio control valve 10o do not always match exactly. If the adjustment is not accurate, the amount of adjustment applied to the air-fuel ratio control valve will deviate from the required value, which also has the disadvantage of reducing control performance.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and aims to reduce gas pressure fluctuations in the bypass supply pipe as much as possible,
The additional supply of gas by the air-fuel ratio control valve in the pipeline can be performed as planned, improving control performance, and making it possible to share a single type of air-fuel ratio control valve with multiple types of gas engines. The purpose is to reduce costs by making it possible to

<Configuration of the Invention> In order to achieve the above object, the present invention provides a case in which a bypass supply pipe is branched from a main supply pipe of gas fuel to a mixer, and an air-fuel ratio control valve is attached to this bypass supply pipe. In the air-fuel ratio control device for an engine, a main pressure regulating valve is provided in the main supply pipe on the upstream or downstream side of the point where the bypass supply pipe branches, and a bypass pressure regulating valve is installed in the bypass supply pipe. .

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.e Fig. 1 is a configuration diagram of an air-fuel ratio control device of the present invention, and in the figure, reference numeral 1 indicates a combustion chamber of an engine; 2 is an intake pipe, 3 is an exhaust pipe, and an upstream portion of the intake pipe 2 is provided with a mixer 4 and a throttle valve 5. A main pressure regulating valve 7 is attached to the main supply pipe 6 that supplies gas fuel to the mixer 4, and a bypass supply pipe 8 branches from the main supply pipe 6 downstream of the main pressure regulating valve 7. Directly connected to the mixer 4, the bypass supply pipe 8 is equipped with a bypass pressure regulating valve 9 and an air-fuel ratio control valve 10 in order from the upstream side.
is connected to the mixer 4 via the bypass pressure regulating valve 9 and the air-fuel ratio control valve 10. 11 is an air-fuel ratio control valve 10
actuator.

In the figure, 12 is a three-way catalyst installed in the exhaust pipe 3, 13 is an oxygen sensor installed upstream of the catalyst 12, and 14 is a governor linked to the throttle valve 5, which outputs a rotation detection signal. do. 15 is an intake pressure sensor as a load detection means;
6 is a microcomputer as a control section.

In the above configuration, an oxygen detection signal from the microcomputer 16 or the oxygen sensor 13, a rotation detection signal from the governor 14, and a load detection signal from the intake pressure sensor 15 of the mixer 4 are introduced, and additions are made based on these detection signals. By calculating the amount of gas to be supplied and opening and closing the air-fuel ratio control valve 10 in response to the command, the ratio of the amount of gas supplied to the intake air is adjusted, and the oxygen concentration at the inlet of the catalyst is kept at a constant value. It is maintained.

Now, due to changes in operating conditions such as an increase in load, mixer 4-
When the gas supply amount increases, the gas pressure in the main supply pipe 6 decreases slightly, or the gas pressure in the bypass supply pipe 8 is readjusted by the bypass pressure regulating valve 9, so it hardly changes. Therefore, the ratio of the gas flow rate to the opening degree of the air-fuel ratio control valve 10 is kept constant, and the flow rate adjustment in the air-fuel ratio control valve IO is performed accurately and as planned.

In addition, since the air-fuel ratio control valve 10 may be one that corresponds to the set pressure of the bypass pressure regulating valve 9, for example, if the set pressure of the bypass pressure regulating valve 9 is set higher than the setting pressure of the main pressure regulating valve 7, the air-fuel ratio can be controlled. The valve 10 may be any valve capable of controlling the required amount of gas supply at high pressure, and a small 8 m air-fuel ratio control valve may be used.

In this embodiment, the gas pressure in the bypass supply pipe 8 is adjusted in two stages by the main pressure regulating valve 7 and the bypass pressure regulating valve 9, and the air-fuel ratio control valve IO is not affected by the gas pressure of the gas supply source. This embodiment is suitable for models in which the gas pressure of the gas supply source is high.

FIG. 2 is a configuration diagram showing another embodiment of the present invention, and in this embodiment, a main pressure regulating valve 71 is provided in the main supply pipe 61 on the downstream side of the point where the bypass supply pipe 81 branches. .

That is, the main supply pipe 61 and the bypass supply pipe 8 branched from each other.
1 are provided with a main pressure regulating valve 71 and a bypass pressure regulating valve 91, respectively. The other components are the same as those in the first embodiment shown in FIG. 1, and the same components are designated by the same reference numerals as in FIG.

Also in this embodiment, the gas pressure in the bypass supply pipe 81 is automatically adjusted by the bypass pressure regulating valve 91, so even if the gas pressure in the main supply pipe 61 fluctuates, it does not fluctuate drastically. Therefore, the ratio of the gas flow rate to the opening degree of the air-fuel ratio control valve IO is kept constant, and the flow mr in the air-fuel ratio control valve 10 is kept constant.
The point that a-alignment is performed accurately as expected is the same as in the first embodiment.

Since the gas pressure from the gas supply source directly acts on the bypass pressure regulating valve 91, this embodiment is suitable for a gas engine with relatively low gas pressure.

<Effects of the Invention> As described above, according to the present invention, even if the gas pressure in the main supply pipe fluctuates slightly depending on operating conditions, the gas pressure in the bypass supply pipe is regulated by the bypass pressure regulating valve and remains almost constant. Therefore, the gas flow rate in the air-fuel ratio control valve is accurately adjusted as expected, and the control performance of the air-fuel ratio control valve is improved.

In addition, by appropriately changing the set pressure of the bypass pressure regulating valve, it is possible to accurately match the additional gas supply amount with the capacity and capacity of the air-fuel ratio control valve. Control performance is further improved.

Furthermore, for large models that require a large amount of gas to be supplied through the bypass supply pipe, by setting the set pressure of the bypass pressure regulating valve to a high pressure, a large amount of additional gas can be supplied using a small capacity air-fuel ratio control valve. The amount can be controlled. Therefore, even if you have a large model that supplies a large amount of additional gas, or a small model that supplies a small amount of additional gas, you can change the setting pressure of the bypass pressure regulating valve. Accordingly, the air-fuel ratio control valve of the same capacity and capacity can be used for both models, making it possible to share the air-fuel ratio control valve and reducing costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of another embodiment, and FIG. 3 is a block diagram of a conventional device. 4 mixer, 661 main supply pipe, 7, 71 main pressure regulating valve,
8,81 Bypass supply pipe, 9.91 No.Pass pressure regulating valve, lO air-fuel ratio control valve.

Claims (1)

[Claims] (1) In an air-fuel ratio control device for a gas engine, in which a bypass supply pipe is branched from a main supply pipe for gas fuel to a mixer, and an air-fuel ratio control valve is attached to this bypass supply pipe, the bypass supply pipe is An air-fuel ratio control device for a gas engine, characterized in that a main pressure regulating valve is provided in a main supply pipe on the upstream or downstream side of a branch point, and a bypass pressure regulating valve is provided in a bypass supply pipe.