JPS60201063A - Air-fuel ratio controlling device for gas engine - Google Patents

Abstract

PURPOSE:To control the air-fuel ratio surely even in the engine using much amount of gas by providing a control valve, such as a needle valve or the like, controlled in accordance with the output of an oxygen detecting sensor in the fuel supplying pipe of the gas engine. CONSTITUTION:Gas is supplied into a mixer 4 through a pressure control valve 8, a fuel supplying pipe 6 and a regulating means 9 together with air in an air supplying pipe 7 and mixture is sucked into the suction pipe 2 of the gas engine 1. The output of an exhaust sensor 13, provided at the upstream of the catalyst 11 of an exhust pipe 3, and the output 15 of the opening degree setter 14 of a throttle valve 15 are inputted into a CPU17 as an interface input 18 while an interface output 19 is outputted based on the control outputs of a ROM20 and a RAM21 to operate an actuator 10. The actuator 10 operates the control valve 9, having a linear property such as the needle valve. Much amount of gas may be controlled more correctly than a gas injector in whcich a time width control is effected.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to an air-fuel ratio control device mainly used in relatively large gas engines, such as stationary gas engines for power generation or heat pump driving. The spread of gas engines requires the use of harmful components (Co, HC, etc.) in exhaust gas.
, NOx) is urgently needed. When using a three-way catalyst as a measure against exhaust gas, an oxygen sensor is generally installed upstream of the three-way catalyst, and the detection signal from the oxygen sensor is fed back to increase or decrease the amount of fuel supplied to the intake air on the intake side. The air-fuel ratio at the inlet of the catalyst is adjusted to be approximately λ=1. Specifically, for small gas engines such as those used in automobiles, it is considered that a gas injector is used as a fuel supply means and the air-fuel ratio is controlled by changing the length of the gas injection time. An air-fuel control device using a gas injector may work effectively in a small gas engine, but since a large waste engine requires a large amount of fuel sludge, the gas injector described above cannot handle it. Therefore, it was virtually impossible to employ an air-fuel ratio control device using a gas injector in a large cass engine. The present invention aims to provide a device that can quickly adjust the fuel supply amount gJ and accurately control the required air-fuel ratio even in a gas engine with a large fuel supply amount. A supply regulating means having a regulating valve such as a knee valve is provided in the middle of the pipe, and this supply amount regulating means is operated in response to an oxygen detection signal from an oxygen sensor in the middle of the exhaust pipe. There is also a slight difference in the way I did it. The details of the present invention will be explained below based on the illustrated embodiments. FIG. 1 shows the (1"η factor) of one embodiment of the present invention. In the figure, ladle number 1 is the combustion chamber of the engine, 2 is the intake pipe, and 3 is the exhaust pipe. A mixer 4 and a throttle valve 5 are arranged in the second flow section, and a fuel supply pipe 6 is connected to the mixer 4 in 111.
It is connected to air supply line 7. The fuel supply pipe 6 is provided with a pressure regulating valve 8' and a supply amount adjusting means 9 in order from the first stream side, and the structure of the supply amount adjusting means 9 will be described in detail later. IO is an actuator such as a step motor, and is installed in the supply amount adjusting means 9. On the other hand, the exhaust pipe 3 is provided with a three-way catalyst 11 and a muffler 12 in this order from the upstream side, and an oxygen sensor 13 is attached to the inlet side of the three-way catalyst 11. 14 is a cabana whose lever is interlocked with the throttle valve 5 to adjust the opening degree of the throttle valve 5. 15 is a load sensor that detects the load through the opening degree of the throttle valve 5. 16 is a control unit that controls the supply amount adjusting means 9 based on the detection signals from the oxygen sensor 13 and the load sensor 15;
It consists of U17, an input interface 18 such as an A/D converter, an output interface 19 consisting of a power transistor, etc., ROM 20, and RAM 21. FIG. 2 is a sectional view of the supply amount adjusting means 9,
The supply amount adjusting means 9 has a regulating valve 23 such as a tapered needle valve in a main body casing 22, and when the shaft portion of the actuator IO is displaced in the axial direction, the regulating valve 20 is displaced in the same direction. , the flow rate is controlled between the regulating valve 23 and the valve port 24. Note that the actuator IO may be a rotary step motor with a screw mechanism provided on the shaft to convert rotational motion into a linear output of the shaft. Next, the operation of the apparatus having the above configuration will be explained based on the flowchart shown in FIG. First, in step 1, an oxygen detection signal output from the oxygen sensor 13 is input to the CPU 17 through the input interface 18. In this case, the oxygen concentration near the oxygen sensor 13 is as shown in Figure 4 (3).
However, the detection by the oxygen sensor 13 is slightly delayed, and therefore the detection by the oxygen sensor 13
As shown in FIG. 4fB), the output waveform from the oxygen concentration waveform is delayed by a minute time a from the oxygen concentration waveform. Next, in step 2, the CPU 17 calculates the drive amount of the actuator based on the oxygen detection signal. The ROM 20 stores programs for this calculation and calculation constants. In step 3, the load detection signal from the load sensor 15 is input to the CPU 17 through the input interface IS. The detection signals of the load sensor I5 and the oxygen sensor 13 are of course inputted at appropriate sampling intervals. As step 4, the actuator drive amount is corrected in the CPU 17+4 based on the load detection signal, and a drive command signal is output to the actuator 10 (step 5).
. Actuator! The drive amount of 0 includes a skip drive amount that rapidly displaces the regulating valve 23, and a tilt drive that displaces the regulating valve 23 slowly.

[Therefore, due to the combination of the amounts of movement of both parts, the regulating valve 23 is displaced in a waveform as shown in FIG. 4(C)1 (step 6). The correction based on the detected load amount is reflected in the form of correcting the amounts of s, b', α, and α' shown in FIG. The rapid displacement due to the skip drive shown in the same waveform is for absorbing the deviation in the response operation of the regulating valve 23 to the actual change in oxygen concentration. The timing of increase and decrease matches the timing of change in oxygen concentration near the oxygen sensor 13. In this way, the amount of fuel supplied increases or decreases in accordance with changes in the oxygen concentration near the oxygen sensor 13, and the air-fuel ratio at the inlet of the three-way catalyst 11 is controlled to a predetermined value. In this embodiment, a load detection signal that reads the position of the electronic governor lever is used as a sensor for correcting the drive amount, but it is also possible to detect the load using an intake pressure sensor. It is also possible to read not only the engine speed but also the engine rotation speed and make more accurate corrections. Note that the embodiment shown in FIG. 1 may be provided with an exhaust gas recirculation device as shown by the chain line. The device consists of a recirculation '4' 25 connected to the exhaust pipe 3 on the downstream side of the muffler 12, a drain pot 26, a pressure regulating valve 27, etc. installed in the middle of the recirculation '4' 25, and a part of the exhaust is sent to the mixer 4.
The air flows into the intake pipe 2 between the throttle valve 5 and the throttle valve 5. Although the amount of NOx in the exhaust gas is further reduced by installing this device, the operation of the entire air-fuel ratio control device is
This is the same as in the operation explanation above. Box 5 is another real jjf! Example configuration! ';:l, in the same embodiment, the fuel supply pipe 6' branches into a main supply pipe 6a and a sub supply pipe 6b on the downstream side of the pressure regulating valve 8, and the main supply pipe 6a is directly connected to the mixer 4. However, the sub-supply pipe 6b is connected to the intake pipe 2 between the mixer 4 and the throttle valve 5, and a supply amount adjusting means 9' with an actuator l' is provided in the middle of the sub-supply pipe 6b. It is provided. Oxygen sensor attached to exhaust pipe 3] # Cumulative detection signal from 3,
In addition, the fuel 24 supply amount is calculated in the control section 16 based on the load detection signal from the load sensor 15 provided in the governor 14, and the actuator 10' operates in response to the drive command signal from the control section 1G. , which is the same as the embodiment shown in FIG. 1, and detailed explanation thereof will be omitted. Also the first
Components that are the same as those in the illustrated embodiment are given the same reference numerals. Note that the embodiment shown in FIG. 5 may be additionally provided with an exhaust gas recirculation device consisting of a recirculation pipe 25, a drain bot 26, a pressure regulating valve 27, etc. shown by chain lines. As described above, the present invention provides a supply amount adjusting means that adjusts the fuel supply level by displacement of a regulating valve in the middle of the fuel supply pipe, and the actuator is connected to the oxygen detection signal from the oxygen sensor provided in the exhaust pipe. It is designed to be controlled based on
Compared to a system that increases or decreases the fuel flow rate by changing the displacement of a regulating valve and adjusts the flow rate by changing the injection time of the gas injector, this method allows you to instantly increase or decrease the amount of fuel even if the supply line is large. It is possible to accurately control the air-fuel ratio even when using large gases (human or human).As shown in the embodiment shown in Fig. 5, the fuel supply pipes are connected to
By branching into the main supply pipe and providing the supply amount adjustment means in the sub supply pipe, the amount of liquid to be adjusted in the supply i adjustment means is significantly reduced, and the supply amount adjustment means is significantly downsized. In addition, the responsiveness of the adjusting means can be improved.

[Brief explanation of the drawing]

Nail, Figure 1 shows the cause of 11° of an embodiment of the present invention, Figure 2 shows the supply amount! The h-plane view of the tlid adjustment means, FIG. 3 is of the embodiment described in 1iir! 19) Show the work 7 o -f ya-h,
Figure 4 (A), (B), C) Waveform diagrams showing the opening of each part of Lt, (2) is the oxygen a degree near the oxygen sensor, (
Bl indicates the output of the oxygen sensor, (C1 indicates the displacement amount of the regulating valve, respectively. Figure 5 shows the cause of 1N in another embodiment. 2...Intake pipe, 3...Face/Exhaust pipe) , 4...
・Mixer, 5...Throttle valve, 6,6'...
...Fuel supply pipe, 6a...Main supply pipe, 6b
...Sub supply pipe, 9,9'...Supply amount adjustment means, 10.10' Old actuator, 13.
...Oxygen sensor, I6...Control unit, 23
・Dan・1. 'i1 valve adjustment. Applicant Yanmar Diesel Co., Ltd. Agent Patent Attorney Oka 1) Kazuhide Figure 2 Stainer 2 Step 3 Step 4 Step A5 Stellar 6 Figure 3

Claims (1)

[Scope of Claims] (1) A supply amount adjusting means that is located in the fuel supply pipe leading to the throttle valve and adjusts the fuel supply amount by displacement of a regulating valve, and a supply amount adjusting means that is located in the middle of the fuel supply pipe leading to the throttle valve and adjusts the fuel supply amount by displacement of the regulating valve, and A cylinder control section that calculates the fuel supply amount based on the oxygen detection signal and outputs a drive command signal according to the amount, and adjusts the supply speed and adjustment means in response to the drive command signal from the control section. An air-fuel ratio control device for a waste engine having an actuator that displaces a valve. (2. In the air-fuel ratio control device for a gas engine according to claim 1, the air-fuel ratio control device for a gas engine is provided with a supply amount adjusting means in a single fuel supply pipe. 3) In the air-fuel ratio control device for a gas engine according to claim 1, the fuel supply pipe is branched into a main supply pipe and a sub-supply pipe, and the sub-supply pipe is configured to adjust the supply amount. A means is provided for gas, air and fuel ratio control devices.