JPS60201064A - Air-fuel ratio controlling device for gas engine - Google Patents

Abstract

PURPOSE:To control air-fuel ratio correctly in the whole operating ragne of an engine by a method wherein the operation of the engine is divided into a plurality of operating areas in accordance with the revolving number and load of the gas engine while feedback control is effected by an oxygen sensor with characteristics in accordance with respective operation areas. CONSTITUTION:A load signl is sent into an A/D convertor 23 by the opening degree detector 17 of a throttle valve 5 for a gas engine 1 and a revolving number signal is sent into a counter circuit 19 by the rotating angle sensor 13 of a crankshaft 14 while the operating area of the engine, which is bein devided previously into a plurality of areas, is selected in accordance with the values of the signals. The outputs of the oxygen sensor 12 in an exhaust pipe 3 are compared with the threshold values proper to the selected area while a control valve 8, consisting of a linearly operating valve such as a needle valve provided in a sub supplying pipe 6b bypassing the main supplying pipe 6a of a gas supplying pipe 6, is controlled by the output of a control circuit 24 for the driving thereof.

Description

[Detailed description of the invention] The present invention relates to an air-fuel ratio side angle device for a gas engine.

In gas engines, a three-way catalyst is already installed as an air-fuel ratio auxiliary device in the exhaust pipe, and an oxygen sensor is attached to the inlet of the catalyst, and the detection signal from the oxygen sensor is fed back to adjust the fuel to the intake air on the intake side. Some control systems control the oxygen concentration at the inlet of the M catalyst by adjusting the ratio of the supply amount.

By the way, three-way catalysts do not always exhibit constant characteristics (
, its characteristics change depending on the engine speed and load.

Therefore, if the rotational speed or load of a fallen tree increases significantly, the output level of the oxygen sensor will deviate from the characteristics of the three-way catalyst, and the oxygen concentration at the catalyst inlet will change to the state of the catalyst at that time. There was a problem in that the catalyst could not be controlled to a suitable value and the exhaust gas could not be sufficiently purified by the catalyst.

Moreover, since the relationship between the output of the oxygen sensor and the amount of fuel supplied based on this was set in a single predetermined pattern, it was not possible to cope with the situation in the high load and high speed rotation range as described in 0if, and the exhaust gas The problem was that the scum purification properties were not satisfactory.

The present invention maintains the efficiency of exhaust gas purification by the catalyst at a high level by making it possible to perform air-fuel ratio control that matches the state of the catalyst at that time even in the high-angle DJ and high-speed rotation range. The entire load area is divided into multiple areas, and the actuator drive amount and acid fan are calculated for each divided area.

Detection (The No. 3 threshold value is set, and this setting relationship is stored in the storage unit in the form of a numerical table, and the air-fuel ratio control is performed based on the numerical table of this setting relationship. .

The details of the present invention will be explained below based on the illustrated embodiment ff1J.

FIG. 1 is a block diagram showing the entire air-fuel ratio control device 11 of the present invention. In the figure, reference numeral 1 is a combustion chamber of an engine, 2 is an intake pipe, 3 is an exhaust pipe, and the intake pipe 2 is an exhaust pipe. Mixer 4 is installed upstream of
and a throttle valve 5 are provided. 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 7, and the main supply pipe 6a is directly connected to the mixer 4, but the sub-supply ')M'6bli supply It is connected to the upstream portion of the mixer 4 via the amount adjusting means 8. The supply amount adjusting means 8 increases or decreases the fuel 'lAt'lfk, and therefore the supply tray, by displacement of a regulating valve such as a tapered needle valve.
This is equipped with an actuator 9, such as a step motor, for displacing the regulating valve. 1o is an air supply pipe. On the other hand, a three-way catalyst 11 is located in the middle of the exhaust pipe 3.
is interposed, and an oxygen sensor 12 is attached to the inlet side thereof. Reference numeral 13 denotes a rotation speed sensor which is a means for detecting the rotation speed of girders and gates, and is installed opposite to the vicinity of the outer periphery of a ring gear 15 fixed to the crankshaft 14. Outputs the same number of speed bows as the number of.

The lever is interlocked with the throttle valve 5 to adjust the opening degree of the throttle valve 5. A load sensor 17 detects the load through the opening degree of the throttle valve 5. 18 is a control unit, which includes an oxygen sensor 12, a load sensor 17, and a rotational speed sensor 13, as will be described in detail later.
The actuator 9 of the supply amount adjusting means 8 is driven and controlled based on each detection signal of the counter circuit 19, CPU 20, ROM 21 serving as a storage section, and RA.
It is composed of an M22, an A/D converter 23, and a drive control circuit 2<.

Therefore, in the ROM 21 described in 01f, the entire range of rotational speed and load is divided into a plurality of regions, and the actuator drive mj M'i and oxygen A detection signal threshold value is set and this relationship is stored in the form of a numerical table.

In this example, first, as shown in Table 1, the entire area of load is divided into 5 parts, and the entire area of rotational speed, that is, the number of revolutions R, is also divided into 5 parts. A control constant N of 1 to 5 is set. As shown in Table 2, four types of actuator drive Mi-E and oxygen detection signal threshold F are set for each of the above-mentioned control constants N. In Table 2, the actuator drive amount E is specified in relation to the drive reference signal as shown in the time chart of FIG. 2, and the valve opening or valve closing skip amount Su, 5d is "3". "Existing" means that the step motor that is the actuator rapidly drives three steps, and the opening tP or valve closing slope ffi Cu, Cd
is "3" means that the step motor is driven one step every three pulses of the drive reference signal.

Table 1 Table 2 Next, the operation of the apparatus having the above configuration will be explained based on flowchart 1 in FIG. First, in step 1, the load detection signal from the load sensor 17 is input to the CPU 20 via the A/D converter 23, and then in step 2, the speed signal from the rotation speed sensor 13 is input to the CPU 20 via the counter circuit 19. The speed (rotation speed) R is calculated (step 3). Based on the calculated load amount and rotation speed, the corresponding control constant N4 is read out from the ROM 21 (step 4), and the read out side leg constant N is used to drive the corresponding actuator. MI E and oxygen detection signal threshold F are read (step 5). oxygen sensor 1
2, the oxygen detection signal is introduced into the CPU 2u through the A/D controller) and the air-fuel ratio is rich,
It is determined whether it is lean (step 7). If the air-fuel ratio is lean, the drive amount on the valve-opening side (valve-opening skip ff1su, valve-opening slope amount cu) is selected, and if the air-fuel ratio is rich, the drive amount on the valve-closing side (valve-closing skip claw 3d) is selected. .

The valve closing inclination amount Cd) is selected and a corresponding drive command signal is output (step 8). As a result, the actuator 9 responds in step 9), and the supply amount adjusting means 8 increases or decreases the fuel supply amount.

As the load sensor, in addition to the one that detects the load through the opening degree of the throttle valve 5 as described above, an intake pressure sensor installed in the middle of the intake pipe can be used, and the form of the load sensor is not limited to the illustrated example. .

IJ of the present invention As mentioned above, the actuator drive amount and oxygen detection signal threshold are set depending on the amount of both in order to respond to increases and decreases in engine speed and load, and the relationship between these settings is This is stored in the memory unit in the form of a numerical table, and even if there is a relative deviation between the catalyst properties and the acid f sensor characteristics in a high load, high speed rotation range, the actuator drive amount for that region is By reading out the oxygen detection signal threshold value from the storage unit, air-fuel ratio control can be performed based on these values to suit the state of the catalyst at the time, and the efficiency of exhaust purification by the catalyst can also be improved. The operating efficiency of the engine can be maintained at a high level, and it also prevents inconveniences such as periodic fluctuations in rotation and misfires.

Note that, as in the above embodiment, if the numerical table showing the setting relationship of rotational speed, load, actuator drive amount, and oxygen detection signal threshold is divided into two tables by intervening control constants, the setting pattern can be changed. When changing the number table, it is easy to change the memory of one of the two tables, and the setting pattern can be easily changed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 (A). (Bl, (C1 is a time chart showing the operating state of the actuator, where the human inputs a drive command signal, fBl represents the drive amount of the actuator, and (C1 represents the sampling signals of the oxygen sensor, load sensor, and rotational speed sensor. Figure 3 is a flowchart showing the operation of the embodiment 1. 1... Combustion chamber, 2... Intake pipe, 3...
...Exhaust pipe, 6...Fuel supply pipe, 8...
Supply m adjustment means, 9...actuator, 11
...Three-way catalyst, 12...Oxygen sensor,
13...Rotation speed sensor, 17...Load sensor, I8...Control unit, 20...CPU
, 21...ROM.

Claims (1)

[Claims] (1) A means for detecting the engine rotational speed, a means for detecting the load, a part 0 that stores the relationship between the actuator drive amount and the oxygen detection signal threshold for both the rotational speed and the load, and an exhaust pipe. Calculate the air-fuel ratio based on the oxygen detection signal from the acid sensor installed on the road, the actuator drive amount and the oxygen detection signal threshold read from the vij storage unit, and output the corresponding drive command signal. CPU and iiJ record 1〉: motion command signal Lc: mJ
a supply amount adjusting means for adjusting the fuel supply amount J'j by an actuator that adjusts the amount of fuel supplied; The air-fuel ratio control device for a gas engine is characterized in that the actuator drive amount and the oxygen output signal threshold are set in advance and this relationship is stored in the form of a numerical table.