JPH0222230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an air-fuel ratio control device for a mixer type gas engine.

<Prior Art> The air-fuel ratio of a mixer-type gas engine is determined by the characteristics of the mixer used, and there is generally no means for correcting the air-fuel ratio depending on the operating state of the engine. Therefore, as the load gradually increases and the throttle opening becomes larger, the actual air-fuel ratio will deviate from the set air-fuel ratio to the lean side due to the general characteristics of the mixer, and the maximum Not only was there no output, but there was a tendency for exhaust emissions to deteriorate.

A known air-fuel ratio control device that can solve this problem is one that controls the amount _of fuel supplied by feeding back the detection signal of an O ₂ sensor placed in the exhaust pipe. It becomes necessary. For this reason, the present applicant has previously proposed a system for controlling the gas supply amount according to the engine speed and throttle opening (see, for example, Japanese Patent Laid-Open No. 58-214655). However, in this proposal, the entire gas supply amount is to be controlled, so there is a possibility that the supply amount adjustment means will be large or the response will be likely to decrease. This caused problems such as the complexity of the control program.

<Object of the Invention> The present invention focuses on the above-mentioned problems and corrects the air-fuel ratio in an operating range where the air-fuel ratio determined by the characteristics of the mixer deviates to the lean side, thereby preventing insufficient output and deterioration of exhaust emissions. The present invention has been made for the purpose of providing an air-fuel ratio control device for a gas engine as described above.

<Configuration of the Invention> In order to achieve the above object, the present invention includes a mixer for mixing gas fuel and air at a predetermined air-fuel ratio, a detection means for detecting the engine speed, and a throttle located downstream of the mixer. A detection means for detecting the opening degree, an additional fuel supply means for additionally supplying an arbitrary amount of gas fuel, and an engine rotation in an operating range where the air-fuel ratio determined by the characteristics of the mixer deviates to the lean side from a predetermined air-fuel ratio. a storage means that stores in advance the relationship between the number and the additional supply amount of gas fuel with respect to the throttle opening; and a determination means that detects that the operating range deviates to the lean side from a predetermined air-fuel ratio;
In the above operating range, a correction calculation is made that determines the additional supply amount of gas fuel based on the stored contents of the storage means according to the detected engine speed and throttle opening, and outputs a control signal to control the additional fuel supply means. In the operating range where the air-fuel ratio shifts to the lean side, gas fuel is automatically additionally supplied from the additional fuel supply means, making it possible to always continue operation at an appropriate air-fuel ratio. It becomes.

<Example> The present invention will be specifically described below with reference to an illustrated example.

Figure 1 is a conceptual system diagram, where 1 is a gas engine, 2
is the mixer, 3 is the throttle, 4 is the electronic governor,
5 is an opening detector of the throttle 3, 6 is a gas injector, 7 is an exhaust pipe, 8 is a rotation speed detector, and 9 is a microcomputer.

The mixer 2 is preset to maintain the air-fuel ratio at λ = 1.4, for example, and after the fuel gas 11a and air 12 are mixed in the mixer 2, they are supplied to the engine 1 via the throttle 3, and the exhaust gas 13 is sent to the exhaust gas. It is discharged from pipe 7. The throttle opening is detected by an opening detector 5, which is made up of, for example, a potentiometer, which is attached to the shaft of the throttle 3, whose opening is controlled by an electronic governor 4, and its output is sent to a microcomputer 9. . The rotational speed of the engine 1 is detected by a rotational speed detector 8, which is, for example, an electromagnetic pickup, attached to the ring gear 14 of the engine 1, and its output is sent to a microcomputer 9.

Microcomputer 9 has CPU 15, ROM
16, RAM 17, I/O port 18, system bus line 19, etc., and the analog output of the opening detector 5 is converted into a digital amount by the A/D converter 21 and input to the microcomputer 9. The pulse output of the rotation speed detector 8 is counted by the counter 22 and sent to the microcomputer 9.
is input. In addition to calculation control programs, the ROM 16 stores the relationship between the additional supply amount of gas fuel and the engine speed and throttle opening in the operating range where the air-fuel ratio deviates to the lean side in the form of a numerical table or calculation formula. In the corresponding operating range, the CPU 15 sends control signals corresponding to the detected engine speed and throttle opening to the I/O port 18.
The gas injector 6 is driven with an arbitrary duty by the signal output in the form of an I/O signal from the power transistor array 23, and the gas fuel 11b is additionally supplied.

Next, the operation of this apparatus will be explained with reference to the flowchart shown in FIG.

The CPU 15 of the microcomputer 9 controls the engine speed Nm at a preset interval time.
The throttle opening S is detected (step 1), and the difference ΔS between the detected throttle opening S and the reference value (12/100Nm+120) is calculated (step 2). Then, in the next step 3, check whether the difference ΔS is positive or negative, and if it is negative, it is determined that the throttle opening, which is a substitute characteristic of the load, and the engine speed are balanced, and that no correction is necessary. Calculate the duty ID = 0 (step 4), and also calculate ΔS
If ≧0, it is determined that the throttle opening is large relative to the engine speed and has entered an overload operating range that requires correction, and the system uses the numerical table or calculation formula stored in the ROM 16 to The injector duty ID=f(ΔS) corresponding to each detected value of engine speed Nm and throttle opening S is calculated (step 5), and a control signal corresponding to the calculated ID is output to the injector 6. Then, the fuel gas 11b is additionally supplied (step 6), and the air-fuel ratio is maintained at a predetermined value.

FIG. 3 is a graph showing an example of a numerical table or calculation formula stored in the ROM 16 and used when calculating the injector duty ID using a numerical table in step 5. The numerical value of the throttle opening of the shaft is a dimensionless number obtained by converting the detection output of the throttle opening detector 5 into a digital value. Furthermore, the above reference value (12/100Nm+120) is just an example, and varies depending on the type and capacity of the engine, and is set according to the results of tests conducted in advance. Note that the "λ=1.4 unoperable region" in the figure means a region where, although it is possible to correct to λ=1.4, it is not possible to produce an output commensurate with the throttle opening.

<Effects of the Invention> As is clear from the description of the embodiments above, the present invention is applicable to operation in which the load gradually increases and the throttle opening increases, and the air-fuel ratio determined by the characteristics of the mixer deviates to the lean side. This system automatically supplies additional fuel to correct the air-fuel ratio in accordance with the operating conditions, thereby preventing insufficient output and deterioration of exhaust emissions, and constantly operating the gas engine at an appropriate air-fuel ratio. Therefore, there is no need for an O ₂ sensor, and the control program is simplified because only a part of the operating range needs to be controlled.Also, only the additional amount of fuel needs to be controlled, rather than the entire amount of fuel supplied, so the amount of fuel supplied can be reduced. The adjustment means can be small-sized, resulting in advantages such as low cost and easy improvement of responsiveness.

[Brief explanation of drawings]

Fig. 1 is a conceptual system diagram of one embodiment of the present invention;
The figure is a control flowchart, and FIG. 3 is a diagram showing an example of the relationship of injector duty to engine speed and throttle opening in a target operating range. 1... Gas engine, 2... Mixer, 3... Throttle, 5... Opening degree detector, 6... Gas injector, 8... Rotation speed detector, 9... Microcomputer, 15... CPU, 16... …ROM.

Claims (1)

[Scope of Claims] 1. A mixer for mixing gas fuel and air at a predetermined air-fuel ratio, a detection means for detecting the engine speed, a detection means for detecting the opening degree of a throttle located downstream of the mixer, and optionally Additional fuel supply means for supplying an additional amount of gas fuel, and addition of gas fuel to engine speed and throttle opening in an operating range where the air-fuel ratio determined by the characteristics of the mixer deviates to the lean side from a predetermined air-fuel ratio. a storage means that stores in advance the relationship between the supply amounts; a determination means that detects that the operating range deviates to the lean side from a predetermined air-fuel ratio; A correction calculation means for determining an additional supply amount of gas fuel based on the stored contents of the storage means in accordance with the storage means and outputting a control signal for controlling the additional fuel supply means. Fuel ratio control device.