JPS6344942B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a gas fuel engine that automatically adjusts the air-fuel ratio according to the load condition of the engine.

In general, in order to avoid the knocking region and misfire region in a gas fuel engine, and to operate the engine efficiently while reducing fuel consumption and harmful exhaust components, it is necessary to control the air-fuel ratio so that the optimum air-fuel ratio is always obtained. be.

Conventional techniques for performing such control include mechanical means such as correcting the amount of air using intake air pressure, and providing a fuel throttle section linked to a butterfly that senses the dynamic pressure caused by the air flow rate in the mixer section. This is common. However, the air-fuel ratio does not have a simple linear relationship with the load factor when considering the need to avoid knocking and misfire, and to reduce fuel consumption and exhaust gas. It is difficult to always obtain the optimum air-fuel ratio depending on the load factor. Figure 1 shows this situation. When the horizontal axis shows the throttle valve opening, which is a substitute characteristic for the load factor, and the vertical axis shows the gas flow adjustment valve opening instead of the air-fuel ratio, fuel efficiency deteriorates. Since there are areas as shown in the diagram, such as the nozzle area, the knocking area, and the misfire or stall area, the permissible gas amount adjustment valve opening is limited to the mountain-shaped area left between these areas. , a linear relationship cannot be obtained.

Another conventional technique is to install an oxygen concentration sensor at the outlet of the combustion chamber and adjust the amount of fuel supplied based on the detection results, but oxygen concentration sensors are generally expensive and have poor durability. There were problems such as poor performance and unstable operation, complicated control circuits, and high replacement costs.

The present invention has focused on these points, and has been made for the purpose of providing a control device for a gas fuel engine that can appropriately control the air-fuel ratio according to the load factor. a governor mechanism that maintains the rotational speed of the engine at a constant level; a means for detecting the opening of the throttle valve; a means for detecting the opening of the gas volume adjustment valve; A means for storing the possible relationship in the form of a numerical table extending to a region exceeding the throttle valve opening at rated output in a steady operating state, and A calculation means for determining the opening degree of the gas amount adjustment valve based on the numerical table according to each detection result and outputting a control output, and an adjustment means for increasing or decreasing the opening degree of the gas amount adjustment valve based on the control output of the calculation means. The gas amount adjustment valve opening is set to provide fuel-rich conditions that do not cause misfire or stall in a region exceeding the throttle valve opening at rated output under steady-state operating conditions. There is.

That is, in a constant speed operating engine controlled by a governor mechanism, the present invention indirectly detects the amount of air using the throttle valve opening, and also detects the load factor using the throttle valve opening, which is a substitute characteristic. Based on the detection results, a calculation means calculates the gas volume adjustment valve opening according to the load and air volume to control the gas supply amount, and the optimal gas volume adjustment valve opening for the throttle valve opening is determined in advance. By determining this through experiments and storing it in the form of a numerical table, it is possible to always obtain an air-fuel ratio suitable for the load factor at that time. Furthermore, in the present invention, the possible relationship of the gas amount adjustment valve opening to the throttle valve opening is memorized even in a region exceeding the throttle valve opening at the rated output in a steady operating state,
In addition, in this region, the opening degree of the gas amount regulating valve is increased to provide a fuel-rich condition. This is to deal with the situation where the governor mechanism may overreact and the throttle valve opening may become larger than the rated value due to a sudden load increase during operation and no turbocharger response. Generally, in order to avoid malfunction of the calculation means, the value for the rated output may be extended as is and set as shown by the broken line in Figure 1, but in the present invention, this part is also controlled. This avoids a temporary increase in the gas supply amount resulting in a stall condition.

Next, embodiments of the present invention will be described with reference to the drawings.

Fig. 2 is a conceptual system diagram, and in the figure, 1 is the engine, 2 is the governor mechanism, 3 is the opening detector which is a means for detecting the throttle valve opening, and 4 is the opening of the gas volume adjustment valve. 5 is a ROM that is a storage means; 6 is a microcomputer that is a calculation means; 7 is an electric motor that is an adjustment means for increasing or decreasing the opening of the gas amount regulating valve; 8 is a throttle valve; 9 is a throttle valve. 10 is a rotational speed detector.

The fuel gas 11 supplied to the combustion chamber of the engine 1 passes through the gas amount adjustment valve 9 and reaches the mixer 12, where it is mixed with air 13 taken in from another port, and then flows into the engine 1 via the throttle valve 8. Supplied. The valve opening of the throttle valve 8 is controlled by the governor mechanism 2 based on the detection result of the rotational speed detector 10, and the engine 1 is maintained in a constant speed operating state. As the governor mechanism 2, a well-known mechanism such as an electronic governor operated by the output signal of the rotational speed detector 10 can be appropriately employed. Also, throttle valve 8
For example, potentiometers can be used as the opening degree detectors 3 and 4 of the gas amount regulating valve 9, and their outputs are sent to the multiplexer A/D converter 14 and converted into digital quantities.

21 of microcomputer 6 is CPU, 22
is RAM, 23 is I/O interface, 24
is a so-called system bus line consisting of a data bus, address bus, control bus, etc.
Each unit constituting the microcomputer 6 may be composed of a discrete LSI, or a so-called one-chip microcomputer may be used. The ROM 5 stores arithmetic control programs and data that represents a possible relationship between the throttle valve opening and the gas amount adjustment valve opening.

The relationship between the throttle valve opening degree and the gas amount adjustment valve opening degree is set as shown in the control line 25 shown in FIG. In other words, in the area below the rated load on the left side of the chain line R, the engine is set in a mountain shape in the area left between these areas, avoiding areas where fuel efficiency deteriorates, knocking, misfiring, or stalling, and exceeds the rated load. In the region to the right of the chain line R, the opening degree of the gas amount regulating valve is set to increase rapidly in order to avoid misfires and stalls. Note that the control line 25 is divided into subdivisions and shown in a numerical table, so it is in the form of steps, but as the storage capacity of the ROM 5 is increased,
Needless to say, it is possible to approximate a fine-grained, smooth curve.

The microcomputer 6 obtains the gas amount adjustment valve opening degree from the control line 25 corresponding to the detection result of the throttle valve opening degree, and compares this with the detection result of the gas amount adjustment valve opening degree to reduce the difference between the two. A control output such as that shown in FIG. By driving this electric motor 7, an internal regulating valve (not shown) in the gas quantity regulating valve 9 is driven via a link 29, and the gas supply quantity is adjusted so as to obtain the optimum air-fuel ratio. . FIG. 3 shows a control flowchart for the above-mentioned operation.

The above explanation assumes that the calorific value of the fuel gas is constant, but according to experiments,
The results show that the knocking region and misfire region shift almost vertically depending on the calorific value of the fuel gas.
It is desirable that the control line 25 in FIG. 1 be set according to the amount of heat generated. Particularly in the high load range, the operable range is narrow, so when the fuel gas components change, the engine tends to enter the knocking range or misfire range, making it impossible to obtain good operating conditions.

In order to solve this problem, Figs. 4 and 5 show that changes in the calorific value of the fuel gas are detected based on the exhaust temperature, and the gas amount adjustment valve is adjusted according to the detection result for the throttle valve opening. This is an embodiment in which the opening degree is automatically corrected, and the differences from the previous embodiments will be described below.

When a gas fuel engine maintains a constant load factor and changes the air-fuel ratio, it enters the knocking region or misfire region, and the fuel efficiency changes, but at the same time, the exhaust temperature also changes, and the The exhaust temperature reaches its peak. Based on this experimental fact, in this example, by operating with the exhaust temperature always near the peak value, λ = 1 is maintained, and the fuel efficiency is also good while avoiding the knocking region and misfire region. It detects changes in the calorific value of fuel gas by changes in exhaust temperature, moves the operating point to around λ = 1 at that calorific value, and always maintains the desired air-fuel ratio. It is configured as follows.

In FIG. 4, 31 is an exhaust temperature sensor that detects the engine exhaust temperature, 32 is an operational amplifier circuit, and 33
is an A/D converter, and the detection output of the exhaust temperature sensor 31 is sent to the A/D converter 33 by the operational amplifier circuit 32.
is operationally amplified to fit the input range of
Microcomputer 6 via A/D converter 33
sent to. Note that the exhaust temperature sensor 31 has
Known techniques such as CA thermocouples can be used as appropriate;
If the engine 1 is a multi-cylinder engine, it may be provided at the outlet of the exhaust manifold, or it may be provided at any specific cylinder.

In this case, if the control simply feeds back the detected exhaust temperature and operates the gas amount adjustment valve to obtain the peak, hunting will occur due to the large time constant and changes in the load factor will become difficult.
If an attempt is made to avoid this, there will be problems such as poor responsiveness, so in this embodiment, a correction amount A is used that is added to the value of the gas amount adjustment valve opening degree based on a stored numerical table. This correction amount A is a variable that is set to zero when the engine is started, and the new sampled exhaust temperature is compared with the exhaust temperature one pitch before.
Control is performed such that if the exhaust gas temperature is rising, the opening degree of the gas amount regulating valve is made larger than the numerical value, and if it is falling, it is made smaller.

The correction amount A can be calculated, for example, as follows. In other words, the indicated value of the gas amount adjustment valve opening is increasing (A is increasing) or decreasing (A is increasing).
The exhaust gas temperature is then compared with the previous value, and if it is increasing, it is approaching the peak, so the flag is left as it is; conversely, it is decreasing. If so, the flag is reversed and the correction amount A is moved in the opposite direction.

FIG. 5 is a control flowchart of arithmetic processing using the above correction amount A. Here, the "counter" in the flowchart regulates the sampling interval for exhaust gas temperature detection. According to the experimental results, the basic operation of detecting the throttle valve opening is sufficient at about 2 times/second, but the operation of exhaust temperature detection has a large time constant, so 20 to 30 seconds/time is good. A counter value corresponding to this frequency is preset. Also, “shift amount” in the same flowchart
is a correction amount that is added to the numerical table value as needed in addition to the correction amount A, and is added separately by manual operation or the like when the operating conditions change significantly.

As described above, in this embodiment, when the load fluctuates, control is performed by first moving to the next operating point in a non-feedback manner based on the stored numerical table, and then making fine adjustments by detecting the exhaust temperature. Therefore, even though the control system includes a feedback loop, it is possible to obtain a control device that has high responsiveness and has fewer problems such as hunting.

In each of the examples, a case is described in which the gas supply amount is controlled by opening and closing a throttle valve using a gas amount adjustment valve, but the gas supply amount may be controlled by adjusting the supply pressure with a gas pressure regulator. It can also be controlled by Furthermore, as in the second embodiment, the correction of numerical table values based on the detection results of exhaust gas temperature is particularly effective in the region to the left of the chain line R in FIG.
This can also be implemented in a control device in which the control line 25 is set only to the left of the dashed line R.

As is clear from the description of the embodiments described above, the present invention stores the possible relationship between the throttle valve opening of the engine and the gas amount adjustment valve opening in the form of a numerical table, thereby adjusting the load factor. Accordingly, the optimal air-fuel ratio can always be obtained, and the engine can be operated stably with low fuel consumption. In addition, in the region where the throttle valve opening exceeds the rated output under steady-state operating conditions, the gas flow adjustment valve opening is increased to create a fuel-rich condition. When the number table is read, the fuel gas increases rapidly, making it possible to avoid a stall. In particular, when the control line is set close to the misfire range and has low fuel consumption, it is easy to stall when the load suddenly changes, but the present invention can maintain good operating conditions even under such setting conditions. It is possible to keep it.

Furthermore, in the present invention, since the opening degree of the throttle valve is detected as a substitute characteristic for the load factor, there is no need to use an expensive device such as a torque sensor and there are many restrictions when using it, and there is no need to measure the air-fuel ratio itself. Therefore, there is no need for an expensive and troublesome device such as an oxygen concentration sensor, and there is an advantage that a control device that is inexpensive and has excellent responsiveness can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the throttle valve opening and the gas amount adjustment valve opening and the control line in a gas fuel engine according to the present invention, and FIG. 2 is a conceptual system diagram of the first embodiment of the present invention. FIG. 3 is a control flowchart similar to the above, and FIG. 4 is a conceptual system diagram of the second embodiment.
FIG. 5 is a control flow chart similar to the above. 1 is an engine, 2 is a governor mechanism, 3 is a throttle valve opening detector, 4 is a gas amount adjustment valve opening detector,
5 is a ROM, 6 is a microcomputer, 7 is an electric motor, 8 is a throttle valve, 9 is a gas amount adjustment valve, 10 is a rotation speed detector, 11 is a fuel gas, 1
3 is air, 25 is a control line, 26 is an increase signal, 2
7 is a reduced signal.

Claims (1)

[Claims] 1. A governor mechanism that adjusts the opening degree of the throttle valve to maintain a constant rotational speed of the engine, a means for detecting the opening degree of the throttle valve, a means for detecting the opening degree of the gas amount adjustment valve, and a governor mechanism that adjusts the opening degree of the throttle valve to maintain a constant rotational speed of the engine. Means for storing in the form of a numerical table the possible relationship between the throttle valve opening and the throttle valve opening at the rated output in a steady operating state, and the sampled throttle valve opening. and a calculation means for determining the opening degree of the gas volume adjustment valve based on the numerical table and outputting a control output according to each detection result of the opening degree of the gas volume adjustment valve; In the region where the throttle valve opening exceeds the rated output under steady-state operating conditions, the gas amount adjustment valve opening is adjusted to provide fuel-rich conditions that do not cause misfires or stalls. A control device for a gas fuel engine, characterized in that: