JPS624675Y2 - - 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 or excess air ratio of the gas fuel engine.

In gas fuel engines, especially electrically ignited gas fuel engines, it is essential to optimize the air-fuel ratio as a means to avoid knock and misfire regions and to improve fuel consumption and exhaust gas characteristics. It is.

Conventional techniques related to such adjustment devices generally do not include a control device, but use mechanical means such as providing a fuel throttle section that is linked to a butterfly that senses the dynamic pressure caused by the air flow in the mixer section.

On the other hand, the air-fuel ratio, which avoids the knocking and misfire range and also takes into account the minimum fuel consumption and exhaust gas, generally does not have a simple linear relationship with the load factor, and the vertical axis in Figure 2 shows the gas amount. The pressure regulating valve opening and the throttle valve opening are expressed on the horizontal axis as a knocking region, a misfire region or stall region, and a fuel efficiency deterioration region.

However, since the above-mentioned conventional technology uses mechanical means, this objective cannot be achieved and adjustment is also difficult.

In addition, as another general conventional technology, there is a method such as installing an oxygen concentration sensor at the outlet of the combustion chamber and adjusting the amount of fuel supplied based on the detection result, but the oxygen concentration sensor used here They are expensive and have a durability of only a few hundred hours, and they also have many disadvantages such as the fact that their output changes significantly depending on the temperature during use, and they require high control circuit costs and frequent replacement. There was a problem that the cost burden was large.

Therefore, the present invention was made to solve the problems of the conventional technology, and provides a gas fuel engine with a control device that avoids the knock region and misfire region and improves the fuel consumption rate and exhaust gas characteristics. It is intended to.

That is, the control device for a gas fuel engine of the present invention is applicable to a gas fuel engine having a governor mechanism that maintains a constant speed by increasing or decreasing the opening degree of a throttle valve. The relationship between the opening of the throttle valve and the engine output based on the opening detection means of each throttle valve provided in the engine, the engine output detection means, and the calorific value of the specific fuel gas, and the relationship between the engine output and the engine output. It has a means for storing the relationship with the opening degree of the gas amount adjustment valve in the form of a numerical table, and also detects the opening degree of the throttle valve and the engine output as appropriate, thereby adjusting the gas amount as a target. Valve opening = Opening of the gas amount adjustment valve as seen from the numerical table + Experimentally determinable coefficient α × (Detected opening value of the throttle valve - Opening of the throttle valve as seen from the numerical table) The present invention is constructed by providing arithmetic control and output means that can increase or decrease the opening degree of the gas amount adjusting valve in order to reduce the difference between this value and the detected opening value of the gas amount adjusting valve.

Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 1 is a conceptual system diagram showing a gas fuel engine according to an embodiment of the present invention. Fuel gas 22 supplied to the combustion chamber of the engine 20 is first mechanically connected to an electric motor 12 by a lever 14. The gas then reaches the mixer 15 via the driven gas amount adjustment valve 11 . Further, air 23 is taken into this mixer 15 from another port, mixed, and then passed through a throttle valve 16 to reach the combustion chamber of the engine 20.

Here, in the present invention, as a prerequisite technology, it is assumed that the throttle valve 16 is controlled by the governor mechanism 18 and is adjusted to a valve opening degree that can always maintain the rotational speed of the engine 20 constant. Although this governor mechanism 18 is outside the scope of the present invention, any method may be used, such as applying an electronic governor that operates in response to a signal from the engine rotational speed detector 21 to the governor mechanism 18.

Next, 13 is an opening detector for the gas amount adjustment valve 11, and 17 is an opening detector for the throttle valve 16, both of which can be provided with known technology such as a potentiometer. can.

The opening degree of the throttle valve 16 and the gas amount adjustment valve 11
As shown in this embodiment, a microcomputer system can be used as the means for storing the possible relationship between the two in the form of a numerical table and the arithmetic control means.

That is, 2 in Figure 1 is the CPU, 3 is the ROM,
Here, a calculation control program and possible values of the gas amount regulating valve 11 can be stored in the form of a numerical table. 4 is a RAM, and 5 is an I/O interface.

It should be noted that each unit shown in 2 to 5 above can not only be constructed from a discrete LSI, but also a one-chip microcomputer as shown in block 1 can have similar functions. Further, 8 indicates a so-called system bus line consisting of a data bus, an address bus, and a control bus.

Furthermore, since the values detected by the two opening degree detectors 13 and 17 are detected as analog values, a multiplexer and an A/D converter 6 are required, which can also be connected to the system bus line 8. .

In addition, the calculation result is the I/O interface 5
When the electric motor 12 is used, the output is output as the opening increase/decrease signal of the electric gas amount adjustment valve 11 from the electric motor 12.
0 and 9, which can be connected via an amplifier 7 such as a power transistor or a relay.

Next, the line indicated by 27 in Figure 1 is the engine output,
That is, it is a load factor detection line.

As an example, a method is possible in which an engine rotational speed detector 21 and a torque sensor 25 are provided at the output section of the engine 20, and the preprocessing circuit 24 multiplies the two and outputs the result as a load factor. As another means, although not shown, if the engine 20 is a generator set, it is also possible to detect the output voltage and current phase, and have the preprocessing circuit 24 convert it into a power value and output it.

To explain the operation of the control device with the above configuration, first, in the case of gas fuel engines, it is necessary to adjust the air-fuel ratio to a predetermined value in order to avoid the misfire region or knock region. The value varies depending on the load factor, but the above-mentioned Figure 2 is a graph of the situation. Optimal control line 31 that should exist
is set.

In addition, in FIG. 2, the air-fuel ratio itself is not taken on the vertical axis, but the opening degree of the gas amount adjustment valve, which is an operable substitute variable, is taken.

Here, the reason why the control line 31 is step-shaped is to perform quantization when converting into a numerical table.
Needless to say, the larger the storage capacity of the numerical table, the finer the lines can be memorized.

According to experimental results, when the fuel gas composition changes, the misfire area and knocking area shown in Figure 2 change by shifting almost vertically. Even if this occurs, the numerical table will be automatically shifted up or down, so all you need to do is create and memorize a numerical table based on the typical gas component calorific value of the new engine.
This point is one of the important features of the present invention.

Next, although the control logic is as shown in the chart of FIG. 4, points to be noted here will be explained below.

First, in a gas fuel engine, as is clear from FIG. 2, the operable range is narrow in the high load range, and this range changes sensitively to changes in the fuel gas calorific value.

Generally, as the calorific value increases, the opening value of the gas amount regulating valve 11, which starts to knock, decreases.

Therefore, it is necessary to detect the calorific value of the supplied gas, but in the present invention, this value is not directly detected, but estimated from the engine output detection value and the opening degree detection value of the throttle valve 16.

In other words, as shown in the chart in Figure 3, where the vertical axis represents the throttle valve opening and the horizontal axis represents the load factor, the engine output based on the calorific value of a typical specific gas,
The relationship with the opening degree of the throttle valve 16 is understood, converted into a numerical table, and stored in the aforementioned ROM3 section.

While the engine 20 is operating, the engine output and the opening degree of the throttle valve 16 are detected, and when compared with FIG. A low calorie gas is plotted in zone l, and a high calorie gas is plotted in zone h. Moreover, the farther the point is from the line, the greater the degree of the difference.

Therefore, it is clear that the correction of the control line 31 in FIG. 2 due to the change in calorific value can be made by adjusting an amount corresponding to the extent to which the detected value of the throttle valve 16 deviates from the line in FIG. 3. It is. Specifically, the correction may be made using the formula shown in the flowchart of FIG. 4, and the coefficient α can be determined experimentally.

Next, when comparing the detected opening value of the gas amount regulating valve 11 with the calculated target value, the comparison should be made with a certain allowance balance in order to prevent chattering.

Furthermore, in consideration of the rotational angular velocity of the electric motor 12, the interval should be selected to be a time length that does not cause much control overshoot, and the interval generation method is as follows:
Possible methods include a method using an external clock and a method using a software timer.

Furthermore, to illustrate some other embodiments other than the embodiments of the present invention that are applicable to the present invention, the electric motor 12 in FIG.
For example, it is possible to use a servo solenoid,
In this case, the output from the control circuit is an analog value, so by assigning the number of bits corresponding to a predetermined precision to the output section of the I/O interface 5 and outputting it via a D/A converter (not shown). It is achievable.

In addition, in the present invention, mixer 1 is used as a control output.
Although the opening degree of the gas amount adjusting valve 11 at the front stage of FIG. In this case, the numerical table pattern shown in FIG. 2 would be appropriate.

Furthermore, it goes without saying that a similar sequence circuit can be constructed using ordinary random logic without using the CPU 2 as a control circuit.

Note that when the opening degree of the gas amount regulating valve 11 is changed by the control device of the present invention, it may cause a change in the rotational speed of the engine 20, but this can be immediately corrected by a separately provided governor mechanism. It is.

Therefore, if the control device of the present invention is applied to a gas fuel engine, the optimal air-fuel ratio pattern for the load factor is memorized in the form of a numerical table, so any pattern can be adopted, and as a result, the misfire region and knock region Optimum patterns that have been tested and confirmed during engine development can be freely set, such as avoiding fuel consumption and minimizing fuel consumption.

However, gas-fueled engines often use gases with variable calorific values, such as municipal waste processing gas, as fuel, and in this case, the optimal air-fuel ratio pattern that should be set above is based on the gas calorific value. Change.

In order to cope with this, it is originally necessary to provide a calorific value meter in the gas line, but there is no suitable one due to space and cost considerations.

Therefore, in the present invention, the calorific value is estimated using the above-described means, and thereby the above numerical table can be automatically corrected. Therefore, even in the case of gas fuel with large fluctuations,
Stable operation is possible without causing misfires or knocks.

Furthermore, since the control device of the present invention does not measure the air-fuel ratio itself, there is no need for an expensive and difficult-to-handle sensor such as an oxygen concentration sensor. Because it uses a numerical table storage system, it has quick response and fewer problems such as hunting.

As described above, the control device of the present invention has a simple mechanism, is low in price, is easy to adjust and maintain, and can control the air-fuel ratio in any pattern, and can control the fuel gas composition. Even if there is a change, the knock range and misfire range are avoided, more reliable engine control is possible, and it greatly contributes to fuel efficiency reduction and exhaust gas countermeasures.

Note that the present invention can be effectively applied to gas fuel engines in general that operate at a constant speed.

[Brief explanation of the drawing]

Fig. 1 is a conceptual system diagram showing a gas fuel engine in an embodiment of the present invention, and Fig. 2 is a control of the gas fuel engine shown in Fig. 1 in relation to the gas amount adjustment valve opening and throttle valve opening of the gas fuel engine. Figure 3 is a diagram showing the relationship between the gas amount adjustment valve opening and load factor of the gas fuel engine in Figure 1, and Figure 4 is a flowchart of the control device for the gas fuel engine in Figure 1. It is. 1...Block, 2...CPU, 3...ROM,
4...RAM, 5...I/O interface,
6...Multiplexer, A/D converter, 7
...Amplifier, 11...Gas amount adjustment valve, 13...Opening degree detector, 15...Mixer, 16...Throttle valve, 17...Opening degree detector, 18...Governor mechanism, 20...Engine, 21... Engine rotation speed detector, 24... Preprocessing circuit, 25... Torque sensor, 27... Detection line, 31... Control line.

Claims (1)

[Scope of utility model registration request] In a gas fuel engine having a governor mechanism that maintains a constant speed by increasing or decreasing the opening of a throttle valve, a means for detecting the opening of each of the gas amount adjusting valve provided in the front stage of the mixer and the throttle valve provided in the rear stage of the mixer, and the engine The relationship between the opening degree of the throttle valve and the engine output based on the output detection means and the calorific value of the specific fuel gas, and the relationship between the engine output and the possible opening degree of the gas amount adjustment valve, respectively. In addition to having a means of memorizing in the form of a numerical table,
By appropriately detecting the opening degree of the throttle valve and the engine output, the target opening degree of the gas amount adjusting valve = the opening degree of the gas amount adjusting valve seen from the numerical table + which can be determined experimentally. The coefficient α×(detected opening value of the throttle valve - opening degree of the throttle valve as seen from the numerical table) is calculated, and the gas is A control device for a gas fuel engine, characterized in that it is provided with arithmetic control and output means that can increase or decrease the opening degree of a quantity regulating valve.