JPH053722Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to an abnormality detection device for gas engines, which detects abnormal ignition of gas-fired engines, and automatically turns off the injected gas in the event of an abnormality. Pertains to devices that can stop supply, etc.

(Prior art) Conventionally, gas engines have adopted a method in which fuel gas is ignited using pilot oil or a spark plug, but with this method, there is a risk that abnormalities may occur in the pilot oil injection valve or spark plug. This may cause the gas not to ignite, or the gas injection valve to malfunction and a large amount of gas to flow into the cylinder. If such an ignition error occurs, unburned gas may flow into the supply/exhaust pipe, causing an explosion within the pipe, or a large amount of gas may flow into the cylinder, causing an explosion. In this case, the problem arises that the cylinder internal pressure increases extremely.

Therefore, there is a need for a device that detects ignition errors and abnormal inflow of gas into the cylinder as described above and automatically stops the supply of injection gas. Kaisho 61-33932)
proposed the following device. That is, this abnormality detection device includes an internal pressure detection means for detecting the internal pressure of the cylinder of a gas engine, a maximum pressure detection means for determining the maximum pressure inside the cylinder for each cycle based on this detected value, and a malfunction detection means for detecting the internal pressure in the cylinder of a gas engine. Compare the above maximum pressure with the reference range that exists between the lower boundary value determined in response to the inflow of a large amount of fuel gas and the upper boundary value determined in response to a large amount of fuel gas inflow, and if the pressure is a value outside the reference range. and a control means for operating a gas cutoff valve or the like based on the signal from the comparison means. The reference range of pressure mentioned above is determined by creating a map of the normal pressure range corresponding to the operating conditions, storing this map in the device, and calculating the normal pressure range at that time based on the electrical signal indicating the operating conditions. This is how it was done.

(Problems to be solved by the invention) The above-mentioned abnormality detection device has the following two drawbacks. The first is that a storage device is required to store the map of the normal pressure range.
This means that the configuration of the device becomes complicated and expensive. Second, when there are multiple factors that indicate operating conditions, such as engine speed and load, multiple detectors are required to detect them. .

This invention was made to solve the above-mentioned conventional drawbacks, and its purpose was to eliminate the need for a storage device for storing maps and multiple detectors for setting reference values, so the structure could be improved. An object of the present invention is to provide a gas engine abnormality detection device that can be simplified.

(Means for Solving the Problems) Therefore, in the gas engine abnormality detection device of this invention, in the device as described above, a supply pressure detection means is further provided for detecting the pressure of supply air supplied to the cylinder. Based on this detected boost pressure value, the above lower boundary value is determined so that the pressure is slightly higher than the cylinder compression pressure obtained by approximation by polytropic change assuming that there is no combustion of fuel gas. The present invention is characterized by comprising a reference value generating means for determining the upper boundary value so that the pressure is higher than the lower boundary value by a predetermined pressure and exceeds the cylinder pressure range during normal operation.

(Function) As a result of the above, if an ignition error occurs, the maximum pressure inside the cylinder in this cycle will be lower than the standard value range, so the gas stop means will stop the gas inside the cylinder based on the signal from the comparison means. At the same time, or in place of this, an alarm is issued by an alarm means. On the other hand, if a large amount of gas flows into the cylinder due to an abnormality in the injection valve, the maximum pressure in that cycle will be higher than the standard value range, so the signal from the comparison means will be Based on this information, gas supply is stopped or an alarm is issued.

The reference value mentioned above is set by the reference value generating means based on the detected value of the air supply pressure detecting means. In this case, the boost pressure used as a parameter in the reference value generation means changes accordingly when the engine speed and load change, so the lower boundary value determined based on the boost pressure The upper boundary value reflects operating conditions such as engine speed and load, and therefore there is no need to store the normal pressure range in a map according to operating conditions. Therefore, the conventional map storage device and multiple detectors for setting reference values are no longer necessary.

(Example) Next, a specific example of the gas engine abnormality detection device of this invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 1 indicates a cylinder head, and reference numeral 2 indicates a cylinder head bolt, and a strain gauge 3 is attached to the cylinder head bolt 2 as means for detecting the internal pressure of the cylinder. This strain gauge 3 generates a strain proportional to the cylinder internal pressure, and its output is amplified by an amplifier 4 and guided to the cylinder maximum pressure means 5. On the other hand, a timing pulse generating means 6 is preferably attached to the camshaft of the gas engine, and the output thereof is guided to the cylinder maximum pressure detecting means 5 via an amplifier 7 in the same way as the above-mentioned detected pressure. ing. This timing pulse generating means 6 has a function of generating a pulse every cycle of the engine (every revolution in a two-cycle engine). The maximum pressure detection means 5 detects an analog value detected by the strain gauge 3;
This is to determine the maximum pressure in the cylinder for each cycle from the timing pulse and output it continuously. A specific example of this is shown in FIG. 2. As shown in the figure, the pressure value inside the cylinder input from the analog input 8 is guided to the peak detector 9, and the peak detector 9 determines the maximum pressure. Once detected, this value is held by the next sample-and-hold circuit 10 and output at analog output 11.
The timing pulse inputted from the timing input 12 is then sent to the timing controller 1.
2a to the peak detector 9 and the sample-and-hold circuit 10, and these pulses detect, hold, and output the maximum pressure as described above every cycle of the engine. It is designed so that it can be done.
Note that the input/output signals of the maximum pressure detection means 5 are
As shown in the figure, the figure a shows the pressure signal input to the analog input 8, the figure b shows the pulse signal input to the timing input 12, and the figure c shows the output signal from the analog output 11. are shown respectively.

On the other hand, in the air supply pipe 13 of the cylinder head 1,
A pressure pickup 14 is installed to detect the supply air pressure PL, and its output is sent to an amplifier 15.
and the reference value generating means 16
being led to. The reference value generating means 16 calculates a lower boundary value P _L determined in response to mis-ignition based on the electric signal corresponding to the supply air pressure, and transmits the corresponding electric signal to the first comparator 17. On the other hand, the above lower boundary value P _L
An electric signal corresponding to an upper boundary value (P _H =P _L +ΔP) determined in response to a large amount of fuel gas inflow is output to the second comparator 18 by a predetermined pressure higher than .

The procedure for determining the lower boundary value _PL and the upper boundary value _PH will be described below.

First, FIG. 4 shows an example of the pressure waveform inside the cylinder. As shown in the figure, when the pressure inside the cylinder is normal, it is first compressed and rises to 21-22. At this time, pilot oil is injected, and the pilot oil ignites and ignites the fuel gas. As a result, the cylinder internal pressure rises rapidly and reaches the maximum value as shown in 22-23, and then as the piston descends,
24, the pressure also decreases. However, if there is an ignition error in the fuel gas, the temperature will rise between 21 and 22 in the same way as above, but after that, if the pilot oil also does not ignite, as in 22 and 23a,
Also, if only the pilot oil ignites, 22−
As in 23b, almost no pressure increase occurs. On the other hand, if a large amount of fuel gas flows into the cylinder due to an abnormality in the gas injection valve,
The maximum pressure value within the cylinder increases significantly, as shown at 22-23c in FIG.

By the way, in general, compression pressure is the cylinder internal pressure immediately before the piston rises, compresses the intake air in the cylinder, and fuel is injected and ignited, that is, usually before the top dead center of the piston (point A in Figure 4). say. However, in the following description, the cylinder internal compression pressure P _cpnp means the cylinder internal pressure (the part indicated by reference numeral 23a in FIG. 4) that can be reached only by compressing the intake air without igniting the fuel gas. If an ignition error occurs in which the pilot oil is not ignited, the cylinder compression pressure P _cpnp reached only by compressing the intake air is given as follows. In other words, if the compression process is approximated by a polytropic change, (compression pressure) = (compression start pressure) x
(Compression ratio) ^m . Since this compression start pressure is approximately the same as the supply air pressure, the cylinder compression pressure P _cpnp is given by the following equation.

P _cpnp = PL×ε ^m PL: Air supply pressure (absolute pressure) ε: Compression ratio m: Polytropic index The above polytropic index is a value that changes every moment in the actual cylinder, but it is approximately a constant value. can be used. If only the pilot oil ignites and the gas fuel does not ignite or burn, the maximum pressure inside the cylinder is slightly higher than the cylinder compression pressure P _cpnp , as shown in the part 23b in Fig. 4. Therefore, the lower boundary value P _L determined in response to the above mis-ignition is:
Given as a value approximately 5 to 10% larger than the cylinder compression pressure P _cpnp , that is, P _L = P _cpnp × (1.05 to 1.1) = PL × ε ^m × (1.05 to 1.1) = PL × C C: given as a constant It turns out.

On the other hand, although the maximum pressure inside the cylinder during normal operation (the part marked 23 in Figure 4) changes depending on the engine load and rotation speed, it is possible that abnormal combustion occurs when a large amount of gas flows in. It does not become as high as in the case (portion 23c in FIG. 4). Therefore, the upper boundary value P _H is set to P _H = P _L + so that the pressure is slightly higher than the maximum pressure range in normal operation.
By setting it as ΔP, it becomes possible to detect the occurrence of abnormal combustion due to the inflow of a large amount of gas.

On the other hand, as shown in FIG. 1, electric signals from the cylinder maximum pressure detection means 5 are input to the first comparator 17 and the second comparator 18, respectively.
The first comparator 17 outputs a signal to the control means 19 when the detected maximum pressure in the cylinder is smaller than P _L , while the second comparator 18 outputs a signal to the control means 19 when the detected maximum pressure in the cylinder Control means 1 when the maximum pressure is higher than P _H = P _L + △P
A signal is output to 9. The control means 19 includes one of the comparators 17,
When there is an output from 18, the gas cutoff valve 20 shown in FIG. 1 is operated to close the gas flow path, and the alarm A is activated to issue an alarm to that effect.

Fig. 5 shows the detected pressure waveform (a in the figure) and the maximum pressure value output (b in the figure) when an ignition error occurs. The maximum pressure value will not reach the lower limit value P _L of the reference range, and this abnormal phenomenon will be detected and the gas cutoff valve 20 and alarm A will be activated as described above. On the other hand, if an abnormality occurs in the gas injection valve and a large amount of gas flows into the cylinder, the maximum pressure value in the cylinder will be
In the figure, the pressure increases significantly as shown at 22-23c, so contrary to the above, the maximum pressure value exceeds the upper limit of the reference range P _H = P _L + △P, and the occurrence of an abnormality is detected. At the same time, it becomes possible to stop the gas supply.

In the gas engine abnormality detection device described above, if an ignition error occurs or a large amount of gas flows into the cylinder, the maximum pressure inside the cylinder in this cycle will be a value outside the standard value range. Therefore, as described above, the gas cutoff valve 20 can be closed in response to a signal from the control means 19, and the supply of fuel gas into the cylinder can be stopped, and an alarm can be issued, which greatly improves the safety of the gas engine. can be improved. Further, since the above-mentioned detection is performed every cycle, it is possible to quickly detect an abnormal phenomenon and stop the gas supply at that time. In this case, since the boost pressure used as a parameter in the reference value generating means 16 changes accordingly when the engine speed or load changes, the lower limit determined based on the boost pressure The value and upper boundary value reflect the operating conditions such as engine speed and load.
Therefore, there is no need to memorize the normal pressure range in a map according to the operating conditions. Therefore, there is no need for a conventional storage device for storing a map of the normal pressure range, and only the pressure pickup 14 for the air supply pipe 13 is required as a detector for setting the reference value. , its configuration is simple.

Although one embodiment of the detection device for a gas engine of this invention has been described above, the abnormality detection device of this invention is not limited to the above embodiment, and can be implemented with various modifications. For example, in the above example, a strain gauge is used as the means for detecting the internal pressure of the cylinder, but it is also possible to use an electric pressure gauge that directly detects the internal pressure of the cylinder. Furthermore, in the above, an example is shown in which the gas cutoff valve 20 is used as a gas stop means for stopping the supply of gas to the cylinder when an abnormality occurs.
A gas injection valve may be used as the gas stop means. That is, in addition to operating the gas cutoff valve 20, or instead of operating the gas cutoff valve 20,
This is to stop the operation of the gas injection valve. Further, in the above description, when an abnormality occurs, the gas supply is stopped and an alarm is issued at the same time, but there are cases where either one of the gas supply is stopped and the alarm is issued. Furthermore, in the above, when an abnormal phenomenon occurs once, the control means 19 operates the gas stop means and the alarm means, but if the control means 19 causes an abnormal phenomenon to occur several times in succession, It is also possible to operate the gas stop means or alarm means only when

(Effect of the invention) The gas engine abnormality detection device of this invention is designed to set the reference value range based on the boost pressure, which varies depending on the engine speed and load, as described above. The range of will reflect the operating conditions. Therefore, a storage device for a map indicating a reference range corresponding to operating conditions and a plurality of detectors for setting the reference are not required, and therefore the configuration can be simplified compared to the conventional one. Moreover, as with conventional systems, it is possible to quickly detect ignition errors in gas engines or large amounts of gas flowing into the cylinder, and automatically stop the gas supply, improving the safety of gas engines. It is possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the overall configuration of an example of the gas engine abnormality detection device of this invention, FIG. 2 is a block diagram of the maximum pressure detection means used in the above, and FIG.
Figures a, b, and c are explanatory diagrams showing the input/output signals in the above over time, Figure 4 is an explanatory diagram showing pressure changes within the cylinder over time, and Figures 5 a and b are diagrams showing the pressure changes within the cylinder. FIG. 3 is an explanatory diagram illustrating a comparison with a maximum pressure value over time. 3...Strain gauge, 5...Maximum pressure detection means, 6
...Timing pulse generating means, 13...Air supply pipe, 14...Pressure pickup, 16...Reference value generating means, 17...First comparator, 18...Second comparator, 19...Control means, 20 ...Gas cutoff valve.

Claims (1)

[Scope of utility model registration request] An internal pressure detection means for detecting the internal pressure of the cylinder of a gas engine, a maximum pressure detection means for determining the maximum pressure inside the cylinder for each cycle based on this detected value, and a pressure detection means determined in response to misignition. Comparing means for comparing the maximum pressure with a reference range that exists between the boundary value and an upper boundary value determined in response to a large amount of fuel gas inflow, and emitting a signal when the pressure is outside the reference range; , a gas engine abnormality detection device comprising a control means for operating at least one of a gas stop means and an alarm means based on a signal from the comparison means, which detects the pressure of air supply supplied to the cylinder. Based on the detected value of the boost pressure, the above pressure is set to be slightly higher than the cylinder compression pressure obtained by approximating polytropic change on the premise that there is no combustion of fuel gas. A reference value generating means for determining a boundary value and determining the upper boundary value such that the pressure is higher than the lower boundary value by a predetermined pressure and exceeds the cylinder pressure range during normal operation. Gas engine abnormality detection device.