JP2000161119A - Comsubtion control method for gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a meticulous operation by calculating the difference between the maximum value in a certain time period in the increasing and decreasing period of rotating speed of a crankshaft during one stroke and the average in a plurality of strokes before and after the certain time period to determine the rotation fluctuation value, and performing the combustion control according to the judgment result of stability of combustion. SOLUTION: A controller 16 for inputting detection signals of a crankshaft rotating speed sensor 19 and a camshaft rotating speed sensor 20 controls an air-fuel ratio control valve 1 for regulating the feed quantity of lean fuel gas G to a mixer 2, an ignition device 17, an EGR control valve 15, a swirl control valve 6, and a valve gear timing variable device 12. In this control, the difference between the maximum value in a certain time period in the increasing and decreasing period of rotating speed of a crankshaft 10 during one stroke and the average in a plurality of strokes before and after this certain time period is determined. The fluctuation determined from the individual calculation result is determined as a rotation fluctuation value to judge the combustion fluctuation, and the air-fuel ratio or ignition timing is controlled, allowing for this combustion fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, in order achieve a reduction in the exhaust NO _X, in the lean air supply and gas engine (4-cycle internal combustion engine), the combustion state so as to stabilize the effective The present invention relates to a combustion control method for performing various types of combustion control based on a method for detecting a specific combustion state.

[0002]

In recent years, gas engine (4-cycle engines), the request of the low NO _X reduction of exhaust, lean burn (lean burn) tendency, i.e. tend to increase the air-fuel ratio. As can be seen from FIG. 2, the NO _X amount Q in the exhaust gas decreases as the air-fuel ratio K (intake air amount / intake fuel amount) increases. However, if the air-fuel ratio K is too high, a misfire will occur. Therefore, it is necessary to detect the misfire state and correct the air-fuel ratio K. As a means for controlling the air-fuel ratio K, an air-fuel ratio adjusting fuel control valve (an air-fuel ratio adjusting fuel control valve 8 described later) or the like for adjusting the amount of fuel mixed during supply is known.

The misfire state is determined to be a state in which combustion is unstable, that is, a state in which the combustion fluctuation value P 'is large. The combustion fluctuation value P ′ is a degree of variation in the output (in proportion to the effective average pressure) of each stroke in a plurality of strokes, and increases substantially in proportion to the increase in the air-fuel ratio K as shown in FIG. Strictly speaking, the combustion fluctuation value P 'is obtained by calculating an effective average pressure by plotting an indicator diagram (a graph in which the horizontal axis represents volume and the vertical axis represents pressure) for each stroke. Such a method requires advanced arithmetic means,
A detection value which is easily obtained by using a detection means such as an existing rotation speed sensor or the like and which increases and decreases in accordance with the combustion fluctuation value P 'is used instead of detecting the actual combustion fluctuation value P' However, it is used as a material for determining the combustion fluctuation value P '. Conventionally, as the detected values, the moving average value Ra of the engine speed and the actual engine speed R (detected by the existing speed sensor) in a stable operation state such as a low load or no change in the speed. The average value of the difference (hereinafter,
This is referred to as “rotational speed fluctuation value R ′”. ) Is greater than or equal to a certain value, it is determined that the combustion is unstable, that is, a misfire state,
An air-fuel ratio is reduced by using an air-fuel ratio control fuel control valve or the like (Japanese Patent Laid-Open No. 8-109852).

[0004]

However, as can be seen from the correlation diagram between the combustion fluctuation value P 'and the rotation speed fluctuation value R' in FIG. 13, the rotation speed fluctuation value R 'has a considerably large combustion fluctuation value P'. Even if it becomes large, it is kept small (that is, there is not much difference between the actual rotational speed and the set rotational speed), and it suddenly becomes large after a large combustion fluctuation P'a such as just before a misfire state occurs. Has properties. That is, when the reference value R′a for determining the misfire state is set, the combustion fluctuation value P ′ is accurately determined until the air-fuel ratio K rises to just above the reference value R′a. A large state cannot be determined, the detection efficiency is low, and there is a risk that a misfire may actually occur during the detection period and the engine may stall.

[0005] Instability of combustion is caused by various factors.
If the cause is removed, NO in exhaust
_XWithout performing air-fuel ratio increase control, which leads to an increase in
It can stabilize baking. As a factor
As for the difference of ignition timing (advance angle),
Deterioration with time and inadequate EGR rate when EGR is adopted
Proper, improper swirl status, intake and exhaust valve overlap
Improper backup period. Among them, the ignition plug
Voltage to meet the demand for higher output.
In the coming years, an ignition device (igniter) is generated in anticipation of deterioration over time
The voltage is set high, and the service life is shortened accordingly.
Had become. In other words, combustion anxiety depends on the life of the spark plug.
The fixed time was to come soon. Also swa
And valve (valve-operating) timing is conventionally constant for each engine.
Although it is fixed to the state, even if it is the same
(Exhaust during swirl or overlap period depending on turns)
NO _XThe optimum value (in terms of volume and thermal efficiency) varies. if
Can also vary swirl and valve timing
If these conditions are close to the optimal value,
Efficient operation with fine-grained efficiency can be achieved.

[0006]

The present invention uses the following means in order to solve the above problems. First, in a gas engine that burns by supplying a lean mixture of fuel gas and air, the maximum value of a certain number of cycles in the increase / decrease cycle of the rotation speed of the crankshaft during one stroke and the number of times The difference from the average value in a plurality of strokes before and after the eye cycle is calculated, and the calculation of this difference is repeatedly performed continuously for a plurality of strokes, and a change obtained from each calculation result is calculated as a rotation change value, and the rotation change value is calculated. The combustion control is performed by determining the stability of combustion based on the above.

Second, in the combustion control method for a gas engine described above, during the detection period of the rotation speed of the crankshaft over the plurality of strokes, the means for adjusting the supply amount of the lean mixture is fixed. .

Third, in the combustion control method for a gas engine described in the first aspect, a threshold value of the rotation fluctuation value is set, and when the rotation fluctuation value is higher than the threshold value, the combustion becomes unstable. Judge that there is.

[0009] Fourth, in the combustion control method for a gas engine described in the third, in the engine operating range, at high speed and load most conditions, so that the NO _X value in the exhaust gas is within the target value Then, the threshold value of the rotation fluctuation value is set.

Fifth, in the gas engine combustion control method described in the fourth aspect, the maximum value of a certain number of cycles in the increase / decrease cycle of the rotation speed of the crankshaft during one stroke, and a plurality of values before and after the number of times of the number of cycles. In calculating the difference from the average value in the stroke, the number of strokes for calculating the average value is set so as to ensure the correlation between the combustion fluctuation value and the rotation fluctuation value.

Sixth, in the combustion control method for a gas engine described in the fifth aspect, the maximum upper limit of the fluctuation of the rotation fluctuation value around the threshold value obtained by the method is related to the thermal efficiency of the rotation fluctuation value. The lower limit of the number of detections of the difference between the maximum value and the average value of the rotation speed for obtaining the rotation fluctuation value is set so as not to exceed the reference value.

Seventh, in a gas engine to which the combustion control method described in the first, second, third, fourth, fifth or sixth aspect is applied, an air-fuel ratio, an ignition timing,
At least one of the EGR rate, the swirl state, and the valve overlap period is controlled.

Eighth, in a gas engine to which the combustion control method described in the seventh aspect is applied, the control value of the control is stored in a storage means which is not erased by stopping the engine and turning off the power.

Ninthly, in a gas engine to which the combustion control method described in the first, second, third, fourth, fifth or sixth aspect is applied, the voltage generated by the igniter is set so that combustion instability is reduced from the start of use. In the one which is set to be small until the detection timing, and is set to be large until the use limit of the ignition plug is detected after the detection of combustion instability, the detection of the rotation fluctuation value is performed by the combustion corresponding to the setting change timing of the ignition device generated voltage. Used to detect unstable state.

Tenthly, in a gas engine to which the combustion control method described in the first, second, third, fourth, fifth or sixth aspect is applied, the detection of the above-mentioned rotation fluctuation value is performed by a combustion which corresponds to a use limit time of a spark plug. Used to detect unstable state.

[0016]

Embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 is a block diagram of a combustion control system in a gas engine according to the present invention, FIG. 2 is an air-fuel ratio K between the exhaust NO illustrating the concept of the stabilization of the reduction and combustion fluctuation target serving exhaust amount of NO _X of the present invention FIG. 3 is a correlation diagram between the _X amount Q and the air-fuel ratio K and the combustion fluctuation value P ′. FIG. 3 shows a crankshaft signal TS ₁ detected by the rotation speed sensor 2 of the crankshaft 1 a in the engine 1, and a camshaft. phase diagram, certain number th period in increasing or decreasing period of the rotation speed of the crankshaft in one stroke is a computing element in FIG. 4 is rotation fluctuation value V 'of the cam shaft signal TS ₂ detected by 1b rotational speed sensor 3 FIG. 5 shows the difference ΔV between the detection of the rotation speed V and the average value Va and the maximum value of the rotation speed in a plurality of strokes before and after the number cycle, and FIG.
FIG. 6 is a diagram showing the correlation between the combustion fluctuation value P ′ and the rotation fluctuation value V ′, and FIG. 7 is a graph showing the correlation between the combustion fluctuation value P ′ and the rotation fluctuation value V ′. correlation diagram of a medium amount of NO _X maximum value Q engine speed illustrating the _first Q N and exhaust amount of NO _X Q, 8 in the exhaust gas in the engine operating range in the case of a constant engine speed N NO load L indicating a maximum value Q ₂ of the _X amount Q
Correlation diagram between the exhaust amount of NO _X Q a, 9 rotation variation value V '
In setting the threshold value V′a, the rotation fluctuation value V ′ indicating the lower limit value V′b for keeping the exhaust NO _X amount Q below the reference value Q ₃ and the exhaust NO _X amount Q FIG. 10 shows a threshold value V′a of the rotation fluctuation value V ′, a degree of variation V ″ of the rotation fluctuation value V ′, and a reference value V′c of the rotation fluctuation value V ′ from the thermal efficiency η. FIG. 11 is a correlation diagram between the rotation fluctuation value V ′ / the air-fuel ratio K and the thermal efficiency η. FIG. 11 shows the number N of data samples and the rotation fluctuation value V ′ of the rotation speed difference ΔV for calculating the rotation fluctuation value V ′.
FIG. 12 is a flowchart of air-fuel ratio control of the present invention, FIG. 13 is a correlation diagram of a conventional rotational speed fluctuation value R ′ and a combustion fluctuation value P ′, and FIG. FIG. 15 is a correlation diagram between the ignition advance angle θ and the rotational fluctuation value V ′ at the rotational speed and the air-fuel ratio. FIG. 15 shows the NO _X amount Q in the exhaust gas and the thermal efficiency η based on the variation of the ignition advance angle θ at the constant engine speed and the air-fuel ratio. 16 is a correlation diagram between the plug usage time t _P and the ignition device generated voltage Ei, FIG. 17 is a correlation diagram between the voltage difference Ec and the rotation fluctuation value V ′, and FIG. 18 is a diagram showing a constant engine speed and 19 is a correlation diagram between the EGR rate X and the exhaust temperature T at the air-fuel ratio, FIG. 19 is a correlation chart between the EGR rate X and the rotation fluctuation value V ′, and FIG. 20 is NO _{X in the} exhaust gas based on a change in the swirl ratio during the rated operation.
FIG. 21 is a correlation diagram between the amount Q and the thermal efficiency η, FIG. 21 is a correlation diagram between the swirl ratio S and the rotation fluctuation value V ′ during low-speed operation, and FIG.
2 is the overlap period CA at a constant engine speed
FIG. 23 is a correlation diagram between the overlap period CA and the rotation fluctuation value V ′ during the low rotation speed operation and the high rotation speed operation.

Referring to FIG. 1, an outline of a combustion control system for a gas engine according to the present invention will be described. First, the flow of the supply / exhaust system will be described. In the mixer 2, the outside air A is mixed with the lean fuel gas G whose supply amount is adjusted via the air-fuel ratio control valve 1 and supplied to the supply pipe 3. A throttle 5 for feeding an air-fuel mixture and adjusting an air supply amount, a swirl control valve 6 for adjusting a swirl state (a swirl ratio S described later) of the air supply,
Then, the air-fuel mixture is sent to the combustion chamber 7a of the engine 7 via an air supply valve (not shown).

A spark plug 8 and a fuel injection valve 9 face the combustion chamber 7a. High-pressure fuel gas G 'is sent from the fuel injection valve 9 into the combustion chamber 7a, and the ignition plug 8 is ignited. As a result, the air-fuel mixture in the combustion chamber 7a explodes, and the crankshaft 10 and the camshaft 11 of the engine 7 are rotated. The camshaft 11 is provided with a valve (valve operating) variable device 12 so that the valve operating timing can be changed to change the valve overlapping period.

The exhaust gas after combustion is sent from the combustion chamber 7a to an exhaust pipe 13 through an exhaust valve (not shown). The gas engine used in this embodiment is an EGR (exhaust gas recirculation method).
The downstream side of the mixer 2 in the air supply pipe 3 and the exhaust pipe 13 are connected by an EGR pipe 14 having an EGR control valve 15 interposed therebetween, and a part of the exhaust gas is supplied from the exhaust pipe 13. It circulates through the trachea 3.

Next, the electrically controlled combustion control system according to the present invention will be described. A controller 16 is provided as a central processing unit for the combustion control, and a crankshaft rotation speed sensor for detecting a rotation speed of the crankshaft 10 which is a calculation element of a combustion fluctuation value for the combustion control according to the present invention described later. 19 and a detection signal of a camshaft rotation speed sensor 20 for detecting the rotation speed of the camshaft 11 are input to the controller 16. The control output means according to the combustion control of the present invention includes the air-fuel ratio control valve 1 for adjusting the supply amount of the lean fuel gas G to the mixer 2 for the air-fuel ratio control, and the ignition plug 8 for the ignition timing control. The ignition device (igniter) 17, which is a voltage generator for the ignition coil 8a, the EGR control valve 15 for controlling an EGR rate, the swirl control valve 6, for controlling a swirl state (a swirl ratio S described later), For controlling the valve overlap period, there is the variable valve timing device 12 and an alarm 18 for notifying the use limit timing of the spark plug 8, and calculates a combustion control calculation value (combustion fluctuation value described later). Based on this, an output signal is issued from the controller 16 to each combustion control output means. In addition, 16a is
A power source for generating a voltage by the igniter 17 to generate a voltage for ignition of the ignition plug 8 in the ignition coil 8a.

Next, both rotation speed sensors 19 of the engine 1
The method for detecting 20 will be described with reference to FIG. The gas engine of the present embodiment is based on a four-cycle type,
FIG. 3 shows the crankshaft signal S ₁ and the camshaft signal TS _2.
FIG. 5 is a time chart (the elapsed time t is plotted on the abscissa) with respect to either the intake valve or the exhaust valve. From the camshaft 11, the camshaft rotation speed sensor 20 detects the cam lift once, that is, every stroke. One pulse signal (camshaft signal TS ₂ ) is issued. In the embodiment of FIG. 3, the crankshaft 10 receives, via the crankshaft rotation speed sensor 19, the number of cylinders × 2 pulses / rotation, that is, 12 pulse signals (in two strokes of the crankshaft) ( Crankshaft signal T
S ₁ ) is issued. During one stroke, the crankshaft 10
The rotational speed (angular speed) V (θ / t) of the motor varies. As a result, the transmission time difference Δt between the crankshaft signals fluctuates back and forth as shown in FIG. Rotational speed V to a crankshaft signal TS ₁ is emitted is 60 ° / Δt. As described above, the crankshaft rotation speed sensor 19
During rotation of 0 1 is for successively detecting the rotational speed V between (period Delta] t) from the crank shaft signal TS ₁ is issued until the next crankshaft signal TS ₁ generated.

In the combustion control system for a gas engine having the above-described configuration, the present invention relates to a rotation speed increase / decrease cycle of the rotation speed in one stroke of the crankshaft 10 detected by the crankshaft rotation speed sensor 19. A difference between a maximum value of a certain cycle and an average value in a plurality of processes before and after the certain cycle is calculated. This calculation is repeated continuously over a plurality of strokes, and the fluctuation obtained from each calculation result is calculated as a rotation fluctuation value, the degree of the fluctuation (degree of variation) is obtained, and the combustion fluctuation is determined based on this. Based on this, the combustion control, that is, the control of the air-fuel ratio and the ignition timing, which will be described later, is performed by using the respective combustion control output means. This variation degree is defined as a rotation fluctuation value V ′,
Since this is substantially proportional to the actual combustion fluctuation value P ′ as shown in FIG. 6, the actual combustion fluctuation is substantially more accurate than the above-mentioned rotation speed fluctuation value ΔR employed in the prior art. In addition, it can be determined in the state of normal operation. Then, assuming that a misfire state determination reference value is set, the conventional rotation speed variation value ΔR
As in the case of (1), it is possible to determine how close the air-fuel ratio K is to the reference value without increasing the air-fuel ratio K just before the misfire state is almost reached, and to perform combustion control with a margin.

A description will be given of a method of detecting a combustion fluctuation for the air-fuel ratio control method of the present invention. As shown in FIG. 4, the gas engine (having three cylinders) of this embodiment is a four-cycle engine in which the crankshaft 1a makes two rotations (720 ° rotation) in one stroke as described above. During one rotation, the rotation speed V increases and decreases as described above, and one stroke (two rotations)
The wave of the increase / decrease occurs three times during the operation (acceleration / deceleration / acceleration / deceleration / acceleration / deceleration). The rotation speed V of the crankshaft is detected for each predetermined crank angle (for example, set to 60 ° in the case of three cylinders) in a certain increase / decrease cycle during this one stroke. Referring to the drawing of the crank signal TS1 in the Si stroke of FIG. 3, V (Si, 0) = 60 ° / Δt (S
i, 0), V (Si, 1) = 60 ° / Δt (Si,
1), V (Si, 2) = 60 ° / Δt (Si, 2), V
(Si, 3) = 60 ° / Δt (Si, 3), and the maximum value of the rotation speed V in a certain stroke Si is Vmax = V (Si, 2) as shown in FIG. Further, an average rotation speed Va of a plurality of strokes n before and after the stroke Si including the stroke Si from which the maximum value of the rotation speed of the crankshaft is extracted is obtained. For example, when the Si = S _0, the following equation 1 (1) if n is even, when n is an odd number can be obtained by the following equation 1 (2).

[0024]

(Equation 1)

That is, the average rotation speed Va is obtained by averaging the rotation speeds V of all the crankshafts detected in a certain stroke in which the maximum value of the rotation speed of the crankshaft is extracted and in a plurality of strokes before and after the stroke. When extracting the maximum value Vmax of the rotation speed of the crankshaft in an arbitrary stroke Si and obtaining the average rotation speed Va in arbitrary plural strokes n before and after the stroke Si, the above equation 1- (1) or the equation 1-
(2) can be applied.

Here, the maximum value Vmax of the rotational speed in a certain stroke Si and the average rotational speed V in a plurality of strokes before and after the maximum value Vmax
The difference ΔV from “a” is calculated by the following equation (3). ΔVi = Vmax−Va (3) Regarding the number of strokes n for calculating the average rotation speed Va, as shown in FIG. 5, the correlation between the combustion fluctuation value P ′ and the rotation fluctuation value V ′ can be ensured. Set. In this embodiment, it is appropriate that n is about 10. The rotation speed difference ΔV is continuously calculated for a plurality of times, and the rotation speed Δ
A rotation fluctuation value V ′ indicating the degree of variation of V is calculated. The rotation fluctuation value V ′ is, for example, a standard deviation of the rotation speed difference ΔV.

As described above (see FIG. 6), the rotation fluctuation value V 'is substantially proportional to the combustion fluctuation value P', and is therefore substantially proportional to the air-fuel ratio K (see FIG. 2). Therefore, as a criterion value for the misfire state (combustion unstable state), the rotation fluctuation value V ′
Is set, and the air-fuel ratio K is reduced when the calculated rotation fluctuation value V ′ exceeds the threshold value V′a. By setting this threshold value V'a to a value lower than the value at the time of complete misfire, misfire can be avoided, but if it is too low, the air-fuel ratio K cannot be sufficiently increased, and exhaust gas The effect of reducing the medium NO _X amount Q is reduced. When the load L is constant as shown in FIG. 7, in the operating range R _D in the engine speed R of the engine, exhaust amount of NO _X Q at the maximum engine speed R _MAX is a maximum value Q _1. On the other hand, when the engine speed R is constant as shown in FIG.
Within the operating range L _D of the engine load L, the exhaust NO _X amount Q becomes the maximum value Q ₂ at the maximum load L _MAX . Therefore, as shown in FIG. 9, the smaller one of the exhaust NO _X amount Q _{1 and} Q ₂ is set as the exhaust NO _X amount reference value Q _3, and the empty NO _X amount reference value Q ₃ appears. The value V′b of the rotation fluctuation value V ′ that falls within the rotation fluctuation corresponding to the fuel ratio K is set as the lower limit value of the threshold value V′a. That is, the air-fuel ratio K is suppressed low by setting the smaller threshold V'a than the lower limit V'b, exhaust amount of NO _X Q is to avoid exceeding the reference value Q _3.

Further, as shown in FIG. 10, the thermal efficiency η is inversely proportional to the air-fuel ratio K or the rotation fluctuation value V ′, and the thermal efficiency η decreases as the air-fuel ratio K, ie, the rotation fluctuation value V ′ increases. Therefore, the lower limit value η ₁ of the thermal efficiency is set, and the value of the rotation fluctuation value V ′ at that time is set as the reference value V′c relating to the thermal efficiency. The threshold value V'a is set within a range from a lower limit value V'b to a reference value V'c relating to thermal efficiency.

By the way, as shown in FIG. 10, when the threshold value V'a is set as described above, the threshold value V'a becomes N
The value is set as high as possible to reduce O _x , that is, a value close to the reference value V′c which is the upper limit. Here, a group of rotation fluctuation values V ′ calculated a plurality of times during engine operation includes variations V ″ around the threshold value V′a (standard deviation or the like using the threshold value V′a as an average value). As shown in FIG. 11, the smaller the number of samples of the rotation speed difference ΔV (ie, the number of strokes N for the calculation) as the calculation element of each rotation fluctuation value V ′, the smaller the value. The variation V "of the calculated rotation fluctuation value V 'becomes large, and the rotation fluctuation value V'd which is the upper limit of the fluctuation V" exceeds the reference value V'c. In this case, the engine operation is performed. during, and it exceeds the often rotation variation value V 'is the reference value V'c, operations to reduce the air-fuel ratio K is performed more than necessary, thereby reducing the effect of reducing the exhaust amount of NO _X. Therefore The number of samples of the rotation speed difference ΔV for calculating each rotation fluctuation value V ′ (that is, one rotation fluctuation value V ′ is calculated) By increasing the number of strokes) for, to reduce the variation V ". Then, the number of samples of the rotation speed difference ΔV, that is, one rotation fluctuation value V ′, is calculated so that the rotation fluctuation value (the upper limit value of the variation V ″) V′d does not exceed the reference value V′c. This is to set the lower limit of the number of strokes N to perform.

As described above, the number of rotation speed differences ΔV for calculating one rotation fluctuation value V ′ (the number of strokes N) is set, and the rotation angular velocity fluctuation value V ′ is sequentially calculated during engine operation. And the rotation fluctuation value V ′ exceeds the upper limit value V′d of the fluctuation V ″, it means that the rotation speed difference is large over a large number of strokes. ΔV is large, indicating that combustion is unstable, and the reliability in controlling the air-fuel ratio K is high.

In order to calculate one rotation fluctuation value V ', the rotation speed difference Δ
Unless the air supply state is constant during the period during which V is detected, the value of the rotation speed difference ΔV during this detection period varies, and the rotation fluctuation value V ′ cannot be calculated accurately. Therefore, the throttle 5 shown in FIG. 1 as a means for adjusting the supply amount of the lean air-fuel mixture is fixed during the detection period. The opening and closing of the throttle 5 is controlled by the governor mechanism of the engine in accordance with the detection of the rotational speed. During the period of detecting the rotational speed difference ΔV for calculating the one-rotation fluctuation value V ′, such a governor mechanism is used. It does not perform opening / closing control based on.

After setting the threshold value V'a and the number of samples of the rotational speed difference ΔV as described above, the flow of combustion control (here, air-fuel ratio control) based on the calculation of the rotational fluctuation value V 'is shown in FIG. This will be described with reference to the flowchart of FIG. First, the controller 16 uses an air-fuel ratio operation permission flag F ₀ , an air-fuel ratio operation flag F ₁ , and an operation execution flag F ₂ as operation flags related to the air-fuel ratio control. In this, operation execution flag F ₂ is a flag for starting detection of the rotational speed difference ΔV for calculating the rotation fluctuation value. The air-fuel ratio operation permission flag F ₀ is a flag for confirming conditions before the execution of the calculation, and is set to F ₀ = 0 during normal engine operation. At a fixed time, F ₀ = 1 is set to confirm the combustion fluctuation, that is, the rotation fluctuation value V ′ (01).

When F ₀ = 1 (01), F ₂ = 1 (02) at the start of the detection period. First, the throttle 5 is fixed for stable air supply (03), and the specified number of samples is set. The rotation speed difference ΔV is detected to calculate a rotation fluctuation value V ′ (04). When the rotation fluctuation value V ′ is calculated, the rotation fluctuation value V ′ is compared with the threshold value V′a,
(05), F ₁ = 1 (06),
The air-fuel ratio operation, that is, the opening degree of the air-fuel ratio adjusting fuel control valve 1 is increased to reduce the air-fuel ratio K (07), and subsequently, F ₀ = 1 (01), and the rotation fluctuation value V ′ for the air-fuel ratio control is obtained. And the air-fuel ratio K is stabilized. If the rotation fluctuation value V ′ does not exceed the threshold value V′a (08), F ₁ = 0
(09), and further, assuming that F ₀ = 0 (010), the normal engine operation is started, and during that time, the rotation fluctuation value V ′ for the air-fuel ratio control is not detected.

[0034] As described above, the lean-burn of for reducing the exhaust NO _X, meet the conflicting demands of air inhibition for misfire avoidance Figure 2 illustrated optimum air-fuel ratio K
_One is determined.

As described above, in FIG.
Although the air-fuel ratio is controlled, the unstable combustion state is not caused by the air-fuel ratio alone, but is caused by other factors or corrected to a stable state by using other combustion control means. You can also. Even if the air-fuel ratio K is increased in spite of other factors of combustion instability, the combustion instability may not be eliminated unless the factors are removed, and the NO
_{For the} purpose of reducing the _X amount Q, it is desired to keep the air-fuel ratio K as small as possible. If there is another means for eliminating combustion instability, the air-fuel ratio K is kept small and the NO
_The combustion instability can be eliminated while suppressing the _X amount Q.

Therefore, hereinafter, combustion control other than the air-fuel ratio control based on the detection of the rotation fluctuation value V 'will be described. First, the control of the ignition advance angle θ will be described with reference to FIGS. As shown in FIG. 14, when the ignition advance angle θ is increased, the rotation fluctuation value V ′ is reduced, the combustion is stabilized, and the thermal efficiency η is improved as shown in FIG. (However,
If the ignition advance angle θ is extremely large, the combustion becomes rather unstable, that is, the rotation fluctuation value V ′ increases. However, since such an ignition advance angle θ is a value larger than the upper limit value θ _H described later, here, I omit it. ) Also, on the other hand, increasing the spark advance angle theta, exhaust amount of NO _X Q is increased as it. Then, based on the characteristics of each engine, FIG.
As in 5, exhaust NO _X based on the operation of the ignition advance angle θ
The correlation between the quantity Q and the thermal efficiency η is determined. In this, exhaust amount of NO _X Q fits within the allowable range, and the thermal efficiency η
Is within the standard range as shown in the drawing.
As a result, first, the allowable upper limit value Q _H of the NO _X amount Q in the exhaust gas
Corresponding to the upper limit value theta _H of the ignition advance angle theta in FIG. 14 shown is set. Furthermore, when the set thresholds V'a ignition advance angle rotation variation value V of the on operation of the theta ', small suppressed as possible exhaust amount of NO _X Q, and the thermal efficiency η lower limit η _L or more and becomes as, within the operating range D in FIG. 15 depicted defines a reference point d between in _the amount of NO _X Q and the thermal efficiency η exhaust, set a threshold V'a so as to obtain the reference point d I do.

[0037] In this way, the ignition advance angle theta, is intended to be controlled in the range of the upper limit theta _H, from the top of the reduction in the exhaust amount of NO _X Q is better to as small as possible, The rotation fluctuation value V ′ increases as the ignition advance angle θ decreases, and when the detected rotation fluctuation value V ′ indicates the threshold value V′a, the ignition advance angle θ is set at that time. Adjust so that it increases above the value.

Next, an embodiment utilizing the rotation fluctuation value V 'for controlling the ignition coil voltage will be described with reference to FIGS. In FIG. 16, B _{1 to} B ₃ indicate an unstable combustion zone, and C _{1 to} C ₃ indicate a misfire zone. The present embodiment is based on the premise that combustion instability is caused by a state in which the voltage generated by the ignition coil does not match the required voltage. Of course, even if combustion instability is detected based on the rotation fluctuation value,
The cause is not necessarily the voltage generated by the ignition coil.In this case, as described later, even if the voltage generated by the ignition device is changed or the spark plug is replaced, the cause is not removed and the generation of the ignition device is not performed. Changing the voltage or replacing the spark plug is useless. To avoid this, the controller 16 is stored in the controller 16 so that the change timing of the ignition device generated voltage described later and the replacement timing of the spark plug are roughly grasped. When they overlap, it is conceivable to determine a change in the ignition device generated voltage or a replacement of the spark plug.

First, as the difference between the generated voltage Ei of the ignition coil 8a and the required voltage Er (hereinafter, the voltage difference Ec) is larger, a spark is more stably generated between the electrodes of the ignition plug 8 to ensure reliable ignition and combustion. obtain. That is, as shown in FIG. 17, as the voltage difference Ec is increased, the rotation fluctuation value V ′, which is a guide for the combustion stability, is reduced. In the rotation fluctuation value V ', the threshold value V'a
By setting the voltage difference Ec, rotation variation value V 'must be higher than the voltage difference Ec ₁ when indicating the threshold V'a. However, since the spark plug 8 is consumed over time, the required voltage Er increases and the voltage difference Ec
Becomes smaller and the ignition reactivity becomes worse, so it is necessary to increase the generated voltage Ei in advance. Conventionally, the generated voltage Ei of the igniter 17 is set to be large so as to correspond to the required voltage Er near the limit of use as shown in a graph α of FIG. However, if the operation is performed with the generated voltage set high from the start of use, the voltage difference Ec becomes unnecessarily large, and the consumption of the ignition plug 8 is rather accelerated, so that the use time t _{P of the} plug is shortened. Had been lost. That is, by increasing the generated voltage Ei, demand voltage Er increases with a large increasing rate δ with plug operating time, the spark plug using time until a misfire region C ₁ t _p
Is shortened.

The ignition reactivity is good for a while from the start of use,
Actually, the required voltage of the spark plug is not so high. Therefore, the generated voltage Ei is reduced for a while from the start of use (Ei ₁ ), and consumption is suppressed to a small value. As described above, the required voltage Er increases with the use time due to the consumption of the ignition plug. In this case, the required voltage Er increases at a small increase rate δ ₁ because the consumption is slow. However, when the battery is used with such a small generated voltage Ei ₁ , the required voltage Er becomes equal to the generated voltage Ei ₁ and unstable combustion occurs (unstable combustion region B _{2 in the} graph β). in unstable combustion timing B _2, change the setting value Ei ₁ of generated voltage Ei, and controls the igniter 19 with a large generator voltage Ei ₂ until use limit. After the switching, the required voltage Er increases at a high rate of increase δ ₂ , and the consumption of the ignition plug is accelerated. However, the unstable combustion timing B ₂ when the generated voltage Ei is switched from the start of use.
Time until, because prolonged by depletion is suppressed in the spark plug 8, correspondingly, the time t _p use until use limit than at the start of the use of the spark plug 8 (time to be misfire region C ₃₎ Can be extended. The generated voltage E
The detection of the rotation fluctuation value V ′ is used for the determination at the time of switching i.
That is, when the rotation fluctuation value V ′ exceeds the threshold value V′a,
In the controller 16, it is to switch from a low generated voltage Ei ₁ that has been used from the start of use to the high voltage generated Ei _2.

Also, regardless of how the generated voltage Ei is set (regardless of whether the generated voltage Ei is set to graph α or β), combustion instability occurring at the limit of use of the ignition plug (The unstable combustion zone B ₁ in the graph α and the unstable combustion zone B _{3 in the} graph β in FIG. 16)
It is detected based on the rotation fluctuation value V ′, and is used for determining when to replace the spark plug 8. That is, when the rotation fluctuation value V 'exceeds the threshold value at the time of replacing the spark plug, an alarm is generated by the controller 16 by an alarm device 18 (a display or a buzzer or the like) for notifying the replacement timing of the spark plug. .

Next, the EG based on the detection of the rotation fluctuation value V '
The control of the R rate X will be described with reference to FIGS. First, as shown in FIG. 18, the EGR has an effect of reducing the exhaust gas temperature. At a constant air-fuel ratio, the exhaust gas temperature T can be reduced as the EGR rate X increases. This is an effective measure to extend the life of the exhaust valve. However, as the EGR rate X increases, the combustion becomes unstable, and the rotation fluctuation value V 'increases as shown in FIG. Therefore, a threshold value V'a of the rotation fluctuation value V 'for determining combustion instability is set, and when the rotation fluctuation value V' has reached the threshold value V'a, the EGR control valve 15 The opening is reduced, the EGR rate X is reduced, the rotation fluctuation value V 'is reduced, and combustion instability is corrected.

Next, the swirl control based on the detection of the rotation fluctuation value V 'will be described with reference to FIGS.
Here, a swirl ratio (impeller rotation speed / engine rotation speed) S is used as a numerical value indicating a swirl state. The impeller generates a swirl when supplying air (lean mixture A + G) to the air supply valve, and the number of revolutions is adjusted according to the opening of the swirl control valve 6. If this rotational speed is increased (that is, if the swirl ratio S is increased), a large swirl is generated, and the thermal efficiency η is increased. However, on the other hand, if the swirl ratio S increases, the exhaust NO _X amount Q increases. Therefore, as shown in FIG. 22, the proper swirl ratio S ₁ during the rated operation is set so that the exhaust NO _X amount Q is suppressed as much as possible. And the opening of the swirl control valve 6 is set.

However, as shown in FIG. 23, when the engine is running at low speed, the appropriate swirl ratio S ₁ at rated speed is used.
In this case, the rotation fluctuation value V ′ becomes high, and combustion becomes unstable.
Rotation variation value V 'is reduced as increase the swirl ratio S _1, i.e. the combustion is stabilized. Therefore, 'with respect to the rotation fluctuation value V generated when at low engine speed operation and with the swirl ratio S _1' rotation variation value V threshold V'e to a value less than
And the swirl ratio S is increased so as not to exceed the threshold value V′e. That is, the controller 16 detects the rotation fluctuation value V ′ and sets the swirl ratio S to at least S so that the detection value is reduced to the threshold value V′e.
Increase it to _two . (If the swirl ratio S greater than S _2, but further combustion is stabilized, from the viewpoint of the purpose of reducing the exhaust amount of NO _X Q, the rotation fluctuation value V 'is the upper limit threshold V It is desirable to keep the swirl ratio S ₂ at 'e.)

Finally, referring to FIGS. 22 and 23, a description will be given of an embodiment in which the valve timing adjusting means as the adjusting means for the overlap period is controlled based on the detection of the rotation fluctuation value V '. First, FIG. 22 shows an overlap period C at the time of operation at a certain rotation speed _NH in a high rotation speed region.
Are those showing the correlation between A and the output W, also correlation diagram between the overlapping engine CA and the rotation variation value V 'in FIG. 23, during operation of the line L is at a low rotational speed N _L (idle rotation ), The graph H shows the high rotational speed N in FIG.
It is when driving in _H.

As can be seen from FIG. 22, the longer the overlap period CA (irrespective of the engine speed), the more the output W
Will be higher. (However, the output W with extremely greatly decreased, but such overlap period is below the t ₂
I omit it because it is larger than the value. However, on the other hand, the rotational fluctuation value V ′ increases as shown in both graphs L and H in FIG. 23, and the combustion becomes unstable. In an engine that does not have the conventional variable valve timing device 12, the valve timing must be fixedly set over the entire engine speed range. At a certain engine speed N (middle to high speed range), combustion stability is also reduced. In view of the above (with respect to the rotation fluctuation value V ′,
The threshold value V'a shown in FIG. 23 is set. ), FIG.
2 as the overlap period CA has set the valve timing such that t _1. Due to the overlap period t ₀ , the output W
₀ could be obtained.

Incidentally, as can be seen from the comparison of the graphs L and H, the rotation fluctuation value V 'increases as the engine speed decreases. Therefore, even if the overlap period CA is set to be long so that the output W can be increased to just before the rotation fluctuation value V 'indicates the threshold value V'a in the high rotation speed region, the overlap period CA set in this manner is set. Then, in the low rotation speed range, the rotation fluctuation value V ′ exceeds the threshold value,
It will cause unstable combustion or misfire. Therefore, in consideration of the combustion stability in the low rotation speed range, the overlap period CA must be set to be somewhat short even if the high output in the high rotation speed range is sacrificed. The overlap period t ₀ in FIG. 22 is set in this way, and the output W ₀ obtained in this case is actually obtained by optimizing the overlap period CA with the engine speed N at this time. The output W is suppressed lower than the maximum output W. In other words, conversely, in the low rotational speed range, the combustion is unstable to some extent because the overlap period CA is set longer.

However, in the gas engine of the present invention, as described above, the variable valve timing device 12 is attached to the camshaft 11, so that the overlap period C
A can be adjusted to an optimum value for each engine speed. Therefore, over the entire engine speed range, the rotation fluctuation value V ′ is equal to the threshold value V ′.
The overlap period CA is adjusted until the limit is reached, with a being the upper limit, thereby improving the combustion stability in the low rotation speed range and improving the output in the middle to high rotation speed range. That is, as can be seen from FIG. 23, first, during the operation at the low rotation speed _NL (idle rotation), the upper limit of the overlap period CA is shortened to t ₁ (<t ₀ ), and the combustion is started. the can be stabilized, when the high rotational speed N _H is overlap period CA is prolonged until t ₂ (> t _0), it can improve the output. Therefore, in order to increase the output W as much as possible while avoiding misfire, the overlap period CA should be increased from t ₁ to t ₂ as the rotation speed is increased from low rotation (idling rotation) to high rotation. Good. Thus, the rotation fluctuation value V ′ is detected according to various rotation speed fluctuations, and each time the overlap period C is detected.
By setting A to the optimum value, the maximum output W can be obtained at each rotation speed.

As described above, by using the detection of the rotation fluctuation value V ', combustion control is performed by using various control means to avoid misfire or combustion instability, increase thermal efficiency and output, or reduce exhaust gas. is intended to reduce the medium amount of NO _X, but the air-fuel ratio K which is set based on the detection of these rotation variation value V '
, The ignition advance angle θ, the EGR rate X, the swirl ratio S,
If the values of the overlap period CA and the like are erased when the operation of the engine is stopped or the power is turned off, at the next start of the operation of the engine, these values are again operated at values apart from the optimum values, and the operation is started from the beginning. These controls based on the rotation fluctuation value V 'must be redone. Therefore, these control values are stored in a nonvolatile memory or the like when the engine operation is stopped or when the power is turned off.
It is configured to store the data in a storage unit that is not erased sometimes. As a result, the operation can be performed with the optimal control for the next engine operation.

[0050]

According to the present invention, the method for controlling combustion of a gas engine as described above has the following effects. First, by adopting the method as set forth in claim 1, the maximum value of a certain cycle in the increase / decrease cycle of the rotation speed of the crankshaft during one stroke and the average rotation speed in a plurality of strokes before and after the certain cycle are determined. The difference is calculated, the calculation is repeated continuously for a plurality of strokes, and the rotation fluctuation value obtained from each calculation result is substantially proportional to the combustion fluctuation value that is the variation of the effective pressure over the plurality of strokes. There is reliability as a calculation value instead of detecting combustion fluctuation, and it is inexpensive and low-cost using a conventional crankshaft rotation speed sensor with the same high accuracy as actually calculating the combustion fluctuation value and controlling the air-fuel ratio. It can easily be a fuel control, a stable combustion, and can provide a gas engine having both NO _X reduction effect in the exhaust gas.

Further, during the detection period of the rotational speed of the crankshaft over a plurality of strokes for calculating the rotational fluctuation value, the means for adjusting the supply amount of the lean air-fuel mixture (throttle) is fixed. , The air supply amount during the detection period becomes constant, and the accuracy of the calculated value increases.

Further, as set forth in claim 3, by setting a threshold value for calculating the rotational fluctuation value, it is determined that combustion is unstable when the threshold value is exceeded, and control is performed to stabilize combustion. ,
Stabilize combustion before the gas engine reaches misfire, and avoid misfire. As described above, since the rotation fluctuation value is proportional to the combustion fluctuation value as described above, it is necessary to perform combustion control with as high accuracy as when the threshold value of the combustion fluctuation value is set. The threshold value can be set. This By performing combustion control of the based on a threshold, a stable combustion, and can provide a gas engine having both NO _X reduction effect in the exhaust gas.

[0053] Further, in setting the threshold value, With such method of claim 4, even when the engine operation at the maximum speed or maximum load exhaust NO _X is highest amount occurs, it is possible to suppress the NO _X in the exhaust gas within the target range. For example, in the control of the air-fuel ratio based on the detection of the rotation fluctuation value according to claim 7 described later, the air-fuel ratio can be suppressed to a low value by setting the threshold value to be low, and the combustion can be stabilized. _the amount of nO _X in the exhaust Te should not exceeds the target value. According to the method of the fourth aspect, the threshold value of the air-fuel ratio is determined within a range in which the NO _X amount does not exceed the target value.
A situation in which the NO _X amount in the exhaust exceeds the target value does not occur. That is, in the operation allowable range, without exhaust NO _X exceeds the target value, it is possible to provide a gas engine capable of stabilizing the combustion.

According to a fifth aspect of the present invention, the difference between the maximum value of a certain cycle in the increase / decrease cycle of the rotation speed of the crankshaft during one stroke and the average value in a plurality of strokes before and after that cycle is calculated. In the calculation, by setting the number of strokes for calculating the average value so as to secure the correlation between the combustion fluctuation value and the rotation fluctuation value, it is possible to secure the proportional relationship between the rotation fluctuation value and the combustion fluctuation value. It is possible to improve the accuracy of the operation value and improve the reliability of the control.

By setting the lower limit of the number of strokes in calculating one rotation fluctuation value by the method as described in claim 6, the rotation fluctuation value is calculated by calculating from the smaller number of strokes. Fluctuations become large, and the rotation fluctuation value often exceeds a reference value provided from the viewpoint of thermal efficiency, so that control of combustion stabilization is performed more than necessary, and NO
An adverse effect such as an increase in the amount of _X can be avoided.
That is, by avoiding unnecessary combustion stabilizing control, the exhaust NO _X reduction effect can be sufficiently obtained, and higher unstable rotation fluctuation value combustion defintely abnormal, exceeds the reference value Only when this occurs, the combustion stabilization is controlled.

According to a seventh aspect of the present invention, at least one of various types of combustion control is performed based on the above-described rotation fluctuation value and its threshold value, so that NO in the target range is reduced. While obtaining the _X amount, thermal efficiency, or output, the air-fuel ratio, ignition timing, EGR rate, swirl state, or valve overlap period that does not cause combustion instability leading to misfire are set, and stable combustion in, and it can provide a gas engine having both NO _X reduction effect in the exhaust gas.

Further, by making the swirl state and the valve overlap period variable, and adjusting them based on the rotational fluctuation value in this manner, an optimum control value can be obtained for each engine speed. as compared with the case had these control value regardless of the engine speed until now it is constant, finely combustion stabilization depending on the engine speed of the various stages, reducing the exhaust amount of NO _X, or the higher output Connected driving can be performed.

In the gas engine to which the combustion method according to the seventh aspect is applied, by using the method according to the eighth aspect, the control value based on the detection of the rotation fluctuation value, which is assumed to be the optimum value, is used to stop the engine or to stop the engine. It is erased when the power is turned off, and the same combustion control based on the rotation fluctuation value is again performed at the time of starting the next engine operation or at the time of turning on the power. The operation is started with the control value set to the
The engine can be operated in the best condition in terms of _X amount, combustion stability, and the like.

Further, by switching the rate of increase of the voltage generated by the ignition coil over time based on the rotation fluctuation value, the service life of the ignition plug can be lengthened, and the voltage generated by the ignition coil can be reliably reduced. The switching timing can be determined, and it is possible to avoid a situation in which a misfire is caused on the way or a situation in which the ignition coil generation voltage is set high unnecessarily, and the ignition control of the ignition plug can be efficiently and reliably performed.

By using the detection of the rotation fluctuation value to determine the use limit of the spark plug, the use limit of the spark plug can be reliably determined, and the use limit of the spark plug is inadvertently exceeded. The situation that leads to misfiring can be avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a combustion control system in a gas engine.

FIG. 2 is a correlation diagram between an air-fuel ratio K and an exhaust NO _X amount Q showing the concept of reducing the amount of NO _X in the exhaust gas and stabilizing the combustion fluctuation, which are the targets of the present invention; It is a correlation diagram with a value P '.

A crankshaft signal TS ₁ that is detected by the rotational speed sensor 2 of the crank shaft 1a in Figure 3 the engine 1 is a phase diagram of the cam shaft signal TS ₂ detected by the rotation speed sensor 3 of the camshaft 1b.

FIG. 4 is a calculation element of the rotation fluctuation value V ′, which is a detection of the rotation speed V in a certain cycle in the increase / decrease cycle of the rotation speed of the crankshaft in one stroke, and an average value Va in a plurality of strokes before and after the cycle. And a difference ΔV from the maximum value of the rotation speed.

FIG. 5 is a diagram showing a correlation between the number of strokes n and the combustion fluctuation value P ′ when calculating the average rotation speed Va.

FIG. 6 is a correlation diagram between a combustion fluctuation value P ′ and a rotation fluctuation value V ′.

FIG. 7 is a correlation diagram between the engine speed N and the exhaust NO _X amount Q indicating the maximum value Q ₁ of the exhaust NO _X amount Q within the engine operating range when the load L is constant.

FIG. 8 is a correlation diagram between the load L and the exhaust NO _X amount Q indicating the maximum value Q ₂ of the exhaust NO _X amount Q within the engine operating range when the engine speed N is constant.

[9] rotation variation value V 'in setting the threshold V'a of rotation variation value V indicating the lower limit V'b for accommodating the exhaust amount of NO _X Q than the reference value Q _3' the exhaust NO _X amount Q
FIG.

FIG. 10 is a diagram showing a rotation fluctuation indicating a threshold value V′a of the rotation fluctuation value V ′, a degree of variation V ″ of the rotation fluctuation value V ′, and a reference value V′c of the rotation fluctuation value V ′ from the thermal efficiency η. FIG. 5 is a correlation diagram between a value V ′ / air-fuel ratio K and thermal efficiency η.

FIG. 11 shows a rotational speed difference Δ for calculating a rotational fluctuation value V ′.
FIG. 10 is a correlation diagram between the number N of data samples of V and the degree of variation V ″ of the rotation fluctuation value V ′.

FIG. 12 is a flowchart of air-fuel ratio control of the present invention.

FIG. 13 is a correlation diagram between a conventional rotational speed fluctuation value R ′ and a combustion fluctuation value P ′.

FIG. 14 is a correlation diagram between an ignition advance angle θ and a rotation fluctuation value V ′ at a constant engine speed and air-fuel ratio.

[15] at a constant engine speed and the air-fuel ratio, a correlation diagram of the ignition advance angle exhaust based on variation of theta NO _X amount Q and heat efficiency eta.

FIG. 16 is a correlation diagram between a plug use time t _P and a required voltage Er.

FIG. 17 is a correlation diagram between a voltage difference Ec and a rotation fluctuation value V ′.

FIG. 18 EGR at a constant engine speed and air-fuel ratio
FIG. 6 is a correlation diagram between a rate X and an exhaust temperature T.

FIG. 19 is a correlation diagram between an EGR rate X and a rotation fluctuation value V ′.

FIG. 20 is a correlation diagram with the amount of NO _{X in} exhaust gas based on a change in swirl ratio during rated operation.

FIG. 21 is a correlation diagram between a swirl ratio S and a rotation fluctuation value V ′ during low-speed operation.

FIG. 22 is a correlation diagram between the overlapped engine CA and the output W at a constant engine speed.

FIG. 23 is a correlation diagram between the overlapped engine CA and the rotation fluctuation value V ′ during low-speed operation and high-speed operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Air-fuel ratio control valve 2 Mixer 3 Air supply pipe 5 Throttle 6 Swirl control valve 7 Engine 7a Combustion chamber 8 Ignition plug 8a Ignition coil 9 Fuel injection valve 10 Crankshaft 11 Camshaft 12 Valve timing variable device 13 Exhaust pipe 14 EGR pipe 15 EGR control valve 16 controller 17 igniter (ignition device) 19 in the increasing or decreasing period of in one stroke with a rotating speed Vmax of the crankshaft rotation sensor Q exhaust amount of NO _X P 'combustion variation value V crankshaft, the maximum value of a certain number of eyes cycle Va Average rotational speed of a plurality of strokes before and after the stroke including the stroke in which the maximum value Vmax of the rotational speed is extracted V ′ Rotational variation value V′a (V′e) Threshold value V′b (based on exhaust NO _X amount Q lower limit V'c for) the threshold to a value Q ₃ or less (for the thermal efficiency eta reference value eta ₁ or more)
Reference value of threshold value K Air-fuel ratio η Thermal efficiency W Output θ Ignition advance angle Ei Ignition device generated voltage Er Required voltage Ec Voltage difference X EGR rate S Swirl ratio CA Overlap period

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) F02D 21/08 301 F02D 21/08 301C 301G 41/02 301 41/02 301K 41/14 310 41/14 310M 43/00 301 43/00 301B 301N 301E 301Z F02M 25/07 550 F02M 25/07 550R F02P 5/15 F02P 5/15 C (72) Inventor Toru Nakazono 1-32 Chaya-cho, Kita-ku, Osaka-shi, Osaka-Yanmar Diesel Co., Ltd. F-term (reference) 3G022 AA00 AA03 AA06 AA10 DA01 EA01 EA09 FA02 FA03 FA05 FA06 FA07 GA01 GA05 GA06 GA08 GA16 GA18 3G062 AA00 AA03 AA06 AA10 BA02 BA06 BA08 BA09 DA04 GA01 GA04 GA07 GA19 3G08 BA04 BA03 BA05 BA04 DA26 DA27 DA28 EA05 EA07 EA11 EB06 EB09 EB20 EB22 EB26 EC04 FA00 FA24 FA28 FA34 FA38 3G092 AA06 AA09 AA10 AA11 AA17 AB06 BA01 BA06 BA08 BA09 DA08 DC01 DC06 DC09 EA10 EA13 EA17 EB01 EC05 EB05 EC05 EC05 4Z HE00Z HE02Z HE04Z HE05Z 3G301 HA04 HA06 HA13 HA15 HA19 HA22 JA23 JB07 JB09 LA00 LA01 LA05 LA07 MA01 NA01 NA06 NA09 NB03 NC04 ND25 NE16 NE20 NE23 PC09Z PD01Z PE00Z PE02Z PE04Z PE05Z

Claims (10)

[Claims] In a gas engine that burns by supplying a lean mixture of fuel gas and air, a maximum value of a certain number of cycles in a cycle of increase and decrease of a rotation speed of a crankshaft during one stroke, and the number of times The difference from the average value in a plurality of strokes before and after the eye cycle is calculated, and the calculation of this difference is repeatedly performed continuously for a plurality of strokes, and a change obtained from each calculation result is calculated as a rotation change value, and the rotation change value is calculated. A combustion control method for a gas engine, wherein combustion control is performed by determining the degree of stability of combustion based on the data. 2. A combustion control method for a gas engine according to claim 1, wherein said means for adjusting the supply amount of the lean air-fuel mixture is fixed during said detection period of the rotation speed of the crankshaft over a plurality of strokes. A combustion control method for a gas engine. 3. The combustion control method for a gas engine according to claim 1, wherein a threshold value of the rotation fluctuation value is set, and when the rotation fluctuation value is higher than the threshold value, it is determined that combustion is unstable. A method for controlling combustion in a gas engine, comprising: determining. 4. A combustion control method for a gas engine according to claim 3, in the engine operating range, at high rotational speed and load is the most state, as NO _X value in the exhaust gas is within the target value, A combustion control method for a gas engine, comprising setting a threshold value of the rotation fluctuation value. 5. The combustion control method for a gas engine according to claim 4, wherein a maximum value of a certain cycle in a cycle of increase and decrease of the rotation speed of the crankshaft during one stroke, and a maximum value of a plurality of strokes before and after the same cycle. A combustion control method for a gas engine, wherein, in calculating a difference from an average value, a number of strokes for calculating the average value is set so as to secure a correlation between a combustion fluctuation value and a rotation fluctuation value. 6. The combustion control method for a gas engine according to claim 5, wherein the upper limit of the fluctuation of the rotation fluctuation value around the threshold value obtained by the method is a reference value relating to the thermal efficiency of the rotation fluctuation value. A combustion control method for a gas engine, wherein a lower limit value of the number of detections of the difference between the maximum value and the average value of the rotation speed for obtaining the rotation fluctuation value is set so as not to exceed the rotation fluctuation value. 7. A gas engine to which the combustion control method according to claim 1, 2, 3, 4, 5, or 6 is applied, based on detection of the rotation fluctuation value, an air-fuel ratio, an ignition timing, and an EGR.
A method for controlling combustion in a gas engine, comprising controlling at least one of a rate, a state of a swirl, or an overlap period of a valve train. 8. A gas engine to which the combustion method according to claim 7 is applied, wherein the control value of said control is stored in a storage means which is not erased by stopping the engine and turning off the power. Control method. 9. A gas engine to which a combustion control method according to claim 1, 2, 3, 4, 5, or 6 is applied, wherein instability of combustion is detected from an ignition device generated voltage at the start of use. In this case, the rotation fluctuation value is set to be large until the use limit of the ignition plug is detected. A combustion control method for a gas engine, wherein the method is used for detecting a state. 10. The method of claim 1, 2, 3, 4, 5, or 6.
In a gas engine to which the described combustion control method is applied,
A combustion control method for a gas engine, wherein the detection of the rotation fluctuation value is used for detecting an unstable combustion state corresponding to a use limit time of a spark plug.