JP3382019B2 - Gas engine control unit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas engine control device, and more particularly to LPG (liquefied propane gas) and L gas.
The present invention relates to a control device for a gas engine that controls a pressurized gas such as BG (liquefied butane gas) as fuel to perform a substantially constant speed operation.

[0002]

2. Description of the Related Art There is known a gas engine in which a pressurized fuel gas such as LPG or LBG is supplied to an engine through a pressure regulator and burned by the engine.

In the conventional gas engine of this type, the pressurized gas is depressurized to a substantially atmospheric pressure via a pressure regulator, and the fuel gas is supplied to the engine by the negative suction pressure of the engine. That is, in the gas engine, the intake air amount is controlled by the throttle valve, and the gas amount suitable for the controlled intake air amount is supplied to the engine. Therefore, in this case, it is necessary to install a throttle valve in the intake pipe,
Since the layout of the intake pipe and the layout of the throttle valve are restricted by the layout of the engine, these layout restrictions occur. Therefore, in the gas engine, it is difficult to reduce the size thereof, and a wire or the like for controlling the throttle valve is required, which makes it difficult to simplify the device.

Therefore, there has been proposed an attempt to control the engine output by controlling only the flow rate of the fuel gas without providing a throttle valve in the intake pipe, thereby making it possible to downsize and simplify the engine. (For example, JP-A-2-
No. 23258).

The above-mentioned gas engine utilizes the characteristic that the pressurized fuel gas such as LPG and LBG has a wider combustible concentration range than liquid fuel such as gasoline and light oil, and controls the intake air amount. Instead, the engine output is controlled only by the fuel gas amount. That is, for example,
In the case of gasoline, the lean limit for combustion is the excess air ratio λ
However, in the case of LPG, the excess air ratio λ can be up to about 1.6. Therefore, by controlling only the fuel gas amount without controlling the intake air amount, The engine output can be controlled within a wide load variation range.

[0006]

However, in the above-mentioned gas engine, although the engine output can be controlled until the lean limit of the air-fuel ratio is reached by reducing the supply gas amount, the air-fuel ratio becomes If the lean limit is exceeded, irregular combustion will occur, resulting in misfire, etc., and therefore an increase in vibration due to engine output fluctuations in the low output range and the amount of unburned gas components such as hydrocarbon (HC) emitted due to irregular combustion. However, there is a problem in that the exhaust gas purification characteristic is deteriorated and the exhaust purification characteristic is deteriorated. That is, in the conventional gas engine, when the excess air ratio λ exceeds, for example, “1.6” and enters the irregular combustion region as shown in FIG.
The engine output has a characteristic of rapidly decreasing (in the figure, point A indicates a lean limit point indicating the boundary between the irregular combustion region and the fuel gas control region). In other words, in the conventional gas engine, when the air-fuel ratio exceeds the lean limit point A, irregular combustion becomes remarkable, and as shown by the broken line, the amount of unburned gas components such as HC is rapidly increased and exhausted. There is a problem that the purification efficiency is extremely deteriorated.

Further, even when an oxidation catalyst or the like is installed for purification, there is a problem that abnormal concentration is likely to occur due to the high concentration.

Further, there is a problem in that vibration may occur due to fluctuations in the rotational speed due to irregular combustion, engine stall, etc. may occur, and the application may be limited.

The present invention has been made in view of the above problems, and controls the engine output even in a low output range when the air-fuel ratio is controlled by the fuel gas supply amount without controlling the intake air amount. It is an object of the present invention to provide a gas engine control device capable of achieving the above.

[0010]

In order to achieve the above object, the present invention relates to a gas engine controller for mixing a fuel gas supplied through a control valve with air and supplying the mixed gas to an engine. The flow rate of the fuel gas
By control Gosuru, the air-fuel ratio control means for controlling the air-fuel ratio of the mixture without controlling the intake air amount of the gas engine, operating condition detecting means for detecting operating conditions of the gas engine, the operating state Ignition timing calculation means for calculating the ignition timing of the gas engine based on the detection result of the detection means, and by retarding the ignition timing when the air-fuel ratio is below a predetermined value and in a lean limit state. And an ignition timing correction means for controlling the output of the gas engine so that the output decreases as the angle retards.

Further, the control system for the gas engine is characterized in that the intake system of the gas engine is not provided with a throttle valve for controlling the intake air amount.

Further, the operating state detecting means includes at least an engine speed detecting means for detecting an engine speed, and the combustion of the gas engine is performed based on the variation amount of the engine speed detected by the engine speed detecting means. as features and combustion state judging means for judging a condition, said air-fuel ratio based on the discrimination result of the combustion state judging means and a lean limit determining means for determining whether to be not more than the predetermined value There is.

[0013]

According to the above construction, the air-fuel ratio is controlled only by the fuel gas amount, the (optimal) ignition timing is calculated according to the operating state of the engine, and the air-fuel ratio of the air-fuel mixture is diluted to a predetermined value or less. In the limit state, the ignition timing is corrected.

Specifically, the air-fuel ratio is controlled only by the fuel gas amount without controlling the intake air amount by the throttle valve. Then, the combustion state of the engine is determined based on the variation amount of the engine speed, and it is determined whether the engine is in the lean limit state based on the combustion state. Further, when it is determined that the engine is in the lean limit state, the engine output is controlled in the lean limit region by gradually reducing the thermal efficiency while continuing combustion by retarding the ignition timing. Be seen.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of a gas engine control device according to the present invention.

In the figure, reference numeral 1 denotes a 4-cycle gas engine (hereinafter, simply referred to as "engine"). An air cleaner 3 is provided at a tip of an intake pipe 2 of the engine 1, and a space between the air cleaner 3 and the engine 1 is provided. Is the fuel supply pipe 4
Is branched from the intake pipe 2.

At the tip of the fuel supply pipe 4, LPG or L
A pressurized gas source 5 such as a gas cylinder filled with a fuel gas such as BG is mounted, and a pressure regulator 6, an on-off valve 7 and a control valve 8 are sequentially provided in the middle of the fuel supply pipe 4 downstream of the pressurized gas source 5. It is installed. Then, these pressure regulator 6 and open / close valve 7
And the control valve 8 is an electronic control unit (hereinafter "EC
U ”) 9 and is controlled by the ECU 9.

The pressure regulator 6 adjusts the pressure of the fuel gas from the pressurized gas source 5 so that the fuel gas has a predetermined pressure slightly higher than the atmospheric pressure, and the fuel gas adjusted to the predetermined pressure is supplied to the engine. Inhaled to 1.

The on-off valve 7 is a normally-closed solenoid valve E
ON / OFF control is performed by a command from the CU 9. That is,
When the engine 1 is stopped, the fuel gas from the pressurized gas source 5 is turned off and closed to prohibit it from being supplied to the engine 1. When the engine 1 is driven, it is turned on and opened to open the fuel gas. Supply to.

The control valve 8 has a variable nozzle whose opening area is variable according to the engine speed NE and the excess air ratio λ, and the fuel gas amount Q passing through the fuel supply pipe 4 in response to a command from the ECU 9. Control the flow rate of. That is, the control valve 8 increases when the engine load increases and the engine speed NE drops below a predetermined speed NEX (eg, 2500 rpm) or when the air-fuel ratio of the air-fuel mixture supplied to the engine 1 becomes lean. The fuel gas flow path is controlled so that the fuel gas amount Q increases, and the engine speed N
The flow path of the fuel gas is controlled so that the amount of the fuel gas is reduced when E is a high rotation speed equal to or higher than the predetermined rotation speed NEX or when the air-fuel ratio of the air-fuel mixture is fuel rich.

A crank angle (CRK) sensor 11 and an ignition pulser 1 are provided around a crank shaft (not shown) of the engine 1.
Two are provided. The CRK sensor 11 outputs a pulse signal (hereinafter referred to as “CRK signal pulse”) at the piston top dead center position, and supplies this CRK signal pulse to the ECU 9. The ignition pulsar 12 generates an ignition pulse signal at a predetermined crank angle position and outputs the ignition pulse signal to the ECU 9
Supply to.

The ignition device 13 of the engine 1 is connected to the ECU 9 and its ignition timing is controlled by a command from the ECU 9. A starter motor 14 is connected to the engine 1, and the engine 1 is started by the starter motor 14.

A wide-range oxygen concentration sensor (hereinafter referred to as "LAF sensor") 16 is provided in the exhaust pipe 15 of the engine 1, and the oxygen concentration in the exhaust gas detected by the LAF sensor 16 is an electric signal. Converted to ECU
9 is supplied.

The ECU 9 shapes an input signal waveform from the various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, and a central processing circuit. (Hereinafter referred to as “CPU”), a storage unit that stores various calculation programs executed by the CPU and calculation results, and an output circuit that supplies a drive signal to the on-off valve 7, the control valve 8 and the like. .
Further, the ECU 9 controls the generation time interval ME of the CRK signal pulse.
Engine speed NE which is the reciprocal of this ME value
To calculate.

Further, the ECU 9 detects the crank angular velocity based on the CRK signal pulse, and determines the combustion state of the engine 1 according to the variation state of the crank angular velocity. That is, the instantaneous rotation speed of the engine 1, that is, the instantaneous crank angular speed is as shown in FIG.
The compression resistance of the air-fuel mixture supplied to the engine causes it to fall most near the position where the ignition pulse signal is generated, and then the crankshaft is accelerated by the gas pressure due to combustion to increase the crank angular velocity, but the engine 1 causes irregular combustion. At this time, the crank angular velocity becomes smaller than that during normal combustion. Therefore, the crank angular velocity at the time when the crank angular velocity reaches a substantially maximum value after a lapse of a predetermined time t from the generation of the ignition pulse signal is taken in to hold the crank angular velocity value, and the deviation Δ of the hold value between cycles
The combustion state of the engine 1 is detected by calculating TREV. That is, the deviation ΔTREV is the predetermined reference value M
When it is less than or equal to FREF, it is determined that the engine 1 is normally burning, and when the deviation ΔTREV is greater than or equal to the predetermined reference value MFREF, it is determined that the engine 1 is irregularly burning. Further, when the deviation ΔTREV is larger than the predetermined misfire determination value MFH, it is determined that the engine 1 is in the misfire state.

Therefore, the control device of the present gas engine is
The optimum ignition advance value θIGY is calculated according to the engine speed NE and the excess air ratio λ, and when the engine 1 reaches the lean limit, the optimum ignition advance value θIGY is retarded and thus retarded. The engine output is controlled by controlling the ignition timing with the set ignition advance value θIG. That is, as described in the [Prior Art] and [Problems to be Solved by the Invention] (see FIG. 8), in the case of a gas engine that uses a gas such as LPG as a fuel, the excess air ratio λ is " The engine output can be controlled only by controlling the fuel gas up to about 1.6 ", but the excess air ratio λ is" 1.
If it exceeds 6 ”, the misfire rate rapidly increases, the rotational fluctuation also increases, and the discharge of unburned gas components also rapidly increases. Therefore, it is impossible to control the engine output substantially only by controlling the fuel gas amount Q. Have difficulty. That is, since the amount of decrease in engine output is controlled by the amount of increase in misfire rate, control of only the fuel gas amount Q allows stable control of engine output over a wide range from the no-load state of the engine to the maximum output range. You cannot do it. On the other hand, there is a relationship as shown in FIG. 3 between the ignition advance value θIG and the engine output η (λ = 1.6), and the engine output η is the optimum ignition advance with respect to the ignition advance value θIG. The value θIGY (for example, 4
It has a parabolic characteristic with a maximum at 5 ° BTDC). That is, the engine output η becomes maximum at the optimum ignition advance value θIGY with respect to the ignition advance value θIG, and gradually decreases with displacement to the advance side or the retard side.
Therefore, the ignition advance value θIG is changed from the optimum ignition advance value (for example, 45 ° BTDC) to the lower limit ignition advance value θIGX (for example, −10 ° BTD) at which the engine output becomes “0”%.
The engine output can be gradually changed by performing the retard correction until reaching C), which makes it possible to continuously and stably control the engine output from the no-load state to the maximum output. Becomes Hereinafter, the control procedure will be described in detail.

FIG. 4 is a flow chart of a gas amount control routine. This program is executed when the complete explosion state of the engine 1 is detected, for example, when the engine is started and the engine speed NE becomes 800 rpm or more. to start.

When this program is started, the engine speed NE (calculated based on the detection signal of the CRK sensor 11) and the excess air ratio λ (calculated based on the detection signal from the LAF sensor 16) are read ( Step S
1) Then, the θIGY map is searched to calculate the optimum ignition advance value θIGY according to the operating state of the engine (step S2).

Specifically, the θIGY map is, as shown in FIG. 5, a map value θIGY (0 for the engine speeds NE00 to NE19 and the excess air ratios λ00 to λ16.
0,00) to θIGY (16,19) are given in a matrix, and the optimum ignition advance value θIGY is such θ.
By searching the IGY map, the optimum value is set according to the operating state of the engine 1.

Next, in step S3, an ignition timing control routine, which will be described later, is executed to perform ignition timing control, and in the following step S4, the engine speed NE is the allowable limit speed N.
It is determined whether or not the rotation speed is higher than EHLT (for example, 4000 rpm). When the engine speed NE exceeds the permissible limit speed NEHLT, the engine 1 is stopped (step S5) and the program ends.

On the other hand, the determination result of step S4 is negative (N
o), that is, when the engine speed NE is lower than the permissible limit speed NEHLT, the process proceeds to step S6, where the engine speed NE is higher than a predetermined speed NEX (eg, 2500 rpm) lower than the permissible limit speed NEHLT. Or not. If the determination result is affirmative (Yes), the valve opening of the control valve 8 is reduced to reduce the fuel gas amount Q, and the air-fuel ratio of the air-fuel mixture is shifted to the leaning direction (step S7). Return to S1.

Further, the determination result of step S6 is negative (N
In the case of o), that is, when the engine speed NE is lower than the predetermined speed NEX, the routine proceeds to step S8, and it is determined whether the excess air ratio λ is “1” or greater than “1”, that is, the air-fuel ratio of the air-fuel mixture is It is determined whether the stoichiometric air-fuel ratio has already been reached or the fuel is lean. And step S
When the determination result of No. 8 is negative (No), that is, when the air-fuel ratio of the air-fuel mixture is fuel-rich, the amount of the fuel gas Q is reduced to control the air-fuel ratio of the air-fuel mixture in the lean direction (step S7). Return to S1. It should be noted that λ = 1 is used as the determination threshold here because the fuel is gas and a sufficient combustion state can be obtained at the theoretical air-fuel ratio, and it is not necessary to make the air-fuel ratio of the air-fuel mixture more fuel rich. is there.

On the other hand, the determination result of step S8 is affirmative (Y
es), that is, when the air-fuel ratio of the air-fuel mixture has not reached fuel rich, the fuel gas amount Q is increased so as to shift the air-fuel ratio of the air-fuel mixture to the rich direction (step S9) and the process returns to step S1.

FIG. 6 is a flow chart of the ignition timing control routine executed in step S3 (FIG. 4).

In step S11, the rotational fluctuation amount ΔTREV of the crank angular velocity is measured, and in the following step S12, it is determined whether or not the flag FMF is set to "1". Here, the flag FMF is "0" when the rotation variation amount ΔTREV of the crank angular velocity is equal to or less than the predetermined reference value MFREF, that is, when the engine 1 does not generate irregular combustion.
Is set to a predetermined reference value MFREF or more, that is, is set to "1" when irregular combustion occurs. As described above, in step S12, it is determined whether or not the engine 1 is causing irregular combustion based on the rotation variation amount ΔTREV of the crank angular velocity. Then, when the flag FMF is set to "1" and it is determined that the engine 1 is causing irregular combustion, it is determined that the air-fuel ratio of the air-fuel mixture is in the lean limit region, and the routine proceeds to step S13.

At step S13, the current ignition advance value θI
G is the lower limit ignition advance value θIGX (for example, −10)
° BTDC) is larger than the above. When the determination result is affirmative (Yes), the ignition advance value θIG
Is retarded by a predetermined angle θIGR (for example, 1 °) to calculate a new ignition advance value θIG (step S14), and the process returns to the main routine (FIG. 4).

When the determination result of step S13 is negative (No), that is, when the ignition advance value θIG is not more than the lower limit ignition advance value θIGX, the ignition advance value θIG is set to a predetermined angle θIGA (for example, 1 A new ignition advance value θIG (step S16) and the process returns to the main routine (FIG. 4).

On the other hand, when the determination result of step S12 is negative (No) and it is determined that the irregular combustion is not performed, the routine proceeds to step S15, where the current ignition advance value θIG is the optimum ignition advance value θIGY ( For example, it is determined whether it is smaller than 45 ° BTDC). When the determination result is affirmative (Yes), the ignition advance value θIG is set to the predetermined angle θI.
A new ignition advance value θIG is calculated by advancing GA (for example, 1 °) (step S16), and the process returns to the main routine (FIG. 4).

When the result of the determination in step S15 is negative (No), the process proceeds to step S14 and the predetermined angle θIG
A new ignition advance value θIG is calculated by retarding R, and the process returns to the main routine (FIG. 4).

As described above, according to the present invention, in the region where irregular combustion does not occur, the ignition timing control is performed so that the ignition advance value θIG becomes the optimum ignition advance value θIGY, and the fuel gas is changed according to the operating state. The amount Q is controlled, and the engine output is controlled substantially only by the air-fuel ratio control.

On the other hand, when the engine 1 is at the lean limit at which irregular combustion can occur, the fuel gas amount is supplied in a substantially fixed amount to ignite while maintaining the air-fuel ratio at the lean limit (for example, λ = 1.6). The engine output is controlled by retarding the timing. That is, even when the engine is in the lean limit at which irregular combustion can occur, the fuel gas amount Q is supplied in a substantially constant amount, so when the engine speed decreases, the air-fuel ratio of the air-fuel mixture becomes rich and the engine speed increases. As the engine speed increases, the air-fuel ratio of the air-fuel mixture becomes thin and the engine speed decreases.Therefore, the engine speed is stabilized and controlled to reduce irregular combustion. Even when the engine is running, the engine speed can be stabilized. That is, when a throttle valve is arranged in the intake system to control the intake air amount like a conventional gas engine, there is a possibility that the engine speed may become unstable or engine stall may occur due to irregular combustion. On the other hand, in this gas engine, since the fuel gas amount Q is supplied in a substantially fixed amount, the engine speed is substantially stabilized even at the lean limit. Therefore, the ignition advance value θIG can be retarded while maintaining the engine rotation in a stable state, and the engine output can be continuously and stably controlled even in the low output range.

FIG. 7 shows the excess air ratio λ and the ignition advance value θIG.
FIG. 6 is a characteristic diagram showing the relationship between the engine output η and the amount of HC discharged.

As is apparent from FIG. 7, until the lean limit region (excess air ratio λ = 1.6) indicated by the point A, the ignition timing is controlled by the optimum ignition advance value θIGY while controlling the flow rate of the fuel gas. The engine output is controlled by the air-fuel ratio control, and after the air-fuel ratio (excess air ratio λ) reaches the lean limit range, the ignition timing is advanced and retarded to stabilize the engine rotation even in the low output range. The engine output can be controlled while being maintained, and the output variable range of the engine 1 can be continuously expanded from the no-load state to the maximum output. Moreover, since the combustion is performed without any trouble, it is possible to prevent the emission amount of HC in the low output region from extremely increasing, as indicated by the broken line.

As described above, in the control system for the present gas engine, the engine output can be controlled by increasing or decreasing the fuel gas amount Q during normal operation, and the ignition timing can be adjusted when the air-fuel ratio reaches the lean limit range. By retarding by a predetermined angle, the engine output can be gradually reduced while maintaining the air-fuel ratio in that state (for example, λ = 1.6). As a result, the engine speed NE can be feedback-controlled to the set speed to maintain stable and substantially constant speed operation, and the engine output can be stably controlled even in the low output range. Moreover, at the same air-fuel ratio, the later the ignition timing is, the more the NOx emission is reduced, so that the NOx can be reduced in the light load operation region. In other words, the engine speed is fed back to the set speed to perform stable, nearly constant speed operation, while avoiding irregular combustion in the low output range while controlling the engine output over a wide range from the no-load state to the maximum output state. can do.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the LAF sensor 16 detects the oxygen concentration to calculate the excess air ratio λ, but since the intake air amount is not controlled by the throttle valve, the intake air amount is substantially constant. The excess air ratio λ can be estimated from the fuel gas amount Q and the engine speed NE, and the LAF sensor 16 may be omitted. Further, although advance / retard control of the ignition timing is performed based on the presence or absence of irregular combustion in step S12, the lean limit of the engine 1 is estimated from the excess air ratio λ, and the ignition timing is increased from the air-fuel ratio immediately before the lean limit. It is also possible to control the engine output by retarding the ignition timing. Therefore, it is possible to omit the irregular combustion determination and the ignition timing advance / retard control and substitute the ignition timing map as shown in FIG.

[0047]

As described above in detail, the control according to claim 1
According to the control device, the air-fuel ratio of the air-fuel mixture falls below a specified value.
When in the lean limit state, retard the ignition timing.
As a result, the output will decrease as the delay angle increases.
Since it controls the output of the gas engine,
Even if you can control the output of the gas engine,
The output controllable range of the engine from the unloaded state to the maximum output state
It is possible to greatly expand to the state, as a result, low output range
Even if the engine is in the combustion state,
Stabilization of engine speed, suppression of vibration generation, and exhaust purification characteristics
It is possible to prevent deterioration as much as possible .

According to the control device of the second aspect, the gas
A throttle valve for controlling the intake air amount in the intake system of the engine
Since it is not installed, the device can be simplified.
It

[0049]

[0050]

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a gas engine according to the present invention.

FIG. 2 is a diagram showing a method for detecting a combustion state of a gas engine.

FIG. 3 is a characteristic diagram showing a relationship between an ignition advance value θIG and an engine output η.

FIG. 4 is a flowchart of a gas amount control routine.

FIG. 5 is a θIGY map for calculating an optimum ignition advance value θIGY.

FIG. 6 is a flowchart of an ignition timing control routine.

FIG. 7 is a characteristic diagram showing a relationship between an excess air ratio λ, an ignition advance value θIG, an engine output η, and an HC discharge amount.

FIG. 8 is a characteristic diagram showing a relationship between an engine output and a HC emission amount of a conventional gas engine.

[Explanation of symbols]

1 internal combustion engine 5 ECU (ignition timing calculation means, air-fuel ratio control means,
Ignition timing correction means, combustion state determination means, lean limit determination means) 8 Control valve 11 CRK sensor (operating state detecting means, rotational speed detecting means) 16 LAF sensor (operating state detecting means)

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02M 21/02 311 F02D 41/02 330 F02D 45/00 362 F02P 5/15

Claims (3)

(57) [Claims] 1. A fuel gas supplied through the control valve in the control device for a gas engine supplied by mixing with air to the engine, by control the flow rate of the fuel gas by the control valve, the gas Air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture without controlling the intake air amount of the engine, operating state detecting means for detecting the operating state of the gas engine, based on the detection result of the operating state detecting means Ignition timing calculation means for calculating the ignition timing of the gas engine,
When the air-fuel ratio is equal to or less than a predetermined value and is in the lean limit state, the ignition timing is retarded to control the output of the gas engine so that the output decreases as the ignition timing retards. A control device for a gas engine, comprising: 2. The gas engine control device according to claim 1, wherein a throttle valve for controlling an intake air amount is not arranged in an intake system of the gas engine. 3. The operating condition detection means includes at least rotation speed detection means for detecting an engine rotation speed,
A combustion state determination unit that determines the combustion state of the gas engine based on the amount of change in engine speed detected by the rotation number detection unit, and the air-fuel ratio is the predetermined value based on the determination result of the combustion state determination unit. The control apparatus for a gas engine according to claim 1 or 2, further comprising: a lean limit determination means for determining whether or not the value is less than or equal to a value.