JPH06241089A - Gas fuel engine operation control device - Google Patents

Abstract

PURPOSE:To provide an operation control device for LPG engine which can protect catalyst at the time of steep deceleration. CONSTITUTION:An operation control device (ECU) 92 is provided for an LPG engine 1 using LPG as fuel and having catalyst 22 in the exhaust device, wherein air-fuel ratio control means (ECU) 92 is furnished to control the fuel shut-off valve 120 of a mixture gas forming device 20 so that the air-fuel ratio of the mixture gas from the device 20 becomes lambda>1 when the engine is in steep decelerating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control system for a gas fuel engine, and more particularly to an improvement of an air-fuel ratio control method capable of protecting a catalyst in an exhaust system during rapid deceleration of the engine.

[0002]

2. Description of the Related Art Generally, liquefied petroleum gas (LPG: Liquid)
ied Petroleum Gas) and liquefied natural gas (LNG: Liquid)
Since gaseous fuels such as ied Natural Gas) have the following features, they are considered to be extremely promising as alternative fuels for gasoline. That is, i) Since there are no harmful lead compounds and irritating aldehydes and the sulfur content is small, the generation of sulfurous acid gas is small. Moreover, since the distribution to each cylinder can be made uniform, the combustion in each cylinder can be made uniform. As a result, the exhaust gas can be cleaned. ii) The amount of carbon generated by combustion is small, and the amount of sludge is also small. In particular, the advantage of i) above is very important from the viewpoint of environmental problems.

[0003]

In a gas fuel engine using such a gas fuel as a fuel, a catalytic converter is generally installed in an exhaust system like a gasoline engine in order to further purify exhaust gas. . In the case where the catalytic converter is provided, the charging efficiency in the combustion chamber is poor due to the closing of the throttle valve at the time of rapid deceleration, which may cause misfire. As a result, the unburned fuel in the combustion chamber may flow into the exhaust device and burn in the catalyst, which may damage the catalyst.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an operation control device for a gas fuel engine capable of protecting the catalyst during sudden deceleration.

[0005]

According to a first aspect of the present invention, in an operation control device for a gas fuel engine that uses a gaseous fuel as a fuel and has a catalyst in an exhaust device, a mixture supplied to a fuel chamber by a mixture forming device. It is characterized in that it is provided with an air-fuel ratio control means for controlling the air-fuel ratio of air to λ> 1 when the engine is rapidly decelerated. According to a second aspect of the present invention, in an operation control device for a gas fuel engine that uses a gaseous fuel as a fuel and has a catalyst in an exhaust device, a fuel chamber opening to an intake passage via a main jet is provided, and an atmosphere is provided in the fuel chamber. And an air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber to λ> 1 by increasing the opening degree of the introduction valve when the engine rapidly decelerates. It is characterized by that.

[0006]

In the operation control device for the gas fuel engine according to the first and second aspects of the present invention, when the engine is rapidly decelerated, the air-fuel mixture of λ> 1, that is, the lean air-fuel mixture is supplied to the engine combustion chamber. As a result, even if a misfire occurs in the combustion chamber, the amount of unburned fuel remaining is reduced, and as a result, combustion of the fuel in the catalyst in the exhaust device is suppressed and the catalyst can be protected. Further, in the operation control device for a gas fuel engine according to the invention of claim 2, the lean mixture is supplied to the engine combustion chamber by increasing the opening amount of the introduction valve to increase the amount of air introduced into the fuel chamber. It suffices if the introduction valve can control a few% of the fuel flow rate at the time of supplying the lean air-fuel mixture, whereby the introduction valve can be downsized, and as a result, the responsiveness at the time of sudden deceleration of the engine can be improved. On the other hand, when the lean air-fuel mixture is supplied by reducing the opening of the fuel supply valve that supplies fuel to the fuel chamber, the fuel supply valve is relatively large so that it can handle the maximum fuel flow rate. It is necessary to use the one of the above, which results in deterioration of responsiveness.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 are diagrams for explaining an operation control device for a gas fuel engine according to an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a gas fuel engine to which the present embodiment is applied, and FIG. 6 is a flowchart showing a control routine of air-fuel ratio feedback control during rapid deceleration of the engine.

In FIG. 1, reference numeral 1 denotes a water-cooled 4-cylinder 4-valve type gas fuel engine, which has a cylinder block 2 and a cylinder head 3 laminated on a crankcase (not shown) and fastened with head bolts. It has a structure in which the head cover 4 is mounted on the surface 3. Pistons 5 are slidably inserted in the four cylinder bores 2a formed in the cylinder block 2, and the pistons 5 are connected to a crankshaft (not shown) via connecting rods.

A combustion recess 3a is provided in the lower portion of the cylinder head 3. A combustion chamber 6 is formed by the combustion recess 3a, the cylinder bore 2a, and the head 5a of the piston 5. The combustion recess 3a has two intake valve openings 3b and two exhaust valve openings 3c. The openings 3b and 3c are formed by the openings of the valve seats 7 and 8 which are substantially ring-shaped and press-fitted into these portions. Further, the valve head 10a of the intake valve 10 can be opened and closed by the intake valve opening 3b, and the valve head 11a of the exhaust valve 11 can be opened and closed by the exhaust valve opening 3c, that is, each of the valve seats 7 and 8 can be opened and closed. It is placed in close contact with the seat surface. These intake and exhaust valves 1
Intake and exhaust lifters 12 and 13 are attached to the upper ends of 0 and 11, respectively. Intake and exhaust cam shafts 14 and 15 for pressing and driving the lifters 12 and 13 are arranged parallel to each other in a direction perpendicular to the cylinder axis. The spark plug 1 is provided inside the cylinder head 3.
6 is mounted, and the electrode portion of the spark plug 16 is arranged at the center of the combustion recess 3a. Further, inside the cylinder block 2 and the cylinder head 3, a cooling jacket 25 in which a coolant liquid circulates by a coolant pump (not shown) is provided. The coolant liquid is cooled by a known method through an external heat exchanger (not shown).

In the side wall 3d of the cylinder head 3,
An intake passage 17 is formed which communicates with the combustion chamber 6 through the intake valve opening 3b, and the side wall 3 of the cylinder head 3 is formed.
An exhaust passage 18 that communicates with the combustion chamber 6 through the exhaust valve opening 3c is formed in e. The intake passage 17
One end of the intake manifold 19 is connected to the wall opening of the exhaust manifold 18, and one end of the exhaust manifold 20 is connected to the wall opening of the exhaust passage 18. A plenum chamber 21 is provided at the other end of the intake manifold 19. At the outlet 20a at the other end of the exhaust manifold 20,
A catalytic converter 22 having a catalyst layer is connected.
This catalyst layer contains carbon monoxide (CO) and hydrocarbons (H
It contains a so-called three-way catalyst for the oxidation of C) and the reduction of nitrogen oxides (NO _x ). Catalytic converter 22
The exhaust gas treated by is discharged into the atmosphere through an exhaust / silencer system (not shown). Further, an O ₂ sensor 23 for detecting the oxygen concentration in the exhaust gas is attached to the exhaust manifold 20.
As the O ₂ sensor 23, the air-fuel ratio (A /
F) is the type to detect when it is on the rich side or A /
Any of the types detected when F is on the lean side may be used.

A gas mixture forming device 30 for forming a gas mixture to be supplied to the combustion chamber 6 via the intake manifold 19 is arranged laterally of the gas fuel engine 1. The air-fuel mixture forming device 30 has a variable venturi mixer 31. The mixer 31 has a main body portion 32 whose lower opening is connected to the intake manifold 19 side. An intake passage 33 is formed in the upper portion of the main body portion 32, and an air cleaner 35 is connected to the intake passage 33. This allows the air cleaner 3
The air introduced from the air introduction port 36 of No. 5 and filtered by the filter element is supplied into the intake passage 33.

The air cleaner 35 is provided with an air flow meter 49 for measuring the amount of intake air, and the output of the air flow meter 49 is input to the ECU 92. Although not shown, the air cleaner 35 is provided with a clogging sensor that detects clogging of the filter element, and the output of the clogging sensor is also input to the ECU 92. Further EC
In U92, the throttle position of the throttle valve 48,
Coolant temperature, engine speed, O ₂ sensor 23
Output, exhaust temperature, and output of negative pressure sensor.

The mixer 31 is provided slidably in the chamber 38 and the chamber 38, and the intake passage 33 is provided.
And a piston 39 projecting inward. Inside the chamber 38, a coil spring 40 for urging the piston 39 in the closing direction of the intake passage 33 is contracted. At the tip of the piston 39, a metering rod (needle valve) 44 that cooperates with the main jet 43 of the fuel supply chamber 42 is provided. The main jet 43 and the needle valve 44 have such a shape that the A / F can be maintained substantially constant while the average value of the opening degree of the bleed air control valve 84, which will be described later, is substantially constant regardless of the intake flow rate. Have A bleed port 46 that communicates with the inside of the chamber 38 is formed at the end of the piston 39, and an atmospheric port 47 that opens to the atmospheric side is formed at the upper part of the chamber 38. The atmospheric pressure acts on the piston 39 in the opening direction of the intake passage 33. The atmosphere port 47 is provided in the intake passage 3 upstream of the venturi portion where the main jet 43 opens.
3, the piston 39 may be opened in this case as well.
Atmospheric pressure acts on the intake passage 33 in the opening direction.

With this configuration, when the portion of the intake passage 33 on the downstream side of the piston 39 becomes negative pressure, the piston 3
9 moves toward the chamber 38 side to open the flow path, which can effectively change the flow path area, and the throat portion where the main jet 43 opens has a substantially constant negative pressure. The condition is maintained. A throttle valve 48 that opens and closes by a throttle operation is provided on the downstream side of the piston 39 in the intake passage 33.

The mixer 31 has an idle discharge line 5 extending from the fuel supply chamber 42.
1, an idle circuit 50 including a fuel shutoff valve 52, an adjustable needle valve 53 and an idle port 54. The idle port 54 opens in the intake passage 33 downstream of the throttle valve 48 at the idle position. The opening and closing of the fuel cutoff valve 52 is controlled by the ECU 92, which controls the amount of fuel passing through the idle discharge line 51. Fuel is supplied from the idle circuit 50 during idling.

A pressure regulator (vaporizer, regulator) 60 for supplying gaseous fuel to the fuel supply chamber 42 is provided. The regulator 60 is configured so that the gaseous fuel stored in a liquid state under pressure in a high-pressure source (not shown) is introduced from the introduction pipe 61.
As the above-mentioned gaseous fuel, for example, butane, propane, a mixture thereof, or other known gaseous fuel is used.

The regulator 60 has a main body portion (housing) 62. An introducing passage 63 communicating with the introducing pipe 61 is formed in the housing 62. The introduction passage 63 extends to the first pressure adjusting port 64, and
The opening / closing of the pressure adjusting port 64 is controlled by the first pressure adjusting valve 65. The first pressure adjusting valve 65 is operated by a first urging member 68 including an adjusting screw 66, a spring 67 and the like. A first cover plate 69 is attached to the housing 62, and a first pressure adjusting chamber 70 is formed in the housing 62. By adjusting the first biasing member 68, the pressure of the gaseous fuel in the first pressure adjusting chamber is set to about 0.3 kg / cm ² .

A diaphragm 72 and a second cover plate 73 are mounted on the side of the housing 62 opposite to the first cover plate 69, whereby a second pressure adjusting chamber 74 is formed. The second pressure adjusting chamber 74 is connected to the first pressure adjusting chamber 74 via the passage 75.
It communicates with the pressure adjusting chamber 70. The second pressure adjusting valve 7 that can be opened and closed is provided at the opening of the passage 75 on the second pressure adjusting chamber side.
6 is provided, and the operation of the second pressure regulating valve 76 is controlled by the second urging member 77 which is interlocked with the diaphragm 72. Further, the atmospheric pressure acts on the back side of the diaphragm 72 through the atmospheric port 73a. By adjusting the second urging member 77, the pressure of the gaseous fuel in the second pressure adjusting chamber 74 is set to a pressure slightly lower than the atmospheric pressure, and the gaseous fuel thus set is supplied to the upper fuel. The fuel is supplied into the fuel supply chamber 42 through the passage 78. A heating passage 80 is provided in the housing 62. The coolant liquid heated by the cooling jacket 25 of the engine 1 is circulated through the heating passage 80. As a result, the regulator 6
A more stable gas temperature is maintained inside the 0, and a better vaporization and adjustment action is performed.

Further, one end of a bleed air passage 82 for introducing bleed air into the fuel supply chamber 42 is opened in the fuel supply chamber 42, and the bleed air passage 82 is provided with a bleed air control valve 84. It is connected to the. The bleed air control valve 84 has a bleed air passage 8 whose one end opens downstream of the air cleaner 35.
Air is introduced from 5. The bleed air control valve 84 includes a valve element 86 that is opened and closed by driving the stepping motor 90, and the operation of the valve element 86 controls the amount of bleed air to the fuel supply chamber 42. The drive of the stepping motor 90 is controlled (feedback control) by the ECU 92 based on the output signals from the O ₂ sensor 23 and the air flow meter 49. The engine operating conditions are as follows:
Flow resistance of the air cleaner 35, atmospheric pressure drop due to use at high altitude, and the like.

The fuel supply control valve 100 is controlled so as to compensate for the fuel amount according to the engine operating conditions in response to the movement of the valve member of the bleed air control valve 84. here,
The engine operating conditions include fuel composition (composition ratio of propane and butane in LPG), flow path resistance of the air cleaner 35, atmospheric pressure drop due to use in high altitude, and the like. That is, the opening degree of the fuel supply control valve 100 is controlled by the compensation function of the fuel supply control valve 100 so that the average number of steps of the bleed air control valve 84 is maintained at a substantially constant value (50). It Therefore, even if the engine operating conditions change due to the use of fuels of various compositions,
Λ = 1 is automatically maintained under all operating conditions without providing a sensor for detecting the engine operating condition, which enables more accurate control of the air-fuel ratio over a wide range.

Now, consider the fuel amount necessary for a certain amount of air for forming the air-fuel mixture in the stoichiometric state (λ = 1). This fuel amount depends on the ratio of propane and butane. For example, the amount of fuel required to form a stoichiometric mixture for 100 liters of air is 100% propane ... 42 liters 100% butane ... 32 liters. That is, 100% propane requires more fuel. Therefore, as fuel 100
When 100% propane is used, the opening degree of the fuel supply control valve 100 is more opened than when% butane is used. For this reason, the fuel supply control valve 10
0 is provided.

If only the bleed air control valve 84 is provided, if the fuel composition changes, the control width on either the lean side or the rich side becomes narrow. This is because when the fuel composition changes, the central value of the number of steps of the bleed air control valve 84 when λ = 1 deviates to the fully closed or fully open side, and the feedback control must be performed based on the deviated value. Because. On the other hand, in order to control the amount of fuel only with the fuel supply control valve 100, the amount of fuel supplied to the intake passage 33 such that the opening area of the throttle portion 42a is always smaller than the opening area of the main jet 43. Is controlled by the opening area of the throttle portion 42a, it is necessary to change the diameter of the throttle portion 42a according to the opening degree of the main jet 43. As a result, when the intake flow rate changes and the opening area of the main jet 43 changes, the opening area of the main jet 43 is reduced before changing the number of steps of the fuel supply control valve 100 for feedback control. It becomes necessary to control the opening area of the diaphragm portion 42a, which causes a delay in feedback control. As described above, by providing the bleed air control valve 84 and the fuel supply control valve 100, it is possible to secure a wide control range of the air-fuel ratio and to quickly perform the feedback control.

The above λ is defined as follows.
That is, λ = F / F _c, where F is the actual air-fuel ratio, and F _c is the stoichiometric stoichiometric air-fuel ratio. Therefore, in a stoichiometric mixture, λ = 1 always regardless of the type and composition of the gaseous fuel.
Is. However, even the stoichiometric air-fuel ratio indicated by the same λ = 1 naturally has different meanings if the ratio of butane and propane is different. The air-fuel ratio of the stoichiometric mixture with λ = 1 is 100% propane ... 15.7 and 100% butane ... 15.5. Therefore, if the butane and propane ratios differ, there will be a large difference in the amount of fuel (volume) required to obtain a stoichiometric air-fuel ratio of λ = 1 for a certain amount of air, which is a major problem. is there.

By providing the fuel supply control valve 100, the fuel amount from the regulator 60 can be directly controlled. The controlled fuel is continuously and surely supplied into the intake passage 33, whereby the A / F can be made uniform over a wide range of the fuel amount. Moreover, since the control of the fuel amount is performed based on the signal from the O ₂ sensor 23, the A / A ratio is within the range of the window where the purification rate of the three-way catalyst is high.
F can be controlled. Further, it is not necessary to provide a slow system or other various parts for adjusting the A / F,
The structure is simple. Although not clearly shown in FIG. 1, the fuel supply control valve 100 has a structure in which the valve body is held at an arbitrary position, that is, the opening is held at an arbitrary intermediate position, As a result, the fuel supply control valve 10
The unnecessary movement of 0 can be eliminated, and quick control becomes possible.

The gaseous fuel engine 1 is also provided with an EGR device for reducing NO _X in the exhaust gas. This EGR device has an EGR valve 56, and the EGR valve 56 allows the exhaust manifold 20 to
From the second EGR line 58 through the first EGR line 57
Through the plenum chamber 2 of the intake manifold 19
The amount of exhaust gas returning to 1 is controlled. An EGR regulator 110 is provided as a part of the EGR device. Further, a negative pressure switch 112 is provided downstream of the throttle valve 48 in the intake passage 33, and a fuel switching valve 114 is provided in the idle discharge line 51.
Is provided.

A fuel cutoff valve 120, an idle speed control valve 130 and an auxiliary fuel supply valve 140 are also provided. The fuel cutoff valve 120 is for shutting off fuel supply to the combustion chamber during rapid deceleration of the engine, and includes a filter element 121 for drawing in the atmosphere. At the time of sudden deceleration, that is, when the throttle valve 48 is rapidly throttled during high-speed rotation of the engine, the fuel cutoff valve 120 is opened, so that a large amount of atmosphere flows from the filter element 121 through the bypass passage 122 into the fuel supply chamber 42. Has been introduced to.

The idle speed control valve 130 is provided in the idle bypass passage 131 formed on the downstream side of the intake passage 33, and is generally an electrically operated control valve. The idle bypass passage 131 is provided in the intake passage 3
Throttle valve 48 in the idle position in 3
The idle speed control valve 130 controls the flow rate of intake air flowing through the idle bypass passage 131 based on a control signal from the ECU 92 to adjust the idle speed (rotation speed). belongs to. That is, when the idle speed decreases, the opening of the idle speed control valve 130 increases to bypass intake air, and when the idle speed is high, the opening of the idle speed control valve 130 decreases. In this way, the idle speed can be stabilized.

The auxiliary fuel supply valve 140 is generally an electrically operated control valve, and is mainly used for the regulator 6 during rapid acceleration.
0 to the flow path 141 to the flow path 142 in the first pressure adjusting chamber 70.
And for supplying enrichment fuel to the plenum chamber 21 through the bypass passage 143. This auxiliary fuel supply valve 140 is also an EC
It is controlled based on the control signal from U92. The enrichment fuel is supplied to determine whether or not the O ₂ sensor 23 is activated when the engine is started.

Next, a method of operating the gas fuel engine 1 during rapid deceleration will be described with reference to FIG. FIG. 2 is a control routine showing an operating method during rapid deceleration. In step S1, the program determines whether the engine speed is higher than a predetermined speed. If it is not higher, it means that the engine is rotating in a normal state where fuel cut is not required, and the process of step S1 is repeated. If the engine speed is higher than the predetermined speed, the process proceeds to step S2, and it is determined whether the intake negative pressure detected by the negative pressure switch 112 is higher than the predetermined pressure. If not, the engine is judged to be in a normal state, and the program repeats the processing of steps S1 and S2. If it is determined in step S2 that the intake negative pressure is higher than the predetermined pressure, the program proceeds to step S3. That is, when the determinations in both steps S1 and S2 are yes, it is determined that the engine is in the high rotation state and the throttle valve 48 is closed, that is, the so-called rapid deceleration state of the engine.

In step S3, the fuel cutoff valve 120 is opened. Then, the atmosphere is introduced from the filter element 121, and this atmosphere is introduced into the fuel supply chamber 42 through the bypass passage 122. If the atmosphere (including bleed air) is supplied into the fuel supply chamber 42, the throttle unit 4
The amount of fuel supplied to the fuel supply chamber 42 through the 2a is reduced, and as a result, the fuel supply into the intake passage 33 is suppressed or cut off. Normally, the amount of fuel supplied to the intake passage 33 is controlled by the function of the bleed air control valve 84 so that the state of λ = 1 is maintained. In this state, the atmosphere is further supplied to reduce the amount of fuel. In order to suppress, the mixture (lean mixture) having the air-fuel ratio of λ> 1 is supplied into the combustion chamber 6 at the time of rapid deceleration, and even if a misfire occurs in the combustion chamber 6, the catalyst converter 22 is provided. The amount of unburned fuel discharged is reduced, combustion in the catalyst is prevented, and the temperature inside the catalyst is prevented from becoming high. As a result, the catalyst can be protected.

Then, the process proceeds to step S4. This step S4 is a step of introducing a hysteresis so that the fuel supply is not restarted immediately after the sudden deceleration state has passed.
That is, in step S4, whether the engine speed is lower than the predetermined value determined in step S1 by a predetermined value α or more, or the intake negative pressure is smaller than the predetermined value by a predetermined value β or more (at atmospheric pressure). Near)). All of these indicate that the rapid deceleration state has ended. If any of these states exists, the process proceeds to step S5. In step S5, the fuel cutoff valve 120 is closed and the fuel supply is restarted using the hysteresis. Next, in step S6, normal feedback control is performed according to other parameters.

As described above, according to this embodiment, since the lean air-fuel mixture is supplied into the combustion chamber 6 by opening the fuel cutoff valve 120 at the time of sudden deceleration, misfire occurs in the combustion chamber 6 at the time of sudden deceleration. However, it is possible to prevent combustion in the catalyst and protect the catalyst. Further, the fuel cutoff valve 12 is used as an atmospheric control valve.
By using 0, it is possible to control the air-fuel ratio to λ> 1 while maintaining the average value of the number of steps of the bleed air control valve 84 at a substantially constant value (50). It is possible to improve the responsiveness of the feedback control.

The fuel cutoff valve 120 is ON.
The valve opening is not limited to the ON / OFF valve, and may be a valve capable of holding an intermediate opening position. In this case, the valve opening of the fuel cutoff valve is changed according to the opening of the throttle valve, and the higher the engine speed, The valve opening may be increased to reduce the amount of fuel supplied to the intake passage. In addition, the fuel supply chamber 4
It is not limited to the fuel cutoff valve 120 that supplies the lean air-fuel mixture into the fuel cell 2 during rapid deceleration. Bleed air control valve 84 during sudden deceleration
The lean air-fuel mixture may be supplied by increasing the opening degree of.

The present invention is not limited to the reciprocating engine but can be similarly applied to the rotary engine. Further, in each of the above-described embodiments, an example in which the present invention is applied to a 4-cylinder engine has been shown, but the present invention can be similarly applied to a multi-cylinder engine other than a 4-cylinder engine.

[0035]

As described above, in the operation control device for a gas fuel engine according to the inventions of claims 1 and 2, when the engine is rapidly decelerated, an air-fuel mixture of λ> 1 is supplied to the engine combustion chamber. Therefore, even if a misfire occurs in the combustion chamber, the amount of unburned fuel flowing in the exhaust device can be reduced, and thus the catalyst can be protected. Further, the operation control device for a gas fuel engine according to the invention of claim 2 has an effect of improving the response during rapid deceleration.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a gas fuel engine in which an operation control device according to an embodiment of the present invention is adopted.

FIG. 2 is a flowchart showing a control routine of air-fuel ratio feedback control when the engine is rapidly decelerating.

[Explanation of symbols]

 1 Gas Fuel Engine 6 Combustion Chamber 20 Exhaust Manifold (Exhaust Device) 22 Catalytic Converter 30 Mixture Forming Device 92 ECU (Operation Control Device, Air-Fuel Ratio Control Means) 120 Fuel Cutoff Valve (Introduction Valve)

Claims (2)

[Claims] 1. An operation control device for a gas fuel engine, which uses a gas fuel as a fuel and has a catalyst in an exhaust system,
An operation control device for a gas fuel engine, comprising air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber by the air-fuel mixture forming device to λ> 1 when the engine is rapidly decelerated. 2. An operation control device for a gas fuel engine, which uses a gas fuel as a fuel and has a catalyst in an exhaust device,
A fuel chamber that opens to the intake passage via the main jet is provided, and an introduction valve for introducing the atmosphere into the fuel chamber is provided. An operation control device for a gas fuel engine, comprising an air-fuel ratio control means for controlling the air-fuel ratio of the supplied mixture to λ> 1.