JPH06241083A - Mixture gas forming device for gas fuel engine - Google Patents

Abstract

PURPOSE:To provide a mixture gas forming device which can perform easily adjustment of the fuel amount under different engine operating conditions, in particular with different composition of the fuel in use. CONSTITUTION:A mixture gas forming device for a gas fuel engine is to form a mixture gas from gas fuel and air to be supplied to the combustion chamber of a gas fuel engine. The arrangement includes a fuel chamber 42 to be open to an intake passage 33 via a main jet 43 and a fuel adjusting valve (control valve for bleed air) 84 which adjusts the amount of fuel supply to the fuel chamber 42 so that a mixture gas having the specified air-fuel ratio is obtained. A throttle control valve (fuel supply control valve) 100 to make change control of the throttle part 42a at the upstream end of the fuel chamber 42 so that the change amount of the opening of this bleed air control valve 84 is compensated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-fuel mixture forming apparatus for a gas-fuel engine, which uses a gas fuel as a fuel.
Even when the composition of the fuel used is different, the fuel amount can be easily adjusted under various engine operating conditions,
The present invention relates to a mixture forming device capable of accurately controlling A / F.

[0002]

2. Description of the Related Art The use of alcohol, natural gas, hydrogen, etc. as a fuel for automobiles in place of gasoline has been studied, but their application to general vehicles is compatible with various engine operating conditions and cost. From this point of view, it is considered that the feasibility is not so high at present. On the other hand,
Since gas fuels such as liquefied petroleum gas (LPG) and liquefied natural gas (LNG) have the following advantages, they are extremely promising as alternative fuels for gasoline. Conceivable. That is, i) Gaseous fuel contains no harmful lead compounds and irritating aldehydes, and has a small amount of sulfur, so that sulfurous acid gas is hardly generated. 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 generated is very small. As a result, the oil replacement period is extended and the engine life is extended. iii) Because the octane number is much higher than gasoline,
Even with a high compression ratio engine, knocking is unlikely to occur. iv) Since it is introduced into the cylinder as a complete gas body,
There is no such thing as accelerating engine wear by washing off the oil on the cylinder wall like gasoline.
This can also improve the life of the engine. v) Do not cause fuel vapor lock or percolation. vi) Generally cheaper than gasoline. In particular, the advantage of i) above is very important in view of environmental problems that have recently been highlighted at the global level.

[0003]

A gas fuel engine using such a gas fuel as a fuel generally includes a pressure regulator (vaporizer) for vaporizing the gas fuel stored in a liquid state under pressure, A fuel chamber to which gaseous fuel is supplied from the pressure regulator and which has a main jet opening to the intake passage at one end and a throttle portion at the other end (end on the pressure regulator side) and an opening of the throttle portion. A throttle control valve for variably controlling the area and a mixer for forming a mixture of the gaseous fuel from the fuel chamber and the atmosphere are provided. The throttle control valve controls the opening area of the throttle portion of the fuel chamber to supply a desired amount of fuel such that the air-fuel ratio of the air-fuel mixture becomes λ = 1.
As described above, in the conventional gas fuel engine, the fuel supply amount is controlled only by the throttle control valve under various engine operating conditions. Therefore, when the composition of the fuel to be used is different, the valve opening degree of the throttle control valve is changed, and the air-fuel ratio control is performed based on the changed position. For this reason, the control width becomes narrow, and it may not be possible to easily cope with various changes in engine operating conditions.

The present invention has been made in view of such circumstances, and even when the composition of the fuel used is different, the fuel amount can be easily adjusted under various engine operating conditions. It is an object of the present invention to provide a mixture forming device capable of accurately controlling F.

[0005]

The invention according to claim 1 is mainly a gas-fuel-engine mixture forming apparatus for forming a mixture of gas fuel and air to be supplied to a combustion chamber of a gas-fuel engine. A fuel chamber opening to the intake passage via a jet is provided, and a fuel adjusting valve for adjusting the amount of fuel supplied to the fuel chamber is provided so as to obtain a mixture having a predetermined air-fuel ratio. A throttle control valve for variably controlling the throttle portion at the upstream end of the fuel chamber is arranged so as to compensate the variation of the valve opening degree. The above-mentioned predetermined air-fuel ratio means an air-fuel ratio within a so-called window region that is above the theoretical air-fuel ratio and within which the three-way catalyst can function. According to a second aspect of the present invention, in the first aspect, the fuel adjustment valve has a valve body that variably controls an opening area of a bleed air passage that opens into the fuel chamber, and an average valve opening degree of the valve body. The mixer is configured so that a mixture having a predetermined air-fuel ratio is obtained while the value is kept substantially constant, and the throttle control valve opens when the valve opening of the fuel adjustment valve changes by a predetermined amount or more. The opening area of the throttle portion is variably controlled according to the amount of change in the valve opening so that the average value of the degrees is kept substantially constant.

[0006]

In the gas-fuel mixture forming device for a gas fuel engine according to the first and second aspects of the present invention, when the composition of the fuel to be used changes, the throttle control valve causes the change amount of the valve opening of the fuel adjusting valve to change. In order to compensate, that is, when the valve opening of the fuel adjusting valve changes by a predetermined amount or more, the average value of the valve opening of the fuel adjusting valve is kept substantially constant according to the change amount of the fuel adjusting valve. The opening area of the throttle portion at the upstream end of the fuel chamber is variably controlled.
Therefore, when the valve opening of the fuel adjusting valve changes and the air-fuel ratio control is performed, the throttle control valve controls the opening position of the fuel adjusting valve to return to the original reference position. As a result, the controllable width of the fuel control valve can be maintained at a constant width, and as a result, it is possible to easily deal with changes in various engine operating conditions. Further, in the air-fuel mixture forming device for a gas fuel engine according to the invention of claim 2, the amount of fuel supplied to the fuel chamber is adjusted by variably controlling the bleed air passage, and the average value of the valve opening of the fuel adjusting valve is set to be substantially equal. Since the mixer is configured so that the air-fuel mixture having the predetermined air-fuel ratio can be obtained while being kept constant, the A / F control can be easily performed.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First Embodiment FIGS. 1 to 3 are views for explaining an air-fuel mixture forming device for a gas fuel engine according to a first embodiment of the present invention.

In the figure, reference numeral 1 is a water-cooled 4-cylinder 4-valve type gas fuel engine to which the first embodiment of the present invention is applied, which has a cylinder block 2 and a cylinder head 3 laminated on a crankcase (not shown). Head bolts, and the head cover 4 is mounted on the cylinder head 3. A piston 5 is provided in each of the four cylinder bores 2a formed in the cylinder block 2.
Are slidably inserted and arranged, and each piston 5 is connected to a crank shaft (not shown) via a connecting rod.

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. In the case of the former type, the O ₂ sensor 2
When 3 outputs a signal, it is determined that the fuel is rich and the fuel is reduced, and when it does not output a signal, it is determined that the fuel is lean and the fuel is increased.

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 (see the arrow in FIG. 1).

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. Various signals such as the throttle position of the throttle valve 48, the coolant temperature of the coolant, the engine speed, the output of the O ₂ sensor 23, the exhaust temperature, the output of the negative pressure sensor, etc. are input to the ECU 92.

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 can maintain the stoichiometric air-fuel ratio while the average value of the opening degree of the bleed air control valve 84, which will be described later, is substantially constant (step number 50) for any intake flow rate. It has a shape. As a result, A / F control can be easily performed. 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 may be opened in the intake passage 33 upstream of the venturi portion in which the main jet 43 is opened. In this case as well, atmospheric pressure acts on the piston 39 in the opening direction side of the intake passage 33.

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. Further, the mixer 31 is provided with an idle circuit 50 including an idle discharge line 51 extending from the fuel supply chamber 42, a fuel cutoff valve 114, 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 fuel cutoff valve 114 is an ECU
The opening and closing is controlled by 92,
As a result, the amount of fuel passing through the idle discharge line 51 is controlled. Fuel is supplied from the idle circuit 50 during idling. Although the variable Venturi mixer 31 is used as the mixer here, a fixed Venturi type mixer may be used to obtain the effects of the present invention.

A pressure regulator (vaporizer, regulator) 60 for supplying gaseous fuel to the fuel supply chamber 42 is connected to the fuel supply chamber 42 via a fuel supply passage 78. Gas fuel stored in a liquid state under pressure in a high pressure source (not shown) is introduced into the regulator 60 through an 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 about 0.3 in gauge pressure.
It is set to 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 functions as a fuel adjusting valve. It is connected to the bleed air control valve 84. Air is introduced into the bleed air control valve 84 from a bleed air passage 85 whose one end opens downstream of the air cleaner 35. The bleed air control valve 84 includes a valve element 86 that opens and closes when driven by a stepping motor 90. The operation of the valve element 86 controls the amount of bleed air to the fuel supply chamber 42, thereby supplying the fuel. The amount of fuel to the chamber 42 is controlled. Further, the stepping motor 90 is
The drive thereof 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.

Now, a control routine for correcting the number of steps of the bleed air control valve 84 at the time of starting the vehicle before the shift to the feedback control will be described with reference to FIG. FIG. 2 shows an example in which the idle switch detects the off-idle state. First, in step S1, it is determined whether or not the idle switch has been turned off, that is, whether or not the idle switch has been turned off. When the vehicle starts and enters the off-idle state, the predetermined number of steps for obtaining the air-fuel mixture having substantially the stoichiometric air-fuel ratio is read from the map in step S2, and the step motor 90 is driven at the maximum speed up to the predetermined number of steps in step S3. . As a result, the air-fuel ratio control at the time of starting can be performed accurately. Next, in step S4, the step motor 9
It is determined whether 0 has moved to a predetermined number of steps. If it has not moved to the predetermined number of steps, the process returns to step S3. If the step motor 90 moves to a predetermined number of steps, the process proceeds to step S5, and after the O ₂ sensor 23 starts to output the control signal, the process proceeds to the feedback control.

In the fuel supply chamber 42, a fuel supply control valve 10 for adjusting the amount of gaseous fuel supplied from the regulator 60 to the fuel supply chamber 42.
0 is provided. The fuel supply control valve 100 functions as a throttle control valve that variably controls the opening area of the fuel supply chamber 42a, and is operated by a stepping motor. The stepping motor, based on a signal from the O ₂ sensor 23 under various engine operating conditions,
It is controlled by U92, which controls the fuel supply amount. 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 at high altitude, and the like.

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 or 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 shifts to the fully closed or fully open side, and the feedback control must be performed based on the shifted value. Is. On the other hand, the fuel supply control valve 100
In order to control the amount of fuel, the amount of fuel supplied to the intake passage 33 depends on the opening area of the throttle portion 42a so that the opening area of the throttle portion 42a is always smaller than the opening area of the main jet 43. In order to be controlled, it is necessary to change the diameter of the throttle portion 42a in accordance with 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, feedback control is performed. Therefore, prior to changing the number of steps of the fuel supply control valve 100, it is necessary to control the opening area of the throttle portion 42a so that the opening area of the main jet 43 becomes small, which causes a delay in feedback control. Become. In this way, the bleed air control valve 84 and the fuel supply control valve 1
By providing 00, a wide control range of the air-fuel ratio can be secured and feedback control can be performed quickly.

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, in order to adjust the A / F, it is not necessary to provide a power system for increasing the fuel amount during acceleration and various other parts, and the structure is simplified. See also FIG.
Although not clearly shown in the above, the fuel supply control valve 100
Has a structure in which the valve body is held at an arbitrary position, that is, the opening degree is held at an arbitrary intermediate position, whereby unnecessary movement of the fuel supply control valve 100 can be eliminated, and the fuel supply control valve 100 can be quickly operated. Control becomes possible.

The fuel supply control valve 100 is controlled so as to compensate the fuel amount in accordance with the engine operating conditions in response to the movement of the valve member of the bleed air control valve 84. That is, as shown in FIG. 3, in order to maintain the stoichiometric air-fuel ratio when different fuels are used or when the filter element is clogged, the number of steps of the bleed air control valve 84 is now from 50 to 50. It is assumed that the amount of fuel supplied to the fuel supply chamber 42 is decreased by rising to 60 and increasing the amount of bleed air (this is indicated by the line a1-a2). The number of steps of the fuel supply control valve 100 at this time is 50. In order to return the number of steps of the bleed air control valve 84 to 50 from this state, the number of steps of the fuel supply control valve 100 is 50 to 40.
And the amount of fuel supplied to the fuel supply chamber 42 is decreased (see line b1-b2), and correspondingly, the number of steps of the bleed air control valve 84 is decreased from 60 to the reference level 50. Will return to. In this case, the number of steps of the fuel supply control valve 100 to be changed from 50 depends on what engine operating condition is the cause of the large change in the number of steps of the bleed air control valve 84.

Next, when the number of steps of the bleed air control valve 84 decreases (see line a4-a5), the number of steps of the fuel supply control valve 100 increases (see line b3-b4).
Accordingly, the number of steps of the bleed air control valve 84 returns to the reference level of 50. Note that FIG.
The number of steps of the bleed air control valve 84 fluctuates little by little because the O ₂ sensor 23 detects a rich state and outputs a control signal to increase the bleed air control valve 84. This is because the number of steps slightly changes due to the repetition of the case where the O ₂ sensor 23 does not output a signal and the case where the bleed air is reduced because the O ₂ sensor 23 does not output a signal. Maintained at. By such a compensation function of the fuel supply control valve 100, the bleed air control valve 8
The average of the number of steps in 4 is kept at a substantially constant value (50). Therefore, even when fuels of various compositions are used, λ is automatically set under all operating conditions without providing a sensor for detecting the engine operating state.
= 1 will be maintained, and more accurate control of the air-fuel ratio will be possible over a wide range.

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. When the throttle valve 48 is suddenly throttled during the rapid deceleration, that is, during the high speed rotation of the engine, this rapid deceleration state is detected by the negative pressure sensor 112, and this detection signal is input to the ECU 92. Then, in response to a control signal from the ECU 92, the fuel cutoff valve 120 is opened, whereby a large amount of atmosphere is introduced into the fuel supply chamber 42 from the filter element 121 through the bypass passage 122. As a result, the fuel supply to the intake passage 33 is cut off. As a result, it is possible to avoid the temperature inside the medium from becoming high due to the incompletely burned fuel being discharged into the catalytic converter during sudden deceleration.

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 ECU
It is controlled based on the control signal from 92. It should be noted that this fuel for enrichment is supplied at the time of engine start.
_{2 This} is performed to determine whether the sensor 23 has been activated.

As described above, in this embodiment, the bleed air control valve (fuel adjustment valve) 84 is provided, and the upstream side of the fuel chamber is compensated so that the variation of the valve opening of the bleed air control valve 84 is compensated. Since the fuel supply control valve (throttle control valve) 100 that variably controls the throttle portion 42a at the end is provided,
Due to the compensation function of the fuel supply control valve 100, the average number of steps of the bleed air control valve 84 can be kept substantially constant. As a result, even when fuels of various compositions are used, the stoichiometric air-fuel ratio can be automatically maintained under all operating conditions, and more accurate control of the air-fuel ratio becomes possible over a wide range.

Second Embodiment FIG. 4 is a diagram for explaining an air-fuel mixture forming device for a gas fuel engine according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding portions. Although the gas fuel engine is omitted here, the gas fuel engine 1 of the first embodiment device (FIG. 1) is omitted.
The same applies to the gaseous fuel engine.

In FIG. 4, in place of the bleed air passage 85, a bypass passage 160 is provided between the fuel supply passage 78 and the valve element 86 of the control valve 84 in the first embodiment device (FIG. 1). Is different from Therefore,
The control valve 84 does not function here as a bleed air control valve, but as a second fuel supply control valve. Since there are two fuel control valves 84 and 100 as described above, the following two control methods can be considered for controlling both control valves. That is, i) feedback control is performed by the control valve 84, and the control valve 1
00 compensates the variation of the control valve 84 according to the engine operating conditions. ii) The feedback control is performed by both the control valves 84 and 100, but the control valve 100 is controlled according to the engine operating conditions so that the average number of steps of the control valve 84 can be kept substantially constant. To compensate for the amount of change. This second embodiment device employs the control method of ii) above, and the opening of each fuel supply control valve 84, 100 is set to a certain value according to the type of gaseous fuel used. . When the composition of the gaseous fuel changes or the filter element 37 becomes clogged,
Each opening degree of the control valves 84, 100 is appropriately changed based on the output signal from the O ₂ sensor 23 so that the air-fuel mixture having the theoretical air-fuel ratio of λ = 1 is obtained. By providing two fuel control valves in this way, both control valves can be miniaturized and the movement amount of each valve can be reduced, whereby the entire device can be made compact and the responsiveness can be improved.

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. Further, in each of the above-described embodiments, the control valve 84 and the fuel supply control valve 100 are opened and closed by the step motor, but the application of the present invention is not limited to this. For example, a proportional control solenoid valve may be adopted and the valve opening may be adjusted by controlling the supply current.

[0035]

As described above, in the gas-fuel mixture forming apparatus for a gas fuel engine according to the inventions of claims 1 and 2, the amount of change in the valve opening of the fuel adjusting valve is compensated, that is, the valve of the fuel adjusting valve. A throttle control valve for variably controlling the throttle portion at the upstream end of the fuel chamber is arranged so that the average value of the valve opening of the fuel control valve is kept substantially constant when the opening changes by a predetermined amount or more. Therefore, the compensating function of the throttle control valve has the effect of keeping the controllable width of the fuel adjustment valve at a constant width. As a result, the predetermined air-fuel ratio can be automatically maintained under all operating conditions, such as when fuels of various compositions are used, and more accurate control of the air-fuel ratio becomes possible over a wide range. Further, the compensation function of the throttle control valve has an effect that the predetermined air-fuel ratio can be automatically maintained under all operating conditions without providing a sensor for detecting operating conditions such as fuel composition.

In the air-fuel mixture forming device for a gas fuel engine according to the second aspect of the present invention, the amount of fuel supplied to the fuel chamber is adjusted by variably controlling the bleed air passage, and the average valve opening of the fuel adjusting valve is adjusted. Since the mixer is configured so that the air-fuel mixture having the predetermined air-fuel ratio is obtained while the value is kept substantially constant, there is also an effect that the A / F control can be easily performed.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a gas fuel engine in which a gas fuel engine mixture forming device according to a first embodiment of the present invention is adopted.

FIG. 2 is a control flow chart for correcting the number of steps of a bleed air control valve in the apparatus of the above embodiment.

FIG. 3 is a diagram showing a mutual relationship between a bleed air control valve and a fuel supply control valve in the apparatus of the above embodiment.

FIG. 4 is a schematic configuration diagram of an air-fuel mixture forming device for a gas fuel engine according to a second embodiment of the present invention.

[Explanation of symbols]

 30 Mixture Forming Device 31 Mixer 33 Intake Passage 42 Fuel Chamber 42a Throttle Section 43 Main Jet 84 Bleed Air Control Valve (Fuel Control Valve) 92 ECU 100 Fuel Supply Control Valve (Throttle Control Valve)

Claims (2)

[Claims] 1. A fuel-fuel mixture forming apparatus for a gas-fuel engine for forming a gas-fuel mixture to be supplied to a combustion chamber of a gas-fuel engine, the fuel chamber opening to an intake passage via a main jet. And a fuel adjusting valve for adjusting the amount of fuel supplied to the fuel chamber so as to obtain a mixture having a predetermined air-fuel ratio, and the amount of change in the valve opening of the fuel adjusting valve is compensated. As described above, the gas mixture forming apparatus for a gas fuel engine, wherein a throttle control valve for variably controlling the throttle portion at the upstream end of the fuel chamber is provided. 2. The fuel control valve according to claim 1, further comprising a valve body that variably controls an opening area of a bleed air passage that opens into the fuel chamber, and an average value of valve opening degrees of the valve body is calculated. The mixer is configured so that an air-fuel mixture having a predetermined air-fuel ratio can be obtained in a state of being held substantially constant, and the throttle control valve is configured to adjust the valve opening degree of the fuel adjustment valve when the valve opening degree changes by a predetermined amount or more. An air-fuel mixture forming device for a gas fuel engine, wherein the opening area of the throttle portion is variably controlled according to the amount of change in the valve opening so that the average value is kept substantially constant.