JP2003214260A - Gas fuel feeding device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas fuel feeding device for an engine which controls a fuel-gas flow rate with a sufficient precision and improves the controllability of an air/fuel ratio. <P>SOLUTION: In this gas fuel feeding device for an engine 1, a gas fuel path 7 is connected at an upstream side from a throttle valve 20 of an intake passage 4 connected with an engine 1, the gas fuel path 7 is connected with a gas fuel supply source 10 through a regulator for gas pressure adjustment, a bleeding air path 11 is connected in the middle of the gas fuel path 7, and an air-bleed control valve 12 controlling the area of the bleeding air path 11 is provided. The interval of the gas fuel path 7 from a junction T1 of a regulator outlet to a junction T2 of a bleeding air path is set shorter than that from the junction T2 of the bleeding air path to a junction T3 of the intake passage. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas fuel supply system for supplying gas fuel such as liquefied petroleum gas (LPG) and compressed natural gas (CNG) to an engine.

[0002]

2. Description of the Related Art As a gas fuel supply device used in a conventional gas engine, there is one provided with a fixed venturi type mixer shown in FIG. 14, and the mixer has the following structure. Fixed venturi portion 33 'upstream of the throttle valve 32' in the intake passage 31 'connected to the engine
A main gas fuel passage 34 'is connected to the main gas fuel passage 34', and a gas flow rate adjusting valve 36 'driven by a step motor 35' is arranged in the middle of the main gas fuel passage 34 '. Further, the gas injector 3 is provided immediately downstream of the throttle valve 32 '.
7'is provided.

In the case of the fixed Venturi type mixer, the inner diameter (passage diameter) of the venturi portion 33 'is limited by the flow rate characteristic of the gas injector 37', and the degree of freedom is small. Therefore, in order to support a large displacement engine and a high output engine, a plurality of injectors are required to increase the diameter of the main venturi, which causes a problem of high cost.

Further, the air-fuel ratio control is performed for the two systems, the main system for supplying fuel from the main venturi and the slow system for supplying fuel from the gas injector, which complicates the control system, which also leads to high cost.

Therefore, the applicant can simplify the structure and reduce the cost by eliminating the need for a gas injector,
Further, a gas fuel supply device applicable to a small displacement engine to a large displacement engine is proposed, which has the following structure (PCT / JP01 / 08988).

That is, a gas fuel supply passage is connected to an upstream side of a throttle valve of an intake passage connected to an engine, a gas fuel tank is connected to the gas fuel passage through a gas pressure adjusting regulator, and the gas is further connected. A bleed air passage is connected to the fuel passage, and an air bleed control valve for controlling the passage area of the bleed air passage is arranged.

In the gas fuel supply system according to the above-mentioned proposal, the high pressure gas fuel from the gas fuel supply source is adjusted to substantially atmospheric pressure by the regulator, and the intake negative pressure acting on the gas fuel passage connection point of the intake passage is used. The gas fuel is sucked in to secure the required fuel amount, and the air-bleed control valve controls the bleed air amount to correct the deviation from the set state of the air-fuel ratio, thus enabling accurate air-fuel ratio control. Has become.

[0008]

Therefore, in the gas fuel supply apparatus according to the above-mentioned proposal, in order to secure a necessary fuel flow rate, the intake negative pressure P1 near the gas fuel passage connection point of the intake passage.
And the negative pressure P2 in the vicinity of the regulator outlet must be in a proportional relationship. However, compared with the distance from the generation point of the intake negative pressure P1 of the intake passage to the bleed air passage connection point, the bleed air passage connection point If the distance from the regulator to the outlet of the regulator is large, the intake negative pressure P
As a result of experiments, it has been found that 1 and the negative pressure P2 near the outlet of the regulator are not necessarily proportional to each other and may have different values depending on the engine speed. In this case, the required fuel flow rate cannot be secured in the intake passage, so the target opening of the air bleed control valve also fluctuates greatly in order to maintain the air-fuel ratio at the set state. Since it is for correcting a slight deviation, the driving stepping motor or the like cannot follow the changing speed of the target opening, and as a result, the controllability of the air-fuel ratio is lost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a gas fuel supply device for an engine, which can control the gas fuel flow rate with high accuracy and improve the controllability of the air-fuel ratio.

[0010]

According to a first aspect of the present invention, a gas fuel passage is connected upstream of a throttle valve of an intake passage connected to an engine, and the gas fuel passage is connected via a gas pressure adjusting regulator. Connect to a gas fuel supply,
A gas fuel supply device for an engine, comprising an air bleed control valve for connecting a bleed air passage in the middle of the gas fuel passage and controlling the area of the bleed air passage, wherein the regulator outlet connection point of the gas fuel passage is connected to the regulator outlet connection point. It is characterized in that the distance to the bleed air passage connecting point is set shorter than the distance from the bleed air passage connecting point to the intake passage.

In the present invention, the distance from the regulator outlet connection point of the gas fuel passage to the bleed air passage connection point is set shorter than the distance from the bleed air passage connection point to the intake passage. Then,
In other words, when the distance from the regulator outlet connection point of the gas fuel passage to the intake passage connection point is fixed, it means that the regulator outlet connection point and the bleed air connection point are made as close as possible.

According to a second aspect of the present invention, in the first aspect, the propagation of intake pulsation generated by the engine at the downstream side of the bleed air passage connection point of the gas fuel passage is mitigated, and the gas fuel and the bleed air are mixed. It is characterized by the provision of a premixing chamber for promoting

According to a third aspect of the present invention, in the first or second aspect, a gas fuel control valve for controlling opening and closing of the intake passage is provided upstream of the connection point of the gas fuel passage in the intake passage. The feature is that the opening is changed according to the operating state of the engine.

According to a fourth aspect of the present invention, in the third aspect, the gas fuel control valve and the throttle valve are provided with a link mechanism that fully opens the gas fuel control valve before the throttle valve is fully opened. It is characterized by being connected.

According to a fifth aspect of the present invention, in the first or second aspect, a fixed venturi for reducing the intake passage area is arranged upstream of the throttle valve in the intake passage, and the fixed venturi has an annular header hole. Having an annular portion having
The header hole has a plurality of slits or a large number of small holes that communicate with the inside of the intake passage, and the gas fuel passage is communicated with the header hole.

[0016]

According to the present invention, the distance from the regulator outlet connection point of the gas fuel passage to the bleed air passage connection point is set to the distance from the bleed air passage connection point to the intake passage connection point. Since the setting is made shorter, in other words, the regulator outlet connection point of the gas fuel passage and the bleed air passage connection point are made as close as possible, so that the controllability of the gas fuel flow rate and thus the air-fuel ratio can be improved. That is, since the regulator outlet connection point and the bleed air connection point are close to each other, the intake negative pressures in both are substantially equal, and the intake negative pressure at the gas fuel passage connection point to the intake passage and the intake air at the regulator outlet connection point are also equal. It is possible to maintain the proportional relationship with the negative pressure even when the engine speed changes, thereby ensuring the required fuel flow rate. Therefore, the target opening of the air bleed control valve does not change greatly, and the stepping motor and the like can sufficiently follow the change of the target opening, and as a result, the controllability of the air-fuel ratio can be secured.

According to the second aspect of the present invention, since the premixing chamber having a large volume is provided on the downstream side of the bleed air passage connecting point of the gas fuel passage, the intake pulsation generated on the engine side is regulated by the regulator or the air. Propagation to the bleed control valve side can be mitigated, and it is possible to prevent intake pulsation from causing a resonance phenomenon with the natural frequency of the diaphragm that constitutes the decompression chamber in the regulator and not being able to supply the required amount of fuel. Mixing of the gas fuel and the bleed air can be promoted before reaching the intake passage. As a result, the gas fuel flow rate can be controlled more accurately, and the controllability of the air-fuel ratio can be improved.

According to the third aspect of the invention, the gas fuel control valve is arranged upstream of the gas fuel passage connecting point, and its opening is changed according to the operating condition of the engine. It is possible to control the intake negative pressure that acts on, for example, in an operating range where the opening of the throttle valve is small, it is possible to generate the intake negative pressure at the gas fuel passage connection point by reducing the opening of the gas fuel control valve. By this negative pressure of intake air, the gas fuel flow rate can be reliably controlled.

Therefore, it is possible to eliminate the need for the main venturi, and in the case of such a configuration, there is no restriction loss of the intake air amount due to the main venturi, and the intake air amount can be increased and a high output can be obtained.

According to the invention of claim 4, the gas fuel control valve and the throttle valve are connected by a link mechanism for fully opening the gas fuel control valve before the throttle valve is fully opened. In the medium and high load operation range where the throttle valve opening becomes large, it is possible to more reliably avoid that the gas fuel control valve is fully opened first and becomes the resistance of the intake air.

According to the fifth aspect of the present invention, a fixed venturi having a plurality of slits or a plurality of small holes for connecting an annular header hole to the inside of the intake passage is provided upstream of the throttle valve in the intake passage. Therefore, the gas fuel can be uniformly supplied to the intake passage, and the gas fuel and the air can be reliably mixed.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 11 are views for explaining an embodiment of the present invention, FIG. 1 is a schematic configuration diagram of a gas fuel supply device for an engine according to the present embodiment, and FIG. 2 is a schematic configuration diagram of a gas mixer portion. 3 is a diagram showing the relationship between the opening of the throttle valve and the opening of the gas fuel control valve, and FIGS. 4 to 6 are diagrams showing the air bleed control valve and the premixing chamber, FIG. 7 to 11 are diagrams showing the regulator.

In the figure, 1 is a gas fuel, for example a gas engine operated with compressed natural gas (CNG),
This connects a piston 1b slidably arranged in a cylinder bore 1a to a crankshaft 1d by a connecting rod 1c,
The exhaust port 1e and the intake port 1f are configured to be opened and closed by the exhaust valve 1g and the intake valve 1h. A catalyst 3 is provided in the middle of the exhaust passage 2 connected to the exhaust port 1e. 2a is a silencer.

A gas mixer 5 is interposed in the intake passage 4 connected to the intake port 1f, and an air cleaner 6 is connected to the upstream end of the intake passage 4. A gas fuel tank 10 is connected to the gas fuel passage 7 of the gas mixer 5 via a premixing chamber 8 and a regulator 9. Further, a bleed air passage 11 is connected to the upstream side of the premix chamber 8 of the gas fuel passage 7, an air bleed control valve 12 is arranged in the bleed air passage 11, and an air cleaner 13 is connected to the upstream end thereof. ing. In addition,
Reference numeral 45 is a blow-by gas recirculation passage that allows blow-by gas to flow into the intake passage 4, and 45a is a pressure control valve that opens when the inside of the passage 45 reaches a predetermined pressure.

In this embodiment, the distance measured along the passage from the regulator 9 outlet connection point T1 of the gas fuel passage 7 to the bleed air passage 11 connection point T2 is the distance of the bleed air passage 11 in the gas fuel passage 7. The distance is set to be shorter than the distance measured along the passage from the connection point T2 to the connection point T3 to the intake passage 4. In other words, when the distance from the regulator outlet connection point T1 to the intake passage connection point T3 is fixed, the regulator 9 outlet connection point T1 and the bleed air passage 11 connection point T2 are made as close as possible. As a result, as will be described later, the controllability of the gas fuel flow rate and thus the air-fuel ratio can be improved.

A negative pressure sensor 14 for detecting intake negative pressure is provided downstream of the gas mixer 5 in the intake passage 4, and an O ₂ sensor 15 for detecting O ₂ concentration in the exhaust gas is provided upstream of the catalyst 3 in the exhaust passage 2. However, the catalyst 3 is provided with a temperature sensor 16 for detecting the temperature of the catalyst. These sensors 1
Intake negative pressure signals a, O detected by 4, 15 and 16
_{2 The} density signal b and the temperature signal c are supplied to the control unit 17. And this control unit 1
7, an air bleed control signal S1 is output to the air bleed control valve 12, and an idle control signal S2 is output to an ISC (idle speed control) valve 18.

The gas mixer 5 has a fixed main venturi portion 19 having a smaller diameter than the intake passage 4, and a butterfly having a controllable intake passage area on the downstream and upstream sides of the main venturi portion 19. A throttle valve 20 and a gas fuel control valve 21 are provided. The gas fuel passage 7 is open to the main venturi portion 19 located upstream of the throttle valve 20, and the opening is a connection point T3 of the gas fuel passage 7 to the intake passage.
Has become.

A drive pulley (not shown) is mounted on one outer end of the valve shaft 20a of the throttle valve 20. The drive pulley is connected to a throttle pedal on the driver's seat via a throttle cable, and the throttle valve 20 rotates in accordance with the amount of pedal depression of the driver.

The valve shaft 2 of the throttle valve 20
0a and the valve shaft 21 of the gas fuel control valve 21
The link mechanism 22 is connected to a. Specifically, a throttle arm 22a is connected to the other outer end portion of the valve shaft 20a of the throttle valve 20 such that the throttle arm 22a cannot rotate relative to the throttle shaft 20a.
It is connected to the control arm 22c of the gas fuel control valve 21 via b.

And the gas fuel control valve 2
1 contacts the stopper at the fully open position, the control arm 22c is connected to the valve shaft 21a of the gas fuel control valve 21 so as to be rotatable relative to it, and is biased to the minimum opening position shown in FIG. It is urged to rotate counterclockwise. The throttle arm 22a is longer than the control arm 22c.

As a result, the gas fuel control valve 2
No. 1 is fully opened before the throttle valve 20 is fully opened, and the control arm 22c is provided with the throttle valve 20 even after the fuel control valve 21 is fully opened.
Also, it can rotate following the movement of the connecting link 22b connected thereto.

Here, when the throttle pedal is not depressed, the throttle valve 20 and the gas fuel control valve 21 are kept at the minimum opening shown in FIG. Then, the opening degree of the throttle valve 20 increases substantially in proportion to the depression amount of the throttle pedal. On the other hand, the opening of the gas fuel control valve 21 is fully opened when the throttle valve opening is about 20 to 30%, and thereafter is held at the fully opened position (see characteristic curve A in FIG. 3).

The main venturi 19 can be removed from the intake passage 4. In this case, as shown by the characteristic curve B in FIG. 3, the gas fuel control valve 21 is not fully opened but is opened at a maximum of 40 to 50%. As a result, the intake negative pressure can be generated in the gas fuel passage connecting portion without providing the main venturi.

The air bleed control valve 12
The premix chamber 8 is integrated as shown in FIGS. The air bleed control valve 12 includes a valve body 12b having a conical valve portion 12a and a stepping motor 1
The air bleed hole 11a is moved forward and backward by 2c to adjust the passage area of the air bleed hole 11a formed in the bleed air passage 11. When the passage area of the air bleed hole 11a is increased, the suction amount of air (outside air) is increased, and the suction amount of gas fuel is relatively decreased. Therefore, the deviation of the gas fuel flow rate from the set state is corrected and The fuel ratio is controlled toward a desired value.

The air cleaner 13 is arranged in the bleed air passage 11 so as to face the air bleed hole 11a from the upstream side thereof. The air cleaner 13 includes an annular element 13b arranged in a substantially rectangular case 13a, and air introduced from an air inlet 13c enters from the outer periphery of the element 13b toward the center side toward the air bleed hole 11a. Becomes

The downstream side chamber 11b of the air bleed hole 11a of the bleed air passage 11 is open to the inlet side joint 7a forming a part of the gas fuel passage 7, and therefore the downstream side chamber 11b is connected to the bleed air passage described above. It becomes a point T2. The downstream end 7b of the inlet joint 7a communicates with the premix chamber 8. The premixing chamber 8 has a cylindrical shape with both openings closed by a bottom wall 8a and a ceiling wall 8b, and is arranged so as to form a right angle with the axis of the inlet side joint 7a, that is, to be horizontal. . The premixing chamber 8 has a sufficient volume to mix the gas fuel and the bleed air sufficiently uniformly and to prevent the intake pulsation from the engine side from propagating to the upstream side of the premixing chamber 8. Have

At the outlet 8c formed in the top wall 8b of the premixing chamber 8, the outlet side joint 2 forming a part of the gas fuel passage 7 is provided.
3 is connected. The outlet side joint 23 is formed by integrally forming a valve body portion 23a forming a part of the diaphragm type fuel cutoff valve 24 and an external connection pipe portion 23b formed at a right angle to the valve body portion 23a. The external connection pipe portion 23b is connected to the venturi portion 19 of the intake passage 4 via a fuel hose forming a part of the gas fuel passage 7.

A valve hole 23c of the valve body portion 23a is opened in the premix chamber 8, and a valve plate 24a of the fuel cutoff valve 24 is arranged in the valve hole 23c so as to open and close the valve hole 23c. ing. The fuel cutoff valve 24 is a diaphragm valve 24 arranged in a diaphragm case 24b.
The valve plate 24a is fixed to the tip of a valve shaft 24d fixed to c.

The diaphragm valve 24c is biased by a return spring 24e in a direction to open the valve plate 24a. The negative pressure chamber 24f surrounded by the diaphragm case 24b and the diaphragm valve 24c is connected to the negative pressure supply port 26a of the three-way switching solenoid valve 26 by the negative pressure introducing passage 25. The three-way switching solenoid valve 26 is a negative pressure introducing hose and is connected to a negative pressure introducing port 26b which is connected to the intake passage 4 downstream of the throttle valve 20.
And an atmospheric air introduction port 26c for introducing atmospheric pressure through the filter 27, and the negative pressure supply port 26a.

The control unit 17 cuts fuel during deceleration by the fuel cutoff valve 24 via the three-way switching solenoid valve 26. When suddenly decelerating,
That is, when the throttle valve 20 is at the idle opening and the engine rotation speed is equal to or higher than the preset deceleration fuel cut rotation speed, the three-way switching solenoid valve 26 connects the negative pressure introduction port 26b and the negative pressure supply port 26a. The intake negative pressure is introduced into the negative pressure chamber 24f of the fuel cutoff valve 24 to shut off the valve hole 23c. On the other hand, when the sudden deceleration state is canceled, the three-way switching solenoid valve 26 has the atmosphere introduction port 26c and the negative pressure supply port 26a.
Are switched to communicate with each other, whereby atmospheric pressure is introduced into the negative pressure chamber 24f of the fuel cutoff valve 24, and the fuel cutoff valve 24 is opened by the return spring 24e.

The external connecting pipe 7 at the upstream end of the inlet side joint 7a.
The regulator 9 is connected to c through a joint or the like that forms a part of the gas fuel passage. This regulator 9
Is a diaphragm type having primary to tertiary decompression chambers # 1 to # 3, and the gas pressure in the gas fuel tank 10 is set to 3
The pressure is reduced to approximately atmospheric pressure in stages, and has the following specific structure.

The case 28 of the regulator 9 includes a tertiary decompression case portion 28a having a tertiary decompression chamber # 3,
It has a primary / secondary decompression case portion 29 having secondary decompression chambers # 1 and # 2. The upper opening of the primary chamber 29a partitioned by the boundary wall 29d of the primary / secondary decompression case 29 can be opened / closed by a primary chamber cover 31.
The primary diaphragm 30 is sandwiched between the primary diaphragm 30 and the primary chamber cover 31. Further, the lower side opening of the secondary chamber 29b partitioned by the boundary wall 29d can be opened and closed by a secondary chamber cover 32, and a secondary chamber is provided between the secondary chamber 29b and the secondary chamber chamber cover 32. The diaphragm 33 is clamped.

At the lower end of the primary rod 30a fixed to the primary diaphragm 30, the valve shaft 3 connected to the primary valve body 34 is connected.
4a are connected. The movement of the primary diaphragm 30 causes the support arm 34 fixed to the valve shaft 34a.
b rotates about the pin 34c as a rotation center to slightly move the primary valve element 34 to the left and right in FIG. 8, thereby opening and closing the valve hole 35a of the gas introduction joint 35. Further, the primary diaphragm 30 is biased downward by the return spring 30b, whereby the primary valve element 34 is constantly biased in the opening direction. Atmospheric pressure is constantly introduced to the return spring 30b side of the primary diaphragm 30 through the through hole 31a. The gas fuel tank 10 is connected to the gas introduction joint 35.

The primary decompression chamber # 1 communicates with the secondary decompression chamber # 2 through a communication hole 29c formed in the boundary wall 29d, and the communication hole 29c can be opened and closed by the secondary valve body 36. ing. An arm 36a, one end of which is fixed to the secondary valve body 36, is rotatable around a pin 36b, whereby the secondary valve body 36 opens and closes the through hole 29c.

A secondary rod 33a fixed to the secondary diaphragm 33 is rotatably connected to the other end of the arm 36a. One end 37a of a return spring 37 of a torsion bar type is opposed to and abuts on the lower end surface of the secondary rod 33a, and the other end 37b of the return spring 37 is bolted and fixed to the primary / secondary decompression case portion 29. There is. The return spring 37 is for returning the secondary valve element 36 to the slightly opened state in FIG. 8 when the pressure in the secondary decompression chamber # 2 is reduced.

The tertiary decompression case portion 28a has the
The secondary decompression case portion 29 has a diameter approximately twice that of the secondary decompression case portion 29, and the lower opening can be opened and closed by the lower cover 39. The lower opening and the lower cover 39 form a large-diameter tertiary diaphragm 38.
Are pinched. The lower cover 39 has a through hole 39a for introducing atmospheric pressure to the side of the tertiary diaphragm 38 opposite to the tertiary decompression chamber # 3. In addition, a gas outlet hole 28c is formed in the tertiary decompression case portion 28a for communicating the tertiary decompression chamber # 3 to the outside, and the gas outlet hole 28c serves as a regulator outlet connection point T1 of the gas fuel passage. The gas outlet hole 28c is connected to the external connecting pipe 7c of the inlet joint 7a.

One end 40a of the arm 40 is connected to the upper end of the tertiary rod 38a fixed to the tertiary diaphragm 38. A tertiary valve body 40c is screwed into the other end 40b of the arm 40 so as to be able to move forward and backward, and a portion adjacent to the tertiary valve body 40c is swingably supported by a pin 40d. The tertiary valve body 40c can open and close the downstream end opening 28d of the valve hole 28b. The third valve body 40
By adjusting the screwing amount of c, the pressure force of the seal rubber 40e to the downstream end opening 28d, that is, the initial seal load can be adjusted. The upstream end opening 28e of the valve hole 28b opens into the secondary decompression chamber # 2.

A stopper piece 40f is bent upward at the other end 40b of the arm 40, and a spring 41 is in contact with the stopper piece 40f. The spring 41 is inserted into the guide hole 42a of the adjusting member 42 screwed into the primary decompression case portion 28a. By adjusting the screwing amount of the adjusting member 42, the clockwise urging force of the arm 40 in FIG. 7 can be adjusted, and thus the load when the tertiary valve body 40c starts to open, that is, the initial load can be adjusted. There is.

Further, a solenoid type driving member 43 is arranged above the tertiary decompression case portion 28a.
This is for keeping the regulator 9 in a shut-off state when the engine is stopped so that it can be operated only when the engine is operating, and the drive rod 43b is retracted by turning on and off the solenoid 43a. When the main switch is turned off, the drive rod 43b protrudes to restrict the counterclockwise rotation of the arm 40, thereby holding the tertiary valve body 40c in the closed state.
When the main switch is turned on, the drive rod 43
b is retracted so that the arm 40 can be rotated.

Next, operation and effect of this embodiment will be described. In the state where fuel has not entered the inside of the regulator 9, the primary valve element 34 and the secondary valve element 36 are open, and the tertiary valve element 40c is closed. Therefore, the high-pressure (20 megapascal) gas fuel from the gas fuel tank 10 enters the primary decompression chamber # 1 through the open valve hole 35a to be decompressed, and also passes through the communication hole 29c to the secondary decompression chamber # 2. It enters and the pressure is further reduced. Primary and secondary decompression chamber # 1, #
When the internal pressure of 2 reaches a predetermined pressure, the primary and secondary valve elements 34 and 36 are closed, so that the internal pressures of the primary and secondary decompression chambers # 1 and # 2 are maintained in a prescribed decompression state.

When the main switch is turned on, the solenoid 4
3a raises the drive rod 43b, and the arm 40 can swing. When the engine is cranked, the intake negative pressure acts on the tertiary decompression chamber # 3 of the regulator 9 from the gas fuel passage connection point T3 through the gas fuel passage 7 and the premixing chamber 8, and the tertiary diaphragm 38 rises to cause the tertiary valve. Body 40c
Opens the valve hole 28b, the gas fuel in the secondary decompression chamber # 2 flows into the tertiary decompression chamber # 3 and is decompressed to substantially atmospheric pressure, and this gas fuel passes through the gas fuel passage 7 and from the intake passage 4. Inhaled by the engine.

When the engine is started and the air-fuel ratio feedback control is started, the air bleed control valve 12 controls the intake pressure and the engine rotation speed until the O ₂ concentration signal b changes to a lean signal when it is a rich signal. It is opened by the specified opening at the specified speed set accordingly,
When the lean signal is replaced, conversely, the specified opening is closed at the specified speed set in the same manner as described above until the O ₂ concentration signal b changes to the rich signal.

When the throttle pedal is not depressed, the throttle valve 20 and the gas fuel control valve 21 are kept at the minimum opening shown in FIG. 2, and the intake negative pressure acting on the gas fuel passage connection point T3 is not changed. It is small, and the gas fuel flow rate is a flow rate according to the throttle valve opening. As the driver depresses the throttle pedal, the opening degree of the throttle valve 20 increases substantially in proportion to the depression amount of the throttle pedal. On the other hand, the opening of the gas fuel control valve 21 is 20
When it reaches about 30%, it is fully opened, and thereafter it is held at the fully opened position (see characteristic curve A in FIG. 3).

In the present embodiment, the distance from the regulator outlet connection point T1 of the gas fuel passage 7 to the bleed air passage connection point T2 is set from the bleed air passage connection point T2 to the connection point T3 to the intake passage 4. Since, in other words, the regulator outlet connection point T1 and the bleed air passage connection point T2 are close to each other, the controllability of the gas fuel flow rate and thus the air-fuel ratio can be improved.

That is, since the regulator outlet connection point T1 and the bleed air connection point T2 are close to each other, the intake negative pressures in both are substantially equal, and the intake negative pressure at the gas fuel passage connection point T3 to the intake passage 4 is also equal. And the intake negative pressure at the regulator outlet connection point T1 can be maintained in a proportional relationship, whereby the required fuel flow rate can be accurately ensured even if the engine speed changes. Since the gas fuel flow rate can be secured with high accuracy in this manner, the target opening degree of the air bleed control valve 12 for securing the required air-fuel ratio does not change significantly. Therefore, the problem that the stepping motor or the like cannot follow the speed of change of the target opening can be solved, and as a result, the controllability of the air-fuel ratio can be improved.

Since the premixing chamber 8 having a large volume is provided on the downstream side of the bleed air passage connecting point T2 of the gas fuel passage 7, the regulator 9 for the intake pulsation generated by the engine and the air bleed control valve 12 are provided.
It is possible to mitigate the propagation to the side, prevent the intake pulsation from causing a resonance phenomenon due to the natural frequency of the diaphragm that constitutes the decompression chamber in the regulator, and not being able to supply the required amount of fuel, and reaching the intake passage. By so doing, the mixing of the gas fuel and the bleed air can be promoted, and from this point as well, the flow rate of the gas fuel can be more accurately secured, and the controllability of the air-fuel ratio can be improved.

Furthermore, since the gas fuel control valve 21 is arranged upstream of the gas fuel passage connection point T3 of the intake passage 4 and the opening thereof is changed according to the operating state of the engine, the gas fuel passage The intake negative pressure acting on the connection point can be controlled. For example, in the operating range where the opening of the throttle valve 20 is small, the gas fuel control valve 2
By reducing the opening of No. 1, the gas fuel passage connection point T
An intake negative pressure can be generated at 3, and the fuel flow rate can be reliably controlled by this intake negative pressure.

Therefore, the main venturi portion 19 can be omitted. When the main venturi portion is eliminated, there is no throttle loss of the intake air amount due to the main venturi portion, and high output can be obtained.

Further, the gas fuel control valve 2
1 and the throttle valve 20 are connected by the link mechanism 22 that fully opens the gas fuel control valve 21 before the throttle valve 20 is fully opened. Therefore, the fuel control valve 21 has a simple structure.
It is possible to prevent the gas fuel control valve 21 from becoming a resistance of the intake air in the medium / high load operation range where the throttle valve opening becomes large and the throttle valve opening becomes large.

FIG. 12 shows a fixed venturi according to a second embodiment of the invention of claim 5. The fixed venturi 44 of this embodiment is made of a pipe material (annular portion) having an annular header hole 44a, and the gas fuel passage 7 is connected to the header hole 44a. A portion of the fixed venturi 44 facing the intake passage 4 is formed in an arc shape, and the header hole 4
It has a large number of small holes 44b for communicating 4a with the intake passage 4. A slit may be provided instead of the large number of small holes.

In this embodiment, the fixed venturi portion 44 having a large number of small holes 44b for communicating the annular header hole 44a with the intake passage 4 is provided upstream of the throttle valve 20 in the intake passage 4, so The fuel can be uniformly supplied into the intake passage 4, and the gas fuel and the air can be reliably mixed.

FIG. 13 shows a fixed venturi according to a modification of the second embodiment. In this fixed venturi 46, an annular body 46c is mounted in the intake passage 4 and a gap between the two is formed as an annular header hole 46a. Also, this header hole 46a
The gas fuel passage 7 is connected to. A portion of the fixed venturi 46 facing the intake passage 4 is formed in an arc shape, and the header hole 46a communicates with the intake passage 4 through a slit 46b. Also in this modified example, the same operational effect as in the case of FIG. 12 can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a gas fuel supply device according to a first embodiment of the inventions of claims 1 to 4.

FIG. 2 is a schematic configuration diagram of a gas mixer portion of the above embodiment.

FIG. 3 is a characteristic diagram showing the relationship between the throttle valve opening and the gas fuel control valve opening in the above embodiment.

FIG. 4 is a sectional side view of an air bleed control valve and a premix chamber of the above embodiment.

FIG. 5 is a plan view of an air bleed control valve and a premix chamber of the above embodiment.

FIG. 6 is a front view of an air bleed control valve and a premix chamber of the above embodiment.

FIG. 7 is a sectional front view of the regulator according to the embodiment.

FIG. 8 is a sectional front view of the regulator according to the embodiment.

FIG. 9 is a bottom view of the regulator according to the above embodiment.

FIG. 10 is a sectional front view of a tertiary valve body portion of the regulator of the above embodiment.

FIG. 11 is a bottom view of the secondary decompression chamber of the regulator of the above embodiment.

FIG. 12 is a sectional side view of the fixed venturi of the second embodiment according to the invention of claim 5;

FIG. 13 is a sectional side view of a fixed venturi according to a modified example of the second embodiment.

FIG. 14 is a schematic configuration diagram of a conventional gas fuel supply device.

[Explanation of symbols]

1 engine 4 Intake passage 7 gas fuel passage 8 premix room 9 regulator 10 Gas fuel tank (supply source) 11 Bleed air passage 12 Air bleed control valve 20 Throttle valve 21 Gas fuel control valve 22 Link mechanism 44,46 Fixed Venturi 44a, 46a Header hole 44b small hole 46b slit T1 regulator outlet connection point T2 bleed air passage connection point Connection point to T3 intake passage

Claims (5)

[Claims] 1. A gas fuel passage is connected upstream of a throttle valve of an intake passage connected to an engine, and the gas fuel passage is connected to a gas fuel supply source via a gas pressure adjusting regulator. In a gas fuel supply system for an engine, wherein a bleed air passage is connected in the middle of the passage and an air bleed control valve for controlling the area of the bleed air passage is provided, the bleed air passage from the regulator outlet connection point of the gas fuel passage. A gas fuel supply system for an engine, wherein a distance to the connection point is set shorter than a distance from the connection point of the bleed air passage to the connection point to the intake passage. 2. The premixing system according to claim 1, wherein the propagation of intake pulsation generated by the engine is reduced downstream of the connection point of the bleed air passage of the gas fuel passage and the mixing of the gas fuel and the bleed air is promoted. A gas fuel supply system for an engine, characterized in that a chamber is provided. 3. The gas fuel control valve according to claim 1, wherein a gas fuel control valve for controlling the opening and closing of the intake passage is provided upstream of the gas fuel passage connection point of the intake passage, and the opening of the gas fuel control valve is set to the engine opening. A gas fuel supply device for an engine, which is changed according to an operating state. 4. The gas fuel control valve according to claim 3, wherein the gas fuel control valve and the throttle valve are connected by a link mechanism that fully opens the gas fuel control valve before the throttle valve is fully opened. The engine gas fuel supply device. 5. The fixed venturi according to claim 1 or 2, wherein a fixed venturi for reducing the intake passage area is arranged upstream of the throttle valve in the intake passage, and the fixed venturi has an annular portion having an annular header hole. A gas fuel supply device for an engine, wherein the header hole has a plurality of slits or a plurality of small holes that communicate with the inside of the intake passage, and the gas fuel passage communicates with the header hole.