JP2000303937A - Low pressure fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low pressure fuel injection device to have high fuel controllability and excellent atomizing characteristics. SOLUTION: In the low opening area of a throttle valve T wherein opening and closing of an intake passage 2 are controlled by a butterfly type throttle valve T, bypass holes B and P extending from a bypass chamber 13 are formed fronting on the outer peripheral end T1 of the throttle valve T. A negative pressure operation valve P is situated at the venturi part V of the intake passage 2 and the venturi part V is variably controlled. At the venturi part V, a nozzle 9 having a bleed hole 9B is opened, an annular well 10 is formed on the outer periphery of the nozzle 9, the annular well 10 and the atmosphere are intercommunicated through a main air passage 12, and the annular well 10 and the bypass chamber are intercommunicated through a low speed passage 13. This constitution boosts fuel in a fuel tank N by a fuel pump S and regulates a fuel pressure to a value lower than 0.8 kg/cm2 by a pressure control valve R, and feed fuel toward the nozzle 9 through a side feed type fuel injection valve J situated approximately in the horizontal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for supplying regulated fuel to an engine.

[0002]

2. Description of the Related Art Conventional fuel supply systems include a carburetor system and a feedback system. The carburetor system is a slow system that covers the fuel supply area when the throttle valve is low opening, a main system that covers the fuel supply area when the throttle valve is high opening, and also supplies the starting fuel when the engine is started. Starting system, and three independent fuel systems. In the feedback system, an actuator (for example, an electromagnetic proportional control valve) is provided in the slow system, the main system, and the starting system of the carburetor system, and a signal from the 02 sensor is output according to the combustion state of the engine. Is controlled by

[0003]

According to the conventional carburetor system, the fuel supply characteristics to the engine are slow system, main system,
This is done by adapting the three systems of the starting system and balancing them. Where 3
When one of the systems is changed, it is necessary to carry out a retest in order to balance with another system, and it is not possible to expect improvement in development efficiency. Further, in order to reduce the harmful exhaust gas components discharged from the engine, it is necessary to improve the manufacturing accuracy of each component constituting the vaporizer. And smooth connection between slow system and main system. is necessary. Further, in order to smoothly connect the slow system and the main system, it is necessary to newly provide a secondary system, which increases the manufacturing cost.

On the other hand, according to the feedback system, fuel control and air control can be performed in accordance with the combustion state of the engine. According to this, an appropriate mixture can be supplied. However, since an actuator is required for at least the slow system and the main system, the number of parts increases, and an increase in manufacturing cost cannot be suppressed.

[0005] The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to accurately supply an appropriate fuel. Improve the atomization characteristics of fuel. Improve development efficiency. It is an object of the present invention to provide an inexpensive low-pressure fuel injection device that can be used.

[0006]

According to the low pressure fuel injection device of the present invention, in order to achieve the above object, a butterfly type throttle valve for opening and closing an intake passage and a venturi portion upstream of the throttle valve are provided. A negative pressure actuating valve that variably controls the area of the venturi section according to the generated negative pressure, an annular air chamber heading toward the venturi section, and at the time of a low opening of the throttle valve, facing the outer peripheral end of the throttle valve, from the bypass chamber A throttle body including a bypass hole that opens into the intake passage, a main air passage that communicates the annular air chamber with the atmosphere, a low-speed passage that communicates the annular air chamber with the bypass chamber, and a throttle body disposed in the annular air chamber. A nozzle having an open end at the venturi portion and having a bleed hole forming an annular well between the nozzle and the annular air chamber; receiving a supply of fuel from the side surface; And a side-feed type fuel injection valve whose longitudinal axis is arranged in a substantially horizontal direction, the pressure in the fuel tank is increased by a fuel pump, and the pressure is controlled by a pressure control valve. / Cm ²
A first feature is that the fuel pressure is adjusted to the following fuel pressure, and the adjusted fuel is supplied to the side-feed type fuel injection valve through a flow passage formed in the throttle body.

According to a second aspect of the present invention, in addition to the first aspect, the fuel injected from the side-feed type fuel injection valve is supplied into an inner flow passage of the nozzle. .

[0008] In addition to the first feature, the present invention is characterized in that fuel injected from the side-feed type fuel injection valve is supplied into the annular well.

Further, in addition to the second and third features, the present invention further comprises an injection hole of the side-feed type fuel injection valve,
The fourth feature is that the side feed type fuel injection valve itself is opened at the lowest position in the direction of gravity.

In a fifth aspect of the present invention, in addition to the first aspect, the fuel pump is a negative pressure operated diaphragm pump and is disposed below the fuel tank in the direction of gravity.

Further, according to the present invention, in addition to the first feature, the sixth feature is that the pressure control valve is disposed at a position higher than the side feed type fuel injection valve in the direction of gravity.

Furthermore, the present invention provides, in addition to the sixth feature,
A seventh feature is that a fuel flow path connecting the pressure control valve and the side-feed type fuel injection valve has a diameter of 5 mm or more.

[0013]

According to the first feature, during each operation of the engine, the side feed type fuel injection valve has a capacity of 0.8 kg / c.
Low-pressure fuel of m ² or less is supplied, and appropriate fuel is controlled and supplied to the nozzle via a side-feed type fuel injection valve. On the other hand, the fuel in the nozzle is satisfactorily mixed with the air, and a good air-fuel mixture is sucked into the intake passage from the bypass hole or the nozzle according to the operation state of the engine. On the other hand, the negative pressure of the venturi portion in the intake passage is appropriately maintained during the intermediate opening of the throttle valve and the full-open low-speed operation, so that the air-fuel mixture sufficiently mixed from the nozzle is sucked into the intake passage. Also, even when the throttle valve of the butterfly type is suddenly opened, such as during rapid acceleration operation of the engine, the decrease in the negative pressure in the venturi section is suppressed by the negative pressure operated valve in the venturi section, that is, the automatically operated valve by the negative pressure. A sufficient mixture can be supplied from the nozzle.

According to a second feature, the side feed type fuel injection valve has a flow rate of 0.8 kg / c in the inner flow path of the nozzle.
fuel having a fuel pressure of less than m ² is directly injected,
Air is mixed with this fuel through the bleed hole. According to this, the flowability of the air-fuel mixture from the nozzle toward the venturi section and the bypass hole is improved. Further, the fuel supply characteristics during the acceleration operation of the engine can be improved.

According to a third feature, fuel is injected from the side-feed type fuel injection valve into the annular well. According to this, the fuel pressure supplied to the side-feed type fuel injection valve is 0.8 kg / kg. Even when the pressure rises above cm ² , the fuel flows into the inner flow path of the nozzle through the bleed hole, so that the fuel does not needlessly jet from the nozzle.

According to the fourth feature, the injection hole from which the side-feed type fuel injection valve injects fuel is opened at a position below the side-feed type fuel injection valve itself in the direction of gravity. There is no accumulation near the injection hole.

According to the fifth feature, the use of a negative pressure operated diaphragm pump as the fuel pump can reduce the manufacturing cost as compared with the electric fuel pump and the mechanical fuel pump, and can reduce the manufacturing cost. The pump performance can be favorably maintained by arranging the negative-pressure operated fuel pump below.

According to the sixth feature, since the pressure control valve is disposed above the side-feed type fuel injection valve, the pressure control valve exists in the fuel flow path between the pressure control valve and the side-feed type fuel injection valve. All of the generated air moves toward the pressure control valve, and this air is discharged into the fuel tank via the return passage of the pressure control valve.

Further, according to a seventh feature, the air present in the fuel flow path between the pressure control valve and the side feed type fuel injection valve has a flow path diameter of 5 mm or more, so that fuel and air , And air is discharged into the fuel tank via the pressure control valve.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a low-pressure fuel injection device according to the present invention will be described below with reference to FIG. Reference numeral 1 denotes a throttle body through which an intake passage 2 penetrates. The intake passage is opened and closed by a butterfly type throttle valve T attached to a throttle valve shaft 3 rotatably supported by the throttle body 1. Further, a venturi portion V having a reduced diameter is formed in an intake passage on the upstream side (right side in the figure) of the throttle valve T, and a negative pressure actuated valve for variably controlling the effective venturi area of the venturi portion V is formed. P is arranged. The above-mentioned venturi portion V is formed by the bottom of the negative pressure operated valve P and the intake passage 2 opposed thereto.
It is slidably disposed in the negative pressure actuated valve guide cylinder 4 which is connected to the upper opening. An umbrella-shaped diaphragm 5 is fixed to the upper end of the negative pressure actuated valve P, and the annular circumferential portion of the diaphragm 5 is formed by a flange 1A of the throttle body 1 and a cover 6 covering the same. Be pinched. An atmosphere chamber A is formed by the lower surface of the diaphragm 5 and the throttle body recess 1B facing the lower surface, and a pressure receiving chamber B is formed by the upper surface of the diaphragm 5 and the cover 6. The atmosphere chamber A and the pressure receiving chamber B are separated by the diaphragm 5, and the atmosphere chamber A is communicated with the atmosphere by an opening 1C, and the pressure receiving chamber B is a negative pressure introducing hole in which the bottom of the negative pressure operating valve P is formed. P1 communicates with the venturi section V. Reference numeral 7 denotes a spring contracted in the pressure receiving chamber B, one end of which is locked by the negative pressure operating valve P, and the other end of which is locked by the cover 6. Further, even when the negative pressure operated valve P descends most, the negative pressure operated valve P does not completely close the venturi portion V.

Reference numeral 8 denotes an annular air chamber heading toward the venturi section V, and a nozzle 9 is disposed in the annular air chamber. The nozzle 9 has a pipe shape, and its inner flow path 9A opens toward the venturi portion V, and a plurality of bleed holes 9B are formed from the outer periphery of the nozzle 9 into the inner flow path 9A. An annular well 10 is formed by the annular air chamber 8 and the outer periphery of the nozzle 9. Since the nozzle 9 is arranged to extend in the longitudinal direction, the annular air chamber is also formed to extend in the longitudinal direction.

BP is a bypass hole which is formed facing the outer peripheral end T1 of the throttle valve T when the throttle valve T is at a low opening degree (idling opening degree, off-idle opening degree). It opens into the intake path 2 from the bypass chamber 11. In this example, three bypass holes are formed, and the first bypass hole BP1 and the second bypass hole BP are arranged from the engine side.
2, referred to as a third bypass hole BP3.

Further, the following flow paths are formed in the throttle body 1. Reference numeral 12 denotes a main air passage which communicates the atmosphere with the annular well 10, and reference numeral 13 denotes a low speed passage which communicates the annular well 10 and the bypass chamber 11.

J is a well-known side-feed type fuel injection valve. A fuel inlet J1 is opened on the side surface and an injection hole J2 is opened on the tip. The longitudinal axis XX of the side-feed type fuel injection valve J is disposed substantially in the horizontal direction, and is fixedly disposed in the injection valve support hole 1 </ b> D of the throttle body 1. A flow path 1E formed in the throttle body 1 is opened toward the fuel inlet J1 of the side-feed type fuel injection valve J, and an injection hole J2 at the tip is opened below the nozzle 9.

The fuel is supplied to the fuel injection valve J as follows. N is a fuel tank. The fuel in the fuel tank N is pressurized by the fuel pump S, and the pressurized fuel is supplied to the pressure control valve R by 0.8 kg / cm.
² (the fuel pressure of 0.8 kg / cm ² or less is referred to as low-pressure fuel) and is supplied to the side-feed type fuel injection valve J through the flow path 1E of the throttle body 1 and the fuel inlet J1. Is done. Side feed type fuel injection valve J
The fuel injected from the ECU is controlled by a signal from an ECU (not shown), and the side-feed type fuel injection valve J injects an appropriate fuel according to an output signal from the ECU according to each operation of the engine. Here, the fuel pressure is 0.8 kg
/ Cm ² or less means that during each operation of the engine,
This is because fuel can be sucked into the intake passage 2 and the venturi portion V by utilizing the negative pressure applied to the bypass hole BP and the nozzle 9. In other words, when the fuel pressure rises above 0.8 kg / cm ² , the fuel is ejected into the intake passage 2 with its own direct impact without being affected by the negative pressure.

The pressure control valve R is of a known type, and is divided into a spring chamber 21 and a fuel chamber 22 by a diaphragm 20, and a fuel passage 23 and a return passage 24 are opened in the fuel chamber 22. . The fuel flow path 23 is connected to a flow path 25 that connects the fuel pump S and the fuel injection valve J,
The return passage 24 is connected to the fuel tank N. The return passage 24 is opened and closed by a valve 26 which moves synchronously with the diaphragm 20. That is, when the fuel pressure in the fuel chamber 22 rises above the set pressure, the diaphragm 20 is displaced toward the spring chamber 21 and the valve 26 opens the return passage 24, and the fuel in the fuel chamber 22 and the return passage 24 released into the fuel tank T via, thereby controlling the fuel pressure in the fuel chamber 22 to 0.8 kg / cm ² or less of the predetermined fuel pressure, the fuel having a fuel pressure in the 0.8 kg / cm ² or less Is supplied to the side-feed type fuel injection valve J. Reference numeral 27 denotes a negative pressure introduction passage communicating with the spring chamber 21 and an intake pipe (not shown).

Next, the operation will be described. First, the engine idling operation will be described. An appropriate low-pressure fuel according to the idling operation is supplied from the side-feed type fuel injection valve J into the inner flow passage 9A through the lower end of the nozzle 9. On the other hand, the throttle valve T is held at the idling opening degree where the intake path 2 is most closed, and at this time, the first bypass hole BP1 downstream of the throttle valve T
, A large negative pressure in the intake passage 2 downstream of the throttle valve T acts, and a large negative pressure does not act on the second bypass BP2 and the third bypass hole BP3 located upstream of the throttle valve T. Further, in the venturi portion V, since the intake path 2 is closed and held at the idling opening, no large negative pressure occurs, and no large negative pressure acts on the opening of the nozzle 9. Accordingly, a large negative pressure in the intake passage 2 downstream of the throttle valve T acts on the bypass chamber 11 via the first bypass hole BP1, and the negative pressure in the bypass chamber 11
It acts on the annular well 10 and the main air passage 12. According to the above description, the air flow from the main air passage 12 to the annular well 10, the air flow from the annular well 10 to the bypass chamber 11 via the low-speed passage 13, the second bypass hole BP <b> 2 upstream of the throttle valve, An air flow is generated from the third bypass hole BP3 toward the bypass chamber 11. On the other hand, as described above, low-pressure fuel of 0.8 kg / cm ² or less, which is suitable for idling operation, is supplied from the side-feed type fuel injection valve J to the inner passage 9A of the nozzle 9. The fuel in the inner flow passage 9A is sucked into the annular well 10 through the bleed hole 9A. At this time, the fuel is mixed well with the air by the bleed hole 9A.
The mixture of fuel and air is supplied to the annular well 1
0, bypass chamber 1 in a negative pressure state through low-speed passage 13
Then, the air-fuel mixture in the bypass chamber 11 is sucked into the intake passage 2 through the first bypass hole BP1, and a good engine idling operation can be performed. During the idling operation, since the large negative pressure in the intake passage 2 does not act on the second bypass hole BP2 and the third bypass hole BP3 as described above, the second bypass hole BP2,
The air-fuel mixture in the bypass chamber 11 is not sucked out from the third bypass hole BP3, and the air-fuel mixture is not sucked out from the nozzle 9 to the venturi portion V. It is sucked into the intake passage 2 through the hole BP1.

The off-idling operation in which the throttle valve T is slightly opened from the idling operation will be described. An appropriate low-pressure fuel according to the off-idling operation is supplied from the side-feed type fuel injection valve J into the inner flow path 9A of the nozzle 9. On the other hand, the throttle valve T is held slightly open from the idling opening, and at this time, the first bypass hole BP1, the second bypass hole BP2, and the third bypass hole BP3 are all located downstream of the throttle valve T. And the first, second, third, bypass holes BP1,
A large negative pressure in the intake passage 2 acts on BP2 and BP3. On the other hand, in the venturi portion V, although the intake passage 2 is slightly opened from the idling opening, no large negative pressure is generated, and no large negative pressure acts on the nozzle 9. According to the above description, the negative pressure that is larger than that at the time of the idling opening acts in the bypass chamber 11, and the fuel that is injected from the side-feed type fuel injection valve J according to the off-idling operation is the same as described above. Bleed hole 9B
And the air-fuel mixture is sucked into the bypass chamber 11. Then, the air-fuel mixture in the bypass chamber 11
The intake air is sucked into the intake passage 2 from the bypass hole BP1, the second bypass hole BP2, and the third bypass hole BP3, so that good off-idling operation of the engine can be performed.

Next, a description will be given of an intermediate opening operation in which the throttle valve T is opened further than the off-idling operation. An appropriate low-pressure fuel according to the intermediate opening operation is supplied from the side feed type fuel injection valve J into the inner flow passage 9A of the nozzle 9. The throttle valve T is maintained at the intermediate opening, and the negative pressure in the intake passage 2 acts on the first to third bypass holes BP1, BP2, and BP3 located downstream and relatively close to the throttle valve T. I do. On the other hand, in the venturi section V, the throttle valve T is opened to the intermediate opening to generate an air flow, thereby generating a negative pressure. As the area increases, the negative pressure of the venturi portion V acts on the nozzle 9. According to the above description, the negative pressure in the intake passage 2 acts on the bypass chamber 11 through the first to third bypass holes BP1, BP2, and BP3, while the venturi portion V
Negative pressure acts. According to the above description, a part of the fuel injected into the inner flow passage 9A of the nozzle 9 and suitable for the intermediate opening operation by the side feed type fuel injection valve J is partly the bleed hole 9B, the annular well 10, and the low speed passage 13 To the bypass chamber 11, and then the first to third bypass holes BP
1, BP2, and BP3 are sucked into the intake passage 2 and supplied to the engine. On the other hand, the other part of the fuel is sucked into the venturi section V from the opening at the tip of the nozzle 9 via the inner flow path 9A. In the fuel flow, the bypass chamber 11
The air-fuel mixture heading toward
The fuel mixed well when flowing into the inside, while flowing through the inner flow passage 9A of the nozzle 9, is favorably mixed with air by the air flowing into the inner flow passage 9A from the annular well 10 through the bleed hole 9B. Mixed. Therefore, a good air-fuel mixture can be supplied, so that a good engine intermediate opening operation can be achieved.

Further, a description will be given of a high opening operation in which the throttle valve T is opened further than the intermediate opening operation. An appropriate low-pressure fuel according to the high opening operation is supplied from the side feed type fuel injection valve J into the inner flow path 9A of the nozzle 9. When the throttle valve T is held at a high opening, the throttle valve T
First to third bypass holes BP located farther apart
Negative pressure in the intake passage 2 does not greatly act on 1, BP2 and BP3. On the other hand, in the venturi section V, the throttle valve T
Is opened at a high opening, a large air flow is generated, and a large negative pressure is generated. In response to this negative pressure, the negative pressure actuating valve P further increases the area of the venturi portion V and causes the nozzle 9 to ventilate. A large negative pressure in the part V acts.
According to the above, in the bypass chamber 11, the inner flow path 9A of the nozzle 9, the bleed hole 9B, the annular well 10, the low-speed passage 13
, A negative pressure in the venturi portion V acts on the inner flow passage 9A of the nozzle 9, and a negative pressure in the venturi portion V acts on the inner flow passage 9A of the nozzle 9. According to the above, the fuel injected into the inner flow passage 9A of the nozzle 9 and suitable for the high opening degree operation from the nozzle 9 to the venturi portion V through the inner flow passage 9A by the side-feed type fuel injection valve J. Sucked out. Air is supplied from the annular well 10 through the bleed hole 9B to the fuel in the inner flow passage 9A sucked from the tip of the nozzle 9, and air and fuel are supplied through the inner flow passage 9A. And Venturi V
, So that good high-opening operation of the engine can be achieved. In the above description, the annular chamber well 10 has the low-speed passage 1 through the first to third bypass holes BP1, BP2, BP3.
The air is supplied through the main air passage 12 and the air is supplied through the main air passage 3.

During the acceleration operation of the engine, the throttle valve T is opened from a low opening state to a high opening state at a stretch. At this time, the negative pressure operated valve P is opened when the throttle valve T is opened. After the negative pressure of the venturi section V increases, the area of the venturi section V is increased. According to this, since a decrease in the negative pressure applied to the nozzle 9 can be suppressed, the accelerated fuel increased from the side-feed type fuel injection valve J can be smoothly sucked into the venturi portion V, whereby a good acceleration operation can be obtained. Further, in this state, air can be supplied from the bleed hole 9B into the inner flow path 9A, whereby the mixing property between fuel and air can be improved, which also leads to an improvement in acceleration operation.

According to the above embodiment, the fuel injected from the fuel injection valve is supplied into the inner flow passage 9A of the nozzle 9, and the straightness of the fuel in the inner flow passage 9A of the nozzle 9 is improved. The responsiveness of the fuel supply during the acceleration operation of the engine can be increased. The fuel flowing toward the low-speed passage 13 is supplied from the inner flow path 9A of the nozzle 9 through the bleed hole 9B. When the fuel passes through the bleed hole 9B, the fuel is finely atomized and the annular well is formed. A favorable air-fuel mixture is formed in the engine 10 and a smoother low-speed operation of the engine can be obtained by the air-fuel mixture supplied from the bypass hole BP. Further, since the longitudinal axis XX of the side-feed type fuel injection valve J is arranged in a substantially horizontal direction, it is effective in shortening the height direction of the throttle body 1, and the arrangement space in the vertical direction is particularly limited. Mountability on a two-wheeled vehicle. or,
According to the use of the side-feed type fuel injection valve, the fuel injection valve is disposed in the injection valve support hole 1D of the throttle body 1 and the side-feed type fuel injection is performed through the flow path 1E formed in the throttle body 1. Since the fuel can be supplied to the fuel inlet J1 formed in the side of the valve J, the fuel can be easily connected to the fuel injection valve.

Further, the fuel pump S can be a negative pressure operated diaphragm pump. That is, the diaphragm 30 is sandwiched between the casing 31 and the cover 32 to form the fuel chamber 33 on the casing 31 side and the pump chamber 34 on the cover 32 side. In the fuel chamber 33, a suction passage 36 having a suction-side check valve 35 and a discharge passage 38 having a discharge-side check valve 37 are opened. The suction passage 36 is connected to the fuel tank T. Pump room 34
A pulsating pressure generated in the engine is introduced through the pulse passage 39 into the pump. Since the negative pressure operated diaphragm pump is known, the description of the pump operation is omitted. And, by arranging such a negative pressure operated diaphragm pump at a position below the fuel tank N in the direction of gravity, the adoption thereof is made possible. That is, according to the arrangement of the negative pressure operated diaphragm pump at the lower position, the fuel can be stored in the suction passage 36 by the difference in the fuel head in the fuel tank N when the engine is stopped. The pump function can be performed immediately, and there is no time delay in the fuel supply from the fuel pump S to the fuel injection valve J. If the negative pressure operated diaphragm pump is arranged above the fuel tank N, it is necessary to first suck the fuel into the suction passage 36 when the engine is started. According to the above, a negative pressure operated diaphragm pump can be adopted. The structure is simpler than that of an electric fuel pump or a mechanical fuel pump, and there is no need to use electricity for driving the fuel pump. In addition, since a complicated mechanical drive unit is not required, it is particularly effective in a fuel pump for a motorcycle.

The pressure control valve R is also known,
By arranging such a pressure control valve R at a position above the fuel injection valve J in the direction of gravity (not shown), the following effects are obtained. (In the example shown in FIG. 1, the pressure control valve R is disposed below the fuel injection valve J.)
That is, air bubbles are generated in the flow path 25 connecting the fuel pump S and the fuel injection valve J during the operation of the engine. However, the pressure control valve R is disposed at a position higher than the fuel injection valve J. According to the above, the air bubbles in the flow path 25 are apt to flow into the pressure control valve R due to the buoyancy of the air bubbles, while the air bubbles flowing into the pressure control valve R are generated by the pressure control valve R
The fuel is not discharged into the fuel tank N via the return passage 24 together with the return fuel discharged at the fuel pressure without stagnation. Therefore, the fuel injection valve T
The fuel more suitable for the operation can be supplied to the nozzle 9.

Further, in the above, if the diameter of the fuel passage 23 connecting the fuel injection valve J and the pressure control valve R is 5 mm or more, the separation of fuel and air bubbles in the fuel passage is performed well. In addition, the bubbles are easily converged toward the pressure control valve R located at the upper position, so that the discharging property of the bubbles can be further improved.

Further, according to the fact that the injection hole J2 of the guide feed type fuel injection valve J is opened toward the inside of the annular well 10, the fuel injected from the injection hole J2 (not shown) is formed in the annular well 10. The mixture with the air supplied from the main air passage 12 is directly mixed with the air supplied from the low speed passage 13.
Is supplied to the bypass chamber 11, which is effective in increasing the responsiveness of the air-fuel mixture sucked out of the bypass hole.
Further, the fuel pressure injected from the fuel injection valve is 0.8 kg /
Even when the pressure exceeds cm ² , the fuel flows into the inner flow path of the nozzle through the bleed hole, so that unnecessary fuel does not flow out of the nozzle toward the venturi.

In the above, the injection hole J2 is the fuel injection valve J
According to being located at the lowest position in the direction of gravity of itself, when the engine is stopped, fuel does not accumulate near the injection hole J2, so that when the engine is not used for a long time, Deteriorated fuel does not adhere to the injection hole J2, and foreign matter does not adhere.

[0038]

As described above, according to the first aspect of the present invention, an appropriate low-pressure fuel suitable for the operating state of the engine is supplied from the side-feed type fuel injection valve to the nozzle.
This fuel is mixed with air to form an air-fuel mixture, and this air-fuel mixture is sucked into the intake passage or the venturi by the negative pressure applied to the bypass hole or the nozzle, so that the air-fuel mixture with particularly excellent atomization properties can be supplied. It is more effective in improving the operability of the engine and reducing harmful exhaust gas components. In addition, according to the fact that the fuel is controlled by the side-feed type fuel injection valve, even if the fuel is changed at each throttle valve opening, the fuel control at other openings is not affected at all. Effective development can be performed. or,
The fuel pressure injected from the side-feed type fuel injection valve is set to a low pressure of 0.8 kg / cm ² or less, so that the mixing property between the fuel and air in the throttle body can be improved, and the atomization property is excellent. This is convenient for supplying an air-fuel mixture. Further, by reducing the fuel pressure, the pressure resistance of components such as the fuel pipe can be reduced, and the manufacturing cost can be reduced. In addition, according to the use of the negative pressure actuating valve, particularly during acceleration operation and full-open low speed operation, it is possible to appropriately control the negative pressure of the venturi portion and to suppress a decrease in pressure applied to the nozzle, thereby obtaining a good operation. Can be Furthermore,
By arranging the longitudinal axis of the side-feed type fuel injection valve in a substantially horizontal direction, the overall height of the throttle body can be reduced. Further, according to the use of the side feed type as the fuel injection valve, the support of the fuel injection valve and the supply connection of the fuel can be easily performed.

According to the second aspect of the present invention, since the straightness of the fuel injected from the side-feed type fuel injection valve in the nozzle can be enhanced, particularly when the engine is rapidly accelerated, the engine is fully opened. This is effective in increasing the fuel responsiveness during low-speed operation.

According to the third aspect of the present invention, the fuel pressure injected from the fuel injector is 0.8 kg / kg.
Even when cm ² is exceeded, unnecessary fuel does not flow out of the nozzle toward the venturi section. Further, the fuel is mixed with the air in the annular well, and the mixed fuel is supplied from the low-speed passage to the bypass chamber, so that the responsiveness of the air-fuel mixture from the bypass hole can be improved.

According to the fourth aspect of the present invention, when the engine is stopped, fuel does not accumulate in the vicinity of the injection hole of the side-feed type fuel injection valve. Good fuel controllability can be maintained.

According to the fifth aspect of the present invention, the negative pressure-operated diaphragm pump is disposed below the fuel tank. An operation type diaphragm pump can be used. According to this, an inexpensive fuel pump can be used, and the degree of freedom of arrangement of the fuel pump can be increased.

Further, according to the sixth aspect of the present invention, the bubbles in the flow passage connected to the side-feed type fuel injection valve can be effectively discharged through the return passage of the pressure control valve. In this manner, the supply of fuel can be performed, and the operability of the engine can be greatly improved.

Further, according to the seventh feature of the present invention, the bubbles contained in the fuel flowing in the fuel flow path are completely separated into the fuel and the bubbles in the fuel flow path, and the bubbles are subjected to pressure control. Since the fuel is discharged through the return passage of the valve, the fuel can be supplied more stably.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a low-pressure fuel injection device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Throttle body 2 Intake path 8 Annular well 9 Nozzle 9A Inner flow path 9B Bleed hole 12 Main air path 13 Low speed path T Throttle valve P Negative pressure operated valve BP Bypass hole J Side feed type fuel injection valve N Fuel tank S Fuel pump R pressure control valve

Claims (7)

[Claims] 1. A butterfly type throttle valve T for opening and closing an intake passage 2, and a negative pressure actuating valve variably controlling an area of the venturi portion V in accordance with a negative pressure generated in a venturi portion V upstream of the throttle valve T. P, an annular air chamber 10 heading to the venturi portion V, and a bypass hole BP facing the outer peripheral end T1 of the throttle valve T and opening from the bypass chamber 11 into the intake passage 2 when the throttle valve T is at a low opening degree. A throttle body 1 having a main air passage 12 communicating the annular air chamber 8 with the atmosphere, a low speed passage 13 communicating the annular air chamber 8 with the bypass chamber 11, and disposed in the annular air chamber 8. A nozzle 9 having one end open to the venturi portion V and having a bleed hole 9B forming an annular well 10 between the nozzle 9 and the annular air chamber 8; Spout And a side-feed type fuel injection valve J whose longitudinal axis is arranged in a substantially horizontal direction. The pressure in the fuel tank N is increased by the fuel pump S, and the pressure in the pressure control valve R is increased. 0.8kg /
A low-pressure fuel injection device, wherein the fuel pressure is adjusted to a fuel pressure of ² cm ² or less, and the adjusted fuel is supplied to the side-feed type fuel injection valve through a flow passage formed in a throttle body. 2. The low-pressure fuel injection device according to claim 1, wherein fuel injected from the side-feed type fuel injection valve is supplied into an inner flow passage 9A of a nozzle 9. 3. The low-pressure fuel injection device according to claim 1, wherein fuel injected from the side-feed type fuel injection valve is supplied into the annular well. 4. The side feed type fuel injection valve according to claim 2, wherein the injection hole J2 of the side feed type fuel injection valve is opened at the lowest position in the gravity direction of the side feed type fuel injection valve J itself. Low pressure fuel injector. 5. The low-pressure fuel injection device according to claim 1, wherein the fuel pump is a negative-pressure operated diaphragm pump and is disposed below the fuel tank N in the direction of gravity. 6. The low-pressure fuel injection device according to claim 1, wherein the pressure control valve is disposed above the side-feed type fuel injection valve J in the direction of gravity. 7. The low-pressure fuel injection device according to claim 6, wherein a fuel passage 25 connecting the pressure control valve and the side-feed type fuel injection valve J has a diameter of 5 mm or more.