JPH09217656A - Fuel supply device of supercharging engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of carrying out stable fuel supply around the whole rotating region concerning a fuel supply device of a supercharging engine. SOLUTION: A venturi part 103a having a fuel discharge port 110a is interposed on the middle of an intake air passage to communicate a supercharging means and a combustion chamber to each other, the fuel discharge port 110a and a float chamber 102 (fuel reservoir part) are communicated to each other by a fuel supply passage, and fuel is supplied to the venturi part 103a by differential pressure of pressure on the fuel reservoir part side and pressure on the side of the fuel discharge port. A part between the supercharging means and the venturi part 103a or a part in the downstream of the venturi part 103a and in the neighbourhood of the venturi part 103a and the inside of the fuel reservoir part 102 are communicated to each other by a pressure pipe (pressure passage) 126, the middle of the same pipe 126 is branched into first and second passages 126a, 126b, large and small throttle diameter throttle parts 130a, 130b are provided on each of the passages, a solenoid valve 131 (selection valve) is interposed in the first passage, and a CPU 132 to close the solenoid valve 131 at the time of a low rotational region is provided.

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 a supercharged engine, which can obtain a required fuel amount even when the supercharging pressure becomes high and can supply a stable fuel over the entire operating range. Regarding

[0002]

2. Description of the Related Art Conventionally, for example, as a supercharged engine,
A connecting rod accommodating chamber surrounded by a crank chamber, a crank web and a piston is divided into a suction chamber and a compression chamber by a connecting rod, and the air sucked by the swing of the connecting rod is compressed to supercharge the combustion chamber. Has been proposed (see Japanese Patent Laid-Open No. 6-93869). In this supercharged engine, air can be pumped to the combustion chamber by the volume swept by the connecting rod each time the crankshaft makes one revolution, so the primary compression ratio can be increased, and the engine output is improved accordingly. it can.

As a fuel supply device for such a supercharged engine, conventionally, a venturi portion having a fuel discharge port is provided in the middle of an intake passage communicating between the compression chamber and the combustion chamber, and the fuel discharge port and the fuel sump part are provided. Is communicated with the fuel supply passage, and the fuel is supplied to the venturi portion by a pressure difference between the pressure on the fuel reservoir side of the fuel supply passage and the pressure on the fuel discharge port side of the fuel supply passage. In this type of device, atmospheric pressure is applied to the fuel in the fuel reservoir.

[0004]

However, in the above-described conventional fuel supply device, when the applied pressure becomes large, the pressure in the venturi portion may become larger than the pressure in the fuel reservoir portion due to the pressure reducing effect of the venturi, which is sufficient. In some cases, fuel cannot be supplied.

[0005] Here, the applicant of the present invention first applies the pressure in the intake passage between the supercharging means and the venturi portion or the pressure in the intake passage between the venturi portion and the combustion chamber to the fuel sump portion by the pressurizing passage. Has been proposed (see Japanese Patent Application No. 7-195031). With this device, a pressure larger than the pressure of the fuel discharge port of the venturi can be applied to the fuel reservoir, and the fuel can be sufficiently supplied even if the supercharging pressure becomes high.

By the way, in the case where the supply pressure is applied to the fuel pool, the required fuel amount can be secured, but the pressure pulsation due to the opening / closing operation of the throttle is applied to the fuel pool, so that, for example, in the low speed / low rotation range. In this case, there is a case where the pressure on the fuel reservoir becomes excessively large and stable fuel supply cannot be performed, and improvement in this respect is required.

The present invention has been made in view of the above circumstances, and it is possible to stably supply the fuel even when the supercharging pressure becomes large and to stably supply the fuel by the pressure pulsation. An object of the present invention is to provide a fuel supply system for a rotary engine.

[0008]

According to a first aspect of the present invention, there is provided a fuel supply device for a supercharged engine, wherein intake air is pressurized by a supercharger and supplied to a combustion chamber. A venturi portion having a fuel discharge port is provided in the middle of an intake passage communicating with the chamber, the fuel discharge port and the fuel reservoir are communicated with each other through a fuel supply passage, and the fuel reservoir side pressure of the fuel supply passage is The fuel is supplied to the venturi portion by the pressure difference from the pressure on the fuel outlet side, and
A portion of the intake passage between the supercharging means and the venturi portion, or a portion downstream of the venturi portion and in the vicinity of the venturi portion and the inside of the fuel reservoir portion are communicated with each other through a pressurizing passage, and the pressurization is performed. It is characterized in that variable damping means for suppressing transmission of pressure pulsation from the supercharging means according to the engine operating state is provided in the middle of the passage.

According to a second aspect of the present invention, in the first aspect, the variable damping means branches the midway of the pressurizing passage into a plurality of passages, and each passage is provided with a fixed throttle portion having a different throttle amount, thereby operating the engine. It is characterized in that one of the above passages is selected from the selection valve according to the state.

According to a third aspect of the present invention, in the first aspect, the variable damping means is provided with a passage area variable valve for continuously changing the passage area in the middle of the pressurizing passage, depending on an operating state of the engine. It is characterized in that it is configured to change the passage area.

According to a fourth aspect of the present invention, in the first aspect, the variable damping means interposes a chamber in the middle of the pressurizing passage, and a piston for changing the volume of the chamber is movably inserted into the chamber. However, it is characterized in that the chamber volume is increased or decreased by the movement of the piston in accordance with the operating state of the engine.

According to a fifth aspect of the present invention, in the first aspect, the fuel reservoir is connected to the fuel tank by a fuel supply passage, and a change in the fuel liquid level in the fuel tank from the fuel reservoir occurs in the middle of the fuel supply passage. It is characterized in that a fuel supply pressure fluctuation influence preventing means for preventing influence on the discharge amount of is arranged.

According to a sixth aspect of the present invention, in the fifth aspect, the fluctuation influence inhibiting means moves up and down according to the fuel liquid level of the fuel pool, and when the float position is above a predetermined level, the fuel tank and the fuel pool. It is characterized in that it is configured with a valve that closes a communication path with the section.

According to a seventh aspect of the present invention, in the fifth aspect, the fluctuation influence inhibiting means is the portion of the intake passage between the supercharging means and the venturi portion, or the downstream side of the venturi portion and the combustion chamber. It is characterized in that the separated portion and the upper portion of the fuel liquid level in the fuel tank are connected by a pressurizing path.

The invention of claim 8 is characterized in that, in claim 6, damping means is arranged in the middle of the pressurizing path.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 are views for explaining a fuel supply device for a crank chamber supercharged engine according to a first embodiment of the invention of claims 1, 2, 5 and 7, and FIG. Is a sectional side view, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIGS. 3 and 4 are a sectional rear view and a sectional side view of the carburetor part, respectively.

In the figure, reference numeral 1 denotes a four-stroke single-cylinder crank chamber supercharged engine with a horizontal crankshaft. An air-cooled cylinder block 3 is connected to a mating surface of a crankcase 2 of the engine 1. A cylinder head 4 is connected to the mating surface of the cylinder block 3. A combustion recess 4a forming a combustion chamber is provided in a portion of the mating surface of the cylinder head 4 facing the cylinder bore 3a, and an ignition plug (not shown) is inserted in the recess 4a.

An intake port 5 and an exhaust port 6 are opened in the combustion recess 4a of the cylinder head 4, respectively.
The intake port 5 is led out to the upper wall side of the cylinder head 4, and the exhaust port 6 is led out to the lower wall side. An intake valve 7 is provided at the combustion chamber opening of the intake port 5, and an exhaust port 6 is provided.
An exhaust valve 8 is arranged at the opening of the combustion chamber so that each opening can be opened and closed. The intake valve 7 and the exhaust valve 8 are urged in a closing direction by a valve spring 9.

Valves 7 and 8 are provided on the cylinder head 4.
A cam shaft 10 as a valve mechanism for opening and closing is arranged in a direction perpendicular to the plane of the drawing. One end of the cam shaft 10 is connected to a drive sprocket 13 (see FIG. 2) connected to a crank shaft 20 described later via a sprocket and a chain (not shown).
The speed is reduced to / 2. Above the camshaft 10 above,
On the lower side, a pair of rocker shafts 1 extending parallel to this
1, 11 are arranged, and a rocker arm 12 is swingably attached to each shaft 11. One end of the rocker arm 12 is in contact with the cam nose of the cam shaft 10, and the other end is in contact with the upper ends of the valves 7 and 8.

Cylinder bore 3 of the cylinder block 3
A piston 16 is slidably inserted and arranged in a. With the piston 16 as a boundary, the crank chamber 2 is provided by the cylinder bore 3a and the crankcase 2 on the side opposite to the combustion chamber.
3 are formed. A small end 17a of a connecting rod 17 is connected to the piston 16 via a piston pin 18 and a bearing 19, and a large end 17b of the connecting rod 17 is connected.
Is connected to a crank pin 21 of the crank shaft 20 via a bearing 22.

The crankshaft 20 is housed in the crankcase chamber 23a of the crank chamber 23, and a pair of disk-shaped crank webs 24 are connected by the crank pins 21 and journals are formed in each crank web 24. The structure is such that the part 25 is integrally formed, and the journal part 25 is supported by the crankcase 2 via a journal bearing 26. The journal portion 25 projects outward from the crankcase 2, and a generator 28 is mounted on one of the projecting portions. In addition, 27 is an oil seal.

The left and right inner side walls 2a of the crankcase 2 orthogonal to the crankshaft 20 are flush with the notches 3c formed in the fitting block 3b of the cylinder block 3 on the upper and lower sides in the drawing. And left and right inner side walls 2
a and the notch 3c have left and right side surfaces 1 of the connecting rod 17.
7c are movable with each other with a minute gap kept in contact with each other, or are in sliding contact with and in contact with each other, and on an arc-shaped inner peripheral wall 2b formed so as to surround the crankshaft 20 of the crankcase 2. Is the large end 17 of the connecting rod 17.
The outer peripheral surfaces of b are movable while facing each other with an extremely small gap, or are in contact with and are in sliding contact with each other. A circular recess 2c into which the crank webs 24 are inserted and arranged on the left and right inner side walls 2a of the crankcase 2.
Is recessed, and a slight gap is provided between the recess 2a and the crank web 24. Then, the connecting rod side wall 24a of the crank web 24 and the connecting rod 17
The left and right side surfaces 17c are also movable so as to be opposed to each other with a minute gap therebetween, or are in sliding contact with each other. A ring 2d is fixedly arranged on the crankcase 2 at the mouth of each of the left and right circular recesses 2c, and the ring 2d comes into contact with the outer periphery of the ridge of the crank web 24 and comes into sliding contact therewith, or almost zero. They face each other with a gap. The ring 2d is made of a material having higher hardness or higher wear resistance than the crankcase 2.

A triangular recess 16a is provided in the skirt of the piston 16 and the recess 16a is formed.
The portion facing the outer periphery of the skirt is a notch 16b. The small end 1 of the connecting rod 17 is placed in the recess 16a.
7a is inserted and arranged. The outer peripheral surface of the small end portion 17a of the connecting rod 17 is movable on the inner peripheral surface of the recess 16a, and the left and right side surfaces 17c are movable on the left and right side surfaces 16c of the recess 16a while facing each other with a minute gap. Or they are in contact with each other and are in sliding contact.

With the above structure, the portion surrounded by the crank chamber 23, the crank web 24 and the piston 16 is a connecting rod accommodating chamber. At a crank angle other than when the piston 16 is located near the top dead center, the connecting rod 17 has at least one of the upper and lower crankcases 2
The connecting rod accommodating chamber is divided into a suction chamber A and a compression chamber B by a connecting rod 17 by fitting in the left and right inner side walls 2a or the notch 3c of the cylinder block 3. Further, when the piston 16 is located at the top dead center, the connecting rod 17 is not fitted to the left and right inner side walls 2a, 2a, but the skirt end of the piston 16 is located at the cylinder bore 3a.
Since it almost coincides with the end portion of a, the division between the suction chamber A and the compression chamber B by the connecting rod 17 is maintained. In this way, as the crankshaft 20 rotates clockwise from the state where the piston 16 is located at the top dead center, as shown in FIG. By moving to the position, the volume of the suction chamber A increases and air is sucked in, and the volume of the compression chamber B decreases, so that the air sucked in the previous stroke is compressed. . Such a structure is described in detail in the above-mentioned Japanese Patent Application Laid-Open No. Hei 6-93869.

A suction passage 35, which communicates with the suction chamber A and opens downward, is integrally formed on the lower surface of the crankcase 2. A suction port 35a is formed on a wall surface of the suction passage 35 on the front side in FIG. 1 so as to be oriented in the crankshaft direction, and a downstream end of a suction pipe 37 is connected to the suction port 35a. The suction pipe 37 extends outward through the side of the engine, and an air cleaner is connected to the upstream end thereof.

A compression chamber B is provided on the upper surface of the crankcase 2.
Is integrally formed with the compression chamber B. The intake passage 38 is formed integrally with the compression chamber B.
A partition part 39 for partitioning and is integrally formed. A valve opening 40 that connects the intake passage 38 and the compression chamber B is formed in the partition wall 39, and the opening area of the valve opening 40 is set to a size that can sufficiently reduce the ventilation resistance.

A reed valve 42 for opening and closing the valve opening 40 is provided on the outer surface of the partition wall 39. This reed valve 4
2 is disposed on the lift side of the valve plate 41a made of a light alloy material containing titanium as a main component and the reed valve 42,
It is composed of a stopper 41b that regulates the opening degree of the valve plate 41a, and one end of the stopper 41b and the valve plate 41a is fastened and fixed to the partition wall 39 together.

The upper end opening of the intake passage 38 has a cover plate 4
5, the cover plate 45 and the intake passage 3 are closed.
A pressure accumulating chamber is constituted by 8 and. An upstream end of an intake pipe 46 communicating with the intake passage 38 is connected to the cover plate 45, and a downstream end of the intake pipe 46 is connected to the intake port 5 of the cylinder head 4.

The intake passage 38 and the intake pipe 37 are communicated with each other via a bypass passage 50. The bypass passage 50 can be opened and closed by a bypass valve 51. The bypass valve 51 has a structure in which the valve body 51a is moved to the open position by the negative pressure in the diaphragm chamber 52. The diaphragm chamber 52 is connected to the downstream end of the intake pipe 46 via a negative pressure passage 53. There is. The bypass valve 51 is
For example, when the intake negative pressure increases when the throttle opening is small, the negative pressure opens the bypass passage 50 to lower the pressure in the intake passage 38. This enables rapid deceleration corresponding to the rapid closing of the throttle valve.

A carburetor 100 which constitutes a fuel supply device is provided in the middle of the intake pipe 46. This carburetor 100 has a float chamber 102, which serves as a fuel reservoir, at an opening on the lower surface of a cab body 101.
The cab body 101 has a cylindrical main body portion 101a having a venturi passage 103 through which intake air flows, and a vertical portion 103a of the venturi passage 103 that extends vertically upward from the main body portion 101a.
And a cylinder portion 101b that opens to the
A fuel introducing portion 101c extending in the float chamber 102 so as to be coaxial with b is integrally formed.

A lid 104 is screwed onto the upper end opening of the cylinder portion 101b, and a cylindrical variable piston valve 105 having a bottom is inserted into the cylinder portion 101b so as to be slidable in the axial direction. A spring 106 that constantly biases the piston valve 105 in the closing direction is disposed between the piston valve 105 and the lid 104. In addition, the throttle valve 1 is connected to the piston valve 105.
One end of the cable 07 is connected, and an extended end of the cable 107 passes through a guide tube 108 connected to the lid 104 and is connected to a throttle grip (not shown). By operating this throttle grip, the piston valve 105 is moved in the vertical direction, and the venturi portion 1 is moved.
The passage area of 03a is changed from fully closed to fully open. Further, the cylinder portion 101b is fitted with a long groove provided in the piston valve 105, and serves as a detent screw 10 for preventing the piston valve 105 from rotating.
9 is attached.

An air bleed sleeve 110 is inserted in the fuel introducing portion 101c, and the sleeve 110
The fuel discharge port 110a is opened below the piston valve 105 in the venturi portion 103a. The main jet 11 is attached to the lower end of the air bleed sleeve 110.
1 is screwed on and opens into the float chamber 102. Needle 1 in the sleeve 110
12 is inserted so that it can move forward and backward, and the upper end of the needle 112 is fixed to the bottom of the piston valve 105. As the piston valve 105 moves up and down, the needle 112 moves back and forth to change the effective area of the fuel discharge port 110a, thereby adjusting the amount of fuel sucked into the venturi passage 103.

A slow fuel introducing portion 101e is formed on the downstream side of the fuel introducing portion 101c.
The slow jet 115 is inserted and arranged in 1e. Further, a bleed air introduction hole 101f opening toward the intake pipe 46 is formed on the upstream side of the fuel introduction portion 101c, and an air jet 116 is inserted and arranged in the introduction hole 101f. A bleed air hole (not shown) is provided on the side wall of the air bleed 110.

The cab body 101 has a fuel inlet 101d communicating with the inside of the float chamber 102. One end of a fuel supply hose 113 is communicatively connected to the inlet 101d, and the other end of the supply hose 113 is communicatively connected to the bottom of the fuel tank 49. The fuel tank 49 is located above the carburetor 100 and supplies fuel into the float chamber 102 by gravity. The pressure pipe 11 connected to the intake passage 38 is connected to the upper wall of the fuel tank 49.
4a is connected to prevent the change in the liquid level of the fuel in the fuel tank 49 from affecting the amount of fuel discharged from the float chamber by applying supercharging pressure to the fuel in the fuel tank 49. Means for preventing the influence of fluctuations. (Invention of Claim 7). The tank cap 114b of the fuel tank 49 is provided with a relief valve 114c that opens when a boost pressure higher than a predetermined pressure is applied.

A float 120 is disposed in the float chamber 102, and the float 120 is supported by a plate 118 and a support shaft 119 so as to be vertically swingable. A fuel intake valve 117 is provided at the fuel inlet 101d in the float chamber 102, and the lower end of the valve body 117a of the intake valve 117 is at the plate 118.
Is supported in contact with. As a result, the float 120 changes in accordance with the change in the liquid level of the fuel in the float chamber 102.
Moves up and down to open and close the fuel introduction hole by the valve body 117a, so that the liquid surface of the fuel in the float chamber 102 is kept constant. As a result, a fluctuation influence prevention unit is configured to prevent the change in the liquid level of the fuel in the fuel tank 49 from affecting the fuel discharge amount from the float chamber. (The invention of claim 6).

Cylinder portion 10 of the cab body 101
A pressurizing passage 125 extending in the axial direction is formed in the axial direction 1b, and the lower end of the pressurizing passage 125 is open in the float chamber 102. Further, one end of the pressure pipe 126 is connected to the upper end of the pressure passage 125, and the other end of the pressure pipe 126 penetrates the cover plate 45 and is connected to the inside of the intake passage 38. Thereby, the supercharging pressure in the intake passage 38 is added to the liquid surface in the float chamber 102.

In the middle of the pressure pipe 126,
It is branched into two paths by the first and second pressurizing passages 126a and 126b. The first and second pressure passages 126a,
126b has a narrowed portion 130 having large and small diameter throttle holes.
a and 130b are formed. Further, the passage 126 is provided upstream of the throttle portion 130a of the first pressurizing passage 126a.
A solenoid valve 131 that opens and closes a is provided, and the solenoid valve 131 is controlled to open and close by a CUP 132.

The CPU 132 is configured to read the engine speed and the throttle opening, and control the solenoid valve 131 to be fully closed in the low speed rotation range at idling and fully open in the medium speed to high speed rotation range. (See the solid line in Fig. 5). Therefore, the supercharging pressure is largely attenuated by the small-diameter throttle hole 130b in the low intake air amount operating range such as idling, and is larger than the throttle hole 130b in the large-diameter throttle hole 130a in the high intake air amount operating range during high-speed rotation. Is attenuated small.

Reference numeral 60 denotes a lubrication device, which is composed of a first lubrication system 61 and a second lubrication system 62 provided independently of the first lubrication system 61. The first lubrication system 61 includes an oil supply pipe 6 with a supply pump 64 interposed in a first storage tank 63 filled with oil for four cycles.
5 and the supply port 65a of the supply pipe 65 is connected to the portion of the camshaft 10 that constitutes the valve mechanism of the cylinder head 4. The oil that lubricated the camshaft 10 returns to the inside of the chain chamber 10b in which the chain is housed, where the chain, the drive sprocket 13, the driven sprocket and the left journal bearing 26 (with a seal ring) in FIG. It is lubricated, and then recovered through the recovery pipe 66 into the first storage tank 63.

In the second lubrication system 62, the main supply pipe 7 is provided in the second storage tank 70 filled with oil for two cycles.
1, the pressure feed pump 72 is connected, the first and second auxiliary supply pipes 73, 74 are connected to the pump 72, the first auxiliary supply pipe 73 is connected to the piston sliding portion of the cylinder block 3, and The second auxiliary supply pipe 74 is connected to the journal bearing portion of the crank chamber 23.

Although not shown, the pressure feed pump 72 is an improved solenoid of an electromagnetic autolube pump, and is of a type in which an armature is fixed to a push rod of a plunger and the armature is sucked by a solenoid. As a result, the discharge pressure from the pump 72 increases, and it is possible to overcome the supercharging pressure and supply oil.

Oil discharge port 73 of the first auxiliary supply pipe 73
Reference character a denotes a piston 1 located at the bottom dead center, which penetrates the liner portion of the cylinder block 3 in a direction orthogonal to the crankshaft 20.
It is located closer to the crank chamber than the second piston ring 6 is. Further, two oil reservoir recesses 75 and 76 are cut out in parallel in the crankshaft direction on the outer surface of the piston 16 closer to the crank chamber than the second piston ring. The recess 75 is formed by the oil supplied from the discharge port 73a when it is aligned with the discharge port 73a by the movement of the piston 16, and the recess 76 is formed by the oil supplied from the discharge port 73a as described below. Thus, lubrication is performed when each of the discharge ports 73a is blocked by the piston 16, and as a result, troubles in lubrication caused by the discharge ports 73a being blocked by the piston 16 are prevented.

Further, an oil guide groove 81 extending in the circumferential direction is formed on the outer peripheral surface of the small end portion 17a of the connecting rod 17, and the guide groove 8 is formed in the piston 16.
A communication hole 77 that communicates 1 with the lower recess 76 is formed. A communication hole 78 that communicates with the piston pin 18 and the bearing 19 is formed on the side of the small end 17a opposite to the communication hole 77. As a result, a part of the oil in the guide groove 81 supplied from the discharge port 73a and the oil recovery hole 80 described below is supplied from the communication hole 78 to the bearing 19, and the remaining part of the oil is discharged from the communication hole 77. Edge 17
It is supplied to the sliding surface between a and the piston 16, and further supplied to the concave portion 76.

Oil discharge port 74 of the second auxiliary supply pipe 74
The letter a passes through the crankcase 2 and reaches the journal bearing 26 on the right side in FIG. The oil supplied to the right journal bearing 26 is supplied to the inner peripheral walls 2a and 2b of the crankcase 2 and the clearance between the circular recess 2c and the crankshaft 20, and to the sliding surfaces.

A small diameter oil recovery hole 80 communicating with the suction passage 35 is formed in the lower portion of the inclined surface of the partition wall 39, and the recovery passage is provided in the cover portion 36 attached to the lower portion of the crankcase 2. 83 is formed. A recovery pipe 84 is connected to the recovery passage 83,
The recovery pipe 84 is connected to the second storage tank 70.

As a result, the first and second auxiliary supply pipes 73,
After the oil supplied from 74 lubricates each sliding surface, it collects on the upper surface of the cover portion 36 in the suction passage 35 and is collected from there. In the present embodiment, the engine 1 is placed horizontally, the compression chamber B having a high supercharging pressure is arranged upward, and air is taken in from below the crankcase 2. Therefore, the lubricating oil collects at the lowermost part of the crankcase 2 due to the interaction between the gravity and the supercharging pressure, so that the oil can be reliably collected and reused. Figure 2 shows the inside of the crankcase 2.
With the seal ring of the left bearing 26 with a seal ring as a boundary, the crank chamber 23 side is 2 cycle oil, and the chain chamber 10b side including the ball portion of the bearing with a seal ring is 4
Lubricated with cycle oil.

Next, the operation and effect of this embodiment will be described. In the engine 1, the large end portion 17b of the connecting rod 17 is connected to the crankcase 2 every time the crankshaft 20 makes one revolution.
That almost all of the volume of air in the compression chamber B at the moment when the crank chamber 23 starts to be partitioned into the suction chamber A and the discharge chamber B when approaching the arc-shaped peripheral wall 2b, is pumped from the intake passage 38 to the intake pipe 46. Becomes Then, when the intake valve 7 is opened during the intake stroke of the engine 1, twice as much compressed air as one revolution of the crankshaft 20 is supercharged into the combustion chamber.

In this engine, since the pressurizing passage 125 communicating with the inside of the float chamber 102 is formed in the cab body 101 and the pressurizing passage 125 and the inside of the intake passage 38 are connected by the pressurizing pipe 126, the supercharging pressure is increased. Even if the pressure of the venturi portion 103a becomes high, a pressure larger than the pressure of the fuel discharge port 110a portion of the venturi portion 103a can be applied to the liquid surface in the float chamber 102, thereby stabilizing the fuel supply. The engine output and fuel consumption can be improved.

In this embodiment, the pressure pipe 1 described above is used.
26 is branched into first and second pressurizing passages 126a and 126b, and small and large throttle portions 130a and 130b are formed in the pressurizing passages 126a and 126b, respectively.
A solenoid valve 131 that opens and closes the pressure passage 126a is arranged to close the first pressure passage 126a in a low rotation range during idling, so that the pressure pulsation causes a reduction in the amount of the second pressure passage 126b. The large throttle portion 130b greatly attenuates the pressure, so that the pressure fluctuation in the float chamber 102 can be suppressed, and the fuel can be stably supplied during low rotation.

On the other hand, in the medium speed / high speed range, since the first pressurizing passage 126a is opened, the supercharging pressure passes through the throttle portion 130a having a small throttle amount in the first pressurizing passage 126a and the float chamber 102. It is possible to stably supply the required amount of fuel in the middle / high speed range while dampening the pressure pulsation.

That is, when a throttle portion common to all operating regions is provided in the middle of the pressurizing pipe 126, if the hole diameter of the throttle portion is set to a diameter capable of attenuating the pressure pulsation even during idling, the hole diameter is too small and high rotation is achieved. There is a concern that the fuel supply will be insufficient in the high speed region and that the throttle effect will not be obtained in the low speed region if the throttle diameter is set to a diameter corresponding to the high speed region.

In the present embodiment, the pressurizing pipe 126 is branched into the first and second pressurizing passages 126a and 126b, the small diameter throttle portion 130b having a large throttle amount is used in the low rotation range, and the medium and high rotation ranges are used. Since the large-diameter throttle portion 130a having a small throttle amount is used, a sufficient throttle effect can be obtained even in the low rotation speed range, and the problem of fuel shortage in the high rotation speed range can be avoided.

FIG. 6 is a diagram for explaining the effect of this embodiment, and FIGS. 6A and 6B are the lift amount of the exhaust / intake valve and the inside of the crankcase when viewed from the crank angle, respectively. 6 is a characteristic diagram showing supercharging pressure, and FIG.
6 (c) and 6 (d) show the pressure difference between the venturi pressure a and the float chamber b or c when the throttle opening is large and when the opening is small (curve b has no throttle,
Curve c has a diaphragm).

As is clear from the figure, in the operating range where the throttle opening is large (see (c) in the figure), the throttle amount is made small, so that the differential pressure between the venturi part and the float chamber is the same as that without the throttle. Since the differential pressure B with the throttle is larger than the differential pressure A, it can be seen that the fuel supply amount can be increased as compared with the case where the throttle is not provided. The differential pressure B increases because the intake valve 7
During the intake stroke in which the valve is open, the intake passage 38 that constitutes the pressure accumulating chamber
This is because the decrease in the cab float chamber pressure when there is a throttle is delayed more than the decrease in the pressure of.

On the other hand, in the operating range in which the throttle opening is small (see FIG. 7D), the throttle amount is increased, so that the differential pressure B with the throttle is smaller than the differential pressure A without the throttle. It can be seen that pulsation can be suppressed. The reason why the differential pressure B becomes small is that even if the pressure in the pressure accumulating chamber increases due to the swing of the connecting rod 17 while the intake valve 7 is closed, the throttle amount is large and the increase in the cab float chamber pressure C is delayed. As a result, the cab float chamber pressure C becomes a flat and small value.

Further, since the fuel in the fuel tank 49 is configured to be fed by gravity and the supercharging pressure is added to the fuel tank 49, the conventional carburetor fuel supply is used in the operating range where the supercharging pressure is low. Fuel is supplied from the fuel tank 49 into the float chamber 102 exactly as in the device. In the supercharging region, the supercharging pressure is applied to both the fuel tank 49 and the float chamber 102, so that the pressure of the fuel is balanced and the gravity causes the fuel to be supplied from the fuel tank 49 to the float chamber 102.

Thus, the fuel can be supplied to the supercharged engine 1 without using a fuel pump or a special carburetor, so that the cost can be reduced and the arrangement space can be reduced.

Further, since it is not necessary to constantly pressurize the fuel with the fuel injection device or the like, neither the problem of time lag of fuel pressure increase at the time of starting nor the problem of increase of electric power consumption occurs. Furthermore, since fuel can be supplied even when the battery is in a discharged state, it is effective as an emergency measure.

Further, the carburetor 100 is installed in the intake passage 38.
Since it is placed close to the combustion chamber, it is easy to vaporize until it reaches the combustion chamber.
In addition, the passage for applying the boost pressure can be shortened. Here, it is possible to dispose the carburetor near the combustion chamber, and in such a case, the responsiveness in the transient region where the fuel supply amount should be changed according to the pressure fluctuation can be improved.

Further, in the present embodiment, the fuel is supplied to the float chamber 102 by gravity, but it goes without saying that the fuel may be pumped by the fuel pump. Further, the needle 112, the slow jet 115, and the air jet 1
By setting 16 etc. to an appropriate diameter, stable rotation can be obtained at the time of starting, low load to high load, low rotation to high rotation, and an operating state in the transient region of acceleration / deceleration, etc.,
High output can be obtained. Further, in this embodiment, 4
Although the present invention is applied to a single-cycle engine with a single cycle, the present invention can also be applied to a multi-cylinder engine with four cycles and a two-cycle engine. When it is adopted in this two-cycle engine, the discharge port of the compression chamber is connected to the scavenging passage.

In the above embodiment, the pressure pipes are
Although it is arranged to branch to the second pressurizing passage and to provide a throttle portion having a different throttle amount in each passage to switch the pressurizing passage, as shown in the second embodiment in FIG. 7, the pressurizing pipe 126 is throttled. A variable throttle valve 140 capable of variably controlling the amount is provided, and CUP1
It is also possible to control the opening / closing control of the throttle variable valve 140 so that the passage area is throttled in the low speed rotation range during idling and the throttle area is continuously increased in the high rotation speed range by idling. Claims 1 and 3 are provided in this way.
3, the same reference numerals as those in FIG. 3 indicate the same or corresponding portions.

In the second embodiment, the throttling amount is variably controlled by throttling the passage area of the pressurizing pipe 126 in accordance with the engine speed and the throttle opening. Therefore, as shown by the broken line in FIG. As the degree increases, the area of the throttle passage increases and the throttle amount (throttle effect) decreases, so that stable fuel supply can be performed over the entire range from low rotation speed to high rotation speed.

FIG. 8 shows the third aspect of the invention according to claims 1 and 4.
It is a figure for explaining the fuel supply system by an embodiment, and the same numerals as Drawing 3 show the same or equivalent portion in the figure.

In the third embodiment, the chamber 15 having a volume capable of absorbing pressure pulsation in the middle of the pressurizing pipe 126.
0 is inserted, a piston 151 for changing its volume is inserted into the chamber 150 so as to be able to move forward and backward, an actuator 153 for driving the piston rod 152 of the piston 151 to move forward and backward is connected, and a CUP 132 is used for idling. The actuator 153 is configured to control the rotation so that the chamber capacity is increased in the low speed rotation range, and the chamber capacity is continuously reduced as the throttle opening is increased (high rotation range).

In the third embodiment, as shown by the alternate long and short dash line in FIG. 5, the chamber volume becomes smaller as the throttle opening becomes larger, and the throttling effect becomes smaller. Fuel can be supplied.

A throttle may be arranged in the middle of the pressure pipe 114a shown in FIGS. 1 and 2, and this is the invention of claim 8. This makes it possible to pressurize the inside of the fuel tank 49 and prevent a decrease in the supercharging pressure in the pressure accumulating chamber due to a decrease in the fuel oil level.

[0067]

As described above, according to the invention of claim 1,
Since the supercharging pressure is supplied into the fuel pool, a pressure larger than the pressure of the fuel discharge port of the venturi part can be applied to the fuel pool, and even if the supercharging pressure becomes high, the required fuel amount can be increased. There is an effect that can be supplied.

Further, since the variable damping means for suppressing the transmission of the pressure pulsation from the supercharging means in accordance with the engine operating state is provided in the middle of the pressurizing passage, the damping force of the pressure pulsation to the fuel reservoir portion is provided in the low speed region. Is sufficiently secured, and there is an effect that a fuel shortage can be avoided in the high rotation speed range. The supplied supercharging pressure increases as the decrease due to the negative pressure in the combustion chamber during the intake stroke decreases.

According to the second aspect of the present invention, the middle of the pressurizing passage is branched into a plurality of passages, and each passage is provided with a fixed throttle portion having a different throttle amount, and one of the above passages is connected depending on the operating state of the engine. Since I chose to select from the selection valve,
In the invention of claim 3, a passage area variable valve for continuously changing the passage area is provided in the middle of the pressurizing passage, and the passage area is changed according to the operating state of the engine. In the invention of item 4, a chamber is provided in the middle of the pressurizing passage, and a piston for changing the volume of the chamber is movably inserted in the chamber, and the chamber volume is variably controlled according to the operating state of the engine. Therefore, in any case, the damping force of the pressure pulsation can be controlled to a value according to the operating state of the engine.

Further, according to the invention of claim 5, there is an effect that the required fuel amount can be supplied to the combustion chamber in the entire throttle opening range even if the fuel liquid level in the fuel tank varies.

According to the invention of claim 6, the action of the position of the fuel pump or, in the case where the fuel pump is provided between the fuel tank and the fuel reservoir, the action of supercharging pressure is added in addition to the action of the fuel pump. Fuel can be reliably supplied from the tank to the fuel reservoir.

Further, according to the invention of claim 7, the influence of the volume change of the fuel liquid level upper space in the fuel tank on the change of the supercharging pressure can be reduced, so that a stable engine output can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional side view for explaining a fuel supply device for a supercharged four-cycle engine according to a first embodiment of the present invention.

FIG. 2 is a sectional rear view (sectional view taken along the line II-II in FIG. 1) showing a crankshaft portion of the engine of the first embodiment.

FIG. 3 is a cross-sectional rear view of the carburetor of the first embodiment device.

FIG. 4 is a cross-sectional side view of the carburetor of the first embodiment device.

FIG. 5 is a diagram for explaining effects of the first embodiment device and the second and third embodiment devices.

FIG. 6 is a diagram for explaining the effect of the first embodiment device.

FIG. 7 is a sectional rear view of the carburetor for explaining the fuel supply device according to the second embodiment of the first and third aspects of the invention.

FIG. 8 is a sectional rear view of the carburetor for explaining the fuel supply device according to the third embodiment of the first and fourth aspects of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Crank chamber supercharged 4-cycle engine 4a Combustion concave part (combustion chamber) 38 Intake passage 46 Intake pipe (intake passage) 100 Carburetor (fuel supply device) 102 Float chamber (fuel reservoir) 103a Venturi part 110a Fuel discharge port 125 Addition Pressure passage 126 Pressure pipe (pressure passage) 126a First pressure passage (branch passage) 126b Second pressure passage (branch passage) 130a, 130b Throttle portion 131 Solenoid valve (selection valve) 132 CPU (throttle means control) 140 Variable throttle valve 150 Chamber 151 Piston

Claims (8)

[Claims] 1. A fuel supply device for a supercharged engine, wherein intake air is pressurized by a supercharging means and supplied to a combustion chamber, and a fuel is provided in the middle of an intake passage communicating between the supercharging means and the combustion chamber. A venturi portion having a discharge port is provided, and the fuel discharge port and the fuel reservoir are communicated with each other through a fuel supply passage,
The fuel is supplied to the venturi portion by the pressure difference between the fuel reservoir side pressure and the fuel discharge port side pressure of the fuel supply passage, and the intake passage between the supercharging means and the venturi portion is formed. A portion, or a portion downstream of the venturi portion and separated from the combustion chamber, and the inside of the fuel reservoir portion communicate with each other through a pressure passage, and transmission of pressure pulsation from the supercharging means is transmitted in the middle of the pressure passage to the engine. A fuel supply device for a supercharged engine, characterized in that a variable damping means for suppressing it according to an operating state is provided. 2. The variable damping means according to claim 1, wherein the variable damping device branches the middle of the pressurizing passage into a plurality of passages, and each passage is provided with a fixed throttle portion having a different throttle amount, and the fixed throttle portion is provided in accordance with the operating state of the engine. A fuel supply system for a supercharged engine, characterized in that one of the passages is selected by a selection valve. 3. The variable damping means according to claim 1, wherein a passage area variable valve for continuously changing the passage area is provided in the middle of the pressurizing passage, and the passage area is changed according to an operating state of the engine. A fuel supply device for a supercharged engine, which is configured as described above. 4. The engine according to claim 1, wherein the variable damping means has a chamber provided in the middle of the pressurizing passage, and a piston for changing the volume of the chamber is movably inserted into the chamber to operate the engine. A fuel supply device for a supercharged engine, characterized in that the chamber volume is increased / decreased by movement of a piston according to a state. 5. The fuel tank according to claim 1, wherein the fuel reservoir is connected to the fuel tank by a fuel supply passage, and a change in the fuel liquid level in the fuel tank affects the discharge amount from the fuel reservoir in the middle of the fuel supply passage. A fuel supply device for a supercharged engine, characterized in that means for preventing the influence of fluctuations in the fuel supply pressure is arranged to prevent this. 6. The float according to claim 5, wherein the fluctuation influence prevention means moves up and down according to the liquid level of the fuel in the fuel reservoir, and a communication passage between the fuel tank and the fuel reservoir when the float position is above a predetermined level. A fuel supply device for a supercharged engine, comprising: 7. The variation influence prevention means according to claim 5, wherein a portion of the intake passage between the supercharging means and a venturi portion, or a portion downstream of the venturi portion and separated from the combustion chamber. A fuel supply device for a supercharged engine, characterized in that it is configured to be connected to a portion above the fuel liquid level in the fuel tank by a pressure passage. 8. The fuel supply device for a supercharged engine according to claim 7, wherein a damping means is arranged in the middle of the pressurizing path.