JP6345549B2 - Engine intake system - Google Patents

Description

  The present invention relates to an intake device for an engine.

An engine intake device mounted on a portable working machine such as a brush cutter is, for example, a carburetor (vaporizer) that mixes fuel with air to generate an air-fuel mixture, and a carburetor and an intake port of the engine. And an intake passage that is disposed and guides the air-fuel mixture from the carburetor to the intake port of the engine. The carburetor includes, for example, a diaphragm fuel pump as a fuel supply device. In general, a diaphragm fuel pump includes a pump chamber that sucks and discharges fuel, and a diaphragm chamber that is supplied with pressure for driving the pump chamber.
Such an engine intake device is disclosed in Patent Document 1.

  In Patent Document 1, a straight tubular intake passage and a diaphragm chamber of a diaphragm fuel pump are communicated with each other through a communication passage. Therefore, the pressure for driving the pump chamber of the diaphragm fuel pump is supplied from the straight pipe intake passage to the diaphragm chamber of the diaphragm fuel pump through the communication passage.

Japanese Utility Model Publication No. 5-19555

  By the way, the portable work machine generally includes a sealed fuel tank. In this fuel tank, as the remaining amount of liquid fuel stored in the fuel tank decreases, the pressure in the fuel tank decreases and the pressure in the fuel tank may become negative. Therefore, in order to suck up the fuel from the negative pressure fuel tank by the diaphragm type fuel pump, the pressure supplied to the diaphragm chamber of the diaphragm type fuel pump has a large fluctuation (in other words, air pulsation). The pressure amplitude is large).

  However, in Patent Document 1, the straight tubular intake passage and the diaphragm chamber communicate with each other. Therefore, the fluctuation of the pressure supplied to the diaphragm chamber of the diaphragm type fuel pump is small, and it may be difficult to suck up the fuel from the negative pressure fuel tank by the diaphragm type fuel pump.

  In view of such a situation, an object of the present invention is to increase the fluctuation of the pressure supplied to the diaphragm chamber.

Therefore, an intake device for an engine according to the present invention is a carburetor having a passage having a large diameter portion and a venturi portion having a smaller diameter than the large diameter portion, and a throttle valve disposed in the passage. a carburetor for generating a mixture engaged mixed fuel to air flowing through, or is disposed between the passage and the engine intake port of the carburetor by directing air mixture from the passageway of the carburetor to the intake port of the engine Or an intake passage that is arranged upstream of the passage of the carburetor and guides air supplied to the intake port of the engine to the passage of the carburetor. The carburetor includes a diaphragm fuel pump. The diaphragm fuel pump includes a pump chamber that sucks and discharges fuel, and a diaphragm chamber to which pressure for driving the pump chamber is supplied. The intake passage includes a throttle portion. The engine intake device further includes a communication path that connects the throttle portion and the diaphragm chamber. The pressure for driving the pump chamber is supplied from the throttle portion to the diaphragm chamber via the communication path.

  According to the present invention, the pressure for driving the pump chamber of the diaphragm fuel pump is supplied from the throttle portion of the intake passage to the diaphragm chamber of the diaphragm fuel pump through the communication passage. As a result, the negative pressure is strengthened at the throttle portion of the intake passage during intake of the engine, so that the fluctuation of the pressure supplied to the diaphragm chamber can be increased.

Sectional drawing which shows schematic structure of the engine intake device in 1st Embodiment of this invention. Sectional drawing which shows schematic structure of the carburetor provided with the diaphragm type fuel pump in embodiment same as the above Explanatory drawing of the nozzle in the same embodiment Sectional drawing which shows schematic structure of the intake passage in embodiment same as the above II sectional view of FIG. Sectional drawing which shows schematic structure of the intake passage in the modification of embodiment same as the above Sectional drawing which shows schematic structure of the intake passage in 2nd Embodiment of this invention. Sectional drawing which shows schematic structure of the intake passage in 3rd Embodiment of this invention. Sectional drawing which shows schematic structure of the intake passage in 4th Embodiment of this invention. Sectional drawing which shows schematic structure of the intake passage in 5th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration of an engine intake device according to a first embodiment of the present invention. FIG. 1 shows the engine when the piston is positioned near the top dead center TDC (Top Dead Center).

  The engine 1 is an OHV (Over Head Valve) type four-stroke engine and is air-cooled. The engine 1 includes a cylinder portion 2, a crankcase 3 attached to the lower portion of the cylinder portion 2, and an oil tank 4 disposed at a lower direction position of the crankcase 3. The intake device 50 of the engine 1 includes a carburetor (vaporizer) 30, an intake passage 21, and an intake valve 17 which will be described later.

The cylinder part 2 has a cylindrical space for sliding the piston 5 in the vertical direction in FIG. In this space, the piston 5 is fitted with a gap slidable in the vertical direction in FIG.
A crank chamber 7 is formed by the cylinder portion 2, the crankcase 3 and the piston 5. That is, the crank chamber 7 is formed by the side surface of the cylinder portion 2 and the cylindrical space on the crankcase 3 side formed by the piston 5 and the space in the crankcase 3. In the crank chamber 7, the volume of the internal space changes as the piston 5 slides.
A combustion chamber 9 is formed by the cylinder head 8, the cylinder part 2 and the piston 5.
The oil tank 4 is defined by an oil tank case, is provided separately from the crankcase 3 and stores lubricating oil.

A check valve 10 is provided between the oil tank 4 and the crankcase 3 to allow only the oil flow from the crankcase 3 (crank chamber 7) to the oil tank 4.
Here, as the piston 5 moves from the bottom dead center BDC (Bottom Dead Center) to the top dead center TDC, the pressure in the crank chamber 7 becomes negative. Conversely, as the piston 5 moves from the top dead center TDC to the bottom dead center BDC, the pressure in the crank chamber 7 becomes positive. Therefore, when the pressure in the crank chamber 7 is positive, the check valve 10 is opened, and the oil flows from the crank chamber 7 to the oil tank 4 in liquid and / or mist form. When the pressure in the crank chamber 7 is negative, the check valve 10 is closed.

  A crank 13 is rotatably supported in the crankcase 3. The crank 13 includes a crankshaft 13a serving as a rotation center, a counterweight, and the like. The piston 5 and the crank 13 are connected by a connecting rod 11. The connecting rod 11 and the piston 5 are rotatably connected. The connecting rod 11 and the crank 13 are rotatably connected. With such a configuration, the piston 5 reciprocates in the cylinder portion 2.

A cylinder head 8 is provided on the upper wall of the cylinder portion 2.
The cylinder head 8 is provided with an intake port 15 and an exhaust port 16. The intake port 15 communicates with the carburetor 30 via the insulator 20. The exhaust port 16 communicates with an exhaust muffler (not shown).
The cylinder head 8 is provided with an intake valve 17 that opens and closes the intake port 15. The cylinder head 8 is provided with an exhaust valve 18 that opens and closes the exhaust port 16. Here, the intake valve 17 and the exhaust valve 18 open and close the combustion chamber 9.

An intake passage 21 is formed through the insulator 20. The intake passage 21 of the insulator 20 is disposed between the carburetor 30 and the intake port 15 and guides the air-fuel mixture from the carburetor 30 to the intake port 15. The intake passage 21 includes a throttle portion 100 that reduces at least a partial cross-sectional area (a mixture flow area).
An annular gasket 27 is interposed as a seal member between the insulator 20 (second member 24 described later) and the carburetor 30 (carburetor body 63 described later). The gasket 27 is made of rubber, for example. A through hole 28 is formed in the gasket 27 (see FIG. 4).

  An air cleaner 40 is provided on the outer side (upstream side) of the carburetor 30. A filter 41 is disposed in the air cleaner 40. As air passes through the filter 41, dust in the air is removed.

The carburetor 30 is a device that generates an air-fuel mixture by mixing fuel with the air that has passed through the air cleaner 40. The carburetor 30 can adjust the mixing ratio of air and fuel. The carburetor 30 can adjust the flow rate of the air-fuel mixture.
The carburetor 30 includes a diaphragm fuel pump 60 for mixing fuel into the air. This diaphragm type fuel pump 60 is driven by pressure fluctuation as power.

In order to supply this power, in this embodiment, the diaphragm chamber 61 of the diaphragm fuel pump 60 and the throttle part 100 of the intake passage 21 are connected by the communication passage 110. Details of the communication path 110 will be described later with reference to FIGS. 4 and 5.
The diaphragm fuel pump 60 is provided with a diaphragm 62 that is displaced according to pressure fluctuation.

  The pressure in the intake passage 21 fluctuates at a rate of once per two rotations of the crankshaft 13a. This pressure fluctuation (air pulsation) is reinforced at the throttle portion 100 of the intake passage 21. Therefore, an air pulsation having a large pressure amplitude is supplied from the throttle portion 100 of the intake passage 21 to the diaphragm chamber 61 of the diaphragm fuel pump 60 through the communication passage 110.

FIG. 2 shows a schematic configuration of the carburetor 30 including the diaphragm fuel pump 60.
The carburetor 30 includes a carburetor main body 63.
The carburetor body 63 is formed with an air pulsation transmission passage 64 that constitutes the communication passage 110 described above. A diaphragm chamber 61 is formed on the first side (upper surface in the drawing) of the diaphragm 62. A pump chamber 65 is formed on the second side (lower surface in the drawing) of the diaphragm 62. One end of the air pulsation transmission passage 64 is connected to the diaphragm chamber 61. The other end of the air pulsation transmission passage 64 faces the through hole 28 (see FIG. 4) of the gasket 27.

The pump chamber 65 communicates with the fuel inlet 72 via the inlet valve 70. The pump chamber 65 communicates with the metering chamber 81 of the metering diaphragm 80 via an outlet valve 74 and a needle valve 76.
The fuel inlet 72 is connected to a sealed fuel tank (not shown) via a suction pipe (not shown). The fuel tank stores liquid fuel.

In the throttle portion 100 of the intake passage 21, a large negative pressure is generated as the intake valve 17 is opened. This negative pressure (air pulsation) acts on the diaphragm chamber 61 via the air pulsation transmission passage 64 constituting the communication passage 110. The diaphragm fuel pump 60 is driven by the negative pressure acting on the diaphragm chamber 61. More specifically, when a negative pressure acts on the diaphragm chamber 61 of the diaphragm fuel pump 60 and the diaphragm 62 bends toward the diaphragm chamber 61, a negative pressure acts on the pump chamber 65 side. Due to the negative pressure in the pump chamber 65, the inlet valve 70 is opened while the outlet valve 74 is closed, and fuel is sucked into the pump chamber 65 from the fuel inlet 72.
In this manner, in the diaphragm fuel pump 60, the diaphragm 62 is waved by pressure fluctuation (air pulsation) supplied to the diaphragm chamber 61, and the wave movement of the diaphragm 62 causes the pump chamber 65 to move from the fuel tank. Fuel is inhaled.

  Next, when the negative pressure acting on the diaphragm chamber 61 of the diaphragm fuel pump 60 turns to a positive pressure in this state, the diaphragm 62 tries to return to the original state by the elastic action of the diaphragm 62. If it does so, a positive pressure will act on the pump chamber 65 side. When positive pressure acts on the pump chamber 65 side by the movement of the diaphragm 62, the outlet valve 74 is opened while the inlet valve 70 is closed, and fuel is discharged from the pump chamber 65. The discharged fuel is supplied to the metering chamber 81 of the metering diaphragm 80 via the needle valve 76.

  The metering chamber 81 is partitioned from the back pressure chamber 82 by a metalling diaphragm 80. The pressure of the engine 1 acts on the back pressure chamber 82, and the metering diaphragm 80 is driven by a pressure difference between the pressure of the engine 1 and the metering chamber 81. A passage for communicating the back pressure chamber 82 and the negative pressure of the engine is not shown.

  The metering diaphragm 80 is connected to the above-described needle valve 76 via the control lever 84, and the needle valve 76 is opened and closed by the operation of the metering diaphragm 80. Specifically, when the metering chamber 81 is filled with fuel, the pressure of the metering chamber 81 is increased and the metering diaphragm 80 is bent toward the back pressure chamber 82. At this time, due to the elastic force of the control lever spring 86, the control lever 84 rotates so that one end (right side in the figure) is pushed down and the other end (left side in the figure) is pushed up. With this turning operation of the control lever 84, the needle valve 76 is pushed up, and the communication between the pump chamber 65 and the metering chamber 81 is cut off.

The carburetor body 63 is formed with a passage 88 that connects the intake passage 21 and the air cleaner 40. The passage 88 has an upstream side (the air cleaner 40 side) as a large diameter portion 88a and a downstream side (the intake passage 21 side) as a venturi portion 88b having a smaller diameter than the large diameter portion 88a. The venturi portion 88b is provided with a throttle valve 90 that displaces the opening degree.
The throttle valve 90 has its rotational axis orthogonal to the passage 88, and rotates while sliding in the vertical direction in the figure by operating the rotation lever 90a, so that the opening degree of the venturi 88b is displaced by the amount of rotation. I have to.

The throttle valve 90 is provided with a first adjuster screw 91 for finely adjusting the amount of fuel mixed with the air flowing through the passage 88 coaxially with the rotating shaft.
The first adjuster screw 91 is provided with a second adjuster screw 92 coaxially with the rotation axis thereof. The second adjustment task screw 92 is provided so as to extend in the vertical direction in the drawing. Further, with respect to the second adjustment task screw 92, the outer dimension is reduced in two steps from the upper side to the lower side from the outer diameter dimension substantially the same as the inner diameter dimension of the nozzle 94 described later.
A switching portion 92 a for switching a main jet 96 described later is provided at the tip of the second adjustment task screw 92.

When the first adjuster screw 91 rotates in one direction (screw tightening direction) with respect to the throttle valve 90, it moves downward in the figure, and conversely, when it rotates in the other direction (screw return direction) with respect to the throttle valve 90, Move upward in the figure.
Similarly to the first adjustment task screw 91, the second adjustment task screw 92 moves downward in the figure when rotated in one direction (screw tightening direction), and conversely, the first adjustment task screw 92 If it rotates to the other side (screw-return direction) with respect to 91, it will move upward in the figure.

  The carburetor body 63 is provided with a nozzle 94 so as to face the second adjuster screw 92, and the tip of the second adjuster screw 92 is inserted into the nozzle tip 94 a of the nozzle 94. The nozzle 94 is formed with a hole 94 b that opens into the passage 88, and a base end 94 c that communicates with the hole 94 b faces the metering chamber 81. A main jet 96 and a main check valve 98 are provided between the hole 94b and the metering chamber 81 as mixing ratio adjusting means and fuel supply amount adjusting means.

FIG. 3 is an explanatory diagram of the nozzle 94.
The main jet 96 has a first main jet part 96a that communicates the hole 94b of the nozzle 94 with the metering chamber 81 with a predetermined opening area, and a hole 94b with the metering chamber with a larger opening area than the first main jet part 96a. 81 and a second main jet part 96 b communicating with 81.

  In the main jet 96, one of the first main jet portion 96a and the second main jet portion 96b is closed by the switching portion 92a of the second adjuster screw 92, and the other communicates the hole 94b of the nozzle 94 and the metering chamber 81. The main jet 96 switches the closing and opening of the first main jet portion 96a and the second main jet portion 96b by rotating the second adjustment task screw 92 with respect to the first adjustment task screw 91. That is, the main jet 96 causes the fuel to flow through one of the first main jet portion 96a and the second main jet portion 96b by rotating the second adjust task screw 92 relative to the first adjust task screw 91 according to the fuel to be used.

Next, details of the communication path 110 will be described with reference to FIGS. 4 and 5.
FIG. 4 shows a schematic configuration of the intake passage 21 in the present embodiment. 5 is a cross-sectional view taken along the line II of FIG.

The insulator 20 in which the intake passage 21 is formed is constituted by two members 23 and 24.
The first member 23 is formed of, for example, a resin or an elastic member such as rubber. The first member 23 has a truncated cone shape that tapers toward the downstream side. In the first member 23, an intake passage 23a is formed in a tapered shape so that a cross-sectional area (a flow area of the air-fuel mixture) decreases toward the downstream side. Here, the first member 23 corresponds to the “first intake passage forming member” of the present invention.

  The second member 24 is formed of, for example, resin. The second member 24 has, for example, a cylindrical shape, and is provided with a recess 24 a that can accommodate the first member 23 on the upstream side (carburetor 30 side). The second member 24 has an intake passage 24b so that the intake passage 23a and the intake port 15 of the first member 23 can communicate with each other in a state where the first member 23 is accommodated in the recess 24a. Is formed. The intake passage 24b is formed in a trumpet shape so that the cross-sectional area (the flow area of the air-fuel mixture) increases toward the downstream side. Here, the second member 24 corresponds to a “second intake passage forming member” of the present invention.

Therefore, the intake passage 21 of the insulator 20 is constituted by the intake passage 23 a of the first member 23 and the intake passage 24 b of the second member 24.
Further, in the throttle portion 100 of the intake passage 21, the “first region where the cross-sectional area decreases toward the downstream side” of the present invention is formed by the intake passage 23 a of the first member 23. The “second region where the upstream end is connected to the downstream end of the first region and the cross-sectional area increases toward the downstream side” is formed by the intake passage 24 b of the second member 24.

  In the present embodiment, a portion 100 a having a minimum cross-sectional area (a mixture flow area) in the throttle portion 100 of the intake passage 21 is an intake passage 23 a of the first member 23 and an intake passage of the second member 24. It is a connection part with 24b.

On the downstream end surface of the first member 23 (contact surface with the recess 24a of the second member 24), the groove portion 23b extends so as to extend radially outward from the portion 100a of the throttle portion 100 of the intake passage 21. Is recessed. The cross section of the groove 23b is semicircular. Further, a groove portion 23c is recessed in the outer surface (side surface in the truncated cone shape) of the first member 23 so as to extend from the groove portion 23b toward the upstream side along the outer surface. The cross section of the groove 23c is semicircular.
Of the recess 24a of the second member 24, a groove 24c is provided at a position facing the grooves 23b and 23c. The cross section of the groove 24c is semicircular.

In the present embodiment, the air pulsation extraction passage 25 is formed by the above-described grooves 23b, 23c, and 24c. The cross section of the air pulsation extraction passage 25 is circular.
One end of the air pulsation extraction passage 25 faces the portion 100 a of the throttle portion 100 of the intake passage 21. The other end of the air pulsation extraction passage 25 faces the through hole 28 of the gasket 27.

  Therefore, the communication passage 110 is constituted by the air pulsation extraction passage 25, the through hole 28 of the gasket 27, and the air pulsation transmission passage 64. In addition, the communication passage 110 communicates the diaphragm chamber 61 with the portion 100 a having the smallest cross-sectional area in the throttle portion 100 of the intake passage 21.

  According to the present embodiment, the intake device 50 of the engine 1 is disposed between the carburetor 30 that mixes fuel with air to generate an air-fuel mixture, and the carburetor 30 and the intake port 15 of the engine 1. And an intake passage 21 that guides the air-fuel mixture from the engine 1 to the intake port 15 of the engine 1. The carburetor 30 includes a diaphragm fuel pump 60. The diaphragm fuel pump 60 includes a pump chamber 65 that sucks and discharges fuel, and a diaphragm chamber 61 to which pressure for driving the pump chamber 65 is supplied. The intake passage 21 includes a throttle unit 100. The intake device 50 of the engine 1 further includes a communication passage 110 that communicates the throttle unit 100 and the diaphragm chamber 61. The pressure for driving the pump chamber 65 is supplied from the throttle unit 100 to the diaphragm chamber 61 through the communication path 110. As a result, the negative pressure is reinforced at the throttle portion 100 of the intake passage 21 during intake of the engine 1, so that the fluctuation of the pressure supplied to the diaphragm chamber 61 can be increased.

  Further, according to the present embodiment, the communication path 110 communicates the diaphragm chamber 61 with the portion 100 a having the smallest cross-sectional area in the throttle unit 100. As a result, the diaphragm chamber 61 communicates with the portion of the throttle portion 100 of the intake passage 21 where the negative pressure is most reinforced, so that air pulsations having a relatively large pressure amplitude are stably supplied to the diaphragm chamber 61. The Therefore, even when the remaining amount of fuel stored in the sealed fuel tank is reduced, the fuel can be stably sucked up by the diaphragm fuel pump 60. The properties can be stabilized, and consequently, stable operation of the engine 1 can be realized.

  Further, according to the present embodiment, the throttle portion 100 of the intake passage 21 has a first area (tapered intake passage 23a) whose sectional area decreases toward the downstream side, and a downstream end of the first area. And a second region (a trumpet-shaped intake passage 24b) having a cross-sectional area that increases toward the downstream side after the upstream end is connected. Thereby, since the formation of the stagnation part of the air-fuel mixture flowing through the throttle part 100 of the intake passage 21 can be suppressed, an increase in pressure loss due to the formation of the throttle part 100 of the intake passage 21 can be suppressed.

  According to the present embodiment, the intake passage 21 includes the first intake passage forming member (first member 23) including the first region (tapered intake passage 23a), and the first intake passage formation. And a second intake passage forming member (second member 24) including a second region (a trumpet-like intake passage 24b) having a recess 24a capable of accommodating the member. Thereby, the throttle part 100 of the intake passage 21 can be formed relatively easily by inserting the first member 23 into the recess 24 a of the second member 24.

  Further, according to the present embodiment, at least a part of the communication passage 110 (the air pulsation extraction passage 25) includes the first intake passage formation member (first member 23) and the second intake passage formation member (second passage). Member 24). Thereby, the air pulsation extraction passage 25 can be formed relatively easily.

  In this embodiment, the air pulsation extraction passage 25 is formed so as to straddle the first member 23 and the second member 24, but the method of forming the air pulsation extraction passage 25 is not limited to this. For example, the air pulsation extraction passage 25 may be formed only in the first member 23 as in a modification of the present embodiment shown in FIG. Alternatively, the air pulsation extraction passage 25 may be formed only in the second member 24.

FIG. 7 shows a schematic configuration of the intake passage 21 in the second embodiment.
A different point from 1st Embodiment shown in FIGS. 1-5 is demonstrated.

In the present embodiment, the first member 23 and the gasket 27 in the first embodiment are integrated to form the first member 123. The first member 123 is formed of an elastic member such as rubber.
The main body portion 124 of the first member 123 has a truncated cone shape similar to that of the first member 23 described above, and includes an intake passage 23a and groove portions 23b and 23c.
The main body portion 124 of the first member 123 can be accommodated in the concave portion 24 a of the second member 24 in the same manner as the first member 23 described above.

The flange portion 125 of the first member 123 has an annular shape, and protrudes radially outward from the upstream end portion of the main body portion 124. The flange portion 125 is interposed between the carburetor main body 63 and the second member 24 and functions as a gasket (that is, a seal member). A through hole 28 is formed in the flange portion 125 in the same manner as the gasket 27 described above.
Here, the first member 123 corresponds to the “first intake passage forming member” of the present invention.

  In particular, according to the present embodiment, the first intake passage forming member (first member 123) is accommodated in the concave portion 24a of the second intake passage forming member (second member 24) and the first region ( The main body portion 124 including the tapered intake passage 23a) and the flange portion 125 projecting outward from the upstream end portion of the main body portion 124 are configured. The flange portion 125 is interposed between the downstream end surface of the carburetor 30 (carburetor body 63) and the upstream end surface of the second intake passage forming member (second member 24). Thereby, since the first member 23 and the gasket 27 can be integrated, the number of components can be reduced.

  According to the present embodiment, the first intake passage forming member (first member 123) is formed of an elastic member. Thereby, since the flange part 125 can be functioned as a gasket, the sealing performance between the carburetor 30 and the insulator 20 can be ensured.

FIG. 8 shows a schematic configuration of the intake passage 21 in the third embodiment of the present invention.
A different point from 1st Embodiment shown in FIGS. 1-5 is demonstrated.

In the present embodiment, the first member 23 and the second member 24 forming the intake passage 21 are integrated, and the insulator 20 including the intake passage 21 is formed by one member. In the present embodiment, the insulator 20 is formed of resin, for example.
A linear air pulsation extraction passage 25 is formed in the insulator 20. One end of the air pulsation extraction passage 25 faces the portion 100 a of the throttle portion 100 of the intake passage 21. The other end of the air pulsation extraction passage 25 faces the through hole 28 of the gasket 27.

  In particular, according to the present embodiment, a linear air pulsation extraction passage 25 is formed in the insulator 20. Thereby, the air pulsation extraction passage 25 can be formed relatively easily using a drill or the like.

FIG. 9 shows a schematic configuration of the intake passage 21 in the fourth embodiment of the present invention.
Differences from the third embodiment shown in FIG. 8 will be described.

In the present embodiment, the air pulsation extraction passage 25 is constituted by two linear passages 25a and 25b.
The passage 25a is formed by cutting from the outer surface of the insulator 20 toward the portion 100a of the throttle portion 100 of the intake passage 21 using a drill or the like. When the passage 25a is formed, the outside of the insulator 20 communicates with the inside of the intake passage 21 through the passage 25a.

  The passage 25b is formed by cutting from the upstream end face (end face on the carburetor 30 side) of the insulator 20 toward the passage 25a using a drill or the like. Here, the opening of the passage 25 b on the upstream end face of the insulator 20 is positioned in advance so as to face the through hole 28 of the gasket 27. Further, when the passage 25b is formed, when the passage 25b is connected to the passage 25a, the cutting for forming the passage 25b is finished.

After the passage 25b is connected to the passage 25a, a rubber or resin cap 25c is fitted into the portion of the passage 25a so as to close a portion outside the passage 25b.
Accordingly, one end of the air pulsation extraction passage 25 constituted by the passages 25 a and 25 b and the cap 25 c faces the portion 100 a of the throttle portion 100 of the intake passage 21. The other end of the air pulsation extraction passage 25 faces the through hole 28 of the gasket 27.

  In particular, according to the present embodiment, the air pulsation extraction passage 25 is constituted by passages 25a and 25b and a cap 25c. Thereby, the air pulsation extraction passage 25 can be formed relatively easily using a drill or the like.

FIG. 10 shows a schematic configuration of the intake passage 21 in the fifth embodiment of the present invention.
Differences from the fourth embodiment shown in FIG. 9 will be described.

  In the present embodiment, the intake passages 23a and 24b are each formed in a plurality of steps. That is, in the present embodiment, the first region (intake passage 23a) of the throttle unit 100 and the second region (intake passage 24b) of the throttle unit 100 are each formed in a step shape. As a result, even if fuel is excessively mixed in the air by the carburetor 30, a fuel pool can be formed on the stepped wall surfaces of the intake passages 23a and 24b. can do.

In the present embodiment, the intake passages 23a and 24b are each formed in a plurality of steps, but one of the intake passages 23a and 24b is formed in a plurality of steps. May be.
Further, the step-like intake passages 23a and 24b in the present embodiment may be applied to the intake passages 23a and 24b in the first to fourth embodiments described above.

  In the first to fifth embodiments described above, the air cleaner 40 is provided adjacent to the upstream side of the carburetor 30. However, in addition to this, a throttle is provided between the air cleaner 40 and the upstream side of the carburetor 30. The intake passage 21 including the portion 100 may be disposed. That is, the intake passage 21 including the throttle unit 100 may be disposed on the upstream side of the carburetor 30 to guide the air supplied to the intake port 15 of the engine 1 to the carburetor 30. Also in this case, the throttle portion 100 of the intake passage 21 and the diaphragm chamber 61 of the diaphragm fuel pump 60 are connected by the communication passage 110 as in the first to fifth embodiments. Even in this case, the pressure in the intake passage 21 fluctuates at a rate of once per two rotations of the crankshaft 13a. This pressure fluctuation (air pulsation) is reinforced at the throttle portion 100 of the intake passage 21. Therefore, an air pulsation having a large pressure amplitude is supplied from the throttle portion 100 of the intake passage 21 to the diaphragm chamber 61 of the diaphragm fuel pump 60 through the communication passage 110. In this case, the intake passage 21 of the insulator 20 may be a straight tube.

  In addition, the engine 1 in the first to fifth embodiments described above can be mounted as a drive source on a portable work machine such as a brush cutter, a digger, or a concrete cutter. The engine 1 can be mounted as a drive source on a backpack type work machine such as a backpack blower, a sprayer (sprayer), a dusting machine, or a backpack type brush cutter.

In the first to fifth embodiments described above, the engine 1 is an OHV type four-stroke engine. However, the configuration of the engine 1 is not limited to this. For example, the engine 1 is an OHC type engine. There may be.
In the first to fifth embodiments described above, in the engine 1, the cylinder head 8 and the cylinder part 2 are shown as separate bodies. However, instead of this, the cylinder head and the cylinder part are integrated. There may be.

  As can be seen from the foregoing, the illustrated embodiments are merely illustrative of the present invention, and the present invention is made by those skilled in the art within the scope of the claims in addition to those directly illustrated by the described embodiments. Needless to say, it includes various improvements and changes.

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder part 3 Crankcase 4 Oil tank 5 Piston 8 Cylinder head 9 Combustion chamber 10 Check valve 11 Connecting rod 13 Crank 13a Crankshaft 15 Intake port 16 Exhaust port 17 Intake valve 18 Exhaust valve 20 Insulator 21 Intake passage 23 First 1 member (first intake passage forming member)
23a Intake passages 23b, 23c Groove 24 Second member (second intake passage forming member)
24a Recess 24b Intake passage 24c Groove 25 Air pulsation take-out passage 25a, 25b Passage 25c Cap 27 Gasket 28 Through-hole 30 Carburetor 40 Air cleaner 41 Filter 50 Intake device 60 Diaphragm fuel pump 61 Diaphragm chamber 62 Diaphragm 63 Carburetor body 64 Air pulsation transmission passage 65 Pump chamber 100 Restriction portion 110 Communication path 123 First member 124 Main body portion 125 Flange portion

Claims (8)

Passage having a small diameter of the venturi section than the large diameter portion and the large diameter portion, and a carburetor having a throttle valve, disposed in said passage, a fuel engaged mixing the air flowing through the passage It said carburetor generating air-fuel mixture,
The engine is disposed between the passage of the carburetor and the intake port of the engine to guide the air-fuel mixture from the passage of the carburetor to the intake port of the engine, or disposed upstream of the passage of the carburetor. An intake passage for guiding the air supplied to the intake port of the carburetor to the passage;
An engine intake system comprising:
The carburetor includes a diaphragm fuel pump,
The diaphragm fuel pump includes a pump chamber for sucking and discharging fuel, and a diaphragm chamber to which a pressure for driving the pump chamber is supplied,
The intake passage includes a throttle portion,
The intake device of the engine further includes a communication passage that communicates the throttle portion and the diaphragm chamber,
An intake device for an engine, wherein the pressure for driving the pump chamber is supplied from the throttle portion to the diaphragm chamber via the communication path.   2. The engine intake device according to claim 1, wherein the communication passage communicates a portion having a minimum cross-sectional area in the throttle portion with the diaphragm chamber.   The narrowed portion has a first area whose cross-sectional area decreases toward the downstream side, and a second area where the upstream end is connected to the downstream end of the first area and the cross-sectional area increases toward the downstream side. The engine intake device according to claim 1 or 2, comprising:   The intake passage includes a first intake passage forming member including the first region and a recess capable of accommodating the first intake passage forming member, and a second intake passage including the second region. The engine intake device according to claim 3, formed by a forming member.   The engine intake device according to claim 4, wherein at least a part of the communication passage is formed in at least one of the first intake passage formation member and the second intake passage formation member. The intake passage, which guides the air-fuel mixture from the passageway disposed in the carburetor between said passage and said intake port of said carburetor in the intake port,
The first intake passage forming member includes a main body portion that is accommodated in a recess of the second intake passage formation member and includes the first region, and a flange that projects outward from an upstream end portion of the main body portion. The flange portion is interposed between the downstream end surface of the carburetor and the upstream end surface of the second intake passage forming member. The engine intake system described.   The engine intake device according to claim 6, wherein the first intake passage forming member is formed of an elastic member.   The engine intake device according to any one of claims 3 to 7, wherein at least one of the first region and the second region is formed in a step shape.