JPH0531258Y2 - - Google Patents

Description

[Detailed explanation of the invention] A. Purpose of the invention (1) Industrial application field This invention consists of an operating shaft rotatably supported on the carburetor body for rotational operation, and a shaft that opens and closes across the intake duct. The present invention relates to a slide valve opening/closing device for a carburetor in which a slide valve slidably fitted on a carburetor body is connected via a link mechanism.

(2) Conventional technology Conventionally, in such devices, a slide valve has a perfectly circular cross-sectional shape, and a link mechanism is connected to a valve plate attached to the center of the upper end of the slide valve with two screw members. are doing.

(3) Problems to be solved by the invention However, connecting the link mechanism to the center of the slide valve causes the slide valve to tilt because the cross-sectional shape of the slide valve is a perfect circle. This is to avoid problems and ensure smooth operation, but if the connection positions are limited, the degree of freedom in setting the link mechanism will be limited. Additionally, the connection between the slide valve and the link mechanism is located in a relatively narrow space;
As mentioned above, because the connection position is in the center and because the valve plate is attached to the slide valve with two screws, it becomes difficult to attach and detach the link mechanism from the slide valve, making maintenance difficult. It is disadvantageous. Furthermore, it is necessary to provide the slide valve with a female threaded portion for screwing the screw member, and as a result, the slide valve needs to be formed of a material that can withstand tightening strength and thermal shock strength.

The present invention was developed in view of the above circumstances, and aims to increase the degree of freedom in setting the link mechanism, facilitate maintenance, and eliminate the need for the material forming the slide valve to be as strong. The purpose of the present invention is to provide a sliding valve opening/closing device for a carburetor.

B. Structure of the invention (1) Means for solving the problems According to the invention, at both ends of the sliding valve in the direction orthogonal to the intake direction, there are cross sections having a radius of curvature smaller than the inner circumferential surface of the intake passage. Convex curved surface portions each having a surface arc shape are formed facing at least the downstream side in the intake direction,
The side surface of the slide valve facing downstream in the intake direction and connecting the two convex curved surfaces is formed into a plane substantially perpendicular to the intake direction, and the upper end of the slide valve has a center line along the intake direction. A connecting part is provided to protrude upward at a position shifted to the left or right from A through hole is formed between the upper end and the inner surface of the bearing hole, and a screw member inserted through the through hole can be screwed into the pin. A screw hole is provided.

(2) Effect At both ends of the sliding valve in the direction perpendicular to the intake direction, there are convex curved surfaces having an arcuate cross section with a smaller radius of curvature than the inner peripheral surface of the intake passage, facing at least the downstream side in the intake direction. The side surface of the sliding valve that faces downstream in the intake direction and connects the two convex curved surfaces is formed into a plane substantially perpendicular to the intake direction, so that the connection part with the link mechanism is centered Even if it is shifted to either the left or right from the line, the slide valve will not fall, and the degree of freedom in setting the link system will increase. Further, by operating the screw member from above the connecting portion, the link mechanism and the slide valve can be attached and detached, which is advantageous for maintenance. Furthermore, since a screw member is not screwed into the sliding valve,
The sliding valve no longer requires that much strength.

(3) Embodiment Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. First, in FIGS.
, a float chamber body 3 connected to the lower part of the carburetor body 2, a throttle valve 4 as a sliding valve that slides across the intake passage 1, and a valve on the upstream side of the throttle valve 4 in the intake passage 1. and a chiyoke valve 5 disposed at.

The intake passage 1 is formed to have a circular cross section, and an air horn 7 is formed at the upstream end along the intake direction 6, which curves smoothly and widens toward the upstream side. Further, a bench lily portion 8 is provided in the intermediate portion of the intake passage 1 on the downstream side of the chiyoke valve 5.

The float chamber body 3 is connected to the lower part of the carburetor body 2 via a seal member 9, and a float chamber 10 for storing fuel is defined between the carburetor body 2 and the float chamber body 3. .

Referring also to FIG. 3, a holding cylinder part 11 which is basically cylindrical and extends downward is integrally connected to the lower part of the carburetor main body 2 at a portion corresponding to the bench lily part 8. A tightening member 12 is brought into contact with the lower end of this holding cylinder portion 11 . In addition, the tightening member 1
A jet cover 13 is connected to the float chamber 2, and the jet cover 13 is in contact with the bottom of the float chamber body 3.

The part corresponding to the bench lily part 8 is the carburetor main body 2.
A large-diameter recess 15 that is coaxial with the hole 14 in the holding cylinder 11 and a small-diameter recess 16 that is smaller in diameter than the large-diameter recess 15 and larger than the hole 14 are provided in this order from above. . Further, an enlarged diameter portion 17 is provided at the lower end of the hole 14 .

A step 18 facing upward is formed between the large diameter recess 15 and the small diameter recess 16.
With a seal member 19 interposed between the large-diameter recess 15 and
The jet block 20 is fitted into the hole. An insertion hole 21 is bored in the center of the jet block 20, and a locking collar 22 that protrudes radially inward is provided on the inner surface of the intermediate portion of the insertion hole 21 over the entire circumference. .

In the insertion hole 21 of the jet block 20,
Main fuel nozzle 23 is inserted. At a portion near the upper end of the main fuel nozzle 23, an engaging flange 24 that can engage with the upper surface of the latching flange 22 protrudes radially outward over the entire circumference. Tsuba 22
When the main fuel nozzle 23 is inserted into the insertion hole 21 by engaging the engagement collar 24 with the main fuel nozzle 23, the upper end of the main fuel nozzle 23 projects into the bench lily portion 8. Moreover, a bleed pipe 25 having a plurality of bleed holes 25a is integrally and coaxially connected to the lower part of the main fuel nozzle 23, and a male threaded portion 26 is formed on the outer periphery of the lower end of this bleed pipe 25.

A cylindrical sleeve 27 concentrically surrounding the main fuel nozzle 23 is inserted into the small diameter recess 16 .
This sleeve 27 has its upper part inserted into the insertion hole 21 of the jet block 20 and is held between the step 28 between the small diameter recess 16 and the hole 14 and the lower surface of the locking flange 22. An annular chamber 29 is defined between the outer surfaces of the main fuel nozzle 23 and bleed pipe 25 and the inner surfaces of the sleeve 27 and hole 14 .

A communication hole 30 is bored in the sleeve 27, and an air passage 31 opens at the upstream end of the intake passage 1 to communicate with the annular chamber 29 through the communication hole 30.
is bored in the carburetor main body 2.

The tightening member 12 is attached to the enlarged diameter portion 17 of the holding cylinder portion 11.
It is basically formed into a cylindrical shape with an outer diameter large enough to be inserted into the cylindrical body, and a flange 32 that protrudes radially outward is provided on the outer surface of the intermediate portion thereof over the entire circumference. In addition, female screw portions 33 and 34 are formed on the inner surface of the tightening member 12 at portions near both ends in the axial direction. The upper female threaded part 33 is screwed into the male threaded part 26 at the lower end of the bleed pipe 25, and is tightened until the collar part 32 comes into contact with the lower end of the bleed pipe 25.
As a result, the jet block 20 is sandwiched and fixed between the engaging collar 24 of the main fuel nozzle 23 and the stepped portion 18 of the carburetor body 2, and the sleeve 27
is clamped and fixed between the jet block 20 and the stepped portion 28. A fuel jet 35 is screwed into the lower female threaded portion 34 of the tightening member 12 .

In the tightening member 12, an engagement groove 36 is provided below the collar portion 32 over the entire circumference. On the other hand, the jet cover 13 is made of synthetic resin and is formed into an upwardly convex bowl shape.
An engagement hole 37 is provided that is large enough to insert the lower part of the holder. The lower part of the tightening member 12 is inserted into the engagement hole 37 such that the peripheral edge of the engagement hole 37 engages with the engagement groove 36, thereby connecting the jet cover 13 to the tightening member 12.

A plug member 38 is removably screwed to the bottom of the float chamber body 3 with a seal member 39 interposed between the float chamber body 3 and a fuel reservoir between the plug member 38 and the jet cover 13. A chamber 40 is defined. Therefore, the fuel jet 35 screwed into the female thread 34 at the bottom of the tightening member 12 is connected to the fuel storage chamber 4.
Opens at 0. Moreover, the jet cover 13 contacts the bottom of the float chamber body 3 with a plurality of protrusions 41 protruding from its lower end, and there is a fuel storage chamber 40 between the jet cover 13 and the float chamber body 3.
A gap 42 is formed that communicates the inside of the float chamber 10.

Referring again to FIG. 2, a float 43 is housed in the float chamber 10.
A float valve 44 that opens and closes in response to
It is arranged to open and close a fuel inlet hole 150 provided in the carburetor main body 2.

A guide tube 45 that opens into the bench lily portion 8 and extends upward is integrally connected to the upper part of the carburetor body 2 in order to slidably guide the throttle valve 4.
The upper end of this guide tube 45 is closed by a cover 46 so as to be openable and closable.

Referring also to FIG. 4, the throttle valve 4 is
The throttle valve 4 has a solid support portion 47 at its lower portion, and is formed into a flat elliptical cylindrical shape whose cross section is long in a direction perpendicular to the intake direction 6 of the intake passage 1. That is, the throttle valve 4 has convex curved surface portions 4a, which are arc-shaped in cross section and have a smaller radius of curvature than the inner peripheral surface of the intake passage 1, at least on the downstream side in the intake direction, at both ends in the direction perpendicular to the intake direction 6.
The side surface 4b, which faces the downstream side in the intake direction 6 and connects the two convex curved surface portions 4a, is formed in a flat shape that is substantially perpendicular to the intake direction 6.
A sliding hole 48 having a flat oval cross section is provided in correspondence with the throttle valve 4.
An operating chamber 49 connected to the upper end of the throttle valve 4 is defined by the throttle valve 4 slidingly fitted in the sliding hole portion 48, the guide cylinder 45 and the cover 46.

A small-diameter guide hole 50 connecting the intake passage 1 and the working chamber 49 is bored in the support portion 47 of the throttle valve 4 . This guide hole 50 prevents the working chamber 49 from being pressurized or depressurized by the operation of the throttle valve 4.
This is to prevent the operation of the throttle valve 4 from being inhibited by the increase or decrease in pressure in the working chamber 49.

The throttle valve 4 has a jet needle 51 inserted into the main fuel nozzle 23 and the bleed pipe 25.
is held by a holder 52 that is engaged with the throttle valve 4.

5, 6, and 7, a locking hole 54 is formed in the upper part of the support portion 47 of the throttle valve 4 and extends vertically with an engagement recess 53 on the bottom surface, and a locking hole 54 is formed in the upper part of the support portion 47 of the throttle valve 4. A holding hole 55 for inserting and holding the engaging recess 53 is formed so as to be continuous with the center of the engaging recess 53. Furthermore, a pair of engagement protrusions 56 protruding toward each other are provided on the upper inner surface of the locking hole 54 .

The holder 52 is made of synthetic resin, and has a holder body 58 that is basically formed in a cylindrical shape.
, an operating section 59 integrally provided at the upper end of the holder main body 58, and a pair of locking collars 60 integrally provided at the lower end of the holder main body 58. The outer diameter of the holder main body 58 is set to be slightly smaller than the distance between the two engaging protrusions 56, and the operating section 59 is formed in a hexagonal shape so that a box wrench or the like can be engaged therewith. Furthermore, both locking collar portions 60
are formed to protrude in an arc shape on both sides along one diameter line of the holder body 58, and the tip edges of both locking flanges 60 form an imaginary circle with a diameter slightly smaller than the inner diameter of the locking hole 54. It is curved along the

A regulating protrusion 61 extending upward along the outer surface of the holder body 58 is provided at one end of each of the locking flanges 60 along the circumferential direction of the holder body 58, and each of the locking flanges 60 along the circumferential direction is provided with a regulating projection 61 that extends upward along the outer surface of the holder body 58. A protrusion 62 for forming an engagement recess 63 between the regulating protrusion 61 and the regulating protrusion 61 is provided at the other end. Moreover, the height h1 of the regulating protrusion 61 from the locking flange 60 is greater than the distance 1 from the bottom surface of the locking hole 54 to the engaging protrusion 56, together with the thickness d1 of the locking flange 60. is also set to be large.

The holder body 58 has a hole 6 opened on its lower surface.
4 is bored, and a short cylindrical projection 65 is provided at the closed end of the hole 64 to project downward.

On the other hand, a retaining ring 66 that can be engaged with the engagement recess 53 is selectively attached to the upper part of the jet needle 51 at one of a plurality of positions spaced apart in the longitudinal direction of the jet needle 51. . A coil spring 67 is interposed between the retaining ring 66 and the holder 52, thereby holding the jet needle 51 in the throttle valve 4. That is, holder 5
2 is inserted into the locking hole 54 with one end of the coil spring 67 inserted into the hole 64 and fitted to the protrusion 65, with both locking collars 60 arranged between both engaging protrusions 56, It can only be rotated 90 degrees. Then, the holder 52 is urged upward by the spring force of the coil spring 67, the engagement protrusions 56 engage with both the engagement recesses 63, and the retaining ring 66 engages with the engagement recesses 53.
The jet needle 51 is held in the throttle valve 4 by being pressed against the throttle valve 4.

In order to manipulate the angular displacement of the holder 52, the holder 5
A cross-shaped groove 68 is provided at the upper end of the operating portion 59 in 2 to engage a driver (not shown).

The sliding direction of the throttle valve 4 and the intake direction 6 are provided on the upper part of the guide tube 45 in the carburetor main body 2.
A throttle shaft 70 serving as an operating shaft orthogonal to the throttle shaft 70 is rotatably supported. A throttle lever 71 is attached to one end of the throttle shaft 70 protruding from the guide tube 45.
is fixedly installed, and a throttle wire (not shown) is connected to the throttle lever 71. Moreover, a spring (not shown) is interposed between the carburetor body 2 and the throttle lever 71, and the spring force urges the throttle lever 71 and the throttle shaft 70 to rotate in the valve closing direction shown by the arrow 72. has been done.

The throttle valve 4 and the throttle shaft 70 are connected through a link mechanism 73 disposed in the working chamber 49, and the rotational movement of the throttle shaft 70 causes the sliding movement of the throttle valve 4 through the link mechanism 73. This is converted into a reciprocating sliding movement in the hole 48, that is, an opening and closing movement.

In FIG. 8, the link mechanism 73 includes a first link arm 75 whose one end is connected to the throttle valve 4 by a first pin 74, and a first link arm 75 whose one end is connected to the throttle shaft 70.
and a second link arm 77 whose other end is connected to the other end of the first link arm 75 by a second pin 76.

A connecting portion 79 is provided at the upper end of the throttle valve 4 to protrude upward at a position offset to the left (to the right in FIG. 4) from a center line 78 (see FIG. 4) along the intake direction 6. Ru. This connecting portion 79 has a bearing hole 8 having an axis perpendicular to the sliding direction of the throttle valve 4, for example, an axis extending left and right perpendicular to the intake direction 6.
0 is punctured. Further, the portion between the upper end of the connecting portion 79 and the upper inner surface of the bearing hole 80 is
A through hole 81 perpendicular to 0 is bored, and a bottomed hole 82 which is coaxial with the through hole 81 and opens at the lower inner surface of the bearing hole 80 is provided in the throttle valve 4 .

The first pin 74 is inserted into the bearing hole 80 by a screw member 83.
The through hole 82 and the bottomed hole 8 are inserted into and fixed to the first pin 74 in a portion near one end of the first pin 74.
A screw hole 84 having a diameter smaller than 2 is provided along one diameter line.

The screw member 83 has a small diameter portion 87 provided between a first male screw portion 85 on the front end side and a second male screw portion 86 on the rear end side that can be screwed into the screw hole 84 . Moreover, the length of the screw member 83 is the same as that of the large diameter head 8 at the rear end.
8 comes into contact with the upper end of the connecting portion 79 via the washer 151, the tip thereof does not come into contact with the bottom of the bottomed hole 82, and in this state, the second male threaded portion 86 is inserted into the screw hole 84. The lengths of the first male threaded portion 85, the small diameter portion 87, and the second male threaded portion 86 are determined so as to be screwed together, and the length of the small diameter portion 87 is the length of the small diameter portion 87.
It is set longer than 4.

The first pin 74 has a length that projects from the connecting portion 79 toward the center line 78 when inserted and fixed in the bearing hole 80, and a spherical portion 89 is provided at the projecting portion. This spherical part 89 has a first
One end of the link arm 75 is connected.

The first link arm 75 has a spherical portion 89 of the first pin 74 at one end of a short cylindrical first cylindrical portion 90.
The second cylindrical part 9 has a hole 91 having a larger diameter than the second cylindrical part 9 and has a length corresponding to the outer diameter of the first cylindrical part 90.
2 are integrally connected at right angles and are made of synthetic resin. Further, at the other end of the first cylindrical portion 90, a hole 93 through which the second pin 76 is inserted is bored along a diameter line parallel to the hole 91. Further, on the inner surface of the hole 91 facing the first cylindrical portion 90, a spherical recess 94 for receiving the spherical portion 89 is provided.
is provided.

Inside the first cylindrical portion 90 of the first link arm 75, a first pressing member 9 is provided with a first sliding surface 95 recessed into a spherical shape for sliding contact with the spherical portion 89 of the first pin 74.
6 and a second pressing member 98 having a second sliding contact surface 97 recessed in an arcuate cross section so as to be in sliding contact with the outer peripheral surface of the second pin 76 are movable in the axial direction of the first cylindrical portion 90. A spring 99 is compressed between the pressing members 96 and 97. Therefore, the first pin 7
The spherical part 89 of No. 4 is sandwiched between the spherical recess 94 and the first sliding surface 95, and the first link arm 75 is allowed to swing in any direction within a limited range. It is rotatable around pin 74.

A second pin 76 inserted into the hole 93 is press-fitted into one end of the second link arm 77 and fixed thereto. Further, a through hole 100 for inserting the throttle shaft 70 is provided at the other end of the second link arm 77, and by screwing the screw member 101 onto the throttle shaft 70 inserted through the through hole 100, The other end of the second link arm 77 is fixed to the throttle shaft 70.

Referring again to FIG. 1, an acceleration pump 102 is attached to the float chamber body 3 at a portion corresponding to the lower side of the throttle shaft 70. This acceleration pump 102 is provided with a drive shaft 103 that extends upward toward the throttle shaft 70 and is elastically biased upward, and when the drive shaft 103 is pushed down, the acceleration pump 102 is activated. It is something to do.

A guide groove 104 is provided on the outer surface of the carburetor body 2 to guide the vertical movement of the drive shaft 103.

A support shaft 105 that is parallel to the throttle shaft 70 is provided below the throttle shaft 70 and protrudes from the guide cylinder 45 of the carburetor main body 2 . The base end of the swing arm 106 thus formed is rotatably supported. This swing arm 106 is made of synthetic resin such as polyacetal resin.

A throttle shaft 70 is attached to the tip of the swing arm 106.
A bottomed cylindrical support tube portion 107 that is open toward is integrally provided. On the other hand, a cam member 108 made of synthetic resin such as polyacetal resin is fixed to the throttle shaft 70. This cam member 108
basically has a short cylindrical shape, but a part of its outer peripheral surface has a flat surface 109 along the axial direction, and the throttle shaft 70 smoothly connects to the flat surface 109 and extends toward the valve closing direction 72. A circular arc surface 110 curved away from the axis is in the valve closing direction 7.
2 in order. Moreover, when the throttle shaft 70 is in the fully closed position, the flat surface 10
The fixed position of the cam member 108 to the throttle shaft 70 is set such that the cam member 9 is located at a position corresponding to the support cylinder portion 107.

A threaded rod 111 is provided at the closed end of the support cylinder portion 107.
A pair of nuts 112 and 113 are screwed into the threaded rod 111 at a portion protruding from the closed end thereof. Also, the threaded rod 11
A short cylindrical follower 114 movable within the support tube 107 is fixed to the inner end of the support tube 107, and a coil surrounding the threaded rod 111 is connected between the follower 114 and the closed end of the support tube 107. Spring 115 is compressed. Therefore, follower 114 is nut 112
protrudes from the support cylinder portion 107 until it abuts the closed end, and the amount of protrusion is determined by the screwing position of the nuts 112, 113 onto the threaded rod 111.

The follower 114 is connected to the flat surface 109 of the cam member 108.
The swing arm 106 swings in accordance with the rotation of the cam member 108. That is, while the follower 114 is in sliding contact with the flat surface 109, the swing arm 106 remains restrained, but the follower 114 is in sliding contact with the circular arc surface 110.
In response to the sliding contact, the swing arm 106 rotates clockwise in FIG. 1 around the support shaft 105.

An umbrella-shaped receiving portion 122 that opens downward is integrally provided in the middle portion of the swing arm 106 .
This receiving portion 122 receives the upper end of the drive shaft 103 of the acceleration pump 102 . Therefore, when the throttle shaft 70, that is, the cam member 108 rotates to open the throttle valve 4 to a certain opening degree or more, the follower 114 slides against the arcuate surface 110 and the swing arm 106 moves as shown in FIG. When the drive shaft 103 is rotated clockwise and the drive shaft 103 is pushed down, the acceleration pump 102 is operated.

In FIG. 9, the carburetor main body 2 is provided with a bypass passage 116 that connects the upstream and downstream sides of the chiyok valve 5 which is in a fully closed state and bypasses the chiyok valve 5. A valve 117 is interposed.

That is, in the bypass passage 116, a passage portion 116a that opens into the intake passage 1 on the downstream side of the Chiyork valve 5, and a passage portion 116b that opens into the intake passage 1 on the upstream side of the Chiyork valve 5, are connected to the carburetor main body 2. It is configured to open into a recess 118 provided on the outer surface of the. The opening end of the recess 118 is closed by press-fitting a lid member 119, and the relief valve 11
7 is constituted by a valve body 120 that can close the opening end of the passage portion 116a to the recess 118, and a valve spring 121 that is contracted between the valve body 120 and the lid member 119.

Therefore, when the force in the valve opening direction corresponding to the difference between the pressure in the passage portion 116a and the pressure in the recess 118, that is, the passage portion 116b becomes larger than the set load of the valve spring 121, the relief valve 117 opens. death,
Air-fuel mixture is allowed to flow from passage portion 116a to passage portion 116b.

Referring also to FIG. 10, a low-speed fuel nozzle 125 is disposed at the bottom of the carburetor main body 2. This low-speed fuel nozzle 125 has a bleed pipe 126
and a low-speed fuel jet 127 are integrally connected in order from above and are attached to the carburetor main body 2 by being screwed into the lower part of the carburetor main body 2. Moreover, in the installed state, the low-speed fuel jet 127 opens below the oil level in the float chamber 10, and the low-speed fuel nozzle 125 opens into the low-speed system fuel chamber 128. In addition, the low speed system fuel chamber 128 and the throttle valve 4
An idle port 129 that opens into the intake path 1 on the downstream side of the engine is in communication with each other, and a low-speed fuel injection port 130 that opens in the bench lily part 8 and is bored in the jet block 20 also communicates with the low-speed system fuel chamber 128. be done.

The carburetor main body 2 is located around the bleed pipe 126.
An annular chamber 131 is defined between the annular chamber 131 and the upstream end of the intake passage 1.
A low-speed air passage 132 is provided in the carburetor body 2. Moreover, an air screw valve 133 is interposed in the middle of the first low-speed air passage 132. In addition, a second low-speed air passage 134 connects the middle of the first low-speed air passage 132 and the upstream end of the intake path 1.
An air cut valve 135 is interposed in the middle of the second low-speed air passage 134. Moreover, the passage diameter of the second low-speed air passage 134 is set larger than the passage diameter of the first low-speed air passage 132.

The air screw valve 133 is a valve hole 13 connected to a downstream portion 132b of the first low-speed air passage 132.
An air screw 138 having a valve body 137 at its tip that can open and close 6 is screwed onto the carburetor main body 2 so that it can be screwed forward and backward from the outside. It is biased in the valve opening direction by a spring 139 installed therein. Also the first
The upstream portion 132a of the low speed air passage 132 is
The valve body 137 is constantly communicated with a valve chamber 140 in which the valve body 137 is housed and arranged to adjust the opening degree of the valve hole 136.

The air cut valve 135 is connected to the second low speed air passage 1
34 upstream portion 134a and downstream portion 134
Valve body 1 communicates with and shuts off the air chamber 141 connected to b.
42, and a rod 145 connected to the center of a diaphragm 144 separating the air chamber 141 and negative pressure chamber 143 is brought into contact with the valve body 142. The diaphragm 144 is connected to the carburetor body 2 and the cover 1 coupled to the carburetor body 2.
46, and the negative pressure chamber 143 is sandwiched between the diaphragm 144 and the cover 146.
is defined, and an air chamber 141 is defined between the diaphragm 144 and the carburetor body 2. A spring 147 is interposed between the carburetor main body 2 and the valve body 142 to bring the valve body 142 into contact with the rod 145, and a diaphragm 144 is bent toward the air chamber 141 in the negative pressure chamber 143. A spring 148 is housed therein for biasing the valve body 142 in the valve opening direction.

A communication passage 149 is provided in the cover 146 and the carburetor body 2 to communicate the negative pressure chamber 143 with the intake passage 1 downstream of the throttle valve 4. 4, the intake negative pressure on the downstream side acts. Therefore, when the force due to the intake negative pressure overcomes the load by the spring 148, the diaphragm 144 moves into the negative pressure chamber 14.
When the valve body 142 is bent toward the 3 side, the valve body 142 closes, but the set load of the spring 148 is such that the boost negative pressure when the throttle valve 4 is closed and the engine brake is applied causes the diaphragm 144 to move into the negative pressure chamber. 143
It is set to close by bending to the side.

Further, the downstream portion 1 of the second low-speed air passage 134
34b is connected to the upstream side of the valve hole 136 in the first low-speed air passage 132, for example, to the valve chamber 140.

Next, to explain the operation of this embodiment, the throttle valve 4 slides up and down in the sliding hole portion 48 in response to the operation of the link mechanism 73 by the rotational operation of the throttle shaft 70, and thereby the intake passage 1 The opening degree of the bench lily part 8 is determined, and air at a flow rate determined by the opening degree flows through the bench lily part 8 from the upstream side of the intake passage 1, and a corresponding amount of fuel is mixed in to form an air-fuel mixture.

Here, it is assumed that a backfire occurs in the engine with the check valve 5 in the closed state when the engine is started. When this backfire occurs, the relief valve 117 opens, and the impact pressure bypasses the choke valve 5 and leaks from the bypass passage 116 to the upstream end of the intake passage 1. Therefore, direct impact pressure is prevented from acting on the chiyoke valve 5, and the chiyoke valve 5
damage and deformation are prevented. Moreover, Chiyoke valve 5
Since the relief valve 117 is not provided in the valve, an increase in the weight of the valve 5 can be avoided, and the valve 5 can be made into a simple flat plate.
Inhalation resistance can be kept small.

Furthermore, the amount of air supplied to the low-speed fuel nozzle 125 during low-speed operation is controlled by adjusting the opening of the air screw valve 133, but the amount of air flowing through the second low-speed air passage 134, which has a relatively large diameter, is also controlled by the air screw valve 133. Since it is controlled by the valve 133, the sensitivity of the control by the air screw valve 133 can be increased to allow delicate adjustment.

Furthermore, assume that the throttle valve 4 is closed to apply engine braking. At this time, the air cut valve 135 is closed, and air is supplied to the low-speed fuel nozzle 125 only from the first low-speed air passage 132. Therefore, idle port 129
The fuel concentration of the mixture discharged from the
The air-fuel mixture discharged from the engine into the exhaust passage becomes too rich, making misfires more likely, and afterburn is suppressed.

Assume that in such a carburetor, the cover 46 is opened to perform maintenance on the throttle valve 4. In this case, the link mechanism 73 and the throttle valve 4
is connected to the throttle valve 4 at a position offset from the center line 78, and a single threaded member 88 is inserted from above.
Since the screw member 88 is tightened and connected with
Simply loosen the link mechanism 73 to connect the throttle valve 4.
It can be removed from the

Moreover, since the screw member 88 has the first and second male screw portions 85 and 86 with the small diameter portion 87 interposed therebetween, the screwing operation cannot be performed unless the screw member 88 is in a tensioned state. This prevents the screw member 88 from falling into a narrow space as much as possible.

By the way, since the throttle valve 4 is formed with a flat oval cross-sectional shape, the center line 78
It is difficult to fall on both the left and right sides. That is, when the throttle valve 4 is sucked downstream in the intake direction 6 by the negative intake pressure generated in the intake passage 1, as shown in FIG.
are pressed against the inner surface of the sliding hole 48, and the convex curved surface portions 4a of the throttle valve 4 are pressed against the inner surface of the sliding hole 48 on both sides relatively far from the center line 78. Here, the sliding hole portion 4 of the convex curved surface portion 4a
8, a reaction force F is applied from the carburetor main body 2 toward the side opposite to the intake direction 6, and the convex curved surface portion 4a is moved along the radial direction of the convex curved surface portion 4a. If α is the angle between the straight line L passing through the contact part on the inner surface of the sliding hole 48 and the direction of action of the reaction force F, then the throttle valve 4 has an angle F tan α from both sides toward the center line 78. The component force of will act. Since the radius of curvature of the convex curved surface portion 4a is relatively small, the angle α is relatively large, and the component force is also relatively large. Therefore, the throttle valve 4 is prevented from falling to the left or right of the center line 78 as much as possible, and the throttle valve 4 is prevented from falling even if the connecting portion 79 is deviated from the center line 78 to either the left or the right. This does not occur, and smooth operation can be realized, and by shifting the connecting portion 79 from the center line 78, the degree of freedom in setting the link system is increased.

On the other hand, as shown in FIG. 12, when the throttle valve 4' is formed to have a perfectly circular cross-sectional shape, that is, the outer surface has a larger radius of curvature than the inner circumferential surface of the intake passage 1. If so, the intake negative pressure generated in the intake passage 1 causes the throttle valve 4'
When the throttle valve 4' is sucked downstream along the intake direction 6, the throttle valve 4'
comes into contact with the sliding hole 48'. Therefore, the angle α' between the straight line L' that passes along the radial direction of the throttle valve 4' and the contact area between the outer surface of the throttle valve 4' and the inner surface of the sliding hole 48' and the direction of action of the reaction force F is By being relatively small, the centerline 78
The force acting on the throttle valve 4' towards is small;
The throttle valve 4' tends to fall to the left or right of the center line 78. Therefore, if the throttle valve 4' is connected to the link system at a position shifted left or right from the center line 78, the throttle valve 4' will fall and smooth operation cannot be ensured.

Further, since the screw member 88 is screwed into the pin 74 and not into the throttle valve 4, it is not necessary to use a material for the throttle valve 4 that requires high tightening strength and thermal shock strength. You can expand the selection range. For example, a material such as synthetic resin with low sliding resistance can be used.

It is desirable to make the parallelism of the first and second pins 74 and 76 accurate when assembling the link mechanism 73, but this is actually difficult. However, since the first link arm 75 and the first pin 74 have a spherical shape and are in sliding contact, the first link arm 75 is allowed to fall down a little, and even if the accuracy of the parallelism is poor, the link Smooth operation of the mechanism 73, that is, smooth operation of the throttle valve 4 is possible.

Moreover, the first and second pins 74, 76 and the first
The link arm 75 is always kept in sliding contact with the link arm 75 by the action of the spring 99, and no rattling occurs. Therefore, good idle opening reproducibility can be obtained even when the throttle valve 4 is suddenly closed and then gradually closed to reach the idle opening.

The jet block 20 is held between the carburetor main body 2 and the engagement collar 24 of the main fuel nozzle 23 by screwing and tightening the tightening member 12 to the bleed pipe 25 integrated with the main fuel nozzle 23. , the main fuel nozzle 23 and the jet block 20 are fixed at the same time, and seal failure between the jet block 20 and the carburetor body 2 can be reliably prevented.

Furthermore, the drive shaft 103 of the acceleration pump 102 is received by the umbrella-shaped receiving part 122 of the swing arm 106, and since some tilting of the drive shaft 103 is allowed, the sliding resistance of the drive shaft 103 can be reduced. The operating load on the throttle shaft 70 can be reduced.

C. Effects of the invention As described above, according to the invention, both ends of the sliding valve in the direction orthogonal to the intake direction have convex curved surfaces whose cross section has an arcuate radius of curvature smaller than that of the inner peripheral surface of the intake duct. a side surface of the sliding valve facing downstream in the intake direction and connecting the two convex curved surfaces is formed in a planar shape substantially orthogonal to the intake direction; At the upper end of the slide valve, a connecting part is provided that projects upward at a position offset to the left or right from the center line along the intake direction, and a pin, which is a component of the link mechanism, is inserted into this connecting part. A bearing hole is drilled with an axis perpendicular to the sliding direction of the slide valve, and a through hole is bored between the upper end and the inner surface of the bearing hole, and the pin has a through hole. Since a screw hole is provided into which a screw member inserted through the through hole can be screwed, maintenance is facilitated, the degree of freedom in setting the link system is increased, and the range of material selection for the slide valve is increased.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a partially cutaway side view of a carburetor, FIG. 2 is an enlarged longitudinal sectional side view of the carburetor, and FIG. 3 is an enlarged view of the main parts of FIG. 2. ,
4 is an enlarged cross-sectional view taken along the - line in FIG. 2, FIG. 5 is an enlarged plan view of the holder, FIG. 6 is an enlarged side view of the holder, FIG.
The figure is an enlarged vertical developed sectional view of the link mechanism, FIG. 9 is an enlarged sectional view taken along the - line in FIG. FIG. 12 is a cross-sectional view showing a state in which the throttle valve is drawn downstream in the intake direction. FIG. 12 is a sectional view showing a throttle valve having a perfect circular cross section in a state drawn in downstream in the intake direction. DESCRIPTION OF SYMBOLS 1... Intake path, 2... Carburizer main body, 4... Throttle valve as a sliding valve, 4a... Convex curved surface portion, 4
b... Side, 6... Intake... Intake direction, 70...
Throttle shaft as an operating axis, 73...Link mechanism, 74...Pin, 78...Center line, 79...Connecting portion, 80...Bearing hole, 81...Through hole, 83...
Screw member, 84...screw hole.

Claims (1)

[Scope of utility model registration request] An operating shaft 70 rotatably supported on the carburetor body 2 for rotational operation and a sliding valve 4 slidably connected to the carburetor body 2 to open and close across the intake passage 1 form a link mechanism 73. In the slide valve opening/closing device of the carburetor connected through the carburetor, both ends of the slide valve 4 in the direction perpendicular to the intake direction 6 have a cross-sectional circle having a smaller radius of curvature than the inner peripheral surface of the intake passage 1. A side surface 4b of the slide valve 4 facing downstream in the intake direction 6 and connecting the two convex curved surfaces 4a facing at least the downstream side in the intake direction 6, each having an arcuate convex curved surface 4a.
is formed in a planar shape substantially perpendicular to the intake direction 6,
At the upper end of the slide valve 4, a connecting portion 79 is provided to protrude upward at a position shifted to the left or right from the center line 78 along the intake direction 6, and the connecting portion 79 has a link mechanism 73. A bearing hole 80 for inserting the pin 74, which is one component, is bored with an axis perpendicular to the sliding direction of the slide valve 4, and extends between the upper end and the inner surface of the bearing hole 80. A sliding valve opening/closing device for a carburetor, characterized in that a through hole 81 is bored, and the pin 74 is provided with a screw hole 84 into which a screw member 83 inserted through the through hole 81 can be screwed.