JP6117307B2 - Slow jet manufacturing method - Google Patents

Description

The present invention relates to a process for the preparation of Suroje' bets fuel passage is formed for supplying fuel to the intake passage from the fuel chamber.

  The carburetor (carburetor) is mainly mounted on a small vehicle such as a motorcycle and plays a role of atomizing fuel and mixing it with intake air as is well known. That is, a fuel chamber and an intake passage are formed in the carburetor, and a slow jet and a needle jet having one end facing the fuel chamber and the other end facing the intake passage are provided. Each of these slow jets and needle jets is a hollow body in which a fuel passage is formed. Therefore, the fuel chamber and the intake passage communicate with each other via the slow jet and the needle jet.

  The fuel in the fuel chamber circulates in the fuel passage by the venturi effect and is sprayed on the intake passage. The fuel flows through at least one of a slow jet fuel passage and a needle jet fuel passage according to the opening of the throttle. The fuel flow path is generally a slow jet when the throttle opening is small (for example, when idling), and a needle jet when the throttle is large.

  Incidentally, as shown in FIG. 4A, an orifice may be provided in the fuel passage 2 of the slow jet 1 (see, for example, FIGS. 1 and 2 of Patent Documents 1 and 2). That is, the fuel passage 2 is formed including the first large diameter hole 3, the small diameter hole 4, and the second large diameter hole 5. In the illustrated example, the first large-diameter hole 3 faces the intake passage, and the second large-diameter hole 5 faces the fuel chamber. The first large-diameter hole 3 is slightly larger in diameter than the second large-diameter hole 5.

  Between the first large-diameter hole 3 and the small-diameter hole 4, and between the small-diameter hole 4 and the second large-diameter hole 5, the diameter increases in a taper shape from the small-diameter hole 4 toward the first large-diameter hole 3, respectively. The diameter-expanded hole 6 and the diameter-reduced hole 7 that decreases in a taper shape from the second large-diameter hole 5 toward the small-diameter hole 4 are interposed. That is, the small diameter hole 4 is connected to the first large diameter hole 3 through the enlarged diameter hole 6 and is connected to the second large diameter hole 5 through the reduced diameter hole 7.

  The 1st large diameter hole 3, the small diameter hole 4, and the 2nd large diameter hole 5 are formed separately. That is, for example, the second large-diameter hole 5 is formed by pressing a drill against one end surface of a solid preform, and then the first large-diameter hole 3 is formed by pressing another drill against the other end surface. . Since the tip of each drill has a tapered diameter, a reduced diameter hole 7 and an enlarged diameter hole 6 are formed correspondingly.

  Next, a small-diameter drill is inserted from the second large-diameter hole 5, and the drill is advanced toward the diameter-enlarged hole 6 with the tip pressed against the bottom surface of the diameter-reduced hole 7. The traveling locus of the drill becomes the small diameter hole 4, and the enlarged diameter hole 6 and the reduced diameter hole 7 communicate with each other through the small diameter hole 4.

  The meat cut when forming the small-diameter hole 4 becomes a burr and protrudes into the large-diameter hole 6. Shot blasting is performed to remove this burr.

JP 11-107859 A JP 2004-360556 A

  When the fuel passage 2 is formed as described above, as shown in FIG. 4A, a so-called misalignment in which the converging position C1 of the tapered portion of the enlarged diameter hole 6 and the central axis L1 of the smaller diameter hole 4 do not coincide with each other. May occur. In other words, the convergence position C1 of the tapered portion of the diameter-expanded hole 6 and the central axis L1 of the small-diameter hole 4 are separated by a predetermined distance D1.

  In addition, fine bumps are formed in the enlarged diameter hole 6 by shot blasting for removing burrs. In combination with the above, as shown in FIG. 4B, the distribution range of the fuel flow rate is often wide. In this case, the fuel flow rate is not stable. Also, the process capability index (Cpk) is small.

  For these reasons, products with a large misalignment are excluded as non-standard products. For this reason, it is difficult to improve the production yield of the slow jet 1.

The present invention has been made to solve the problems described above, to give ensures stable flow rate of fuel, moreover, an object of the invention to provide a Suroje' preparative method of manufacturing that can be obtained with good yield.

In order to achieve the above object, the present invention provides a carburetor having a slow jet in which a fuel passage for supplying fuel from a fuel chamber to an intake passage is formed.
The fuel passage includes a small-diameter hole and a large-diameter hole larger in diameter than the small-diameter hole,
Between the small-diameter hole and the large-diameter hole, a small-diameter-hole-side enlarged hole that expands in a tapered shape from the small-diameter hole toward the large-diameter hole, and a taper angle as compared with the small-diameter-hole-side enlarged hole A large-diameter large-diameter hole is formed,
One end of the small-diameter hole-side enlarged hole is connected to the small-diameter hole, the other end is connected to one end of the large-diameter hole-side enlarged hole, and the other end of the large-diameter hole-side enlarged hole is the large-diameter hole. It is characterized by being connected.

  In this configuration, the converging position of the tapered portion of the large-diameter hole-side enlarged hole is close to the central axis of the small-diameter hole. That is, the degree of misalignment is smaller than when no small-diameter hole-side enlarged hole is formed. For this reason, the distribution width of the flow rate of the fuel flowing through the fuel passage is narrowed. Therefore, the flow rate can be stabilized.

  In addition, since a predetermined flow rate is obtained as a slow jet, the ratio of non-standard products is reduced. For this reason, the production yield of the slow jet is improved.

The present invention also relates to a method of manufacturing a slow jet in which a fuel passage for supplying fuel from a fuel chamber to an intake passage is formed.
A large-diameter hole extending along the longitudinal direction from one end of the preform, and a large-diameter extending in the same direction as the large-diameter hole and expanding in a tapered shape as the large-diameter hole approaches. Forming a hole-side enlarged hole;
A step of forming a small-diameter hole that is continuous with the large-diameter hole-side enlarged hole and is smaller in diameter than the large-diameter hole;
Forming a small-diameter hole-side enlarged hole having a smaller taper angle than the large-diameter hole-side enlarged hole between the large-diameter hole-side enlarged hole and the small-diameter hole;
A fuel passage is formed through the above.

  By going through such a process, the converging position of the tapered portion of the large-diameter hole-side enlarged hole can be brought close to the central axis of the small-diameter hole. That is, a slow jet having a small misalignment and a stable flow rate can be obtained with a high yield.

  The small diameter hole may be located between two large diameter holes. That is, in this case, the small diameter hole is interposed between the large diameter hole and another large diameter hole having a larger diameter than the small diameter hole. Then, the small-diameter hole may be connected to the another large-diameter hole via a reduced-diameter hole that decreases in a taper shape from the other large-diameter hole toward the small-diameter hole.

  In order to obtain such a slow jet, before or after forming the large-diameter hole and the large-diameter hole-side enlarged hole, another large diameter extending along the longitudinal direction from the other end of the preform. Forming a hole and a diameter-reduced hole that extends in the same direction as the other large-diameter hole and decreases in a tapered shape as the distance from the other large-diameter hole increases. After forming the diameter hole and the reduced diameter hole, and the large diameter hole and the large diameter hole side enlarged hole, the large diameter hole side enlarged hole and the reduced diameter hole communicate with each other, and What is necessary is just to form the said small diameter hole so that it may become a small diameter compared with a large diameter hole. In addition, as above-mentioned, you may form any of a large diameter hole and a large diameter hole side enlarged hole, and another large diameter hole and a diameter-reduced hole previously.

  The small-diameter hole can be formed, for example, by advancing a drilling tool inserted into another large-diameter hole toward the large-diameter hole-side enlarged hole. In this case, it is preferable to form the small-diameter hole before forming the small-diameter hole-side enlarged hole. When a drilling tool is advanced from the other large-diameter hole toward the large-diameter hole so as to form a small-diameter hole, a burr protrudes into the large-diameter-side enlarged hole. If this burr is removed when the small-diameter hole-side enlarged hole is formed, shot blasting becomes unnecessary.

  Therefore, it is possible to avoid the formation of a bulge caused by shot blasting on the inner wall of the large-diameter hole-side enlarged hole or the small-diameter hole-side enlarged hole. This also makes it easier to stabilize the fuel flow rate.

  Note that if the misalignment between the small diameter hole and the passage located downstream in the fuel flow direction is reduced, the flow rate of the fuel is further stabilized. Therefore, it is preferable that the small-diameter hole is on the upstream side in the fuel flow direction, and the downstream side is closer to the small-diameter hole-side enlarged hole, the large-diameter hole-side enlarged hole, and the large-diameter hole. That is, it is preferable that the large diameter hole faces the intake passage and the small diameter hole faces the fuel chamber.

  According to the present invention, between the small-diameter hole and the large-diameter hole serving as the fuel passage of the slow jet, the small-diameter hole-side enlarged hole, one end is connected to the small-diameter hole-side enlarged hole, and the other end is the large-diameter. A large-diameter-side enlarged hole that is continuous with the hole is interposed. Since the taper angle of the large-diameter-side enlarged hole is larger than that of the small-diameter-side enlarged hole, the converging position of the tapered portion of the large-diameter-side enlarged hole can be brought close to the central axis of the small-diameter hole. Easy. That is, the misalignment can be reduced.

  In a slow jet with a small misalignment, the distribution width of the flow rate of the fuel passing through the fuel passage becomes narrow. For this reason, the flow rate can be stabilized.

  Moreover, for the reasons described above, the ratio of non-standard products that cannot obtain a predetermined flow rate is reduced. Therefore, the production yield of the slow jet is improved.

It is a principal part schematic longitudinal cross-sectional view of the vaporizer | carburetor which concerns on embodiment of this invention. 2A is an enlarged vertical cross-sectional view of the main part of the slow jet constituting the vaporizer of FIG. 1, and FIG. 2B shows the relationship between the distribution width of the fuel flow rate when the slow jet is used and Cpk. It is a graph. FIG. 3A is a longitudinal cross-sectional enlarged view of a main part of a slow jet in which the length of the small-diameter hole side enlarged hole (first enlarged hole) is larger than that in FIG. 2A. FIG. 3B is a view when the slow jet is used. It is a graph which shows the relationship between the distribution width | variety of the flow volume of a fuel, and Cpk. FIG. 4A is an enlarged vertical cross-sectional view of the main part of a slow jet constituting a carburetor according to the prior art, and FIG. 4B shows the relationship between the distribution width of the fuel flow rate when the slow jet is used and Cpk. It is a graph to show.

Hereinafter, the production method of engaging Luz row jets to the present invention, exemplified by preferred embodiments in relation to a carburetor including the slow jet, will be described in detail with reference to the accompanying drawings. For convenience of explanation, the fuel chamber side may be referred to as “lower” and the intake passage side may be referred to as “upper”.

  FIG. 1 is a schematic vertical sectional view of a main part of a vaporizer 10 according to the present embodiment. The carburetor 10 is mounted on a small vehicle such as a motorcycle, and after mixing fuel and intake air, supplies it to the combustion chamber of the internal combustion engine. The carburetor 10 may be used for a general-purpose internal combustion engine that drives various types of work machines other than the vehicle, for example.

  The carburetor 10 includes a float chamber body 14 for forming a float chamber 12 as a fuel chamber, and a carburetor body 18 in which an intake passage 16 is formed. In the intake passage 16, the right side in FIG. 1 is the upstream side in the flow direction, and the left side is the downstream side.

  The float chamber body 14 is formed by attaching the float chamber body 14 to the vaporizer body 18. A certain amount of fuel Fu is stored in the float chamber 12 as a liquid. That is, in the float chamber 12, the float 20 floats on the liquid level of the fuel Fu. When the fuel Fu is consumed and the liquid level is lowered, the float 20 is lowered accordingly, and the fuel inflow valve 22 is opened, and new fuel Fu is supplied to the float chamber 12. On the other hand, when the fuel Fu is supplied and the liquid level and the float 20 are raised to a predetermined position, the fuel inflow valve 22 is closed and further supply of the fuel Fu is stopped.

  The carburetor body 18 has a boss portion 24 that extends to the lower side of the liquid level of the fuel Fu. In the boss portion 24, a slow jet insertion port 30, a slow port communication path 32, a slow port 34, a needle jet insertion port 36, and a bleed air path 38 are formed. The slow jet insertion port 30 communicates with the slow port 34 via the slow port communication passage 32, while the needle jet insertion port 36 communicates with the bleed air passage 38. Further, the slow jet insertion port 30 and the needle jet insertion port 36 extend along the vertical direction in FIG. 1 so as to go from the float chamber 12 to the intake passage 16. On the other hand, the slow port communication passage 32 and the bleed air passage 38 extend substantially parallel to the intake passage 16.

  A slow jet 40 is inserted into the slow jet insertion port 30. Here, an internal thread portion is formed on the inner wall of the slow jet insertion port 30, and an external thread portion is formed on the outer wall of the slow jet 40. The slow jet 40 is held in the slow jet insertion port 30 by screwing the male screw portion into the female screw portion.

  The slow jet 40 is a hollow body in which a fuel passage 42 is formed along the longitudinal direction, and has a substantially cylindrical shape. The fuel passage 42 has a first large-diameter hole 44 (large-diameter hole), a small-diameter hole 46, and a second large-diameter hole 48 (another large-diameter hole) in order from the upper intake passage 16 toward the lower float chamber 12. The maximum diameter hole 50 having the maximum inner diameter is formed.

  The inner diameter of the small diameter hole 46 is the smallest in the fuel passage 42. That is, an orifice is formed in the fuel passage 42 by interposing the small diameter hole 46 between the first large diameter hole 44 and the second large diameter hole 48. In this case, the inner diameter of the first large diameter hole 44 is set larger than that of the second large diameter hole 48.

  As shown in detail in FIG. 2A, between the first large-diameter hole 44 and the small-diameter hole 46, a first large-diameter hole 52 that expands in a tapered shape from the small-diameter hole 46 toward the first large-diameter hole 44. The (small diameter hole side diameter expansion hole) and the second diameter expansion hole 54 (large diameter hole side diameter expansion hole) are interposed. That is, the lower end of the first enlarged diameter hole 52 is connected to the upper end of the small diameter hole 46, and the upper end is connected to the lower end of the second enlarged diameter hole 54. Furthermore, the upper end of the second enlarged diameter hole 54 is connected to the lower end of the first large diameter hole 44.

  The taper angle θ2 of the second diameter expansion hole 54 is set larger than the taper angle θ1 of the first diameter expansion hole 52. Typically, the taper angle θ1 is about 5 ° and θ2 is about 10 °. The converging position C2 of the tapered portion of the second diameter expansion hole 54 and the center axis L2 of the small diameter hole 46 are close to each other, and the separation distance D2 is extremely small. That is, D2 <D1 (see FIG. 4A) and the degree of misalignment is small. Note that the length M2 of the second diameter expansion hole 54 to the convergence position C2 is larger than the length M1 of the first diameter expansion hole 52, for example.

  Moreover, both the 1st diameter expansion hole 52 and the 2nd diameter expansion hole 54 have the inner wall formed as a smooth surface. That is, no fine bumps formed due to shot blasting are observed.

  On the other hand, between the second large-diameter hole 48 and the small-diameter hole 46, there is a diameter-reduced hole 56 that decreases in a taper shape from the second large-diameter hole 48 toward the small-diameter hole 46. That is, the upper end of the reduced diameter hole 56 is connected to the lower end of the small diameter hole 46, and the lower end is connected to the second large diameter hole 48. For example, the taper angle θ3 of the diameter-reduced hole 56 is set larger than θ1 and smaller than θ2, but is not particularly limited thereto.

  The main jet 58 and the needle jet 60 are held in the needle jet insertion port 36 (see FIG. 1). A part of the main jet 58 located below the needle jet 60 is exposed to the float chamber 12 and contacts the fuel Fu.

  One needle jet 60 includes a main nozzle 64 in which a throttle into which a jet needle 62 is inserted is formed, and a hollow air bleed pipe 66 that is connected to the main nozzle 64 and extends toward the float chamber 12. It is configured by being provided integrally. A plurality of bleed holes 68 for communicating the hollow interior of the air bleed tube 66 and the bleed air passage 38 are formed in the side wall of the air bleed tube 66.

  The diameter (cross-sectional area) of the jet needle 62 increases stepwise from the float chamber 12 toward the intake passage 16. Therefore, when the jet needle 62 is displaced, the distance (clearance) between the side wall of the jet needle 62 and the inner wall of the main nozzle 64 (throttle) changes according to the amount of displacement.

  The jet needle 62 is held by the throttle valve 70. That is, the throttle valve 70 is configured as a hollow body, and the jet needle 62 is inserted into the insertion hole 72 formed therein. The jet needle 62 has a flange portion 74 having a diameter larger than that of the insertion hole 72 at the upper end portion thereof. The flange portion 74 is blocked in the vicinity of the opening of the insertion hole 72, so that the jet needle 62 is prevented from coming off from the insertion hole 72. The jet needle 62 controls the flow rate of fuel according to the opening degree of the throttle valve 70.

  In the throttle valve 70, a retainer 78 for pressing the first return spring 76 is disposed above the jet needle 62. That is, the jet needle 62 is floatingly supported by being elastically biased toward the float chamber 12 side (downward) by the first return spring 76. A part of the retainer 78 is exposed in a spring chamber 80 formed in the throttle valve 70.

  The intake passage 16 formed in the carburetor body 18 communicates with the air cleaner of the internal combustion engine on the upstream side of the intake air flow direction, and communicates with the combustion chamber of the internal combustion engine on the downstream side. A choke valve 82 is disposed on the upstream side of the intake passage 16. On the downstream side, a substantially cylindrical guide portion 84 is provided in a direction intersecting the intake passage 16. The throttle valve 70 is slidably supported by the guide portion 84.

  The throttle valve 70 is a sliding throttle valve composed of a cylindrical piston that is slidably guided by the guide portion 84, and is closed by a second return spring 88 sandwiched between the bottom wall of the spring chamber 80 and the cover 86. The bullet is always energized in the direction. An operation wire (not shown) connected to a throttle grip as an accelerator operation member is connected to the throttle valve 70. In accordance with the operation of the throttle grip, the opening degree of the throttle valve 70 is changed within an opening degree range from the idle opening degree to the full opening.

  That is, the venturi passage 90 is formed in the vicinity of the slow port 34 by the bottom wall of the throttle valve 70 and the inner wall of the intake passage 16 facing the bottom wall. The passage cross-sectional area of the venturi passage 90 changes according to the position (height) of the throttle valve 70. Specifically, the throttle valve 70 is located at the bottom dead center at the idle opening, and the passage cross-sectional area of the venturi passage 90 is minimized. On the other hand, when the throttle grip is operated to raise the throttle valve 70, the passage cross-sectional area of the venturi passage 90 increases. When the throttle valve 70 reaches the top dead center, the passage cross-sectional area of the venturi passage 90 is maximized. At this time, the opening degree of the throttle valve 70 is fully open.

  The vaporizer 10 according to the present embodiment is basically configured as described above. Next, the operation and effect will be described.

  The above-described slow jet 40 can be manufactured as follows, for example. That is, first, a stepped drill is pressed against one end surface of a solid preform, and the maximum diameter hole 50 corresponding to the large diameter portion of the stepped drill and the second large diameter corresponding to the small diameter portion are advanced. A hole 48 is formed. Usually, since the tip of the drill is tapered, the maximum diameter hole 50, the second large diameter hole 48, and the diameter reduction hole 56 are simultaneously formed by this pressing and progression.

  Next, another drill is pressed against the other end surface and advanced to form a first large-diameter hole 44 and a second large-diameter hole 54 (large-diameter hole-side large-diameter hole). At this time, the diameter-reduced hole 56 and the second diameter-expanded hole 54 are separated by a predetermined distance and are not in communication.

  Thereafter, a small-diameter drill (drilling tool) is inserted from the second large-diameter hole 48, and the drill is advanced toward the second large-diameter hole 54 with the tip pressed against the bottom surface of the reduced-diameter hole 56. The traveling path of the drill becomes a small diameter hole 46, and the reduced diameter hole 56 and the second expanded diameter hole 54 communicate with each other through the small diameter hole 46. The meat cut at this time protrudes as a burr into the second enlarged diameter hole 54.

  In this case, since the diameter of the drill is very small, it is not easy for the drill to advance along the longitudinal direction of the preform. For this reason, the axial center of a drill and the convergence position of the taper part of the 2nd diameter expansion hole 54 may not correspond.

  Next, the first enlarged diameter hole 52 (small diameter hole side enlarged diameter hole) is formed between the second enlarged diameter hole 54 and the small diameter hole 46. That is, for example, a punch having a smaller taper angle than the drill having the first large diameter hole 44 is inserted into the first large diameter hole 44.

  Since the taper angle of the punch is smaller than the taper angle θ2 of the second diameter expansion hole 54, when the tip end of the punch reaches the vicinity of the lower end of the second diameter expansion hole 54, the surrounding meat is cut. Along with this, the burr is removed, and a first diameter-expanded hole 52 whose lower end is connected to the small diameter hole 46 and whose upper end is connected to the second diameter-expanded hole 54 is formed.

  Since the burrs have already been removed as described above, it is not particularly necessary to perform shot blasting on the first large-diameter hole 44, the first large-diameter hole 52, and the second large-diameter hole 54. Accordingly, in this case, the inner walls of the first diameter-expanded hole 52 and the second diameter-expanded hole 54 are smooth so that no bulging is observed.

  In addition, since the first enlarged diameter hole 52 is larger in diameter than the smaller diameter hole 46, the converging position C2 of the tapered portion of the second enlarged diameter hole 54 and the central axis L2 of the small diameter hole 46 come close to each other. That is, when the first diameter expansion hole 52 is formed, it is easy to align the convergence position C2 of the second diameter expansion hole 54 and the central axis L2 of the small diameter hole 46. In other words, the misalignment can be made as small as possible.

  The slow jet 40 thus produced is held in the slow jet insertion port 30 by screwing between the screw portions as described above.

  When the internal combustion engine is operated, the intake air flows through the intake passage 16 from the right side to the left side in FIG. As the intake air passes through the venturi passage 90 formed by the bottom wall of the throttle valve 70 and the inner wall of the intake passage 16, the inside of the intake passage 16 becomes negative pressure. Accordingly, the fuel Fu in the float chamber 12 is sucked up through the slow jet 40. That is, the fuel Fu flows through the fuel passage 42 inside the slow jet 40.

  The fuel Fu further passes through the slow port communication passage 32 and is introduced from the slow port 34 into the intake passage 16. The fuel Fu is also introduced into the intake passage 16 from an idle port (not shown). The fuel Fu that has reached the intake passage 16 is atomized by the intake air flowing through the intake passage 16, and is accompanied by the intake air and supplied to the combustion chamber of the internal combustion engine.

  As described above, the fuel passage 42 in the slow jet 40 extends from the float chamber 12 toward the intake passage 16 with the largest diameter hole 50, the second large diameter hole 48, the reduced diameter hole 56, the small diameter hole 46, and the first enlarged diameter hole. The diameter hole 52, the second diameter expansion hole 54, and the first large diameter hole 44 are provided in this order. Accordingly, from the small diameter hole 46 to the slow port 34, the fuel Fu passes through the first large diameter hole 52, the second large diameter hole 54, and the first large diameter hole 44.

  Here, as shown in FIG. 2A, the separation distance D2 between the central axis L2 of the small diameter hole 46 and the converging position C2 of the tapered portion of the second large diameter hole 54 is extremely small. Further, the inner walls of the first diameter expansion hole 52 and the second diameter expansion hole 54 are smooth and no bulge is observed. For the above reasons, as shown in FIG. 2B, the distribution width of the flow rate of the fuel Fu passing through the fuel passage 42 becomes narrower and Cpk becomes larger.

  FIG. 3A is a cross-sectional view in the flow direction when the first enlarged hole 52 is formed with the same taper angle θ1 and the length M1 ′ set to be larger than the length M1 (see FIG. 2A). In this case, the central axis L2 of the small diameter hole 46 and the convergent position C2 'of the tapered portion of the second large diameter hole 54 substantially match. That is, the distance D2 'between them is much smaller than D2 (see FIG. 2A). The taper angles θ2, θ3 and the length M2 are the same as θ2, θ3 and M2 in FIG. 2A, and M1 ′ is about 0.1 to 0.2 mm longer than M1. Also in this case, no bulging is observed in the first diameter expansion hole 52 and the second diameter expansion hole 54.

In this case, as shown in FIG. 3B, the distribution width of the flow rate passing through the fuel passage 42 becomes narrower and Cpk becomes larger. Therefore, the convergence position of the taper portion of the second enlarged diameter hole 54, by reducing as much as possible the distance between the center axis L2 of the small-diameter hole 46, narrowing the flow rate of the distribution width of the fuel Fu It can be seen that Cpk can be increased.

  As described above, even when the distance between the converging position of the tapered portion of the second enlarged diameter hole 54 and the central axis L2 of the small diameter hole 46 is large, by forming the first enlarged diameter hole 52, The converging position of the tapered portion of the second diameter expansion hole 54 can be brought close to the central axis L <b> 2 of the small diameter hole 46. In other words, when the small diameter hole 46 is formed, the first large diameter hole 52 is formed even if the center axis L2 of the small diameter hole 46 and the converging position of the second large diameter hole 54 are large. By doing so, the misalignment can be reduced.

  In the slow jet 40 in which the first diameter expansion hole 52 and the second diameter expansion hole 54 are formed, the flow width distribution of the fuel Fu flowing through the fuel passage 42 is narrow. Accordingly, the flow rate of the fuel Fu can be stabilized. In addition, the number of products that are removed as non-standard products for this reason is reduced, so that the production yield of the slow jet 40 is improved.

2B, the comparison to FIG. 3B and 4B, when the length and diameter of the small-diameter hole 4 6 are the same, the convergence position of the taper portion of the second enlarged diameter hole 54 and the center axis L2 of the small-diameter hole 46 It can also be seen that the median value of the flow distribution width of the fuel Fu increases as the distance between the first and second diameter-expanded holes 52 increases. From this, the flow rate of the fuel Fu can be set to a desired value by adjusting the separation distance and the length of the first diameter expansion hole 52.

  That is, according to the present embodiment, the flow rate of the fuel Fu can be variously changed while keeping the same number of jets (jet hole diameter). For this reason, it is not necessary to prepare the slow jet 40 having a different number of jets for each target flow rate. Therefore, the slow jet insertion port 30 can be formed with substantially the same hole diameter even when producing vaporizers with different standards, so that the formation of the slow jet insertion port 30 is facilitated.

  When the driver operates the throttle grip in the opening direction so as to increase the load on the internal combustion engine, the throttle valve 70 is pulled through the tensioned operation wire. Accordingly, the second return spring 88 is compressed, and the throttle valve 70 is displaced upward in FIG. 1 along the guide portion 84. As a result, the opening degree of the throttle valve 70 increases and the passage cross-sectional area of the venturi passage 90 increases.

  When the throttle valve 70 moves up, the jet needle 62 held floating on the throttle valve 70 moves up and compresses the first return spring 76. Further, as the jet needle 62 is displaced, the small diameter portion faces the inner wall of the main nozzle 64 instead of the large diameter portion of the jet needle 62. That is, the clearance between the side wall of the jet needle 62 and the inner wall of the main nozzle 64 is increased. Accordingly, a large amount of fuel Fu is sucked up from the main jet 58 and mixed with the intake air flowing into the air bleed pipe 66 from the intake passage 16 through the bleed air passage 38 and the bleed hole 68.

  The mixture of the fuel Fu and the intake air is further introduced from the main nozzle 64 into the intake passage 16 and further mixed with the intake air. A mixture of the fuel Fu and the intake air atomized in the above process is supplied to the internal combustion engine.

  As the rising amount (displacement amount) of the jet needle 62 is larger, the portion facing the inner wall of the main nozzle 64 has a smaller diameter. Accordingly, much fuel Fu is taken into the needle jet 60 from the main jet 58. As described above, the fuel Fu corresponding to the opening of the throttle grip (accelerator) is introduced into the intake passage 16.

  When the driver operates the throttle grip in the closing direction from this state, the operation wire is relaxed and the throttle valve 70 is released from the restriction of the operation wire. Accordingly, the throttle valve 70 is elastically biased from the second return spring 88 and displaced downward in FIG. Further, the jet needle 62 is elastically biased from the first return spring 76 and displaced downward. As a result, the throttle valve 70 and the jet needle 62 return to the positions shown in FIG.

  The present invention is not particularly limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  For example, in this embodiment, the first large diameter hole 44 connected to the small diameter hole 46 via the first diameter expansion hole 52 and the second diameter expansion hole 54 is formed so as to face the intake passage 16, and The two large diameter holes 48 are formed so as to face the float chamber 12, but the first large diameter hole 44, the first large diameter hole 52, and the second large diameter hole 54 are formed so as to face the float chamber 12. Also good.

  Further, a second reduced diameter hole having a smaller taper angle than the reduced diameter hole 56 may be formed between the reduced diameter hole 56 and the small diameter hole 46.

  Furthermore, the process of forming the first large-diameter hole 44 and the second large-diameter hole 54 and the process of forming the second large-diameter hole 48 and the reduced-diameter hole 56 are in no particular order, and either may be performed first.

10 ... Vaporizer 12 ... Float chamber (fuel chamber)
DESCRIPTION OF SYMBOLS 14 ... Float chamber body 16 ... Intake passage 18 ... Vaporizer body 40 ... Slow jet 42 ... Fuel passage 44 ... 1st large diameter hole 46 ... Small diameter hole 48 ... 2nd large diameter hole 50 ... Maximum diameter hole 52 ... 1st expansion Diameter hole (small hole diameter side expansion hole)
54 ... 2nd diameter expansion hole (large diameter side diameter expansion hole) 56 ... Diameter reduction hole 58 ... Main jet 60 ... Needle jet 64 ... Main nozzle 66 ... Air bleed pipe 70 ... Throttle valve 84 ... Guide part 90 ... Venturi passage Fu ... fuel

Claims (4)

In a method of manufacturing a slow jet in which a fuel passage for supplying fuel from a fuel chamber to an intake passage is formed,
A large-diameter hole extending along the longitudinal direction from one end of the preform, and a large-diameter extending in the same direction as the large-diameter hole and expanding in a tapered shape as the large-diameter hole approaches. Forming a hole-side enlarged hole;
A step of forming a small-diameter hole that is continuous with the large-diameter hole-side enlarged hole and is smaller in diameter than the large-diameter hole;
Forming a small-diameter hole-side enlarged hole having a smaller taper angle than the large-diameter hole-side enlarged hole between the large-diameter hole-side enlarged hole and the small-diameter hole;
When forming a fuel passage through,
Before or after forming the large-diameter hole and the large-diameter-hole-side enlarged hole, another large-diameter hole extending along the longitudinal direction from the other end of the preform, and another large-diameter hole The method further includes a step of forming a reduced diameter hole that continuously extends in the same direction and decreases in a tapered shape as the distance from the another large diameter hole increases.
After forming the another large-diameter hole and the reduced-diameter hole, and the large-diameter hole and the large-diameter hole-side enlarged hole, the large-diameter hole-side enlarged hole and the reduced-diameter hole communicate with each other, The method for producing a slow jet is characterized in that the small-diameter hole is formed to have a smaller diameter than the other large-diameter hole . 2. The slow jet according to claim 1 , wherein the small-diameter hole is formed by advancing a drilling tool inserted into the other large-diameter hole toward the large-diameter hole-side enlarged hole. Manufacturing method. 3. The manufacturing method according to claim 2 , wherein the small-diameter hole is formed before the small-diameter hole-side enlarged hole is formed, and the burrs projecting into the large-diameter hole-side enlarged hole when the small-diameter hole is formed. Is removed when the small-diameter hole-side enlarged hole is formed. The manufacturing method according to any one of claims 1 to 3 , wherein the large diameter hole is formed on a side facing the intake passage, and the small diameter hole is formed on a side facing the fuel chamber. A method of manufacturing a slow jet.

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