JP6084650B2 - Vaporizer - Google Patents

Description

  The present invention relates to a carburetor, particularly a carburetor main body, an intake passage that forms part of an intake passage connected to a combustion chamber of an internal combustion engine, a throttle valve that opens and closes the intake passage, and a main nozzle that opens to the intake passage. An air bleed chamber formed on the outer periphery of the main nozzle and communicating with the main nozzle through a number of bleed holes, and first and second bleeds connected to the air bleed chamber and communicating the air bleed chamber with the atmosphere. The carburetor is provided with an air passage, and the second bleed air passage is in a conductive state only in a partial opening region of the throttle valve by a control valve.

  In such a carburetor, the air inlet of the second bleed air passage formed in the carburetor main body is directly opened at the end face on the intake upstream side of the carburetor main body, and the atmosphere in the intake passage is introduced from the opening. This is already known, for example, as disclosed in Patent Document 1 below.

JP 2004-137828 A

  In the conventional carburetor, the air inlet of the second bleed air passage formed in the carburetor main body and opened to the intake upstream end surface of the carburetor main body is used as the air inlet facing the intake passage. Is limited to a limited region on the intake upstream end surface of the carburetor body. Therefore, depending on the opening position of the air introduction port, the bleed air cannot be optimally introduced from there into the second bleed air passage, and the air introduction amount may not be sufficient. Adjustment was not easy. Accordingly, it is difficult to finely adjust the amount of air introduced from the intake passage to the second bleed air passage in the specific opening region of the throttle valve in which the second bleed air passage is brought into conduction by the control valve. Adjustment and control of the air-fuel ratio of the air-fuel mixture generated by the carburetor could not be accurately performed.

  The present invention has been made in view of the above. While simplifying the structure, the bleed air can be optimally and sufficiently introduced into the second bleed air passage and the air introduction amount can be easily adjusted. An object of the present invention is to provide a vaporizer capable of solving the above-described problems of the conventional structure.

In order to achieve the above object, the present invention provides a carburetor body, an intake passage that forms part of an intake passage connected to a combustion chamber of an internal combustion engine, a throttle valve that opens and closes the intake passage, and an opening in the intake passage. A main nozzle that is formed on the outer periphery of the main nozzle and communicates with the main nozzle through a number of bleed holes, and a first bleed chamber that is connected to the air bleed chamber and communicates with the atmosphere. And a second bleed air passage, wherein the second bleed air passage is in a conductive state only in a partial opening region of the throttle valve by the control valve. an air inlet opening into the vessel body, a pipe for introducing air from the intake passage into the second bleed air passage is connected, the pipe is mounted is in the carburetor body is formed in a cylindrical shape , Together with at least front portion overhangs the intake passage thereof, the pipe tip is first characterized in that it opens into the intake passage.

In addition to the first feature, the present invention is mounted on a power working machine in which the opening degree of the throttle valve is operated so as to maintain the engine speed at a constant speed during operation of the internal combustion engine. The second feature.

The present invention, in addition to the first or second feature, the throttle valve is a butterfly type valve, the proximal end portion of the pipe to the air inlet of the second bleed air passage is connected A third feature is that a tip portion of the pipe serving as an air introduction port is disposed closer to the central axis of the intake passage than the air inlet and on the intake upstream side.

In addition to any one of the first to third features, the present invention has a fourth feature that the open surface of the tip of the pipe passes through the central axis of the intake passage.

  As described above, according to the first feature of the present invention, in the carburetor in which the second bleed air passage is in a conductive state only in a partial opening region of the throttle valve by the control valve, The pipe that introduces air from the intake passage is connected to the air inlet that opens in the carburetor body, and this pipe is formed in a cylindrical shape and attached to the carburetor body, so that the pipe is simply attached to the carburetor body With this simple structure, the degree of freedom in selecting the shape and position of the air inlet for taking air from the intake passage into the second bleed air passage is increased. Not only can the air introduction be optimal and sufficient, but the amount of air introduction can be easily adjusted. As a result, fine adjustment of the air introduction amount from the intake passage to the second bleed air passage is facilitated in the specific opening region of the throttle valve where the second bleed air passage is brought into conduction by the control valve, and the same opening region. Therefore, the air-fuel ratio of the air-fuel mixture generated by the carburetor can be adjusted and controlled with high accuracy.

Also, the pipes with at least front portion of it protrudes into the intake passage, so that pipe tip is open to the intake passage, Ya opening position of the intake passage of the pipe tip (i.e. air inlet) The degree of freedom in selecting the opening size is further increased, and the amount of air introduced from the intake passage to the second bleed air passage can be adjusted more easily.

In particular, according to the second feature, the carburetor is mounted on the power working machine in which the opening degree of the throttle valve is operated so as to keep the engine speed at a constant speed during operation of the internal combustion engine. Fine adjustment of the air introduction amount from the intake passage to the second bleed air passage in the specific opening range of the valve is facilitated, and the air-fuel mixture is reduced in the constant load operation region of the power working machine corresponding to the same opening range. By optimizing the air-fuel ratio, it is possible to improve fuel efficiency and optimize exhaust gas.

In particular, according to the third feature, in the carburetor in which the intake air amount is controlled by the butterfly type throttle valve, the intake air flow velocity is higher at the center of the passage than near the wall of the intake passage. The tip of the pipe can be protruded into the intake passage with the mounting position facing the pipe tip (ie, the air inlet), and the air in the intake passage can be efficiently and smoothly taken into the pipe from the tip. Therefore, air can be introduced more optimally and sufficiently from the intake passage to the second bleed air passage.

The front view which looked at one Embodiment of the carburetor which concerns on this invention from the intake upstream side, and principal part sectional drawing of the intake passage of a pipe and its periphery 2-2 sectional view of FIG. Cross-sectional view of the venturi portion of the embodiment (cross-sectional view taken along line 3-3 in FIG. 2) FIG. 4 is a cross-sectional view taken along line 4-4, and a partially enlarged cross-sectional view showing the opening change state of the control valve in accordance with the opening change of the throttle valve.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on preferred embodiments of the present invention shown in the drawings.

  First, in FIGS. 1 and 2, the carburetor C is used to generate a mixture of fuel and air to be supplied to an internal combustion engine mounted on a power working machine (not shown) (for example, a power generator, a power lawn mower, etc.). A carburetor main body 1 having an intake passage 2 extending in the horizontal direction and a carburetor main body 1 joined to an outer periphery of the lower surface of the carburetor main body 1 through an O-ring 23. And a float chamber body 3 defining a float chamber 4.

  The upstream end face 1a of the carburetor body 1 is connected to the upstream end of the intake pipe P connected to the combustion chamber of the internal combustion engine and fastened with a bolt. 1b is connected to a downstream end of an intake pipe P 'connected to an air cleaner (not shown) and fastened with a bolt. Thus, the intake pipe P, the intake passage 2 of the carburetor body 1, the intake pipe P ', and the air cleaner constitute a series of intake passages I connected to the combustion chamber. An air cleaner may be directly connected to the upstream end of the intake passage 2 without using the intake pipe P ′.

  The lower end of the venturi portion 2a of the intake passage 2 is open at the upper end of a main nozzle 5 that is formed in a cylindrical shape and extends in the vertical direction, and is upstream of the intake passage 2 (that is, in FIG. 2) with the venturi portion 2a interposed therebetween. A choke valve 6 is disposed on the lower side, and a throttle valve 7 is disposed on the downstream side of the intake passage 2 (that is, the upper side in FIG. 2). Thus, in the operating state of the internal combustion engine, the air that has passed through the air cleaner flows into the intake passage 2 of the carburetor C toward the combustion chamber of the internal combustion engine. At this time, the carburetor C is in the float chamber 4. The stored fuel F is sprayed in the form of a mist through the main nozzle 5 to the venturi portion 2a of the intake passage 2 and mixed with the air flow passing therethrough to generate an air-fuel mixture.

  The throttle valve 7 passes through the intake passage 2 and is rotatably supported by the carburetor body 1 and extends in the vertical direction, and a disc-like valve fixed to the valve shaft 8 in the intake passage 2. It is configured as a butterfly valve having a plate 9. An upper end 8u and a lower end 8d of the valve shaft 8 are rotatably fitted and supported in an upper bearing hole 1u and a lower bearing hole 1d formed in the peripheral wall immediately above and below the intake passage 2 of the carburetor body 1, respectively. The In the present embodiment, the “valve shaft 8 extending in the vertical direction” includes those in which the valve shaft 8 is accurately arranged vertically as indicated by arrows a, b, and c in FIGS. Means to include the one arranged slightly tilted from the vertical line.

  At the outer end of the upper end portion 8u of the valve shaft 8, an extension shaft portion 8e that protrudes upward from the carburetor body 1 is integrally connected, and a throttle lever 10 is connected and fixed to the extension shaft portion 8e. . Then, if the throttle lever 10 (and hence the valve shaft 8) is turned, the intake passage 2 can be opened and closed by the valve plate 9 rotating together with the throttle lever. The throttle lever 10 can be manually held at an arbitrary rotational operation position by a holding mechanism provided between the carburetor body 1 and a holding mechanism provided between the general-purpose machine and other devices. It has become. A choke lever 6L for arbitrarily rotating the choke valve 6 is connected and fixed to the valve shaft upper end.

  As shown in FIG. 3, the vaporizer body 1 has a nozzle support portion 1a that supports the main nozzle 5 extending downward in the float chamber 4, and a float chamber body at the lower end of the nozzle support portion 1a. The float chamber body 3 is fixed to the vaporizer body 1 by screwing bolts 11 penetrating the center of the liquid-tight 3. A certain amount of fuel F supplied from a fuel tank (not shown) is always stored in the float chamber 4, and a float 19 that controls opening and closing of a float valve (not shown) floats in the fuel F.

  A main fuel jet 12 that communicates the lower end of the main nozzle 5 with the float chamber 4 is screwed to the nozzle support portion 1a, whereby the fuel flowing from the float chamber 4 to the main nozzle 5 is measured. A cylindrical air bleed chamber 13 extending in the vertical direction is formed between the main nozzle 5 and the nozzle support portion 1a. A large number of bleed holes communicating the air bleed chamber 13 into the main nozzle 5 are formed. 14, 14... Are formed in the peripheral wall of the main nozzle 5. Further, the carburetor body 1 is provided with first and second bleed air passages 15 and 16 for supplying air to the air bleed chamber 13 from the intake passage I (upstream intake pipe P ′ in the illustrated example).

  In the upper part of the air bleed chamber 13, the downstream end of the first bleed air passage 15 formed in the carburetor body 1 and always in a conductive state is directly open. Further, in the middle of the downstream passage portion 15 d of the first bleed air passage 15, the downstream end of the second bleed air passage 16 formed in the carburetor body 1 and opened and closed by the control valve 8 u is formed in the carburetor body 1. Merge and connect. Accordingly, the downstream end of the second bleed air passage 16 communicates with the upper portion of the air bleed chamber 13 via a part of the first bleed air passage 15 (downstream passage portion 15d).

  The upstream ends of the first and second bleed air passages 15 and 16, that is, the air inlets 15 i and 16 i, open to the end surface 1 b on the upstream side of the intake passage 2 of the carburetor body 1. The air inlet 15i of the passage 15 directly communicates with the intake pipe P ′ on the upstream side.

  On the other hand, the air inlet 16i of the second bleed air passage 16 communicates with the upstream intake pipe P ′ via the pipe PP according to the present invention. The pipe PP functions as an air introduction pipe that takes in the air in the intake passage I (in the illustrated example, the upstream intake pipe P ′; hereinafter the same) into the second bleed air passage 16 and is in contact with the fuel. However, it is formed from a rigid material that does not corrode, such as a metal material such as stainless steel, in a cylindrical and straight shape with both ends open.

  Moreover, the pipe PP is manufactured separately from the vaporizer body 1 and is attached to the vaporizer body 1 as a retrofit. That is, the base end portion PPa of the pipe PP is connected and fixed to the air inlet 16i of the second bleed air passage 16 that opens to the end surface 1b on the intake upstream side of the carburetor body 1. As the connection and fixing means, in the illustrated example, the end face of the base end portion PPa of the pipe PP is abutted against the annular seat surface 1bs recessed in the end face 1b of the carburetor body 1 so as to surround the air inlet 16i. w. As the connection fixing means for the pipe PP, various fixing means other than welding, such as caulking, press-fitting, adhesion, and screwing, can be implemented.

  Further, the pipe PP has at least a front end portion (most part of the pipe excluding the base end portion PPa in the illustrated example) extending long in the intake passage I, particularly in the intake pipe P ′, and the pipe distal end portion PPb is opened. The leading end faces the intake pipe P ′. In addition, the pipe PP is in a mounting posture inclined toward the central axis Ic side of the intake passage I toward the intake upstream side. Therefore, the tip PPb serving as an air inlet of the pipe PP is shown in FIGS. As clearly shown in FIG. 2, the second bleed air passage 16 is located closer to the central axis Ic of the intake passage I than the air inlet 16 i and on the intake upstream side.

  Further, particularly in the present embodiment, the open surface O of the distal end portion PPb of the pipe PP is arranged so that the central axis Ic of the intake passage I passes through the central portion thereof, and the distal end open surface O is the base end portion PPa. The cut surface is inclined with a larger gradient with respect to the pipe axis than the open surface O ′. Therefore, when viewed from the projection plane orthogonal to the central axis Ic of the intake passage I, the distal end open surface O of the pipe PP is substantially the same size as the base end open surface O ′ (and therefore the base end open surface O ′). Since the opening area is wider than the air inlet 16i) of the second bleed air passage 16 connected to the end opening surface O ', and therefore has a wider opening area, intake air in the intake passage I can be easily introduced.

  Further, a first air jet 17 that regulates the maximum air flow rate in the first bleed air passage 15 is screwed into the upstream side passage portion 15 u of the first bleed air passage 15. A second air jet 18 that regulates the maximum air flow rate in the second bleed air passage 16 is screwed into the upstream passage portion 16 u of the second bleed air passage 16.

  The control valve that opens and closes the second bleed air passage 16 is configured as a rotary control valve by the upper end portion 8 u of the valve shaft 8 of the throttle valve 7. More specifically, the second bleed air passage 16 has an upper bearing hole 1u provided in the upper portion of the intake passage 2 of the carburetor body 1 so as to rotatably support the upper end portion of the valve shaft 8, that is, the control valve 8u. It is arranged and configured to intervene in the middle part of the 2 bleed air passage 16. Thus, the second bleed air passage 16 is divided by the upper bearing hole 1u into an upstream passage portion 16u connected to the air cleaner via the intake pipe P 'and a downstream passage portion 16d connected to the air bleed chamber 13. The

  The cylindrical upper end of the valve shaft 8, that is, the control valve 8u is provided with a groove-like notch 22 in a part of its outer peripheral surface 8ur, and the notch 22 is the second bleed air. The second bleed air passage 16 is conducted when the passage 16 faces the openings 16uo and 16do to the bearing hole 21 of the downstream passage portions 16u and 16d at the same time. When the notch 22 faces only one of the two openings 16uo and 16do, the second bleed air passage 16 is blocked.

  Further, in this embodiment, as is apparent from FIGS. 3 and 4, the openings 16uo and 16do of the downstream passage portions 16u and 16d above the second bleed air passage 16 are formed by the openings 16uo and 16do. The openings 16uo and 16do are partially located in the same position in the axial direction of the valve shaft 8 so that they are aligned with each other by a predetermined distance e in the circumferential direction of the bearing hole 1u when viewed from the projection plane orthogonal to the shaft 8. Are arranged as follows. The openings 16uo and 16do may be formed so that all the openings 16uo and 16do are located at the same position in the axial direction of the valve shaft 8.

  In addition, the central angle θ1 of the bearing hole 1u corresponding to the predetermined distance e when viewed on the projection plane orthogonal to the valve shaft 8 is an acute angle and the central angle θ2 of the bearing hole 1u corresponding to the circumferential region of the notch 22. Is set smaller. Further, the notch 22 is recessed toward the center L side of the bearing hole 1u from a virtual straight line connecting both circumferential ends of the notch 22 on the outer peripheral surface 8ur of the valve shaft upper end 8u when viewed from the projection surface. (In this embodiment, it is formed in a groove shape having a U-shaped cross section). In this case, in particular, if the notch 22 has a U-shaped groove shape as in the present embodiment, the bleed air can be stored in a deep recess (that is, the chamber) of the notch 22. The direction of the air that enters the recess from the upstream passage portion 16u of the bleed air passage 16 or exits from the recess to the downstream passage portion 16d is stabilized, and the second bleed air passage 16 enters the air bleed chamber 13. The air supply amount is stable.

  As shown in FIG. 4, the upper end portion of the valve shaft 8, that is, the control valve 8u is, in this embodiment, the throttle valve 7 at an idle opening or a predetermined low opening region (for example, with respect to the intake channel axis). The second bleed air passage 16 is shut off even in a state where it is opened approximately 20 ° with respect to the orthogonal plane), or in a sufficiently wide middle / high opening range (for example, opened approximately 40 ° or larger), The throttle valve 7 conducts the second bleed air passage 16 only in a specific narrow intermediate opening region between the low opening region and the middle / high opening region (for example, opened at 30 ° or in the vicinity thereof). It is supposed to let you.

  The first bleed air passage 15 is disposed on one side of the valve shaft 8 (right side in FIGS. 1 and 3) as seen from the projection plane orthogonal to the axis of the intake passage 2 as is apparent from the drawings. On the other hand, the passage portion 16u upstream of the control valve 8u of the second bleed air passage 16 is disposed above the intake passage 2. In addition, the passage portion 16d on the downstream side of the control valve 8u of the second bleed air passage 16 is disposed on the one side of the valve shaft 8 when viewed from the projection plane, and is downstream of the downstream passage portion 16d. The end joins and is connected to the middle of the first bleed air passage 15 (in the illustrated example, the middle of the downstream passage portion 15d) on the one side of the valve shaft 8 when viewed from the projection plane.

  In particular, in the present embodiment, the upstream passage portion 15u of the first bleed air passage 15 is formed by drilling or molding along the intake passage axis from the end surface of the carburetor body 1 on the upstream side of the intake passage, and downstream thereof. The side passage portion 15d is formed by being drilled obliquely downward so as to open from the outer right side upper surface of the carburetor body 1 to the upper portion of the air bleed chamber 13, and the middle of the downstream passage portion 15d is formed by drilling or molding. It intersects with and communicates with the inner end portion of the formed upstream passage portion 15u. In this case, the outer end of the drill hole for forming the downstream passage portion 15d is liquid-tightly closed by the plug 24 that is closely fitted and fixed thereto.

  On the other hand, the upstream side passage portion 16u of the second bleed air passage 16 formed by drilling or molding is inclined to the axis of the intake passage upstream from the end surface on the upstream side of the intake passage of the carburetor body 1 while being slightly inclined with respect to the axis of the intake passage. It is drilled substantially along and formed so that its inner end opens into the upper bearing hole 1u. Further, the downstream passage portion 16d extends from the upper outer surface of the carburetor main body 1 across the upper bearing hole 1u and extends toward the upstream side of the intake passage 1, and the first drill hole 25 having a slightly downward slope and the first drill hole 25. The drill hole 25 is formed with a downwardly steeply inclined second drill hole 26 which is drilled from the outer surface of the upper right portion of the carburetor body 1 so as to communicate the inner end of the drill hole 25 with the downstream passage portion 15 d of the first bleed air passage 15. It should be noted that the outer end of the second drill hole 26 is liquid-tightly closed by a plug 27 that is closely fitted and fixed thereto. The outer end of the first drill hole 25 is also liquid-tightly closed with a plug not shown.

  Further, the upstream side passage portion 16u of the second bleed air passage 16 is formed with a larger diameter than the downstream side passage portion 16d (and therefore wider when viewed in the projection plane orthogonal to the valve shaft 8), and the upstream side passage portion 16u. Is constituted by a first passage portion 16u1 having one end opened in the bearing hole 1u and a second passage portion 16u2 having a relatively large diameter connected to the other end of the first passage portion 16u1 via an annular stepped portion. An insertion shaft 18a on the front side of the second air jet 18 is inserted into the first passage portion 16u1, and a fixing is performed by engraving a male screw on the outer periphery on the base side of the second air jet 18. The shaft portion 18b is screwed. As described above, the second air jet 18 is screwed into the passage portion 16u with the insertion shaft portion 18a on the front portion side inserted into the upstream passage portion 16u (first passage portion 16u1) of the second bleed air passage 16. A fixed shaft portion 18b on the base portion side to be fixed, and the first passage portion 16u1 of the upstream-side passage portion 16u into which the insertion shaft portion 18a is inserted opens directly into the bearing hole 1u with a uniform inner diameter. For this reason, the upstream side passage portion 16u of the second bleed air passage 16 can be easily drilled.

  Further, the carburetor body 1 is part of the stored fuel in the float chamber 4 on the other side of the valve shaft 8 (left side in FIGS. 1 and 3) as viewed in the projection plane orthogonal to the axis of the intake passage 2. And a slow passage 30 that mixes air with air and ejects the air downstream of the throttle valve 7 in the intake passage 2 is formed. The slow passage 30 is drilled along the intake passage axis from the end surface of the carburetor main body 1 on the upstream side of the intake passage, or formed by molding, and the slow passage main body having an upstream end opened in the intake pipe P ′. 31, a slow port 32 serving as an injection port whose one end opens at the inner end of the slow passage main body 31 and the other end opens downstream of the throttle valve 7 of the intake passage 2, and is formed in the middle of the slow passage main body 31. The mixing chamber 33 has a large volume, and a slow fuel passage 34 that communicates between the mixing chamber 33 and the lower portion of the air bleed chamber 13. The slow passage body 31 is screwed with a slow jet 36 that adjusts the amount of air passing therethrough. The mixing chamber 33 is formed by drilling or molding from the outer surface of the vaporizer main body 1, and its opening end is liquid-tightly closed by a lid 35 that is closely fitted and fixed thereto. .

  Thus, when the opening of the throttle valve 7 is at the minimum idle opening or a low opening close thereto in the operating state of the internal combustion engine, the slow passage 30 has an intake negative generated in the intake passage 2 downstream of the throttle valve 7. Due to the pressure, the air sucked into the slow passage main body 31 from the intake pipe P ′ and the fuel from the air bleed chamber 13 sucked into the slow fuel passage 34 are mixed in the mixing chamber 33, and are then introduced from the slow port 32 into the intake passage 2. Therefore, the air-fuel mixture required for idling operation or low load operation of the internal combustion engine can be supplied to the intake passage 2.

  Next, the operation of this embodiment will be described.

  During operation of the internal combustion engine, the amount of intake air flowing through the intake passage 2 toward the internal combustion engine is controlled by the opening degree of the throttle valve 7, and the negative pressure generated in the venturi portion 2 a according to the intake amount is the main nozzle 5. As a result, the fuel F in the float chamber 4 is ejected from the main nozzle 5 to the intake passage 2 and is sucked into the internal combustion engine while generating an air-fuel mixture together with the intake air.

  Meanwhile, the secondary air flows into the air bleed chamber 13 through the first bleed air passage 15 and enters the main nozzle 5 through the multiple bleed holes 14, 14..., And the rising fuel in the main nozzle 5 is emulsified. And atomization of the fuel ejected from the main nozzle 5 is promoted.

  At this time, the throttle valve 7 is in an idling opening or a predetermined low opening region in which the throttle valve 7 is opened slightly (for example, a state where the throttle valve 7 is opened about 20 ° with respect to the plane orthogonal to the intake passage axis), or the throttle valve 7 is sufficiently opened When in the middle / high opening range (for example, opened to 40 ° or more), the notch 22 of the control valve 8 u constituted by a part of the valve shaft 8 is located upstream and downstream of the second bleed air passage 16. Since only one of the openings 16uo and 16do to the bearing hole 1u of the side passage portions 16u and 16d faces each other, that is, the cylindrical outer peripheral surface 8ur of the control valve 8u makes the second bleed air passage 16 shut off. The amount of air in the fuel ejected from the main nozzle 5 is reduced by the amount that the secondary air has not passed through the second bleed air passage 16, and the air-fuel mixture sucked by the internal combustion engine becomes rich. Accordingly, the air-fuel ratio of the air-fuel mixture generated by the carburetor C is enriched during idling operation or high load or full load operation of the internal combustion engine, thereby stabilizing the operation during idling operation. When the engine is operating at a high load or full load, the output is increased and the occurrence of knocking is suppressed.

  On the other hand, while the throttle valve 7 is in a specific narrow intermediate opening region between the low opening region and the middle / high opening region (for example, a state opened at 30 ° or in the vicinity thereof) The notch portion 22 of 8u opens both of the openings 16uo and 16do to the bearing holes 1u of the downstream passage portions 16u and 16d above the second bleed air passage 16, so that the second bleed air passage 16 is formed. Make it conductive. As a result, the secondary air also passes through the second bleed air passage 16 and merges with the secondary air that has passed through the first bleed air passage 15, and then passes from the air bleed chamber 13 through the bleed holes 14, 14. The fuel enters the nozzle 5 to emulsify the fuel in the main nozzle 5. As a result, the amount of air in the fuel ejected from the main nozzle 5 is increased, and the air-fuel mixture sucked by the internal combustion engine is diluted and leaned, so that the specific narrow intermediate opening region of the throttle valve 7, that is, It is possible to reduce fuel consumption and optimize exhaust gas during specific load operation of the internal combustion engine.

  Further, in the present embodiment, air is introduced from the intake passage I (in the illustrated example, the upstream side intake pipe P ′, the same applies hereinafter) to the air inlet 16i of the second bleed air passage 16 that opens in the carburetor body 1. Cylindrical pipe PP, that is, a pipe PP that serves as an air inlet of the second bleed air passage 16, is simply structured to be retrofitted and fixed to the vaporizer body 1, and the degree of freedom in selecting the shape and position of the air inlet Is effectively enhanced. That is, according to the specifications and required performance of the carburetor C, the optimum pipe is selected from a plurality of types of pipes PP of different sizes and shapes and attached to the carburetor body 1 so that the second from the intake passage I. Not only can the air introduction into the bleed air passage 16 be optimal and sufficient, but the amount of air introduction can be easily adjusted. As a result, it is easy to finely adjust the amount of air introduced from the intake passage I to the second bleed air passage 16 in the specific opening region of the throttle valve 7 in which the second bleed air passage 16 is brought into conduction by the control valve 8u. Therefore, the adjustment and control of the air-fuel ratio of the air-fuel mixture generated by the carburetor C in the same opening range can be performed with high accuracy.

  In this case, in particular, the pipe PP has at least a tip portion that protrudes into the intake passage I in a slanted posture, and the pipe tip is open into the intake passage I. The degree of freedom in selecting the opening position and opening size of the intake passage I is further increased, and the adjustment of the amount of air introduced from the intake passage I to the second bleed air passage 16 is further facilitated. For example, the amount of air introduced into the second bleed air passage 16 can be increased without difficulty by causing the tip opening of the pipe PP to face the portion of the intake passage I where the flow velocity of the intake air is particularly high (for example, the central portion of the passage). In addition, for example, by selecting the length of the pipe PP, the end opening surface O of the pipe PP faces the portion where the intake pulsation effect can be expected in the intake passage I, and the second bleed air passage is utilized using the intake pulsation effect. The amount of air introduced into 16 can be increased without difficulty. Further, for example, by forming the open end O of the pipe PP larger than the air inlet 16i of the second bleed air passage 16 that opens to the carburetor body 1, the amount of air introduced into the second bleed air passage 16 cannot be increased. It can be increased without.

  Further, in particular, the carburetor C of the present embodiment is a power lawn mower that is often operated with the opening degree of the throttle valve 7 to a specific opening degree so as to keep the rotation speed during operation of the internal combustion engine at a constant rotation speed. Installed in power working machines such as generators. And in such a power working machine, while the opening degree of the throttle valve 7 is operated so as to keep the internal combustion engine at a constant rotational speed, the throttle valve 7 is placed in the most used area (recommended load area) in the power working machine. By making the specific narrow intermediate opening range (for example, 20 ° to 40 °) lean, the lean state is continuously maintained, effective fuel consumption is reduced, exhaust gas is optimized, that is, harmful exhaust gas is generated. Suppression is achieved. In this case, in particular, according to the special effect of the pipe PP serving as the air introduction part of the second bleed air passage 16, the intake passage I to the second bleed air passage 16 in the specific opening region of the throttle valve 7. Since fine adjustment of the air introduction amount becomes easier, the air-fuel ratio of the air-fuel mixture can be leaned more optimally in the most used region (recommended load region) of the power work equipment corresponding to the same opening range. Improved fuel economy and exhaust gas optimization.

  By the way, in the carburetor C in which the intake passage I is controlled to be opened and closed by the butterfly throttle valve 7 as in this embodiment, the intake flow velocity is higher in the center of the passage than near the wall surface of the intake passage I. Since the tip portion of the pipe PP can be protruded into the intake passage I in an inclined posture with the front end opening surface O (that is, the air inlet) of the pipe PP facing the center of the passage, The intake air in the intake passage I can be taken in efficiently and smoothly from the open surface O. In addition, in the present embodiment, the distal end open surface O of the pipe PP is a cut inclined with a larger gradient than the proximal end open surface O ′ with respect to the pipe axis, and thus is orthogonal to the central axis Ic of the intake passage I. When viewed from the projection surface, the distal end open surface O is wider than the proximal end open surface O ′ (therefore, the air inlet 16i of the second bleed air passage 16 abutted against the proximal end open surface O ′). The intake air in the intake passage I can be taken into the pipe PP more efficiently and smoothly from the open end O of the pipe PP. As a result, air can be introduced from the intake passage I to the second bleed air passage 16 more optimally and sufficiently, and the amount of air introduced can be increased without difficulty.

  Further, particularly in the present embodiment, the openings 16uo and 16do of the upstream side passage portion 16u and the downstream side passage portion 16d of the second bleed air passage 16 to the bearing hole 1u are formed in the valve shaft 8 by the openings 16uo and 16do. Are arranged so as to be separated from each other by a predetermined distance e in the circumferential direction of the bearing hole 1u when viewed from a projection plane orthogonal to the axis. As a result, the central angle corresponding to the predetermined distance e of the bearing hole 1u from the central angle θ2 of the notch 22 regardless of the size of the opening widths of both the openings 16uo and 16do, as viewed on the projection plane orthogonal to the valve shaft 8. Only in a very narrow specific opening range θ2-θ1 obtained by subtracting θ1, the control valve 8u is opened (that is, the notch 22 faces both openings 16uo and 16do at the same time), and the opening width is increased or decreased. Regardless of this, the second bleed air passage 16 can be placed in the conducting state, so that the control valve 8u is opened only in a specific narrow opening region of the throttle valve 7 while simplifying the structure of the carburetor C, The amount of bleed air passing through the bleed air passage 16 can be accurately adjusted. In addition, the valve opening timing is set in such a relationship that the bleed air amount can be adjusted by opening the control valve 8u in a narrow specific opening region of the throttle valve 7 regardless of the opening width of both the openings 16uo and 16do. The upstream side passage portion 16u of the second bleed air passage 16 can be increased in diameter without affecting the air flow, and the large air jet 18 can be easily and securely attached thereto.

  In addition, since the center angle θ1 of the bearing hole 1u corresponding to the predetermined distance e is set to an acute angle, the openings 16uo and 16do of the second bleed air passage 16 and the downstream passage portions 16u and 16d are mutually connected to the bearing hole 1u. The second bleed air passages 16 can be gathered around in a compact manner, which is advantageous in reducing the size of the carburetor. In addition, the notch portion 22 on the outer peripheral surface 8ur of the upper end portion of the valve shaft 8 is viewed from a virtual straight line connecting both circumferential ends of the notch portion 22 on the outer peripheral surface 8ur when viewed from the projection plane orthogonal to the valve shaft 8. Is also formed to be recessed toward the center O side of the bearing hole 1u, so that the passage resistance when the bleed air passes through the control valve 8u (that is, the notch portion 22) can be reduced, and for example, the valve shaft 8 is vaporized. Even if some backlash occurs due to dimensional errors or assembly errors with respect to the main body 1, fluctuations in the passage resistance in the control valve 8 u are suppressed as much as possible, the amount of bleed air is stabilized, and the passage is closed. The variation of the set specific opening area can be reduced.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, the pipe PP functioning as an air introduction port for introducing air from the intake passage I to the second bleed air passage 16 is shown as a straight cylindrical shape without bending. The pipe PP may be formed in a cylindrical shape in which at least a part is curved or bent.

  In the above embodiment, the pipe PP functioning as the air inlet is shown as a cylindrical cylinder having a circular cross section. However, in the present invention, the pipe PP may be a rectangular cylinder having a polygonal cross section. .

  In the embodiment, the air inlet 16i of the second bleed air passage 16 to which the base end portion PPa of the pipe PP is connected and fixed is opened to the end surface 1b on the intake upstream side of the carburetor body 1. However, in the present invention, the opening position of the air inlet 16i is not limited to the end face 1b, but can be set on an appropriate wall surface of the carburetor body 1 (for example, the peripheral wall surface of the intake passage 2).

  In the above embodiment, the control valve 8u that opens and closes the second bleed air passage 16 is shown to be opened in a specific narrow intermediate opening region (for example, around 30 °) of the throttle valve 7. In the present invention, the setting of the opening range of the throttle valve that opens the control valve is arbitrary, and is not limited to the setting mode of the above-described embodiment (that is, the control valve is opened around 30 °). For example, the control valve may be opened in a relatively wide opening range of the throttle valve, for example, a middle / high opening range (for example, 40 ° or more).

  Moreover, although the carburetor of the internal combustion engine for power working machines was shown in the said embodiment, the internal combustion engine in which the carburetor of this invention is provided is not limited to the internal combustion engine for power working machines, For example, for motorcycles and other vehicles It can also be applied to a carburetor of an internal combustion engine to be mounted.

  Moreover, in the said embodiment, although the notch part 22 formed in the outer peripheral surface 8ur of the control valve 8u showed what is a groove | channel of a cross-sectional channel shape, formation of a notch part is not limited to the said embodiment, For example, it may be a groove having a circular cross section.

  In the above-described embodiment, the slow port 32 of the slow passage 30 is opened downstream of the throttle valve 7, but in order to adjust the amount of fuel injected downstream of the throttle valve 7 in accordance with the operating state, You may install between the nozzle 5 and the throttle valve 7. FIG.

C... Carburetor I... Intake passage Ic... Central axis PP of intake passage... Pipe 1. ... Main nozzle 7 ... Throttle valve 8u ... Upper end 13 of valve shaft constituting control valve ... Air bleed chamber 14 ... Bleed hole 15 ... 1 bleed air passage 16 ··· second bleed air passage 16i ··· air inlet PPa ··· pipe proximal end portion PPb ··· pipe end portion

Claims (4)

The carburetor body (1) includes an intake passage (2) constituting a part of the intake passage (I) connected to the combustion chamber of the internal combustion engine, a throttle valve (7) for opening and closing the intake passage (2), and an intake air A main nozzle (5) opening in the passage (2), and an air bleed chamber (13) formed on the outer periphery of the main nozzle (5) and communicating with the main nozzle (5) via a number of bleed holes (14). ) And first and second bleed air passages (15, 16) connected to the air bleed chamber (13) and communicating the air bleed chamber (13) with the atmosphere, and the second bleed air passage (16 In the carburetor which is in a conductive state only in a part of the opening region of the throttle valve (7) by the control valve (8u),
A pipe for introducing air from the intake passage (I) to the second bleed air passage (16) into the air inlet (16i) of the second bleed air passage (16) opening in the carburetor body (1). PP) is connected,
The pipe (PP) is formed in a cylindrical shape and is attached to the carburetor body (1). At least a tip of the pipe (PP) projects into the intake passage (I), and the tip of the pipe (PP) vaporizer characterized that you have opened the passage (I). 2. The power working machine according to claim 1, wherein the throttle valve (7) is operated so that the opening of the throttle valve (7) is maintained so as to maintain the engine speed at a constant speed during operation of the internal combustion engine. Vaporizer. The throttle valve (7) is a butterfly type valve, and a base end (PPa) of the pipe (PP) is connected to the air inlet (16i) of the second bleed air passage (16). The tip (PPb) of the pipe (PP) serving as an air inlet is disposed closer to the central axis (Ic) of the intake passage (I) than the air inlet (16i) and on the upstream side of the intake. characterized vaporizer of claim 1 or 2. The carburetor according to any one of claims 1 to 3, wherein an open surface (O) at a tip of the pipe (PP) passes through a central axis (Ic) of the intake passage (I).

Images