JP2016156308A - Carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carburetor with fuel cut means for reducing the amount of fuel to be supplied from the carburetor to an intake passage during the deceleration of an internal combustion engine, for simplifying the structure of the fuel cut means and the shape of the internal of a float chamber, while eliminating an electrical drive part to eliminate the need for specially considering heat generation countermeasures and lead wire layout and achieve a lower cost.SOLUTION: A carburetor C includes a float chamber 4 outward of which there are provided an atmosphere introduction path A having one end communicated with the middle of a bleeding air passage Bs and the other end communicated with a passage portion 18 of a fuel passage Ls between the float chamber 4 and an intake passage 2 where bleeding air mixed fuel flows, an on-off valve V for normally closing the atmosphere introduction path A, a negative pressure introduction path Pv for introducing intake negative pressure from near a throttle valve T or the intake passage 2 on the downstream side thereof, and a negative pressure actuator AQ to be operated with the intake negative pressure to open the on-off valve V.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a throttle valve that can change the cross-sectional area of an intake passage connected to a combustion chamber of an internal combustion engine, a float chamber that stores fuel, and an intake negative pressure that is generated in a negative pressure generating portion of the intake passage when the internal combustion engine is operated. A fuel passage capable of supplying fuel in the float chamber to the intake passage using pressure, and a bleed opening at one end to the atmosphere and the other to the middle of the fuel passage to mix the bleed air with the fuel flowing through the fuel passage The present invention relates to an improvement in a structure having an air passage, and more particularly, a fuel cut means for reducing the amount of fuel supplied from a carburetor to an intake passage during deceleration of an internal combustion engine.

  Conventionally, such a vaporizer is known as described in Patent Document 1 below.

JP 2002-235605 A

  However, in the carburetor described in Patent Document 1, the fuel cut means for reducing the amount of fuel supplied from the carburetor to the intake passage when the internal combustion engine is decelerated includes an on-off valve that opens and closes the fuel passage in the float chamber, And an electromagnetic actuator for driving the on-off valve.

  However, in this conventional structure, the electromagnetic fuel cutting means is installed in the float chamber, and its on-off valve is immersed under the reservoir oil surface in the float chamber. ), The structure of the fuel cut means, the internal shape of the float chamber, and the like are complicated. In addition, the electromagnetic actuator is expensive and consumes power, and it is necessary to consider heat generation and the handling of the lead wire for energization.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide the vaporizer that can solve the above-mentioned problems at once with a simple structure.

  In order to achieve the above object, the present invention provides a throttle valve capable of changing a passage cross-sectional area of an intake passage connected to a combustion chamber of an internal combustion engine, a float chamber for storing fuel, and a negative pressure of the intake passage during operation of the internal combustion engine. A fuel passage capable of supplying the fuel in the float chamber to the intake passage using the intake negative pressure generated in the pressure generating portion, and one end to the atmosphere and the other end to mix the bleed air with the fuel flowing through the fuel passage In a carburetor having a bleed air passage that opens in the middle of the fuel passage, one end communicates with the atmosphere and the other end communicates with a portion of the fuel passage through which the fuel mixed with the bleed air flows. An air introduction path, an on-off valve that closes the air introduction path during normal times, and a negative pressure introduction path that introduces intake negative pressure generated in the vicinity of the throttle valve or from an intake passage downstream of the throttle valve And further comprising a negative pressure actuator for opening said closing valve operating in the introduced intake negative pressure in the negative pressure introduction passage to the outside of the float chamber and the first feature.

  According to the present invention, in addition to the first feature, the fuel passage includes an air mixing portion that mixes bleed air from the bleed air passage into the fuel, a fuel injection port that jets fuel from the fuel passage to the intake passage, and An intermediate passage portion located between the air mixing portion and the fuel injection port and having a flow passage cross-sectional area larger than that of the fuel injection port, and the downstream end of the atmospheric introduction passage is opened in the intermediate passage portion. Two features.

  Further, according to the present invention, in addition to the first or the second feature, the passage portion having the smallest flow passage cross-sectional area of the atmosphere introduction passage has a flow passage smaller than the passage portion having the smallest flow passage cross-sectional area of the bleed air passage. A third feature is that the cross-sectional area is large.

  Furthermore, in addition to the third feature, the present invention provides a case in which the negative pressure actuator is attached to one side surface of the carburetor body and defines a space between the one side surface, the case and the carburetor body. A first chamber in which the valve body of the on-off valve that accommodates and shuts off the space, the upper and lower passage portions of the atmosphere introduction passage being opened and the passage portions being electrically connected and cut off, is housed in the space. A diaphragm partitioned into a second chamber connected to the negative pressure introduction path; and a spring that repels the diaphragm toward the first chamber and urges the valve body in a valve closing direction. An upstream end of the upstream passage portion is opened in the middle of the bleed air passage, and the upstream passage portion is upstream in the direction along the intake passage as viewed from the negative pressure actuator, and the negative pressure is introduced. The roads are arranged downstream in the same direction The fourth characteristic.

  In addition to the fourth feature of the present invention, the bleed air passage has a passage portion that extends substantially along one side edge of the intake passage, and the upstream side of the air introduction passage in the middle of the passage portion. An upstream end of the passage portion is open, and at least a portion of the downstream passage portion of the atmospheric introduction passage that extends linearly from the first chamber is downstream of the upstream passage portion in a direction along the intake passage. In addition, a fifth feature is that it is disposed upstream of the negative pressure introduction path.

  According to the first aspect of the present invention, the atmosphere introduction path having one end communicating with the atmosphere and the other end communicating with the passage portion of the fuel passage through which the fuel mixed with bleed air flows, and the atmosphere introduction path in normal time. Operates with a closed on-off valve, a negative pressure introduction path for introducing intake negative pressure generated in the vicinity of the throttle valve or on the downstream side of the throttle valve, and an intake negative pressure introduced in the negative pressure introduction path Since the negative pressure actuator that opens the open / close valve is provided outside the float chamber, the open / close valve is opened by the negative pressure actuator that responds to the intake negative pressure when the internal combustion engine decelerates, and the atmosphere introduction path is made conductive. Thus, the atmosphere can be introduced into the passage portion of the fuel passage through which the bleed-air mixed fuel flows, and as a result, the fuel passage from the fuel passage to the intake passage side is effectively sucked by approaching the outlet side of the fuel passage. Suppressed Therefore, without installing a fuel cut means for electromagnetic the float chamber as in the prior art, it becomes possible to reduce the amount of fuel supplied from the vaporizer during deceleration. As a result, not only the structure of the fuel cut means is simplified, but the shape of the float chamber is simplified as much as possible, and there is no electrical drive and power consumption, making it special for measures against heat generation and lead wire handling. It is no longer necessary to pay attention to the cost, which can contribute to cost reduction as a whole.

  According to the second feature of the present invention, the downstream end of the air introduction passage opens in an intermediate passage portion that is located between the air mixing portion and the fuel injection port in the fuel passage and has a larger flow path cross-sectional area than the fuel injection port. The atmospheric pressure directly acts directly above the air mixing section in the fuel passage, so that the suction of the air-bleed fuel from the fuel passage to the intake passage can be suppressed quickly and effectively, and therefore the fuel cut during deceleration operation Responsiveness is improved.

  According to the third aspect of the present invention, the passage portion having the smallest flow passage cross-sectional area of the air introduction passage has a larger flow passage cross-sectional area than the passage portion having the smallest flow passage cross-sectional area of the bleed air passage. When the valve is opened, the atmospheric pressure can be applied more rapidly from the atmosphere introduction path to the outlet side of the fuel passage, thereby quickly sucking out the air-bleeded fuel to the intake passage side. Since it can suppress effectively, the responsiveness of the fuel cut at the time of engine deceleration is improved.

  According to the fourth feature of the present invention, a diaphragm type actuator can be used as the negative pressure actuator, which can contribute to further simplification of the structure and cost reduction. In addition, this diaphragm-type negative pressure actuator can be compactly concentrated on one side of the carburetor main body, and the air introduction path can be integrated on one side of the carburetor main body and compactly laid out. Molding and the like can be simplified. In addition, since a part of the bleed air passage for supplying bleed air to the fuel passage also serves as an inlet side passage portion of the air introduction passage, the air introduction passage itself can be shortened and the structure simplified. Further cost savings are achieved.

  According to the fifth aspect of the present invention, the negative pressure introduction path and the air introduction path can be easily and centrally deployed on one side of the carburetor main body without causing interference with each other, contributing to a compact carburetor. Can do.

1 is an overall side view of a vaporizer according to an embodiment of the present invention. Main part plane sectional view of the vaporizer (sectional view taken along line 2-2 in FIG. 1) Longitudinal sectional view of the vaporizer (sectional view taken along line 3-3 in FIG. 2) Sectional view along line 4-4 in FIG.

  Embodiments of the present invention will be described below on the basis of preferred embodiments of the present invention shown in the accompanying drawings.

  First, in FIG. 1, a carburetor C of an internal combustion engine for a motorcycle is connected to an intake port of the internal combustion engine and has an intake passage 2 as an intake passage extending in a horizontal direction. A float chamber body 5 joined to the lower end surface via an O-ring 3 to define a float chamber 4 therebetween, and a throttle valve T for changing the passage sectional area of the intake passage 2 directly above the float chamber 4 The float chamber body 5 is detachably fastened to the carburetor body 1 by bolts. Further, the intake passage 2 upstream of the throttle valve T has a choke valve as a dedicated start device for performing rich control of the air-fuel ratio at the time of start-up operation of the internal combustion engine (that is, at the time of start-up or during the warm-up operation immediately thereafter). Cv is provided.

  A valve cylinder 1v extending upward from the intake passage 2 is formed integrally with the upper portion of the carburetor body 1, and the piston valve type throttle valve T for opening and closing the intake passage 2 from above is formed in the valve cylinder 1v. It is housed slidably up and down. Between the throttle valve T and the valve cylinder 1v, a return spring 20 that constantly urges the throttle valve T in the valve closing direction (downward) is interposed.

  A throttle wire 21 for opening / closing the throttle valve T is connected to the throttle valve T, and the throttle wire 21 is linked to a throttle operation unit (not shown) such as an accelerator grip. Accordingly, by operating the throttle operating portion, the passage cross-sectional area of the negative pressure generating portion of the intake passage 2 (that is, the venturi portion 2a facing the lower end portion of the throttle valve T of the intake passage 2), that is, the opening of the throttle valve T. Can be changed within the opening range from the idle opening position (downward limit) to the fully open position (upward limit), and the amount of air flowing through the intake passage 2 is controlled.

  The carburetor body 1 is integrally provided with a fuel boss 1a that protrudes into the float chamber 4 from the center of its lower surface, and has a superior arc shape in a plan view surrounding the fuel boss 1a and opening the upstream side of the intake passage 2. The hollow float 7 is accommodated in the float chamber 4. A support plate 8 fixed to the rear part of the float 7 is supported by the float chamber body 5 via a pivot 9 so as to be swingable up and down. A float valve 10 that opens and closes the fuel inflow hole 11 is connected. A fuel conduit extending from a fuel tank (not shown) is connected to the fuel inflow hole 11 so that fuel flows in.

  Thus, the float 7 closes the float valve 10 at the horizontal position, and opens the float valve 10 when the float 7 descends from the horizontal position. The fuel inflow hole 11 by the float valve 10 is opened. As a result of opening and closing, the float chamber 4 always stores the fuel F that forms the fuel oil level Fa at a constant level. The float valve 10 has a built-in spring 10s that allows the float 7 to rise above the horizontal position and relaxes the impact on the float valve 10.

  As shown in FIG. 1, an annular upper space 12 that expands the float chamber 4 above the fuel oil surface Fa is recessed in the lower surface of the carburetor main body 1. Allow rise over position.

  The fuel boss 1a is provided with a main jet 13 and a slow jet 16 that are opened below the fuel oil surface Fa. The main jet 13 is screwed and connected to a lower portion of a needle jet 15 that is screwed to the fuel boss 1a and extends in the vertical direction. The needle jet 15 has a main nozzle 15n that opens to the venturi portion 2a of the intake passage 2 and is formed in a substantially cylindrical shape integrally with the upper portion, and a fuel metering is directly below the main nozzle 15n of the needle jet 15. The throttle part 15s is configured as an air bleed pipe part 15b having a large number of small holes in the peripheral wall.

  The fuel measured by the main jet 13 can be ejected from the main nozzle 15n to the intake passage 2 through the needle jet 15, that is, the air bleed pipe portion 15b and the fuel metering throttle portion 15s sequentially. A main system bleed air passage Bm for introducing bleed air from the upstream side of the intake passage 2 to the space around the air bleed pipe portion 15b is provided directly below the intake passage 2 of the carburetor body 1 in a plan view. 2 along the center line.

  On the other hand, the slow jet 16 is formed in a substantially cylindrical shape and extends in the vertical direction, and its lower outer periphery is screwed to the fuel boss 1a. A slow nozzle 16n is formed at the upper end portion of the slow jet 16, and an air bleed pipe portion 16b as an air mixing portion having a large number of small holes in the peripheral wall is formed below the slow nozzle 16n. A fuel metering throttle portion 16s is formed. Further, the carburetor main body 1 has a slow port 17 as a fuel injection port opened downstream of the main nozzle 15 in the venturi portion 2a of the intake passage 2 and a lower end of the slow port 17 and is further disconnected from the flow path. A relay passage 18 having a large area is formed, and the opening end of the slow nozzle 16n faces the relay passage 18. Accordingly, the slow nozzle 16 n is communicated with the slow port 17 through the relay passage 18.

  In particular, in the present embodiment, the slow port 17 and the slow nozzle 16n are offset from each other, and the relay passage 18 includes a coaxial portion 18a that is coaxially connected to the slow nozzle 16n, and the coaxial portion 18a. It has a lateral passage portion 18b extending in the lateral direction, and is formed in an L shape as a whole. The slow port 17 and the slow nozzle 16n can be coaxially arranged from the viewpoint of workability and the like. In this case, the relay passage 18 is also formed coaxially with the slow nozzle 16n, and the relay passage 18 The lateral passage portion 18b is not necessarily provided.

  Thus, the fuel measured at the throttle portion 16s of the slow jet 16 is jetted from the slow port 17 to the intake passage 2 via the air bleed pipe portion 16b, the slow nozzle 16n, and the relay passage 18 in order. . Further, the carburetor main body 1 has a slow bleed air passage Bs for introducing bleed air from the upstream side of the intake passage 2 to the space around the air bleed pipe portion 16b immediately below one side edge of the intake passage 2. , So as to extend substantially along the one side edge in plan view.

  By the way, at the center of the throttle valve T, an elongated needle valve 19 that is inserted into the needle jet 15 and moves up and down together with the throttle valve T projects downward. Thus, the main nozzle 15n provided integrally with the upper portion of the needle jet 15 opens directly below the center of the throttle valve T, and the slow port 17 opens near the downstream edge of the throttle valve T. It becomes.

  Further, the tip of the needle valve 19 is formed on a tapered surface having a gentle gradient. Therefore, the annular fuel passage formed between the fuel metering throttle portion 15 s formed immediately below the main nozzle 15 n of the needle jet 15 and the outer periphery of the needle valve 19 has a passage cross-sectional area of the throttle with the needle valve 19. The amount of fuel drawn from the main nozzle 15n to the intake passage 2 with negative intake pressure is increased or decreased according to the opening of the valve T.

  Thus, the fuel passage from the main jet 13 through the needle jet 15 to the main nozzle 15n is the main fuel passage Lm, while the fuel passage from the slow jet 16 through the relay passage 18 to the slow port 17 is provided. Is a slow fuel passage Ls, and these fuel passages Lm, Ls are arranged in a vertical plane passing through the center line of the intake passage 2. The fuel passages Lm and Ls supply the fuel in the float chamber 4 to the intake passage 2 using the intake negative pressure of the venturi portion 2a of the intake passage 2, that is, the float chamber is generated by the intake negative pressure. 4 fuel is sucked into the intake passage 2 through the respective fuel passages Lm and Ls and sprayed in a mist form, and the mist fuel is mixed with the intake air flow in the intake passage 2 to be supplied to the engine combustion chamber. A mixture is generated.

  In particular, when the throttle valve T is from the intermediate opening to the fully opened opening and the internal combustion engine is operated at medium speed or high speed, the throttle amount of the needle valve 19 relative to the fuel metering throttle portion 15s of the main system fuel passage Lm is Since it is small (that is, the cross-sectional area of the annular passage between the throttle portion 15s and the needle valve 19 is relatively large), the fuel is sufficiently sucked from the main fuel passage Lm to the intake passage 2. On the other hand, when the throttle valve T is at the idle opening position, that is, the lower limit and the internal combustion engine is idling, the fuel metering throttle portion 15s of the main system fuel passage Lm is blocked or sufficiently throttled by the needle valve 19. Therefore, fuel is mainly sucked out from the slow port 17 of the slow fuel passage Ls into the intake passage 2 in an amount necessary for idling operation.

  Furthermore, in the present embodiment, one end of the passage is connected to the atmosphere (in the illustrated example, in the middle of the slow bleed air passage Bs) and the other end of the slow fuel passage Ls is a passage portion (in the illustrated example) through which fuel mixed with bleed air flows. The air introduction path A communicated with the relay passage 18), the open / close valve V that closes the air introduction path A in normal times, and the intake air generated there from the intake passage 2 near the throttle valve T or downstream of the throttle valve T A negative pressure introduction path Pv for introducing a negative pressure and a negative pressure actuator AQ that operates by the intake negative pressure introduced through the negative pressure introduction path Pv and opens the on-off valve V are located outside the float chamber 4. Arranged in the vaporizer body 1.

  On one side 1s of the carburetor main body 1, the on-off valve V and the negative pressure actuator AQ for opening and closing the passage portions Au and Ad on the downstream side of the air introduction path A and for connecting and blocking between the openings are provided. Is provided. In particular, in the present embodiment, a valve housing recess 25 is formed by embedding a bottomed cylindrical sleeve 24 sideways integrally in the bottom of a recess 23 provided on one side 1 s of the vaporizer body 1. In addition, on the inner surface (the inner peripheral surface and the inner end surface in the illustrated example) of the valve housing recess 25, the air passage A and the downstream passage portions Au and Ad are opened, respectively. And the said opening / closing valve V is comprised by making the column-shaped front-end | tip part 26a of the valve body 26 fit to the valve accommodation recessed part 25 so that sliding is possible. That is, the on-off valve V is closed when the tip portion 26a of the valve body 26 is in contact with the inner end of the valve housing recess 25 and shuts off the downstream passage portions Au and Ad (see FIG. 2). And the leading end 26a of the valve body 26 is spaced apart from the inner end of the valve housing recess 25, and the open position for conducting between the downstream passage portions Au and Ad (partial cross section showing the valve open state in FIG. 2). (See the figure).

  The negative pressure actuator AQ is mounted on one side 1s of the carburetor body 1 and defines a space 31 between the side surface 1s, and is interposed between the case 30 and the carburetor body 1. The space 31 has a first chamber 41 in which the upstream and downstream passage portions Au and Ad are opened, and the valve body 26 of the on-off valve V is accommodated. 42, a pair of support plates 34 and 35 for airtightly clamping the inner peripheral bead portion between the diaphragm 33 and the center portion of the diaphragm 33, and the center portions of the support plates 34 and 35 and the diaphragm 33. Are closed to the first chamber 41 via the support plates 34 and 35, and the valve body 26 is closed by means of a bolt 37 for fastening to the stepped shaft-like base portion 26b of the valve body 26 and the central portion of the diaphragm 33. Energize in the valve direction (upward in Fig. 2) And a Shibane 36.

  The case 30 is formed in a cap shape, and an open end thereof is detachably fixed to the vaporizer main body 1 with a bolt 38, and the case 30 is fixed between the open end of the case 30 and the vaporizer main body 1. The outer peripheral bead part of the diaphragm 33 is airtightly clamped. Further, a first introduction passage portion Pv1 of the negative pressure introduction passage Pv having one end opened in the case 30 (particularly, the second chamber 42) is formed on the peripheral wall of the case 30. The other end of the first introduction passage portion Pv1 is in direct communication with one end of the second introduction passage portion Pv2 of the negative pressure introduction passage Pv formed substantially horizontally in the carburetor body 1, and the second introduction passage portion. The other end of Pv2, that is, the negative pressure introduction port, is opened downstream of the throttle valve T of the intake passage 2. Accordingly, intake negative pressure is introduced from the opening into the second chamber 42 of the negative pressure actuator AQ via the negative pressure introduction path Pv.

  As described above, the slow system fuel passage Ls serves as an air bleed pipe portion 16b serving as an air mixing portion for mixing the bleed air from the slow system bleed air passage Ls into the fuel, and a fuel injection port for ejecting fuel to the intake passage 2. Of the air bleed pipe portion 16b and the slow port 17, and a relay passage 18 serving as an intermediate passage portion having a relatively large flow path cross-sectional area. The downstream end of the downstream passage portion Ad of the introduction path A is opened.

  As is clear from FIG. 2, the upstream side passage portion Au of the air introduction path A is upstream in the direction along the intake passage 2 when viewed from the negative pressure actuator AQ, and the negative pressure introduction path Pv is downstream in the same direction. Arranged on each side. Further, the upstream end passage portion Au of the air introduction path A has an upstream end opened in the middle of the slow bleed air passage Bs, and the slow passage bleed air passage Bs upstream from the opening. It communicates with the atmosphere. On the other hand, the first passage portion Ad1 extending linearly from the space 31 (particularly the first chamber 41) in the negative pressure actuator AQ in the downstream passage portion Ad of the air introduction path A is apparent from FIG. In the direction along the intake passage 2, the air intake passage A is disposed downstream of the upstream passage portion Au and upstream of the negative pressure introduction passage Pv. According to such an arrangement of the negative pressure introduction path Pv and the atmospheric introduction path A, the negative pressure introduction path Pv and the atmospheric introduction path A can be easily and centrally deployed on one side of the carburetor body 1 without interfering with each other. Thus, the vaporizer C can be made compact.

  Of the downstream passage portion Ad of the air introduction passage A, the second passage portion Ad2 connected to the downstream end of the first passage portion Ad1 is a passage portion through which the bleed air mixed fuel passes, the inner end of which is the slow fuel passage Ls. A straight line is drilled from the downstream end face of the carburetor body 1 by drilling so as to directly communicate with the relay passage 18 (in the illustrated example). The outer end of the drill hole is closed by a plug 28 that is press-fitted into the hole after drilling.

  Incidentally, the slow bleed air passage Bs includes a first bleed air passage portion Bs1 extending linearly along the intake passage 2 and having an upstream end opened upstream of the throttle valve T of the intake passage 2 and the slow fuel passage Ls. There is a second bleed air passage portion Bs2 that has one end communicating with the middle (that is, the annular space surrounding the air bleed pipe portion 16b) and the other end extending obliquely upward toward one side 1s of the carburetor body 1. doing. The upstream end of the upstream passage portion Au of the atmosphere introduction path A is opened, that is, directly communicated with the intermediate portion of the first bleed air passage portion Bs1, and the downstream end of the first bleed air passage portion Bs1 is the second bleed air. It opens to the peripheral wall of the passage portion Bs2.

  The opening Bs1e is in the direction along the intake passage 2 and is located downstream of the communication portion between the first bleed air passage portion Bs1 and the upstream passage portion Au of the atmosphere introduction passage A, and the downstream passage of the atmosphere introduction passage A. The carburetor main body 1 is disposed on the upstream side of the portion Ad and on the one side surface 1s side of the carburetor body 1 when viewed from the slow fuel passage Ls. An air screw AS capable of arbitrarily adjusting the opening area of the opening Bs1e is formed in the carburetor body 1 so as to be coaxial with the other end of the second bleed air passage portion Bs2, and above the negative pressure actuator AQ. The screw hole 45 that opens obliquely upward in the one side surface 1 s is screwed from above.

  Further, the passage portion having the smallest flow passage cross-sectional area of the air introduction passage A has a larger flow passage cross-sectional area than the passage portion having the smallest flow passage cross-sectional area of the bleed air passage Bs (the opening Bs1e in the illustrated example). It is set as follows. According to this setting, when the on-off valve V is opened, the atmospheric pressure is more quickly applied from the atmosphere introduction path A to the outlet side of the slow fuel passage Ls (that is, directly above the air mixing section 16b). Therefore, the suction of the air-bleeded fuel to the intake passage 2 side can be quickly and effectively suppressed, and the fuel cut response during engine deceleration is enhanced.

  Next, the operation of this embodiment will be described. In the normal operating state of the internal combustion engine (that is, not during non-deceleration), the intake negative pressure on the downstream side of the throttle valve T of the intake passage 2 is relatively small, so the negative pressure actuator AQ into which the intake negative pressure is introduced is In an inoperative state, the on-off valve V blocks the air introduction path A. In this state, based on the differential pressure between the intake negative pressure of the intake passage 2, particularly the venturi portion 2 a, and the atmospheric pressure (atmospheric pressure in the embodiment) of the upper space 12 of the float chamber 4, During high speed operation, fuel is mainly sucked into the intake passage 2 from the float chamber 4 through the main fuel passage Lm, and during low speed operation or idling operation, fuel is sucked into the intake passage 2 mainly through the slow fuel passage Ls. .

  Further, when the internal combustion engine is decelerated while the internal combustion engine is running at a high speed and the throttle valve T is in a low opening state, the intake negative pressure on the downstream side of the throttle valve T in the intake passage 2 increases, and this is a specified limit value. When the pressure exceeds the negative pressure, the negative pressure actuator AQ is activated against the spring force of the spring 36 in response to the intake negative pressure, and the open / close valve V is opened in conjunction with this (partial sectional view of FIG. 2). The air introduction path A is made conductive.

  As a result, the atmosphere passes through the slow system bleed air passage Bs (that is, the first bleed air passage portion Bs1) and the air introduction passage A, and the passage portion (relay passage 18) through which the bleed air mixed fuel flows in the slow system fuel passage Ls. Thus, the fuel suction from the slow fuel passage Ls to the intake passage 2 side is suppressed when the outlet side of the slow fuel passage Ls approaches the atmospheric pressure. Accordingly, at the time of engine deceleration, the amount of fuel supplied to the intake passage 2 via the slow fuel passage Ls can be reduced. In this deceleration operation state, the fuel metering throttle portion 15s of the main system fuel passage Lm is blocked or sufficiently throttled by the needle valve 19 of the throttle valve T. Therefore, even if the intake negative pressure is large, the main system fuel A large amount of fuel is not sucked into the intake passage 2 through the passage Lm.

  According to the present embodiment described above, one end communicates with the atmosphere (in the illustrated example, in the middle of the slow bleed air passage Bs) and the other end of the slow fuel passage Ls has a passage portion through which the bleed air mixed fuel flows (see FIG. In the illustrated example, the air intake passage A communicated with the relay passage 18), the open / close valve V that closes the air introduction passage A during normal times, and the intake negative pressure from the intake passage 2 near the throttle valve T or downstream of the throttle valve T are provided. A negative pressure introduction path Pv to be introduced and a negative pressure actuator AQ that is operated by the intake negative pressure introduced through the negative pressure introduction path Pv and opens the on-off valve V are disposed outside the float chamber 4 in the carburetor body 1. Deployed. Accordingly, when the engine is decelerated, the bleed air mixed fuel flows in the slow fuel passage Ls by opening the on-off valve V by the negative pressure actuator AQ that responds to the increased intake negative pressure and conducting the air introduction path A. Since the atmosphere can be introduced into the passage portion 18, the fuel suction from the fuel passage Ls to the intake passage side 2 is effectively suppressed when the outlet side of the fuel passage Ls approaches atmospheric pressure.

  As a result, the amount of fuel supplied from the carburetor C during deceleration can be reduced without installing an electromagnetic fuel cut means in the float chamber 4 as in the prior art, so that the structure of the fuel cut means for deceleration operation is simplified. In addition, the shape in the float chamber 4 is simplified. In addition, since there is no electrical drive part and no power consumption, it is not necessary to give special consideration to measures against heat generation, lead wire handling, etc., and the overall cost can be greatly reduced.

  In addition, in this embodiment, a part of the slow bleed air passage Bs (that is, the first bleed air passage portion Bs1) also serves as an inlet side passage portion of the air introduction passage A, and accordingly, the air introduction passage A is shortened accordingly. In addition, structural simplification is achieved and further cost savings are achieved. In addition, the open / close valve V and the negative pressure actuator AQ are opened on one side 1 s of the carburetor body 1 so that the upper and downstream passage portions Au and Ad are opened on the atmosphere introduction path A and are electrically connected to each other. Therefore, the negative pressure operation type fuel cut means can be compactly and centrally arranged on one side of the carburetor main body 1, and not only the air introduction path A can be integrated on one side of the carburetor main body 1 as much as possible. The layout can be made compact, and the processing and molding of the air introduction path A can be simplified. Moreover, since a diaphragm type actuator is used as the negative pressure actuator AQ and the on-off valve V is directly driven by the diaphragm 33, further simplification of the structure and cost reduction are achieved.

  Furthermore, in the present embodiment, an intermediate passage portion (relay passage) having a large passage cross-sectional area located between the air bleed pipe portion 16b as an air mixing portion in the slow fuel passage Ls and the slow port 17 as a fuel injection port. 18), the downstream end of the air introduction path A is open. For this reason, since atmospheric pressure directly acts directly on the air mixing portion 16b in the slow fuel passage Ls, the suction of the air-bleeded fuel to the intake passage 2 side can be suppressed quickly and effectively. The fuel responsiveness of the fuel cut is improved.

  In the present embodiment, the slow bleed air passage Bs for supplying bleed air to the slow fuel passage Ls extends substantially along one side edge of the intake passage 2, and the upstream passage portion Au of the air introduction passage A. Has an upstream end opened in the middle of the bleed air passage Bs, and communicates with the atmosphere via the bleed air passage Bs upstream of the opening. Then, at least a portion Ad1 extending linearly from the first chamber 41 in the downstream passage portion Ad of the air introduction passage A is introduced downstream of the upstream passage portion Au in the direction along the intake passage 2 and introduced with negative pressure. It arrange | positions upstream from the path | route Pv. For this reason, the negative pressure introduction path Pv and the atmosphere introduction path A can be centrally deployed on one side of the carburetor body 1 without causing interference with each other.

  Further, in the present embodiment, the slow system fuel passage Ls constituting the fuel passage Ls of the present invention, and the main system fuel capable of supplying the fuel in the float chamber 4 to the intake passage 2 on the intake upstream side of the slow system fuel passage Ls. The passage Lm is arranged so as to be aligned on a vertical plane passing through the center line of the intake passage 2, and the main bleed air passage Bm extends substantially along the center line of the intake passage 2 in plan view, while the slow system A first bleed air passage portion Bs1 of the bleed air passage Bs extends so as to substantially follow one side edge of the intake passage 2. The air introduction path A has an upstream end thereof, that is, an upstream opening end of the upstream passage portion Au opened in the middle of the first bleed air passage portion Bs1 of the slow bleed air passage Bs. The air is communicated with the atmosphere, that is, the upstream side of the throttle valve T of the intake passage 2 via the first bleed air passage portion Bs1 on the upstream side. According to such a passage configuration, the main bleed air passage Bm can be easily formed because it can be formed in a straight line directly under the center line of the intake passage 2, while the main bleed air passage Bm is easily processed. The 1 bleed air passage portion Bs1 can be disposed immediately below or near one side edge of the intake passage 2 without interfering with the main system bleed air passage Bm, and a part of the first bleed air passage portion Bs1 is an air introduction passage. Since it also serves as the inlet side passage portion of A, the air introduction path A can be shortened and the structure can be simplified.

  Furthermore, the slow bleed air passage Bs of the present embodiment includes a first bleed air passage portion Bs1 extending linearly along the intake passage 2 and a bleed air mixing portion (that is, an air bleed pipe portion 16b) of the slow fuel passage Ls. ) And a second bleed air passage portion Bs2 having one end communicating with the other end side and extending upwardly toward one side 1s of the carburetor body 1, and an intermediate portion of the first bleed air passage portion Bs1. The upstream side passage portion Au of the air introduction path A communicates with the portion, and the other end of the first bleed air passage portion Bs1 is opened in the peripheral wall of the second bleed air passage portion Bs2, and the opening Bs1e In the direction along the passage 2, downstream of the communication portion between the first bleed air passage portion Bs 1 and the upstream passage portion Au of the atmosphere introduction path A and from the downstream passage portion Ad of the atmosphere introduction path A. Upstream, it is and also disposed on one side surface 1s side of the carburetor main body 1 as viewed from the slow-based fuel passage Ls. An air screw AS capable of arbitrarily adjusting the opening area of the opening Bs1e is formed in the carburetor main body 1 so as to be coaxially connected to the other end of the second bleed air passage portion Bs2, and opens to the one side surface 1s. It is screwed into the screw hole 45 obliquely from above.

  According to such an arrangement configuration of the air screw AS, the air introduction path A, and the negative pressure actuator AQ, the air introduction path A and the negative pressure actuator AQ that are centrally arranged on one side of the carburetor body 1, the air screw AS, The air screw AS can be easily deployed to the carburetor body 1 so that it can be easily screwed obliquely upward from the one side surface 1s side. In addition, the upstream passage portion (first bleed air passage portion Bs1) and the downstream passage portion (second bleed air passage portion Bs2) of the slow bleed air passage Bs can be easily formed with straight lines, respectively. The bleed air passage portion Bs2 and the screw hole 45 into which the air screw AS is screwed can be easily formed coaxially, and an air screw for adjusting the air amount is used for closing the outer end of the second bleed air passage portion Bs2. Simplification of the structure is achieved by using it as a stopper. Further, even if the downstream opening end Bs1 of the first bleed air passage portion Bs1 is restricted by the air screw AS, the first bleed air passage portion Bs1 itself can secure a large passage cross-sectional area. The atmosphere can be efficiently introduced through the first bleed air passage portion Bs1 into the atmosphere introduction path A communicating with the intermediate portion of the passage portion Bs1.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various design change is possible in the range which does not deviate from the summary.

  For example, in the above embodiment, the throttle valve T is applied to a sliding throttle type carburetor constituted by a slidable piston valve. However, in the present invention, the throttle valve is constituted by a butterfly type valve. It may be implemented in a vaporizer. In the above embodiment, the intake passage 2 of the carburetor C extends in the horizontal direction. However, the present invention may be applied to a carburetor in which the intake passage 2 extends in the vertical direction.

  In the above-described embodiment, the negative pressure introduction port to the intake passage 2 of the negative pressure introduction path Pv is disposed on the downstream side of the throttle valve T. However, in the present invention, the vicinity of the throttle valve T, for example, A negative pressure introduction port of the negative pressure introduction path Pv may be opened in the venturi portion 2a formed at a position corresponding to the throttle valve T in the intake passage 2. In this case, the negative pressure inlet may be opened either upstream or downstream of the needle jet 15 of the venturi portion 2a.

  In the above embodiment, the on-off valve V that is opened and closed by the negative pressure actuator AQ is a slide valve that opens and closes the air introduction path A by the sliding displacement of the valve body 26 with respect to the carburetor body 1. In the invention, the on-off valve V may be a rotary valve that opens and closes the air introduction path A by the rotational displacement of the valve body. Alternatively, the air introduction path A may be opened and closed by floatingly supporting the valve body of the on-off valve V on the vaporizer body 1 via the diaphragm 33 of the negative pressure actuator AQ.

  In the above embodiment, the one side 1 s of the carburetor main body 1 is provided with the on-off valve V for opening and closing the atmosphere introduction path A and the negative pressure actuator AQ for driving the valve, but the present invention ( The on-off valve and the negative pressure actuator according to the first and second aspects are not limited to the arrangement of the embodiment, and may be provided in the carburetor body 1 at least outside the float chamber 4.

  In the embodiment, the upstream end of the air introduction path A (upstream passage portion Au) is opened in the middle of the slow bleed air passage Bs, so that the slow bleed air passage Bs upstream from the opening. In the present invention (Claims 1 to 3), the upstream end of the air introduction path A is slowed down by connecting the air introduction path A to the atmosphere, that is, the upstream side of the throttle valve T of the intake passage 2. The air may be directly communicated with the atmosphere, for example, the upstream side of the throttle valve T of the intake passage 2 without passing through the system bleed air passage Bs.

A: Atmospheric introduction path Au: Upstream passage portion Ad of the atmospheric introduction path Ad ... Downstream passage portion Ad1 of the atmospheric introduction path: First of the downstream passage portion of the atmospheric introduction path Part AQ extending linearly from one chamber ... Negative pressure actuator Bs ... Slow system bleed air passage C as bleed air passage ... Vaporizer Ls ... Slow system as fuel passage Fuel passage Pv... Negative pressure introduction passage T... Throttle valve V .. Opening and closing valve 1... Carburetor body 2. ... Venturi section 4 as negative pressure generating section ... Float chamber 16b ... Air bleed pipe section 17 as air mixing section ... Slow port 18 as fuel injection port ... Intermediary passage 26 as intermediate passage part ... Valve 30 ... Over scan 31 ... space 33 ... Diaphragm 36 ... spring 41 ... first chamber 42 .... second chamber

Claims (5)

A throttle valve (T) provided in the carburetor body (1) and a fuel connected to the carburetor body (1) so that the passage cross-sectional area of the intake passage (2) connected to the combustion chamber of the internal combustion engine can be changed. Of the float chamber (4) in the intake passage (2) using the intake negative pressure generated in the negative pressure generating portion (2a) of the intake passage (2) during operation of the internal combustion engine. A fuel passage (Ls) capable of supplying fuel, and a bleed air passage having one end opened to the atmosphere and the other end opened in the middle of the fuel passage (Ls) to mix the bleed air with the fuel flowing through the fuel passage (Ls) A vaporizer comprising (Bs),
An atmosphere introduction path (A) having one end communicating with the atmosphere and the other end communicating with a passage portion (18) through which the fuel mixed with the bleed air flows of the fuel passage (Ls), and the atmosphere introduction path (A ) Is closed during normal times, and a negative pressure introduction path for introducing intake negative pressure generated there from the intake passage (2) in the vicinity of the throttle valve (T) or downstream of the throttle valve (T). (Pv) and a negative pressure actuator (AQ) that operates with the intake negative pressure introduced through the negative pressure introduction passage (Pv) to open the on-off valve (V), is provided outside the float chamber (4). A vaporizer, characterized by being prepared for.   The fuel passage (Ls) has an air mixing section (16b) that mixes bleed air from the bleed air passage (Bs) into the fuel, and jets fuel from the fuel passage (Ls) to the intake passage (2). A fuel injection port (17), and an intermediate passage portion (18) located in the middle of the air mixing part (16b) and the fuel injection port (17) and having a flow passage cross-sectional area larger than that of the fuel injection port (17), The carburetor according to claim 1, characterized in that the downstream end of the atmosphere introduction path (A) is opened in the intermediate passage portion (18).   The passage portion having the smallest flow path cross-sectional area of the atmosphere introduction path (A) has a flow passage cross-sectional area larger than the passage portion having the smallest flow path cross-sectional area of the bleed air passage (Bs), The vaporizer according to claim 1 or 2.   The negative pressure actuator (AQ) is attached to the one side surface (1s) of the vaporizer body (1), and defines a space (31) between the one side surface (1s); The space (31) is interposed between the case (30) and the vaporizer body (1), and the downstream passage portions (Au, Ad) are opened above the atmosphere introduction path (A), respectively, and Partitioned into a first chamber (41) in which the valve element (26) of the on-off valve (V) that conducts and blocks between the openings is accommodated, and a second chamber (42) connected to the negative pressure introduction path (Pv). And a spring (36) for repelling the diaphragm (33) toward the first chamber (41) and urging the valve body (26) in the valve closing direction, The upstream end of the upstream passage portion (Au) of the air introduction passage (A) is in the middle of the bleed air passage (Bs). The upstream passage portion (Au) is opened upstream in the direction along the intake passage (2) when viewed from the negative pressure actuator (AQ), and the negative pressure introduction passage (Pv) is in the same direction. The carburetor according to claim 3, wherein the carburetor is disposed on the downstream side.   The bleed air passage (Bs) has a passage portion (Bs1) extending substantially along one side edge of the intake passage (2), and upstream of the air introduction passage (A) in the middle of the passage portion (Bs1). The upstream end of the side passage portion (Au) is open, and at least the portion (Ad1) extending linearly from the first chamber (41) in the downstream passage portion (Ad) of the atmosphere introduction path (A) is In the direction along the intake passage (2), it is disposed downstream of the upstream passage portion (Au) and upstream of the negative pressure introduction passage (Pv). The vaporizer described.

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