Title of Invention

A CARBURETOR WITH AN IMPROVED AIR VENT

Abstract

A carburetor with an improved air vent comprises : a float chamber (6) formed below a suction passage (2) extending through a carburetor main body (1) ; and a liquid surface upper chamber (6A) located above the fixed fuel liquid surface (X-X) formed within the float chamber, the upper chamber being adapted to communicate with atmospheric air via an air vent passage (A), wherein an open end (A1) in the atmospheric air side of the air vent passage (A) is open in the downward direction substantially orthogonal to a fixed fuel liquid surface (X-X), and a wind prevention wall (9) is integrally provided with the carburetor main body at the front side of said open end (A1) of the air vent passage (A), whereby negative pressure generated by traveling wind near said open end is prevented from affecting said liquid surface upper chamber (6A), thereby enabling maintenance of stable atmospheric pressure state.

Full Text

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a carburetor with an improved air vent which adjusts and controls an amount and a concentration of air-fuel mixture supplied to an internal combustion engine, and particularly relates to an air vent passage which communicates a liquid surface upper chamber above a fixed fuel liquid surface formed within a float chamber with an atmospheric air. DESCRIPTION OF THE RELATED ART A first example of a conventional air vent apparatus in a carburetor is disclosed in Japanese Unexamined Utility Model Publication No. 57-171163. In accordance with this disclosure, an open end in the atmospheric air side of the air vent passage for communicating the liquid surface upper chamber above the fixed fuel liquid surface formed within the float chamber with the atmospheric air is open in the downward direction orthogonal to the fixed fuel liquid surface. Further, a second example of the conventional air vent apparatus in the apparatus in the carburetor is disclosed in 1A Japanese Utility Model Publication No. 1-8683. In accordance with this structure, there is disclosed a technique in which the open end in the atmospheric air side of the air vent passage is open in the horizontal direction extending along the fixed fuel liquid surface, and the upper and both sides of the open end in the atmospheric air side are covered by a shielding portion formed substantially in a U sectional shape open downward. In accordance with the conventional air vent apparatus in the carburetor of the first example mentioned above, since the open end in the atmospheric air side of the air vent passage is open in the downward direction, water or a foreign matter hardly intrudes into the air vent passage when the carburetor is mounted on a vehicle (for example, a motor cycle), whereby a preferable air vent effect can be achieved, however, this is not preferable at a time when the vehicle travels. That is, since a traveling wind passes by the open end in the atmospheric air side in accordance that the vehicle travels, a negative pressure is generated in the open end portion, and the negative pressure reaches the liquid surface upper chamber of the float chamber via the air vent passage. 2 The negative pressure state in the liquid surface upper chamber causes a change of a differential pressure between the negative pressure applied to the fuel injection port such as a main fuel nozzle open to a suction passage, a low speed injection port and a pressure in the liquid surface upper chamber, thereby generating a dispersion in a fuel sucked out from the fuel injection port, so that there is a risk of deterioration of drivability or an increased generation of harmful material contained in an exhaust gas. Further, in accordance with the second conventional art, since the open end in the atmospheric air side of the air vent passage is open in the horizontal direction, it is not possible to effectively prevent water from entering even when it is surrounded by the shielding portion. Further, the shielding portion is formed in a cooling air guide plate which is an member independent from a carburetor main body. So, it is necessary to particularly provide with an independent member or utilize the other member. SUMMARY OF THE INVENTION The present invention is made by taking the problems mentioned above into 3 consideration, and an object of the present invention is to provide a carburetor with an air vent apparatus without being intruded by water or foreign matter, without being affected by traveling wind at a time when a vehicle is moving, and without increasing the number of parts and the number of man-hours for assembling and to achieve a low cost. in order to achieve the objectives mentioned above, the present invention provides a carburetor with an improved air vent comprising: a float chamber formed below a suction passage extending through a carburetor main body; and a liquid surface upper chamber located above a fixed fuel liquid surface formed within said float chamber, said upper chamber being adapted to communicate with atmospheric air via an air vent passage, wherein an open end in the atmospheric air side of the air vent passage is open in the downward direction substantially orthogonal to a fixed fuel liquid surface, and a wind prevention wall is integrally provided with the carburetor main body at the front side of said open end of the air vent passage, whereby negative pressure generated by traveling wind near said open end is prevented from affecting said liquid surface upper chamber, thereby enabling maintenance of stable atmospheric pressure state. Further, in accordance with a second aspect of the present invention, the wind prevention wall comprises a mounting boss integrally formed with the carburetor main 4 body and mounting the other member. In accordance with the first aspect, since the traveling wind generated at the time when the vehicle travels is shut by the wind prevention wall, no negative pressure is generated in the open end in the atmospheric air side of the air vent passage, and it is possible to keep the liquid surface upper chamber within the float chamber in a stable atmospheric pressure state, whereby it is possible to execute an accurate fuel supply from the fuel injection port. Further, in accordance with the second aspect of the present invention, since the mounting boss integrally formed with the carburetor main body is utilized for the wind prevention wall, it is not necessary to particularly provide a new wall portion. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS In the accompanying drawings - Fig. 1 is a vertical cross-sectional view of a main portion showing a first embodiment of an air vent apparatus in a carburetor in accordance with the present invention (corresponding to a cross-sectional view along line P-P in Fig. 2); Fig. 2 is a right side elevational view of Fig. 1 ; and Fig. 3 is a side elevational view showing another 5 embodiment of an air vent apparatus in a carburetor in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT A description will be given of an embodiment of an air vent apparatus in a carburetor in accordance with the present invention with reference to the accompanying drawings. Fig. 1 is a vertical cross sectional view of a carburetor and Fig. 2 is a side elevational view thereof. Reference numeral 1 denotes a carburetor main body through which a suction passage 2 extends. The suction passage 2 is controlled so as to be opened and closed by a throttle valve 4 mounted to a throttle valve shaft 3 . A float chamber main body 5 is arranged below the carburetor main body 1, a float chamber 6 is formed by a lower recess portion of the carburetor main body 1 and the float chamber main body 5. A fixed fuel liquid surface X-X is formed by a fixed liquid surface control mechanism constituted of a float 7, a valve seat connected to a fuel inflow passage (not shown) and a float valve opening and closing the valve seat is formed within the float chamber 6. Further, a liquid surface upper chamber 6A is formed at an upper position of the fixed fuel liquid 6 surface X-X within the float chamber 6, and the liquid surface upper chamber 6A is communicated with atmospheric air by an air vent passage A. The air vent passage A in accordance with the present embodiment extends from an upper portion in the left side of the liquid surface upper chamber 6A in the upward direction and next bends rightward in the horizontal direction, and an open end A1 in the atmospheric air side is open toward B in the downward direction substantially orthogonal to the fixed fuel liquid surface X-X. In this case, reference numeral 8 denotes a plug closing an opening in the horizontal direction of the air vent passage A extending in the horizontal direction. A wind prevention wall 9 mentioned below is integrally provided with the carburetor main body 1 in the atmospheric air side open end A1 of the air vent passage A. At first, in a state that the carburetor is mounted on an engine of a vehicle such as a motor cycle (not shown), the wind prevention wall 9 is integrally formed with the carburetor main body 1 in the left side of the atmospheric air side open end A1 on the assumption that a forward moving direction Y 7 of the vehicle corresponds to the leftward direction in Fig. 2 . The wind prevention wall 9 is continuously provided vertically so as to face to an opening A2 in the forward moving direction side of the atmospheric air side open end Al. In other words, in the opening A2 in the forward moving direction side of the atmospheric air side open end Al, the wind prevention wall 9' is arranged in the forward moving direction thereof. In this case, when the engine is operated and the vehicle is in the traveling state, the traveling wind flows rightward from a left side in Fig. 2. In an upper portion of the air vent passage A, a stream U of the traveling wind is generated along the air vent passage A (in particular, an air vent passage boss), and in a lower portion of the air vent passage A, a stream D of the traveling wind is generated. Then, paying attention to the stream D of the traveling wind in the lower portion, the traveling wind once collides with the wind prevention wall 9 and changes the direction to flow apart from the atmospheric air open end Al of the air vent passage A. In accordance with the structure mentioned above, it is possible to largely reduce an influence of the 8 traveling wind near the atmospheric air side open end A1 of the air vent passage A due to the stream of the traveling wind D, and it is possible to largely restrict generation of negative pressure near the atmospheric air side open end A1. Accordingly, the negative pressure generated by the traveling wind is not applied to the liquid surface upper chamber 6A via the atmospheric air side open end A1 and the air vent passage A, and it is possible to always keep the liquid surface upper chamber 6A in a stable atmospheric pressure state, whereby it is possible to always maintain the differential pressure stable between the fuel injection port such as the main nozzle or the low speed injection port, and the liquid surface upper chamber 6A, and it is possible to accurately suck out the fuel into the suction passage 2. Further, the wind prevention wall can be integrally formed with the carburetor main body 1, for example, in accordance with a casting, whereby it is not necessary to employ a peculiar member, a number of parts, a number of man-hours for assembly are not increased, the manufacturing cost is not increased in comparison with the conventional structure, and it is possible to easily execute in 9 comparison with the conventional structure. Further, an opening degree sensor 20 electrically detecting an opening degree of the throttle valve 4 so as to output may be arranged in the carburetor as shown in Fig. 3, and a mounting boss 11 for mounting the opening degree sensor 20 may be integrally provided with the carburetor main body 1, whereby the mounting boss 11 can be used as the wind prevention wall 9. In accordance with the structure mentioned above, the mounting boss 11 can be utilized as the wind prevention wall 9 without peculiarly providing with a new wind prevention wall. In addition, a passage boss or the like of a starter is integrally provided in the carburetor main body in addition to the mounting boss for mounting the opening degree sensor, and such boss may also be used. It is sufficient that the atmospheric air side open end AT of the air vent passage A is open in the downward direction substantially orthogonal to the fixed fuel liquid surface X-X. As mentioned above, in accordance with the air vent apparatus of the carburetor of the present invention, since the atmospheric air side open end of the air vent passage is open in the downward direction substantially orthogonal to the fixed fuel liquid 10 surface, and the wind prevention wall for shutting the traveling wind applied to the atmospheric air side open end is provided in the front side in the vehicle forward moving direction of the atmospheric air side open end, it is possible to always keep the liquid surface upper chamber within the float chamber in the stable atmospheric pressure state at a time when the vehicle travels, whereby it is possible to supply stable and accurate fuel toward the engine. Accordingly, it is possible to provide the air vent apparatus in the carburetor which can prevent water or foreign matter from entering into the float chamber via the air vent passage, has an excellent drivablity and can reduce the harmful material contained in the exhaust gas. Further since the wind prevention wall is integrally formed with the carburetor main body, the number of parts and the number of man-hours for assembly are not increased and the manufacturing cost is not increased. In particular, the present invention is possible to be easily carried out in comparison with the conventional structure. Further, in the case that the mounting boss for the other member integrally formed with the carburetor main body is used as the wind prevention wall, it is 11 possible to increase a design freedom of the wind prevention wall and it is easy to carry out the structure . 12 WE CLAIM : 1. A carburetor with an improved air vent comprising : a float chamber (6) formed below a suction passage (2) extending through a carburetor main body (1); and a liquid surface upper chamber (6A) located above a fixed fuel liquid surface (X-X) formed within said float chamber, said upper chamber being adapted to communicate with atmospheric air via an air vent passage (A), wherein an open end (A1) in the atmospheric air side of the air vent passage (A) is open in the downward direction substantially orthogonal to a fixed fuel liquid surface (X-X), and a wind prevention wall (9) is integrally provided with the carburetor main body at the front side of said open end (A1) of the air vent passage (A), whereby negative pressure generated by traveling wind near said open end is prevented from affecting said liquid surface upper chamber (6A), thereby enabling maintenance of stable atmospheric pressure state. 2. A carburetor with an improved air vent as claimed in claim 1, wherein the wind prevention wall comprises a mounting boss (11) integrally formed with the carburetor main body (1) and mounting the other member. 13 14 3. A carburetor with an improved air vent, substantially as herein described, particularly with reference to and as illustrated in the accompanying drawings. A carburetor with an improved air vent comprises : a float chamber (6) formed below a suction passage (2) extending through a carburetor main body (1) ; and a liquid surface upper chamber (6A) located above the fixed fuel liquid surface (X-X) formed within the float chamber, the upper chamber being adapted to communicate with atmospheric air via an air vent passage (A), wherein an open end (A1) in the atmospheric air side of the air vent passage (A) is open in the downward direction substantially orthogonal to a fixed fuel liquid surface (X-X), and a wind prevention wall (9) is integrally provided with the carburetor main body at the front side of said open end (A1) of the air vent passage (A), whereby negative pressure generated by traveling wind near said open end is prevented from affecting said liquid surface upper chamber (6A), thereby enabling maintenance of stable atmospheric pressure state.

Documents:

00044-cal-2002-abstract.pdf

00044-cal-2002-claims.pdf

00044-cal-2002-correspondence.pdf

00044-cal-2002-description(complete).pdf

00044-cal-2002-drawings.pdf

00044-cal-2002-form-1.pdf

00044-cal-2002-form-19.pdf

00044-cal-2002-form-2.pdf

00044-cal-2002-form-3.pdf

00044-cal-2002-form-5.pdf

00044-cal-2002-g.p.a.pdf

00044-cal-2002-priority document.pdf

44-CAL-2002-FORM-27.pdf

44-cal-2002-granted-abstract.pdf

44-cal-2002-granted-acceptance publication.pdf

44-cal-2002-granted-claims.pdf

44-cal-2002-granted-correspondence.pdf

44-cal-2002-granted-description (complete).pdf

44-cal-2002-granted-drawings.pdf

44-cal-2002-granted-examination report.pdf

44-cal-2002-granted-form 1.pdf

44-cal-2002-granted-form 19.pdf

44-cal-2002-granted-form 2.pdf

44-cal-2002-granted-form 3.pdf

44-cal-2002-granted-form 5.pdf

44-cal-2002-granted-gpa.pdf

44-cal-2002-granted-letter patent.pdf

44-cal-2002-granted-priority document.pdf

44-cal-2002-granted-reply to examination report.pdf

44-cal-2002-granted-specification.pdf

44-cal-2002-granted-translated copy of priority document.pdf