JP2008303843A - Main nozzle positioning structure of carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a main nozzle positioning structure of a carburetor enabling cost reduction since the number of parts and the number of man-hours for machining are reduced, and capable of improving the stability of the flow of air-fuel mixture by improving the directivity of a main nozzle. <P>SOLUTION: In this main nozzle 10 positioning structure of a carburetor 1, a main fuel passage 3 and a slow fuel passage 4 opening to a mixing passage are arranged parallel to each other, these both passages 3, 4 communicate with each other through a communication passage. and the main nozzle 10 is inserted into the main fuel passage 3 and fixed. A positioning pin 20 is press-fitted to the portion (machined hole), other than the communication passage 16, of the through hole machined when the communication passage 16 is formed, a slit-like positioning groove 10b is axially formed in the outer peripheral surface of the main nozzle 10, and the positioning pin 20 is engaged with the positioning groove 10b for circumferentially positioning the main nozzle 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positioning structure for a main nozzle inserted and fixed in the main fuel passage of a carburetor having a main fuel passage and a slow fuel passage arranged in parallel.

  Some general-purpose carburetors have a main fuel passage and a slow fuel passage that are open to the mixing passage, and are connected to each other by a communication passage, and a main nozzle is inserted and fixed in the main fuel passage. Conventional examples of this type of carburetor are shown in FIGS.

  4 is a longitudinal sectional view of a conventional carburetor, FIG. 5 is an enlarged detailed view of a portion C in FIG. 4, and FIG. 6 is a sectional view taken along the line D-D in FIG. 2, a main fuel passage 3 and a slow fuel passage 4 which are long in the vertical direction are formed in parallel with each other, and bleed air is introduced into the main fuel passage 3 and the slow fuel passage 4 from a mixing passage (not shown). Bleed air passages 5 and 6 are connected to each other.

  A cylindrical jet holder 7 is inserted and fixed in the lower half portion of the main fuel passage 3, and a main jet 8 is held at the lower end inner diameter portion of the jet holder 7. The float chamber 9 attached to the lower part of the mixing body 2 contains fuel, and the main jet 8 is immersed in the fuel and opened.

  A main nozzle 10 is inserted and fixed in the upper half portion (small diameter portion) of the main fuel passage 3 by screwing or press-fitting the lower surface of the main nozzle 10 against the upper surface of the jet holder 7. Grooves 11 are formed on the entire outer periphery of the upper half (see FIG. 5). A large number of small circular bleed holes 12 are formed in the upper half of the main nozzle 10. That is, a plurality of these bleed holes 12 are formed in a row in the vertical direction (seven in the illustrated example), and a plurality of these bleed holes 12 are arranged in the circumferential direction.

  Thus, the lower end of the main fuel passage 3 opens into the fuel in the float chamber 9 via the main jet 8, and the upper end opens to a mixing passage (not shown). Further, the bleed air passage 5 opens into the groove 11 (see FIG. 5) formed on the outer periphery of the main nozzle 10, so that the bleed air passage 5 and the main fuel passage 3 are connected to the main nozzle 10. The formed grooves 11 and a plurality of bleed holes 12 communicate with each other.

  On the other hand, a slow jet 13 and a slow nozzle 14 are inserted and fixed in the upper half portion (large diameter portion) of the slow fuel passage 4, and a plurality of circular bleed holes 15 are formed in the lower end portion of the slow nozzle 14. Has been.

  Thus, the slow fuel passage 4 and the bleed air passage 6 communicate with each other through a plurality of bleed holes 15 formed in the slow nozzle 14. Note that the upper end of the slow fuel passage 4 opens into a mixing passage (not shown).

  Further, the main fuel passage 3 and the slow fuel passage 4 communicate with each other via a communication passage 16. That is, as shown in detail in FIGS. 5 and 6, a groove 10 a is formed on the entire outer periphery of the lower portion of the main nozzle 10, and the lower portion of the main nozzle 10 is open to the groove 10 a 2. Two circular holes 17 are formed.

  By the way, although the communication hole 16 is machined (drilled), a linear through hole is formed in the mixing body 2 during machining. One of the through holes is used as the communication passage 16, but the other hole 18 is an unnecessary processing hole, and thus the processing hole 18 is closed by a ball brag 19.

  The carburetor 1 ′ having the above-described configuration is provided in the intake system of the engine to be used for air-fuel mixture formation. When the engine rotates at low speed, the fuel in the float chamber 9 flows from the main jet 8 to the main fuel passage 3 and the communication passage. The air is sucked into the slow fuel passage 4 through the passage 16 and mixed with the bleed air introduced from the bleed air passage 6 to the slow fuel passage 4 in the process of flowing through the slow fuel passage 4 to be a predetermined air-fuel ratio (A / F). The air-fuel mixture is ejected into a mixing passage (not shown), sucked into the intake system of the engine, and used for combustion in the engine.

  When the engine is rotating at medium or high speed, the fuel in the float chamber 9 is mainly sucked from the main jet 8 into the main fuel passage 3 and flows from the bleed air passage 5 to the main fuel passage 3 in the course of flowing through the main fuel passage 3. The air-fuel mixture is mixed with the bleed air introduced to form a predetermined air-fuel ratio (A / F), and this air-fuel mixture is ejected into a mixing passage (not shown) and sucked into the intake system of the engine. Used for combustion.

  By the way, in the conventional carburetor 1 shown in FIGS. 4 to 6, the main nozzle 10 is inserted and fixed in the main fuel passage 3 by a press-fitting type or a screw type, and therefore the bleed hole 12 formed in the main nozzle 10. The direction of the bleed air passage 5 is not constant, and there is a problem that the flow rate of the air-fuel mixture to be formed varies.

  In order to solve the above problem, it is necessary to position the main nozzle 10 in the circumferential direction with a positioning pin so that the main nozzle 10 has directivity. However, this method requires a positioning pin in addition to the ball plug 19. Therefore, there is a problem that the number of parts is increased and machining such as grooving is increased to increase the number of processing steps, resulting in an increase in cost.

  Further, if the positioning of the main nozzle 10 in the circumferential direction is not performed accurately, the positions of the circular holes 17 formed in the main nozzle 10 and the communication passage 16 do not coincide with each other, and the slow fuel passage 4 from the main fuel passage 3 to the slow fuel passage 4 The directionality of the fuel feeding to the is deteriorated. For this reason, conventionally, as shown in FIGS. 5 and 6, a configuration has been adopted in which a groove 10 a is formed over the entire circumference of the main nozzle 10 and two circular holes 17 are opened in the groove 10 a. In this configuration, there is a problem in that cost increases due to an increase in machining for forming the groove 10a.

  The present invention has been made in view of the above-mentioned problems, and the purpose of the process is to reduce the number of parts and the number of processing steps and to reduce the cost, and to improve the directivity of the main nozzle to improve the flow rate stability of the air-fuel mixture. It is an object of the present invention to provide a carburetor main nozzle positioning structure that can be improved.

  To achieve the above object, according to the present invention, a main fuel passage and a slow fuel passage that are open to a mixing passage are provided side by side, and both passages are connected by a communication passage, and a main nozzle is inserted and fixed in the main fuel passage. As a positioning structure of the main nozzle of the carburetor, a positioning pin is press-fitted into a portion other than the communication path of the through hole processed when forming the communication path, and a slit-shaped positioning groove is formed on the outer periphery of the main nozzle Is formed in the axial direction, and the positioning of the main nozzle in the circumferential direction is performed by engaging the positioning pin with the positioning groove.

  According to the present invention, the positioning pin is press-fitted into a portion other than the communication path of the through hole processed when forming the communication path, that is, an unnecessary processing hole, and the positioning pin is formed on the outer periphery of the main nozzle. Since the positioning of the main nozzle in the circumferential direction is performed by engaging with the groove, the directivity of the main nozzle is enhanced, and variations in the flow rate of the air-fuel mixture are suppressed. In addition, since an unnecessary machining hole is used and a positioning pin is press-fitted into the hole, parts such as a ball plug for closing the unnecessary machining hole and work for press-fitting this to close the machining hole become unnecessary. The carburetor cost can be reduced by reducing the number of points and work man-hours.

  Further, since the positioning of the main nozzle in the circumferential direction is accurately performed, a groove formed on the outer periphery of the main nozzle is not necessary to ensure high directivity for feeding fuel from the main fuel passage to the slow fuel passage. In addition, only one hole (hole communicating with the communication passage) is formed in the main nozzle, so that the number of processing steps can be reduced and the cost of the carburetor can be further reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a longitudinal sectional view of a carburetor having a main nozzle positioning structure according to the present invention, FIG. 2 is an enlarged detail view of a part A in FIG. 1, and FIG. 3 is a sectional view taken along line BB in FIG. In the figure, the same elements as those shown in FIGS. 4 to 6 are denoted by the same reference numerals, and the repetitive description thereof will be omitted, and the main nozzle positioning structure which is the main point of the present invention will be described below. To do.

  In the present invention, positioning pins 20 are press-fitted into unnecessary processing holes 18 other than the through-hole communication passages 16 processed when forming the communication passages 16 in the mixing body 2, and are shown in detail in FIGS. As described above, the slit-like positioning groove 10b is formed in the outer periphery of the main nozzle 10 in the axial direction, and the distal end of the positioning pin 20 is engaged with the positioning groove 10b so that the main nozzle 10 is positioned in the circumferential direction. It is characterized by that.

  Thus, when the positioning of the main nozzle 10 in the circumferential direction is accurately performed by the engagement of the positioning pin 20 with the positioning groove 10b, the position of the bleed hole 12 formed in the main nozzle 10 with respect to the bleed air passage 5 is changed. Since it is maintained appropriately, the directivity of the main nozzle 10 is increased, the variation in the flow rate of the air-fuel mixture is suppressed, and the flow rate stability of the air-fuel mixture is improved.

  In the present invention, since the unnecessary machining hole 18 is used and the positioning pin 20 is press-fitted into the hole, a component such as a ball plug for closing the unnecessary machining hole 18 and the machining hole are press-fitted. Since the work of closing is unnecessary, the number of parts and the number of work steps can be reduced, and the cost of the carburetor 1 can be reduced.

  Furthermore, since the positioning of the main nozzle 10 in the circumferential direction is accurately performed as described above, the outer periphery of the main nozzle 10 is secured in order to ensure high directivity for feeding fuel from the main fuel passage 3 to the slow fuel passage 4. The formed groove (groove 10a shown in FIGS. 5 and 6) is not necessary, and only one hole (hole communicating with the communication path 16) 17 is formed in the main nozzle 10, and the number of processing steps is reduced. Thus, the cost of the carburetor 1 can be further reduced.

It is a longitudinal cross-sectional view of the carburetor provided with the positioning structure of the main nozzle which concerns on this invention. It is the A section enlarged detail drawing of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2. It is a longitudinal cross-sectional view of the conventional carburetor. FIG. 5 is an enlarged detail view of a C part in FIG. 4. It is the DD sectional view taken on the line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carburetor 2 Mixing body 3 Main fuel passage 4 Slow fuel passage 5, 6 Bleed air passage 7 Jet holder 8 Main jet 9 Float chamber 10 Main nozzle 10a Groove 10b Positioning groove 11 Groove 12 Bleed hole 13 Slow jet 14 Slow nozzle 15 Bleed hole 16 Communication path 17 Circular hole 18 Processing hole 19 Ball plug 20 Positioning pin

Claims (1)

A positioning structure for the main nozzle of the carburetor in which the main fuel passage and the slow fuel passage that open in the mixing passage are arranged side by side, and both passages are connected by a communication passage, and the main nozzle is inserted and fixed in the main fuel passage. There,
A positioning pin is press-fitted into a portion other than the communication path of the through hole that is processed when forming the communication path, and a slit-shaped positioning groove is formed in the axial direction on the outer periphery of the main nozzle, and the positioning groove A main nozzle positioning structure for a carburetor characterized in that positioning of the main nozzle in the circumferential direction is performed by engaging a positioning pin.

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