US3779529A - Differential diaphragm carburetor - Google Patents

Differential diaphragm carburetor Download PDF

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Publication number
US3779529A
US3779529A US00233988A US3779529DA US3779529A US 3779529 A US3779529 A US 3779529A US 00233988 A US00233988 A US 00233988A US 3779529D A US3779529D A US 3779529DA US 3779529 A US3779529 A US 3779529A
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US
United States
Prior art keywords
fuel
diaphragm
pressure
chamber
regulating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00233988A
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English (en)
Inventor
R Kimura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mikuni Corp
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Mikuni Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP6477071A external-priority patent/JPS4831330A/ja
Priority claimed from JP8596471A external-priority patent/JPS4851135A/ja
Priority claimed from JP9489171A external-priority patent/JPS5143206B2/ja
Priority claimed from JP10265371A external-priority patent/JPS4867623A/ja
Application filed by Mikuni Corp filed Critical Mikuni Corp
Application granted granted Critical
Publication of US3779529A publication Critical patent/US3779529A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M17/00—Carburettors having pertinent characteristics not provided for in, or of interest apart from, the apparatus of preceding main groups F02M1/00 - F02M15/00
    • F02M17/02—Floatless carburettors
    • F02M17/04—Floatless carburettors having fuel inlet valve controlled by diaphragm
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S261/00—Gas and liquid contact apparatus
    • Y10S261/68—Diaphragm-controlled inlet valve

Definitions

  • 261/35 261/DIG' chamber is applied to either one or both of the dia- [581 Fieid 68 69 A phragms and the operation of the valve is regulated by 5 the difference in the size of the two diaphragms.
  • This invention relates to a carburetor for internal combustion engines. More particularly, this invention relates to a novel carburetor which can be easily adjusted so as to exhibit any desired fuel feed characteristics accommodated to any engine.
  • the rate of fuel feed is determined by the difference between the fuel feed pressure conventionally, the head of fuel (mm Aq) in the fuel feed system which is referred to as primary pressure hereinafter, and the pressure (negative pressure) in the fuel mixing chamber, which is referred to as secondary pressure hereinafter.
  • the pressure in the mixing chamber which varies in a range as the engine is operated, is specific to the design of an engine. Therefore, in order to achieve desired fuel feed ratio, an appropriate difference between the primary and secondary pressures must be achieved.
  • the fuel head of a carburetor is specific to the individual carburetor, and cannot easily be changed.
  • This invention provides a novel carburetor in which the fuel feed pressure can easily be varied so as to be adjusted to the engines of any design.
  • a novel carburetor which comprises a negative pressure chamber which communicates with a nozzle means for introducing fuel into afuel mixing chamber; a fuel-pressureregulating chamber which communicates with the negative pressure chamber by way of a passage having'a fuel jet orifice provided therein; a valve which controls inflowof fuel into the fuel-pressure-regulating chamber; whereby at least one wall of said negative pressure chamber and at least one wall of said fuel-pressureregulating chamber consist of respectively a negative pressure diaphragm and a fuel-pressure-regulating diaphragm; said two diaphragms being interlocked with each other by means of a movement-imparting means; said valve being interlocked with said fuel pressure regulating diaphragm; and the difference in effective areas of the two diaphragms determines the fuel feed pressure on the upstream side of said fuel jet orifice.
  • the negative pressure generated in the fuel mixing chamber is applied to the negative pressure diaphragm or both of the negative pressure diaphragm and the fuel-pressure-regulating'diaphragm and a displacement or movement, the direction of which is determined by that of the larger diaphragm and the degree of which is determined by the difference of the effective areas of the two diaphragms, is generated, and the displacement is imparted to the valve controlling inflow of fuel, and thus the fuel'feed to the engine is regulated more sensitively and more delicately than the carburetors of the prior art.
  • the primary pressure is adjusted bychanging effective area of one or both of the diaphragms.
  • the change indiaphragm size can quite easily be effected by employing diaphragm-supporting plates of annular shape explained in detail hereinafter.
  • the carburetor of this invention is characterized in that the primary pressure or the fuel'pressure on the upstream side of the fuel jet orifice can easily be varied,
  • contraction is not provided at the fuel feed nozzle and the negative pressure in the fuel mixing chamber instantly transmitted to the fuel feed system.
  • FIG. I shows a characteristic curve representing the relation between the fuel feed pressure and the quantity of fuel to be supplied to the engine.
  • FIG. 2. shows characteristic curves representing the relation between the size of the fuel jet orifice and the quantity of fuel to be supplied for 3 different sizes of fuel jet orifice.
  • FIGS. 3 through 7 are sectional views of carburetors representing four embodiments of this invention.
  • FIG. 1 shows a typical curve (Curve A) for fuel feed characteristics of a carburetor of an engine operated at full load.
  • the ordinate stands for quantity of fuel fed Q and the abscissa stands for the above-mentioned pressure difference P p.
  • the change in fuel feed quantity is not linearly proportional to the pressure difference P p.
  • Point a stands for a primary pressure I and a secondary pressure p,, and point a, stands for the primary pressure P, and a secondary pressure p
  • Point a stands for another primary pressure P and the secondary pressure p and point a stands for the primary pressure P and the secondary pressure p
  • the absolute amount of the fuel to be supplied can be changed by changing the size of the fuel jet orifice as shown in FIG. 2.
  • the ordinate and the abscissa stand for quantity of the fuel supplied Q and the pressure difference P p respectively as in FIG. I.
  • FIG. 2 shows fuel feed characteristics curves for an engine when fuel jet orifices of different sizes are used.
  • Curve B stands for a carburetor having a fuel jet orifice of a larger size
  • Curve D stands for the same curburetor having a fuel jet orifice of a smaller size
  • Curve C for the same curburetor having a fuel jet orifice of a size between B and D.
  • the primary pressure is kept constant and adjustement is made only by alteration of the jet orifice.
  • This invention provides a novel carburetor in which the primary pressure is easily altered, and characteristics of which can optionally be accomodated to an engine with any operation characteristics.
  • a differential diaphragm carburetor of this invention comprising a negative pressure chamber composed of two diaphragms a negative pressure diaphragm and a fuel-pressure-regulating diaphragm to which a poppet valve for controlling the passage of fuel is attached.
  • Member 1 is a fuel mixing chamber
  • 2 is a venturi of said chamber
  • 3 is a fuel feed nozzle
  • 4 is a passage for fuel
  • 5 is a negative pressure chamber
  • 6 is a negative pressure diaphragm
  • 7 is an atmospheric pressure chamber provided in a carburetor body or casing 8 communicating with the atmosphere.
  • the diaphragm 6 is secured by the casing per se and an annular plate 9.
  • Annular plates of various sizes are prepared, and the effective area of the diaphragm is altered by selecting an annular plate of a suitable size.
  • Member 10 is a fuel-pressure-regulating diaphragm, the effective area of which is smaller than the negative pressure diaphragm is this case.
  • the effective area can be also changed by employment of an annular plate (not shown) as used for the diaphragm 6.
  • Member 1 l is a helicoidal spring which interlocks the negative pressure diaphragm and the fuel-pressureregulating diaphragm
  • 12 is a fuel-pressure-regulating chamber
  • 13 is a fuel canal connecting the fuelpressure-regulating chamber and the negative-pressure chamber
  • 14 is a fuel jet orifice
  • 15 is a valve chamber
  • 16 is a passage for fuel connecting the valve chamber 15 and the fuel-pressure-regulating chamber 12, which is opened or closed by the poppet valve 17 placed in the valve chamber 15 and supported by a spring 19 and attached to the diaphragm 10 by means of a needle 18.
  • Member 20 is a fuel duct communicating with a fuel pump or'tank. When the engine is not in operation, the valve 17 closes the passage 16 by the force of the spring 19.
  • the fuel pressure in the fuel-pressure-regulating chamber that is, primary pressure P on the upstream 10 side of the fuel jet orifice 14 responds to displacement of the fuel-pressure-regulating diaphragm. Therefore, when the area difference between the fuel-pressureregulating diaphragm 10 and the negative pressure diaphragm 6 is varied, the primary pressure P is varied, l5 and thus the amount of the fuel which is drawn in through the jet orifice 14 and is sprayed through the nozzle 3 via negative pressure chamber 5 is varied.
  • FIG. 1 the embodiment of this invention represented by FIG. 1
  • the effective area of the negative pressure diaphragm 20 is varied by selecting an annular plate 9 of a suitable size.
  • the fuel feed characteristics for instance, as represented by :1 a, portion of Curve A in FIG. 1. is shifted to a a, portion of the same curve.
  • the atmospheric pressure chamber 7 has a cove 21, where the chamber is contiguous to a fuel chamber 23 separated by a third diaphragm 22.
  • the fuel chamber 23 communicates with the valve chamber 15 by way of a canal 24.
  • the third diaphragm 22 is interlocked with the negative pressure diaphragm 6 by means of a spring 25.
  • an annular wall 26 is provided in order to prevent excessive distorsion or displacement of the diaphragm 22.
  • FIG. 4 represents a second embodiment of this invention.
  • This embodiment is characterized in that the poppet valve is not directly connected to the pressureregulating diaphragm but is interlocked with it by means of a lever. This mechanism makes possible a more sensitive and more delicate accommodation.
  • FIG. 4 parts or members are the same as or correspond to the parts or members represented by the same number in FIG. 3.
  • Fuel is introduced through the fuel duct into the valve chamber 15 and then into the fuel-pressure-regulating chamber 12 by waY of the passage 16 which is controlled by the poppet valve 17.
  • the fuel-pressure-regulating chamber is composed of the fuel-pressure-regulating diaphragm 10 and the negative pressure diaphragm 6 and it communicates with the negative pressure chamber 5 via an jet orifice 14 as shown in the figure.
  • the communication between the fuel-pressure-regulating chamber 12 and the negative pressure chamber 5 can be achieved by a canal 13 with a jet orifice 14' as shown in broken line, too.
  • the fuel which is brought into the negative pressure chamber 5 is sprayed from the nozzle 3.
  • a lever 31 which is supported by a fulcrum 32 and is connected to the fuel-pressure-regulating diaphragm and the poppet valve 17 at the ends thereof, is provided in the fuel pressure-regulating chamber 12.
  • the end connected with the poppet valve 17 is pressed by a spring 19 so as to close the fuel passage 16 when the engine is not. in operation.
  • This carburetor works substantially in the same way as the embodiment represented by FIG. 3.
  • the negative pressure is applied to the negative pressure chamber 5 through the nozzle 3 and draws up the negative pressure diaphragm 6.
  • This displacement of the diaphragm 6 raises the fuel-pressure-regulating diaphragm 10 and opens the passage 16.
  • the fuel flows into the fuelpressure-regulating chamber 12 and pressurizes the chamber.
  • the effective area of the diaphragm 10 is larger that that of the diaphragm 6.
  • the pressure of the fuel introducedvin thev chamber works so as to close the passage 16, that is, to control the inflow of the fuel. Therefore, the pressure in the fuel-pressure-regulating chamber is kept rather low and the fuel supply to the engine is maintained rather high in high speed operation and rather low in low speed operation, which corresponds to the a a, portion of Curve A in FIG. 1.
  • FIG. 5 stands for a third embodiment of this invention.
  • parts and members are the same as or correspond to the parts or member represented by the same number in FIG. 3, too.
  • the two diaphragms are arranged in a plane, and the negative pressure chamber 5 and the fuel-pressureregulating chamber 12 are placed on one side, that is, on the upper side of the plane, and the other side or the lower side constitutes an atmospheric pressure chamber 7.
  • the negative pressure chamber 5 and the fuel-pressure-regulating chamber 12 communicate by a canal 13 in which a fuel jet orifice is provided.
  • a lever 32 is provided in the atmospheric pressure chamber.
  • the lever 32 is supported by a fulcrum 31 and is connected to the negative pressure diaphragm 6 by means of a needle 33 thereof at the free end thereof and to the fuel pressure regulating diaphragm'by means of a pressing spring 34 at a pointbetween the free end and the fulcrum.
  • the poppet valve is supported by a spring 19 so that the passage 16 is closed when the engine is not in operation in the same way as in the'first embodiment.
  • the valve 17 is connected to.the fuelpressureregulating diaphragm by means of a needle 18. When a negative pressure is applied to the negative pressure chamber, the negative pressure diaphragm 6 is raised and therefore the fuel-pressure-regulating diaphragm is raised so as to open the passage 16.
  • the fuel supply characteristics correspond to Curve a 2 a in FIG. 1 as a general tendency.
  • control of the fuel pressure in the fuel-pressureregulating chamber 12 can be modified by changing the arm length ratio of the lever 32.
  • the poppet valve closes the fuel passage connecting the fuel-pressureregulating chamber and the fuel supply vsystem from the fuel supply system side. Therefore, the poppet valve may be pressed by dynamic pressure of the inflowing fuel and may not work sensitively responding the displacement of the negative-pressure diaphragm.
  • This disadvantage can be eliminated by employing the mechanism of the fuel chamber and the third diaphragm explained in connection with the embodiment v of FIG. 3 as shown in FIG. 6.
  • a fuel chamber 23 with a third diaphragm is provided under the atmospheric pressure chamber 7, and connected with the fuel duct 20 by means of a canal 24.
  • the third diaphragm is interlocked .with the lever means provided in the atmospheric pressure chamber 7 by means of a resilient means 25.
  • the dynamic pressure applied to the poppet valve is simultaneously applied to the third diaphragm through the canal 24.
  • the displacement of the third diaphragm is imparted to the fuel-pressureregulating diaphragm so as to cancel the dynamic pressure applied to the poppet valve.
  • FIG. 7 shows an embodiment in which this invention is applied to a piston type throttle valve carburetor.
  • the numbers represent parts and members the same as or corresponding to those represented by the same numbers in FIGS. 3 and 5.
  • the basic construction of the carburetor of this embodiment is the same as the carburetor of FIG. 5 except that the negative pressure chamber 5 and the fuel-pressureregulating chamber 12 are placed on the opposite sides ofthe atmospheric pressure chamber.
  • Member 41' is a piston type throttle valve
  • 42 is a fuel supply control needle valve, the upper end of which is freely supported by the throttle valve.
  • a carburetor of this type has a long nozzle 3 in which the needle 42 moves up and down.
  • the negative pressure diaphragm (larger diaphragm) 6 is of an annular shape and a cylinwhich communicates with a nozzle for introducing fuel to a fuel mixing chamber; a fuel pressure regulating chamber which communicates with the negative pressure chamber by way of a passage having a fuel jet orifice; a valve which controls inflow of fuel into the fuelpressure-regulating chamber; whereby at least one wall of said negative pressure chamber and at least one wall of said fuel-pressure-regulating chamber consist of respectively a negative pressure diaphragm and a fuelpressure-regulating diaphragm; said two diaphragms being interlocked with each other by means of a movement-transmitting means; said valve being interlocked with said fuel pressure regulating diaphragm; and said two diaphragms have different effective areas so as to create a desired fuel pressure on the upstream side of said fuel jet orifice.
  • valve controlling inflow of fuel is a poppet valve which closes the fuel passage, in
  • valve is a poppet valve which closes the passage connecting the fuel pressure regulating chamber and the fuel supply system from the fuel supply system side being pressed by a resilient means.
  • valve controlling inflow of fuel is a poppet valve which closes the fuel passage in which it is placed from the fuel supply system side being pressed by a resilient means.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of The Air-Fuel Ratio Of Carburetors (AREA)
US00233988A 1971-08-26 1972-03-13 Differential diaphragm carburetor Expired - Lifetime US3779529A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP6477071A JPS4831330A (it) 1971-08-26 1971-08-26
JP8596471A JPS4851135A (it) 1971-10-30 1971-10-30
JP9489171A JPS5143206B2 (it) 1971-11-27 1971-11-27
JP10265371A JPS4867623A (it) 1971-12-20 1971-12-20

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US3779529A true US3779529A (en) 1973-12-18

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US00233988A Expired - Lifetime US3779529A (en) 1971-08-26 1972-03-13 Differential diaphragm carburetor

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US (1) US3779529A (it)
DE (1) DE2241723A1 (it)
IT (1) IT974915B (it)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960126A (en) * 1974-01-12 1976-06-01 Toyota Jidosha Kogyo Kabushiki Kaisha Pressure regulator of liquefied-gas fuel system for internal combustion engines
US4632788A (en) * 1985-06-25 1986-12-30 Jones James S Carburetor fuel feed system with bidirectional passage
US4965023A (en) * 1989-04-07 1990-10-23 David Ward Carburetor having bidirectional fuel passage
US5843345A (en) * 1995-12-22 1998-12-01 Briggs & Stratton Corporation Pneumatic accelerator for low emission charge forming devices
US20050274364A1 (en) * 2004-06-14 2005-12-15 Kirk J D Evaporative emissions control system for small internal combustion engines
US20080191368A1 (en) * 2006-08-28 2008-08-14 Emak S.P.A. Diaphragm carburettor with single pump and meter block for internal combustion engines

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2068939A (en) * 1933-02-10 1937-01-26 Winterhalter Martin Slide fastener
US2144017A (en) * 1935-05-18 1939-01-17 Zenith Carburateurs Soc Gen Carburetor
US3003754A (en) * 1958-12-16 1961-10-10 Tillotson Mfg Co Charge forming apparatus
US3009794A (en) * 1958-06-09 1961-11-21 Bendix Corp Gas fuel supply system
US3201096A (en) * 1962-02-05 1965-08-17 Mcculloch Corp Charge forming device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2068939A (en) * 1933-02-10 1937-01-26 Winterhalter Martin Slide fastener
US2144017A (en) * 1935-05-18 1939-01-17 Zenith Carburateurs Soc Gen Carburetor
US3009794A (en) * 1958-06-09 1961-11-21 Bendix Corp Gas fuel supply system
US3003754A (en) * 1958-12-16 1961-10-10 Tillotson Mfg Co Charge forming apparatus
US3201096A (en) * 1962-02-05 1965-08-17 Mcculloch Corp Charge forming device

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960126A (en) * 1974-01-12 1976-06-01 Toyota Jidosha Kogyo Kabushiki Kaisha Pressure regulator of liquefied-gas fuel system for internal combustion engines
US4632788A (en) * 1985-06-25 1986-12-30 Jones James S Carburetor fuel feed system with bidirectional passage
US4965023A (en) * 1989-04-07 1990-10-23 David Ward Carburetor having bidirectional fuel passage
US5843345A (en) * 1995-12-22 1998-12-01 Briggs & Stratton Corporation Pneumatic accelerator for low emission charge forming devices
US20050274364A1 (en) * 2004-06-14 2005-12-15 Kirk J D Evaporative emissions control system for small internal combustion engines
US7165536B2 (en) 2004-06-14 2007-01-23 Tecumseh Products Company Evaporative emissions control system for small internal combustion engines
US20080191368A1 (en) * 2006-08-28 2008-08-14 Emak S.P.A. Diaphragm carburettor with single pump and meter block for internal combustion engines
US7527248B2 (en) * 2006-08-28 2009-05-05 Emak S.P.A Diaphragm carburettor with single pump and meter block for internal combustion engines

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Publication number Publication date
IT974915B (it) 1974-07-10
DE2241723A1 (de) 1973-03-08

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