US3810606A

US3810606A - Carburetor output control device

Info

Publication number: US3810606A
Application number: US00326993A
Authority: US
Inventors: K Masaki
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1972-02-01
Filing date: 1973-01-26
Publication date: 1974-05-14
Anticipated expiration: 1991-05-14
Also published as: DE2304968A1; GB1390868A; AU5150873A; CA964951A; DE2304968B2; FR2170021A1; JPS5032907B2; DE2304968C3; FR2170021B1; JPS4880923A

Abstract

A device for optimizing the air/fuel ratio of a combustible mixture produced in a carburetter when atmospheric pressure and temperature deviate from given levels. When a bellows extends in response to the deviation from the given levels, atomospheric air is supplied downstream of a carburetter throttle valve through a diaphragm valve assembly responsive to the extension of the bellows during idling or light-load operation of an engine, while air is supplied to a main mixture supply passage through another diaphragm valve assembly responsive to the operation of the first-mentioned assembly during full-load operation.

Description

United States Patent Masaki [451 May 14, 1974 CARBURETOR OUTPUT CONTROL DEVICE Inventor: Kenji Masaki, Yokohama, Japan Nissan Motor Company Limited, Yokohama City, Japan Filed: Jan. 26, 1973 Appl. No.: 326,993

Assignee:

Foreign Application Priority Data Feb. 1, 1972 Japan 47-11972 US. Cl 261/39 A Int. Cl. F02m l/10, F02m l/l4 Field of Search 261/39 A, 121 B References Cited UNITED STATES PATENTS 2/1954 Sager 261/39 A Primary Examiner-Francis S. Husar Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato [57] ABSTRACT A device for optimizing the air/fuel ratio of a combustible mixture produced in a carburetter when atmospheric pressure and temperature deviate from given levels. When a bellows extends in response to the deviation from the given levels, atomospheric air is supplied downstream of a carburetter throttle valve through a diaphragm valve assembly responsive to the extension of the bellows during idling or light-load operation of an engine, while air is supplied to a main mixture supply passage through another diaphragm valve assembly responsive to the operation of the firstmentioned assembly during full-load operation.

10 Claims, 1 Drawing Figure 1 CARBURETOR OUTPUT CONTROL DEVICE This invention relates, in general, to a carburetter for use with an automotive internal combustion engine and more particularly to a device connected to the carburetter for optimizing the air/fuel ratio of a combustible mixture in accordance with climatic conditions such as atmospheric pressure and temperature.

It has been commonly observed that the operational characteristics of a carburetter, particularly the working strength of the combustible mixture are affected by changes in atmospheric pressure and temperature. When a vehicle is driven in summer or at high altitudes, air/fuel mixture is found to be richer than in other, more normal circumstances. This effect is due to the fact that the density of air diminishes with the rise of its temperature and the drop of its pressure, and therefore relatively small weight of air is drawn into the engine. As a result, a portion of mixture supplied to a combustion cylinder will remain unburned, since the quantity of air does not suffice for a complete combustion in the cylinder. The unburned contents thus contained in the exhaust gases are passed through the exhaust system of the engine to the atmosphere, thus causing serious air pollution. Moreover, in case of the engine being provided with an exhaust gas cleaning device such as a thermal reactor or a catalytic converter or the like, the unburned contents may be deposited onto parts of the cleaning device. Whilst such deposition alone will adversely affect the performance of the device, an untimely and incomplete burning of the deposited unburned contents may happen, thus almost entirely eliminating the effects of such cleaning device.

A primary object of the present invention is therefore to provide a new and improved device which can obviate the drawbacks accompanied by conventional carburetters as mentioned.

Another object is to provide a device for correcting and optimizing the air/fuel ratio of a combustible mixture for the climatic condition in which the carburetter is used at any one time.

Still another object is to supply an unnecessarily enriched combustible mixture with fresh air when the atmospheric temperature is high and the atmospheric pressure is low.

A further object is to provide optimization of the air/fuel ratio of the mixture under all driving conditions of a vehicle including idling and acceleration.

A still further object is to raise the engine operational performance particularly when a vehicle is running at a high altitude.

Other objects and advantages will appear from the following description of an embodiment of the present invention when taken together with the accompanying drawing, wherein A single FIGURE is a schematic sectional view of a carburetter equipped with a device according to the present invention.

Reference is now made to the single FIGURE, wherein a carburetter generally designated by numeral is, as usual, constituted by an induction passage 11 leading to an intake manifold (not shown), a throttle valve 12 located intermediate the induction passage 11, a float chamber 13 with a float 14, a main mixture circuit l5 and an idling and slow-running mixture circuit 16, the former being connected between the float chamber 13 and the induction passage 11 and the latter branching off from the circuit 15. The induction passage 11 is formed with a venturi or choke tube 17 upstream of the throttle valve 12. The main mixture circuit 15 comprises a main fuel jet 18 adjacent the float chamber 13, a main air/fuel mixer 19 which encloses therein an air bleed tube 20, and a main nozzle 21 opening into the venturi portion 17 of the induction passage. The idle and slow running mixture circuit 16 is branched off from the main mixture circuit 15 posterior to the main jet 18 and leads to a slow running port 22 and further to an idling port 23, the former of which opens into the induction passage 11 adjacent the periphery of the closed throttle valve, and the latter downstream of the throttle valve. The effective area of this idling port 23 is preferably adjustable by a needle valve 24. The idling and slow-running mixture circuit 16 further comprises a plurality of air bleed restrictors as indicated at 24 and 25.

Whilst the construction heretofore described is that of the average state of the art, the device according to the invention and its operation will be described in detail below in connection with the above and known carburetter.

Represented by numeral is a device for compensating for the mixture enrichment above a given level of atmospheric temperature and below another given level of atmospheric pressure. The device 30 substantially consists of a combined bellows and diaphragm valve assembly 31 and another diaphragm valve assembly 32. The valve assemblies are disposed axially and spacedly opposite to each other forming a control chamber 33 between a valve seat 46 of the valve assembly 31 and a diaphragm 49 of the valve assembly 32. A housing 34 forms a chamber accommodating the first assembly 31 and divided by a diaphragm 35 into an upper chamber 36 and a lower chamber 37. The upper chamber 36 accommodates therein a bellows 38 which is filled with an inert gas such as nitrogen. The top of the bellows 38 is connected to a pressure regulator valve 39 which is, in turn, mounted on the upper wall of the housing 34 for maintaining the pressure in the inert gas at a constant level. The bottom of the bellows 38 is supported on and secured to the diaphragm 35. Penetrating through the side wall of the upper chamber 36, a plurality of air vents 40 are formed, through which atmospheric air circulates around the bellows and influences the inert gas filling the bellows 38. The bellows, thus sensing a change in temperature and pressure, will extend and when they reach given levels the bellows will move the diaphragm 35. The assembly 31 further includes a stem 41 secured to and extending I from the diaphragm 35 through the lower chamber 37.

The diaphragm 35 is biased upwardly in the drawing by a spiral spring 42 mounted in the lower chamber 37. The lower chamber 37 is connected through a conduit 43 to an air cleaner (not shown) of the engine. From the center portion of the lower chamber 37, a tubular small housing 44 defining the control chamber 33 extends toward the opposite side of the' housing 34 or downwardly in the drawing. An annular valve seat 46 is provided on the inner circumferential w'allof the tubular housing to form the valve 45 which separates the control chamber 33 from the space continuing to the lower chamber 37. The valve stem 41 has at its leading end a valve head 47 which is tapered upwardly in the I drawing. The valve 45 controls the flow therethrough by the tapered valve head 47 in accordance with the degree of displacement of the diaphragm 35. With this construction, air is fed through the air cleaner into the chamber 33 through the lower chamber 37 in varying amounts which depend on the changes in the open area of the valve 45.

, A housing 48 accommodating the other diaphragm valve assembly 32 is similarly formed as, but smaller in diameter than the housing 34, and made integral with the tubular housing 44. The inner space of this housing 48 is also divided by a diaphragm 49 into an upper chamber 50 continuing to the control chamber 33 and another control chamber 51. Just as in the first assembly 31, a spiral spring 52 is mounted in the upper chamber 50 for slightly biasing the diaphragm 49 downwardly. Through the control chamber 51, a valve stem 53 extends from the diaphragm 49 and has an upwardly tapered valve head 54 at its leading end. The control chamber 51 is communicable with air through a valve 55 formed by an annular valve seat 56 and the valve head 54. The movement of the diaphragm 49, in this assembly, occurs in response to the air pressure established in the control chamber 33 and hence only indirectly responds to the extension of the bellows 38.

The

control chambers

33 and 51 respectively communicate with the induction passage 11 downstream of the throttle valve 12 through a conduit 60 and with the main air/fuel mixer 19 through a conduit 61. Thus, air present in these chambers is admitted into conduits 60 and 61 in dependence on various driving conditions, as will be hereinafter discussed. The conduits 60 and 61 are respectively provided with

restrictors

62 and 63 for throttling purposes.

lnoperation, the valve 45 is kept closed by the valve head 47 of the stem 41 under normal temperature and pressure, the carburetter then functioning as usual. Neither does the assembly 32 operate, since depression in the induction passage 11 is transmitted to the control chamber 33.

As the temperature rises or the pressure falls, or both occur concurrently, the gas filling the bellows 38 tends to expand, thus extending the bellows toward the lower chamber 37. The diaphragm 35 is then moved downward to open the valve 45. As a result, air flowing through, the conduit 43 is allowed into the control chamber 33 through the lower chamber37 and the valve 45. if the throttle valve takes an idlingposition indicated at a solid line in the drawing or a slightly more opened position, a pressure difference is established between the induction passage downstream of the throttle valve and the control chamber 33 which is supplied with air in the above described manner. Air in the control chamber 33 is therefore sucked into the induction passage downstream of the throttle valve through the conduit 60.

If, however, the throttle valve is fully opened to the dotted position, the suction in the induction passage downstream of the throttle valve is, if any, not enough to draw air in the control chamber 33, while at the same time suction develops in the venturi portion 17. Supply of air to the induction passage downstream of the throttle valve therefore stops under such heavyload operation of the engine. Since, in the meantime, the air pressure which is higher than the pressure in the venturi portion 17 remains in the control chamber 33,

, 6 the diaphragm 49 of the second assembly 32 18 also moved downward mostly by the pressure in the chamber 33 and partly by the biasing force of the spring 52.

Thus the valve 55 is open to allow air therethrough into the control chamber 51. As the air pressure in the chamber 33 approximates the atmospheric pressure, the opening degree of the valve 55 increases and the correspondingly increasing amount of air feeds the chamber 51. The suction established in the venturi portion 17 now starts to draw air present in the chamber 51 through the conduit 61 into the lower portion of the main mixer 19. Since only a small amount of air feeding the main mixer is sufficient for the purpose of weakening the mixture, the conduit 61 leading to the main mixer 19 may be of small diameter. The quantities of air flowing through the conduits and 61 are respectively controlled by the

restrictors

62 and 63.

Throughout the description above, it will be noted that the present invention provides an optimum mixture strength under any climatic condition. It should be also appreciated that the device of the present invention operates independently for idling or light-load operation and for full load operation.

Moreover, certain kind of troubles in the engine performance are solved by the device of the present invention. The troubles are, e.g., such that the engine speed at idling decreases and finally the engine tends to stall when atmospheric pressure is low at high altitudes. This effect is again caused by the enrichment effect of the mixture, which can be weakened through supplying the induction passage downstream of the throttle valve with air in the manner described.

While 1 have shown and described a specific embodiment of my invention, it will be readily understood that many changes and modifications in structure and operation can be made without departing from the scope of the invention as defined only by the appended claims.

What is claimed is:

1. in a carburetter for an internal combustion engine including an induction passage, a throttle valve dividing said induction passage into an upstream part and a downstream part, and a main mixture supply passage opening into said upstream part of the induction passage,

a carburetter control device comprising:

a first control chamber communicating with the downstream part of the induction passage and being communicable with the atmosphere;

a second control chamber communicating with said main mixture supply passage and communicable with atmosphere;

means operable in response to at least one of an atmospheric pressure below a given pressure level and an atmospheric temperature above a given temperature level, for providing communication between said first control chamber and the atmosphere to introduce additional air into the downstream part of the induction passage in an amount varying in degrees; and

air pressure responsive means operable in response to an air pressure prevailing in said first control chamber, for providing communication between said second control chamber and the atmosphere to introduce additional air into said main mixture supply passage in an amount varying in degrees.

2. A device according to claim 1, further comprising a first air supply conduit connected between said first control chamber and said downstream part of the induction passage.

3. A device according to claim 2, wherein said first air supply conduit includes a flow restrictor.

4. A device according to claim 1, further comprising a second air supply conduit connected between said second control chamber and said main mixture supply passage.

5. A device according to claim 4, wherein said second air supply conduit includes a flow restrictor.

6. A device according to claim 1, wherein said firstmentioned means comprises a bellows filled with an inert gas to extend in response to said at least one ofthe atmospheric pressure and temperature, a diaphragm member secured to said bellows and movable therewith, and a valve member connected to said diaphragm member and movable therewith, said valve member having a tapered valve head to vary the degree of communication between said first control chamber and the atmosphere.

7. A device according to claim 6, wherein said inert gas is nitrogen.

8. A device according to claim 6, wherein said firstmentioned means further comprises a spring for biasing said diaphragm member to cause said valve member to interrupt communication between said first control chamber and the atmosphere.

9. A device according to claim 1, wherein said air pressure responsive means comprises a diaphragm member yieldably disposed between said first and second control chambers and a valve member connected to said diaphragm member and movable therewith, said valve member having a tapered valve head to vary the degree of communication between said second control chamber and the atmosphere.

10. A device according to claim 9, wherein said air pressure responsive means further comprises a spring disposed in said first control chamber for biasing said diaphragm member in a direction to cause said valve member to establish communication between said second control chamber and the atmosphere.

Claims

1. In a carburetter for an internal combustion engine including an induction passage, a throttle valve dividing said induction passage into an upstream part and a downstream part, and a main mixture supply passage opening into said upstream part of the induction passage, a carburetter control device comprising: a first control chamber communicating with the downstream part of the induction passage and being communicable with the atmosphere; a second control chamber communicating with said main mixture supply passage and communicable with atmosphere; means operable in response to at least one of an atmospheric pressure below a given pressure level and an atmospheric temperature above a given temperature level, for providing communication between said first control chamber and the atmosphere to introduce additional air into the downstream part of the induction passage in an amount varying in degrees; and air pressure responsive means operable in response to an air pressure prevailing in said first control chamber, for providing communication between said second control chamber and the atmosphere to introduce additional air into said main mixture supply passage in an amount varying in degrees.

6. A device according to claim 1, wherein said first-mentioned means comprises a bellows filled with an inert gas to extend in response to said at least one of the atmospheric pressure and temperature, a diaphragm member secured to said bellows and movable therewith, and a valve member connected to said diaphragm member and movable therewith, said valve member having a tapered valve head to vary the degree of communication between said first control chamber and the atmosphere.

7. A device according to claim 6, wherein said inert gas is nitrogen.

8. A device according to claim 6, wherein said first-mentioned means further comprises a spring for biasing said diaphragm member to cause said valve member to interrupt communication between said first control chamber and the atmosphere.