Abstract:
A fuel-air mixture heating device for use with an internal combustion engine wherein a combustion chamber of an auxiliary burner is disposed adjacent to an intake manifold of the engine for heating the same, said combustion chamber being communicated with said intake manifold through a control valve which varies its opening degree in response to a parameter or signal representative of at least one of the operating conditions of the engine.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a fuel-air mixture heating device for use with an internal combustion engine of the type which heats the intake manifold by an auxiliary burner, thereby attaining the complete combustion of the fuel-air mixture. 
     In the conventional fuel-air mixture heating devices, a part of the intake manifold at the downstream side of the carburetor is heated by exhaust gases or by the water circulating through the cooling system, or the intake manifold is heated by a burner formed integral with the intake manifold. In the former devices, the intake manifold cannot be heated above 100°C because the water in the cooling system will not rise above 100°C. In the devices of the type utilizing the exhaust gases, a passage for the exhaust gases is provided in the wall of the intake manifold so that it is also extremely difficult to heat the fuel-air mixture above 100°C. When the exhaust gases heat the intake manifold too much, the temperature of the exhaust gases drops to such an extent that the efficiency of the catalytic converter for purifying the exhaust gases drops. Thus both of the heating devices utilizing the exhaust gases and the cooling water are not so effective that some of the atomized fuel particles are delivered into the engine cylinders without being completely vaporized, resulting in the unsatisfactory fuel-air mixture distribution especially in case of a multi-cylinder engine. Consequently, the smooth engine operation is not ensured in case of the acceleration or deceleration. To overcome these problems, the rich fuel-air mixture must be delivered to the engine cylinders. In the fuel-air mixture heating devices of the type which heat the mixture by means of a burner formed integral with the intake manifold, a part of the intake manifold may be easily raised in temperature above 100°C, but the combustion products from the burner are discharged into the surrounding atmosphere or recirculated through the air conditioning system for automobiles after they have been used to heat the intake manifold. Consequently, the combustion gases containing toxic components are directly discharged into the surrounding atmosphere or the compartment of the automobile if the combustion conditions in the burner are not satisfactory. The emission of the toxic pollutants must be prevented in view of atmospheric pollution and the safety of the driver and passengers. 
     SUMMARY OF THE INVENTION 
     The present invention was made to overcome the above and other defects and problems encountered in the conventional fuel-air mixture heating devices, and has for its object to provide an improved fuel-air mixture heating device for use with internal combustion engines wherein the intake manifold is heated by the heat of the combustion in an auxiliary burner disposed adjacent to the intake manifold so that the fuel-air mixture delivered from the carburetor may be sufficiently preheated before it is charged into the engine cylinders, wherein the combustion products discharged from the auxiliary burner are discharged into the intake manifold. However, when the combustion chamber of the auxiliary burner and the intake manifold are directly communicated with each other, the negative pressure in the intake manifold is admitted into the combustion chamber so that the stable and complete combustion in the auxiliary burner is not ensured. To overcome this problem, according to the present invention, the intake manifold and the combustion chamber in the auxiliary burner are communicated with each other through a control valve which varies its opening degree in response to a parameter or signal representative of the operating conditions of the engine so as to control the negative pressure admitted into the combustion chamber, thereby ensuring the stable and complete combustion in the auxiliary burner. 
     According to one embodiment of the present invention an exhaust gas recirculating pipe extends from the exhaust manifold of the engine to pipe intercommunicating the intake port of the control valve and the combustion chamber in the auxiliary burner, so that the content of nitrogen oxides in the exhaust gases may be reduced. 
     According to another embodiment of the present invention, an air control valve, which varies its opening in response to a parameter or signal representative of the operating conditions of the engine, is interposed between an air pump and the combustion chamber in the auxiliary burner so that the flow rate of the air to be delivered from the air pump into the combustion chamber may be controlled. As a result, the combustion in the auxiliary burner is so controlled in accordance with the quantity of the fuel-air mixture demanded by the engine that the intake manifold may be satisfactorily heated to a temperature not higher or not lower than a suitable required temperature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic sectional view illustrating the fundamental arrangement of a fuel-air mixture heating device in accordance with the present invention; 
     FIG. 2 is a schematic sectional view of a first embodiment of the present invention; 
     FIG. 3 is a schematic sectional view of a second embodiment of the present invention; 
     FIG. 4 is a schematic sectional view of a control valve which is used in both first and second embodiments shown in FIGS. 2 and 3, respectively; 
     FIG. 5 is a diagrammatic view, partly in section, of a third embodiment of the present invention; and 
     FIG. 6 is a schematic sectional view of an air control valve used in the third embodiment. 
     Same reference numerals are used to designate similar parts throughout the figures. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Fundamental Arrangement, FIG. 1 
     Referring first to FIG. 1, the fundamental arrangement of the present invention will be described to explain the underlying principle thereof. One end of an intake manifold 2 is connected to the lower end of a carburetor barrel 1 while the other end is fastened in the conventional manner to an engine cylinder shown as comprising an intake valve 16, a combustion chamber 17, an exhaust valve 18, and an exhaust manifold 19. The intake manifold 2 is also communicated through a port 12 provided on its lower wall with a heat-exchanging chamber 3 which in turn is communicated with a combustion chamber 6 of an auxiliary burner generally indicated by 4. Any suitable burner may be employed as far as the stable ignition and combustion of the fuel-air mixture are ensured even under the negative pressure admitted from the intake manifold 2, and in the instant arrangement, the auxiliary burner 4 is of the turbulent type. The auxiliary burner 4 further comprises an ignition chamber 6a at the bottom of which is disposed an evaporator 8. The combustion chamber 6 is supplied with the air through an air pipe 5 from an air pump 21. A spark plug 7 screwed into the side wall of the ignition chamber 6a is electrically connected to an ignition device 7a. The ignition chamber 6a is communicated through the evaporator 8 with a mixing chamber 6b which is also supplied with air through another air pipe 10 from the air pump 21. A fuel injection nozzle 9 which is communicated through a fuel pipe 11 with a fuel pump 24, is disposed in such a way that the nozzle port opens immediately below the evaporator 8. The fuel injection nozzle 9 serves to meter and atomize the fuel supplied under pressure from the fuel pump 24. 
     Next to the mode of operation will be described. In the mixing chamber 6b, the fuel supplied from the fuel pump 24 through the fuel pipe 11 and injected from the nozzle 9 is mixed with air supplied from the air pump 21 through the air pipe 11 and atomized. The fuel-air mixture flows through the evaporator 8 into the ignition chamber 6a where the mixture is ignited by the spark plug 7, and the complete combustion takes place in the combustion chamber 6 with the air supplied from the air pump through the air pipe 5. The air pipe 5 opens at the cylindrical side wall of the combustion chamber 6 in such a way that the air may be discharged at a tangent to the cylindrical side wall and swirled within the combustion chamber 6, thereby ensuring stable combustion. The combustion products or gases flow from the combustion chamber 6 into the heat-exchanging chamber 3 so that the intake manifold 2, which partly defines the former, is heated. Consequently, the fuel-air mixture from the carburetor to be delivered into the engine cylinders may be heated so that the fuel particles in the mixture may be completely vaporized. From the heat-exchanging chamber 3, the combustion products or gases flow into the intake manifold 2 through port 12. Thus the direct discharge of the combustion products containing the pollutants into the surrounding atmosphere may be prevented. 
     First Embodiment, FIGS. 2 and 4 
     In the fundamental arrangement described so far with reference to FIG. 1, the intake manifold 2 is directly communicated through the port 12 with the combustion chamber 6 in the auxiliary burner 4 so that the combustion in the burner 4 is unstable under the negative intake pressure. The first embodiment of the present invention which was made to overcome the above problem is substantially similar in construction to the fundamental arrangement with the exception that, as shown in FIG. 2, the intake manifold 2 is communicated with the heat-exchanging chamber 3 of the burner 4 through a pipe 14 inserted with a control valve 13 adapted to control the rate of the exhaust or combustion gases flowing through the pipe 14. 
     As shown in FIG. 4, the control valve 13 comprises an intake pipe 131 through which flows the combustion gases from the burner 4 into the control valve 13; a discharge pipe 132 in communication with the intake manifold 2; a valve 133 vertically movably interposed between the intake and discharge pipes 131 and 132 for establishing or interrupting the fluidic communication therebetween; a diaphragm 136 which, together with a valve cover 134, defines a working pressure chamber 135; an input pipe 137 opening into the working pressure chamber 135 for transmitting thereto the signal pressure such as the venturi pressure as a parameter representing the operating conditions of the engine; a spring 138 disposed within the working pressure chamber 135 for limiting or controlling the displacement of the diaphragm 136; a valve rod 139 having its upper and lower ends fastened to the diaphragm 136 and the valve 133, respectively; a guide member 140 which not only guides the valve rod 139 but also seals it; and an adjusting screw 141 for adjusting the biasing pressure of the spring 138. 
     Next, referring to FIGS. 2 and 4, the mode of operation of the first embodiment with the above construction will be described hereinafter. The combustion gases, which are produced in the combustion chamber 6 of the burner 4, flow into the heat-exchanging chamber 3 to heat the intake manifold, and therafter are discharged through the pipe 14 and the control valve 13 into the intake manifold 2. In the instant embodiment, the venturi pressure produced in the carburetor 1 is admitted through the input pipe 137 into the working pressure chamber 135 of the control valve 13 so that the opening degree or position of the valve 133 is dependent upon the engine&#39;s demand for the air supply and that the negative pressure admitted into the combustion chamber 6 of the burner 4 is dependent upon the volume of the air following into the carburetor 1. In other words, as the quantity of the fuel-air mixture to be delivered to the engine cylinders is greater, the negative pressure admitted into the combustion chamber 6 is more negative while as the quantity of the fuel-air mixture is less, the negative pressure is less negative. Thus the stable combustion in the burner 4 may be ensured. 
     In the first embodiment, the venturi negative pressure has been described as being admitted into the working pressure chamber 135, but it is understood that any pressure signal representing the operating conditions of the engine may be admitted. 
     Second Embodiment, FIGS. 3 and 4 
     The second embodiment shown in FIG. 3 is substantially similar in construction to the first embodiment shown in FIG. 2 except that the pipe 14 between the heat-exchanging chamber 3 of the burner 4 and the control valve 13; that is, the intake pipe 131 (See FIG. 4) is communicated through an exhaust gas recirculating pipe 15 with the exhaust manifold 19. The control valve 13 is of the type described in detail hereinbefore with particular reference to FIG. 4 so that depending upon the operating conditions of the engine, the combustion gases from the burner 4 and the recirculated exhaust gases from the exhaust manifold 19 may be discharged into the intake manifold 2. Thus the nitrogen oxide (NOx) emission may be considerably reduced by the recirculation of the exhaust gases. On the other hand, when the engine&#39;s demand for the fuel-air mixture is less so that the opening degree of the control valve is small, the combustion gases from the burner 14 are discharged through the pipe 15 into the exhaust manifold 19. That is, the quantity of fuel burnt in the burner 4 is so limited or controlled as to satisfactorily heat the intake manifold only to a required temperature, and the combustion gases from the burner 4 are discharged either into the intake or exhaust manifold. Moreover, depending upon the operating conditions of the engine, the combustion gases and/or exhaust gases in quantity exactly meeting the engine&#39;s demand are discharged and recycled into the intake manifold. Thus the recirculation of the exhaust gases may be effected under a highly precise control. 
     Third Embodiment, FIGS. 5 and 6 
     The important feature of the third embodiment shown in FIG. 5 is its ability to control the combustion in the auxiliary burner 4 in such a way that the intake manifold 2 may be heated to a suitable temperature not higher or not lower than a temperature that is required. The third embodiment is substantially similar in construction to the second embodiment shown in FIG. 3 with the exception that both the air pipes 5 and 10 are communicated with a discharge port 21a of the air pump 21 through a surge tank 22 which may absorb the pulsation of the air discharged from the air pump 21; and the discharge port 21a of the air pump 21 is communicated through an air control valve 20 with an air injection nozzle 23 which opens into the exhaust port in the vicinity of the exhaust valve 18 in order to supply the exhaust gases with the secondary air so that the unburnt components in the exhaust gases may be oxidized and purified. 
     As shown in FIG. 6, the air control valve 20 comprises an intake port 201 in communication with the discharge port 21a of the air pump 21; a discharge port 202 in communication with the air injection nozzle 23; a valve 203 which is horizontally movably disposed between the intake and discharge ports 201 and 202 in order to control the sectional area of the passageway therebetween; a pair of diaphragm casings 204a and 204b; a diaphragm 205; a first pressure chamber 206 defined by the casing 204a and the diaphragm 205; a second pressure chamber 207 defined by the casing 204b and the diaphragm 205; a valve rod 208 interconnecting the valve 203 and the diaphragm 205; a guide member 209 for the valve rod 208; an input signal admitting port 210 for admitting into the first pressure chamber 206 the signal pressure representative of the operating conditions of the engine; an adjusting spring 211 interposed within the first pressure chamber 206 between the diaphragm 205 and an adjusting screw 213; and a fine adjustment spring 212 interposed between the valve 203 and the guide member 209. The spring forces of both the adjustment springs 211 and 212 may be adjusted by turning the adjusting screw 213. 
     In the instant embodiment, the negative pressure in the intake manifold 2 is admitted into the first pressure chamber 206 through the signal pressure admitting port 210. The air discharged from the air pump 21 is admitted into the second pressure chamber 207 through the clearance between the valve rod 208 and the guide member 209. 
     Next the mode of operation of the third embodiment with the above construction will be described hereinafter. The air discharged from the air pump 21 flows into the surge tank 22 and the intake port 201 of the air control valve 20. The degree of opening or position of the valve 203 is dependent upon the displacement of the diaphragm 205 which in turn is dependent upon the difference between the negative pressure in the intake manifold admitted into the first pressure chamber 206 and the pressure of the air discharged from the air pump 21 and admitted into the second working pressure chamber 207. In case of engine acceleration, the opening degree of the valve 203 is smaller than in case of the steady or normal engine operation so that the quantity of the secondary air to be delivered to the air injection nozzle 23 for oxidizing and purifying the exhaust gases is decreased while the quantity of the air to be delivered to the auxiliary burner 4 is increased. That is, the combustion in the burner 4 is accelerated in case of the engine acceleration, thereby effectively heating the intake manifold 2. A part of the air discharged from the air pump 21 is delivered through the air pipe 10 into the mixing chamber 6b of the burner 4 while the fuel is delivered from the fuel pump 24 through the fuel pipe 11 to the fuel injection nozzle 9 which injects the fuel into the mixing chamber 6b. The quantity of the fuel injected is in proportion to the flow rate or volume of the air discharged from the air pipe 10 into the mixing chamber. As with the first and second embodiments, the fuel-air mixture flows through the evaporator 8 into the ignition chamber 6a and is ignited by the spark plug 7. The complete combustion of the air-fuel mixture is carried out in the combustion chamber 6 with the air delivered through the air pipe 5 from the air pump 21. The combustion products or gases flow into the heat-exchanging chamber 3, and heat the intake manifold 2. 
     The excess air delivered from the discharge port 202 of the air control valve 30 is injected through the air injection nozzle 23 into the exhaust port, whereby the unburnt components in the exhaust gases are oxidized and purified. In case of the engine equipped with the catalytic converter type exhaust gas emission control system, the excess air may be injected upstream in this system so that the effective purification of the exhaust gases may be effected. 
     In the third embodiment, the opening degree of the air control valve has been described as being controlled in response to the difference between the negative pressure in the intake manifold admitted into the first working pressure chamber and the discharge pressure of the air pump admitted into the second pressure chamber, but it is to be understood that the air control valve may be so arranged as to be fluidly or electromagnetically in response to any suitable signals or parameters representative of the operating conditions such as the air consumption, the rotational speed of the engine and so on.