Abstract:
In each fuel injection valve forming part of a fuel injection apparatus and associated with an internal combustion engine, there is disposed an electric heater which transmits heat to the fuel by contact-type heat exchange. The heat output of each heater is controlled by a device which processes input signals representing different engine variables.

Description:
This is a continuation of application Ser. No. 201,901, filed Nov. 24, 1971, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus for the cold starting and warming run of externally ignited internal combustion engines and is of the type that electrically heats the fuel immediately adjacent the locus of injection and includes means which regulates its heat output in such a manner that the major portion of the fuel admitted for injection is transformed into a gaseous phase necessary for its combustion in the engine. 
     An apparatus of the aforenoted type has to avoid as much as possible or at least keep within permissible limits the emission of pollutants into the atmosphere for the protection of the environment and because of the ever stricter laws regarding air pollution. 
     It is known to heat the fuel under pressure to effect its vaporization upon expansion. Such a heating of the fuel prior to its admission in the suction tube is disclosed in German Patent Application Ser. No. D 71 833. Ia, while a heating of the fuel prior to its introduction into the combustion chamber is disclosed, for example, in German Pat. No. 905,902. 
     It is further known to enhance the heating of the fuel, in addition to the utilization of the engine heat and the exhaustion heat, by electrical heating means, as disclosed in German Pat. No. 929,884 or to effect such heating solely by electrical means, as disclosed in Austrian Pat. No. 197,133. 
     It is further known to control the heat output in accordance with the heat requirement as a function of the operational conditions of the engine, as disclosed in Austrian Pat. No. 127,239 and French Pat. No. 1,011,288. 
     It is, however, a common characteristic of all the aforenoted apparatuses which preheat fuel under pressure that they seek to facilitate the combustion of heavy oil in gasoline engines or they simply seek to improve the fuel preparation in Diesel engines and, even if they are concerned with the pressureless preheating of a mixture, cold starting and warm running must be ensured by additional means. 
     During cold starting of an engine, the fuel, the engine, as well as the fuel metering and preparing devices draw heat from the environment. Over the fuel there prevails, as over all liquids, a vapor pressure corresponding to its temperature and thus, the fresh combustion air flowing to the internal combustion engine is, dependent upon the vapor pressure and the period of contact, enriched with fuel vapor. At low temperatures this fuel concentration is not sufficient to form an ignitable mixture, so that for the same duration of contact a larger fuel surface has to be provided in order to reach the temperature limit of ignitability. In conventional cold starting apparatuses associated with carburetor or intake tube injection systems, this results in the introduction of fuel quantities during the period of cold starting that are 30-50 times more than those for normal operation. Consequently, there will be commensurate effects of pollutant emission, lubricating oil thinning and fuel consumption. During the warming run of the engine, these additional fuel quantities are then gradually decreased as the engine temperature increases, until the operating temperature of the engine has reached its normal value. 
     OBJECT, SUMMARY AND ADVANTAGES OF THE INVENTION 
     It is an object of the invention to provide an improved apparatus for the cold starting and warming run of an engine operating on Otto-fuel to ensure, without additional fuel quantities, a combustion and an rpm increase to idling run possibly from the first compression stroke on and to effect a warming run without enriching the fuel mixture. 
     Briefly stated, according to the invention, means are provided to effect the heating of the fuel during cold or temporarily cool engine as a function of the engine temperatures that govern the fuel mixture preparation. 
     The advantages that may be achieved with the invention reside particularly in the fact that the emission of pollutants during cold engine operation or warming run is not higher than during normal engine operation and that the apparatus is of much simpler construction than conventional devices. 
     The invention will be better understood, as well as further objects and advantages will become more apparent, from the ensuing detailed specification of a preferred, although exemplary, embodiment of the invention taken in conjunction with the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic illustration of a fuel injection system incorporating the preferred embodiment of the apparatus for cold starting and warming run and 
     FIG. 2 is a longitudinal sectional view on an enlarged scale of one component shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the figures, from a fuel tank 1 fuel is delivered by a fuel pump 2 to a fuel metering device 3. An air sensor throttle 4 disposed in the intake manifold M senses the throughgoing air quantities and, as a function thereof, the fuel metering device 3 meters fuel that is admitted to the fuel injection valves 6 through pressure conduits 5. The fuel injection valves 6 inject fuel into the individual intake tubes 7 of the internal combustion engine. In each fuel injection valve 6 there is situated a heater 8 provided with electric conductors 9 and a heat insulation 10 for a good thermal separation of the heater 8 from the surrounding components of the engine. 
     The fuel-filled space of each fuel injection valve 6 is closed off by a valve needle 11, the opening pressure for which is determined by a closing spring 12 urging the valve needle 11 into its closed position. 
     The heat output of the heater 8 is regulated by a control device 13 which receives signals from temperature sensors 14, 15, 16, 17 and from a switch 18. The temperature sensor 14 monitors the maximum fuel temperature in the fuel injection valve 6 downstream of the heater. The temperature sensor 15 is responsive to the temperature of the intake air at the location of injection, the sensor 16 is responsive to the temperature of the cylinder head, while the sensor 17 is responsive to the temperature of the coolant in water-cooled engines. Switch 18 transmits a signal when there is an air flow in the intake manifold and thus indicates whether the engine is running or whether it is at a standstill. 
     OPERATION OF THE PREFERRED EMBODIMENT 
     As the fuel flows through the fuel injection valve 6, the electrical heating body 8 heats it to a temperature at which a preponderant portion of the fuel is vaporized as it expands in the intake conduit subsequent to injection. To enhance a good atomization of the fuel, the opening pressure of the fuel injection valve is selected in such a manner that upon the expansion of fuel it will travel at sonic speeds in the narrowest cross section. As it is known, such speed conditions will prevail when the ratio between the opening pressure and the pressure of the suction chamber is larger than or equal to the critical pressure ratio. The upper limit value of the fuel temperature is set by the safety requirement that the mixture in the suction chamber must not reach the temperature of self ignition. 
     In order to enhance a rapid functioning of the heater body at the moment of cold starting, the heater body preferably has a small mass and a large surface of contact. For this purpose it was found to be advantageous to use a heater body which is formed of a great plurality of capillary tubes or is a closely slitted material, such as a whisker packet. 
     The heat output is controlled by the control device 13 so as to meet the aforenoted temperature requirements. For this purpose the device 13 processes the signals transmitted by the sensors 14-17. 
     The extent of heat output and its duration may also be made dependent on additional engine variables such as engine rpm, load, external temperature, cooling air temperature, combustion chamber temperature, exhaust gas temperature or the combination thereof. Heat output is supplied during normal engine operation at all times when the temperature conditions of the engine require it, for example, after an extended downhill travel. 
     In order to achieve the goal of an as small a pollutant emission as possible and to avoid an overheating of the heater body 8, the control device 13, by processing the signals from the switch 18, provides that the heater 8 is energized only when the engine runs. Otherwise, the heating of the fuel and the volume increase connected therewith could cause the pressure in the fuel chamber of the fuel injection nozzle to attain the opening pressure and consequently, an uncontrolled fuel injection could take place. 
     It is also possible to provide a heat control device wherein the effect of the signals from the switch 18 are eliminated for cold starting, so that the fuel may be heated prior to the operation of the engine starter. 
     Several functions which are shown individually in the drawing for clarity, may be combined in the actual structure. For this purpose, for example, in case of an electric resistance heater, the temperature-dependence of the resistance material may be selected in such a manner (cold conductor) that the control of the fuel temperature is effected directly (i.e. by means of a heater-fuel contact) without the intermediary of the sensor 14 and the control device 13.