Fuel injection system

The invention described and claimed herein below is also described in German Patent Application DE 10 2005 036 952.9 filed on Aug. 5, 2009. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d).

The present invention relates to a fuel injection system.

The related art refers to, e.g., a fuel injector with a heating device for heating the fuel on its discharge side, as described in DE 196 29 589 A1. In the fuel injector described in DE 196 29 589 A1, the power loss of the energized solenoid coil is used to heat the fuel, and, as the heat-exchange section, a Peltier element which functions as a heat pump is provided; the Peltier element includes the nozzle needle and the fuel inside it.

The disadvantage is that the fuel in the fuel injector described in DE 196 29 589 A1 is also heated when it has a temperature that is already high enough for combustion. As a result, it is possible that too much thermal energy will be supplied to the fuel.

A further disadvantage is the fact that a Peltier element is provided as a heat pump to heat the fuel in the fuel injector; it is relatively cost-intensive and, when used in the fuel injector, it requires a large quantity of electrical power.

Publication DE 20 57 972 A1 makes known a cold-start and warm-up device for internal combustion engines with externally-supplied ignition; it provides that the fuel injector is heated by an electrically operated heater core which is permanently installed in the inlet fitting of the fuel injector.

The disadvantage is that a fuel injector is provided for the cold-start and warm-up device described, which includes an electrically operated heater core which is permanently installed in the inlet fitting. Fuel injectors without permanently installed heater cores can not be used in the device described in DE 20 57 972 A1.

It is the object of the present invention, therefore, to heat the fuel injector before the engine is started, independently of an electronic control unit, without supplying an unnecessarily large amount of heat; heating is prevented when the temperature of the fuel in the fuel rail is above a previously defined threshold temperature.

An advantage of the present invention is that the heating concept of the inventive fuel injection system is independent of the control-unit platform and of the type of fuel injector used, since the heatable adapter can be inserted into a direct-injection fuel injector and into a fuel injector for manifold injection.

This results in the advantage that the individual components of the inventive fuel injection system can also be marketed for foreign systems.

A further advantage of the present invention is increased starting reliability, in particular when fuels containing ethanol are used, because the fuel is heated as a function of the fuel temperature.

A further advantage of the inventive fuel injector is the fact that, in the cold state, the idling quality of the engine is improved by heating the fuel using the inventive fuel injection system.

It is also an advantage that the fuel can be heated independently of the start of the engine or the actuation of the ignition.

The fuel injection system described in the present invention is simple, robust, and flexible; it therefore also results in a cost-optimizing effect in production.

Due to the fact that heated fuel is injected in the combustion chamber, complete combustion of the fuel is ensured. This advantageously results in lower emissions.

It is also advantageous that the risk of bubbles forming when the fuel is heated is reduced, since thermal energy is supplied only when the threshold temperature of the fuel is fallen below. Advantageously, the fuel is heated only when it is too cold.

An exemplary embodiment of the present invention is presented—in a simplified view—in the drawing and is described in greater detail in the description below.

FIG. 1 shows an inventive fuel injection system, which is composed of several fuel injectors, a heatable adapter, and a fuel rail.

FIG. 1 shows an inventive fuel injection system 1 with at least one fuel injector 1 a and a heatable adapter 1 b , which is connected to a fuel rail 1 c and to fuel injector 1 a of fuel injection system 1 ; a thermoswitch 2 is provided in fuel rail 1 c , which is connected with a device 3 which establishes external contact, and with heatable adapter 1 b.

Thermoschalter 2 includes a thermosensor, which triggers a switching procedure of thermoswitch 2 when fuel 8 located in fuel rail 1 c has a temperature that is below a specified threshold temperature. Thermoswitch 2 itself can be designed as a bimetallic strip or a thermistor. Electrical heating elements 5 are provided in heatable adapter 1 b ; they heat fuel 8 that flows from fuel rail 1 c into related fuel injector 1 a . Heating fuel 8 is advantageous when atomized fuel 8 would condense on the cold combustion chamber wall because the combustion chamber had become cold.

Thermoswitch 2 is composed of a pressure-resistant material to ensure that it remains in a stable position inside fuel rail 1 c , in which a certain pressure prevails. To prevent a chemical reaction of fuel 8 in contact with thermoswitch 2 with the surface material of thermoswitch 2 , surface 6 of thermoswitch 2 is composed of a fuel-resistant material.

Thermoswitch 2 includes at least two electrical connections 7 , 7 a . One electrical connection 7 a is connected with device 3 , which establishes the external contact. A closed switch position 9 of device 3 is at least one prerequisite for actuation of thermoswitch 2 and, therefore, for the heating of fuel 8 .

External device 3 can be, e.g., a door contact switch, a remote control, a seat sensor, or the like, by way of which it is possible to initiate heating of fuel 8 even before the internal combustion engine is started (e.g., 10 to 30 s in advance).

The switch position of the external door contact switch is coupled, e.g., with an actuation of a door. When this door is opened, the switch position of the door contact switch changes from an open switch position to closed switch position 9 , and the heating of fuel 8 begins.

Electrical heating elements 5 are located in heatable adapter 1 b and are connected with a contact 7 of thermoswitch 2 and with a circuit ground 10 .

Thermoswitch 2 is located in fuel rail 1 c such that it is fully immersed in fuel 8 located in fuel rail 1 c , thereby making it possible to close a circuit depending on the temperature of fuel 8 , to supply current to electrical heating elements 5 in heatable adapter 1 b.

The present invention is not limited to the exemplary embodiments shown, and can be used, e.g., with direct-injection fuel injectors and with fuel injectors that inject fuel into a manifold.