Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a fuel injector, and more specifically to a method of determining a temperature of backflow fuel that flows through the fuel injector.

Background of the invention
[0002] US 4753205 A describes a fuel injection apparatus. The fuel injection apparatus for separately ignited internal combustion gas engines is proposed. The fuel injection apparatus comprises an air intake stack in which an injection valve is arranged upstream of a throttle valve. A ring slot developed approximately venturi-shaped is formed between the casing of the injection valve and the cylindrical inner wall of the air intake stack. An air bypass line discharges into the narrowest cross-section of the ring slot developed approximately venturi-shaped which begins upstream of the approximately venturi-shaped ring slot. An air measuring organ with at least one temperature dependent resistance for measuring the air mass flowing through is arranged in the air bypass line. Downstream of the temperature dependent resistance the air bypass line has a section developed in the shape of a funnel into which a cone shaped brake body concentrically protrudes which is supported axially displaceable and through which not only an optimal output signal of the air measuring organ in dependence on the sucked in air mass can be adjusted, but a balancing of the characteristic curve of the air measuring organ can take place as well. The proposed fuel injection apparatus allows a compact construction which permits the accommodation in the engine room of the internal combustion engine of motor vehicles even with cramped conditions as well as a reliable method of operation.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a flowchart depicting an algorithm for determining a temperature of backflow fuel flowing through the fuel injector in one embodiment of the invention.
Detailed description of the embodiments
[0004] Figure 1 illustrates a method 100 for determining a temperature of backflow fuel flowing through the fuel injector to an outlet flow path. The method comprises determining 110 an equivalent electrical resistance between an engine control unit and a fuel injector by dividing a voltage across the fuel injector by a current flowing through the fuel injector, and determining 120 an electrical resistivity loss between the engine control unit and the fuel injector. The method further comprises determining 130 a magnet coil resistance at an operation temperature, wherein the magnet coil resistance at the operation temperature is equal to a difference between the equivalent electrical resistance between the engine control unit an injector, injector magnet coil resistance at a reference temperature measured at a production plant and the electrical resistivity loss between the engine control unit and the fuel injector, and determining 140 a temperature of a magnet coil of the fuel injector at an operation temperature by adding a reference temperature of the injector magnet coil to a product of a reciprocal of a temperature coefficient of resistance for the injector magnet coil material and a difference between a ratio of the magnet coil resistance at the operation temperature and the injector magnet coil resistance at the reference temperature measured at the production plant and a scalar constant equal to unity.

[0005] Figure 1 illustrates a flowchart depicting a method 100 for determining a temperature of backflow fuel flowing through the fuel injector in one embodiment of the invention. The method comprises determining 110 an equivalent electrical resistance between an engine control unit and a fuel injector. More specifically, the equivalent electrical resistance between the engine control unit and the fuel injector is determined by dividing a voltage across the fuel injector by a current that flows through the fuel injector. The equivalent electrical resistance between the engine control unit and the fuel injector is equal to electrical resistance of coils of the solenoid valve of the fuel injector. The method further comprises determining 120 an electrical resistivity loss between the engine control unit and the fuel injector. The electrical resistivity loss between the engine control unit and the fuel injector comprises of electrical harness/wire cable resistance loss, and engine control unit power stage resistance loss. These losses are fixed and pre-determined by a user during a stage of assembling the engine control unit and the fuel injector respectively. The method further comprises determining 130 a magnet coil resistance at an operation temperature. More specifically, the magnet coil resistance at the operation temperature is equal to a difference between the equivalent electrical resistance between the engine control unit, and the fuel injector and an algebraic sum of an injector magnet coil resistance at a reference temperature measured at a production plant and the electrical resistivity loss between the engine control unit and the fuel injector.

[0006] Once the equivalent electrical resistance between the engine control unit and the fuel injector is determined, the electrical resistivity loss between the engine control unit and the fuel injector is determined, and the injector magnet coil resistance at the reference temperature measured at the production plant is determined, the magnet coil resistance at the operation temperature is determined. Once the magnet coil resistance at the operation temperature is determined, the temperature of the magnet coil of the fuel injector at an operation temperature is determined 140 by adding a reference temperature of the injector magnet coil to a product of the reciprocal of a temperature coefficient of resistance for the injector magnet coil material and a difference between the ratio of the magnet coil resistance at the operation temperature and the injector magnet coil resistance at the reference temperature measured at the production plant and a scalar constant equal to unity. The temperature coefficient of resistance for the injector magnet coil material is a fixed constant based on a given injector magnet coil material and does not vary for the same injector magnet coil material. The temperature of the magnet coil of the fuel injector at the operation temperature is the temperature of the magnet coil of the solenoid valve of the fuel injector. Therefore, by using this methodology, the temperature of the magnet coil of the fuel injector at the operation temperature may be determined accurately.

[0007] This solution is better than an existing solution of positioning a temperature transducer on the magnet coil of the solenoid valve of the fuel injector to determine the temperature of the fuel injector as the real time temperature of the fuel injector may be determined during an operation state of the fuel injector. Moreover, the elimination of the temperature transducer eliminates the use of a mechanical component on the fuel injector, which substantially contributes to a reduction in the material cost of the fuel injector.

[0008] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.
, Claims:We Claim

1. A method (100) for determining a temperature of backflow fuel flowing through the fuel injector to an outlet flow path, the method (100) comprising:
determining (110) an equivalent electrical resistance between an engine control unit and a fuel injector by dividing a voltage across the fuel injector by a current flowing through the fuel injector;
determining (120) an electrical resistivity loss between the engine control unit and the fuel injector;
determining (130) a magnet coil resistance at an operation temperature, wherein the magnet coil resistance at the operation temperature is equal to a difference between the equivalent electrical resistance between the engine control unit, and the fuel injector and an algebraic sum of an injector magnet coil resistance at a reference temperature measured at a production plant and the electrical resistivity loss between the engine control unit and the fuel injector; and
determining (140) a temperature of a magnet coil of said fuel injector at an operation temperature by adding a reference temperature of the injector magnet coil to a product of a reciprocal of a temperature coefficient of resistance for the injector magnet coil material and a difference between a ratio of the magnet coil resistance at the operation temperature and the injector magnet coil resistance at the reference temperature measured at the production plant and a scalar constant equal to unity.

2. The method (100) for determining a temperature of backflow fuel flowing through the fuel injector in accordance with Claim 1, wherein determining (120) an electrical resistivity loss between the engine control unit and the fuel injector wherein the electrical resistivity loss between the engine control unit and the fuel injector comprises wiring harness losses and the engine control unit power stage resistance losses.