Fuel injector, method for ascertaining the position of a movable armature, and motor control

1. A fuel injection apparatus for an internal combustion engine of a motor vehicle, the fuel injection apparatus comprising:

a fuel injector, comprising

a pole piece;

an armature which may be moved along a movement axis;

a coil;

a permanent magnet; and

at least one electrically insulating element, the movable armature having the at least one electrically insulating element, which is designed to reduce eddy currents in the armature;

wherein the permanent magnet is fitted such that the permanent magnet generates a magnetic field which produces a force which acts on the armature in the direction of the pole piece.

2. The fuel injection apparatus of claim 1 , the at least one electrically insulating element further comprising a slot which is filled with at least one of air, an electrically insulating material, or a non-magnetic material.

3. The fuel injection apparatus of claim 1 , wherein the armature is formed from two or more sheet metal parts which are substantially insulated from one another by the at least one electrically insulating element.

4. The fuel injection apparatus of claim 1 , wherein the at least one electrically insulating element extends radially relative to the movement axis of the armature.

5. The fuel injection apparatus of claim 1 , wherein the permanent magnet is fitted onto the coil subsequently in the direction of the movement axis of the armature.

6. The fuel injection apparatus of claim 1 , wherein the permanent magnet is subsequently fitted radially toward the outside of the coil relative to the movement axis of the armature.

7. The fuel injection apparatus of claim 1 , further comprising a coil housing which contains the permanent magnet.

8. The fuel injection apparatus of claim 7 , wherein the coil housing has at least one electrically insulating element which is designed to reduce eddy currents in the coil housing.

9. The fuel injection apparatus of claim 7 , the coil housing further comprising a material which generates few eddy currents.

10. The fuel injection apparatus of claim 1 , the armature further comprising a material which generates few eddy currents.

11. The fuel injection apparatus of claim 1 , the pole piece further comprising a material which generates few eddy currents.

12. The fuel injection apparatus of claim 1 , wherein the pole piece has at least one electrically insulating element which is designed to reduce eddy currents in the pole piece.

13. A method for ascertaining a position of a movable armature in a fuel injector for an internal combustion engine of a motor vehicle, wherein the fuel injector has a coil, the armature has at least one electrically insulating element which is designed to reduce eddy currents, and the fuel injector has a permanent magnet which is fitted such that it generates a magnetic field which produces a force which acts on the armature in the direction of a pole piece the method comprising the steps of:

detecting the time profile of the electrical voltage across the coil;

analyzing the detected time profile of the electrical voltage in order to identify an induced voltage which is induced on account of the armature movement and the magnetic field, which is generated by the permanent magnet, in the coil, and

determining the armature position based on the induced voltage.

14. The method as claimed in claim 13 , comprising the further steps of:

supplying an operating current to the coil in order to move the armature from a closed position, in the direction of the pole piece, to an open position for the purpose of injecting fuel;

disconnecting the operating current in order to initiate a closing process during which the armature returns from the open position to the closed position, wherein the time profile of the electrical voltage across the coil is detected during the closing process.

15. The method of claim 13 , further comprising the steps of:

providing an engine controller for a vehicle, wherein the engine controller performs the steps of detecting the time profile, analyzing the detected time profile, and determining the armature position.

16. A method for ascertaining a position of a movable armature in a fuel injector for an internal combustion engine of a motor vehicle, wherein the fuel injector has a coil, the armature has at least one electrically insulating element which is designed to reduce eddy currents, and the fuel injector has a permanent magnet which is fitted such that it generates a magnetic field which produces a force which acts on the armature in the direction of a pole piece, the method comprising the steps of:

detecting the time profile of the electric current intensity through the coil;

analyzing the detected time profile of the current intensity in order to identify an induced current which is induced on account of the armature movement and the magnetic field, which is generated by the permanent magnet, in the coil; and

determining the armature position based on the induced current.

17. The method as claimed in claim 16 , comprising the further steps of:

supplying an operating current to the coil in order to move the armature from a closed position, in the direction of the pole piece, to an open position for the purpose of injecting fuel;

disconnecting the operating current in order to initiate a closing process during which the armature returns from the open position to the closed position, wherein the time profile of the electric current intensity through the coil is detected during the closing process.

18. The method of claim 16 , further comprising the steps of: providing an engine controller for a vehicle, wherein the engine controller performs the steps of detecting the time profile, analyzing the detected time profile, and determining the armature position.

19. The fuel injection apparatus of claim 1 , further comprising an engine controller which provides an operating current to the coil in order to move the armature, the engine controller configured to perform a method comprising

detecting a time profile of at least one of an electrical voltage across and an electric current intensity through the coil;

analyzing the detected time profile in order to identify at least one of an induced voltage and an induced current which is induced on account of the armature movement and the magnetic field, which is generated by the permanent magnet, in the coil;

determining the armature position based on the at least one of the induced voltage and the induced current; and

supplying an operating current to the coil in order to move the armature from a closed position, in the direction of the pole piece, to an open position for the purpose of injecting fuel; and

disconnecting the operating current in order to initiate a closing process during which the armature returns from the open position to the closed position, wherein the time profile is detected during the closing process.