Patent ID: 7452492

Claim:
A method of fabricating a magnetic coder device usable for accurately and dynamically positioning electromagnetically-driven valves of a motor vehicle, comprising: making a mixture of ferromagnetic particles in a matrix having a viscosity that is sufficiently low to enable the particles to migrate, placing the mixture in a mold having a mold cavity with a mold shape configured for producing a magnetic coder device with alternating geometrical shapes having high concentrations of ferromagnetic particles to form alternating north and south poles which are separated in pairs by zones that are empty of ferromagnetic particles, and wherein this device includes magnetic singularities which constitute absolute angle reference points, so that the device is usable for accurately and dynamically positioning electromagnetically-driven valves of a motor vehicle, positioning on either side of the mold, two soft iron concentrators, each presenting an etching in the form of projections which mutually face one another for channeling magnetic field lines through the alternating geometrical shapes of the magnetic coder device, applying a magnetic field to the mixture in the mold during a molding step in which the mixture is molded in the mold while maintaining the matrix at a given temperature to reduce the viscosity of the matrix thereby making it easier to cause the ferromagnetic particles to migrate and become oriented in their direction of easy magnetization, and cooling the matrix while the magnetic field is maintained so as to freeze the particles in the matrix.