Ferrite core coil device, sensor device for determining rotational speed of a rotatable object with such a ferrite core coil device and turbocharger with such a sensor device

A sensor device for determining rotational speed of a rotatable object, comprising:

• a sensor segment;
• a mounting segment;
• a connector segment;
• and
• a ferrite core coil device arranged at a sensor tip of the sensor segment, the ferrite core coil device including a coil having a first sector and a second sector and a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector.

A turbocharger, comprising:

• a turbocharger housing;
• a compressor impeller arranged in the turbocharger housing;
• and
• a sensor device including a sensor segment, a mounting segment, a connector segment, and a ferrite core coil device arranged at a sensor tip of the sensor segment, the ferrite core coil device including a coil having a first sector and a second sector and a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector, the sensor segment is arranged in a wall of the turbocharger housing that has a recess, the ferrite core coil device protrudes through the wall and faces the compressor impeller at a predefined distance from the compressor impeller.

A method for determining a rotational speed of a rotatable object, comprising:

• providing a sensor device including a sensor segment, a mounting segment, a connector segment, and a ferrite core coil device arranged at a sensor tip of the sensor segment, the ferrite core coil device including a coil having a first sector and a second sector and a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector;
• placing the sensor device with the sensor tip at a predefined distance from the rotatable object;
• applying an electrical input current to the ferrite core coil device;
• reading an amplitude modulated output voltage signal output from the sensor device;
• and
• determining the rotational speed by evaluating a demodulated output voltage signal of the sensor device.