Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1998-06-02
2000-07-11
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Rotary
310156, H02K 500
Patent
active
060877480
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a magnetic pole rotor having a plurality of magnetic poles which are arranged on a base ring.
The field of application of the invention is the measurement of the rotational speed of shafts such as turbine shafts, generator shafts, machine shafts, drive shafts and the like. A particular field of application can be seen in automotive engineering in the case of gear shafts, speedometer shafts, crankshafts, camshafts, gears and the like.
PRIOR ART
The use of gearwheel-type rotors is known. These bring about very steep shift gradients when scanning. Consequently, rotary oscillations of the shaft can generate shift pulses and simulate rotational speed. False pulses of this type lead to the recognition of undefined driving conditions which result in disconnection of the controls, so that the motor vehicle is no longer operative and has to be towed away.
DE 36 36039 A1 discloses magnetic pole gears of a plastics-bonded magnetic material which have a desired number of poles. These magnetic pole gears have a relatively smooth shifting behaviour, so that the said rotary oscillations cannot lead to false measurements. However, since the strength of the plastics material decreases at high operating temperatures of 200.degree. C., at high rotational speeds of several thousand revolutions per minute the magnetic pole gear can be displaced in the peripheral direction with respect to the shaft, with the result that it is no longer possible to measure the rotational speed accurately.
STATEMENT OF INVENTION
The object of the invention is to construct the magnetic pole gear such that a non-rotational connection to the shaft remains assured even at high operating temperatures.
This object is achieved according to the invention in that a plastics ring surrounding the magnetic poles is pressed onto a cylindrical surface of the base ring, and in that a cage ring covers the plastics ring.
The invention differs from the prior art in that the plastics ring is pressed firmly onto the base ring by the cage ring so that, in the event of high temperatures causing the strength of the plastics material to decrease, said plastics ring cannot be displaced in the peripheral direction on the shaft, even at high rotational speeds. This ensures accurate rotational speed measurement.
The press fit is improved in that the cylindrical surface has a knurl-type profile.
Precise alignment of the plastics ring on the base ring is ensured in that the plastics ring abuts against an annular wall of the base ring in the axial direction.
Reliable sheathing of the plastics ring is achieved in that the cage ring has an L-shaped profile and thus covers the outer surface of the plastics ring entirely.
A durable press connection is achieved in that there is seated on the inner edge of the cage ring an annular sheathing which is pressed onto the base ring.
The number of poles of the magnetic pole rotor is selected according to the required accuracy of measurement. To a large extent, there can be any number of poles.
BRIEF DESCRIPTION OF THE DRAWING
An exemplary embodiment of the invention is explained with reference to the drawing, in which:
FIG. 1 shows a partially sectional view of the magnetic pole rotor; and
FIG. 2 shows a view in the axial direction.
EXEMPLARY EMBODIMENT
The magnetic pole rotor includes a base ring 1 of steel, ceramic or composite material, which is tensioned in the axial direction on a shaft whereof the rotational speed is to be measured, and can thus take up the high tensile force. The shaft can be the gear shaft of a motor vehicle. The base ring 1 has an outer cylindrical surface 2 which adjoins an outwardly directed annular wall 3. The cylindrical surface 2 is provided with a knurl-type profile 4.
A plastics ring 5 contains embedded magnetic poles whereof the orientation N, S is specified in FIG. 2. These can be magnetic parts inserted in an annular connection. Frequently, however, plastics rings 5 of this type are injection moulded parts. The magnetic poles are polarized
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Ramirez Nestor
Schindler Edwin D.
Waks Joseph
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