MACHINE

The present invention refers to an apparatus and a method for assembling a magnetic position sensor on the rotor of an electrical machine; in particular, it refers to the rotary part of a magnetic position sensor for measuring the angular position of the rotor of an electrical machine.

More in particular, the invention refers to an apparatus and a method for assembling a magnetic element, which is the magnetic position sensor, on the rotor of an asynchronous reluctance motor, for example of the type assisted by permanent magnets, to allow its accurate assembly on the rotor, in order to guarantee a high measuring accuracy of the angular position of the rotor.

Electrical machines are known, in particular electric motors, and it is known how to use inverters connected to the motors to check its operation .

A control parameter of synchronous reluctance electric motors assisted by permanent magnets, used by the inverter, is the instantaneous angular position of the magnetic poles of the rotor with respect to the magnetic field created by the stator windings .

In known motors, and in particular in high- performance synchronous reluctance electric motors, for example to be used in the motor vehicle field, it is necessary to accurately know the angular position of the rotor to check the motor operation.

For such purpose, it is known to use a magnetic position sensor having a part fastened to the rotor shaft to measure its angular position, for example as disclosed in International patent application O2018099667.

Such known sensor comprises a magnet, fastened to the rotation shaft of the rotor, and a fixed part connected to a frame of the electric motor, said fixed part comprising Hall-effect sensors and means for transmitting the output signals of the sensor .

In order to obtain an accurate measure of the angular position of the rotor, it is necessary that the magnetic sensor is accurately fastened to the rotation shaft of the rotor, so that the magnetic field of the magnet fastened to the rotary part is aligned with the magnetic field of the rotor with a minimum error.

Object of the present invention is solving this problem, by providing an apparatus and a method for assembling a magnetic position sensor on the rotor of an electrical machine, which allows performing an optimum assembly of the sensor on the rotor, allowing to fasten it to the rotor with maximum accuracy, so that the magnetic field of the sensor, in particular of the magnet contained in the sensor, is aligned with the magnetic field of the rotor with a minimum error.

The above and other objects and advantages of the invention, as will result from the following description, are obtained with an apparatus and a method for assembling a magnetic position sensor on the rotor of an electrical machine as claimed in the independent claims.

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appears from the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows a perspective view of a magnetic position sensor and of a rotor to be assembled with the apparatus according to the invention; and

Figure 2 shows a front view of an apparatus for assembling a magnetic position sensor on the rotor of an electrical machine according to the invention .

With reference to the Figures, an apparatus 10 for assembling a magnetic position sensor on a rotor 20 of an electrical machine will be described below, said rotor 20 comprising a rotation shaft 21 and rotation means 22, for example two ball bearings, connected in a known way to the shaft 21 and configured to connect the rotor 20 in a rotating way to a stator.

In particular the apparatus 10 of the invention is configured to assemble on the rotor 20 of an electrical machine the magnetic element 15 of a magnetic position sensor of a known type, for example of the type disclosed in International patent application O2018099667.

The magnetic position sensor comprises a fixed element, not shown in the Figures, adapted to be connected to the fixed structure of the electrical machine and preferably comprising a plurality of Hall-effect magnetic sensors; the magnetic position sensor further comprises the magnetic element 15 adapted to be assembled on the rotor 20, preferably fastened to the rotation shaft 21, so that, during the rotation of the rotor 20, the magnetic element 15 is rotated with respect to the fixed element; the magnetic element 15 comprises a magnet 19, for example inserted in a seat obtained therein.

With reference to the Figures, the apparatus 10 for assembling a magnetic position sensor on the rotor 20 of an electrical machine according to the invention comprises: a pressure device 11, preferably a hydraulic press 11, comprising pressure means 14 configured for exerting a pressure on the sensor, in particular on the magnetic element 15, to fasten it in a seat of the rotor 20, preferably obtained on the rotation shaft 21 of the rotor 20; in a preferred way, the pressure means 14 comprise a hydraulic cylinder 14 of a known type comprising a piston actuated by means of a hydraulic circuit.

Preferably, the apparatus 10 comprises a supporting structure 12 to which the pressure device 11 is connected, for example fastened thereto, and a support 18, associated to the supporting structure 12, against which the rotor is abutted 20 before assembling thereon the position sensor, in particular the magnetic element 15 of the position sensor; for example, the support 18 is abutted or fastened to the supporting structure 12.

In an embodiment of the apparatus 10 of the invention, the supporting structure 12 comprises a base cross-member 25 to which the support 18 is associated, for example abutted or fastened; the supporting structure 12 can comprise a plate 26 connected, preferably assembled sliding, to the base cross-member 25, on which the support 18 is assembled.

For example, the rotation means 22 are abutted or fastened to the support 18, preferably to the base cross-member 25 or to the plate 26 connected thereto, so that the rotor 20 is free of rotating under the action of a magnetic field, as will be explained below in more detail.

The apparatus 10 further comprises magnetic means 31, 32 configured to create a magnetic field which crosses the rotor 20 and the magnetic element 15, and in particular the magnet 19 inserted therein, in order to orient the rotor 20 and the position sensor, in particular the magnetic element 15, according to said magnetic field, to align the magnetic field of the magnet 19 with the magnetic field of the rotor with a minimum error, preferably so that the axis X of the shaft 21 of the rotor 20 forms with the axis of the magnet 19 an angle a less than 5 ⁰ .

The apparatus 10 further comprises connecting and orienting means 34 connected to the pressure means 14 and configured to connect the magnetic element 15 to the pressure means 14, so that the magnetic element 15 is free of being oriented under the action of the magnetic field created by the magnetic means 31, 32, aligning the magnetic field of the magnetic element 15 to the magnetic field created by the magnetic means 31, 32.

In a preferred way, the connecting and orienting means 34 are connected to the magnetic means 32, for example fastened thereto, in turn connected to the pressure means 14, and comprise an air bearing 34 of a known type connected to the magnetic means 32 and to the magnetic element 15 and configured to allow the magnetic element 15 rotation and/or oscillation movements and thereby align the magnetic field of the magnetic element 15 to the magnetic field created by the magnetic means 31, 32.

For example, the magnetic means 32 are made shaped as a hollow cylinder or sleeve, and the air bearing 34 is obtained inside them, for example a known pneumatic-static bearing.

Preferably, the apparatus 10 for assembling a magnetic element 15 of a position sensor on the rotor 20 of an electrical machine according to the invention comprises first magnetic means 31, configured to generate a magnetic field which crosses the rotor 20, and second magnetic means 32, configured to generate a magnetic field, aligned with the magnetic field generated by the first magnetic means 31, which crosses the magnetic element 15 of the position sensor, and in particular the magnet 19 inserted therein.

Preferably, the first magnetic means 31 comprise two magnetic apparatuses arranged one in front of the other at the sides of the support 18, and the second magnetic means 32 comprise a magnetic cylinder fastened to the pressure means 14; as described above in an embodiment of the apparatus 10 of the invention, the magnetic cylinder 32 comprises a seat inside which the air bearing 34 is obtained.

In the operation of the apparatus 10 for assembling a magnetic element 15 of a position sensor on the rotor 20 of an electrical machine according to the invention, in a first step the magnetic element 15 of the position sensor is inserted into the connecting and orienting means 34, and the rotor 20 is abutted onto the support 18 in order to be free of rotating around its own axis X, preferably with the rotation means 22, for example the bearing, abutted onto the support 18.

In a second step, the magnetic means 31, 32 are activated, to create the magnetic field which, by crossing the rotor 20 and the magnet 19 of the magnetic element 15, orients them according to said magnetic field, to align the magnetic field of the magnet 19 with the magnetic field of the rotor with a minimum error, preferably so that the axis X of the shaft 21 of the rotor 20 forms with the axis of the magnet 19 an angle a. less than 5°.

In the embodiment of the invention which comprises an air bearing 34, once the magnetic element 15 is in its assembly position, with the magnetic field of the magnet 19 aligned with the magnetic field of the rotor 20, the air flow in the bearing 34 is interrupted, air is removed from inside it and the sensor is kept in position by the friction generated by the attraction force of the magnetic field.

In a third step, the pressure means 14, for example of the hydraulic press, are activated for exerting a force on the magnetic element 15 in order to fasten it, for example with a forced coupling, to the rotor 20, preferably fastening it inside a seat obtained in the shaft 21 of the rotor 20; in a preferred way, the pressure means 14 exert on the magnetic element 15 a force of about 5000 N (500 kg) .

Advantageously, the apparatus 10 for assembling a magnetic element 15 of a position sensor on the rotor 20 of an electrical machine according to the invention allows performing an optimum assembly of the magnetic element 15 of the sensor on the rotor 20, allowing to fasten it to the rotor with maximum accuracy, so that the magnetic field of the sensor, in particular of the magnet 19 contained in the rotary part of the sensor, is aligned with the magnetic field of the rotor with a minimum error.