CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2019 110 714.8 filed on Apr. 25, 2019, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

Field of the Invention

The invention relates to a rotor of an electric machine and to a method for producing same.

Related Art

A rotor of an electric machine has a shaft mounted in bearings, a laminated core positioned on the shaft, and magnets positioned in magnet pockets of the laminated core. The magnets form pole pairs. The laminated core of the rotor of an electric machine can take the form of a segmented laminated core made up of laminated core segments positioned next to one another or behind one another, as viewed in the axial direction of the shaft.

Manufacturing deviations in the individual subassemblies of the rotor lead may occur in spite of a symmetrical design of the rotor and result in an imbalance. Unwanted vibrations, noise or premature failure may occur during operation of the electric machine if the imbalance of the rotor exceeds a limit value.

A rotor of an electric machine can be balanced by mass compensation at the rotor to compensate for the imbalance of a rotor. Mass compensation during balancing can be carried out by removal of mass by so-called negative balancing or by addition of mass as so-called positive balancing. Negative balancing also is referred to as subtractive balancing, and positive balancing is also referred to as additive balancing.

Balancing a rotor of an electric machine typically involves negative balancing. However, the damage to the rotor of an electric machine with negative balancing cannot be tolerated for high-power machines.

Therefore, a rotor often will have a sacrificial mass, in addition to the subassemblies of the shaft, the laminated core and the magnets. The sacrificial mass can be removed for negative balancing. Sacrificial masses for negative balancing also are referred to as balancing disks. However, balancing disks have the disadvantages of increasing the overall axial length and the mass of the rotor.

Positive balancing avoids the disadvantages of negative balancing when balancing a rotor of an electric machine. Positive balancing applies material at points on the rotor at which the additional mass is required for minimizing the imbalance. Rotors balanced by positive balancing are lighter than rotors balanced by negative balancing.

The known methods for negative balancing and for positive balancing are unsuitable for rotors of electric machines that are operated at a rotational speed of more than 15,000 rpm or even at a rotational speed of more than 17,000 rpm particularly with respect to industrial manufacture of such rotors within short cycle times.

There is therefore a need for a novel rotor of an electric machine, in particular a quick-running electric machine, that can be produced within short cycle times with small imbalance. The invention further relates to a method for producing such a rotor.

SUMMARY

The rotor according to invention has a shaft and a laminated core on the shaft.

The rotor of the invention further has balancing bodies arranged on the shaft. Each balancing body has an aperture situated outside the center of gravity. Each balancing body is mounted by way of the aperture on the shaft of the rotor in a defined angular position. The respective aperture situated outside the center of gravity may be incorporated in a blank of the respective balancing body in dependence on a magnitude of an initial imbalance of the rotor to be balanced. The defined angular position at which the respective balancing body is mounted on the shaft of the rotor may depend on the orientation of the determined initial imbalance.

The rotor may have positioning sleeves arranged on the shaft to define a distance between the laminated core or the balancing bodies and bearings of the shaft and to provide an anti-rotational safeguard for the balancing bodies.

The rotor according to the invention can be produced within short cycle times with small imbalance.

The balancing bodies on the shaft of the rotor function for balancing the shaft and eliminating the initial imbalance thereof.

The positioning sleeves on the shaft of the rotor function primarily for axially positioning the laminated core and balancing bodies and for rotationally securing the balancing bodies.

The positioning sleeves may be positioned on the shaft of the rotor on both sides of the laminated core to define a distance between the bearings of the shaft and the laminated core or the balancing bodies. The positioning sleeves secure the laminated core and the balancing bodies in their axial position on the shaft at high rotational speeds and correspondingly high centrifugal forces. The positioning sleeves also secure the balancing bodies against rotation. Thus, a small imbalance of the rotor can be ensured even at high rotational speeds.

Each positioning sleeve may have a projection that engages in a cutout of an adjacent or adjoining balancing body. The projection extends in the axial direction into the respective cutout of the adjacent or adjoining balancing body. The anti-rotational safeguard for the balancing bodies on the shaft can thereby be provided in a particularly advantageous manner.

At least one positioning sleeve may define a contact surface of a sliding contact via which an electrical voltage between the rotor and a stator of the electric machine can be decreased. Accordingly, in addition to the spacer function or axial securing function and in addition to the anti-rotational safeguarding function, the respective positioning sleeve performs a further function of decreasing an electrical potential difference and hence electrical voltage between the rotor and the stator of the electric machine that may be formed during operation. For this purpose, the positioning sleeve formed as a contact surface of a sliding contact may be silver-plated on its radial circumferential surface or radial outer side, with the sliding contact sliding along this silver-plated surface.

The invention also relates to a method that comprises providing a rotor is to be balanced for use in an electric machine. The rotor has a shaft and a laminated core arranged on the shaft. The method also includes providing balancing bodies that have an aperture situated outside the center of gravity, mounting the balancing bodies on the shaft in a defined angular position, providing positioning sleeves, and mounting the positioning sleeves on the shaft. The sleeves define a distance between the laminated core or the balancing bodies and bearings of the shaft and provide an anti-rotational safeguard for the balancing bodies. This method enables the rotor of the electric machine to be produced advantageously within short cycle times with small imbalance.

The step of providing the balancing bodies preferably comprises providing blanks having a length that is less than an outside diameter of the laminated core, determining a magnitude and an orientation of an initial imbalance of the rotor to be balanced, and processing the blanks to form the balancing bodies by incorporating the respective aperture situated outside the center of gravity in the respective blank in dependence on the magnitude of the determined initial imbalance. These details also can produce the rotor of the electric machine within short cycle times with small imbalance.

The defined angular position at which the respective balancing body is mounted on the shaft may be dependent on an orientation of the determined initial imbalance. This detail also serves for producing the rotor of the electric machine within short cycle times with small imbalance.

The method also may include determining an axial distance between the bearings of the shaft and determining an axial width of the laminated core. The positioning sleeves are processed depending on the axial distance of the bearings and the axial dimension of the rotor to set the axial dimension of the sleeves. This aspect of the method ensures in a simple manner that the rotor of the electric machine is situated, with respect to the stator thereof, in the correct axial position. In particular performance losses during the operation of the electric machine can be prevented as a result.

