ELECTRIC MOTOR WITH ROTOR AND SHORT-CIRCUIT CAGE

Description

[0001] The invention relates to an electric motor with rotor and squirrel cage.

[0002] It is generally known that an electric motor with a squirrel cage can be operated as an asynchronous motor.

[0003] From the DE 18 60 673 U An alternating current motor is known.

[0004] From the DE 72 24 206 U A reluctance motor powered by a single-phase network is known.

[0005] From the US 1 945 028 A The most readily available state of the art is a synchronous motor.

[0006] From the GB 1 141 922 A An alternating current motor is known.

[0007] From the EP 1 524 755 A1 A reluctance synchronous motor that can be started from the mains is known.

[0008] From the KR 2009 0007050 A is a rotor of an electric motor.

[0009] From the KR 102 010 026 B1 The rotor of an electric motor is also known.

[0010] The invention is therefore based on the objective of further developing an electric motor which, despite simple manufacturing, enables improved operation of the electric motor.

[0011] According to the invention, the problem is solved in the electric motor according to the features specified in claim 1.

[0012] Important features of the invention for the electric motor with rotor and squirrel cage are that the squirrel cage has two rings spaced apart axially from each other, in particular in the direction of the axis of rotation of the rotor, and connected to each other by rods, in particular electrically connected, wherein the rotor has axially through recesses for receiving rods, wherein the recesses are spaced apart from each other in the circumferential direction, wherein the rotor has radially outwardly open axial grooves, wherein the radial spacing range covered by the axial grooves includes the radial spacing range covered by the rods.

[0013] A key advantage is that the electric motor can be operated in a simple combination of both asynchronous and reluctance modes. The electric motor is thus designed to enable efficient starting and continuous operation synchronously with the frequency of the rotating magnetic field generated by the motor's stator. Furthermore, its manufacture is very straightforward, requiring only the milling of additional axial grooves into the rotor of the asynchronous motor to enable reluctance operation.

[0014] In an advantageous embodiment, the ring axis of the rings, particularly the rings preferably designed as circular rings, is aligned coaxially with the axis of rotation of the rotor. It is advantageous that the squirrel cage is aligned coaxially with the rotor shaft.

[0015] In an advantageous embodiment, the axial slots have a vanishing helix angle. An advantage of this is that reluctance operation can be performed in parallel with asynchronous operation.

[0016] In an advantageous embodiment, the axial grooves have a first helix angle, wherein the rods have a second helix angle, wherein the first helix angle is different from the second helix angle, in particular wherein the first helix angle is zero and the second helix angle has a value between 5° and 30°. It is advantageous that the asynchronous operation produces a different pole detent than the reluctance operation, so that an overall reduced pole detent can be achieved.

[0017] In an advantageous embodiment, the circumferential angle range covered by the respective axial groove at a given axial position is independent of the axial position. It is advantageous that the axial groove extends only in the axial direction and thus, unlike the bars of the squirrel cage, causes a different pole detent, so that the superposition of the cogging torque fluctuations during rotation of the motor results in a reduced amplitude.

[0018] In an advantageous embodiment, the axial grooves have a cross-section that is independent of the axial position. A further advantage is that the axial grooves can be easily manufactured by using a milling tool that can be moved axially along the rotor.

[0019] In an advantageous embodiment, the circumferential angle range covered by each axial groove at a given axial position is greater in magnitude than the range covered circumferentially by the respective rod, in particular at least three times greater. It is advantageous that the effect of each groove can be dimensioned more extensively than the effect of a single rod, especially at the synchronous speed of the motor. This is because the groove width creates correspondingly dimensioned reluctance poles.

[0020] In an advantageous embodiment, the respective ring is attached to the rotor by means of a bayonet fitting, In particular, the ring has a circumferentially extending elongated hole through which a screw, screwed into an axially oriented threaded bore of the rotor, protrudes, the screw head pressing the ring onto the ends of rods, the axial wall thickness of the ring at the edge of the elongated hole increasing with increasing circumferential angle or decreasing with decreasing circumferential angle. An advantage of this is that it enables a simple yet secure fastening, allowing for reliable contact.

[0021] In an advantageous embodiment, the recesses are regularly spaced apart in the circumferential angle range not interrupted by the axial grooves. It is advantageous that the squirrel cage has bars that are regularly spaced apart in the circumferential direction, particularly at least in the areas not interrupted by axial grooves.

[0022] In an advantageous embodiment, the rotor material exhibits a higher magnetic permeability than the rotor shaft material. This is advantageous because a sufficiently strong reluctance effect can be generated.

[0023] In an advantageous embodiment, the axial slots are regularly spaced apart in the circumferential direction, particularly where the number of axial slots is between three and nine. An advantage of this is that synchronous operation of the motor can be achieved by means of the reluctance effect.

[0024] In an advantageous embodiment, the axial grooves are incorporated axially through the rotor. The advantage here is that the largest possible reluctance effect can be achieved.

[0025] In an advantageous embodiment, the rotor is designed as a laminated core, In particular, the rotor is designed as a stack of individual laminations, each manufactured as a stamped part, wherein the individual laminations are welded together and / or pressed together by means of a tie rod axially extending through the stack, and in particular wherein the stacking direction is aligned parallel to the axial direction. It is advantageous that low losses are achieved despite the rotating field, in particular an alternating magnetic field. The stacking direction is parallel to the axial direction. Preferably, electrical steel is used as the lamination material, in particular iron silicide-containing sheet metal.

[0026] By filling the recesses with the material, especially aluminium or copper, the sheet metal stack is mechanically stabilized after the material has cooled, so that the grooves can be milled.

[0027] According to the inventionThe first bars of the short-circuit cage connect the two rings, while other bars terminate blindly in their respective grooves. This design offers the advantage of simple manufacturing, as material is first poured into recesses and then the grooves are milled.

[0028] Further advantages arise from the dependent claims. The invention is not limited to the combination of features of the claims. For those skilled in the art, further meaningful combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent, in particular from the problem statement and / or the problem arising from a comparison with the prior art.

[0029] The invention will now be explained in more detail with reference to schematic illustrations: In the Figure 1 An electric motor according to the invention is shown in an exploded view at an angle. Figure 2The electric motor is shown in an oblique view. In the Figure 3 The rotor, pushed onto rotor shaft 2, is shown in an oblique view. Figure 4 The short-circuit cage is shown in an oblique view. In the Figure 5 The rotor without a squirrel cage is shown in an oblique view. Figure 6 The rotor with squirrel cage is shown in an oblique view. In the Figure 7 A front view of the rotor is shown.

[0030] As shown in the figures, the electric motor has a stator housing 1, on the outside of which cooling fins are formed and a terminal box is arranged.

[0031] A bearing shield 3 and a bearing flange 4 are connected to the stator housing 1, wherein the stator housing 1 is arranged between the bearing shield 3 and the bearing flange 4.

[0032] The rotor shaft 2 is supported by a first bearing located in the bearing shield 3 and a second bearing located in the bearing flange 4. On the side of the bearing shield 3 facing away from the stator housing 1, a fan 5 is pushed onto the rotor shaft 2 and connected in a rotationally fixed manner.

[0033] A fan shroud 6 surrounds the fan 5 and is attached to the bearing shield 3.

[0034] A preferably ring-shaped rotor 8 is pushed onto the rotor shaft 2 and connected, in particular by frictional connection, to the rotor shaft 2.

[0035] The rotor 8 is made of a material that has a higher permeability than the rotor shaft 2. Preferably, the rotor shaft 2 is made of case-hardened steel.

[0036] The rotor 8 has axially through recesses, in particular cavities 50, which are designed to receive bars of a squirrel cage. For this purpose, liquid aluminum-containing or liquid copper-containing material is injected into the recesses, so that after this material cools, the bars are formed.

[0037] Rings 7 are pressed axially against both sides of the rotor 8, electrically contacting the rods, particularly their axial ends, and thus completing the squirrel cage. For this purpose, the rings have elongated holes extending circumferentially, through which a screw protrudes. The head of each screw, acting like a bayonet fitting, presses the respective ring 7 increasingly axially against the rotor 8 as the rings 7 rotate relative to the rotor 8, because the wall thickness of the area of ​​the ring 7 accommodating the elongated holes increases circumferentially.

[0038] The recesses are designed with a bevel angle. This means that the recesses increase in width from the axial direction to the circumferential direction. The recesses are always arranged at the same radial distance.

[0039] Axially directed grooves 30 without helix angle are open radially outwards and / or incorporated into the rotor 8, in particular wherein the grooves 30 are arranged at a constant radial distance and always remain at the same circumferential angle position in the axial direction, in particular thus not extending increasingly in the circumferential direction.

[0040] The grooves 30 are spaced apart from each other in the circumferential direction, in particular uniformly spaced. Preferably, four grooves 30 are provided on the outer circumference of the rotor 8.

[0041] By introducing these axially oriented grooves 30, which are radially open to the outside environment on the rotor 8, some of the recesses, along with the injected material, open into a respective groove 30. This means that the corresponding bars in the respective grooves terminate blindly and therefore cannot conduct current from one ring to another. This is because the grooves 30 are only introduced into the rotor 8 after the material has been injected and cooled.

[0042] The remaining areas of the originally cylindrical rotor 8, located circumferentially between the slots 30, function as pole regions, enabling reluctance operation. These remaining areas extend radially beyond the slots and attempt to align themselves in such a way that the magnetic field lines are as short as possible. This generates a torque during reluctance operation, which aims to achieve a rotational movement of the rotor that is as synchronous as possible within the rotating field generated by the stator.

[0043] In addition, rotor 8 also features a squirrel cage, enabling operation as an asynchronous motor. Overall, this allows for improved starting of the electric motor, which, once started, operates synchronously with the rotating magnetic field.

[0044] The circumferential width of the grooves is smaller than the circumferential distance between any two adjacent grooves.

[0045] Preferably, the rotor 8 comprises silicon steel. This is because iron silicide has a very high magnetic permeability. In this way, the rotor 8 can be equipped with a higher magnetic permeability than the rotor shaft 2. Reference symbol list

[0046] 1 Stator housing 2 Rotor shaft 3 Bearing shield 4 Bearing flange 5 Fan 6 Fan cover 7 Ring 8 Rotor, in particular rotor with pole areas 30 Slot 50 Cavity for squirrel cage rod

Claims

1. Electric motor comprising a rotor (8) and a squirrel cage, the squirrel cage having two rings (7) which are spaced apart from one another axially, i.e. in particular in the direction of the axis of rotation of the rotor (8), and which are electrically interconnected by means of bars, the rotor (8) having axially through-going cut-outs (50) for receiving the bars, the cut-outs (50) being spaced apart from one another in the circumferential direction, the rotor (8) having axial grooves (30) that are open radially outwards, the radial clearance region covered by the axial grooves (30) encompassing the radial clearance region covered by the bars, characterised in that first bars of the squirrel cage interconnect the two rings (7), and other bars end blind in respective axial grooves such that they cannot conduct any current from one of the rings to the other of the rings, in particular once the axial grooves (30) have been made by means of milling in the laminated core, which is stabilised by the bars, of the rotor (8).

2. Electric motor according to claim 1, characterised in that the ring axis of the rings (7), in particular rings (7) formed preferably as annuli, is oriented coaxially with the axis of rotation of the rotor (8).

3. Electric motor according to any of the preceding claims, characterised in that the axial grooves have an infinitesimal angle of skew.

4. Electric motor according to any of the preceding claims, characterised in that the axial grooves have a first angle of skew, the bars having a second angle of skew, the first angle of skew being different from the second angle of skew, in particular the first angle of skew being zero and the second angle of skew having a value between 5° and 30°.

5. Electric motor according to any of the preceding claims, characterised in that the circumferential-angle region covered by each axial groove at a particular axial position is independent of the axial position.

6. Electric motor according to any of the preceding claims, characterised in that the axial grooves have a cross section that is independent of the axial position.

7. Electric motor according to any of the preceding claims, characterised in that the magnitude of the circumferential-angle region covered by each axial groove at a particular axial position is greater, in particular at least three times greater, than the region covered by each bar in the circumferential direction.

8. Electric motor according to any of the preceding claims, characterised in that each ring (7) is fastened to the rotor (8) by means of a bayonet joint.

9. Electric motor according to claim 8, characterised in that each ring (7) has a slot which extends in the circumferential direction and through which there projects a screw, which is screwed into an axially directed threaded bore in the rotor (8) and the screw head of which presses the ring (7) against the ends of bars.

10. Electric motor according to claim 9, characterised in that the axial wall thickness of the ring (7) at the edge region of the slot is configured to increase as the circumferential angle increases or to increase as the circumferential angle decreases.

11. Electric motor according to any of the preceding claims, characterised in that in each circumferential-angle region not broken up by the axial grooves, the cut-outs are regularly spaced apart from one another in the circumferential direction.

12. Electric motor according to any of the preceding claims, characterised in that the material of the rotor (8) has a higher magnetic permeability than the material of the rotor shaft (2), the material of the rotor (8) in particular comprising iron and silicon and / or comprising iron silicide, and / or in that the axial grooves are regularly spaced apart from one another in the circumferential direction, the number of axial grooves in particular being between three and nine.

13. Electric motor according to any of the preceding claims, characterised in that the axial grooves are made in the rotor (8) in an axially through-going manner.

14. Electric motor according to any of the preceding claims, characterised in that the rotor (8) is configured as a laminated core, the rotor (8) in particular being configured as a stack of laminations that are each produced as punched parts, the laminations being interconnected by welding and / or being pressed together by means of tie rods that extend axially through the stack, the stacking direction in particular being oriented in parallel with the axial direction.