Device and method for testing a rotating electric machine

Abstract

The invention relates to a device (1) for testing a rotating electric machine (2), in particular an electric motor, the machine (2) comprising a rotor having a rotor shaft (3), which device comprises a load machine (4) having a drivable shaft (5) for exerting a torque on the rotor shaft (3), wherein: the drivable shaft (5) can be coupled to the rotor shaft (3) of the machine (2) for torque transmission; the drivable shaft (5) is a hollow shaft, and a coolant lance (6) extends through the drivable shaft (5) of the load machine (4) such that coolant can be fed into the rotor shaft (3) of the machine (2) to be tested. The invention also relates to a corresponding method and to a machine test bench.

Description

[0001] Device and method for testing a rotating electrical machine

[0002] The invention relates to a device for testing a rotating electrical machine, in particular an electric motor, wherein the machine has a rotor with a rotor shaft, comprising a loading machine with a drivable shaft for exerting a torque on the rotor shaft, wherein the drivable shaft can be coupled to the rotor shaft of the machine for torque transmission. The invention further relates to a method for testing a rotating electrical machine, in particular an electric motor, wherein the machine has a rotor with a rotor shaft.

[0003] In e-mobility, the rotating electrical machine, in particular the electric motor, is a crucial component that, for reasons of space and weight, should have the highest possible power density. To ensure adequate cooling of the electric motor, cooling can be achieved, for example, via the rotor shaft: a liquid coolant (e.g. oil) is pumped axially into the hollow rotor shaft of the electric motor and from there, via appropriate channels and with the help of centrifugal forces, is guided through the rotor, thereby cooling it (see, for example, WO 2021 / 185542 A1).

[0004] On the electric motor test bench, the electric motor must be operated under realistic conditions. This means that on the test bench too, the coolant must be pumped into the hollow rotor shaft of the electric motor. In contrast to the later installation location in the vehicle, where this coolant supply can be provided via the downstream gearbox, the test bench usually has the following setup due to the high speeds: test specimen, intermediate shaft with gearing, bearing unit, cardan shaft consisting of torsionally rigid joints with synchronous rotation properties such as multi-plate clutches, and a load machine. The following methods are conceivable for transporting the coolant to the rotor shaft of the test specimen: by means of a radial feed via the hollow shaft or by means of an axle offset gear. With radial feed, the coolant is supplied via radial holes in the shaft of the bearing unit, which is sometimes also designed as a hollow shaft.However, this variant has two major disadvantages: Firstly, the coolant must be supplied at a significantly higher pressure in order to force it through the radial bores into the hollow shaft of the bearing unit, especially at high speeds, against centrifugal forces. Secondly, the coolant is subjected to a strong swirl by flowing through the radial bores, which is maintained all the way into the hollow rotor shaft of the test specimen and significantly influences the coolant distribution within the test specimen.

[0005] When supplied via an axle offset gear, the coolant is supplied via a lance that is guided through the hollow shaft of an axle offset gear. This eliminates some of the disadvantages of the previous variant. However, the additional gear in the drive train impairs the dynamic load capacity of the test object due to the gear play, the additional inertia, and the additional order excitations from the gears in the gear. Furthermore, the gear also requires additional maintenance in test bench operation and increases the acquisition costs for the testing equipment.

[0006] The object of the present invention is to remedy or mitigate at least one of the disadvantages of the prior art. In particular, the object is to provide a method and a device for testing a rotating electrical machine (in particular with a liquid-cooled rotor shaft) with improved operating characteristics, which, in particular, impairs the dynamic load capacity of the test object less and requires less maintenance.

[0007] The object is achieved by a device as mentioned above, wherein the driven shaft is a hollow shaft and a coolant lance is guided through the driven shaft of the loading machine, so that coolant can be supplied to the rotor shaft of the machine to be tested. The object is further achieved by a method for testing a rotating electrical machine, in particular an electric motor, wherein the machine has a rotor with a rotor shaft, comprising the steps:

[0008] - coupling the rotor shaft to a drivable shaft of a loading machine for torque transmission between the rotor shaft and the drivable shaft;

[0009] - Driving or braking the rotor shaft with the machine;

[0010] - Exerting a torque with the driven shaft onto the rotor shaft;

[0011] - Supplying coolant into the rotor shaft with a coolant lance which is guided through the drivable shaft, wherein the drivable shaft is a hollow shaft.

[0012] The coolant lance is therefore guided directly through the loading machine and the coolant is thus supplied to the rotor shaft. The coolant is therefore supplied in a way that is as similar as possible to the supply during actual engine operation (e.g. at the later installation location in the vehicle), where it can be supplied via the downstream gearbox, for example. Because the coolant can be supplied axially, the coolant distribution in the rotor is distorted as little as possible compared to actual operation. The supply can take place at a pressure similar to that during actual machine operation without the dynamic load capabilities of the test object being influenced by an intermediate test bench gearbox. In addition, maintenance of the device is simplified.

[0013] The loading machine is in particular designed to exert a load or a counter torque on the machine to be tested. This is exerted in particular by means of the drivable shaft by coupling this to the rotor shaft (in particular in a rotationally fixed or torsionally rigid manner). The loading machine is preferably designed to simulate different load states. The coolant lance is in particular guided through the hollow space of the drivable shaft and / or runs substantially along or parallel to its axis of rotation. The loading machine preferably has a torque measuring device. Exerting the torque with the drivable shaft onto the rotor shaft can be either an acceleration or deceleration. The coolant is preferably fed into the hollow space of the (hollow) rotor shaft. The coolant lance is preferably stationary, i.e. it does not rotate with the rotor shaft or the drivable shaft.

[0014] A rotating electrical machine is understood to be an electromechanical energy converter, in particular an electric motor, an electric generator or an electric motor generator. The machine has in particular a liquid-cooled rotor, i.e. a rotor which can be temperature-controlled and in particular cooled using a liquid medium. The liquid used for temperature control is preferably a lubricant and more preferably an engine or gear oil. Depending on the design of the machine, the rotor is designed as an electrically passive or active element. The liquid-cooled rotor has a rotor shaft which is designed to deliver drive power in the case of motor operation and to absorb drive power (torque, speed) in the case of generator operation and which is mounted so as to be rotatable about a rotor axis. The rotor shaft is preferably designed as a hollow shaft, at least in sections.The rotor shaft preferably has a first, open axial end. The coolant lance can preferably be guided or is guided through the open axial end. In addition, the liquid-cooled rotor preferably has a liquid guide device, wherein the liquid guide device is designed to guide liquid which is provided for tempering the rotor. The rotor shaft preferably has a rotor shaft end piece with which it is preferably closed off at its second axial end. Further preferably, the rotor shaft end piece is received in or on the rotor shaft and further preferably the rotor shaft end piece is formed integrally with the rotor shaft or is preferably connected to it.

[0015] It is advantageous if the device has a shaft train, wherein the drivable shaft can be coupled to the rotor shaft via a shaft train, wherein the coolant lance is guided through the shaft train. The shaft train can have one or more shafts and / or couplings. The shaft train preferably has a bearing unit. The shaft train is preferably coupled (at one end) to the drivable shaft in particular in a torsionally rigid or non-rotatable manner. The shaft train is preferably hollow and the coolant lance is guided through an axially extending cavity in the shaft train.

[0016] It is preferred if the shaft train has at least one hollow shaft through which the coolant lance is guided.

[0017] It is advantageous if the shaft train has an intermediate shaft that can be coupled to the rotor shaft via a toothing, with the coolant lance being guided through the intermediate shaft. The intermediate shaft is preferably designed as a hollow shaft.

[0018] Advantageously, the shaft train comprises a cardan shaft having torsionally rigid joints, preferably with synchronous operation, such as multi-plate clutches, with which the rotor shaft of the machine and the driven shaft of the loading machine can be coupled and uncoupled, preferably under load, wherein the coolant lance is guided through the cardan shaft having the torsionally rigid joints. Synchronous operation refers to the ability to ensure smooth, synchronous movement or power transmission between the connected parts with essentially no phase shift or speed fluctuations.

[0019] Preferably, the shaft train has a bearing unit for supporting the intermediate shaft and the cardan shaft.

[0020] The coolant lance preferably has at least one joint that connects two adjacent lance sections to one another in an articulated manner. The coolant lance is therefore preferably a multi-part lance.

[0021] It is preferred if two adjacent lance sections have different diameters, the lance sections being provided so as to overlap at the joint point, with at least one O-ring (in particular comprising an elastomer material) preferably being clamped in the gap between the two lance sections. The shaft train (in particular the cardan shaft) preferably has at least one joint point. The coolant lance preferably has a joint point in each joint point of the shaft train (in particular the cardan shaft) and / or the loading machine itself. The coolant lance is preferably divided into several lance sections at each joint point of the shaft train or the cardan shaft and joined together in an articulated manner. This can prevent distortion. The joining area between the lance sections preferably has play between overlapping diameters.This clearance is preferably sealed with O-rings. Due to their elastic properties, these can simultaneously ensure axial, lateral, and angular compensation between the lance sections. Likewise, the O-rings, which are preferably preloaded in the gap, can prevent the lance sections from twisting relative to each other (e.g., due to the frictional torque of the bearings).

[0022] It is advantageous if the coolant lance is mounted in the drivable rotor of the loading machine and preferably in the shaft train with at least one elastically adjusted bearing (in particular fully functional). The bearing preferably has ball bearings (in particular lubricated for life). The bearing is preferably adjusted by means of springs (e.g. disc springs). This can prevent the rolling elements from sliding in the ball bearings, which are otherwise only subject to minimal external load. The elastic adjustment should ensure that this bearing preload is maintained even when there are large temperature differences between the coolant lance and the rotating shaft train (e.g. cold oil flows through the coolant lance while the drivable rotor of the loading machine gets hot during continuous operation).These fully supported lance sections are preferably connected by spacers of appropriate length, which are supported at both ends in the joint points described above.

[0023] It is advantageous if the coolant lance has a double-walled tube (particularly with an air layer in between), with O-rings preferably being provided in the gap between the two tubes. The O-rings in the gap between the tubes prevent the inner tube from fitting into the outer tube on one side. This insulating design minimizes condensation on the outside of the lance and protects the rolling bearings from the extreme temperatures of the medium flowing through it. The coolant lance preferably has one or more steel tubes.

[0024] The device preferably comprises a flow meter for measuring a volume flow of the coolant. The flow meter is preferably configured to measure the volume flow before the coolant enters the coolant lance (e.g., in an external conditioning unit).

[0025] The device preferably has a thermometer for measuring a temperature of the coolant. The thermometer is preferably set up to measure the temperature of the coolant in a region of the coolant lance which, in the coupled state, lies within the rotor shaft, and / or in the region of the tip of the coolant lance. The tip of the coolant lance is that end of the coolant lance which is intended to lie in the rotor shaft. The thermometer is preferably guided through the entire coolant lance. Due to the long lance length, it is advantageous if the temperature of the medium flowing through is only measured at the lance outlet in the test object. A holder is preferably provided in the coolant lance which holds a measuring tip of the thermometer coaxially in a center of the coolant lance.To prevent the measuring tip from touching the inner wall of the pipe and thus distorting the measurement, the ring is held coaxially in the center of the pipe, particularly with a plastic ring. Particularly with longer lances, these plastic rings can be placed multiple times along the entire length to reduce deflection of the stainless steel jacket. The plastic rings preferably have axial openings for the passage of the coolant, with the axial openings preferably making up at least half the cross-section of the coolant lance cavity. The thermometer is, in particular, a resistance thermometer.

[0026] It is advantageous if the driven shaft can be coaxially coupled to the rotor shaft. The invention also relates to a machine test bench, in particular an engine test bench, comprising the device according to this disclosure. The device or the machine test bench is preferably configured to test the power, torque, and / or behavior of the machine.

[0027] The invention further relates to the combination of the device according to this disclosure and the machine to be tested, wherein the rotor shaft is coupled to the drivable shaft of the loading machine for torque transmission and wherein a tip of the coolant lance is provided in the rotor shaft of the machine to be tested.

[0028] With reference to the method according to the invention , it is advantageous if it further comprises the step of measuring a temperature of the coolant in a region of the coolant lance which lies within the rotor shaft .

[0029] The method preferably further comprises the step of measuring a volume flow of the coolant. The method preferably further comprises the step of measuring a rotational speed of the rotor shaft.

[0030] The invention is explained in more detail below with reference to a preferred embodiment shown in the figure.

[0031] Fig. 1 shows schematically a preferred embodiment of the device for testing a rotating electrical machine.

[0032] Fig. 1 shows schematically a preferred embodiment of the device 1 for testing a rotating electrical machine 2, as well as the machine 2 to be tested coupled to the device 1. The device 1 is in particular part of an engine test bench. The rotating electrical machine 2 is in particular an electric motor and has a liquid-cooled rotor with a rotor shaft 3. The device has a loading machine 4 with a drivable shaft 5 for exerting a torque on the rotor shaft 3. The drivable shaft 5 can be coupled to the rotor shaft 3 for torque transmission and is therefore rotationally fixed, or coupled in Fig. 1. The drivable shaft 5 is a hollow shaft and a coolant lance 6 is guided through the drivable shaft 5 of the loading machine 4, so that coolant can be supplied to the rotor shaft 3 of the machine 2 to be tested. The tip 12 of the coolant lance 6 lies within the rotor shaft 3 of the machine 2 .Thus, coolant can be supplied to the liquid-cooled rotor without affecting its operating characteristics, i.e., as similar as possible to the coolant supply during operation of the machine 2, for example, via a gearbox. The drivable shaft 5 is coaxially coupled to the rotor shaft.

[0033] The driven shaft 5 can be coupled to the rotor shaft in a rotationally fixed manner via the shaft train 7. The shaft train 7 is hollow and the coolant lance 6 is also guided through the axial cavity of the shaft train 7. The shaft train 7 has an intermediate shaft 13 which can be coupled to the rotor shaft 3 via a toothing. In addition, the shaft train 7 has a cardan shaft 8 which has torsionally rigid joints with synchronous running properties such as multi-plate clutches 9, with which the rotor shaft 3 of the machine 2 and the driven shaft 5 of the loading machine 4 can be coupled and uncoupled, in particular under load. Furthermore, the shaft train 7 has a bearing unit 10 for supporting the intermediate shaft 13 and the cardan shaft 8. The intermediate shaft 13 and the cardan shaft 8 are each hollow shafts. The coolant lance is guided through the entire shaft train 7 , i.e. through the intermediate shaft 13 , the bearing unit 10 and the cardan shaft 8 .

[0034] The coolant lance 6 is mounted in the drivable rotor 5 of the loading machine 4 and in the shaft train 7 at several points by means of an elastically adjusted bearing 11. In addition, the coolant lance has several joint points (not shown), which each connect two adjacent lance sections to one another in an articulated manner. The two adjacent lance sections each have different diameters, with the lance sections being provided so as to overlap at the joint point. At least one O-ring is clamped in the gap between the two lance sections. The coolant lance 6 has a double-walled tube, with O-rings being provided in the gap between the two tubes. In addition, the device has a flow meter (not shown) for measuring a volume flow of the coolant and a thermometer (not shown) for measuring a temperature of the coolant.

Claims

Patent claims:

1. Device (1) for testing a rotating electrical machine (2), in particular an electric motor, wherein the machine (2) has a rotor with a rotor shaft (3), comprising a loading machine (4) with a drivable shaft (5) for exerting a torque on the rotor shaft (3), wherein the drivable shaft (5) can be coupled to the rotor shaft (3) of the machine (2) for torque transmission, characterized in that the drivable shaft (5) is a hollow shaft and a coolant lance (6) is guided through the drivable shaft (5) of the loading machine (4) so that coolant can be supplied to the rotor shaft (3) of the machine (2) to be tested.

2. Device (1) according to claim 1, comprising a shaft train (7), wherein the drivable shaft (5) can be coupled to the rotor shaft (3) via a shaft train (7), wherein the coolant lance (6) is guided through the shaft train (7).

3. Device (1) according to claim 2, wherein the shaft train (7) has at least one hollow shaft through which the coolant lance (6) is guided.

4. Device (1) according to one of claims 2 and 3, wherein the shaft train (7) has an intermediate shaft (13) which can be coupled to the rotor shaft (3) via a toothing, wherein the coolant lance (6) is guided through the intermediate shaft (13).

5. Device (1) according to one of claims 2 to 4, wherein the shaft train (7) has a cardan shaft (8) which has torsionally rigid joints, wherein the rotor shaft (3) of the machine (2) and the drivable shaft (5) of the loading machine (4) can be coupled and uncoupled preferably with the cardan shaft (8) under load, wherein the coolant lance (6) is guided through the cardan shaft (8).

6. Device (1) according to claim 4 and 5, wherein the shaft assembly (7) has a bearing unit (10) for supporting the intermediate shaft (13) and the cardan shaft (8).

7. Device (1) according to one of the preceding claims, wherein the coolant lance (6) has at least one joint point which connects two adjacent lance sections to one another in an articulated manner.

8. Device (1) according to claim 7, wherein two adjacent lance sections have different diameters, wherein the lance sections are provided overlapping at the joint point, wherein preferably at least one O-ring is clamped in the gap between the two lance sections.

9. Device (1) according to one of the preceding claims, wherein the coolant lance (6) is mounted in the drivable rotor (5) of the loading machine (4) and preferably in the shaft train (7) with at least one elastically adjusted bearing (11).

10. Device (1) according to one of the preceding claims, wherein the coolant lance (6) has a double-walled tube, preferably with O-rings provided in the gap between the two tubes.

11. Device (1) according to one of the preceding claims, wherein the drivable shaft (5) can be coupled coaxially to the rotor shaft (3).

12. Machine test bench, in particular engine test bench, comprising the device (1) according to one of the preceding claims.

13. Combination of the device (1) according to one of claims 1 to 11 and the machine to be tested (2), wherein the rotor shaft (3) is coupled to the drivable shaft (5) of the loading machine (4) for torque transmission and wherein a tip (12) of the coolant lance (6) is provided in the rotor shaft (3) of the machine to be tested (2).

14. Method for testing a rotating electrical machine (2), in particular an electric motor, wherein the machine (2) a rotor with a rotor shaft (3), comprising the steps: - coupling the rotor shaft (3) to a drivable shaft (5) of a loading machine (4) for torque transmission between the rotor shaft (3) and the drivable shaft (5); - driving or braking the rotor shaft (3) with the machine (2); - exerting a torque with the drivable shaft (5) on the rotor shaft (3); - Supplying coolant into the rotor shaft (3) with a coolant lance (6) which is guided through the drivable shaft (5), wherein the drivable shaft (5) is a hollow shaft.

15. The method of claim 14, further comprising the step: - Measuring a temperature of the coolant in an area of the coolant lance (6) which lies within the rotor shaft (3).

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