Method for leak testing of a liquid-cooled electric split-ear traction motor

Abstract

The traction motor (10) features: a fluid-tight stator chamber (38) with a motor stator (30), wherein the stator chamber (38) has a fluid inlet (36) and a fluid outlet (37), and a rotor chamber (28) with a motor rotor (20), wherein the rotor chamber (28) has an air inlet (26) and an air outlet (27). The examination order (100) indicates: a test gas source (102) with a detectable test gas (103) which is fluidically connected to the stator chamber fluid inlet (36) via a fluidic inflow control (105), a switchable outlet valve (110) connected to the stator chamber fluid outlet (37), a test gas detector (112) that can detect the test gas (103) and that is fluidically connected to the rotor chamber air outlet (27), and a vacuum gas pump (114) through which rotor chamber air is pumped or drawn from the rotor chamber (28) through the rotor chamber air outlet (27) to the test gas detector (112), and an electronic test control (120) which is connected via signal links to the test gas inflow control (105), the stator chamber outlet valve (110) and the test gas detector (112). The electronic test control (120) generates the following process steps: Introducing the test gas (103) from the test gas source (102) into the stator chamber (38) such that the stator chamber gas pressure (p38) is at a defined above-atmospheric test gas overpressure (ps), and Activating the gas pump (114) and the test gas detector (112), thereby quantitatively detecting leakage test gas flowing into the air-filled rotor chamber (28).

Description

[0001] The invention relates to a method for leak testing of a liquid-cooled electric canned tube traction motor during its manufacture, using an external testing arrangement.

[0002] In a motor vehicle traction motor, even at high system voltages of, for example, 800 V, peak electrical currents of more than 1000 A can flow, causing the heat generated in the stator coils of the motor stator to become so great that liquid cooling of the motor stator is necessary. In a liquid-cooled electric canned-tube traction motor, the motor stator, which contains the stator coils, is directly cooled by means of a circulating coolant, for example, a cooling oil. To prevent damage to the motor rotor or the entire traction motor—caused by fluidic leaks in the stator housing—the fluidic separation of the motor rotor from the motor stator must be perfect from the outset. Such a motor vehicle traction motor is known from DE 10 2021 114 159 A1.

[0003] Methods for leak testing of a fluid-cooled electric motor using a detectable test gas are known from DD 120 546 A1 and DE 2 154 979 A.

[0004] From DE 1 167 435 A, an electric machine is known in which the tightness of the stator compartment is continuously monitored during operation. However, this method cannot prevent the installation of a traction motor that is already leaking.

[0005] In contrast, the object of the invention is to create a fast and easy-to-implement testing method for leak testing of a liquid-cooled electric canned tube traction motor during motor manufacturing.

[0006] This problem is solved according to the invention by a method having the features of claim 1.

[0007] The method for leak testing a liquid-cooled electric canned tube traction motor using an external test setup comprises a traction motor and the external test setup.

[0008] The traction motor features a fluid-tight stator chamber containing a motor stator with multiple electrical stator coils. For liquid cooling of the motor stator, the stator chamber has a fluid inlet and a separate fluid outlet, allowing a fluid, such as cooling oil, to flow through the motor stator during operation. This enables heat to be continuously or as needed dissipated from the immersion-cooled stator coils. The stator chamber is fluid-tightly separated from a rotor chamber, in which the motor rotor is mounted for rotation, by a so-called canned tube. The motor rotor can be, for example, a permanent magnet rotor. The motor rotor is not liquid-cooled. The rotor chamber has an air inlet and a separate air outlet.

[0009] The external test setup includes a test gas source containing a test gas detectable by a test gas detector. The test gas is fluidically connected from the test gas source to the stator chamber fluid inlet via a fluidic flow control, for example, a pressure regulating valve. The test gas can be, for example, helium, argon, CO2, or, particularly preferably, a hydrogen-containing forming gas.

[0010] The test setup also includes a switchable outlet valve that is fluidically connected to the stator chamber fluid outlet. Furthermore, downstream of the rotor chamber air outlet, the test setup features a test gas detector and a vacuum gas pump. This pump draws the rotor chamber gas, consisting of air and, in the event of a leak, additional traces of the test gas, from the rotor chamber air outlet to the test gas detector. The test gas detector can reliably detect even the smallest concentrations of the test gas in the rotor chamber air and thus determine them qualitatively or even quantitatively.

[0011] Finally, the test setup includes an electronic test control unit that is connected via signal links to the test gas supply control, the stator chamber outlet valve, and the test gas detector. The electronic test control unit is designed to initiate the following process steps: First, the test gas is introduced from the test gas source into the stator chamber and pressurized to a defined test gas overpressure, i.e., an absolute stator chamber gas pressure above the ambient atmospheric pressure. The stator chamber gas pressure thus corresponds to atmospheric pressure plus the test gas overpressure. As soon as the defined stator chamber gas pressure, or test gas overpressure, is reached, the gas pump associated with the rotor chamber is activated, pumping or drawing air from the rotor chamber to the test gas detector. In this way, the stator chamber gas pressure is regulated to a value just above ambient pressure, and the measurement phase begins.

[0012] The test gas detector can qualitatively or even quantitatively detect even the smallest concentrations of the leakage test gas, which may be distributed in the rotor chamber air. This allows for a determination of the fluidic tightness of the stator chamber or the canned tube separating the stator chamber from the rotor chamber within a very short time, from a few minutes to less than a minute. Because this type of leak test requires very little time, this method is particularly well-suited for the high-volume production of traction motors, as it does not significantly affect the cycle time.

[0013] Preferably, the test gas detector is a mass spectrometer capable of quantitatively detecting even minute quantities of a test gas. Mass spectrometers represent an established technology that is relatively inexpensive.

[0014] Preferably, the test setup includes a pressure sensor fluidically associated with the stator chamber, which continuously detects the stator chamber gas pressure. The pressure sensor is connected via a wired or wireless signal link to the electronic test controller, which monitors and maintains the stator chamber gas pressure during a test cycle.

[0015] Preferably, the rotor chamber gas pressure during a test cycle is at most atmospheric pressure. The carrier airflow through the rotor chamber is therefore formed by ambient air that is not significantly depressurized.

[0016] Preferably, the absolute stator chamber gas pressure during a test cycle is less than 5.0 bar, and particularly preferably less than 4.0 bar. The test gas overpressure is therefore a maximum of 4.0 bar or 3.0 bar, so that no particularly high demands are placed on pressure generation. For example, the chamber is filled to 4.0 to 1.0 bar, then the pressure is reduced, and the measurement is started.

[0017] The following describes an embodiment of the inventive method for leak testing a liquid-cooled electric canned-tube traction motor with reference to the drawing. The figure schematically shows a test setup for leak testing an electric canned-tube traction motor, including a test arrangement.

[0018] The figure schematically shows a test arrangement 200 for carrying out a method for leak testing a liquid-cooled electric canned tube traction motor 10 using an external test arrangement 100.

[0019] The canned-tube traction motor 10 is an electronically commutated internal rotor motor comprising an annular motor stator 30 and a centrally located, permanent-magnet excited motor rotor 20. Within a motor housing 40, the motor stator 30 has an annular stator chamber 38 in which a plurality of stator coils 32 are arranged circumferentially. The fluid-tight stator chamber 38 is fluid-tightly separated from a substantially cylindrical motor chamber 28, in which the motor rotor 20 is rotatably mounted, by a so-called canned tube 48. The motor rotor 20 includes, among other things, a rotor shaft 22 and a permanent-magnet excited motor rotor body 24, which is held by the rotor shaft 22.

[0020] The motor housing 40 has an air inlet 26 at one longitudinal end of the rotor chamber 28 and an air outlet 27 at the other longitudinal end of the rotor chamber 28, so that a substantially axial airflow can be generated in the rotor chamber 28. The absolute rotor chamber gas pressure p28 in the rotor chamber 28 is approximately atmospheric pressure. The air inlet 26 and / or the air outlet 27 can be temporary openings that can be closed again after completion of the leak test.

[0021] Furthermore, the motor housing 40 has a fluid inlet 36 and a fluid outlet 37 at one longitudinal end of the stator chamber 38. In principle, the fluid inlet and fluid outlet can also be located at opposite longitudinal ends of the annular stator chamber 38. In a traction motor installed in a motor vehicle, a cooling fluid, for example, a cooling oil, flows through the fluid inlet 36 and the fluid outlet 37 to cool the stator coils 32 of the motor stator 30. The stator coils 32 are thus immersion-cooled. However, during the manufacturing process of the canned-tube traction motor 10 described here, the fluid inlet 36 and the fluid outlet 37 are temporarily used for introducing or passing a test gas through the stator chamber 38. A stator chamber gas pressure p38 prevails in the stator chamber 38.

[0022] For this purpose, the stator chamber fluid inlet 36 is temporarily fluidically connected to a test gas source 102 via a switchable inlet control 105. The test gas source 102 is, in this case, a test gas tank 102' in which a detectable test gas 103 is stored under overpressure. The test gas 103 can be helium, argon, or CO2, but is preferably a hydrogen-containing forming gas. The switchable inlet control 105 comprises a controllable gas pump 106 and a switchable 3 / 2-way gas valve 104. The inlet control 105 ensures that the stator chamber 38 can be selectively filled with either test gas 103 or atmospheric air in order to purge residual gas from the stator chamber at the end of the test.

[0023] The external test setup 100 includes, in addition to the test gas source 102 and the fluidic inflow control 105, a test gas detector 112 downstream of the rotor chamber outlet 27, which can detect even the smallest traces of the test gas in air. In this case, the test gas detector 112 is a mass spectrometer. Downstream of the test gas detector 112, a suction gas pump 114, fluidically connected to the detector 112, is provided, which generates a continuous airflow through the rotor chamber 28 and the test gas detector 112 during testing. A switchable stator chamber outlet valve 110 is provided downstream of the stator chamber fluid outlet 37. Furthermore, a pressure sensor 118 is provided in the fluid line between the stator chamber fluid outlet 37 and the stator chamber outlet valve 110, which detects the stator chamber gas pressure p38.

[0024] The external test arrangement 100 also includes an electronic test control 120, which is connected via cables or wirelessly to the gas pumps 106, 114, the switchable 3 / 2 way gas valve, the stator chamber outlet valve 110, the pressure sensor 118 and the test gas detector 112.

[0025] For a leak test of the traction motor 10, it is first fluidically connected to the test setup 100 via suitable quick-release couplings or automatically supplied sealing elements, as shown in the figure. The test gas 103 is then introduced from the test gas source 102 into the stator chamber 38 or pumped by the gas pump 106, with the stator chamber outlet valve 110 initially open to expel the air from the stator chamber 38. This ensures a high test gas concentration in the stator chamber 38.

[0026] Finally, the stator chamber outlet valve 110 is closed and an absolute stator chamber gas pressure p38 of, for example, 3.0 bar is set. Subsequently, the test gas detector 112 and the gas pump 114 fluidically associated with the test gas detector 112 are switched on, and the measurement signals from the test gas detector 112 are evaluated by the electronic test control 120. If no significant concentration of test gas is detected in the airflow passing through the test gas detector 112, sufficient fluidic tightness of the stator chamber 38 with respect to the rotor chamber 28 can be assumed.

Claims

[1] Method for leak testing of a liquid-cooled electric canned tube traction motor (10) using an external test arrangement (100), wherein the traction motor (10) comprises: a fluid-tight stator chamber (38) with a motor stator (30), wherein the stator chamber (38) has a fluid inlet (36) and a fluid outlet (37), and a rotor chamber (28) with a motor rotor (20), wherein the rotor chamber (28) has an air inlet (26) and an air outlet (27), the examination order (100) includes: a test gas source (102) with a detectable test gas (103) which is fluidically connected to the stator chamber fluid inlet (36) via a fluidic inflow control (105), a switchable outlet valve (110) connected to the stator chamber fluid outlet (37), a test gas detector (112) that can detect the test gas (103) and that is fluidically connected to the rotor chamber air outlet (27), and a gas pump (114) through which rotor chamber air is pumped from the rotor chamber (28) through the rotor chamber air outlet (27) to the test gas detector (112), and an electronic test control (120) which is connected via signal connections to the test gas inflow control (105), the stator chamber outlet valve (110) and the test gas detector (112), with the process steps controlled by the electronic test control (120): Introducing the test gas (103) from the test gas source (102) into the stator chamber (38) such that the stator chamber gas pressure (p38) is at a defined above-atmospheric test gas overpressure, and Activating the gas pump (114) and the test gas detector (112), thereby detecting leakage test gas flowing from the stator chamber (38) into the air-filled rotor chamber (28). [2] Method for leak testing according to claim 1, wherein the test arrangement (100) has a pressure sensor (118) fluidically associated with the stator space (38), wherein the electronic test control (120) monitors and keeps constant the stator space gas pressure (p38) during a test cycle via the pressure sensor (118). [3] Method for leak testing according to one of the preceding claims, wherein a rotor chamber gas pressure (p28) of maximum atmospheric pressure prevails in the air-filled rotor chamber (28) during a test cycle. [4] Method for leak testing according to any of the preceding claims, wherein the test gas detector (112) is a mass spectrometer [5] Method for leak testing according to any of the preceding claims, wherein the test gas is a hydrogen-containing forming gas or helium. [6] Method for leak testing according to one of the preceding claims, wherein the stator chamber gas pressure (p38) is less than 5.0 bar, preferably less than 4.0 bar.

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