Electric traction machine

Abstract

Traction machine comprising a bearing system (10) with a rotor (22) and a stator (16), wherein the bearing system (10) is a combination of at least one bearing (11a, 11b) for the rotor (22) arranged on a rotor shaft (23), a cooling system (12) and an insulation system (13), characterized in that the at least one bearing (11a, 11b) is designed as a plain bearing, wherein the plain bearing comprises at least one bearing shell which is firmly locked in a bearing, and the cooling system (12) is set up and designed to cool at least one plain bearing and / or the rotor (22) or a rotor shaft (23) of the rotor (22), wherein the cooling system (12) comprises the plain bearing and uses it to guide an oil for cooling into the plain bearing and the rotor (22), wherein an oil film or an oil volume flow is fed via bores (26) in the bearing shell into a lubricating gap (25) and via holes in the rotor (22) into the rotor shaft (23).

Description

[0001] The present invention relates to an electric traction machine with a special bearing system.

[0002] Today, electric traction machines are exclusively equipped with roller bearings. Along with the organic insulation materials of the electrical components, the roller bearings of electric traction machines are usually the cause of premature drive failures.

[0003] One reason for this is the electromagnetic operating environment of a bearing in the bearing system, in which the rolling bearing has the critical disadvantage of stochastic contact between the rotor and stator. The associated discharge processes and currents circulating through the bearing attack the bearing and cause its premature failure. Furthermore, rolling bearings are only partially suitable for the demanding speed requirements that modern high-speed drives in the automotive sector must meet.

[0004] A rotating unit for a medical imaging device is known from document DE 10 2013 215 806 A1. Such a rotating unit comprises at least one stator, at least one rotor, and at least part of a circulation system for circulating a liquid bearing medium. The rotor is supported or supported hydrostatically by the bearing medium relative to the stator. The document thus discloses a hydrostatic plain bearing concept in medical technology.

[0005] Document DE 10 2012 209 812 A1 discloses a rotor mounted on a rotor shaft in a rotationally fixed manner. The rotor shaft is mounted in a plain bearing for operational rotation relative to the stator. The stator is arranged in a housing of the machine. The bearing is designed as an oil-lubricated plain bearing, an oil-tight closed bearing, a hydrodynamic plain bearing, or a hydrostatic plain bearing. An oil pump is assigned to the bearing and pumps lubricating oil into the plain bearing when the rotor is accelerated from a standstill. The document thus discloses an integrated cooling concept for a rotor of electric traction machines.

[0006] Document DE 3 736 390 A1 discloses that, in a plain bearing arrangement comprising a radial plain bearing and an axial (thrust) plain bearing, fresh, cooled lubricant is also supplied to the axial plain bearing, which lubricant can be mixed with the escaping hot lubricant. Thus, bearing cooling is disclosed.

[0007] Document AT 509 624 A1 discloses a wind turbine with a rotor and a generator. A gear, in particular a planetary gear, is arranged between the rotor and the generator and is operatively connected to the rotor and the generator. The gear comprises several gear wheels, in particular planetary gears, each mounted on an axle via a plain bearing, and an oil supply for lubricating the running surfaces of the plain bearings. The lubrication is implemented purely hydrodynamically without hydrostatic support. The document thus discloses a bearing arrangement for planetary gears of a wind turbine gearbox.

[0008] The document US 4294494 A discloses a special type of plain bearing for high-speed machines.

[0009] Document DE 11 02 271 A discloses an arrangement for limiting bearing currents in electrical machines. If the machine bearings are not insulated from the foundation, bearing currents arise as a result of such induction voltages, since the machine shaft, the bearing supports, and the foundation form a closed circuit in this case. This circuit can be suddenly interrupted by the oil film in the bearings, leading to the formation of a high induction voltage with flashovers in the bearings.

[0010] The document JP H06 272 708 A concerns an improvement of the piston cooling system of an internal combustion engine.An increase in the strength of a connecting rod while maintaining the lubricity in the large end part of the connecting rod is achieved by forming an oil passage inside a connecting rod on the center line of the connecting rod, and forming an inner circumferential groove of the large end part on the inner peripheral surface of a large end part, which extends forward in the rotational direction from the opening of the oil passage inside the connecting rod, and forming a metallic oil hole in a bearing metal so as to face the front end in the rotational direction of the inner circumferential groove, and forming a crank pin bearing groove in a crank pin, which communicates with the metallic oil hole within a prescribed rotational angle range including the top dead center of a piston, and further forming an oil passage inside the crankshaft with the crank pin bearing groove.

[0011] It is an object of the present invention to provide a system that improves the service life and reliability of traction machines and also meets required tree space and cooling requirements.

[0012] This object is achieved by a traction machine according to claim 1. Advantageous further developments and embodiments are the subject of the description and the description of the figures.

[0013] The present invention relates to an electric traction machine with a bearing system having a rotor and a stator, wherein the bearing system is a combination of at least one bearing for the rotor arranged on a rotor shaft, a cooling system, and an insulation system. A traction machine comprising such a bearing system offers the advantage that a traction machine designed in this way has a longer service life and higher reliability than, for example, rolling bearings.

[0014] According to the invention, the at least one bearing is designed as a plain bearing, wherein the plain bearing comprises at least one bearing shell which is firmly locked in a bearing, and the cooling system is set up and designed to cool at least one plain bearing and / or the rotor or a rotor shaft of the rotor, wherein the cooling system comprises the plain bearing and uses it to guide an oil for cooling into the plain bearing and the rotor, wherein an oil film or an oil volume flow, analogous to the implementation in internal combustion engines, reaches a lubricating gap via bores in the bearing shell and the rotor shaft via bores in the rotor. The bearing system comprises the bearing for the rotor arranged on a rotor shaft. The rotor shaft is rotatably mounted or arranged in the bearing relative to the stator. The stator is generally arranged in a housing of the traction machine.

[0015] The storage system thus includes the cooling system and the insulation system. The cooling system and the insulation system are therefore formed from components of the storage system. One component of the storage system is the bearing. Combining a bearing with a cooling system and an insulation system offers the advantage that the effects of a storage concept or storage system are compatible with the effects of an insulation concept or insulation system and a cooling concept or cooling system.

[0016] Overall, the bearing system offers a long service life and high reliability. Furthermore, the bearing system features low acoustics and low vibration. The bearing system also features improved cooling and power availability, as well as increased continuous performance.

[0017] The plain bearing typically comprises at least one bearing shell, which is firmly locked in a bearing. Oil is pressed into the plain bearing through a bore in the bearing shell. During normal operation, the rotor shaft slides over the oil or oil film without touching the bearing shell.

[0018] The plain bearing is therefore usually designed as an oil-lubricated plain bearing or an oil-tight sealed bearing. Typically, the plain bearing is associated with an oil pump designed to pump lubricating oil or oil into the plain bearing, for example, when the rotor is accelerated from a standstill. The use of a plain bearing in the traction machine contributes to an increase in the service life and reliability of the bearing system, among other things, due to the reduced wear.

[0019] In one embodiment, the at least one plain bearing is designed hydrodynamically. Hydrodynamic means that a lubricant pressure of the oil in the plain bearing is automatically generated during operation of the plain bearing at the point where the force is transmitted between the two bearing parts. Alternatively, the at least one plain bearing is designed hydrostatically.

[0020] The plain bearing typically includes a lubrication gap, which is usually formed in the bearing shell of the plain bearing. The lubrication gap is designed to accommodate the oil introduced into the plain bearing via the bore. The resulting lubricating film or fluid film in the area of ​​the lubrication gap allows the rotor to slide independently of the stator.

[0021] By decoupling the rotor and stator with the help of the fluid film or oil film in between, the requirements for the plain bearing to withstand both the electromagnetic working environment and very high speeds are met far better than with currently used rolling bearings.

[0022] In this design, the cooling system and the insulation system are integrated into the bearing system. The components already present in the bearing system are used for the cooling system and the insulation system. In particular, the plain bearing is used for the implementation of the cooling system and the insulation system. The cooling system and the insulation system are thus characterized by a high degree of functional integration.

[0023] The cooling system is configured and designed to cool at least one plain bearing and / or the rotor or rotor shaft of the rotor. The existing components of the bearing system, such as the plain bearing, are used for cooling.

[0024] The cooling system thus encompasses the plain bearing and uses the plain bearing to supply cooling oil to the plain bearing and rotor. The fluid or oil is introduced into the plain bearing and rotor via bores, particularly small tap holes, in the rotor and the plain bearing. The fluid or oil can thus actively cool the plain bearing and rotor. This improves the cooling performance of critical components, such as the winding head and the rotor's short-circuit ring.

[0025] The oil or lubricating oil introduced through the bores can optionally be cooled, providing additional cooling of the rotor or rotor shaft. The introduced oil and the resulting oil film thus enable targeted heat dissipation from critical active components of electric traction machines.

[0026] Alternatively, the bearing system can be configured and designed to perform air gap cooling if a sufficient air gap height is present. The housing of the traction machine and / or the rotor can comprise an air gap that is configured and designed to guide an air flow for cooling the rotor around critical components, such as the winding head of the rotor.

[0027] In one embodiment, the insulation system is configured and designed to insulate the rotor shaft of the rotor using an insulating oil. The insulation system is formed from components of the bearing system. The insulation system comprises at least the plain bearing and a bore in a bearing shell of the plain bearing or the rotor, through which the oil can be introduced into the rotor or the plain bearing.

[0028] The oil film or oil flow, similar to the implementation in internal combustion engines, enters the lubrication gap via the bores in the bearing shell and the hollow shaft via bores in the rotor. Since the oil flows into the housing at virtually zero pressure at the respective outlet points and collects at the bottom, only a simple sealing of the housing from the environment is necessary. A reverse oil flow direction is also conceivable. The oil isolates the rotor from the stator.

[0029] The insulation system with the fluid film or oil film thus creates insulation between the rotor and stator, which, among other things, contributes to reduced wear on the plain bearings and thus reduced acoustics. The cooling system and the insulation system are usually connected, with oil being used to cool and insulate the bearing system.

[0030] In a further development of the invention, the bearing system comprises two plain bearings, wherein a first plain bearing is formed at an output-side end of the rotor and a second plain bearing is formed at an opposite end of the rotor.

[0031] In a further development, the first plain bearing is a thrust bearing and the second plain bearing is a main bearing. In an alternative embodiment, the first plain bearing is designed as the main bearing and the second plain bearing is designed as a thrust bearing. In a further alternative embodiment, the first plain bearing and the second plain bearing can each be designed as main bearings or both as thrust bearings. The two plain bearings ensure low-wear maintenance of the rotational degree of freedom and absorb radial and axial forces.

[0032] In a further development, at least one plain bearing is designed as a fixed bearing and at least one plain bearing is designed as a floating bearing. In one embodiment, the first plain bearing can be designed as a fixed bearing, while the second plain bearing is designed as a floating bearing. In an alternative embodiment, the first plain bearing is designed as a floating bearing and the second plain bearing is designed as a fixed bearing.

[0033] In a further embodiment, the first plain bearing and the second plain bearing are each designed as a fixed bearing or as a floating bearing. Optionally, the bearing system can include a B-side thrust bearing if an input shaft in a flange-mounted gearbox is designed with a two-point bearing.

[0034] The invention is schematically illustrated by means of embodiments in the drawing and will be further described with reference to the drawing, wherein like components are designated by like reference numerals. It shows: Fig. 1 a side view of an embodiment of the bearing system with two plain bearings with a driven-side thrust bearing for absorbing axial forces, Fig. 2 a side view of a structure of the - in Fig. 1 - storage system with an integrated cooling system, Fig. 3 a simplified representation of a mechanical decoupling of a rotor by eliminating a rolling element, Fig. 4 a simplified representation of an electrical decoupling of a rotor from a stator via a lubrication gap, Fig. 5 a simplified representation of an evaluative comparison of a rolling bearing and a plain bearing system with regard to requirements in electric traction machines.

[0035] Fig. Figure 1 shows a side view of a bearing system 10 with two plain bearings 11a and 11b and a thrust bearing 18 on the output side for absorbing axial forces. The bearing system 10 for an electric traction machine is thus a combination of at least one bearing 11, here, for example, the bearing 11a shown, a cooling system 12, and an insulation system 13.

[0036] The Fig. The bearing system 10 shown in Figure 1 comprises the bearing 11a for a rotor 22 arranged on a rotor shaft 23. The rotor shaft 23 is rotatably mounted or arranged in the bearing 11a relative to a stator. The bearing system 10 also comprises the cooling system 12 and the insulation system 13. The cooling system 12 and the insulation system 13 are formed from components of the bearing system 10. One component of the bearing system 10 is, for example, the bearing 11a. By integrating the cooling system 12 and the insulation system 13 into the bearing 11a, a bearing concept or bearing system can be combined with the effects of an insulation concept or insulation system 13 and a cooling concept or cooling system 12. Alternatively, a component of the bearing system 10 can be the bearing 11b.

[0037] In particular, in the Fig. 1 shows two plain bearings 11a, 11b, one at the output end of the rotor 22 designed as a thrust bearing 18 and one at the opposite end of the rotor 22 designed as a main bearing 17.

[0038] The two plain bearings 11a, 11b ensure low-wear rotational freedom and absorb radial and axial forces of a traction machine. It is shown that in the present embodiment, the plain bearing 11a is designed as a fixed bearing 19 and the plain bearing 11b is designed as a floating bearing 20. In alternative embodiments, the plain bearing 11a can be designed as a floating bearing 20 and the plain bearing 11b can be designed as a fixed bearing 19.

[0039] The arrangement of fixed bearing 19 and floating bearing 20 can thus be reversed. Depending on the drive concept or traction machine, it is also conceivable that at least one plain bearing 11a or 11b is supported only by a B-side thrust bearing, provided that the input shaft in the flange-mounted gearbox is designed with a two-point bearing.

[0040] The insulation system 13 includes a lubrication gap 25. An oil can be guided across the lubrication gap 25 as an insulating layer. The oil, or rather the oil volume flow, enters the lubrication gap 25 via bores 26 in the bearing shell of the plain bearing 11a, 11b, as well as through the bores 26 into the cavity 24. Since the oil flows into the rotor shaft 23 at virtually no pressure at the respective outlet points and collects at the bottom, only a simple seal of the bearing system 10 from the environment is necessary. A reverse oil flow direction is also conceivable.

[0041] As a rule, an initial oil pressure p 1 in at least one of the plain bearings 11a, 11b is greater than a second oil pressure p 2 in the cavity 24, wherein he second oil pressure p 2 is usually greater than an atmospheric pressure p 0 Thus, p 1 > p 2 > p 0 . The atmospheric pressure p 0 is usually 1 bar. In the Fig. 1 are also the forces F A,X , F A,Y and F B,Y which act on the bearings 11a and 11b respectively.

[0042] Fig. 2 shows a side view of a structure of the - in Fig. 1 - storage system 10 with an integrated cooling system 12.

[0043] Fig. 2 shows the use of the same bearing system 10 for cooling the traction machine components rotor 22, bearings, in particular the bearing 11a shown here and winding head 14. In the Fig. In the cooling system 13 shown in Figure 2, the bores 26 in the housing of the traction machine or in the rotor 22 ensure improved cooling of critical components such as the winding head 14 and short-circuit ring 15 or the rotor core 28 via the introduced oil.

[0044] Air gap cooling via air gaps 21 is also conceivable if the air gap height is sufficient. Air or an air flow for cooling can be guided via the air gaps 21 over the rotor 22, in particular over a winding head 14. In an alternative embodiment, the cooling system 12 can be provided using the Fig. 1 - bearing 11b.

[0045] Fig. Figure 3 shows a simplified representation of a mechanical decoupling of the rotor 22 by eliminating a rolling element. Due to the principle, this also results in mechanical decoupling and electrical insulation of the rotor 22 from the stator 16. The electrical insulation of the rotor 22 can thus be ensured by the properties of the oil.

[0046] Fig. 4 shows a simplified representation of an electrical decoupling of the rotor 22 from the stator 16 via a lubrication gap 25.

[0047] Fig. 5 shows a simplified representation of an evaluative comparison of a roller bearing and a plain bearing bearing system 10 according to the invention with regard to requirements in electric traction machines.

[0048] The requirements include service life, efficiency, cooling, installation space, weight, cost, and acoustics. In terms of service life, the plain bearing has a significantly longer service life than the rolling bearing. The efficiency of a plain bearing and a rolling bearing was assessed as similar. The cooling capacity and weight of the plain bearing are higher than those of the rolling bearing. Compared to the service life and coolability of the plain bearing, a bearing system with a plain bearing is more cost-effective than the previously used rolling bearing. List of reference symbols 10 storage system 11a a first plain bearing 11b a second plain bearing 12 Cooling system 13 Insulation system 14 winding head 15 short-circuit ring 16 Stator 17 main bearings 18 pass camps 19 fixed bearings 20 loose bearings 21 Air gap 22 Rotor 23 Rotor shaft 24 Cavity 25 Lubrication gap 26 holes 27 rolling elements 28 rotor lamination stack

Claims

[1] Traction machine comprising a bearing system (10) with a rotor (22) and a stator (16), wherein the bearing system (10) is a combination of at least one bearing (11a, 11b) for the rotor (22) arranged on a rotor shaft (23), a cooling system (12) and an insulation system (13), characterized by in that the at least one bearing (11a, 11b) is designed as a plain bearing, wherein the plain bearing comprises at least one bearing shell which is firmly locked in a bearing, and the cooling system (12) is set up and designed to cool at least one plain bearing and / or the rotor (22) or a rotor shaft (23) of the rotor (22), wherein the cooling system (12) comprises the plain bearing and uses it to guide an oil for cooling into the plain bearing and the rotor (22), wherein an oil film or an oil volume flow passes via bores (26) in the bearing shell into a lubricating gap (25) and via bores in the rotor (22) into the rotor shaft (23). [2] Traction machine according to claim 1, characterized by that the at least one plain bearing (11a, 11b) is designed hydrodynamically. [3] Traction machine according to one of the preceding claims, characterized by that the cooling system (12) and the insulation system (13) are integrated into the storage system (10). [4] Traction machine according to one of the preceding claims, characterized by that the insulation system (13) is arranged and designed to insulate the rotor shaft (23) of the rotor (22) by using an insulating oil. [5] Traction machine according to one of the preceding claims, characterized by that the bearing system (10) comprises two plain bearings (11a, 11b), wherein a first plain bearing (11a) is formed at an output-side end of the rotor (22) and a second plain bearing (11b) is formed at an opposite end of the rotor (22). [6] Traction machine according to claim 5, characterized bythat the first plain bearing (11a) is a thrust bearing and the second plain bearing (11b) is a main bearing. [7] Traction machine according to one of claims 5 or 6, characterized by that at least one plain bearing (11a, 11b) is designed as a fixed bearing (19) and at least one plain bearing (11a, 11b) is designed as a loose bearing (20).

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