Electric machine, vehicle and manufacturing method

Abstract

The disclosure concerns an electric machine (4) comprising a rotor shaft (20), a rotor body (24) arranged on the rotor shaft (20), a bearing (30), a housing (28), and a grounding ring (32). The bearing (30) is arranged on the rotor shaft (20) and the rotor shaft (20) is journaled in relation to the housing (28) via the bearing (30). The grounding ring (32) is fixed in relation to the housing (28) and arranged around the rotor shaft (20) in an axial position along the rotational axis (22) between the bearing (30) and the rotor body (24). A lubricant barrier member (36) is arranged in an axial position along the rotational axis (22) between the bearing (30) and the grounding ring (32). The lubricant barrier member (36) has an annular shape and a radial extension in relation to the rotational axis (22).

Description

[0001] ELECTRIC MACHINE, VEHICLE AND MANUFACTURING METHOD

[0002] TECHNICAL FIELD

[0003] The invention relates to an electric machine, to a vehicle comprising an electric machine, and to a method for assembling a portion of an electric machine.

[0004] BACKGROUND

[0005] In an electric machine, such as an electric machine used in an electric or hybrid vehicle, so- called shaft voltages or bearing currents can cause electric discharge in the bearings of the electric machine. Also gears of a transmission connected to the electric machine may be subjected by such electric discharge. The electric discharge causes surface damage, which can lead to severe damage to the relevant parts, and which can eventually lead to failure of the electric machine.

[0006] In order to protect parts, such as bearings and gears, grounding solutions are implemented in electric machines to prevent electric discharge.

[0007] One such solution includes a so-called grounding ring, which is arranged to lead electric current from the shaft of the electric machine to a grounded portion of the electric machine, such as to the housing of the electric machine. The grounding ring includes one or more electrically conductive members, such as bristles, which are arranged in contact with the shaft thus, contributing to electrically grounding the shaft.

[0008] US 2010 / 001602 discloses a kit and a method for attaching a grounding ring to an electrical motor. The method may be used to retroactively install a grounding ring on an electrical motor used with an inverter to reduce the likelihood that shaft currents affect motor bearings. The method includes securing a ring of conductive material to an endplate of an electrical motor at a position that enables a shaft extending through the endplate to pass through the ring, the ring of conductive material includes conductive material that extends from the ring to contact the shaft when the ring is secured to the endplate, and covering the ring of conductive material with a bearing cap that has an opening that enables the shaft to pass through the bearing cap. A water slinger and a bearing cap to which the slinger is mounted help form a barrier to debris that may be in the operating environment for the electric motor. SUMMARY

[0009] In order to secure the grounding function of a grounding ring in an electric machine, an interface between the grounding ring and a rotor shaft should not be contaminated with lubricant, such as oil. However, the grounding ring may have to be positioned on the rotor shaft in the vicinity of an oil lubricated / cooled bearing.

[0010] It would be advantageous to achieve a proper grounding function of a grounding ring in an electric machine. In particular, it would be desirable to prevent an interface between the grounding ring and a rotor shaft of the electric machine from being contaminated with oil. To better address one or more of these concerns, one or more of an electric machine, a vehicle, and a method for assembling a portion of an electric machine having the features defined in one or more of the independent claims is provided.

[0011] According to an aspect, there is provided an electric machine comprising a rotor shaft configured to rotate about a rotational axis, a rotor body arranged on the rotor shaft, a bearing, a housing, and a grounding ring. The bearing is arranged on the rotor shaft and the rotor shaft is journaled in relation to the housing via the bearing. The grounding ring is fixed in relation to the housing and arranged around the rotor shaft in an axial position along the rotational axis between the bearing and the rotor body. A lubricant barrier member is arranged in an axial position along the rotational axis between the bearing and the grounding ring. The lubricant barrier member has an annular shape and a radial extension in relation to the rotational axis.

[0012] Since the lubricant barrier member is arranged in the axial position between the bearing and the grounding ring, and since the lubricant barrier member has the annular shape and the radial extension in relation to the rotational axis - the lubricant barrier member prevents liquid lubricant, such as oil, from the bearing to reach the grounding ring.

[0013] In this manner, an electrically grounding contact between grounding ring and the rotor shaft can be kept free from lubricant during use of the electric machine. Thus, formation of an oil film on the rotor shaft at the interface between the grounding ring and the rotor shaft can be avoided. Accordingly, ideal conditions for securing the grounding function of the grounding ring are provided.

[0014] The present arrangement of the lubricant barrier member may provide further advantages, such as: - Preventing lubricant from the bearing reaching an air gap between the rotor body and a stator of the electric machine.

[0015] - Ensuring proper lubrication / cooling of the bearing. This so, since supply of lubricant to the bearing has not to be limited for the sake of preventing lubricant from reaching the grounding ring.

[0016] - Reliable guiding of lubricant from the bearing to lubricant passageways leading away from the bearing.

[0017] According to a further aspect, there is provided a vehicle comprising an electric machine according to any one of aspects and / or embodiments discussed herein.

[0018] As discussed above with reference to the electric machine, the lubricant barrier member prevents lubricant from the bearing to reach the grounding ring. Thus, the electrically grounding contact between the grounding ring and the rotor shaft can be ensured.

[0019] The electric machine may form part of a propulsive system of the vehicle. The electric machine may propel the vehicle and / or the electric machine may form a generator for transforming kinetic energy of the vehicle into electric power to be utilised for charging battery cells of the vehicle.

[0020] Electric energy may be provided to the electric machine from battery cells aboard the vehicle or from a power source external of the vehicle, such as an overhead power line or a rail arranged in, or at, a surface travelled by the vehicle.

[0021] The vehicle may be an electrically propelled vehicle and may be one of a battery electric vehicle (pure electric vehicle) or a hybrid electric vehicle. A further alternative may be that the vehicle is a fuel cell electric vehicle or similar vehicle.

[0022] In an electrically propelled vehicle, battery cells arranged in one or more battery packs may be configured for storing electric energy and for supplying electric power to the electric machine. The battery cells may be charged by mains power via an external or onboard battery charger. Additionally, the battery cells may be charged by electric power generated by the electric machine, as discussed above.

[0023] Herein, references to axial and radial directions are seen in relation to the rotational axis of the electric machine. The rotor shaft and the rotor body of the electric machine are arranged to rotate about the rotational axis in relation to a stator of the electric machine.

[0024] The rotor shaft is arranged to rotate about the rotational axis in relation to the housing of the electric machine.

[0025] The housing may comprise one or more separate parts. The housing may form at least part of a protective encapsulation of at least some components of the electric machine, such as one or more of the rotor body, the rotor shaft, the bearing, and the grounding ring. The housing may at least partially support some components of the electric machine.

[0026] The grounding ring may be arranged directly in the housing or indirectly e.g., via a sleeve member as discussed below.

[0027] The grounding ring being fixed in relation to the housing means that the grounding ring does not rotate together with the rotor shaft. Depending on the manner in which the grounding ring is arranged in the housing, a small relative movement about the rotational axis of the grounding ring may occur during use of the electric machine. However, in comparison with the rotation of the rotor shaft about the rotational axis at hundreds and / or thousands of rotations per minute, the small relative movement of the grounding ring is to be considered as fixed in relation to the housing.

[0028] The annular lubricant barrier member extends around the rotational axis. The lubricant barrier member may have a larger radial extension than an axial extension thereof. Accordingly, it may be seen as ring-shaped or disc-shaped with a central hole, or as having the shape of a washer.

[0029] During use of the electric machine, lubricant, such as oil, from the bearing is prevented from reaching the grounding ring by the lubricant barrier member.

[0030] The lubricant barrier member is arranged to direct lubricant in a radial direction namely, lubricant that has passed the bearing in an axial direction towards the grounding ring. Thus, the lubricant is prevented from reaching the grounding ring.

[0031] The lubricant barrier member may guide lubricant in a direction radially outwardly from the rotor shaft to a lubricant return channel. The lubricant return channel is arranged in fluid communication with an oil reservoir, from which the lubricant is distributed within the electric machine during use thereof.

[0032] The lubricant barrier member may be fixed in relation to the housing or in relation to the rotor shaft.

[0033] A sleeve member may be arranged in the housing and may extend concentrically with the rotational axis, wherein the bearing, the lubricant barrier member, and the grounding ring may be positioned inside the sleeve member.

[0034] The sleeve member may contribute to an efficient assemblage of part of the electric machine e.g., as discussed herein with reference to the method for assembling a portion of an electric machine.

[0035] Moreover, the sleeve member may be utilised for forming at least part of a lubricant directing passageway, such as one or more of a lubricant supply passage and a lubricant return channel as discussed herein.

[0036] According to a further aspect, there is provided a method for assembling a portion of an electric machine, the electric machine comprising a rotor shaft configured to rotate about a rotational axis, a rotor body arranged on the rotor shaft, a bearing, a housing, a grounding ring, a lubricant barrier member, and a sleeve member. The method comprises steps of:

[0037] - fitting the bearing into the sleeve member,

[0038] - positioning the lubricant barrier member in the sleeve member next to the bearing,

[0039] - fitting the grounding ring in the sleeve member next to the lubricant barrier member,

[0040] - placing the sleeve member with the grounding ring closest to the rotor body onto the rotor shaft,

[0041] - fitting the bearing onto the rotor shaft, and

[0042] - fitting the sleeve member into the housing.

[0043] In this manner, an efficient method for mounting the bearing, the lubricant barrier member, and the grounding ring in an electric machine is provided.

[0044] Further features of, and advantages with, the invention will become apparent when studying the appended claims and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Various aspects and / or embodiments of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:

[0046] Fig. 1 illustrates embodiments of a vehicle,

[0047] Fig. 2 schematically illustrates a section through a portion of an electric machine according to embodiments,

[0048] Fig. 3 schematically illustrates a section through a portion of an electric machine according to embodiments, and

[0049] Fig. 4 illustrates a method for assembling a portion of an electric machine.

[0050] DETAILED DESCRIPTION

[0051] Aspects and / or embodiments of the invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.

[0052] Fig. 1 illustrates embodiments of a vehicle 2 configured for land-based propulsion. Fig. 1 represents a schematic sectional top view of the vehicle 2. The vehicle 2 comprises at least one electric machine 4 according to aspects and / or embodiments discussed herein, such as the electric machine 4 discussed below with reference to Figs. 2 - 3.

[0053] In these embodiments, the vehicle 2 is a heavy load vehicle in the form of a truck. However, the invention is not limited to any particular type of vehicle configured for land-based propulsion. The vehicle 2 may be e.g., a bus, a truck, a heavy truck, a car, or a train. The vehicle may alternatively be of another type.

[0054] The vehicle 2 may be an electric vehicle, EV, for example a hybrid electric vehicle, HEV, or a battery electric vehicle, BEV. It is to be noted that the herein discussed electric machine 4 may be utilised in further means of transportation, such as in boats or other marine vessels.

[0055] The at least one electric machine 4 may comprise an electric motor and / or an electric generator. The at least one electric machine 4 may be configured for propelling the vehicle 2. The at least one electric machine 4 may be configured for charging one or more electric battery cells 8 and / or one or more electrical battery packs 12. The vehicle 2 comprises a powertrain 10, for example configured for one of an EV, a HEV, and a BEV. The vehicle 2 may comprise one or more electrical battery packs 12 including two or more electric battery cells 8. The powertrain 10 may include further electrical and / or mechanical components e.g., a combustion engine 14 and / or other devices required for a vehicle 2, such as for an EV, a HEV, or a BEV. A transmission may be provided e.g., as part of, or in connection with, the electric machine 4.

[0056] The powertrain 10 and / or the at least one electric machine 4 is / are configured to propel, or drive, the vehicle 2. The powertrain 10 may include the electrical battery pack 12. The at least one electric machine 4 may be arranged in other positions of the vehicle 2 than shown in Fig. 1. For example, in connection with one or more wheels 16 of the vehicle 2 or in connection with the combustion engine 14 to operate as an electric generator.

[0057] The vehicle 2 may comprise an electrical system 18. The electrical system 18 may be configured for direct current. The electrical system 18 may be a low voltage system such as a 24 Volt system. The electrical system 18 may be a higher voltage system configured for a high voltage such as 48 V or a voltage of 60 V or above for example, 400 V, or 450 V, such as 650 V. For example, the high voltage system may be configured for a voltage up to 1500 V and / or for a voltage above 1500 V. The electric power, or the electric current, for example the direct current, of the electrical system 18 may be transferred for example, at one or more of the voltage levels mentioned above.

[0058] The electrical system 18 may be electrically connected, or connectable, to one or more electrical battery packs 12. The electrical battery packs 12 may be configured for one or more of the voltage levels mentioned above.

[0059] The electrical system 18 may be configured to electrically connect the electrical battery pack 12 to the powertrain 10 of the vehicle 2. The electrical system 18 may be configured for electrically connecting the electrical battery pack 12 to the at least one electric machine 4 of the vehicle 2. The electrical system 18 may be configured to transfer electric power, and / or electric current, e.g., between the at least one electric machine 4 and the electrical battery pack 12.

[0060] Alternatively, the electrical system 18 may be configured for alternating current. A further option may be for the electrical system 18 to be configured in part for direct current and in part for alternating current. According to some embodiments, alternatively, or in addition to the electrical battery pack 12, the electrical system 18 may be fed from an electrical power source external of the vehicle 2, such as an overhead power line or a powered rail arranged in, or at, a travelling surface.

[0061] Fig. 2 schematically illustrates a section through a portion of an electric machine 4 according to embodiments. The electric machine 4 may form part of a vehicle, such as a vehicle 2 discussed above with reference to Fig. 1.

[0062] The electric machine 4 may be operated as an electric motor e.g., for propelling a vehicle and / or as an electric generator e.g., for charging one or more electric battery cells and / or one or more electrical battery packs of a vehicle.

[0063] The electric machine 4 comprises a rotor shaft 20 configured to rotate about a rotational axis 22.

[0064] The rotor shaft 20 is configured for transmitting torque produced by the electric machine 4 to the powertrain of the relevant vehicle and / or or for transmitting torque from the powertrain, such as from an ICE and / or from drive wheels of the vehicle to the electric machine 4.

[0065] A rotor body 24 is arranged on the rotor shaft 20. The rotor body 24 may be directly connected to the rotor shaft 20. For instance, the rotor body 24 may be connected to the rotor shaft 20 via a splined connection including internal and external splines (not shown).

[0066] The rotor shaft 20 may comprise two or more shaft portions (not shown). For instance, two or more shaft portions may be connected to each other and / or to the rotor body 24 via splined connections including internal and external splines. For instance, a portion of the rotor shaft 20 may extend from the rotor body 24.

[0067] The rotor shaft 20 may comprise concentrically arranged shaft portions, such as in the form of one or more sleeves and / or collars arranged on the rotor shaft 20. Such concentrically arranged shaft portions may be provided for various operational functions of the electric machine 4 and / or associated with the mounting of the rotor shaft 20 in the electric machine 4 and / or with the mounting of components on the rotor shaft 20.

[0068] In a known manner, the electric machine 4 comprises a stator 26. The body rotor 24 may include one or more permanent magnets. Thus, the electric machine 4 may be a permanent magnet, PM, machine. According to alternative embodiments, the electric machine 4 may be configured to operate according to other electrical operation schemes for electric machines. For example, the rotor body 24 may include one or more rotor windings. Conventional electrical operation schemes for electric machines are known to the skilled person and thus, are not discussed herein in further detail.

[0069] The electric machine 4 comprises a housing 28. In the housing 28, inter alia the rotor shaft 22, the rotor body 24, and the stator 26 are arranged.

[0070] The electric machine 4 comprises a bearing 30 and a grounding ring 32. The rotor shaft 20 is directly or indirectly journalled in the housing 28 via the bearing 30 i.e., the bearing 30 is arranged on the rotor shaft 20 and the rotor shaft 20 is journaled in relation to the housing 28 via the bearing 30.

[0071] In the embodiments of Fig. 2, the bearing 30 is arranged in a seat 34 formed in the housing 28.

[0072] The bearing 30 may be a rotary bearing comprising an inner ring configured to rotate with the rotor shaft 20 and an outer ring configured to be stationary in relation to the housing 28.

[0073] Such bearings are commonly known and may be e.g., a ball bearing or a roller bearing.

[0074] The rotary bearing requires lubrication and often cooling by a lubricant, such as oil, to ensure its proper operation. Accordingly, a lubricant is supplied to the bearing 30 e.g., as discussed below.

[0075] Further bearings (not shown) may be provided for journaling the rotor shaft 20 and / or the rotor body 24.

[0076] The grounding ring 32 is fixed in relation to the housing 28 and is arranged around the rotor shaft 20 in an axial position along the rotational axis 22 between the bearing 30 and the rotor body 24. In the illustrated embodiments, the grounding ring 32 is arranged in the seat 34 formed in the housing 28.

[0077] The grounding ring 32 is provided as a protective measure to prevent electric discharge via e.g., the bearing 30. As such, the grounding ring 32 forms part of an electric conductive path from the rotor shaft 20 to the housing 28. In a known manner, the grounding ring 32 comprises one or more electrically conductive members, such as bristles, which are arranged in contact with the rotor shaft 20.

[0078] The rotor shaft 20 may comprise a sleeve (not shown) arranged in an axial position of the grounding ring 32. The sleeve may be configured for ensuring a proper electrically conductive connection between the rotor shaft 20 and the grounding ring 32. For instance, the material of the sleeve may have better electrical conductivity than the material of the rotor shaft 20, the latter mainly being chosen for strong and durable torque transmission properties. Such better electrical conductivity may be provided e.g., by a silver coating.

[0079] The electric machine 4 further comprises a lubricant barrier member 36. The lubricant barrier member 36 is arranged in an axial position along the rotational axis 22 between the bearing 30 and the grounding ring 32. The lubricant barrier member 36 has an annular shape and a radial extension in relation to the rotational axis 22.

[0080] The annular lubricant barrier member 36 being arranged in the axial position between the bearing 30 and the grounding ring 32 prevents oil from the bearing 30 to reach the grounding ring 32. Thus, the electrical grounding function of the grounding ring 32 is not compromised by lubricant reaching the grounding ring 32.

[0081] According to embodiments, such as the illustrated embodiments, the lubricant barrier member 36 may be fixedly arranged in relation to the rotor shaft 20 and has a radial extension at least partially along the bearing 30. That is, the lubricant barrier member 36 extends from the rotor shaft 20 radially outwardly along the bearing 30.

[0082] For instance, the lubricant barrier member 36 may extend radially outwardly from the rotor shaft 20 to the outer ring of the bearing 30.

[0083] The bearing 30 has a first axial side 38 close to the lubricant barrier member 36 and a second axial side 40 opposite to the lubricant barrier member 36. A lubricant supply passage 42 is provided in the electric machine 4. The lubricant supply passage 42 extends to the second axial side 40 of the bearing 30 for supply of lubricant to the bearing 30. In this manner, proper lubrication of the bearing 30 may be ensured during operation of the electric machine 4.

[0084] Lubricant, such as oil, may be supplied to the lubricant supply passage 42 in any suitable manner. For instance, an oil pump may be provided for pumping oil to relevant portions of the electric machine 4 where lubrication is required, such as to the lubricant supply passage 42 and the bearing 30.

[0085] In the illustrated embodiments, the lubricant supply passage 42 is provided as a passage between the rotor shaft 20 and a portion of the housing 28. The lubricant supply passage may alternatively be provided in any other suitable position at the second axial side 40 of the bearing 30.

[0086] The lubricant supplied to the second axial side 40 of the bearing 30 lubricates and cools the bearing 30 and at least some of the lubricant passes through the bearing 30 to its first axial side 38. Here, the lubricant barrier member 36 prevents the lubricant from reaching the grounding ring 32.

[0087] The lubricant that has passed through the bearing 30 and which reaches the lubricant barrier member 36 is flung radially outwardly from the lubricant barrier member 36 to an arrangement in the housing 28, from which the lubricant is conducted e.g., back to a lubricant reservoir of the electric machine 4.

[0088] According to some embodiments, a lubricant return channel 44 may extend at least partially around the rotational axis 22 at a radial position outside the bearing 30. At least one lubricant return passage 46 may extend from the first axial side 38 of the bearing 30 to the lubricant return channel 44. In this manner, the lubricant that has passed through the bearing 30 and has been directed by the lubricant barrier member 36 away from the grounding ring 32 may be conducted away from the bearing 30, such as towards a lubricant reservoir, via the lubricant return passage 46 and the lubricant return channel 44.

[0089] The lubricant return passage 46 may form part of the lubricant return channel 44.

[0090] For the sake of clarity, distance members, such as sleeves in the seat 34 of the housing 28 and / or sleeves around the rotor shaft 20, have been omitted in Fig. 2. Such distance members may contribute to the axial positioning of one or more of the bearing 30, the grounding ring 32, and the lubricant barrier member 36. One or more biasing members, such as one or more spring members, (not shown) may be provided for the axial positioning of one or more of the bearing 30, the grounding ring 32, and the lubricant barrier member 36. Fig. 3 schematically illustrates a section through a portion of an electric machine 4 according to embodiments. Again, the electric machine 4 may form part of a vehicle, such as a vehicle 2 discussed above with reference to Fig. 1.

[0091] The electric machine 4 of the Fig. 3 embodiments resembles in much the electric machine 4 of the Fig. 2 embodiments. Accordingly, reference is also made to the above discussion of the Fig. 2 embodiments. In the following mainly, the specificities of the Fig. 3 embodiments will be discussed.

[0092] Again, the electric machine 4 comprises a rotor shaft 20, a rotor body 24 arranged on the rotor shaft 20, a housing 28, a bearing 30, a grounding ring 32, and a lubricant barrier member 36.

[0093] Again, the annular lubricant barrier member 36 is arranged in an axial position along the rotational axis 22 between the bearing 30 and the grounding ring 32. The lubricant barrier member 36 has a radial extension in relation to the rotational axis 22.

[0094] Again, the bearing 30 may be a rotary bearing comprising an inner ring 48 configured to rotate with the rotor shaft 20 and an outer ring 50 configured to be stationary in relation to the housing 28.

[0095] According to embodiments, such as the illustrated embodiments, the electric machine 4 comprises a sleeve member 52 arranged in the housing 28 and extending concentrically with the rotational axis 22. The bearing 30 is positioned inside the sleeve member 52 with the inner ring 48 arranged around the rotor shaft 20. The grounding ring 32 is positioned inside the sleeve member 52. In this manner, an easy mounting of the bearing 30 and the grounding ring 32 in the electric machine 4 may be provided.

[0096] Namely, for instance, the bearing 30 and the grounding ring 32 may be arranged within the sleeve member 52 and thereafter the sleeve member 52 with the bearing 30 and the grounding ring 32 may be arranged on the rotor shaft 20. Subsequently, the sleeve member 52 with the rotor shaft 20 may be arranged in the housing 28.

[0097] The lubricant barrier member 36 may be arranged within the sleeve member 52 between the bearing 30 and the grounding ring 32. The sleeve member 52 may be interference fitted, such as press fitted, into the housing 28. Alternatively, as illustrated, the sleeve member 52 may be fitted with a transition fit in the housing 28. One or more O-rings 54 may be provided for positioning the sleeve member 52 in the housing 28.

[0098] When interference fitted in the housing 28, the sleeve member 52 is fixed in relation to the housing 28, both in an axial and in a circumferential direction. When transition fitted in the housing 28, the sleeve member 52 may be axially fixed with an O-ring 54, as exemplified. In a circumferential direction however, the sleeve member 52 may be rotatable about the rotational axis 22 in relation to the housing 28. Such rotation of the sleeve member 52 is sometimes caused by the rotation of the rotor shaft 20. However, such rotation of the sleeve member 52 is ignorable in comparison with the rotation of the rotor shaft 20.

[0099] Accordingly, during operation of the electric machine 4, the sleeve member 52 is considered to be fixed in relation to housing 28 irrespective of whether the sleeve member 52 is arranged in the housing 28 with an interference fit or with a transition fit.

[0100] Similarly, the outer ring 50 of the bearing 30 is considered to be fixed, or stationary, in relation to the housing 28 even though the outer ring 50 may rotate minutely about the rotational axis 22 together with the sleeve member 52 and / or within the sleeve member 52. Again, any rotation of the outer ring 50 is minimal in comparison with the rotation of the rotor shaft 20.

[0101] In the embodiments of Fig. 3, the rotor shaft 20 is indirectly journalled in the housing 28 via the bearing 30 i.e. , the bearing 30 is arranged on the rotor shaft 20 and the bearing 30 is arranged in the sleeve member 52, which in turn is arranged in the housing 28.

[0102] Again, the grounding ring 32 is fixed in relation to the housing 28 and is arranged around the rotor shaft 20 in an axial position along the rotational axis 22 between the bearing 30 and the rotor body 24. In the illustrated embodiments, the grounding ring 32 is arranged in the sleeve member 52.

[0103] The grounding ring 32 being fixed in relation to the housing 28 means that the grounding ring 32 does not rotate together with the rotor shaft 20.

[0104] As discussed above with reference to the sleeve member 52 and the outer ring 50 of the bearing, the grounding ring 32 is considered to be fixed, or stationary, in relation to the housing 28 even though the grounding ring 32 may rotate minutely about the rotational axis 22 together with the sleeve member 52. Again, any rotation of the grounding ring 32 is minimal in comparison with the rotation of the rotor shaft 20.

[0105] According to embodiments, such as the illustrated embodiments, the lubricant barrier member 36 may be fixedly arranged within the sleeve member 52 between the bearing 30 and the grounding ring 32. In this manner, the lubricant barrier member 36 may be assembled in the sleeve member 52 before it is arranged in the housing 28, which facilitates assembly of the electric machine 4.

[0106] Accordingly, in these embodiments, the lubricant barrier member 36 is fixed in relation to the housing 28. Since the lubricant barrier member 36 is arranged in the sleeve member 52, in analogy with the discussion above, fixed in relation to the housing 28 may encompass minute rotation of the lubricant barrier member 36 together with the sleeve member 52.

[0107] Accordingly, assembly may follow a sequence of; the bearing 30, the lubricant barrier member 36, and the grounding ring 32 being arranged within the sleeve member 52 and thereafter the sleeve member 52 with the bearing 30, the lubricant barrier member 36, and the grounding ring 32 being arranged on the rotor shaft 20. Subsequently, the sleeve member 52 with the rotor shaft 20 may be arranged in the housing 28.

[0108] However, alternatively, the lubricant barrier member 36 may be fixed in relation to the rotor shaft 20, as discussed above with reference to the Fig. 2 embodiments.

[0109] In these embodiments, the outer ring 50 and the grounding ring 32 are arranged in abutment with the sleeve member 52. In this manner, the bearing 30 and the grounding ring 32 may be arranged and / or positioned within the sleeve member 52 for further arrangement in the housing 28 of the electric machine 4.

[0110] For instance, one or both of the outer ring 50 and the grounding ring 32 may be arranged in an interference fit with the sleeve member 52 or in a transition fit with the sleeve member 52.

[0111] Also the lubricant barrier member 36 may be arranged in abutment with the sleeve member 52.

[0112] In the embodiments of Fig. 3, the sleeve member 52 comprises a pipe portion 56 and a flange portion 58. The bearing 30, the lubricant barrier member 36, and the grounding ring 32 are arranged within the pipe portion 56. The flange portion 58 extends radially inwardly from the pipe portion 56 towards the rotational axis 22 at an end of the sleeve member 52 farthest away from the rotor body 24. In this manner, positioning of the bearing 30, the lubricant barrier member 36, and the grounding ring 32 in the sleeve member 52 may be facilitated. Moreover, the flange portion 58 may prevent excessive amounts of lubricant from reaching the bearing 30, the lubricant barrier member 36, and the grounding ring 32.

[0113] Again, to ensure proper lubrication of the bearing 30, the bearing 30 has a first axial side 38 close to the lubricant barrier member 36 and a second axial side 40 opposite to the lubricant barrier member 36. A lubricant supply passage 42 is provided in the electric machine 4. The lubricant supply passage 42 extends to the second axial side 40 of the bearing 30 for supply of lubricant to the bearing 30.

[0114] In these embodiments, the lubricant supply passage 42 to the second axial side 40 of the bearing 30 extends at least partially as a passage between the rotor shaft 20 and the flange portion 58 of the sleeve member 52.

[0115] Again, at least part of the lubricant supplied to the bearing 30 passes through the bearing 30 from its second axial side 40 to its first axial side 38. Again, the lubricant barrier member 36 prevents the lubricant from reaching the grounding ring 32.

[0116] Also in these embodiments, the lubricant barrier member 36 is arranged to direct lubricant in a direction radially outwardly from the rotor shaft 20. Due to bearing parts that rotate during operation of the electric machine 4, the lubricant is propelled radially outwardly from the rotating bearing parts. Accordingly, lubricant does not spread along the rotor shaft 20 at the first side 38 of the bearing 20. Thus, the lubricant barrier member 36 does not have to be arranged in contact with the rotor shaft 20 for directing all lubricant at the first side 38 of the bearing 30 away from the grounding ring 32.

[0117] Again, a lubricant return channel 44 extends at least partially around the rotational axis 22 at a radial position outside the bearing 30 and at least one lubricant return passage 46 extends from the first axial side 38 of the bearing 30 to the lubricant return channel 44.

[0118] Accordingly, during use of the electric machine 4, the lubricant that has passed through the bearing 30 and which reaches the lubricant barrier member 36 is directed along the lubricant barrier member 36 radially outwardly to the at least one lubricant return passage 46 and the lubricant return channel 44, from which the lubricant may be conducted e.g., back to a lubricant reservoir of the electric machine 4.

[0119] For instance, the lubricant barrier member 36 may extend radially inwardly from the sleeve member 52 to the inner ring 48 of the bearing 30.

[0120] In the illustrated embodiments, the sleeve member 52 is provided with a circumferential recess 60 at its radially outer surface. The at least one lubricant return passage 46 extends through the sleeve member 52 from an inner periphery thereof to the circumferential recess 60. The lubricant return channel 44 is formed at least partially between the sleeve member 52 and the housing 28 by the circumferential recess 60. In this manner, the sleeve member 52 may be utilised for forming at least part of the lubricant return channel 44.

[0121] The lubricant return passage 46 may extend from an axial position between the first side 38 of the bearing 30 and the lubricant barrier member 36 to the lubricant return channel 44.

[0122] In alternative embodiments, the lubricant return channel 44 may be formed at least partially in the housing 28, such as shown in Fig. 2, or the lubricant return channel 44 may be formed partially in the housing 28 and partially in the sleeve member 52.

[0123] Again, for the sake of clarity, distance members, such as sleeves in the sleeve member 52 of the housing 28 and / or sleeves around the rotor shaft 20, have been omitted in Fig. 3. Such distance members may contribute to the axial positioning of one or more of the bearing 30, the grounding ring 32, and the lubricant barrier member 36. One or more biasing members, such as one or more spring members, (not shown) may be provided for the axial positioning of one or more of the bearing 30, the grounding ring 32, and the lubricant barrier member 36.

[0124] Fig. 4 illustrates a method 100 for assembling a portion of an electric machine. The electric machine may be an electric machine 4 of a vehicle 2 as discussed above with reference to Figs. 1 - 3. Accordingly, reference is also made to the discussions above related to Figs. 1 - 3.

[0125] Hence, the electric machine 4 comprises a rotor shaft 20 configured to rotate about a rotational axis 22, a rotor body 24 arranged on the rotor shaft 20, a bearing 30, a housing 28, a grounding ring 32, and a lubricant barrier member 36. The method 100 relates mainly to an electric machine 4 comprising a sleeve member 52 and as specifically discussed, inter alia with reference to Fig. 3.

[0126] The method 100 comprises steps of:

[0127] - Fitting 102 the bearing 30 into the sleeve member 52.

[0128] - Positioning 104 the lubricant barrier member 36 in the sleeve member 52 next to the bearing 30.

[0129] - Fitting 106 the grounding ring 32 in the sleeve member 52 next to the lubricant barrier member.

[0130] - Placing 108 the sleeve member 52 with the grounding ring 32 closest towards the rotor body 24 onto the rotor shaft 20.

[0131] - Fitting 110 the bearing 30 onto the rotor shaft 20.

[0132] - Fitting 112 the sleeve member 52 into the housing 28.

[0133] Thus, an efficient mounting of the bearing 30, the lubricant barrier member 36, and the grounding ring 32 in an electric machine 4 is provided.

[0134] In step 108, the term closest towards the rotor body 24, refers to an axial position towards where the rotor body 24 is in the assembled electric machine 4.

[0135] According to embodiments, the step of positioning 104 the lubricant barrier member 36 in the sleeve member 52 next to the bearing 30 may comprise a step of:

[0136] - Press fitting 114 the lubricant barrier member 36 into the sleeve member 52.

[0137] According to alternative embodiments of the electric machine 4, wherein the lubricant barrier member 36 is arranged on the rotor shaft 20, the method 100 may comprise, in connection with the step of fitting 110 the bearing 30 onto the rotor shaft 20, a step of:

[0138] - Press fitting 116 the lubricant barrier member 36 onto the rotor shaft 20.

[0139] The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including" when used herein specify the presence of stated features, integers, actions, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and / or groups thereof.

[0140] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.

[0141] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0142] It is to be understood that the foregoing is illustrative of various examples and that the invention is defined only by the appended claims. A person skilled in the art will realize that the examples may be modified, and that different features of the examples may be combined to create examples other than those described herein, without departing from the scope of the invention, as defined by the appended claims.

Claims

CLAIMS1. An electric machine (4) comprising a rotor shaft (20) configured to rotate about a rotational axis (22), a rotor body (24) arranged on the rotor shaft (20), a bearing (30), a housing (28), and a grounding ring (32), wherein the bearing (30) is arranged on the rotor shaft (20) and the rotor shaft (20) is journaled in relation to the housing (28) via the bearing (30), wherein the grounding ring (32) is fixed in relation to the housing (28) and arranged around the rotor shaft (20) in an axial position along the rotational axis (22) between the bearing (30) and the rotor body (24), wherein a lubricant barrier member (36) is arranged in an axial position along the rotational axis (22) between the bearing (30) and the grounding ring (32), and wherein the lubricant barrier member (36) has an annular shape and a radial extension in relation to the rotational axis (22).

2. The electric machine (4) according to claim 1, wherein the bearing (30) is a rotary bearing comprising an inner ring (48) configured to rotate with the rotor shaft (20) and an outer ring (50) configured to be stationary in relation to the housing (28)3. The electric machine (4) according to claim 2, comprising a sleeve member (52) arranged in the housing (28) and extending concentrically with the rotational axis (22), wherein the bearing (30) is positioned inside the sleeve member (52) with the inner ring (48) arranged around the rotor shaft (20), and wherein the grounding ring (32) is positioned inside the sleeve member (52).

4. The electric machine (4) according to claim 3, wherein the sleeve member (52) comprises a pipe portion (56) and a flange portion (58), wherein the bearing (30), the lubricant barrier member (36), and the grounding ring (32) are arranged within the pipe portion (56), and wherein the flange portion (58) extends radially inwardly from the pipe portion (56) towards the rotational axis (22) at an end of the sleeve member (52) farthest away from the rotor body (24).

5. The electric machine (4) according to claim 3 or 4, wherein the outer ring (50) and the grounding ring (32) are arranged in abutment with the sleeve member (52).

6. The electric machine (4) according to any one of the preceding claims, wherein the bearing (30) has a first axial side (38) close to the lubricant barrier member (36) and a second axial side (40) opposite to the lubricant barrier member (36), wherein a lubricant supply passage (42) is provided in the electric machine (4), and wherein the lubricant supply passage (42) extends to the second axial side (40) of the bearing (30) for supply of lubricant to the bearing (30).

7. The electric machine (4) according to claim 6, wherein a lubricant return channel (44) extends at least partially around the rotational axis (22) at a radial position outside the bearing (30), and wherein at least one lubricant return passage (46) extends from the first axial side (38) of the bearing (30) to the lubricant return channel (44).

8. The electric machine (4) according to claim 7 and according to any one of claims 3 - 5, wherein the sleeve member (52) is provided with a circumferential recess (60) at its radially outer surface, wherein the at least one lubricant return passage (46) extends through the sleeve member (52) from an inner periphery thereof to the circumferential recess (60), and wherein the lubricant return channel (44) is formed between the sleeve member (52) and the housing (28) by the circumferential recess (60).

9. The electric machine (4) according to any one of claims 3 - 5 or claim 8, wherein the lubricant barrier member (36) is fixedly arranged within the sleeve member (52) between the bearing (30) and the grounding ring (32).

10. The electric machine (4) according to any one of claims 1 - 9, wherein the lubricant barrier member (36) is fixedly arranged in relation to the rotor shaft (20) and has a radial extension at least partially along the bearing (30).

11. A vehicle (2) comprising an electric machine (4) according to any one of the preceding claims.

12. A method (100) for assembling a portion of an electric machine (4), the electric machine (4) comprising a rotor shaft (20) configured to rotate about a rotational axis (22), a rotor body (24) arranged on the rotor shaft (20), a bearing (30), a housing (28), a grounding ring (32), a lubricant barrier member (36), and a sleeve member (52), wherein the method (100) comprises steps of:- fitting (102) the bearing (30) into the sleeve member (52),- positioning (104) the lubricant barrier member (36) in the sleeve member (52) next to the bearing (30),- fitting (106) the grounding ring (32) in the sleeve member (52) next to the lubricant barrier member (36),- placing (108) the sleeve member (52) with the grounding ring (32) closest towards the rotor body (24) onto the rotor shaft (20),- fitting (110) the bearing (30) onto the rotor shaft (20), and- fitting (112) the sleeve member (52) into the housing (28).

13. The method (100) according to claim 12, wherein the step of positioning (104) the lubricant barrier member (36) in the sleeve member (52) next to the bearing (30) comprises a step of:- press fitting (114) the lubricant barrier member (36) into the sleeve member (52).

14. The method (100) according to claim 12, comprising in connection with the step of press fitting the bearing (30) onto the rotor shaft (20), a step of:- press fitting (116) the lubricant barrier member (36) onto the rotor shaft (20).

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