SE538971C2

SE538971C2 - Arrangement for distributing oil in an electric machine

Info

Publication number: SE538971C2
Application number: SE1550822A
Authority: SE
Inventors: Forsberg Jörgen; Lamadrid Artiom
Original assignee: Scania Cv Ab
Priority date: 2015-06-16
Filing date: 2015-06-16
Publication date: 2017-03-07
Also published as: WO2016204670A1; SE1550822A1

Description

Arrangement for distributing oil in an electric machine BACKGROUND TO THE INVENTION AND PRIOR ART The present invention relates to an arrangement for distributing oil in an electrical machine according to the preamble of claim 1.

Hybrid vehicles usually comprise an electrical machine which serves as prime mover during running of the vehicle and as generator at times when the vehicle is being braked. The electrical machine is usually situated within a housing or the like. Whether running as prime mover or as generator, the electrical machine is subject to temperature rise. Temperature rise in an electrical machine is substantially confined to specific components, e.g. its stator windings or rotor. Conventional cooling of electrical machines in hybrid vehicles may be performed by air or water led past an external surface of the housing which encloses the electrical machine. A more effective cooling method is to spray oil on the stator windings of the electrical machine. However, a relatively large part of the oil which hits the stator windings bounces away and hits a wall of the housing where it flows downwardly without taking up any heat from the electrical machine.

US 2005/0206251 shows an arrangement for cooling an electrical machine which is situated in a housing. The electrical machine comprises in a conventional way a stator and a rotor which is mounted on a rotatable shaft. In this case, oil is used as cooling medium. The oil is led via a duct situated within the rotatable shaft to a location radially internal to the electrical machine. The oil is led thereafter into a radial duct in the hub of the rotor. The radial duct ends with apertures which lead the oil to two lateral surfaces of the rotor from which the oil is flung radially outwards by the centrifugal force which occurs when the rotor rotates. The oil thereupon comes into contact with protruding portions of the rotor windings and the stator windings.

SUMMARY OF THE INVENTION The object of the invention is to propose an arrangement which provides a very effective cooling of an electrical machine in a relatively simple way and at low cost.

This object is achieved with the arrangement defined in the introduction which ischaracterized bythe features indicated in the characterising part of claim 1. The arrangement comprises an oil system supplying oil to the stator windings. However, a part of the oil hitting the stator windings bounces away and hits a wall of the housing enclosing the electrical machine. This part of the oil flowing downwardly on the wall until it achieves contact with a guiding member. The guiding member comprises a surface leading the oil from the wall to the rotor. The oil obtains a rotating movement by the rotor and it is thrown radially outwardly by the centrifugal force in a direction towards the stator windings. Consequently, the part of the oil which leaves the stator windings can be lead back from the wall of the housing, via the rotor, to the stator windings by means of the guiding member. In this case, substantially all oil supplied to the electrical machine can be used to cool the stator windings in an effective manner. The guiding member may have a simple design and be manufactured to a low cost. The rotor may be arranged on a rotary shaft by a splined connection or arranged on a ring wheel of a planetary gear.

According to an embodiment of the present invention, the free edge portion of the guiding surface comprises drip formations. The free edge portion of the guiding member inclines in relation to a horizontal plane. Thus, there is a risk that the oil entering the free edge portion may form an oil flow downwardly along the free edge portion of the guiding member. The drip formations stop such an oil flow and directs the oil out of the free edge portion and to the rotor. The drip formations may be arranged around the whole free edge portion of the guiding member at constant intervals. The drip formations may be arbitrary irregularities in the edge portion such as recesses or protruding portions.

According to an embodiment of the present invention, the guiding member is annular. An annular guiding member has a simple design and it is easy to manufacture. The guiding member may be manufactured of a sheet metal. The annular guiding member may comprise a first guiding surface formed by a radially outer surface of the annular guiding member and a second guiding surface formed by a radially inner surface of the annular guiding member. It is possible to use the radially outer surface and the radially inner surface of the guiding member as a guiding surfaces and lead the oil out from the wall to the rotor. Alternatively, the guiding member may have another shape such as an oval shape.

According to an embodiment of the present invention, said part of the rotor comprises an axially protruding portion located radially inwardly of the free edge portion of the guiding member. Such a protruding portion may receive oil and prevent a downwardly directed oil flow past the rotor at the free edge portion of the guiding member.

Said axially protruding portion may have radially outer surface located at a constant radial distance from the rotational axis. A surface with such a shape is usually enough for retaining the oil on the rotor.

According to an embodiment of the present invention, said part of the rotor comprises an axially protruding portion located radially outwardly of the free edge portion of the guiding member. Said protruding portion may have a radially outer surface retaining oil which is used to cool the rotor. Said protruding portion may have a radially inner surface sloping successively radially outwardly towards a free end of the axially protruding portion. The oil retained on the rotor obtains a rotating movement by the rotor. As a consequence, the oil flows radially outwardly by the centrifugal force. The radially inner surface has a shape directing the oil flow towards the stator windings.

According to an embodiment of the present invention, at least one of the axially protruding portions has a free end located in a vertical plane extending through the guiding member. Such a design of the protruding portions may form an axial recess in said part of the rotor which receives the free edge portion of the guiding member. In this case, it is formed a curved gap between the free edge portion of the guiding member and the surfaces of the axial recess. It is difficult for the oil to pass through such a curved gap without coming in contact with a surface of the rotor.

According to an embodiment of the present invention, the arrangement comprises two guiding members connected to opposite walls of the housing. The stator windings extend axially out beyond both sides of the stator core. Thus, it is suitable to supply oil to the stator windings on both sides of the stator core. The house may have side walls arranged to enclose the stator winding on both sides of the stator core. In this case, it is suitable to arrange a guiding member on the opposite side walls of the housing.

According to an embodiment of the present invention, the oil system comprises an annular oil channel arranged radially outside of the stator and outlet ducts supplying oil to the stator windings. A pump may direct an oil flow to the annular oil channel. The oil may have a positive pressure in the oil channel such that the oil is sprayed out of the outlets duct in a direction towards the stator windings.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention is described below by way of an example with reference to the attached drawings, on which: Fig. 1 shows an arrangement for cooling of an electrical machine, Fig. 2 shows a part of the arrangement more in detail and Fig. 3 shows one of the oil guiding members in Fig. 1 in a separate state. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig. 1 shows a housing 1 enclosing an electrical machine 2 which may be arranged in a hybrid vehicle. A rotatable shaft 3 extends substantially centrally through a first side wall la of the housing 1 and a second side wall lb of the housing 1. At least one of the side walls la, lb is releasably connected to a periphery wall lc of the housing 1. The shaft 3 is rotatably arranged in relation to the side walls of the housing 1 by means of bearings 4. The shaft 3 is driven by a not shown combustion engine of a hybrid vehicle. The electrical machine 2 comprises in a conventional way a rotor 5 and a stator 6. The rotor 5 comprises a rotor core 5 a supported by a rotor hub 5b. The rotor hub 5b is fastened on the rotatable shaft 3 by means of a splined connection. Alternatively, it may be arranged on a ring wheel of a planetary gear. The rotor 5 and the shaft 3 rotates around a common rotation axis 7. The stator 6 comprises a stator core 6a, stator windings 6b mounted on the inside of the periphery wall lc of the housing 1 and a mantle 6c enclosing the stator core 6b. An annular oil channel 8 is arranged in a radial space between the periphery wall lc of the housing 1 and the mantle 6c. Oil is supplied to the annular oil channel 8 via an oil conduit 10 by a not visible oil pump. The oil is supplied with a positive pressure to the annular oil channel 8. The annular oil channel 8 comprises a number of outlet ducts 9 in the mantle 6c spraying oil from the annular oil channel 8 in a direction towards the stator windings 6b. A first guiding member 11 is connected to an inner surface of the first side wall la of the housing and a second guiding member 12 is connected to an inner surface of the second side wall lb of the housing 1. Fig. 2 shows a part of the guiding members 11, 12 more in detail. Each guiding member 11,12 comprises a fixed edge portion 11a, 12a connected to the respective side walls la, lb and a free edge portion 1 lb, 12b located at a distance from the respective side walls la, lb. Each guiding member 11, 12 has an extension between the fixed edge portion 11a, 12a and the free edge portion 1 lb, 12b. Each guiding member 11, 12 is annular. As a consequence, each guiding member 11,12 comprises a radially outer surface forming a first guiding surface 11c, 12c and a radially inner surface forming a second guiding surface lid, 12d.

In a mounted position, the first guiding surface 11c, 12c forms an upwardly directed surface of an upper half of the guiding member 11,12 and the second guiding surface lid, 12d forms an upwardly directed surface of a lower half of the guiding member 11. The first guiding surfaces 11c, 12c receives oil flowing downwardly on a part of the side walls la, lb located at an outer radial position of the fixed edge portions 11a, 12a of the guiding members 11, 12. The second guiding surfaces lid, 12d form guiding surfaces for oil flowing downwardly on a part of the side walls la, lb located at an inner radial position of the fixed edge portions 11a, 12a of the guiding members 11, 12. The guiding surfaces 1 lc, d, 12c, d of the guiding members 11,12 may slope downwardly within an angle range of 30-60 degrees.

The rotor hub 5b comprises on a first side portion a first axially protruding portion 5 c and a second axially protruding 5d located at a somewhat outer radial position in relation to the first axially protruding portion 5c. The first protruding portion 5c comprises an outer radial surface 5ci arranged at a constant radial distance from the rotation axis 7. The second protruding portion 5d comprises a radial inner curved surface 5di inclining radially outwardly towards a free end of the second protruding portion 5d. The first protruding portion 5 c and the second protruding portion 5d form a first annular recess 5e receiving the free edge portion 1 lb of the first guiding member 11. The rotor hub 5b comprises on an opposite second side portion a third axially protruding portion 5f and a fourth axially protruding 5g located at a somewhat outer radial position in relation to the third axially protruding portion 5f. The third protruding portion 5f comprises a radial outer surface 5fi arranged at a constant radial distance from the rotation axis 7. The second protruding portion 5g comprises a radial inner curved surface 5gi inclined radially outwardly towards a free end of the fourth protruding portion 5g. The third protruding portion 5f and the fourth protruding portion 5g form a second annular recess 5h receiving the free edge portion 12b of the second guiding member 12.

Fig. 3 shows the first guiding member 11 in a separated state. It is here visible that the first guiding surface 1 lc of the guiding member 11 comprises drip formations at the free edge portion 1 lb which in this case is designed as drip notches lie. The drip notches 1 le are arranged at substantially constant intervals along the free edge portion 1 lb. The second guiding surface 1 Id may have a corresponding design with drip notches 1 le at the free end portion 1 lb. The second member 12 may have a corresponding design with drip formations 1 le at the free end portion 12b.

During operation of the electrical machine 2, oil is supplied to the annular channel 8. The oil in the annular channel reaches the oil ducts 9 where it is sprayed out towards the stator windings 6b. The oil provides an effective cooling of the stator windings 6b. A part of the oil hitting the stator windings 6b get caught on the stator winding during a period of time. Inevitably, a part of the oil hitting the stator windings will bounce away and hit the inner surface of the side walls la, lb. This part of the oil flows downwardly along the inner surface of the side walls la, lb. The oil hitting the respective side wall la, lb in a position located radially outside of the fixed edge portion 11a, 12a of the guiding members 11,12 comes in contact with the first surface 11c, 12c of the respective guiding members 11,12 when it flows downwardly along the side walls la, lb. The first surface 11c, 12c leads the oil out from the wall la, lb and in a direction towards the free edge portion 1 lb, 12b. At the free edge portion 1 lb, 12b the oil leaves the first guiding surfaces 11c, 12c and enters the recesses 5e, 5g of the rotor 5.

Since the free edge portions 1 lb, 12b are inclined in relation to a horizontal plane, a part of the oil may start to flow downwardly along the free edge portion 1 lb, 12b. However, this part of the oil will relatively soon reach one of the drip notches lie which directs the oil out from the free edge portion 1 lb, 12b and into the recesses 5e, 5h of the rotor hub 5b. A vertical plane through a free end of the first protruding portion 5 c extends through the first guide member 11. A vertical plane through the free end of the third protruding portion 5f extends the second guiding member 12. In view of these facts, the oil leaving the free edge portions 1 lb, 12b of the guiding members 11,12 will hit a bottom surface of the recesses 5e, 5h or the outer radial surfaces 5ci, 5fi of the protruding portions 5c, 5f. The oil retained on the surfaces of the recesses 5e, 5h obtains a rotating movement by the rotor 5. As a consequence, the oil is pressed radially outwardly by the centrifugal force. The oil reaches the inner radial surfaces 5di, 5gi which slope radially outwardly towards the free ends of the protruding portions 5d, 5g. The oil leaves the free ends of the protruding portions 5d, 5g in a radially outwardly towards the stator windings 6b.

However, a part of the oil in the recesses 5e, 5h may fall downwardly into an inner space defined by the guiding members 11, 12. This oil may hit an inner surfaces of the side walls la, lb located between the fixed edge portions 11a, 12a of the guiding members 11, 12. The oil hitting the side walls la, lb flows downwardly and reaches the second guiding surfaces lid, 12d of the guiding members 11, 12. Alternatively, the oil may hit the second guiding surfaces lid, 12d directly. The second guiding surfaces lid, 12d leads the oil towards the free edge portions 1 lb, 12b. The oil leaves the second guiding surfaces lid, 12d at the free edge portions 1 lb, 12b and enters the recesses 5e, 5h of the rotor 5. The oil in the recesses 5e, 5h obtains a rotating movement by the rotor 5. As a consequence, the oil is pressed radially outwardly by the centrifugal force. The oil is directed by the surfaces 5di, 5gi radially outwardly towards the stator windings 6b. Consequently, also this part of the oil can be used to cool the stator windings 6b.

The invention is in no way limited to the embodiment to which the drawing refers but may be varied freely within the scopes of the claims.

Claims

1. An arrangement for distributing oil in an electrical machine (2), wherein the electrical machine (2) comprises a rotor (5) rotatably arranged around a rotation axis (7), a stator (6) arranged radially outside of the rotor (5), a housing (1) enclosing the rotor (5) and the stator (6), and an oil system supplying oil to the stator windings (6b), wherein the arrangement comprises an annular guiding member (11, 12) comprising a guiding surface (11c, 1 Id, 12c, 12d) having an extension between a fixed edge portion (1 la, 12a) connected to a wall (la, lb) of the housing (1) and a free edge portion (1 lb, 12b) located close to the rotor (5), wherein the fixed edge portion (11a, 12a) of the guiding surface (11c, 12c) is arranged at a higher height than the free edge portion (1 lb, 12b) of the guiding surface (11c, 12c) such that the guiding surface (11c, lid, 12c, 12d) leads oil from the wall (la, lb) to a part of the rotor (5) located radially inwardly of the stator windings (6b),characterizedin that the annular guiding member (11, 12) comprises a first guiding surface (11c, 12c) formed by a radially outer surface of the annular guiding member (11, 12) and a second guiding surface (lid, 12d) formed by a radially inner surface of the annular guiding member (11, 12).

2. An arrangement according to claim 1,characterized in that the free edge portion (1 lb, 12b) of the guiding surface (11c, lid, 12c, 12d) comprises drip formations (lie).

3. An arrangement according to any one of the preceding claims,characterized in that said part of the rotor (5) comprises an axially protruding portion (5c, 5f) located radially inwardly of the free edge portion (1 lb, 12b) of the guiding member (11, 12).

4. An arrangement according to claim 3,characterized in that said axially protruding portion (5 c, 5 f) has a radially outer surface located at a constant radial distance from the rotational axis (7).

5. An arrangement according to any one of the preceding claims,characterized in that said part of the rotor (5) comprises an axially protruding portion (5d, 5g) located radially outwardly of the free edge portion (1 lb, 12b) of the guiding member (11, 12).

6. An arrangement according to claim 5,characterized in that said axially protruding portion (5d, 5g) has radially inner surface sloping successively radially outwardly towards an outer end of the axially protruding portion (5 c, 5 f).

7. An arrangement according to claim 5,characterized in that at least one of the axially protruding portions (5c, 5d, 5f, 5g) has a free end located in a vertical plane extending through the guiding member (11, 12).

8. An arrangement according to any one of the preceding claims,characterized in that the arrangement comprises two guiding members (11, 12) connected to opposite walls (la, lb) of the housing (1).

9. An arrangement according to any one of the preceding claims,characterized in that the oil system comprises an annular oil channel (8) arranged radially outside of the stator (5) and outlet ducts (9) supplying oil to the stator windings (6b).