Electrically driven machine, in particular pump

Abstract

Electrically driven machine (1), in particular pump, with an electric motor (3) comprising a rotor (4) arranged on a rotor shaft (7) which is rotatable in a stator (6) and with two bearings (20;13) to support the rotor shaft (7) axially and radially with the rotor (4), wherein the rotor shaft (7) is supported radially and axially with a radial-axial plain bearing (20) both in the direction of a rotating machine element (8) and in the opposite axial direction, characterized in that the stator (6) is overmolded with a stator housing body (16) made of a plastic material (17), wherein the radial-axial plain bearing (20) comprises a bearing bushing (21) with two axially opposing thrust surfaces (22, 23), wherein the bearing bushing (21) of the radial-axial plain bearing (20) is overmolded with the stator housing body (16) made of the plastic material (17) together with the stator (6), and wherein the bearing bushing (21) of the radial-axial plain bearing (20) has at least one positive locking geometry feature (33, 34) which ensures a rotationally fixed anchoring of the bearing bushing (21) in the stator housing body (16).

Description

The invention relates to an electrically driven machine, in particular a pump, with an electric motor comprising a rotor arranged on a rotor shaft, rotatable in a stator which is overmolded with a stator housing body made of a plastic material, and with two bearings to support the rotor shaft axially and radially with the rotor. From German utility model DE 20 2011 100 921 U1 and international patent application WO 2012 / 156360 A1, an electric motor, in particular an external rotor motor for driving a fan, is known, comprising a stator, a rotor and a plain bearing for a shaft of the rotor, wherein the plain bearing has a bearing element made of a plastic with at least one sliding surface which is movably paired with a counter sliding surface, wherein plain bearings with bearing elements made of plastic are provided for supporting the shaft of the rotor in a bearing support tube, wherein at least one bearing element can be formed by an integral part of the stator or a stator bushing or can be injection-molded onto the stator or the stator bushing.German patent application DE 10 2011 121 935 A1 discloses an electrical machine with a rotor connected to a shaft or axle rotatably mounted in a bearing, and with a stator arranged together with a bearing bushing in an injection-molded plastic housing. GB 1 551 391 A discloses features which fall under the preamble of claim 1. The object of the invention is to improve the design of an electrically driven machine, in particular a pump, comprising an electric motor comprising a rotor arranged on a rotor shaft, rotatable in a stator which is overmolded with a stator housing body made of a plastic material, and comprising two bearings to support the rotor shaft axially and radially with the rotor, particularly with regard to an undesirably long tolerance chain in the rotor shaft bearing. The invention is defined by the independent claims.The problem is solved in an electrically driven machine, particularly a pump, with an electric motor comprising a rotor arranged on a rotor shaft, rotatably within a stator overmolded with a stator housing made of a plastic material, and with two bearings for axially and radially supporting the rotor shaft and rotor. This is achieved by supporting the rotor shaft radially and axially with a radial-axial plain bearing in both the direction of a rotating machine element and in the opposite axial direction. The electrically driven machine is particularly designed as an electrically driven pump. In this case, the rotating machine element is preferably a rotating pump element, such as an impeller. The pump is, for example, designed as a water pump and, together with the impeller, is also referred to as an impeller pump. The stator housing can be a single piece or made of multiple parts.The stator can be completely or partially overmolded with the plastic material. The term axial refers to an axis of rotation of the rotor of the electrically driven machine. Axial means in the direction of or parallel to the axis of rotation of the rotor of the electrically driven machine. Analogously, radial means perpendicular to the axis of rotation of the rotor of the electrically driven machine. The invention is characterized in that the radial-axial plain bearing comprises a bearing bushing with two axially opposed contact surfaces. This is cost-effective to manufacture and offers the advantage that a second axial bearing for the rotor shaft can be omitted. Furthermore, this allows for a shorter tolerance chain, enabling the rotor shaft to be supported with less axial play. The invention is characterized in that the bearing bushing of the radial-axial plain bearing, together with the stator, is overmolded with the stator housing body made of the same plastic material. This creates a simple, cast-in fixed bearing with axial contact on both sides. The bearing bushing of the radial-axial plain bearing is advantageously also made of a plastic material, but preferably a different plastic material than the stator housing body. The plastic material for the bearing bushing of the radial-axial plain bearing is advantageously selected with regard to its tribological properties. The plastic material for the stator housing body is advantageously selected with regard to high stability and elasticity. Another preferred embodiment of the electrically driven machine is characterized in that the bearing bushing of the radial-axial plain bearing has at least one positive-locking geometric feature that ensures stable axial anchoring of the bearing bushing in the stator housing body. Since the bearing bushing of the radial-axial plain bearing and the stator housing body are made of different materials, in particular different plastic materials, it can happen that the bearing bushing of the radial-axial plain bearing is not, or not completely, materially bonded to the stator housing body. The positive-locking geometric feature comprises, for example, a substantially annular disc-shaped rib that projects radially outward from the bearing bushing of the radial-axial plain bearing. Particularly preferably, the bearing bushing of the radial-axial plain bearing comprises two such ribs.If the rib or ribs are overmolded with the plastic material, then axial relative movements between the bearing bushing and the stator housing body are excluded. The invention is characterized in that the bearing bushing of the radial-axial plain bearing has at least one positive-locking geometric feature that ensures rotationally fixed anchoring of the bearing bushing in the stator housing body. The positive-locking geometric feature for rotationally fixed anchoring of the bearing bushing in the stator housing body comprises, for example, a rectangular recess in at least one of the previously described ribs. This allows for the simple prevention of unwanted rotation of the bearing bushing in the stator housing body. Another preferred embodiment of the electrically driven machine is characterized in that the bearing bushing of the radial-axial plain bearing is designed as a double-flange bushing with a first bearing flange on which the rotor is axially supported, and a second bearing flange on which a machine element bushing is axially supported. The machine element bushing is also referred to as a pump element bushing if the electrically driven machine is designed as an electrically driven pump. The first bearing flange of the double-flange bushing is advantageously supported axially on a rotor disk of the rotor. The rotor disk is, for example, made of a metallic material. The rotor disk of the rotor is advantageously made of steel. The machine element bushing, in particular the pump element bushing, is also advantageously made of a metallic material, for example, steel. Another preferred embodiment of the electrically driven machine is characterized in that the first and second bearing flanges of the double-flange bushing each have at least one radially extending recess that allows the passage of a cooling and / or lubricating medium. The cooling and / or lubricating medium can also be a working medium of the machine, in particular a pump. The working medium of the machine, in particular a pump, is preferably water or oil. The water or oil is not used in pure form, but preferably with approximately fifty percent of a synthetic additive intended to prevent freezing. Another preferred embodiment of the electrically driven machine is characterized in that the machine element bushing is designed as a flanged bushing with a flange that is axially supported on the second bearing flange of the double-flange bushing. The machine element bushing, in particular the pump element bushing, is rigidly connected to the machine element, in particular the pump element. The machine element bushing with the machine element, in particular the pump element bushing with the pump element, is in turn rigidly connected to the rotor shaft. The rigid connection between the machine element bushing and the rotor shaft is realized, for example, by an interference fit. Another preferred embodiment of the electrically driven machine is characterized in that the rotor shaft is supported radially only in a floating bearing on a side of the rotor facing away from the radial-axial plain bearing. The floating bearing is advantageously designed as a second plain bearing, but unlike the radial-axial plain bearing, the second plain bearing does not have an axial bearing surface. The floating bearing is advantageously designed as a pure radial bearing. The floating bearing comprises, for example, a machine element bushing, in particular a pump element bushing, which is pressed into a heat sink of a control housing. The invention further relates to a radial-axial plain bearing, a bearing bushing, in particular a double-flange bushing, a bearing arrangement and / or a stator, in particular a stator housing body, for a previously described electrically driven machine, in particular a pump. The aforementioned parts are available for separate sale. The invention may also relate to a method for manufacturing and / or assembling a previously described machine, in particular a pump. The invention may also relate to a tool for manufacturing a previously described machine, in particular a pump, or a previously described bearing bushing, in particular a double-flange bushing. Further advantages, features, and details of the invention will become apparent from the following description, in which various exemplary embodiments are described in detail with reference to the drawings. The drawings show: Fig. 1 an electrically driven machine designed as an impeller pump with a rotor shaft radially and axially supported by a radial-axial plain bearing, in longitudinal section; Fig. 2 an enlarged detail from Fig. 1 showing the radial-axial plain bearing; and Fig. 3 a perspective view of a double-flange bushing of the radial-axial plain bearing from Figs. 1 and 2. Figure 1 shows a longitudinal section of an electrically driven machine 1. The electrically driven machine 1 is designed as an electrically driven pump, in particular a water pump. The electrically driven pump 1 comprises an electric motor 3, which is controlled by a pump controller 2. The pump 1 is preferably designed as an electrically driven water pump. The electric motor 3 comprises a rotor 4, which is rotatably arranged about an axis of rotation 5 in a stator 6. The rotor 4 is rotatably mounted relative to the stationary stator 6 about the axis of rotation 5 in a pump housing 10 by means of a rotor shaft 7. The rotor shaft 7 of the electric motor 3 is connected to a machine element 8 at its left end, as shown in Fig. 1. The machine element 8 is preferably a pump element, in particular an impeller 9, of the electrically driven pump 1, which is also referred to as an impeller pump. The pump housing 10 comprises a pump housing body 11, which, on the right in Fig. 1, serves to accommodate the pump control 2. A corresponding receiving space for the pump control 2 in the pump housing body 11 is closed by a housing cover 12. The pump housing body 11 is designed as a heat sink and is advantageously made of a highly conductive metallic material for this purpose. A plain bearing 13 for the right end of the rotor shaft 7 (as shown in Fig. 1) is arranged in the pump housing body 11. The plain bearing 13 is designed as a floating bearing. The floating bearing comprises a radial bearing bushing 14, which supports the right end of the rotor shaft 7 (as shown in Fig. 1) only radially. The stator 6 of the electric motor 3 is arranged in a stator housing 15. The stator housing 15 comprises a stator body 16 made of a plastic material 17, with which the stator 6 is overmolded. The stator 6 comprises a stator lamination stack arranged axially between two rotor disks 18, 19. The rotor disks 18, 19, together with the rotor 4, are rotationally fixed to the rotor shaft 7. In Fig. 1, to the left of the stator 6, the rotor shaft 7 is supported in a radial-axial plain bearing 20. Figure 2 shows an enlarged section of the radial-axial plain bearing 20 for the rotor shaft 7. The radial-axial plain bearing 20 comprises a bearing bushing 21 with two axially opposed running surfaces 22, 23. The axial running surface 22 faces a machine element bushing 24, in particular a pump element bushing 24. The pump element bushing 24 is designed as a flanged bushing with a flange 25 that is supported axially on the axial contact surface 22 of the radial-axial plain bearing 20. The pump element bushing 24 is, for example, made of a preferably hardened steel material and is pressed onto the rotor shaft 7, which is also preferably made of a steel material. This creates a force-fit connection between the pump element bushing 24 and the rotor shaft 7. The axial contact surface 23 of the radial-axial plain bearing 20, shown on the right in Fig. 2, faces the rotor disk 18 of the rotor 4. The rotor disk 18 of the rotor 4 is supported axially to the left in Fig. 2 against the axial contact surface 23 of the radial-axial plain bearing 20. A comparison of Figures 2 and 3 shows that the radial-axial plain bearing 20 comprises a double-flange bushing 26 with a first bearing flange 27 and a second bearing flange 28. The axial running surface 23 for the rotor disk 18 is arranged on the first bearing flange 27. The axial running surface 22 for the flange 25 of the pump element bushing 24 is arranged on the second bearing flange 28. The double-flange bushing 26 comprises a total of four positive locking geometry features 31 to 34 between the first bearing flange 27 and the second bearing flange 28. The positive locking geometry features 31, 32 are annular disc-like ribs that project radially from a substantially circular cylindrical base body of the double-flange bushing 26. In the axial direction, the ribs 31, 32 are spaced evenly apart from each other and from the first bearing collar 27 and the second bearing collar 28. Figure 2 shows that the double-column bushing 26 is stably anchored in the axial direction in the stator housing body 16 by overmolding the ribs 31, 32 with the plastic material 17. The positive locking geometry features 33, 34 are advantageously combined with the positive locking geometry features 31, 32. The positive locking geometry features 33, 34 are designed as essentially rectangular recesses radially outward in the ribs 31, 32. By overmolding or injection molding the rectangular recesses 33, 34 with the plastic material 17, the double-flange bushing 26 is anchored rotationally fixed in the stator housing body 16. Figure 3 further shows that a total of three radial recesses 36 to 38 are provided in the axial running surface 22. These recesses allow cooling and / or lubricating medium to flow radially through. This advantageously allows the lubricating and / or cooling medium to flow radially from the outside to the inside between the rotor shaft 7 and the double-flange bushing 26. Analogous recesses are provided in the axial running surface 23 of the double-flange bushing 26, but these are not visible in Figure 3. Reference symbol list 1 Machine, in particular pump 2 Pump control 3 Electric motor 4 Rotor 5 Shaft of rotation 6 Stator 7 Rotor shaft 8 Machine element, in particular pump element 9 Impeller 10 Pump housing 11 Pump housing body 12 Housing cover 13 Plain bearing 14 Radial bearing bushing 15 Stator housing 16 Stator housing body 17 Plastic material 18 Rotor disc 19 Rotor disc 20 Radial-axial plain bearing 21 Bearing bushing 22 Running surface 23 Running surface 24 Machine element bushing, in particular pump element bushing 25 Collar 26 Double collar bushing 27 First bearing collar 28 Second bearing collar 31 Positive locking geometry feature 32 Positive locking geometry feature 33 Positive locking geometry feature 34 Positive locking geometry feature 36 Recess 37 Recess 38 Recess

Claims

Electrically driven machine (1), in particular pump, with an electric motor (3) comprising a rotor (4) arranged on a rotor shaft (7) which is rotatable in a stator (6) and with two bearings (20;13) to support the rotor shaft (7) axially and radially with the rotor (4), wherein the rotor shaft (7) is supported radially and axially with a radial-axial plain bearing (20) both in the direction of a rotating machine element (8) and in the opposite axial direction, characterized in that the stator (6) is overmolded with a stator housing body (16) made of a plastic material (17), wherein the radial-axial plain bearing (20) comprises a bearing bushing (21) with two axially opposing thrust surfaces (22, 23), wherein the bearing bushing (21) of the radial-axial plain bearing (20) is overmolded with the stator housing body (16) made of the plastic material (17) together with the stator (6), and wherein the bearing bushing (21) of the radial-axial plain bearing (20) has at least one positive locking geometry feature (33, 34) which ensures a rotationally fixed anchoring of the bearing bushing (21) in the stator housing body (16). Electrically driven machine according to claim 1, characterized in that the bearing bushing (21) of the radial-axial sliding bearing (20) has at least one positive locking geometry feature (31, 32) which ensures a stable axial anchoring of the bearing bushing (21) in the stator housing body (16). Electrically driven machine according to one of claims 1 to 2, characterized in that the bearing bushing (21) of the radial-axial plain bearing (20) is designed as a double-flange bushing (26) with a first bearing flange (27) on which the rotor (4) is axially supported, and a second bearing flange (28) on which a machine element bushing (24) is axially supported. Electrically driven machine according to claim 3, characterized in that the first and the second bearing collar (27, 28) of the double collar bushing (26) each have at least one radially extending recess (36-38) which allows the passage of a cooling and / or lubricating medium. Electrically driven machine according to claim 3 or 4, characterized in that the machine element bushing (24) is designed as a flanged bushing with a flange (25) which is axially supported on the second bearing flange (28) of the double flanged bushing (26). Electrically driven machine according to one of the preceding claims, characterized in that the rotor shaft (7) is only radially supported in a floating bearing (13) on a side of the rotor (4) facing away from the radial-axial sliding bearing (20).

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