Electric motor for driving a media separating work machine

Abstract

The invention relates to an electric motor having a motor housing (2) with a shaft portion for accommodating a motor shaft (4) and a motor portion in which motor electronics (5) and motor windings (6) are arranged, which shaft portion and motor portion are separated from one another in a sealed manner by means of a gap cup (7) arranged in the motor housing (2), wherein in the shaft portion an inner rotor and an axially adjoining metal ball bearing cup (8) are mounted in the gap cup (7), and ball bearings (9) for supporting the motor shaft (4) are fixed in the ball bearing cup (8).

Description

TECHNICAL FIELD

[0001] The invention relates to an electric motor for driving a work machine that must be separated from the medium, for example in the case of a pump, centrifuge or separator. BACKGROUND

[0002] In electric motors of this type, the motor shaft generates a high rotational speed, and the power loss of the ball bearing that supports the motor shaft increases significantly due to the strongly generated heat. This is particularly the case in the case of compact designs of the electric motor, in which the ball bearing is arranged directly adjacent to a number of other components, so that the generated heat cannot be dissipated sufficiently. SUMMARY

[0003] It is therefore an object of the invention to provide an electric motor as a drive for a work machine that is separated from the medium, which, in addition to separating the motor electronics from the motor shaft, also improves the heat dissipation of the ball bearing that supports the motor shaft.

[0004] This object is achieved by the combination of the features according to the patent claim.

[0005] According to the invention, an electric motor is proposed, which has a motor housing with a shaft portion for accommodating a motor shaft and a motor portion for accommodating motor electronics and motor windings. The shaft portion and the motor portion are separated from one another in a sealed manner by means of a gap cup arranged in the motor housing in order to ensure a separation from the medium. In the shaft portion, an inner rotor and a metal ball bearing cup axially adjoining the same are arranged in the gap cup, wherein ball bearings for supporting the motor shaft and the inner rotor are fixed in the ball bearing cup. The inner rotor is specially designed and has a shaft channel that forms an axial stop face. The axial stop face can be realized, for example, by a recess of a stepped inner sleeve surface. Furthermore, a press sleeve, into which the motor shaft can be pressed, is arranged in the shaft channel in such a way that it abuts against the stop surface.

[0006] The shaft channel is preferably realized by means of a plastic injection-moulded encapsulation of a ferrite permanent magnet, in the case of a radial expansion and the associated increase in the outer diameter, the press sleeve can be pushed at least slightly radially into the shaft channel.

[0007] The gap cup serves to separate the shaft portion and the motor portion and to prevent an exchange of gases between the crankcase and the electronics or the motor windings. For example, polyphenylene sulfide is suitable as a material.

[0008] The gap cup, however, in which the ball bearing cup is arranged, results in a structure of the ball bearing that has to be arranged in a severe center filling and that is hardly able to dissipate the heat generated during operation to the outside. According to the invention, the heat dissipation is achieved by connecting the gap cup with the ball bearing cup that accommodates the ball bearings to the motor housing, in particular to the housing cover.

[0009] In an embodiment variant of the electric motor it is provided that the gap cup is integrally formed by the motor housing around the axis of rotation of the motor shaft. This ensures a sealing without additional sealing elements. In particular, the motor housing forms a surrounding outer wall, which on one axial side adjoins an axial wall, into which the gap cup is sunk. The housing is preferably designed as a hollow cylinder with sections of different diameters, wherein the ball bearing cup is arranged in the section which axially projects furthest into the motor housing.

[0010] In this case, an embodiment is advantageous, wherein the gap cup and the ball bearing cup are designed to have the same shape in the section of the gap cup in which the ball bearing cup is arranged. In other words, the ball bearing cup and the gap cup determine the same outer contour.

[0011] In a first embodiment variant, the gap between the housing cover and the gap cup has a gap size of zero. The housing cover thus directly abuts against the gap cup. In turn, the ball bearing located in the gap cup is thus also directly connected with the housing cover, so that heat is dissipated from the ball bearing cup to the outside environment via the gap cup on the housing cover.

[0012] In an alternative embodiment, the gap between the housing cover and the gap cup has a small gap size, which has a value of up to 1 / 20 of the maximum outer diameter of the ball bearing. The small gap hardly influences the heat dissipation from the ball bearing cup to the housing cover, but allows a relative arrangement of the components without contact.

[0013] An embodiment of the electric motor is also advantageous, wherein a heat-conducting paste or a heat-conducting glue is provided between the gap cup and the housing cover. The heat-conducting paste preferably forms an intermediate layer and enables a thermal bonding of the housing cover to the gap cup without the components contacting one another. This keeps the vibrations of the individual components from acting on one another. When using the heat-conducting glue, in addition to the advantageous effects of the heat-conducting paste, the housing cover can also be adhesively connected to the gap cup.

[0014] In an exemplary embodiment, the housing cover is detachably attached to the motor housing and is placed on one side in the axial direction of the remaining part of the motor housing. The housing cover thus forms such a part of the motor housing which is indirectly connected to the ball bearing cup and thus to the ball bearing via the gap cup. If the gap cup is integrally formed with the motor housing, the assembly of the components of the electric motor can be carried out on the side which is axially opposite the gap cup, on which side the housing cover is removably positioned. At the same time, the solution with the housing cover as a heat sink provides a large area for the dissipation of heat to the outside environment.

[0015] It is advantageous if the motor housing is also integrally provided with an insertion device to which the motor electronics are connected, into which a customer-specific plug can be inserted. The communication interface can also be integrated into the insertion device.

[0016] In a variant of the electric motor with further improved heat dissipation, the housing cover has a cooling element projecting axially in the direction of the external environment, which locally increases the cooling surface of the housing cover. A plurality of cooling fins distributed over the housing cover are preferably formed as the cooling element on the housing cover. The cooling fins can in particular be integrally formed on the housing cover or can be attached to the housing cover in a material bond. It is furthermore advantageous if, viewed in axial projection, a plurality of cooling fins extend above the ball bearing cup, so that the heat generated locally on the ball bearing cup is conducted particularly quickly and effectively to the external environment.

[0017] Also in the axially opposite direction, i.e. facing the gap cup, in an embodiment of the electric motor with improved heat dissipation, the connection surface to the ball bearing cup can be locally increased indirectly via the gap cup, since a cooling body projecting towards the ball bearing cup is formed on the housing cover.

[0018] It is specified as an advantageous embodiment that the cooling body is cylindrical or conical and has an axial connection surface to the axially outer wall surface of the gap cup. The heat of the ball bearing is thus transferred from the ball bearing cup to the gap cup, from the axially outer wall surface thereof to the connection surface of the cylindrical cooling body and finally to the entire surface of the housing cover comprising the cooling element.

[0019] The housing cover is made of metal or thermally conductive plastic, which also contributes to the heat dissipation.

[0020] In a preferred embodiment, the ball bearing cup forms a ball bearing seat into which the ball bearing is pressed.

[0021] Furthermore, a variant of the electric motor is distinguished in that the ball bearing cup has a free space between the ball bearing and the part of the motor housing connected to the external environment. The ball bearing can thus emit heat directly to the air in the free space and is not in direct contact with the axial surface of the ball bearing cup, which is in abutment with the gap cup and the cooling body.

[0022] In a further development of the electric motor it is provided that the gap cup extends axially through the motor housing up to the housing cover. In axial direction, i.e. along the axis of rotation of the motor shaft, the gap cup thereby defines a larger portion of the motor housing interior which is centered around the axis of rotation. The gap cup preferably extends in axial direction over 60-95%, more preferably over 70-95%, even more preferably over 80-90% of the total axial extension of the motor housing.

[0023] In an advantageous exemplary embodiment the motor housing and the gap cup are made of plastic and the metal ball bearing cup is directly encapsulated with plastic in the injection molding process.

[0024] For a compact design it is advantageously provided in the case of the electric motor that the winding surrounds the gap cup in circumferential direction. It is also advantageous that the winding is arranged axially spaced apart from the ball bearing. Thereby the heat generated by the motor winding is kept separate from the heat generated by the ball bearing.

[0025] It is further advantageous for a compact design of the electric motor that the motor electronics are arranged axially single-sided on a circuit board having a central opening and that a heat sink protruding from the housing cover extends through the central opening. Alternatively fixed, the gap cup extends through the central opening. BRIEF DESCRIPTION OF DRAWINGS

[0026] Further advantageous developments of the application are shown in more detail below with reference to the drawings together with the description of a preferred embodiment of the application. In the drawings:

[0027] Figure 1 a side sectional view of an electric motor showing an exemplary embodiment;

[0028] Figure 2 a detailed view of Figure 1 . DETAILED DESCRIPTION

[0029] In Figure 1 and Figure 2 an exemplary embodiment of an electric motor 1 according to the application is shown in a side sectional view or a detailed view.

[0030] The electric motor 1 comprises an integral motor housing 2 made of PPS (polyphenylene sulfide), which has a housing cover 3 that can be fixed axially on the motor housing 2 and, in the fixed state, forms part of the motor housing. On the side axially opposite the housing cover 3, the motor housing 2 integrally forms a gap cup 7 that extends axially into the interior of the motor housing 2. A motor portion, in which the motor winding 6 and the motor electronics 5 axially on one side fixed on a circuit board 14 are accommodated, is located between the inner wall of the motor housing 2 and the outer jacket of the gap cup 7. The components of the motor electronics 5 extend in the direction of the motor winding 6 in the cavity of the motor portion. A shaft portion, which is in contact with the medium conveyed by the work machine and along whose axis of rotation the motor shaft 4 extends, is located in the gap cup 7 and is sealed off by the gap cup 7. The gap cup 7 extends in the axial direction substantially through the entire motor housing 2 up to the housing cover 3. Furthermore, an insertion device 77 with connections to the motor electronics 5 connected on the circuit board 14 is integrated on the motor housing 2 for connecting a customer-specific plug.

[0031] An inner rotor 44 is positioned in the shaft portion in the gap cup 7, the ferrite permanent magnets 55 of which are provided with a plastic injection-molded encapsulation that determines the inner jacket surface thereof, which forms a shaft passage for the motor shaft 4. A press-on sleeve 22 is arranged on the inner jacket surface, which is supported on an axial stop (not shown) in order to be able to press on the motor shaft 4.

[0032] Seen in the axial direction, in the deepest portion of the gap cup 7, a ball bearing cup 8 is arranged, which is formed of a thermally conductive material, in particular of metal. The motor housing 2 with the gap cup 7 is injection-molded around the ball bearing cup 8 in an injection-molding process, so that the gap cup 7 and the ball bearing cup 8 have the same shape or inner and outer contour and lie directly against one another. The ball bearing cup 8 determines a bearing seat for the press-on ball bearing 9, in which the motor shaft 4 is supported. A free space 13 is formed between the ball bearing 9 and the axially inner wall surface of the gap cup 7, into which the motor shaft 4 extends with its free end.

[0033] A heat sink 11 made of solid material, which is cylindrical and projects axially in the direction of the ball bearing cup 8, is integrally formed on the housing cover 3 around the axis of rotation. Between the cooling element 11 and the axially outer wall surface of the gap cup 7 there is a gap 121 in the axial direction, the gap size of which is at most 1 / 20 of the ball bearing outer diameter. In the embodiment shown, a layer of thermally conductive paste 10 is provided in the gap 121, which can also be replaced by a thermally conductive adhesive.

[0034] The heat generated by the ball bearing 9 during operation is transferred from the ball bearing 9 to the ball bearing cup 8, further to the gap cup 7 and in axial direction through the heat conducting paste 10 to the heat sink 11 of the housing cover 3 of the motor housing 2. From the housing cover 3 the heat is further transferred to the outside environment. The motor housing, in particular its housing cover 3, thus serves as a heat sink. In an alternative embodiment, not shown, the heat conducting paste 10 is dispensed with and the heat sink 11 is in direct contact with the gap cup 7. The gap size of the gap 121 is zero.

[0035] The gap cup 7 is a hollow cylinder and is divided into three axial sections, each having a different inner diameter. The free space 13 is located in the region of the smallest diameter, the intermediate region is the bearing seat with the ball bearing 9, and in the region of the largest inner diameter the motor winding 6 is arranged radially around the gap cup 7. Thus, viewed in axial direction, the ball bearing 9 does not overlap the motor winding 5.

[0036] The circuit board 14 defines a central opening 15 around the rotational axis of the motor shaft 4, through which the heat sink 11 protruding axially from the housing cover 3 extends in axial direction to the gap cup 7. In an alternative variant, not shown but also belonging to the present disclosure, instead of the heat sink 11, the region of the smallest diameter of the gap cup 7 extends through the opening 15 or at least into the opening 15, so that the contact between the gap cup 7 and the heat sink 11 takes place flush with the circuit board 14 or axially above the circuit board 14. It is also provided in a further alternative embodiment that the housing cover 3 is designed without a heat sink 11 and that the gap cup 7 is in contact with the axially inner wall of the housing cover 3, either directly or through a heat conducting paste 10 or a heat conducting glue.

[0037] The housing cover 3 forms a plurality of cooling ribs 111, which are arranged distributed on the surface of the housing cover facing the outside environment and partially extend centrally, i.e. viewed in axial projection, over the ball bearing cup 8. Thus, the heat accumulated in the region of the ball bearing cup 8 is conducted more quickly into the outside environment.

Claims

1. An electric motor having a motor housing (2) having a shaft portion and a motor portion, the shaft portion for receiving a motor shaft (4), wherein motor electronics (5) and motor windings (6) are arranged in the motor portion, wherein the shaft portion and the motor portion are sealed apart from each other by a gap cup (7) arranged in the motor housing (2), wherein an inner rotor (44) and a metal ball bearing cup (8) axially adjacent to the inner rotor are mounted in the gap cup (7) in the shaft portion, and wherein a ball bearing (9) for supporting the motor shaft (4) is fixed in the ball bearing cup (8), and wherein the inner rotor (44) has a shaft channel forming an axial stop surface, a pressure sleeve (22) is provided in the shaft channel abutting against the stop surface, and the motor shaft (4) is pressed into the pressure sleeve (22). The inner rotor (44) includes a ferrite permanent magnet (55), wherein the ferrite permanent magnet (55) of the inner rotor (44) is provided with a plastic injection-molded package defining the surface of its inner sheath. The plastic injection molding encapsulation forms a shaft channel for the motor shaft (4), and the axial stop surface at the shaft channel is formed by a groove in the surface of the inner sheath, which constitutes a step.

2. The electric motor according to claim 1, characterized in that, The ball bearing cup (8) indirectly abuts against the part of the motor housing that is connected to the external environment through the gap cup (7), thereby making the motor housing act as a heat sink. The heat generated by the ball bearing (9) during operation is discharged to the motor housing and the external environment through the ball bearing cup (8) and the gap cup (7).

3. The electric motor according to claim 1 or 2, characterized in that, The gap cup (7) is integrally formed by the motor housing (2) around the rotation axis of the motor shaft (4).

4. The electric motor according to claim 1 or 2, characterized in that, The gap cup (7) and the ball bearing cup (8) are designed to have the same shape in the portion of the gap cup (7) where the ball bearing cup (8) is arranged.

5. The electric motor according to claim 1 or 2, characterized in that, Thermal paste (10) or thermal adhesive is provided between the gap cup (7) and the outer cover (3).

6. The electric motor according to claim 1 or 2, characterized in that, The motor housing (2) has a removable housing cover (3) which can be placed on one side of the rest of the motor housing (2) in the axial direction and forms the part of the motor housing that is indirectly connected to the ball bearing cup (8) through the gap cup (7).

7. The electric motor according to claim 6, characterized in that, The outer casing (3) has at least one cooling element that protrudes axially in the direction of the external environment, and the cooling element partially increases the cooling surface of the outer casing (3) in contact with the external environment.

8. The electric motor according to claim 7, characterized in that, The at least one cooling element is designed as a plurality of heat sinks (111) distributed on the housing cover (3), and at least one of the heat sinks (111) extends above the ball bearing cup (8) when viewed from an axial projection.

9. The electric motor according to claim 8, characterized in that, The outer casing (3) has a heat sink (11) that protrudes axially along the direction of the ball bearing cup (8) and indirectly and locally increases the connection surface with the ball bearing cup (8) through the gap cup (7).

10. The electric motor according to claim 9, characterized in that, The heat sink (11) is cylindrical or conical and has an axial connection surface with the axial outer wall surface of the gap cup (7).

11. The electric motor according to claim 1 or 2, characterized in that, The ball bearing cup (8) forms a ball bearing housing, and the ball bearing (9) is pressed or pushed into the ball bearing housing.

12. The electric motor according to claim 1 or 2, characterized in that, The ball bearing cup (8) has free space (13) between the ball bearing (9) and the part of the motor housing (2) that is connected to the external environment.

13. The electric motor according to claim 6, characterized in that, The gap cup (7) and the ball bearing cup (8) extend axially through the motor housing (2) to the housing cover (3).

14. The electric motor according to claim 1 or 2, characterized in that, The motor winding (6) surrounds the gap cup (7) in the circumferential direction and is axially spaced from the ball bearing (9).

15. The electric motor according to claim 6, characterized in that, The electro-electronic device (5) is axially arranged on one side of a circuit board (14), which has a central opening (15) that defines a direct fluid connection between the gap cup (7) and the housing cover (3), so that the heat generated by the ball bearing (9) during operation can be directly transferred to the housing cover (3).

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