CN108696085B

CN108696085B - Electronically commutated DC motor and method for assembling an electronically commutated DC motor

Info

Publication number: CN108696085B
Application number: CN201810300546.7A
Authority: CN
Inventors: 克里斯蒂娜·布罗克霍夫
Original assignee: Buehler Motor GmbH
Current assignee: Buehler Motor GmbH
Priority date: 2017-04-06
Filing date: 2018-04-04
Publication date: 2020-11-06
Anticipated expiration: 2038-04-04
Also published as: CN108696085A; CN208820647U; DE102017205847A1; KR102081805B1; KR20180113455A; JP6643386B2; JP2018183042A

Abstract

The invention relates to an electronically commutated DC motor and a method for assembling an electronically commutated DC motor. An electronically commutated direct current motor has a wound stator with a stator lamination stack and a can-shaped housing, and a permanent magnet rotor accommodated within the stator lamination stack. The object of the invention is to find an easy and economical means of introducing a pre-magnetized permanent magnet rotor into a can-like motor housing without damaging the magnetic coating, without forming debris and without damaging the user interface on the shaft section. This object is achieved according to the invention by the features of claim 1.

Description

Electronically commutated DC motor and method for assembling an electronically commutated DC motor

Technical Field

The invention relates to an electronically commutated direct current motor having a wound stator with a stator lamination stack and a pot-shaped housing, and a permanent magnet rotor which is accommodated within the stator lamination stack and has a shaft, a plastic sleeve and magnetized permanent magnets.

Background

Such direct current motors are used widely and in different fields of application. They may be used in dry or wet areas, where they are filled with liquid or externally exposed to liquid. These direct current motors serve, for example, as drives for oil pumps. In the case of high sealing requirements, these electrical machines often have a pot-shaped housing, since the number of connections to be sealed is therefore low. Permanent magnet rotors used in electronically commutated dc motors tend to become magnetized in the final assembled state. However, the magnetization of the permanent magnet rotor is often negatively influenced by the stator geometry. In order to obtain a better magnetization of the permanent magnet rotor and thus an optimized efficiency of the direct current motor, the permanent magnet rotor is preferably magnetized in a magnetization device prior to assembly. A large radial force is a problem here, which acts between the permanent magnet rotor and the stator during the assembly process. These radial forces may cause the permanent magnet rotor to be impacted and/or scraped, especially at the stator lamination stack. Debris may occur which negatively affects bearing performance, bearing life, grinding characteristics, etc. The coating of the permanent magnet may also be damaged. This shortens the service life and affects the functionality of the machine by corroding the magnetic material.

In order to ensure contactless installation of the dc motor into the stator, complex joining devices are required, which likewise hold the dc motor and the stator securely and join them together in a defined manner. Here, the preassembled rotor must be accommodated on the shaft section of the device. In many applications, these shaft sections form or comprise user interfaces which may be damaged when accommodated in the makeup tool. Furthermore, these devices should be manufactured separately for each rotor type, and are therefore also uneconomical.

Disclosure of Invention

The object of the invention is therefore to find an easy and economical means of introducing a pre-magnetized permanent magnet rotor into a can-like motor housing without damaging the magnetic coating, without forming debris and without damaging the user interface on the shaft section.

This object is achieved according to the invention by an electronically commutated dc motor according to the invention or a method according to the invention for producing an electronically commutated dc motor. The permanent magnet is connected with the shaft through a plastic sleeve. This is a possible measure for fastening the permanent magnet. The plastic sleeve also has the additional function of a guide which projects radially beyond the permanent magnet. Such a guide allows the permanent magnet rotor to be in contact with the stator in the region of the guide without damaging the coating of the permanent magnets, since it is kept at a small distance from the stator lamination stack. This solution can be implemented in an easy and economical way and allows to split the permanent magnet rotor without damaging the user interface on the shaft end.

The pot-shaped housing has, on the one hand, a closed pot bottom and, on the other hand, an assembly opening. The guide is arranged on the end of the permanent magnet rotor close to the tank bottom. This ensures that the guide is first introduced into the rotor recess of the stator lamination stack and the permanent magnets follow the guide.

In a suitable manner, the radially projecting guide should have a smaller radial extent than half the inner diameter of the stator lamination stack. This design ensures that the permanent magnet rotor can be split into the stator without forced wear.

The guide portion preferably has an annular shape. In this way, the permanent magnet rotor can be magnetically drawn in any radial direction without damaging the permanent magnets or their cladding.

Furthermore, a lead-in bevel is provided which is at 15 ° to 30 °, preferably 20 °, to the mating direction. The lead-in chamfer increases the alignment tolerance between the stator shaft and the rotor shaft during the makeup process.

According to a further development of the invention, the plastic sleeve achieves a form-locking (formschlussig) connection of the permanent magnet and the shaft against relative rotation by means of a molding process (urformlocking). For this purpose, the permanent magnet has a recess into which the projection of the plastic sleeve engages. The shaft is provided with knurls. The polyamide is provided as a plastic material.

In order to avoid material accumulation, recesses are provided between the shaft and the permanent magnets, which are interrupted by spokes.

The stator lamination stack consists of layered individual sheets which have rounded inner edges on the first sheet-side edge (which faces the assembly opening of the pot-shaped housing). Rounded inner edges are produced by a punching process (shearing), wherein the sheet material near the edge is usually pulled into the sheet plane on one side and pulled out of the sheet plane on the opposite side. The orientation of the sheets is usually selected such that the stator lamination stack is fitted into the can-shaped housing with rounded outer edges leading. In this case, the inner edges are also generally rounded or provided with burrs in the same manner and orientation. The invention avoids an increased scraping effect by the punching direction of the rotor receptacle being antiparallel to the punching direction of the free punching of the stator outer diameter.

For tolerance reasons and to further reduce the scraping effect of the lamination stack on the pot-shaped housing, the stator is fastened by means of radially projecting tongues. In order to simplify the assembly of the stator in the housing, no tongues are provided on the end sections. In the following section, the tongues are located only on each second sheet, and in the other section the tongues are located on each two following sheets separated by a tongue-free sheet. This stator design serves as a compensation means for the slightly conical inner contour of the deep-drawn housing. The tongue-free sheet allows for easy deflection (bending), thereby reducing the scraping effect. The section with the more loosely arranged singlets with free space behind each tongue is provided for the region of the housing with the smaller inner diameter, while the section with the more densely and rigidly arranged singlets is provided for the region of the housing with the larger inner diameter.

If debris occurs, particularly due to scraping of the end sheets over the housing, the debris is collected by a containment pocket in one or both of the winding insulators. Other debris scraped off the tongues is generally retained in the free space between the tongues.

Another solution consists in a method for producing an electronically commutated direct current motor having a wound stator with a stator lamination stack and a pot-shaped housing, and a permanent magnet rotor accommodated within the stator lamination stack, the stator lamination stack having a shaft, a plastic sleeve and magnetized permanent magnets, wherein the permanent magnets are connected to the shaft by the plastic sleeve, characterized by the following method steps:

a) the shaft is prepared for the knurling,

b) a permanent magnet having a following geometry is prepared,

c) the shaft and the permanent magnet are introduced into a cavity of an injection mold,

d) in the case of forming the guide portion with the introduction slope, the thermoplastic plastic substance is injected into the remaining hollow space of the cavity,

e) the permanent magnet rotor is taken down from the injection molding machine,

f) the permanent magnet is magnetized in the magnetizing device,

g) the housing bearing is sleeved on the shaft,

h) the housing is prepared and the casing is prepared,

i) the pre-assembled stator is prepared and,

j) the stator is pressed into the housing with the rounded side of the single sheet,

k) the magnetized permanent magnet rotor is fitted into the stator recess with the guide portion in the front and the housing bearing is fitted into the housing.

Other intermediate and final assembly steps are required for complete assembly, but they are not the subject of the present invention.

Drawings

Embodiments of the present invention are further described below with reference to the accompanying drawings. In the drawings:

figure 1 shows a cross-section of a stator and a permanent magnet rotor;

FIG. 2 shows an exploded view of a permanent magnet rotor;

FIG. 3 shows a partial cross-sectional view of the stator;

FIG. 4 shows a cross-sectional view of a permanent magnet rotor; and

fig. 5 shows an end side view of a permanent magnet rotor.

Description of the drawings:withReference numerals and corresponding references (a, b …)Is free ofReference numerals indicate details with the same names in the figures and the description of the figures. It is here an application in further embodiments, the prior art, and/or that the details are variants. The claims, the introductory part of the description, the list of reference signs and the abstract contain only non-numbered reference signs for reasons of simplicity.

Detailed Description

Fig. 1 shows a sectional view of a stator 2 and a structural assembly consisting of a permanent magnet rotor 5 and a bearing cap 36. The stator 2 comprises a pot-shaped housing 4, a housing bearing 20 and a stator lamination stack 3 consisting of a single sheet 12 with rounded edges 13 and burrs 28. The rounded edges are formed during the stamping process. The punching direction in which the rotor accommodating portion 43 is punched is opposite to the punching direction in which the outer peripheral edge 44 of the single sheet 12 is free to be punched. This allows an optimal assembly of both stator lamination stack 3 and rotor 5. At the outer periphery 44, the tongue 26 projects radially. The stator 2 is shown simplified (without windings, winding insulation and contacts) and the sheet material dimensions are exaggerated in order to be able to identify the rounded edges 13, the burrs 28 and their orientation more clearly. The orientation of the stator lamination stack is chosen such that the direction of the split of the permanent magnet rotor 5 to be split points towards the rounded side of the single sheet 12. The end sheets 49 on both ends of the stator lamination stack have no tongues and form as little clearance as possible with the housing 4. The housing 4 comprises a cylindrical region 29 and a pot bottom 10, which is lengthened in the axial direction by a bearing receptacle 30. The permanent magnet rotor 5 comprises a shaft 6 (with a truncated portion 23, which serves as a user interface), a plastic sleeve 7, a permanent magnet 8 and a guide 9 with a lead-in chamfer 14 (see fig. 3), wherein the guide 9 is arranged on the first end 11 of the permanent magnet rotor 5 facing the pot bottom 10. The diameter of the guide 9 is greater than the diameter of the permanent magnets 8 so that the permanent magnets 8 cannot come into contact with the stator lamination stack 3. The housing bearing 20 is fitted with a force-fitting (kraftschlussig) onto the shaft end 31 facing the pot bottom 10. The ball bearing serves as a housing bearing 20, the outer ring of which comes into sliding fit with the pot housing 4, in particular the bearing receptacle 30, once the stator 2 has been assembled. The spring washer 41 is responsible for enabling the ball bearing to be assembled without play. The bearing cap 36 includes a seal in the form of an O-ring 37 that seats in a groove 38. The O-ring rests in the assembled state against the housing flange 42. In addition, a bearing cap bearing 39 is accommodated in the bearing cap 36, which is fastened by means of a beryllium clamping washer 40.

Fig. 2 shows an exploded view of a permanent magnet rotor 5 with a shaft 6, a plastic sleeve 7 and permanent magnets 8. The shaft 6 has a truncated portion 23 as a user interface, a guided shaft end 31 and a knurling 15, with the aid of which a plastic sleeve can be molded on the shaft 6 in a rotationally fixed and axially fixed manner. The plastic sleeve 7 comprises a magnet receiving area 32, a guide 9, a retaining ring 21, a projection 19, a recess 16, a spoke 24, a recess 17 and a shaft recess 22. The magnet receiving region 32 is axially delimited by the retaining ring 21 and the guide 9. The recesses 16 are arranged between the shaft recess 22 and the magnet receiving area 32 and are separated from each other by spokes 24; they are used above all to avoid material accumulation. The permanent magnets 8 are designed here as plastic-bonded permanent magnet rings which are provided with indentations 18 which correspond to the elevations of the plastic sleeve 7. The outer contour of the magnet receiving region 32 and the inner contour of the permanent magnet 8 are polygonal, so that an additional torsional protection is formed.

Fig. 3 shows a partial cross-section of a stator 2 (without housing) with a stator lamination stack 3, single sheets 12 with tongues 26 projecting partly in the radial direction. Typically a single sheet without a tongue is followed by a single sheet 12 with a tongue 26. In one region, two individual sheets with tongues follow each other and are separated from one another by a single sheet without tongues. The end sheets 49 in the initial zone 33 and the terminal zone 34 are free of tongues. The sheet diameter is smaller than the housing inside diameter in these areas, so that it can be easily inserted into the assembly opening 25 (see fig. 1). The gap between the end sheet 49 and the housing 4 is chosen as small as possible in order to keep at least the larger debris within the stack. Furthermore,

insulation

27a, 27b are shown, which serve to accommodate the stator windings and to electrically insulate the stator windings with respect to the stator lamination stack 3. Insulator 27a has a receiving pocket 35 to receive and retain debris that is generated when stator stack 3 is assembled in the housing. The arrow indicates the direction of lamination of stator stack 3 when it is assembled into the housing. The first insulating piece 27a first sinks into the housing, then follows the initial region 33 of the stator lamination stack 3, the loosely delaminated first region 45, the tightly delaminated second region 46, the terminal region 34, and finally the second insulating piece 27 b. In the loosely layered first region 45, the single sheets 12a with tongues 26 and the single sheets 12b without tongues alternate with each other. In the tightly layered second region 45, every two adjacent single sheets 12a with tongues 26 alternate with one single sheet 12b without tongues. The reason for this is that the housing is slightly conical and possibly scratched off due to the preceding single sheet of the first region 45. The tongue 26 in the first region 45 must be deformed more significantly than the tongue 26 in the second region 46 on the basis of the tapering housing diameter. The first insulating part has a sealing edge 47 which rests against the housing.

Fig. 4 shows a sectional view of the permanent magnet rotor 5 with the shaft 6, the truncated portion 23, the guided shaft end 31, the knurling 15, the plastic sleeve 7, the recess 16, the web 24, the retaining ring 21, the guide 9 on the first end 11 of the permanent magnet rotor 5 and the recess 17 for the defined accommodation of the permanent magnet 8 in the injection mold. Detail a shows enlarged a guide 9 with a lead-in chamfer 14 inclined at an angle α of 20 ° with respect to the split direction (axis-parallel direction).

Fig. 5 shows an end-side view (side view) of the permanent magnet rotor 5 with the guided shaft end 31, the plastic sleeve 7, the recess 16, the spoke 24, the guide 9, the lead-in chamfer 14 and the recess 17. In the example shown, three recesses 16 and six notches 17 are provided.

List of reference numerals

1 DC motor 30 bearing housing

2 shaft end guided by stator 31

3 stator lamination stack 32 magnet receiving area

4 initial area of the housing 33

5 permanent magnet rotor 34 terminal area

6 axle 35 accommodating pocket

7 plastic sleeve 36 bearing cap

8 permanent magnet 37O-ring

9 guide 38 groove

10 tank bottom 39 bearing cap bearing

11 first end 40 beryllium clamping washer

12 single sheet 41 spring shim

13 rounded edge 42 housing flange

14 lead-in ramp 43 rotor receiving portion

15 knurled 44 outer periphery

16 recess 45 first region

17 second region of recess 46

18 indented portion 47 sealing edge

19 convex 48 outer edge

20 casing bearing 49 end sheet

21 retaining ring

22 shaft recess

23 truncated portion

24 spoke

25 assembly opening

26 tongue part

27 insulating member

28 burrs

29 columnar region

Claims

1. Electronically commutated direct current motor (1) having a wound stator (2) having a stator lamination stack (3) and a pot-shaped housing (4), and a permanent magnet rotor (5) accommodated within the stator lamination stack (3) having a shaft (6), a plastic sleeve (7) and magnetized permanent magnets (8), wherein the permanent magnets (8) are connected to the shaft (6) via the plastic sleeve (7) and the plastic sleeve (7) has a guide (9) projecting radially over the permanent magnets (8), wherein the stator lamination stack (3) consists of a layered single sheet (12) and has a recess acting centrally as a rotor receptacle (43), wherein the single sheet (12) is provided with a rounded inner edge (13) facing a mounting opening (25) of the pot-shaped housing (4) and facing away from a pot base (10) of the housing (4), and wherein in a first section behind the end sheet the single sheets (12) with tongues (26) and the single sheets without tongues alternate with each other, and in a second section every at least two following single sheets (12) with tongues alternate with one single sheet without tongues.

2. Electronically commutated direct current motor according to claim 1, wherein the pot-shaped housing (4) has a closed pot bottom (10) on the one hand and a fitting opening (25) on the other hand, wherein the guide (9) is arranged on the end (11) of the permanent magnet rotor (5) close to the pot bottom (10).

3. Electronically commutated direct current motor according to claim 1 or 2, characterized in that the radially protruding guide (9) has a smaller radial extent than half the inner diameter of the stator lamination stack (3).

4. Electronically commutated direct current motor according to claim 1 or 2, wherein the guide (9) has an annular shape.

5. Electronically commutated DC motor according to claim 1 or 2, wherein the guide (9) has a lead-in chamfer (14) or a radius with respect to the tank bottom (10).

6. Electronically commutated DC motor according to claim 1 or 2, characterized in that the plastic sleeve (7) achieves a form-locking connection with the permanent magnet (8) and the shaft (6) against relative rotation by means of a moulding process.

7. Electronically commutated DC motor according to claim 1, characterized in that the same single sheet (12) has on its outer periphery a rounded outer edge (48) facing away from the assembly opening (25) of the pot-shaped housing (4) and facing the pot bottom (10).

8. Electronically commutated direct current motor according to claim 1 or 2, characterised in that the stator lamination stack (3) consists of different sheet sections, wherein a plurality of individual sheets (12) have a protruding tongue (26) in an angular range, with the aid of which tongue the stator lamination stack (3) is clamped in the housing (4), and a plurality of further individual sheets have a recess in the same angular range.

9. The electronically commutated DC motor of claim 8, wherein the plurality of single sheets have neither tongues nor notches.

10. Electronically commutated direct current motor according to claim 8, characterized in that the end sheets (49) on one or both ends of the stator lamination stack (3) have neither tongues nor notches.

11. Electronically commutated direct current motor according to claim 10, characterized in that as little clearance as possible remains between the housing (4) and the end sheet (49).

12. Electronically commutated direct current motor according to claim 1 or 2, characterized in that an insulation (27) is coupled to the stator lamination stack (3), which insulation has a receptacle pocket (35) for debris.

13. Electronically commutated DC motor according to claim 12, wherein the sealing edge (47) of the receiving pocket (35) bears against the housing (4).

14. Method for producing an electronically commutated DC motor (1) having a wound stator (2) with a stator lamination stack (3) and a pot-shaped housing (4) and a permanent magnet rotor (5) accommodated within the stator lamination stack (3) with a shaft (6), a plastic sleeve (7) and magnetized permanent magnets (8), wherein the permanent magnets (8) are connected to the shaft (6) by means of the plastic sleeve (7), characterized in that,

the method comprises the following method steps:

a) a shaft (6) to be knurled,

b) preparing a permanent magnet (8) having a following geometry,

c) introducing the shaft (6) and the permanent magnet (8) into a cavity of an injection mold,

d) in the case of forming a guide (9) of the plastic sleeve (7) which projects radially beyond the permanent magnet (8) and has a lead-in chamfer (14), a thermoplastic plastic substance is injected into the remaining hollow space of the cavity,

e) the permanent magnet rotor (5) is taken down from the injection molding machine,

f) the permanent magnet (8) is magnetized in a magnetizing device,

g) the housing bearing is fitted to the shaft (6),

h) preparing a housing (4),

i) preparing a preassembled stator (2), wherein the stator lamination stack (3) is composed of layered individual sheets (12) and has a recess which centrally serves as a rotor receptacle (43), wherein the individual sheets (12) are provided with a rounded inner edge (13) which faces the assembly opening (25) of the can-shaped housing (4) and faces away from the can bottom (10) of the housing (4), and wherein, in a first section behind an end sheet, individual sheets (12) with tongues (26) and individual sheets without tongues are alternately followed by one another, and in a second section, every second individual sheet (12) with tongues which follows is alternated by one individual sheet without tongues,

j) pressing the stator (2) into the housing (4),

k) a magnetized permanent magnet rotor is fitted into a rotor receiving portion (43) with a guide portion (9) in front and the housing bearing (20) is fitted into the housing (4).