EP2059993A1

EP2059993A1 - Shaft support system for electric motor, electric motor and method for making same

Info

Publication number: EP2059993A1
Application number: EP07731738A
Authority: EP
Inventors: Franck Debrailly; Domenico Restaino; Olivier Message; Franck Landrieve
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2006-03-15
Filing date: 2007-03-14
Publication date: 2009-05-20
Also published as: JP5085568B2; JP2009531003A; FR2898739B1; WO2007104894A1; CN101401280B; US20090261693A1; US8258659B2; CN101401280A; FR2898739A1

Abstract

The invention concerns a shaft support system (7) for an electric motor (1), comprising an antifricton bearing (17) provided with an inner race (33) and an outer race (34), at least one angular position sensor (20) for detecting the angular position of the inner race, an encoder (19) mounted on the inner race, a flange (16) for supporting the outer race of the bearing, and a processing module (18) supported by the flange.

Description

B 05 / 4310EN - GK / DD

Swedish Law Society known as: Aktiebolaget SKF

Tree support system for electric motor, electric motor and method of manufacture

Invention of: DEBRAILLY Franck RESTAINO Domenico MESSAGE Olivier

The present invention relates to the field of electric motors and more particularly that of the supports for ensuring the mechanical connection between a rotating shaft and an electric motor housing.

The abstract of JP-A-08023666 discloses a brushless motor, comprising a fastener associated with a Hall effect sensor for detecting magnets mounted on the shaft. The shaft is rotatably mounted in the fastener by means of bearings.

In a conventional engine of this type, the motor assembly steps are relatively numerous and complicated because of the large number of separate parts that provide the mechanical functions, electrical and rotation angle detection functions of the rotor.

The present invention aims to overcome the disadvantages of the state of the art mentioned above. The present invention provides a multifunctional shaft support.

The present invention provides a bearing and flange subassembly ensuring the mechanical connection between the shaft and the motor housing, and serving as a support for the sensor and the signal processing electronics.

The shaft support system for an electric motor comprises a rolling bearing provided with an inner ring adapted to be mounted on the shaft and an outer ring, at least one angular position sensor for detecting the angular position. of the inner ring, an encoder mounted on the inner ring, a flange support of the outer ring of the bearing, and a processing module supported by the flange. The support is a subset providing the functions of bearing, flange, and angular detection.

In one embodiment, the sensor is mounted on the processing module connected to an output of the sensor.

In one embodiment, the processing module is configured to receive an output signal of the sensor or sensors representative of the angular position of the encoder relative to the sensor and to output processed information representative of the angular position of the encoder relative to to the sensor. The support also provides the function of processing the angular detection information

In one embodiment, the flange is sealed. In one embodiment, the flange comprises fixing means on an electric motor. The fixing means may comprise through holes for screwing the flange on the sensor of the electric motor.

In one embodiment, the system includes sealing means with an end of the inner ring. The flange thus forms the axial end of an engine and prohibits an entry of liquid or pollutants. The seal may be of the narrow passage type or friction lip with the encoder or the inner ring or the motor shaft. In one embodiment, the angular position sensor is capable of detecting an absolute angular position. It is thus possible to know precisely the angular shoulder position of the rotor relative to the stator, which is particularly useful in the case of a brushless DC motor. In one embodiment, the processing module comprises an electronic card supporting the one or more sensors.

In one embodiment, the processing module is configured to output output information in analog or digital form.

In one embodiment, the flange is overmolded on the outer ring.

In one embodiment, the outer ring comprises a surface in contact with the flange provided with hooking reliefs. Said surface may be the outer surface of the outer ring.

The hooking reliefs can be obtained by knurling.

In one embodiment, the processing module is configured to output output information in the form of pulse width modulation. The invention also relates to an electric motor comprising a shaft, a rotor, a stator and a system as above supporting the shaft, mounted in the stator and capable of outputting the angular position of the rotor relative to the stator.

In one embodiment, said system closes an axial end of the engine. This gives an excellent seal.

The method of manufacturing a shaft support system for an electric motor comprises the steps of fixing a flange on a bearing outer ring equipped with an encoder, mounting on the flange of a treatment module. equipped with an angle sensor, the sensor and the processing module being connected.

In one embodiment, the flange and the rolling bearing are fixed to one another in a way that can not be dismantled.

In one embodiment, the flange is overmolded on the outer ring. This gives an excellent seal. The assembly of the motor can be carried out by orienting the rotor, bringing the shaft support system by an axial movement, the rotor shaft passing in the rolling bearing and fixing the flange on the housing of the electric motor. Fixing can be done by screwing.

It is thus possible to provide an electric motor manufacturer with a multifunction subassembly providing the mechanical connection between the shaft and the housing, supporting the electronic signal processing circuit and supporting the rotation sensor or sensors. The encoder is advantageously supported by a bearing ring. The support system is compact axially, is capable of sealing the engine by mounting a single subassembly, locally provides a processing of the output signals of the sensor or sensors in the immediate vicinity of the sensor or sensors. where better signal quality. Indeed, the processed output information is less sensitive to external noise or influences than the output signals of the sensor or sensors, especially when the processed output information is in digital form or pulse width modulation.

The present invention will be better understood on reading the detailed description of an embodiment taken by way of non-limiting example and illustrated by the appended drawings, in which:

FIG 1 is an exploded sectional view of an electric motor;

FIG 2 is a sectional view of the electric motor; FIG. 3 is a perspective view of the shaft support;

FIG. 4 is a perspective view opposite to FIG. 3 of the shaft support;

FIG. 5 is an exploded perspective view of the shaft support; and FIG 6 is an axial sectional view of the shaft support.

As illustrated in FIGS. 1 and 2, the electric motor referenced 1 as a whole comprises a housing 2, a stator 3 mounted in the housing 2, a rotor 4 and a shaft 5 integral in rotation with one another, a rolling bearing 6 disposed between one end of the shaft 5 and the housing 2, and a shaft support system

7 more particularly, the housing 2 comprises an axial portion 8, a radial bottom 9 closing one of the ends of the axial portion 8, and an axial flange 10 fixed to the radial bottom 9, centered on the axis of the motor and provided for receiving the rolling bearing 6.

The rolling bearing 6 may be of conventional type with an inner ring January 1, an outer ring 12, a row of rolling elements 13, here balls, arranged between an outer raceway of the inner ring January 1 and a path The bearing 6 may be provided with a cage for holding the circumferential spacing of the rolling elements 13 as well as a seal 14 disposed on the opposite side to the radial bottom 9. The presence of a seal on the side of the radial bottom 9 is not essential, insofar as the closed radial bottom 9 effectively protects the bearing 6 against the intrusion of external pollutants. One end of the shaft 5 is fitted into the inner ring January 1.

The stator 3 is in the form of a tubular piece, coming close to the radial bottom 9 of the casing 2 and in contact with the bore of the axial portion 8. The stator 3 further comprises three axial pins 15 projecting from direction opposite to the radial bottom 9. The rotor 4 is fixed on the shaft 5 and is mounted inside the stator 3 while being rotatable relative to said stator 3. The support system 7 for the shaft 5, seen in more detail in FIGS. 3 to 5, comprises a flange 16, a rolling bearing 17 supported by the flange 16, an electronic processing module 18 also supported by the flange 16 , an encoder 19 supported by the rolling bearing 17 and at least one sensor 20 supported by the module

18. In the embodiment shown, four sensors 20 are provided. In the assembled state, the support system 7 closes the end of the casing 2 on the opposite side to the radial bottom 9.

The flange 16 comprises a wall of generally radial annular shape 21 extending outwardly by four equally radial ears 22. Each lug 22 is provided with a through hole 23 allowing the passage of a dowel or a screw to fix the support system 7 on the housing 2. The flange 16 is provided with an annular rib 24 extending axially towards the radial bottom 9 and in contact with the bore of the axial portion 8 of the casing 2, thus ensuring the centering of the flange 7 in the casing 2. A plurality of recesses 25, in the form of an arc of a circle, are formed on the outer face of the flange 16 radially at the rib 24 for reasons of demolding withdrawal and differential cooling , thus avoiding that a thick part is cooled more slowly than finer parts.

A plurality of through holes 26, here three in number, are formed in the annular radial portion 21 and are provided to receive the fingers 15 of the stator 3. The stator 3 is thus immobilized in rotation relative to the support system 7. The 15 fingers and holes

26 may be circumferentially uniformly distributed or otherwise distributed at an angle other than 120 ° in order to index the stator 3 relative to the support system 7. The flange 16 comprises a frustoconical portion 27 extending from the annular radial portion 21, radially inwardly and axially towards the radial bottom 9 of the casing 2, an annular radial portion 28 extending inwardly the frustoconical portion. 27 and an annular axial portion 29 for housing the bearing

17. Rigidification ribs may be provided between the radial portion 28 and the axial portion 29 in the extension of the frustoconical portion 27.

More precisely, the radial portion 28 has a bore 29a delimited by two inwardly directed radial flanges 30 and 31. A plurality of axial fingers 32 are provided projecting from the radial portion 28, in a direction opposite to the radial bottom 9 of the housing 2. The flange 16 is advantageously made integrally in a synthetic material coming from molding, for example comprising polyamide 6-6 or polyethylene terephthalate loaded with glass or carbon fibers, for example in a proportion of the order of 10 to 50%, preferably of the order of 20 to 40%, for example about 30%.

The rolling bearing 17 comprises an inner ring 33, an outer ring 34, a row of rolling elements 35, here balls, a cage 36 for maintaining the regular circumferential spacing of the rolling elements 35 and a sealing flange 37 The bearing 17 represents a similar structure to the bearing 6 with two solid deep groove rings forming a raceway in the bore of the outer ring and on an outer bearing surface of the inner ring. The flange 37 is mounted in a groove of the outer ring 34 and forms a narrow passage with an outer bearing surface of the inner ring 33 being disposed on the side of the rotor 4. The outer ring 34 is in contact with the bore 29a of the axial portion 29 and the radial flanges 30 and 31 of the flange 16. Advantageously, the flange 16 is overmolded on the outer ring 34. This provides excellent sealing and mechanical strength between these two parts. The encoder 19 comprises a support 38, in the form of a sheet metal cup, and an active part 39. The support 38 comprises an axial portion fitted on an outer surface of the inner ring 33, on the opposite side to the sealing flange 37, a radial portion directed inwardly from the axial portion and in contact with a radial front surface of the inner ring 33 and a frustoconical portion directed radially inward and axially opposite the sealing flange 37 and extending the small diameter end of the radial part.

The active part 39, for example a magnetized plasto-ferrite comprising a plurality of circumferentially alternating north and south poles, is overmolded on the outer face of the frustoconical portion, one face of the radial portion opposite the inner ring 33 and part of the outer face of the axial part. The active portion 39 has an axial outer surface and may comprise a number of poles not multiple of the number of sensors.

The electronic module 18 comprises an electronic card 40 of generally annular shape, in which are formed a plurality of through holes 41, here three in number, provided to cooperate with the fingers 32 of the flange 16. During assembly, the fingers

32 pass through the holes 41 and thus ensure the angular retention of the module 18 relative to the flange 16 and its indexing. The electronic card 40, for example of the printed circuit type, supports a plurality of electronic components making it possible to process the output signals of the sensors 20 and generate an output signal transmitted to other organs not shown, by wire or radio. The electronic card 40 also supports the sensors 20 by means of four groups of three holes 43 formed near its inner edge and in which lugs 44 of the sensor elements 20 are arranged and then fixed, generally by brazing. The sensors 20 may be arranged circumferentially evenly distributed or not.

In the mounted state of the support system 7, illustrated in FIG. 6, the electronic module 18 is disposed near the outer face of the radial portion 28 of the flange 16. The sensor elements 20 project axially relative to the electronic board 40 and are arranged radially between the encoder 19 and the radial flange 31 of the radial portion 28, while being separated from the axial outer surface of the active portion 39 of the encoder 19 by a small radial gap. The electronic module 18 and the encoder 19 have an inside diameter greater than the bore of the inner ring 33 in order to pass an end of the shaft 5 of the electric motor.

There is thus a shaft support system forming a pre-assembled subassembly intended to be disposed at the open axial end of the casing 2 and providing the support functions of the rotating shaft of the electric motor. closing the open radial face of the casing 2, anti-rotation of the stator 3, detection of rotation parameters of the shaft 5, in particular the speed, the angular position, the acceleration, etc.

The shaft support system also supports the signal processing electronics and the one or more sensors. A cover can then come to protect the electronic module 18. The cover can be sealed, thus ensuring 10

high level protection for the interior of the electric motor and for the electronic card. It can be provided that the annular cover, fixed on the flange 16, comes to form a narrow passage with the encoder 19 and / or the inner ring 33 of the bearing 17. The cover can also be provided with a friction seal.

The manufacture of the shaft support system 7 may include the following steps. The flange 16 is over-molded on the outer ring 34 of the bearing 17. In order to ensure that the plastic material is securely fastened to the outer ring 34 of the bearing 17, knurling can be provided on at least a portion of the cylindrical outer surface. of said outer ring 34. The encoder 19 is connected to the inner ring 33. The electronic module 18 is mounted on the flange 16, then the assembly is closed with the cover. The mounting of the electric motor can be performed by a small number of relatively simple operations. First, it comes to place the bearing 6 in its housing at the bottom of the housing 2. It has the stator 3 in the housing 2. It has the shaft 5 supporting the rotor 4 in the bore of the inner ring 1 1 of the bearing 6. The shaft support subassembly 7 is arranged and fixed in the housing

2. The cover can then be attached to the flange. These steps are performed by simple axial movements. The mounting of the engine is thus greatly simplified.

Of course, the processing module 18 and more particularly the electronic circuits 42, may be designed to emit an output information in analog or digital form. The relative angular position of the poles of the encoder 19 and the sensors 20 can make it possible to detect the absolute angular position and thus to know with very high precision the position 11

relative to the poles of the rotor 4 relative to the poles of the stator 3. Alternatively, the electronic circuits 42 may be configured to emit an output information in the form of pulse width modulation. The output signal can thus be directly used by other external devices.

Claims

12

1 -shaft support system (7) for an electric motor (1), characterized in that it comprises a rolling bearing (17) provided with an inner ring (33) intended to be mounted on said shaft ( 5), and an outer ring (34), at least one angular position sensor (20) for detecting the angular position of the inner ring, an encoder (19) mounted on the inner ring, a flange (16). ) supporting the outer ring of the bearing, and a processing module (18) supported by the flange. 2-System according to claim 1, wherein the sensor (20) is mounted on the processing module (18) connected to an output of the sensor.

3-System according to claim 1 or 2, wherein the processing module (18) is configured to receive an output signal of the sensor or sensors representative of the angular position of the encoder relative to the sensor and to output processed information representative of the angular position of the encoder (19) relative to the sensor (20).

4-System according to any one of the preceding claims, wherein the flange (16) comprises fixing means on an electric motor (1).

5-System according to any one of the preceding claims, comprising a sealing means with one end of the inner ring. A system according to any one of the preceding claims, wherein the angular position sensor (20) is capable of detecting an absolute angular position. 13

7-System according to any one of the preceding claims, wherein the processing module (18) comprises an electronic card (40) supporting the sensor (20).

8-System according to any one of the preceding claims, wherein the flange (16) is overmolded on the outer ring (34) of the rolling bearing (17).

9-System according to any one of the preceding claims, wherein the outer ring (34) comprises a surface in contact with the flange provided with hooking reliefs. The system of any preceding claim, wherein the processing module is configured to output output information as pulse width modulation.

1 1 -Electric motor (1) comprising a shaft (5), a rotor (4), a stator (3) and a system (7) according to any one of the preceding claims supporting said shaft, mounted on the stator and capable to output the angular position of the rotor relative to the stator.

12-motor according to claim 1 1, wherein said system (7) closes an axial end of the engine.

13-A method of manufacturing a shaft support system for an electric motor, in which a flange (16) is fixed to an outer bearing ring (34) equipped with an encoder (19), a processing module (18) equipped with an angle sensor (20) is mounted on the flange (16), and the sensor and the processing module are connected.

14-Process according to claim 13, wherein the flange (16) is overmolded on the outer ring (34).

15-A method according to claim 13 or 14, wherein a rotor (4) is oriented, the tree support system (7) is brought by a 14

axial movement, the rotor shaft passing in the rolling bearing (17), and the flange is fixed on a housing (2) of electric motor (1).