EP0165257A1

EP0165257A1 - Electric motor with disk-shaped magnetized rotor

Info

Publication number: EP0165257A1
Application number: EP84904086A
Authority: EP
Inventors: Claude Oudet; Gilbert Drey
Original assignee: Portescap SA
Current assignee: Portescap SA
Priority date: 1983-11-30
Filing date: 1984-11-29
Publication date: 1985-12-27
Also published as: WO1985002503A1; KR850700189A; FR2555835A1

Abstract

Dans le présent moteur, la partie aimantée annulaire (5) du rotor est fixée sur une partie (9) d'un roulement à billes par l'intermédiaire d'un disque annulaire plan (7), dont les surfaces annulaires planes sont en contact avec des surfaces annulaires planes respectives de ladite partie de rotor (5) et de ladite partie du roulement (9). L'invention s'applique plus particulièrement à des moteurs du type susmentionné à deux étages. Elle permet, dans le cadre d'une structure simple et économique, de réaliser une très grande précision dans la définition de la position de la partie aimantée du rotor par rapport au stator.In the present motor, the annular magnetic part (5) of the rotor is fixed to a part (9) of a ball bearing by means of a planar annular disc (7), the planar annular surfaces of which are in contact. with respective planar annular surfaces of said rotor part (5) and said bearing part (9). The invention applies more particularly to motors of the above-mentioned type with two stages. It allows, within the framework of a simple and economical structure, to achieve a very high precision in the definition of the position of the magnetized part of the rotor relative to the stator.

Description

ENGINE ^"ELECTRIC ROTOR MAGNETIC DISK SHAPED

The present invention relates to an electric motor comprising both a stator and at least one rotary member comprising a rotor part essentially in the form of a flat annu¬ disk mounted rotatably with respect to the stator by means of at least one bearing. with balls comprising at least two coaxial bearing rings forming ball raceways, at least one of these bearing rings having a planar annular surface perpendicular to the axis of rotation.

.n such a motor is described for example in US Patent No. 4,330,727 in the form of a synchronous motor with magnetic rotor.

In motors of this type, it is important that the disc-shaped rotor part is arranged very precisely relative to the stator. Even in mass production, the position of the annular disc must be defined with great precision with respect to the parts of the stator with which this disc cooperates, and this in particular as regards the position of the disc in the axial direction and with regard to relates to the orientation of the plane of the disc which must be strictly perpendicular to the axis of rotation.

Usually the annular disc-shaped part of the rotary member is fixed thereto by means of a support piece mounted on the motor shaft, so that the dimensional and positional tolerances of this part are added to the sets of ball bearings. Furthermore, it is difficult by means of such a support piece to ensure a plane of rotation exactly perpendicular to the motor shaft.

The present invention aims to provide an engine of the type mentioned above, the construction of which is simple and economical and which makes it possible to achieve very great precision in defining the position of the disc-shaped rotor part relative to the stator.

To this end, the motor according to the invention is characterized in that the rotor part is fixed on a rolling part, directly, so that respective flat annular surfaces are in contact with each other, or indirectly, via a support part having a planar annular surface in contact with the planar annular surface of said rolling part, and in contact with said rotor part, or via a support part in the form of a flat annular disc of which one or more flat annular surfaces are in contact with the respective flat annular surfaces of said rotor part and said rolling part.

The invention applies more particularly to a synchronous motor with a magnetic rotor and, according to a preferred embodiment, to a motor of this type with two stages. In this case, the stator comprises two parts, each forming a magnetic circuit with an air gap, and being coupled with at least one control coil, as well as two rotary members cooperating respectively with each of these stator parts.

The advantages and the particularities of the motor according to the invention will become more clearly apparent from the following description, from various embodiments given without limitation and illustrated in the appended drawing, in which

FIG. 1 is a view in axial section of a two-stage two-phase synchronous motor,

Figure 2 is a sectional view along line II-II of the

WIPO figure 1 ,

FIG. 3 is a view in partial axial section of a motor similar to that of FIG. 1 comprising a double ball bearing, with a common ring,

FIG. 4 is a view in partial axial section of another alternative embodiment of the motor of FIG. 1 comprising two juxtaposed ball bearings,

FIG. 5 is a view in partial axial section of an alternative embodiment similar to that of FIG. 4 comprising a ball bearing with three rings and a single row of balls,

FIG. 6 is a view in axial section of a two-phase synchronous motor having two rotary members resiliently coupled in the axial direction,

FIG. 7 is a view in partial axial section of an alternative embodiment of the engine according to FIG. 6,

FIG. 8 is a view in partial axial section of another embodiment of the engine of FIG. 6, and

FIG. 9 is a view in partial axial section of another alternative embodiment of the engine according to FIG. 6.

The motor shown in FIG. 1 is a two-stage motor, each of which comprises a respective stator part 1,2 and a corresponding rotary member 3,4. Each rotary member comprises a respective rotor part 5, 6, in the form of a thin, planar annular disc, made of a magnetizable material such as samarium-cobalt. These discs are magnetized parallel to their axis so as to present on each of their flat surfaces alternately positive and negative magnetic poles, distributed regularly along an annular zone of each surface. They are glued or fixed in some other appropriate manner on a portion of 7.8 ^* corresponding support also having a disc-shaped annular plane. The support discs are in turn fixed, for example by welding, on the cheeks of respective inner rings 9, 10 of two ball bearings, the corresponding outer rings of which are designated by 11 and 12 respectively, the rows of balls of each bearings being designated by 13 and 14. The inner rings of the two ball bearings are mounted on an axis 15 of the motor so as to be integral with this axis in their final position determined during the assembly of the motor.

The two stator parts 1,2 of the motor of FIG. 1 each comprise a corresponding electrical control coil 16 and 17, of annular shape, arranged coaxially with respect to the axis of the motor. Each coil is coupled with a magnetic circuit comprising two annular parts designated 18.19 and 20.21 respectively. These annular parts are made of a material of very good magnetic permeability, and they are in two-by-two contact along peripheral plane contact zones 22 and 23 so that the magnetic resistance also remains low at this location. On the other hand, the parts 18 to 21 each have an inner annular part comprising a series of teeth, such as 24, distributed over the entire circumference so as to form in each of the stator parts a variable annular air gap along this circumference . As shown in FIG. 1, the axial section of the magnetic circuits thus has a C shape and an annular zone of each rotor part is disposed in the respec¬ tive air gap formed by these magnetic circuits.

In the motor of FIG. 1, the external parts 18 and 21 of the magnetic circuits are mounted on the corresponding external rings 11 and 12 of the ball bearings of the motor. A support plate 25 is also

OMH fixed on a part of the outer cylindrical surface of the ring 11 of one of the ball bearings.

The internal parts 19 and 20 of the two stator parts 1 and 2 are in contact along an annular cylindrical surface 26 perpendicular to the axis of the motor. An intermediate piece with parallel flat surfaces could be arranged, according to an alternative embodiment, between the parts 19 and 20, so that these parts would be spaced apart while preserving the parallelism of their flat annular surfaces such as the surface 26.

In FIG. 1, a distinction is also made between carcass parts such as 27 in which the control coils are housed, and a separation piece 28, made of plastic, which can be placed between the two rotor parts to facilitate mounting of the engine.

FIG. 2 shows the configuration of certain elements of the motor in section along the line II-II of FIG. 1, and in particular the teeth 24 oriented radially and arranged essentially regularly along the inner periphery of the visible annular part 19.

The assembly of the engine, and in particular the fixing of the inner rings 9 and 10 of the ball bearings on the axis 15 of the engine and the fixing of the outer rings 11, 12 on the parts 18 and 21, is carried out so as to eliminate the clearance between the inner and outer rings of each ball bearing. Figure 1 shows that the inner rings 9 and 10 are thus slightly offset axially relative to the outer rings 11 and 12. The elasticity cited in the chain of elements 15, 9, 13, 11, 18, 19, 20 , 21, 12, 14, 10, 15 eliminates the play in the ball bearings without significant increase in friction. This achieves a very high precision in the positioning of the rotor and stator parts relative to each other, in a relatively simple manner even in mass production, this precision is preserved over the life of the engine thanks to the elasticity mentioned.

Figure 3 shows an alternative embodiment which uses, instead of two separate ball bearings, two combined roule¬ ments having one of their bearing rings in common. The stator parts, designated respectively by 31 and 32, have a configuration similar to that of FIG. 1 and are mounted on the common ring 33 of the combined ball bearings. Two inner rings 34 and 35 cooperate with the common ring by means of two rows of balls 36, 37. The rings 34 and 35 are in contact with one another along an annular surface 38 and each comprise a respective support part 39, 40 having planar annular support surfaces perpendicular to the axis of rotation of the motor. Annular rotor parts 41, 42 are mounted on these support parts so as to be arranged in the air gaps of the two stator parts. The assembly of the rings 34 and 35 is carried out so that the two combined ball bearings have practically no resulting play. The motor axis and the engine support parts are no longer shown in Figure 3 and in some of the following figures.

FIG. 4 illustrates an embodiment which differs essentially from the examples of FIGS. 1 and 3 by the presence of two juxtaposed ball bearings which each include a first rolling ring 43,44 and a second rolling ring 45, 46 cooperating with two rows of respective balls 47,48. The two bearings are mounted side by side so that the assembly has no resulting play. The rotor parts 49, 50 are fixed to the cheeks formed by the front surfaces of the rings 45, 46 by means of corresponding support discs 51, 52. The stator parts shown in FIG. 4 each have two annular sheet metal parts 53, 54 and 55, 56, formed so as to present a housing for the control coils 57, 58 and opposite teeth, similar to those of the figure. 1, such as the teeth designated by 59. The parts 54 and 55 are fixed to the outer rings 43 and 44 of the juxtaposed ball bearings, by means of a common support piece 60 which can be welded to the pieces 54, 55, 44 and 43 so as to make these integral. A pin 61 can be mounted inside the rings 45 and 46 of the ball bearings, as shown in the figure.

5 shows an alternative embodiment of the engine of Figure 4 in which a single bearing with a row of balls and three bearing rings is used in place of the two juxtaposed bearings of Figure 4. An outer ring of the bearing designated by 62 cooperates, via a row of balls 63, with two inner rings 64,65 juxtaposed axially, the whole of the bearing being adjusted so that it presents practically no play. The rotor parts and stator can be fixed, in a similar manner to that of the previous examples, respectively to the inner rings and the outer ring of this bearing. In the example shown in Figure 5, the support part 60 of Figure 4 has been deleted, but the other parts of the rotor and stator parts, are similar to those of Figure 4 and have been designated by the same reference figures. Figure 5 further shows two closure parts 66,67 placed on the stator parts so as to protect the interior of the motor. The shaft 61 shown is constituted by a long, cut pinion which, owing to the fact that it is centered by its teeth ends, ensures very good mounting precision with respect to the ball bearing. Figure 6 shows, in section along an axial plane, another two-phase synchronous motor, comprising two separate rotary members 71 and 72, arranged coaxially opposite one another. Each of these rotary members comprises a respective magnetic annular disc 73, 74, fixed by one of its flat surfaces on an annular flat surface, such as 75, of a corresponding rolling part 76, 77, forming part of a rolling bearing. respective axial balls 78, 79.

The two rolling parts 76 and 77 are coupled by means of a coupling device, constituted, in the present example, by two spring washers 80 and 81, which are housed in a corresponding recess of each rolling part, to tend to separate these two parts in the axial direction. The two outer bearing parts, designated by 82, 83 form axial stops, by means of the ball bearings, for the inner bearing parts 76 and 77, so that the position of the two rotor parts relative to the stator is defined, without play, by the. two ball bearings. Coupling in the circumferential direction, that is to say in the direction of rotation, can be ensured by welding the two washers with each other during their mounting, and by welding each them on the corresponding bearing part. In some cases, the friction of the spring washers and / or a notching of these may be sufficient to ensure that the two rolling parts are integral in their rotation.

The stator 84 of the motor comprises two annular electric coils 85 and 86, which are each coupled with a corresponding magnetic circuit 87 and 88. Each magnetic circuit is formed by two parts 89, 90 and 91, 92 made, for example, of a material magnetically permeable frit. These parts have an annular shape and are in contact along a respective flat annular zone 93, 94 with low magnetic resistance. Rooms 89 to 92 on the other hand, each have an annular part provided with a series of teeth such as 95, distributed over the entire circumference, so as to form a variable air gap cooperating with the magnetized zones of the corresponding disc 73 or 74.

The position of the magnetized discs 73 and 74 in the gaps of the magnetic circuits 87 and 88 is defined by the dimensions of the two ball bearings 78 and 79, and by the flat contact surfaces of the parts 89 to 92. The corresponding dimensions can be produced with all the desired precision and in a very economical manner, so that the arrangement described makes it possible to obtain in an extremely advantageous manner an excellent centering in the axial direction and a very good parallelism of the rotor parts with respect to the air gaps.

Figures 7, 8 and 9 show alternative embodiments of the motor of Figure 6.. ^' .

In the embodiment of Figure 7, the magnetic circuits corresponding to the circuits 87 and 88 of Figure 6 are made in several pieces. A first stator part comprises a pole part 96, made of a sintered material, having an annular shape and forming the toothing 95, and a pole part 97, forming the opposite toothing. These two pole parts are magnetically connected to each other by annular connection parts 98 and 99, formed according to the sectional view of FIG. 7, for example by stamping, and joined together and to parts 96 and 97, for example by welding. In this case, as in the case of the previous figures, the electric coil, designated here by 100, is closely surrounded by the corresponding magnetic circuit, so as to reduce losses and to make optimum use of the available volume. A second part of stator 101 is produced in a similar manner to the first. Organs rotary 71, 72 are similar to those of Figure 6, and are designated by the same reference numerals.

The variant embodiment according to FIG. 8 comprises removable radial ball bearings 102, 103. As in FIGS. 6 and 7, one of the rolling parts 104 or 105 of each rotary member 106, 107 carries a corresponding magnetic disc 108, 109, this disc being fixed on a surface perpendicular to the axis of rotation. The device for coupling the two rotary members and the two stator parts are produced in a similar manner to FIG. 7, and the corresponding parts are designated by the same reference numerals as in this figure.

FIG. 9 shows another alternative embodiment of the motor of FIG. 6, in which support parts 110, 111 are used for fixing the magnetized rotor parts 112, 113 to the corresponding rolling parts 114, 115 The rolling parts each have an annular planar surface in contact with a first zone of an annular plane surface 116, 117 of the respective support part 110, 111, and a second zone of these same surfaces 116, 117 is in contact with one of the flat surfaces of the annular discs 112, 113.

The coupling between the two rotary members is carried out in the axial direction by two spring washers 80, 81, as in the examples of Figures 6 to 8, while a pin 118 is provided in the example of Figure 9 to ensure coupling in the circumferential direction. This pin is arranged so as not to hinder the separation of the two rotary members under the effect of the springs 80, 81.

The magnetic circuits of the motor of FIG. 9 each comprise annular, toothed polar parts, similar to parts 96, 97 of FIG. 7, and annular connection parts 119, 120, formed and assembled according to the section view of FIG. 9, so as to ensure "very low magnetic resistance and good dimensional accuracy in the axial direction.

The present motor can be produced in the form of an extremely flat and small assembly, the useful parts of which occupy a minimum volume. At the same time, given the configuration of the magnetic circuits and the precision of the assembly, the efficiency reaches an optimal value, all the more since, in the two-phase versions shown, the entire circumference of the magnetic disc cooperates with polar parts of the stator. The two rotary members or the two stator parts can moreover be easily adjusted in their mutual angular position before their final immobilization, by welding or gluing for example.

In all the different embodiments of the present motor, the excellent definition of the position of the magnetically active part of the rotor with respect to the stator parts with which they cooperate, is a decisive advantage, obtained in a relatively simple manner and economic. Indeed, the precision of the ball bearings is found, thanks to the flat contact surfaces between the bearing part, the possible support part and the corresponding magnetized rotor part, at the air gaps of the stator parts.

Of course, a motor of which a single rotary member carries a magnetic disc can be designed in a similar manner to the motor shown, and various embodiments of rotary members, in particular rotary members axially displaceable relative to each other and provided with coupling devices, as well as alternative embodiments of the stator parts and ball bearings, can be envisaged by the skilled person. It should be noted, on the other hand, that the present principle of mounting of the rotary member, although it is particularly

_CMPI interesting for motors of the type described in the examples, "is also very useful in other configurations and for other types of electric motors, where the accuracy of centering the rotor relative to the stator is important.

C ... PI

Claims

1. Electric motor comprising a stator and at least one rotary member comprising a rotor part essentially in the form of a flat annular disc mounted in a rotary manner with respect to the stator by means of at least one ball bearing comprising at least two coaxial rolling parts forming ball raceways, at least one of these rolling parts having a planar annular surface perpendicular to the axis of rotation, characterized in that said rotor part (5, 41 , 49, 73, 108, 112) is fixed on said rolling part (9, 34, 64, 45, 76, 104, 114), directly, so that respective planar annular surfaces are in contact with one another. other, or indirectly, via a support part (110) having a planar annular surface in contact with said planar annular surface of said rolling part (114) and in contact with said rotor part ( 112), or through of a support part (7, 51) having the form of a plane annular disk, one or more of the plane annular surfaces of which are in contact with the respective plane annular surfaces of said rotor part (5, 49 ) and said rolling part (9, 64, 45).

2. Motor according to claim 1, characterized in that the rotary member (3,4) comprises two rotor parts (5,6), two ball bearings with two bearing rings (9,11 and 10,12) being mounted on a common axis, the rotor parts being fixed directly or via a respective support part (7,8) in the form of a flat annular disc on a corresponding cheek of a first rolling ring (9 , 10) of the corresponding ball bearing, and in that the stator comprises two parts of stator (1,2) each secured to a second bearing ring (11,12) of each of the ball bearings, both stator parts being assembled in such a way that the two ball bearings have practically no resulting play.

3. Motor according to claim 1, characterized in that the rotary member comprises two rotor parts (41,42), two ball bearings being combined so as to have one of their bearing rings (33) in common each rotor part being fixed directly or by the intermediary of a respective support part in the form of a flat annular disc, on corresponding cheeks of a first or first rolling rings (34, 35), and in that the stator comprises two stator parts (31, 32) each mounted on seconds or a second (33) bearing rings of the ball bearings, the two combined ball bearings exhibiting practically no resulting play.

4. Motor according to claim 1, characterized in that the rotary member comprises two rotor parts (49,50), two ball bearings each comprising a first (45,46). and a second (43,44) bearing ring, being mounted side by side so that the assembly of the two roule¬ ments presents practically no resulting play, said rotor parts being fixed directly or by means of a respective support part (51, 52), in the form of a flat annular disc, on the respective cheeks of the first two bearing rings arranged side by side.

5. Motor according to claim 4, characterized in that the stator comprises two stator parts (53,54 and 55,56) mounted on at least one common support piece (60) integral with the two second bearing rings.

6. Motor according to claim 1, characterized in that the rotary member comprises two rotor parts (49, 50), the motor comprising a bearing with a row of balls (63) and three bearing rings, the first of which ( 64) and the second (65) are juxtaposed axially and arranged opposite the third (62), each rotor part being fixed directly or by means of a respective support part, in the form of a flat annular disc, on a corresponding flat annular surface of the first and second bearing rings , the ball bearing exhibiting practically no resulting play.

7. Engine according to claim 1, characterized in that it comprises two rotary members (71, 72) coupled via at least one coupling device (80, 81, 118) arranged so as to make these two rotary members that are practically integral in the direction of the rotation and separate them elastically in the axial direction, and in that each of the two rotary members comprises a rolling part (76, 77) of a ball bearing, the other rolling part (82, 83) forms a stop in the axial direction so as to limit the spacing of the two rotary members under the effect of the coupling device (80, 81).

8. Motor according to claim 7, characterized in that the rotary members (71, 72) are arranged one opposite the other in the axial direction, at least one of them having a housing portion of the coupling device (80, 81).

9. Motor according to claim 8, characterized in that the coupling device consists of at least one piece (80, 81) resilient in the axial direction.

10. Motor according to claim 8, characterized in that the coupling device consists of at least one compression spring (80, 81) bearing, by its respective ends, on the two rotary members (71, 72).

11. Motor according to claim 10, characterized in that the coupling device consists of at least one

spring washer (80, 81).

12. Motor according to one of claims 7 to 11, caracté¬ ized in that the ball bearing is an axial ball bearing (78, 79).

13. Motor according to one of claims 7 to 11, caracté¬ ized in that the ball bearing is a radial ball bearing (102, 103).

14. Motor according to one of claims 7 to 13, caracté¬ ized in that the ball bearing is a removable ball bearing (102, 103).

15. Motor according to one of claims 7 to 14, caracté¬ ized in that the coupling device comprises means (80, 81, 118) for coupling the rotary members in the direction of rotation.

16. Motor according to one of the preceding claims constituting a synchronous motor with magnetic rotor, caracté¬ ized in that the rotor part (s) (5, 6, ...) are axially magnetized so as to present on each of their flat surfaces a series of alternating positive and negative magnetic poles in the direction of the circumference of the disc, and in that the stator or each of the stator parts (1, 2, ...) comprises at least one magnetic circuit (18 , 19, ...) coupled with at least one control coil (16, ...), this magnetic circuit presents a gap formed by polar parts arranged on either side of each rotor part.

17. Motor according to claim 16, characterized in that it comprises two parts of the stator (1, 2, ...) each having a flat annular surface (26, ...), per¬ pendicular to the axis of rotation of the rotary member, these two stator parts being in contact on at least part of the periphery of said planar annular surfaces,

directly with each other or with corresponding parallel flat surfaces of an intermediate piece.

18. Motor according to one of claims 16 or 17, charac¬ terized in that the control coil is an annular coil (16, 100) arranged coaxially with respect to the axis of rotation, and the air gap is formed by two annular pole parts (18, 19, 96, 97, ...), at least one of said pole parts comprising, in the direction of its circumference, a series of teeth (24, 95) arranged to cooperate with the magnetic poles of the corresponding rotor part (5, 73).

19. Motor according to one of claims 16 to 18, caracté¬ ized in that the magnetic circuit includes connection parts (98, 99) for connecting the pole parts (96, 97) forming the air gap, these parts of connection being arranged to close the magnetic circuit between the pole parts around the correspon¬ dante control coil (100).