HK1007205B

HK1007205B - Electromagnetic motor having two rotation directions, in particular for timepiece

Info

Publication number: HK1007205B
Application number: HK98106289.0A
Authority: HK
Inventors: Daho Taghezout
Original assignee: Eta草图制造公司
Priority date: 1991-04-19
Filing date: 1998-06-24
Publication date: 1999-04-01

Description

The present invention relates to a low power two-way electromagnetic motor capable of operating in an n-phase power mode, n being greater than 1.

In particular, the invention concerns such a small-sized electromagnetic motor comprising a stator of essentially flattened shape having n magnetic circuits arranged in such a way as to define an opening in which a rotor equipped with, for example, a permanent magnet can twirl. The magnetic circuits are generally magnetically decoupled from each other and each cooperate with the rotor by means of two stator magnetic poles placed in positions approximately diametrically opposite to the rotor's rotational axis, this axis extending perpendicular to the general plane of the stator.

The Japanese patent application JP 61-10958 describes a symmetrical two-phase two-way stepper motor, which consists of two single-phase static parts superimposed on each other and offset angularly by 90° from each other.

The two single-phase stator parts are attached to each other but are in different planes, are magnetically isolated from each other, and each has an excitation coil, and each stator part defines an opening for a common permanent magnet rotor, the openings being aligned with the rotation axis of the rotor.

In order to define a stable rotor position, the edge of each opening of these stator parts is provided with two positioning notches which are diametrically aligned in a direction 45° offset from the main direction of the magnetic flux passing through the rotor and generated by the excitation of the corresponding coil.

The two static parts work under exactly the same conditions with the rotor, but because of their 90° shift, they each rotate the rotor in their own direction.

This known motor has several disadvantages. First, the volume occupied by the rotor permanent magnet is only partially used, as each magnetic circuit encircles less than half of this volume. This disadvantage is further aggravated by the fact that the magnetic circuits are necessarily spaced apart from each other according to the rotor axis to ensure magnetic insulation. This results in a comparatively large height which is especially inconvenient when the motor is used in watchmaking applications.

Another disadvantage is that the openings of the magnetic circuits must be precisely aligned with the rotor axis, which creates manufacturing difficulties and increases the cost of the motor excessively.

The purpose of the invention is to provide an electric motor of the type described above without these disadvantages.

It is therefore intended to be an n-phase electromagnetic motor, n being greater than 1, with two-way rotation, comprising: a stator containing a stator hole and at least four magnetic poles, each containing a polar expansion partially defining the stator hole, a polar arm and a polar ear for magnetic contact at the other end of the stator arm, separated by high magnetic resistance zones forming isthmus;a rotor mounted rotating around a stator in the stator hole;at least two magnetic shunts connecting one to the other of the two non-adjacent magnetic poles;shunts mounted on each magnetic axis for the means of inducing the magnetic flux in the two associated poles;Each of these shunts, together with the magnetic poles and the permanent magnet of the rotor, forms a magnetic circuit magnetically separated from the other magnetic circuits of the engine, the latter being characterised by the fact that the magnetic poles are formed by the branches of a single star-shaped piece at the centre of which the stator is intended, the polar outlets being situated in a single plane perpendicular to the rotation axis of the rotor.

The engine of the present invention is not particularly difficult to manufacture or assemble because of these characteristics; in addition, all the magnetic circuits of the engine contain the same volume of the permanent magnet of the rotor, since all the polar outlets are located in a similar plane; and this is achieved by the magnetic decoupling of each magnetic circuit from the other magnetic circuits.

The following description and illustrative drawings will be used to better understand the invention by way of example only. Figure 1 shows a schematically represented two-phase two-way stepping motor according to the invention;Figure 2 shows a larger scale cut according to line II-II of Figure 1 showing schematically a first engine variant to obtain a magnetic insulation gap;Figures 3 to 5 show cutting views of the second, third and fourth possible engine variants according to the invention, respectively, in order to determine a gap;Figure 6 shows a partial view of another way of making a two-phase two-way stepping motor according to the invention;Figure 7 shows another way of making a two-phase non-rotating stepping motor according to the invention;Figures 8 to 11 and 13 to 16 represent,Figures 12 and 17 show schematically one way in which the coils must be fed to control the engine according to the first and second modes respectively;Figure 18 shows on the same scale as Figure 1 and schematically a three-phase two-way rotary engine according to one embodiment of the other invention.

A first method of making a two-phase symmetrical two-way electromagnetic stepper motor according to the invention is described below, using Figure 1.

This engine consists of a stator 1 and a rotor 2 rotating in the stator in a stator hole 3 of essentially circular shape fitted in the stator. The axis of rotation X-X of the rotor 2 is perpendicular to the general plane of the stator 1.

The stator 1 consists of four magnetic poles 4a to 4d and two magnetic shunts 5a, 5b. Each of these magnetic poles ends in a polar expansion 6a, 6b, 6c and 6d respectively, which determines part of the edge of the stator hole 3. These magnetic poles 4a to 4d extend outward by polar arms 7a to 7d, each ending in a polar ear 8a to 8d, serving as a means of attachment and magnetic contact, applied against a corresponding ear 9a to 9d belonging to the magnetic shunts 5a and 5b respectively. Each of these magnetic poles carries a coil 10a, 10b of which it forms the core and extends from the 11a to 11d arms ending in the 9a to 9d ears respectively.

The ears 8a to 8d and 9a to 9d are connected to each other by pins 12 respectively, other known means of attachment being available.

To magnetically isolate each statoric pole from its neighbouring poles, the polar outcrops 6a to 6d are connected to each other by means of isthmus 13a to 13d which form areas of high magnetic resistance, while keeping the poles rigidly relative to each other.

It is thus seen that the central part of stator 1 defining the stator hole 3 and comprising the polar arms 7a to 7d, the outgrowths 6a to 6d and the isthmus 13a to 13d forms a single flat star-shaped piece designated by general reference 14. This piece therefore has here four arms, each arm extending 90° from its two neighbouring arms from the stator hole 3, two of these arms being the arms 7a and 7b, which are cubed at right angles.

This configuration combines two diametrically opposed stator magnetic poles in each of the two magnetic circuits with respect to the X-X rotation axis of the rotor 2.

In order to magnetically isolate these magnetic circuits from each other, an insulation gap is provided in the region 15R where the said arms 7a and 11d intersect in superposition, due to the fact that the two magnetic circuits are at least partly in two adjacent parallel planes. In the embodiment of Figure 1, this gap is obtained by providing in the cubic arm 11d of shunt 5b, and to facilitate the construction of this engine also in the cubic arm 11c of shunt 5a, a notch 16. This can be obtained by simple milling. In this case, the gap 15 is filled with an ambient magnetic fluid (see also Figure 2).

Figures 3 to 5 show three other variants of the clearance between arm 7a of star piece 14 and 11d of shunt 5b.

In Figure 3, shunt 5b also has a notch 16, but in this case this notch is filled with a non-magnetic material 17, e.g. plastic, acting as a gap. This arrangement allows for increased stiffness of the stator as a whole, as shunt 5b is no longer in a backward position compared to its fixation on pole 4d.

As shown in Figure 4, the gap 15 can also be saved between arm 7a and shunt 5b by deforming arm 11d of this shunt 5b by a stamping operation.

According to another variant shown in Figure 5, the shunt 5b has a 16C deformation in its area of connection with the ear 9d, which transports the bulk of the shunt to another plane. A similar deformation (not visible in the drawing) must then be provided in arm 11b of the same shunt 5b to bring its attachment ear 9b to the appropriate level.

It should be noted that other similar variants are not excluded, in particular variants where notches 16 and 16B are provided, not in arm 11d of shunt 5b, but similarly in arm 7a of starred piece 14.

As can be seen from Figure 1, the magnetic shunts 5a and 5b are advantageously identical, resulting in a reduction in manufacturing cost and greater flexibility for assembly, each shunt bearing its coil being used for either magnetic circuit.

If the application of the motor does not require as low a thickness as possible, as may be the case in watchmaking, a stator on three parallel planes may be considered. This method of engine construction according to the invention is partially shown in Figure 6. In this case, a single star 14a is located in the median plane, while shunts 5a-A and 5b-A are located on either side of this median plane in corresponding parallel and adjacent planes. Of course, one of the shunts 5a-A then has the general shape of a U with one of the 11a-A arms superimposed over the 11d-A arm of the other 5b-A. The 11a-A arm is terminated by an 8a-A ear, which is fixed to the 9a-A shore.

The gap 15A is then approximately the same thickness as the star-shaped part 14A.

Figure 7 shows another embodiment of the invention for a more compact assembly than Figure 1, in which a star-shaped piece 14B is provided with arms 7b-B and 7c-B folded so as to extend parallel to each other from their respective polar outlets. The parts of the shunts 5a-B and 5b-B, forming the cores of the engine coils, are then curved to join the attachment points formed by the corresponding ears 9a-B to 9d-B of these shunts.

The motor according to the above-described invention can operate mainly in two different modes, i.e. continuous or step-by-step.

The step-by-step operation is examined by reference to Figures 8 to 17, Figures 8 to 11 for the implementation of Figure 1, while Figures 13 to 16 refer to Figure 7.

In order to operate in step-by-step mode, it is necessary to give the rotor stable rest positions relative to the stator. This can be achieved by providing in the edge of the stator hole 3 two notches 20, respectively 20B, in diametrically opposite positions. Under these conditions, since the permanent magnet rotor has a given magnetization direction, it will be positioned in such a way that, in the absence of excitation of coils 10a and 10b, this DR direction (rest direction) is oriented perpendicular to the DE direction (notch direction) defined by notches 20 (see Figures 8 and 13).

It should be noted that in the case of Figures 1 and 8 to 11, notches 20 are aligned with the polar outcrops 6b and 6d, while in the case of Figures 7 and 13 to 16, notches 20 coincide with two diametrically opposed isthmas 13b-B and 13d-B.

Figure 12 shows schematically a way in which the coils 10a and 10b can be fed to control the engine in Figure 1.

It can be seen that this displacement is made in the (negative) anti-clockwise direction (as seen in Figures 8 and 9) when the coils receive current pulses of the same polarity in steps, the directions of the corresponding flows being indicated in Figures 8 and 9 by the ±F1 and ±F2 references and the resulting magnetic fields in the permanent magnet of the rotor by the ±B1 references.

The displacement is clockwise (positive) when the pulses applied to coils 10a and 10b are of opposite polarities (see Figures 10 and 11 respectively), the resulting magnetic fields being ±B2.

However, the engine coils in Figure 7 must be controlled according to the scheme shown in Figure 17, the flow directions being also indicated here by the ±F1 and ±F2 references and the resulting magnetic fields in the rotor permanent magnet by ±B3 and ±B4 in Figures 13 to 16.

For the engine in Figure 7, we see that to take two counterclockwise steps, one applies control pulses successively of opposite polarities, only to coil 10a; then to take two counterclockwise steps, it is coil 10b which receives two consecutive pulses of opposite polarities.

The engines in both Figure 1 and Figure 7 have centre parts 14 and 14B, each high-resistance isthmus oriented at 90° to the two neighbouring isthmus.

Furthermore, the relative position of the positioning notches 20 in relation to the polar outlets, as shown in Figures 1 and 7 respectively, allows the engine to operate in a strictly identical manner, regardless of the direction of rotation, by means of a control using equally identical current pulses, regardless of their polarity.

Figure 18 shows another embodiment of the invention which is a three-phase motor.

This engine comprises a stator 31 defining a stator hole 33 into which is rotatively mounted a rotor 32 with bipolar permanent magnet.

The stator comprises a single central star-shaped part 34 with the stator hole 33 at its centre.

For each phase of the motor, the stator comprises a magnetic circuit 35 magnetically disconnected from other magnetic circuits by isthmus 36.

Each magnetic circuit includes: a long branch 37 belonging to one pole of the starred part;a short branch 38 belonging to another pole of the starred part in a diametrically opposite position;a C-shaped magnetic shunt 39, attached by ears 40 to corresponding ears (not visible in the drawing) provided at the free ends of branches 37 and 38 of the starred part 34;a coil 41 mounted on the magnetic shunt 39.

In this engine there are three cross-sectional regions in superposition 42 in which a gap 43 is provided for magnetic insulation of the magnetic circuits concerned.

It should be noted that the magnetic circuits of this motor, belonging to its three phases respectively, are of identical construction, each circuit being offset by 120° from the two adjacent circuits.

This three-phase motor is shown in Figure 18 without positioning notch; however, it is quite possible to provide for suitable positioning notches for a step-by-step mode of operation.

Claims

Electromagnetic motor of n phases, n being greater than 1, having two senses of rotation, such motor including :
- a stator (1; 31) defining on the one hand a stator cavity (3; 33) and on the other hand at least four magnetic poles (4a to 4d; 37, 38), each of such poles comprising a polar expansion (respectively 6a to 6d) partially defining said stator cavity, a polar arm (respectively 7a to 7d) which extends said expansion and a polar attachment lug (respectively 8a to 8d) serving as magnetic contact at the end of said polar arm, said polar expansions being separated from one another by high magnetic reluctance zones forming necks (13a to 13d; 13b-B; 13d-B; 36);

- a permanent magnet rotor (2; 32) mounted in the stator cavity to rotate relative to said stator around an axis;

- at least two magnetic shunts (5a, 5b; 5a-A, 5b-A; 5a-B, 5b-B; 39) which couple two non-adjacent magnetic poles (4a, 4c, respectively 4b, 4d; 37, 38);

- - means (10a, 10b; 41) mounted on each magnetic shunt for generating a magnetic flux (respectively ±F1, ±F2) in the poles with which they are associated; each of said shunts forming, with said magnetic poles and the permanent magnet of the rotor (2, 32), a magnetic circuit which is magnetically decoupled from the other magnetic circuits of the motor, the latter being characterized in that said magnetic poles are formed by the branches of a single star-shaped piece (14; respectively 14A; 14B; 34) in the center of which said stator cavity (3, 33) is provided, said polar expansions (6a to 6d) being situated in a single and common plane perpendicular to the rotation axis (X-X) of said rotor.
Motor according to claim 1, characterized in that the totality of said single star-shaped piece (14; respectively 14A; 14B; 34) for the stator extends in a single and common plane.
Motor according to claim 1 or 2, characterized in that said stator is situated essentially on two adjacent parallel planes perpendicular to said rotor axis, each magnetic circuit of the motor having at least one intersection in superposition respectively with at least one other of said magnetic circuits, each superposed intersection occurring between the arm (11d) of the shunt (5b) of a first magnetic circuit and a polar arm (7a) of the single star-shaped piece (14), such latter arm belonging to a second affected magnetic circuit, the magnetic insulation in the region (15R, 42) of said superposed intersection being assured by a gap (15, 43).
Motor according to claim 3, characterized in that a recess (16), machined in said arm (11d) of said shunt (5b) of said first magnetic circuit or in said polar arm (7a) of said second magnetic circuit, defines said gap (15, 43) in said region of said superposed intersection.
Motor according to claim 3, characterized in that a swaged portion (18) in said arm (11d) of said shunt (5b) of said first magnetic circuit or in said polar arm (7a) of said second magnetic circuit forms a recess (16B) in said region of superposed intersection, such recess defining said gap (15, 43).
Motor according to claim 3, characterized in that it is a two-phase motor and that the lugs (9b, 9d) of said shunt (5b) of said first magnetic circuit are swaged in a manner to offset the remainder of such shunt into a neighbouring plane which defines said gap (15).
Motor according to claim 1 or 2, characterized in that it is a two-phase motor and in that said stator is situated essentially on three neighbouring parallel planes perpendicular to the rotor axis (X-X), the single star-shaped piece (14A) being situated in the median plane while said shunts (5a-A, 5b-B) are situated on either side of such median plane, said magnetic circuit being magnetically insulated from one another by means of a gap (15A) situated between an arm (11a-A) of one (5a-A) of the two shunts and an arm (11d-A) of the other (5b-A) of the two shunts, the gap depth being the thickness of said single star-shaped piece.
Motor according to any one of claims 1 to 7, characterized in that it is a two-phase motor and in that the stator cavity (3) is essentially circular, each of said magnetic insulating necks forming with the two adjacent necks a central angle of substantially 90°.
Motor according to claim 8, characterized in that two positioning notches (20, 20B) of the rotor (2) are provided on the edge of said stator cavity (3) in positions which are diametrally opposite relative to the center of said stator cavity.
Motor according to claim 9, characterized in that the positioning notches (20) are aligned along a direction defined by two non-adjacent polar expansions (6b, 6d).
Motor according to claim 9, characterized in that the positioning notches (20b) are aligned along a direction defined by two non-adjacent necks (13b-B, 13d-B).
Motor according to any one claims 1 to 5, characterized in that it is a three-phase motor and in that said single star-shaped piece (34) exhibits six branches, each of such branches being roughly angularly offset by 60° adjacent thereto, each magnetic circuit (35) having a single region of superposed intersection (42) in which the magnetic insulation between the circuits is assured by a gap (43).
Motor according to any one of claims 3 to 7, 12, characterized in that the gap is filled in with a solid nonmagnetic material (17, 19).
Motor according to claim 12, characterized in that rotor positioning notches (32) are procided on the edge of said stator cavity (33).
Motor according to any one of claims 1 to 14, characterized in that said magnetic shunts (5a, 5b; 39) are identical to one another.