EP3172816A1

EP3172816A1 - Electric stepper motor

Info

Publication number: EP3172816A1
Application number: EP15738095.7A
Authority: EP
Inventors: Hubert Poinceau; Alfonso Heredia; Yvan Meyer
Original assignee: MMT SA
Current assignee: MMT SA
Priority date: 2014-07-22
Filing date: 2015-07-15
Publication date: 2017-05-31
Also published as: WO2016012329A1; EP2978105A1

Abstract

The invention relates to an electric stepper motor having at least two electric phases, including a stator (2) having a plurality of magnetic stator poles (P) for each electric phase. The stator includes a magnetic armature (6) comprising a plurality of coil cores (14) and a plurality of coils (8, 9) for each electric phase, which coils are mounted on the coil cores. Each coil defines one of said magnetic poles of the stator. The plurality of coils of each electric phase are formed from at least two conductive wires (11, 21, 31, 41) which are connected in parallel. One or more coils includes one of the conductive wires and one or more other coils comprise the other one of said conductive wires.

Description

ELECTRIC MOTOR PAS-A-PAS

The present invention relates to the field of step-by-step electric motors and in particular hybrid stepper motors for low voltage applications, for example for applications in the field of vehicles.

In many applications it is sought to have step-by-step electric motors capable of providing high power, that is, high torque at high speed, for a small motor footprint. In general, the torque is a function of the current or the ampere turns (product of the current by the number of turns of a coil) circulating in the coils of a motor phase. Because of the rotation of the motor, each coil creates an induced voltage, proportional to the speed, which opposes the supply voltage, thus limiting the maximum current in the coils. In applications where the supply voltage is low, for example for machines operating with batteries such as in embedded applications (eg vehicles, planes, boats), it is necessary to be able to maintain the current at high speed to have more torque and more mechanical power. However, the current can not be established or maintained at high speed due to the induced voltage. Moreover, the application, by its constraints of maximum supply voltage, does not make it possible to counteract the effects of the induced voltage by increasing the supply voltage.

A conventional solution to improve the situation is to change the theoretically constant copper volume winding, especially using larger wire with fewer turns. The induced voltage is decreased since it is proportional to the number of turns. The resistances and inductances are proportional to the square of the number of turns and are of which very strongly diminished. As a result, the current can be increased and maintained to higher rotational speeds. This solution makes the manufacturing process, especially winding, more difficult as the wire diameter increases. On the other hand, the design of the stator may limit the diameter of the wire that can pass into the spaces available for winding. Indeed, in a traditional hybrid engine, the poles are flared and the distance between two poles does not greatly increase the wire diameter used by the winding.

A known solution to circumvent this last limitation is to provide an articulated stator. Referring to Figure 1a, a conventional motor winding comprising a plurality of coils per electrical phase is illustrated, the coils 8a'-8d 'being connected in series. A known solution for improving the high-speed torque is to put wires 11 ', 21' in parallel (bi-wire or multi-wire winding), ie several series of coils 8a'-8d 'are produced for the same phase. as schematically illustrated in Figure 1b. The wires are then connected in parallel, which is equivalent to increasing the wire diameter. For the poles of the same phase, we can put a lot of son in parallel, to increase the effect. This can be difficult to manage in terms of the number of wires and electrical connections between wires.

An object of the invention is to provide a compact electric motor step by step, efficient and economical to manufacture.

It is advantageous to provide a step-by-step electric motor having high torque at high speed.

It is advantageous to provide a step-by-step electric motor with a high efficiency. In the present invention, there is disclosed a step-by-step electric motor having at least two electrical phases, comprising a stator with a plurality of magnetic stator poles for each electrical phase. The stator comprises a magnetic armature comprising a plurality of coil cores and a plurality of coils for each electrical phase mounted on the coil cores, each coil defining one of said magnetic poles of the stator. The plurality of coils of each electrical phase is formed of at least two conductive wires connected in parallel. One or more of the plurality of coils of each electrical phase comprises a first of said at least two leads but not a second of said at least two leads, and one or more of said plurality of coils of each electrical phase includes the second but not the first of said at least two leads.

In one embodiment, each coil is single-wire, ie it is formed of only one of the conductive wires.

In one embodiment, the plurality of coils of each electrical phase is formed of more than two conductive wires connected in parallel and each coil is multifilar, ie it is formed of several conductive wires. The number of turns formed by a conductive wire may be different or equal to the number of turns formed by another conductive wire of the same multi-wire coil.

In one embodiment, each coil is connected in parallel with the other coils of the same electrical phase.

In one embodiment, the plurality of coils of each electrical phase comprises at least two groups of coils connected in series. In an advantageous embodiment, the motor has two electrical phases.

In an advantageous embodiment, the motor comprises at least eight magnetic poles distributed between the electrical phases.

In an advantageous embodiment, the motor comprises four coils per electrical phase.

In an advantageous embodiment, the stator comprises electrical terminals, each electrical terminal comprising one or more wire connection part (s) configured for connection with one or more ends of the conductive wires and a connection part. configured circuit for connection with a circuit board. In one embodiment, each electrical terminal comprises a single wire connection portion configured for connection to only one of the lead wires.

In one embodiment, each electrical terminal includes a plurality of wire connection portions interconnected to the circuit connection portion by a bridge portion.

In an advantageous embodiment, the stator comprises an insulator body mounted on the magnetic armature, the insulative body including a coil core housing portion mounted around the coil core to protect the lead wire from direct contact. with the magnetic armature, the insulating body further comprising an electrical terminal support part for mounting electrical terminals on the insulating body. In an advantageous embodiment, the magnetic armature comprises a support body, the magnetic poles extending radially inwardly of the support body and comprising an enlarged head, the coil core interconnecting the head to the support body , the heads of the adjacent magnetic poles being separated from each other by a space allowing a wire guide to wind said conductive wires around the coil core.

Other objects and advantageous aspects of the invention will appear on reading the claims and / or the following detailed description of embodiments of the invention in relation to the figures, in which:

Fig. 1a is a diagram of a single-wire winding of a phase of a known step-by-step motor;

Fig. 1b is a diagram of a two-wire winding of a phase of a known step-by-step motor;

Fig. 2a is a diagram of a single-phase winding of a phase of a step-by-step electric motor according to a first variant of an embodiment of the invention;

Fig. 2b is a diagram of a single-phase winding of a phase of a step-by-step electric motor according to a second variant of an embodiment of the invention;

Fig. 2c is a diagram of a multi-wire winding of a phase of a step-by-step electric motor according to a third variant of an embodiment of the invention;

Fig. 2d is a diagram of a multi-wire winding of a phase of a step-by-step electric motor according to a fourth variant of an embodiment of the invention;

Fig. 3a is a view of a magnetic armature of a stator of an electric motor according to the invention;

Fig. 3b is a perspective view of the armature of FIG. 3a; Fig. 4 is a perspective view of a stator of a step-by-step electric motor according to a first embodiment of the invention; Fig. 5 is a perspective view of a stator of a step-by-step electric motor according to a second embodiment of the invention;

Fig. 6a is a perspective view of a stator of a step-by-step electric motor according to a third embodiment of the invention;

Fig. 6b is a plan view of the stator of FIG. 6a and FIG. 6c is a sectional view along the line A-A of Figure 6b;

Fig. 7 is a perspective view of a stator connected to a circuit board of a step-by-step electric motor according to one embodiment of the invention; and

Fig. 8 is a graph showing a relationship between motor speed and torque / power for a conventional winding is windings according to embodiments of the invention. Referring to the figures, a step-by-step electric motor according to various embodiments of the invention comprises a rotor (not shown) and a stator 2 comprising coils 8 and a magnetic armature 6. The rotor, known in itself, comprises a magnetized portion defining a plurality of rotor poles, the rotor rotating about an axis defining an axial direction. Figures 4 to 7 illustrate a two-phase motor comprising eight magnetic poles P to the stator, each magnetic phase thus comprising four poles. The invention can however be extended to motors comprising three or more phases, each of the phases comprising two or more poles, for example a stepper motor comprising three phases and nine poles. magnetic. The plurality of stator poles may be equal to or different from the number of poles of the rotor.

Referring more particularly to Figures 3a, 3b, the magnetic armature 6 comprises a support body 16, for example in the form of a ring, and a plurality of magnetic poles P extending radially inwardly of the support body . The magnetic poles P comprise an enlarged head 12 and a coil core 14 interconnecting the head 12 to the body of the support 16. A coil 8, 9 is wound around the coil core 14. In the illustrated example, the electric motor comprises eight magnetic poles P1 to P8 for a two-phase motor, that is to say four poles per phase. The heads 12 of the magnetic poles P are separated from each other by a space £, the space £ allowing a wire guide to wind a conductive wire 1 1, 21, 31, 41 around the coil core 14. The width of the The space therefore limits the thickness or diameter of the wire that can be used for the coil.

The construction of the magnetic armature 6 is in itself known and can be formed by a stack of sheets of soft iron or other magnetically soft materials. In the case of the invention it is possible to have different outer forms of the magnetic armature, a different number of magnetic poles, and a different number of motor phases. The shape of magnetic pole heads as well as coil cores may also vary depending on rotor diameter, materials used and other characteristics per se known in step motor construction. For a stepper motor used in embedded low voltage applications (eg 12 volts, 24 volts or 48 volts) the illustrated configuration including a two-phase motor with eight poles can provide, using a winding configuration according to the invention, an economical engine to manufacture with good torque / speed performance. The stator 2 also includes one or more insulators 7 mounted on the magnetic armature 6, the insulative body 7 including a coil core housing portion mounted around the coil core 14 to protect the wire. 1 1, 21, 31, 41 of direct contact with the magnetic armature. The insulating body 7 may for example be made in two parts assembled on either side on the magnetic armature in an axial direction. The insulating body 7 may also include another electrical terminal support portion 18 for mounting electrical terminals 10 (variant of Figures 5 and 6) on the insulating body. The insulating body 7 may include other aspects such as fastening means for assembling housings or other engine components around or on the stator. In the illustrated example of a two-phase motor, the coils 8 of one of the phases are disposed interposed between the coils 9 of the other phase, the coils 8 being connected together to form one of the electrical phases, and the coils 9 being connected together to form another phase of the electric motor. Referring to Figures 2a to 2d, beginning with Figure 2a, the interconnection of the coils of one of the phases is illustrated. The connection scheme of the other phase is identical. The connection and arrangement diagrams of the coils 8, 9 according to the different variants of FIGS. 2a to 2d can be used in all the embodiments illustrated in FIGS. 4 to 7 and again in other embodiments of the invention. illustrated having more or fewer poles and / or electrical phases.

In the connection variant of the coils of FIG. 2a, two coils 8a, 8b, respectively 8c, 8d are connected in series, each pair of coils being formed by a wire 11, respectively 21, connected at its ends to conductors. the corresponding electric phase PhE. The first pair of coils 8a, 8b connected in series is thus wound with a wire 1 1 around two coil cores 14, and the other pair of coils 8c, 8d, connected in series is formed of a second wire 21 around of two cores of coils 14. The son 1 1, 21 of the two pairs each have two ends connected to the same electrical phase PhE by means of connections disposed on the circuit board or other means otherwise known. The ends of the wires may be connected to respective electrical terminals on an external connector, or to the circuit board 4. Alternatively, the ends of the wires of the coils, as illustrated in Figure 4, may be connected. directly to conductive tracks of the circuit board by soldering, soldering, or by mechanical connections, such as crimping or winding around a pin or other terminal mounted on the circuit board.

In the embodiment of FIG. 5, electrical terminals 10 are integrated in the stator 2, the terminals being housed in the insulating body 7. In the illustrated configuration, there are as many electrical terminals 10 as there are ends of wires. used for winding. According to the realization of the electrical terminals 10, several wires can be connected to it. This can be particularly useful, especially in the case of two-wire or multi-wire windings. In the illustrated example, there are eight magnetic poles P1 to P8 and eight electrical terminals 10, this implies that the winding diagram corresponds to a variant according to Figure 2a comprises a wire 1 1, 21 wound around two coil cores , the two coils being connected in series. There are therefore, in this specific example, two pairs of coils for each phase.

The embodiment illustrated in FIG. 5 may, however, vary according to the number of wires used for the winding and the number of coils connected in series. For example, referring to the configuration schematically illustrated in FIG. 2b, each coil 8a, 8b, 8c, 8d of one phase is formed by a different conductor wire 11, 21, 31, 41. A phase is thus formed by four coils having eight ends and in this case the variant of Figure 5 can be modified in that there would be sixteen electrical terminals. In a variant, it is possible to reduce the number of terminals electrically by connecting an electrical terminal to two ends of conductive wires, or even to three or four ends of conductive wires, for example by providing a terminal having a crimping means, or by welding the two or more ends together.

In order to reduce the number of electrical terminals connected to an external connector or to the circuit board 4, the electrical terminals 10 of the same polarity and of the same phase may comprise a circuit connection part 25 intended to be connected to the circuit board. or another conductor of the electrical phase and a plurality of wire connection portions 24 connected to the ends of the coil wires by means of a bridge portion 26 interconnecting the plurality of wire connection portions as illustrated in FIGS. at 6c. In this last embodiment, the electrical terminals are for example formed by a stamping of a metal sheet. The wire connecting portions 24 may be in the form of slits having blades provided to remove the insulation of the wire and pinch the wire to establish an electrical connection between the wire and the blades, this type of electrical contact between an insulated wire and an electrical terminal being known per se. The connection portions of the circuit 25 may for example be in the form of pins configured to be inserted into metallized holes of the circuit board 4. The wire connection portions 24 and the circuit connection portions 25 described in connection with the variant of Figure 6a can be applied to the variant illustrated in Figure 5.

Referring to Figures 2c and 2d, for each coil 8a, 8b, 8c, 8d (Figure 2d) or for each pair of coil connected in series 8a, 8b, respectively 8c, 8d (Figure 2c), several son are wound around each coil core 14. In these examples, three wires (a, b, c) are wound around each coil core 14, but it is of course possible to have only two wires in the case of this multi-wire winding or four wires, the number of three wires shown being only an example of a multi-wire winding. The connections of the ends of the wires can be made in various ways described in connection with the single-wire configurations illustrated in FIGS. 2a and 2b above. Different conductive wires of the same multi-wire coil can form a different number of turns or equal. Also, the diameter or even the materials of different conductive wires of the same coil may be different. This can be advantageous depending on the characteristics sought in relation to the winding process, the electrical, thermal and mechanical properties of the conducting wires, and the costs of materials and production.

In a configuration where two coils are connected in series, as illustrated in FIG. 2a, the two coils connected in series can be arranged consecutively, that is to say separated by a pole of another phase. or in the opposite way. For example, with reference to FIG. 3a, the positions P1 and P5 are opposite positions and the positions P1 and P1 are consecutive positions. The positions P1, P7, P5 and P3 belong to one phase and the positions P2, P4, P6, P8 belong to a second phase. Referring to Fig. 8, a relationship curve between the dynamic torque, mechanical power (vertical axis) and rotational speed of the rotor (horizontal axis) for three different coil connection configurations is illustrated. The MDO and PMecO curve represents a configuration according to the state of the art represented by FIG. 1a (four coils of a phase connected in series) for a stepper motor having two phases with each four poles. The torque and power curves MD1, PMed and MD2, PMec2, correspond to the configuration illustrated in FIG. 2a, namely for MD1, PMed a configuration of two consecutive coils connected in series (for example P1 and P3 in series with P5 and P7) and for MD2, PMec2 a configuration of two opposite coils connected in series (for example P1 and P5 in series with P3 and P7). It is found that at high speeds the engine torque variants according to the invention is maintained while for a configuration according to the prior art the torque decreases at high speed.

List of references in the figures

Engine

Stator 2

Magnetic armature 6

Magnetic pole P, P1 to P8

Head 12

Core coil 14

Body (ring) support 16

Insulating body 7

Electric terminal support part 18

Coil core housing part Windings 8, 9

coils 8a, 8b, 8c, 8d (phase one) coils 9a, 9b, 9c, 9d (phase two) Conductor wire 1 1, 21, 31, 41

Electrical terminal 10

Wire connection part 24

Circuit connection part 25 Bridge part 26

Circuit board 4

Axial direction

Space between E poles

Claims

claims

A step-by-step electric motor having at least two electrical phases, comprising a stator (4) with a plurality of stator magnetic poles (P) for each electrical phase, the stator comprising a magnetic armature (6) comprising a plurality coil cores (14) and a plurality of coils (8, 9) for each electrical phase mounted on the coil cores, each coil defining one of said magnetic poles of the stator, characterized in that said plurality of coils of each electrical phase is formed of at least two conductor wires (1 1, 21, 31, 41) connected in parallel, and in that one or more of said plurality of coils of each electrical phase comprises a first of said at least two conducting wires but not a second of said at least two leads, and one or more of said plurality of coils of each electrical phase includes the second but not the first of said at least two leads conductors.

2. Electric motor according to claim 1, characterized in that each coil is single-wire, being formed of only one of said at least two conductive son.

3. Electric motor according to claim 1, characterized in that the plurality of coils of each electrical phase is formed of more than two son connected in parallel and each coil is multi-wire, being formed of several of said conductive son.

4. Motor according to the preceding claim, characterized in that the number of turns formed by at least one of said conductive wires of a multi-wire coil is different from the number of turns formed by at least one of said conductive wires of said multi-wire coil.

5. Motor according to any one of the preceding claims, characterized in that each coil is connected in parallel with the other coils of the same electrical phase.

6. Motor according to any one of claims 1 to 4, characterized in that said plurality of coils of each electrical phase comprises at least two groups of coils connected in series.

7. Motor according to any one of the preceding claims, characterized in that it has two electrical phases.

8. Motor according to any one of the preceding claims, characterized in that it comprises at least eight magnetic poles (P1-P8) distributed between the electrical phases.

9. Motor according to any one of the preceding claims, characterized in that the motor comprises four coils per electrical phase.

10. Motor according to any one of the preceding claims, characterized in that the stator comprises electrical terminals (10), each electrical terminal comprising one or more wire connection part (s) (24) configured for a connection with one or more ends of the conductive wires and a circuit connecting portion (25) configured for connection with a circuit board (4).

1 1. Engine according to the preceding claim, characterized in that each electrical terminal comprises a single wire connection part configured for connection with only one of the conductive wires.

An engine according to claim 10, characterized in that each electrical terminal comprises a plurality of wire connection portions (24) interconnected to the circuit connection portion by a bridge portion (26).

Motor according to one of the preceding claims, characterized in that the stator comprises an insulating body (7) mounted on the magnetic armature, the insulating body comprising a coil core housing portion mounted around the coil core. in order to protect the lead wire from direct contact with the magnetic armature, the insulative body further comprising an electrical terminal support part (18) for mounting electrical terminals (10) on the insulating body.

14. Motor according to any one of the preceding claims, characterized in that the magnetic armature comprises a support body (16), the magnetic poles (P) extending radially inwardly of the support body and comprising a head (12) widened, the coil core (14) interconnecting the head to the support body, the heads of the adjacent magnetic poles being separated from each other by a space (£) allowing a wire guide to coax said conductive wires around the coil core.