AXIAL FLUX INDUCTOR FOR ROTATING ELECTRIC TRACTION MACHINE

Abstract

The invention relates to a homopolar inductor (11) with axial flux and p poles, for a rotating electrical machine (10) around an axis of rotation (X), in particular a traction machine, characterized in that it comprises an annular disc with an axis of symmetry coinciding with the axis of rotation (X), p clamps integral with the annular disc, p being an even whole number, a concentric inductor winding mounted between the clamps, the clamps not being axially opposite the inductor winding, the clamps being capable of being polarized under the effect of the inductor current flowing in the inductor winding so as to form the p poles of the inductor. Figure for the abstract: Figure 3

Description

Title of the invention: AXIAL FLUX INDUCTOR FOR ROTATING ELECTRIC TRACTION MACHINE

[0001] The invention relates to an axial flux inductor for a rotating electric traction machine for a motor vehicle. The invention finds a particularly advantageous application for the propulsion of low-power electric vehicles, in particular between 4kW and 5kW. The invention can thus advantageously be implemented in particular with low-power four-wheeled electric vehicles ("microcars" in English), two-wheeled vehicles of the motorcycle type, or heavy quadricycles.

[0002] Almost all known systems for the traction of electric vehicles are based on alternating current motors, either synchronous with permanent magnets or asynchronous.

[0003] Propulsion systems for electric vehicles based on a brushed direct current motor with separate excitation are also known. The motor control essentially consists of a power adjustment on the armature (the usual speed control method for a brushed direct current motor) supplemented by a continuous flux variation on the inductor. Since such control is free from jolts, handling is often considered disconcerting, or even unpleasant, by drivers who enjoy dynamic driving.

[0004] Axial flux machines are known from the prior art, the inductor and the armature of which are opposite each other in the axial direction, as described in French application 1750497 filed on January 17, 2017. These axial flux machines have the advantage of being axially compact. In this configuration, it is known that the inductor can be of the homopolar claw type, as illustrated in [fig.l]. The inductor 11 described here comprises a single inductor winding 12, regardless of the number of poles p of the inductor. The claws, forming the different poles p of the inductor, are divided into two groups of different polarities, a first group and a second group. The two groups are circumferentially alternated.

[0005] The inductor 11 of [fig.l] comprises an annular disc 13 from which the claws extend.

[0006] Each claw of the first group, also called first claw 14, has a first axial base 15 which extends from an inner periphery of the disc and a first claw beak of radial extension towards the outside.

[0007] Each claw of the second group, also called second claw 18, has a second axial base 19 which extends from an outer periphery of the disc and a second claw beak 20 extending radially inwards.

[0008] The inductor winding 12 is mounted axially between the disc 13 and the claw beaks 15, 20 and radially between the first bases 15 and the second bases 19.

[0009] The claws are polarized under the effect of the current flowing in the inductor winding 12 so as to form the p poles of the inductor.

[0010] Such an inductor structure is nevertheless complex to produce and assemble. Steps of machining the claw tips, mounting the inductor winding and installing the claws make this type of inductor expensive.

[0011] The invention aims in particular to effectively remedy the aforementioned drawbacks by proposing a homopolar inductor with axial flux and p poles for an electrical machine rotating around an axis of rotation, in particular a traction axis, characterized in that it comprises: - an annular disc with an axis of symmetry coincident with the axis of rotation (X), - p crampons integral with the annular disc, p being an even whole number, - a concentric inductor winding mounted between the clamps, the clamps not being axially opposite the inductor winding, the clamps being capable of being polarized under the effect of the inductor current flowing in the inductor winding so as to form the p poles of the inductor.

[0012] The manufacture and assembly of the inductor are simplified and less expensive compared to the prior art illustrated. The assembly composed of the annular disc and the studs does not have an undercut area which would complicate its manufacture, in particular with a need for machining. There is no axial interlocking between the annular disc and the studs on the one hand and the inductor winding on the other hand.

[0013] The inductor has substantially identical performance compared to the inductor of [fig.l] in the same axial and radial dimensions, which makes the inductor a very good cost / performance compromise.

[0014] The inductor winding is axially opposite the annular disc in one of the two axial directions and does not have any metal retainer in the other of the two axial directions.

[0015] The clamps form the poles of the inductor when the inductor winding is energized. Each pole comprises a single clamp.

[0016] According to one aspect of the invention, all of the studs are trapezoidal in shape. Each stud has a radially outer cylindrical surface. Each stud has a radially inner cylindrical surface.

[0017] According to one aspect of the invention, the crampons do not protrude radially from the annular disc.

[0018] According to one aspect of the invention, the inductor has a number p of studs between 2 and 16, in particular between 4 and 8. The inductor having a polar pitch equal to 2*ir / p, expressed in radians.

[0019] According to one aspect of the invention, the annular disc has an outer radius. The value of the outer radius Rext may be between 10 cm and 40 cm, preferably between 10 cm and 20 cm, in particular 15 cm.

[0020] According to one aspect of the invention, the annular disc has an inner radius. The value of the inner radius Rint may be between 0.25*Rext and 0.75*Rext, in particular between 0.40*Rext and 0.60*Rext, for example 0.5*Rext.

[0021] According to one aspect of the invention, the annular disc and the studs have an axial inductor dimension, the value Lz of which may be between 2cm and 10cm, in particular between 3cm and 5cm, for example 3.6cm. The annular disc has an axial thickness. The value of the axial thickness of the annular disc ezl may be between 0.25 * Lz and 0.4 * Lz.

[0022] According to one aspect of the invention, each crampon has an axial dimension. This axial dimension may be identical for each of the crampons. The value of this axial dimension ez2 may be between 0.5 * Lz and 0.75 * Lz.

[0023] The possible reduction in flux exchanges caused by the removal of the claw tips can be compensated by an increase in the axial dimension of the clamps. This increase is possible because the clamps are not axially opposite the inductor winding and they do not hold it axially.

[0024] According to one aspect of the invention, the crampons are made of a single material with the annular disc. This reduces the number of operations during assembly and simplifies the process. The annular disc and the crampons form a single piece.

[0025] According to one aspect of the invention, the crampons extend from a radially inner periphery of the disc and / or from a radially outer periphery of the disc.

[0026] When a stud extends from both peripheries then it is radially through and extends from edge to edge.

[0027] The radially outer and inner surfaces of the studs may be contiguous, respectively, with the radially outer and inner surfaces of the annular disc.

[0028] According to a first embodiment of the invention, the p crampons are divided into two groups, p / 2 upper crampons and p / 2 lower crampons. The upper crampons are radially further from the axis of rotation than the lower crampons. The lower crampons and the upper crampons are circumferentially alternated.

[0029] According to this first embodiment, the concentric inductor winding is mounted radially between the lower clamps and the upper clamps.

[0030] According to this first embodiment, the lower crampons are all capable of having the same polarity and the upper crampons are all capable of having the same polarity opposite to the polarity of the lower crampons.

[0031] This arrangement makes it possible to optimize the efficiency of the inductor winding, with no portion being outside the studs. Joule and copper losses are minimized.

[0032] The lower studs and the upper studs are circumferentially alternated when a lower stud is angularly framed by two upper studs, without taking into account the radial height.

[0033] All the lower studs may have the same shape. All the lower studs may be uniformly distributed in the circumferential direction.

[0034] All the upper studs may have the same shape. All the upper studs may be uniformly distributed in the circumferential direction.

[0035] According to this first embodiment, each lower cleat has an external angular opening. The value of the external angular opening of the lower cleats [31 can be between 0.5*(polar pitch) and 0.95*(polar pitch).

[0036] According to this first embodiment, each lower cleat has an internal angular opening. The value of the internal angular opening of the lower cleats [32 can be between 0.5*(polar pitch) and 0.95*(polar pitch). For the lower cleats, the external angular opening is larger than the internal angular opening.

[0037] According to this first embodiment, each upper clamp has an external angular opening. The value of the external angular opening of the upper clamps [33 can be between 0.5*(polar pitch) and 0.95*(polar pitch).

[0038] According to this first embodiment, each upper cleat has an internal angular opening. The value of the internal angular opening of the upper cleats [34 can be between 0.5*(polar pitch) and 0.95*(polar pitch). For the upper cleats, the internal angular opening is larger than the upper angular opening.

[0039] According to this first embodiment, the lower crampons extend from the radially inner periphery of the annular disc and the upper crampons extend from the radially outer periphery of the annular disc.

[0040] According to a second embodiment of the invention, the crampons are distributed circumferentially and the concentric inductor winding is mounted circumferentially between the crampons.

[0041] According to this second mode, the adjacent clamps are capable of having opposite polarities under the effect of the inductor current flowing in the inductor winding so as to form the p poles of the inductor.

[0042] According to this second mode, the crampons are not radially offset from each other.

[0043] According to this second embodiment, the inductor winding is mounted circumferentially between the adjacent studs. The inductor winding passes radially around the studs from the inside and the outside.

[0044] According to this second mode, all the studs can have the same shape. All the studs can be distributed uniformly in the circumferential direction.

[0045] According to this second embodiment, each crampon has an internal angular opening. The value of the internal angular opening of the crampons [35 can be between 0.5*(polar pitch) and 0.95*(polar pitch). Each crampon has an external angular opening, the external angular opening being larger than the internal angular opening.

[0046] According to this second mode, the crampons can extend between the radially inner periphery of the annular disc and the radially outer periphery of the annular disc.

[0047] According to one aspect of the invention, the inductor winding comprises at least one coil. The inductor winding may comprise a plurality of coils, in particular three, in series.

[0048] According to one aspect of the invention, the inductor winding is fixed to the annular disc, for example by overmolding. Alternatively, the winding may be mounted in a sheath fixed to the annular disc or to the studs. As a further variant, the winding may be pressed by axial holding elements against the annular disc. The inductor does not include axial metal retention of the inductor winding.

[0049] The invention also relates to a rotating electrical machine, in particular a traction machine, with direct current and brushes comprising an armature provided with a winding and an inductor as described above. The inductor winding is traversed by an inductor current independent of an armature current supplying the armature.

[0050] According to one aspect of the invention, the inductor is capable of discretely generating, by selecting coils of the inductor winding traversed by the inductor current, at least three different levels of magnetic flux, each corresponding to a traction mode of the rotating electrical machine.

[0051] According to one aspect of the invention, the armature is electrically connected to a battery via a rheostat-type switch configured to make resistance changes in synchronization with the change in magnetic flux level in the inductor.

[0052] According to one aspect of the invention, the armature winding may be corrugated or nested or fractional pitch.

[0053] The invention also relates to a motor vehicle characterized in that it comprises a rotating electrical machine as previously defined to propel said vehicle.

[0054] According to one embodiment, the electric traction machine is installed on a rear axle between a wheel and a differential of said motor vehicle. Alternatively, the electric machine may be installed directly in the wheel of the vehicle in a "wheel-motor" type assembly.

[0055] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.

[0056] [Fig. 1] is a perspective view of an example of an inductor according to the prior art.

[0057] [Fig.2] is a schematic view of an example of an electric machine according to the present invention.

[0058] [Fig. 3] is a perspective view of an inductor according to a first embodiment of the invention.

[0059] [Fig.4] is an enlargement of the inductor of [Fig.3]

[0060] [Fig.5] is a perspective view of an inductor according to a second embodiment of the invention.

[0061] [Fig.6] is an enlargement of the inductor of [Fig.5]

[0062] [Fig.7] is a schematic view of a motor vehicle comprising a electric machine according to the invention

[0063] [Fig.2] shows an example of a direct current electric traction machine 10 and brushes according to the invention. This electrical machine 10 rotating around an axis of rotation X comprises an inductor 11 and an armature 9. This electrical machine 10 is axial flux. The inductor is here homopolar. The armature 9 is constituted by a rotor provided with a winding, for example corrugated or nested.

[0064] In the example considered, a contactor electromagnet is provided with a mechanical power contact KO belonging with the armature 9 to a power circuit C_Puis. This power contact KO is controlled by a coil B_cmd belonging to a control circuit C_Com. This circuit C_com also comprises a contact S whose closure controls the excitation of the control coil B_cmd causing the closing of the power contact KO. The electrical energy is supplied by a battery Batt having a supply voltage preferably worth 48 Volts.

[0065] In the example considered, the inductor 11 comprises an inductor winding 12 traversed by a current Is independent of an armature current Ir supplying the armature 9. The inductor 11 is electrically connected to the control coil B_cmd via a voltage source 15 controlled to ensure, by regulation, a constant current Is in the inductor 11.

[0066] The armature 9 may be electrically connected to the battery Batt via a rheostat-type switch 14 to allow adjustment of the armature voltage 12 in order to refine the adjustment. of the rotation speed of the armature 9.

[0067] With reference to [fig.3], the inductor 11 comprises a metallic annular disc 16 with an axis of symmetry coinciding with the axis of rotation X and p metallic clamps integral with the annular disc 16. All the clamps have a trapezoidal shape and each has a radially outer cylindrical periphery and a radially inner cylindrical periphery. In the example considered, the number p of clamps is equal to 16.

[0068] In the example considered and according to the first embodiment of the invention, the p crampons are divided into two groups, p / 2 upper crampons 19 distributed uniformly in the circumferential direction and p / 2 lower crampons 20 distributed uniformly in the circumferential direction, here 8 of each. The upper crampons 19 are radially further from the axis of rotation X than the lower crampons 20. The upper crampons 19 and the lower crampons 20 are circumferentially alternated.

[0069] In the example considered, all the upper crampons 19 are identical and are made of the same material as the annular disc 16. All the lower crampons 20 are also identical and are made of the same material as the annular disc 16.

[0070] In the example considered, the concentric inductor winding 12 is mounted radially between the upper clamps 19 and the upper clamps 20. The inductor winding 12 extends only these clamps.

[0071] Under the effect of the inductor current Is flowing in the inductor winding 12, the clamps form the poles of the inductor. The upper lower clamps all have the same polarity and the lower clamps all have the same polarity opposite to the polarity of the upper clamps 19. The inductor 11 thus has 16 poles. The polar pitch of the inductor considered is equal to 2*ir / p, or ir / 8 radians or 22.5 degrees.

[0072] Although not shown, the armature associated with the inductor 11 presented in [fig.3] may comprise a three-phase corrugated winding distributed in 48 slots, i.e. 1 slot per pole and per phase.

[0073] In the example considered, the inductor winding 12 may comprise at least one coil. Alternatively, a plurality of coils, in particular three in series, may be provided.

[0074] In the example considered, the clamps are not axially opposite the inductor winding 12. The inductor winding 12 is axially opposite the annular disc 16 in one of the two axial directions and does not have a metal retainer in the other of the two axial directions. The inductor winding 12 can be fixed to the annular disc by overmolding. Alternatively, the winding can be mounted in a sheath fixed to the annular disc or to the clamps. As a further variant, the winding can be pressed against the annular disc by axial holding elements.

[0075] With reference to [fig.4], different dimensions of the inductor described in [fig.3] are illustrated. The annular disc 16 has an outer radius whose value Rext can be between 10 cm and 40 cm, for example here 15 cm. The annular disc 16 also has an inner radius whose value Rint can be between 0.25*Rext and 0.75*Rext, for example here Rext / 2, or 7.5 cm. All the cleats are radially between these two radii; they do not extend beyond them. The upper cleats 19 extend from an outer periphery of the annular disc 16, a periphery being at a distance Rext from the axis of rotation. The lower cleats 20 extend from an inner periphery of the annular disc 16, a periphery being at a distance Rint from the axis of rotation.

[0076] In the example considered, the annular disc 16 and the studs have an axial inductor dimension whose value Lz can be between 2 cm and 10 cm, for example here 3.6 cm. This axial inductor dimension is broken down into the axial thickness of the inductor disc and the axial thickness of the studs. In the example considered, all the upper studs and all the lower studs have the same axial thickness. The value of the axial thickness of the annular disc ezl can be between 0.25 * Lz and 0.4 * Lz and the value of the axial dimension of the studs ez2 can be between 0.5 * Lz and 0.75 * Lz.

[0077] In the example considered, each lower clamp 20 has an external angular opening whose value [31 is between 0.5*(polar pitch) and 0.95*(polar pitch) and an internal angular opening whose value [32 is between 0.5*(polar pitch) and 0.95*(polar pitch). Here [31>[32.

[0078] In the example considered, each upper clamp 19 has an external angular opening whose value [33 is between 0.5*(polar pitch) and 0.95*(polar pitch) and an internal angular opening whose value [34 can be between 0.5*(polar pitch) and 0.95*(polar pitch). Here [33<[34

[0079] The example of inductor 12 illustrated in Figures 5 and 6 is according to a second embodiment of the invention. There is a single row of studs without radial offset between them. The studs, all identical, extend between the radially inner periphery of the annular disc and the radially outer periphery of the annular disc 16.

[0080] The concentric inductor winding 12 is mounted circumferentially between the studs and radially circumvents the studs from the inside and the outside. The inductor winding thus forms crenellations around the studs.

[0081] In the example considered, the adjacent clamps have opposite polarities under the effect of the inductor current flowing in the inductor winding so as to form the p poles.

[0082] In the example considered, each crampon has an internal angular opening whose value [35 can be between 0.5*(polar pitch) and 0.95*(polar pitch).

[0083] [fig.7] shows a motor vehicle 25 comprising an electric traction machine 10 installed on its rear axle 26 between a wheel 28 and the differential of the vehicle. Alternatively, the electric traction machine 10 may be installed on the front axle 27. Alternatively, the electric traction machine 10 may be installed in at least one wheel 28 of the vehicle. In particular, one machine 10 is used in each rear wheel.

[0084] Of course, the preceding description has been given by way of example only and does not limit the scope of the invention, which would not be exceeded by replacing the various elements with any other equivalents.

Claims

Claims

1. Homopolar inductor (11) with axial flux and p poles, for a rotating electrical machine (10) around an axis of rotation (X), in particular a traction machine, characterized in that it comprises - an annular disc (16) with an axis of symmetry coincident with the axis of rotation (X), - p clamps (19, 20) integral with the annular disc, p being an even whole number, - a concentric inductor winding (12) mounted between the clamps, the clamps not being axially opposite the inductor winding, the clamps being capable of being polarized under the effect of the inductor current flowing in the inductor winding so as to form the p poles of the inductor.

2. Inductor (11) according to claim 1, characterized in that the crampons (19, 20) are made of the same material as the annular disc (16).

3. Inductor (11) according to any one of the preceding claims, the lugs (19, 20) extend from a radially inner periphery of the annular disc and / or from a radially outer periphery of the annular disc (16).

4. Inductor (11) according to any one of the preceding claims, characterized in that: - the p crampons are divided into two groups, p / 2 upper crampons (19) and p / 2 lower crampons (20), the upper crampons (19) being radially further from the axis of rotation (X) than the lower crampons (20), the lower crampons and the upper crampons being circumferentially alternated, and in that - the concentric inductor winding (12) is mounted radially between the lower crampons and the upper crampons.

5. Inductor (11) according to the preceding claim taken in combination with claim 3, characterized in that the lower lugs (20) extend from the radially inner periphery of the disc annular (19) and in that the upper cleats (19) extend from a radially outer periphery of the annular disc (16).

6. Inductor (11) according to any one of claims 1 to 3, characterized in that: - the studs are distributed circumferentially, and in that - the concentric inductor winding is mounted circumferentially between the studs, the adjacent studs having opposite polarities under the effect of the inductor current flowing in the inductor winding so as to form the p poles of the inductor.

7. Inductor (11) according to the preceding claim taken in combination with claim 3, the cleats extend between the radially inner periphery of the annular disc (16) and the radially outer periphery of the annular disc (16).

8. Rotating electric machine (10), in particular traction, with direct current and brushes comprising an armature (9) provided with a winding and an inductor (11) according to one of the preceding claims, characterized in that the inductor winding (12) is traversed by an inductor current (Is) independent of an armature current (Ir) supplying the armature.

9. Motor vehicle (25) characterized in that it comprises a rotating electrical machine as defined according to the preceding claim to propel said vehicle.

10. Motor vehicle according to the preceding claim, characterized in that the electric traction machine is installed on a rear axle (26) between a wheel and a differential of said motor vehicle (25).

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