CN113474978A - Mechanical commutator multiphase synchronous motor - Google Patents

Abstract

Mechanical switch (40) for an electric machine (1), suitable for exciting a rotating electric machine rotor (3) having 2 × p poles with a polyphase current system comprising q phases, where q is a positive integer strictly greater than 1, said switch comprising: -a slip ring (41) rotating around the axis (X) of the machine, having a basic pitch equal to 2X pi/(p X q); at least one pair of radially extending brushes, namely a positive brush (45) and a negative brush (46), these brushes are adapted to rub against said slip ring (41) and are rotationally fixed, each brush being defined on an angular sector and being adapted to be connected to the same voltage source, in particular a vehicle battery (B), characterized in that the mechanical slip ring (41) comprises n p q circumferentially successive conductor segments (60), wherein in particular n-1 or n-2, each segment (60) is defined on an angular sector, adjacent segments being insulated from each other, the segments being distributed in q groups (a ', b ', c '), all segments (60) of the same group being electrically connected together, the q groups alternating circumferentially, and the brushes (45,46) of the same pair are circumferentially offset from each other by [ (2k +1) × 2 × pi ]/(2 × p) ], k being a natural integer.

Description

Mechanical commutator multiphase synchronous motor

Technical Field

The present invention relates to a mechanical switch for energizing a rotating electrical machine with a polyphase current system. The invention also relates to an electric machine for a motor vehicle equipped with such a switch.

Background

The invention is particularly advantageously applicable in the field of rotating electrical machines, such as alternators, starter-alternators, electric motors and reversible electrical machines. The invention is also particularly suitable for low power motor vehicle traction, in particular motor vehicle traction with a power between 4kW and 25kW, for example between 4kW and 8kW, for example between 15kW and 25 kW.

Thus, the invention will be particularly likely to be advantageously implemented in low power four-wheel electric vehicles (micro-vehicles), two-wheel vehicles such as motorcycles, or heavy ATVs.

A small electric motor for generating vibrations is known from document EP 1037362 a 2. This motor, which is independent of the automotive field, comprises an axially eccentric commutator against which flexible tabs, energized by a DC, rub. The machine also includes an eccentric rotor including a three-phase coreless winding. Thus, the electric motor can rotate at very high speeds without torque. Without the iron core, such machines produce neither torque nor any armature reaction and are therefore unsuitable for automotive traction.

DC motors are known from the prior art, which are used in particular for motor vehicle starters, but also for propelling a vehicle. These machines are equipped with a stator, here a field magnet, comprising a plurality of permanent magnets or wound poles (electromagnets), and a rotor, here an armature, comprising conductors forming a rotor winding. The armature includes a segmented mechanical commutator against which the brushes rub to excite the armature with DC.

The brush/commutator assembly forms a mechanical switch that allows the robot to control the energization of the windings. Each change in the angular position of the armature, by virtue of the angular arrangement of the positions of the segments and brushes, corresponds to a new excitation of the winding. The manner in which the brushes and commutator are positioned depends on the angular position of the field poles.

The main disadvantage of these machines is that the magnetic energy changes abruptly whenever the current in the conductors, in particular the armature part of the winding, is switched. The current switching causes excessive wear of the brushes. Furthermore, the performance of such machines is insufficient for application in motor vehicle drive trains, compared to multiphase, in particular three-phase synchronous ac, synchronous rotating machines.

Such multiphase synchronous machines generally comprise a rotor which is rotationally movable about an axis and a stationary stator surrounding the rotor. In alternator mode, as the rotor rotates, the rotor induces a voltage on the stator, which converts the voltage into a current for subsequent delivery of power to the vehicle's power consumers and recharging of the battery. In the motor mode, the stator is electrically excited and generates a rotating magnetic field, which then generates a torque relative to the field poles, driving the rotor in rotation, for example, to start an internal combustion engine. These machines have significant advantages in terms of performance per unit volume compared to DC machines.

Such machines generally comprise a shaft firmly fixed to the rotor, the rear end of which supports a slip ring belonging to the commutator. The brushes are placed to rub against the slip ring. The brush holder is connected to a voltage regulator for use in alternator mode.

The stator comprises a body formed by a stack of thin laminations forming a crown, the inner face of which is provided with slots open towards the inside in order to receive windings comprising phase coils connected together, for example in a star or delta arrangement. These coils pass through slots in the body of the stator and form beams that project on either side of the stator body. The phase coils are obtained, for example, using continuous wires covered with enamel, or using conductive elements in the form of pins and connected to each other by welding. The windings are electrically connected to the electronic assembly through the inputs and outputs. Unlike a DC motor, the coil is open.

The electronic assembly includes an electronic power module that allows excitation of the phases of the drive winding. The switches here are electronic and require a semiconductor inverter. For example, in the case of electric traction by means of a three-phase synchronous machine, the phases of the windings are usually excited by an electronic inverter comprising 6 MOSFET power stages, the control of which requires rotor position data obtained by means of various position sensors. In the case of a dual three-phase configuration, each MOSFET-based inverter requires 6 inverter arms, twice as many as the three-phase configuration. In the case of a brushless dc (bldc) synchronous motor excited in the form of a square wave, the position sensor may be a hall effect sensor. In the case of an alternating current (BLAC) synchronous motor excited in the form of a brushless sine, the position sensor may also be a resolver which is more expensive than a hall effect sensor.

Such electronic components are expensive. The reliability of semiconductor components in extreme temperature or vibration environments is not optimal because these components are fragile. These components also rely on materials such as silicon, the supply of which may prove unreliable.

There is therefore a need for an electrical machine to be excited with a polyphase current system in a manner that is cheaper and/or less dependent on power electronics, or even completely independent of power electronics.

Disclosure of Invention

The present invention aims to effectively remedy this drawback by providing a mechanical switch for an electric machine, said switch being able to excite a rotating electric machine rotor having 2 × p poles with a polyphase current system comprising q phases, where q is a positive integer strictly greater than 1, comprising:

-a commutator rotationally movable about the axis of the motor, the basic pitch being equal to 2 x pi/(p x q),

at least one pair of radially extending brushes, i.e. a positive brush and a negative brush, which are capable of rubbing against the commutator, are rotationally fixed, each brush being defined on an angular sector and being capable of being connected to the same voltage source, in particular a vehicle battery.

The mechanical switch is characterized in that the mechanical commutator comprises n p q circumferentially consecutive electrically conductive segments, where n is an integer, in particular n-1 or n-2, each segment being defined on an angular sector, adjacent segments being insulated from each other, the segments being divided into q groups, all segments of a given group being electrically connected together, the q groups alternating circumferentially.

The mechanical switch is further characterized in that the brushes of a given pair are circumferentially offset from each other by [ (2k +1) × 2 × pi ]/(2 × p) ], k being a natural integer.

Thus, this arrangement is more robust and less expensive. The performance is also much better than DC motors.

Such a switch allows the motor to be excited with a polyphase current system without an electronic converter, as a result of which the number of power electronics and the associated costs are greatly reduced or even eliminated. This automatically controlled activation also makes it possible to dispense with a rotor position sensor.

According to one aspect of the invention, the angular offset between the brushes is measured from center to center, i.e., between the mid-planes of each brush. The brush may have a substantially parallelepiped shape. According to one aspect of the invention, the brushes may always be in contact with the segments. The brush may comprise a cylindrical radially inner surface which is in contact with the commutator, in particular with the segments.

According to one aspect of the invention, the number of brush pairs is between 1 and p. For example, for a machine with two pairs of poles, the number of brush pairs may be equal to 1 or 2. All brush pairs rub against the same segment. According to the invention, the number of brushes is therefore even.

According to one aspect of the invention, the brush may rub radially against the commutator. Such switches are called radial switches. As a variant, the friction may occur in the axial direction.

According to one aspect of the invention, the commutator may be cylindrical. The friction surface between the brushes and the commutator is cylindrical.

According to one aspect of the invention, the diverter is segmented, i.e. it is not printed.

According to one aspect of the invention, the commutator comprises a fan.

The presence of the fan allows to generate an air flow, allowing the hot air to be discharged, thus cooling the commutator itself and its environment.

According to one aspect of the invention, the fan may be made of an insulating material, in particular of plastic.

According to an aspect of the present invention, the fan may be forwardly curved. As a variant, the fan may be bent backwards.

According to one aspect of the invention, the fan may be placed axially beside the segment. The fan may be a single piece having a unitary construction.

According to one aspect of the invention, the fan may include a plurality of blades. The number of blades may be between 2 and 16, in particular 8, in particular 6 or 10.

The blades may be regularly distributed in the circumferential direction. As a variant, the blades may be distributed irregularly, for example logarithmically. Irregular or variable spacing may make the system quieter.

The vanes may be curved. The vanes may be curved to cause the air to flow inwardly. As a variant, the vanes may be curved in order to cause the air to flow outwards. The vanes may extend radially to the radial height of the segment. The blades may all be a single piece having a unitary construction. The blades may be separate pieces from each other.

According to one aspect of the invention, the commutator may comprise a plurality of capacitors, each capacitor being mounted between two different sets of segments.

The presence of the capacitor can reduce current discontinuities during switching. Thus, the commutator and the motor that can be integrated therein have better durability and improved efficiency.

In the context of the present application, when referring to insulation of adjacent segments, it is to be understood as referring to insulation in the circumferential direction. Directly adjacent segments may belong to the same group of segments while being electrically isolated from each other without departing from the scope of the invention.

The capacitor may be positioned axially on the opposite side of the fan. Thus, the segments are placed between the capacitor and the fan. This allows a greater degree of freedom in positioning each of the two functions. As a variant, the fan and the capacitor may be located on the same axial side with respect to the segment.

According to one aspect of the invention, at least one capacitor is mounted between two different segment groups. The commutator comprises at least q capacitors.

According to one aspect of the invention, each capacitor comprises two electrodes separated by a polarizable insulator. The two electrodes of a given capacitor are electrically connected to two different sets of segments. The electrodes may be fixed directly to the segments. Although the capacitor connects the two sets of segments, the polarizable insulator allows the electrical insulation between the segments to be respected.

According to one aspect of the invention, a single capacitor is provided between two different sets of segments. As a variant, a plurality of capacitors may be provided between two different segment groups. The plurality of capacitors may be arranged in series or in parallel between the two sets of segments.

The capacitors may be identical. Each capacitor may have a substantially parallelepiped shape.

Each capacitor may have a capacitance of between 1 and 100 microfarads, for example 25 microfarads, for example 50 microfarads. When multiple capacitors are connected in series or parallel between two different segment sets, the equivalent capacitance is between 1 and 100 microfarads.

Each capacitor may include a housing enclosing a polarizable insulator and/or all or part of the electrodes.

According to one aspect of the invention, all or some of the capacitors are axially offset from the segments. There is a plane perpendicular to the axis of rotation that intersects the capacitor but not the segment.

According to a first embodiment of the capacitor, the commutator comprises only q capacitors. With a single capacitor between each set of segments. A reduction in current discontinuities is obtained with a minimum number of capacitors.

According to a second embodiment of the capacitor, the commutator comprises at least one capacitor which is located between two stack segments of different circumferentially consecutive stacks. The commutator comprises at least p × q capacitors, in particular only p × q capacitors. When n is 1, each segment is electrically connected to two capacitors. When n-2, each segment is associated with only a single capacitance.

According to one aspect of the invention, each capacitor may be secured to an axially-oriented finger of one segment. The capacitor electrodes may be fixed directly to the fingers, in particular by welding. The capacitor may be fixed only to the finger.

According to an aspect of the invention, the capacitors may be placed all in a given angular sector, in particular an angular sector smaller than 90 °, in particular an angular sector smaller than 45 °. As a variant, the capacitors may be regularly distributed around the circumference of the commutator. The capacitors may all be offset from each other in the circumferential direction.

The capacitor may be at the same radial level as the segments. As a variant, the capacitor may be placed radially closer to the axis than the segments. The capacitors may be placed one above the other.

According to one aspect of the invention, the capacitors may all be located on the same axial side of the segment.

According to an aspect of the invention, the commutator may include an element for protecting the capacitor. The protective element may be a single piece having a unitary construction. The protection element may include a plurality of cavities that house the capacitors. As a variant, a single continuous circular cavity may house the capacitor. As a further variant, the protective element may be formed by as many protective portions as there are capacitors, which are separated from each other.

According to one aspect of the invention, the fan and the protective element may be a single piece having a unitary structure. This allows functionality to be incorporated.

According to one aspect of the invention, the commutator has p × q channels from one type of segment to another type of segment. The commutator may comprise as many passages from one type of segment to another as there are capacitors in the second embodiment. The type of segment is defined by the fact that it belongs to a certain segment group. Thus, when n is 2, two line segments of a given type are continuous in the circumferential direction. The commutator may have a basic electrical segment motif that repeats p times.

According to one aspect of the invention, the segments all have the same angular sector and/or axial dimension. In particular, all segments are identical. The segments cannot be axially offset. The segments may be made of copper. The radial thickness of the segments may be between 1 mm and 3 mm, for example 2 mm. This thickness allows the current density in the segment to be reduced. The axial dimension of the segments may be between 8 mm and 12 mm, for example 10 mm. According to the invention, the commutator has a single circumferential arrangement of conductive segments about an axis.

According to one aspect of the invention, the commutator comprises a skeleton that revolves around the axis of the motor to hold the segments in place. The backbone may be made of an electrically insulating material, such as plastic. The skeleton may be a single piece having a unitary construction. The skeleton may comprise radial holes, in particular n × p × q holes accommodating segments. The backbone may be overmolded onto the segments. The backbone may include a central bore for receiving the rotor shaft. The commutator may include a sleeve placed in the central hole of the skeleton and may be securely fastened to the rotor shaft. The sleeve is fixed relative to the frame. The sleeve is more rigid than the armature to strengthen the connection between the commutator and the rotor shaft.

According to one aspect of the invention, the capacitor may be secured to the backbone. The housing of the capacitor may be secured to the axially oriented face of the backbone.

According to one aspect of the invention, the fan and the frame may be a single piece having a unitary construction. As a variant, each blade may be attached to the skeleton. As a further variation, the fan may be a single piece having a unitary construction and attached to the skeleton.

According to an aspect of the invention, q may be equal to 3. The switch is thus able to energize the motor using a three-phase current system.

According to an aspect of the invention, the radial distance of the friction area between the brush and the segment with respect to the axis may be between 20 mm and 45 mm, in particular 25 mm, in particular 35 mm

According to one aspect of the invention, the angular sector defining a given part is the smallest sector containing the given part in a plane perpendicular to the machine axis.

According to another aspect of the invention, the segments of a given set may all be electrically connected to a ring placed radially inside the segment.

According to a first embodiment of the capacitor, each of the q capacitors may be placed between two different rings.

Such a ring can aggregate the electrical connections between the segments of a given set, which simplifies the manufacture of the switch. In the application environment, the brushes do not rub against the ring, but rather against the segments.

According to another aspect of the invention, a bridge may be provided between each segment and the associated ring. The bridges extend radially from the ring, in particular without axial offset from the ring. The bridges and associated rings are in the interior space of the backbone, while the segments are flush with the exterior for electrical contact with the brushes. The given set of segments, bridges and rings form a ring body that is a single piece having a unitary structure. The rings and ring bodies associated with the segments of group q are referred to as type q.

According to another aspect of the invention, a bridge is associated with a single segment. As a variant, the bridge may be shared by a plurality of segments, for example two, for example when n is 2 and when two segments of a given type are consecutive on the circumference.

According to another aspect of the invention, the commutator comprises q connecting arms, each of which is firmly fixed to one of the rings, in particular by welding. Each arm has a free end that can be connected to one or more phases of the rotor winding in order to excite it. Each connecting arm projects, in particular radially, from the carcass of the commutator through a radial hole in the carcass.

According to an aspect of the invention, in particular according to the first embodiment of the capacitor, the capacitor is connected to the connection arms of the q segment groups. The capacitor may be placed on the same axial side as the connecting arm with respect to the segment. Each electrode may be directly fixed to one free connecting arm end. As a variant, each electrode may be fixed by means of a connecting member, for example a metal wire, for example a metal conductor.

According to one aspect of the invention, the rings of each set may be axially successive.

This axial juxtaposition improves the compactness of the commutator.

According to one aspect of the invention, bridges of a given type q are offset from bridges of other types. The rings may be distributed axially over the length of the axial segment.

The bridge may be connected to the central region of the segment or to one end thereof. In particular, when q is 3 (i.e. when the current system is three-phase), the commutator comprises three rings, a central ring and two end rings on either side of the central ring. The bridges associated with the center rings are axially connected to the center of the segments and the bridges associated with the end rings are connected to the corners of the segments.

Alternatively, the rings may be concentric.

According to one aspect of the invention, each segment may be separated from two adjacent segments by an interlude portion.

The inter-segment portion is defined to prevent circumferential contact between two consecutive segments.

According to one aspect of the invention, the intermediate portions may all have the same angular extent.

Thus, the angular extent of each segment is expressed in radians equal to [2 x pi-n x q x p (the extent of an inter-segment portion) ]/(n x p q).

According to one aspect of the invention, the angular extent of the inter-segment portion is smaller than the angular extent of one of the segments. As a variant, the angular extent of the intersegment portions may be greater than the angular extent of one of the segments.

According to one aspect of the invention, the minimum dimension in the circumferential direction between two consecutive segments, i.e. the circumferential dimension of the segment pitch, is selected to prevent dielectric breakdown. The minimum dimension may be between 1.6 mm and 2.4 mm when the switch is energized at 48 volts

This sizing of the segment spacing can prevent arcing between adjacent segments while leaving sufficient space for the segments, which simplifies the fabrication of the framework. Such inter-segment dimensions may also allow for continuity of friction between the brushes and the segments.

The minimum radial dimension of the commutator is determined by the number of segments required and the minimum dimension of the interpositional segments required.

The angular extent of one of the intersegments is derived from the radial distance of the friction region and the circumferential dimension of the intersegment.

The angular extent of the segments may be the same as the angular extent of the inter-segment portions. Each segment and each intersegment each extend over 2 x pi/(2 x p q).

According to one aspect of the invention, the intersegment portions may be insulated. The interlude section may be a blank space between two consecutive sections. The intermediate portion may comprise non-conductive protrusions, in particular protrusions formed by the skeleton.

According to an aspect of the invention, a section, in particular each section, may comprise an insulation section. The isolated segment is not electrically connected to any other segment. The isolation segment is not electrically connected to any capacitor. The segments are said to be isolated in contrast to the electrically connected conductive segments that form the q groups. As a variant, the intersegment portions can be joined together to form a set of isolated segments, which are subjected to the same conditions with respect to the electrical potential.

According to one aspect of the invention, the spacer segments may be secured to the intersegment ring. The intersegment rings may be placed in the interior space of the scaffold. The intersegment rings may be radially outward of the q-type rings. Each spacer segment includes a foot that is inserted into a hole of the inter-segment ring to secure the spacer segment in place. The intersegment rings may include windows for the passage of bridges between the segments of one of the q groups and the associated ring.

The isolated segment is separated from the conductive segment by a gap. The gap may be between 1 and 5 mm in the circumferential direction. The spacer segment is received in the radial bore. The commutator may then comprise 2 x n x p x q segments, the conducting segments alternating with the isolating segments. The isolated section is at a floating potential.

According to an aspect of the invention, the angular range of the isolated segments may comprise 20% to 50%, in particular 40% to 50%, of the angular range of the conductive segments.

The spacer allows for uniform contact between the commutator and the brushes. Specifically, the brush rubs almost continuously against the insulated or conductive segments.

According to one aspect of the invention, the angular extent of each brush is greater than the angular extent of the land portion. Thus, each brush is always in contact with at least one segment. Each brush can contact at most two different segment sets simultaneously.

According to one aspect of the invention, the degree of overlap may be a ratio of a difference between an angular extent of the brush and an angular extent of the land divided by a base pitch of the commutator.

According to an aspect of the invention, the degree of overlap may be between 10% and 55%. This degree of overlap allows the rotor to be excited using a polyphase current system, which may be, for example, in the form of a square waveform, for example, quasi-sinusoidal, while keeping the current of the voltage source at a non-zero average value and ensuring that the sign of the current remains the same over time.

In the context of the present application, overlap is the period of time a given brush is in contact with two segments of different sets. During this overlap, the brush can therefore excite two different segment groups simultaneously. Simultaneous excitation of both sets of segments with the same brush has an effect on the form of the multiphase current system. The waveform of each phase is modified.

According to one aspect of the application, for a given commutator (given angular extent of segments and intersegments), the extent of the brushes can be selected to obtain various forms of current systems. For a given commutator, a plurality of current systems is thus available.

According to one aspect of the invention, the armature reaction is taken into account when defining the angular offset between the brushes. In case the angular offset is different from the one defined in the present invention, there is a risk of asymmetry.

According to one aspect of the invention, armature reaction is also taken into account when setting the degree of overlap. In particular, the armature reaction depends on the current system, which itself depends on the degree of overlap. In the case of a machine that produces torque, the degree of overlap will not be defined in the same manner as in the case of a coreless machine that is not intended to produce torque, since the armature reaction is significantly different.

The invention also relates to a mechanical switch for an electric machine, said switch being able to excite a rotor of a rotating electric machine having 2 × p poles with a polyphase current system comprising q phases, where q is a positive integer strictly greater than 1, the mechanical switch comprising:

-a commutator, which is rotationally movable about the axis (X) of the motor, having a basic pitch equal to 2 π/(p × q),

at least one pair of brushes having a radial extent, namely a positive brush and a negative brush, which are capable of rubbing against the commutator, are rotationally fixed with respect to each other, each brush being defined on an angular sector and being capable of being connected to the same voltage source, in particular a vehicle battery,

characterized in that the mechanical commutator comprises n p q circumferentially consecutive electrically conductive segments, where n is an integer, in particular n-1 or n-2, each segment being defined on an angular sector, adjacent segments being insulated from each other, the segments being divided into q groups, all segments of a given group being electrically connected together, the q groups alternating circumferentially, and the commutator comprises a fan.

Everything that is said about the fan also applies to this part of the invention.

The invention also relates to a mechanical switch for an electric machine, said switch being able to excite a rotor of a rotating electric machine having 2 × p poles with a polyphase current system comprising q phases, where q is a positive integer strictly greater than 1, the mechanical switch comprising:

-a commutator, movable in rotation about the axis (X) of the motor, having a basic pitch equal to 2 π/(p × q),

at least one pair of brushes with a radial extension, namely a positive brush and a negative brush, which are able to rub against the commutator, are rotationally fixed with respect to each other, each brush being defined on an angular sector and being able to be connected to the same voltage source, in particular a vehicle battery.

The mechanical switch is characterized in that the mechanical commutator comprises n p q circumferentially consecutive electrically conductive segments, where n is an integer, in particular n 1 or n 2, each segment being defined on an angular sector, adjacent segments being insulated from each other, the segments being divided into q groups, all the segments of a given group being electrically connected together, the q groups alternating circumferentially, and the commutator comprises a plurality of capacitors, each capacitor being connected between two different groups of segments.

Everything that is said about the capacitor also applies to this part of the invention.

The invention also relates to an electric machine comprising:

-a mechanical switch as described above,

a rotationally fixed stator comprising 2 x p poles, the stator forming a field magnet of the machine,

-a rotor which is rotationally movable about the axis of the electrical machine, the rotor together with a commutator forming an armature of the electrical machine, the rotor comprising:

i. rotor shaft, and

a rotor body comprising:

1. a lamination stack comprising axially stacked laminations having axially extending (2 x p) m x q slots, wherein m is an integer,

2. at least one winding divided into q phases excited by the switches, the phases comprising winding portions housed in slots, portions of each phase being circumferentially consecutive, each phase having two ends.

Such a multiphase synchronous motor is economical because it does not require expensive electronic components to achieve AC excitation of the multiple phases of the motor from a DC input.

The lamination stack is particularly important in propulsion applications. Without it, the machine cannot produce the required torque. However, the armature reaction must be taken into account when defining the switch.

The switch, in particular through the parameters of overlap and angular offset of the brushes as defined above, allows to obtain a machine that generates torque but does not vibrate. Vibrations are particularly disadvantageous in motor vehicle propulsion applications.

According to one aspect of the invention, the rotor is cylindrical.

This and the particular noteworthy aspect thereof is that the rotor is supplied with a polyphase current system and the stator is excited with DC current. The rotor and stator derive their voltage and current from a voltage source (e.g., a battery) that is DC rather than AC.

The brushes are also energized by DC; they are connected to the same voltage source. They are not connected to the phases of the rotor, but instead each segment group is connected to the q phases of the rotor.

According to one aspect of the invention, the fan may be placed axially on the side of the rotor body.

According to an aspect of the invention, the fan may extend at least partially into the interior space of the rotor body. The fan may extend radially between the rotor shaft and the rotor body. This makes it possible to agitate the air in the rotor body and to cool the windings.

According to one aspect of the invention, the capacitors are located axially on opposite sides of the rotor body, particularly when they are fastened directly to the segments.

The machine may have a number of pole pairs of 1 to 12. In particular, the machine may have 6 pairs of poles or 6 pairs of poles.

The integer m is here the number of slots per pole and per phase, which is for example 1, for example 2.

According to one aspect of the invention, when m is strictly higher than 1, the slots associated with a given phase are circumferentially consecutive.

According to one aspect of the invention, each phase may have a single conductor forming a respective portion of the winding. Each phase may have a plurality of conductors that are connected together outside of the slot. The conductors may be pins, such as U-pins or I-pins. The pins may be inserted axially and then connected together. The pins allow to obtain better performances, in particular in terms of motor torque.

According to another aspect of the invention, the number of slots may be a multiple of the number of segments. Each segment is aligned with a mid-plane that equally divides the q m slots of one of the p successive poles. Each segment is aligned with the centroids of m consecutive segments. For example, when n-m-1, each segment is aligned with one tooth of the rotor body that separates two of the slots that receive a given phased portion.

According to another aspect of the invention, the phases of the winding may be connected to segments of the commutator, in particular the rings of the commutator, by connecting arms.

According to another aspect of the invention, the brushes may be axially aligned with the poles of the stator.

According to another aspect of the invention, the stator may have a claw-pole topology. The stator may comprise windings, claws and inter-pole magnets, in particular made of an inexpensive material ferrite. The inter-pole magnets may also be made of neodymium iron boron to benefit from better performance per unit volume. As a variant, the stator may comprise a yoke equipped with a plurality of circumferentially distributed electromagnets. The stator can be connected to a voltage source, in particular a vehicle battery.

As a variant, the stator may comprise a yoke equipped with one or more claw-free, circumferentially distributed permanent magnets, in particular winding-free permanent magnets.

According to another aspect of the invention, the motor may further include a rotationally fixed brush holder assembly in which the brushes of the switch are received. The brush holder may surround the commutator.

The motor may include a rotationally fixed sheath. The sheath may completely surround the stator, rotor and switch. The sheath may be made of two parts, a front part and a rear part. The brush holder may be fixed to a rear portion of the housing. The stator may be fixed to the front of the sheath.

According to another aspect of the invention, the commutator may be fixed to the rotor shaft so as to rotate therewith; in particular, the sleeve of the commutator may be an interference fit. As a variant, the commutator can be mounted on the rotor shaft in a reversible manner. Rolling members may be placed between the rotor shaft and the sheath to support the rotor.

According to the first winding pattern, each of the q segment groups is electrically connected to one of two ends of one of q phases of the rotor, and the other ends of the q phases are electrically connected together to form a star connection winding.

According to an aspect of the invention, the degree of overlap may be between 10% and 50% when the winding is according to the first mode. When the degree of overlap is between 10% and 20%, the system current is in the form of a square wave. When the overlap is between 20% and 50%, the system current is sinusoidal or quasi-sinusoidal.

In the context of the present application, the current is quasi-sinusoidal if the harmonics of the signal up to the 15 th harmonic are less than 12%, in particular 10%, in particular 8%, of the fundamental value.

In one particular example of this first winding pattern, q is equal to 3, so the switch energizes the rotor using a three-phase current system. One end of each phase of the three-phase winding may be fixed to one end of one of the three connecting arms, in particular by welding.

According to another aspect of the invention, only one of the two ends of each phase may be connected to a connecting arm. Each segment group may excite one of q phases (in particular three phases) of the rotor. Each segment group, in particular each ring of the commutator, excites a different phase.

According to an aspect of the invention, the commutator may further comprise a connector capable of electrically interconnecting the ends of the phases of the winding. The connector may be placed circumferentially beside the free end of the connecting arm. The connector may extend radially from the backbone. The connector comprises q, in particular three, terminals, each for receiving a respective phase terminal.

According to the second winding pattern, each of the q segment groups is electrically connected to both ends of two different phases of q phases of the rotor, thereby forming a polygon-connected winding.

According to an aspect of the invention, the degree of overlap may be comprised between 10% and 55% when the winding is according to the second mode.

In one particular example of this second winding pattern, q is 3, so the switch energizes the rotor using a three-phase current system. Thus, the windings are delta-connected. One end of each phase of the three-phase winding may be fixed to one end of one of the three connecting arms, in particular by welding.

According to another aspect of the invention, each phase of the rotor may be connected to two different sets of segments. Each phase of the winding may be connected to two connection arms. Each connecting arm may be connected to two phases of the winding. The potentials at both ends of each phase of the winding may be the same.

The invention also relates to a traction system for a vehicle, said system comprising:

an electric machine as described above, and

a chopper electrically connected to the brushes of the mechanical switch and connectable to a battery of the vehicle.

The vehicle may be a vehicle, in particular a motor vehicle. The vehicle may be an autonomous vehicle, in particular a wheeled autonomous vehicle, in particular a propelled autonomous vehicle, such as an unmanned aircraft, for transporting the object.

The chopper allows the voltage to be regulated and thus functions as a power transmission. The chopper is not an inverter here, which allows a sinusoidal current signal to be generated. Instead of a chopper, a varistor may be provided, allowing the power electronics to be eliminated entirely in terms of excitation of the motor.

Such a traction system allows to propel the motor vehicle at low cost.

As a variant, the invention may also relate to an alternator comprising an electric machine. The invention also relates to a system comprising an electric machine capable of operating in an electric motor mode and an alternator mode.

Drawings

Further features and advantages of the invention will become more apparent from the following description on the one hand and from a number of non-limiting exemplary embodiments given by way of indication with reference to the accompanying drawings, in which:

fig. 1 and 2 are schematic cross-sectional views of a motor according to the present invention.

Fig. 3 and 4 schematically show the electrical excitation of the motor windings in a first star-connected winding mode.

Fig. 5, 6 and 7 show examples of an electrical machine according to the invention, the windings of which are excited in a first mode, and in which the capacitor is according to a second mode of implementation.

Fig. 8 shows a variant of the commutator shown in fig. 5, in which the capacitor is according to the first embodiment mode.

Fig. 9 and 10 show another example of a switching commutator according to the invention for energizing the coils in the first mode.

Fig. 11 schematically shows a segment of the commutator of fig. 9.

Fig. 12 schematically shows a modification of the switch of fig. 9 to 11.

Fig. 13 and 14 show another example of a switching commutator according to the invention for energizing the coils in the first mode.

Fig. 15 shows a ring of the commutator of fig. 13.

Fig. 16 and 17 schematically illustrate the electrical excitation of the motor windings in the second delta connection winding mode.

Fig. 18, 19 and 20 show examples of a switching commutator according to the invention for exciting the windings in the first mode, and fig. 21 shows an isolation ring of the commutator of fig. 18.

Detailed Description

Fig. 1 schematically shows a cross section of an electrical machine 1. A traction system for a vehicle, in particular a motor vehicle, may be equipped with a machine 1.

In the example in question, the machine comprises a rotor 3 movable in rotation about a rotation axis X of the machine, and a rotationally fixed stator 4 comprising 2 × p poles. The rotor forms the armature and the stator forms the magnetic field of the motor.

The machine 1 also comprises a rotationally fixed jacket 5, where the jacket 5 is made up of two parts, a front part 5a and a rear part 5 b. The jacket completely surrounds the stator and the rotor. The sheath may be made of two parts. The stator 4 is fastened to the front of the sheath, for example by interference fit.

In the example in question, the rotor 3 comprises a rotor shaft 10 and a rotor body 11.

In the example in question, the rotor shaft 10 passes through a front bearing 13 and a rear bearing 14. The rotor shaft 10 is mounted to be rotatable relative to the sheath 5, for example by rolling members mounted on bearings 13, 14.

For example, the rotor 3 comprises a first driving member 20 belonging to the machine 1. A second drive member 21 is provided, mounted on an element of the drive train of the motor vehicle, for example the crankshaft, and an element 22 which transmits the rotary motion of the second drive member 21 to the first drive member 20. According to one particular example, the driving members 20, 21 are pulleys and the element 22 transmitting the motion is a belt.

As shown in fig. 2, the pulley 20 is fixedly mounted on the rotor shaft 10 so as to rotate therewith. Thus, the rotor shaft may be driven in rotation by the rotational movement of the pulley 20. The pulley 20 is placed at a first end of the shaft 14, which end is referred to as the front end. The shaft 14 has a second end opposite the front end, referred to as the rear end.

In the example in question, the stator 4 may be a stator with a claw-pole topology. Such a stator may comprise two pole wheels in the form of annular flanges placed transversely with respect to the rotor shaft 10. Each pole wheel may comprise claw-shaped teeth at its outer circumference, the claw-shaped teeth extending in a direction substantially parallel to the X-axis. The teeth of one pole wheel are angularly offset with respect to the teeth of the other pole wheel so that the teeth of the two pole wheels alternately fit into each other. The stator 4 also comprises an excitation winding 24 mounted between the pole wheels. The permanent magnets may be arranged between the teeth of the pole wheels.

In the example in question, the field winding is excited by a DC field current EXC delivered by a chopper of the stator 25. The stator 4 is excited by a voltage source, here the battery B of the vehicle, via a stator chopper. The field winding is connected to terminal B + of battery B.

In the example in question, the rotor body 11 comprises a lamination stack made of ferromagnetic material, comprising axially stacked laminations. The lamination stack includes axially extending (2 × p) m × q slots. The rotor body 11 also comprises at least one winding 30, which is divided into q phases. These phases comprise portions of the winding 31 housed in the slots, the portions of each phase being circumferentially successive. Each phase has two ends 32. The slots are separated from each other by rotor body teeth.

In the problem example in fig. 2, q is 3, so the winding is a three-phase winding with phases a, b and c. The rotor 3 is therefore excited using a three-phase current system.

The phases of the winding 30 may be star-connected or polygon-connected. In this embodiment the rotor comprises three phases a, b, c connected triangularly, as shown in fig. 2.

In the example discussed, each lamination may have an annular shape and include radially disposed grooves. The slots of the stacked laminations form slots of the lamination stack, the slots extending in a direction substantially parallel to the X-axis.

In the example discussed, there may be a separate conductor for each phase a, b, c forming a different part of the winding.

In the example in question, the bundles 35 formed by the windings 30 are arranged on either side of the lamination stack.

The machine 1 according to the example in question is particularly notable in that it comprises a mechanical switch 40 for exciting the q phases of the rotor 3. In the example in question, in fig. 1 and 2, the mechanical switch thus energizes the rotor 3 with a three-phase current system. The switch 40 is placed within the sheath.

In the example in question, the switch 40 comprises a commutator 41 movable in rotation about the axis x. The commutator will be described in more detail with reference to fig. 3 to 14. The commutator 41 is fixed to the rotor shaft 10 so as to rotate therewith and forms an armature of the motor 1 together with the rotor 3.

In the example in question, the switch 40 also comprises at least one pair of radially extending brushes, namely a positive brush 45 and a negative brush 46, which are able to rub against the commutator 41. The brushes 45,46 are rotationally fixed, they are each defined on an angular sector, and they are connected to the same voltage source, here the battery B of the vehicle. Thus, the brushes are excited with DC.

In the example in question, a chopper 48 is placed between the brushes 45,46 and the terminal B + of the battery B to regulate the voltage and to act as a voltage converter.

In the example in question, the brushes 45,46 have a substantially parallelepiped shape. Each brush includes a cylindrical radially inner surface that contacts the commutator 41.

In the example being discussed, the machine 1 includes a rotationally fixed brush holder assembly 50 in which the brushes 45,46 are housed. The brush holder 50 supports brushes. The brush holder 50 surrounds the commutator 41. The brush holder is fixed to the sheath, in particular to the rear portion 5b of the sheath. The brush holder can be fixed to the rear bearing 14 or directly to the yoke of the stator.

When the machine 1 is operating in generator mode, the pulley 20 and the rotor 3 are driven in rotation, the windings of the rotor 30 being excited via the switch 40. The rotor 3 is then magnetized-generating a magnetic field and inducing currents in the windings of the stator.

The operation and structure of the switch will now be described in detail.

Fig. 3 and 4 schematically show the excitation of the windings of the rotor 3 of the machine 1 comprising two pairs of poles (i.e. p 2) by a three-phase current system in a first star-connected winding mode. Fig. 3 and 4 show the switch 40 and the rotor winding 30 laid flat.

Referring to fig. 3, commutator 41 comprises n × p × q circumferentially successive conductor segments 60, where n ═ 1, p ═ 2, and q ═ 3, and thus 6 conductor segments. Each segment 60 is defined over an angular sector and adjacent segments are insulated from each other. The conductive segments are divided into q groups, here three groups a ', b ', c '. All the segments 60 of a given set a ', b ', c ' are electrically interconnected and the three sets alternate circumferentially.

In the example in question, commutator 41 has the basic motif of a segment repeated p times, here twice. The basic motifs of the segments are the segments of group a ', the segments of group b ' and the segments of group c '. The commutator 41 has p × q channels, here 6 channels, from one type of segment to another type of segment. The type of segment is defined by the group to which it belongs. The basic pitch of the commutator is therefore equal to 2 x pi/(p x q), i.e. pi/3 or 60 °.

In the example in question, each of the three segment groups a ', b ', c ' is electrically connected to one of the two ends 32 of one of the three phases a, b, c of the rotor 3. The other ends 32 of the three phases are electrically interconnected to form a wye-connected winding.

In the example in question, the rotor may comprise two slots per phase and per pole (m ═ 1), i.e. here 12 slots. Each of the six segments of the commutator is aligned with one of the rotor body teeth. Each slot accommodating a portion belonging to a q-type phase is axially aligned with a segment of the commutator 41 of the same type.

In the example discussed, all segments have the same angular sector and the same axial dimension. In particular, all the segments 60 are identical and have no axial offset. The segment 60 may be made of copper. The radial thickness of the segment 60 may be between 1 mm and 3 mm, for example 2 mm. The axial dimension of the segments may be between 8 mm and 12 mm, for example 10 mm

Referring to fig. 4, the switch includes a pair of brushes 45,46 that are always in contact with the segment 60. It is contemplated that two pairs of brushes may be used, as the number of brush pairs may be between 1 and p. The brush pairs shown are offset from each other in the circumferential direction [ (2k +1) × 2 × pi ]/(2 × p) ], k being a natural integer. In the example in question, the brushes can therefore be offset by an angle of pi/2 or 3 pi/2, where the brushes 45,46 are offset by pi/2.

The angular offset between the brushes 45,46 is measured from center to center, i.e., between the mid-planes of each brush.

In the example discussed, each segment 60 is separated from two adjacent segments 60 by an insulated inter-segment portion 62. The angular extent of each of the intermediate portions 62 is the same.

In the example under discussion, the angular extent of each brush 45,46 is greater than the angular extent of the land portion 62. Thus, during overlap, each brush is always in contact with at least one segment and two segments.

Fig. 7 shows an armature of the electrical machine 1, the commutator of which is described in detail with reference to fig. 5 and 6. In the example in question, the machine 1 has five pairs of poles (p-5) excited using a three-phase current system (q-3). Commutator 41 here comprises fifteen conductor segments 60(n ═ 1). In the example in question, the phases of the windings are star-connected.

Fig. 5 shows segment groups a ', b ', c ' of the commutator 41. Fig. 6 shows the complete commutator, in particular the skeleton 65 of the commutator is visible.

In the example in question, the segments 60 of a given group a ', b ', c ' are all electrically connected to rings placed radially inside the segments. In the example discussed, the commutator includes a-rings 70, b-rings 71 and c-rings 72 for interconnecting the segments 60 of group a'. In the example in question, the rings 70,71,72 are axially successive. The b-type ring is a center ring, and the a-type ring and the c-type ring are end rings. The rings are distributed axially over the axial length of the segment 60.

In the example in question, a bridge 75 is provided between each segment 60 and the associated ring 70,71, 72. Each bridge is associated with a single segment 60. The bridges 75 extend radially from the ring without axial offset.

The bridge 75 of the b-shaped centering ring 71 is connected to the central region of the segment 60. The bridges 75 of the end rings 70, 72 are connected to the corners of the segment 60.

The bridges and rings are in the interior space of the skeleton 65, while the segments 60 are flush with the outside so as to be in electrical contact with the brushes. In the example in question, the segments 60, the bridges 75 and the rings 70,71,72 of a given group a ', b ', c ' form a ring body, which is a single component with unitary structure.

With reference to fig. 6, a skeleton 65 made of insulating material, for example plastic, is turned around the axis X in order to hold the segment 60 in position. The skeleton is substantially cylindrical. The armature 65 is here a single component having a unitary construction. The backbone includes fifteen radial holes 67 that receive the segments 60. The backbone includes a central bore 68 that receives the rotor shaft 10. Commutator 41 also includes a central hub 69 for the passage of the rotor shaft. The armature is fixed to the central hub, for example, overmolded to the central hub 69.

In the example in question, the commutator 41 comprises three connecting arms 80, each of which is fixedly secured to one of the rings 70,71, 72. Each connecting arm comprises a portion integral with and made of the same material as the ring body, and a portion comprising a free end 81. The two parts are fixed to each other, for example by welding. Each free end 81 is connected to a phase winding a, b, c for energizing it. Each connecting arm 80 extends radially from the backbone 65 through a radial hole 82 in the backbone.

In the example in question, for a star-connected winding, only one of the two ends 32 of each phase a, b, c is connected to the connecting arm. Thus, each segment group a ', b ', c ' excites one and only one of the 3 phases of the rotor.

In the example in question, commutator 41 also comprises connectors 90 for electrically interconnecting the ends 32 of the phases a, b, c. The connector 90 also comprises connecting arms alternating with connecting arms integral with the ring. The connectors 90 extend radially from the backbone 65. The connector comprises three terminals 91, each for receiving each phase terminal 32. Thus, each phase a, b, c comprises an end 32 connected to the connection arm 80 and an end connected to the connector 90.

In the example in question, commutator 41 also comprises fifteen capacitors 100, each capacitor being mounted between two adjacent segments, and thus between two segments of groups in different groups. Each segment 60 is thus electrically connected to two capacitors. When n-2, each segment is associated with only a single capacitance.

In the example discussed, the capacitors 100 may all be identical. Each capacitor 100 has a substantially parallelepiped shape. Each capacitor comprises two electrodes 101 separated by a polarizable insulator. Each capacitor 100 includes a housing 102 that encloses a polarizable insulator and a portion of the electrodes.

In the example discussed, each capacitor 100 may have a capacitance between 1 and 100 microfarads, for example 20 microfarads.

In the example discussed, capacitor 100 is on the same axial side relative to segment 60. Each capacitor 100 is directly secured to an axially oriented finger 103 of one segment 60. The electrodes 101 may be fixed directly to the fingers, in particular by welding. The capacitors are all at the same radial level as the segments 60.

In the example in question, the commutator also comprises a protection element 110 for protecting the capacitor. The protective element is here a single component of unitary construction and comprises a plurality of cavities 111, each housing one capacitor 100.

In the example in question, the commutator 41 also comprises a fan 115, which is a single component of unitary construction and is made of insulating material, in particular plastic. The fan and the skeleton 65 together form a single component having a unitary structure. The fan 115 includes eight blades 116 regularly distributed in the circumferential direction. The vanes 116 are curved here and they extend radially to the height of the segment.

In the example discussed, the fan 115 is placed axially beside the segment, on the side opposite to the capacitor 100. Thus, the segment 60 is placed between the capacitor 100 and the fan 115. More specifically, the capacitor 100 is located axially on the opposite side of the rotor body 11, while the fan 115 is located axially on that side of the rotor body 11. The fan extends at least partially into the inner space of the rotor body 11. The fan 115 extends radially between the rotor shaft and the rotor body.

In the example of fig. 8, the capacitors are according to different modes of implementation. Providing only three capacitors; each mounted between two different segment groups.

In this example, the housing 102 of the capacitor is fixed to an axially oriented face of the bobbin, preferably opposite the rotor body 11.

In the example in question, the capacitors 100 are connected to the connection arms 80 of the q groups of segments 60. Here, each electrode 101 is fixed in place by a connecting member 118, the connecting member 118 being, for example, a low-resistance metal wire, such as a copper tab.

In the example in question, the capacitors 100 are all placed in a given angular sector, in particular an angular sector smaller than 90 °, in particular an angular sector smaller than 45 °, and they are placed one above the other, radially closer to the axis than the segments 60.

With reference to fig. 9 to 12, a modified commutator 41 for exciting a machine 1 with eight pole pairs and star-connected windings with a three-phase current system (q 3) will now be described. The basic pitch of the commutator is therefore equal to 2 x pi/(p x q), i.e. pi/12 or 15 °.

In the example discussed, each intermediate segment 62 includes an isolated segment 63 that is not electrically connected to any other segment. In contrast to electrically connected conductive segments 60, which form three sets of segments, segments 63 are referred to as isolated. The isolated section is at a floating potential. The isolated segment 63 is separated from the conductive segment 60 by a gap 64, which gap 64 may be between 1 and 5 millimeters in the circumferential direction.

According to one aspect of the present invention, the angular range of isolation segment 63 comprises 40% to 50% of the angular range of conductive segment 60.

In the example in question, the commutator comprises 48 segments, namely 24 conducting segments 60 (n-1, p-8 and q-3) and 24 isolating segments 63, the conducting segments 60 alternating with the isolating segments 63.

In the example discussed, commutator 41 has p × q channels, here 24 channels, from one type of conductive segment to another type of conductive segment. The type of segment is defined by the group to which it belongs. The isolated segments do not belong to any group. Commutator 41 has the basic motif of a segment repeated p times (here 8 times). The basic motif is the segment of group a ', the segment of group b ', the segment of group c ', and the segment of group c ' (a ', b ', c ').

In the example discussed, the skeleton 65 holds the segments 60, 63 in place. The skeleton is substantially cylindrical. The armature 60 is here a single component having a unitary construction. The skeleton comprises 48 radial holes 67 which accommodate the segments 60, 63. The backbone includes a central bore 68 that receives the rotor shaft 10. Commutator 41 also includes a central hub 69 for the passage of the rotor shaft. The armature is fixed to the central hub, for example, overmolded to the central hub 69.

Fig. 10 is an exploded view of the commutator of fig. 9. The segments 60 of a given set a ', b ', c ' are all electrically connected to rings placed radially inside the segments.

In the example discussed, the spacer segments are secured to the intersegment ring 73. The intersegment ring 73 is placed in the inner space of the skeleton 65. The intersegment rings 73 are radially outside the rings 70,71, 72. The spacer 63 includes a foot 74 that is inserted into the bore of the inter-segment ring for securing the spacer in place.

The intersegment rings 73 comprise windows 76 for the passage of bridges 75 between the segments 60 of group b and the centrally located ring 72. Thus, the bridge 75 of the b-ring 78 passes through the intersegment ring 73.

Fig. 11 shows a cross-section of a conducting segment 60 of the commutator 41. The isolated sections of the intersegment are not shown here.

In the example in question, the angular extent β of the intermediate portion 62 is equal to the angular extent α of the segment 60. The angular extent of each segment and each inter-segment portion is equal to 7.5 degrees, i.e. 2 x pi/48 radians. The basic motifs of the commutator are: a segment followed by an intersegment; the basic pitch of the commutator is therefore equal to 15.

Referring to the example referred to in fig. 12, a variation of the switches of fig. 9 to 11 is shown. The basic pitch of the commutator is still equal to 15 deg., but the segments 60 and the intersegment portions 62 are of different sizes. The range of the segment gap is equal to 20%, i.e. 3, of the basic pitch, since the range of the brush θ is equal to 45%, i.e. 6.75 °, of the basic pitch, and the range of the segment β is equal to 80%, i.e. 12 °, of the basic pitch of the commutator.

In the example in question, the degree of overlap is equal to (12-3)/15, 60%, the degree of overlap being the ratio of the difference between the angular extent of one of the brushes 45,46 and the angular extent of one of the intermediate segments 62 divided by the basic pitch of the commutator.

In the example in question, the switch 40 comprises a pair of brushes 45,46, which are always in contact with the segment 60. The pair of brushes shown are offset from each other in the circumferential direction by [ (2k +1) × 2 × pi ]/(2 × p) ], k being 0. In the example in question, the brushes 45,46 are offset by π/8 radians, i.e., 22.5. Thus, each brush 45,46 undergoes an overlapping segment during which it is in contact with two segments 60 of different groups a, b, c.

In the example in question, the windings are star-connected and the 60% overlap with the switches 40 of fig. 8 allows the rotor to be excited using a quasi-sinusoidal form of the three-phase current system.

With reference to fig. 13 to 15, a modified commutator 41 will now be described for exciting a machine 1 with six pairs of poles and wye-connected windings with a three-phase current system (q 3).

This example differs from the previous example in that n-2 and the interlude sections 62 do not include any isolated sections, but are instead formed by annular spaces 36 located circumferentially between the conductive sections 60.

In the example in question, commutator 41 has p × q channels, here 18, from one type of segment to another. The type of segment is defined by the group to which it belongs. Commutator 41 has a basic segment motif that repeats p times (here 8 times). The basic motifs are here segments of group a ', segments of group b', segments of group c 'and segments of group c' (a ', a', b ', b', c ', c'). The commutator 41 therefore has a basic pitch equal to 2 x pi/(p x q), i.e. pi/9 or 20 °.

In the example discussed, bridge 75 is associated with a single segment. As a variant, when n is 2 and when two segments of the same type are circumferentially consecutive, the bridge may be shared by the two segments.

In the example discussed, the angular extent of the inter-segment portion 62 is equal to the angular extent of the segment. The angular extent of each segment and each intersegment is equal to 5 degrees, i.e. 2 x pi/72. Fig. 15 shows the central ring 78 associated with the segments of group b.

Fig. 16 and 17 schematically show the excitation of the windings of the rotor 3 of the machine 1 comprising two pairs of poles (p 2) with a three-phase current system in a second winding mode (delta connection). Fig. 16 and 17 show the switch 40 and the rotor winding 30 laid flat.

This example differs from that shown in fig. 3 and 4 in that each of the 3 segment groups a ', b ', c ' is electrically connected to both ends 32 of two different phases a, b, c, thereby forming a delta-connected winding.

In the example in question, each phase a, b, c is connected to two different segment groups a ', b ', c '.

With reference to fig. 18 to 21, a switch 40 will now be described for energizing a machine 1 with a three-phase current system (q 3) having six pairs of poles and delta-connected windings.

In the example in question, the commutator here comprises 18 conductor segments 60(n 1, p 6, q 3). Commutator 41 has p × q channels, here 18, from one type of segment to another type of segment. Commutator 40 has a basic motif of segments that are repeated p times (here 6 times). The basic motifs are here segments of group a ', segments of group b and segments of group c ' (a ', b ', c ').

The commutator 40 discussed herein differs from the previously described commutator in that it does not include a connector. The commutator comprises only 3 connecting arms 80, each of which accommodates two phase ends 32. The end 32 is fixed, for example by welding. Thus, each phase a, b, c is connected to two connecting arms 80, and each connecting arm 80 is connected to two phases of the winding. The potentials at the two ends 32 of each phase a, b, c are the same.

In the example in question, the degree of overlap may be between 10% and 55% according to this variant.

Claims (13)

1. Mechanical switch (40) for an electric machine (1), said switch being capable of exciting a rotating electric machine rotor (3) having 2 x p poles with a polyphase current system comprising q phases, where q is a positive integer strictly greater than 1, said switch comprising:

a commutator (41) capable of rotary motion about an axis (X) of the machine, having a basic pitch equal to 2 π/(p × q),

at least one pair of radially extending brushes, namely a positive brush (45) and a negative brush (46), which can rub against said commutator (41) and are rotationally fixed, each brush being defined on an angular sector and being connectable to the same voltage source, in particular a vehicle battery (B),

characterized in that the mechanical commutator (41) comprises n p q circumferentially successive conductive segments (60), where n is an integer, in particular n 1 or n 2, each segment (60) being defined on an angular sector, adjacent segments being insulated from each other, the segments being divided into q groups (a ', b ', c '), all segments (60) of a given group being electrically connected together, the q groups alternating circumferentially,

and the brushes (45,46) of a given pair are circumferentially offset from each other by [ (2k +1) × 2 × pi ]/(2 × p) ], k being a natural integer.

2. The mechanical switch (40) of claim 1, the segments (60) of a given group (a ', b ', c ') all being electrically connected to a ring (70,71,72) placed radially inside the segments (60).

3. The mechanical switch (40) of claim 2, the rings (70,71,72) of each set being axially sequential.

4. The mechanical switch (40) according to any one of the preceding claims, each segment (60) being separated from two adjacent segments by an intersegment portion (62), the circumferential dimension of which is selected to prevent dielectric breakdown.

5. Mechanical switch (40) according to any of the preceding claims, an overlap being defined as the difference between the angular extent of the brushes (45,46) and the angular extent of the inter-segment portion (62) divided by the basic pitch of the commutator, the overlap being between 10% and 55%.

6. The mechanical switch (40) according to any one of the preceding claims, the commutator comprising a fan (115).

7. The mechanical switch (40) according to any of the preceding claims, the commutator comprising a plurality of capacitors (100), each capacitor being mounted between two different segment groups.

8. An electric machine (1) comprising:

the mechanical switch (40) according to any one of claims 1 to 5,

a rotationally fixed stator (4) comprising 2 x p poles, the stator (4) forming a field magnet of the electrical machine,

-a rotor (3) movable in rotation about an axis (X) of the machine, the rotor (3) forming, together with a commutator (41), an armature of the machine, the rotor comprising:

a rotor shaft (10), and

a rotor body (11) comprising:

a lamination stack comprising axially stacked laminations, said lamination stack (10) having p x q slots extending axially,

at least one winding (30) divided into q phases (a, b, c) excited via switches (40), the phases comprising portions of the winding housed in slots, portions (31) of each phase being circumferentially consecutive, each phase having two ends (32).

9. The electric machine (1) according to claims 6 and 8, a fan extending at least partially into the inner space of the rotor body.

10. The electrical machine (1) according to claims 7 and 8, a capacitor being located axially on the opposite side of the rotor body.

11. The electrical machine (1) according to claim 10, each of the q segment groups (a ', b ', c ') being electrically connected to one of the two ends (32) of one of the q phases (a, b, c) of the rotor, the other ends (32) of the q phases being electrically connected together to form a star-connected winding (30).

12. The mechanical switch (1) according to claim 6, each of the q group segments (60) being electrically connected to two ends (32) of two different phases of the q phases (a, b, c) of the rotor to form a polygon-connected winding (30).

13. A traction system for a vehicle, the system comprising:

the electrical machine (1) according to any of claims 6 to 8, and

and a chopper (48) electrically connected to the brushes (45,46) of the mechanical switch (40) and connectable to a battery (B) of the vehicle.

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