Brushed machine for electrical machine and corresponding electrical machine

Abstract

A brushed machine 10, suitable for an electrical machine (fig.12), comprises a collector 12 having an axis of rotation C and at least one brush 14 configured to contact an outer surface S of the colle

Description

TITLE OF THE INVENTION: Brushed machine for electrical machine and corresponding electrical machine TECHNICAL FIELD This invention relates to a brushed machine for an electrical machine, in particular a DC electrical machine. More specifically, the invention relates to the field of cooling a collector with blades and brushes of a brushed machine. The invention also relates to a corresponding electrical machine, in particular an electrical machine of an aircraft. PRIOR ART Generally speaking, an electrical machine comprises a casing, an axis of rotation, a stator attached to the casing, also known as the inductor, which is the stationary portion of the electrical machine, and a rotor, also known as the armature, placed inside the stator, the rotor being a rotating portion of the electrical machine. Some electrical machines, particularly the DC machines, also comprise a rotary collector to create an electrical connection between the fixed portion (stator) and the rotating portion (rotor) of the electrical machine. To this end, these electrical machines also comprise brush collectors, also known as "rubbers" or "carbon brushes". These brush collectors are conductive parts that provide the electrical connection between the stationary portions and the rotating or moving portions of the electrical machines. They supply power to the collector during motor operation and recover current from the collector during generator operation. Figure 1 shows schematically a brushed machine 10A according to the prior art comprising a collector 12A with blades and brushes 14A, two brushes in the example shown. In this example, the brushes 14A, generally made of graphite, are arranged in parallel with each other. The collector 12A comprises collector blades 16A, generally made of copper. The blades 16A are electrically insulated from each other by thin insulating inter-blades 18A, often made of mica. Figure 2 shows a half-section view of a brushed machine 10A comprising a collector 12A and two brushes 14A. In the example shown, the collector is molded. The collector 12A comprises a hollow shaft 20A, generally made of steel, supporting the collector blades 16A. The assembly of the parts of the collector 12A are held secured together by an insulating resin 22A. In addition, to resist centrifugal forces, hoops 24A are advantageously inserted into the collector. The brushed machine also comprises one or more brush holders 26A to hold the brushes in contact with the collector. For example, as shown in Figure 2, the machine 10A comprises one brush holder 26A per brush. Each brush holder 26A comprises a cage to house a brush 14A. Each brush 14A may move inside the cage by sliding and is held under pressure against the collector by a spring 28A. For certain types of DC machine, the sum of mechanical and electrical losses in a brushed machine may represent a significant proportion of the losses and lead to excessive heating of the brushes and of the collector at the brush-blade interface. The brushes 14A and the blades 16A of the collector may therefore reach extreme temperatures of several hundred degrees at full power. Figure 3 shows a brush wear curve as a function of operating temperature. As the figure shows, at operating temperatures of up to 200°C, the service life of the brushes is very limited, averaging around 1,000 hours. However, at an operating temperature of 100°C, the service life of the brushes last much longer. Brush wear is a highly complex and non-linear phenomenon. However, there seems to be an ideal operating temperature for brushes at around one hundred degrees, where wear is minimal. To reduce the rate of wear and the frequency of maintenance, it is important to ensure that the collectors and / or brushes are properly cooled. Traditionally, cooling a brushed machine involves circulating air inside the machine. A fan is often used for this purpose. The fan is mounted directly on the shaft of the machine. The air is taken from outside, then enters and circulates in the machine, "licking" the surface of the collector and the brushes before being exhausted outside the machine. However, this type of cooling device does not keep the temperature of the collector and brushes within an optimum operating range, because the temperature of the brushes and collector is the result of several phenomena: mechanical losses in the collector and brushes, which increase with the speed of rotation of the machine; - electrical losses in the collector and brushes, which depend on the load of the machine; - the air flow rate, which depends on the speed of rotation of the machine in the case of a self-ventilated machine; and - the quality of the ventilation, which depends on factors such as the temperature of the cooling air, the speed of the air and its path. Channeling the air as close as possible to where losses are created, in particular at the interface between the collector and the brushes, is not always easy to achieve given the configuration of the collector and the brushes. The existing solutions are unsatisfactory for the following reasons. The surface of the collector is smooth, which limits the exchange surface with the flow of cold air generated by the ventilation system. The temperature of the cooling air may be high (over 50°C), which further limits the amount of heat that may be exchanged with the reduced surface area of the collector and brushes. The air circulating in the casing of the electrical machine is difficult to channel along the surfaces to be cooled, the surface of the collector and the surfaces of the brushes, because of the rotational movement of the rotor. Depending on the environmental conditions, the cooling air may be at a high temperature. The brushes are guided around their entire periphery inside the cage, which must be high enough to prevent them becoming jammed. For economic reasons, this cage is often made of folded or pressed sheet steel, and acts as a heat shield against the surrounding air circulation. As a result, the cage severely limits the exchange surface of the brushes with the surrounding air circulating around the cage. Moreover, to avoid the risk of jamming, the brushes are guided with an adequate clearance, and 0.3 mm deep counterbores are also provided on the faces of the brushes. All this tends to limit the thermal contact between the brush and its cage and consequently the efficiency of heat transfer from the brush towards the cooling ribs of the cage. The aim of the present invention is therefore to offer a brushed machine that may overcome at least some of these disadvantages and, in particular, maintain the brushes and the collector at an ideal operating temperature to optimize their service life. SUMMARY OF THE INVENTION To this end, the invention relates to a brushed machine for an electrical machine comprising a collector having an axis of rotation and at least one brush configured to contact an outer surface of the collector, the collector comprising a plurality of collector blades arranged around the periphery of the collector, each blade comprising a body extending longitudinally along the axis of rotation and an external surface forming a portion of the outer surface of the collector. According to the invention, blades of the plurality of blades advantageously comprises at least one channel formed within the body of the blade and proximate the external surface of the blade and configured to be at least partially filled with a liquid under vacuum. In addition, according to the invention, the brushed machine comprises at least one heat removal device and connecting elements, each configured to connect the at least one channel of a blade to the at least one cooling device. Advantageously, a brushed machine of this type may significantly extend the service life of the brushes when they are subject to high temperature loads. The invention allows the collector blades and the brushes to be cooled more efficiently by effectively draining the losses created mainly at the interface between the collector and the brushes, as this is where the greatest losses are generated. Losses are drained by channels built directly into the collector blades. These channels, filled with a certain amount of liquid, act as heat pipes, increasing the thermal conductivity of each collector blade. According to the invention, the body of the collector blades serves both as an electrical conductor and as a heat pipe. The fact of not inserting a heat pipe into each blade but of making it directly in the body of the blade saves space and above all avoids the thermal interface between the collector blade and the collector. This also avoids electrical insulation between the body of the collector blade and the body of the heat pipes since the body of the heat pipe is the collector blade itself and therefore the heat pipe part is at the same electrical potential as the collector blade. The absence of electrical insulation between the body of the collector blade and the heat pipe(s) simplifies the production of the brushed machine for small blades and greatly improves the efficiency of the heat transfer from the collector blade to the heat pipe. This solution for draining losses at the brush / collector blade interface reduces the operating temperature and consequently increases the service life of the brushes and of the collector blade. In this way, the brushes are cooled more efficiently to bring them down to the "ideal" operating temperature and make their service life acceptable to users (for example, by aligning the brush maintenance intervals with the general machine overhaul intervals). The brushed machine according to the invention may comprise one or more of the following characteristics, taken alone or in combination with each other in any technically possible combination: - the collector is rotatable about the axis of rotation and the heat removal device is secured to the collector during rotation thereof; - for each collector blade equipped with a channel, the at least one channel extends parallel to the axis of rotation of the collector; - for each collector blade equipped with a channel, the at least one channel extends longitudinally between a first end connected to the heat removal device and a second end opposite the first end while being inclined with respect to the axis of rotation of the collector by an angle of approximately 10°, the first end being closer to the axis of rotation than the second end; - each channel is centered in the body of the blade in a plane transverse to the blade; - two consecutive blades are separated by an inter-blade bulkhead and each blade extends radially between a radially internal surface and a radially external surface and comprises two side surfaces each connecting the radially internal and external surfaces; and each channel is formed in one of the side surfaces and bounded by the adjacent inter-blade bulkhead; - the inter-blade bulkhead is made of metal; - each blade is formed of a first portion and a second portion juxtaposed, the channel of the blade being formed at the interface of the first portion and the second portion; - each blade equipped with at least one channel comprises several channels parallel to one another; - the channels of the blades are non-circular in cross-section; - the cross-section of the channels of the blades is semicircular, square or rectangular; - the liquid is water, ethanol or a coolant; - the brushed machine comprises a plurality of heat removal devices, each being connected to the at least one channel of a blade by the connecting elements, each blade being at the same electrical potential as the heat removal device to which it is connected; - the channels of the blades are connected by the connecting elements to the same heat removal device, the channels each being electrically insulated from the heat removal device; - the heat removal device is a finned radiator; - each fin is fitted to a corresponding collector blade; - each fin and each corresponding collector blade are made entirely of the same material; - the channels of the blades are connected by the connecting elements to the same heat removal device, the brushed machine comprising an electrically insulating gasket arranged between the collector and the heat removal device, the gasket comprising a plurality of passage orifices each for a channel of a collector blade; - the channels of the blades are connected to each other two by two by being connected to each other by insulated U-shaped connecting elements; - each connecting element comprises a connecting tube extending between a first end fitted into the blade, surrounding the first end of the channel, and a second end fluidly connected to the heat removal device; - the collector comprises between 30 and 50 collector blades; - the collector is a molded collector or screwed collector. The invention also concerns an electrical machine, in particular for an aircraft, having a longitudinal axis and comprising a stator, a rotor placed inside the stator and rotatable about the longitudinal axis and a brushed machine according to the invention and as described above, the axis of rotation of the brushed machine being co-linear with the longitudinal axis of the electrical machine. BRIEF DESCRIPTION OF FIGURES The invention will be better understood and other details, characteristics and advantages of the present invention will become clearer from the following description made by way of non-limiting example and with reference to the attached drawings, wherein: Figure 1, already described, is a schematic three-dimensional view of a brushed machine in the prior art; Figure 2, which has already been described, shows a schematic half-section view of a brushed machine in the prior art; Figure 3, already described, shows a brush wear curve as a function of their operating temperature; Figure 4 is a schematic half-sectional view of a brushed machine in a first embodiment; Figure 5 shows schematically a transverse view of a collector of the brushed machine of Figure 4; Figure 6 shows an enlarged view of the connection between the collector of the machine in Figure 4 and a cooling device; - Figure 7 illustrates an example wherein the cooling device is a finned radiator rotatable in two different positions; - Figure 8 illustrates another example wherein the cooling device is a finned radiator that may be rotated to two different positions; Figure 9 shows a second embodiment of the invention wherein each collector blade comprises an independent cooling device; Figure 10 is a schematic three-dimensional view of a collector of a brushed machine according to a third embodiment of the invention; Figure 11 schematically illustrates various possible positions of the channel in a collector blade according to the invention; and Figure 12 schematically represents a three-dimensional view of an electrical machine comprising a brushed machine according to the invention. The elements with the same functions in the different implementations have the same references in the figures. In the figures, the scales and the proportions are not strictly respected for the purposes of illustration and clarity. Furthermore, in the description and the claims, the terms axial, radial and transverse will be adopted with reference to the trihedron A, R, T shown in the figures, the axial axis A being parallel to the longitudinal axis of the lubrication enclosure according to the invention. DESCRIPTION OF THE EMBODIMENTS The invention is applicable to all types of brushed machines comprising a collector and brushes, where losses in the brushes and the collector lead to an excessive heating and an increased wear of the brushes and of the collector. In terms of excessive heating, 100°C is considered an acceptable temperature limit, since temperatures above this often lead to accelerated wear of the brushes (Figure 3). In particular, the invention applies to low-power brushed machines, of the order of 10kW, whose collector blades have very small dimensions. Figure 4 illustrates a schematic half-section view of such a brushed machine 10 according to a first embodiment of the invention. The brushed machine 10 comprises a collector 12 and at least one line of brushes. In the example illustrated, a single line of brushes is shown for the sake of clarity, this line of brushes comprising in this example two brushes 14. However, according to the invention, the brushed machine 10 may comprise a single brush or several brushes per line of brushes. Each brush 14 is configured to be in contact with an outer surface S of the collector 12. By convention in the present application, the terms "internal" and "external", "inner" and "outer" are defined radially with respect to the longitudinal axis C of the brushed machine 10, which is in particular the axis of rotation of the collector 12 of the brushed machine. The lines of brushes each extend parallel to the axis of rotation C of the collector 12 and are arranged around the collector. Preferably, the lines of brushes are evenly distributed around the collector. The brushed machine 10 also comprise one or more brush holders not shown in Figure 4, as described for example with reference to Figure 2. These brush holders are configured to hold the brushes in contact with the collector, for example by means of a spring as described above. The brushes are generally made of graphite. In the example shown in Figure 4, the brushes are arranged parallel to each other. However, other configurations are possible according to the invention. The collector 12 will now be described in detail. In the example shown, the collector 12 is molded. However, the invention may also be applied to other types of collector, such as screwed collectors. The collector 12 comprises a hollow cylindrical shaft 20 with a longitudinal axis C, which is also an axis of rotation of the collector during operation. The collector 12 may be rotated about the axis of rotation C. Preferably, the shaft 20 of the collector is made of steel. The shaft 20 of the collector is configured to peripherally support collector blades 16. Preferably, the collector 12 comprises between 30 and 50 blades 16. In addition, to resist centrifugal forces, hoops 24 are advantageously inserted into the collector. The collector blades are juxtaposed to form an annular ring of blades. Preferably, the collector blades 16 are made of copper or a copper-based alloy. The blades 16 are electrically insulated from each other by thin insulating inter-blades 18. Two successive collector blades are separated by an insulating inter-blade bulkhead 18. In other words, the periphery alternates between collector blades 16 and inter-blade bulkheads 18. The inter-blade bulkheads 18 extend longitudinally along the longitudinal axis C of the collector. The inter-blade bulkheads 18 are preferably made of mica. With reference to Figure 5 which illustrates a cross-sectional view of the collector 12, each collector blade 16 comprises a body 161 extending longitudinally along the longitudinal axis C of the collector which is also the axis of rotation of the collector in operation. The body 161 extends radially between an internal surface 162 and an external surface 163. The external surface 163 forms a segment of the outer surface S of the collector. The body 161 also comprises two lateral surfaces 164 each connecting the radially internal 162 and external 163 surfaces. The body 161 also comprises one or more feet 165, in particular dovetail-shaped, extending from the internal surface 162 radially inwards, i.e. towards the shaft 20 of the collector. The feet 165 are shaped to cooperate with the hoops 24 in order to hold the blades in position despite centrifugal forces when the brushed machine is in operation. The parts of the collector 12 are held secured together by an insulating resin 22, in particular the shaft 20, the hoops 24 and the blades 16 of the collector. According to the invention, each blade 16 advantageously comprises at least one channel 166 formed inside the body 161 of the blade. For the sake of clarity, only a few channels are shown in Figure 5. Each channel 166 is arranged close to the external surface 163 of the blade 16. Each channel 166 is thus arranged in the immediate vicinity of an interface between the blade 16 and a brush 14. "Nearby" or "in the immediate vicinity" means that each channel is closer to the outer surface S of the collector than to the axis of rotation C of the collector 12. In other words, each channel 166 is closer to the outer surface S of the collector than to the shaft 20 of the collector. For example, each channel 166 is advantageously arranged at a distance from the external surface 163 of the blade 16 of between 1 mm and 5 mm. Preferably, each channel 166 extends along substantially the entire length of the collector, the length being the dimension along the longitudinal axis C of the collector. Each channel is configured to be partially filled with a liquid, for example water, ethanol or a coolant. For the purposes of the invention, "partially" filled with liquid means that each channel contains liquid but is not completely filled with liquid. More specifically, each channel is filled with liquid at a rate varying from a few % to 20 %. The filling ratio is defined as the ratio between the volume of liquid placed inside the channel and the volume inside the channel corresponding to the evaporation section, i.e. the volume of the channel directly subjected to heating under the brushes. Each channel is also evacuated to function as a heat pipe, i.e. to transport the heat generated at the blade / brush interface towards the outside of the collector 12. Once the quantity of liquid has been introduced into the channel, it is evacuated, i.e.: - by heating the liquid until it evaporates, expelling the air trapped in the channel. The channel is then sealed. using a vacuum pump. In addition, according to the invention, the brushed machine 10 advantageously comprises at least one heat removal device 30 and connecting elements 40. Each connecting element 40 is configured to connect the channel or channels 166 of each blade to a heat removal device 30. According to the first embodiment of the invention shown in Figure 4, the brushed machine 10 comprises a single heat removal device 30 for all the blades. As a result, each connecting element 40 is configured to connect the channel or channels 166 of each blade to the heat removal device 30 common to all the blades. Thus, each liquid-filled, evacuated channel 166 connected to the common heat removal device 30 is adapted to function as a heat pipe, i.e. to transport the heat generated at the blade / brush interface towards the outside of the collector 12 and in particular towards the common heat removal device 30. The common heat removal device 30 is secured to the collector 12 as it rotates. For example, as shown in Figure 4, the common heat removal device 30 and all the parts of the collector 12 are held secured together by the insulating resin 22. For each collector blade 16, the channel 166 extends longitudinally between a first end 166A connected to the heat removal device 30 and a second end 166B opposite the first end 166A. Preferably, for each blade, the channel 166 is inclined with respect to the axis of rotation C of the collector 12 so that the first end 166A is closer to the axis of rotation C than the second end 166B. The angle between the channel 166 and the axis of rotation C is less than 10°, preferably 5°. In a particular case, for each blade, the channel 166 extends parallel to the axis of rotation C of the collector 12, i.e. at an angle of 0°. If the blades comprise several channels 166, these are parallel to each other and may therefore all be inclined with respect to the axis of rotation C or be parallel to the axis of rotation C. Figure 6 shows an enlarged view of the brushed machine 10 at the level of a connecting element 40 of a channel 166 of a blade to the cooling device 30 common to all the blades. In the illustrated embodiment, each connecting element 40 comprises a connecting tube 42 extending between a first end 42A and a second end 42B. The first end 42A is fitted into the blade 16, surrounding the first end 166A of the channel 166. In this way, the inner diameter of the connecting tube 42 is equal to the outer diameter of the channel 166. The connecting tube is preferably made of copper. The second end 42B is fluidly connected to the heat removal device 30. The second end 42B is also electrically insulated from the heat removal device 30 in the event that the heat removal device 30 is electrically conductive and connected to several collector blades 16 in order to prevent the collector blades 16 from short-circuiting each other. To this end, the second end 42B of the connecting tube is covered by a thin layer of electrical insulator of sufficient thermal conductivity, for example the same insulating resin 22 as the resin holding the elements of the collector 12 together, or by any other known insulating means. In this way, the assembly formed by channel 166 and the connecting tube 42 is filled with liquid and evacuated to form a heat pipe designed to transport heat from the collector blade / brush interface towards the heat removal device 30. Alternatively, to prevent the collector blades 16 from short-circuiting with each other, the brushed machine 10 may comprise an electrically insulating gasket arranged between the collector 12 and the heat removal device 30. The gasket then comprises a number of passage orifices, each for a channel 166 of a collector blade. The common heat removal device 30 may comprise a plate supporting fins 32 as in the example shown in Figures 7 and 8. Figures 7 and 8 show the case of a brushed machine 10 wherein the heat removal device 30 is a rotary finned radiator 34 which is attached securely to the collector 12 and more precisely to one end of the collector from which the ends 166A of the channels of the blades 16 open out with a view to their connection to the heat removal device 30. The rotating finned radiator 34 may thus be rotated about the axis of rotation C of the collector in a manner secured to the collector 12. In Figures 7 and 8, the brush lines are deliberately not illustrated for the sake of clarity. Figures 7 and 8 differ from each other in the diameter of the rotating finned radiator 34. In Figure 7, the outer diameter of the rotating finned radiator 34 is substantially equal to the outer diameter of the collector of the brushed machine. In Figure 8, the diameters are different. More specifically, the outer diameter of the rotary finned radiator 34 is greater than the outer diameter of the collector of the brushed machine. Figure 9 schematically illustrates a second embodiment of the invention. The electrical machine 100 according to this second embodiment of the invention differs from the electrical machine 10 according to the first embodiment in that the brushed machine 100 comprises several heat removal devices 300. Each heat removal device 300 is associated with a blade 16 and connected to the or all channels 166 of this blade 16 by one or more connecting elements 40. Each collector blade 16 has its own dedicated heat removal device 300. The heat removal device 300 is therefore at the same electrical potential as the collector blade 16 without any risk of short-circuit between the blades. This embodiment therefore has the advantage of not requiring electrical insulation of each collector blade 16 of the heat removal device 300. In the example shown, each heat removal device 300 is a fin 320 fitted to the blade 16 of the collector. For example, the fin 320 is brazed to the associated blade 16. Alternatively, the fins 320 may be made in one piece with the collector blades 16. Figure 10 shows schematically a third embodiment of the invention wherein the channels 166 of the blades are connected to each other two by two in series. To this end, the channels are interconnected by electrically insulated U-shaped connecting elements 400. Preferably, the U-shaped connecting elements 400 are integrated into one or more heat removal devices, such as a rotary radiator as shown in Figures 7 and 8. Connecting the channels in series in this way allows to form a self-contained serpentine tube, filled with liquid and evacuated allowing to form an oscillating heat pipe. In this embodiment, each channel 166 of each blade extends longitudinally between a first end 166A and a second end 166B opposite the first end 166A. The first end 166A and the second end 166B open respectively onto a first transverse face 12A of the collector and onto a second transverse face 12B of the collector 12. In addition, each connecting element 400 comprises a U-shaped connecting tube 420 with two ends 420A, 420B. On the side of the first transverse face 12A of the collector, the ends 420A, 420B of a connecting tube 400 connect the first ends 166A of the channels of two adjacent blades 16. Similarly, on the side of the second transverse face 12B of the collector, the ends 420A, 420B of a connecting tube 400 connect the second ends 166B of the channels of two adjacent blades 16 so as to form a continuous tube filled with liquid. The connection tube 420 is preferably made of copper. The connecting tube 420 is also electrically insulated so as to prevent the collector blades 16 from short-circuiting each other. To this end, the connecting tube 420 is covered by a thin layer of electrical insulation. The brushed machine according to this third embodiment may also comprise a heat removal device for cooling the liquid in the channels in order to cool the blade / brush interface. The heat removal device is then arranged at one end of the collector. The advantage of this third embodiment is that the whole assembly only needs to be evacuated once, rather than channel by channel. Regardless of how the embodiment of the invention and the number of channels per collector blade, the channels of the blades preferably have a non-circular cross-section. For example, the cross-section of the blade channels is semicircular, square or rectangular. Figure 11 illustrates several methods of creating a channel in a blade. The blade referenced I has no channel. Preferably, each channel 166-11 is centered in the body of the blade in a plane transverse to the blade, such as in the blade referenced II. Such a channel 166-11 is produced by piercing or electro-erosion, for example. Alternatively, each channel 166-111 may be formed in one of the lateral surfaces 164 and delimited by the adjacent inter-blade bulkhead 18. Alternatively, the inter-blade bulkhead 18 is made of metal or covered with a metal wall 182 and each channel 166-IV is formed in one of the lateral surfaces 164 and delimited by the metal wall 182 of the adjacent inter-blade bulkhead 18. According to another alternative, each blade (here referred to as V) is formed from a first portion and a second portion which are juxtaposed and the channel 166-V of the blade being formed at the interface of the first portion and of the second portion. The channels of the type 166-111, 166-IV and 166-V, for example, are produced by machining or stamping. The invention also relates to an electrical machine, in particular for aircraft, having a longitudinal axis and comprising a stator and a rotor placed inside the stator and rotatable about the longitudinal axis. The electrical machine also comprises a brushed machine according to the invention and as described above. The axis of rotation of the brushed machine is co-linear with the longitudinal axis of the electrical machine. The electrical machine is preferably a DC machine such as a motor, a generator, a starter or a starter-generator. Figure 12 shows an example of such an electrical machine 1000 equipped with a brushed machine 10 according to the invention. The brush lines are deliberately not illustrated for the sake of clarity. The collector 12 of the brushed machine comprises a heat removal device 30. For example, as shown in Figure 12, the heat removal device 30 is a rotating finned radiator 34. In the example shown, the electrical machine 1000 comprises a rotor 1020. The rotor 1020 comprises a shaft 1030 on which an assembly of ferromagnetic discs 1040 is stacked. Notches 1050 are fitted axially in the periphery of the cylinder formed by the stacked discs. In addition, the rotor 1020 comprises armature coils 1060 made up of windings wound in a very precise pattern. The armature coils 1060 are inserted into the notches 1050 of the magnetic circuit. Each winding is made up of a series of sections, themselves made up of turns. As is well known, a turn is a loop, the forward part of which is placed in a notch of the armature and the return part in the diametrically opposite notch. The armature coils 1060 are connected to the collector 12. The invention, as presented, describes a brushed machine having more efficient cooling than a conventional brushed machine, and in particular the invention allows the collector blades and the brushes of the brushed machine to be cooled more efficiently. Of course, the invention is not limited to the above-described embodiments, which are provided by way of example only. It encompasses various modifications, alternative forms and other variants that may be envisaged by the person skilled in the art within the framework of the invention, and in particular all combinations of the various embodiments described above, which may be taken separately or in combination. For example, according to the invention, the collector may comprise a plurality of collector blades comprising at least one channel formed within the body of the blade as described above and a plurality of other blades having no channels. The blades with a channel and the blades without channels are arranged alternately. For example, one blade in two or one blade in three comprises a channel, while the other blades have no channels. According to another example, a collector according to the invention may comprise one or more blades each comprising several channels.

Claims

1. A brushed machine (10; 100; 200) for an electrical machine comprising a collector (12) having an axis of rotation (C) and at least one brush (14) configured to contact an outer surface (S) of the collector, the collector (12) comprising a plurality of collector blades (16) arranged around the periphery of the collector, each blade (16) comprising a body (161) extending longitudinally along the axis of rotation and an external surface (163) forming a portion of the outer surface (S) of the collector;characterized in that blades (16) of the plurality of blades each comprise at least one channel (166) formed within the body of the blade and proximate the external surface (163) of the blade and configured to be at least partially filled with a liquid under vacuum; and in that the brushed machine (10) comprises at least one heat removal device (30; 300) and connecting elements (40; 400), each configured to connect the at least one channel (166) of a blade (16) to the at least one cooling device (30).

2. The brushed machine as claimed in claim 1, wherein the collector (12) is rotatable about the axis of rotation (C) and the heat removal device (30) is secured to the collector (12) during rotation thereof.

3. The brushed machine according to claim 1 or 2, wherein for each collector blade (16) equipped with a channel the at least one channel (166) extends parallel to the axis of rotation (C) of the collector or the at least one channel (166) extends longitudinally between a first end (166A) connected to the heat removal device (30) and a second end (166B) opposite the first end while being inclined with respect to the axis of rotation (C) of the collector by an angle of approximately 10°, the first end being closer to the axis of rotation than the second end.

4. The brushed machine according to any one of the preceding claims, wherein each blade (16) equipped with at least one channel comprises several channels (166) parallel to one another.

5. The brushed machine according to any one of the preceding claims, wherein the liquid is water, ethanol or a coolant.

6. The brushed machine (100) according to any one of the preceding claims, comprising a plurality of heat removal devices (300), each being connected to the at least one channel (166) of a blade (16) by the connecting elements (40), each blade (16) being at the same electrical potential as the heat removal device (300) to which it is connected.

7. The brushed machine according to any one of claims 1 to 5, wherein the channels (166) of the blades are connected by the connecting elements to the same heat removal device (30), the channels each being electrically insulated from the heat removal device.

8. The brushed machine according to any one of claims 1 to 5, wherein the channels (166) of the blades are connected by the connecting elements (30) to the same heat removal device, the brushed machine comprising an electrically insulating gasket arranged between the collector and the heat removal device, the gasket comprising a plurality of passage orifices each for a channel of a collector blade.

9. The brushed machine according to any one of claims 1 to 5, wherein the channels (166) of the blades are connected to each other two by two in series by being connected to each other by electrically insulated U-shaped connecting elements (400).

10. The brushed machine according to any one of the preceding claims, wherein each connecting element (40) comprises a connecting tube (42) extending between a first end (42A) fitted into the blade surrounding the first end of the channel and a second end (42B) fluidly connected to the heat removal device.

11. An electrical machine (1000), in particular for an aircraft, having a longitudinal axis and comprising a stator, a rotor (1020) placed inside the stator and rotatable about the longitudinal axis, and a brushed machine according to any one of the preceding claims, the axis of rotation of the brushed machine being co-linear with the longitudinal axis of the electrical machine.

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