Electric motor for a motor vehicle wiper system

Abstract

The invention relates to a DC electric motor (1) for a motor vehicle wiper system, the motor comprising at least three brushes (14) in sliding radial contact against a rotor (11) of the electric motor (1), including: - a first brush (14A) associated with an electrical ground of the electric motor (1) and enabling control of a first speed of rotation of the electric motor (1); - a second brush (14C) associated with a first positive pole of the electric motor (1) and enabling control of a second speed of rotation of the electric motor (1) higher than the first speed of rotation; - a third brush (14B) associated with a positive pole of the electric motor (1); characterized in that a bearing surface (142) of the first brush (14A) against the rotor (11) is larger than that of the (142) second brush (14C) or the third brush (14B) against the rotor (11).

Description

electric motor for automotive vehicle wiper system

[0001] The technical context of the present invention is that of wiper systems for motor vehicles, and in particular the drive devices for such wiper systems. More specifically, the invention relates to a DC electric motor for such a motor vehicle wiper system.

[0002] In the prior art, the use of direct current (DC) electric motors to drive wiper systems used to clean the glass surfaces of motor vehicles, such as windshields or rear windows, is known. Such DC electric motors consist of a rotor and a stator that bring electrical windings and permanent magnets into contact through their relative rotation about a rotor axis. Additionally, these DC electric motors also include several brushes distributed around the periphery of the rotor to collect the electric current generated between the rotor and a stator. Each brush slides radially against a rotor of the electric motor, relative to the axis of rotation.Finally, the electric motor also includes electrical switches that allow the flow of an electric current in each electric winding to be controlled according to the rotation of the rotor and the position of said electric windings relative to the brushes.

[0003] In the field of wiper systems, known DC electric motors exhibit a brush alignment that results in the number of interconnected windings between the brushes varying during rotor rotation. This variation in the number of interconnected windings depends, in particular, on the angular alignment between a commutator and the brush located opposite it: if, for example, for a given angular configuration, the brush extends between two adjacent windings, such that one lateral edge of the brush is located opposite the first winding while an opposite lateral edge of said brush is located opposite the second winding, then the first and second windings are interconnected and contribute to the production of current collected by the brush.On the other hand, if for a second given angular configuration, the brush is on either side of a single winding, so that the lateral edge of the brush is located on one side of said winding while the opposite lateral edge of said brush is located on a second side of said winding, then the winding is short-circuited by the brush and said winding does not participate in the production of current collected by the brush.

[0004] In known electric motors, the size of the brushes is such that it leads to instantaneous variations in the torque supplied by the electric motor and / or variations in the rotor's rotational speed. These situations are obviously undesirable.

[0005] The present invention aims to provide a new DC electric motor for a wiping system in order to address at least largely the previous problems and to lead to other advantages.

[0006] Another aim of the invention is to improve the performance of such an electric motor.

[0007] Another objective of the invention is to reduce torque variations during the operation of such an electric motor.

[0008] Another aim of the invention is to improve the reliability and robustness of such an electric motor.

[0009] According to a first aspect of the invention, at least one of the aforementioned objectives is achieved with a DC electric motor for a motor vehicle wiper system, the electric motor comprising at least three brushes in radial contact sliding against a rotor of the electric motor, so as to collect an electric current generated between the rotor and a stator of said electric motor, the at least three brushes comprising:

[0010] - a first brush associated with an electrical mass of the electric motor;

[0011] - a second brush associated with a first positive pole of the electric motor in order to control its rotation according to a first rotation speed;

[0012] - a third brush associated with a second positive pole of the electric motor in order to control its rotation according to a second rotation speed different from the first rotation speed, preferably higher than the first rotation speed.

[0013] In the electric motor according to the first aspect of the invention, a bearing surface of the first brush against the rotor is greater than a bearing surface of the second brush against the rotor.

[0014] Possibly, the bearing surface of the first brush against the rotor is greater than a bearing surface of the third brush against the rotor.

[0015] In the context of the present invention, the axis of rotation corresponds to the direction of elongation of a drive shaft of the electric motor, that is to say, the axis of rotation of the rotor with respect to the stator. Consequently, the adjective "radial" is understood as a direction taken perpendicular to the axis of rotation.

[0016] In the context of the present invention, each brush takes the form of a sliding mechanical contact on the rotor. Each brush is thus arranged radially around the rotor with respect to the rotor's axis of rotation, and at predetermined angular positions on the stator. Each brush, through its frictional contact with the rotor, transmits an electric current between the rotor of the electric motor and an external electrical circuit to which the electric motor conforming to the first aspect of the invention is connected. Generally, in the context of the present invention, each brush comprises one or more graphite-based blocks.Without the following list being exhaustive, brushes may for example be (i) of the type of carbo-graphitic brushes formed from an agglomerated mixture of carbon powder and graphite powder, (ii) of the type of soft graphitic brushes or (iii) of the type of resin-graphite brushes comprising a mixture of graphite and a thermosetting resin, or (iv) of the type of metall-graphitic brushes formed from a mixture of graphite powders and metal, such as copper or silver.

[0017] In the context of the present invention, the rotor preferably comprises a plurality of electrical windings located opposite the stator, the electrical windings being arranged and organized circumferentially around the axis of rotation. Each electrical winding is associated with a commutator bar which allows the corresponding electrical winding to be electrically coupled to the electrical circuit during the operation of the electric motor, or conversely, to be electrically decoupled, depending on the angular position of the rotor relative to the stator, and more particularly on the angular position of each electrical winding and its commutator bar relative to one of the brushes located opposite it.

[0018] In the context of the invention, the contact surface of a brush is the effective surface of said brush that rubs radially against the rotor during its rotation. The effective surface thus corresponds to the area where the electric current induced in the windings is collected during the rotor's rotation. In other words, the contact surface is the surface that is located opposite, in radial contact with the rotor, and in friction with said rotor during its rotation around the axis of rotation.

[0019] It is understood that, according to the invention, an area of ​​the bearing surface of the first brush is greater than an area of ​​the bearing surface of the second brush and / or the area of ​​the bearing surface of the third brush.

[0020] The present invention is limited exclusively to wiping systems, and in particular those used in the automotive field, because the technical problems mentioned above, which are solved by the electric motor according to the first aspect of the invention, induce malfunctions in wiping systems as well as reductions in the quality of the wiping performed.

[0021] Thus, the electric motor conforming to the first aspect of the invention features a new geometric arrangement of the brushes, which in turn leads to improved operation and reduces electrical faults arising from the electrical commutation between each winding and the adjacent brush during rotor rotation. Indeed, the first brush is always in use during the operation of the electric motor conforming to the first aspect of the invention; that is, an electric current flows through this first brush regardless of the rotor's angular position relative to the stator. This continuous use leads to premature wear compared to the use and wear of the second and third brushes.Thus, the relative increase in the contact area of ​​the first brush, compared to that of the second and / or third brush, in turn improves the reliability of the electric motor conforming to the first aspect of the invention, reduces its operating noise, and enhances its overall quality. The invention therefore presents a clever and novel geometric alternative to phase-shift control of the commutator bars during rotor rotation, which can be more complex to implement and less reliable.

[0022] The electric motor conforming to the first aspect of the invention advantageously comprises at least one of the improvements below, the technical characteristics forming these improvements being able to be taken alone or in combination:

[0023] - As mentioned previously, the contact surface is the surface of a given brush located opposite and in radial contact with the rotor of the electric motor. Preferably, the contact surface of the first brush against the rotor is simultaneously greater than the contact surface of the second and third brushes against the rotor. This advantageous configuration allows for better adaptation, i.e., synchronization, of the wear of the second and third brushes relative to that of the first brush;

[0024] - the bearing surface of the second brush against the rotor is equal to the bearing surface of the third brush against the rotor. More generally, the second and third brushes are advantageously identical, by virtue of their shape and / or dimensions, and in particular the dimensions of their bearing surface;

[0025] - According to a first embodiment, the bearing surfaces of the second and third brushes are defined with respect to the bearing surface of the first brush only. Thus, generally, the bearing surface of the second or third brush is at least equal to 40% of the bearing surface of the first brush. Preferably, the bearing surface of the second and third brushes is at least equal to 40% of the bearing surface of the first brush. More particularly, the bearing surface of the second or third brush is between 40% and 60% of the bearing surface of the first brush. Preferably, the bearing surface of the second and third brushes is between 40% and 60% of the bearing surface of the first brush. According to a preferred embodiment of the invention, the bearing surface of the second or third brush is equal to half the bearing surface of the first brush.Preferably, the bearing surface of the second broom and the bearing surface of the third broom are equal to half the bearing surface of the first broom;

[0026] - According to a second embodiment, complementary or alternative to the first embodiment, the bearing surfaces of the second and third brushes are defined relative to the bearing surface of the commutator bars present on the rotor and associated with the electrical windings. In the context of the present invention, the commutator bars are electrical devices that control the flow of an electric current in each associated electrical winding, as a function of the rotor's rotation and the angular position of said electrical windings with respect to the first and / or second and / or third brush.Thus, in this embodiment, the bearing surface of the second and / or third brush is at most equal to half the bearing surface of a commutator bar of the electric motor, and the bearing surface of the first brush is greater than half the bearing surface of the commutator bar. In particular, the bearing surface of the first brush is between 50% and 100% of the bearing surface of the commutator bar.

[0027] - According to a third embodiment, complementary or alternative to the first and / or second embodiment, the bearing surfaces of the second and third brushes are defined with respect to an angular opening of said bearing surfaces. In the context of the present invention, the angular opening corresponds to the angle delimited by two lateral edges of a given brush, said lateral edges defining the bearing surface of said brush against the rotor of the electric motor, measured around the axis of rotation of said electric motor. Thus, in this embodiment, the bearing surface of the second and / or third brush is delimited by two lateral edges, the angular opening between the two lateral edges of the second brush and / or the angular opening between the two lateral edges of the third brush being less than 15°.Advantageously, the angular opening between the two lateral edges of the second and / or third brush is between 12° and 8°. Preferably, the angular opening between the two lateral edges of the second and / or third brush is equal to 10.5°.

[0028] - More generally, the angular opening between the two lateral edges of the second and / or third brush is defined relative to that of the first brush. Thus, in this embodiment, the angular opening between the two lateral edges of the second and / or third brush is reduced by at least 2° compared to the angular opening between the two lateral edges of the first brush. Preferably, the angular opening between the two lateral edges of the second and / or third brush is reduced by at least 4° compared to the angular opening between the two lateral edges of the first brush;

[0029] - relative to an axis of rotation of the electric motor, the angular position of the second and / or third brush exhibits a non-zero angular offset with respect to a neutral line of the electric motor. In other words, the invention provides that the angular position of the second brush exhibits a non-zero angular offset with respect to a neutral line along which said second brush is generally placed, relative to the first brush, and / or the angular position of the third brush exhibits a non-zero angular offset with respect to a neutral line along which said third brush is generally placed, relative to the first brush. Put another way, the invention provides that the angular position of the second brush is not located at 180° with respect to the angular position of the first brush for a 2-pole magnetic electric motor.Conversely, the angular position of the second brush is located at a value 180° different from the angular position of the first brush, according to a non-zero angular offset, for such a 2-pole magnetic electric motor. This advantageous configuration allows for improved operation and reduces electrical faults arising from the electrical commutation between each winding and the brush located opposite it during rotor rotation. This advantageous configuration, in turn, improves the reliability of the electric motor conforming to the first aspect of the invention, reduces its operating noise, and improves its overall quality. Typically, the angular offset is less than 10°.

[0030] - preferably, the angular offset is between 30% and 70% of an angular opening between the two lateral edges of the bearing surface of the third brush against the rotor;

[0031] The bearing surfaces of the second and third brushes are respectively delimited by lateral edges, with the angular distance between the proximal lateral edges of the second and third brushes being greater than the angular opening of a commutator bar of the electric motor. In this embodiment, the invention provides that the angular distance between the second and third brushes, measured from their nearest lateral edges, is greater than the angular opening of one of the commutator bars and / or one of the electrical windings located opposite them. This advantageous configuration allows for the desynchronization of the angular alignment between the commutator bars and / or electrical windings and the brushes located opposite them.This clever geometric configuration thus allows the number of interconnected electrical windings to remain constant for any angular configuration of the rotor relative to the brushes located opposite it;

[0032] - The contact area of ​​the first brush against the rotor is greater than the contact area of ​​the second brush against the rotor and / or the contact area of ​​the third brush against the rotor. This advantageous configuration thus offers a new geometric arrangement of the brushes, which in turn leads to improved operation and reduces electrical faults arising from the electrical commutation between each winding and the brush located opposite it during rotor rotation. Indeed, the first brush is always in use during the operation of the electric motor according to the first aspect of the invention; that is, an electric current flows through said first brush for any angular position of the rotor relative to the stator. This continuous use leads to premature wear compared to the use and wear of the second and third brushes.Thus, the relative increase in the contact area of ​​the first brush, compared to that of the second and / or third brush, in turn improves the reliability of the electric motor conforming to the first aspect of the invention, reduces its operating noise, and enhances its overall quality. The invention therefore presents a clever and novel geometric alternative to phase-shift control of the commutator bars during rotor rotation, which can be more complex to implement and less reliable.

[0033] According to a second aspect of the invention, a wiping system for motor vehicles is proposed, the wiping system comprising:

[0034] - at least one windshield wiper blade with a scraper blade resting against a glass panel of the motor vehicle;

[0035] - at least one drive arm, one free end of which is connected to at least one wiper blade via a connector;

[0036] - a drive device coupled to one coupling end of each at least one drive arm, the drive device being configured to shape a movement of the wiper blade on the glass surface;

[0037] - at least one electric motor conforming to the first aspect of the invention or according to any of its improvements, a drive shaft of the electric motor being coupled in rotation to the drive device.

[0038] In the context of the present invention, the windshield wiper extends along its own axis of elongation and its scraping blade, made of a deformable material such as rubber or an elastomer, is held in contact with the glass wall from which dirt or water is to be removed.

[0039] In the context of the present invention, the drive arm is a mechanical device that supports the wiper blade and presses it against the glass surface. The drive arm has a straight or substantially straight extension arm, to which the wiper blade is mechanically coupled at a free end by means of an adapter.

[0040] In the context of the present invention, the drive device transforms the rotation of the electric motor's drive shaft into a more complex movement of the drive arm and wiper blade on the glass surface. Specifically, the drive device produces a rotational and / or translational movement of the wiper blade on the glass surface, in order to clean the entire area within the driver's field of vision.

[0041] In the context of the present invention, the motor shaft of the electric motor is coupled in rotation with the rotor on one side, and with the drive device on a second side.

[0042] According to a third aspect of the invention, a motor vehicle is proposed comprising a wiping system conforming to the second aspect of the invention.

[0043] Various embodiments of the invention are envisaged, incorporating, according to all their possible combinations, the different optional features described herein.

[0044] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:

[0045] illustrates a first example of the realization of an electric motor conforming to the first invention and comprising 2 magnetic poles;

[0046] illustrates a second example of the realization of an electric motor conforming to the first invention and comprising 4 magnetic poles;

[0047] illustrates a third example of the realization of an electric motor conforming to the first invention and comprising 2 magnetic poles;

[0048] illustrates a fourth example of the realization of an electric motor conforming to the first invention and comprising 2 magnetic poles.

[0049] Of course, the features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may include only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from prior art.

[0050] In particular, all the variants and embodiments described can be combined with each other if there are no technical obstacles to this combination.

[0051] In the figures, elements common to several figures retain the same reference.

[0052] With reference to Figures 1 to 4, the invention addresses a DC electric motor 1 for a vehicle wiper system. In other words, such an electric motor 1 is configured to drive a wiper blade across a glazed surface of a motor vehicle, such as, for example, a windshield or a rear window. More specifically, the electric motor 1 according to the invention generates motor torque on a drive shaft that is rotationally coupled to a drive mechanism connected to the wiper blade via a drive arm. Consequently, the rotation of the drive shaft is converted into a sweeping motion of the wiper blade—and in particular its squeegee blade—across the glazed surface.

[0053] As mentioned previously, the present invention is limited exclusively to the field of wiping systems, and in particular those used in the automotive sector. The invention is not limited to any particular wiper blade technology, drive arm, or drive device, but it is certainly limited to the sole purpose of generating movement for such wiping systems.

[0054] In general, the electric motor 1 according to the invention comprises at least three brushes 14 in radial sliding contact against a rotor 11 of the electric motor 1, so as to collect an electric current generated between the rotor 11 and a stator of said electric motor 1. The rotor 11 comprises a plurality of electrical windings 12 which are located opposite the stator, the electrical windings 12 being arranged circumferentially around the axis of rotation O1 of the rotor 11. In other words, the electrical windings 12 are all distributed around the periphery of the rotor 11, opposite the stator, and they are angularly regularly distributed with respect to each other and with respect to the axis of rotation O1.

[0055] Each electrical winding 12 comprises a winding of electrically conductive wire with any number of turns. Each electrical winding 12 is associated with a commutator bar that allows the winding 12 corresponding to the electrical circuit to be electrically coupled, or conversely, to be electrically decoupled, depending on the angular position of the rotor 11 relative to the stator, and more particularly on the angular position of each electrical winding 12 and its commutator bar 13 relative to one of the brushes 14 located opposite it. Thus, the rotor 11 of the electric motor 1 according to the invention comprises a plurality of commutator bars 13 located opposite the stator, the commutator bars 13 being arranged circumferentially around the axis of rotation O1 of the rotor 11.In other words, the commutator bars 13 are all distributed around the periphery of the rotor 11, opposite the stator, and they are regularly spaced angularly with respect to each other and relative to the axis of rotation O1.

[0056] In the embodiments illustrated in the FIGURES, the electric motor 1 comprises:

[0057] - at least one first 14A brush associated with an electrical ground of the electric motor 1;

[0058] - at least one second brush 14C associated with a first positive pole of the electric motor 1 in order to control its rotation according to a first rotation speed;

[0059] - at least one third brush 14B associated with a second positive pole of the electric motor 1 in order to control its rotation according to a second rotation speed different from the first rotation speed, preferably higher than the first rotation speed.

[0060] Each brush is thus arranged radially around the rotor 11 with respect to the rotor 11's axis of rotation O1, and at predetermined angular positions on the stator. The predetermined angular positions of the brushes 14 depend in particular on the number of magnetic poles considered, although at least one first brush 14A is, in all cases, always oriented along a vertical axis in the schematic figures illustrated here. On the other hand, the angular positions of at least one second brush 14C and at least one third brush 14B depend on the type of electric motor 1 considered:

[0061] – in the case of an electric motor 1 having 2 magnetic poles, at least one second brush 14C is located opposite the angular position of the first brush 14A, excluding the diametrically opposite angular position (i.e. at 180° or substantially equal to 180°), i.e. at an angular position between 160° and 200° relative to the axis of rotation O1; and the angular position of at least one third brush 14B is located in a direction secant with respect to the position of the second brush 14C, i.e. at an angular position between 30° and 70° with respect to said second brush 14C, i.e. at an angular position between 170° and 90° with respect to the first brush 14A. In general, in known 2-pole magnetic electric motors, the brushes 14 are aligned along a neutral line LN represented by dotted lines in the FIGURES;

[0062] – in the case of an electric motor 1 having 4 magnetic poles, at least one second brush 14C is located substantially orthogonally to the position of the first brush 14A, excluding the angular position at 90° with respect to the first brush, i.e. at an angular position between 80° and 120° relative to the axis of rotation O1; and the angular position of at least one third brush 14B is located in a direction secant with respect to the position of the second brush 14C, i.e. at an angular position between 30° and 90° with respect to said second brush 14C, i.e. at an angular position between 90° and 10° with respect to the first brush 14A. In general, in known 4-pole magnetic electric motors, the brushes 14 are aligned along a neutral line LN represented by dotted lines in the FIGURES.

[0063] Each brush takes the form of a sliding mechanical contact on the rotor 11 so that, through friction with the rotor 11 as it rotates around the axis of rotation O1, it transmits an electric current between the rotor 11 and an external electrical circuit to which the electric motor 1 is connected. Generally, each brush has a body 141 that extends radially from the rotor 11 and forms a "bearing head" against the rotor 11. The body 141 of each brush is thus in radial contact with the rotor 11, forming a bearing surface 142 against said rotor 11. The bearing surface 142 of each brush therefore has a surface area complementary to that of the rotor 11.

[0064] According to the invention, the dimensions of the bearing surface 142 of the brushes 14 are adjusted to resolve the technical problems mentioned above. In particular, as shown in FIGURES 1 and 2, the bearing surface 142 of each at least one first brush 14A against the rotor 11 is greater than the bearing surface 142 of each at least one second brush 14C against the rotor 11 and / or the bearing surface 142 of each at least one third brush 14B against the rotor 11. The invention further provides that the area of ​​the bearing surface 142 of each at least one first brush 14A against the rotor 11 is greater than the area of ​​the bearing surface 142 of each at least one second brush 14C against the rotor 11 and / or the bearing surface 142 of each at least one third brush 14B against the rotor 11.

[0065] Advantageously, each at least one second brush 14C is identical to each at least one third brush 14B, in their shapes and / or in their dimensions, in particular with respect to their bearing surface 142. In particular, regardless of the shape and dimensions of each brush beyond their bearing surface 142, the invention here provides for constraining the dimensions and contact areas of the bearing surfaces 142 of each at least one second brush 14C and of each at least one third brush 14B with respect to each at least one first brush 14A.

[0066] According to a first embodiment illustrated in FIGURES 1 and 2, the bearing surface 142 of at least one second brush 14C and at least one third brush 14B are defined in relation to the bearing surface 142 of at least one first brush 14A. By way of non-limiting examples, in general, the bearing surface 142 of the second brush 14C and / or the third brush 14B is at least equal to 40% of the bearing surface 142 of the first brush 14A, preferably between 40% and 60% of the bearing surface 142 of the first brush 14A.

[0067] According to a second embodiment shown in Figures 1 and 2, the bearing surface 142 of at least one second brush 14C and at least one third brush 14B are defined relative to the bearing surface 142 of the commutator bars 13 of the rotor 11. By way of non-limiting example, in general, the bearing surface 142 of at least one second brush 14C and / or the bearing surface 142 of at least one third brush 14B is at most equal to half the bearing surface 142 of one of the commutator bars 13 of the electric motor 1, while the bearing surface 142 of at least one first brush 14A is greater than half the bearing surface 142 of the commutator bars 13. In particular, the area of ​​the bearing surface 142 of at least one first brush 14A is between 50% and 100% of the area of ​​the bearing surface 142 of the switching bars 13 located opposite.In the context of the invention, the bearing surface 142 of the switching bars 13 corresponds to the peripheral surface of said switching bars 13 located radially outside with respect to the axis of rotation O1. In other words, the bearing surface 142 of the switching bars 13 corresponds to the surface located directly opposite the brushes 14.

[0068] According to a third embodiment visible in FIGURES 1 and 2, the bearing surface 142 of at least one second brush 14C and of at least one third brush 14B are defined with respect to an angular opening of said bearing surfaces 142, determined by a predetermined value.

[0069] The angular opening of the brushes 14 is defined by the angle measured around the axis of rotation O1 between two lateral edges 143 of said brushes 14 and delimiting the bearing surface 142 of said brushes 14 against the rotor 11.

[0070] Thus, by way of non-limiting examples, in general, the angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one second brush 14C and / or the angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one third brush 14B is less than 15°, preferably between 12° and 8°, preferably also equal to 10.5°.

[0071] According to a fourth embodiment visible in FIGURES 1 and 2, the bearing surface 142 of at least one second brush 14C and of at least one third brush 14B are defined with respect to the angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one first brush 14A. Thus, by way of non-limiting examples, in general, the angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one second brush 14C and / or the angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one third brush 14B is less than at least 2° compared to the angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one first brush 14A, preferably by at least 4°.

[0072] Figures 3 and 4 illustrate two embodiments of the electric motor 1 according to the invention, in which the angular positions of at least one second brush 14C or at least one third brush 14B are modified, relative to at least one first brush 14A and the corresponding neutral line LN. Figures 3 and 4 thus illustrate respectively the electric motors 1 shown in Figures 1 and 2, but combining the technical characteristics of Figures 1 and 2 with the angular offset DA mentioned herein.

[0073] In particular, as seen in FIGURES 3 and 4, the angular position of at least one second brush 14C or the angular position of at least one third brush 14B has a non-zero angular offset DA with respect to a neutral line LN of the electric motor 1 and along which said at least one second brush 14C or said at least one third brush 14B are respectively placed, relative to at least one first brush 14A, in the electric motors 1 known from the prior art.

[0074] In other words, the electric motor 1 according to the invention exhibits such an angular offset DA for the angular position of at least one second brush 14C or at least one third brush 14B, relative to the neutral line LN, compared with the angular positions generally implemented in known electric motors.

[0075] As seen in FIGURES 3 and 4, the angular offset DA is counted positively in the direction of rotation of the rotor 11 of the electric motor 1. In other words, the angular offset DA introduced is such that at least one second brush 14C or at least one third brush 14B is now in phase advance with respect to the neutral line LN along which it was aligned in previously known electric motors.

[0076] According to a first embodiment shown in Figures 3 and 4, the angular offset DA is defined by a predetermined numerical value. By way of non-limiting examples, the angular offset DA of the second brush 14C with respect to the neutral line LN is less than 10°, preferably less than 5°, and preferably between 1° and 5°. In particular, in the case of an electric motor 1 with two magnetic poles, as illustrated in Figure 1, it is advantageous for the angular offset DA to be equal to 5°. Conversely, in the case of an electric motor 1 with four magnetic poles, as illustrated in Figure 2, it is preferable for the angular offset DA to be equal to 2.5°.

[0077] According to a second embodiment visible in FIGURES 3 and 4, the angular offset DA is defined with respect to an angular opening delimited by the two lateral edges 143 of the bearing surface 142 of at least one second brush 14C or at least one third brush 14B.

[0078] The angular opening delimited by the two lateral edges 143 of the brushes 14 is defined by the angle measured around the axis of rotation O1 between two lateral edges 143 of said brushes 14 and delimiting the bearing surface 142 of said brushes 14 against the rotor 11.

[0079] Thus, by way of non-limiting examples, the angular offset DA of at least one second brush 14C or at least one third brush 14B with respect to the corresponding neutral line LN is advantageously between 30% and 70% of the angular opening between the two lateral edges of the bearing surface 142 of the second brush 14C or the third brush 14B against the rotor 11. Preferably, the angular offset DA is equal to 50% of the angular opening between the two lateral edges of the bearing surface 142 of the second brush 14C or the third brush 14B against the rotor 11.

[0080] According to a third embodiment shown in Figures 3 and 4, the angular offset DA is defined relative to the angular opening of the commutator bars 13 of the rotor 11. Generally, the angular distance between at least one second brush 14C and at least one third brush 14B, measured from their nearest lateral edges 143, is greater than the angular opening of one of the commutator bars 13 and / or one of the electrical windings 12 located opposite it. In particular, by way of non-limiting example, the angular distance between the proximal lateral edges 143 of at least one second brush 14C and at least one directly adjacent third brush 14B is greater than or equal to 18°.

[0081] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the various features, forms, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. Specifically, all the variants and embodiments described above are combinable.

Claims

DC electric motor (1) for a motor vehicle wiper system, the electric motor (1) comprising at least three brushes (14) in radial support sliding against a rotor (11) of the electric motor (1), so as to collect an electric current generated between the rotor (11) and a stator of said electric motor (1), the at least three brushes (14) comprising: - a first brush (14A) associated with an electrical ground of the electric motor (1); - a second brush (14C) associated with a first positive pole of the electric motor (1) in order to control its rotation according to a first rotational speed; - a third brush (14B) associated with a second positive pole of the electric motor (1) in order to control its rotation according to a second rotational speed different from the first rotational speed, preferably greater than the first rotational speed;characterized in that a bearing surface (142) of the first brush (14A) against the rotor (11) is greater than a bearing surface (142) of the second brush (14C) against the rotor (11).; Electric motor (1) according to the preceding claim, in which the bearing surface (142) of the first brush (14A) against the rotor (11) is simultaneously greater than the bearing surface (142) of the second brush (14C) and the third brush (14B) against the rotor (11). Electric motor (1) according to any one of claims 1 or 2, wherein the bearing surface (142) of the second brush (14C) or the third brush (14B) is at least equal to 40% of the bearing surface (142) of the first brush (14A). Electric motor (1) according to the preceding claim, wherein the bearing surface (142) of the second brush (14C) or the third brush (14B) is equal to half of the bearing surface (142) of the first brush (14A). Electric motor (1) according to any one of claims 1 or 2, wherein the bearing surface (142) of the second brush (14C) and / or the third brush (14B) is at most equal to half of a bearing surface (142) of a commutator bar (13) of the electric motor (1), and the bearing surface (142) of the first brush (14A) is greater than half of the bearing surface (142) of the commutator bar (13). Electric motor (1) according to any one of claims 1 or 2, wherein the bearing surface (142) of the second brush (14C) and / or the third brush (14B) is delimited by two lateral edges (143), an angular opening between the two lateral edges (143) of the second brush (14C) and / or the angular opening between the two lateral edges (143) of the third brush (14B) being less than 15°. Electric motor (1) according to the preceding claim, wherein the angular opening between the two lateral edges (143) of the second brush (14C) and / or the third brush (14B) is reduced by at least 2° compared to the angular opening between two lateral edges (143) of the first brush (14A). Electric motor (1) according to any one of the preceding claims, wherein, relative to an axis of rotation (O1) of the electric motor (1), an angular position of the second brush (14C) and / or the third brush (14B) has a non-zero angular offset (DA) with respect to a neutral line (LN). Electric motor (1) according to the preceding claim, in which the angular offset (DA) is less than 10° Electric motor (1) according to claim 8 taken in combination with claim 6, wherein the angular offset (DA) is between 30% and 70% of an angular opening between the two lateral edges (143) of the bearing surface (142) of the third brush (14B) against the rotor (11). Electric motor (1) according to claim 8, wherein the bearing surface (142) of the second brush (14C) and the bearing surface (142) of the third brush (14B) are respectively delimited by lateral edges (143), an angular distance between the lateral edges (143) of the second brush (14C) and the lateral edges (143) of the third brush (14B) closest to those of the second brush (14C) being greater than the angular opening of a commutation bar of the electric motor (1). Electric motor (1) according to claim 8, wherein the bearing surface (142) of the first brush (14A) against the rotor (11) is greater than the bearing surface (142) of the second brush (14C) against the rotor (11) and / or the bearing surface (142) of the third brush (14B) against the rotor (11). A motor vehicle wiper system, the wiper system comprising: - at least one wiper blade having a scraper blade bearing against a glazed wall of the motor vehicle; - at least one drive arm, one free end of which is connected to one of the at least one wiper blades via a connector; - a drive device coupled to one coupling end of each at least one drive arm, the drive device being configured to shape a movement of the wiper blade on the glazed wall; - at least one electric motor (1) according to any one of the preceding claims, a drive shaft of the electric motor (1) being rotationally coupled to the drive device. Motor vehicle comprising a wiping system according to the preceding claim.

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