FR3037199A1 - MOTOR VEHICLE STARTER PROVIDED WITH A THERMAL PROTECTIVE MEMBER - Google Patents

Abstract

The invention relates primarily to a motor vehicle engine starter comprising: - at least one blade (35), - a braid (93) physically connected to each of the at least one blade (35) to provide an electrical connection, - a conductor (91) for electrically connecting each of the brush braids (93) to a positive or negative polarity, characterized in that - a thermal protection member (94) is mounted between the at least one braid (93) and said conductor (91) for electrically connecting said conductor (91) to said braid (93), said thermal protection member (94) comprising: - a solder (104) by material supply, for electrically connecting said braid (93) to said conductor (91), and - an elastic member (105) resiliently biased between said braid (93) and said conductor (91) for electrically disconnecting said conductor (91) from said braid (93) by moving said braid (93) ) or said con driver (91) in the event of fusion of said solder (104) between said conductor (91) and said braid (93).

Description

The present invention relates to a motor vehicle starter provided with a thermal protection member. The invention finds a particularly advantageous, but not exclusive, application with the starters of systems for stopping and automatic restart of the engine, known as "stop and start" system in English. In a manner known per se, the starters comprise an overcurrent protection means in the form of one or more electric fuses and / or one or more circuit breakers. FIG. 1 thus shows an example of a starter motor 1 comprising a fuse 2 connected in series between a power supply terminal 3 of the electric machine 1 and windings 4 of the motor stator. The fuse is intended to melt to cut off the power supply to the motor when it is traversed by a maximum predetermined current. This avoids damaging the starter or its environment because of the heat produced by an overcurrent. Such overcurrent occurs especially in the case where the rotor of the motor is locked in rotation. When the machine is running at idle or low load (ie it runs between 0 and 25% of the rated load), the idle rotation speed of the rotor also causes the electric machine to heat up. may damage the starter over time. However, in this case, the current flowing through the fuse may be too weak to cause fusing of the fuse 2 and this even for a long time.

The document FR1450573 describes a thermal protection system 5 for cutting the power supply of the motor in the two aforementioned cases (in case of blockage and in low-load operation). More precisely, this system is configured so that, in the event of overheating, an overmoulded part on the platen of the brush holder deforms, so that the positive polarity brush cages subjected to the action of springs enter 3037199 2 in contact with each other. with the board connected to the negative polarity terminal. This creates a short circuit generating an opening of the starter fuse. The invention aims to improve the thermal protection of the starter in case of low level of charge of the vehicle battery may make it difficult to open the fuse, even in the event of a short circuit. For this purpose, the invention proposes a starter for a motor vehicle engine comprising: at least one broom, a braid physically connected to each of the at least one broom to provide an electrical connection, and a conductor for electrically connecting each of the brush braids has a positive or negative polarity, characterized in that a thermal protection member is mounted between the at least one braid and said conductor to electrically connect said conductor to said braid, said thermal protection member comprising: a solder by material supply, for electrically connecting said braid to said conductor, and an elastic member mounted in elastic stress for electrically disconnecting said conductor with respect to said braid by moving said braid or said conductor in case of fusion of said solder between said conductor and said braid. The invention thus makes it possible, thanks to the use of the thermal protection member positioned near the hottest zone of the starter. In fact, the heating of the starter is particularly due to the mechanical friction between the brushes and the collector. This heating occurs for example in overspeed phase when the starter gear driven by the engine is running faster than the shaft driven by the starter rotor.

Thus the invention makes it possible to ensure an electrical disconnection between the conductor and the braid in order to guarantee a power failure of the electric motor in the event of malfunction of the starter.

According to one embodiment, the elastic member may advantageously be mounted in elastic tension between said braid or a part integral with said braid and said conductor. This makes it possible to use the braid or a piece integral with the braid and the conductor to constrain the elastic member between two physical pieces. According to another embodiment, the elastic member is located against another part of the starter such as a broom plate and the braid or a part integral with the braid. According to one embodiment, the material-welding is carried out to weld the braid directly to the conductor and in that the starter further comprises a braid guide piece to prevent it from coming into contact with the driver when of the disconnection. According to one embodiment, said thermal protection member further comprises an intermediate piece, more rigid than said braid, situated between said conductor and said braid for electrically connecting them and in that said braid is welded to said intermediate piece, and in that said solder by material supply connected by welding said intermediate piece to said conductor, said elastic member being located between said intermediate piece and said conductor to move said intermediate piece 20 relative to said conductor to ensure electrical disconnection. The intermediate piece thus ensures disconnection of the brush to the driver even during vibration of the starter (especially when the engine of the vehicle has started) and to refrain from guiding means of the braid. Indeed, in the case where the solder of the braid on the conductor is made by adding material, the braid because of its flexibility can come into contact with the driver during the vibrations of the vehicle. According to one embodiment, said conductor is a bridge for connecting at least two brushes of the same polarity, and in that it comprises at least one protective member for each brush connected electrically to said bridge.

Thus, all the brushes of the same polarity are disconnected without making a short circuit to melt the fuse of the starter. This limits the heat generated while the temperature in the starter has already reached a temperature that could damage the machine.

In one embodiment, the material input of said solder has a melt characteristic of 200 to 250 degrees Celsius and is preferably 220 degrees Celsius. Such a range of value makes it possible at the same time to ensure that the starter is switched off before it can cause a fire and can furthermore enable the user to start the thermal engine in the event of very low temperature when the latter is at a very low temperature. asks a bigger couple to start. According to one embodiment, the material supply of said weld is tin. Such a weld allows both to ensure the mechanical function of the weld but also to soften sufficiently after 200 ° C so that the elastic member can disconnect the braid relative to the conductor. According to one embodiment, said elastic member is electrically insulating. This ensures electrical disconnection without additional parts. According to one embodiment, said starter further comprises an insulating piece between said elastic member and said conductor or said intermediate piece.

This makes it possible to produce the elastic member in a conductive material. According to one embodiment, said thermal protection member further comprises an insulating member comprising a first housing for receiving a portion of said conductor and a second housing for receiving a portion 25 of said intermediate piece, the two housings being separated from one of the other by an insulating wall. This makes it possible to ensure in case of vibration an insulation of the two conductive parts. According to one embodiment, said elastic member comes from a material with said insulating wall. This makes it easier to achieve the assembly by having to manufacture a single piece.

According to one embodiment, said insulating member has a bent shape. This prevents the intermediate piece can rotate to return to electrical contact during disconnection. According to one embodiment, said elastic member is located between said housing 5 and said weld. The more the elastic member is located near the weld plus the elastic member facilitates electrical disconnection during the fusion of the weld. According to one embodiment, said intermediate piece and said conductor have a flat shape. This facilitates the realization of welding on planar contact faces. In one embodiment, said conductor is connected to at least one electric coil output. According to one embodiment, a set of inductive electrical coils is connected in series between the output terminal of the contactor and said brushes.

According to one embodiment, the set of electric coils comprises two half-assemblies connected in parallel, each half-assembly comprising electric coils connected in series. In one embodiment, the number of electrical coils is at least four.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention. Figure 1, already described, shows a block diagram of an electric motor starter motor with a thermal protection system; Figure 2 is a longitudinal sectional view of a motor vehicle engine starter according to the present invention; FIG. 3 represents a perspective view of a brush holder according to the invention belonging to the starter of FIG. 2; FIG. 4 is a perspective representation of the protection member providing an electrical connection between brushes and a bridge electrically connected to a power supply terminal; Figure 5 is a representation of the circuit diagram for mounting the coils in the starter according to the present invention; In FIGS. 2 to 5, identical, similar or similar elements retain the same reference from one figure to another. With reference to FIG. 2, the starter 11 according to the invention comprises, in particular, a drive shaft 12, a launcher 13 mounted on the drive shaft 12, and an electric motor 15 composed of an inductor stator 16 and an armature rotor 17 integral with a shaft 18. The motor 15 comprises a carcass 21 mounted on a support 22 of the starter 11 intended to be fixed on a fixed part of the motor vehicle. An epicyclic gear type gear reducer 23 is preferably interposed between a rear end of the drive shaft 12 and the shaft 18 of the electric motor 15. The starter 11 also has an electromagnetic contactor 25 extending therefrom. parallel to the electric motor 15 being implanted radially above it. The contactor 25 has a metal tank 28 equipped with a set of excitation coils 29a, 29b. Terminals 31, 32 are shaped to each form a fixed contact inside the tank 28. One of the terminals 31 is intended to be connected to the positive terminal of the vehicle battery. The other terminal 32, said positive output terminal, is connected to the input of the stator inductor winding 16 and the brushes 35 of positive polarity, as is explained in more detail below. These brushes 35 rub on conductive blades 38 of a manifold 39 to feed the rotor winding. The brushes 35 belong to a brush holder 42 equipped with cages 43 for guiding and receiving the brushes 35. These brushes 35 are biased towards the conductive blades 38 by resilient means 44 of the spring type. A bearing 45 of the rear flange serves for rotatably mounting one end of the shaft 18 of the electric motor 15.

In known manner, during the excitation of the call coil 29a, a mobile core 48 is attracted by magnetic attraction towards a fixed core 49 of the contactor 25 to, firstly, act after retrofitting. a play on a rod 50 carrying a movable contact 51 to cause the closing of the contacts 31, 32 of the contactor 25 and supplying the electric motor 15, and secondly, actuating a control lever 52 acting on the launcher 13. The upper end of the lever 52 is mounted in known manner to articulation on a movable rod 55 elastically connected to the movable core 48 via a spring 56, said tooth against tooth spring, housed in the movable core 48.

The launcher 13 can thus pass from a rest position in which a drive pinion 60 is located away from the starting ring of the heat engine to an active position in which the drive pinion 60 cooperates with the ring gear. start of the engine. The drive shaft 12 then transmits a torque from the electric motor 15 to the drive sprocket 60 through a pinion body 61, via a freewheel device 62. Following the deactivation of the contactor 25, the launcher 13 returns from its active position to its rest position. When the launcher 13 is in an active position, the pinion body 61 is driven, via the freewheel device 62, by a driver 65. For this purpose, the pinion body 61 is mounted on the drive shaft. by means of two pads 68, 69 of annular shape. The pinion body 61 is rotatably mounted in a front bearing 70 of the support 22. This bearing 70 is constituted by way of example by a ball bearing or alternatively by a needle bearing, or a plain bearing. The freewheel device 62 is for example of the roller type, but could alternatively be replaced by a conical clutch device or a clutch provided with several friction disks, as described in the document FR2978500.

In known manner, the driver 65 is internally provided with helical splines in complementary engagement with external helical gears carried by the drive shaft 12. The launcher 13 is thus driven by a helical movement when it is moved by the lever 52 to come into the active position, through the pinion 60, in engagement with the starter ring of the engine. With the drive gear 60 being rotatably connected and axially slidable relative to the pinion body 61 via complementary shaped groove formations, a spring 71 biases the drive pinion 60 toward a stop axial 72 formed for example by a circlip. The spring 71 will be compressed so that the pinion 60 retreats in case of impact of the pinion 60 with the starter ring.

FIG. 3 is a detailed view of the X-axis brush holder 42 comprising a support plate 75 of substantially annular shape on which is fixed the set of stands 43 each serving as a housing for a brush 35. The support plate 75 and the cages 43 that it carries are attached to the flange forming the rear bearing 45 for the shaft 18 of the electric motor 15.

In addition, the central part of the plate 75 has an opening 78 through which the assembly that it forms with the cages 43 and the brushes 35 is mounted around the shaft 18 of the electric motor 15. Each blade 35 is mounted sliding inside a cage 43, which is open on the X-axis side to allow electrical contact of the brushes 35 with the blades 38 of the collector 39. One of the side walls has a notch to allow the passage of the arm of the corresponding spring 44. On the side of the face opening on the side of the collector 39, each cage 43 may comprise flaps 85 extending on either side of the blade 35 to prevent the dust generated by the friction of the brushes 35 with the blades 38 come altering the operation of the brush holder 42. Each cage 43 may be fixed to the plate 75 by means of lugs cooperating with the corresponding openings in the plate 75. Alternatively, the cages 43 are fixed to the plate 75 by means of 30 rivets . Moreover, a spiral spring 44 associated with each cage 43 radially biases the corresponding blade 35 towards the contact blades 38 of the collector 39. Each spring 44 is in this case mounted around a holding system 87 formed by a pin extending axially with respect to the axis X. The brushes 35 of positive polarity are electrically connected to the positive output terminal 32 of the contactor 25 via a conductor 91 formed by a bridge.

The bridge 91 preferably has a curved shape so as to extend along a circumference of the support plate 75. In a variant, the bridge 91 may have a rectilinear shape as shown in FIG. 4. In addition, the bridge 91 is connected to two electric coil outputs 92. Indeed, as can be seen in FIG. 5, a set of stator inductive electrical coils 92 is connected in series between the positive output terminal 32 of the contactor and the brushes 35. L coil assembly comprises two half-assemblies connected in parallel, each half-assembly comprising coils 92 connected in series. The number of coils 92 in the set is here equal to four, but this number may be adapted according to the application. Specifically, each braid 93 physically connected to a brush 35 of positive polarity is connected to the bridge 91 via a thermal protection member 94. As can be seen in Figure 4, each thermal protection member 94 comprises an insulating member 95, here of bent shape, located at one end of the bridge 91. The insulating member 95 comprises a first housing 96 for receiving an end portion of the bridge 91 and a second housing 97 for receiving an intermediate part 101 , said "leg", more rigid than the braid 93 and to which is welded said braid 93. The two housings 96, 97 are separated from one another by an insulating wall 98. The portions of the bridge 91 and the leg 101 protruding from the insulating member 95 are electrically connected to each other via a weld 104 by adding material. The material supply of the weld 104 has a melting characteristic of between 200 and 250 degrees Celsius and is preferably 220 degrees Celsius. Such a range of value makes it possible at the same time to ensure an electric break of the starter before this one can cause a fire and to allow the user to start the engine in case of very low temperature, when this last one asks a 3037199 10 more important torque to boot. The supply of material from the weld 104 is advantageously tin. The leg 101 and the bridge 91 have a flat shape in order to facilitate the realization of the weld 104 on planar contact faces.

In addition, an elastic member 105 is mounted elastically between the leg 101 and the bridge 91 at the time of producing the weld 104. The elastic member 105 thus electrically disconnects the bridge 91 relative to the braid 93. by separating the leg 101 from the bridge 91 in case of fusion of the weld 104 to ensure a power failure of the electric motor. In order to facilitate the construction of the assembly, the elastic member 105 is preferably made of material with the insulating wall 98 of the insulating member 95. Advantageously, the elastic member 105 is located between the housings 96, 97 and the weld 104. The more the elastic member 105 is located close to the weld 104, the elastic member 105 facilitates electrical disconnection during the melting of the weld 104. Furthermore, the brushes 35 of negative polarity intended for the return of the current are electrically connected to the ground of the machine by means of their respective braid 93 welded to the plate 76. The brushes 35 of positive polarity and their corresponding cage 43 are electrically isolated from the negative polarity for proper operation of the starter 11. This insulation can be obtained by producing a plastic layer overmolded on the plate 76. The following describes the activation of the thermal protection in the event of a malfunction. In the case where the charge level of the vehicle battery is low and overheating occurs, for example due to the starter motor running idle for a long time, the temperature rises in the starter. 11 while the current does not reach a threshold current for melting an electrical protection fuse of the machine. Then, when the temperature near the brushes reaches the melting temperature of the weld 104, the leg 101, which is no longer held by the weld 104, is separated from the bridge 91 due to the force exerted by the body elastic 105 which decompresses and is maintained at a distance due to the thickness of the insulating wall 98 extending between the leg 101 and the bridge 91. The molten tin can then flow by gravity inside of the brush holder. According to a preferred embodiment, the amount of tin is adapted to remain adhered to one or both of the welded faces without being in contact with the other faces, the two faces being then electrically disconnected. This has the effect of electrically disconnecting the output terminal 32 relative to the brushes 35 of positive polarity. The starter 11 then switches from the operating state to an off state of the starter 11 in which the motor 15 is no longer powered. The power failure thus occurs without having to make a short circuit as in the prior art that generates heat while the temperature in the starter 11 has already reached a temperature likely to deteriorate the machine.

Those skilled in the art will of course be able to modify the configuration of the brush holder 42 previously described without departing from the scope of the invention. Thus, in a variant, the thermal protection member 94 is devoid of insulating member 95. The disadvantage of such a configuration is that it is impossible to accurately predict the positioning of the leg 101 following the fusion of As a variant, it would also be possible to eliminate the use of the leg 101, the braid 93 then being directly welded to the bridge 91. The elastic member 105 is then mounted compressed directly between the braid 93 and the bridge 91. The disadvantage of such a configuration is that the braid 93, because of its flexibility, can come into contact with the bridge 91 during vehicle vibrations. In another embodiment, it is possible to position an insulating piece between the elastic member 105 and the bridge 91 or the intermediate piece 101. This will be the case for example when the elastic member 105 takes the form of a spring made of in an electrically conductive material and that at least one of the ends of the spring is covered by an insulating tip.

Alternatively, the plate 75 is electrically connected to the positive polarity while the bridge 91 is connected to the negative polarity. The coil spring 44 can also be replaced by a cylindrical spring bearing on the hood to push the corresponding blade 35 against the blades 38 of the manifold 39. In a variant, the brush holder 42 comprises more than four brushes 35, each blade 35 may for example be associated with another blade 35 positioned on the opposite side of the plate 75.

Claims (16)

REVENDICATIONS1. Starter (11) for an automotive engine comprising: - at least one broom (35), - a braid (93) physically connected to each of the at least one broom (35) to provide an electrical connection, - a conductor (91) for electrically connecting each of the brush braids (93) to a positive or negative polarity, characterized in that - a thermal protection member (94) is mounted between the at least one braid (93) and said conductor (91) to electrically connecting said conductor (91) to said braid (93), said thermal protection member (94) comprising: - a material supply weld (104) for electrically connecting said braid (93) to said conductor (91), and an elastically resilient member (105) resiliently engaged to electrically disconnect said conductor (91) from said braid (93) by moving said braid (93) or said conductor (91) upon fusion of said solder (104) between said driver (91) and lad this braid (93). 2. Starter according to claim 1, characterized in that said thermal protection member (94) further comprises an intermediate piece (101) more rigid than said braid (93) between said conductor (91) and said braid (93) for electrically connecting them and in that said braid (93) is welded to said intermediate piece (101), and in that said solder (104) by supplying material connected by welding said intermediate piece (101) to said conductor (91) ), said resilient member (105) being located between said intermediate piece (101) and said conductor (91) to move said intermediate piece (101) away from said conductor (91) to provide electrical disconnection. 3. Starter according to claim 1 or 2, characterized in that said conductor is a bridge (91) for connecting at least two brushes (35) of the same polarity, and in that it comprises at least one protective member 3037199 14 for each broom (35) electrically connected to said bridge (91). A starter according to any one of claims 1 to 3, characterized in that the material supply of said solder (104) has a melting characteristic of between 200 and 250 degrees Celsius and is preferably 220 degrees Celsius. 5. Starter according to any one of claims 1 to 4, characterized in that the material supply of said weld (104) is tin. 6. Starter according to any one of claims 1 to 5, characterized in that said elastic member (105) is electrically insulating. 7. Starter according to any one of claims 2 to 6, characterized in that it further comprises an insulating piece between said elastic member (105) and said conductor (91) or said intermediate piece (101). 15 8. Starter according to any one of claims 2 to 7, characterized in that said thermal protection member (94) further comprises an insulating member (95) having a first housing (96) for receiving a portion of said conductor (91). and a second housing (97) for receiving a portion of said intermediate member (101), the two housings (96, 97) being separated from each other by an insulating wall (98). 9. Starter according to claim 8, characterized in that said elastic member (105) is made of material with said insulating wall (98). 10. Starter according to claim 8 or 9, characterized in that said insulating member (95) has a bent shape. 25 11. Starter according to any one of claims 8 to 10, characterized in that said elastic member (105) is located between said housing (96, 97) and said weld (104). 12. Starter according to claim 2, characterized in that said intermediate piece (101) and said conductor (91) have a flat shape. 3037199 15 13. Starter according to any one of claims 1 to 12, characterized in that said conductor (91) is connected to at least one electric coil outlet (92). 14. Starter according to any one of claims 1 to 13, characterized in that a set of inductive electrical coils (92) is connected in series between the output terminal of the contactor and said brushes (35). A starter according to claim 14, characterized in that the set of electric coils (92) comprises two half-assemblies connected in parallel, each half-assembly comprising electrical coils (92) connected in series. 16. Starter according to claim 14 or 15, characterized in that the number of electrical coils (92) is at least four.