FR2838884A1 - Combined starter motor and alternator includes sensor and magnetic element attached to fan to detect angular position of rotor - Google Patents

Abstract

The combined motor and alternator includes a rotor held between front and rear bearing supports (14). A magnetic device for following the shaft rotation comprises a sensor (52) and a magnetic target (50) carried on a part of the fan (44). The polyphase electric motor and alternator for a motor vehicle comprises a shaft carrying a rotor with magnetic poles surrounded by a stator comprising polyphase windings within a hollow casing. The rotor is held between front and rear bearing supports (14) with bearings (12) in contact with the shaft. A magnetic device for following the shaft rotation comprises a sensor (52) associated with a target (50). The target is fixed on a target carrier (60) on a part of the fan (44). This is fixed to the rotor so that it is positioned axially between the rotor and one of the bearings. The target carrier may have an annular shape, whilst the target itself may be crenellated. The target may be made from ferrite or rare earth material.

Description

i Polyphase rotating electric machine The present invention relates to

  a polyphase rotary electrical machine able to be used in a motor vehicle with internal combustion engine, on the one hand, as an electric generator to perform an alternator function and, on the other hand, as an electric motor to perform in particular a function of combustion engine start

internal of the vehicle.

  Such a machine, of the reversible type, makes it possible to transform mechanical energy into electrical energy and vice

  versa and has a polyphase stator surrounding a rotor.

  This rotating electric machine is called

usually <<Alterno-starter>>.

  The polyphase nature requires a monitoring of the angular position of the rotor using tracking means for the control in electric motor mode in order to inject at the right time electric current into the phase winding concerned of the stator winding as described for example in the document FR B-2 745 444 and EP-AO 260 176. These wind monitoring means of the magnetic type. For this follow-up we can use an instrumental ball bearing. Such a solution is expensive and can be prohibitive considering the size of the machine.

rotating electric.

  However, it is advantageous because it allows it to be able to monitor the angular position of the rotor for

high rotational speeds.

  It is therefore an object of the invention to propose a polyphase rotary electric machine suitable for use as an electric generator and as an electric starter motor and which comprises space-saving, economical and efficient means with high rotational speeds of the rotor for the followed

  of the rotation of the rotor of said machine.

  According to the invention a rotary electrical machine of the above-mentioned type comprising a hollow support provided with a front bearing and a rear bearing connected together and each having centrally a bearing means traversed by the end of a shaft carrying a rotor with magnetic pins surrounded by a polyphase stator internally carried by the support and in which the means for monitoring the rotation of the rotor of the magnetic wind type provided and comprise at least one sensor associated with a target, is characterized in that the target is a target with axial reading or radial, in that the target is fixed on a coffee target holder rotating on the rotor and located axially between the rotor and one of the front or rear bearings while being adjacent to the latter, and in that the bearing front or rear adjacent to the target holder carries the sensor detecting the passage of

the magnetic target.

  In one embodiment, the target is a magnetic target and advantageously comprises a number of pads of magnetic poles identical to that of the rotor of the electric machine, while facing this target fixed wind on the bearing preferably relates to Hall effect sensors. or magneto-resistive for better monitoring, the sensors being

magnetic type.

  These sensors wind in an embodiment of the threshold type adapted to take two values as described in the

document EP-A-O 260 176.

  The target holder can be magnetic or non-magnetic in nature. The nature of the material constituting the target can be ferrites, rare earths or comprise only inert sectors in magnetic head fluxed by the field

  magnetic rotor. The target can be crenellated.

  In general, the wind monitoring means adjusted so as to optimize the starting torque and make it possible according to the invention to monitor the rotation of the rotor for

high speeds of it.

  Thanks to the invention, a solution is obtained which, while being efficient, is economical because it uses standard components of a conventional alternator produced in large eerie. This solution makes it possible to integrate the means for monitoring the rotation of the rotor in the dimensions of an alternator.

  S standard without the need for an instrumental ball bearing.

  In addition, the target is protected since it is positioned between the lateral faces opposite the rotor and one of the front and rear bearings without contact with said bearing. Advantageously the bearing concerned is the rear bearing since the bearing means, in the form of a ball bearing in the case of a conventional alternator, is smaller in size so that the target holder conforms so as not to interfere with the non-rotating ring of the ball bearing will be as small as possible. In addition the electrical connections and

  wind connections easier to install.

  In addition, a rear cover is mounted on the rear bearing, in particular to protect the brush holder, so that said

  better protected and easier to implement wind monitoring systems.

  Preferably the wind sensor or sensors mounted on an adjustable or angularly fixed sensor holder implanted on the side of the front or rear bearing face concerned, rotated in opposition

rotor.

  For example for an electric machine of the three-phase type, one can use sensor trots as described

in document EP-0260 176.

  Preferably the sensor holder is circumferentially adjustable because it is mounted on the bearing concerned, while the target and the target wind carrier mounted on the shaft-rotor assembly. We can therefore realize the two souls and assemble everything in the end with an adjustment to overcome the

manufacturing tolerances.

  This arrangement does not increase the axial size between the lateral faces facing the

  rotor and front or rear bearing concerned.

  The sensor (s) locally pass through the bearing concerned by means of at least one opening that conventionally presents it. This or these openings constitute air inlets which makes it possible to ensure cleaning of the air gap (s) between the target and the active part or parts of the sensor (s).

  This or these active parts is also protected.

  In addition, this makes axial readings possible so that, as a variant, the sensor or sensors do not necessarily cross the

  or said openings but penetrate at least therein.

  In all cases the target is well cooled. This cooling is further accentuated by the fan or fans

worn by the rotor.

  Of course as a variant, the bearing or bearings can also be water-cooled, which further favors a lowering of the temperature, the fan or fans being

then has axial action.

  In general, the magnetic type monitoring means according to the invention withstand higher temperatures than optical reading monitoring means. These means are more manageable and are not likely to get dirty

  unlike optical reading tracking means.

  To this machine is associated an electronic command and control module as described for example in the

  documents FR-B-2 745 444 and EP-A-O 260 176 cited above.

  This module comprises an alternating current to direct current converter as well as control means receiving

  information on means of monitoring and means of regulation.

  This module is installed in an embodiment outside the machine. As a variant, it is implanted on the support on the external periphery thereof, in particular when the

support is water cooled.

  All this frees up space at the rear bearing, which is thus better cooled so that the monitoring means

wind still household.

  In one embodiment the target holder is linked in

  rotation with the rotor by cooperation of forms.

  In order not to modify the rotor and thus make the solution more economical, the target holder is linked by cooperation of shapes to the central part of the fan fixed on the rotor. The target holder for example has lugs each engaged in a complementary manner in recesses, for example in the form of notches, made in the annular central part of the fan. The target holder surrounds the wire connections of the rotor excitation winding to the ring-shaped collecting tracks carried by the rear end

of the rotor shaft.

  The target holder is therefore hollow. This target holder has an internal rim in the form of a socket adapted to come to bear on the internal ring of the ball bearing of the front bearing

or back concerns.

  Thus the target holder is moved axially with clearance between the bearing and the rotor while being linked in rotation by

  direct or indirect way to the rotor by cooperation of shapes.

  The mounting of the target holder is thus easy, the latter not being able to interfere with the bearing concerned because of its axial setting. This target holder is an adaptation piece occupying the

better available space.

  The target holder partially surrounds the outer ring of the ball bearing concerned as well as the bush that said bearing presents for mounting the outer ring of the bearing.

ball bearing.

  In one embodiment, this socket, advantageously internally machined, serves as a centralizer for the sensor holder so that a precise air gap exists between the

sensor holder and target.

  This gives good reading accuracy and good information transmission to the electronic module.

command and control.

  No interference can thus take place with the bearing concerned. In addition, we take advantage of the available space

  without increasing the size of the machine.

  As is evident from the description, the

  target holder advantageously has an annular shape and it is

likewise of the target.

  The target holder can be obtained by stamping a sheet so that it can be made of magnetic or magnetizable material. As a variant, the target holder is a piece molded in

  plastic material so that it is made of non-magnetic material.

  As a variant, the target holder is bi-material and comprises a plastic part wedged axially on the rotor shaft and carry a metal part supporting the magnetic target. As a variant, the target holder is in one piece with the fan, which allows the number of parts to be reduced and

  keep as many parts as possible of a conventional alternator.

  This target holder replaces the spacer provided between the bearing of the bearing concerned and the rotor. We use the indexing notches of the rotor fans to stall in

rotation of the target holder.

  In one embodiment, the rear bearing, which the machine comprises, has studs with each at least one hollow projection penetrating into an opening of the sensor holder, or of any other support of a component, for retaining a member for fixing to said component by view of an automatic assembly of

fasteners.

  The following description illustrates the invention in

  Regarding the accompanying drawings in which: - Figure 1 is an axial sectional view of an alternator starter for a motor vehicle according to the invention, the non-cutting rotor as well as the target and the target holder according to the invention; - Figure 2 is a view according to arrow 2 in Figure 1 without the cover; - Figure 3 is a partially cut view to show the excitation winding of the rotor-shaft assembly; - Figure 4 is a view along the arrow in Figure 3; S - Figure 5 is a front view of the target holder; - Figure 6 is a sectional view along line 6-6 of Figure 5; - Figure 7 is a view similar to Figure 1 for yet another embodiment, the rotor being represented by its outline; - Figure 8 is a view of the rear face of the machine of Figure 7 without the protective cover to better show the parts carried by the rear bearing; - Figure 9 is a perspective view of the sensor holder of Figures 7 and 8; - Figure 10 is a view of the front face of the rear bearing without the stator; - Figure 11 is a larger scale of the insert of Figure 10; - Figure 12 is a partial view in axial section of the rear part of the machine showing an alternative embodiment of the target holder; - Figure 13 is a front view of the rear face of the rear bearing of Figure 7; - Figure 14 is an axial sectional view of one of the studs

  from the rear bearing carry the sensor holder.

  The rotating electrical machine, shown in the figures, is reversible and is suitable for transforming from

  mechanical energy into electrical energy and vice versa.

  This machine consists of an alternator-starter for

  motor vehicle with internal combustion engine.

  In the figures, identical or similar elements will be represented by the same reference signs, the front of the machine corresponds to the right of FIG. 1 and the rear

  of the machine on the left of figure 1.

  The alternator-starter comprises a movement transmission member 1 belonging to a movement transmission device (not shown) intervening between the engine of the

vehicle and machine.

  The transmission of movement can comprise gears, chalnes, pulleys with variable spacing, at

minus a strap.

  Many possible wind variants, organ 1 can therefore have many configurations - gear,

toothed wheel, pulley etc. -.

  The member 1 is a driven member, when the machine operates in current generator mode (alternator), and a driving member, when the machine operates as an electric motor (starter), in particular for starting the engine of the

vehicle.

  In a simple and economical manner, the rotary electrical machine here has the conventional structure of a three-phase alternator for a motor vehicle, so that the organ 1 consists of an internally hollow pulley and externally grooved for the reception of a belt (not shown) provided with projections in V and belonging to the precise movement transmission device. Of course as a variant, the machine has a number

higher of phases.

  The pulley 1 has a bottom with a central hole and serves as a housing for a fixing nut 2 and a support washer (referenced 200 in FIG. 7) interposed between the nut 2 and

the bottom of the pulley 1.

  This bottom, transverse diorientation, is crossed centrally by the threaded end of a rotating shaft 3, whose axis of axial symmetry X-X defines the axis of rotation of the machine. For convenience, the threaded end of the shaft 3 will be cited at the front end, while its other end will be cited.

rear end.

  The shaft 3 carries a fastening rotor 4 with claws provided with an excitation coil 5 whose wind ends are connected by wire connections to two collector tracks 6,7, in the form of a ring, carried by the rear end of the shaft 3. The rotor 4 coil constitutes the inductor associated with the two rings 6,7 by which the excitation current is brought via two brushes connected to a voltage regulating device protecting

  in particular the battery of the motor vehicle.

  The excitation rotor 4 is surrounded by a coil stator 8 provided here with winding trots for definition of phase trots, the outputs of which are shown at 10 in FIG. 2. The stator

8 constitutes an armature.

  An air gap exists between the external periphery of the rotor 4

  and the internal periphery of the stator 8.

  In a known manner, the stator 8 comprises a package of soles internally provided with notches to define a plurality of axial grooves for housing the wires of the windings, of which the volts (in references) are shown in axial projection extending from on either side of the stator 8 t81es package. Poles exist between the grooves. One or more

  windings can be provided by machine phase.

  All this is well known to those skilled in the art.

  It is the same for the constitution of the rotor 4, which comprises two pole wheels with claws 41,42 fixed on the shaft 3 by means of knurled portions, which the shaft presents locally for this purpose (FIG. 3). These wheels each have a transverse flange bearing teeth at its outer periphery

  axial orientation 143 directed towards the other flange.

  The teeth 143 are substantially parallel to the axis of the rotor 4. The teeth 143 of a polar wheel are angularly offset relative to the teeth of the other polar wheel.

  so that the teeth of the two pole wheels are

  penetrate being therefore intertwined with each other.

  The winding 5 of the rotor 4 being supplied with direct current, the teeth of one of the pole wheels define north poles, while the teeth of the other pole wheel define south poles. This magnetizes the rotor 4 dexcitation. There is then creation of padres of north-south poles. In electric generator mode, the movement of the teeth in front of the stator poles, by the rotation of the rotor, creates an alternating current in the stator winding. This current is rectified by a poet. The coil 5 is mounted in a coil-shaped support (not referenced) of annular shape and having a U-shaped section. For mounting the coil and its coil, each pole wheel 41, 42 has an annular sleeve with its internal periphery. The wind sleeves are directed towards each other. The teeth 143 of a polar wheel are separated from each other by indentations. With a view to

  above, the teeth have a trapezoidal shape.

  Alternatively, as described in US Patent 5,747,913, permanent magnets can be implanted at the level of

  teeth 143 which, in all cases, surround the winding 5.

  The wheels 41,42 are perforated for the forced passage of the shaft 3. More precisely, the shaft 3 is harder than the wheels 41,42 for fixing them by its portions

molletees.

  This shaft 3 extends on either side of the rotor 4 and

  forms a soul-together with this one.

  The polar wheels, by means of their flange, carry a fixing, here by electric welding, each one

  fan 43,44 with blades 45.

  As a variant, the front fan 43 is eliminated, this fan 43 being less powerful than the rear fan 44. The shaft 3, through its front end, passes through a front bearing 11, while through its rear end it passes through a

  rear bearing 12 smaller than bearing 11.

  The shaft 3 is forcibly fitted into the inner rings of the bearings 11 and 12, the outer rings of which are secured respectively to a first support 13 and to a second support 14. These supports 13, 14 are usually named front bearing 13 and rear bearing respectively 14. They are made of moldable material, here based on aluminum. These supports 13,14 openwork wind as better visible in Figures 1 and 7 to allow air circulation amplified by the fans

43.44 and cool the machine.

  They have a hollow shape and each have a centrally perforated bottom for passage of the shaft 3, said bottom being of transverse orientation and centrally presenting a shoulder housing for mounting and axial setting in a direction of the outer ring of the bearing respectively. 11 and the 12-door bearing thus fixed. The outer ring of the bearing 11 is force-fitted into the bearing housing

before 13.

  At their external periphery, the bottoms, forming veils, bearings each carry an annular rim of axial orientation. The flanges wind directed axially towards each other and wind fixed with each other by a plurality of screws (not referenced) here in the form of tie rods as visible in the figure

  1. The length of the edges depends on the applications.

  The edges are internally tiered in diameter and therefore each have internally at their free end an end portion of larger internal diameter and axially delimited by a shoulder formed by the change of internal diameter at said edge. There is a space here between the two edges. Alternatively the adjoining wind flanges. In Figure 1 the stator 8 is forcibly fitted into the free ends of the edges while being axially caffeinated by the shoulder s said edges; the flange fixing screws therefore also make it possible to tighten the stator 8 making in FIG. 1 a spacer between the two flanges of the bearings 13,14. In Figure 7 the

joined wind edges.

  The front bearing 13 has ears for fixing it to a fixed part of the vehicle and tensioning the belt. One of these ears, in this case a fixing ear has a part

  fixed of the motor vehicle, is visible at 300 in FIG. 7.

  As a variant, each bearing 13, 14, at least at its peripheral rim, presents in its thickness a fluid circulation channel to cool the machine so that the presence of the fans is not essential, nevertheless the

  landings remain open.

  Alternatively one of the two bearings has no flange S and forms a cover for the other bearing provided alternatively

  internally of a fluid circulation channel.

  Where the cooling channels can be connected

  on the vehicle cooling system.

  Of course, this type of cooling can be combined with the presence of one or two axially acting fans integral in rotation with the rotor as described for example in

  the document FR01 01526 filed on February 5, 2001.

  All possible wind combinations. In all cases the bearings 13,14 connected together belong to a hollow support S endowed with a front bearing 13 and a rear bearing 14 connected to each other and each having centrally a bearing means 11,12 such as a ball bearing , traversed by the shaft 3. I1 emerges from the above, going axially from right to left in FIG. 1, that the machine has a shaft 3 at a threaded end for mounting the pulley 1, a front bearing 13 with its central bearing 11 for rotary mounting of the front end of the shaft 3, a washer (not referenced) for axial maintenance in the other direction of the outer ring of the bearing 11, a spacer washer 70, the stator 8 surrounding the rotor 4, a target 50 carried by a target holder (described below), the rear bearing 14 with its central bearing 12 for rotary mounting of the rear end of the shaft 3, a brush holder 16 fixed on the face rear of the rear bearing 14 rotated opposite the rotor 4 and a fixed cover 17

  also on the rear face of the rear bearing 14.

  The fans 43,44 are vented through the faces of the

  polar wheels 41,42 turned towards the bottom of the bearings 13,14.

  It will be noted that the pulley 1 has a bushing at the rear (not referenced) for contact with the internal ring of the bearing 11 and that the nut 2 makes it possible to tighten the pulley 1 in contact with the internal ring of the bearing 11. This ring internal is clamped between the pulley bushing and the spacer

ring shape.

  In practice the bearing 12 is carried by the shaft 3, as well as the spacer ring fixed to the shaft 3 in favor

a knurling on said shaft.

  Here the rear paller 14 has an annular housing delimited by a wall of transverse orientation and a bush 46 of axial orientation. The same applies to the bearing housing

  before. The sockets are internally produced here.

  In this housing is mounted a plastic ring 47 attached by snap-fastening therein as best seen in Figure 7. Thus the ring 47 has at its end before projections engaged in the recesses of the socket. The outer ring of the bearing 12 is mounted in this

  housing without being retained axially.

  In a conventional alternator, a spacer washer is mounted between the rear fan 44 and the internal ring of the

bearing 12.

  Here, this ring is replaced by a target-holder part 60 carrying a target 50 with axial or radial reading. The target here is magnetic and includes for example an alternation

  of south and north sections distributed regularly.

  The target holder 60 is here a piece in t81e stamped in

  so that it is magnetic in nature.

  Alternatively the target holder 60 is a piece of material

  molded plastic and is therefore non-magnetic in nature.

  The target holder 60 is adjacent to the bottom of the rear bearing 14 and is rotated on the rotor 4. This setting is carried out

  preferably by a cooperative link of forms.

  In FIG. 1 the target holder is rotated indirectly on the rotor using the fan 44 fixed here on the pole wheel 42. This arrangement makes it possible not to

modify the rotor.

  The fan 44 is also not modified because it has in a standard manner two notches 48 at its internal periphery forming a polarizer to fix the fan angularly in the right position relative to the teeth 143 of the

associated polar wheel 42.

  The fan 44 is in stamped sheet metal and has the blades 45 at its outer periphery and at its internal periphery a transverse flange 145 which shifts axially in the direction of the

bearing 12.

  It is in this ledge that the notches 48 form.

  In FIG. 4, the wire connections with the ends of the winding 5 are shown. These connections are diametrically opposed and each pass through an obviousness between two teeth of

the pole wheel 42.

  Then this connection passes between the flange of the polar wheel 42, hollowed out locally for this purpose, and the fan 44 to end in a rectilinear portion engaged in a loop respectively 49,49 'belonging to a device for

connection 80 with tracks 6,7.

  The ends of the wire connections of the winding 5 wind welded here electrically with the loops 49,49 ', the

  device 80 comprising an electrical isolation block 61.

  The target holder 60 is of hollow annular shape. It has at its external periphery an external annular rim 62,63 of axial orientation and stage in diameter. The portion of larger diameter 63 extends in part radially above the bush 46, turned towards the rotor 4, of the rear bearing 14

  and therefore also of the outer ring of the bearing.

  In the portion of smaller diameter 62 wind formed radially by stamping two lugs 64 diametrically opposite each penetrating in a complementary manner in a

indentation 48, here semi-circular.

  The lugs 64 axially oriented and semi-shaped

  circular in section. The axial length of the lugs 64 allows

  to overcome manufacturing tolerances.

  The portion is connected to a bottom 65 floor overall

transverse orientation.

  The bottom 65 is connected at its external periphery to the portion 62 and at its internal periphery to an internal annular rim 66 of axial orientation, stage in diameter like the external rim. The outer and inner edges therefore wind in

S form of stage socket.

  The rim 66 is axially shorter than the outer rim 62,63. Each flange 62, 63 and 66 has, at its free end, a stiffening flange 67 and 68 respectively directed respectively radially outward and radially inward. The flange 68 is intended to come into abutment against the internal ring of the bearing 12, while the flange 67 is adjacent to the bottom of the rear bearing 14,

a game exist.

  The portion 62 and the bottom floor 65 pass through the transverse IS rim 145 of the fan 44 of annular shape and have a hole

  centrally. The bottom is capable of coming to bear on the rotor 4.

  The target holder 60 forms an axial spacer between the rotor 4 and the internal bearing of the bearing 12 so that it is axially cafe with mounting clearance and does not risk interfering with the bearing 14, the length of the outer rim 62, 63 being

  determined accordingly and dependent on applications.

  Opposite windows 69, 69 ′ affect the bottom 65 of the target holder. These windows allow access to the loops 49,49 '

  and therefore authorize welding with the ends of the coil 5.

  The bottom 65 is therefore also a protective bottom during

  of welding time at the loops 49,49 '.

  The target 50 here includes a number of padres of poles

  identical to that of rotor 4.

  The nature of the material constituting the target can be ferrites, rare earths or comprise only inert sectors in magnetic sheet fluxed by the magnetic field of the rotor. Facing the target 50 wind implanted here sensor trots 52 because the machine is of the three-phase type, alternatively more sensor trots, carried by a sensor holder 53 fixed on the bottom of the rear bearing 14 more precisely on the face thereof

  opposite the target 50 and the target holder 60.

  The magnetic target 50 is fixed to the portion 63 of larger diameter of the target holder 60 and is at its free end adjacent to the bottom of the rear bearing 14. The sensors 52 are magnetic in nature. This wind in a first embodiment of Hall effect sensors, as a variant of magneto-resistive sensors whose resistance varies

depending on the magnetic flux.

  The sensors 52 wind implant radially above the target 50 with definition of an air gap between the sensors and the target so that the reading is radial. As will have been understood, the target assembly 50 sensor 52 constitutes a means of monitoring the rotation of the rotor of the magnetic type, which is not likely to get dirty due to the one hand of the ventilation created by

the fan 44.

  This ventilation is due to the fact that the bearings 13 and

  14 openwork wind at their bottom and rim.

  In FIG. 1, the holes made in

the bottom of the rear bearing 14.

  The sensor holder 53, here made of plastic, has portions 55 of axial orientation. These portions 55 pass through the bearing 14 in the favor here of a hole 54. The sensors 52 are integral with the portions 55 and wind implanted radially between the target 50 and the blades 45 while being very close to the target 50. The electrical connections of the sensors 52 wind housed in the sensor holder 53 fixed by means of two ears 56 on the bottom of the rear bearing 14 of the side opposite the target 50 and the

rotor 4.

  The ear holes 56 are oblong in shape for

  passage of fixing bolts 57 at the bottom of the bearing 14.

  Likewise the brush holder 16 is fixed on the same face of the bottom of the bearing 14 by means of bolts and ears not

references.

  The brush holder 16 comprises in known manner two cages for guiding brushes each cooperating with a slip ring 6,7 attached to the rear end of the shaft 3 and each connected to one of the loops 49,49 '. Wind brooms

  Subject to the action of springs housed in cages.

  The outputs 10 of the stator 8 wind phases integral with a part 59 also fixed on the rear bearing by means of ears and bolts not referenced. For each phase 10

wind connections provided.

  In Figure 7 the brush holder 16 and the outputs of

  phases belong to one and the same piece.

  In Figure 2 we see the circumferential distribution

  electrically insulating parts 53, 16, 59.

  Note that the sensor holder 53 is adjustable

circumferentially.

  We therefore occupy at best the available space by having a

  protection by cover 17 and good ventilation.

  Here the sensor holder 53 is adjustable angularly or circumferentially and has an appendage directed radially inwards to carry the trots portions 55

  and the sensor trots 52, the hole 54 having a large size.

  More precisely the passage hole 54 of the axial portions 55 has a larger size than the other holes as

visible in Figure 2.

  Advantageously, the portions 55 wind connected together

* to form a single sector.

  Of course the ends of phases 10, and the parts 16.58 can be connected to an electronic command and control module as described for example in documents FR-A-2 745 444 and EP-A-0260 176 to which we can see more details. In the light of these documents it is felt that the sensors, for example Hall effect, wind in a type of embodiment with thresholds. This module is installed outside the machine. Alternatively it can be installed on the edges of

steps 13.14.

  The electronic module includes switches such as MOSFET transistors and includes control means for synchronously controlling the phases of the stator, for example using square signals, in sinusoidal or trapezoidal form. The electronic command and control module is a management unit that includes a computer and receives information from the sensors. This unit also includes the aforementioned switches belonging to the rectifier bridge connected to the different phases of the armature and mounted between earth and the positive terminal of the battery. Each switch is associated in parallel with a diode for rectifying the alternating current into direct current during the operation of the machine as an electric generator. The voltage regulating device is also mounted in this module. For more details, refer to the aforementioned documents, the phases of the machine being for example mounted in a star as visible for example in Figures 4 and 12 to 14

of document EP-A-0 260 176.

  In summary, the switches connected in parallel with the diodes of the rectifier bridge, wind controlled from an electronic assembly, comprising a computer, which receives information on the angular position of the rotor via the

sensors.

  When the machine is operating in electric motor mode

  the phases are fed sequentially.

  For more details, see for example

document EP-A-0 260 176.

  The monitoring means of the invention can be connected to these control means to make the machine work.

  with an electric motor and start the vehicle engine.

  Of course it is possible to stop the engine at red light to restart then and save fuel,

  ['management unit being conformed accordingly.

  Alternatively the machine can work as an auxiliary motor when the vehicle engine is stopped to

train an accessory.

  In the figures, the reading of the magnetic target 50 is a radial reading. Alternatively thanks to the hole the reading can

  8tre axial, the sensors 52 being implanted axially in vis-

  vis-à-vis the target 50, that is to say opposite the slice thereof. We will appreciate that a radial reading is more precise

than an axial reading of the target.

  The target 50 is here fixed by bonding to the portion 63 of the target holder. As a variant, it can be molded onto the target holder 60. This target 50 is protected because it is installed between the opposite side faces of the bearing 14 and of the rotor 4, said faces belonging respectively to the bottom of the

  bearing 14 and to the flange of the pole wheel 42.

  As a variant, the target holder 60 can be implanted between the bottom of the front bearing 13 and the flange of the pole wheel 41 in place of the spacer 70. The sensor holder 53 is then fixed on

  the face of the bearing 13, turned away from the rotor.

  As a variant, the rotor 4 may include protruding poles, each of which is associated with a winding. I1 may include

  two polar wheel pads with excitation winding.

  As a variant, the rotor may include magnets

  permanent and separate windings.

  The rotor can therefore have any tail shape.

  Likewise, it is conceivable that the bearings 11 and 12 can be replaced by other types of bearing, for example smooth bearings. In all cases the target set - target holder

  belongs to the rotor 4 - shaft 3 - bearing 12 assembly.

  As a variant, the structures can be inverted, the fan 43 or 44 comprising projections, such as lugs, engaged in recesses, such as notches,

carried out in the target holder.

  At least one projection is planned, the number of projections

can be greater than two.

  As can be seen from the drawings, the shelves of the

  target 60 wind due to the presence of surrounding rooms to occupy the space as well as possible. Of course we can overexcite the winding 5 of the rotor 4 when the machine works with an electric motor (mode

  to maximize the starting torque of the alternator

  starter. This overexcitation can also be achieved when the machine is operating as an electric generator (alternator mode). The accessory driven when the machine is operating as an auxiliary motor may be the air conditioning device compressor or an assistance pump for assisted hydraulic steering. For more details, refer to document FR01 01341 filed on January 31, 2001,

  describing all possible strategies.

  Of course, as described in document FROO 16738 filed on December 21, 2000, the rotary electric machine can

have more phase trots.

  Each phase can include several windings. The electrically conductive elements may consist of bars advantageously of rectangular section; the phase inputs being connected to each other by a connecting piece in the form of a bar. For more details, see this document. The distribution of magnetic pins on the target may not be symmetrical. In fact, when the winding 5 of the rotor 4 is active, this creates a magnetic field so that this influences the means for monitoring the magnetic type of the rotation of the rotor. The asymmetry of the distribution of the magnetic p81s of the target allows to restore a symmetric for

  triggering of the threshold sensors.

  Thus, depending on the applications, the North or South magnetic p81s have a greater circumferential extent than the other South or North magnetic p81es. This difference in circumferential extent of the poles depends on the excitation of the winding In all cases the magnetic target has poles

North and South asymmetrical.

  Of course, the present invention is not limited to

examples of realization described.

  In this way, in a real mode, sat centering means intervene between the sensor holder and its associated bearing to obtain a precise air gap between the target and the sensors.

associated.

  This gives an accurate reading and information

precise from the sensors.

  The sensor holder is therefore compliant to come into contact

intimate with the landing concerned.

  In one embodiment the bearing relates centrally to a socket, which is extended to cooperate with

  an axial orientation rim coming from the sensor holder.

  More precisely in the embodiment of Figure 7 the socket referenced at 246 is extended towards the rear at

  direction of the cover 17 with openwork bottom.

  The sensor holder 53 has at the rear an annular rim of axial orientation 253 penetrating into the rear end of the socket 246. The rim 253 is therefore axially directed with the bearing 12 supported by the socket 246 with

  interposition of the plastic ring 47.

  The rim 253 is in intimate contact by its external periphery with the internal periphery of the sleeve 246 advantageously machined at the level of the rear end thereof. Here the flange 253 is in local contact with the internal periphery of the socket 246 to obtain an even more centering

precis of the sensor holder 53.

  This sensor holder 53 has here (FIG. 9) a flange 253 S 'extending circumferentially over less than 360 with three protruding zones 254, 255,256 for local contact with

  the rear end of the socket 246.

  Here the rim 253 extends circumferentially over more than 180. All of this depends on the applications and more precisely on the presence of the brush holder 16 projecting radially inwards in the direction of the axis XX as better visible in FIG. 8. The flange 253 is therefore circumferentially conform so as not to interfere with the brush holder. 16, knowing that the sensor holder 253 is adjustable angularly or circumferentially by means of the ears 56 each provided with an oblong opening 156 allowing circumferential adjustment. In FIG. 9 the sensor holder 53 is made of moldable plastic as in FIG. 2 and the portions 55 belong here to the same angular sector 55 passing through

  the opening 54 made in the bottom of the rear bearing.

  This opening is circumferentially more extensive

  than sector 55, in which the sensors are buried.

  The sensors 55 wind radially implanted above the magnetic target 50 with definition of a precise air gap, thanks to the socket 246 and to the portions 254 to 256, between the external periphery of the target 50 and the internal periphery of the

  angular sector 55, the target being here with radial reading.

  Generally, greater precision is obtained with a target with a radial reading which with a target with

axial reading.

  The sensor holder has at its external periphery a connector 257 passing through the annular rim of axial orientation of the cover 17, endowed for this purpose with an oblong opening. The sensor holder 53 is provided with holes on either side of the sector 55 as visible in FIGS. 8 and 9. The

  holes extend below the openings 156.

  This sensor holder 53 has a non-symmetrical shape at its internal periphery so as not to interfere with the brush holder 16 and occupy circumferentially the best space

available.

  Here the brush holder 16 is of the type described in

  Patent application FR01 00931 filed on January 24, 2001.

  Thus the brush holder 16 belongs to a support 160 provided with a first soul-assembly 161 belonging to a connector for making an electrical connection via a second sub-assembly, electrical cables and a second connector with the electronic command and control module. with a

  boltier containing the components to said module.

  The sensors of the sensor holder are connected via connector 257 and another invisible connection device

  to the electronic command and control module.

  The brush holder 16 also includes a connector 162 for connecting the brushes to the electronic control and

  control via a third connection device.

  The support 160 is therefore made of electrically insulating material. In this wind support submerged the strips of electrically conductive material connecting the inputs of the outputs 163 to 165 of the phases of the stator 8 to the first contact spans 166 to 168 of the first soul-assembly 161. These spans belong to a protuberance of the support 160 as described in this document FR01 00931, strips of material separating the contact surfaces from one another with electrical insulation, the second of the connector has a casing delimited by a bolt box and a closing cover. This casing contains second electrically conductive elements flexibly mounted inside the casing and having two second contact ranges homologous to the ranges 166 to 168 as described in the document FR01 00931 precise to which reference will be made for more details, the support 160 being fixed to the rear bearing by screws 169 by means of studs of the rear bearing 14 and columns

from support 160.

  Thanks to the clearances presented by the sensor holder 53 at the level of the brush holder 16, to the ears 56 and to the flange 253, the sensor holder 53 can be adjusted circumferentially without risk of interference with the support 160. In all cases the sensor holder has oblong openings for fixing it with angular adjustment on the bearing concerned here using

  fastener as described below.

  It will be appreciated that lton occupies at best the space available at the rear bearing 14, the holes of the holder.

  sensors 53 and the rear bearing favoring ventilation.

  It will be noted that the stator 8 is mounted elastically in the support S as described in the application FR00 13527 filed on

October 6, 2000.

  More precisely, four buffers 147 with pastes 148 of wind positioning positioned radially between the stator 8 and the outer peripheral rim of axial orientation 114 of the

rear bearing 14.

  The wind buffers are distributed here circumferentially from

regularly.

  These square cross-section pads operate axially and radially between the precise rim 114 of the bearing 14 and the rear end of the stator pack of soles 8

constitute the body of it.

  To do this, the flange 114 has housings 115 of

  reception of buffers 148 for positioning buffers 147.

  The housings 115 have a dovetail shape complementary to that of the pastes. The free end of the rim 114 has spouts that are better visible in FIG. 11. An elastically deformable thermally conductive resin is interposed radially between the body of the stator 8 and the rim 114. More precisely circumferentially, elastically deformable sectors in thermoconductive resin 149 alternate circumferentially with regularly with the buffers 147 being interposed radially between the peripheral flange 114

  external of the rear bearing 14 and the stator body.

  An elastically deformable flat annular seal 150 is interposed axially between the front bearing 13 and the outer end

  front of the stator body 8 as better visible in FIG. 7.

  It will be noted that the outer peripheral annular rim of axial orientation 113, which the front bearing presents, carries

pastes 300.

  The free ends of the edges 113,114 are winded S so that the edges 113,114 are internally stepped in diameter with the formation of transverse shoulders for support

  buffers 147 and washer 150.

  Thus a mechanical and vibratory decoupling of the stator 8 is obtained relative to the rear bearing 14 carry the sensor holder 53, while having, thanks to the sectors 149, good

heat dissipation.

  The vibrations of the sensor holder 53 are therefore reduced

  as well as the heat transmission so that the carrier

  sensors 53 made of plastic is cleaned and that the reading accuracy of the means for monitoring the rotation of the rotor is improved. Thanks to the sectors 149, the target holder 60 can be in two parts and include, as shown in FIG. 7, a shoulder ring 260 of plastic material wedged axially on the shaft 3 by virtue of a change in diameter 301 thereof. this. This ring has an openwork bottom, generally of transverse orientation, extended at its external periphery by an annular rim axially oriented in which is anchored a metallic piece 261 in the form of a staircase carrying the target.

magnetic 50.

  The edge of the ring 260 is molded on the base of the axial orientation of the part 261, the top portion of which is axially oriented carries the target 50 and is connected to the said

  base by a transverse orientation part.

  The base and the upper portion are axially offset

one in relation to the other.

  The rim of the ring 260 has an overall average diameter identical to that of the sleeve 246. Here the average diameter of said rim is slightly smaller than that of the sleeve 246 and the top portion of the piece 261 lies radially above

of the socket (figure 7).

  As a variant (FIG. 12) the target holder is in one piece with the fan by forming a sleeve 60 axially oriented at the internal periphery of the fan.

  integral, for example by spot welding of the rotor 4.

  It will be noted that the brush holder 16 has at its internal periphery a tube open locally for passage of the brushes, a seal (not reference) being interposed between the front end of the internal tube of the brush holder and the ring 47

as shown in Figure 7.

  Here the rear bearing 14 has studs 401,405,406 for respectively support of the sensor holder 53 and of the support 160 on the rear bearing. The studs 401 and 405 are internally tapped while the stud 406 has an internal bore hole in diameter for housing the head and passage of the part of a fixing screw passing centrally through the first connector assembly and in particular the first bearings 166 to 168 of the latter for fixing the second sub-assembly of the connector as better visible in FIG. 2 of the

document FR01 00931 precise.

  The screw therefore has a knurling in the vicinity of its head

  for fixing the screw to stud 406.

  A nut is supported via a washer on the cover of the second connector assembly by being screwed on the

threaded part of the rod.

  The 405 studs are internally tapped to receive

  the screws 169 for fixing the support 160 to the rear bearing 14.

  The studs 401 wind intended to receive studs 400 comprising two threaded parts arranged on either side of a nut intended to come to bear on the ear 56 concerned of the sensor holder 253 with interposition of a support washer 407 between the stud of the stud 400 and the ear 56. Each stud 400 passes through its threaded part before the oblong opening 156; the washer 407 being wider than the opening 156 for

  block the sensor holder 53 following the screwing of the studs 400.

  It is for this reason that the stud 401 is internally tapped at 401 ′ to receive the threaded part before the

studs 400.

  The rear threaded part of each stud 400 is snapped into the cover 17 comprising, at the rear,

  chimneys 170 transverse axial diorientation of the cover 17.

  Each chimney 170 has, at its base for connection to the transverse bottom 172, an annular projection 173, possibly split, intended to come into engagement with the

  rear threaded part of stud 400 concerned.

  Thus the cover 17 is mounted by snap-fastening on the studs 400, its projections 173 engaging with the rear threads of the studs 400, knowing that the cover 17 is made of plastic. Each pad 401 has, like the other pads, an upper face 402 for support of the sensor holder 53, more

  precisely ears 56 thereof.

  According to a characteristic two low walls 403 wind coming in axial projection from the face 402, here by molding. These walls constitute a hollow projection and internally delimit a hole 404 intended each to receive the threaded part before the

  stud concerns. A slit separates the walls between them.

  The hole 404 has the same axis of axial symmetry as the tapped part 401 'of the stud 401. This hole 404 extends the tapped part 401' by being of internal diameter greater than that of the tapped part 401 '. All these provisions favor the

  automatic mounting of studs 400.

  Indeed we engage with these in the holes 404 in

  so they wind prepositioned and do not risk tipping over.

  Then we screw the studs with a screwdriver.

  It will be appreciated that the lateral edges of the walls 403 are generally rectilinear as better visible in FIG. 13, which makes it possible to guide the ears 56, the walls penetrating into the oblong openings 156, advantageously without protruding axially beyond the ears. . The low walls 403 are generally in the shape of an arc of a circle, being therefore housed in the thickness of the ears 56. The low walls are centered on the axis of the tapped holes 401 ′. The rectilinear lateral edges of the low walls make it possible to reduce the diametral size of the

  low walls and therefore not to enlarge the openings 156.

  Of course, this type of mounting with studs fitted with low walls is applicable to any tail piece supporting one or more components carried by the bearing 14. This type of mounting can apply to the support 59 of FIG. 1, the openings

  then being circular and the screw fixing members.

  The walls of FIG. 14 allow a circumferential adjustment of the sensor holder and follow the shape of the circumferential ends of the oblong openings 156. As a variant, the wind walls are connected together to form a socket. The rear bearing here has hollows 411 on its face

back for his lightening.

  It will be noted that the pastes 148 wind circumferentially adjacent to the tapped holes provided for the screws or

  tie rods for fixing the bearings 13.14 to each other.

  A bearing surface 410 for the sensor holder 53 is provided between one of the recesses 411 and the hole 54, of larger

  circumferential extent, than the other holes, of the bearing 14.

  The installation of monitoring means at the rear of the machine is

favorable for connections.

  Of course the precise connector housing participates in

  fixing the cover 17, in association with the chimneys 170.

  As a variant, the centering of the sensor holder is carried out using a pin from the sensor holder and engaged in a light in the rear bearing, the pin cooperating with the circumferential edges of the groove. Centering means therefore advantageously exist between the sensor holder and its associated bearing.

Claims (31)

  1- Polyphase rotary electric machine - to be used in a motor vehicle with internal combustion engine, on the one hand, as an electric generator and, on the other hand, as an electric motor for starting the internal combustion engine - comprising a shaft (3) carry a rotor (4) with magnetic pins surrounded by a polyphase stator (8) internally carried by a hollow support (S) provided with a front bearing (13) and a rear bearing (14) connected together each centrally having a bearing means (11,12) traversed by the end of the shaft (3) carry the rotor (4), in which means for monitoring the magnetic type of the rotation of the rotor (50,52) wind forecast and include at least one sensor (52) associated with a target (50), characterized in that the target (50) is fixed on a target holder (60) in one piece with a fixed fan (43,44) on the rotor so that the target is located axially between the rotor (4) and one of the front (13) or rear ( 14), said first landing, adjacent to the target holder (60).   2 Machine according to claim 1, characterized in that the target (50) and the target holder (60) have an annular shape. 3- Machine according to claim 1 or 2, characterized in what the target is crenelee.   4- Machine according to any one of the claims   previous, characterized in that the target (50) is a magnetic target - Machine according to claim 4, characterized in that   that the target has inert sectors in magnetic t81e.   6- Machine according to Claim 4, characterized in that the target (50) comprises ferrites or rare earths 7. Machine according to Claim 4 or 6, characterized in that the target comprises an identical number of pads of p81es to that which comprises the rotor (4).   8- Machine according to any one of claims 4,   6,7, characterized in that the target (50) has poles   magnets distributed in a non symmetrical manner.   9- Machine according to claim 8, characterized in that the target has larger North magnetic blades   circumferential extent as South p81es or vice versa.   - Machine according to any one of claims 4,   6, 7, characterized in that the target comprises an alternation of   North and South poles distributed regularly.   11- Machine according to any one of claims   previous, characterized in that the target holder (60) forms an axially oriented sleeve at the internal periphery of the fan (44).   12- Machine according to any one of claims   previous, characterized in that the fan (44) is   metallic and has blades (45) at its outer periphery.   13 - Machine according to any one of the claims   previous, characterized in that the target (50) is molded onto the target holder (60)   14 - Machine according to any one of claims 1 a   12 characterized in that the target (50) is fixed by gluing on the target holder (60).   - Machine according to any one of the claims   previous, characterized in that the first bearing adjacent to the target holder (60) carries the sensor (s) (52) detecting the passage of the target (50), in that the sensor (s) (52 ) wind mounted on a sensor holder (s) (53) fixed on the first bearing on the side thereof opposite the rotor (4) and in that the first bearing has at least one opening (54) for access to the target and radial or axial target reading   (50) by the sensor (s) (52).   16- Machine according to claim 15, characterized in that the sensor (s) (52) wind implant (s) radially between the target (50) and the blades (45) that presents the fan (44) integral with the rotor (4).   17- Machine according to claim 15 or 16, characterized in that several sensors (52) provided wind, in that the wind sensors integral with portions (55) of axial orientation that presents the sensor holder (53) and in that said portions (55) pass through the first bearing thanks to said at least opening (54) for a radial reading of the target (50). 18- Machine according to claim 17, characterized in that the portions (55) of the sensor holder (53) wind connected together to form a single sector (55) passing through the opening   (54) consist of a through hole (54).   19- Machine according to claim 15, characterized in that the sensor (s) (52) penetrate at least in the opening (54) in the form of a reading hole and wind implants lS axially opposite target (50) for axial reading of it.   - Machine according to any one of claims 15   19, characterized in that the sensor holder (s) (53) is fixed with angular adjustment on the first bearing by means of fixation.   21- Machine according to claim 20, characterized in that the sensor holder (s) (53) has ears (56) with oblong openings (156) for its fixing with angular adjustment   on the first bearing using fasteners.   22- Machine according to any one of claims 1 a   21, characterized in that at least three sensor trots (52) are provided, in that the first bearing is of hollow shape and has a bottom which is centrally perforated for passage of the shaft (3) carry the rotor (4) and in what the sensor holder (53) is fixed on said bottom.   23 - Machine according to claim 22, characterized in that the sensor holder (53) is made of plastic and in that the electrical connections of the sensors (53) are housed in the sensor holder (53).   24- Machine according to any one of claims   previous taken in combination with claim 20, characterized in that centering means exist between the   sensor holder and its bearing (14) associated.   - Machine according to claim 24, caracteriseeen that the bearing (14) associated with the sensor holder (53) has a socket (246) for mounting the bearing means (11,12) and in that the sensor holder (53 ) has an axially oriented rim (253) for intimate contact with the periphery internal of the socket (246).   26- Machine according to claim 25, characterized in that the flange (253) is in intimate contact by its periphery   external with the internal periphery of the socket (246).   27- Machine according to claim 26, characterized in that the flange (253) has protruding areas (254 to 256)   for local contact with the socket (246).   28- Machine according to any one of claims   precedents, characterized in that the first bearing is the rear bearing (14) of hollow form, the bottom of which - hole centrally for passage of the shaft (3) of the rotor (4) - carries a brush holder (16) and in that the bearing means is a bearing (12).   29- Machine according to claim 28, characterized in that the rotor (4) comprises an excitation winding (5) whose wind ends connected by wire connections to two collector tracks (6, 7) carried by the rear end of the 'shaft (3) carry the rotor (4) and in that the target holder (60) surrounds wire connections.   - Machine according to any one of claims 1 a   29, characterized in that the sensor (s) (52) wind from the   hall effect type, such as threshold hall type.   31- Machine according to any one of claims 1 a   29, characterized in that the sensor (s) (52) wind from the magneto-resistive type.   32 - Machine according to any one of the claims   previous, characterized in that the stator (8) is resiliently mounted in the support (S) by means of buffers (147) carried by a flange (114) external peripheral of axial orientation that includes the rear bearing (14) carry a brush holder (16).   33- Machine according to claim 32, characterized in that the stator (8) comprises a body and in that an elastically deformable thermally conductive resin S is interposed radially between the body of the stator (8) and the periphery support (S).   34- Machine according to claim 33, characterized in that several deformable sectors in thermally conductive resin (149) alternate circumferentially regularly with the pads (147) being interposed radially between the external periphery of the support (S) and the body of the stator (8) and in that the rim (114) external periphery of the rear bearing (14) has housings (115) for receiving steps (148)   1S for positioning the buffers (147).   - Machine according to claim 33 or 34, characterized in that the buffers (147) intervene axially and radially between the outer peripheral rim (114) of the rear bearing (14) and the rear end of a packet of soles constitute a body presented by the stator (8) and in that an elastically deformable flat annular seal (150) is interposed axially between the front bearing (13) and the end front of the stator body (8).   36- Machine according to any one of claims   previous, characterized in that the stator (8) comprises phases and in that each phase comprises several windings with electrically conductive elements in the form of bars rectangular section.   37- Machine according to any of the claims   previous, characterized in that the rotor (4) comprises at least two pole wheels (41,42) fixed on the shaft (3) and a winding (5), in that each pole wheel (41,42) has a transverse flange carry on its outer periphery axially oriented teeth (143) directed towards the flange of the other pole wheel, in that the teeth (143) of a pole wheel are angularly offset relative to the teeth of the other wheel polar so that the teeth are interwoven with each other and in that the fan (43,44) integrally with the target holder (60) is fixed on the flange of the polar wheel concerned. 38- Machine according to claim 37, characterized in that permanent magnets wind implanted at the teeth (143) of the pole wheels (41,42) which surround the winding (5) of the rotor (4).   39-. Machine according to claim 37 or 38, characterized in that the rotor has two padres of wheels poles with excitation winding.   - Machine according to any one of claims 1 a   36, characterized in that the rotor (4) has poles   protruding to each of which is associated a winding.   41- Machine according to any one of claims 1 a   36 and 40, characterized in that the rotor (4) has   permanent magnets and separate coils.   42 - Machine according to any one of claims   previous, characterized in that the front bearings (13) and   rear (14) openwork wind to allow air circulation.   43- Machine according to any one of claims 1 a   41, characterized in that at least one of the bearings internally has a fluid circulation channel, such as the   motor vehicle coolant.   44- Machine according to claim 43, characterized in that the rotor (4) carries at least one fan fastening   axially acting in one piece with the target holder (60).   -. Machine according to any one of the claims   above, characterized in that the rotor carries a fan (8, 9) at each of its axial ends, of which   one is in one piece with the target holder (60).   46. Machine according to any one of claims   above, characterized in that the rotor (4) is provided with at least one excitation winding (5) and in that the excitation winding (5) is overexcited when the machine is used