Coupling device for a reduction gear with two gear ratios

Abstract

The invention relates to a device for coupling shafts, comprising a main shaft oriented along a main axis (A1), two idler gears mounted to rotate freely on the main shaft, and a coupling system (50) interposed between the two idler gears. According to the invention, the coupling system comprises: - a hub (540) integral in rotation with the main shaft, - a selection sliding ring (520) mounted slidably with respect to the hub between a position coupled to one of the idler gears and a position coupled to the other of the idler gears, - a locking sliding ring (530) mounted slidably with respect to the hub between a position coupled to one of the idler gears and a position coupled to the other of the idler gears, and - elastic return means (550, 551) which, at rest, maintain the sliding rings at the same height and which, under stress, allow a height offset of the sliding rings.

Description

DESCRIPTION TITLE OF THE INVENTION: COUPLING DEVICE FOR A TWO-GEAR REDUCER TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates generally to shaft coupling systems, allowing torque to be transmitted from one shaft to the other, and in particular to speed reduction systems with two speed ratios.

[0002] It relates more particularly to a shaft coupling device, comprising: - a main shaft oriented along a main axis, - two idler gears mounted freely rotating on the main shaft around the main axis, and - a coupling system interposed between the two idler gears.

[0003] The invention also relates to a speed reducer comprising a shaft coupling device as mentioned above, and a motor vehicle equipped with such a reducer.

[0004] It finds a particularly advantageous application in the transmission of torque from an electric machine. STATE OF THE ART

[0005] An internal combustion engine develops torque that varies with the crankshaft rotation speed. Such an engine therefore has a limited operating range. In a motor vehicle equipped with such an engine, it is then necessary to couple the engine with a gearbox.

[0006] In this field, many gearbox systems have been developed. Typically, such a gearbox comprises two shafts with facing gears of different diameters that mesh with each other, the gears of one of the shafts being, for example, loosely mounted on this shaft (i.e., left free to rotate on this shaft) while the others are fixedly mounted on the other shaft. In order to change gear, these gearboxes use coupling devices designed to couple one of the loose gears with the gearbox shaft on which it is mounted so as to equalize their rotational speeds.

[0007] For this, the coupling devices generally include a sliding gear which is linked in rotation to one of the shafts of the box and which is adapted to slide on this shaft to come, by means of fingers, to engage a toothing of an idler gear.

[0008] In an electric (or hybrid) motor vehicle, the electric machine is coupled to a speed reducer. As a general rule, this reducer is single-ratio. It is therefore generally not provided with a gearbox. An electric machine is in fact adapted to deliver a substantially constant torque over a wide range of rotational speeds. It can therefore be used with such a reducer in a motor vehicle. The advantage of a single-ratio reducer is that it is simple, inexpensive, and does not pose any problem of torque loss (when changing gears).

[0009] However, it should be noted that an electric machine, beyond a certain rotational speed threshold, sees the torque it can deliver reduce sharply. Then the power it can generate saturates. In other words, the torque delivered by an electric motor is not constant indefinitely. Associating a multi-ratio reducer with such an electric machine can therefore remain of interest, particularly in the automotive field. Typically, a dual-ratio reducer makes it possible either to reduce the size of the electric machine, or to use the electric machine in speed ranges where its consumption remains low, or to install the electric machine on private vehicles such as utility vehicles likely to move heavy loads, or in sports vehicles capable of reaching high speeds.

[0010] The disadvantage of a two-speed gearbox is that it is currently complex, expensive, and heavy, or it is slow when it comes to changing from one gear to another, which causes torque breaks that are not compatible with the automotive sector. PRESENTATION OF THE INVENTION

[0011] In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a two-speed reducer, of simple architecture and capable of causing almost no torque loss during a gear change.

[0012] More particularly, the invention provides a coupling device as defined in the introduction, in which the coupling system comprises: - a hub integral in rotation with the main shaft, - a selection lever mounted to slide relative to the hub along said main axis between a position coupled to one of the idler gears and a position coupled to the other of the idler gears, - a member for moving the selection slider from one to the other of the two coupled positions, - a locking slider mounted to slide relative to the hub along said main axis between a position coupled to one of the idler gears and a position coupled to the other of the idler gears, and - elastic return means which are adapted to return the locking slider to a position coupled to the same idler gear as the selection slider.

[0013] In other words, at rest, the elastic return means maintain the selection slider and the locking slider at the same height along the main axis whereas, under stress, they allow a height shift of the selection slider relative to the locking slider.

[0014] According to the invention, the selection sliding lever therefore allows, thanks to the displacement member, to change a gear ratio when it is moved from one coupled position to another. For its part, the locking sliding lever allows each gear ratio to be locked. The elastic return means allow, during a gear ratio change, to allow the selection sliding lever to move to its position coupled to the new idler gear even if the locking sliding lever was hindered in its movement by this other idler gear (or vice versa). The kinematics of these different components will be detailed in the description of the figures.

[0015] It can be noted that, preferably, this architecture will allow the two sliding gears to be placed in a neutral position, between the two idler gears, so that they are not coupled to any of these idler gears.

[0016] This neutral position can be used in different ways. For example, it can be used to synchronize the angular speeds of the sliding gears with that of the idler gear to be engaged when changing gear. It can also be used, in a hybrid vehicle, to no longer drive the electric machine during phases where it is preferable for the vehicle's drive to be provided solely by the internal combustion engine.

[0017] Other advantageous and non-limiting characteristics of the coupling device according to the invention, taken individually or in all technically possible combinations, are the following: - each idler gear has at least one dog gear facing the other idler gear; - the selection slider and the locking slider comprise fingers adapted to engage the dogs of the idler gears so that, when the selection slider and the locking slider are in the coupled position with the same one of said idler gears, their fingers sandwich each dog of said idler gear; - the fingers of the selection sliding lever and of the locking sliding lever having a first end facing one of the idle gears and a second end facing the other of the idle gears, the distance measured along the main axis separating the two ends of each finger is strictly less than the distance separating the dogs of one of the idle gears from the dogs of the other of the idle gears; - a computer is provided which is programmed to control said member in three stable positions, including a first position in which the selection slider is in the position coupled to one of the idler gears, a second position in which the selection slider is coupled to the other of the idler gears, and a third intermediate position in which the selection slider is not coupled to either of the idler gears; - each idler gear has a number of dogs regularly distributed around the main axis which is greater than or equal to two; - the selection slider and the locking slider have an identical number of fingers regularly distributed around the main axis; - the angular space around the main axis delimited between two dogs is strictly greater than twice the angular space around the main axis occupied by a finger of the selection lever; - the hub has several hollow notches in its external face and distributed around the main axis, adapted to guide the sliding of the fingers of the selection slider and the locking slider; - the locking slider is located inside the selection slider, between two stops of the selection slider, and the elastic return means comprise elements interposed between each stop and the selection slider; - said elements are springs, preferably three or more pairs in number, each pair of springs comprising a compressed spring between one of the stops and the selection slider and a compressed spring between the other of the stops and the selection slider; - each idler gear has a ramp and the locking slider has at least two ramps respectively adapted to slide against the ramps of the first of the idler gears after the selection slider has been moved to the position coupled to this first idler gear.

[0018] The invention also proposes a speed reducer comprising a primary shaft which carries fixed gears and a coupling device as mentioned above, the idle gears of which mesh with said fixed gears.

[0019] The invention also provides a motor vehicle comprising an electric machine, a differential, drive wheels coupled to the differential and, between the electric machine and the differential, a speed reducer as mentioned above, one of the primary and main shafts of which is coupled to the electric machine and the other of the primary and main shafts of which is coupled to the differential.

[0020] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. DETAILED DESCRIPTION OF THE INVENTION

[0021] The description which follows with regard to the attached drawings, given for the purpose of non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0022] On the attached drawings:

[0023] [Fig. 1] is a schematic perspective view of a speed reducer comprising a shaft coupling device according to the invention;

[0024] [Fig. 2] is an exploded perspective schematic view of the dog clutch system of the coupling device of Figure 1;

[0025] [Fig. 3] is an exploded perspective schematic view of one of the idler gears and the selector slider of the coupling device of Figure 1;

[0026] [Fig. 4] is a schematic view showing from different angles the two idler gears and the dog clutch system of the coupling device of Figure 1;

[0027] [Fig. 5] is a schematic sectional view showing a dog clutch of a first idler gear, the dog clutch system and the second idler gear of the coupling device of Figure 1, seen from a first angle, when the first idler gear is engaged;

[0028] [Fig. 6] is a schematic sectional view showing the first idler gear, the dog clutch system and the second idler gear of the coupling device of Figure 1, in the neutral position when none of the idler gears are dog clutched;

[0029] [Fig. 7] is a schematic view showing the first idler gear, the dog clutch system and the dogs of the second idler gear of the coupling device of Figure 1, seen from a second angle, during a gear change;

[0030] [Fig. 8] is a schematic view similar to that of Figure 7, at the end of the gear change.

[0031] In the remainder of the description, the term "coupled" will be used to designate a connection between two elements which allows a torque to be transmitted from one to the other of these elements.

[0032] Figure 1 shows a 1-speed dual-ratio reducer with three stable positions, including two positions with gear engaged and one neutral position.

[0033] The term "stable position" means a position in which the speed reducer 1 can remain for a prolonged period (for example, more than one second), according to a control instruction imposed on it.

[0034] This speed reducer 1 is called dual-ratio in that it offers exactly two speed reduction ratios, which is perfect for use in a motor vehicle.

[0035] This speed reducer 1 is preferably intended to be installed in a motor vehicle, but it could be used in other fields (robotics, aviation, etc.).

[0036] The motor vehicle in which this reducer is installed will be considered includes: - an electric machine, hereinafter called an electric motor although it could be used as an alternator, - wheels, typically four in number and two of which are, for example, driven, and - a 30 differential which is placed between the two drive wheels.

[0037] The speed reducer 1 is then placed between the electric motor and the differential 30 in order to be able to transmit the engine torque to the wheels (or vice versa).

[0038] It has a casing (not shown) which houses various components.

[0039] As shown in Figure 1, this speed reducer 1 comprises two stages of shafts housed in the casing. It thus comprises a primary shaft 10 which is coupled to the shaft of the electric motor, and a main shaft 21 which is coupled to the differential 30 (the reverse would also be possible).

[0040] The primary shaft 10 is preferably directly coupled to the shaft of the electric motor. However, as a variant and for reasons detailed below, a torque limiter or a clutch could be interposed between these two shafts in order to facilitate gear changes.

[0041] The primary shaft 10 carries two fixed gears 12, 13, that is, two gears which always rotate at the same speed as that of the primary shaft. These two fixed gears 12, 13 have different diameters to provide distinct speed ratios.

[0042] The main shaft 21 extends along a main axis A1 parallel to the axis of the primary shaft 10. For this purpose, it is engaged at its two ends in bearings 29.

[0043] This main shaft 21 carries two idler gears 22, 23 which respectively mesh with the two fixed gears 12, 13. These gears are described as idler in the sense that they are mounted free to rotate on this shaft around the main axis A1 and that they are blocked in translation along this axis.

[0044] It can be seen in Figure 1 that this main shaft 21 also carries a fixed pinion meshed with a pinion of the differential 30.

[0045] To transmit the torque from the primary shaft 10 to the main shaft 21, a dog clutch system 50 of the idler gears 22, 23 is provided. This dog clutch system 50 makes it possible to couple one or other of the idler gears with the main shaft 21, depending on the gear ratio engaged. It also makes it possible, in the neutral position, to leave the idler gears free to rotate around the main shaft 21.

[0046] This dog clutch system 50, which is more specifically the subject of the present invention, comprises four main components illustrated in FIG. 2.

[0047] It thus comprises a hub 540 which is coupled to the main shaft 21, two so-called selection 520 and locking 530 sliders, and a selection member 510 making it possible to move the 520 selection player.

[0048] It should be noted here that the 520 selection slider is made of two assembled monobloc parts, while the other components are each made of a single piece. All these components are, for example, made of hardened steel.

[0049] It could be provided that the hub 540 comes from formation with the main shaft 21. However, here, the hub 540 is a part independent of the main shaft 21. It then has a central opening through which it is threaded onto this shaft, the edge of which has grooves or serrations engaged in reliefs provided in correspondence on the main shaft 21 in order to permanently couple this hub 540 to the main shaft 21.

[0050] The two selection 520 and locking 530 sliding gears are then mounted relative to the hub 540 so as to be movable in translation along the main axis A1 but locked in rotation around this axis. They thus make it possible to engage one or other of the idler gears 22, 23 so as to couple this idler gear to the main shaft 21.

[0051] As clearly shown in Figures 3 and 4, these idler gears 22, 23 each conventionally comprise a main disc 225, 235 which has a central opening, here bordered by a crown, for its mounting on the main shaft 21 and which is bordered externally by a toothing allowing its meshing with one of the fixed gears 12, 13. To allow its dog engagement, each idler gear 22, 23 comprises at least one dog 220, 230, that is to say a relief which here projects from one of the faces of the main disc 225, 235 (the one facing the other idler gear) and by which the idler gear can be driven in rotation.

[0052] There are provided here exactly three dogs 220, 230 on each idler gear 22, 23, which are regularly distributed around the main axis A1, at 120° from each other.

[0053] Here, each dog clutch 220, 230 extends over a restricted angular sector of approximately 30° and has a substantially prism shape, the base of which is located on the aforementioned face of the main disc 225, 235. Each dog clutch thus has four lateral faces and an end face facing the other idler gear.

[0054] The inner lateral face (located on the side of the main axis A1) is here curved around this axis, and the same is true of the outer lateral face. The other two lateral faces (hereinafter called radial faces) each extend at least partly in a radial plane (i.e. in a plane containing the main axis A1).

[0055] It is observed that the main face connects to most of the lateral faces by fillets. However, it connects to only one of the two radial faces by an inclined flat forming a ramp 231, the function of which will become clear below.

[0056] It will be noted here that the ramps 221, 231 of the three dogs 220, 230 of each idler gear 22, 23 are oriented in the same direction around the main axis A1, and that this direction is opposite to the direction in which the ramps of the dogs of the other idler gear are oriented.

[0057] It will also be noted that the ramps 221, 231 extend over only part of the thickness of the dogs 220, 230.

[0058] As shown in Figure 2, the selection slider 520 and the locking slider 530 both have annular shapes such that they can be nested inside each other (the selection slider 520 being located outside the locking slider 530).

[0059] The locking slider 530 thus comprises an annular body 533 whose internal diameter is adjusted to the external diameter of the hub 540 so that it can slide freely on the latter, parallel to the main axis A1.

[0060] In the same way, the selection slider 520 comprises an annular body 523 whose internal diameter is adjusted to the external diameter of the annular body 533 of the locking slider 530 so that it can slide freely on the latter, parallel to the main axis A1. It will be noted that the locking slider 530 then comprises a smooth cylindrical external face of revolution.

[0061] These two sliding gears are locked in rotation around the main axis A1 relative to the main shaft 21 by means 540.

[0062] For this, as shown in Figure 2, the hub 540 has a notched shape called a “tulip”. Thus, if it has a constant thickness along the main axis A1, the hub 540 has an outer face which is not cylindrical but which has several recesses, here identical, regularly distributed around the main axis A1. These recesses therefore form notches 541 by which the two sliding gears are blocked in rotation.

[0063] Each notch 541 is profiled in the sense that its cross-section (i.e. its section in a plane orthogonal to the main axis A1) is uniform along the main axis A1. This cross-section here has a U-shape, so that each notch has a flat bottom bordered by two flat lateral faces extending in radial planes. Six identical notches 541 are provided here.

[0064] The locking slider 530 comprises in correspondence at least one finger adapted to slide in one of the notches 541. In practice, it comprises exactly three which are regularly distributed around the main axis A1 and whose cross sections are uniform and have identical shapes, in negative, to those of the notches 541. These fingers 531 are fixed on the internal face of the annular body 533 of this slider. They thus have radial faces which slide against the radial faces of the notches 541 to block any rotational movement of this slider relative to the hub 540.

[0065] Similarly, the selection player 520 has at least one finger adapted to slide in one of the notches 541 delimited by the hub 540. In practice, it comprises exactly three which are regularly distributed around the main axis A1 and whose cross sections are uniform and have identical shapes, in negative, to those of the notches 541.

[0066] As shown in Figure 2, if the fingers 531 of the locking slider 530 are fixed on the internal face of the annular body 533 of this slider, the same is not true of the fingers 521 of the selection slider 520.

[0067] Here, as shown in Figure 3, the selection slider 520 has, at one end, a rim 527 projecting from its internal face which extends over at least part of its periphery. Here, this rim 527 is interrupted in three places by notches for passage of the fingers 531 of the locking slider 530.

[0068] As clearly shown in Figure 5 in section, the fingers 521 of the selection slider 520 extend at a distance from the internal face of the annular body 523 of this slider, which, it is recalled, slides along the external face of the annular body 533 of the other slider. In practice, these fingers 521 are connected to the annular body 523 by one of their ends only, via the rim 527.

[0069] Thus, as shown in this figure 5, the annular body 533 of the locking slider 530 can slide between the annular body 523 of the selection slider 520 and the fingers 521 of the latter.

[0070] The fingers 521 have radial faces which slide against the radial faces of the notches 541 to block any rotational movement of this slider relative to the hub 540.

[0071] If the position of the selection slider 520 along the main axis A1 is imposed by the selection member 510, the same is not true of that of the locking slider 530.

[0072] Elastic return means are then provided to return the latter to the same height as the selection slider 520 along the main axis A1, so that when these return means are at rest, the ends of the fingers 521, 531 of the two sliders extend to the same height, along the main axis A1.

[0073] As shown in Figure 2, these elastic return means are presented here in the form of three pairs of springs 550, 551 distributed at the level of the three fingers 521 of the selection slider 520.

[0074] As shown in Figure 5, each pair of springs includes a first spring 550 which is interposed between one side of the annular body 533 of the locking slider 530 and a stop formed by the selection slider 520, and a second spring 551 which is interposed between the other side of the annular body 533 of the locking slider 530 and another stop formed by the selection slider 520.

[0075] One of these stops is formed by the rim 527, which, as a reminder, connects the fingers 521 to the annular body 523 of the selection slider 520.

[0076] The other of these stops is here attached to the annular body 523 of the selection slider 520. As specified above, the selection slider 520 is in fact made in two separate and assembled single-piece parts, namely: - the assembly formed by the annular body 523 and the fingers 521, and - the other stop.

[0077] This other stop is here in the form of an annular flange 526, which is fixed rigidly and immobile on the assembly (for example by welding), after having put in place the springs 550, 551 and fitted the locking slider 530 into the selection slider 520.

[0078] This flange 526 has in practice a shape homologous to that of the rim 527.

[0079] It will be noted in Figure 5 that this flange 526 has notches so as not to form an obstacle to the passage of the fingers 531 of the locking slider 530.

[0080] The two sliding gears are therefore free to slide between the idler gears 22, 23, between two extreme positions, namely a position coupled to a first of the idler gears, and a position coupled to the other of the idler gears.

[0081] In the remainder of the description, the first idler gear 23 will designate, for example, the one allowing a first gear ratio to be established, while the second idler gear 22 will designate the one allowing a second gear ratio to be established.

[0082] As shown in Figure 5, in which only the dogs 230 of the first idler gear 23 have been shown, when a gear ratio is engaged (the first gear in this Figure 5), the two selection 520 and locking 530 sliding levers are in the coupled position.

[0083] In this position, the first ends of their fingers 521, 531 are positioned at the same height, on either side of each dog 230 of the corresponding idler gear 23, such that the radial faces of the dogs are in contact with the corresponding radial faces of the fingers 521, 531 of the sliding gears. Thus the hub 540 is locked in rotation relative to this idler gear 23.

[0084] It will be noted here that the contacting faces of the fingers and the dogs being radial (that is to say, they extend in planes that are substantially radial relative to the main axis A1), the transmission of torque can be done without difficulty. Of course, these different faces could alternatively not be exactly radial.

[0085] The first end of each finger 521, 531 (the one facing the first idler gear 23) extends at a distance from the second end of this finger which is less than the distance separating the end faces of the two dogs 220, 230, so that a single sliding gear cannot simultaneously engage the two idler gears 22, 23. In practice, this distance is substantially equal to the thickness of the hub 540 (along the main axis A1).

[0086] It is therefore necessary to move it to change gear.

[0087] The selection slider 520 is designed to be moved from one coupled position to the other by means of the selection member 510. As clearly shown in FIG. 2, this selection member 510 here comprises a single fork which is engaged in a groove 528 delimited by two peripheral ribs provided projecting from the external face of the selection slider 520.

[0088] Thus, by moving the selection member 510 along the main axis A1, it is possible to place the fingers 521 of the selection slider 520 in abutment against the dogs 220, 230 of one or other of the idler gears 22, 23 in order to change gear.

[0089] The locking slider 530 is not controlled. No fork is therefore associated with it. It is designed to move automatically and mechanically from a position coupled to any one of the idler gears to a position coupled to the other idler gear by virtue of the movement of the selection slider 520, thanks to the springs 550, 551.

[0090] To ensure that during a gear change, the ends of the fingers 521, 531 of the two sliding gears are positioned on either side of each dog 220, 230 of the corresponding idler gear 22, 23, it is first of all provided that these dogs are applied against the fingers of the selection sliding gear 520 before the locking sliding gear 530 is put in place. To this end, it is then necessary that the fingers 531 of the locking sliding gear 530 can be retracted from the passage of the dogs of the idler gear towards the fingers 521 of the selection sliding gear 520.

[0091] For this, as clearly shown in Figure 2, the end faces 534 of the fingers 531 of this locking slider 530 extend in planes which are not orthogonal to the axis of rotation A1 but which are inclined relative to it, in order to form slope ramps combined with the slopes of the ramps 221, 231 of the dogs.

[0092] Thus the end faces 534 of the fingers 531 extend parallel to the ramps 221, 231 of the dogs 220, 230 which face them.

[0093] The angle of inclination of a slope relative to a plane orthogonal to the main axis A1 is preferably between 5 and 45 degrees. Here it is 20 degrees.

[0094] The two end faces 534 of each finger 531 extend here in parallel planes.

[0095] It will be noted that the end faces of the fingers 521 of the selection slider 520 extend for their part in planes which are orthogonal to the main axis A1.

[0096] The speed reducer also includes an actuator for sliding the selection member 510 and a computer for controlling this actuator.

[0097] This calculator comprises for example a processor, a memory and various input and output interfaces. Thanks to its input interfaces, the calculator is adapted to receive data such as for example the rotation speed of the electric motor and the delivered torque. Thanks to its output interfaces, the calculator is adapted to control the actuator of the selection member 510. Thanks to its memory, the calculator stores a computer application, consisting of computer programs comprising instructions whose execution by the processor allows the implementation by the calculator of the method described below.

[0098] At this point, we can describe how the dog clutch of an idler gear is carried out.

[0099] As shown in Figure 5, we can start from the situation in which the first idler gear 23 is initially coupled to the main shaft 21 by means of the two sliding gears.

[0100] As explained, in this situation, the dogs 230 of the first idler gear 23 are sandwiched between the fingers 521, 531 of these two sliding gears. The faces of the fingers bearing against each dog are radial, so that this support guarantees good torque transmission.

[0101] In practice, when the first gear ratio is engaged, it is the locking slider 530 which transmits the torque to the main shaft 21 (when the torque is positive). Thus, the forces applied to the selection slider remain restricted, in particular during the acceleration phase just before engaging the second gear.

[0102] At this stage, the dogs 220 of the second idler gear 22 are left free since nothing hinders their freedom to pivot on the main shaft 21. Thus, this idler gear 22 rotates at a different speed than that of the first idler gear 23, due to the fact that these two idler gears are meshed in fixed gears 12, 13 of different diameters. In this case, this second idler gear 22 rotates faster than the first idler gear 23.

[0103] When the computer commands the change of a gear ratio (for example because the speed of the electric motor exceeds a predetermined threshold), the selection member 510 slides the selection slider 520 from its position coupled to the first idler gear 23 (figure 5) to an intermediate neutral position in which it is not coupled to any of the idler gears 22, 23 (figure 6).

[0104] By means of the springs 550, 551, the locking slider 530 is also driven to an intermediate neutral position, in which it is not coupled to any of the idler gears 22, 23. Due to the friction between its fingers 531 and the dogs of the first idler gear 23, this movement can be slower. This movement can be assisted by reducing the torque exerted by the electric motor.

[0105] At this stage, the fingers 521, 531 of the two sliding gears are at the same height and are therefore not pressing against any of the dogs 220, 230 of the idler gears.

[0106] The players are here preferably kept a few hundredths of a second. seconds in this neutral position by the computer, so as to be able to slow down the electric motor and therefore, as a result, the rotation speed of the second idler gear 22. The objective is that at the end of this step, the second gear still rotates faster than the selection slider 520 but that the speed difference between these two elements has decreased, for example by at least half.

[0107] To engage second gear, the computer controls the selection member 510 so that it continues its movement in order to slide the selection slider 520 from this intermediate neutral position to the position coupled to the second idler gear 22 (figure 7).

[0108] During this passage, the selection sliding gear 520 always rotates less quickly than the second idler gear 22. But thanks to the large angular spacing between two successive dogs 220, the second ends of its fingers 521 can slide into the space left between two dogs. The speed of movement of the selection member 510 is then sufficiently rapid for the dog engagement to take place quickly.

[0109] It is understood that this dog clutch is all the less brutal as the angular speed difference between the selection slider 520 and the second idler gear 2 is reduced. In any case, this dog clutch will impose a deceleration on the second idler gear 22 and therefore on the primary shaft 10.

[0110] In other words, when the dog clutch is engaged, the primary shaft 10 is slowed down by the second idler gear 22, the dogs 220 of which come to bear for this purpose against the fingers 521 of the selection sliding lever 520, the rotation speed of which is imposed by the forward speed of the motor vehicle.

[0111] During this sliding movement of the selection slider 520, the locking slider 530 is also driven towards the second idler gear 22 by the springs 550, 551. But, as clearly illustrated in Figure 7, when the second ends of the fingers 521 of the selection slider 520 slide between two dogs 220, it may happen that the second ends of the fingers 531 of the locking slider 530 strike the dogs 220 of the second idler gear 22 or even that they are placed between the dogs and the fingers 521 of the selection slider 520.

[0112] The combined ramps of the dogs and the second ends of the fingers 531 of the locking slider 530 then allow, in combination with the springs 550, 551, the locking slider 530 to move back towards its neutral position in order to allow the dogs to pass (see arrow F1 in figure 7) so that they come to bear against the fingers 521 of the selection slider 520.

[0113] As shown in Figure 8, once the dogs 220 have reached their final position, pressing against the fingers 521 of the selection slider 520, the springs 550, 551 allow the locking slider 530 to be automatically returned to the second idler gear 22, so that the lateral faces of its fingers 531 are applied against the dogs 220 of the second idler gear 22.

[0114] At this stage, when the second gear ratio is engaged, it is the selection sliding lever 520 which transmits the torque to the main shaft 21 (when the torque is positive). Thus, the forces applied to the locking sliding lever remain restricted.

[0115] It will be noted at this stage that the locking of an idler gear by two fingers located on either side of each dog clutch is useful in particular in the event of torque inversion, that is to say when the torque at the wheels becomes greater than the engine torque (for example in the regenerative braking phase where the engine takes on the role of alternator). In this situation, it is in fact the fingers 531 of the locking slider 530 which will be mainly constrained.

[0116] During a subsequent gear change, the kinematics will be substantially the same as those explained above, the only difference being that the primary shaft 10 will this time not be braked but accelerated, so that the orientation of the ramps will have to be reversed, as is clearly illustrated in the figures.

[0117] It should be noted here that when changing from first to second or vice versa, it is always the selection slider 520 which, controlled by the selection member 510, begins to slide before the locking slider 530. The latter then slides under the effect of the springs.

[0118] When changing gear from first to second or vice versa, it may happen that when the selection member 510 moves the selection slider 520, the fingers of the latter come into contact with the end faces of the dogs of the selected idler gear.

[0119] To avoid any breakage, different solutions are possible.

[0120] The first solution would be to control the gear change at the right time, that is to say when the dogs are angularly offset in relation to the fingers of the selection lever.

[0121] Another solution, adopted here, is shown in Figure 1. It can be seen that between the electromechanical actuator which moves the selection member 510 and this member, an elastic system 40 is provided.

[0122] In this case, the output of the actuator is here fixed to a U-shaped stirrup 41 whose two arch-shaped arms overlap a selection shaft 42 which is fixed to the fork forming the selection member 510. This selection shaft 42 has a central part of reduced section, at the level of which slides 43 are mounted movable in translation, between the two arms of the stirrup 41. These two slides 43 are kept at a distance from each other by a spring 44. Thus, when the actuator moves the stirrup 41 and the fork is locked in position (by the dogs on which the ends abut of the fingers of the selection lever 520), the spring compresses so that the caliper can continue to move.

[0123] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

[0124] Typically, in the embodiment described above, the gear change is carried out without synchronization, but it does require braking or accelerating the electric motor when the sliding levers are in the neutral position so that the shock at the time of dog engagement is as small as possible. Alternatively, it would be possible not to keep the two sliding levers in the neutral position, but to directly move the selection sliding lever from one coupled position to the other. In this variant, the shock resulting from dog engagement would be greater. Therefore, it would be preferable to place, between the electric motor and the speed reducer, a torque limiter or a controlled clutch.

[0125] Conversely, changing gear could be carried out with synchronization, so that when the selection sliding lever engages between the dogs of the idler gear to be engaged, it is guaranteed that the fingers of this sliding lever are positioned correctly against the dogs.

[0126] In another embodiment, the electric motor and the speed reducer described above could be installed in a hybrid vehicle, also comprising an internal combustion engine. In this mode, the neutral position provided by the speed reducer could be used to decouple the electric motor from the internal combustion engine, when it is desired that the vehicle be propelled solely by the internal combustion engine.

Claims

DEMANDS

1. Shaft coupling device (20), comprising a main shaft (21) oriented about a main axis (A1), two idler gears (22, 23) mounted freely to rotate on the main shaft (21) about the main axis (A1), and a coupling system (50) interposed between the two idler gears (22, 23), characterized in that the coupling system (50) comprises: - a hub (540) fixed in rotation to the main shaft (21), - a selection slider (520) mounted to slide relative to the hub (540) along said main axis (A1) between a position coupled to one of the idler gears (22, 23) and a position coupled to the other of the idler gears (22, 23), - a moving element (510) for the selection slider (520) from one of the two coupled positions to the other, - a locking slider (530) mounted to slide relative to the hub (540) along said main axis (A1) between a position coupled to one of the idler gears (22, 23) and a position coupled to the other of the idler gears (22, 23), and - elastic return means (550, 551) which are adapted to return the locking slider (530) into a position coupled to the same idler pinion (22, 23) as the selection slider (520).

2. Coupling device (20) according to claim 1, in which each idler gear (22, 23) has at least one dog (220, 230) facing the other idler gear (22, 23), and in which the selection slider (520) and the locking slider (530) have fingers (521, 531) adapted to engage the dogs (220, 230) of the idler gears (22, 23) so that, when the selection slider (520) and the locking slider (530) are in the coupled position with the same of said idler gears (22, 23), their fingers (521, 531) sandwich each dog (220, 230) of said idler gear (22, 23).

3. Coupling device (20) according to claim 2, wherein the fingers (521, 531) of the selection slider (520) and the locking slider (530) have a first end turned towards one of the idler gears (22, 23) and a second end turned towards the other of the idler gears (22, 23), the distance measured along the main axis (A1) separating the two ends of each finger (521, 531) is strictly less than the distance separating the dogs (220, 230) of one of the idler gears (22, 23) from the dogs (220, 230) of the other of the idler gears (22, 23).

4. Coupling device (20) according to claim 3, wherein it is provided a computer which is programmed to control said organ (510) in three stable positions, including a first position in which the selection slider (520) is in position coupled to one of the idler gears (22, 23), a second position in which the selection slider (520) is coupled to the other of the idler gears (22, 23), and a third intermediate position in which the selection slider (520) is not coupled to any of the idler gears (22, 23).

5. Coupling device (20) according to any one of claims 2 to 4, wherein: - each idler gear (22, 23) has a number of dogs (220, 230) regularly distributed around the main axis (A1) which is greater than or equal to two, - the selection slider (520) and the locking slider (530) have an identical number of fingers evenly distributed around the main axis (A1), and - the angular space around the main axis (A1) delimited between two dog teeth (220, 230) is strictly greater than twice the angular space around the main axis (A1) occupied by a finger (521) of the selection slider (520).

6. Coupling device (20) according to any one of claims 2 to 5, wherein the hub (540) has several recessed notches in its outer face distributed around the main axis (A1), adapted to guide the sliding of the fingers (521, 531) of the selection slider (520) and the locking slider (530).

7. Coupling device (20) according to any one of claims 1 to 6, wherein the locking slider (530) is located inside the selection slider (520), between two stops of the selection slider (520), and the elastic return means (550, 551) comprise elements interposed between each stop and the selection slider (520).

8. Coupling device (20) according to claim 7, wherein said elements are springs, preferably in the number of three or more pairs, each pair of springs comprising a spring compressed between one of the stops and the selection slider (520) and a spring compressed between the other of the stops and the selection slider (520).

9. Coupling device (20) according to any one of claims 1 to 8, wherein each idler gear (22, 23) has a ramp (221, 231) and the locking slider (530) has at least two ramps (531) respectively adapted to slide against the ramps (221, 231) of one of the first idler gears (22, 23) after the selection slider (520) has been moved to the position coupled to this first idler gear (22, 23).

10. A speed reducer (1) comprising a primary shaft (10) carrying fixed gears (12, 13), characterized in that it further comprises a coupling device (20) according to any one of claims 1 to 9, the free-running gears (22, 23) of which mesh with said fixed gears (12, 13).

11. A motor vehicle comprising an electric machine, a differential (30), and drive wheels coupled to the differential (30), characterized in that it further comprises, between the electric machine and the differential (30), a speed reducer (1) according to claim 10, one of whose primary (10) and main (21) shafts is coupled to the electric machine and the other of whose primary (10) and main (21) shafts is coupled to the differential (30).

Images