EP0995056A1

EP0995056A1 - Synchronised gearbox

Info

Publication number: EP0995056A1
Application number: EP99918021A
Authority: EP
Inventors: Gonzalo-Antoine Hennequet; Jean-Michel Lamy
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 1998-05-05
Filing date: 1999-04-30
Publication date: 2000-04-26
Also published as: WO1999057459A1; US6289757B1; KR20010021702A; FR2778443B1; FR2778443A1

Abstract

The invention concerns a motor vehicle gearbox (10), comprising at least two parallel primary (14) and secondary (16) shafts, respectively connected in rotation to an engine and, through a main transmission (20), to a wheel (18), and wherein the primary shaft bears a first idler (22) geared to a second stationary pinion (24) borne by the secondary shaft, which first idler (22) is capable of being jaw clutched on the primary shaft for transmitting engine power to the wheel (18). The invention is characterised in that it comprises self-disengaging controlled means (28) for accelerating or braking selectively the primary shaft (14) which bears the idler (22) so as to synchronise them before linking them in rotation, self-disengaging acceleration means for accelerating the primary shaft (14) as long as its speed is less than that of the idler (22), and self-disengaging braking means for braking the primary shaft (14) as long as its speed is greater then that of the idler (22).

Description

1

"Synchronized gearbox"

The invention relates to a motor vehicle gearbox.

The invention relates more particularly to a gearbox for a motor vehicle, of the type which comprises at least two primary and secondary parallel shafts, respectively connected in rotation to a vehicle engine and, via a transmission, to at least a vehicle wheel, and of the type in which one of the shafts carries at least one first idler gear meshing with a second fixed gear carried by the other shaft, which first gear is capable of being linked in rotation to the shaft which door to transmit the motive power from the engine to the vehicle wheel.

Numerous gearboxes are known which allow the establishment of various gear ratios by clutching idler gears on their shafts.

In the case, for example, of a gearbox with two parallel shafts, when a user commands, by means of a gearbox command, the change from a first gear ratio to a second gear ratio, the first idler gear corresponding to the first gear is "clutched" from the first shaft that carries it before the second idler gear corresponding to the second gear is in turn clutched to the first shaft. The operation being very fast, it turns out that the first shaft continues to rotate at a speed close to that which it had when the first idler gear was clutched on it. The second idler gear, for its part driven by a second fixed gear of the other shaft with which it meshes, rotates at a speed substantially different from that of the first shaft due to a different gear ratio. 2

To be able to be clutched to the first shaft, the second idler gear must first be brought to a speed of rotation substantially equal to that of the first shaft. This is the role conventionally assigned to devices called synchronizers.

Each idler gear is coupled to an axially disengageable device, generally controlled by a movable ring axially controlled by the movement, parallel to the shaft carrying the idler gear, of a control fork.

The device allows, once engaged, to achieve a rotation connection of the idler gear to its shaft by friction so as to gradually bring it to an adequate speed of rotation, but without being able to transmit significant torque .

The device then makes it possible, in a second step, (the pinion and the shaft rotating at the same speed) to make the connection of the idler pinion to the shaft, for example by means of a gear coupling, thus establishing a relationship gearbox reduction.

Such a device is advantageous insofar as it makes it possible to facilitate the interconnection of idler pinions on their shafts. Indeed, the majority of dog clutch devices comprising toothed couplings, it is important that the idler gears are synchronized beforehand with their shaft (s) before being clutched, in order to limit the wear of the teeth and guarantee silent operation of the dog clutch device.

On the other hand, devices comprising synchronizers have the drawback of using a idler synchronizer, which considerably increases the axial size of the gearbox and its weight. 3

In addition, in the case of a so-called robotic gearbox, that is to say a gearbox whose different members are moved by piloted actuators, these actuators being controlled by control electronics on which the driver of the vehicle, the use of synchronizers is particularly difficult. Indeed, compared to a conventional control by selection fingers and rchettes rches, the control of synchronizers by actuators rs is particularly inappropriate, the actuators having a large footprint.

To remedy these drawbacks, the solution according to the invention consists, no longer in bringing the pig not to be clutched at a speed close to that of the shaft on which it must be clutched, but on the contrary in bringing the shaft on which it must be clutched at a speed close to that of the pinion to be clutched.

To this end, the invention provides a gearbox of the type described above, characterized in that it includes controlled disengageable means making it possible to selectively accelerate or brake the primary shaft in order to synchronize the speed of the idler gear with that of the shaft which carries it before linking it in rotation to said shaft, and being capable of accelerating the primary shaft as long as its speed is lower than that of the idler gear, and of braking the primary shaft as long as its speed is greater than that of the non-crazy pig. According to other characteristics of the invention:

- the disengageable means for accelerating the primary shaft comprise means for temporary connection in rotation with sliding from the primary shaft to the secondary shaft;

the means for rotationally connecting the primary shaft to the secondary shaft comprise a first toothed wheel, 4

coaxial with the primary shaft, which meshes with a second toothed wheel carried by the secondary shaft and linked in rotation to the latter, and which is capable of being temporarily linked in rotation to the primary shaft by means of d 'an accelerating coupling device with slip;

- The disengageable controlled braking means of the primary shaft comprise means for temporary connection in rotation with sliding of the primary shaft to the casing of the gearbox; the means for rotationally connecting the primary shaft to the gearbox casing have a fixed frustoconical bearing surface of the gearbox casing, coaxial with the primary shaft, to which the primary shaft is capable of being temporarily linked via a slip brake coupling device;

- the acceleration coupling devices and braking coupling with sliding comprise a common contact wheel, which is linked in rotation to the primary shaft by splines, which comprises two opposite annular frustoconical bearing, and which is capable of being controlled to slide along the primary shaft towards a first extreme active axial position in which a first annular frustoconical bearing cooperates by friction with an annular frustoconical bearing complementary to said first toothed wheel, to accelerate the shaft primary, or towards a second opposite extreme active axial position in which a second annular frustoconical bearing cooperates by friction with the fixed, annular and complementary frustoconical bearing of the gearbox housing, to brake the primary shaft, 5

passing through an indexed intermediate axial position of rest;

- the annular bearings are truncated;

- The annular frustoconical surfaces are flat, and the contact wheel is a disc of a clutch covered with a material of a friction lining; the acceleration coupling devices and braking coupling with sliding comprise an electromagnetic clutch, including two radial cages coaxial with the primary shaft, which are carried respectively by the first toothed wheel and by the fixed truncated bearing of the gearbox housing, are capable of cooperating selectively with sliding with two ends of a rotor in two parts secured to the primary shaft to respectively accelerate or brake the primary shaft when a magnetic flux is established between a rotor part and clutch cage;

- the electromagnetic clutch is a metal powder clutch; the gearbox comprises a motor pump, of which a fixed casing carrying axial pistons is integral with the casing of the gearbox, of which a control plate is linked in rotation to the primary shaft of the gearbox, and which is capable of operating selectively by hydraulic motor or hydraulic pump to respectively accelerate or brake the primary shaft;

- The gearbox is a robotic gearbox which includes automated control means acting on the disengageable means of acceleration and braking of the primary shaft, and automated means of clutching idler gears on the shafts which carry them . 6

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: - Figure 1 is a schematic sectional view through a long median plane itudinal passing through the axes of the two shafts of a gearbox produced according to the invention, comprising a non-idler non-clutched pig and a contact wheel coupling device represented according to a rest mode; - Figure 2 is a view similar to Figure 1, the coupling device being shown in an active mode of acceleration of the primary shaft;

- Figure 3 is a view similar to Figure 1, the coupling device being shown in an active mode of braking of the primary shaft;

- Figure 4 is a view similar to Figure 1, the idler gear being clutched and the coupling device being shown in an inactive mode;

- Figure 5 is a schematic sectional view through a longitudinal median plane of a gearbox produced according to a variant of the invention and comprising a coupling device by friction clutch; and

- Figure 6 is a schematic sectional view through a longitudinal median plane of a gearbox produced according to another variant of the invention and comprising a coupling device by electromagnetic clutch.

Throughout the description, identical reference numerals denote identical or similar elements.

In known manner, a gearbox 1 0 comprises a casing 12 which rotatably carries two parallel longitudinal primary 14 and secondary 16 shafts 16. The primary shaft 14 receives motive power from a motor (not shown) of the 7

vehicle, while the secondary shaft 16 is capable of transmitting the driving power to at least one wheel 18 of the vehicle via a transmission 20. A non-crazy pig 22, carried by the primary shaft 14, is capable to be clutched to a fixed pinion 24 of the secondary shaft to transmit the motive power of the primary shaft 14 to the secondary shaft 16. The gearbox casing 12 has an end 26 of the casing which comprises controlled disengageable means 28 acceleration or braking of the primary shaft 14.

According to a first embodiment, the controlled disengageable means 28 comprise a toothed wheel 40, integral in rotation with one end of the secondary shaft 16, which meshes with a toothed wheel 42 carried in rotation by the end 26 of the casing. box 12, and which is coaxial with the primary shaft 14. The meshing of the toothed wheels 40 and 42 is permanent, so that the toothed wheel 42 is indirectly driven in rotation by the wheel 1 8 of the vehicle.

The controlled disengageable means 28 also comprise a coupling device 30 of which a contact wheel 32, comprising a hub 50, is linked in rotation to the primary shaft by splines 34. The contact wheel 32 can be controlled sliding along the primary shaft, and comprises on two opposite faces a first annular frustoconical bearing 36 and a second annular frustoconical bearing 38. An axial sliding gear 38 cooperating with a hub 50 of the contact wheel 36 makes it possible to control its movements in axial sliding along the grooves 34 of the primary shaft 14. Furthermore, the coupling device 30 has a fixed annular frustoconical bearing 44, carried by the end of the gearbox 26 and coaxial with the primary shaft 14 who the 8

crosses. The annular frustoconical bearing 44 is arranged opposite the first annular frustoconical bearing 36 of the contact wheel 32.

In addition, the coupling device 30 comprises, opposite the second annular frustoconical bearing 38 of the contact wheel 32, an annular frustoconical bearing 46 carried by the toothed wheel 42, and therefore coaxial with the primary shaft 14.

In this way, the contact wheel 32 of the coupling device is, in an intermediate rest position shown in FIG. 1, arranged axially between the annular frustoconical bearing surfaces 44 of the end 26 of the gearbox housing and 46 of the toothed wheel 42, without contact with the latter. Indeed, the gearbox 1 0 shown in the figure

1 is in a neutral position in which the idler gear 22 of the primary shaft 14 is not clutched with the fixed gear 24 of the secondary shaft 16. This configuration corresponds to a state in which the vehicle is at stop or is in an intermediate state in which another idler gear (not shown), carried by the primary shaft 14, is clutched on the primary shaft and in which the non-idler pig 22 will for example be clutched later on the 'primary shaft 14 to initiate another gear ratio. In this state, the contact wheel 32 occupies an intermediate position along the grooves 34 in which it does not cooperate with any of the elements of the coupling device 30. The toothed wheel 42 is then driven at a speed proportional to that of the wheel 18 due to its engagement with the toothed wheel 40 of the secondary shaft and of the transmission 20. 9

The view of FIG. 2 illustrates a state in which the secondary shaft 16 rotates at a speed substantially higher than the primary shaft 14. In this state, the driver of the vehicle has declutched the idler gear (not shown) previously mentioned, disengaged, and commanded the engagement of the gear ratio corresponding to the idler gear 22. The primary shaft 14 slows down, while the secondary shaft is driven by the wheel 18 of the vehicle.

In this case, to effect the interconnection of the non-crazy pig 22 on the primary shaft 14 and cause it to mesh, by longitudinal sliding of its hub 50 along the shaft 14, with the fixed pinion 24 of the shaft secondary 16, it is necessary to bring it beforehand to a sufficiently high speed of rotation so that the teeth 52 of the idler gear 22 and 54 of the fixed gear 24 can cooperate without noise.

To do this, the controlled walkman 48 first moves the hub 50 of the contact wheel 32 to the left, so that its annular frustoconical bearing 38 cooperates by friction with the annular frustoconical bearing 46 of the toothed wheel 42. From this way, the contact wheel 32 is rotated with sliding by the toothed wheel 42 whose speed is linked to that of the secondary shaft 16. The contact wheel 32 then drives, via the grooves 34, the primary shaft 14 and gradually brings it to a sufficient speed of rotation to allow the idler pinion 22 to engage on the shaft 14 to mesh with the fixed pinion 24 of the secondary shaft 16, as will be seen later with reference to the fig ure 4. The configuration described with reference to FIG. 3 illustrates the case in which the primary shaft 14 rotates at a speed substantially higher than the secondary shaft 16. 10

To make the idler pinion 22 interconnect and allow the idler pinion 22 to gear with the fixed pinion 24, it is necessary to brake the primary shaft 14. This operation is carried out by axially moving the sliding gear 48 to the right so that q ue the frustoconical annular bearing 36 of the contact wheel 32 cooperates by friction and sliding with the annular frustoconical bearing fixed 44 of the gearbox housing end 26. In this way, a braking torque is applied to the hub 50 of the contact wheel 32 and gradually brakes the primary shaft 14, thus allowing the pinion 22 to clutch together and its engagement with the fixed pinion 24, as described with reference to FIG. 4.

FIG. 4 illustrates the last phase of interconnection of the idler gear 22 on the primary shaft 14 so as to mesh with the fixed gear 24 of the secondary shaft 16.

In this configuration, the primary shaft 14 has been brought to an adequate speed of rotation by means of the coupling device 30. The sliding gear 48 of the coupling device 30 is then controlled so that the contact wheel 32 occupies again, as described with reference to FIG. 1, an intermediate rest position between the annular frustoconical bearing surfaces 46 of the toothed wheel 42 and the fixed frustoconical bearing surface 44 of the end 26 of the gearbox casing.

The primary shaft then rotates, by its inertia, at an adequate speed, and a device (not shown) moves the idler pinion axially to the left so that it is made to rotate with the primary shaft 14 and that its teeth 52 mesh with the teeth 54 of the fixed pinion of the secondary shaft 16, thus allowing the transmission of the driving power coming from the engine (not shown) to the secondary shaft 16 to drive the vehicle. 1 1

This embodiment is particularly advantageous because it allows simple synchronization of the primary shaft 14 with the secondary shaft 16 to be achieved.

Thus, a single device 28, located for example at the end of the gearbox 12, or in another location of the gearbox 12, allows synchronization of all the crazy pig nons of the gearbox. Indeed, such a device is applicable, both to the idler gear 22 of the primary shaft 14 (as it has been described) than to idler gears which would be carried by the secondary shaft, since the nature of the operation carried out by the device 28 is a speed synchronization, to the gear ratio chosen close, of the primary and secondary shafts.

In addition, the device 28 makes it possible to significantly influence the compactness and the weight of the gearbox, since the conventional synchronizer devices associated with each idler gear become superfluous. A single device 28 in fact governs all of the synchronization operations of the gearbox, by means of an appropriate control logic which adequately controls the movements of the contact wheel 32 by means of the wander 48. .

FIG. 5 illustrates an alternative embodiment of the invention. In this embodiment, the operating principle of the controlled disengageable means 28 is similar to that described with reference to Figures 1 to 4, but the cooperating surfaces are significantly different. The coupling device 30 here consists of a friction clutch, the contact wheel 32 consisting of a clutch disc covered on its two faces with friction lining, the planar annular surfaces 44 of the end of 12

casing 26 and 46 of the toothed wheel 42 being plates, made for example of rectified steel.

In fact, the contact wheel 32 has two flat annular bearings 38 and 36 intended to cooperate with the complementary planar annular bearings 44 and 46. No such design has a favorable effect on manufacturing costs since it makes it possible to dispense with the production frustoconical surfaces whose machining is generally expensive. As a variant (not shown), the clutch formed by the coupling device 30 can advantageously consist of an electromagnetic clutch in which the contact wheel 32 constitutes a rotor, and in which the toothed wheel 42 and the end of gearbox housing 26 each have a cage coaxial with the primary shaft 14, these cages being capable of being traversed by an electromagnetic flux which drives the rotor formed by the wheel 32.

In addition, the electromagnetic clutch considered can be an electromagnetic powder clutch, the electric power consumed by such a device then being much lower than that consumed by a conventional electromagnetic clutch. Such a device has the advantage of being able to be controlled in a simple manner by a control logic which ensures the synchronization of the primary shaft 14 to the secondary shaft 16.

Fig ure 6 illustrates a last embodiment of the invention in which the disengageable means 28 controlled comprise a motor pump 56 which is arranged at the end 26 of the gearbox casing, and which is linked in rotation to the primary shaft 14 In this configuration, the disengageable means 28 do not receive energy from the secondary shaft 16 but from the motor, which supplies, for example, a hydraulic compressor. 13

The motor pump 56 includes, for example, axial pistons (not shown) and can operate selectively as a hydraulic motor to accelerate the primary shaft 14, or as a hydraulic pump to brake the primary shaft 14. This variant is particularly advantageous because it makes it possible to produce synchronization of the primary shaft 14 to the secondary shaft 16 by hydraulic means, the power of which is supplied, for example, by a hydraulic compressor supplied by the engine of the vehicle. Thus, such disengageable means can be controlled by an extremely simplified control logic involving very few electronic components. These disengageable means are particularly suitable for an automatic robotic gearbox in which the control hydraulics generally occupies a predominant place.

Claims

14R EVEN DICATIONS

1. Gearbox (1 0) for a motor vehicle, of the type which comprises at least two primary (14) and secondary (16) parallel shafts, respectively linked in rotation to a vehicle engine and, via a transmission (20), at least one wheel (1 8) of the vehicle, and of the type in which one of the shafts carries at least one first non-idler pig (22) meshing with a second fixed pinion (24) carried by the other shaft , which first idler gear (22) is capable of being linked in rotation to the shaft which carries it to transmit the motive power of the engine to the wheel (1 8) of the vehicle, characterized in that, in order to synchronize the speed of the primary shaft (14) with that of the idler gear (22) before linking them in rotation, it comprises controlled disengageable means (28) consisting of a single device, carried by the primary shaft (14), which selectively accelerates the primary shaft (14) which carries the idler gear (22), as long as its speed is lower than that of the idler gear (22), using disengageable acceleration means comprising means for temporary connection in rotation with sliding of the primary shaft (14) to the secondary shaft (16), or brake the primary shaft (14) which carries the idler gear (22), as long as its speed is higher than that of the idler gear (22). using disengageable braking means comprising means for temporary connection in rotation with sliding of the primary shaft (14) to the gearbox casing (12).

2. Gearbox (1 0) according to the preceding claim, characterized in that the means for temporary connection in rotation of the primary shaft (14) to the secondary shaft (16) comprise a first toothed wheel (42), 15

coaxial with the primary shaft (14), which meshes with a second toothed wheel (40) carried by the secondary shaft (16) and linked in rotation to the latter, and which is capable of being temporarily linked in rotation to the primary shaft (14) by means of a coupling device (30) for acceleration with sliding.

3. Gearbox (10) according to any one of the preceding claims, characterized in that the means for rotationally connecting the primary shaft (14) to the gearbox housing (12) have an annular bearing ( 44) fixed to the casing (12) of the gearbox (1 0), coaxial with the primary shaft (14), to which the primary shaft (14) is capable of being temporarily linked by means of a braking coupling device (30) with sliding.

4. Gearbox (10) according to sells ications 2 and 3 taken in combination, characterized in that the coupling devices (30) for acceleration and braking coupling with sliding comprise a contact wheel (32) common, which is linked in rotation to the primary shaft (14) by grooves (50), which has two opposite annular bearings (36, 38), and which is capable of being controlled by sliding along the primary shaft (14) towards a first extreme active axial position in which a first annular bearing (38) cooperates by friction with an annular bearing (46) complementary to said first toothed wheel (42), to accelerate the primary shaft ( 14), or towards a second opposite extreme active axial position in which a second annular bearing (36) cooperates by friction with the fixed (44), annular and complementary bearing, of the casing (12) of the gearbox (1 0 ), to brake the primary shaft (14), 16

passing through an indexed intermediate axial position of rest.

5. Gearbox (10) according to claim 4, characterized in that the annular bearing surfaces (36, 38, 44, 46) are frustoconical.

6. Gearbox according to claim 4, characterized in that the annular bearings (36, 38, 44, 46) are planar, and in that the contact wheel (32) is a disc of a clutch covered with a material of a friction lining.

7. Gearbox according to resells ications 1 to 3, characterized in that the acceleration coupling devices and braking coupling with sliding comprise an electromagnetic clutch, including two radial cages coaxial with the primary shaft (14 ), which are carried respectively by the first toothed wheel (42) and by the fixed bearing (44) of the casing (12) of the gearbox (1 0), are capable of cooperating selectively with sliding with two ends of the wheel (32), forming a two-part rotor which is integral with the primary shaft (14) for respectively accelerating or braking the primary shaft (14) when a magnetic flux is established between a part of the wheel ( 32) forming a rotor and a clutch cage.

8. Gearbox (1 0) according to claim 7, characterized in that the electromagnetic clutch is a metal powder clutch.

9. Gearbox according to one of the preceding claims, characterized in that the gearbox (1 0) is a robotic gearbox which comprises automated control means acting on the disengageable means of acceleration and braking the shaft 17

primary (14), and automated means for interconnecting the idler gears (22).