FR2918433A1 - Transmission component for e.g. automobile, has hydraulic control system for controlling inclination of pivoting axis of each roller to control distribution of engine torques transmitted to disks - Google Patents

Abstract

The component has a case (6) rotatingly driven by an inlet crankshaft (1) for driving right and left coaxial transmission axle shafts (2d, 2g). Right and left coaxial disks turns with respect to the case. The disks are rigidly connected to the transmission axle shafts, respectively. Upper and lower rollers (5a, 5b) are pivoted between toroidal concave surfaces of the disks while being driven by the surfaces. A hydraulic control system (12) controls the inclination of a pivoting axis of each of the rollers to control the distribution of engine torques transmitted to the disks.

Description

TRANSMISSION DEVICE FOR INTERPOSING BETWEEN A MOTOR SHAFT AND

  TWO HALF-SHAFTS AND FOR CONTINUOUSLY PILOTING THE DISTRIBUTION OF THE TORQUE TRANSMITTED TO THE HALF-TREES.

  The present invention relates to a transmission member for a vehicle, in particular for a motor vehicle, which transmits the rotational movement of a driving shaft, such as the gearbox output shaft, to two coaxial half-shafts such as two half-shafts. two-wheel drive shafts of the vehicle. This transmission member may be implanted as a differential by being interposed between the two-half drive shafts of two opposite drive wheels, such as the front wheels or rear wheels. It can also be integrated into the all-wheel drive of a four-wheel drive vehicle, being interposed between a drive shaft to the front wheels and a drive shaft to the rear wheels.

  When interposed between two opposite drive wheels of a vehicle, a differential allows these wheels to be driven by the same motor shaft while rotating at different speeds, which is necessary especially in bends.

  However, if one of the wheels loses grip on the ground, the torque transmitted by this wheel drops and can become almost zero. The torque transmitted to the ground by the opposite wheel via a free differential, being necessarily equal, it falls in the same proportions.

  The sum of the torque transmitted to the ground then becomes zero or almost: the vehicle lacks motor skills. This can be solved by using a self-locking or limited-slip differential, equipped with preloading friction discs, or a torque-sensitive Torque Sensing differential, or a viscose-type viscous coupling member. speed. The objective in all cases is to postpone a portion of the engine torque to the wheel that turns the fastest and therefore the one that has more grip so that the vehicle regains traction.

  Anyway, the distribution of the engine torque between the two wheels and the possible transfer torque allowed by a self-locking system are fixed by construction in the differential. However the control of the torque applied to each wheel makes it possible to improve the efficiency of the transmission by making the most of the potential of adhesion of each wheel, in any situation. This also makes it possible to act on the behavior of the vehicle: by increasing the torque applied to one of the wheels, the vehicle is subjected to a so-called yaw moment, that is to say at a moment around an axis vertical. This is called the torque vectoring effect. This allows for example to improve cornering agility. This mode of action is already present on models such as Honda Legend and Mitsubishi Lancer Evo and has proven its effectiveness, but these systems use a series of gear trains and clutches that make them bulky, complex and expensive to enforce.

  The invention provides a simple solution for driving two shafts from the same motor shaft, being able to control the distribution of torque applied to each driven shaft. For this purpose, the invention relates to a transmission member intended to be interposed between a drive shaft and two transmission half-shafts, this member comprising a housing intended to be rotated by the drive shaft to drive the two half-shafts, characterized in that the casing carries semi-toroidal transmission elements including: - a right disk and a coaxial left disk and rotatable relative to the housing, the right disk being rigidly secured to the right half-shaft and the left disk being rigidly secured to the left half-shaft, these disks having toroidal concave surfaces facing each other, - at least one upper roller and one lower roller arranged to be pivotable between the toroidal concave surfaces of the disks being driven by these surfaces, - a control system for controlling the inclination of the pivot axis of each roller in order to control the distribution of c ouples transmitted respectively to the right disk and the left disk. Preferably, the control system is a hydraulically controlled system.

  Advantageously, the respective disks and rollers are always separated by a thin film of oil, for example of a thickness between 0.05 and 0.4 μm, the transmission of the torque being done by shearing this film of oil having a high viscosity.

  Each roller can be held on a roller door connected to the control system. The rollers can be rotatably mounted on needle bearings. The invention also relates to a motor vehicle 25 equipped with such a transmission member. The invention also relates to a motor vehicle equipped with such a transmission member and an electronic control system of the anti-lock type (ABS), anti-electronic slip (ASR), programmed electro-stabilizer (ESP) associated with this transmission organ.

  The invention will now be described in more detail but in a nonlimiting manner, with reference to the single appended figure, in which is shown a sectional view of the transmission member according to the invention.

  The transmission member according to the invention can be implanted as a differential by being interposed between a drive shaft and the two-half drive shafts of the front wheels or rear wheels. It can also be integrated in the transmission of a four-wheel drive vehicle, being interposed between a motor shaft and a transmission shaft to the front wheels and a transmission shaft to the rear wheels. The figure shows the transmission member according to the invention and its interposition in the torque transmission to the right and left rear half drive shafts, in the case for example of a propulsion vehicle or four-wheel drive. The engine torque is transmitted to the transmission member by an input shaft 1 connected via a pinion gear 3a meshing in a ring 3b rigidly secured to the housing 6 of the transmission member. The transmission housing 6 and its crown 3b are inserted between the 2 transmission half-shafts left 2g and right 2d. This transmission unit is based on the technology of toroidal drives. Reference is made to US-A-6,053,841 for a detailed description of the operation of such a drive. The housing 6 of the transmission member is connected to the motor shaft 1 to be rotated by it. This housing 6 carries at least one upper roller 5a and a lower roller 5b interposed respectively between two right disks 4d and 4g left coaxial forming between them a cavity having the general shape of a torus. The right 4d and left 4g discs are rigidly secured to the right and left 2d left drive shaft, respectively. Each roller 5a and 5b has two degrees of freedom: a possibility of rotation about its axis of rotation which coincides with its axis of revolution, and a possibility of inclination by turning in the sectional plane of the figure. The inclination of the rollers is adjusted by rotating them about an axis marked by 7a for the roller 5a and 7b for the roller 5b, the axes 7a and 7b being normal to the plane of the figure. Each roller has its axis of rotation and its axis of inclination which are concurrent. The intersection of these two axes is carried by the base circle, coaxial with the half-shafts, of a torus with circular section which defines a surface coinciding with the toroidal faces of each disk. The motor torque of the housing 6 is transmitted by means of the rollers 5a and 5b respectively to the right disks 4d 15 and left 4g. The inclination of the rollers 5a, 5b around the axes 7a and 7b is controlled by a hydraulic control system 12. The upper roller 5a is carried by a rod 8a 20 which it is rigidly secured and extending along its pivot axis. This rod 8a is able to pivot on itself and to rotate about the axis 7a to modify the inclination of the roller. This rod 8a has a free spherical end 9a sandwiched between two thrust bearings 10a and 10b carried by a circular rail 10c integral with a carriage 11a, or piston, which is movable in translation parallel to the axis of rotation of the half trees 2g and 2d. The rail 10c is a U-section ring, the two ball bearings being carried respectively by one and the other of the inner flanks of this U-section ring. The free end 9 of the rod 8a passes through a opening in the housing 6 to allow its movement. The piston 11a is carried by a guide structure 12a integral with the deck housing, and which is connected to the hydraulic control system identified by the pipe 12a and in which is engaged an end of the piston 11a. When this pipe 12a is pressurized by the hydraulic control system, the end of the piston 11a is itself subjected to a pressure, which displaces the piston 11a to the right in the figure, to incline the roller 5a in the rotating about the axis 7a, in the indirect direction in the figure.

  Similarly, when the pipe 12a is depressurized, or when pressure is exerted on the other side of the carriage on the other piston, the piston 11a is then moved to the left in the figure, the tilting of the roller leaving then in the indirect direction. The lower roller 5b is driven in the same way, it also comprises a rod 8b with a spherical end 9b clamped between the two ball bearings 10a and 10b carried the circular rail which is integral with another piston 11b movable in translation. This other piston is carried by another guide structure 12b and having a pipe 12b connected to the hydraulic control system 12. Advantageously, the rollers 5a, 5b are mounted on their pivot axes by needle bearings. Torque transmission is performed by traction, that is to say by shearing an extremely thin film of oil permanently present between the metal components vis-à-vis. There is thus no metal contact between the rollers 5a, 5b and the discs 4d and 4g. For the sake of argument, this oil film has a thickness of 0.05 to 0.4 μm. One of the difficulties encountered in producing the transmission member lies in the high pressure existing between the rollers 5a, 5b and the discs 4d and 4g which can reach 3.5 GPa. This pressure is called Hertz pressure. The oils which are used to make the disc-roller contact preferably have a viscosity which increases when they are subjected to the pressure between the rollers 5a, 5b and the discs 4d and 4g.

  The regulation of the transmission consists in modifying the inclination of the rollers according to the situation in which the vehicle is located, in order to adjust accordingly the distribution of engine torque transmitted to the right wheel and the left wheel.

  The torque delivered by the motor shaft 1 is distributed on the left and right half shafts, 2g and 2d, respecting the ratio D / d. D is the distance between the bearing points of the upper roller 5a and the lower roller 5b on the disk 4d associated with the left wheel, and d the distance between the bearing points of the upper roller 5a and the lower roller 5b with the 4d disc associated with the right wheel. Thus, in the configuration of the single figure where the upper roller is inclined in the indirect direction, the distance D is greater than the distance d. In this case, the torque available on the left half-shaft 2g is greater than the torque transmitted on the right half-shaft 2d, these couples respecting the ratio D / d. One can provide a single hydraulic control system 12 which is connected to the two lines 12a and 12b to jointly control the lower roller 5b and the upper roller 5a.

  An important technical effect of the continuously variable transmission member is obtained when it is combined with an electronic control system 13. As electronic control systems, there may be mentioned for example the ABS system, the ASR system and the system. ESP.

  The ASR system (Anti Slip Regulation) is an electronic traction control acting on the driving wheels. This system acts on the brakes, via the ABS unit (anti-lock system of the wheels), and on the engine control by cutting the power supply. The ASR can work in conjunction with the electronic throttle control and uses the components of the ABS. If the speed of a drive wheel increases sharply, which is the case when this wheel is spinning, the ASR system intervenes on the engine control, reduces power and eliminates slippage.

  A first example is given below in the case of a loss of adhesion on the right wheel in a straight line, the inclination in the indirect direction of the upper roller has the effect of: - reducing the torque sent on the right wheel, 15 - to increase the one sent on the left wheel which is not in loss of adhesion, - any braking torque applied to the right wheel by the ASR system by using the components of the ABS will be multiplied by a ratio D / d as defined above. This braking torque will then be returned to the left wheel by the rollers 5a and 5b interposed in the torus It is found that in case of loss of adhesion, the inclination of the rollers has a triple effect: the reduction of the torque sent on the wheel slipping, the transfer of torque to the drive wheel and the amplification of the ASR having the effect of limiting engine torque losses.

  Another example is given below in a steep right-turn curve where the inclination of the upper roller has the effect of: reducing the torque sent on the right wheel, increasing the torque sent on the right wheel; the left wheel, - these two effects have the effect of causing a yaw moment proper to promote turning maneuver.

  The creation of a yaw moment by torque vectoring effect or yaw torque regulation effect, the yaw being a rotation around the vertical axis of the vehicle, significantly improves the handling of the vehicle cornering. However, do not go to oversteer. Regulation should therefore incorporate this threshold not to be achieved. It can therefore advantageously have a system of suppression of regulation when the oversteer threshold may be reached.

  The ESP system is the electronic control system for all the dynamic behavior of a vehicle. Among other things, it makes it possible to maintain the stability of the vehicle and its trajectory when cornering by action on the braking circuit. In case of understeer, for example by loss of adhesion of the outer front wheel, it tries to slow down, the inner rear wheel. In case of oversteer, for example when starting a spin, he tries to slow down the front outer wheel. A first example of ESP control with the system according to the invention is given in right turn curve in case of understeer, where the indirect rotation of the upper roller 5a has the effect of - reducing the torque sent on the wheel inside, - to increase the one sent on the outer wheel, - the effect of torque vectoring caused will have the effect of supporting the ESP regulation which contributes to generate a moment of yaw in the same direction, - moreover, any braking torque applied on the rear inner wheel by ESP regulation will be multiplied by a ratio D / d and transmitted using the rollers to the outer rear wheel, D and d being the distances previously defined. It follows a better efficiency of ESP.

  Another example is given below for right-turn curve ESP control in the case of oversteer, where the forward rotation of the upper roller has the effect of: reducing the torque sent on the outer wheel which is drifting and therefore has less potential for adhesion, - to increase that sent on the inner wheel, - the effect of torque vectoring or regulation of the yaw moment caused will result in supporting the ESP regulation seeking to generate a yaw moment in the same direction by exerting a braking torque on the outer front wheel.

  In this case too, a better efficiency of the ESP is obtained.

  It can be seen that the transmission member according to the invention makes it possible to manage the wheel individually on each other, demonstrating its effectiveness especially when an electronic control system is being driven. The response of such an extremely fast organ and its size is small compared to that presented by those of the state of the art.

  The invention being thus described, it is obvious that identical elements can vary in many ways. Such variations should not be considered to depart from the spirit and scope of the invention, and all of these modifications, as will be apparent to one skilled in the art, are intended to be included in the scope of the invention. the scope of the following claims. torque transmitted a half-shaft and it is associated with and transmission aid is

Claims (7)

  A transmission member intended to be interposed between a drive shaft (1) and two transmission half-shafts (2d, 2g), this member comprising a housing (6) intended to be rotated by the drive shaft (1). ) for driving the two half-shafts (2g, 2d), characterized in that the housing carries semi-toroidal transmission elements including: - a right disk (4d) and a left disk (4g) coaxial and rotatable relative to to the housing (6), the right disk (4d) being rigidly secured to the right half shaft (2d) and the left disk (4g) being rigidly secured to the left half shaft (2g), these disks (4d, 4g) having toroidal concave surfaces facing each other, - at least one upper roller (5a) and one lower roller (5b) pivotally arranged between the toroidal concave surfaces of the discs (4d, 4g) being driven by these surfaces; a control system for controlling the inclination of the pivot axis of each roller (5a, 5b) in order to control the distribution of the couples transmitted respectively to the right disk (4d) and the left disk (4g).   Transmission member according to Claim 1, characterized in that the control system is a hydraulic control system (12).   3. Transmission member according to any one of the preceding claims, characterized in that the discs (4d, 4g) and the rollers (5a, 5b) are separated by a thin film of oil, for example of a thickness of between 0.05 and 0.4 μm, the transmission of torque being by shear of this oil film having a high viscosity.   4. Transmission member according to any one of the preceding claims, characterized in that each roller (5a, 5b) is held by a roller holder connected to the control system (12).   5. Transmission member according to any one of the preceding claims, characterized in that the rollers (5a, 5b) are rotatably mounted on their pivot axes via needle bearings.   6. Motor vehicle, characterized in that it comprises a transmission member according to one of claims 1 to 5.   7. Motor vehicle comprising a transmission member according to one of claims 1 to 5 and an electronic control system (13) included in the group of systems of the anti-lock type (ABS), anti-electronic skating (ASR) programmed electrostabilizer (ESP) associated with this transmission member.