WO2015028726A1

WO2015028726A1 - Continuous variation transmission with power recirculation

Info

Publication number: WO2015028726A1
Application number: PCT/FR2014/051520
Authority: WO
Inventors: Matthieu POGAM; Frederic Genin
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2013-08-27
Filing date: 2014-06-19
Publication date: 2015-03-05
Also published as: FR3010166B1; FR3010166A1

Abstract

The invention concerns a continuous variation transmission (102), comprising a first circular transmission surface (116), a second circular transmission surface (118) arranged facing the first surface, transmission planetary gears (108) engaging with the first and second surfaces (116, 118), a planet carrier (120), the planetary gears (108) being mounted on the planet carrier via axes of rotation (110) of which the tilt γ can be varied with a view to modifying the transmission ratio between the first and second surfaces. The planet carrier (120) is linked in rotation with the input shaft (122) and the first circular surface (16) according to a transmission ratio Rf different from 0 and 1 providing power recirculation intended to increase the range of variation of the transmission. An intermediate shaft (152) with a three-position dog provides the link between the output shaft (124) and the differential (156).

Description

CONTINUOUS VARIATION TRANSMISSION WITH RECIRCULATION OF

POWER

The invention relates to the field of mechanical rotary motion transmission. More particularly, the invention relates to a continuously variable transmission as well as a powertrain and a vehicle provided with such a transmission.

FIG. 1 illustrates a Nuvinci® continuously variable transmission from Fallbrook Technologies Inc. This transmission 2 essentially comprises an input shaft (not shown) connected to a first ring 4 with a first circular transmission surface 16, a transmission shaft output (not shown) aligned with the input shaft and connected to a second ring gear 6 with a second transmission surface 18. The transmission 2 also comprises a series of balls 8 forming satellites distributed in a circle centered on the axis 14 of the input and output shafts, the balls being rotatably mounted on axes of rotation 10. A planet carrier (not shown) supports the axes of rotation 10 of the balls 8. The first and second transmission surfaces 16 and 18 are in pressure contact with the balls 8. The latter are also in pressure contact with an inner ring 12 free in rotation. The pressure contact of the balls with the ring 12 makes it possible to take up the forces resulting from the pressure contact of the transmission surfaces 16 and 18. During the rotation of the input shaft and the first ring 4, the balls 8 are driven in rotation about their respective axes 10. The rotation of the balls 8 then causes the rotation of the second ring 6 in the same direction as the first ring 4. The inclination of the axes of rotation 10 of the balls 8 allows to vary the transmission report. Indeed, when the axes of rotation 10 of the balls 8 are inclined relative to the main axis 4 of the transmission, the transmission surfaces 16 and 18 are then in contact with the balls on circular paths centered on the axes 10 which have different radii, thus generating different rotational speeds between the first and second crowns. US patent document 2012/01 15667 A1 discloses a continuously variable transmission of the type described above.

The transmission described above is interesting in that the variation of the transmission ratio is continuous. It also has compactness benefits. The transmission ratio of this device can vary from 0.51 to 1.96 (for an angle γ inclination of the axes of rotation of the balls between -18 ° and + 18 °) thus providing an interesting opening but not sufficient especially for a transmission automobile. The opening of a transmission is the ratio between the maximum and minimum transmission ratios (r _ma x / r _min ), ie 3.85 for an angle γ between -18 ° and + 18 °. It should be noted, however, that the efficiency of this transmission drops rapidly as we move away from the transmission ratio of 1. In comparison with a conventional gear transmission, the efficiency of a continuously variable transmission, in particular such as that described above, is lower. Its use may, however, make it possible to operate a driving device or a driven device at better operating points, thereby resulting in improved overall efficiency. To maintain a gain from an overall performance point of view, it is therefore necessary to limit the range of inclination of the axes of rotation of the balls. The invention aims to provide a continuously variable transmission with satellites, providing a compatible opening of an automotive transmission and satisfactory transmission efficiency. More particularly, and without allowing the opening increase, the invention also aims to reduce the yield losses of a satellite continuously variable transmission when operating at extreme transmission ratios for a given opening. .

The invention relates to a continuously variable transmission comprising: a first circular transmission surface; a second circular transmission surface disposed opposite the first surface; transmission satellites cooperating with the first and second surfaces; a satellite carrier, the satellites being mounted on the planet carrier via rotational axes whose inclination can be varied to change the transmission ratio between the first and second transmission surfaces; remarkable in that the planet carrier is rotatably connected to the first transmission surface in a transmission ratio R _f other than 0 and 1.

A transmission ratio R _f equal to 1 would cancel the continuously variable ratio aspect of the system and a transmission ratio of 0 would amount to one. Nuvinci® continuously variable transmission system where the planet carrier would be locked in rotation.

The transmission ratio R _f corresponds to the ratio between the planet carrier and the first transmission surface. The first and second circular transmission surfaces are preferably arranged facing each other axially.

According to an advantageous embodiment of the invention, the transmission ratio R _f is less than 0, the planet carrier rotating in the opposite direction to the first transmission surface. According to an advantageous embodiment of the invention, the transmission ratio R _f is greater than -1, the planet carrier rotating at a rotational speed lower than that of the first transmission surface.

According to an advantageous embodiment, the transmission ratio R _f is greater than 0 (R _f equal to 1 being excluded), the planet carrier rotating in the same direction as the first rotating surface at a lower or higher rotational speed.

According to an advantageous embodiment, the transmission ratio R _f is less than -1, the planet carrier rotating in the opposite direction to the first rotating surface and at a higher speed.

According to an advantageous embodiment of the invention, the planet carrier comprises a ring gear meshing with one or more toothed wheels rotatably mounted on a stationary casing of the transmission, said wheel or said wheels being engaged with a toothed gear wheel. rotation with the first circular transmission surface.

These power recirculation means has the advantage of being simple, robust and have a high efficiency. Other means of recirculation between the planet carrier and the first circular transmission surface are however possible, such as belt means.

According to an advantageous embodiment of the invention, the transmission further comprises: a primary shaft connected in rotation, preferably in direct engagement with the first circular transmission surface; a secondary shaft connected in rotation, preferentially in direct contact with the second circular transmission surface; an intermediate shaft selectively engaged in two ratios of intermediate transmission Rint_av and Rint_ar with the secondary shaft, said ratios being of opposite signs. According to an advantageous embodiment of the invention, the transmission further comprises: a first set of gears providing the first intermediate transmission ratio Ri _n t_av between the intermediate shaft and the secondary shaft; a second set of gears providing the second ratio of intermediate transmission Rint_ar between the intermediate shaft and the secondary shaft; means for clutch and / or synchronization on the intermediate shaft, able to link in rotation with said shaft, selectively, a wheel of the first and second set of gear wheels, disposed on said shaft.

According to an advantageous embodiment of the invention, the clutch and / or synchronization means are configured to allow the intermediate shaft to be free in rotation with respect to the first and second set of gear wheels.

According to an advantageous embodiment of the invention, the transmission further comprises a differential engaged with the intermediate shaft.

According to an advantageous embodiment of the invention, the transmission further comprises a clutch in direct engagement with the primary shaft. The invention also relates to a powertrain, comprising: a motor, preferably with combustion; a continuously variable transmission coupled to the engine; remarkable in that the continuously variable transmission is in accordance with the invention.

The continuously variable transmission may be of the ball type or the toroidal type.

The measures of the invention are interesting in that they allow the power recirculation between the planet carrier and the input shaft to change the transmission range and in particular to increase the opening. The increase in the opening of the transmission makes it possible in particular to work on a range of the variation of the satellite angle is more limited, which helps to keep the yield within satisfactory limits.

Other features and advantages of the present invention will be better understood from the description and drawings in which: FIG. 1 is an illustration of the principle of a known continuously variable transmission of the Nuvinci® type;

FIG. 2 is a schematic illustration of the operating principle of the transmission of FIG. 1;

FIG. 3 is a schematic illustration of the operating principle of a continuously variable transmission with recirculation of power according to the invention;

FIG. 4 is a detailed representation of the transmission of FIG. 3 according to the invention;

FIG. 5 is a detailed illustration of the geometry relating to the contact of the transmission surfaces with the balls;

- Figure 6 is a representation of a powertrain comprising the transmission of Figure 4, according to the invention and in neutral mode;

- Figure 7 is an illustration of the powertrain of Figure 6 in forward mode;

- Figure 8 is an illustration of the powertrain of Figure 6 in reverse mode;

- Figure 9 is a graphic illustration of the speed of a vehicle equipped with the transmission according to the invention, in forward and reverse.

FIG. 1 illustrating the principle of a known continuously variable transmission of the Nuvinci® type has already been described previously in the section relating to the description of the state of the art.

FIG. 2 schematically illustrates the operating principle of the satellite continuously variable transmission of FIG. 1.

In the left part of the figure, the input shaft is shown schematically by the first ring 4 comprising a first surface 16 in contact with the ball 8. The output shaft is schematized by the second ring 8 with a second surface 18 in contact with the ball 8. The axis of rotation 10 of the ball 8 is mounted on a planet carrier 20 adapted to vary its angle of inclination γ. The ball 8 bears on the ring 12.

The right-hand part of FIG. 2 is a functional representation of the transmission of FIG. 1, in the form of a box with four elements, namely:

an input element E corresponding to the input shaft;

an output element S corresponding to the output shaft;

a fixed element F corresponding to the planet carrier; and

a free element L corresponding to the free rotation of the balls around their respective axes.

The invention consists in reviewing the architecture of the transmission of FIG. 2 in order to increase its opening.

According to the invention, the fixed element F of Figure 2 becomes rotatable relative to the input shaft and in a fixed transmission ratio. This situation is illustrated in FIG. 3 where it can be observed that the element F is no longer fixed but is connected in rotation with the input E, this link being represented by the sign F-> E. The reference numbers of FIGS. 1 and 2 are used in FIGS. 3 to 8 for the same elements or the corresponding elements, these numbers however being increased by 100 in order to clearly distinguish the invention from the state of the art. Specific numbers between 100 and 200 are used for specific elements.

The connection in rotation between the input E and the carrier is preferably a fixed ratio link, in particular of the gear type. Figure 4 illustrates in more detail the principle of construction of such a transmission. In comparison with FIGS. 1 and 2, it can be seen that the transmission 102 of FIG. 4 comprises a gear transmission 126 between the first ring gear 104 and the planet carrier 120. The gears 128, 130 and 132 effectively provide a gear transmission. fixed ratio between the planet carrier 120 and the first ring gear 104. It is interesting to note that this fixed ratio transmission comprises an intermediate gear 130 rotatably mounted on the casing 132 of the transmission 102, this intermediate gear 132 meshing with a gear 134 fixed in rotation with the input shaft 122 and a toothing 128 of the planet carrier. The presence of the intermediate gear 130 ensures a reversal of the direction of rotation between the input shaft 122 (in direct contact with the first ring gear 104) and the planet carrier 120. The ratio of the transmission, expressed as a ratio between the speed of rotation of the planet carrier and the speed of rotation of the input shaft can be between -1 and 0, preferably between -0.9 and -0.1, more preferably between -0.7 and -0.2. For example, it can be -0.4.

The transmission between the planet carrier 120 and the first ring gear 104 has the effect of modifying the range of the transmission ratios, as will be detailed hereinafter with reference to FIG.

FIG. 5 illustrates in detail the geometry of the continuously variable transmission of FIG. 4. The transmission ratio of the transmission R _g i ₀ bai is as follows:

N output

R ^■ g, lobal

N, where Nsortie input is the rotational speed at the output of transmission tree and _N is the rotational speed at the transmission input.

If r is the radius of the ball, RA and Rc are the radii of contact points A and C of the friction surfaces of the first and second rings with respect to their axis of rotation, e and <¾ the contact angles of first and second rings relative to a transverse direction passing through the center of the balls, and R _f the transmission ratio between the planet carrier 120 and the input shaft 122 (FIG. 4) in direct contact with the first ring 104 , that is to say

N, planet carrier

entry we can write

Gold AB = r sin β = r sin (90 ^° -oc- y) = r cos (a + y) CD = r sin δ = r sin (90 ^° -oc + y) = r cos (a-y)

We then have:

_D _ Nsorted _ _DN , RA- COS (^ C ^~ r)

^¾i06ai - - ^{β + (1 "β)} cos ( _{¾ +} y)

However, in the absence of power recirculation, the overall transmission ratio would be:

_ R _A. cos (o: _c - y)

K ^lobal R _c . cos (¾ + y)

The rate of change of the transmission ratio according to this first embodiment of the invention is thus affected by the factor (1 - R _f ) in comparison with the case of the transmission of the state of the art where the satellite carrier is motionless.

This means that for a given variation of the angle of inclination γ of the axes of the balls, the opening of the transmission according to this embodiment will be increased as soon as the ratio R _f is less than zero. Physically, this amounts to saying that the directions of rotation of the first ring gear and the planet carrier are reversed, which makes it possible to increase the rotational speed of the balls around their axes.

Similarly, when Rf is greater than λ:

₃ _ ⁿ ? max - ^ I- ⁿ ? min

^~ Ί ⁿ Ρ max ^{τ n} p 'min _ 1

(Value greater than 1 depending on the amplitudes of the angle y)

That is to say when the planet carrier rotates at least λ times faster than the first crown and in the same direction, the opening of the transmission will also be increased. Physically, if the first ring gear and the planet carrier rotate at the same speed, the balls do not rotate about their respective axes and the second ring rotates at the same speed and in the same direction as the first ring. This is the situation where R _f is equal to 1 and the global ratio R _g i ₀ bai is also equal to 1. When the planet carrier rotates more than λ times faster than the first crown, the rotation speed of the balls around their respective axes is increased compared to a conventional transmission where the planet carrier is fixed. At this increased relative rotational speed is added the speed of rotation of the planet carrier. Not only the overall transmission ratio but also the rate of change of the transmission ratio are then increased.

Recirculation of power between the planet carrier and the first ring thus makes it possible to increase the rate of variation of the transmission ratio with respect to the angle γ of inclination of the axes of the balls on the planet carrier. In other words, the opening of the transmission is increased for a given variation of the angle γ, which then makes it possible to limit the range of variation of the angle γ for a given required opening and therefore, of increase the efficiency of the transmission.

FIGS. 6 to 8 illustrate a power train comprising the transmission of FIG. 4. It can indeed be observed that the power unit 103 comprises a motor 136, preferably with combustion, connected via a clutch 138 to the input or input shaft 122 of the transmission 102. The secondary or output shaft 124 supports two gear wheels 140 and 142, preferably different numbers of teeth. An intermediate shaft 152 is disposed in parallel with the primary and secondary shafts 122 and 124. The secondary shaft 152 supports two toothed wheels 146 and 148 free to rotate relative to said shaft. One of the free-rotating gears of the intermediate shaft meshes with a 140 of the two gears 140 and 142 of the output shaft 124 and the other 146 of these gears of the intermediate shaft meshes with an intermediate wheel. 144, mounted free in rotation relative to the fixed casing of the transmission, this intermediate wheel 144 meshing with the other 142 of the two toothed wheels of the output shaft 124. The presence of the intermediate wheel 144, constituting an additional wheel by relative to the meshing of the wheels 140 and 148 makes it possible to reverse the direction of rotation. The set of gears 140 and 148 provides a transmission in a negative fixed ratio, which may correspond to a transmission in forward, while the set of gears 142, 144 and 146 may correspond to a transmission in reverse. The intermediate shaft 152 also comprises a gear 154 fixed with said shaft, said wheel meshing with a gear wheel 1 56 of a differential, well known to those skilled in the art.

A dog 150 with possibly synchronizing cones is provided on the intermediate shaft 152, able to selectively link the shaft in question with each of the two toothed wheels 146 and 148. In central position, as illustrated in FIG. Figure 6, the dog engages with none of the two gears 146 and 148. This is the configuration of the transmission in neutral mode, that is to say without transmission torque. In this position, the clutch can remain closed.

Figure 7 illustrates the powertrain of Figure 6, the group being however in forward mode. Indeed, the dog 150 is in the left position, that is to say in engagement with the gear wheel 148 corresponding to the forward intermediate transmission. Figure 8 illustrates the powertrain of Figures 6 and 7, the group being however in reverse mode. Indeed, the dog 150 is in the upright position, that is to say in engagement with the toothed wheel 146 corresponding to the intermediate reverse transmission

The absolute value of the ratio of the secondary reverse gear is preferably less than that of the forward gear. By way of example, the intermediate forward gear ratio Rint_av may be equal to -0.8 and the reverse gear Ri _n t_ar may be equal to 0.5. The transmission ratio of the differential R _d iff may be equal to -0.22.

FIG. 9 graphically illustrates the speed of a vehicle provided with the powertrain described above, in forward and reverse gear at a speed of 1000 rev / min of the engine, as a function of the angle γ of the transmission. continuously variable. The angle γ can vary in a range of -18 ° to + 18 °. The vitsse of the vehicle in the same conditions in forward but with a transmission without recirculation is also illustrated. It can be seen quite clearly that the range of variation of the speed of the vehicle is substantially wider with a transmission according to the invention.

Claims

claims

Continuously variable transmission (102) comprising:

a first circular transmission surface (1 16);

- a second circular transmission surface (1 18) disposed opposite the first surface (1 16);

transmission satellites (108) cooperating with the first and second surfaces (1 16, 1 18);

- a planet carrier (120), the satellites (108) being mounted on the planet carrier via rotation axes (1 10) whose inclination can be varied in order to modify the transmission ratio between the first and second transmission surfaces (1 16, 1 18);

the planet carrier (120) being rotatably connected to the first circular transmission surface (1 16) in a transmission ratio R _f other than 0 and 1, said transmission (102) being characterized in that the transmission ratio R _f is less than 0, the planet carrier (120) rotating in the opposite direction to the first circular transmission surface (1 16).

Continuously variable transmission (102) according to claim 1, characterized in that the transmission ratio R _f is greater than -1, the planet carrier (120) rotating at a rotational speed less than that of the first circular surface of transmission (1 16).

Continuously variable transmission (102) according to one of claims 1 or 2, characterized in that the planet carrier (120) comprises a ring gear (128) engaged with one or more gear wheels (130) mounted free to rotate on a fixed housing (132) of the transmission, said one or more wheels (130) being engaged with a gear (134) rotatably connected to the first circular transmission surface (1 16).

Continuously variable transmission (102) according to one of claims 1 to 3, characterized in that it further comprises:

- A primary shaft (122) rotatably connected, preferably in direct engagement with the first circular transmission surface (1 16);

- A secondary shaft (124) rotatably connected, preferably in direct engagement with the second circular transmission surface (1 18); an intermediate shaft (1 52) in selective engagement in two intermediate transmission ratios Ri _n t_av and Ri _n t_ar with the secondary shaft (1 24), said ratios being of opposite signs.

5. continuously variable transmission (1 02) according to claim 4, characterized in that it further comprises:

a first set of gears (140, 148) providing the first intermediate transmission ratio Ri _n t_av between the intermediate shaft (1 52) and the secondary shaft (1 24);

a second set of gears (142, 144, 146) providing the second intermediate transmission ratio Ri _n t_ar between the intermediate shaft (152) and the secondary shaft (1 24);

- clutch and / or synchronization means (1 50) on the intermediate shaft (1 52), able to rotate said shaft selectively with a wheel (146, 148) of the first (140, 148) and second sets (142, 144, 146) of toothed wheels disposed on said shaft.

6. continuously variable transmission (1 02) according to claim 5, characterized in that the clutch and / or synchronization means (1 50) are configured to allow the intermediate shaft (1 52) to be free in rotation relative to the first (140, 148) and second sets (142, 144, 146) of gears.

7. continuously variable transmission (1 02) according to one of claims 4 to 6, characterized in that it further comprises:

- A differential (156) in engagement, preferably direct, with the intermediate shaft (152).

8. continuously variable transmission (1 02) according to one of claims 4 to 7, characterized in that it further comprises:

- a clutch (1 38) in direct contact with the primary shaft (122).

9. Power train (1 03), comprising:

an engine (1 36), preferably with combustion;

- a continuously variable transmission (1 02) coupled to the engine;

characterized in that the continuously variable transmission (102) is according to one of claims 1 to 8.