FIELD OF THE INVENTION

The present invention concerns an automatic and continuously variable transmission device.

BACKGROUND OF THE INVENTION

The present invention concerns more precisely an automatic and continuously variable transmission device comprising :

- a housing,

- a first shaft for an input rotation,

- a second shaft for an output rotation, and

- a first planetary gearset connected to the first shaft and comprising a sun gear, a planet gear having a planet shaft and being meshed with said sun gear, a planet carrier supporting said planet shaft, and a ring gear meshed with said planet gear.

It is known from the applicant's own patent application FR 2 902 073, an automatic and continuously variable transmission adapted for a bicycle having such planetary gearset. However, in this transmission device a coupling device is connected between the sun gear and the planet carrier to adapt the transmission speed ratio.

Unfortunately, this kind of automatic transmission works difficultly. When rotating, the torque is insufficient to control the coupling device and to brake the planet carrier. Therefore, the coupling device is unable to change the rotation speed ratio of the transmission device.

OBJECTS AND SUMMARY OF THE INVENTION

One object of the present invention is to provide an automatic and continuously variable transmission device that overcomes the above drawbacks. To this effect, the continuously variable transmission device of present invention comprises:

- a control carrier,

- a control device linked with one element of the first planetary gearset and connected to the second shaft, said control device being adapted to induce a displacement of the control carrier according to a torque difference value that is a difference between a first torque from said one element and a second torque from the second shaft, and

- a coupling device connected to the control carrier and linked with the ring gear, said coupling device being adapted to induce a coupling between the ring gear and the control carrier, said coupling having an amplitude depending on said displacement.

Thanks to these features, the coupling device is linked with the ring gear, so that the automatic and continuously variable transmission device works properly.

The control device and the coupling device are producing a torque feedback from the second shaft to the ring gear via a displacement of a control carrier. It continuously and correctly couples the second shaft (output) to the ring gear: It brakes the ring gear rotation. It therefore adapts the rotation speed ratio of the transmission device.

Such feedback is purely mechanical: it does not need any external energy to control the rotation speed of the ring gear.

The one element of the first planetary gearset is one element chosen in the list of the sun gear, and the planet carrier. The transmission device can increase or reduce the rotation speed between the first and second shafts .

In various embodiments of the device, one and/or other of the following features may optionally be incorporated .

According to an aspect of the invention, the coupling increases when the torque difference value is positive, and the coupling decreases when the torque difference value is negative.

According to an aspect of the invention, the device further comprises an elastic element between the housing and the control carrier, and the control device comprises:

- a tubular body connected to the second shaft, said tubular body having an elongated hole having an helical predetermined shape, and

- a control shaft linked with said one element and extending through said hole, said control shaft having a first position at a first end of the hole and a second position at a second end of the hole, said second position being opposite to the first position according to the direction of the displacement, and

wherein

the control shaft is urged to the second position by the first torque, and

the control shaft is urged to the first position by the second torque and by the elastic element.

According to an aspect of the invention, the control carrier is positioned between the control shaft and the elastic element.

According to an aspect of the invention, the control shaft is equipped with a wheel adapted to reduce friction interaction between the control shaft and the control carrier.

According to an aspect of the invention, the control carrier is mounted on the tubular body of the control device and is able to move on said tubular body according to the direction of the displacement.

According to an aspect of the invention, the coupling device comprises first magnets linked with the control carrier and second magnets linked with the ring gear, said first and second magnets generating the coupling .

According to an aspect of the invention, the first and second magnets have a magnetic characteristic with a hysteresis for dissipating kinetic energy.

According to an aspect of the invention, the coupling is a braking the rotation of the ring gear.

According to an aspect of the invention, the device further comprises a free-wheel situated between the first shaft and the one element, or situated between the planet carrier and the housing.

According to an aspect of the invention, the one element is chosen in a list comprising the sun gear and the planet carrier.

According to an aspect of the invention, the device further comprises a second planetary gearset connected to said one element of the first planetary gearset and connected to the control device.

According to an aspect of the invention, the device further comprises a third planetary gearset connected to the ring gear of the first planetary gearset, said third planetary gearset comprising a ring gear directly connected to the coupling device.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from the following detailed description of three of its embodiments given by way of non-limiting example, with reference to the accompanying drawings. In the drawings :

- Figure 1 is a schematic view of a first embodiment of a transmission device according to the invention, said device being in a first speed ratio;

- Figure 2 is a schematic view of the first embodiment of figure 1, said device being in a second speed ratio ; - Figure 3 is a schematic view of a second embodiment of a transmission device according to the invention, said device being in a first speed ratio;

- Figure 4 is a schematic view of the second embodiment of figure 3, said device being in a second speed ratio ;

- Figure 5 is a schematic view of a third embodiment of a transmission device according to the invention, said device being in a first speed ratio;

- Figure 6 is a cut view of a transmission device according to the third embodiment of figure 5; and

- Figure 7 is a view of an example of control device according to anyone of the embodiments.

In the various figures, the same references denote elements that are identical or similar.

MORE DETAILLED DESCRIPTION

The automatic and continuously variable transmission device 1 according to the invention is a mechanic transmission device without any outside control command. The device itself adapts the transmission speed ratio between the input shaft and the output shaft according to the torques applied on these elements. Moreover, it does not need any outside energy input, and it is only a passive mechanical device.

Such transmission device 1 may be used inside any vehicle, such as a bicycle, or a car, or a truck.

Such transmission device may be a reduction transmission that reduce the rotation speed or an overdrive transmission that increase the rotation speed between the input and output shafts.

Figures 1 and 2 are schematic views of a first embodiment of an automatic and continuously variable transmission device 1 according to the invention. The device 1 of this embodiment is an overdrive transmission device .

The transmission device 1 comprises a first shaft 2 (input shaft) for an input rotation, a second shaft 3 (output shaft) for an output rotation, a first planetary gearset 10, and a housing 6. The first and second shafts 2, 3 are coaxial and adapted to rotate around a main axis 2a.

The housing 6 is considered here as a fixed part (not moving) . The displacement or rotation of any part belonging to the transmission device 1 is then relative to said housing 6.

The first planetary gearset 10 is connected to the first shaft and comprises:

- a sun gear 11,

- a planet gear 12 rotating around a planet shaft 13 supported by a planet carrier 14, said planet gear 12 being meshed with said sun gear 11, and

- a ring gear 15 meshed with said planet gear 12. The planet shaft 13 extends according to a planet axis 13a. The first planetary gearset 10 can comprise, as usual, a plurality of planet gears 12 situated around the main axis 2a and meshed with the sun gear 11.

A planetary gearset is a well-known transmission device or gearbox having three elements (sun gear, ring gear, and planet carrier) . The speed transformation relation of such planetary gearset (such as the first planetary gearset 10, is given by the following Willis formulae : ω« - « C ^N s

where

a _s is the rotational speed of the sun gear,

C0p _C is the rotational speed of the planet carrier, a> _R is the rotational speed of the ring gear,

N _s is the number of teeth of the sun gear,

N _R is the number of teeth of the ring gear,

K is the ratio of the planetary gearset.

Therefore, knowing the rotational speed of two elements of a planetary gearset determines the rotational speed of the third one. Such planetary gearset can be used in various combinations of input and output to have a desired speed ratio. Optionally, a plurality of planetary gearsets connected in series may be used.

In the first embodiment of present invention, the first shaft 2 is directly connected to the planet carrier 14 for input transmission. This transmission device 1 is an overdrive transmission.

The first shaft is also linked to the sun gear 11 via a free wheel 60. The sun gear 11 can only rotate according to one rotating direction around the main axis 2a.

The device 1 according to the invention further comprises :

- a control carrier 44 that is a non rotating part,

- a control device 40 adapted to induce a displacement d (see figure 2) of the control carrier 44 according to a direction parallel to the main axis 2a,

- a coupling device 50 adapted to induce a coupling to the ring gear 15, said coupling having an amplitude depending on the displacement d.

The ring gear 15 supports the coupling device 50 that couples the rotation of the ring gear 15 to the control carrier 44 that is not rotating. The coupling is a braking with sliding of the ring gear 15.

For example, the coupling device 50 comprises an outer ring having first magnets 51 secured to said outer ring, and an inner ring having second magnets 52 secured to said inner ring. Such magnetic coupling device has a high efficiency .

The inner and outer rings are coaxial according to the main axis 2a, and they can be moved one relative to the other according to the direction of said displacement d.

The outer ring can surrounds the inner ring (figure 2) to couple to the inner ring to the outer ring. The first and second magnets 51, 52 are facing each other. And, a magnetic interaction between them is high.

The outer ring can be moved laterally according to the direction of the displacement d (figure 1) to decouple the inner and outer rings. The first and second magnets 51, 52 are not facing each other. And, the magnetic interaction between them is very low, or much reduced compared to the previous position of the outer ring.

Such magnetic rings can therefore generate braking when the inner ring is positioned inside the outer ring.

The outer ring and the first magnets 51 are directly connected to the control carrier 44 (not rotating part) .

The inner ring and the second magnets 52 are linked to the ring gear 15. In the first embodiment, they are directly connected to the ring gear 15 of the first planetary gearset. The coupling of the coupling device 50 can continuously brake the rotation of the ring gear 15. This coupling has an amplitude depending on the displacement d that moves the outer ring inside or outside of the inner ring.

The first and second magnets 51, 52 have advantageously magnetic characteristics adapted to dissipate energy. The magnets may have hysteresis characteristic corresponding a material property: The magnetisation of the material remains even when the magnetic field is removed. Such well known phenomenon is characterized by H-M curve.

The first and second magnets 51, 52 may be composed of the same or a different magnetic material. The magnetic material is for example AINiCo material, or NdFeB material.

The control device 40 is adapted to control the displacement of the control carrier 44 to control the coupling of the coupling device 50.

The control device 40 is connected to one element of the first planetary gearset 10. As illustrated on he figures of the first embodiment, it is connected to the sun gear 11 via a sliding link 48 for receiving an input rotation with a first torque.

The control device 40 comprises:

- a control shaft 42 linked with the first planetary gearset 10 for receiving the input rotation movement with the first torque.

- a tubular body 41 directly connected to the second shaft 3 for outputting the rotation movement.

The second shaft 3 receives a second torque from an output load (for example a wheel) .

The tubular body 41 comprises a hole 41a that is situated laterally and that extends substantially according to the main axis 2a with a predetermined shape. This predetermined shape is generally a helical shape. This predetermined shape is determined experimentally or by simulation calculations, and determines the behaviour of the automatic transmission device.

The control shaft 42 extends through the sliding link 48 in the main axis direction and through the hole 41a of the tubular body 41 in a radial direction.

The control shaft 42 can moves inside the sliding link 48 and inside the tubular body 41 according to the direction of displacement d between a first position at a first end of the hole 41a and a second position at a second end of the hole 41a. The first and second positions are opposite to each other in said direction.

The control shaft 42 firstly interacts with the opening surfaces of the hole 41a of the tubular body) .

The control shaft 42 secondly interacts with the control carrier 44. It moves said control carrier 44 according to said direction d.

The control carrier 44 is advantageously equipped with a wheel (see figure 7) adapted to reduce friction interaction between the control shaft 42 and the control carrier 44. The control device efficiency is therefore improved .

The transmission device 1 further comprises at least one elastic element 43. The elastic element 43 provides a return force that urges the control carrier 44 and control shaft 42 back to the first position.

The transmission device 1 may comprise a plurality of elastic elements placed around the main axis 2a for providing a return force that is centred on said main axis.

The control carrier 44 may be mounted above the tubular body 41 so to move on it according to the displacement. The tubular body guides said displacement. The transmission device is smaller.

The control carrier 44 may be positioned between the control shaft and the elastic element so as the displacement of the control carrier directly depends on the interactions thereon.

The control shaft 42 is subjected to a mechanical equilibrium that depends on the hole 41a shape and that combines :

- the first torque applied to the control shaft 42 and coming from the first planetary gear set 10, so as this first torque urges the control shaft 42 to the second position inside the tubular body 41,

- the second torque applied to the tubular body 41 and coming from the second shaft 3, so as this second torque urges the control shaft 42 to the first position, and

- the return force applied to the control shaft 42 and coming from the elastic element 43, so as this second torque urges the control shaft 42 to the first position.

The displacement d of the control carrier 44 is controlled by said mechanical equilibrium.

The shape of the hole 41a can be predetermined experimentally or by numerical simulations to obtain a desired behaviour for the control device 40.

Therefore, the control device 40 induces a displacement d of the control carrier 44 according to a torque difference value. The torque difference value is a difference (subtraction) between the first torque from the input (one element of the first planetary gearset) and a second torque from the output (the second shaft 3) .

The displacement d depends on or is proportional to the torque difference value.

Thanks to the control device 40, that is similar as a mechanical sensor element, the transmission device 1 of present invention is an automatic transmission.

Thanks to the coupling device 50, the transmission device 1 of present invention is a continuously variable transmission .

The control carrier 44 is a non rotating part. It is for example linked to the housing 6 via a sliding link 49 so as it can translate according to the direction of the main axis 2a of said displacement d.

The control carrier 44 acts as a feedback device to control (to brake or to free) the rotational movement of the ring gear 15 of the first planetary gearset 10.

Thanks to the control carrier 44, the transmission device 1 of present invention is an automatic and continuously variable transmission device.

The working of the device 1 of this first embodiment will be now explained in view of figures 1 and 2. The rotational direction of the parts belonging to the transmission device 1 are indicated on the figure 2 via arrows and plus and minus signs next to the parts.

At startup, the transmission device 1 is in any state. For example, it can be in the state of figure 2. A resisting load torque is applied to the second shaft 3. This resisting load torque is a maximum torque, therefore preventing any rotation of the second shaft 3.

An input rotation of the first shaft 2 drives into rotation the planet carrier 14 and the sun gear 11 in the same first directional rotation. This quickly moves the control shaft 42 at second end of the hole 41a as in figure 1 to directly drives the second shaft 3 with the same rotation speed. In this state, the control carrier 44 is moved to decouple the inner and outer rings of the coupling device 50, and the elastic element 43 is compressed. The transmission ratio of the transmission device 1 is equal to one, and is a minimum ratio.

As the second shaft 3 starts rotating, the resisting load torque decreases a lot. The elastic element 43 then urges the control carrier 44 and the control shaft 42 in the opposite direction towards the first end of the hole 41a and back to the first position. The control carrier 44 is then moved to couple the inner and outer rings of the coupling device 50.

The coupling depends on the displacement d of the control carrier 44, i.e. the displacement d of the control shaft 42 between the first and second ends of the hole 41a.

The outer ring of the coupling device 50 then starts to brake the rotation of the inner ring. It therefore progressively brakes to rotation of the ring gear 15 of the first planetary gearset 10. The transmission ratio increases.

When the outer ring of the coupling device 50 is completely coupled to the inner ring, the ring gear 15 is prevented of rotating, and the planet gear 12 accelerates the rotation speed of the sun gear 11 relative to the rotation speed of the first shaft 2 (or planet carrier 14) . The second shaft 3 rotates at a higher speed than the first shaft 2, and the transmission ratio becomes a maximum ratio .

In that case, the rotational speed of the ring gear 15 is null, and the rotational speed of the sun gear 11 may be calculated via the Willis formulae (1) :

co _u = (l + ^ ₁₀ ).co ₁₄

where ω _π is the rotational speed of the sun gear 11, ω ₁₄ is the rotational speed of the planet carrier 14,

ω ₁₅ = 0 is the rotational speed of the ring gear 15, K _l0 is a ratio of the first planetary gearset 10.

Therefore, in case of complete coupling of the coupling device 50, the transmission speed ratio of the transmission device 1 is:

7i=^ = l ₊ * ₁₀ .

And, the transmission device 1 of first embodiment is an overdrive transmission device.

Figures 3 and 4 are schematic views of a second embodiment of an automatic and continuously variable transmission device 1 according to the invention.

This transmission device 1 comprises the same elements as described for the first embodiment.

It further comprises a second planetary gearset 20 situated between the first planetary gearset 10 and the control device 40. The transmission device 1 can have a large range of transmission speed ratio by designing the first and second planetary gearsets.

The second planetary gearset 20 comprises (as the first planetary gearset 10) :

- a sun gear 21,

- a planet gear 22 rotating around a planet shaft 23 supported by a planet carrier 24, said planet gear being meshed with the sun gear 21, and

- a ring gear 25 meshed with said planet gear 22. How the gears of the first and second planetary gearsets 10, 20 are connected together and are connected to the other elements of the transmission device 1, is explained in the followings.

In this second embodiment, the first shaft 2 is directly connected to the sun gear 11 of the first planetary gearset 10 and to the sun gear 21 of the second planetary gearset 20 for transmission input. This transmission device 1 is then a reduction transmission.

The planet shaft 13 of the first planetary gearset 10 is connected to the ring gear 25 of the second planetary gearset 20.

As illustrated on the figures 3 and 4, the control shaft 42 of the control device 40 is connected to the planet carrier 24 of the second planetary gearset 20 via a sliding link 48 for receiving an input rotation with a first torque. The planet shaft 23 supports the planet gear 22 that is meshed to the ring gear 25, and then linked with the planet carrier 14 of the first planetary gearset 10.

The control device 40 is consequently linked with one element of the first planetary gearset 10 (the planet carrier 14 ) .

In this embodiment, the free wheel 60 is connected between the planet carrier 14 of the first planetary gearset 10 (the ring gear 25 of the second planetary gearset 20), and the housing 6.

This second embodiment further comprises a control carrier 44, a control device 40, and a coupling device 50. These elements are very similar or identical to those described in the first embodiment of present invention.

The control device 40 induces a displacement d of the control carrier 44 according to a torque difference value. The torque difference value is a difference (subtraction) between the first torque from the input (one element of the first planetary gearset) and a second torque from the output (the second shaft 3) .

The displacement d depends on or is proportional to the torque difference value.

The control carrier 44 moves the outer ring of the coupling device 50. The inner ring of the coupling device 50 is connected to the ring gear 15 of the first planetary gearset 10. The coupling device 50 is similar or identical to the one of the first embodiment.

The control carrier 44 acts as a feedback device to control (to brake or to free) the rotational movement of the ring gear 15 of the first planetary gearset 10.

Thanks to the control device 40 that senses the torque difference between the input and output, the transmission device 1 is an automatic transmission.

Thanks to the coupling device 50, the transmission device 1 is a continuously variable transmission.

The working of the device 1 of this second embodiment will be now shortly explained in view of figures 3 and 4. It is similar to the working of the first embodiment of the invention.

At startup, the transmission device 1 is for example in the state of figure 4. A resisting load torque is applied to the second shaft 3 that prevents any rotation of the second shaft 3.

An input rotation of the first shaft 2 drives into rotation the sun gears 11, 21. As in the first embodiment, this quickly moves the control shaft 42 at second end of the hole 41a to directly drives the second shaft 3 with the same rotation speed. The control carrier 44 is moved to decouple the inner and outer rings of the coupling device 50, and the elastic element 43 is compressed. The transmission ratio of the transmission device 1 is equal to one, and is a maximum ratio.

As the second shaft 3 starts rotating, the resisting load torque decreases a lot. The elastic element 43 then urges the control carrier 44 and the control shaft 42 in the opposite direction towards the first end of the hole 41a and back to the first position. The control carrier 44 is then moved to couple the inner and outer rings of the coupling device 50.

The coupling depends on the displacement d of the control carrier 44, i.e. the displacement d of the control shaft 42 between the first and second ends of the hole 41a.

The outer ring of the coupling device 50 then starts to brake the rotation of the inner ring. It therefore progressively brakes to rotation of the ring gear 15 of the first planetary gearset 10. The transmission ratio decreases.

When the outer ring of the coupling device 50 is completely coupled to the inner ring, the ring gear 15 is prevented of rotating, and the planet gear 12 accelerates the rotation speed of the planet carrier 14 relative to the rotation speed of the first shaft 2. This accelerates the rotation speed of the ring gear 25 of the second planetary gearset 20, and reduces the rotational speed of the planet carrier 24 of the second gearset 20. The second shaft 3 rotates at a lower speed than the first shaft 2, and the transmission ratio becomes a minimum ratio.

In that case, the rotational speed of the ring gear 15 is null, and the rotational speed of the planet carrier 14 of the first planetary gearset 10 may be calculated via the Willis formulae (1) :

(1+AT ₁₀ )

where

ω _π is the rotational speed of the sun gear 11, ω ₁₄ is the rotational speed of the planet carrier 14,

ω ₁₅ = 0 is the rotational speed of the ring gear 15, K _l0 is a ratio of the first planetary gearset 10.

Additionally, the rotational speed of the planet carrier 24 of the second planetary gearset 20 may be calculated again via the Willis formulae (1) applied to this second planetary gearset 20:

ω21 ^{~ ω} 24 _ _v

- ^_ 20

co ₂₅ -co ₂₄

where

ω ₂₁ is the rotational speed of the sun gear 21, ω ₂₄ is the rotational speed of the planet carrier 24,

ω ₂₅ is the rotational speed of the ring gear 25,

K ₂₀ is the ratio of the second planetary gearset 20.

For the second embodiment, we have the following added equations (connections between first and second planetary gearsets 10, 20):

ω ₂₁ = ω _π , and

ω ₂₅ = ω ₁₄ .

The above equations can be directly solved.

Therefore, in case of complete coupling of the coupling device 50, the transmission speed ratio of the transmission device 1 is:

_{T =} g> _{3 =} l+^ ₁₀ +^ ₂₀

¹ co ₂ (l +^ ₁₀ ).(l+ ^ ₂₀ )

And, the transmission device 1 of second embodiment is a reduction transmission device.

Figure 5 is schematic view of a third embodiment of an automatic and continuously variable transmission device 1 according to the invention. The device 1 of this embodiment is a reduction transmission device.

This transmission device 1 comprises the same elements as described for the second embodiment.

It further comprises a third planetary gearset 30 situated between the ring gear 15 of the first planetary gearset 10 and the coupling device 50.

The third planetary gearset 30 comprises (as the first planetary gearset 10) :

- a sun gear 31,

- a planet gear 32 rotating around a planet shaft 33 supported by a planet carrier 34, said planet gear being meshed with the sun gear 31, and

- a ring gear 35 meshed with said planet gear 32. Thanks to this third planetary gearset 30 the rotational speed of the inner ring of the coupling device 50 can be adapted to the coupling device 50.

For example, in case of a coupling device 50 using magnets 51, 52, the size of the magnets can be reduced. Therefore, the transmission device is less expensive and easier to manufacture.

The third planetary gearset 30 may be implemented with or without the second planetary gearset 20.

Figure 6 is a perspective cut view of a real device corresponding to the third embodiment of figure 5. The similar elements can be identified with the same reference numbers as in figure 5.

The second shaft 3 outputs the rotational movement on an output gear.

Figure 7 shows a perspective view of the control device 40 designed for the transmission device of figure 6. Such control device 40 may be used in any embodiment of the invention .

The control device 40 comprises a tubular body 41 and a control shaft 42 that goes through a hole 41a of said tubular body 41.

The hole 41a has for example an helical shape. The shape is adapted to provide a desired behaviour (for the automatic behaviour) to the transmission device 1. Such shape can be predetermined.

The control shaft 42 is equipped with a wheel so as to reduce the friction interaction between the control shaft 42 and the control carrier 44.

Such transmission device is purely mechanical without any actuator (electric, pneumatic or hydraulic) for changing the transmission ratio.

The transmission ratio can have any value in a predetermined range, said predetermined range for example depending on the first and second planetary gearsets designs .

The transmission device 1 is continuously variable. The transmission ratio is automatically adapted to the first input torque and the second output torque according to a law that is predetermined by the control device 40 (for example by the shape of the hole 41a) .

Consequently, the transmission device 1 of present invention may be used in many applications, for having an automatic and continuously variable transmission.