WO2016200251A1

WO2016200251A1 - Continuously variable transmission

Info

Publication number: WO2016200251A1
Application number: PCT/NL2016/000015
Authority: WO
Inventors: Tom KLABBERS
Original assignee: Klabbers Tom
Priority date: 2015-06-10
Filing date: 2016-06-08
Publication date: 2016-12-15
Also published as: NL1041352B1; NL1041352A

Abstract

Continuously variable transmission (100) for transmitting torque from an input axle (200) to an output axle (300), comprising a primary planetary gear set (130) having a primary first gear (131 ), a primary second gear (132) and a primary carrier (133), the primary carrier carrying at least one primary planet gear (134) driveably coupling the primary first gear to the primary second gear, wherein one of the primary first gear, the primary second gear and the primary carrier is driveably coupled to the input axle, wherein another one of the primary first gear, the primary second gear and the primary carrier is driveably coupled to the output axle, the continuously variable transmission further comprising a primary variator (140) for varying the rotational speed of the remaining one of the primary first gear, the primary second gear and the primary carrier, the primary variator comprising a primary worm (141) for restraining said remaining one of the primary first gear, the primary second gear and the primary carrier through one-way interaction with a primary worm wheel, the continuously variable transmission comprising a continuously variable gearing unit (150) driveably coupling the primary worm to the input axle, the continuously variable transmission comprising control means (160) for controlling the transmission ratio of the continuously variable gearing unit, the continuously variable transmission comprising reduction means (142, 1331) for speed-reducing the primary worm wheel as compared to said remaining one.

Description

TITLE: Continuously variable transmission

The present invention relates to a continuously variable transmission for transmitting torque from an input axle to an output axle.

Many types of continuously variable transmissions comprise an element such as a belt, a wheel, a ball or a roll, that ultimately interacts through friction with each of the input axle and the output axle for transmitting torque from the one to the other.

Also, in various types of continuously variable transmissions, friction is used for manipulating the transmission ratio, for instance through a brake or an electric magnet acting on some part of the transmission. Such types of continuously variable transmissions may comprise steel or rubber beits on adjustable pulleys, friction wheels, toroidal rollers, cones, etc.

In transmissions of the above types, gains in energy efficiency resulting from the continuous variability of the transmission ratio have been found to be largely cancelled out by internal losses.

An objective of the invention is to provide a continuously variable transmission having an energy efficiency that is relatively high as compared to that of continuously variable transmissions of the described known types.

According to the invention, a continuously variable transmission comprises a primary planetary gear set having a primary first gear, a primary second gear and a primary carrier, the primary carrier carrying at least one primary planet gear driveably coupling the primary first gear to the primary second gear, wherein one of the primary first gear, the primary second gear and the primary carrier is driveably coupled to the input axle, wherein another one of the primary first gear, the primary second gear and the primary carrier is driveably coupled to the output axle, the transmission further comprising a primary variator for varying the rotational speed of the remaining one of the primary first gear, the primary second gear and the primary carrier, the primary variator comprising a primary worm for restraining said remaining one of the primary first gear, the primary second gear and the primary carrier through one-way interaction with a primary worm wheel, the transmission comprising a continuously variable gearing unit driveably coupling the primary worm to the input axle, the transmission comprising control means for controlling the transmission ratio of the continuously variable gearing unit.

The primary worm is driven to rotate by the input axle through the

continuously variable gearing unit. While rotating, the primary worm allows said remaining one gear or carrier either to rotate substantially freely, while being driven by the one gear or carrier that is coupled to the input axle, or to rotate at only a limited speed. In the latter case, the one gear or carrier that is coupled to the input axle not only drives said remaining one gear or carrier, but also the one gear or carrier that is coupled to the output axle. The ratio in which each of said remaining one gear or carrier and the one gear or carrier coupled to the output axle is driven, depends on the speed of the primary worm as compared that of the input axle, and hence on the transmission ratio set for the continuously variable gearing unit. As a result, by varying the transmission ratio set for the continuously variable gearing unit, the transmission ratio between the input axle and the output axle can be also varied. Due to the positive engagement between the various gears of the planetary gear set, losses in the transfer of power from the input axle to the output axle are relatively low. Furthermore, thanks to the one-way interaction between the primary worm and the primary worm wheel, the power requirements for driving the primary worm are relatively low as well. As a result, the energy efficiency of the transmission according to the invention is relatively high.

For even better energy efficiency, the continuously variable gearing unit may comprise a secondary planetary gear set having a secondary first gear, a secondary second gear and a secondary carrier, the secondary carrier carrying at least one secondary planet gear driveably coupling the secondary first gear to the secondary second gear, wherein one of the secondary first gear, the secondary second gear and the secondary carrier is driveably coupled to the input axle, wherein another one of the secondary first gear, the secondary second gear and the secondary carrier is driveably coupled to the primary worm, said control means forming a secondary variator for varying the rotational speed of the remaining one of the secondary first gear, the secondary second gear and the secondary carrier.

The secondary variator may comprise a secondary worm for restraining said remaining one of the secondary first gear, the secondary second gear and the secondary carrier through one-way interaction with a secondary worm wheel, so as for the secondary variator itself to have low power requirements. The transmission may comprise a drive unit, for instance an electric motor, for driving the secondary worm independently from the input axle. Alternatively, said secondary worm may be driveably coupled to the input axle, so as to avoid any additional electric systems.

In addition to any means for controlling the rotational speed of the remaining one of the secondary first gear, the secondary second gear and the secondary carrier, the transmission may comprise a braking system operable for instantly halting that same remaining one. With such a system, at the cost of only limited power, the remaining one in the secondary planetary gear set can be slowed down or halted so as for the remaining one in the primary planetary gear set to be sped up in case the output axle is to be slowed down or halted itself.

The transmission ratios within the primary planetary gear set, i.e., those between the primary sun gear, the primary annular gear and the primary carrier, and the transmission ratios within the secondary planetary gear set, i.e., those between the secondary sun gear, the secondary annular gear, and the secondary carrier, can be chosen such that when the secondary worm, and hence the secondary carrier, is stationary, the primary worm, and hence the primary carrier, is driven at such a speed, that also the output axle is stationary. Said transmission ratios may also be chosen such, however, that the output axle is stationary at a predetermined speed of the secondary worm. This allows for the output axle to be driven in reverse using torque provided by the input axle, part of the torque in that case being transferred through the secondary variator and the primary worm, by the secondary worm being driven at only a limited speed, lower than said predetermined speed.

The primary worm may be arranged to be disengaged from said remaining one of the primary first gear, the primary second gear and the primary carrier, in order to enable undriven output.

The transmission may comprise a flywheel driveably coupled to said remaining one of the primary first gear, the primary second gear and the primary carrier, for storing energy transferred to said remaining one primary gear or carrier rather than to the one primary gear or carrier that is coupled to the output axle.

The flywheel may be arranged to turn faster than said remaining one of the primary first gear, the primary second gear and the primary carrier, so as for the flywheel itself and for the whole of the continuously variable transmission to be able to relatively lightweight, allowing for further energy savings. A radially more outwardly located portion of the flywheel may have a larger specific weight than a radially more inwardly located portion thereof, adding to the ability of the flywheel to be relatively lightweight, and hence to the further energy savings.

To decrease the strain on the primary worm, the primary worm may be supported in the interaction with the primary worm wheel by one or more additional worms, that may be driveably coupled to the primary worm. A vehicle provided with a drive train comprising a continuously variable transmission according to the invention may comprise an automatic blocking system for automatically blocking the output axle from rotating when the vehicle comes to a halt, to prevent the vehicle from rolling backwards when coming to a halt on a slope, the engine stopping as a result of the permanent connection between the wheels and the engine, through the transmission.

In the following, the invention will be described in more detail with reference to the drawings, wherein:

Figure 1 shows an embodiment of a continuously variable transmission according to the invention in a perspective view;

Figure 2 shows a blocking system to be applied in combination with the transmission of Figure 1 ;

Figure 3 shows a detail of the transmission of Figure 1 ;

Figure 4 shows an alternative embodiment of part of the transmission of Figure 1 ;

Figure 5 shows an alternative embodiment of another part of the transmission of Figure 1.

With reference to Figure 1 , a continuously variable transmission 100 for transmitting torque from an input axle 200 to an output axle 300 comprises a primary planetary gear set 130 having a primary sun gear 131 , a primary annular gear 132, and a primary carrier 133. The primary carrier 133 carries three primary planet gears 134 driveably coupling the primary sun gear 131 to the primary annular gear 132. The primary sun gear 131 is connected to the input axle 200 so as for a rotation of the input axle 200 to be directly transferred to the primary sun gear 131. The primary annular gear 132 is connected to the output axle 300 so as for a rotation of the primary annular gear 132 to be directly transferred to the output axle 300. The primary carrier 133 is mounted so as to be able to rotate independently from each of the primary sun gear 131 and the primary annular gear 132, in this case by being rotatably mounted on the input axle 200. The primary planet gears 134 are each rotatably mounted on the primary carrier 133, each engaging the primary sun gear 131 as well as the primary annular gear 132.

The transmission 100 further comprises a primary variator 140 for varying the rotational speed of the primary carrier 133. The primary variator 140 comprises a primary worm 141 , a primary worm wheel 142 and a primary transitional gear 143. The primary worm 141 engages the primary worm wheel 142 so as to be able to restrain the latter from rotating at certain higher speeds by rotating itself at only a limited speed. The primary worm wheel 142 is connected to the primary transitional gear 143 so for any rotation of the primary transitional gear 143 to be directly transmitted to the primary worm wheel 142. The primary transitional gear 143 is arranged engaging a toothed, more inwardly positioned circumference 1331 of the primary carrier 133 so as for the primary transitional gear 143 to be able to be driven by the primary carrier 133.

The primary worm 141 and the primary worm wheel 142 are configured such that they can only interact in one way, i.e., that under normal operational conditions of the continuously variable transmission 100, the primary worm 141 is unable, or at least able to only a limited extent, to be driven by a rotation of the primary worm wheel 142. In other words, the combination of the primary worm 141 and the primary worm wheel 142 is self-locking. The lead angle of the primary worm 141 may for instance be smaller than 30 degrees, such as 15 degrees. Other lead angles are possible, however, depending on the occuring rotational speeds of the combination of primary worm 141 and primary worm wheel 142. Self-locking behaviour may already occur at a worm/worm-wheel transmission ratio greater than 7 (i.e., a lead angle smaller than 51 degrees), and can continue until a transmission ratio of 180 (i.e., a lead angle of 2 degrees).

It is noted that the toothed, more inwardly positioned circumference 1331 and the primary transitional gear 143 together form reduction means that enable the primary worm wheel 142 to rotate at a reduced speed as compared to the primary carrier 133. This allows the primary worm 141 to rotate at a relatively low speed, while still being able to restrain the primary carrier 133 at a relatively high speed of the latter. A low speed of the primary worm 141 is required in view of the one-way interaction between the primary worm 141 and the primary worm wheel 142 and self- locking character of the primary worm 141 , which leaves the primary worm 141 with a relatively low lead angle as noted above. At a relatively low speed of the primary worm 141 , the load on the worm/worm-wheel combination 141 , 142 can be higher.

In an alternative embodiment, the reduction means may also comprise other means than a gear 143 or a toothed circumference 1331. The reduction means may also comprise, for instance, an auxiliary worm coupled to the primary carrier 133 to be able to be driven by the primary carrier 133, which auxiliary worm engages a worm wheel that is arranged to rotate at only a limited speed by ultimately being restrained by the primary worm 14 . Said worm wheel may be an auxiliary worm wheel that is driveably coupled to the primary worm wheel 142, or even be the primary worm wheel itself. By a worm/worm-wheel combination, a relatively large speed reduction can be obtained more easily or efficiently than by using a gear combination. The transmission 100 further comprises a continuously variable gearing unit

150 driveably coupling the primary worm 141 to the input axle 200, and control means 160 for controlling the transmission ratio of the continuously variable gearing unit 150. An automatic blocking system 400 is provided, serving to automatically block the output axle 300 from rotating when a vehicle that the transmission 100 is part of comes to a halt. In the shown example, the blocking system 400 comprises a worm wheel 401 mounted on the output axle 300, engaged by a worm 402 that can be controlled to be driven at certain speeds in order for the output axle 300 to be allowed to rotate, or to be kept still in order for the output axle 300 to be blocked.

With reference to Figure 2, an alternative embodiment of a blocking system 400 envisaged is the combination of a gear 403 mounted on the output axle 300, which gear 403 can be selectively blocked from rotating by a hook 404 controllably engaging the gear 403, or any other automatic braking system.

With reference to Figure 3, the continuously variable gearing unit 150 comprises a secondary planetary gear set having a secondary sun gear 151 , a secondary annular gear 152, and a secondary carrier 153. The secondary carrier 153 carries three secondary planet gears 154 driveably coupling the secondary sun gear

151 to the secondary annular gear 152.

The secondary annular gear 152 is coupled to the input axle 200 through a gear system 190 as partly shown in Figure 1 , for the secondary annular gear 152 to be able to be driven by the input axle 200. The secondary sun gear 151 is coupled to the primary worm 141 , in the shown example by being connected to an axle 144 carrying said primary worm 141 , so as for any rotation motion of the secondary sun gear 151 to be directly transmitted to the primary worm 141. The secondary carrier 153 is mounted so as to be able to rotate independently from each of the secondary sun gear 151 and the secondary annular gear 152, in this case by being rotatably mounted on the axle 144 carrying the primary worm 141. The secondary planet gears 54 are each rotatably mounted on the secondary carrier 153, each engaging the secondary sun gear 151 as well as the secondary annular gear 152.

With further reference to Figure 3, the control means 160 for controlling the variable gearing unit 150 form a secondary variator 160 for varying the rotational speed of the secondary carrier 153. The secondary variator 160 comprises a secondary worm 161 , a secondary worm wheel 162 and a secondary transitional gear 163.

The secondary worm 161 engages the secondary worm wheel 162 so as to be able to restrain the latter from rotating at certain higher speeds by rotating itself at only a limited speed. The secondary worm wheel 162 is connected to the secondary transitional gear 163 so for any rotation of the secondary transitional gear 163 to be directly transmitted to the secondary worm wheel 62. The secondary transitional gear 163 is arranged engaging a toothed, inwardly positioned circumference (not shown) of the secondary carrier 53 so as for the secondary transitional gear 63 to be able to be driven by the secondary carrier 153.

The secondary worm 161 and the secondary worm wheel 162 are configured such that they can only interact in one way, i.e., that under normal operational conditions of the continuously variable transmission 00, the secondary worm 161 is unable to be driven by a rotation of the secondary worm wheel 162. In other words, the combination of the secondary worm 161 and the secondary worm wheel 162 is self-locking. The lead angle of the secondary worm 161 may for instance be smaller than 30 degrees. Ideally, the angle is 15 degrees.

With further reference to Figure 1 , the transmission 100 further comprises a flywheel assembly 80 for storing and feeding back energy put into the primary carrier 133.

The flywheel assembly 180 comprises a flywheel 181 rotatably mounted on the input axle 200, that is driveably coupled to the primary carrier 133 through a pair of transitional gears 181 , 182 connected by an axle 183. A first, smaller transitional gear 181 engages a toothed, more outwardly positioned circumference 1332 of the primary carrier 133. A second, larger transitional gear 182 engages a toothed circumference 1811 of the flywheel 181. The axle 183 ensures that any rotation of the smaller transitional gear 181 that is brought about by the primary carrier 133 is transmitted to the larger transitional gear 182 in order for the latter to drive the flywheel 181.

It is noted that the first transitional gear 181 , interacting with the primary carrier 133 as a relatively small gear being driven by a relatively large gear, is configured to turn faster than the primary carrier 133, which enables also the flywheel 181 to turn faster than the primary carrier 133. This enables the flywheel 181 to be relatively light, while still being able to store a certain amount of energy, or at least an amount of energy that could be stored by a flywheel of larger weight, mounted directly on the input axle 200 so as to rotate at the same speed as the primary carrier 133.

For the flywheel 181 to be able to be even more lightweight while still being able to store a certain amount of energy, the flywheel 181 may have a distributed weight so as for a radially more outwardly located portion of the flywheel 181 to have a larger specific weight, i.e., a larger weight in relation to its circumferential dimension, than a radially more inwardly located portion of the flywheel 181. For instance, the flywheel 181 could be thicker at further distances from its center, or be made of heavier material.

The primary planetary gear set 130 acts as a differential. As a result, the amount of torque transmitted from the primary sun gear 131 to the primary annular gear 132 depends on the speed of the primary carrier 133. In case the primary carrier 133 is stationary, any torque from the primary sun gear 131 is transmitted only to the primary annular gear 132. In case the primary carrier 133 is rotating at a certain speed, or is at least able to rotate at a certain speed, however, the amount of torque that is transmitted from the primary sun gear 131 to the primary annular gear 32 is limited by an amount depending on the speed of the primary carrier 133.

Any rotation of the primary carrier 133 is driven by the primary sun gear 131. The speed of the primary carrier 133 is limited, however, by the speed of the primary worm 141. In case the speed of the primary worm 141 is such, that the primary carrier 133 is able to rotate substantially freely, any torque from the primary sun gear 131 is transmitted to the primary carrier 133, and none, or only little, being

transmitted to the primary annular gear 132. In a similar way, also the secondary gear set 150 acts as a differential. With the secondary worm 161 being able to limit the rotational speed of the secondary carrier 153, depending on the speed of the secondary worm 161 , any torque from the secondary annular gear 152 is either transmitted to only the secondary sun gear 151 , partly to the secondary sun gear 151 and partly to the secondary carrier 153, or only to the secondary carrier 151.

The transmission ratio for the transmission of torque from the input axle 200 to the output axle 300 through the primary planetary gear set 130 is varied through changing the speed of the primary worm 141 by controlling the transmission ratio of the secondary planetary gear set 150 with the help of the secondary worm 161.

In case the secondary worm 161 is held stationary, all torque from the secondary annular gear 152 is transmitted to the secondary sun gear 152, whereby the primary worm 141 is driven at a speed at which the primary carrier 131 is enabled to rotate substantially freely, as a result of which torque is transmitted mainly from the primary sun gear 131 to the primary carrier 133, the primary annular gear 132 thereby being held stationary. When the speed of the input axle 200 is increased, the speed of the primary carrier 133, driven by the primary sun gear 131 , and the speed of the primary worm 141 are increased in corresponding ways, so as for the primary annular gear 132 to remain stationary.

In case the secondary worm 161 is rotating at a certain speed, driven by the drive unit or through a transmission connecting the secondary worm to the input axle 200, the secondary worm 161 enables the secondary carrier 153 to be driven by the secondary annular gear 152 at a certain speed, so that the torque transmitted to the secondary sun gear 151 and hence the primary worm 141 is limited. The primary carrier 133 is thereby limited from rotating at a certain speed, and part of the torque from the primary sun gear 131 is transmitted to the primary annular gear 132, allowing the primary annular gear 132 to be in motion.

Input variables for setting the speed of the secondary worm 161 may be any parameter, or change of a parameter, from which a certain desired change in transmission ratio can be derived. In case the transmission is part of a vehicle drive train, such a parameter may for instance be the accelerator position, the number of engine revolutions per time unit, or vehicle speed.

In order to decrease the strain on the primary worm 141 while interacting with the primary worm wheel 142 as depicted in Figure 1 , with reference to Figure 4, an interaction with the primary worm wheel 142 may also involve one or more additional worms 241 , that may be driveably coupled to the primary worm 141 , for instance through gears 201 , 202 connected to each of the primary worm 141 and the additional worm 241 , so as for the primary worm 141 and the additional worm 241 to restrain the primary worm wheel 142 together.

It should be clear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the appending claims. Even if certain features are recited in different dependent claims, the present invention also relates to an embodiment comprising these features in common. Any reference signs in a claim should not be construed as limiting the scope of that claim. In the shown embodiment, in each of the primary planetary gear set 130 and the secondary planetary gear set 150, the carrier 133, 153 is the rotating element whose rotational speed is controlled by a respective variator 140, 160. Within the scope of the invention, however, in either planetary gear set 130, 150, it may also be the sun gear 131 , 151 or the annular gear 132, 152 whose speed is controlled by the variator 133, 153, in order to control the transfer of torque between either of the carrier 133, 153 and the other one of the sun gear 131 , 151 and the annular gear 132, 152, and the other of the carrier 133, 153 and the other one of the sun gear 131 , 151 and the annular gear 132, 152, and any axles connected to the latter two. As an alternative embodiment to the secondary planetary gear set 150, any other type of a continuously variable gearing unit may be applied, for instance a belt- based or a push-belt-based system, through which the primary worm 141 is driven by the input axle 200. In the embodiment of Figure 1 , the primary planetary gear set 130 and the secondary planetary gear set 150 each comprise a sun gear 131 , 151 positioned inside an annular gear 132, 152, the planet gears 134 arranged to move together with the carrier 133 with their rotational axes with respect to said carrier 133 oriented in parallel to a common rotational axis of the sun gear 131 , the annular gear 151 , and the carrier 133. With reference to Figure 5, as an alternative for either planetary gear set 130, 150, an embodiment is envisaged comprising an input gear 501 and an output gear 502 spaced along a common rotational axis of the input gear 501 , the output gear 502 and a carrier 503, the planet gears 504 arranged to move together with the carrier 503 with their rotational axes with respect to said carrier 503 oriented orthogonally to the common rotational axis. As depicted, a worm 505 driven to control the rotational speed of the carrier 503 may directly engage a circumferential portion 5031 of the carrier 503, that is configured for the carrier 503 itself to act as a worm wheel. The latter is an alternative to an engagement through transitional gears, which allows the rotational speed of a worm to be reduced while the worm is still able to restrain a carrier, or any rotational element of a planetary gear set for that matter, that is rotating at a relatively high speed.

Claims

1. Continuously variable transmission (100) for transmitting torque from an input axle (200) to an output axle (300), comprising a primary planetary gear set (130) having a primary first gear (131), a primary second gear (132) and a primary carrier (133), the primary carrier carrying at least one primary planet gear (134) driveably coupling the primary first gear to the primary second gear, wherein one of the primary first gear, the primary second gear and the primary carrier is driveably coupled to the input axle, wherein another one of the primary first gear, the primary second gear and the primary carrier is driveably coupled to the output axle, the continuously variable transmission further comprising a primary variator (140) for varying the rotational speed of the remaining one of the primary first gear, the primary second gear and the primary carrier, the primary variator comprising a primary worm (141) for restraining said remaining one of the primary first gear, the primary second gear and the primary carrier through one-way interaction with a primary worm wheel, the continuously variable transmission comprising a continuously variable gearing unit (150) driveably coupling the primary worm to the input axle, the continuously variable transmission comprising control means (160) for controlling the transmission ratio of the continuously variable gearing unit, the continuously variable transmission comprising reduction means (142, 1331 ) for speed-reducing the primary worm wheel as compared to said remaining one.

2. Continuously variable transmission according to claim 1 , the reduction means comprising a worm/worm-wheel transmission.

3. Continuously variable transmission according to claim 2, the reduction means comprising an auxiliary worm driveably coupled to said remaining one, which auxiliary worm engages the primary worm wheel.

4. Continuously variable transmission according to any one of the preceding claims, the continuously variable gearing unit (150) comprising a secondary planetary gear set having a secondary first gear (151 ), a secondary second gear (152) and a secondary carrier (153), the secondary carrier carrying at least one secondary planet gear (154) driveably coupling the secondary first gear to the secondary second gear, wherein one of the secondary first gear, the secondary second gear and the secondary carrier is driveably coupled to the input axle, wherein another one of the secondary first gear, the secondary second gear and the secondary carrier is driveably coupled to the primary worm, said control means forming a secondary variator (160) for varying the rotational speed of the remaining one of the secondary first gear, the secondary second gear and the secondary carrier.

5. Continuously variable transmission according to claim 4, the secondary variator comprising a secondary worm for restraining said remaining one of the secondary first gear, the secondary second gear and the secondary carrier through one-way interaction with a secondary worm wheel.

6. Continuously variable transmission according to claim 5, comprising a drive unit for driving the secondary worm independently from the input axle.

7. Continuously variable transmission according to claim 6, said drive unit comprising an electric motor.

8. Continuously variable transmission according to claim 5, said secondary worm being driveably coupled to the input axle.

9. Continuously variable transmission according to any one of claims 4-8, comprising, in addition to the secondary variator, a braking system operable for instantly halting the remaining one of the secondary first gear, the secondary second gear and the secondary carrier.

10. Continuously variable transmission according to claim 8 insofar as dependent on claim 4, wherein the transmission ratios within the primary planetary gear set and those within the secondary planetary gear set are chosen such, that the output axle is stationary at a predetermined speed of the secondary worm.

11. Continuously variable transmission according to any one of the preceding claims, the primary worm being arranged to be disengaged from said remaining one of the primary first gear, the primary second gear and the primary carrier.

12. Continuously variable transmission according to any one of the preceding claims, comprising a flywheel (181 ) driveably coupled to said remaining one of the primary first gear, the primary second gear and the primary carrier.

13. Continuously variable transmission according to claim 12, the flywheel being arranged to turn faster than said remaining one of the primary first gear, the primary second gear and the primary carrier.

14. Continuously variable transmission according to claim 12 or 13, a radially more outwardly located portion of the flywheel having a larger specific weight than a radially more inwardly located portion thereof.

15. Continuously variable transmission according to any one of the preceding claims, wherein the primary worm is supported in the interaction with the primary worm wheel by one or more additional worms (241) driveably coupled to the primary worm.

16. Continuously variable transmission according to any one of the preceding claims, further comprising reduction means (142, 1331) for reducing a turning speed of the primary worm as compared to the remaining one of the primary first gear, the primary second gear and the primary carrier.

17. Continuously variable transmission according to claim 16, the reduction means comprising an auxiliary worm driveably coupled to said remaining one of the primary first gear, the primary second gear and the primary carrier, which auxiliary worm engages a worm wheel arranged to be restrained by the primary worm.

18. Vehicle having a drive train for propelling the vehicle, the drive train

comprising a continuously variable transmission according to any one of the preceding claims.

19. Vehicle according to claim 18, further comprising an automatic blocking system (400) for automatically blocking the output axle when the vehicle comes to a halt.