WO2020259955A1

WO2020259955A1 - Transmission element and gearbox for a power transmission system

Info

Publication number: WO2020259955A1
Application number: PCT/EP2020/065023
Authority: WO
Inventors: Konstantinos Kontopoulos; Grigorios Maximilian Kontopoulos
Original assignee: Kontopoulos, Leonidas Kyros; KONTOPOULOS, Kyros Philippos
Priority date: 2019-06-28
Filing date: 2020-05-29
Publication date: 2020-12-30
Also published as: AU2020304584A1; WO2020259964A1

Abstract

The present invention is generally directed to a transmission element comprising at least one first part (112; 122; 212) and at least one second part (111; 121; 211) which is rotatable relative to the at least one first part about a common axis (2) by a limited degree, and at least one first elastic element (114; 124), wherein the at least one first part and the at least one second part together form at least one compartment in which the at least one first elastic element (114; 124) is arranged between the at least one first part (112; 122; 212) and the at least one second part (111; 121; 211) to bias the at least one first part and the at least one second part rotationally away from each other in opposite directions. To achieve instant load transmission the transmission element (3) further comprises at least one second elastic element (113; 113a; 113b; 123) arranged within the at least one compartment between the at least one first part and the at least one second part. The at least one second elastic element (113; 113a; 113b; 123) is arranged parallel to the at least one first elastic element (114; 124) and the elastic elements (113, 113a, 113b, 123; 114, 124) comprise different suspension rates and/or different lengths. Further, the present application re- lates a gearbox comprising such a transmission element (3).

Description

TRANSMISSION ELEMENT AND GEARBOX FOR A POWER TRANSMISSION SYSTEM

Description

The present invention is generally directed to a transmission element, a gearbox and a power transmission system suitable to be used e.g. in a marine engine or in an automobile. Such a transmission element may comprise at least one first part, at least one second part which is rotatable relative to the at least one first part about a common axis by a limited degree, and at least one first elastic ele ment, wherein the at least one first part and the at least one second part together form at least one compartment in which the at least one first elastic element is arranged between the at least one first part and the at least one second part to bias the at least one first part and the at least one second part rotationally away from each other in opposite directions.

Transmission elements such as gear wheels or dog clutches are well known and used in gearboxes for example of automobiles as well as of motor boats. During gear changing the gears are constantly rotating such that high wear and tear forces act on the gearbox components while shifting from one gear to another, i.e. when a dog clutch locks different gears to the rotating shafts. Such forces are commonly limited by using synchronizing mechanism that match the speed of the gear to that of the shaft.

Therefore, a short pause is often required, for example between changing from forward to reverse gear of a motorboat. During this pause, i.e. the neutral stage, the power source is disengaged from the transmission. Thus, the speed of the engine more closely matches the speed of the new gear and torque spikes are reduced when the engine is re-engaged to the transmission. Further, to allow a quicker and smoother shifting, elastic elements are arranged within power transmission systems especially gearboxes to absorb the impact on the components during shifting processes. This can reduce unwanted noises and provide the user with a higher quality shifting feel, as well as increasing the life time of the transmission.

Damping mechanisms arranged to damp the locking between the gear elements are known in the prior art. WO 2008/062192 A1 discloses a damping system to absorb the energy in torque spikes generated during locking of a gear element to a shaft. Therefore, the damping system uses resilient means such as rubber blocks or springs arranged in series within an inner and outer part of a gear wheel.

As all elastic elements can only withstand a maximum load, determined by the suspension rate, without being damaged, elastic elements are often selected ac cording to the maximum load, the so-called critical load. Hence, the elastic ele ment only becomes "active", i.e. is being compressed or extended, when sufficient load is applied.

Therefore, the object of the present invention is to provide a transmission element of a gearbox that allows a smooth gear changing, e.g. when the selector engages the shaft with the gear wheel, while simultaneously absorbing maximum shocks. Especially, it is an object of the present invention to develop a system with mini mum constructive and cost expenditures. It is a further object to provide an im proved gearbox and an improved transmission system suitable, e.g. for use in maritime or automotive drive trains.

This object is solved by a transmission element for use in a gearbox according to claim 1 and a gearbox according to claim 10. A transmission element of a power transmission system according to the present invention comprises at least one first part and at least one second part which is rotatable relative to the at least one first part about a common axis by a limited degree. Further, the transmission element comprises at least one first elastically deformable element (first elastic element). The elastic element is arranged be tween the at least one first part and the at least one second part in at least one compartment formed by the at least one first part and the at least one second part, wherein the elastic element biases the at least one first part and the at least one second part rotationally away from each other in opposite directions. The transmission element further comprises at least one second elastically deforma ble element (second elastic element) arranged within the at least one compart ment between the at least one first part and the at least one second part, wherein the at least one second elastic element is arranged parallel to the at least one first elastic element, and in that the elastic elements comprise different suspension rates and/or different lengths.

The transmission element may be a divided gear wheel or a selector, e.g. a dog clutch type selector. Typically, the transmission elements form more than one compartment. Each compartment then comprises at least one and may also com prise two elastic elements. Regardless of whether one compartment comprises one or two elastic elements, the elastic elements are always arranged parallel to each other even when they are arranged in separate compartments. Preferably, the elastic elements in each compartment are held by supports. The parts, i.e. the at least one first and the at least one second part, may be arranged within each other. In addition, the first part may form the inner and the second part may form the outer part. The use of several elastic elements makes it possible to select one elastic element according to the lowest occurring load, and one elastic element according to the highest occurring load. As a result, a smooth shifting process is guaranteed by a direct response of an elastic element. In case of multiple com partments (each may comprise at least one first and at least one second elastic element), the compartments are evenly arranged circumferentially. Using multiple compartments comprising elastic elements may reduce the maximum deflection angle and thus the available engagement time. Preferably, the compartments are closed. Still further, in a different embodiment, the compartments may be open for heat exchange and facilitate maintenance of the elastic elements.

In a preferred embodiment the at least one second elastic element biases the at least one first part and the at least one second part rotationally away from each other in opposite directions after the at least one first elastic element is loaded. Thus, the at least one second part only becomes "active", i.e. is being loaded, after the at least one first elastic element has been deformed to a certain degree.

Preferably, the first elastic element of the transmission element comprises a lower suspension rate than the second elastic element. If multiple elastic elements are used, the first elastic element comprises the lowest and the last elastic element, i.e. the second elastic element, comprises the highest suspension rate. The elas tic elements in between the frist and the last eleastic element have an ascending suspension rate, wherein the next elastic element after the first elastic element would have a higher suspension rate than the first elastic element and a lower suspension rate than the following elastic element. Further, the suspension rate of the elastic element with the highest suspension rate, i.e. the second elastic element, may be adopted to the maximum torque provided by the motor. Never theless, if the transmission element comprises multiple first and/or second elastic elements, those first elastic elements comprise the same suspension rates and those second elastic elements comprise the same suspension rates, wherein the suspension rates of the first elastic elements differ from the suspension rates of the second elastic elements.

However, independent of the exact arrangement of the elastic elements it can be said that the elastic element with the lowest suspension rate is more responsible for a soft and smooth engagement of the transmission elements, wherein the elas tic element with the highest suspension rate is more responsible for power trans mission. The elastic element with the smaller suspension rate may only handle less than 0.5% of the maximum occurring load. Thus, due to the existence of elastic elements with very low and high suspension rates, the engagement of the transmission elements with another transmission element is achieved by the elas tic elements with low suspension rates, wherein the stiffer elastic elements, i.e. the elastic elements with higher suspension rates, transfer the significant load. For the engagement of two transmission elements, e.g. the engagement of a gear wheel and a selector, it is not mandatory that both transmission elements com prise elastic elements and/or are designed according to the invention.

In one embodiment, the at least one first elastic element of the transmission ele ment is partially arranged within the at least one second elastic element. Thus, the at least one first elastic element is protruding from the at least one second elastic element and can therefore be independently deformed. If there are multiple elastic elements arranged within one compartment, the first elastic element has the greatest length and the last spring element has the smallest length. The spring elements arranged between the first and the last spring element have a longer length one after the other, so that the second spring element would be the second longest spring element and thus longer than the last and shorter than the first. There may also be compartments comprising at least two elastic elements that are not partially arranged within each other even though they are arranged in the same compartment. In addition, the elastic elements may be held by supports, wherein the supports may comprise at least one recess. If the elastic elements are not arranged within each other, one elastic element may be held by the first part of the support, wherein additional elastic elements may be held by the re cessed part of the support. If the elastic elements are partially arranged within each other, the length of the first elastic element protruding from the second spring element can be used to determine the load at which the second elastic element becomes active. Obvi ously, the at least one first elastic element can also enclose the at least one sec ond elastic element and thus the second elastic element is arranged within the at least one first elastic element.

In a preferred embodiment, the at least one first and the at least one second elas tic elements are spring elements. Alternatively, the at least one first elastic ele ment may be provided by a spring element and the at least one second elastic element may be provided by a rubber element such as a rubber block. Regardless of which elastic element is used, the elastic elements always comprise different suspension rates as described above. Of course, the invention also includes an interchange of possible arrangements of elastic elements, the use of alternative elastic means as well as the use of different lengths of elastic elements in alter native sequences.

According to a preferred embodiment of the present invention, the first elastic element, i.e. the elastic element with the lowest suspension rate, is preloaded. When the elastic element comprises a spring arranged within a divided gear wheel, for example a torsional spring, the spring is preloaded so that:

Tpre — J * ^max f-

Where T_pre is the preloaded torque of the spring, J is the moment of inertia of the inner part of the divided gear wheel, i.e. the first part of the divided gear wheel, m_ax is the maximum angular acceleration/deceleration that can be achieved by the inner part of the divided bevel gear and T_f is the torque created by friction forces between the inner part and the assigned shaft. The preloaded spring is adapted in order to have negligibly deformed first elastic element before the engagement, regardless if the components accelerate, decel erate or both rotate with a constant angular velocity. As a result when the divided gear wheel is not in engagement, it stays in a neutral position with the first spring element being negligibly deformed, despite any occurring acceleration or decel eration of the divided gear wheel parts, due to the existence of the preloaded spring.

If the so-called neutral position occurs without the first elastic element being pre- loaded a higher suspension rate, in comparison to the suspension rate of the pre- loaded spring, has to be adopted.

In a preferred embodiment, the at least one compartment comprises at least one damping element. Therefore, the number of damping elements may refer to the number of compartments. Further, the at least one damping element may be com prised by the supports, i.e. the inner or the outer supports. The at least one damp ing element may also be arranged on another component. Regardless of the po sition of the at least one damping element, the damping element is provided to damp the recoil or kickback that occurs when the transmission element is disen gaged from another transmission element, wherein at least one transmission ele ment is designed according to the invention. This recoil or kickback may lead to a collision of the inner and outer parts.

In a further embodiment, the at least one first part is arranged at least partially within the at least one second part. This means, that the two transmission element parts are at least partially arranged within each other and therefore an inner and an outer part may exist. Forming a compartment by at least partially arranged transmission elements within each other, allows the elastic elements to be better protected and a more compact installation space to be achieved. As mentioned above, the transmission elements may be gear wheels, preferably bevel or spur gear wheels, or selectors such as dog clutch type selectors.

Therefore, a gearbox according to the present invention comprises at least one drive shaft, at least one drive wheel coupled to the at least one drive shaft, an output shaft, at least one selector coupled to the output shaft or the at least one drive shaft, and at least one gear wheel, wherein the at least one gear wheel and/or the at least one selector are transmission elements according to the inven tion. The drive shaft is coupled to an engine and therefore receives power. The output shaft forms the output side. The output side might be a propeller of a boat. The selector is used to engage the at least one gear wheel as defined above to the output shaft so that a power transmission between the drive shaft to the output shaft is realized via the drive wheel, the gear wheel and the selector.

Typically the at least one gear wheel is in constant engagement with the at least one drive wheel or with at least one other gear wheel. Thus, by coupling the se lector located on the output shaft to the gear wheel, the above described power transmission between the drive and the output shaft can be realized.

The drive wheel is preferably given by a bevel pinion. For a functioning transmis sion system, the gear wheel must be adapted to the drive wheel or vice versa. Hence, if a bevel pinion forms the drive wheel, the divided gear wheel must be given by a bevel gear wheel. Other types of gear wheels may be used. Further, also the gear wheel must be adapted to the selector or vice versa. Thus, if a dog clutch type selector is given, the gear wheel needs to comprise respective cou pling elements.

In a preferred embodiment the rotational axis of the at least one gear wheel and the rotational axis of the drive wheel form a 90° angle. Different angles may be realized using different gear and drive wheels. Preferably, the selector comprises first coupling elements for rotationally coupling and/or de-coupling with corresponding first coupling elements of the at least one gear wheel and/or comprises second coupling elements for rotationally coupling and/or de-coupling with corresponding coupling elements of the output shaft. The number of coupling elements intended for mutual coupling and/or de-coupling may differ, e.g. the first coupling elements of the selector may be less than the first coupling elements of the gear wheel. The coupling elements may be formed by cavities or protrusions. Thus, if the first coupling elements are for example formed by protrusions and may be less than the second coupling elements that are for example formed by cavities, there may be a greater number of coupling possibilities. The same applies of course also vice versa.

Additionally, the selector may be axially or helically movable along the axis of the output shaft. A helical movement is understood as a combination of an axial and a rotational movement. Further, the selector may be torque proof fixed to the as signed shaft, i.e. the drive or the output shaft. The movement of the selector al lows engagement with corresponding engagement means of a gear wheel, which may be a divided gear wheel. The axial movement of the selector may be guided by guiding means. Those guiding means may be arranged linear or helically. As a consequence of helical guiding means, the selector will additionally rotate when axially moving, contributing in a smaller difference in angular velocities between the two engaging components, and therefore achieving an even smoother en gagement. In this case the shifting mechanism would have to secure the engage ment of the two components with the help of a securing mechanism (e.g. a worm gear mechanism, a hydraulic mechanism etc.).

In addition, the selector may be a dog clutch type selector. Such a dog clutch type selector may comprise teeth or other engagement means which can be coupled with engagement means of the gear wheel. Thus, by engaging the selector, power transfer may be achieved. If the gearbox comprises two gear wheels, the selector may be engaged with one of the gear wheels to provide a rotation of the assigned shaft in one direction and may be engaged with the other gear wheel to provide rotation of the assigned shaft in an opposite direction. The selector may be ar ranged concentrically to the output shaft.

In addition or as an alternative, at least one sensor for measuring the angular velocity of the drive wheel and/or the at least one gear wheel and/or the output shaft and/or the drive shaft and/or the selector is arranged within the gearbox. By using the sensor information, the throttle may be adjusted in order not to experi ence stalling. Thus, the throttle may be adjusted automatically in relation to the sensor information. The sensor data can also be used for monitoring systems or the like.

The object of the present invention is further solved by a transmission system comprising a transmission element and/or a gear box as defined above.

Irrespective of the above described embodiments, the present invention is further based on the following embodiments of a transmission element such as a divided gear wheel, a power transmission system and a method for operating a power transmission system:

A transmission element, e.g. a divided gear wheel, wherein said transmission el ement comprises an inner part being engageable with the assigned shaft and an outer part comprising a gear teething suitable for the provided meshed gear wheel, adapted for torque transmission to the other gear wheel, wherein the inner part comprises engagement means that are adapted to engage the inner part with the assigned shaft, wherein upon engagement, the inner part is torque proof en gaged with an assigned shaft, wherein the inner part and the outer part have a common rotational axis, wherein the inner part is at least partially arranged within the outer part, wherein the inner part is arranged angularly deflectable with re spect to the outer part around the common rotational axis, wherein the inner part is coupled to the outer part by means of at least one set of two elastic elements wherein each set of two elastic elements is arranged in a circumferential direction and received within a compartment formed by the inner part and the outer part, wherein each set of two elastic elements is positioned in a way that, the first elastic element consisting the set of two elastic elements is initially deformed upon deflection of either the inner part or the outer part with the deformation of the second elastic element consisting the set of two elastic elements, following after the completion of the engagement of the inner part with the assigned shaft, with said deformation of a second elastic element being accompanied by a simultane ous and continuing deformation of the first elastic element, wherein the first elastic element and the second elastic element consisting the set of two elastic elements of each set of two elastic elements have different spring constants in relation to each other, with the spring constant of the first elastic element being smaller than the spring constant of the second elastic element, wherein the inner part com prises at least one inner support and the outer part comprises at least one outer support that support each set of two elastic elements, wherein the first elastic element is in constant contact with the inner support and the outer support, wherein the at least one inner support and the at least one outer support are in accordance to the number of the selected sets of two elastic elements and their formation is in relation to each other, and wherein the inner part and the outer part are adapted to rotate with the same angular speed if each set of two elastic ele ments is fully loaded under the occurring load.

Further, the at least one inner support of the inner part and/or the at least one outer support of the outer part may comprise a surface with a damping character istic. In a preferred embodiment, a power transmission system, e.g. for an inboard / outboard motor for a marine engine, comprising: a drive shaft, supporting one drive gear wheel, torque proof fixed with the shaft; a output shaft, supporting two transmission elements according to the invention, e.g. two divided gear wheels, wherein each of the two transmission elements constantly meshes with the pro vided drive gear wheel, thereby defining a forward and a reverse gear ratio, wherein divided gear wheels are adapted to freely rotate when not engaged with the output shaft; and one engagement component/dog clutch type selector, that is assigned to the output shaft and assigned to both the divided gear wheels, wherein the engagement component/dog clutch type selector is positioned con centrically to the output shaft, torque proof fixed with the output shaft, arranged axially movable along the output shaft in order to select forward or reverse gear ratio, adapted to engage the inner part of the divided gear wheels and thereby torque proof fixing the inner part with the output shaft.

The power transmission system, e.g. for an inboard / outboard motor for a marine engine, may comprise: a output shaft, supporting a torque proof fixed with the output shaft gear wheel; two drive shafts, each supporting a torque proof fixed with the drive shaft drive gear wheel, and a divided gear wheel as described above, wherein each of the two divided gear wheels constantly meshes with the provided gear wheel, thereby defining a forward and a reverse gear ratio, wherein divided gear wheels are adapted to freely rotate when not engaged with the as signed drive shafts; and an engagement component/dog clutch type selector, that is assigned to each of the respective drive shafts and assigned to each of the divided gear wheels, wherein the engagement component/dog clutch type selec tor is positioned concentrically to each of the respective drive shafts, torque proof fixed with each of the respective drive shafts, arranged axially movable along each of the respective drive shafts in order to select forward or reverse gear ratio, adapted to engage the inner part of the divided gear wheels and thereby torque proof fixing the inner part with the respective drive shaft. Preferably, the axial movement of each of the engagement component/dog clutch type selector along the assigned output shaft or the assigned drive shaft is guided by guiding means that can have any suitable form or shape, wherein upon inter action with the engagement surface, which is in accordance with the selection of the guiding means, the engagement component/dog clutch type selector may be rotated in relation to the assigned output shaft or the assigned drive shaft when is axially moved.

In addition or as an alternative, the engagement component/dog clutch type se lector comprises engagement means facing the assigned divided gear wheel, po sitioned in accordance to the corresponding engagement means of the inner parts of the divided gear wheels formed in relation and in accordance to the form and to the position of the engagement means of the inner parts adapted to interact with them, engaging the engagement component/dog clutch type selector with the inner parts wherein upon engagement the inner part is torque proof engaged with the assigned output shaft or the assigned drive shaft.

Further, the power transmission may comprise a mechanic, electric or hydraulic gear shifting mechanism that is adapted to axially move the at least one engage ment component/dog clutch type selector, selecting or deselecting the desired divided gear wheel by engaging or disengaging the according inner part, by an according movement of the gear shifting lever which is connected in the respec tive gear selector coupling, changing gear ratios.

Preferably, a method for operating a power transmission system may comprise the following steps: rotating drive shaft and transferring power to output shaft by means of a forward gear ratio; performing a gear ratio changing action from a forward gear ratio to a reverse gear ratio; axially moving the respective engage ment component/dog clutch type selector and thereby disengaging the inner part of the divided gear wheel of the forward gear ratio from the torque proof fixing with the assigned output shaft or the assigned drive shaft, and engaging the inner part of the divided gear wheel of the reverse gear ratio, thereby torque proof fixing said inner part with the assigned output shaft or the assigned drive shaft, wherein the inner part of the divided gear wheel of the second gear ratio is angularly de flected with respect to the outer part and each set of two elastic elements is being loaded as a result of this deflection; transferring power to the output shaft by means of a reverse gear ratio.

As an alternative the method comprises the following step, wherein during axial moving the at least one engagement component/dog clutch type selector is guided by helical means and rotates in relation to the assigned output shaft or to the assigned drive shaft to compensate the difference in angular velocity at the beginning of the gear ratio changing action between the assigned output shaft or the assigned drive shaft and the divided gear wheel, to be engaged, of the second gear ratio.

Furthermore, a boat with an inboard / outboard motor may comprise the above described at least one divided gear and/or a power transmission.

The present invention will now be described in further detail with reference to the accompanying schematic drawings, wherein

Figure 1 shows a perspective cross-sectional view of a power trans mission system according to the invention,

Figure 2 shows an exploded view of the power transmission system of

Figure 1 , Figure 3 shows an exploded view of an embodiment of the inventive transmission element shown here as a divided gear wheel of Figure 1 , Figure 4 shows an exploded view of an alternative embodiment of the divided gear wheel,

Figure 5 shows a perspective view of an alternative embodiment of the invention,

Figure 6 shows a perspective cross-sectional view of an alternative embodiment of a power transmission system,

Figure 7 shows an exploded view of a divided gear wheel of the alter native embodiment shown in Figure 6,

Figure 8A to 8G show gear changing action sequences,

Figure 9 shows a gear gifting mechanism,

Figure 10 shows a perspective cross-sectional view of an embodiment of the inventive transmission element shown here as a dog clutch type selector, Figure 1 1 shows an exploded view of the dog clutch type selector of Fig ure 10

Figure 12 shows an exploded view of an alternative embodiment of the inventive transmission element shown here as a selector, Figure 13 shows an exploded view of a power transmission system com prising a dog clutch type selector according to Figure 10,

Figure 14 shows a perspective cross-sectional view of an alternative embodiment of the inventive transmission element shown here as a dog clutch type selector,

Figure 15 shows an exploded view of an alternative embodiment of a power transmission comprising a dog clutch type selector ac cording to Figure 14,

Figure 16 shows an alternative embodiment of a power transmission system comprising divided gear wheels,

Figure 17 shows a schematic view of an output shaft with two gear wheels,

Figure 18 shows an alternative embodiment of a power transmission system,

Figure 19 shows a side view of an embodiment of a transmission ele ment shown here as a selector,

Figure 20 shows a cross sectional view of a first embodiment of two gear wheels defining a gear ratio,

Figure 21A to 21 C show gear changing action sequences,

Figure 22A to 22C show gear changing action sequences of a power transmis sion system according to Figure 20, Figure 23 shows a cross sectional top view of an alternative embodi ment of a power transmission system,

Figure 24 shows a top view of the power transmission system according to Figure 23,

Figure 25 shows a cross sectional view of a second embodiment of two gear wheels defining a gear ratio,

Figure 26 shows a detailed view of section C of Figure 24, Figure 27 shows a detailed view of section D of Figure 24, Figure 28 shows a perspective cross sectional view of a transmission element here shown as a selector,

Figure 29 shows a perspective view of an alternative embodiment of a power transmission system, and

Figure 30A to 30B show a schematic view of a power transmission system. Figures 1 and 2 show a power transmission system according to the invention and illustrate the component parts incorporated into the gearbox which are a drive wheel 13, e.g. a bevel pinion, a first divided gear wheel 1 1 and a second divided gear wheel 12. In Figures 1 and 2, both the first and the second divided gear wheels 11 , 12 are constantly meshed with the drive wheel 13, and their main axis form a 90° angle. Furthermore, a transmission element 3 according to the present invention is depicted by either one of the divided gear wheels 11 and 12.

The drive wheel 13 is torque proof fixed with a drive shaft 20 that receives power from an engine. The divided gear wheels 11 , 12 are supported by an output shaft 10, which may have a propeller of a boat torque proof fixed with the shaft in one end.

The divided gear wheels 1 1 , 12 comprise a first part 1 12, 122, i.e. an inner part 112, 122 and a second part 1 11 ,121 , i.e. an outer part 111 , 121. Both the divided gear wheels 1 1 , 12 are supported by the prop shaft 10 but are not constantly torque proof fixed with the prop shaft 10 and therefore are free to rotate about an axis 2 when not engaged to the output shaft.

The torque proof connection of the inner part 112 to the output shaft 10 is achieved by a selector 14 which interacts with the inner part 112, 122 of the di vided gear wheels 1 1 , 12. Such a selector may be a dog clutch type selector as depicted. The selector 14 is positioned in between the divided gear wheels 1 1 , 12 and is assigned to both the divided gear wheels. In addition, the dog clutch type selector 14 is provided as torque proof fixed to the assigned shaft but has the ability to be moved axially. The axial movement may be guided by coupling ele ments 101 of the output shaft 10. Those coupling elements may be arranged lin ear or helically.

The dog clutch type selector 14 in Figures 1 and 2 shows a gear selector coupling 143 which may be coupled to a throttle lever that controls the axial position of the selector 14. By moving the throttle lever in the according position, the selector 14 engages either the first divided gear wheel 1 1 or the second divided gear wheel 12. The movement of the throttle lever may be manually or automatically. Addi tionally, the selector 14 may not interact with any of the divided gear wheels 1 1 , 12 by staying in a neutral position in between the divided bevel gears 1 1 , 12.

The selector 14 has engagement means such as first coupling elements 141 , 142 facing each divided gear wheel 11 , 12. As can be seen, the first coupling elements 141 of the selector are assigned to the divided gear wheel 11 and the first coupling elements 142 are assigned to the divided gear wheel 12. The first coupling ele ments 141 , 142, i.e. the engagement means 141 , 142, are presented as protru sions. It goes without saying, that the engagement means can also be formed as cavities or a combination of both in accordance to the first coupling elements 1121 , 1221 of the inner parts of the first and second divided gear wheels 1 1 , 12. In addition, preferably, both the first coupling elements 1121 , 1221 of the first and second divided gear wheels 11 , 12 and the engagement means 141 , 142 of the selector 14, comprise a great number of teeth or the like. This is preferred due to the fact that a collision between the engagement means 141 , 142 and the front face of the inner parts 1 12, 122 of the divided gear wheels 1 1 , 12 is not desired, and therefore a great number of teeth is preferred with each teeth having a pointed face which facilitates the engagement. In addition, when using several teeth, the load can be distributed over the teeth. When the engagement means 141 , 142 and the engagement means of the first coupling elements 1121 , 1221 of the di vided gear wheels meet, the significant compression of the elastic element 114, 124 will begin. The elastic elements are depicted as spring elements in the figures shown, wherein the elastic elements 114, 124 depict spring elements with low and the elastic elements 113, 123 depict spring elements with high suspension rates. It goes without saying that engagement means 141 , 142 are in accordance with first coupling elements 1121 , 1221 in relation to their number, form, engagement surfaces etc. In addition, the provision of a great number of engagement means, in both the inner parts 1 12, 122 and in the dog clutch type selector 14, decreases the demanded tooth depth of the engagement means.

Therefore it is made clear that the decreased occurred inertia (due to the fact that initially upon engagement, only the inner parts 112, 122 of the divided gear wheels 1 1 , 12 take part in the engagement/gear selection) accompanied by the softer springs 114, 124 result in a quicker and smoother gear change. The divided gear wheel 11 comprises an inner part 112 supported by the output shaft 10, free to rotate when not engaged to the output shaft 10 by the selector 14, and a second part 11 1 that is supported by the first part 112. The second part 11 1 has a teething, presented here as a bevel gear teething, on its outer surface which meshes with the teething of the drive wheel 13. Both parts are coupled by one set of springs (two springs in total) where the set comprises one spring that has a lower suspension rate and protrudes on a front face of a second spring that has a higher suspension rate. Thus, the first spring is partially arranged within the other spring. Those spring elements may be different elastic elements such as rubber elements. The springs are positioned concentrically to each other with the first elastic element protruding out of the second elastic element on a front face, and are housed in a spring compartment formed in between the first part 112 and second part 11 1 , i.e. the inner 1 12 and outer 1 11 part. As mentioned before, each spring consisting the set of springs can be positioned in a separate compartment but always the divided gear wheel will behave as described. The inner part 1 12 and the outer part 1 11 have the ability to deflect angularly in relation to each other, until the set of springs is fully loaded. When the set of springs is fully loaded both, the inner part 1 12 and the outer part 11 1 , rotate with the same angular velocity. Similarly divided gear wheel 12 comprises an inner part 122 and an outer part 121.

Figure 2 demonstrates individual parts of the proposed power transmission sys tem. In this figure, a more clear view of the parts comprising the proposed power transmission system can be seen.

As mentioned before, the selector 14 may be a dog clutch type selector, which is torque proof fixed with the output shaft 10 but has the ability to slide axially de pending on the position of the throttle lever, engaging and disengaging the desired gear ratio. The engagement to the shaft takes place by engagement means such as second coupling elements 144, which are arranged on the inner cylindrical face of the selector 14. The coupling elements are in accordance to the coupling ele ments 101 of the output shaft 10, which extend for a suitable length in relation to the distance of the first and second divided bevel gears 11 , 12.

When the first gear ratio is desired, an according movement of the throttle lever, positions the selector 14 towards the position of the first divided gear wheel 11. As a consequence, the engagement means 141 of the selector 14 interact with the engagement means 1121 positioned on the front surface of the inner part 112 of the divided gear wheel 11 , facing the engagement means 141 , and therefore forcing the selector 14 to rotate. Since the selector 14 is torque proof engaged with the output shaft 10, the output shaft 10 also rotates.

When the inner part 112 is not engaged to the selector 14 the softer spring or the softer elastic element, i.e. the elastic element with a lower suspension rate, inside the divided gear wheel 11 is considered not to be deformed (the occurring defor mation is negligible for example if the elastic element is preloaded) and the stiffer spring or the stiffer elastic element is also not deformed since it is“shorter” in relation to the softer spring or the softer elastic element and the deflection of the outer part of the divided gear wheel in relation to the inner part is negligible.

When the selector 14 begins to engage to the inner part 112 by the interaction of the engagement means 141 of the selector 14 with the engagement means 1121 of the inner part 1 12, the rotational force is transferred from the outer part to the softer elastic element and therefore the deformation of the softer elastic element begins, since it was considered not to be deformed. Due to the fact that the softer elastic element has a smaller suspension rate, the engagement takes place easily with a small demand in axial force. As it is obvious, the softer elastic element is deformed initially and after the completion of the engagement, the deformation of the stiffer elastic element follows accompanied by the continuance in deformation of the softer elastic element. When the stiffer elastic element begins to bear load in a progressive manner, the substantial amount of power begins to be trans ferred. When the load is fully borne by the set of elastic elements, both the inner part 1 12 and the outer part 11 1 will rotate with the same angular velocities, and so will the selector 14.

It is worth mentioning that the engagement, i.e. the coupling, of the divided gear wheel and another power transmission component such as the selector is com pleted during the initial deformation of the softer elastic element, before the be ginning of the deformation of the stiffer elastic element. The gear changing action is completed when the load is fully borne by the selected gear ratio.

Figure 3 shows an exploded view of the divided gear wheel of Figure 1 and 2. The divided gear wheel 11 comprises an outer part 11 1 , an inner part 112 and two elastic elements such as springs which are positioned as one set of two, with softer elastic element 114 paired with stiffer elastic element 113. As mentioned before, the stiffer elastic element 1 13 does not necessarily have to be a spring element but can also be any type of elastic element such as a rubber block. In any case, the elastic element has to be positioned in a configuration which permits the softer elastic element to deform initially upon deflection of the outer part in relation to the inner part or the deflection of the inner part in relation to the outer part of the divided gear wheel. After the engagement is completed, the defor mation of the stiffer elastic element follows, and is accompanied by a simultane ous deformation of the softer elastic element that continuous to be deformed as the deflection progresses. In the presented layout, only one set of two elastic el ements is presented but more can be added with a corresponding change in both the inner and outer parts of the divided gear wheel. In addition the presented layout positions the set of two elastic elements in a single compartment but each of the elastic elements comprising the set of two elastic elements, can be position in a separate compartment, with the divided bevel gear always operating as de scribed. As can be seen, the softer elastic element 1 14 has an increased length in com parison to the length of the stiffer elastic element 113, resulting in an initial defor mation. The elastic elements are supported by outer support 1112 positioned in the outer part 1 11 and inner support 1122 positioned in the inner part 112 of the divided gear wheel 11. In general, depending on the embodiment, it is not man datory to divide the supports 1100 into an inner and an outer support 1122, 11 12.

The outer support 1112 of the outer part 1 11 can be“sandwiched” in between the inner support 1122 of the inner part 112 which have a suitable opening in be tween. In addition, the inner support 1122 has a back that stops the outer support 1 112 and as a result restricts the rotation range of the outer part 1 11. This back has a damping element 1 141 with a damping effect in order to prevent the fierce collision of the inner and outer parts, when the previously engaged inner part 1 12 is disengaged. It goes without saying, that a damping element with a damping effect can also be adopted in the outer support 1 112 (in addition or instead of the damping element of the inner support 1122).

The presented divided gear wheel 1 1 has an analogous layout to the divided gear wheel 12. As a consequence, the divided gear wheel 12 has an outer part 121 and an inner part 122 and two elastic elements in total positioned as one set of two, with the softer elastic element 124 paired with stiffer elastic element 123.

Again, the softer elastic element 124 has an increased length in comparison to the length of the stiffer elastic element 123. The elastic elements are supported by outer support 1212 positioned in the outer part 121 and inner support 1222 positioned in the inner part 122 of the divided gear wheel 12. Damping element 1241 with a damping effect is analogously provided. In general, depending on the embodiment, it is not mandatory to divide the supports 1200 into an inner and an outer support 1222, 1212. Figure 4 shows an exploded view of an alternative embodiment of the divided gear wheel. Similar to the divided gear wheel of the previous embodiment, the divided gear wheel 11 comprises a first part 112, i.e. the inner part, a second part 1 11 , i.e. the outer part, coupling elements 1 121 , inner supports 1122a, 1122b, outer supports 1 112a, 1 112b, damping elements 1141 a, 1141 b as well as elastic elements 113a, 113b, 1 14.

Further, the divided gear wheel 1 1 shows two compartments. The first compart ment comprises the inner support 1122a and the damping element 1141 a and the second compartment comprises the inner support 1122b and the damping ele ment 1141 b. The three elastic elements 1 13a, 113b, 1 14, depicted as spring ele ments, are arranged within compartments in the assembled state, wherein the elastic elements 113a, 1 13b comprise a different length than the elastic element 114. The spring element 114 is longer than the other spring elements 113a, 1 13b. Further, the spring element 1 14 may have a lower suspension rate, which is shown by the larger distance of the spring coils. The spring elements 113a and 113b have the same suspension rate. In the assembled state, the spring elements 113a and 113b are arranged within the depicted first compartment and the spring element 114 is arranged in another compartment. Therefore, the first elastic ele ment, i.e. the elastic element 1 14 which is initially compressed, is received in one compartment and the two second elastic elements, i.e. the elastic elements 113a, 113b which bear the significant amount of the occurring load and which comprise a higher spring rate in relation to the elastic element 1 14, are received in another compartment. Furthermore, once the spring elements 1 13a and 114 are assem bled in the adjacent compartments, the spring elements 113a and 114 are parallel to each other.

Upon engagement of the divided gear wheel 11 with a power transmission com ponent, the first spring element 114, i.e. the longer spring element with a lower suspension rate, is activated and deforms. As soon as the initial engagement is completed and the actual power transmission begins, wherein the load to be transmitted increases significantly, the other spring elements 113a, 1 13b, i.e. the shorter and stiffer spring elements with a higher suspension rate, are activated and deformed (together with the first spring element 1 14) until the load is fully borne by the selected gear ratio.

Further, in the assembled state, the outer support 1 112a of the outer part 1 11 is arranged within the inner support 1 122a of the inner part 112 and the outer sup- port 1112b of the outer part 11 1 is arranged within the inner support 1 122b of the inner part 1 12.

Figure 5 shows a perspective view of an alternative embodiment of the invention. In this alternative, the engageable gear wheels are provided as divided gear wheels 11 , 12 with their outer parts 112, 121 comprising a spur gear teething instead of a bevel gear teething.

In addition, the divided gear wheels 1 1 , 12 are supported by separate drive shafts 20, 30 and not by the output shaft. Therefore, the divided gear wheel 11 is sup- ported by the drive shaft 20 and the divided gear wheel 12 is supported by the drive shaft 30. In addition, the drive shaft 20 supports the drive gear wheel 23 and the drive shaft 30 supports the drive gear wheel 33, which constantly meshes with the drive gear wheel 23. Both the drive gear wheel 23 and the drive gear wheel 33 are torque proof fixed with their respective drive shafts 20, 30 (i.e. rotate as the respective shaft rotates).

As mentioned before, the divided gear wheels 11 , 12 are free to rotate when a selector 14 does not engage their inner parts 11 1 , 121. In this alternative, each divided gear wheel 11 , 12 has a separate selector 14 (14a, 14b) and the two divided gear wheels do not share a single selector as in the previously described configurations.

The selector 14 (now comprising the dog clutch type selectors 14a and 14b), is torque proof fixed (i.e. rotating with the same angular velocity) with the assigned drive shaft 20, 30 but has the ability to move axially in relation to the main axis of the shaft, and the axial position is defined by the respective position of the throttle lever.

In this configuration, the power is transferred from drive shaft 20, 30 to the inner parts 112, 122 of the divided gear wheels 11 , 12 and via the set of two elastic elements to the outer parts 11 1 , 121 of the divided gear wheels 1 1 , 12. From there, and since the outer parts 11 1 , 121 are constantly meshed with gear wheel 50, which is torque proof fixed with the output shaft 10, the power is transferred to the output shaft.

In the previously described configurations, the divided gear wheels 1 1 , 12 were engaged to the drive gear wheel. In this alternative configuration, both the divided gear wheels 11 , 12 are constantly meshed with the provided gear wheel 50 that is torque proof fixed with output shaft 10. A propeller may be torque proof fixed to one end of the output shaft 10.

The operation of the alternative configuration is analogous to the one described in detail above. Therefore, upon engaging the desired divided gear wheel 11 , 12 the direction of rotation of the gear wheel 50 changes and as a result a forwards or backwards movement can be achieved.

Figure 6 shows a partial sectional view of an alternative embodiment of a power transmission system. The main difference of this configuration, in relation to the power transmission systems presented before, is that the selector is guided by helical means instead of linear guiding mean. Further, the engagement takes place in the inner circumferential surface of the inner part 112, 122 instead of the front face of said parts.

Therefore coupling elements 101 have a helical shape and are integrally formed in the outer circumferential surface of output shaft 10.

In addition, the selector may be a different type of selector, which acts as an en gagement component. The selector is reshaped accordingly, with the first cou pling elements 140 being at the distant end of selector arms. In comparison to the previously presented configurations, the engagement means 142, 141 are com bined into a single element, the engagement means 140 that engages both the divided bevel gear 11 and the divided bevel gear 12.

Furthermore, the engagement of the inner parts 112 and 122 takes place on their inner circumferential surface, right on top of output shaft 10. Therefore, when the inner part 1 12 of the divided bevel gear 11 needs to be engaged with the first coupling elements 140 of the selector 14, the first coupling elements 140 will firstly come through the provided cavities of the bearings 1131 , 1231 and then will in teract with the cavities of the inner part 1 12. The number of engagement means of the inner part 112 is purposely increased in relation to the provided first cou pling elements 140, i.e. the engagement means 140, (the illustration depicts two engagement means 140) in order to facilitate the engagement of the components.

In Figure 6, none of the divided bevel gears 11 , 12 is engaged with the output shaft, and the engagement means 140 are positioned in between the divided bevel gears 1 1 , 12 in a neutral position. When the throttle lever is moved (either forwards or backwards) and due to the fact that the selector has a gear selector coupling 143, the engagement means 140 will be moved either towards the di vided gear wheel 11 or towards divided gear wheel 12. As a result, either the inner part 1 12 of the divided gear wheel 11 or the inner part 122 of the divided gear wheel 12 will be torque proof engaged with the output shaft 10, with the desired gear change being completed.

Since the coupling elements 101 have a helical shape, and the selector 14 is guided by them, an additional (in relation to the angular velocity of output shaft 10) angular velocity will be provided when the selector 14 is moved axially. As a result differences in angular velocities between the engaging components can be compensated, resulting in even quicker and smoother gear change.

In addition, due to the fact that axial forces act to the selector 14, the selector has to be secured in position.

It goes without saying, that the proposed alternative is operational even if the coupling elements 101 are linear instead of the depicted helical.

Figure 7 shows an exploded view of a divided gear wheel of the alternative em bodiment shown in Figure 6. In Figure 7, a more clear view of the inner part 112 of the divided gear wheel 11 can be seen. As it is obvious, the engagement means 1121 are provided on the inner circumferential surface of the inner part 112, di rectly above the output shaft 10. Therefore, as the selector 14 is moved axially, the engagement means 140 of the selector 14 can interact with the engagement means 1121 , torque proof fixing inner part 1 12 with output shaft 10.

In addition, since the axial movement of the selector 14 encounters bearings 1131 , cavities 1132 are provided. In addition, as mentioned above, the increased number of engagement means 1121 can be seen (in relation to the number of engagement means 140), which are formed with respect to the engagement means 140 of the selector 14. Therefore, since the engagement means 140 of the selector have a helical form in this alternative, the engagement means 1121 of the inner part 112 of the divided gear wheel 1 1 will also have a helical form. The increased number of engagement means 1121 facilitate the engagement prevent ing any collision problems.

Figures 8A to 8G represent a gear changing action from neutral to forward and then to backward in relation to the embodiment presented in Figures 1 and 2. In Figure 8A, the gear lever is positioned in neutral and therefore the selector 14 is positioned in between the divided bevel gears 11 , 12 and none of the inner parts 112, 122 is torque proof engaged with the assigned output shaft 10.

The divided gear wheels 11 , 12 are in engagement with the drive wheel 13 via their outer parts 111 , 121. Elastic elements 114, 124 connect the inner parts 1 12, 122 and the outer parts 11 1 , 121.

In addition, inner supports 1122, 1222 support the elastic elements 114, 124, and outer supports 1 112, 1212 are provided supporting the elastic elements 113, 114, 123, 124.

The arrows provided in the figures show the direction of rotation of each of the divided gear wheels 11 , 12, the direction of rotation of the assigned output shaft 10, and the direction of rotation of the drive wheel 13.

In Figure 8B, the selection of the first gear ratio, which is assigned to a forward movement (divided gear wheel 11 ) begins. Thus, the selector 14 is axially moved towards the divided gear wheel 11 and the engagement means of the selector 14 interact with the engagement means of the inner part 112 of the divided gear wheel 11 , and therefore the softer elastic element begins to compress. As a result, of the beginning of the engagement, the inner part 1 12 of the divided gear wheel 1 1 rotates with fewer rotations in relation to the outer part 11 1. The softer elastic element compresses and the stiffer elastic element does not.

In Figure 8C, the engagement of divided gear wheel 11 has been completed and the softer elastic element is compressed until the stiffer elastic element is reached, due to the deflection of the components.

Progressively, the stiffer elastic element 113 compresses until the entire occurring load is received by the element and the elastic element is not further compressed. Afterwards, when both of the elastic elements 1 13, 114 are fully compressed un der the occurring load, the inner part 112 and the outer part 1 11 of the divided gear wheel 11 have the same angular velocities in relation to each other and therefore rotate as one. The output shaft 10 has also the same angular velocity as the divided gear wheel 11.

The divided gear wheel 12 also rotate as one but the elastic elements 123, 124 are fully decompressed as it is not engaged with the selector 14.

In Figure 8D, a reverse gear command is being given with divided gear wheel 11 being now disengaged and the divided gear wheel 12 begins to be engaged with a corresponding movement of the gear lever and as a consequence with a corre sponding movement of the selector 14 towards the divided gear wheel 12.

The output shaft 10 rotates as previously (direction is shown by the arrow) due to the inertia and the speed of the boat. The inner part 122 starts to be engaged by the selector 14 and as a result the softer spring element 124 inside the divided gear wheel 12 begins to compress and the assigned output shaft 10 decelerates. The inner part 122 has a smaller angular velocity in relation to the angular velocity of the outer part 121. The elastic elements 1 13, 1 14 decompress and the inner part 1 12 of the divided gear wheel 11 has an increased angular velocity in relation to the outer part 11 1.

Figure 8E shows that the reverse gear engagement has been completed by the engagement of the inner part 122 of the divided gear wheel 12 with the selector 14, and the elastic elements 123, 124 are fully loaded under the occurring load. Both, the inner part 122 and the outer part 121 of the divided bevel gear 12 have the same angular velocity and so does the output shaft 10.

The divided gear wheel 11 is not engaged with the selector 14 and the elastic elements 113, 114 are fully decompressed. The inner part 112 rotates with the same angular velocity as the outer part 1 11.

Figure 8F and Figure 8G show the relative rotational movement of the selector in relation to the axial movement of the selector 14, when helical coupling elements 101 are adopted.

By the adaptation of helical coupling elements 101 , the selector 14 rotates in the same direction as the inner part of the divided gear wheel that is going to be engaged with the selector.

In comparison, the two additional rotational movements have an opposite direc tion of rotation in relation to each other but so do the divided gear wheels 1 1 , 12 and therefore the desired feature is achieved, assisting with a smoother engage ment.

In Figure 8F, the selector 14 is moved towards the divided gear wheel 11 and rotates as the divided gear wheel 11 and in Figure 8G the selector 14 is moved towards the divided gear wheel 12 and rotates as the divided gear wheel 12. In Figure 9 an exemplary gear shifting mechanism is presented.

The exemplary gear shifting mechanism comprises a gear shifter 15 that controls the position of the selector 14, and therefore the selected gear ratio. The axial movement of the gear shifter 15 is achieved with the help of a hydraulic cylinder 16, which is controlled by a solenoid valve.

When a first gear ratio is desired to be selected, the second chamber 162 is filled with pressurized hydraulic fluid, the selector is axially moved towards the first di vided gear wheel 11 , and the engagement means 141 of the selector 14, interact with the engagement means of the first divided gear wheel, torque proof fixing said divided gear wheel with the output shaft 10 and therefore selecting the first gear ratio as described in detail above.

When the second gear ratio is desired, the first chamber 161 is filled with pres surized hydraulic fluid (with a corresponding emptying of the second chamber 162), the selector 14 is axially moved and therefore second coupling elements 144 interact with the engagement means of the second divided gear wheel.

The selector 14 is guided by guiding means, i.e. coupling elements 101 of the output shaft 10, positioned in the outer circumferential surface of the output shaft 10, that are shaped helically with a corresponding change in the second coupling element 144 of the dog clutch type selector 14. Therefore, the additional benefits described in detail above can be achieved.

It goes without saying, that the use of the hydraulic cylinder 16 is not restrictive and other types of mechanisms that move the gear shifter 15 can be adapted (e.g. electric motor etc.). Furthermore, the presented guiding means, i.e. coupling ele ments 101 of the output shaft 10, have a helical form but the exemplary gear shifting mechanism can be adapted for any form of guiding means (e.g. linear guiding means). As it is obvious, when linear guiding means are selected the se lector does not have an additional angular velocity upon axial movement.

Figure 10 shows one embodiment of the inventive transmission element 3 here shown as a dog clutch type selector 14. The transmission element 3, i.e. here the selector 14, comprises a first part 212, i.e. an inner part, and a second part 211 , i.e. an outer part. Further, the selector 14 comprises elastic elements as well as first coupling elements 142 such as teeth that are adapted to engage with corre sponding coupling elements of a free, engageable gear wheel. The first part 212 and the second part 21 1 are angularly deflectable in relation to each other and the deflection is limited by the existence of the elastic elements.

The first part 212 is torque proof engaged with an assigned shaft by the second coupling elements 144 provided in the inner circumferential surface of the first part 212. The second coupling elements 144 of the selector torque proof fix the first part 212 directly to the shaft ( may be torque proof engaged to the shaft via a dog hub which is torque proof engaged to the shaft). A second part 21 1 com prises first coupling elements 142, adapted to interact with the corresponding cou pling elements of a free, engageable gear wheel.

Upon engagement the gear wheel, is torque proof engaged with the second part

21 1. Since the second part 21 1 is connected to the first part 212 via the elastic elements, the elastic elements will eventually be compressed so that the rotational forces and/or torque from the second part 21 1 will be transferred to the first part

212. Since the first part 212 is torque proof engaged with the shaft, a power trans mission between the shaft and the gear wheel is realized via the selector.

The selection of different gear ratios is achieved by axially moving the selector 14 along the shaft. The presented selector 14 is axially moved as an entity, when an axial movement of the selector is initiated by a gear selector that acts on a gear selector coupling 143 of the selector 14. The gear selector coupling 143 is posi tioned on the circumferential surface of the second part 21 1.

The first coupling elements 142 are provided in both sides of the second part 21 1. Therefore, both sides face an engageable gear wheel. The specific shape of the first coupling elements 142 may vary and the presented one is not restrictive. Thus, the first coupling elements 142 may be protrusions, cavities or a combina tion of both according to the corresponding coupling elements of the engageable gear wheels. However, the number of the first coupling elements 142 of the se lector and the number of the corresponding coupling elements of the gear wheel do not necessarily have to match. The coupling elements provided as cavities may be greater in number than the corresponding coupling elements provided as protrusions.

As mentioned above, the first part 212 is coupled to the second part 21 1 by means of at least two elastic elements. In the presented cross-sectional view only the softer elastic element 144 can be seen but a second elastic element is also pro vided (not shown). Both elastic elements are concentrically positioned, wherein both elastic elements may be arranged partially within each other.

Both first part 212 and second part 211 comprise elastic element supports, with the inner supports 1122 being visible in Figure 1. Inner supports 1 122 are pro vided as two elastic element supports with a“gap” in between in which the outer support (not shown) can be housed.

Furthermore, locking elements 201 are provided, that secure the first part 212 and the second part 21 1 , so that the two parts 211 and 212 are angularly deflectable in relation to each other, but can axially be moved as one. In Figure 11 an alternative embodiment of the transmission element 3, here shown as an alternative dog clutch type selector 14, is depicted. In this alternative em bodiment, the inner supports 1122 comprise a damping element 1141 that damps the return of the second part 211 when it stops being engaged and it recoils. Both damping elements 1141 shown are arranged on the inner face of the inner sup ports 1122. Therefore, both damping elements 1 141 face each other. Depending on structure of the selector, a different arrangement of the damping elements, for example on different surfaces of the supports, may be favorable.

Further, two elastic elements 1 13 and 1 14 are shown in Figure 11 , wherein the first elastic element 114, i.e. the softer elastic element, surrounds the second elastic element 113, i.e. the stiffer elastic element. As shown in Figure 1 1 , the first elastic element is provided by a spring element and the second elastic element is provided by a rubber block.

Figure 12 presents yet another alternative embodiment of an inventive dog clutch type selector 14. In this alternative embodiment, the selector 14 comprises first coupling elements 142 on an inner circumferential surface of the second part 21 1. Due to the fact, that the first coupling elements 142 on the inner circumferential suface of the selector are only provided on one side of the selector 14 and not on both sides, using this type of selector requires that each engageable gear wheel comprises its own selector. Therefore, the movement of the selectors can be in dependent of each other.

Further, in comparison to the alternative embodiment presented in Figure 11 , the second (stiffer) elastic element 113 is positioned on top of the first (softer) elastic element 114, wherein the first elastic element 114 is provided by a spring element and the second elastic element 1 13 is provided by a rubber block. Figure 13 shows an exemplary power transmission system 1 comprising two gear wheels 1 1 and 12, one drive wheel 13 and the selector 14 according to Figure 10. As mentioned before, the selector 14 is torque proof fixed with the output shaft 10 via second coupling elements 144 of the selector 14 and coupling elements 101 of the output shaft 10. Further, the selector 14 is adapted to slide axially along the output shaft 10 depending on the position of the gear shifter 15. The coupling between the output shaft 10 and the selector 14 is provided by the interaction of the coupling elements 101 and 144.

When the first gear ratio is desired, a movement of the gear shifter, positions the selector 14 towards the position of one of the gear wheels 11 or 12. Consequently, the first coupling elements 142 of the selector 14 interact with the first coupling elements 1 121 or 1221 of the gear wheel 11 or 12. Upon engagement, the selec tor 14 and the respective gear wheel 1 1 or 12 rotate together. Since the selector 14 is torque proof fixed with the output shaft 10, the output shaft 10 also rotates. When the second part 211 of the selector 14 is not engaged with either one of the gear wheels 11 or 12, the first (softer) elastic element of the second part 211 of the selector 14 is considered not to be deformed (the occurring deformation is negligible) and the second (stiffer) elastic element is also not deformed since it is shorter in relation to the first elastic element.

Nevertheless, during engagement of the clutch, the first (softer) elastic element is deformed initially and after the completion of the engagement, the deformation of the second (stiffer) elastic element follows, wherein the deformation of the first elastic element is continued throughout the deformation of the second elastic el ement. As soon as the second elastic element starts to be compressed, the load, i.e. power, begins to be transferred. When the load is fully borne by the set of elastic elements, both the first part 212 and the second part 211 rotate with the same angular velocity. A further embodiment of a selector according to the invention is shown in Figure 14. The selector 14 differs from the selector depicted in Figure 10 in that the sec ond coupling elements 144 are formed helically. As shown in Figure 15, the cor responding coupling elements 101 of the output shaft 10 are also formed helically. The coupling elements 101 and 144 may comprise helical grooves or protrusions that are adapted to guide the first part 212 helically i.e. in combined axial and rotational movement.

Figure 16 illustrates individual parts of an alternative embodiment of a power transmission system 1 , comprising two divided gear wheels per gear ratio. The divided gear wheels in Figure 16 comprise an inner part, i.e. a first part 112, 122, and an outer part, i.e. a second part 121 , 122, with the inner part being coupled to the outer part by means of two sets of elastic elements. Each set of elastic elements comprises a first elastic element 114, 124 and a second elastic element 113, 123 with all the elastic elements being received inside the spring compart ments that are formed by the inner part 112, 122 and the outer part 121 , 122, with two springs received in a single compartment. The spring constant of the first elastic element 114, 124 is smaller than the spring constant of the second elastic element 113, 123.

The presented configuration illustrates a single gear ratio, comprising two divided gear wheels. This is not obligatory since only a single gear wheel per gear ratio has to be a divided gear wheel. In the scenario where only a single divided gear wheel would be adopted in one gear ratio, this divided gear wheel would be en gageable to the assigned shaft and therefore free to rotate when not engaged.

The divided gear wheel assigned to the output shaft 10 is engageable by an en gaging part, i.e. the selector 14, and the divided gear wheel assigned to the drive shaft 20 being constantly engaged to the assigned shaft. The engagement of each of the divided gear wheels takes place via their inner parts 112, 122. Therefore, the inner part 1 12 is engaged upon demand and inner part 122 is torque proof engaged with the drive shaft 20. When the inner part 122 is not engaged with the output shaft 10, the divided gear wheel is free to rotate.

The selector 14 is guided by coupling elements 101 , here a helical groove and a gear selector coupling 143 is provided. Upon axial movement of the engaging part 14, helical groove 101 provides an additional angular velocity in relation to the angular velocity of the assigned shaft, contributing to a smoother engagement. In another alternative straight guiding means instead of helical can be adopted, helix angle is zero, with a corresponding change in the engaging part, i.e. the selector 14The engagement still being possible since the inertia of the inner part 112, 122 is very small and the spring constant of the first elastic element is also very small.

Bearing 1231 assists the rotation of the inner part 122 and is positioned between the output shaft 10 and the inner part 122. Bearing 1231 is shaped accordingly in order to permit the engagement of the inner part 122, which takes place with the interaction of the first coupling elements 140 of the selector 14 with the first cou pling elements 1221 of the inner part 122 which are formed in relation to each other. The number of first coupling elements 1221 of the inner part 122, i.e. of the gear wheel, can be greater in relation to the number of first coupling elements 140 of the selector 14 in order to assist with the engagement.

Figure 17 shows a schematic view of an output shaft 10, supporting two output gear wheels 12. The output shaft 10 is provided with coupling elements 101 that are provided in form of a helical groove. The coupling elements 101 serve to guide an engaging part 14. The engaging party 14 is depicted in greater detail in Figure

19. The output gear wheels 12 may be divided gear wheels, as depicted in Figure

20. The coupling elements 101 have a helix angle a that follows the equation

wherein Dw defines a difference in angular velocity at the beginning of a gear ratio changing action between the assigned shaft and a gear wheel to be engaged, wherein U_a is a desired velocity of the axial movement, and wherein R is the ef fective radius of the helical means. U_v is the vertical velocity of the engaging part. The given parameters are depicted in Figure 17.

Figure 18 shows an alternative embodiment of a power transmission system. The power transmission system 1 that is depicted in Figure 18 comprises adrive shaft 20 and an output shaft 10. The drive shaft 20 supports the (input) gear wheels 11. The output shaft 10 supports the (output) gear wheels12. It is apparent that the power transmission system can comprise multiple input and output gear wheels and is not limited to the two pairs of input/output gear wheels, depicted in Figure 18.

Input gear wheels 1 1 are fixed gear wheels, i.e. they rotate with the same speed as the drive shaft 20. Further, input gear wheels 1 1 can be divided gear wheels, wherein an inner part of the respective gear wheel is torque proof fixed to the drive shaft 20 (see e.g. Figure 20). Output gear wheels 12 are free gear wheels and are provided as divided gear wheels. Accordingly, if the selector 14 is not engaged with the respective output gear wheel 12, the output gear wheel 12 can freely rotate on the output shaft 10. This means that the output shaft 10 and the respective output gear wheels 12 may have different angular velocities. The se lector 14 is guided by the coupling elements 101 , which defines two helical grooves. The helical grooves receive respective selector arms 145 of the selector 14. Further, the selector 14 comprises a bushing portion having acoupling gear selector coupling in form of a groove or a notch, that is adapted to couple with an actuator that moves the selector 14 axially along the output shaft 10 as will be described in detail with respect to Figures 21 A to 22C.

Figure 19 shows a side view of a selector 14. The selector 14 comprises a bushing portion that is guided on the output shaft 10. Selector arms 145 extend from the bushing portion and are provided at a distal end with corresponding first coupling elements140 that are adapted to engage with first coupling elements 1221 of inner parts 122 of output gear wheels 12. The bushing portion may further be provided with a gear selector coupling 143in form of a groove.

Figure 20 shows a cross sectional view of a first embodiment of two gear wheels 11 , 12 defining a gear ratio, wherein the two gear wheels 1 1 ,12 are engaged. The (input) gear wheel 11 is provided as a fixed gear wheel, wherein the (output gear wheel) 12 is provided as a free gear wheel. Accordingly, the inner part 112 of the first gear wheel 11 is permanently torque prove fixed to the drive shaft 20. An outer part 11 1 is coupled to the inner part 112 by means of spring elementsl 13, 114. The spring elements are received in spring compartments, formed by the inner and outer part 11 1 , 112. A bearing 1131 allows the outer part 11 1 to be deflected angularly around the inner part 112. The spring elements 1 13, 114 are supported by supportsl 100, that are preferably integrally formed with the inner part 112 or the outer part 11 1 , respectively.

The first spring element 114 may be arranged concentrically within a second spring element 113, wherein the first spring element 114 has a smaller spring rate than the second spring element 113. The outer part 11 1 is provided with a gearing comprising gear teeth, to transfer torque to the output gear wheel 12. The output gear wheel 12 is also a divided gear wheel, comprising an inner part 122 and an outer part 121. The outer part 121 is provided with a gearing, comprising teeth. Further, the inner part 122 is coupled to the outer part 121 by means of spring elements 123, 124. The spring elements are supported by respective supports 1200 which are preferably integrally formed with the inner part 122 or the outer part 121 , respectively. Spring element 124 may be a first spring element that is concentrically arranged within a second spring element 123 and that has a smaller spring rate as the second spring element 123. Further, the outer part 121 is sup ported by a bearing 1231 that allows for deflecting the inner part 122 relative to the outer part 121. The inner part 122 further comprisesfirst coupling elements 1221 , in form of grooves provided on an inner circumferential surface of the inner part 122, facing the output shaft 10. The corresponding first coupling elements 140 of the selector 14 can be inserted into said first coupling elements 1221 and achieve a temporary torque proof connection between the output shaft 10 and the inner part 122 of the output gear wheel 12. The permanent torque proof connec tion between the drive shaft 20 and the inner part 112 of the input gear wheel 11 is achieved by corresponding first coupling elements 1121 , such as a spline shaft or the like.

A schematic sequence of a gear ratio changing action is illustrated in Figures 21 A to 22C. In particular, Figures 21 A to 21 C show how a selector, being assigned to multiple divided gear wheels, works. Figures 22A to 22C show the function of the divided gear wheels. Figures 21 A to 22C show schematically a power transmis sion system, comprising a drive shaft 20, an output shaft 10 and two gear wheels 1 1 and two gear wheels 12. The power transmission system 1 may comprise fur ther gear wheels that are not depicted. The first pair of gear wheels 11 , 12 defines a first gear ratio and the second pair of gear wheels 11 , 12 defines a second gear ratio. Further, the power transmission system 1 comprises a selector 14. As illus trated, gear wheels 11 are fixed gear wheels that can be conventional gear wheels or divided gear wheels. The gear wheels 12 are free gear wheels that are provided as divided gear wheels. Accordingly, the first gear wheel 12 comprises an inner part 122 that is coupled to an outer part 121 by means of an elastic element 124. The second gear wheel 12 comprises an inner part 122 that is coupled to an outer part 121 by means of a set of two elastic element 123, 124.

Figures 21 A and 22A depict the power transmission system 1 being operated at the first gear ratio, i.e. the first gear wheel 12 is engaged with the output shaft 10 by means of the selector 14. The second gear wheel 12 is disengaged and rotates freely. Figures 21 B and 22B depict the power transmission system 1 upon a gear ratio changing action from the first gear ratio to the second gear ratio and Figures 21 C and 22C depict the power transmission system being operated at the second gear ratio, i.e. the second gear wheel 12 is engaged with the output shaft 10 by means of the selector 14. The first gear wheel 12 is disengaged and rotates freely.

To arrive at the state shown in Figures 21A and 22A, i.e. operating the power transmission system 1 at the first gear ratio, the power transmission system may be transferred from neutral to the first gear ratio with help of a clutch (not shown). Accordingly, the first pair of gear wheels 1 1 , 12 starts moving and the engine’s power is transferred from the drive shaft 20 to the output shaft 10 via the first pair of gear wheelsl 1 , 12, defining the first gear ratio.

The second pair of gear wheels 11 , 12are also engaged with each other. Flow- ever, as gear wheel 12 is a free gear wheel and is not engaged with the output shaft (cf. Figures 21 A and 22A), gear wheel 12 can rotate freely with respect to the output shaft freely. Accordingly, the second pair of gear wheels 1 1 , 12 does not transfer torque to the output shaft 10 (or vice versa). The same applies to further pairs of gear wheels (not shown) that define additional gear ratios.

When engine reaches a desired speed level, e.g. as it tends to leave a desired operation point, or when the driver commands a gear ratio changing action (e.g. from the first gear ratio to the second gear ratio), a control unit may command the respective gear ratio changing action. Accordingly, an actuator (not shown) may push (or pull) the selector 14 linearly. Due to the axial movement of the selector 14, the selector 14 will engage the following divided spring gear 12. As the actu ator moves the engaging part axially, the selector will be forced to accelerate in rotational and axial direction due to the helical guiding. Thus, the selector 14 will rotate with the output shaft 10 and in addition with an angular velocity Dw. The dimensions and in particular the helix angle a of the helical means and the desired velocity of the axial movement of the engaging part U_a may be chosen so that the angular velocity of the selector 14 matches the angular velocity of the following divided spring gear 12, upon engaging. Accordingly, when the selector 14 reaches the divided spring gear 12, they will have the same angular velocity and as a result a smooth engagement can be achieved.

As shown in Figures 21 B and 22B, when the selector 14 begins entering/engaging the inner part 122 of divided gear 12 the elastic element 124 in its interior begins to be compressed due to the deflection of the inner part 122. In this point of time, the selector 14 is still partially engaged with the first gear wheel 12. This is, as the length of the corresponding first coupling elements140 that engage with the first coupling elements 1221 of the inner parts 122 of the divided gear wheels 12 may be equal to the distance from center to center between two consecutive divided gear wheels 12.

The set of elastic elements may comprise a first spring element 124 that is par tially arranged within a second spring element 123 and protrudes out of the sec ond spring element 123 on a front face. The spring rate of the first spring element 124 may be smaller than the spring rate of the second spring element. Thus, ini tially, the first spring element 124 is compressed. Subsequently, if the inner part 122 reaches the second, stiffer spring element the second spring element 123 starts to be compressed. Accordingly, power can be transferred via the spring elements and the inner part 122 to the output shaft 10. The elastic elements of the other gear ratio begin to decompress simultaneously up till the selector 14 fully engages the desired gear ratio.

As further shown in Figures 21 B and 22B, when the selector 14 is engaged with both gear wheels 12 of the first and second gear ratio, the flow of power is trans ferred from both gear ratios. Consequently, when the selector 14 is engaged only with one output gear wheel 12 of either the first or the second gear ratio, the flow of power is transferred exclusively by the pair of gear wheels, defining the respec tive gear ratio, as illustrated in Figures 21 C and 22C. As the engagement pro gresses, a greater amount of power will be transferred by the second gear ratio with equivalent decrease of transferred power by the first gear ratio. The reverse action will take place when a smaller gear ratio is desired, e.g. if the gear ratio changing action is from the second to the first gear ratio.

In the following, an example gear ratio changing action is described, using random numbers of angular velocity of the respective gear wheels. The first input gear wheel 11 may rotate with an angular velocity of 1000 rpm and the first output gear wheel 12 with an angular velocity of 900rpm (both inner and outer parts 121 , 122). The second input gear wheel 11 may also rotate with an angular velocity of 1000 rpm, as first and second input gear wheels are fixed gear wheels, as shown in Figures 21 A and 22A. The second output gear wheel may rotate freely with an angular velocity of l OOOrpm (both inner and outer parts 121 , 122). Therefore, the first gear ratio will be 0.9 and the second gear ratio will be 1.

The selector 14 rotates with the same angular velocity as the output shaft 10, i.e. with 900 rpm. Thus, the difference in angular velocity between the selector 14 and the second output gear wheel 12 is about 100rpm. When a command is given to change the gear ratio, the selector 14 begins to move axially with the help of an actuator and is at the same time rotationally ac celerated (due to the helical guiding). As a result, when the selector 14 reaches the inner part 122 of the second output gear wheel 12 it has an angular velocity, equal to the sum of the rotational speed of the shaft (900rpm) and the rotational speed due to the helical guiding (e.g. 100rpm).

Upon engaging the selector 14 with the inner part 122 of the divided gear wheel 12, the selector 14 begins to decelerate, continuing the engagement between the two parts up till it is fully engaged. The outer part 121 of the divided gear wheel 12 still rotates with l OOOrpm and the inner part 122 also decelerates due to the engagement, i.e. it rotates with about 900 rpm. Accordingly, the first elastic ele ment 124 and in particular, a first spring element is compressed as the selector 14 engages the inner part 122 of the divided gear wheel 12. When the second spring element 123 begins to bare load, the elastic element 124 (such as the second spring element) of the other gear ratio (i.e. the first gear ratio) begins to decompress. When the decompression of the other elastic element 124 is com pleted and the compression of the following elastic element 124 is also completed the power is only transferred via the pair of gear wheels 1 1 , 12, form ing the sec ond gear ratio, as shown in Figures 21 C and 22C.

When the engagement of the selector 14 and the second output gear wheel 12 is completed, the second output gear wheel 12 rotates with an angular velocity of 900 rpm, and so does the second input gear wheel 11 , resulting in an engine velocity of 900 rpm.

In particular, as the selector 14 starts to engage/disengage with any of gear wheels 12, the elastic elements 123, 124 are compressed, or decompressed, re spectively. As soon as elastic elements 123, 124 begins to compress, the other elastic element 124 begins to decompress. The total needed torque is the sum of torques in the output gear wheels 12, when the selector 14 is partially engaged in both (scenario of Figures 21 B and 22B). Consequently, as the elastic elements 123, 124 compress, managing greater torque, and the elastic element 124 de compresses, managing lesser torque up till the torque is fully beared by the sec ond output gear wheel 12. As a result, when the engagement of the selector 14 with the second output gear wheel 12 is completed, the flow of power is as follows: drive shaft 20 - second input gear wheel 11 - second output gear wheel 12 - output shaft 10. As power can be transferred during the gear ratio changing ac tion, a continuous power transfer is established.

Figure 23 shows a cross sectional top view of an alternative embodiment of a power transmission system. The power transmission system 1 shown in Fig. 23 comprises a drive shaft 20 and an output shaft 10. The drive shaft 20 supports input gear wheelsl 1 and the output shaft 10 supports output gear wheels 12. As the skilled person will notice, the power transmission system 1 can provide further input and/or output gear wheels that are supported on the drive or output shaft, respectively. Flowever, these gear wheels are not shown.

The gear wheels 11 and the gear wheels 12 are provided as divided gear wheels, each having an inner part 112, 122 and an outer part 111 , 121. The first pair of gear wheels 1 1 , 12 defines a first gear ratio and the second pair of gear wheels 1 1 , 12 defines a second gear ratio.

The input gear wheel 1 1 is a fixed gear wheel, wherein the inner part 112 is per manently torque proof attached to the drive shaft 20. So is the output gear wheel 12. Accordingly, the inner part 122 is permanently torque proof attached to the output shaft 10. As will become apparent from Figure 23, each gear ratio is de fined by a pair of gear wheels, wherein one of the pair of gear wheels is a fixed gear wheel and the respective other one is a free gear wheel. Accordingly, the output gear wheel 12 is a free gear wheel, comprising an inner part 122 that can freely rotate on the output shaft 10, if it is not engaged with a selector 14, as will be described later. Similarly, the input gear wheel 11 is a free gear wheel, com prising an inner part 112 that can freely rotate on the drive shaft 20, if not engaged with a respective selector 14. To provide a freely rotating gear wheel, bearings 1 131 , 1231 are provided between the drive shaft 20 and the inner part 112, re spectively between the output shaft 10 and the inner part 122.

The gear wheels 1 1 , 12 are provided with respective gearings, comprising teeth. Further, the divided gear wheels 11 , 12 each comprise respective inner parts 112, 122, that are coupled to respective outer parts 1 11 , 121 by means of elastic ele ments 113, 114, 123, 124. This coupling allows for an angular deflection of the inner parts relative to the outer parts. If the elastic elements are fully loaded, torque is transferred from the respective inner parts to the outer parts with a ratio of 1 : 1.

As shown, the automatic power transmission system 1 , as depicted in Fig. 23, differs from the automatic power transmission system 1 , as e.g. depicted in Fig. 18, in particular in that the selector(s) is designed differently. This different selec tors 14 allow to provide an automatic transmission system, having reduced length dimensions. This is, as each free divided gear wheel 11 , 12 is assigned to a sep arate selector 14. Accordingly, the free gears of adjacent gear ratios can be pro vided alternatingly on the drive and output shaft 10, 20.

The selectors 14 are helically guided by respective coupling elements 101 that are provided as separate parts and that are attached torque proved to the respec tive drive and output shafts 10, 20. The coupling elements 101 are provided with teeth. The teeth guide the selector 14 helically, i.e. in an axial and rotational di rection as described above. Further, each free divided gear wheel comprises at its inner part 1 12, 122first coupling elements 1 121 , 1221 that are adapted to engage with first coupling ele ments 142 of the selector 14.

Figure 24 shows a top view of the power transmission system 1 of Figure 23. The power transmission system comprises a driveshaft 20 and an output shaft 10 as well as input gear wheels 11 and output gear wheels 12. The free gear wheels 11 , 12 can be temporarily torque proof attached to the respective drive shaft 20 or output shaft 10 by means of selectors 14. In the configuration shown in Figure 24, the output gear wheel 12 is engaged with the selector 14 thereby being able to transfer torque to the output shaft 10. The other selector 14 is disengaged and thus, the respective other input gear wheel 11 cannot transfer torque to the drive shaft 20.

Figure 25 shows a cross sectional view of two gear wheels 11 , 12 defining a gear ratio,. The design of the input and output gear wheels 11 and12 corresponds to the design of the gear wheels, discussed with respect to Figure 20. In particular, the input gear wheels 11 in Figure 20 and 25 are identical. Flowever, the output gear wheel 12 in Figure 25 differs from the output gear wheel 12depicted in Figure 20 with respect to the inner part 122. In particular, the inner parti 22 of Figure 25 is supported by a bearing 1231 on the output shaft 10. No engagement means are provided on the inner circumferential surface of the inner part 122. Therefore, first coupling elements 122T are provided on a front face of the inner part 122 as shown in Figure 23.

Figures 26 and 27 show a detailed view of sections C and D of Figure 24, i.e. of the selectors 14. As shown in Figure 26, the selector 14 is disengaged and first coupling elements 1121 of input gear wheel 1 1 are not engaged with the selector 14. Figure 27 shows an engaged selector 14. Accordingly, the first coupling ele ments of output gear wheel 12 are covered by the selector 14 and the coupling elements 101 can be seen in the top view of Figure 27.

Figure 28 shows a perspective cross sectional view of a transmission element here shown as a selector 14. The selector 14 comprises a bushing portion that has on its inner circumferential surface corresponding helical second coupling el ements 144 that are adapted to engage with respective helicalcoupling elements 101 , as shown e.g. in the previous figures. Thus, helical guiding of the selector 14 can be achieved. Further, corresponding first coupling elements 142 are pro vided, which are adapted to engage with engagement means of respective inner parts of the divided gear wheels 11 , 12. On an outer circumferential surface of the bushing portion , an gear selection coupling 143 is provided in form of a groove that allows an actuator to move the engaging part axially.

Figure 29 shows a perspective view of an alternative embodiment of a power transmission system comprising six gear ratios, defined by respective pairs of input gear wheels 11 and output gear wheels 12. The input gear wheels are sup ported by the drive shaft 20 and the output gear wheels are supported by the output shaft 10.

Figures 30A and 30B show a schematic view of a power transmission system wherein according to Figure 30A a first gear ratio is operated and according to Figure 30B, a second gear ratio is operated. The first gear ratio is defined by a first pair of gear wheels and the second gear ratio is defined by a second pair of gear wheels.

The flow of power is illustrated as a bold dashed line. According to Figure 30A, the power is transferred via the drive shaft 20 and the selector 14 to the input gear wheel1 1 and then via the output gear wheel 12 to the output shaft 10. According to Figure 30B, the power is transferred via the drive shaft 20 and the input gear wheel 11 to the output gear wheel 12’. Then, the power is transferred via the selector to the output shaft 10.

Further, the power transmission system 1 may comprise an additional set of gear wheels provided upstream the first gear ratio, to reduce the engines revolutions. This set of gear wheels may comprise a drive gear wheel 23, provided on an additional drive shaft 20. The drive gear wheel 23 may be coupled to a comple mentary drive gear wheel 33, which is provided on the drive shaft 20. The flow of power may then be transferred from the additional drive shaft 20 via the set of gear wheels 23, 33 to the drive shaft 20.

Additionally, or alternatively, the power transmission system 1 may comprise a set of gear wheels provided downstream the last gear ratio of the power transmis sion system, i.e. at the end of the output shaft 10. This set of gear wheels may comprise a subsequent output gear wheel 50, provided on the output shaft 10. The subsequent output gear wheel 50 may be coupled to a subsequent comple mentary output gear wheel 50, which is provided on a subsequent output shaft 10. The flow of power may then be transferred from the output shaft 10 via the set of gear wheels 50 to the subsequent output shaft 10. As shown, the divided gear wheels that are free gear wheels are provided alternately on the drive shaft 20 and the output shaft 10. Each free gear wheel is assigned with a respective se lector 14. To operate the depicted power transmission system, only one engaging part of the set of selectors 14 is engaged with the respective divided gear wheel, at a time where no power ratio changing action is performed, i.e. when a gear ratio is operated. During power transfer changing actions, two engaging parts may at least partly be engaged with the respective gear wheels, as described above with respect to Figures 21 A to 22C. To change the gear ratio, the power transmis sion system requires to change gear ratios sequentially. That means that to change a gear ratio from the first to e.g. the fifth gear ratio, all gear ratios that are sandwiched between the first and fifth gear ratio must be operated for a short period of time. Thus, no direct gear ratio change from the first to the fifth gear ratio is possible. The above described power transmission system, comprising divided gear wheels allows for a continuous power transfer during gear ratio changing actions and for reduced power losses.

Furthermore, the power transmission systems can, for example, be used in ma- rine engines or automobiles, comprising transmission elements according to the invention allowing a smoother and quicker gear change as well as lesser gear wear.

Reference numerals

1 power transmission system 114 first elastic element

2 axis

3 transmission element 121 second part

122 first part

10 output shaft 123 second elastic element

1 1 (divided) gear wheel 124 first elastic element

12 (divided) gear wheel

13 drive wheel 140 first coupling elements

14 selector (selector)

14a separate selector 141 first coupling elements 14b separate selector (selector)

15 gear shifter 142 first coupling elements

16 hydraulic cylinder (selector)

143 gear selector coupling

20 drive shaft 144 second coupling elements 23 drive gear wheel (selector)

30 drive shaft 145 selector arms

33 drive gear wheel

50 gear wheel 161 first chamber

162 second chamber

101 coupling elements

101 a coupling elements 201 locking element

101 b coupling elements 21 1 second part (selector)

212 first part (selector)

11 1 second part (gear wheel)

1 12 first part (gear wheel) 1 100 supports

113 second elastic element 1 112 outer support

113a second elastic element 1 112a outer support

1 13b second elastic element 1 112b outer support 1121 first coupling elements

(gear wheel)

1 122 inner support

1 122a inner support

1 122b inner support

1131 bearings

1132 cavities

1141 damping element 1141 a damping element 1 141 b damping element

1200 supports

1212 outer support

1221 first coupling elements

(gear wheel)

1222 inner support

1231 bearings

1241 damping element

Claims

1. Transmission element of a power transmission system (1 ), wherein the transmission element comprises at least one first part (1 12; 122; 212), at least one second part (1 11 ; 121 ; 21 1 ) which is rotatable relative to the at least one first part (112; 122; 212) about a common axis (2) by a limited degree, and at least one first elastic element (114; 124),

wherein the at least one first part (112; 122; 212) and the at least one second part (1 11 ; 121 ; 21 1 ) together form at least one compartment in which the at least one first elastic element (114; 124) is arranged between the at least one first part (112; 122; 212) and the at least one second part (1 11 ; 121 ; 211 ) to bias the at least one first part (112; 122; 212) and the at least one second part (1 11 ; 121 ; 211 ) rotation- ally away from each other in opposite directions,

characterized in that the transmission element (3) further comprises at least one second elastic element (113; 113a; 1 13b; 123) arranged within the at least one compartment between the at least one first part (1 12; 122; 212) and the at least one second part (1 11 ; 121 ; 21 1 ), wherein the at least one second elastic element (1 13; 113a; 1 13b; 123) is arranged parallel to the at least one first elastic element (1 14; 124),

and in that the elastic elements (113, 113a, 113b, 123; 114, 124) comprise different suspension rates and/or different lengths.

2. Transmission element according to claim 1 , wherein the at least one second elastic element (1 13; 113a; 1 13b; 123) biases the at least one first part (1 12; 122; 212) and the at least one second part (1 1 1 ; 121 ; 211 ) rotationally away from each other in opposite directions after the at least one first elastic element (114; 124) is loaded.

3. Transmission element according to claim 1 or 2, wherein the first elastic el ement (114; 124) comprises a lower suspension rate than the second elastic ele ment (113; 1 13a; 113b; 123).

4. Transmission element according to any of the preceding claims, wherein the first elastic element (114; 124) is partially arranged within the second elastic ele ment (113; 1 13a; 113b; 123).

5. Transmission element according to any of the preceding claims, wherein the at least one first and the at least one second elastic element (1 13; 1 13a; 113b; 123) are spring elements, or wherein the at least one first elastic element (114; 124) is provided by a spring element and the at least one second elastic element (113; 113a; 113b; 123) is provided by a rubber element.

6. Transmission element according to any of the preceding claims, wherein the first elastic element (114; 124) is preloaded.

7. Transmission element according to any of the preceding claims, wherein the at least one compartment comprises at least one damping element (1141 ; 1141 a; 1141 b; 1241 ).

8. Transmission element according to any of the preceding claims, wherein at least one first part (1 12; 122; 212) is arranged at least partially within the at least one second part (11 1 ; 121 ; 211 ).

9. Transmission element according to any of the preceding claims, wherein the transmission element (3) is a gear wheel (11 ; 12; 13; 13a; 13b; 50), preferably a bevel or a spur gear wheel, or a selector (14; 14a; 14b), preferably a dog clutch type selector.

10. Gearbox comprising at least one drive shaft (20; 30), at least one drive wheel (13; 23; 33) coupled to the at least one drive shaft, an output shaft (10), at least one selector (14; 14a; 14b) coupled to the output shaft or the at least one drive shaft, and at least one gear wheel (11 ; 12), wherein the at least one gear wheel (11 ; 12) and/or the at least one selector (14; 14a; 14b) are transmission elements (3) according to any of the preceding claims.

1 1. Gearbox according to claim 10, wherein the at least one gear wheel (1 1 ; 12) is in constant engagement with the at least one drive wheel (13) or with at least one other gear wheel (50).

12. Gearbox according to any of claims 10 or 1 1 , wherein the drive wheel (13) is a bevel pinion.

13. Gearbox according to any claims 10 to 12, wherein the selector (14) com prises first coupling elements (140; 141 ; 142) for rotationally coupling and/or de coupling with corresponding first coupling elements (1 121 ; 1221 ) of the at least one gear wheel (11 ; 12) and/or comprises second coupling elements (144) for rotation- ally coupling and/or de-coupling with corresponding coupling elements (101 ) of the output shaft (10).

14. Gearbox according to claim 13, wherein the selector (14) is axially or helically movable along the axis (2) of the output shaft (10), and wherein the helical move ment along the axis (2) comprises an axial and a rotational movement.

15. Gearbox according any of claims 10 to 14, wherein at least one sensor for measuring the angular velocity of the drive wheel (13) and/or the at least one gear wheel (11 ; 12) and/or the output shaft (10) and/or the drive shaft (20) and/or the selector (14) is arranged within the gearbox.