WO2013053988A2

WO2013053988A2 - Power transmission arrangement, method for power transmission in a gear system and use of power transmission arrangement

Info

Publication number: WO2013053988A2
Application number: PCT/FI2012/050947
Authority: WO
Inventors: Taimo Majalahti; Pekka Majalahti
Original assignee: Taimo Majalahti; Pekka Majalahti
Priority date: 2011-10-12
Filing date: 2012-10-03
Publication date: 2013-04-18
Also published as: EP2802791A4; WO2013053988A3; EP2802791A2; WO2013053981A1

Abstract

The power transmission arrangement according to the invention comprises at least a gear arrangement that has a first axle (2) rotating around its central axis, and a second axle (3, 3b) rotating around its central axis, and two or more pinion gear assemblies (13), having at least two pinion gears (15-17) with mutually different reference diameters and fitted coaxially on the same rotating support shaft (14). In addition the gear arrangement comprises internally geared ring gears (18-20) meshing with the pinion gears (15-17), and one ring gear (18, 19) at a time is arranged to be stationary locked non-rotary in relation to the housing (1 ). The pinion gears (15-17) rotate at the same speed and to the same direction with their support shafts (14) and mutually with each other, and that at least one pinion gear (15a, 17) of each pinion gear assembly (13) is arranged to mesh with the rotary internally geared ring gear (18a, 20).

Description

POWER TRANSMISSION ARRANGEMENT, METHOD FOR POWER TRANSMISSION IN A GEAR SYSTEM AND USE OF POWER TRANSMISSION ARRANGEMENT

The present invention relates to a power transmission arrangement as defined in the preamble of claim 1 and a method for power transmission in a gear system as defined in the preamble of claim 9.

Diverse machines, devices and vehicles have often a gearbox whose purpose is to convey the torque and rotational speed produced by a drive unit forward in a suitable extent. In motor vehicles like cars and motor bicycles used in traffic, a gearbox usually contains some gears for moving forward, and in addition cars have one reverse gear.

Whereas in some other type of vehicles different type of gearings may be needed. In some vehicles one gear is used the most of time but in some special situations a different trans- mission is needed. For example for cross-country vehicle, such like all-terrain vehicles that are used time to time in troublesome terrain, a good gearing would be such that it contains one gear for forward moving and additionally a reduction gear that transmits high torque to the wheels. By the help of the reduction gear it would be easier to cope with troublesome terrain spots and sharp hills. This kind of gearing would be suitable also for example for a fishing boat where in normal driving a normal gear could be used, and when trolling a gear allowing a slow speed could be used. This kind of gearing is, however, known to be complicated to put into practice in a traditional way.

In wind power plants producing electricity a gearing is needed to transmit the slow rotation of the wind rotor to a faster rotation suitable for the rotor of the electric generator. In the gearing of the wind power plant a fairly high gear ratio is needed, and because of this known gearings are extremely complicated and expensive with several gear wheels and other components. Several components make also the size and the mass of the gearing larger.

The object of the present invention is to eliminate the drawbacks described above and to achieve a cost effective and by its structure straightforward power transmission arrangement and method for transmitting power in a gearbox that contains a gear suitable for normal driving, and additionally one or more reduction gears and possibly also a reverse gear. In addition the object is to achieve a simply feasible power transmission arrangement and method for transmitting power in a gearing where the gear ratio is extremely high. The power transmission arrangement according to the invention is characterized by what is presented in the characterization part of claim 1 , and the method according to the invention is characterized by what is presented in the characterization part of claim 9. Other embodiments of the invention are characterized by what is presented in the other claims.

The solution of the invention has among other things the advantage that because only rotational force is aimed to the housing of the gearing, the housing can be extremely small, simple and lightweight by its structure. Yet, an advantage is that the power losses of the gearing are extremely small. One advantage is also that in addition to a normal gear, one or more reduction gears, and if wanted also a reverse gear can be made to the gearing with ease and using simple structures. A further advantage is also that the gear ratio of the gearing can be done easily and simply extremely high in which case the gearing suits well to use for example in wind power plants. One advantage is also that at least in some embodiments of the invention the contact surface of the teeth of the gearing is large, which has an advantageous effect among other things on the noise level, lubrication and material choices. Yet, an advantage is that the arrangement is simple, versatile and inexpensive to realize.

In the following, the invention will be described in detail by the aid of two embodiment examples by referring to the attached drawings, wherein

Fig. 1 presents in a side view and in a simplified way and in a cross section one embodiment according to the invention,

Fig. 2 presents in a oblique side view a power-in unit or primary unit according to the solution of Fig. 1 ,

Fig. 3 presents in a side view and in a partial cross a power-in unit according to

Fig. 2,

Fig. 4 presents in a side view and in a simplified way and in a cross section one gear assembly with its bearings used in the arrangement according to the invention, Fig. 5 presents in a side view and in a simplified way and in a cross section one gear assembly according to Fig. 4 in its location in the primary unit, Fig. 6 presents in a side view and in a simplified way and in a cross section along the line B-B in Fig. 7 another embodiment according to the inven- tion,

Fig. 7 presents a solution according to Fig. 6 in a simplified way and in a transversal section along the line A-A of Fig. 6,

Fig. 8 presents a transmission unit according to the solution of Fig. 6 in a side view, in a simplified way and in a cross section along the line B-C of Fig. 7,

Fig. 9 presents in a side view and in a simplified way and in a cross section one gear assembly used in the solution according to Fig. 6, and

Fig. 10 presents in a side view, schematically and in a simplified way and in a cross section a third embodiment of the arrangement according to the invention.

In Figs. 1 -5 an embodiment according to the invention is shown with its components. In Fig. 1 one embodiment according to the invention is presented in a side view and in a simplified way and in a cross section. Correspondingly in Figs. 2 and 3 a power-in unit 8 or primary unit according to the invention is shown in a more precise way, and in Figs. 4 and 5 one pinion gear assembly 13 according to the invention is shown in a more precise way and in a side view, and in a simplified way and in a cross section.

Fig. 1 presents a gearbox where a gearing is fitted in an essentially cylindrical housing 1 that is for example essentially circular in its cross section and made of metal, such as aluminum by casting. The housing 1 contains at least an essentially cylindrical frame 1 a and at the first end of the frame a a first end part 1 b equipped with a center hole and a bearing housing, and at the second end of the frame 1 a a second end part 1 c equipped with a center hole and a bearing housing. The end parts 1 b and 1 c have been fastened to the frame 1 a for example by screw fastening.

The main parts of the gearing inside the housing 1 are the first axle or power-in axle 2, the second axle or power-out axle 3, the power-in unit 8, a power-out unit 21 , pinion gear assemblies 13, ring gears 18, 19, 20 with internal gears, brake units 29, 30 acting as gear actuators, clutch unit 22 and a clutch actuator for the clutch unit 22.

The first axle 2, later the power-in axle 2 of the gearbox or primary axle, has been guided into the housing 1 through the first end of the housing 1 , and correspondingly the second axle 3, later the power-out axle 3 of the gearbox or secondary axle, has been guided out from the housing 1 through the second end of the housing 1 . The power-in axle 2 and power-out axle 3 are mounted in bearings 4 and 5 on the end parts 1 b and 1 c of the housing 1 . In addition there are seals 6 and 7 between the end parts 1 b and 1 c and the axles 2 and 3.

The primary axle 2 equipped with grooves 2a at its first end has been fitted to the housing 1 of the gearbox in a way that only the first end of the primary axle 2 is outside the housing 1 . Inside the housing 1 with an axial distance to each other a first carrier flange 9 and a second carrier flange 10 are connected fixedly to the primary axle 2 and the carrier flanges form together with the coaxial primary axle 2 an essentially uniform power-in unit 8 or a primary unit cast for example of metal. Thus both the primary axle 2 and the carrier flanges 9, 10 rotates always together with the same speed towards the same direction around the central axis of the gearing, which central axis is coaxial with the rotation axis of the primary axle 2.

In addition the primary unit 8 contains a cylindrical extension 1 1 that extends axially from the second carrier flange 10 and having the diameter of the inner surface advantageously larger than the diameter of the outer surface of the second carrier flange 10, and into which inner surface of the cylindrical extension a group of clutch discs 22a of the clutch unit 22 are fastened in order to couple the primary unit 8 to the power-out unit 21 or secondary unit equipped with the secondary axle 3.

The gearing according to the invention comprises additionally a group of mutually essen- tially similar pinion gear assemblies 13 whose gears 15, 16, 17 function like planet gears though the gearing does not contain a sun gear. The pinion gear assemblies 13 are mounted in bearings 36 and 37 by their support shaft 14 on the carrier flanges 9 and 0 situated in the axial direction between the pinion gears 15-1 7. The pinion gear assem- blies 13 can be radially at even angle intervals for example two, three, four, five, six or even more depending the size of the gearing. The solution according to the example has four pinion gear assemblies 13 at even angle intervals, in which case the angle between them is 90 degrees. Fig. 1 is simplified and made clearer among other things in a way that behind the second pinion gears 16 the corresponding pinion gear is not shown, the central axis of the support shaft 14 of the non-visible pinion gear would be in Fig. 1 at the height of the central axis of the primary axle 2.

Each pinion gear assembly 13 according to the example has three coaxial pinion gears 15-17 with an axial distance to each other and arranged to rotate with the support shaft 14 as one unit mutually at the same speed around the rotation axis of the support shaft 14, and the reference diameters of the pinion gears 15-17 are mutually of different sizes. In that case for example the first pinion gear 15 having the smallest diameter is machined directly to the axle 14, whereas the middle or second pinion gear 16 having the largest diameter and the third pinion gear 17 having the second largest diameter are non-rotatably mounted in relation to the support shaft 14 by the help of grooves 38 and 39. The gearing according the example comprises four mutually essentially identical pinion gear assemblies 13 that while rotating around their own support shaft 14 revolve at the same time also around the common rotation axis of the center axle or primary axle 2 and the secondary axle 3 of the whole gearing.

The ring gears 18-20 with internal gears are fitted to mesh with pinion gears 15- 7 of the pinion gear assemblies 13 so that all the first pinion gears 15 of the pinion gear assemblies 13 are mutually simultaneous meshing with smallest diameter internally geared first ring gear 18 that is mounted on a bearing 2b to the primary unit 8 to rotate in relation to the primary unit 8. Correspondingly all the second pinion gears 16 of the pinion gear assemblies 13 are mutually simultaneous meshing with largest diameter internally geared second ring gear 19 that is freely supported on the second pinion gears 16, and all the third pinion gears 17 of the pinion gear assemblies 3 are mutually simultaneous meshing with the internally geared third ring gear 20 having a diameter that is only slightly larger than the diameter of the first ring gear 18, and being fixedly connected to the secondary unit 21 that is mounted on a bearing 4a to the second end 12 of the primary unit 8 to rotate in relation to the primary unit 8. All the internally geared ring gears 18-20 are mutually coaxial and fitted to rotate around the common rotation axis of the center axle or primary axle 2 and the secondary axle 3 of the whole gearing.

In addition the gearing comprises the brake unit 29 of the first ring gear 18 and the brake unit 30 of the first ring gear 19, which brake units 29, 30 are arranged to stop the rotational movement of the ring gears 18, 19 one at a time when using the gearing. The brake units guided electrically or hydraulically to move axially are coupled non-rotatably to the inner surface of the cylindrical frame 1 a of the gearbox housing 1 for example by the help of axially directed grooves 31 .

In the example each pinion gear assembly 13 shows only three pinion gears 15-17 having different reference diameters, but on the same support shaft 14 there can be also more coaxial pinion gears with mutually different reference diameters, and the inner surface of the housing 1 comprises in that case internally geared and non-rotatable lockable ring gears corresponding each pinion gear. The largest diameter pinion gear produces to the secondary axle 3 the slowest speed of rotation in the direction of the primary axle 2, and the smallest diameter pinion gear produces the reverse rotation in the direction of the primary axle 2 as long as even the smallest pinion gear has a larger reference diameter than the pinion gear 17 meshing with the ring gear 20 of the secon- dary unit 21 . When the pinion gear meshing with the ring gear locked on the perimeter of the housing 1 has a smaller diameter than the pinion gear 17 meshing with the rotating ring gear 20 of the secondary unit, the secondary axle 3 rotates with a slow speed towards the opposite direction as the primary axle 2. The gearing comprises in addition also the clutch unit 22 whose clutch discs 22a, 22b are situated between the inner surface of the cylindrical extension 1 1 of the primary unit 8 and the outer surface of the third internally geared ring gear 20. The first clutch discs 22a are fitted into their location by the help of the axial grooves 23 of the primary unit 8, and the second clutch discs 22b are fitted into their location by the help of the axial grooves 24 of the secondary unit 21 . When using the clutch the clutch discs 22a, 22b are pressed tightly against each other with an electric or hydraulic actuator 27 by the help of a thrust bearing 25 and a pressing member 26, and then all the gears and other rotating components of the gearing are rotating as one unit mutually the same speed, and inside the gearbox the gears or other rotating components do not have a different rotation speed in relation to each other. The electric or hydraulic driving power for the actuator 27 of the clutch unit 22 is conducted via an energy interface 28 through the second end part 1 c of the gearing housing 1 .

In Figs. 2 and 3 the power-in unit 8 or primary unit according to the invention is presented in a more precise way. As mentioned previously, the primary unit 8 comprises at least the primary axle 2, the first carrier flange 9, the second carrier flange 10 and the cylindrical extension 1 1 of the primary unit extending from the second carrier flange 10. All the components 2 and 9-1 1 mentioned are mutually coaxial. In addition the primary unit 8 comprises at least bridges 32 connecting the carrier flanges 9 and 10, the number of the bridges being advantageously as many as the number of the pinion gear assemblies 13, that is four pieces in the case according to the example, and the bridges 32 are advantageously mutually at even angle intervals on the outer perimeter of the flanges 9, 10 or near the mentioned outer perimeters. The second pinion gears 16 are fitted between the flanges 9 and 10, and between the bridges there are openings 33 through which the teeth of the second pinion gears 16 are arranged to extend at least outside the outer perimeter of the first carrier flange 9, and to mesh with the second ring gear 19. The primary axle 2, the first carrier flange 9, the second carrier flange 10 and the cylindrical extension 1 of the primary unit extending from the second carrier flange 10, and the bridges 32 form a uniform entity, for example cast of the same material, like metal, called the primary unit 8 where all the mentioned components 2, 9-1 1 and 32 are fixedly integral to each other and rotate always mutually to the same direction and the same speed of rotation around the central axis of the primary unit 8 and at the same time around the central axis of the primary axle 2.

The first carrier flange 9 of the primary unit 8 has holes 34 mutually at even angle intervals for the first bearings 36 of the pinion gear assemblies 13, and correspondingly the second carrier flange 10 of the primary unit 8 has holes 35 mutually at even angle intervals for the second bearings 37 of the pinion gear assemblies 13. In addition, the inner surface of the cylindrical extension 1 1 of the second carrier flange 10 comprises axial grooves 23 in order to fit the first clutch discs 22a of the clutch unit 22 into their location non-rotary in relation to the primary unit 8 but movable in the axial direction. For the sake of clarity the grooves 23 are not shown in Fig. 2, and in Fig. 3 they are shown only in the upper and lower edge of the inner surface of the extension 1 1. In Figs. 4 and 5 one pinion gear assembly 13 according to the invention is shown in a more precise way in a side view, simplified and in a cross section. In Fig. 4 the pinion gear assembly 13 is disconnected and in Fig. 5 it is installed to the primary unit 8. As mentioned earlier, the first pinion gear 15 having the smallest diameter is machined directly to the support shaft 1 , whereas the middle or second pinion gear 16 having the largest diameter and the third pinion gear 17 having the second largest diameter are non-rotatably mounted in relation to the support shaft 14 by the help of grooves 38 and 39. The first bearing 36 of the support shaft 14 is situated between the first pinion gear 15 and the second pinion gear 16, and correspondingly the second bearing 37 of the support shaft 14 is situated between the second pinion gear 16 and the third pinion gear 17. Between the second pinion gear 16 and the bearings 36, 37 and between the third pinion gear 17 and the bearing 37 there are spacer plates 14a in order to fit the pinion gears 16, 17 axially to their correct location on the support shaft 14. In addition at the second end of the support shaft 14 there is a locking ring 14b in order to lock the pinion gears 16 and 17 into their locations in the axial direction.

The second pinion gear 16 can be a spur gear, but advantageously it is a double-helical gear that cannot move in the axial direction and is therefore at the same time arranged to keep the freely supported internally geared ring gear 18 meshing with it axially at its location, which ring gear 19 has in that case also herringbone teeth.

The power transmission arrangement according to the invention functions as follows: All rotational directions are looked as axial view from the primary axle 2 towards the secondary axle 3. When the primary axle 2 of the primary unit 8 is being rotated clockwise by an external power source, for example by a motor, the support shafts 14 of the pinion gear assemblies 13 with their pinion gears 15-17 are also revolving clockwise around the rotation axis of the primary axle 2. Because all the pinion gears 15-17 of the same support shaft 14 are non-rotatably mounted on their support shaft and there is no mutually relational rotation between them, all the pinion gears 15-17 with their support shafts 14 are forced to rotate together at the same clockwise speed around the rotation axis of the primary axle 2.

The third pinion gears 17 of the pinion gear assemblies 13 are meshing with the third internally geared ring gear 20 that belongs integrally to the secondary unit 21 . As a result of this when the support shafts 14 of the pinion gear assemblies 13 and the pinion gears 15-17 on them are revolving clockwise around the rotation axis of the primary axle 2 the tooth contact of the third pinion gears 17 with the third internally geared ring gear 20 compels all the support shafts 14 with their pinion gears 16-17 to rotate on their own bearings 36, 37 counter-clockwise around the own rotation axis of the support shafts 14.

Because the diameter and number of teeth of the second pinion gears 16 is larger than the diameter and number of teeth of the third pinion gears 17, the second pinion gears 16 rotating counter-clockwise around their own support shafts 14 compel the second internally geared ring gear 19 freely meshing with them to rotate counter-clockwise around the rotation axis of the primary axle 2 of the gearing. Correspondingly, because the diameter and number of teeth of the first pinion gears 15 is smaller than the diameter and number of teeth of the third pinion gears 17, the first pinion gears 15 rotating counter-clockwise around their own support shafts 14 compel the first internally geared ring gear 8 meshing with them to rotate clockwise around the rotation axis of the primary axle 2 of the gearing. Thus the difference of the diameters and numbers of teeth of the pinion gears 15-17 defines the direction of rotation of the ring gears 18, 19 when both the brake units 29, 30 and the clutch unit 22 are not activated. In that case there is no force between the primary axle 2 and the secondary axle 3 to rotate the secondary axle 3, in which case their mutual torque is zero and the gear is then in its neutral state.

When to highest speed of rotation of the secondary axle 3 is wanted the clutch unit 22 is activated, in which case the clutch discs 22a, 22b are pressed tightly against each other with an electric or hydraulic actuator 27 by the help of a thrust bearing 25 and a pressing member 26, as already mentioned above. In that case, when the brake units 29, 30 are not activated, all the gears 15-17 and 18-20, axles 2, 3, 14 and other rotating components 9- 14 and 21 -26 of the gearing are rotating around the rotation axis of the primary axle 2 of the gearing as one unit mutually the same speed, and inside the gearbox the gears or other rotating components do not have a different rotation speed in relation to each other. In that case the secondary axle 3 is forced to rotate to the same direction and with the same speed than the primary axle 2, in which case the transmission of the gearing is direct, or the transmission ratio is 1 :1 . Because inside the gearbox there are now no mutually rotational movements between each other, the internal structure of the gearing is in a dormant state, in which case the power loss between the primary axle 2 and the secondary axle 3 is at its minimum, and conversely the efficiency is at its maximum. In this situation a gear suitable for example for fast forward driving is coupled on in the gearing. When a slower speed and/or more power or torque to the secondary axle 3 is needed, the clutch 22 is released and the brake unit 30 of the second ring gear 19 is activated in order to stop the second ring gear 19. Now, the gearing having been internally in the dormant state springs into action and rotation speed differences come into existence between the rotation speeds of the pinion gears 15-17 of the pinion gear assemblies 13 and the ring gears 18-20 meshing with the pinion gears. The rotation speed and the torque of the primary axle 2 is now transferred to the secondary axle 3 due to and in relation to the mutual differences of the reference diameters of the pinion gears 16 and 17 and of the ring gears 19 and 20. In that case the secondary axle 3 begins to rotate towards the direction of rotation of the primary axle 2, but with a slower speed of rotation and with a larger torque than the primary axle 2. The speed of rotation and the torque of the secondary axle

3 depend on the mutual differences of the reference diameters and the numbers of teeth. In this situation a gear suitable for example for slow and power requiring forward driving is coupled on in the gearing. When the reverse gear is needed the brake unit 30 and at the same time the ring gear 19 are released and correspondingly the brake unit 29 of the first ring gear 18 is activated in order to stop the first ring gear 18. Because the reference diameter of the first ring gear 18 is smaller than the reference diameter of the third ring gear 20 and the reference diameter of the pinion gear 15 meshing with the first ring gear 18 is smaller than the reference diameter of the pinion gear 17 meshing with the third ring gear 20, the secondary axle 3 is now forced to rotate in the opposite direction as the primary axle 2. In that case the mutual differences of the reference diameters of the pinion gears 15 and 17, and the ring gears 18 and 20 cause the secondary axle 3 to rotate in the opposite direction. In this situation a gear suitable for example for slow and power requiring reverse driving is coupled on in the gearing

In the solution according to Figs. 1 -5 all the tooth contacts of the gear arrangement are arranged to take place only between the pinion gears 15-17 of the pinion gear assemblies 13 and the internally geared ring gears 18-20, and so that the difference of the reference diameters of the toothings defines the direction of rotation and the gear ratio. In addition only rotational force is aimed to the housing 1 of the gearing. In Fig. 6-9 another embodiment of the arrangement according to the invention is shown. The structure shown in Fig. 6 suits well for an accelerating or reducing gearing providing an extremely high gear ratio. The applications can be for example wind power plants where the gear ratio as high as 1 :100...1 :200, advantageously 1 :120...1 :150 between the primary axle 2 and the rotor unit 42a acting as a power-out unit, is possible to achieve. One advantage of the structure is among other things the fact that thanks to the high gear ratio the rotor unit 42a is made to rotate extremely fast, in which case the size of the rotor unit 42a and the size of the whole generator 41 can be much smaller than the structures of prior art. Likewise the size of the gearing according to the invention realized with extremely few gearing components can be much smaller than the corresponding structures of prior art. In addition only rotational force is aimed to the housing 1 , which further helps in making the size of the housing smaller and lighter. Consequently, when used as an accelerating gearing in a wind power plant the structure according to the invention can be by its size and weight as much as about 50% smaller and lighter than the corresponding structures of prior art.

Correspondingly the structure according to the invention can be also used as a reduction gearing, in which case the generator 41 acts as an electric motor and the axle 2 acts as a power-out axle. In that case an extremely high torque is obtained from the power-out axle with a slow speed of rotation.

In Fig. 6 a gearbox according to the invention is shown, in which gearbox the gearing is fitted into an essentially cylindrical housing 1 that is for example circular in its cross section and made of some appropriate metal. The housing 1 contains at least an essentially cylindrical frame 1 a and at the f irsf end of the frame 1 a a first end part 1 b equipped with a center hole and a bearing housing, and at the second end of the frame 1 a a second end part 1 c equipped with a center hole and a bearing housing. The end parts 1 b and 1 c have been fastened to the frame 1 a for example by screw fastening.

The main parts of the gearing in the housing 1 are the first axle 2 called later the power-in axle 2 or the primary axle, power-in unit 8, power transmission unit 21 a, pinion gear assemblies 13, internally geared ring gears 18a and 19, generator 41 and as a power-out unit acting rotor unit 42a that is a part of the generator 41 .

The power-in axle 2 or the primary axle is placed in the housing 1 of the gearbox so that only the first end of the first axle 2 equipped with the grooves 2a is outside the housing 1. Inside the housing 1 the primary axle 2 extends to a first flange 40, at the vicinity of the outer rim of which the first internally geared ring gear 18a coaxial with the primary axle 2 is mounted for example with a screw fastening. In that case the primary axle 2, the first flange 40 and the first ring gear 18a form the power-in unit 8 or the primary unit that is mounted with its first end on the first end 1 b of the housing 1 with a bearing 4, and with its second end 12 on the on the power transmission unit 21 a with a bearing 12a. For the bearing of the second end of the primary unit 8 there is a cylindrical recess 21 b at the first end of the power transmission unit 21 a.

The power transmission unit 21 a that is shown more precisely in Fig. 8 consists of at least three support flanges 9a, 10a and 1 1 a, and a second axle 3b called later the transmission unit support axle 3b, all the parts 3b and 9a-1 1 a being mutually coaxial. The transmission unit 21 a mounted on bearings to rotate freely is mounted with its first end to the second end of the primary axle 2 by the help of the bearing 12a, and with its second end to the second end part 1 c of the housing 1 by the help of the bearing 5. In addition, the power transmission unit 21 a comprises a group of mutually essentially similar pinion gear assemblies 13, which can be radially at even angle intervals for example two, three, four, five, six or even more depending the size of the gearing. The solution according to the example shown in Figs. 6-9 has three pinion gear assemblies 13 at even angle intervals, in which case the angle between them is 120 degrees. On the same shaft 14 each pinion gear assembly 13 has two pinion gears of which the first pinion gears 15a are smaller by their reference diameter than the second pinion gears 16. The pinion gears 15a and 16 are fitted to rotate around the rotation axis of the support shaft 14 at the same speed of rotation with each other and with the support shaft 14. The support shaft 14 is mounted with its first end to the first support flange 9a of the transmission unit 21 a by the help of a bearing 36, and with its second end to the third flange 1 1 a of the transmission unit 21 a by the help of a bearing 37. In addition, the first pinion gear 15a is arranged to mesh with the internally geared ring gear 18a having a smaller reference diameter, whereas the second pinion gear 16 is arranged to mesh with the internally geared ring gear 19 having a larger reference diameter, which ring gear 19 is locked nonrotary in relation to the housing 1 to the inner surface of the frame part 1 a of the housing 1 by the help of grooves 31 or the corresponding locking elements.

The rotor unit 42a of the generator 41 is mounted with its first end to a stationary support flange 43 inside the housing 1 by the help of a bearing 5a, and with its second end 42b to the second end part 1 c of the housing 1 by the help of a bearing 5b. The shaft of the rotor unit 42a is hollow and is fitted over the support axle 3b of the transmission unit 21 a. At the first end of the rotor unit 42a there is a hollow-shafted sun gear 42 that is arranged to mesh with the second pinion gears 16 of the pinion gear assemblies 13. Correspondingly at the second end of the rotor unit 42a there is an isolating, anti-magnetic flange 44 in connection of which there is a rotor 45. The stator coil 46 of the generator 41 is at the second end of the housing 1 inside an isolating, anti-magnetic protective sheath 47. In addition, a tapping point 48 of the produced electricity has been conveyed from the generator 41 through the second end part 1 c of the housing 1 .

Between the primary axle 2 and the first end part 1 b of the housing 1 there is further a seal 6, and correspondingly at the second end of the housing 1 there are seals 7a in order to seal the oil space of the gearing and to separate it from the generator 4 . In Fig. 7 a solution according to Fig. 6 is shown in a simplified way and in a transversal section along the line A-A of Fig. 6. Correspondingly in Fig. 8 a transmission unit 21 a according to the solution of Fig. 6 is shown in a more precise way in a side view and in a simplified way and in a cross section along the line B-C of Fig. 7. Fig. 7 shows the second support flange 10a of the transmission unit 21 a and in front of it three pinion gears 16 that are on their shafts 14 and are meshing with the second internally geared ring gear 19. In addition Fig. 7 shows bridges 32a between the second flange 10a and the third support flange 1 1 a of the transmission unit 21 a, which bridges are three pieces at even angle intervals in the gaps between the second pinion gears 16. Between the bridges 32a there are gaps 33a for the second pinion gears 16 in order to make the tooth contact with the pinion gears 16 and the second internally geared ring gear 19 feasible.

The second pinion gears 16 of the pinion gear assemblies 13 have been mounted on the support shaft 14 through an elastic joint 16a, in which case the torque transmitting to the pinion gear 16 effects a small spring between the second pinion gear 16 and the support shaft 1 and the first pinion gear 15a. By the help of the spring small tolerance errors originated in connection with a machining and thermal treatment are compensated in the tooth contact. In place of the elastic joint 16a the support shaft 14 can be realized so that it yields optimally in its twist direction so that the support shaft 14 makes an even pressure caused by the flank contact possible in the tooth contact.

In Fig. 8 one transmission unit 21 a according to the invention is shown in a cross section. At the first end of the transmission unit 21 a there is the first support flange 9a, at an axial distance from it there is the second support flange 10a, further at an axial distance from it there is the third support flange 1 a. At the second end of the transmission unit 21 a there is the support axle 3b whose first end extends to the second support flange 10a through the center hole 50 of the third support flange 11 a, through which center hole 50 the sun gear 42 of the rotor unit 42a has been fitted to its location.

The first carrier flange 9a has holes 34 at even angle intervals for the first bearings 36 of the pinion gear assemblies 13, and the third carrier flange 1 1 a has holes 35 at even angle intervals for the second bearings 37 of the pinion gear assemblies 13. In addition the second carrier flange 10a has holes 49 at even angle intervals for the support shafts 14 of the pinion gear assemblies 13. The support flanges could be also only two, for example only the support flanges 9a and 10a, in which case the second bearing 37 should be placed on the second support flange 0a. In that case, however, the axial distance of the bearings 36 and 37 becomes shorter compared to what is presented above. The short distance saves room and material but correspondingly the longer distance presented earlier and the three support flanges make extremely balanced and steady bearing structure possible. On the outer perimeter of the support flanges 9a-1 1 a or near the outer perimeters there are bridges 32a situated at even angle intervals, the number of the bridges being for example as many as the number of the pinion gear assemblies 13, that is in the solution according to the example three pieces mutually at 120 degrees intervals. The bridges 32a are for example the same casting with the support flanges 9a-1 1 a and the support axle 3b as shown in Fig. 8, or they can also be separate and for example fastened to the support flanges with a screw fastening. One advantageous embodiment is such that the support flanges 9a, 10a and the support axle 3b are the same casting and only the third support flange 11 a is of different material and fastened to the bridges 32a with a screw fastening. In Fig. 9 one pinion gear assembly 13 used in the solution according to Fig. 6 is shown in a side view, in a simplified way and in a cross section. The first pinion gear 15a with a smaller reference diameter is mounted on its support shaft 14 with grooves 38 to be nonrotary in relation to the support shaft 14. Correspondingly the second pinion gear 16 with a larger reference diameter is mounted on its support shaft 14 with the elastic joint 16a to be non-rotary in relation to the support shaft 14 as mentioned earlier. Hence the pinion gears

15a and 16 and the support shaft 14 rotate as one unit always mutually at the same speed and to the same direction around the central axis or the rotation axis of the support shaft 14. The consequence of the structure according to the invention is that the transmission unit 21 a with its flanges 9a-11 a, support axle 3b and bridges 32a, and pinion gear assemblies 13 form a solid entity that rotates as one unit always to the same direction and at the same rotation speed around the central axis of the gearing, which central axis is at the same time the rotation axis of the primary axle 2 and the support axle 3b of the transmission unit 2 a, and the rotor unit 42a.

The gearing arrangement according to the invention shown in Figs. 6-9 works as follows: All directions of rotation is seen from direction of the primary axle 2 towards the second end of the gearing. When the primary axle 2 of the primary unit 8 is rotated clockwise by the help of an external power source, for example the rotors of the wind power plant, the first internally geared ring gear 18a is also rotating clockwise with the same speed, and meshing with the first pinion gears 15a of the pinion gear assemblies 13 causes a large clockwise torque to the first pinion gears 15a. Because the first pinion gears 15a of the pinion gear assemblies 13, support shafts 14 and the second pinion gears 16 cannot rotate in relation to each other, they have no mutual relative rotary motion between them, in which case the essentially same clockwise torque is transmitted through the support shafts 14 and the second pinion gears 16 to the second internally geared ring gear 19 that is locked with the grooves 31 non-rotary in relation of the housing 1 of the gearing. Because the second internally geared ring gear 19 does not rotate, the mentioned clockwise torque forces the support shafts 14 and the first and second pinion gears 15a, 16 of the pinion gear assemblies 13 to rotate counter-clockwise around the central axis of the support shafts 14 on the bearings 36, 37 of the support shafts 14.

Because the diameter and number of teeth of the first pinion gears 15a is smaller than the diameter and number of teeth of the second pinion gears 16, which second pinion gears 16 are meshing with the non-rotary second ring gear 19, the pinion gears 15a, 16 rotating together to the same direction and the same speed are forced to rotate counter-clockwise around the central axis of the support shaft 14. This counter-clockwise motion forces correspondingly the pinion gears 15a, 16 to revolve clockwise in relation to the meshing with the ring gears 18a, 19, in which case in addition to their own counter-clockwise motion all the pinion gear assemblies 13 with their pinion gears 15a, 16 and support shafts 14 are revolving clockwise around the central axis of the whole gearing with the speed whose gear ratio is determined by the mutual difference of the reference diameters of the pinion gears 15a and 16. In that case also the whole transmission unit 21 a with its flanges 9a-11 a and bridges 32a is revolving clockwise around the central axis of the primary axle 2 of the gearing at the speed of rotation caused by the same gear ratio, the central axis of the primary axle 2 being congruent with the central axis of the whole gearing.

If the mutual differences in the diameters of the pinion gears 15a, 16 of the pinion gear assembly 13, and correspondingly the mutual differences in the diameters of the ring gears 18a, 19 are changed to opposite, then the direction of rotation of all the other components changes to opposite, but the direction of rotation of the primary unit 8 keeps the same.

The mentioned second pinion gears 16 are also meshing with the sun gear 42 at the first end of the rotor unit 42a, which sun gear belongs as an integrated structure to the rotor unit 42a, or is coupled to rotate with the rotor unit 42a for example by the help of a groove fastening.

When rotating counter-clockwise around the central axis of their own support shafts 14 the second pinion gears 16 revolve at the same time clockwise in relation to the toothing of the second ring gear 19 around the central axis of the whole gearing, and by this way force the sun gear 42 to rotate clockwise at the speed caused by an extremely high gear ratio. In that case both the speed of rotation of the transmission unit 21 a around the central axis of the whole gearing and the speed of rotation of the pinion gears 16 rotating to the opposite direction around their own support shaft 14 contribute together to the speed of rotation of the sun gear 42. Because the sun gear 42 has been fastened non-rotary in relation to the rotor unit 42a, the rotary motion of the sun gear 42 forces also the rotor unit 42a with its rotor 45 to rotate clockwise at the same high speed of rotation. In this way the gear ratio determined by the differences of the reference diameters of the first and second pinion gears 15a, 16, and the gear ratio between the second ring gear 19 and the sun gear 42 together form an extremely high combined gear ratio that forces the rotor unit 42a with its rotor 45 to rotate at an extremely high speed. The solution according to the invention makes it possible to achieve for example a gear ratio between 1 :100...1 :200, suitably for example between 1 :120... :150. For instance, when the total gear ratio is 1 :140 and the primary unit 8 rotates for example rotated by the rotor blades of the wind power plant at the speed of rotation of 10 rpm, the rotor unit 42a of the generator with its rotor 45 rotates at the speed of 1400 rpm. Thanks to an extremely high speed of rotation about 60% smaller magnetic flux resistance is achieved in the air gap between the rotor 45 and the stator winding 46, which feature makes an essentially equal output power of the generator 41 possible as in prior art generators of double size, which prior art generators are used for example with double planet gears that achieve a gear ratio of at maximum only about 1 :50. The mentioned smaller magnetic flux resistance or braking power in the air gap between the rotor 45 and the stator winding 46, thanks to the high speed of rotation of the rotor unit 42a, makes also much smaller flank pressures or surface pressures possible to the teeth of the sun gear 42. In that case for example the speed of rotation of the rotor 45 more than twice as high as with the conventional solutions, and the sun gear 42 with its diameter 30% larger than in the conventional solutions make about 50-60% smaller Hertzian surface pressure possible on the contact surfaces of the sun gear 42 than in prior art solutions with double planet gears and with sun gears of the same width and under the same load.

In Fig. 10 a third embodiment of the arrangement according to the invention is shown. Also this structure suits very well to either an accelerating or a reduction gearing allowing a high gear ratio. The applications can be for example wind power plants where it is possible to achieve a gear ratio as high as 1 :100...1 :200, suitably for example 1 :120 ...1 :150 between the primary axle 2 and the second axle 3 acting as a power-out unit. An advantage of the structure is among other things the fact that thanks to the high gear ratio the second axle 3 is made to rotate extremely fast, in which case the size of the generator or the electric motor coupled to the second axle 3 can be much smaller than the structures of prior art. The structure according to Fig. 10 has more components, weight and axial measurements than the corresponding structure according to Fig. 6, but correspondingly the structure according to Fig. 10 is extremely robust and it has no large diameter bearings whose large diameter and speed of rotation might cause too high circumferential speeds of the bearing surface. The size of the gearing according to Fig. 10 can also be much smaller than the corresponding structures according to prior art. In addition the housing 1 is only loaded by rotational counterforce, which further helps in reducing the size and weight of the housing. Thus, when used as an accelerating gear in a wind power plant the structure according to the invention can be by its size and weight as much as about 50% smaller and lighter than the corresponding structures according to prior art. Yet, a big advantage of the gearing according to Fig. 10 is a possibility to use just a usual series-produced generator/electric motor that is then coupled to the second axle 3 equipped with the groove fastening. Particularly, when used as a reduction gear in applications where the size and weight are not essential, the more inexpensive price of the mentioned electric machine or other machine can be just a decisive factor. In the solution shown in Fig. 10 the first axle 2 acting as a power-in axle or power-out axle, in this example the primary axle is fitted in the housing 1 of the gearbox in the way that only the first end of the primary axle 2 equipped with grooves 2a is outside the housing 1. Inside the housing 1 the primary axle 2 extends to the flange 40 at the proximity of whose perimeter the first internally geared ring gear 18a, coaxial with the primary axle 2, is fastened for example by a screw fastening 40a. In that case the primary axle 2, first flange 40 and the first ring gear 18a form together the power-in unit 8 or primary unit that is mounted at its first end on the first end flange 1b of the housing in a bearing 4, and at its second end on the power transmission unit 21 a in a bearing 12a. In the hub of the flange 43a that is fastened with screws 60 to the non-rotary housing 1 there is a bearing 5a by which the second end of the power transmission unit 21 a is bearing-mounted on the flange 43a.

The power transmission unit 21 a has two support flanges 9a and 1 1 a, of which the first support flange 9a coupled to the power transmission unit 21 a with a groove fastening 52, is the nearest to the power-in unit 8. The second support flange 1 1 a is integrally the same metal with the power transmission unit 21 a. Between the support flanges 9a and 1 a and bearing-mounted in relation to them there are pinion gear assemblies 13 each consisting of the first pinion gear 15a with a smaller reference diameter and integrally the same metal with the support shaft 14 of the pinion gear assembly 13, and of the second pinion gear 16 with a larger reference diameter, and coupled with a groove joint 16b to rotate together at the same speed with the first pinion gear 15a and with the support shaft 14. The internally geared ring gear 18a belonging to the primary unit 8 is meshing with the smaller reference diameter first pinion gears 15a of the pinion gear assemblies 13, and the internally geared ring gear 19 screw fastened non-rotary to the non-rotary housing 1 a is meshing with the larger reference diameter second pinion gears 16 of the pinion gear assemblies 13. The pinion gear assemblies 13 are at even angle intervals for example 2, 3, 4 or even more.

The groove joint 6b of the second pinion gears 16 to the support shaft 1 has an inclined serration when the meshing contacts 15a, 18a and 16, 19 have spur gears. Correspondingly, when the mentioned meshing contacts 15a, 18a and 16, 19 have helical gears it is sufficient to make the groove joint 16b with a straight serration. When spur teeth are used in the pinion gears 15a and 16 of the pinion gear assemblies 3 and correspondingly in the internally geared ring gears 18a and 19, the mentioned inclined serration joint has been cut so that the second pinion gear 16 having a larger reference diameter is pressed by the influence of the rotating load axially towards the smaller first pinion gear 15a. An elastic ring 16a made of flexible material is fitted on the both sides of the pinion gear 16, which elastic ring yields optimally a short way in the axial compression caused by the inclined serration joint 16b. Depending on the direction of rotation the small axial movement of the pinion gears 16 can take place also away from the pinion gear 15a. If more traction load is directed to one of the larger pinion gears 16 of the pinion gear assemblies 13 than to the corresponding pinion gears 16 of the other pinion gear assemblies 13, then the more rotary loaded pinion gear 16 minimally moves in the axial direction slightly closer to the smaller pinion 15a being its pair. In that case the inclined serration 16b makes with the same movement the most loaded pinion gear 16 also yield optimally a little bit in the rotary direction, in which case more traction load passes to the other correspond- ing pinion gear pairs. Consequently, in the meshing contacts 15a, 18a and 16, 19 an even traction load is distributed to all the flanks of the pinion gears. The pinion gear 16 is supported axially from the side of the flange 1 1 a on its support shaft 14 with a fitting ring 51 . The aim of the inclined serration 16b is a small flexibility in the rotary direction, which flexibility makes the load of the pinion gears more even.

As mentioned previously, if the pinion gears 15a, 16 and correspondingly the internally geared ring gears 18a, 19 have a helical cut, then the second pinion gears 16 having the larger reference diameter are fitted with straight serration joints 16b on the support shafts 14. The helical toothing causes axial pressure in the rotary load, in which case a suitably resilient elastic ring 16a between the pinion gears 15a and 16 yields a little bit. When the most traction loaded second pinion gear 16 of the pinion gear assemblies 13 so moves towards the first pinion gear 15a it yields minimally at the same time also in its rotary direction in relation to the first pinion gear 15a being as its pair on the same support shaft 14, in which case the rotary load directed to the second pinion gear 16 becomes lighter and correspondingly the rotary load increases to the corresponding meshing contacts 15a,

18a and 16, 19 of the other pinion gear assemblies 13. Consequently, in the meshing contacts 15a, 18a and 16, 19 an even traction load is distributed to all the flanks of the teeth. The first part of the gearing structure according to Fig. 10 is a gear arrangement that forms one fixed gear ratio, which arrangement has no sun gear but the pinion gears 15a and 16 working partially as planet gears are meshing only with the internally geared ring gears 18a and 19. For that reason the teeth of the pinion gears 15a and 16, and the teeth of the internally geared ring gears 18a and 19 have been able to cut so that the radius of curvature of their tooth flank has an exceptionally large diameter, and because of that surface area of the tooth contacts has essentially about double compared to what the radius of curvature of the tooth flank has to be in the traditional sun gear - planet gear connection. Consequently, when the Hertzian surface pressure halves also the danger of the pitting corrosion in the tooth contact surfaces decreases about by half.

The embodiment according to the invention shown in Fig. 10 works for instance as follows: All rotational directions are looked from the direction of the primary axle 2 towards the second end of the gearing. When the primary axle 2 of the primary unit 8 is being rotated clockwise by an external power source, for example by the rotors of the wind power plant, also the internally geared ring gear 18a rotates clockwise at the same speed and torque and when meshing with the first pinion gears 15a causes a high clockwise torque to the first pinion gears 15a of the pinion gear assemblies 13. Because the first pinion gears 15a, support shafts 14 and the second pinion gears 16 of the pinion gear assemblies 13 cannot rotate in relation to each other, the same clockwise torque is directed through the support shafts 14 to the second pinion gears 16 and through them to the second internally geared ring gear 19 screw-fastened to the non-rotary housing 1 a. Because the internally geared ring gear 19 does not rotate, the mentioned clockwise torque forces the first and second pinion gears 15a, 16 of the pinion gear assemblies 13 to rotate counter-clockwise with their support shafts 14 on the bearings 36, 37 around the central axis of the support shafts 14. The reference diameter of the first pinion gears 15a is smaller than the reference diameter of the second pinion gears 16, which second pinion gears 16 are meshing with the non-rotary second internally geared ring gear 19. Consequently, the pinion gears 15a, 16 rotating together to the same direction and at the same speed are forced to rotate counter-clockwise together around the central axis of the support shafts 14. This counter-clockwise rotary motion correspondingly forces the pinion gears 15a, 16 to revolve circumferentially clockwise in their meshing contacts in relation to both the internally geared ring gears 8a, 19. The circumferentially revolving support shafts 14 force through the bearings 36, 37 the whole power transmission unit 21 a to rotate clockwise with the accelerating factor or gear ratio dictated by the difference of the refer- ence diameters of the pinion gears 15a, 16.

If the same gearing is used as a reduction gearing and the first axle 2 serves as a power- out axle, then the same difference of the reference diameters between the pinion gears 15a, 16 dictates the gear ratio of the reduction gearing. If, however, the mutual differences of the diameters of the pinion gears 15a and 16 of the pinion gear assembly 13 and the internally geared ring gears 8a and 9 are changed to opposite, then also the direction of rotation of all the other rotating components of the gearing changes to opposite, only the direction of rotation of the primary unit 8 stays the same. When the first axle 2 is as a primary axle the mentioned power transmission unit 21 a rotates a traditional planet carrier 54 of the planet gears coupled to the second end of the transmission unit 21 a with a groove fastening corresponding the groove fastening 52, the planet carrier 54 having flanges 55a and 55b joined together with bridges of the same cast-steel construction and corresponding to the bridges shown for example in Figs. 7 and 8, which bridges are, however, for the sake of clarity not shown in Fig. 10. The first flange

55a is fastened to the transmission unit 21 a with the mentioned groove fastening and the second flange 55b is bearing-mounted on the end flange 1 c of the gearing with a bearing 56. The planet shafts 58 have been fitted according to the traditional way for example with a groove joint through the flanges 55a and 55b of the planet carrier 54, and between the flanges through the planet gears 57 equipped with bearings 61 . This way the planet gears 57 can freely rotate in their spaces between the support bridges. The internally geared ring gear 59 of the planet gearing comprising the planet gears 57 is, for example, non-rotary fastened with a screw-fastening 60 at the second end of the housing 1 of the gearing. The sun gear 42 belonging as an essential part to the planet gearing is the same steel with the second axle 3 acting now as a power-out axle, or is, for example, groove fastened to the mentioned second axle 3. Both the internally geared ring gear 59 fastened non-rotary to the housing 1 and the sun gear 42 are in meshing contact with the planet gears 57 on the shafts 58. The entity formed by the sun gear 42 and the second axle 3 is bearing-mounted at its first end on the second end of the power transmission unit 21 a with a bearing 53, and at its second end with a bearing 5 on the second end flange 1c of the housing 1 of the gearing. In addition there is a seal 7 between the second end flange and the second axle 3 in order to keep the lubricating oil in the housing 1 of the gearing. The housing 1 of the gearing can be assembled for instance in a way that a part of the first end flange 1 b of the housing 1 of the gearing, a part of the second internally geared ring gear 19, a part of the flange 43a, and a part of the internally geared ring gear 59 of the planet gearing form together a cylindrical frame 1 a of the gearing where all the aforementioned parts are tightly fastened to each other with screws 60.

When rotating counter-clockwise around the central axis of their own support shafts 14 the pinion gear assemblies 13 revolve simultaneously as a unity circumferentially towards right around the central axis of the whole gearing. Through the bearings 36, 37 the pinion gear assemblies 13 carry and force the whole transmission unit 21 a to revolve right at the gear ratio dictated by the difference of the reference diameter of the pinion gears 15a and 16. Consequently, for example: If the primary axle rotates 10 rpm and the difference of the reference diameter of the pinion gears 15a and 16 dictates the gear ratio of 1 :35, then the power transmission unit 21 a rotates 350 rpm. The planet carrier 54 of the traditional planet gearing is fastened to the power transmission unit 21 a with a groove fastening corresponding the groove fastening 52, which power transmission unit therefore revolves the planet carrier 54 and the planet gears 57 rotatably bearing mounted in relation to the planet carrier to the right. Because the internally geared ring gear 59 of the planet gearing is non- rotatably screw-fastened to the housing 1 , the meshing contact between the internally geared ring gear 59 and the planet gears 57 forces these to the right circumferentially revolving planet gears 57 to a simultaneous fast counter-clockwise rotation around the central axis of their own planet shafts 58. Because the planet gears 57 are also meshing with the sun gear 42, the sun gear 42 rotates extremely fast to the right. Consequently, the rotation of the power transmission unit 2 a multiplies through the traditional planet gearing about quadruple to the power-out axle, or in this case to the second axle 3, in which case when the primary shaft 2 rotates 10 rpm the mechanical power-out axle or the second axle 3 rotates right about 1400 rpm, in which case the total gear ratio is 1 :140. It is obvious to the person skilled in the art that the invention is not restricted to the embodiment described above but that it may be varied within the scope of the claims presented below.

Claims

1. Power transmission arrangement comprising at least a housing (1 ) and a gear arrangement that has at least a first axle (2) rotating around its central axis, and a second axle (3, 3b) rotating around its central axis and coaxial with the first axle (2), and two or more mutually essentially similar pinion gear assemblies (13), having at least two pinion gears (15-17) with mutually different reference diameters and fitted coaxially on the same rotating support shaft (14), and which gear arrangement comprises internally geared ring gears (18-20) meshing with the pinion gears (15-17), and at least one ring gear (18, 19) at a time is arranged to be stationary locked non-rotary in relation to the housing (1 ), characterized in that the pinion gears (15-17) fitted on the support shaft (14) are arranged to rotate at the same speed and to the same direction with their support shafts (14) and mutually with each other, and that at least one pinion gear (15a, 17) of each pinion gear assembly (13) is arranged to mesh with the rotary internally geared ring gear (18a, 20).

2. Power transmission arrangement according to claim 1 , characterized in that each pinion gear assembly ( 3) comprises at least two or more mutually coaxial pinion gears (15-17) on the same support shaft (14) and non-rotary in relation to their support shaft (14), and all the pinion gears (15-17) having a mutually different sized reference diameter, and that each internally geared ring gear (18, 20) has a mutually different sized reference diameter, and that the arrangement comprises a primary unit (8) with the pinion gear assemblies (13) rotating around its central axis, and a secondary unit (21 ) rotated by the primary unit (8) around its central axis, which secondary unit is coaxial with the primary unit (8) and arranged to be locked to the primary unit (8) with a locking element, such as a clutch unit (22) to rotate along with the primary unit (8) to the same direction and at the same speed with the primary unit (8), and that the arrangement comprises gear changing means, such as brake units (29, 30) to lock one ring gear (18, 19) at a time non-rotary in relation to the housing (1 ).

3. Power transmission arrangement according to claim 1 or 2, characterized in that each pinion gear assembly (13) rotating around the central axis of the gearing along with the primary unit (8) has a pinion gear (17) meshing with the internally geared ring gear (20) of the secondary unit (21 ), which pinion gear together with one or more pinion gears (16) on the same support shaft (14) and having a larger reference diameter than its own diameter, is arranged to rotate the secondary unit (21 ) to the direction of rotation of the primary unit (8) at the speed slower than the speed of the primary unit (8); or which pinion gear (17) together with one or more pinion gears (15) on the same support shaft (14) and having a smaller reference diameter than its own diameter, is arranged to rotate the secondary unit (21 ) to the opposite direction in relation to the direction of rotation of the primary unit (8) at the speed slower than the speed of the primary unit (8).

4. Power transmission arrangement according to claim 1 , characterized in that the rotary internally geared ring gear (18a) is fastened to the primary unit (8) to rotate with the primary unit (8) around the central axis of the gearing at the same speed and to the same direction as the primary unit (8), and that the gearing comprises a transmission unit (21 a), on which two or more pinion gear assemblies (13) are bearing-mounted to rotate along with the transmission unit (21 a) around the central axis of the gearing at the same speed and to the same direction as the transmission unit (21 a), and that the first pinion gears (15a) of the pinion gear assemblies (13) are meshing with the rotary internally geared ring gear (18a) and the second pinion gears (16) are meshing with the internally geared ring gear (19) locked non- rotary in relation to the housing (1 ), and with a sun gear (42) of a rotor unit (42a).

5. Power transmission arrangement according to claim 4, characterized in that a planet carrier (54) with its planet gears (57) is coupled in connection with the second end of the transmission unit (21 a) to rotate along with the transmission unit (21 a), which planet gears are arranged to mesh with the internally geared ring gear (59) locked non-rotary in relation to the housing (1 ) and with the sun gear (42) bearing-mounted on the second end of the transmission unit (21 a) and/or on the housing (1 ), to which sun gear (42) the second axle (3) working as a primary or secondary axle is connected.

6. Power transmission arrangement according to claim 4 or 5, characterized in that the reference diameters of the first pinion gears (15a) of the pinion gear assemblies (13) are of different size as the reference diameters of the second pinion gears (16), either smaller or larger.

7. Power transmission arrangement according to any of the claims above, characterized in that each pinion gear assembly (13) comprise means, such as an elastic joint (16a) or a support shaft (14) designed to optimally twist against torsional direction for 5 transmitting torque with a small rotational twist angle between the pinion gears (15-17) on the same support shaft (14), which means are arranged to compensate machining tolerance errors in the tooth meshing and simultaneously serve as a vibration damper in the gearing

10 8. Power transmission arrangement according to any of the claims above, characterized in that the gear ratio of the gearing or at least a part of it is arranged to be based on the mutual size difference of the reference diameters of the pinion gears (15-17) on the same support shaft (14) of the pinion gear assemblies (13), which pinion gears (15-17) are arranged to rotate around the central axis of their own support shaft (14) and simul-

15 taneously with their own support shaft (14) around the central axis of the whole gearing.

9. Method for power transmission in a gear system comprising at least a housing (1 ) and a gear arrangement that has at least a first axle (2) rotating around its central axis, and a second axle (3, 3b) rotating around its central axis and coaxial with the first axle (2), and

20 two or more mutually essentially similar pinion gear assemblies (13), having at least two pinion gears ( 5-17) with mutually different reference diameters and fitted coaxially on the same rotating support shaft (14), and which gear arrangement comprises internally geared ring gears (18-20) meshing with the pinion gears (15-17), and at least one ring gear (18, 19) at a time is stationary locked non-rotary in relation to the housing (1 ), characterized in

25 that the pinion gears (15-17) fitted on the support shaft (14) are arranged to rotate at the same speed and to the same direction with their support shafts (14) and mutually with each other, and that at least one pinion gear (15a, 17) of each pinion gear assembly (13) is arranged simultaneously to mesh with the rotary internally geared ring gear (18a, 20).

30 10. Method according to claim 9, characterized in that around its own central axis rotating primary unit (8) of the arrangement comprising the pinion gear assemblies (13), and around its own central axis rotating secondary unit (21 ) being coaxial with the primary unit (8) and rotated by the primary unit (8) are locked mutually together with a locking element, such as a clutch unit (22) to a unit rotating to the same direction and at the same speed, and that to change the gear ratio one ring gear (18, 19) at a time is locked non-rotary in relation to the housing (1 ) with the gear changing means, such as brake units (29, 30).

1 1. Method according to claim 9, characterized in that the rotary internally geared ring gear (18a) is rotated around the central axis of the gearing along with the primary unit (8) at the at the same speed and to the same direction as the primary unit (8), and that the pinion gear assemblies ( 3) bearing-mounted on the transmission unit (21 a) belong- ing to the gearing are rotated along with the transmission unit (21 a) around the central axis of the gearing along with the primary unit (8) at the at the same speed and to the same direction as the transmission unit (21 a), at the same time the first pinion gears (15a) of the pinion gear assemblies (13) are arranged to mesh with the rotary infernally geared ring gear (18a), and the second pinion gears (16) are arranged to mesh with the internally geared ring gear (19) locked non-rotary in relation to the housing (1 ) and to also mesh with the sun gear (42) of the rotor unit (42a) belonging to the arrangement.

12. Method according to claim 9, characterized in that the rotary internally geared ring gear (18a) is rotated around the central axis of the gearing along with the primary unit (8) at the at the same speed and to the same direction as the primary unit (8), and that the pinion gear assemblies (13) bearing-mounted on the transmission unit (21 a) belonging to the gearing are rotated along with the transmission unit (21 a) around the central axis of the gearing along with the primary unit (8) at the at the same speed and to the same direction as the transmission unit (21 a), at the same time the first pinion gears (15a) of the pinion gear assemblies (13) are arranged to mesh with the rotary internally geared ring gear (18a), and the second pinion gears (16) are arranged to mesh with the internally geared ring gear (19) locked non-rotary in relation to the housing (1 ), and at the same time the planet carrier (54) coupled to rotate along with the transmission unit (21 a) is rotated around its central axis so that the planet gears (57) of the planet carrier are meshing with both the internally geared ring gear (59) fastened non-rotary in relation to the housing (1 ) and with the sun gear (42) coupled with the second axle (3) working as a secondary axle

13. Method according to any of the claims 9-12 above, characterized in that the gear ratio of the gearing or at least a part of it is realized by the mutual size difference of the reference diameters of the pinion gears (15-17) on the same support shaft (14) of the pinion gear assemblies (13) by rotating the pinion gears (15-1 7) around the central axis of their own support shaft (14) and simultaneously with their own support shaft (14) around the central axis of the whole gearing.

14. Method according to any of the claims 9-13 above, characterized in that machining tolerance errors in the tooth meshing are compensated and vibrations of the gearing are dampened by transmitting the torque from the primary unit (8) forward between the pinion gears ( 5-17) on the same support shaft (14) either through an elastic joint (16a) or through a small twist angle arranged by the optimally designed support shaft (14) yielding against a torsional direction, or using together with the elastic joint (16a) an axial pressure and movement achieved through a small yield of the twist angle caused by a helical toothing of the pinion gear (16) or by an inclined serration joint (16b) of the pinion gear (16).

15. Use of the power transmission arrangement according to claim 1 as a reducing gearing of a vehicle, such as an all-terrain vehicle or a boat.

16. Use of the power transmission arrangement according to claim 4 or 5 as a reducing gearing providing a high gear ratio or an accelerating gearing providing a high gear ratio for example in a wind power plant.