[00011POWER SPLIT TRANSMISSION

[0002]

[0003]

[0004] The Invention relates to a power split transmission of the type defined in detail
in the preamble of Claim 1.

[0005]

[0006] Such power split transmissions have a continuously variable power branch and a mechanical power branch that are summed by a summing gear set.

[0007] The document DE10 2006 004 223 A1 discloses a power spilt transmission
with a continuously variable power branch and a mechanical power branch that are summed in a summing gear set, wherein the summing gear set consists of a planetary gear set with a double planetary gear, two sun wheels, and an internal geared wheel.

[0006] I n working machinery, for example such as wheel loaders, the drive motor is
positioned above the drive axle so that a transmission is needed that has a large axial distance between the input drive for the transmission and the transmission output drive. In addition, the structural space for the width and depth of the transmission is extremely limited in working machines, so that narrow, short transmissions with large axial separations are often used.

[0009] The underlying problem of this invention is to provide a power split transmission that makes possible a compact structure and a large axial separation.

[0010]

[0011] The power split transmission should also be easy to shift from a first operating
range to a second operating range. The problem Is solved with a power split transmission of the type described that also has the characterizing features of the main claim.

[0012] In accordance with the invention, the power split transmission has a continuously variable power branch and a mechanical power branch.

[0013] The continuously variable power branch can be designed as a hydrostatic power branch that can have continuously variable hydrostatic units of swash plate design or inclined axle design. These hydrostatic units can be interconnected so that they can be varied by way of a common yoke. However, this can be set that so in a first position, the first hydrostatic unit Is at zero displacement and the second hydrostatic unit exhibits its maximum displacement, in the second end position of the yoke, the first hydrostatic unit Is adjusted to maximum displacement and the second hydrostatic unit Is at zero displacement.

[0014] However, it is also possible to design the continuous units as electrical units.
The continuously variable power branch and the mechanical power branch are summed in a summing gear set; with the summing gear set being designed as a planetary gear set that has at least one double planetary gear that meshes with a ring geared gear and two sun gears.

[0015] The power split transmission has shafts on which there are clutches, by
means of which on the one hand a forward drive and a reverse drive can be switched, and on the other hand at least two operating ranges can be switched, and within which the output drive rotational speed can be continuously varied. The shafts are positioned apart from one another and there is only one single clutch on each shaft, so that a large axial separation and an otherwise compact transmission is provided. A clutch for forward drive and a clutch for reverse drive precede the summing gear set through gear wheels, whereby the clutches for the operating ranges can follow the summing gear set.

[0016] The clutch for forward drive is preferably positioned coaxially with the drive
of the power split transmission, and the clutch for reverse drive is on a shaft separated from the clutch for forward drive. The gear ratios of the gear wheels are preferably designed so that the shaft that is connected to the clutch for reverse drive has a higher rotational speed than the drive shaft that is connected to the clutch for forward drive. This makes it possible to place one or more consumers on the shaft with the clutch for reverse drive, for example a hydraulic pump, which has sufficient rotational speed even with lower rotational speeds on the input drive to the transmission. This hydraulic pump, for example, can be used for the hydraulic supply of the transmission system, as well as for cooling and lubricating. Another hydraulic pump can be used to supply the working hydraulic mechanism.

[0017] The planet carrier of the summing gear set, wheels carries at least one double
planetary gear, can be connected through gear wheels and the clutch for forward drive and the clutch for reverse drive, to the input shaft of the power split transmission, A first sun gear of the summing gear set is connected to the first continuously variable unit, and the ring gear of the summing gear set Is in active connection with the second continuously variable unit. To switch to a first operating range, the second continuously variable unit is connected, via a clutch for the first operating range and other gears, to the output drive of the power split transmission. Except for the summing planetary gear set, the gear wheels of the power split transmission are designed as spur gears.

[0018] To switch to a second operating range, the clutch for the first operating range
is actuated in the disengaging direction and the clutch for the second operating range is actuated in the engaging direction, so that the second sun gear of the summing planetary set can be brought into active connection with the output drive of the power split transmission.

[0019] The gear ratios of the range gears are chosen preferably so that at the end
of the first operating range, at which the clutch for the first operating range is still engaged, the clutch for the second operating range has no differential rotational speed and can thus be engaged synchronously. During the change of ranges, the clutch for the first operating range is actuated in the disengaging direction and the clutch for the second operating range Is actuated In the engaging direction, with only little need during this switch to correct the rotational speeds of the continuously variable units, for example the hydrostatic units, since the correction has to compensate only for leakage that occurs from the changing pressure conditions. When switching back from the second to the first operating range, the engaging and disengaging of the clutches take place in correspondingly different directions. In the second operating range, the second continuously variable unit is then adjusted from zero displacement toward maximum displacement, and the first continuously variable unit is adjusted from maximum displacement toward minimal displacement.

[0020]

[0021 ] Other features can be found In the Figures and Specification.

[0022] The Figures show:

[0023] Fig. 1 a power split transmission with two operating ranges for forward drive
and two operating ranges for reverse drive; and

[0024] Fig. 2 a power split transmission with three operating ranges for forward drive
and three operating ranges for reverse drive.

[0025]

[0026] Fig. 1:

[0027] A drive motor 1 drives the input drive shaft 2 for the power split transmission.
The drive shaft 2 is connected in a rotationally fixed manner, to a spur gear 3, designed as a fixed gear, and a clutch for forward drive 4. An idler 5 that is connected in a rotationally fixed manner to the clutch for forward drive 4, Is located on the input drive shaft 2. The spur gear 3 meshes with a spur gear 6 designed as a fixed gear, which is connected in a rotationally fixed manner, to the shaft 7. The clutch for forward drive 8 Is positioned on the shaft 7 and is connected in a rotationally fixed manner to the spur gear 6. The idler 9 is placed on the shaft 7 and is connected in a rotationally fixed manner to the clutch for reverse drive 8. A consumer 10, for example a hydraulic pump, is driven by the shaft 7. The gear ratios are preferably chosen so that the shaft 7. And thus the consumer 10 has a greater rotational speed than the shaft 2. The idler 5 and the idler 9 mesh with the idler 11, which is connected in a rotationally fixed manner to the planet carrier 12 of the summing planetary gear set 13. The planet carrier 12 carries at least one double planetary gear 14, with the double planetary gear meting on the one hand with the ring gear 15 and on the other hand with the first sun gear 16 and the second sun gear 17. The first sun gear 16 is connected to the first continuously variable unit 18, for example a hydrostat. The ring gear 15 is connected, rotationally fixed, to the idler 19, which meshes with the spur gear 20 designed as a fixed gear. The spur gear 20 Is connected to the second continuously variable unit 21, for example a hydrostat. The second sun gear 17 is connected in a rotationally fixed manner to the spur gear 22, which is designed as a fixed gear. The output drive 23 of the power split transmission is connected in a rotationally fixed manner to the spur gear 24, designed as a fixed gear, which can be connected, via the spur gear 25 designed as a fixed gear, to the clutch for the first operating range 26, and in the Idler 27 to the spur gear 20, or, via the spur gear 25, the idler 28 can be connected to the clutch for the second operating range 29, and the spur gear 30 designed as a fixed gear can be connected to the spur gear 22. It is thus possible, by engaging the clutch for the first operating range 26 and disengaging the clutch for the second operating range 29, to operate the output drive 23 in a first operating range, and by disengaging the clutch 26 and engaging the clutch 29, to operate the output drive 23 in a second operating range. The gear ratios are established so that when the end of the first operating range is reached with the clutch 26 engaged, the idler 28 and the spur gear 30 rotate synchronously, so that the clutch 29 can be actuated in the engaging direction with no differential rotational speed. Because of the structural space, it may also be necessary to divide the gear train consisting of the idler 19, the spur gear 20, and the idler 27, into two pairs of gears, whereby two spur gears are placed on the shaft 31 in the form of fixed gears. This makes it possible to provide a larger gear ratio.

[0028] Because the shaft 2, the shaft 7, and the shafts 31,32, and 33 are positioned
separated from one another, and only a single clutch is placed on each of these shafts, a power split transmission can be provided that has a compact design and has a large axial separation.

[0029] Fig. 2:

[0030] This differs from Fig. 1 only in that a third operating range is present in
addition. A clutch for a third operating range 34 connects the Idler 35 with the spur gear 36, designed as a fixed gear, to switch to a third operating range, with the spur gear 36 meshing with the spur gear 30 or the spur gear 22, and the idler 35 meshing with the spur gear 25. A first operating range is engaged by actuating the clutch for the first operating range 26 in the engaging direction and actuating the clutch for the second operating range 29 and the clutch for the third operating range 34 in the disengaging direction, a second operating range is engaged by actuating the clutch 29 for the second operating range in the engaging direction and the clutch 26 and the clutch 34 in the disengaging direction, and a third operating range is engaged by actuating the clutch 34 in the engaging direction and actuating the clutch 26 and 29 to disengage.

Reference labels
1 Drive motor
2 Input drive shaft
3 Spur gear
4 Clutch for forward drive
5 Idler
6 Spur gear
7 Shaft
8 Clutch for reverse drive
9 Idler
10 Consumer
11 Idler
12 Planet carrier
13 Summing planetary gear set
14 Double planetary gear
15 Ring gear
16 First sun gear
17 Second sun gear
18 First continuously variable unit
19 Idler
20 Spur gear
21 Second continuously variable unit
22 Spur gear
23 Output drive
24 Spur gear
25 Spur gear
26 Clutch for the first operating range
27 idler
28 Idler
29 Clutch for the second operating range
30 Spur gear
31 Shaft
32 Shaft
33 Shaft
34 Clutch for the third operating range
35 Idler
36 Spur gear
37 Shaft

Scope of Patent Claims

1. Power split transmission with a continuously variable branch and a mechanical branch, with the two branches being summed in a summing gear set (13), with the summing gear set being designed as a planetary gear set, with at least two operating ranges that can be switched through clutches (26, 29), and with a clutch for a forward drive direction (4) and a clutch for a reverse drive direction (8) and shafts (32,33) on which gear wheels (27,25,28,30) are placed, characterized in that only a single clutch (4,8,26,29) is placed on each shaft (2,7; 32,33) and the shafts (2,7; 32,33) are spaced apart from one another.

2. Power split transmission pursuant to Claim 1, characterized In that the summing gear set (13) has ring gear (15) and at least one double planetary gear (14) on a planet carrier (12) that Is engaged with the ring gear (15) and with two sun gears (16,17), herein the planet carrier (12) can be connected to a drive (2) via the clutch for forward drive (4) and the clutch for reverse drive (8).

3. Power split transmission pursuant to Claim 2, characterized In that a sun gear (17) is connected to a first continuously variable unit (18) and the ring gear (15) is connected to a second continuously variable unit (21).

4. Power split transmission pursuant to Claim 1, characterized In that the clutch for forward drive (4) is arranged coaxially with the input drive (2).

5. Power split transmission pursuant to Claim 1, characterized in that one or more consumers (10) is/are connected to the shaft (7) on which the clutch for reverse drive (8) is arranged.

6. Power split transmission pursuant to Claim 2, characterized in that the second sun gear (18) is in active connection with an output drive (23) via a clutch for a second operating range (29).

7. Power split transmission pursuant to Claim 3, characterized in that the second continuously variable unit (21) is in active connection with an output drive (23)via a clutch for a first operating range (26).

8. Power split transmission pursuant to Claim 2, characterized in that the second sun gear (18) is in active connection with an output drive (23) via a clutch for a third operating range (34).

9. Power split transmission pursuant to Claim 1, characterized in that the gear ratios are established so that when shifting from a first operating range to a second operating range, the clutch for the second operating range (29) has a synchronous rotational speed.

10. Power split transmission pursuant to Claim 5, characterized in that the shaft (7) with the clutch for the reverse travel direction (8) has a greater rotational
speed than the Input drive shaft (2).

11. Power split transmission pursuant to Claim 1, characterized in that the continuously variable power branch has two inclined axle hydraulic units that are adjustable via a common yoke.