POWER SPLIT GEARBOX AND METHOD FOR OPERATING A POWER SPLIT GEARBOX

Abstract

A power split gearbox with a secondary coupling and a drive range has an adjusting unit (13), where its position control valve (15) interacts with the cylinder (14) in such a way that, during a de-energized condition of the position control valve (15), the cylinder (14) adjusts the second hydraulic unit (9) so that the unit has a zero stroke volume.

Claims

1-9. (canceled)

10. A power split gearbox comprising: a drive shaft (2) being connectable with a drive motor (1), an output shaft (10) being connectable with vehicle wheels, a first hydraulic unit (7) having an adjustable stroke volume and being operable as either a motor or a pump, an adjustable second hydraulic unit (9) having an adjustable stroke volume and being be operable as either a motor or a pump, a summing gearbox (5) having a first shaft (4), a second shaft (6) and a third shaft (8), the first shaft (4) being operably connected, via a clutch (3), with the drive shaft (2), the second shaft (6) being operably connected with the first hydraulic unit (7), and the third shaft (8) being operably connected with the second hydraulic unit (9) and the output shaft (10), an adjusting device (13) being powered by an electrical current to adjust the stroke volume of the first hydraulic unit (7) and the stroke volume of the second hydraulic unit (9), and the adjusting unit (13), in a de-energized condition, adjusting the second hydraulic unit (9) to a zero stroke volume.

11. The power split gearbox according to claim 10, wherein the adjusting unit (1), in the de-energized condition, adjusts the first hydraulic unit (7) to a maximum stroke volume.

12. The power split gearbox according to claim 10, wherein the clutch (3) is activated towards disengagement, during the de-energized condition of the adjusting unit (13).

13. The power split gearbox according to claim 10, wherein the first hydraulic unit (7) and the second hydraulic unit (9) are coupled, via a common yoke (12), by which the stroke volume of the first and the second hydraulic units are adjusted.

14. The power split box according to claim 10, wherein the adjusting unit has an adjustment cylinder (14) for adjusting the stroke volumes of the first and the second hydraulic units and a position control valve (15) cooperating therewith, the position control valve has a regulating magnet which, in the de-energized condition, interacts with the position control valve such that the adjusting cylinder (14) adjusts the second hydraulic unit (9) to the zero stroke volume.

15. The power split box according to claim 11, wherein the stroke volume of the first hydraulic unit (7) and the stroke volume of the second hydraulic unit (9), in the de-energized condition of the adjusting unit (14), corresponds to a stroke volume of a maximum rotational speed of the output shaft.

16. A method of operating a power split box with a drive shaft (2), which is connectable with a drive motor (1) and a drive shaft (10) that is connectable with vehicle wheels, a hydraulic unit (7) has an adjustable stroke volume which is operable either as a motor or as a pump, a second hydraulic unit (9) has an adjustable stroke volume which is operable either as a motor or as a pump, and a summing gearbox (5) with a first shaft (4) and a second shaft (6) and a third shaft (8), the first shaft (4) being operably connected, via a clutch (3), with the drive shaft (2), the second shaft (6) being operably connected with the first hydraulic unit (7), and the third shaft (8) being operably connected with the second hydraulic unit (9) and the output shaft (10), and an adjustment device (13) being operated through electric current for adjustment of the stroke volume of the first hydraulic unit (7) and the stroke volume of the second hydraulic unit (9), the method comprising: always adjusting the second hydraulic unit (9), with the adjusting device (13), to a zero stroke volume when the adjusting device (13) is de-energized.

17. The method of operating the power split box according to claim 16, further comprising, when no current is applied to the adjusting unit (13), always adjusting the first hydraulic unit (7), with the adjusting unit (13), to a maximum stroke volume.

18. The method of operating the power split box according to claim 17, further comprising actuating the clutch (3) in a disengaging direction when the adjusting device (13) is de-energized.

19. A power split gearbox comprising: a drive shaft (2) being connectable to a drive motor (1), and an output shaft (10) being connectable to vehicle wheels; first and second hydraulic units (7, 9), each of the first and the second hydraulic units being operable as either a motor or a pump, and having an adjustable stroke volume; a summing gearbox (5) having first, second and third shafts (4), the first shaft (4) being operably connected, via a clutch, to the drive shaft (2), the second shaft (6) being connected to the first hydraulic unit (7), and the third shaft (8) being operably connected to the second hydraulic unit (9) and the output shaft (10); an adjusting device (13) being connected to the first and the second hydraulic units; and the adjusting device being electrically actuatable for adjusting the stroke volumes of the first and the second hydraulic units such that, in a de-energized condition of the adjusting device, the second hydraulic unit is adjusted to a zero stroke volume.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These show:

[0013] FIG. 1 a power split gearbox with a drive range for forward and a drive range for reverse; and

[0014] FIG. 2 a hydraulic schematic to control the stroke volume of the power split gearbox as in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] FIG. 1

[0016] A drive motor 1, for instance a combustion engine, drives the driveshaft 2.

[0017] The driveshaft 2 drives a first shaft 4 of a summing gearbox 5 via a clutch for forward drive 3. The second shaft 6 of the summing gearbox 5 is connected with the first hydraulic unit 7. The first hydraulic unit 7 is also defined as pump. The third shaft 8 of the summing gearbox 5 is an operating connection with the second hydraulic unit 9 and the output shaft 10, The second hydraulic unit 9 is also defined as a motor. Through the clutch, the output shaft 10 can be driven for a reverse drive 11 in the opposite direction. The first hydraulic unit 7 and the second hydraulic unit 9 are connected through a common yoke 12 through which the stroke volume of the first hydraulic unit 7 and the second hydraulic unit 9 can be adjusted. The yoke 12 interacts together with the adjustment device which is schematically presented in FIG. 2. The additional details of the summing gearbox 5 and the function of the adjustment of the first hydraulic unit 7 and the second hydraulic unit can be seen in DE 102013204746A1.

[0018] FIG. 2

[0019] The adjustment device 13 has a cylinder 14 which is connected with the yoke 12 and which adjusts the stroke volume of the first hydraulic unit 7 and the second hydraulic unit 9. The cylinder 14 operates together with a position control valve 15 which, depending on applying an electrical current or its current strength, respectively, adjusts the position of the cylinder 14. The position control valve 15 cooperates with the cylinder 14 so that in a de-energized state, meaning when no current is applied to the position control valve 15, the cylinder 14 is adjusted so that the second hydraulic unit 9 is adjusted to a zero stroke volume and the first hydraulic unit 7 to the maximum stroke volume. To start the power split gearbox as in FIG. 1, a maximum current is applied to the position control valve 15, whereby the cylinder 14 is adjusted so that the second hydraulic unit 9 is adjusted to its maximum stroke volume and the first hydraulic unit 7 is adjusted to its minimum stroke volume. The function of the additional valves which interact together with the first hydraulic unit 7 and the second hydraulic unit 9 can be seen in DE 1020132003990A1.

[0020] If the vehicle is now at high speed and a defect causes a de-energized condition and the position control valve 15 is without current, the cylinder 14 is adjusted so that the second hydraulic unit 9 is adjusted to a zero stroke volume and the first hydraulic unit 7 is adjusted to the maximum stroke volume, and at the same the clutch for forward drive 3 and the clutch for the reverse drive 11 are disengaged in the opening direction, so that the second hydraulic unit 9 cannot support torque, and that the output shaft 10 is not decelerated to the extent that this situation will cause uncontrolled sliding of the vehicle. Thus, driving safety is ensured even if an electric defect occurs.

REFERENCE CHARACTERS

[0021] 1 Drive Motor [0022] 2 Drive Shaft [0023] 3 Clutch, Forward Drive [0024] 4 First Shaft [0025] 5 Summing Gearbox [0026] 6 Second Shaft [0027] 7 First Hydraulic Unit [0028] 8 Third Shaft [0029] 9 Second Hydraulic Unit [0030] 10 Output Shaft [0031] 11 Clutch, Reverse Drive [0032] 12 Bay [0033] 13 Adjusting Device [0034] 14 Cylinder [0035] 15 Position Control Valve