Hydraulic mechanical transmission with increased efficiency

Patent metadata

Field	Value
Publication number	US-10487940-B2
Application number	US-201715680805-A
Country	US
Kind code	B2
Filing date	Aug 18, 2017
Priority date	Aug 19, 2016
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

A hydraulic mechanical transmission includes a first hydraulic unit having a first shaft and a second hydraulic unit having a second shaft. The second hydraulic unit is connected in hydraulic fluid communication with the first hydraulic unit by high and low pressure lines. A mechanical torque transfer arrangement transfers torque between the first shaft of the first hydraulic unit and a rotatable housing of the second hydraulic unit. One of the first and second hydraulic units operates as a hydraulic pump and the other operates as a hydraulic motor, and both of the first and second hydraulic units have variable displacement.

First claim

What is claimed is:

1. A hydraulic mechanical transmission comprising:
a first hydraulic unit having a first shaft;
a second hydraulic unit connected in hydraulic fluid communication with the first hydraulic unit by high and low pressure lines, the second hydraulic unit including a second shaft and a rotating group that is coupled to the second shaft so as to rotate in unison with the second shaft about an axis defined by the second shaft, the rotating group including a cylinder block that defines a plurality of axial cylinders, the rotating group also including pistons mounted to slide within the axial cylinders, the second hydraulic unit further including a rotatable housing that is rotatable relative to the second shaft about the axis of the second shaft, the rotatable housing supporting a swashplate that opposes ends of the pistons, the rotatable housing including a swashplate mount that mounts the swashplate such that the swashplate rotates in unison with the rotatable housing, the swashplate mount also allows the swashplate to pivot relative to the rotatable housing and the axis of the second shaft to vary a stroke length of the pistons within the axial cylinders such that a displacement of the rotating group can be varied, the rotatable housing also including a commutation structure for providing fluid communication between the high and low pressure lines and the axial cylinders of the rotating group while maintaining separation between the high and low pressure lines;
a mechanical torque transfer arrangement for transferring torque between the first shaft of the first hydraulic unit and the rotatable housing of the second hydraulic unit; and
wherein in use one of the first and second hydraulic units operates as a hydraulic pump and the other of the first and second hydraulic units operates as a hydraulic motor, and wherein both of the first and second hydraulic units have variable displacement.

2. The hydraulic mechanical transmission of claim 1 , wherein the first hydraulic unit is a hydraulic motor and the second hydraulic unit is a hydraulic pump.

3. The hydraulic mechanical transmission of claim 2 , wherein the pistons reciprocate within the cylinders as the relative rotation occurs between the rotatable housing and the rotating group about the axis of the second shaft, and wherein an angle of the swashplate relative to the axis of the second shaft determines a stroke length the pistons reciprocate within the cylinders as relative rotation occurs between the rotatable housing and the rotating group about the axis of the second shaft.

4. The hydraulic mechanical transmission of claim 3 , wherein the commutation structure maintains fluid communication between the high pressure line and the rotating group regardless of a rotational position of the rotatable housing about the axis defined by the second shaft, the commutation structure also maintaining fluid communication between the low pressure line and the rotating group regardless of a rotational position of the rotatable housing about the axis defined by the second shaft, and wherein the commutation structure is adapted to rotate in unison with the swashplate relative to the second shaft such that in operation a rotational position of the commutation structure about the axis of the second shaft does not change relative to the swashplate.

5. The hydraulic mechanical transmission of claim 4 , wherein the commutation structure includes a first annular groove in fluid communication with the high pressure line and a second annular groove in fluid communication with the low pressure line, wherein the commutation structure includes first porting in fluid communication with the first annular groove and second porting in fluid communication with the second annular groove, the first porting including a first fluid exchange interface in fluid communication with a first plurality of the cylinders of the rotating group as the rotating group rotates relative to the commutation structure, the second porting including a second fluid exchange interface in fluid communication with a second plurality of the cylinders of the rotating group as the rotating group rotates relative to the commutation structure, the first fluid exchange interface being fixed in rotational alignment with a first portion of an arcuate path around the swashplate, and wherein the second fluid exchange interface being fixed in rotational alignment with a second portion of an arcuate path around the swashplate.

6. The hydraulic mechanical transmission of claim 5 , wherein the first portion of the arcuate path around the swashplate corresponds to an extension stoke of the pistons within the cylinder and the second portion of the arcuate path corresponds to a retraction stroke of the pistons within the cylinders.

7. The hydraulic mechanical transmission of claim 6 , wherein the first and second fluid exchange interfaces each include a generally semi-circular slot.

8. The hydraulic mechanical transmission of claim 7 , wherein the first and second annular grooves have open sides that face in a radial direction relative to the axis to the second shaft.

9. The hydraulic mechanical transmission of claim 1 , further comprising one or more bearings between the rotatable housing and the second shaft for allowing relative rotation between the rotatable component and the second shaft about the axis of the second shaft.

10. The hydraulic mechanical transmission of claim 9 , wherein the second hydraulic unit includes an outer housing, and wherein one or more bearings are provided between the rotatable housing and the outer housing for allowing relative rotation between the outer housing and the rotatable housing, and wherein one or more bearings are provided between the shaft and the outer housing.

11. The hydraulic mechanical transmission of claim 1 , wherein the first hydraulic unit includes a rotating group coupled to the first shaft so as to rotate in unison with the first shaft, the rotating group including a cylinder block defining a plurality of cylinders and pistons adapted to slide in the cylinders, the first hydraulic unit further including a swashplate upon which shoes of the pistons ride, the swashplate being capable of being angled with respect to an axis of the first shaft with an angle of the swashplate determining a stroke length of the pistons within the cylinders, the angle of the swashplate being variable to vary the stroke length of the pistons and thus the displacement of the first hydraulic unit.

12. The hydraulic mechanical transmission of claim 1 , wherein the mechanical torque transfer arrangement includes a component selected from the group consisting of a belt, a chain, a pulley and a gear.

13. The hydraulic mechanical transmission of claim 1 , wherein the mechanical torque transfer arrangement includes a gear arrangement including intermeshing gears.

14. The hydraulic mechanical transmission of claim 1 , wherein the hydraulic mechanical transmission can be arranged in a U or Z shaped configuration.

15. The hydraulic mechanical transmission of claim 14 , wherein the gear arrangement includes three intermeshing gears.

16. The hydraulic mechanical transmission of claim 1 , wherein the hydraulic mechanical transmission does not include a planetary gear set.

17. The hydraulic mechanical transmission of claim 1 , wherein the rotatable housing includes an actuator for pivoting the swashplate relative to the axis of the second shaft, the actuator including a hydraulic cylinder, and the cylinder being in fluid communication with a control communication passage including an ann

Assignees

• Eaton Intelligent Power Ltd

Inventors

• Yuan Qinghui
• Creswick Matthew E

Classifications

• F16H47/02 Primary

  the fluid gearing being of the volumetric type · CPC title

• F16H39/12

  with stationary cylinders · CPC title

• F16H61/0009

  Hydraulic control units for transmission control, e.g. assembly of valve plates or valve units · CPC title

• F16H2037/0866

  Power-split transmissions with distributing differentials, with the output of the CVT connected or connectable to the output shaft · CPC title

• F16H61/438 Primary

  Control of forward-reverse switching, e.g. control of the swash plate causing discharge in two directions · CPC title