Variable length bent-axis pump/motor

A hydraulic machine, comprising:

• a rotatable shaft;
• a drive plate, rotationally coupled to the shaft, the drive plate and shaft being configured to rotate together about a first axis;
• a cylinder barrel, configured to rotate about a second axis that intersects the first axis at a third axis lying perpendicular to the first and second axes, the cylinder barrel having a plurality of cylinders radially distributed therein;
• a plurality of pistons, first ends of each being positioned in a respective cylinder of the barrel and second ends of each engaging the drive plate;
• and
• a back plate, including a valve surface on which the cylinder barrel rotates, the back plate configured to pivot with the cylinder barrel around the third axis such that an angle of the second axis changes, relative to the first axis, thereby defining a stroke angle, the back plate, further configured to control a distance of the cylinder barrel from the third axis by moving in a direction along the second axis closer to the third axis as the stroke angle decreases and in a direction farther from the third axis as the stroke angle increases, such that the distance between the cylinder barrel and the third axis is variable as the cylinder barrel moves along the second axis.

A method of establishing the displacement of a variable displacement bent-axis hydraulic machine, comprising:

• establishing a stroke angle by pivoting a first axis, around which a cylinder barrel of the machine rotates, relative a second axis, around which a drive plate of the machine rotates, around a point that is common to the first and second axes;
• moving, while pivoting the first axis relative to the second axis, the cylinder barrel along the first axis to a preselected total axial distance of the cylinder barrel from the drive plate that is a function of the stroke angle;
• and
• modifying, while moving the cylinder barrel along the first axis, a total distance along which a fluid passage transports a working fluid between a fluid source and a valve surface of the cylinder barrel, such that the total distance along which the fluid passage transports the working fluid varies as the cylinder barrel moves along the first axis.

A hydraulic machine, comprising:

• a drive plate and power shaft configured to rotate about a first axis;
• a cylinder barrel configured to rotate about a second axis, the cylinder barrel having a plurality of cylinders and a corresponding plurality of pistons positioned therein, each bearing against the drive plate, the first and second axes intersecting at a third axis that lies perpendicular to the first and second axes;
• a back plate supporting the cylinder barrel and including a valve surface over which the cylinder barrel rotates;
• angle control means for controlling an angle of the second axis relative to the first axis, the angle control means including a yoke that is pivotable around the third axis, and to which the back plate is coupled, wherein the yoke includes a fluid channel that extends in a leg of the yoke and is coupled to the back plate via a telescoping junction that accommodates translation of the back plate along the second axis while maintaining fluid communication of the back plate with a source of pressurized fluid;
• and
• axial position control means for controlling a distance, along the second axis, of the cylinder barrel from the third axis.