EP4133179A1

EP4133179A1 - Assistive torque electro-hydraulic piston pump system

Info

Publication number: EP4133179A1
Application number: EP21722706.5A
Authority: EP
Inventors: David Geiger
Original assignee: Moog Inc
Current assignee: Moog Inc
Priority date: 2020-04-10
Filing date: 2021-04-09
Publication date: 2023-02-15
Anticipated expiration: 2041-04-09
Also published as: JP2023522176A; EP4133179B1; JP7408836B2; WO2021207638A1; US20230151800A1; EP4133179C0

Abstract

An electro-hydraulic piston pump system comprising an electric motor (16), first and second hydraulic piston pumps (30,60), a first hydraulic actuator (90) having a first port (93) connected directly to a first port (48) of the first pump and a second port (94) connected directly to a second port (49) of the first pump, a second hydraulic actuator (100) having a third port (103) connected directly to a third port (78) of the second pump and a fourth port (104) connected directly to a fourth port (79) of the second piston pump, wherein an external force applied to the first hydraulic actuator (90) that provides a negative pressure differential to the first pump applies an assistive torque to a common motor shaft (18) driving both the first pump (30) and the second pump (60), and an external force applied to the first and second actuators (90,100) that provides a summed negative pressure differential to the first and second pumps (30,60) recharges a power supply for the motor (16).

Description

ASSISTIVE TORQUE ELECTRO-HYDRAULIC PISTON PUMP SYSTEM

TECHNICAL FIELD

[0001] The present invention relates generally to the field of electro-hydraulic pump systems, and more particularly to an improved assistive torque electro-hydraulic piston pump system.

BACKGROUND ART

[0002] Hydrostatic radial piston pumps are generally known in the prior art. The drive torque of a shaft is transmitted to a radial piston cylinder block rotationally mounted on a control stud or journal with pistons arranged radially in the cylinder block and supported at their outer end by a thrust or stroke ring via slide shoes in the thrust ring. When the cylinder block rotates, the pistons exert a stroke movement as a result of an eccentric position of the thrust ring. The pump flow is routed into and out of the housing and control stud via channels and is controlled by means of suction and pressure windows in the control stud. If a differential cylinder is to be actuated by means of a hydrostatic radial piston motor, proportional or control valves are interposed. Differential cylinders comprise two working spaces, each with its own working connection, a first working connection leading to the working space on the piston-end and a second working connection leading to the working space on the rod-end of the differential cylinder. The volume flow of the hydraulic fluid supplied by the hydrostatic radial piston motor can be routed to the particular working connection and thereby the particular working space via the valves.

BRIEF SUMMARY

[0003] With parenthetical reference to corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, an electro-hydraulic pump system (15, 115, 215, 315) is provided comprising: an electric motor (16) adapted to be supplied with a current and having a drive shaft (18, 18A, 18B, 18C, 23, 123, 318, 323); a first hydraulic piston pump (30, 330) comprising a first fluid control journal (31, 331), a plurality of pistons (32, 332) in a first cylinder block (33, 333) adapted to rotate relative to the first fluid control journal (31, 331) about a first block axis (34, 334) with rotation of the drive shaft (18, 318), and a first displacement drive (35, 335) having a first displacement axis (38, 338); the first displacement drive (35, 335) adapted to move in a first positive displacement range (40, 340) between a first neutral position between the first displacement axis (38, 338) and the first block axis (34, 334) and a first maximum positive displacement position between the first displacement axis (38, 338) and the first block axis (34, 334); the first displacement drive (35, 335) adapted to move in a first negative displacement range (44, 344) between the first neutral position and a first maximum negative displacement position between the first displacement axis (38, 338) and the first block axis (34, 334); the first fluid control j oumal (31, 331) comprising a first pump port (48, 348) and a second pump port (49, 349), wherein rotation of the drive shaft (18, 318) when the first displacement drive (35, 335) is in the first positive displacement range (40, 340) provides higher pressure to the first pump port (48, 348) relative to the second pump port (49, 349), and wherein rotation of the drive shaft (18, 318) when the first displacement drive (35, 335) is in the first negative displacement range (44, 344) provides higher pressure to the second pump port (49, 349) relative to the first pump port (48, 348); a second hydraulic piston pump (60, 360) comprising a second fluid control journal (61, 361), a plurality of pistons (62, 362) in a second cylinder block (63, 363) adapted to rotate relative to the second fluid control journal (61, 361) about a second block axis (64, 364) with rotation of the drive shaft (18, 318), and a second displacement drive (65, 365) having a second displacement axis (68, 368); the second displacement drive (65, 365) adapted to move in a second positive displacement range (70, 370) between a second neutral position between the second displacement axis (68, 368) and the second block axis (64, 364) and a second maximum positive displacement position between the second displacement axis (68, 368) and the second block axis (64, 364); the second displacement drive (65, 365) adapted to move in a second negative displacement range (74, 374) between the second neutral position between the second displacement axis (68, 368) and the second block axis (64, 364) and a second maximum negative displacement position between the second displacement axis (68, 368) and the second block axis (64, 364); the second fluid control journal (61, 361) comprising a third pump port (78, 378) and a fourth pump port (79, 379), wherein rotation of the drive shaft (18, 318) when the second displacement drive (65, 365) is in the second positive displacement range (70, 370) provides higher pressure to the third pump port (78, 378) relative to the fourth pump port (79, 379), and wherein rotation of the drive shaft (18, 318) when the second displacement drive (65, 365) is in the second negative displacement range (74, 374) provides higher pressure to the fourth pump port (79, 379) relative to the third pump port (78, 378); a first hydraulic actuator (90, 390) having a first working port (93, 393) hydraulically connected (52, 352) to the first pump port (48, 348) of the first piston pump (30, 330); the first hydraulic actuator (90, 390) having a second working port (94, 394) hydraulically connected (53, 353) to the second pump port (49, 349) of the first piston pump (30, 330); a second hydraulic actuator (100, 400) having a third working port (103, 403) hydraulically connected (82, 382) to the third pump port (78, 378) of the second piston pump (60, 360); the second hydraulic actuator (100, 400) having a fourth working port (104, 404) hydraulically connected (83, 383) to the fourth pump port (79, 379) of the second piston pump (60, 360); wherein an external force (FI) applied to the first hydraulic actuator (90, 390) that provides higher pressure (51) to the second pump port (49, 349) relative to the first pump port (48, 348) when the first displacement drive (35, 335) is in the first positive displacement range (40, 340) applies an assistive torque to the drive shaft (18, 318); and wherein an external force (F2) applied to the first hydraulic actuator (90, 390) that provides higher pressure (51) to the first pump port (48, 348) relative to the second pump port (49, 349) when the first displacement drive (35, 335) is in the first negative displacement range (44, 344) applies an assistive torque to the drive shaft (18, 318).

[0004] An external force (F3) applied to the second hydraulic actuator (100, 400) that provides higher pressure (81) to the fourth pump port (79, 379) relative to the third pump port (78, 378) when the second displacement drive (65, 365) is in the second positive displacement range (70, 370) may apply an assistive torque to the drive shaft (18, 318); and an external force (F4) applied to the second hydraulic actuator (100, 400) that provides higher pressure (81) to the third pump port (78, 378) relative to the fourth pump port (79, 379) when the second displacement drive (65, 365) is in the second negative displacement range (74, 374) may apply an assistive torque to the drive shaft (18, 318).

[0005] The electro-hydraulic pump system may comprise a battery (21) supplying the current to the electric motor (16). The motor (16) may be configured to selectively supply a current to the battery (21) in a regeneration mode when: an external force (FI) applied to the first hydraulic actuator (90, 390) provides higher pressure to the second pump port (49, 349) relative to the first pump port (48, 348) when the first displacement drive (35, 335) is in the first positive displacement range (40, 340) or an external force (F2) applied to the first hydraulic actuator (90, 390) provides higher pressure (51) to the first pump port (48, 348) relative to the second pump port (49, 349) when the first displacement drive (35, 335) is in the first negative displacement range (44, 344); and an external force (F3) applied to the second hydraulic actuator (100, 400) provides higher pressure (81) to the fourth pump port (79, 379) relative to the third pump port (78, 378) when the second displacement drive (65, 365) is in the second positive displacement range (70, 370) or an external force (F4) applied to the second hydraulic actuator (100, 400) provides higher pressure (81) to the third pump port (78, 378) relative to the fourth pump port (79, 379) when the second displacement drive (65, 365) is in the second negative displacement range (74, 374).

[0006] The first hydraulic actuator (90, 390) may be configured to actuate a first object (118) of an electrically powered vehicle (116) and the second hydraulic actuator (100, 400) may be configured to actuate a second object of the electrically powered vehicle (116). The electric motor may be selected from a group consisting of a brushless DC servo-motor, a stepper motor, a brush motor and an induction motor. The first hydraulic actuator may comprise a linear hydraulic actuator or a rotary hydraulic actuator. The first hydraulic actuator may comprise a linear hydraulic actuator having a first chamber (91, 241, 391), a second chamber (92, 242, 392) and a piston (95, 245, 395) separating the first and second chambers. The first hydraulic actuator may comprise a cylinder (98, 248, 398) having a first end wall (98A, 248A), the piston (95, 245, 395) disposed in the cylinder (98, 248, 348) for sealed sliding movement therein, and the piston (95, 245, 395) may comprise a first actuator rod (96, 246, 396) having a portion sealingly penetrating the first end wall (98 A, 248 A). The cylinder (98) may have a second end wall (98B) and the piston (95) may comprise a second actuator rod (97) having a portion sealingly penetrating the second end wall (98B). The electro-hydraulic pump system may comprise a position sensor configured to sense the position of the piston (95, 245, 395). The electro-hydraulic pump system may comprise a pressure sensor configured to sense pressure in the first and second chambers (91, 92, 141, 142, 391, 392).

[0007] The electro-hydraulic pump system may comprise a third hydraulic piston pump

(130) comprising a third fluid control journal (131), a plurality of pistons (132) in a third cylinder block (133) adapted to rotate relative to the third fluid control journal (131) about a third block axis (134) with rotation of the drive shaft (18), and a third displacement drive (135) having a third displacement axis (138); the third displacement drive (135) adapted to move in a third positive displacement range (140) between a third neutral position between the third displacement axis (138) and the third block axis (134) and a third maximum positive displacement position between the third displacement axis (138) and the third block axis (134); the third displacement drive (135) adapted to move in a third negative displacement range (144) between the third neutral position between the third displacement axis (138) and the third block axis (134) and a third maximum negative displacement position between the third displacement axis (138) and the third block axis (134); the third fluid control journal

(131) comprising a fifth pump port (148) and a sixth pump port (149), wherein rotation of the drive shaft (18) when the third displacement drive (135) is in the third positive displacement range (140) provides higher pressure to the fifth pump port (148) relative to the sixth pump port (149), and wherein rotation of the drive shaft (18) when the third displacement drive (135) is in the third negative displacement range (144) provides higher pressure to the sixth pump port (149) relative to the fifth pump port (148); a third hydraulic actuator (190) having a fifth working port (193) hydraulically connected (152) to the fifth pump port (148) of the third piston pump (130); the third hydraulic actuator (190) having a sixth working port (194) hydraulically connected (153) to the sixth pump port (149) of the third piston pump (130); wherein an external force applied to the third hydraulic actuator (190) that provides higher pressure to the sixth pump port (149) relative to the fifth pump port (148) when the third displacement drive (135) is in the third positive displacement range (140) applies an assistive torque to the drive shaft (18); and an external force applied to the third hydraulic actuator (190) that provides higher pressure to the fifth pump port (148) relative to the sixth pump port (149) when the third displacement drive (135) is in the third negative displacement range (144) applies an assistive torque to the drive shaft (18). The shaft may comprise a first portion (18A) mechanically connected to the first cylinder block (33), a second portion (23, 18B) mechanically connected to the second cylinder block (63), and a third portion (123) mechanically connected to the third cylinder block (133).

[0008] The electro-hydraulic pump system may comprise a first displacement drive actuator (54, 354) mechanically connected to the first displacement drive (35, 335) and configured to selectively move the first displacement drive (35, 335) in the first positive displacement range (40, 340) and to selectively move the first displacement drive (35, 335) in the first negative displacement range (44, 344). The electro-hydraulic pump system may comprise a second displacement drive actuator (84, 384) mechanically connected to the second displacement drive (65, 365) and configured to selectively move the second displacement drive (65, 365) in the second positive displacement range (70, 370) and to selectively move the second displacement drive (65, 365) in the second negative displacement range (74, 374).

[0009] The first fluid control j oumal may comprise a first central control journal (31); the first displacement drive may comprise a first stroke ring (35) orientated about the first displacement axis (38); the first neutral position between the first displacement axis (38) and the first block axis (34) may comprise a position in which the first displacement axis (38) and the first block axis (34) are coaxial; the first stroke ring (35) may be adapted to move radially relative to the first neutral position; the first maximum positive displacement position between the first displacement axis (38) and the first block axis (34) may comprise a first positive eccentric position wherein the first displacement axis (38) is radially offset from the first block axis (34) in a first positive direction (41) relative the first neutral position a first positive maximum eccentric distance (42); the first positive displacement range may comprise a first positive eccentric range (40) between the first neutral position and a first positive eccentric position; the first maximum negative displacement position between the first displacement axis (38) and the first block axis (34) may comprise a first negative eccentric position wherein the first displacement axis (38) is radially offset from the first block axis (34) in a first negative direction (45) relative the first neutral position a first negative maximum eccentric distance (46); the first negative displacement range may comprise a first negative eccentric range (44) between the first neutral position and a first negative eccentric position; rotation of the drive shaft (18) when the first stroke ring (35) is in the first positive eccentric range (40) may provide higher pressure (51) to the first pump port (48) relative to the second pump port (49), and rotation of the drive shaft (18) when the first stroke ring (35) is in the first negative eccentric range (44) may provide higher pressure (51) to the second pump port (49) relative to the first pump port (48); the second fluid control journal may comprise a second central control journal (61); the second displacement drive may comprise a second stroke ring (65) orientated about the second displacement axis (68); the second neutral position between the second displacement axis (68) and the second block axis (64) may comprise a position in which the second displacement axis (68) and the second block axis (64) are coaxial; the second stroke ring (65) may be adapted to move radially relative to the second neutral position; the second maximum positive displacement position between the second displacement axis (68) and the second block axis (64) may comprise a second positive eccentric position wherein the second displacement axis (68) is offset from the second block axis (64) in a second positive direction (71) relative the second neutral position a second positive maximum eccentric distance (72); the second positive displacement range may comprise a second positive eccentric range (70) between the second neutral position and a second positive eccentric position; the second maximum negative displacement position between the second displacement axis (68) and the second block axis (64) may comprise a second negative eccentric position wherein the second displacement axis (68) is radially offset from the second block axis (64) in a second negative direction (75) relative the second neutral position a second negative maximum eccentric distance (76); the second negative displacement range may comprise a second negative eccentric range (74) between the second neutral position and a second negative eccentric position; rotation of the drive shaft (18) when the second stroke ring (65) is in the second positive eccentric range (70) may provide higher pressure to the third pump port (78) relative to the fourth pump port (79), and rotation of the drive shaft (18) when the second stroke ring (65) is in the second negative eccentric range (74) may provide higher pressure to the fourth pump port (79) relative to the third pump port (78); an external force (FI) applied to the first hydraulic actuator (90) that provides higher pressure (51) to the second pump port (49) relative to the first pump port (48) when the first stroke ring (35) is in the first positive eccentric range (40) may apply an assistive torque to the drive shaft (18); and an external force (F2) applied to the first hydraulic actuator (90) that provides higher pressure (51) to the first pump port (48) relative to the second pump port (49) when the first stroke ring (35) is in the first negative eccentric range (44) may apply an assistive torque to the drive shaft (18).

[0010] The electro-hydraulic pump system may comprise a third hydraulic piston pump (130) comprising a third central control j oumal (131), a plurality of pistons (132) in a third cylinder block (133) adapted to rotate relative to the third central control journal (131) about a third block axis (134) with rotation of the drive shaft (18), and a third stroke ring (135) orientated about a third stroke axis (138) and adapted to move radially relative to a third center position in which the third stroke axis (138) and the third block axis (134) are coaxial; the third stroke ring (135) adapted to move linearly in a third positive eccentric range (140) between the third center position and a third positive eccentric position, wherein the third stroke axis (138) is offset from the third block axis (134) in a third positive direction relative the third center position a third positive maximum eccentric distance; the third stroke ring (135) adapted to move linearly in a third negative eccentric range (144) between the third center position and a third negative eccentric position, wherein the third stroke axis (138) is offset from the third block axis (134) in a third negative direction opposite to the third positive direction relative to the third center position a third negative maximum eccentric distance; the third control journal (131) comprising a fifth pump port (148) and a sixth pump port (149), wherein rotation of the drive shaft (18) when the third stroke ring (135) is in the third positive eccentric range (140) provides higher pressure to the fifth pump port (148) relative to the sixth pump port (149), and wherein rotation of the drive shaft (18) when the third stroke ring (135) is in the third negative eccentric range (144) provides higher pressure to the sixth pump port (149) relative to the fifth pump port (148); a third hydraulic actuator (190) having a fifth working port (193) hydraulically connected (152) directly to the fifth pump port (148) of the third piston pump (130); the third hydraulic actuator (190) having a sixth working port (194) hydraulically connected (153) directly to the sixth pump port (149) of the third piston pump (130); wherein an external force applied to the third hydraulic actuator (190) that provides higher pressure to the sixth pump port (149) relative to the fifth pump port (148) when the third stroke ring (135) is in the third positive eccentric range (140) applies an assistive torque to the drive shaft (18); and an external force applied to the third hydraulic actuator (190) that provides higher pressure to the fifth pump port (148) relative to the sixth pump port (149) when the third stroke ring (135) is in the third negative eccentric range (144) applies an assistive torque to the drive shaft (18B). The shaft may comprise a first portion (18A) mechanically connected to the first cylinder block (33), a second portion (23, 18B) mechanically connected to the second cylinder block (63), and a third portion (123) mechanically connected to the third cylinder block (133).

[0011] The electro-hydraulic pump system may comprise a first hydraulic ring actuator (54) mechanically connected to the first stroke ring (35) and configured to selectively move the first stroke ring (35) linearly in the first positive eccentric range (40) between the first center position and the first positive eccentric position and to selectively move the first stroke ring (35) linearly in the first negative eccentric range (44) between the first center position and the first negative eccentric position. The electro-hydraulic pump system may comprise a second hydraulic ring actuator (84) mechanically connected to the second stroke ring (65) and configured to selectively move the second stroke ring (65) linearly in the second positive eccentric range (70) between the second center position and the second positive eccentric position and to selectively move the second stroke ring (65) linearly in the second negative eccentric range (74) between the second center position and the second negative eccentric position.

[0012] The first fluid control journal may comprise a first port plate (331); the first displacement drive may comprise a first swash plate (335) orientated about the first displacement axis (338); the first neutral position between the first displacement axis (338) and the first block axis (334) may comprise a position in which the first displacement axis (338) and the first block axis (334) are coaxial; the first swash plate (335) may be adapted to move angularly relative to the first neutral position; the first maximum positive displacement position between the first displacement axis (338) and the first block axis (334) may comprise a first positive angular position wherein the first displacement axis (338) is offset from the first block axis (334) in a first positive angular direction relative the first neutral position a first positive maximum cam angle (340); the first positive displacement range may comprise a first positive angular range (340) between the first neutral position and a first positive angular position; the first maximum negative displacement position between the first displacement axis (338) and the first block axis (334) may comprise a first negative angular position wherein the first displacement axis (338) is offset from the first block axis (334) in a first negative angular direction relative the first neutral position a first negative maximum cam angle (346); the first negative displacement range may comprise a first negative angular range (344) between the first neutral position and a first negative angular position; rotation of the drive shaft (318) when the first swash plate (335) is in the first positive angular range (340) may provide higher pressure to the first pump port (348) relative to the second pump port (349), and rotation of the drive shaft (318) when the first swash plate (335) is in the first negative angular range (344) may provide higher pressure to the second pump port (349) relative to the first pump port (348); the second fluid control j oumal may comprise a second port plate (361); the second displacement drive may comprise a second swash plate orientated about the second displacement axis (368); the second neutral position between the second displacement axis (368) and the second block axis (364) may comprise a position in which the second displacement axis (368) and the second block axis (364) are coaxial; the second swash plate (365) may be adapted to move angularly relative to the second neutral position; the second maximum positive displacement position between the second displacement axis (368) and the second block axis (364) may comprise a second positive angular position wherein the second displacement axis (368) is offset from the second block axis (364) in a second positive angular direction relative the second neutral position a second positive maximum cam angle (372); the second positive displacement range may comprise a second positive angular range (370) between the second neutral position and a second positive angular position; the second maximum negative displacement position between the second displacement axis (368) and the second block axis (364) comprises a second negative angular position wherein the second displacement axis (368) is offset from the second block axis (364) in a second negative angular direction relative the second neutral position a second negative maximum cam angle (376); the second negative displacement range may comprise a second negative angular range (374) between the second neutral position and a second negative angular position; rotation of the drive shaft (318) when the second swash plate (365) is in the second positive angular range (370) may provide higher pressure to the third pump port (378) relative to the fourth pump port (379), and rotation of the drive shaft (318) when the second swash plate (365) is in the second negative angular range (374) may provide higher pressure to the fourth pump port (379) relative to the third pump port (378); an external force applied to the first hydraulic actuator (390) that provides higher pressure to the second pump port (349) relative to the first pump port (348) when the first swash plate (335) is in the first positive angular range (340) may apply an assistive torque to the drive shaft (318); and an external force applied to the first hydraulic actuator (390) that provides higher pressure to the first pump port (348) relative to the second pump port (349) when the first swash plate (335) is in the first negative angular range (344) may apply an assistive torque to the drive shaft (318).

[0013] An external force (F3) applied to the second hydraulic actuator (400) that provides higher pressure to the fourth pump port (379) relative to the third pump port (378) when the second swash plate (365) is in the second positive angular range (374) may apply an assistive torque to the drive shaft (318); and an external force (F4) applied to the second hydraulic actuator (400) that provides higher pressure to the third pump port (378) relative to the fourth pump port (379) when the second swash plate (365) is in the second negative angular range (374) may apply an assistive torque to the drive shaft (318).

[0014] The electro-hydraulic pump system may comprise a battery (21) supplying the current to the electric motor (16) and the motor (16) may be configured to selectively supply a current to the battery (21) in a regeneration mode when: an external force (FI) applied to the first hydraulic actuator (390) provides higher pressure to the second pump port (349) relative to the first pump port (348) when the first swash plate (335) is in the first positive angular range (340) or an external force (F2) applied to the first hydraulic actuator (390) provides higher pressure to the first pump port (348) relative to the second pump port (349) when the first swash plate (335) is in the first negative angular range (344); and an external force (F3) applied to the second hydraulic actuator (400) provides higher pressure to the fourth pump port (379) relative to the third pump port (378) when the second swash plate (365) is in the second positive angular range (370) or an external force (F4) applied to the second hydraulic actuator (400) provides higher pressure to the third pump port (378) relative to the fourth pump port (379) when the second swash plate (365) is in the second negative angular range (374).

[0015] The electro-hydraulic pump system may comprise a third hydraulic piston pump comprising a third port plate, a plurality of pistons in a third cylinder block adapted to rotate relative to the third port plate about a third block axis with rotation of the drive shaft, and a third swash plate orientated about a third swash plate axis and adapted to move angularly relative to a third neutral position in which the third swash plate axis and the third block axis are coaxial; the third swash plate adapted to move angularly in a third positive angular range between the third neutral position and a third positive angular position, wherein the third swash plate axis is offset from the third block axis in a third positive angular direction relative the third neutral position a third positive maximum cam angle; the third swash plate adapted to move angularly in a third negative angular range between the third neutral position and a third negative angular position, wherein the third swash plate axis is offset from the third block axis in a third negative angular direction opposite to the third positive angular direction relative to the third neutral position a third negative maximum cam angle; the third port plate comprising a fifth pump port and a sixth pump port, wherein rotation of the drive shaft when the third swash plate is in the third positive angular range provides higher pressure to the fifth pump port relative to the sixth pump port, and wherein rotation of the drive shaft when the third swash plate is in the third negative angular range provides higher pressure to the sixth pump port relative to the fifth pump port; a third hydraulic actuator having a fifth working port hydraulically connected to the fifth pump port of the third piston pump; the third hydraulic actuator having a sixth working port hydraulically connected to the sixth pump port of the third piston pump; wherein an external force applied to the third hydraulic actuator that provides higher pressure to the sixth pump port relative to the fifth pump port when the third swash plate is in the third positive angular range applies an assistive torque to the drive shaft; and wherein an external force applied to the third hydraulic actuator that provides higher pressure to the fifth pump port relative to the sixth pump port when the third swash plate is in the third negative angular range applies an assistive torque to the drive shaft. The shaft may comprise a first portion connected to the first cylinder block, a second portion connected to the second cylinder block, and a third portion connected to the third cylinder block.

[0016] The electro-hydraulic pump system may comprise a first hydraulic swash plate actuator (354) connected to the first swash plate (335) and configured to selectively move the first swash plate (335) in the first positive angular range (340) between the first neutral position and the first positive angular position and to selectively move the first swash plate (335) in the first negative angular range (344) between the first neutral position and the first negative angular position. The electro-hydraulic pump system may comprise a second hydraulic swash plate actuator (384) connected to the second swash plate (365) and configured to selectively move the second swash plate (365) in the second positive angular range (370) between the second neutral position and the second positive angular position and to selectively move the second swash plate (365) in the second negative angular range (374) between the second neutral position and the second negative angular position.

[0017] The first fluid control j oumal may comprise a first central control journal (31); the first displacement drive may comprise a first stroke ring (35) orientated about the first displacement axis (38); the first neutral position between the first displacement axis (38) and the first block axis (34) may comprise a position in which the first displacement axis and the first block axis are coaxial; the first stroke ring (35) may be adapted to move radially relative to the first neutral position; the first maximum positive displacement position between the first displacement axis (38) and the first block axis (34) may comprise a first positive eccentric position wherein the first displacement axis (38) is offset from the first block axis (34) in a first positive direction (41) relative the first neutral position a first positive maximum eccentric distance (42); the first positive displacement range may comprise a first positive eccentric range (40) between the first neutral position and a first positive eccentric position; the first maximum negative displacement position between the first displacement axis (38) and the first block axis (34) may comprise a first negative eccentric position wherein the first displacement axis (38) is offset from the first block axis (34) in a first negative direction (45) relative the first neutral position a first negative maximum eccentric distance (46); the first negative displacement range may comprise a first negative eccentric range (44) between the first neutral position and a first negative eccentric position; rotation of the drive shaft when the first stroke ring (35) is in the first positive eccentric range (40) may provide higher pressure to the first pump port (48) relative to the second pump port (49), and rotation of the drive shaft when the first stroke ring is in the first negative eccentric range (44) may provide higher pressure to the second pump port (49) relative to the first pump port (48); the second fluid control journal may comprise a first port plate (361); the second displacement drive may comprise a first swash plate (365) orientated about the second displacement axis (368); the second neutral position between the second displacement axis (368) and the second block axis (364) may comprise a position in which the second displacement axis (368) and the second block axis (364) are coaxial; the first swash plate (365) may be adapted to move angularly relative to the second neutral position; the second maximum positive displacement position between the second displacement axis (368) and the second block axis (364) may comprise a first positive angular position wherein the second displacement axis (368) is offset from the second block axis (364) in a first positive angular direction relative the second neutral position a first positive maximum cam angle (372); the second positive displacement range may comprise a first positive angular range (370) between the second neutral position and a first positive angular position; the second maximum negative displacement position between the second displacement axis (368) and the second block axis (364) may comprise a first negative angular position wherein the second displacement axis (368) is offset from the second block axis (364) in a first negative angular direction relative the second neutral position a first negative maximum cam angle (376); the second negative displacement range may comprise a first negative angular range (374) between the second neutral position and a first negative angular position; rotation of the drive shaft when the first swash plate (365) is in the first positive angular range (370) may provide higher pressure to the third pump port (378) relative to the fourth pump port (379), and rotation of the drive shaft when the second swash plate (365) is in the first negative angular range (374) may provide higher pressure to the fourth pump port (379) relative to the third pump port (378); an external force applied to the first hydraulic actuator (90) that provides higher pressure to the second pump port (49) relative to the first pump port (48) when the first stroke ring (35) is in the first positive eccentric range (40) may apply an assistive torque to the drive shaft; and an external force applied to the first hydraulic actuator (90) that provides higher pressure to the first pump port (48) relative to the second pump port (49) when the first stroke ring is in the first negative eccentric range (44) may apply an assistive torque to the drive shaft.

[0018] An external force applied to the second hydraulic actuator (400) that provides higher pressure to the fourth pump port (379) relative to the third pump port (378) when the first swash plate (365) is in the first positive angular range (370) may apply an assistive torque to the drive shaft; and an external force applied to the second hydraulic actuator (400) that provides higher pressure to the third pump port (378) relative to the fourth pump port (379) when the first swash plate (365) is in the first negative angular range (374) may apply an assistive torque to the drive shaft.

BRIEF DESCRIPTION OF THE DRAWINGS [0019] FIG. 1 is a schematic view of a first radial embodiment of an assistive torque electro-hydraulic piston pump system.

[0020] FIG. 2 is a transverse cross-sectional view of the radial piston pumps shown in FIG. 1 and FIG. 27.

[0021] FIG. 3 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a first drive-drive configuration.

[0022] FIG. 4A is a transverse cross-section view of the first radial piston pump shown in FIG. 3.

[0023] FIG. 4B is a transverse cross-section view of the second radial piston pump shown in FIG. 3. [0024] FIG. 5A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 4A.

[0025] FIG. 5B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 4B.

[0026] FIG. 6 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a second drive-drive configuration.

[0027] FIG. 7A is a transverse cross-section view of the first radial piston pump shown in FIG. 6.

[0028] FIG. 7B is a transverse cross-section view of the second radial piston pump shown in FIG. 6.

[0029] FIG. 8A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 7A.

[0030] FIG. 8B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 7B.

[0031] FIG. 9 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a first regen-drive configuration.

[0032] FIG. 10A is a transverse cross-section view of the first radial piston pump shown in FIG. 9.

[0033] FIG. 10B is a transverse cross-section view of the second radial piston pump shown in FIG. 9.

[0034] FIG. 11A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 10 A.

[0035] FIG. 1 IB is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 10B.

[0036] FIG. 12 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a second regen-drive configuration.

[0037] FIG. 13 A is a transverse cross-section view of the first radial piston pump shown in FIG. 12.

[0038] FIG. 13B is a transverse cross-section view of the second radial piston pump shown in FIG. 12. [0039] FIG. 14A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 13 A.

[0040] FIG. 14B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 13B.

[0041] FIG. 15 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a first drive-regen configuration.

[0042] FIG. 16A is a transverse cross-section view of the first radial piston pump shown in FIG. 15.

[0043] FIG. 16B is a transverse cross-section view of the second radial piston pump shown in FIG. 15.

[0044] FIG. 17A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 16 A.

[0045] FIG. 17B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 16B.

[0046] FIG. 18 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a second drive-regen configuration.

[0047] FIG. 19A is a transverse cross-section view of the first radial piston pump shown in FIG. 18.

[0048] FIG. 19B is a transverse cross-section view of the second radial piston pump shown in FIG. 18.

[0049] FIG. 20A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 19 A.

[0050] FIG. 20B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 19B.

[0051] FIG. 21 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a first regen-regen configuration.

[0052] FIG. 22A is a transverse cross-section view of the first radial piston pump shown in FIG. 21.

[0053] FIG. 22B is a transverse cross-section view of the second radial piston pump shown in FIG. 21. [0054] FIG. 23A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 22A.

[0055] FIG. 23B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 22B.

[0056] FIG. 24 is a partial longitudinal cross-sectional view and partial schematic view of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1 in a second regen-regen configuration.

[0057] FIG. 25A is a transverse cross-section view of the first radial piston pump shown in FIG. 24.

[0058] FIG. 25B is a transverse cross-section view of the second radial piston pump shown in FIG. 24.

[0059] FIG. 26A is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 25 A.

[0060] FIG. 26B is a schematic view of the eccentric and resulting port pressure profile of the radial piston pump shown in FIG. 25B.

[0061] FIG. 27 is a schematic view of a second embodiment of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 1, this view showing three radial piston pumps and hydraulic actuators in the system.

[0062] FIGS. 28 and 29 are schematic views of the assistive torque electro-hydraulic radial piston pump system shown in FIG. 27 employed on an electric vehicle.

[0063] FIG. 30 is a schematic view of a third embodiment of an assistive torque electro- hydraulic radial piston pump system shown in FIG. 1, this view showing an unequal piston area and single actuating rod form.

[0064] FIG. 31 is a schematic view of a fourth axial embodiment of an assistive torque electro-hydraulic piston pump system.

[0065] FIG. 32 is a cross-section view of the first axial piston pump shown in FIG. 31.

[0066] FIG. 33 is a cross-section view of the second axial piston pump shown in FIG. 31.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0067] At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross- hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms "horizontal", "vertical", "left", "right", "up" and "down", as well as adjectival and adverbial derivatives thereof (e.g., "horizontally", "rightwardly", "upwardly", etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms "inwardly" and "outwardly" generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.

[0068] Referring now to the drawings, and more particularly to FIG. 1 thereof, the present invention broadly provides an assistive torque electro-hydraulic piston pump system, of which a first embodiment is indicated at 15. As shown in FIG. 1, system 15 is adapted to actuate at least two objects and generally includes electrical power source 21, motor controller 22, variable speed electric motor 16, shaft 18 driven to rotate about axis 20 by motor 16, first radial piston pump 30 mechanically connected to shaft 18, first hydraulic actuator 90 hydraulically connected to first radial piston pump 30, second radial piston pump 60 mechanically connected to shaft 18, and second hydraulic actuator 100 hydraulically connected to second radial piston pump 60.

[0069] In this embodiment, motor 16 is a brushless DC variable-speed servo-motor that is supplied with a current. Motor 16 has an inner rotor with permanent magnets and a fixed non-rotating stator with coil windings. When current is appropriately applied through the coils of the stator, a magnetic field is induced. The magnetic field interaction between the stator and the rotor generates torque which may rotate output shaft 18. There are no mechanical brushes that commutate the stator fields in this embodiment of the motor. In this embodiment, motor 16 rotates shaft 18 in only one direction about axis 20. Accordingly, motor 16 will selectively apply a torque on shaft 18 in one direction about axis 20 at varying speeds. Other motors may be used as alternatives. For example, a variable speed stepper motor, brush motor or induction motor may be used.

[0070] Motor controller 22 includes drive electronics that, based on a resolver angular position feedback, generate and commutate the stator fields to vary the speed of motor 16. Controller 22 receives drive commands and feedback from sensors in system 15 and controls motor 16 accordingly. For example, pressure transducers and position transducers in system 15 may be fed back to motor controller 22.

[0071] In this embodiment, power source 21 comprises a battery and includes a regenerative power circuit to take advantage of the regenerative mode described below in which motor 16 is controlled to operate as a generator in a power generation mode when external regenerative forces FI, F2, F3 and/or F4, such as gravity loads, on hydraulic actuators 90 and 100 exceed a threshold drive pressure differential of pumps 30 and 60 and drive torque of motor 16.

[0072] As shown in FIGS. 1-8B, radial piston pump 30 generally comprises central control journal 31, a plurality of pistons 32 in cylinder block 33 adapted to rotate relative to control journal 31 about block axis 34 with rotation of drive shaft 18, stroke ring 35 orientated about stroke axis 38 and adapted to move radially relative to the neutral or center position N1 in which stroke axis 38 and block axis 34 are coaxial and stroke ring 35 and cylinder block 33 are concentric. Stroke ring 35 does not rotate with rotation of cylinder block 33. As shown, hydraulic ring actuator 54 is controlled to move stroke ring 35 linearly, or radially from the center position Nl, to positions in positive eccentric range 40 between the center position Nl and the positive eccentric position shown in FIG. 5 A in which stroke axis 38 is offset from block axis 34 in positive direction 41 relative the center position Nl a maximum positive eccentric distance 42. Hydraulic ring actuator 54 is also controlled to move stroke ring 35 linearly, or radially from the center position Nl, to positions in negative eccentric range 44 between the center position Nl and the negative eccentric position shown in FIG. 8A in which stroke axis 38 is offset from block axis 34 in negative direction 45 opposite to positive direction 41 relative to the center position Nl a maximum negative eccentric distance 46.

[0073] As shown, drive torque from motor 16 is transferred from shaft 18 to cylinder block 33 by cross-key coupling 18A. Cylinder block 33 rotates on central j oumal 31 and central journal 31 is shrunk fit into housing 17. Pistons 32 are arranged radially in cylinder block 33 and are held in contact with stroke ring 35 by slipper pads 36, with each piston 32 and slipper pad 36 connected to each other by a ball-and-socket joint. Slipper pads 36 are held in stroke ring 35 by overlapping retainer rings and pressed against stroke ring 35 during operation by centrifugal force and oil pressure. With rotation of cylinder block 33 by shaft 18, pistons 32 execute a radial stroking motion due to the eccentricity of stroke ring 35.

[0074] The pressure flow from and suction flow into the cylinder chamber is controlled by control journal 31. Control journal 31 includes pump port 48 and pump port 49. Rotation 19 of drive shaft 18 when stroke ring 35 is in positive eccentric range 40 provides higher pressure 51 to pump port 48 relative to pump port 49. Alternatively, rotation of drive shaft 18 when stroke ring 35 is in negative eccentric range 44 provides higher pressure 51 to pump port 49 relative to pump port 48. Thus, for positive eccentric range 40, the normal drive pressure differential is P48/P49 and it is positive (P48/P49 > 0) in normal drive, and for negative eccentric range 44, the normal drive pressure differential is P49/P48 and it is positive (P49/P48 > 0) in normal drive. In this embodiment, piston stroke “h” equals double the eccentricity “e” of stroke ring 35.

[0075] Hydraulic ring actuator 54 is connected to stroke ring 35 and selectively moves stroke ring 35 in both positive eccentric range 40, between the center position N1 and the positive eccentric position, shown in FIG. 5A, and negative eccentric range 44, between the center position N1 and the negative eccentric position, shown in FIG. 8 A. Thus, hydraulic servo-valve 54 varies the radial eccentricity of stroke ring 35. In this embodiment, the normal flow direction, whether from port 48 or from port 49, is determined by the direction of the eccentricity from the neutral center position, with positive eccentricity 40 providing flow out of port 48 and negative eccentricity 44 providing flow out of port 49. So in this embodiment, motor 16 rotates shaft 18 in only one direction about axis 20 and the direction of flow is not determined by the direction of rotation of shaft 18.

[0076] As shown in FIG. 2, hydraulic ring control actuator 54 includes hydraulic control pistons 55 and 56 in opposed alignment on axis 54A that vary the eccentricity of stroke ring 35. The effective areas of pistons 55 and 56 differ, with the effective area of piston 56 being greater than the effective area of piston 55. Hydraulic pressure is constantly applied to small area control piston 55 to press stroke ring 35 against large area control piston 56. Large area control piston 56 is selectively pressurized to maintain stroke ring 35 in a neutral center position with equal pressure, to move stroke ring 35 into positive eccentric range 40 towards maximum positive eccentric distance 42 with greater pressure, or to move stroke ring 35 into negative eccentric range 44 towards maximum negative eccentric distance 46 with less pressure. Thus, hydraulic ring actuator 54 controls the position of stroke ring 35 and thereby the flow rate, flow direction and system pressure.

[0077] As shown in FIGS. 1, 3 and 6, hydraulic actuator assembly 90 includes piston 95 slidably disposed within cylindrical housing 98 orientated about axis 99. In this embodiment, rod 96 is mounted to one side of piston 95 for movement with piston 95 and extends to the right and sealably penetrates right end wall 98A of housing 98. Rod 97 is mounted to the other side of piston 95 for movement with piston 95 and extends to the left and sealably penetrates left end wall 98B of housing 98. Piston 95 is slidably disposed within cylinder 98, and sealingly separates left chamber 91 from right chamber 92. In this embodiment, the leftwardly-facing annular vertical end surface of piston 95 faces into left chamber 91 and the rightwardly-facing annular vertical end surface of piston 95 faces into right chamber 92, creating an equal piston area configuration. Left chamber 91 has fluid port 93 and right chamber 92 has fluid port 94. Thus, hydraulic actuator 90 comprises chamber 91, chamber 92 and piston 95 separating the first and second chambers 91, 92. The hydraulic actuator may include a position sensor configured to sense the position of piston 95. While in this embodiment actuator 90 is shown as a linear hydraulic actuator, a rotary hydraulic actuator that imparts a rotary output may be used as an alternative.

[0078] As shown in FIG. 1, port 48 of pump 30 is hydraulically connected directly with left chamber 93 via fluid line 52, and the opposite side or port 49 of pump 30 is hydraulically connected directly with right chamber 93 via fluid line 53. With such direct hydraulic connection 52, no one way check valves or proportional valves are provided in line 52 between pump port 48 and actuator chamber port 93. With such direct hydraulic connection 53, no one way check valves or proportional valves are provided in line 53 between pump port 49 and actuator chamber port 94.

[0079] Piston 95 will move to the right when motor 16 is rotated and pump 30 is in positive eccentric range 40, thereby pressurizing port 48 relative to port 49 and driving fluid out port 48 through conduit 52 and into chamber 91 and drawing fluid from chamber 92 in through port 94, conduit 53 and port 49, and thereby creating a differential pressure on piston 55 and causing it to extend rod 96 to the right. Piston 95 will move to the left when motor 16 is rotated and pump 30 is in negative eccentric range 44, thereby pressurizing port 49 relative to port 48 and driving fluid out port 49 through conduit 53 and into chamber 92 and drawing fluid from chamber 91 in through port 93, conduit 52 and port 48, and thereby creating a differential pressure on piston 55 and causing it to extend rod 97 to the left. Thus, in a normal drive mode rotation of drive shaft 18 when stroke ring 35 is in positive eccentric range 40 provides higher pressure 51 to pump port 48 relative to pump port 49, and rotation of shaft 18 when stroke ring 35 is in negative eccentric range 44 provides higher pressure 51 to pump port 49 relative to pump port 48.

[0080] As shown in FIG. 3, central control j oumal 31 includes a cylindrical center bore orientated on central axis 20 and configured to receive through-shaft 23 of drive shaft 18. Through-shaft 23 of drive shaft 18 extends through and rotates in such center bore in central journal 31. Through-shaft 23 therefore rotates with rotation of shaft 18.

[0081] As shown in FIGS. 1-8B, radial piston pump 60 is configured and functions in substantially the same manner as radial piston pump 30. Radial piston pump 60 generally comprises central control journal 61, a plurality of pistons 62 in cylinder block 63 adapted to rotate relative to control journal 61 about block axis 64 with rotation of drive shaft 18, stroke ring 65 orientated about stroke axis 68 and adapted to move radially relative to the neutral or center position N2 in which stroke axis 68 and block axis 64 are coaxial and stroke ring 65 and cylinder block 63 are concentric. Stroke ring 65 does not rotate with rotation of cylinder block 63. As shown, hydraulic ring actuator 84 is controlled to move stroke ring 65 linearly, or radially from the center position N2, to positions in positive eccentric range 70 between the center position N2 and the positive eccentric position shown in FIG. 5B in which stroke axis 68 is offset from block axis 64 in positive direction 71 relative the center position N2 a maximum positive eccentric distance 72. Hydraulic ring actuator 84 is also controlled to move stroke ring 65 linearly, or radially from the center position N2, to positions in negative eccentric range 74 between the center position N2 and the negative eccentric position shown in FIG. 8B in which stroke axis 68 is offset from block axis 64 in negative direction 75 opposite to positive direction 71 relative to the center position N2 a maximum negative eccentric distance 76.

[0082] As shown, drive torque from motor 16 is transferred via through-shaft 23 of drive shaft 18 to cylinder block 63 by cross-key coupling 18B. Cylinder block 63 rotates on central journal 61 and central journal 61 is shrunk fit into housing 17. Pistons 62 are arranged radially in cylinder block 63 and are held in contact with stroke ring 65 by slipper pads 66, with each piston 62 and slipper pad 66 connected to each other by a ball-and-socket joint. Slipper pads 66 are held in stroke ring 65 by overlapping retainer rings and pressed against stroke ring 65 during operation by centrifugal force and oil pressure. With rotation of cylinder block 63 by shaft 23 of drive shaft 18, pistons 62 execute a radial stroking motion due to the eccentricity of stroke ring 65.

[0083] The pressure flow from and suction flow into the cylinder chamber is controlled by control journal 61. Control journal 61 includes pump port 78 and pump port 79. Rotation 19 of drive shaft 18 when stroke ring 75 is in positive eccentric range 70 provides higher pressure 71 to pump port 78 relative to pump port 79. Alternatively, rotation of drive shaft 18 when stroke ring 65 is in negative eccentric range 74 provides higher pressure 71 to pump port 79 relative to pump port 78. Thus, for positive eccentric range 70, the normal drive pressure differential is P78/P79 and it is positive (P78/P79 > 0) in normal drive, and for negative eccentric range 74, the normal drive pressure differential is P79/P78 and it is also positive (P79/P78 > 0) in normal drive. In this embodiment, piston stroke “h” equals double the eccentricity “e” of stroke ring 65.

[0084] Hydraulic ring actuator 84 is connected to stroke ring 65 and selectively moves stroke ring 65 in both positive eccentric range 70, between the center position N2 and the positive eccentric position, shown in FIG. 5B, and negative eccentric range 74, between the first center position N2 and the first negative eccentric position, shown in FIG. 8B. Thus, hydraulic servo-valve 84 varies the radial eccentricity of stroke ring 65. In this embodiment, the normal flow direction, whether from port 78 or from port 79, is determined by the direction of the eccentricity from the neutral center position, with positive eccentricity 70 providing flow out of port 78 and negative eccentricity 74 providing flow out of port 79. [0085] As shown in FIG. 2, hydraulic ring control actuator 84 includes hydraulic control pistons 85 and 86 in opposed alignment on axis 84A that vary the eccentricity of stroke ring 65. The effective areas of pistons 85 and 86 differ, with the effective area of piston 86 being greater than the effective area of piston 85. Hydraulic pressure is constantly applied to small area control piston 85 to press stroke ring 65 against large area control piston 86. Large area control piston 86 is selectively pressurized to maintain stroke ring 65 in a neutral center position with equal pressure, to move stroke ring 65 into positive eccentric range 70 towards maximum positive eccentric distance 72 with greater pressure, or to move stroke ring 65 into negative eccentric range 74 towards maximum negative eccentric distance 76 with less pressure. Thus, hydraulic ring actuator 84 controls the position of stroke ring 75 and thereby the flow rate, flow direction and system pressure.

[0086] As shown in FIGS. 1, 3 and 6, hydraulic actuator assembly 100 includes piston 105 slidably disposed within cylindrical housing 108 orientated about axis 109. In this embodiment, rod 106 is mounted to one side of piston 105 for movement with piston 105 and extends to the right and sealably penetrates right end wall 108 A of housing 108. Rod 107 is mounted to the other side of piston 105 for movement with piston 105 and extends to the left and sealably penetrates left end wall 108B of housing 108. Piston 105 is slidably disposed within cylinder 108, and sealingly separates left chamber 101 from right chamber 102. In this embodiment, the leftwardly-facing annular vertical end surface of piston 105 faces into left chamber 101 and the rightwardly-facing annular vertical end surface of piston 105 faces into right chamber 102, creating an equal piston area configuration. Left chamber 101 has fluid port 103 and right chamber 102 has fluid port 104. Thus, hydraulic actuator 100 comprises chamber 101, chamber 102 and piston 105 separating the first and second chambers 101, 102. The hydraulic actuator may include a position sensor configured to sense the position of piston 105. While in this embodiment actuator 100 is shown as a linear hydraulic actuator, a rotary hydraulic actuator that imparts a rotary output may be used as an alternative. [0087] As shown in FIG. 1, port 78 of pump 60 is hydraulically connected directly with left chamber 101 via fluid line 82, and the opposite side or port 79 of pump 60 is hydraulically connected directly with right chamber 102 via fluid line 83. With such direct hydraulic connection 82, no one way check valves or proportional valves are provided in line 82 between pump port 78 and actuator chamber port 103. With such direct hydraulic connection 83, no one way check valves or proportional valves are provided in line 83 between pump port 79 and actuator chamber port 104.

[0088] Piston 105 will move to the right when motor 16 is rotated and pump 60 is in positive eccentric range 70, thereby pressurizing port 78 relative to port 79 and driving fluid out port 78 through conduit 82 and into chamber 101 and drawing fluid from chamber 102 in through port 104, conduit 83 and port 79, and thereby creating a differential pressure on piston 85 and causing it to extend rod 106 to the right. Piston 105 will move to the left when motor 16 is rotated and pump 60 is in negative eccentric range 74, thereby pressurizing port 79 relative to port 78 and driving fluid out port 79 through conduit 83 and into chamber 102 and drawing fluid from chamber 101 in through port 103, conduit 82 and port 78, and thereby creating a differential pressure on piston 85 and causing it to extend rod 107 to the left. Thus, in a normal drive mode rotation of drive shaft 18 when stroke ring 65 is in positive eccentric range 70 provides higher pressure 81 to pump port 78 relative to pump port 79, and rotation of shaft 18 when stroke ring 65 is in negative eccentric range 74 provides higher pressure 81 to pump port 79 relative to pump port 78.

[0089] FIGS. 3-8B show assistive torque electro-hydraulic rotary pump system 15 in different example normal drive modes. FIGS. 3-5B show a normal drive mode in which the desired drive direction D1 of actuator 90 is down and the desired drive direction D3 of actuator 100 is down. In this configuration, ring actuator 54 is commanded so stroke ring 35 is in positive eccentric range 40. As shown, rotation of shaft 18 provides greater pressure 51 to pump port 48 and therefore chamber 91 of actuator 90 relative to pump port 49 and chamber 92, driving actuator rod 96 in direction Dl. In this configuration, ring actuator 84 is commanded so stroke ring 65 is in positive eccentric range 70. As shown, rotation of shaft 18 provides greater pressure 81 to pump port 78 and therefore chamber 101 of actuator 100 relative to pump port 79 and chamber 102, driving actuator rod 106 in direction D3.

[0090] FIGS. 6-8B show a normal drive mode in which the desired drive direction D2 of actuator 90 is up and the desired drive direction D4 of actuator 100 is up. In this configuration, ring actuator 54 is commanded so stroke ring 35 is in negative eccentric range 44. As shown, rotation of shaft 18 provides greater pressure 51 to pump port 49 and therefore chamber 92 of actuator 90 relative to pump port 49 and chamber 91, driving actuator rod 97 in direction D2. In this configuration, ring actuator 84 is commanded so stroke ring 65 is in negative eccentric range 74. As shown, rotation of shaft 18 provides greater pressure 81 to pump port 79 and therefore chamber 102 of actuator 100 relative to pump port 78 and chamber 101, driving actuator rod 107 in direction D4. Other combinations of actuator directions, such as D1/D4 or D2/D3 with a 40/74 or 44/70 stroke ring eccentric range, respectively, may also be commanded.

[0091] FIGS. 9-26B show assistive torque electro-hydraulic rotary pump system 15 in different example regenerative modes. FIGS. 9-20B showing mechanical torque assist regenerative modes in which one of either pump/actuator combinations 30/90 or 60/100 provides an assistive torque applied through shaft 18 to the other of either pump/actuator combination 30/90 or 60/100. FIGS. 21-26B show electrical generation regenerative modes in which the pump/actuator combinations 30/90 and 60/100 provide a net regenerative torque on shaft 18 that is used by motor 16 and drive electronics 22 to charge battery 21.

[0092] FIGS. 9-1 IB show a first example mechanical regenerative mode. As show, the commanded drive direction of actuator 90 is D1 with resulting commanded stroke ring eccentric range 40, and the commanded drive direction of actuator 100 is D3 with resulting commanded stroke ring eccentric range 70. However, as shown, an external force having a force component FI in direction D1 is applied to actuator 90. This results in higher pressure in chamber 92 relative to chamber 91 and, because of direct hydraulic connection 53, higher pressure at port 49 relative to port 48. Such negative pressure differential P48/P49, given the commanded positive pressure differential, provides added torque on cylinder block 33 that is transferred forward, via shaft connection 18a, through-shaft 23 and shaft connection 18B, to cylinder block 63 of pump 60 to assist in driving actuator 100. Thus, when an external force FI is applied to hydraulic actuator 90 that provides higher pressure 51 to pump port 49 relative to pump port 48 (P48/P49 < 0) when stroke ring 35 is in positive eccentric range 40, then an assistive torque is applied to drive shaft 18. As a result, less power is needed from motor 16.

[0093] FIGS. 12-14B show a second example mechanical regenerative mode. As show, the commanded drive direction of actuator 90 is D2 with resulting commanded stroke ring eccentric range 44, and the commanded drive direction of actuator 100 is D4 with resulting commanded stroke ring eccentric range 74. However, as shown, an external force having a force component F2 in direction D2 is applied to actuator 90. This results in higher pressure in chamber 91 relative to chamber 92 and, because of direct hydraulic connection 52, higher pressure at port 48 relative to port 49. Such negative pressure differential (P49/P48), given the commanded positive pressure differential, again provides added torque on cylinder block 33 that is transferred, via shaft connection 18 A, through-shaft 23 and shaft connection 18B, to cylinder block 63 of pump 60 to assist in driving actuator 100. Thus, when an external force F2 is applied to hydraulic actuator 90 that provides higher pressure 51 to pump port 48 relative to pump port 49 (P49/P48 < 0) when stroke ring 35 is in negative eccentric range 44, then an assistive torque is applied to drive shaft 18. As a result, less power is needed from motor 16.

[0094] FIGS. 15-17B show a third example mechanical regenerative mode. As show, the commanded drive direction of actuator 90 is D1 with resulting commanded stroke ring eccentric range 40, and the commanded drive direction of actuator 100 is D3 with resulting commanded stroke ring eccentric range 70. However, as shown, an external force having a force component F3 in direction D3 is applied to actuator 100. This results in higher pressure in chamber 102 relative to chamber 101 and, because of direct hydraulic connection 83, higher pressure at port 79 relative to port 78. Such negative pressure differential, given the commanded positive pressure differential, provides added torque on cylinder block 63 that is transferred back, via shaft connection 18B, through-shaft 23 and shaft connection 18A, to cylinder block 33 of pump 30 to assist in driving actuator 90. Thus, when an external force F3 is applied to hydraulic actuator 100 that provides higher pressure 81 to pump port 79 relative to pump port 78 (P78/P79 < 0) when stroke ring 65 is in positive eccentric range 70, then an assistive torque is applied to drive shaft 18. As a result, less power is needed from motor 16.

[0095] FIGS. 18-20B show a fourth example mechanical regenerative mode. As show, the commanded drive direction of actuator 90 is D2 with resulting commanded stroke ring eccentric range 44, and the commanded drive direction of actuator 100 is D4 with resulting commanded stroke ring eccentric range 74. However, as shown, an external force having a force component F4 in direction D4 is applied to actuator 100. This results in higher pressure in chamber 101 relative to chamber 102 and, because of direct hydraulic connection 82, higher pressure at port 78 relative to port 79. Such negative pressure differential, given the commanded positive pressure differential, again provides added torque on cylinder block 63 that is transferred, via shaft connection 18B, through-shaft 23 and shaft connection 18 A, to cylinder block 33 of pump 30 to assist in driving actuator 90. Thus, when an external force F4 is applied to hydraulic actuator 100 that provides higher pressure 81 to pump port 78 relative to pump port 79 (P79/P78 < 0) when stroke ring 65 is in negative eccentric range 74, then an assistive torque is applied to drive shaft 18. As a result, less power is needed from motor 16.

[0096] This also applies with other combinations of actuator directions, such as when a D1/D4 or D2/D3 with a 40/74 or 44/70 stroke ring eccentric range, respectively, are commanded and the subject pressure differentials are negative. Thus, a regenerative mode is employed when the commanded pump port pressure differential is positive for the subject eccentricity and the resulting operational pump port pressure differential is negative.

[0097] FIGS. 21-23B show a first example electrical generator regenerative mode. As show, the commanded drive direction of actuator 90 is D1 with resulting commanded stroke ring eccentric range 40, and the commanded drive direction of actuator 100 is D3 with resulting commanded stroke ring eccentric range 70. However, as shown, an external force having a force component FI in direction D1 is applied to actuator 90 and an external force having a force component F3 in direction D3 is applied to actuator 100. This results in higher pressure in chamber 92 relative to chamber 91 and, because of direct hydraulic connection 53, higher pressure at port 49 relative to port 48. This also results in higher pressure in chamber 102 relative to chamber 101 and, because of direct hydraulic connection 83, higher pressure at port 79 relative to port 78. Such summed negative pressure differential, given the commanded positive pressure differentials, provides added torque on cylinder block 33 that is transferred, via shaft connection 18a, to shaft 18 and motor 16, and provides added torque on cylinder block 63 that is transferred, via shaft connection 18B and through-shaft 23, to shaft 18 and motor 16. Motor 16 functions as a generator and converts such regenerative torque into electrical current that is stored in battery 21. Thus, when external forces FI and F3 are applied to hydraulic actuators 90 and 100 that provide a combined higher pressure to pump ports 49 and 79 relative to pump ports 48 and 78 (å(P48/P49 + P78/P79) < 0) when stroke rings 35 and 65 are in positive eccentric ranges 40 and 70, respectively, then such torque is used to charge battery 21.

[0098] FIGS. 24-26B show a second example electrical generator regenerative mode. As show, the commanded drive direction of actuator 90 is D2 with resulting commanded stroke ring eccentric range 44, and the commanded drive direction of actuator 100 is D4 with resulting commanded stroke ring eccentric range 74. However, as shown, an external force having a force component F2 in direction D2 is applied to actuator 90 and an external force having a force component F4 in direction D4 is applied to actuator 100. This results in higher pressure in chamber 91 relative to chamber 92 and, because of direct hydraulic connection 52, higher pressure at port 48 relative to port 49. This also results in higher pressure in chamber 101 relative to chamber 102 and, because of direct hydraulic connection 82, higher pressure at port 78 relative to port 79. Such summed negative pressure differential, given the commanded positive pressure differentials, again provides added torque on cylinder block 33 that is transferred, via shaft connection 18A, to shaft 18 and motor 16, and provides added torque on cylinder block 63 that is transferred, via shaft connection 18B and through-shaft 23, to shaft 18 and motor 16. Motor 16 functions as a generator and converts such regenerative torque into electrical current that is stored in battery 21. Thus, when external forces F2 and F4 are applied to hydraulic actuators 90 and 100 that provide a combined higher pressure to pump ports 48 and 78 relative to pump ports 49 and 79 (å(P49/P48 + P79/P78) < 0) when stroke rings 35 and 65 are in negative eccentric ranges 44 and 74, respectively, then such torque is used to charge battery 21.

[0099] This also applies with other combinations of actuator directions, such as when a D1/D4 or D2/D3 with a 40/74 or 44/70 stroke ring eccentric range, respectively, are commanded and the subject pressure differentials are negative. Thus, a regenerative mode is employed when the commanded pump port pressure differentials are positive for the subject eccentricities and the sum of the resulting operational pump port pressure differentials is negative.

[00100] Controller 22 controls the current to motor 16 at the appropriate magnitude. The position of pistons 95 and 105 are monitored via position transducers, and the position signals are then fed back to motor controller 22. In addition, or alternatively, the pressure in lines 52, 53, 82 and 83 to and from chambers 91, 92, 101 and 102, respectively, are monitored with pressure transducers and the pressure signals are fed back to controller 22. Variable speed motor 16 and ring actuators 54 and 84 of pumps 30 and 60 control the direction, speed and force of pistons 95 and 105, and in turn rods 96, 97, 106 and 107, by changing the flow and pressure acting on pistons 95 and 105, respectively. This is accomplished by looking at the feedback of the position transducer and/or the pressure transducers and then closing the control loop by adjusting the motor 16 speed and the eccentricity of stroke rings 35 and 65 accordingly.

[00101] Referring now to FIG. 27, a second embodiment 115 of an assistive torque electro-hydraulic pump system is shown. As shown, system 115 is adapted to actuate at least three objects and generally includes electrical power source 21, motor controller 22, variable speed electric motor 16, shaft 18 driven to rotate about axis 20 by motor 16, first radial piston pump 30 mechanically connected to shaft 18, first hydraulic actuator 90 hydraulically connected to first radial piston pump 30, second radial piston pump 60 mechanically connected to shaft 18, second hydraulic actuator 100 hydraulically connected to second radial piston pump 60, third radial piston pump 130 mechanically connected to shaft 18, and third hydraulic actuator 190 hydraulically connected to third radial piston pump 130.

[00102] Electrical power source 21, motor controller 22, variable speed electric motor 16, first radial piston pump 30 mechanically connected to shaft 18, first hydraulic actuator 90 hydraulically connected to first radial piston pump 30, second radial piston pump 60 mechanically connected to shaft 18, and second hydraulic actuator 100 hydraulically connected to second radial piston pump 60 are configured substantially the same as in embodiment 15. However, in this embodiment a third pump and hydraulic actuator combination 130/190 has been added in series with pump and hydraulic actuator combinations 30/90 and 60/100.

[00103] Radial piston pump 130 is substantially the same as radial piston pump 60. Accordingly and with reference to FIG. 2, radial piston pump 130 generally comprises central control journal 131, a plurality of pistons 132 in cylinder block 133 adapted to rotate relative to control journal 131 about block axis 134 with rotation of drive shaft 18, stroke ring 135 orientated about stroke axis 138 and adapted to move radially relative to the neutral or center position in which stroke axis 138 and block axis 134 are coaxial and stroke ring 135 and cylinder block 133 are concentric. Stroke ring 135 does not rotate with rotation of cylinder block 133. As shown, hydraulic ring actuator 154 is controlled to move stroke ring 135 linearly, or radially from the center position, to positions in positive eccentric range 140 between the center position and the positive eccentric position in which stroke axis 138 is offset from block axis 134 in a positive direction relative the center position a maximum positive eccentric distance. Hydraulic ring actuator 154 is also controlled to move stroke ring 135 linearly, or radially from the center position, to positions in negative eccentric range 144 between the center position and the negative eccentric position in which stroke axis 138 is offset from block axis 134 in a negative direction opposite to the positive direction relative to the center position a maximum negative eccentric distance.

[00104] In this embodiment, central control j oumal 61 of radial piston pump 60 includes a cylindrical center bore orientated on central axis 20 and configured to receive through-shaft 123 of drive shaft 18. Through-shaft 123 of drive shaft 18 extends through and rotates in such center bore in central j oumal 61. Through-shaft 123 therefore rotates with rotation of shaft 18.

[00105] Drive torque from motor 16 is transferred from shaft 18 via through-shafts 23 and 123 of drive shaft 18 to cylinder block 133. Cylinder block 133 rotates on central j oumal 131 and central journal 131 is shrunk fit into housing 117. Pistons 132 are arranged radially in cylinder block 133 and are held in contact with stroke ring 135 by slipper pads 136, with each piston 132 and slipper pad 136 connected to each other by ball-and-socket joints. Slipper pads 136 are held in stroke ring 135 by overlapping retainer rings and pressed against stroke ring 135 during operation by centrifugal force and oil pressure. With rotation of cylinder block 133 by shaft 18, pistons 132 execute a radial stroking motion due to the eccentricity of stroke ring 135.

[00106] The pressure flow from and suction flow into the cylinder chamber is controlled by control journal 131. Control journal 131 includes pump port 148 and pump port 149. Rotation 19 of drive shaft 18 when stroke ring 135 is in positive eccentric range 140 provides higher pressure to pump port 148 relative to pump port 149. Alternatively, rotation of drive shaft 18 when stroke ring 135 is in negative eccentric range 144 provides higher pressure to pump port 149 relative to pump port 148. Thus, for positive eccentric range 140, the normal drive pressure differential is P148/P149 and it is positive (P148/P149 > 0) in normal drive, and for negative eccentric range 144, the normal drive pressure differential is P149/P148 and it is positive (P149/P148 > 0) in normal drive. In this embodiment, the piston stroke equals double the eccentricity of stroke ring 135.

[00107] Hydraulic ring actuator 154 is connected to stroke ring 135 and selectively moves stroke ring 135 in both positive eccentric range 140 and negative eccentric range 144. Thus, hydraulic servo-valve 154 varies the radial eccentricity of stroke ring 135. In this embodiment, the normal flow direction, whether from port 148 or from port 149, is determined by the direction of the eccentricity from the neutral center position, with positive eccentricity 140 providing flow out of port 148 and negative eccentricity 144 providing flow out of port 149.

[00108] As shown in FIG. 2, hydraulic ring control actuator 154 includes hydraulic control pistons 155 and 156 in opposed alignment on the same axis that vary the eccentricity of stroke ring 135. The effective areas of pistons 155 and 156 differ, with the effective area of piston 156 being greater than the effective area of piston 155. Hydraulic pressure is constantly applied to small area control piston 155 to press stroke ring 135 against large area control piston 156. Large area control piston 156 is selectively pressurized to maintain stroke ring 135 in a neutral center position with equal pressure, to move stroke ring 135 into positive eccentric range 140 towards the maximum positive eccentric distance with greater pressure, or to move stroke ring 135 into negative eccentric range 144 towards the maximum negative eccentric distance with less pressure. Thus, hydraulic ring actuator 154 controls the position of stroke ring 135 and thereby the flow rate, flow direction and system pressure.

[00109] As shown in FIG. 27, hydraulic actuator assembly 190 includes piston 195 slidably disposed within cylindrical housing 198 orientated about axis 199. In this embodiment, rod 196 is mounted to one side of piston 195 for movement with piston 195 and extends to the right and sealably penetrates the right end wall of housing 198. Rod 197 is mounted to the other side of piston 195 for movement with piston 195 and extends to the left and sealably penetrates the left end wall of housing 198. Piston 195 is slidably disposed within cylinder 198, and sealingly separates left chamber 191 from right chamber 192. In this embodiment, the leftwardly-facing annular vertical end surface of piston 195 faces into left chamber 191 and the rightwardly-facing annular vertical end surface of piston 195 faces into right chamber 192, creating an equal piston area configuration. Left chamber 191 has fluid port 193 and right chamber 192 has fluid port 194. Thus, hydraulic actuator 190 comprises chamber 191, chamber 192 and piston 195 separating the first and second chambers 191, 192. The hydraulic actuator may include a position sensor configured to sense the position of piston 195. While in this embodiment actuator 190 is shown as a linear hydraulic actuator, a rotary hydraulic actuator that imparts a rotary output may be used as an alternative.

[00110] As shown in FIG. 27, port 148 of pump 130 is hydraulically connected directly with left chamber 191 via fluid line 152, and the opposite side or port 149 of pump 130 is hydraulically connected directly with right chamber 192 via fluid line 153. With such direct hydraulic connection 152, no one way check valves or proportional valves are provided in line 152 between pump port 148 and actuator chamber port 193. With such direct hydraulic connection 153, no one way check valves or proportional valves are provided in line 153 between pump port 149 and actuator chamber port 194.

[00111] Piston 195 will move to the right when motor 16 is rotated and pump 130 is in positive eccentric range 140, thereby pressurizing port 148 relative to port 149 and driving fluid out port 148 through conduit 152 and into chamber 191 and drawing fluid from chamber 192 in through port 194, conduit 153 and port 149, and thereby creating a differential pressure on piston 155 and causing it to extend rod 196 to the right. Piston 195 will move to the left when motor 16 is rotated and pump 130 is in negative eccentric range 144, thereby pressurizing port 149 relative to port 148 and driving fluid out port 149 through conduit 153 and into chamber 192 and drawing fluid from chamber 191 in through port 193, conduit 152 and port 148, and thereby creating a differential pressure on piston 155 and causing it to extend rod 197 to the left. Thus, in a normal drive mode rotation of drive shaft 18 when stroke ring 135 is in positive eccentric range 140 provides higher pressure to pump port 148 relative to pump port 149, and rotation of shaft 18 when stroke ring 135 is in negative eccentric range 144 provides higher pressure to pump port 149 relative to pump port 148. [00112] As with embodiment 15, all three actuators 90, 100 and 190 may be driven in either direction with rotation of shaft 18 as a function of the eccentricity of stroke ring centers 38, 68, and 138 relative to block axes 34, 64, and 134, respectively. Thus, various combinations of actuator directions may be commanded, such as for example and without limitation: directions D1/D3/D5 with stroke ring eccentric ranges 40/70/140, respectively; directions D2/D4/D6 with stroke ring eccentric ranges 44/74/144, respectively; directions D1/D4/D5 with stroke ring eccentric ranges 40/74/140, respectively; directions D2/D4/D5 with stroke ring eccentric ranges 44/74/140, respectively; and directions D2/D3/D5 with stroke ring eccentric ranges 44/70/140, respectively. In normal drive, eccentric ranges 40, 70 and 140 generate pressure differentials P48/P49, P78/P79 and P148/P149 that are positive, and eccentric ranges 44, 74 and 144 generate pressure differentials P49/P48, P79/P78 and PI 49/P 148 that are positive.

[00113] Similar to pump actuator combinations 30/60 and 60/100, an external force having a force component in direction D5 applied to actuator 190 may result in higher pressure in chamber 192 relative to chamber 191 and, because of direct hydraulic connection 153, higher pressure at port 149 relative to port 148. Such negative pressure differential P148/P149, given the commanded positive pressure differential, provides added torque on cylinder block 133 that is transferred, via through-shaft 123 and shaft connection 18B, to cylinder block 63 of pump 60 to assist in driving actuator 100. And an external force having a force component in direction D6 applied to actuator 190 may result in higher pressure in chamber 191 relative to chamber 192 and, because of direct hydraulic connection 152, higher pressure at port 148 relative to port 149. Such negative pressure differential (P149/P148), given the commanded positive pressure differential, again provides added torque on cylinder block 133 that is transferred, via though-shaft 123 and shaft connection 18B, to cylinder block 63 of pump 60 to assist in driving actuator 100. Thus, when an external force is applied to hydraulic actuator 190 that provides higher pressure to pump port 149 relative to pump port 148 (P148/P149 < 0) when stroke ring 135 is in positive eccentric range 140, then an assistive torque is applied to drive shaft 18. And when an external force is applied to hydraulic actuator 190 that provides higher pressure to pump port 148 relative to pump port 149 (P149/P148 < 0) when stroke ring 135 is in negative eccentric range 144, then an assistive torque is applied to drive shaft 18.

[00114] Similar to embodiment 15, one or more of pump/actuator combinations 30/90, 60/100 and 130/190 may provide an assistive torque applied through shaft 18 to the other of pump/actuator combination 30/90, 60/100, 130/190 when any of pressure differentials P48/P49, P78/P79 and P148/P149 for eccentric ranges 40, 70 and 140 or P49/P48, P79/P78 and P149/P148 for eccentric ranges 44, 74 and 144 are negative. Thus, a regenerative mode is employed when the commanded pump port pressure differential is positive for the subject eccentricity and the resulting operational pump port pressure differential is negative.

[00115] Pump/actuator combinations 30/90, 60/100 and 130/160 may also provide a net regenerative torque on shaft 18 that is used by motor 16 and drive electronics 22 to charge battery 21. For example, and without limitation, when external forces are applied to hydraulic actuators 90, 100 and/or 190 that provide a combined higher pressure to pump ports 49, 79 and 149 relative to pump ports 48, 78 and 148 (å(P48/P49 + P78/P79 + P148/P149) < 0) when stroke rings 35, 75 and 135 are in positive eccentric ranges 40, 70 and 140, respectively, then such torque is used to charge battery 21. Motor 16 functions as a generator and converts such regenerative torque into electrical current that is stored in battery 21. Also, for example, and without limitation, when external forces are applied to hydraulic actuators 90, 100 and/or 190 that provide a combined higher pressure to pump ports 48, 78 and 148 relative to pump ports 49, 79 and 149 (å(P49/P48 + P79/P78 + P149/P148) < 0) when stroke rings 35, 75 and 135 are in negative eccentric ranges 44, 74 and 144, respectively, then such torque is used to charge battery 21. Thus, a regenerative mode is employed when the commanded pump port pressure differentials are positive for the subject eccentricities and the sum of the resulting operational pump port pressure differentials is negative.

[00116] Again, controller 22 controls the current to motor 16 and ring actuators 54, 84 and 154 of pumps 30, 60 and 130 to control the direction, speed and force of pistons 95, 105 and 195, and in turn rods 96, 97, 106, 107, 196 and 197, by changing the flow and pressure acting on pistons 95, 105 and 195, respectively, and closing the control loop by adjusting the motor 16 speed and the eccentricity of stroke rings 35, 65 and 135 accordingly.

[00117] FIGS. 28 and 29 show system 115 actuating the tilt cylinder, lift cylinder and accessory implements cylinder of skid steer 116. Direct hydraulic lines run from housing 117 of the motor and pumps assembly to the respective hydraulic cylinders, with lines 52 and 53 feeding accessory implements cylinder 98 from pump 30, lines 82 and 83 feeding bucket 119 tilt cylinder 108 from pump 130, and lines 152 and 153 feeding bucket 119 lift cylinder 198 from pump 60. System 15 may be employed in a variety of other applications, including without limitation in applications in which diesel engines are replaced with electrical systems. For example, and without limitation, the system may be employed in excavators, wheel loaders and in other mobile equipment that requires multiple actuation.

[00118] Referring now to FIG. 30, a third embodiment 215 of an assistive torque electro- hydraulic pump system is shown. Electrical power source 21, motor controller 22, variable speed electric motor 16, first radial piston pump 30 mechanically connected to shaft 18, second radial piston pump 60 mechanically connected to shaft 18, and third radial piston pump 130 mechanically connected to shaft 18 are configured substantially the same as in embodiment 115. However, in this embodiment dual piston rod and equal piston area actuators 90, 100, and 190 have been replaced with single rod and unequal piston area actuators 220, 230 and 240. With reference to actuator 240, each of actuators 220, 230 and 240 include piston 245 slidably disposed within cylindrical housing 248 orientated about an axis 249. In this embodiment, a single rod 246 is mounted to one side of piston 245 for movement with piston 245 and extends to the right and sealably penetrates the right end wall 248A of housing 248. Piston 245 is slidably disposed within cylinder 248, and sealingly separates left chamber 241 from right chamber 242. In this embodiment, the leftwardly- facing circular vertical end surface 245B of piston 245 faces into left chamber 241 and the rightwardly-facing annular vertical end surface 245A of piston 245 faces into right chamber 242, creating an unequal piston area configuration. Thus, almost all of leftwardly-facing circular vertical end surface 245B of piston 245 faces into left chamber 241. However, only annular rightwardly-facing vertical end surface 245A of piston 245 faces rightwardly into right chamber 242 due to the addition of rod 246 through chamber 242 and outside housing 248. This creates an unequal piston area configuration, with the surface area of face 245B being greater than the surface area of face 245 A.

[00119] Referring now to FIG. 31, a fourth embodiment 315 of an assistive torque electro- hydraulic pump system is shown. Electrical power source 21, motor controller 22, and variable speed electric motor 16 are configured substantially the same as in embodiment 15 In addition, hydraulic actuator 390 in system 315 is configured substantially the same as actuator 90 in embodiment 15 and hydraulic actuator 400 in system 315 is configured substantially the same as actuator 100 in embodiment 15. However, in this embodiment radial piston pumps 30 and 60 have been replaced with axial piston pumps 330 and 360. [00120] As shown in FIG. 32, axial piston pump 330 generally comprises fluid control journal plate 331, a plurality of pistons 332 in cylinder block 333 adapted to rotate relative to plate 331 about block axis 334 with rotation of drive shaft 318, swash plate 335 positioned axially adjacent one end face of cylinder block 333 and orientated about swash plate axis 338 and adapted to move angularly relative to a neutral or center position in which swash plate axis 338 and block axis 334 are coaxial and the cam surface of swash plate 335 is perpendicular to cylinder block axis 334. Swash plate 335 does not rotate with rotation of cylinder block 333. Hydraulic plate actuator 354 is controlled to adjust the tilt or cam angle of swash plate 335 relative to cylinder block 333 from the center position, to positions in positive angular range 340 between the center position and a positive angular position in which swash plate axis 338 is angularly offset from block axis 334 in a positive angular direction relative to the center position a maximum positive angle 342. Hydraulic plate actuator 354 is also controlled to adjust the tilt or cam angle of swash plate 335 relative to cylinder block 333 from the center position to positions in negative angular range 344 between the center position and a negative angular position in which swash plate axis 338 is angularly offset from block axis 334 in a negative angular direction, opposite to the positive angular direction, relative to the center position a maximum negative angle 346.

[00121] Drive torque from motor 16 is transferred from shaft 318 to cylinder block 333 and cylinder block 333 rotates with shaft 318. Pistons 332 are arranged axially in cylinder block 333 and are held in contact with swash plate 335 by slipper pads 336, with each piston 332 and slipper pad 336 connected to each other by ball-and-socket joints. With rotation of cylinder block 333 by shaft 318, pistons 332 execute an axial stroking motion due to the tilt angle of swash plate 335.

[00122] Port plate 331, on the opposite side of cylinder block 333 to swash plate 335, includes pump port 348 and pump port 349. Rotation 19 of drive shaft 318 when swash plate 335 is in positive angular range 340 provides higher pressure to pump port 348 relative to pump port 349. Alternatively, rotation of drive shaft 318 when swash plate 335 is in negative angular range 344 provides higher pressure to pump port 349 relative to pump port 348. Thus, for positive angular range 340, the normal drive pressure differential is P348/P349 and it is positive (P348/P349 > 0) in normal drive, and for negative angular range 344, the normal drive pressure differential is P349/P348 and it is positive (P349/P348 > 0) in normal drive. [00123] Hydraulic swash plate actuator 354 is connected to swash plate 335 and selectively moves swash plate 335 in both positive angular range 340 and negative angular range 344. Thus, hydraulic servo-valve 354 varies the angularity or cam angle of swash plate 335. In this embodiment, the normal flow direction, whether from port 448 or from port 449, is determined by the direction of the angularity from the neutral center position, with positive angularity 440 providing flow out of port 448 and negative angularity 444 providing flow out of port 449.

[00124] As shown in FIG. 31, hydraulic actuator assembly 390 includes piston 395 slidably disposed within cylindrical housing 398 orientated about axis 399. In this embodiment, rod 396 is mounted to one side of piston 395 for movement with piston 395 and extends to the right and sealably penetrates the right end wall of housing 398. Rod 397 is mounted to the other side of piston 395 for movement with piston 395 and extends to the left and sealably penetrates the left end wall of housing 398. Piston 395 is slidably disposed within cylinder 398, and sealingly separates left chamber 391 from right chamber 392. Left chamber 391 has fluid port 393 and right chamber 392 has fluid port 394. Thus, hydraulic actuator 390 comprises chamber 391, chamber 392 and piston 395 separating the first and second chambers 391, 392. The hydraulic actuator may include a position sensor configured to sense the position of piston 395.

[00125] As shown in FIG. 31, port 348 of pump 330 is hydraulically connected directly with left chamber 391 via fluid line 352, and the opposite side or port 349 of pump 330 is hydraulically connected directly with right chamber 392 via fluid line 353. With such direct hydraulic connection 352, no one way check valves or proportional valves are provided in line 352 between pump port 348 and actuator chamber port 393. With such direct hydraulic connection 353, no one way check valves or proportional valves are provided in line 353 between pump port 349 and actuator chamber port 394.

[00126] Piston 395 will move to the right when motor 16 is rotated and pump 330 is in positive angular range 340, thereby pressurizing port 348 relative to port 349 and driving fluid out port 348 through conduit 352 and into chamber 391 and drawing fluid from chamber 392 in through port 394, conduit 353 and port 349, and thereby creating a differential pressure on piston 355 and causing it to extend rod 396 to the right. Piston 395 will move to the left when motor 16 is rotated and pump 330 is in negative angular range 344, thereby pressurizing port 349 relative to port 348 and driving fluid out port 349 through conduit 353 and into chamber 392 and drawing fluid from chamber 391 in through port 393, conduit 352 and port 348, and thereby creating a differential pressure on piston 355 and causing it to extend rod 397 to the left. Thus, in a normal drive mode rotation of drive shaft 318 when swash plate 335 is in positive angular range 340 provides higher pressure to pump port 348 relative to pump port 349, and rotation of shaft 318 when swash plate 335 is in negative angular range 344 provides higher pressure to pump port 349 relative to pump port 348. [00127] In this embodiment, through-shaft 323 of drive shaft 318 extends through swash plate 335 and rotates with rotation of shaft 318. Through shaft 323 is connected to swash plate 365 of axial piston pump 360.

[00128] As shown in FIG. 33, axial piston pump 360 generally comprises fluid control journal plate 361, a plurality of pistons 362 in cylinder block 363 adapted to rotate relative to plate 361 about block axis 364 with rotation of drive shaft 318, swash plate 365 positioned axially adjacent one end face of cylinder block 363 and orientated about swash plate axis 368 and adapted to move angularly relative to a neutral or center position in which swash plate axis 368 and block axis 364 are coaxial and the cam surface of swash plate 365 is perpendicular to cylinder block axis 364. Swash plate 365 does not rotate with rotation of cylinder block 363. Hydraulic plate actuator 384 is controlled to adjust the tilt or cam angle of swash plate 365 relative to cylinder block 363 from the center position, to positions in positive angular range 370 between the center position and a positive angular position in which swash plate axis 368 is angularly offset from block axis 364 in a positive angular direction relative to the center position a maximum positive angle 372. Hydraulic plate actuator 384 is also controlled to adjust the tilt or cam angle of swash plate 365 relative to cylinder block 363 from the center position to positions in negative angular range 374 between the center position and a negative angular position in which swash plate axis 368 is angularly offset from block axis 364 in a negative angular direction, opposite to the positive angular direction, relative to the center position a maximum negative angle 376.

[00129] Drive torque from motor 16 is transferred from shaft 318 via through-shaft 323 to cylinder block 363 and cylinder block 363 rotates with shaft 318. Pistons 362 are arranged axially in cylinder block 363 and are held in contact with swash plate 365 by slipper pads 366, with each piston 362 and slipper pad 366 connected to each other by ball-and-socket joints. With rotation of cylinder block 363 by shaft 318, pistons 362 execute an axial stroking motion due to the tilt angle of swash plate 365.

[00130] Port plate 361, on the opposite side of cylinder block 363 to swash plate 365, includes pump port 378 and pump port 379. Rotation 19 of drive shaft 318 when swash plate 365 is in positive angular range 370 provides higher pressure to pump port 378 relative to pump port 379. Alternatively, rotation of drive shaft 318 when swash plate 365 is in negative angular range 374 provides higher pressure to pump port 379 relative to pump port 378. Thus, for positive angular range 370, the normal drive pressure differential is P378/P379 and it is positive (P378/P379 > 0) in normal drive, and for negative angular range 374, the normal drive pressure differential is P379/P378 and it is positive (P379/P378 > 0) in normal drive. [00131] Hydraulic swash plate actuator 384 is connected to swash plate 365 and selectively moves swash plate 365 in both positive angular range 370 and negative angular range 374. Thus, hydraulic servo-valve 384 varies the angularity or cam angle of swash plate 365. In this embodiment, the normal flow direction, whether from port 448 or from port 449, is determined by the direction of the angularity from the neutral center position, with positive angularity 440 providing flow out of port 448 and negative angularity 444 providing flow out of port 449.

[00132] As shown in FIG. 31, hydraulic actuator assembly 400 includes piston 405 slidably disposed within cylindrical housing 408 orientated about axis 409. In this embodiment, rod 406 is mounted to one side of piston 405 for movement with piston 405 and extends to the right and sealably penetrates the right end wall of housing 408. Rod 407 is mounted to the other side of piston 405 for movement with piston 405 and extends to the left and sealably penetrates the left end wall of housing 408. Piston 405 is slidably disposed within cylinder 408, and sealingly separates left chamber 401 from right chamber 402. Left chamber 401 has fluid port 403 and right chamber 402 has fluid port 404. Thus, hydraulic actuator 400 comprises chamber 401, chamber 402 and piston 405 separating the first and second chambers 401, 402. The hydraulic actuator may include a position sensor configured to sense the position of piston 405.

[00133] As shown in FIG. 31, port 378 of pump 360 is hydraulically connected directly with left chamber 401 via fluid line 382, and the opposite side or port 379 of pump 360 is hydraulically connected directly with right chamber 402 via fluid line 383. With such direct hydraulic connection 382, no one way check valves or proportional valves are provided in line 382 between pump port 378 and actuator chamber port 403. With such direct hydraulic connection 383, no one way check valves or proportional valves are provided in line 383 between pump port 379 and actuator chamber port 404.

[00134] Piston 405 will move to the right when motor 16 is rotated and pump 360 is in positive angular range 370, thereby pressurizing port 378 relative to port 379 and driving fluid out port 378 through conduit 382 and into chamber 401 and drawing fluid from chamber 402 in through port 404, conduit 383 and port 379, and thereby creating a differential pressure on piston 385 and causing it to extend rod 406 to the right. Piston 405 will move to the left when motor 16 is rotated and pump 360 is in negative angular range 374, thereby pressurizing port 379 relative to port 378 and driving fluid out port 379 through conduit 383 and into chamber 402 and drawing fluid from chamber 401 in through port 403, conduit 382 and port 378, and thereby creating a differential pressure on piston 385 and causing it to extend rod 407 to the left. Thus, in a normal drive mode rotation of drive shaft 318 when swash plate 365 is in positive angular range 370 provides higher pressure to pump port 378 relative to pump port 379, and rotation of shaft 318 when swash plate 365 is in negative angular range 374 provides higher pressure to pump port 379 relative to pump port 378. [00135] As with embodiment 15, both actuators 390 and 400 may be driven in either direction with rotation of shaft 318 as a function of the angularity of swash plates axes 338 and 378 relative to block axes 334 and 364, respectively. Thus, various combinations of actuator directions may be commanded, such as for example and without limitation: directions D1/D3 with swash plate angular ranges 340/370, respectively; directions D2/D4 with swash plate angular ranges 344/374, respectively; directions D1/D4 with swash plate angular ranges 340/374, respectively; and directions D2/D3 with swash plate angular ranges 344/370, respectively. In normal drive, angular ranges 340 and 370 generate pressure differentials P348/P349, and P378/P379 that are positive, and angular ranges 344 and 374 generate pressure differentials P349/P348 and P379/P378 that are positive.

[00136] Similar to pump actuator combinations 30/60 and 60/100, an external force having a force component in direction D1 applied to actuator 390 may result in higher pressure in chamber 392 relative to chamber 391 and, because of direct hydraulic connection 353, higher pressure at port 349 relative to port 348. Such negative pressure differential P348/P349, given a commanded positive pressure differential, provides added torque on cylinder block 333 that is transferred, via through-shaft 323 to cylinder block 363 of pump 360 to assist in driving actuator 400. And an external force having a force component in direction D2 applied to actuator 390 may result in higher pressure in chamber 391 relative to chamber 392 and, because of direct hydraulic connection 352, higher pressure at port 348 relative to port 349. Such negative pressure differential (P349/P348), given a commanded positive pressure differential, again provides added torque on cylinder block 333 that is transferred, via though- shaft 323, to cylinder block 363 of pump 360 to assist in driving actuator 400. Thus, when an external force is applied to hydraulic actuator 390 that provides higher pressure to pump port 349 relative to pump port 348 (P348/P349 < 0) when swash plate 335 is in positive angular range 340, then an assistive torque is applied to drive shaft 318. And when an external force is applied to hydraulic actuator 390 that provides higher pressure to pump port 348 relative to pump port 349 (P349/P348 < 0) when swash plate 335 is in negative angular range 344, then an assistive torque is applied to drive shaft 318.

[00137] Similar to embodiment 15, one or more of pump/actuator combinations 330/390 and 360/400 may provide an assistive torque applied through shaft 318 to the other of pump/actuator combinations 330/390 and 360/400 when any of pressure differentials P348/P349 and P378/P379 for angular ranges 340 and 370 or P349/P348 and P379/P378 for angular ranges 344 and 374 are negative. Thus, a regenerative mode is employed when the commanded pump port pressure differential is positive for the subject angularity and the resulting operational pump port pressure differential is negative.

[00138] Pump/actuator combinations 330/390 and 360/400 may also provide a net regenerative torque on shaft 318 that is used by motor 16 and drive electronics 22 to charge battery 21. For example, and without limitation, when external forces are applied to hydraulic actuators 390 and/or 400 that provide a combined higher pressure to pump ports 349 and 379 relative to pump ports 348 and 378 (å(P348/P349 + P378/P379) < 0) when swash plates 335 and 375 are in positive angular ranges 340 and 370, respectively, then such torque is used to charge battery 21. Motor 16 functions as a generator and converts such regenerative torque into electrical current that is stored in battery 21. Also, for example, and without limitation, when external forces are applied to hydraulic actuators 390 and/or 400 that provide a combined higher pressure to pump ports 348 and 378 relative to pump ports 349 and 379 (å(P349/P348 + P379/P378) < 0) when swash plates 335 and 375 are in negative angular ranges 344 and 374, respectively, then such torque is used to charge battery 21. Thus, a regenerative mode is employed when the commanded pump port pressure differentials are positive for the subject angularities and the sum of the resulting operational pump port pressure differentials is negative.

[00139] Again, controller 22 controls the current to motor 16 and swash plate actuators 354 and 384 of pumps 330 and 360 to control the direction, speed and force of pistons 395 and 405, and in turn rods 396, 397, 406 and 407, by changing the flow and pressure acting on pistons 395 and 405, respectively, and closing the control loop by adjusting the motor 16 speed and the angularity of swash plates 335 and 365 accordingly.

[00140] Assistive torque electro-hydraulic piston pump systems 15, 115, 215 and 315 provide a number of benefits. Unexpectedly, the systems provide actuating forces that are high enough to meet the rigorous demands of mobile equipment. The systems allow for variable speed actuation and full control of the location of the actuator within its range of motion. The system can operate in a closed system with self-contained hydraulic supply and return porting and limited fluid contamination and leakage concerns. The systems do not use proportional valves to meter flow between the pumps and the hydraulic actuators, and instead the pumps control the direct flow to the respective actuators. The systems are battery powered and extremely efficient, are robust for harsh impacts, are compact, and are low cost. Regenerative power from gravity loads are transferred directly on the pump and motor shaft instead of going to a battery first and then back. The systems can handle extreme impact, do not require sensitive electromechanical solutions, and the actuator cylinders in the systems are easy to replace. And the increased energy efficiency of the systems minimizes the battery pack size, lowering costs.

[00141] Many changes and modifications may be made. Therefore, while an embodiment of an improved assistive torque electro-hydraulic piston pump system has been shown and described, and a number of alternatives discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the scope of the invention, as defined and differentiated by the following claims.

Claims

CLAIMS What is claimed is:

1. An electro-hydraulic pump system comprising: an electric motor adapted to be supplied with a current and having a drive shaft; a first hydraulic piston pump comprising a first fluid control j oumal, a plurality of pistons in a first cylinder block adapted to rotate relative to said first fluid control journal about a first block axis with rotation of said drive shaft, and a first displacement drive having a first displacement axis; said first displacement drive adapted to move in a first positive displacement range between a first neutral position between said first displacement axis and said first block axis and a first maximum positive displacement position between said first displacement axis and said first block axis; said first displacement drive adapted to move in a first negative displacement range between said first neutral position and a first maximum negative displacement position between said first displacement axis and said first block axis; said first fluid control journal comprising a first pump port and a second pump port, wherein rotation of said drive shaft when said first displacement drive is in said first positive displacement range provides higher pressure to said first pump port relative to said second pump port, and wherein rotation of said drive shaft when said first displacement drive is in said first negative displacement range provides higher pressure to said second pump port relative to said first pump port; a second hydraulic piston pump comprising a second fluid control journal, a plurality of pistons in a second cylinder block adapted to rotate relative to said second fluid control journal about a second block axis with rotation of said drive shaft, and a second displacement drive having a second displacement axis; said second displacement drive adapted to move in a second positive displacement range between a second neutral position between said second displacement axis and said second block axis and a second maximum positive displacement position between said second displacement axis and said second block axis; said second displacement drive adapted to move in a second negative displacement range between said second neutral position between said second displacement axis and said second block axis and a second maximum negative displacement position between said second displacement axis and said second block axis; said second fluid control journal comprising a third pump port and a fourth pump port, wherein rotation of said drive shaft when said second displacement drive is in said second positive displacement range provides higher pressure to said third pump port relative to said fourth pump port, and wherein rotation of said drive shaft when said second displacement drive is in said second negative displacement range provides higher pressure to said fourth pump port relative to said third pump port; a first hydraulic actuator having a first working port hydraulically connected to said first pump port of said first piston pump; said first hydraulic actuator having a second working port hydraulically connected to said second pump port of said first piston pump; a second hydraulic actuator having a third working port hydraulically connected to said third pump port of said second piston pump; said second hydraulic actuator having a fourth working port hydraulically connected to said fourth pump port of said second piston pump; wherein an external force applied to said first hydraulic actuator that provides higher pressure to said second pump port relative to said first pump port when said first displacement drive is in said first positive displacement range applies an assistive torque to said drive shaft; and wherein an external force applied to said first hydraulic actuator that provides higher pressure to said first pump port relative to said second pump port when said first displacement drive is in said first negative displacement range applies an assistive torque to said drive shaft.

2. The electro-hydraulic pump system set forth in claim 1, wherein: an external force applied to said second hydraulic actuator that provides higher pressure to said fourth pump port relative to said third pump port when said second displacement drive is in said second positive displacement range applies an assistive torque to said drive shaft; and an external force applied to said second hydraulic actuator that provides higher pressure to said third pump port relative to said fourth pump port when said second displacement drive is in said second negative displacement range applies an assistive torque to said drive shaft.

3. The electro-hydraulic pump system set forth in claim 1, comprising a battery supplying said current to said electric motor.

4. The electro-hydraulic pump system set forth in claim 3, wherein said motor is configured to selectively supply a current to said battery in a regeneration mode when: an external force applied to said first hydraulic actuator provides higher pressure to said second pump port relative to said first pump port when said first displacement drive is in said first positive displacement range or an external force applied to said first hydraulic actuator provides higher pressure to said first pump port relative to said second pump port when said first displacement drive is in said first negative displacement range; and an external force applied to said second hydraulic actuator provides higher pressure to said fourth pump port relative to said third pump port when said second displacement drive is in said second positive displacement range or an external force applied to said second hydraulic actuator provides higher pressure to said third pump port relative to said fourth pump port when said second displacement drive is in said second negative displacement range.

5. The electro-hydraulic pump system set forth in claim 1, wherein said first hydraulic actuator is configured to actuate a first object of an electrically powered vehicle and said second hydraulic actuator is configured to actuate a second object of said electrically powered vehicle.

6. The subsea actuation system set forth in claim 1, wherein said electric motor is selected from a group consisting of a brushless DC servo-motor, a stepper motor, a brush motor and an induction motor.

7. The electro-hydraulic pump system set forth in claim 1, wherein said first hydraulic actuator comprises a linear hydraulic actuator or a rotary hydraulic actuator.

8. The electro-hydraulic pump system set forth in claim 7, wherein said first hydraulic actuator comprises a linear hydraulic actuator having a first chamber, a second chamber and a piston separating said first and second chambers.

9. The electro-hydraulic pump system set forth in claim 8, wherein said first hydraulic actuator comprises a cylinder having a first end wall, said piston is disposed in said cylinder for sealed sliding movement therein, and said piston comprises a first actuator rod having a portion sealingly penetrating said first end wall.

10. The electro-hydraulic pump system set forth in claim 9, wherein said cylinder has a second end wall and said piston comprises a second actuator rod having a portion sealingly penetrating said second end wall.

11. The electro-hydraulic pump system set forth in claim 8, comprising a position sensor configured to sense the position of said piston.

12. The electro-hydraulic pump system set forth in claim 8, comprising a pressure sensor configured to sense pressure in said first and second chambers.

13. The electro-hydraulic pump system set forth in claim 1, comprising: a third hydraulic piston pump comprising a third fluid control journal, a plurality of pistons in a third cylinder block adapted to rotate relative to said third fluid control journal about a third block axis with rotation of said drive shaft, and a third displacement drive having a third displacement axis; said third displacement drive adapted to move in a third positive displacement range between a third neutral position between said third displacement axis and said third block axis and a third maximum positive displacement position between said third displacement axis and said third block axis; said third displacement drive adapted to move in a third negative displacement range between said third neutral position between said third displacement axis and said third block axis and a third maximum negative displacement position between said third displacement axis and said third block axis; said third fluid control j oumal comprising a fifth pump port and a sixth pump port, wherein rotation of said drive shaft when said third displacement drive is in said third positive displacement range provides higher pressure to said fifth pump port relative to said sixth pump port, and wherein rotation of said drive shaft when said third displacement drive is in said third negative displacement range provides higher pressure to said sixth pump port relative to said fifth pump port; a third hydraulic actuator having a fifth working port hydraulically connected to said fifth pump port of said third piston pump; said third hydraulic actuator having a sixth working port hydraulically connected to said sixth pump port of said third piston pump; wherein an external force applied to said third hydraulic actuator that provides higher pressure to said sixth pump port relative to said fifth pump port when said third displacement drive is in said third positive displacement range applies an assistive torque to said drive shaft; and an external force applied to said third hydraulic actuator that provides higher pressure to said fifth pump port relative to said sixth pump port when said third displacement drive is in said third negative displacement range applies an assistive torque to said drive shaft.

14. The electro-hydraulic pump system set forth in claim 13, wherein said shaft comprises a first portion connected to said first cylinder block, a second portion connected to said second cylinder block, and a third portion connected to said third cylinder block.

15. The electro-hydraulic pump system set forth in claim 1, comprising a first displacement drive actuator connected to said first displacement drive and configured to selectively move said first displacement drive in said first positive displacement range and to selectively move said first displacement drive in said first negative displacement range.

16. The electro-hydraulic pump system set forth in claim 15, comprising a second displacement drive actuator connected to said second displacement drive and configured to selectively move said second displacement drive in said second positive displacement range and to selectively move said second displacement drive in said second negative displacement range.

17. The electro-hydraulic pump system set forth in claim 1, wherein: said first fluid control journal comprises a first central control journal; said first displacement drive comprises a first stroke ring orientated about said first displacement axis; said first neutral position between said first displacement axis and said first block axis comprises a position in which said first displacement axis and said first block axis are coaxial; said first stroke ring is adapted to move radially relative to said first neutral position; said first maximum positive displacement position between said first displacement axis and said first block axis comprises a first positive eccentric position wherein said first displacement axis is offset from said first block axis in a first positive direction relative said first neutral position a first positive maximum eccentric distance; said first positive displacement range comprises a first positive eccentric range between said first neutral position and a first positive eccentric position; said first maximum negative displacement position between said first displacement axis and said first block axis comprises a first negative eccentric position wherein said first displacement axis is offset from said first block axis in a first negative direction relative said first neutral position a first negative maximum eccentric distance; said first negative displacement range comprises a first negative eccentric range between said first neutral position and a first negative eccentric position; rotation of said drive shaft when said first stroke ring is in said first positive eccentric range provides higher pressure to said first pump port relative to said second pump port, and rotation of said drive shaft when said first stroke ring is in said first negative eccentric range provides higher pressure to said second pump port relative to said first pump port; said second fluid control journal comprises a second central control journal; said second displacement drive comprises a second stroke ring orientated about said second displacement axis; said second neutral position between said second displacement axis and said second block axis comprises a position in which said second displacement axis and said second block axis are coaxial; said second stroke ring is adapted to move radially relative to said second neutral position; said second maximum positive displacement position between said second displacement axis and said second block axis comprises a second positive eccentric position wherein said second displacement axis is offset from said second block axis in a second positive direction relative said second neutral position a second positive maximum eccentric distance; said second positive displacement range comprises a second positive eccentric range between said second neutral position and a second positive eccentric position; said second maximum negative displacement position between said second displacement axis and said second block axis comprises a second negative eccentric position wherein said second displacement axis is offset from said second block axis in a second negative direction relative said second neutral position a second negative maximum eccentric distance; said second negative displacement range comprises a second negative eccentric range between said second neutral position and a second negative eccentric position; rotation of said drive shaft when said second stroke ring is in said second positive eccentric range provides higher pressure to said third pump port relative to said fourth pump port, and rotation of said drive shaft when said second stroke ring is in said second negative eccentric range provides higher pressure to said fourth pump port relative to said third pump port; an external force applied to said first hydraulic actuator that provides higher pressure to said second pump port relative to said first pump port when said first stroke ring is in said first positive eccentric range applies an assistive torque to said drive shaft; and an external force applied to said first hydraulic actuator that provides higher pressure to said first pump port relative to said second pump port when said first stroke ring is in said first negative eccentric range applies an assistive torque to said drive shaft.

18. The electro-hydraulic pump system set forth in claim 17, wherein: an external force applied to said second hydraulic actuator that provides higher pressure to said fourth pump port relative to said third pump port when said second stroke ring is in said second positive eccentric range applies an assistive torque to said drive shaft; and an external force applied to said second hydraulic actuator that provides higher pressure to said third pump port relative to said fourth pump port when said second stroke ring is in said second negative eccentric range applies an assistive torque to said drive shaft.

19. The electro-hydraulic pump system set forth in claim 17, comprising a battery supplying said current to said electric motor and wherein said motor is configured to selectively supply a current to said battery in a regeneration mode when: an external force applied to said first hydraulic actuator provides higher pressure to said second pump port relative to said first pump port when said first stroke ring is in said first positive eccentric range or an external force applied to said first hydraulic actuator provides higher pressure to said first pump port relative to said second pump port when said first stroke ring is in said first negative eccentric range; and an external force applied to said second hydraulic actuator provides higher pressure to said fourth pump port relative to said third pump port when said second stroke ring is in said second positive eccentric range or an external force applied to said second hydraulic actuator provides higher pressure to said third pump port relative to said fourth pump port when said second stroke ring is in said second negative eccentric range.

20. The electro-hydraulic pump system set forth in claim 17, comprising: a third hydraulic piston pump comprising a third central control j oumal, a plurality of pistons in a third cylinder block adapted to rotate relative to said third central control journal about a third block axis with rotation of said drive shaft, and a third stroke ring orientated about a third atroke axis and adapted to move radially relative to a third neutral position in which said third stroke axis and said third block axis are coaxial; said third stroke ring adapted to move linearly in a third positive eccentric range between said third neutral position and a third positive eccentric position, wherein said third stroke axis is offset from said third block axis in a third positive direction relative said third neutral position a third positive maximum eccentric distance; said third stroke ring adapted to move linearly in a third negative eccentric range between said third neutral position and a third negative eccentric position, wherein said third stroke axis is offset from said third block axis in a third negative direction opposite to said third positive direction relative to said third neutral position a third negative maximum eccentric distance; said third control j oumal comprising a fifth pump port and a sixth pump port, wherein rotation of said drive shaft when said third stroke ring is in said third positive eccentric range provides higher pressure to said fifth pump port relative to said sixth pump port, and wherein rotation of said drive shaft when said third stroke ring is in said third negative eccentric range provides higher pressure to said sixth pump port relative to said fifth pump port; a third hydraulic actuator having a fifth working port hydraulically connected to said fifth pump port of said third piston pump; said third hydraulic actuator having a sixth working port hydraulically connected to said sixth pump port of said third piston pump; wherein an external force applied to said third hydraulic actuator that provides higher pressure to said sixth pump port relative to said fifth pump port when said third stroke ring is in said third positive eccentric range applies an assistive torque to said drive shaft; and wherein an external force applied to said third hydraulic actuator that provides higher pressure to said fifth pump port relative to said sixth pump port when said third stroke ring is in said third negative eccentric range applies an assistive torque to said drive shaft.

21. The electro-hydraulic pump system set forth in claim 20, wherein said shaft comprises a first portion connected to said first cylinder block, a second portion connected to said second cylinder block, and a third portion connected to said third cylinder block.

22. The electro-hydraulic pump system set forth in claim 17, comprising a first hydraulic ring actuator connected to said first stroke ring and configured to selectively move said first stroke ring linearly in said first positive eccentric range between said first neutral position and said first positive eccentric position and to selectively move said first stroke ring linearly in said first negative eccentric range between said first neutral position and said first negative eccentric position.

23. The electro-hydraulic pump system set forth in claim 22, comprising a second hydraulic ring actuator connected to said second stroke ring and configured to selectively move said second stroke ring linearly in said second positive eccentric range between said second neutral position and said second positive eccentric position and to selectively move said second stroke ring linearly in said second negative eccentric range between said second neutral position and said second negative eccentric position.

24. The electro-hydraulic pump system set forth in claim 1, wherein: said first fluid control journal comprises a first port plate; said first displacement drive comprises a first swash plate orientated about said first displacement axis; said first neutral position between said first displacement axis and said first block axis comprises a position in which said first displacement axis and said first block axis are coaxial; said first swash plate is adapted to move angularly relative to said first neutral position; said first maximum positive displacement position between said first displacement axis and said first block axis comprises a first positive angular position wherein said first displacement axis is offset from said first block axis in a first positive angular direction relative said first neutral position a first positive maximum cam angle; said first positive displacement range comprises a first positive angular range between said first neutral position and a first positive angular position; said first maximum negative displacement position between said first displacement axis and said first block axis comprises a first negative angular position wherein said first displacement axis is offset from said first block axis in a first negative angular direction relative said first neutral position a first negative maximum cam angle; said first negative displacement range comprises a first negative angular range between said first neutral position and a first negative angular position; rotation of said drive shaft when said first swash plate is in said first positive angular range provides higher pressure to said first pump port relative to said second pump port, and rotation of said drive shaft when said first swash plate is in said first negative angular range provides higher pressure to said second pump port relative to said first pump port; said second fluid control journal comprises a second port plate; said second displacement drive comprises a second swash plate orientated about said second displacement axis; said second neutral position between said second displacement axis and said second block axis comprises a position in which said second displacement axis and said second block axis are coaxial; said second swash plate is adapted to move angularly relative to said second neutral position; said second maximum positive displacement position between said second displacement axis and said second block axis comprises a second positive angular position wherein said second displacement axis is offset from said second block axis in a second positive angular direction relative said second neutral position a second positive maximum cam angle; said second positive displacement range comprises a second positive angular range between said second neutral position and a second positive angular position; said second maximum negative displacement position between said second displacement axis and said second block axis comprises a second negative angular position wherein said second displacement axis is offset from said second block axis in a second negative angular direction relative said second neutral position a second negative maximum cam angle; said second negative displacement range comprises a second negative angular range between said second neutral position and a second negative angular position; rotation of said drive shaft when said second swash plate is in said second positive angular range provides higher pressure to said third pump port relative to said fourth pump port, and rotation of said drive shaft when said second swash plate is in said second negative angular range provides higher pressure to said fourth pump port relative to said third pump port; an external force applied to said first hydraulic actuator that provides higher pressure to said second pump port relative to said first pump port when said first swash plate is in said first positive angular range applies an assistive torque to said drive shaft; and an external force applied to said first hydraulic actuator that provides higher pressure to said first pump port relative to said second pump port when said first swash plate is in said first negative angular range applies an assistive torque to said drive shaft.

25. The electro-hydraulic pump system set forth in claim 24, wherein: an external force applied to said second hydraulic actuator that provides higher pressure to said fourth pump port relative to said third pump port when said second swash plate is in said second positive angular range applies an assistive torque to said drive shaft; and an external force applied to said second hydraulic actuator that provides higher pressure to said third pump port relative to said fourth pump port when said second swash plate is in said second negative angular range applies an assistive torque to said drive shaft.

26. The electro-hydraulic pump system set forth in claim 24, comprising a battery supplying said current to said electric motor and wherein said motor is configured to selectively supply a current to said battery in a regeneration mode when: an external force applied to said first hydraulic actuator provides higher pressure to said second pump port relative to said first pump port when said first swash plate is in said first positive angular range or an external force applied to said first hydraulic actuator provides higher pressure to said first pump port relative to said second pump port when said first swash plate is in said first negative angular range; and an external force applied to said second hydraulic actuator provides higher pressure to said fourth pump port relative to said third pump port when said second swash plate is in said second positive angular range or an external force applied to said second hydraulic actuator provides higher pressure to said third pump port relative to said fourth pump port when said second swash plate is in said second negative angular range.

27. The electro-hydraulic pump system set forth in claim 24, comprising: a third hydraulic piston pump comprising a third port plate, a plurality of pistons in a third cylinder block adapted to rotate relative to said third port plate about a third block axis with rotation of said drive shaft, and a third swash plate orientated about a third swash plate axis and adapted to move angularly relative to a third neutral position in which said third swash plate axis and said third block axis are coaxial; said third swash plate adapted to move angularly in a third positive angular range between said third neutral position and a third positive angular position, wherein said third swash plate axis is offset from said third block axis in a third positive angular direction relative said third neutral position a third positive maximum cam angle; said third swash plate adapted to move angularly in a third negative angular range between said third neutral position and a third negative angular position, wherein said third swash plate axis is offset from said third block axis in a third negative angular direction opposite to said third positive angular direction relative to said third neutral position a third negative maximum cam angle; said third port plate comprising a fifth pump port and a sixth pump port, wherein rotation of said drive shaft when said third swash plate is in said third positive angular range provides higher pressure to said fifth pump port relative to said sixth pump port, and wherein rotation of said drive shaft when said third swash plate is in said third negative angular range provides higher pressure to said sixth pump port relative to said fifth pump port; a third hydraulic actuator having a fifth working port hydraulically connected to said fifth pump port of said third piston pump; said third hydraulic actuator having a sixth working port hydraulically connected to said sixth pump port of said third piston pump; wherein an external force applied to said third hydraulic actuator that provides higher pressure to said sixth pump port relative to said fifth pump port when said third swash plate is in said third positive angular range applies an assistive torque to said drive shaft; and wherein an external force applied to said third hydraulic actuator that provides higher pressure to said fifth pump port relative to said sixth pump port when said third swash plate is in said third negative angular range applies an assistive torque to said drive shaft.

28. The electro-hydraulic pump system set forth in claim 27, wherein said shaft comprises a first portion connected to said first cylinder block, a second portion connected to said second cylinder block, and a third portion connected to said third cylinder block.

29. The electro-hydraulic pump system set forth in claim 24, comprising a first hydraulic swash plate actuator connected to said first swash plate and configured to selectively move said first swash plate in said first positive angular range between said first neutral position and said first positive angular position and to selectively move said first swash plate in said first negative angular range between said first neutral position and said first negative angular position.

30. The electro-hydraulic pump system set forth in claim 29, comprising a second hydraulic swash plate actuator connected to said second swash plate and configured to selectively move said second swash plate in said second positive angular range between said second neutral position and said second positive angular position and to selectively move said second swash plate in said second negative angular range between said second neutral position and said second negative angular position.

31. The electro-hydraulic pump system set forth in claim 1 , wherein: said first fluid control journal comprises a first central control journal; said first displacement drive comprises a first stroke ring orientated about said first displacement axis; said first neutral position between said first displacement axis and said first block axis comprises a position in which said first displacement axis and said first block axis are coaxial; said first stroke ring is adapted to move radially relative to said first neutral position; said first maximum positive displacement position between said first displacement axis and said first block axis comprises a first positive eccentric position wherein said first displacement axis is offset from said first block axis in a first positive direction relative said first neutral position a first positive maximum eccentric distance; said first positive displacement range comprises a first positive eccentric range between said first neutral position and a first positive eccentric position; said first maximum negative displacement position between said first displacement axis and said first block axis comprises a first negative eccentric position wherein said first displacement axis is offset from said first block axis in a first negative direction relative said first neutral position a first negative maximum eccentric distance; said first negative displacement range comprises a first negative eccentric range between said first neutral position and a first negative eccentric position; rotation of said drive shaft when said first stroke ring is in said first positive eccentric range provides higher pressure to said first pump port relative to said second pump port, and rotation of said drive shaft when said first stroke ring is in said first negative eccentric range provides higher pressure to said second pump port relative to said first pump port; said second fluid control journal comprises a first port plate; said second displacement drive comprises a first swash plate orientated about said second displacement axis; said second neutral position between said second displacement axis and said second block axis comprises a position in which said second displacement axis and said second block axis are coaxial; said first swash plate is adapted to move angularly relative to said second neutral position; said second maximum positive displacement position between said second displacement axis and said second block axis comprises a first positive angular position wherein said second displacement axis is offset from said second block axis in a first positive angular direction relative said second neutral position a first positive maximum cam angle; said second positive displacement range comprises a first positive angular range between said second neutral position and a first positive angular position; said second maximum negative displacement position between said second displacement axis and said second block axis comprises a first negative angular position wherein said second displacement axis is offset from said second block axis in a first negative angular direction relative said second neutral position a first negative maximum cam angle; said second negative displacement range comprises a first negative angular range between said second neutral position and a first negative angular position; rotation of said drive shaft when said first swash plate is in said first positive angular range provides higher pressure to said third pump port relative to said fourth pump port, and rotation of said drive shaft when said second swash plate is in said first negative angular range provides higher pressure to said fourth pump port relative to said third pump port; an external force applied to said first hydraulic actuator that provides higher pressure to said second pump port relative to said first pump port when said first stroke ring is in said first positive eccentric range applies an assistive torque to said drive shaft; and wherein an external force applied to said first hydraulic actuator that provides higher pressure to said first pump port relative to said second pump port when said first stroke ring is in said first negative eccentric range applies an assistive torque to said drive shaft.

32. The electro-hydraulic pump system set forth in claim 31, wherein: an external force applied to said second hydraulic actuator that provides higher pressure to said fourth pump port relative to said third pump port when said first swash plate is in said first positive angular range applies an assistive torque to said drive shaft; and an external force applied to said second hydraulic actuator that provides higher pressure to said third pump port relative to said fourth pump port when said first swash plate is in said first negative angular range applies an assistive torque to said drive shaft.