Hydrostatic drive arrangement for vehicles with automatic adaptation of circumferential forces and wheel speeds to friction and curvature conditions

Claim 2

A hydrostatic drive for a vehicle having front and rear wheels, said drive comprising: respective hydraulic-motor means operatively connected to said front wheels and to said rear wheels for respectively driving same, each of said hydraulic-motor means including respective driving hydromotors connected to the corresponding right and left wheels, respectively; at least one main hydraulic pump connected in hydraulic circuit with said hydraulic-motor means for hydraulically energizing same; a hydromotor flow distributor connected in said circuit between said hydraulic-motor means and said main pump for the distribution of a hydraulic medium therebetween to adapt the rotary speeds of the individual wheels to road curvature encountered by said vehicle; and a respective further flow distributor including valve means connected between the drive hydromotors of each pair of right and left wheels, and between the respective hydromotors and the corresponding hydromotor flow distributor for individually adapting the circumferential force applied to each wheel to the respective road-wheel friction, said circuit including a respective primary hydraulic connection between said hydromotor flow distributor and each of said further flow distributors for supplying fluid to the latter, and a respective secondary hydraulic connection between each of said further flow distributors and the driving hydromotors of the corresponding pair of right and left wheels, said hydromotor flow distributor including: a respective constant-displacement hydraulic motor having an input connected to said main pump and an output communicating with a respective one of said primary connections; a hydraulic control pump having its opposite sides connected across the outputs of said constant-displacement hydraulic motors, said constant-displacement hydraulic motors and said control pump having respective shafts; and means mechanically connecting said shafts for joint operation thereof in a fixed predetermined relationship.

Claim 3

The hydrostatic drive defined in claim 1 for a vehicle having a low-speed, high-torque operating mode wherein the outlets of said driving hydromotors are connected in parallel through a valve-type distributor system.

Claim 4

The hydrostatic drive defined in claim 1 wherein said vehicle has an intermediate-speed, intermediate-torque operating condition, further comprising valve means shunted across said control pump in said operating condition.

Claim 5

The hydrostatic drive defined in claim 1 for a vehicle having a low-speed, high-torque operating mode, further comprising a four-way distributor connected to one side of said constant-displacement hydraulic motors and further valves distributors connecting the other side of said constant-displacement hydraulic motors to said driving motors of said front and rear wheels in parallel.

Claim 6

The hydrostatic drive defined in claim 4 wherein said vehicle has a steering mechanism, said drive further comprising a control valve connected across said control pump for selectively shunting same in response to operation of said steering mechanism.

Claim 7

The hydrostatic drive defined in claim 1 wherein said vehicle has an intermediate-speed, intermediate-torque condition, said drive further comprising a four-way distributor connected to said further flow distributor for operating said hydromotors in parallel.

Claim 8

The hydrostatic drive defined in claim 6, further comprising valve means for shunting the driving hydromotors of one of said pairs of wheels in said intermediate-speed, intermediate-torque condition of said vehicle.

Claim 9

The hydrostatic drive defined in claim 1 wherein said vehicle has a high-speed, low-torque condition, further comprising a four-way distributor connected to said hydromotor flow distributor, the pressure side of said main pump being connected to one side of one of said constant-displacement hydraulic motors via said four-way distributor in said condition, said drive further comprising another distributor connecting said main pump with one side of one of said driving hydromotors and the other side of said driving hydromotor in series through the other driving hydromotor of a respective pair of wheels, and means connecting the discharge side of the other driving hydromotor with the other of said constant-displacement hydraulic motors, said control pump being shunted in said condition.

Claim 10

The hydrostatic drive defined in claim 8, further comprising means for shunting the hydromotors of the other pair of wheels in said condition.

Claim 11

A hydrostatic drive for a vehicle having front and rear wheels, said drive comprising: respective hydraulic-motor means operatively connected to said front wheels and to said rear wheels for respectively driving same, each of said hydraulic-motor means including respective driving hydromotors connected to the corresponding right and left wheels, respectively; at least one main hydraulic pump connected in hydraulic circuit with said hydraulic-motor means for hydraulically energizing same; a hydromotor flow distributor connected in said circuit between said hydraulic-motor means and said main pump for the distribution of a hydraulic medium therebetween to adapt the rotary speeds of the individual wheels to road curvature encountered by said vehicle; and a respective further flow distributor including valve means connected between the drive hydromotors of each pair of right and left wheels, and between the respective hydromotors and the corresponding hydromotor flow distributor for individually adapting the circumferential force applied to each wheel to the respective road-wheel friction, said circuit including a respective primary hydraulic connection between said hydromotor flow distributor and each of said further flow distributors for supplying fluid to the latter, and a respective secondary hydraulic connection between each of said further flow distributors and the driving hydromotors of the corresponding pair of right and left wheels, each of said further flow distributors and the associated valve means comprising a feeler assembly sensing flow-pressure differences in the hydraulic medium at the hydromotors of the respective pair of wheels caused by slippage thereof for controlling the hydraulic fluid supply to said drive hydromotors, said feeler assembly comprising: a casinG; throttle-valve means in said casing and including means defining a pair of valve seats communicating with the respective primary hydraulic connection, a pair of throttle-valve chambers respectively communicating with said seats, and a throttle-valve member shiftable for throttling the flow of hydraulic medium from each of said throttle-valve seats to the respective throttle-valve chambers in reciprocal senses; said chambers communicating with the respective secondary connections; a four-way spool-type distributor valve having a pair of outputs communicating with said throttle valve means and effective to bias said throttle-valve member in opposite directions, and a pair of inputs connected to a source of a control fluid; reversing-valve means between said outputs of said distributing valve and said throttle-valve means; and a piston-type servomotor mounted on said distributing valve and connected thereto while communicating with said chambers for controlling said spool-type distributing valve.

Claim 12

A hydrostatic drive for a vehicle having front and rear wheels, said drive comprising: respective hydraulic-motor means operatively connected to said front wheels and to said rear wheels for respectively driving same, each of said hydraulic-motor means including respective driving hydromotors connected to the corresponding right and left wheels, respectively; at least one main hydraulic pump connected in hydraulic circuit with said hydraulic-motor means for hydraulically energizing same; a hydromotor flow distributor connected in said circuit between said hydraulic-motor means and said main pump for the distribution of a hydraulic medium therebetween to adapt the rotary speeds of the individual wheels to road curvature encountered by said vehicle; and a respective further flow distributor including valve means connected between the drive hydromotors of each pair of right and left wheels, and between the respective hydromotors and the corresponding hydromotor flow distributor for individually adapting the circumferential force applied to each wheel to the respective road-wheel friction, said circuit including a respective primary hydraulic connection between said hydromotor flow distributor and each of said further flow distributors for supplying fluid to the latter, and a respective secondary hydraulic connection between each of said further flow distributors and the driving hydromotors of the corresponding pair of right and left wheels, each of said further flow distributors and the associated valve means comprising a feeler assembly sensing flow-pressure differences in the hydraulic medium at the hydromotors of the respective pair of wheels caused by slippage thereof for controlling the hydraulic fluid supply to said drive hydromotors, said feeler assembly comprising: a casinG; throttle-valve means in said casing and including means defining a pair of valve seats communicating with the respective primary hydraulic connection, a pair of throttle-valve chambers respectively communicating with said seats, and a throttle-valve member shiftable for throttling the flow of hydraulic medium from each of said throttle-valve seats to the respective throttle-valve chambers in reciprocal senses; said chambers communicating with the respective secondary connections; a four-way spool-type distributor valve having a pair of outputs communicating with said throttle valve means and effective to bias said throttle-valve member in opposite directions, and a pair of inputs connected to a source of a control fluid; reversing-valve means between said outputs of said distributing valve and said throttle-valve means; and a piston-type servomotor mounted on said distributing valve and connected thereto while communicating with said chambers for controlling said spool-type distributing valve.

Claim 13

The hydrostatic drive defined in claim 10 wherein said throttle-valve means includes a housing defining a valve bore formed with said seats and said chambers and slidably receiving said throttle-valve member, a space along said bore communicating in common with said seats and a channel between a respective primary connection and said space, said throttle valve member having a pair of valve heads tapered in the direction of the respective seats and cooperating therewith, and respective small-diameter portions on the ends of said member, said throttle-valve means further comprising spring means bearing on said member in opposite directions for centering same relative to said seats, said spring means including a coil spring surrounding each of said ends and bearing outwardly upon said casing and respective supporting plates seated against said springs and bearing upon said heads around said ends.

Claim 14

The hydrostatic drive defined in claim 10 wherein said servomotor includes a piston operatively connected to the spool of said distributor valve and formed with a pair of spaced-apart piston members, a servomotor housing surrounding said piston defining a pair of working chambers each slidably receiving one of said piston members and subdivided thereby into a pair of oppositely effective working compartments, and respective duct means connecting each pair of said working compartments to a respective one of said throttle-valve chambers for displacement of said piston in response to pressure differential created in the hydraulic medium of said throttle-valve chambers.

Claim 15

The hydrostatic drive defined in claim 10 wherein said spool-type distributing valve comprises a control piston having a central spool and a pair of outer spools spaced from said central spool; a valve housing slidably receiving said control piston and formed with a central space communicating with a source of a hydraulic medium and a pair of further spaces respectively connected with said reversing valve and communicating selectively with said central space upon displacement of said central spool in either direction from an intermediate position of the control piston, said valve housing being further provided with a pair of outer spaces communicating with a reservoir of the hydraulic medium and with each of said further spaces respectively but blockable by said outer spools upon displacement of said control piston; and spring means acting upon said control piston for biasing same into said intermediate position upon displacement of said control piston by said servomotor.

Claim 16

The hydrostatic drive defined in claim 13 wherein said spring means includes a pair of shoulders formed on said control piston in axially spaced relation, a pair of support plates slidably mounted on said control piston between said shoulders and engageable with opposite walls of said valve housing, and a coil spring surrounding said control piston and seated against said plates, said valve housing defining an abutment engageable with said control piston to limit the displacement thereof in one direction.

Claim 17

The hydrostatic drive defined in claim 10 wherein said feeler assembly further comprises: means on said casing defining a pair of control compartments respectively connected with said throttle-valve chambers and formed internally with respective partitions, said compartments each being connected on one side of a respective partition to the respective chamber and on the other side of the partitions to a respective one of said secondary hydraulic connections; means hydraulically connecting the opposite sides of each of said partitions to said servomotor for biasing same in accordance with the pressure differential across said partitions; respective throttle heads traversing said partitions for controlling the pressure differential developed thereacross, each of said heads being formed with an upstanding stem; and spring means cooperating with said stems for biasing said heads into intermediate positions relative to said partitions.

Claim 18

The hydrostatic drive defined in claim 15 wherein said servomotor comprises a piston rod connected with said spool and formed with a pair of spaced-apart piston members, and cylinder means surrounding said piston members and defining a pair of working chambers subdivided by said piston members into respective pairs of working compartments, said feeler means including first duct means communicating with said control compartments along the side of the partition connected with the associated throttle-valve chamber and communicating with the working compartments of said servomotor acting upon said piston members in opposite directions, and second duct means connected to said control compartments on the sides of said partitions remote from said throttle-valve chambers and connected to the remaining working compartments of said servomotor.

Claim 19

The hydrostatic drive defined in claim 15 wherein each of said heads is generally cylindrical and is formed with at least one longitudinal slot of a cross section increasing continuously outwardly from a relative small cross section centrally of the head.

Claim 20

The hydrostatic drive defined in claim 15 wherein each of said stems is provided with a pair of axially spaced shoulders and said spring means includes a coil spring surrounding each stem between said shoulders, and a pair of supporting plates forming seats for said coil spring and urged thereby against said shoulders, said casing being provided with further compartments receiving said spring means and having walls engageable with said plates while permitting displacement of said stems, the plate between said further compartment and said control compartment being provided with a bore for equalization of the pressure between said further compartment and the respective control compartment, said casing being formed with blind bores slidably receiving said stems remote from said heads, and respective passages connecting said blind bores and said further compartments for equalization of the fluid pressure therebetween.