Steering system for turning multiple sets of steerable wheels

Patent metadata

Field	Value
Publication number	US-9238481-B2
Application number	US-201414477930-A
Country	US
Kind code	B2
Filing date	Sep 5, 2014
Priority date	Mar 15, 2013
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

A steering system for turning multiple sets of steerable wheels comprises three steering gears operatively connected to the steerable wheels. Each steering gear includes a control valve assembly and has an associated hydraulic motor. The first control valve assembly directs pressurized fluid to a first hydraulic motor and also directs pressurized fluid to a second hydraulic motor. The third control valve assembly directs pressurized fluid to a third hydraulic motor. When a torque below a predetermined value is applied to an output shaft of the second steering gear, the output shaft rotates in response to movement of the first control valve assembly, and the second control valve assembly remains in a neutral condition. When a torque above the predetermined value is applied to the output shaft of the second steering gear, the output shaft rotates to cause the second control valve assembly to assume an actuated condition to direct pressurized fluid away from the second hydraulic motor.

First claim

The invention claimed is:

1. A steering system for turning multiple sets of steerable wheels comprising:
a first steering gear operatively connected to a steering wheel and to a first set of steerable wheels to effect turning of the first set of steerable wheels in response to rotation of the steering wheel, the first steering gear including a first control valve assembly, the first control valve assembly directing pressurized fluid to a first hydraulic fluid motor and allowing fluid to return from the first hydraulic fluid motor, the first hydraulic fluid motor being operatively connected to the first set of steerable wheels; and
a second steering gear operatively connected to the first set of steerable wheels and fluidly connected to the first steering gear to assist in turning of the first set of steerable wheels in response to rotation of the steering wheel, the second steering gear including a second control valve assembly,
the first control valve assembly being fluidly connected to the second control valve assembly such that the first control valve assembly directs pressurized fluid to a second hydraulic fluid motor and allows fluid to return from the second hydraulic fluid motor, an output shaft of the second steering gear rotating in response to movement of the first control valve assembly when a torque below a predetermined value is applied to the output shaft, the second control valve assembly remaining in a neutral condition when said torque below a predetermined value is applied to the output shaft, the output shaft rotating to cause the second control valve assembly to assume an actuated condition to direct pressurized fluid away from the second hydraulic fluid motor when a torque above the predetermined value is applied to the output shaft of the second steering gear.

2. A steering system as set forth in claim 1 wherein the output shaft of the second steering gear is coupled to a portion of the second control valve assembly by a torsion bar.

3. A steering system as set forth in claim 1 wherein the output shaft of the second steering gear is coupled to a portion of the second control valve assembly by a releasable latch assembly.

4. A steering system as set forth in claim 1 wherein the output shaft of the second steering gear is operatively connected to a second set of steerable wheels.

5. A steering system as set forth in claim 1 further comprising a third steering gear operatively connected to a second set of steerable wheels and to the output shaft of the second steering gear to effect turning of the second set of steerable wheels in response to rotation of the steering wheel, the third steering gear including a third control valve assembly, the third control valve assembly directing pressurized fluid to a third hydraulic fluid motor and allowing fluid to return from the third hydraulic motor, the third hydraulic fluid motor being operatively connected to the second set of steerable wheels.

6. A steering system for turning multiple sets of steerable wheels comprising:
a first steering gear operatively connected to a steering wheel and to a first set of steerable wheels to effect turning of the first set of steerable wheels in response to rotation of the steering wheel, the first steering gear including a first control valve assembly, the first control valve assembly directing pressurized fluid to a first hydraulic fluid motor and allowing fluid to return from the first hydraulic fluid motor, the first hydraulic fluid motor being operatively connected to the first set of steerable wheels;
a second steering gear operatively connected to the first set of steerable wheels and fluidly connected to the first steering gear to assist in turning of the first set of steerable wheels in response to rotation of the steering wheel, the second steering gear including a second control valve assembly, the second control valve assembly being capable of allowing fluid to return from a second hydraulic fluid motor; and
a third steering gear operatively connected to a second set of steerable wheels and to an output shaft of the second steering gear to effect turning of the second set of steerable wheels in response to rotation of the steering wheel, the third steering gear including a third control valve assembly, the third control valve assembly directing pressurized fluid to a third hydraulic fluid motor and allowing fluid to return from the third hydraulic fluid motor, the third hydraulic fluid motor being operatively connected to the second set of steerable wheels,
the second hydraulic fluid motor being fluidly connected to the first control valve assembly such that the first control valve assembly directs pressurized fluid to the second hydraulic fluid motor and allows fluid to return from the second hydraulic fluid motor, the output shaft of the second steering gear rotating in response to movement of the first control valve assembly when a torque below a predetermined value is applied to the output shaft, the second control valve assembly remaining in a neutral condition when said torque below a predetermined value is applied to the output shaft, the output shaft rotating to cause the second control valve assembly to assume an actuated condition to direct pressurized fluid away from the second hydraulic fluid motor when a torque above the predetermined value is applied to the output shaft of the second steering gear.

Assignees

• Trw Automotive Us Llc

Inventors

• Johnson James R
• Boyle Kevin E

Classifications

• F16D7/044

  the axially moving part being coaxial with the rotation, e.g. a gear with face teeth · CPC title

• B62D7/1527

  comprising only mechanical parts, i.e. without assistance means · CPC title

• B62D7/1536

  provided with hydraulic assistance · CPC title

• B62D7/1563 Primary

  provided with fluid control means (B62D7/1572 takes precedence) · CPC title

• B62D7/14 Primary

  the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering · CPC title