USOO6575264B2

(12) United States Patent (10) Patent No.: US 6,575,264 B2

Spadafora (45) Date of Patent: Jun. 10, 2003

(54) PRECISION ELECTRO-HYDRAULIC 3,908,779 A 9/1975 Inoue

ACTUATOR POSITONING SYSTEM 3,939.938 A 2/1976 Inoue
4010.815. A 3/1977 Strauff
(75) Inventor: William Glenn Spadafora, Clarkston, 4,019,616 A 4/1977 Thorne
MI (US) 4.410,059 A 10/1983 Nakayama et al.
4,872,310 A 10/1989 Kaye
5,080,186 A 1/1992 Elser et al.
(73) Assignee: Dana Corporation, Toledo, OH (US) 5,230,396 A 7/1993 Yasui
5,279,380 A 1/1994 Frank et al.
(*) Notice: Subject to any disclaimer, the term of this 5,313,389 A 5/1994 Yasui
patent is extended or adjusted under 35 5,373.911 A 12/1994 Yasui
U.S.C. 154(b) by 0 days. 5,445.239 A 8/1995 Miller et al.
5,558,177 A 9/1996 Inaguma et al.
(21) Appl. No.: 10/169,634 5,655,371 A 8/1997 Chuang et al.
(22) PCT Filed: Jan. 26, 2001 5,704,250 A 1/1998 Black
5,725,023 A 3/1998 Padula
(86) PCT No.: PCT/US01/02624 6,298.941 B1 10/2001 Spadafora
S371 (c)(1),
(2), (4) Date: Jul. 3, 2002 Primary Examiner Anne Marie Boehler
(74) Attorney, Agent, or Firm-Reising, Ethington, Barnes,
(87) PCT Pub. No.: WO01/54960 Kisselle & Learman, P.C.
PCT Pub. Date: Aug. 2, 2001 (57) ABSTRACT
(65) Prior Publication Data An electro-hydraulic actuator system (10 or 140) includes a
US 2003/0000765 A1 Jan. 2, 2003 hydraulic actuator (27) having a pair of fluid filled chambers
(29, 30) and being operable to provide an actuator output
Related U.S. Application Data (12) as a function of fluid pressures at the chambers. An
electric-hydrostatic actuator (34 or 141) includes an electric
(63) Continuation-in-part of application No. 09/492.623, filed on motor (35 or 142) responsive to motor control signals for
Jan. 27, 2000, now Pat. No. 6.298.941. providing an output to a motor shaft (40 or 150), one or more
(60) Provisional
1999.
application No. 60/117,890, filed on Jan. 29, pistons (56 or 166, 170) coupled to the shaft, and one or
more hydraulic housings (92 or 160, 162) mounted on the
(51) Int. Cl. .............................. B62D 5/04; B62D 5/10 motor and cooperating with the pistons for providing a pair
(52) U.S. Cl. ......................... 180/422; 180/417; 60/.571; of fluid cylinders (54 or 164, 168) respectively coupled to
701/41 the fluid chambers at the hydraulic actuator. A Solenoid valve
(58) Field of Search ................................. 180/417,421, (33) is connected between the cylinders, and is responsive to
180/422, 428, 441, 442, 443, 444, 446; Valve control Signals for feeding fluid between the actuator
701/41; 417/44.1, 45, 44.11, 18; 60/571, chambers and thereby short circuiting the hydrostatic actua
572, 573, 494 tor cylinders. A pair of pressure sensors (80, 82) are coupled
to the actuator chambers for providing respective preSSure
(56) References Cited Signals as a function of fluid pressure at the chambers, and
a controller (92 or 202) is responsive to the pressure signals
U.S. PATENT DOCUMENTS for providing the valve and motor control Signals.
1,364,872 A 1/1921 Feightner
3,901,343 A 8/1975 Inoue 31 Claims, 7 Drawing Sheets

Steering Wheel
or Yoke input
Joy Stick Input System
Control
2623 Electronics
GPS Input
Voice input
a fo

A2
U.S. Patent Jun. 10, 2003 Sheet 1 of 7 US 6,575,264 B2

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U.S. Patent Jun. 10, 2003 Sheet 2 of 7 US 6,575,264 B2
U.S. Patent Jun. 10, 2003 Sheet 3 of 7 US 6,575,264 B2
U.S. Patent Jun. 10, 2003 Sheet 4 of 7 US 6,575,264 B2

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96

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U.S. Patent Jun. 10, 2003 Sheet 5 of 7 US 6,575,264 B2

92 p
1026 AO6 129

lOO
Piston Position -
interface
() Watchdog
Reset and
Circuit
//O
Steering Wheel Hy /30
1O2 ox Position interface
Vehicle Bus

Steering Wheel
|O4 X Torque Sensor ) MCU 132
Signal Conditioning 56
1/4 Solenoid C
Pressure Sensor
8OO Signal Conditioning ->
16
P S | Motor Winding /26
feSSufe SerSOr {C Tem t
82 C Signal Conditioning R Eyre

//6 35
Communication Circuit

Motor Control
e Motor
C inverter Circuit C

---
U.S. Patent Jun. 10, 2003 Sheet 6 of 7 US 6,575,264 B2

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U.S. Patent Jun. 10, 2003 Sheet 7 of 7 US 6,575,264 B2
 US 6,575,264 B2
1 2
PRECISION ELECTRO-HYDRAULC with the pistons for providing a pair of fluid cylinders
ACTUATOR POSITONING SYSTEM respectively coupled to the fluid chambers at the hydraulic
actuator. A Solenoid valve is connected between the
This application claims priority from application PCT/ chambers, and is responsive to valve control Signals for
US01/02624 filed Jan. 26, 2001, and is a continuation-in feeding fluid between the actuator chambers and thereby
part of application Ser. No. 09/492,623 filed Jan. 27, 2000, Short circuiting the hydroStatic actuator cylinders. A pair of
now U.S. Pat. No. 6,298,941, which claims priority from preSSure Sensors are coupled to the actuator chambers for
application Ser. No. 60/117,890 filed Jan. 29, 1999. providing respective preSSure signals as a function of fluid
This invention relates to actuator positioning Systems, preSSure at the chambers, and a controller is responsive to
and more particularly to an electro-hydraulic System for the pressure Signals for providing the valve and motor
precisely positioning the output of a hydraulic actuator. In control Signals. The electro-hydraulic actuator System of the
presently preferred embodiments of the invention, the inven present invention is disclosed in conjunction with electro
tion relates yet more specifically to electro-hydraulic vehicle hydraulic Steering assist modules for automotive Steering
power Steering Systems that incorporate an electric/ applications. However, the electro-hydraulic actuator System
hydroStatic Steering assist module. 15 of the present invention may also be employed in conjunc
tion with marine applications Such as rudder and engine tilt
BACKGROUND AND OBJECTS OF THE controls, aerospace applications. Such as landing gear, cargo
INVENTION door and flight control Surface controls, and industrial appli
Typical power assisted Steering Systems in use today cations Such as assembly line diverters and horizontal fork
positioning controls on fork truckS.
include a belt-driven high rpm rotary hydraulic pump, The electric motor in accordance with the preferred
Specifically engineered hoses, tubes, couplings, an array of embodiments of the invention comprises a rotary motor, and
brackets and fasteners, and a rack and pinion Subassembly. the motor output Shaft comprises a leadscrew operatively
All of these components are engineered to endure the rigors coupled to the piston or pistons for moving the piston or
of extreme thermal cycling brought about by a combination 25 pistons linearly in associated cylinders. In one disclosed
of ambient temperatures in the engine compartment, and embodiment of the invention, the leadscrew is a rotary
various operational loads handled by the Steering pump leadscrew disposed in axially Stationary position, and the
under the usual driving conditions. Such power-assisted piston or pistons are axially movable along the rotary
Systems are a Source of noise, operating inefficiency and leadscrew. In another disclosed embodiment of the
leakage, and consume a large amount of engine power. invention, the leadscrew is non-rotatable and has external
Power assisted Steering pumps are built to very exact threads coupled to internal threads on a rotatable armature
tolerances. Many components of these pumps are fabricated sleeve disposed within the motor, and a piston is mounted on
under tightly controlled manufacturing processes in order to one or both ends of the leadscrew. Rotation of the armature
maintain design specifications. Small discrepancies in sleeve translates the leadscrew axially with respect to the
manufacturing processes can lead to many performance 35 motor and reciprocates the piston(s) within the associated
problems. cylinder(s). In one embodiment of the invention, a single
A general object of the present invention is to provide an piston is disposed within the cylinder of a housing mounted
electro-hydraulic System for positioning a hydraulic actuator to the motor, and the fluid cylinders are formed on opposite
that obtains improved accuracy at reduced cost. Another Sides of the piston. In another embodiment of the invention,
object of the present invention is to limit, if not entirely 40 housings are Secured to the axial ends of the motor, and the
eliminate, many of the problems described above associated leadscrew extends from the axial ends of the motor for
with conventional electro-hydraulic actuator positioning coupling to pistons within the associated housings. The
Systems, including Specifically power Steering Systems. housing or housings preferably are formed by an extrusion
Another object is to provide a power Steering System which that has a central chamber within which a piston is disposed,
is composed of a relatively few parts, is rugged and durable 45 and at least one peripheral chamber that cooperates with
in use, and is capable of being inexpensively manufactured passages in end caps for forming fluid passages to and from
and readily installed. A further object of the invention is to the fluid cylinders. The control electronics may be mounted
provide an electro-hydraulic Steering assist module for auto in another peripheral chamber, and may include a magnetic
motive applications that eliminates any requirement for a Sensor for monitoring position of the piston within its
conventional rotary-driven power Steering fluid pump, 50 asSociated chamber through the extrusion wall that divides
which in turn eliminates a major Source of fluid-borne noise the chambers.
and increases fuel economy. Another object of the invention In the disclosed embodiments of the invention having
is to provide a power Steering assist module that employs a particular utility in electro-hydraulic power Steering assist
rack and pinion assembly that is currently in production, applications, an elongated rack is adapted to be connected at
thereby eliminating any necessity for redesigning or requali 55 opposite ends to Steerable wheels on a vehicle. A rotatable
fying the rack and pinion portion of the Steering System. Steering gear is in mesh with a Series of teeth along a Section
SUMMARY OF THE INVENTION of the rack, and is adapted to be operatively connected to a
Steering wheel of a vehicle So as to receive vehicle operator
An electro-hydraulic actuator System in accordance with Steering input. The rack extends lengthwise within an elon
a presently preferred embodiment of the invention includes 60 gated housing constructed to form a power assist cylinder. A
a hydraulic actuator having a pair of fluid chambers and piston is carried by the rack and Separates the power assist
being operable to provide an actuator output as a function of cylinder into first and Second power assist working fluid
fluid pressures at the chambers. An electric-hydroStatic chambers that are respectively coupled to the fluid cylinders
actuator includes an electric motor responsive to motor of the electric-hydrostatic actuator. The power assist Steering
control Signals for providing an output to a motor Shaft, one 65 System preferably is entirely Self contained, requiring no
or more pistons coupled to the Shaft, and one or more fluid input from an external rotary pump or the like. The
hydraulic cylinderS mounted on the motor and cooperating power Steering rack and pinion arrangement may be of
 US 6,575,264 B2
3 4
conventional design, eliminating any requirement for rede ports of a power assist module 34 in accordance with the
Signing or requalifying this portion of the Steering System. present invention. A normally open Solenoid valve 33 is
Control parameterS Such as Steering "feel” may be readily connected between fluid lines 31, 32 for operation as will be
configured by Software in the control electronics. described. In the absence of an electrical valve control
Signal, caused for example by an electrical control unit or
BRIEF DESCRIPTION OF THE DRAWINGS power failure, valve 33 will open so as to short circuit
module 34 and provide full manual (non-assisted) Steering.
The invention, together with additional objects, features FIGS. 2-4 illustrate power assist module 34 in greater
and advantages thereof, will be best understood from the detail. Module 34 includes an electric motor 35 having a
following description, the appended claims and the accom stator 36 with associated stator windings, and a rotor 38
panying drawings in which: having associated radially extending poles. Motor 35 may be
FIG. 1 is a Schematic diagram of a vehicle electro of any Suitable type, including a Switched reluctance motor,
hydraulic power Steering System in connection with one a brushleSS dc motor, a brushed dc motor and an ac motor.
presently preferred implementation of the invention; A Switched reluctance motor is currently preferred. Rotor 38
FIG. 2 is an exploded perspective view of the electro 15 in this embodiment is secured to a leadscrew 40 by a
hydraulic Steering assist module in the System of FIG. 1; coupling 39 or other suitable means such that rotor 38 and
FIG. 3 is an exploded perspective view of a portion of leadscrew 40 rotate coaxially and in unison. The leadscrew
FIG. 2; is preferably press fitted and epoxied to the rotor. The rotor
FIG. 4 is a sectional view of the electro-hydraulic steering and leadscrew can alternatively be made as a single unit.
assist module in FIGS. 1-3; Rotor 38 is Supported at opposite axial ends by bearings 42,
44 carried by respective motor end bells 46, 48. Bearing 44
FIG. 5 is an electronic functional block diagram of the is mounted within a keeper 49. A resolver 50 or other
control unit in the steering assist module of FIGS. 1-4; Suitable rotary position Sensor is coupled to the end of rotor
FIG. 6 is a Schematic diagram of an electro-hydraulic 38 within end bell 46 (or end bell 48) for providing to control
Steering assist module and System in accordance with 25 electronicS a Signal indicative of rotary position of the rotor
another embodiment of the invention; and leadscrew shaft. Sensorless commutation may also be
FIG. 7 is an exploded perspective view of the steering employed utilizing the Stator windings as a position Sensor.
assist module illustrated in FIG. 6; A housing 52 is mounted on end bell 48. Housing 52
FIG. 8 is a sectional view of the steering assist module preferably is in the form of an elongated extrusion, as best
illustrated in FIGS. 6 and 7; seen in FIGS. 2 and 3, having a central chamber 54 that is
FIG. 9 is a sectional view taken substantially along the coaxial in assembly with and Surrounds leadscrew 40, and a
line 9-9 in FIG. 8; plurality of peripheral chambers Surrounding the central
FIG. 10 is an elevational view of the leadscrew and piston chamber. Being an extrusion, the central chamber and
peripheral chambers are of uniform geometry throughout the
Subassembly in the module of FIGS. 6-8; and 35 length of the extruded housing body. A piston 56 is slidably
FIG. 11 is a fragmentary Sectional view taken Substan disposed within chamber 54 and has internal threads opera
tially along the line 11-11 in FIG. 8. tively coupled to the external threads of leadscrew 40. Thus,
DETAILED DESCRIPTION OF THE
axial position of piston 56 with respect to leadscrew 40 is
PREFERRED EMBODIMENTS controlled by rotation of the leadscrew, which in turn is
40 controlled by rotation of rotor 38 within stator 36. Chamber
Referring now more particularly to the drawings, FIG. 1 54 and piston 56 are non-circular, preferably elliptical in
shows, in an exemplary first system embodiment 10 of the lateral croSS Section So that piston 56 does not rotate within
invention, an elongated rack 12 adapted to be connected at chamber 54 during rotation of leadscrew 40 and axial
opposite ends to the steerable wheels 14, 16 of a motor translation of piston 56 lengthwise of chamber 54. A port cap
vehicle. The rack has a series of teeth 18 along a section of 45 60 is mounted on the end of extrusion housing 52 remote
its length. A rotatable pinion gear 20 in mesh with the rack from end bell 48. Port cap 60 has a fluid port 62 connected
teeth 18 is connected to a steering wheel 22 of the vehicle by a cross passage 64 (FIG. 3) to a central internal pocket 66,
by a column 24 So as to receive operator Steering input. (In which aligns in assembly with central chamber 54 of extru
many applications, there is an intermediate Steering column sion 52. The end of chamber 54 on the opposing side of
or shaft connected to pinion gear 20 and shaft 24 by 50 piston 56 communicates with a central pocket 68 in end bell
universal joints. This intermediate shaft is not illustrated in 48. Pocket 68 is connected by a cross passage 70 (FIG. 3) to
the Schematic diagram of FIG. 1, and is not germane to the a pocket 72 that is aligned in assembly with a peripheral
illustrated embodiments of the present invention.) Rack 12 extrusion passage 74. The opposing end of passage 74 aligns
extends lengthwise within an elongated housing 26, which is with a pocket 76 in port cap 60, which is connected to a fluid
constructed to form an elongated power assist linear actuator 55 port 78. Thus, port 62 is in fluid communication with the
cylinder 27 adjacent to one end. Spaced apart circular working chamber formed on one side of piston 56 by means
interior portions of reduced diameter define the ends of the of cross passage 64, pocket 66 and chamber 54, and port 78
cylinder and have a Sealed engagement with the rack in order is in fluid communication with the working chamber on the
to close opposite ends of the cylinder. A piston 28 carried by opposing side of piston 56 by means of pocket 76, chamber
the rack within cylinder 27 has a Sealed engagement with the 60 74, pocket 72, cross passage 70 and pocket 68.
interior of the cylinder and Separates the cylinder into In assembly of module 34 with steering system 10 (FIG.
cylinder chambers 29, 30 on opposite sides of the piston. 1), fluid lines 31, 32 are connected to ports 62,78 of port cap
Hydraulic fluid fills the chambers. A fluid line 31 commu 60. A pair of pressure sensors 80, 82 are secured on port cap
nicates with one chamber 29 adjacent to one end of the 60 in fluid communication with the opposing Sides of piston
actuator cylinder. A fluid line 32 communicates with the 65 56 in extrusion 52. These pressure sensors 80, 82 provided
other chamber 30 adjacent to the opposite end of the electrical pressure Signals as a function of fluid preSSure
cylinder. Fluid lines 31, 32 are connected to corresponding within fluid lines 31, 32 (FIG. 1). Fluid pressure in these
 US 6,575,264 B2
S 6
lines varies not only as a function of position of piston 56 left or right); (2) contact with an external obstruction (e.g.,
within extrusion 52, but also as a function of position of rack a curb or a rut in the driving Surface); (d) continued
12 under control of Steering wheel 22. A pair of gaskets 84, application of Steering force to offset external forces: (1)
86 are mounted between port cap 60 and end bell 48 and the constant radius turns (e.g., ramp onto freeway); (2) driving
opposing ends of extrusion 52. A shaft seal 88 is mounted on Surfaces that pitched perpendicular to direction of travel
the end of leadscrew 40 within port cap 60, and a second (e.g., a crowned road). Data obtained from torque Sensor 104
shaft seal 90 Surrounds armature 38 within end bell 48. An can be used in conjunction with data taken from preSSure
electronic controller 92 is disposed within a peripheral sensors 80, 82, and integrated to determine and control the
chamber 94 in extrusion 52. A pair of openings 96 in one magnitude of the torque output of motor 35 to be applied to
outside wall of extrusion 52 provide for electrical connec develop the hydraulic fluid preSSure to assist vehicle Steering
tion to electronic controller 92 from outside module 34. An operations. This data can also be used to differentiate
opening 97 in end bell 46 provides for electrical connection between operator input and road induced phenomena
to the windings of motor 35, as best seen in FIG. 4. Piston through suitable software systems in controller 92.
56 carries a magnetic 98 adjacent to the wall 99 of chamber FIG. 5 is a functional block diagram of electronic con
54 that separates chamber 54 from chamber 94. Electronic 15 troller 92. Controller 92 includes a microprocessor-based
controller 92 includes a magnetic position sensor 100 dis motor control unit 106. Unit 106 receives an input from
posed in assembly adjacent to wall 99. Sensor 100 carries piston position Sensor 100 through an associated interface
Hall effect or other Sensor elements responsive to magnetic circuit 108, an input from Steering column position Sensor
energy from magnet 98 on piston 56 for sensing the axial 102 through an associated interface circuit 110, an input
position of piston 56 along chamber 54 of extrusion 52. from Steering column torque Sensor 104 through an associ
Inasmuch as piston 56 is non-rotatably mounted within ated Signal conditioning circuit 112, and Signals from pres
chamber 54, magnetic 98 is continuously positioned adja Sure Sensors 80, 82 through associated Signal conditioning
cent to sensor 100. The mating threads of leadscrew 40 and circuits 114, 116. A motor control circuit 118 is connected to
piston 56 are engineered and fabricated to provide Smooth control unit 106 through a communication interface 120, and
low friction operation with minimal leakage between the 25 is connected to motor 35 through an inverter circuit 122.
opposed fluid chambers. However, a Small controlled leak Motor control circuit 118 receives position feedback infor
age of fluid between the leadscrew and the piston may be mation from resolver 50 through a resolver signal condi
desirable because the fluid would act as a lubricant between tioning circuit 124 for closed loop Servo control of motor
the leadscrew and the piston. A boundary layer of fluid rotation. Motor 35 also provides input to motor control unit
would also aid in limiting backlash typically associated with 18 indicative of motor winding temperature through an
threaded components. associated interface circuit 126. Motor control unit 106 is
A Steering wheel position Sensor 102 is operatively connected to a reset and watchdog timer 128 for monitoring
coupled to steering wheel column 24 (FIG. 1) for providing continued operation of the motor control unit, and is con
an electrical signal indicative of absolute position of the nected to other control units on the vehicle through an
Steering wheel. This Steering wheel position Sensor may be 35 interface 130. Motor control unit 106 can obtain information
monitored to provide the following Steering wheel informa indicative of vehicle on/off Status and vehicle Speed through
tion: (a) the angular displacement in degrees (left or right) interface 130. Control unit 106 provides a valve control
from a center position, which is defined as the point where signal output to solenoid valve 36 (FIG. 1) through a
the Steerable wheels are Straight ahead; (b) the rate at which Solenoid valve driver 132. Controller 92 is powered by the
the Steering wheel is being turned (measured in degrees per 40 dc power System of the vehicle through Suitable Voltage
Second, for example). The Steering wheel position informa regulation. In the embodiment illustrated in FIG. 1, rack 12
tion from sensor 102 may be analyzed by controller 92 and is directly coupled to Steering column 24, So Steering column
used for: (a) initialization and positioning of piston 48 in the position Sensor 102 provides an indication of rack position.
Steering assist module at the time of vehicle start-up. (b) all In other applications, a position Sensor may be coupled to
Steering maneuvers. The Steering wheel position information 45 rack 12 for providing a direct indication of absolute rack
may be used to calculate the required rpm of electric motor position.
35 for Steering assist operations. Steering wheel position In operation, the vehicle operator provides a steering
Sensor 102 may be of any Suitable type, Such as an optical input to rack 12 (FIG. 1) by means of steering wheel 22,
disk and associated Sensors. Steering column 24 and pinion gear 20. Motion of the rack,
A torque sensor 104 (FIG. 1) is also coupled to steering 50 and consequent motion of piston 30 within cylinder 28,
column 24. During vehicle operation, a measurable amount creates a pressure differential at lines 31, 32, which is Sensed
of torque is applied to Steering column 24, either by the by pressure sensors 80, 82. Electronic controller 92 receives
vehicle operator through Steering wheel 22 or in reaction to these pressure signals, and provides a control Signal to motor
road forces reflected back through the Steering gear of the 35 So as to command rotation of leadscrew 40 and motion of
vehicle into the system. This torque value reflected in 55 piston 56 within chamber 54 to minimize this pressure
Steering column 24 is affected by a number of factors differential between the two sensors. This electromotively
including: (a) the coefficient of friction between the vehicle developed motion of piston 56, and the consequent
tires and the driving or road surface. This coefficient of hydraulically-developed fluid flow forces, provide the power
friction in turn is affected by: (1) vehicle weight, (2) vehicle to assist the vehicle operator in manually applying torque
Speed, and (3) driving Surface conditions (e.g., dry 60 through Steering column 24 to achieve the desired motion at
pavement, Surface temperature, gravel, Sand, water, ice); (b) rack 12 and move steerable wheels 14, 16. When the vehicle
friction between components of the mechanical Steering is operated at relatively low Speed, it is important that the
System: (1) articulating joints (e.g., Steering column power Steering assist System be effective. Normally open
universals, bearings, tie-rod ends, balljoint); (2) mating gear Solenoid valve 33 is closed by a valve control signal from
Surfaces; (3) lubrication and contamination Seals; (c) con 65 control unit 106, and assist module 34 is fully effective.
tinued application of force to steering wheel after: (1) design However, at higher Speeds, power assist is normally not
travel limits of steering System have been met (i.e., full turn needed. Under Such circumstances, a vehicle Speed Sensor
 US 6,575,264 B2
7 8
will provide appropriate input to motor control unit 106 housing 192 to form sensor assembly 182. Cover 194 is
through vehicle bus interface 130, whereupon control unit secured to port cap 176 and end bell cap 159, as best seen
106 will de-energize Solenoid valve 33, opening the valve in FIG. 8. Piston 166 carries a magnet 196, and a piston
and disabling the power assistance. In an emergency position sensor 198 identical to sensor 182 is mounted to
Situation, Such as when the operator of the vehicle makes a housing 160 (FIGS. 7 and 8). Sensors 182, 198 are con
Sudden lane change, a first indication of the Steering maneu nected to motor control electronics 200 and system control
ver is provided by steering column torque sensor 104. There electronics 202 (FIG. 6), as are motor stator 144, pressure
is also a momentary increase in fluid pressure will be Sensed sensors 80, 82 and Solenoid valve 33.
by preSSure Sensors 80, 82, Sending a Signal to the controller In operation, the embodiment of FIGS. 6-9 functions in a
to energize Solenoid valve 33 to close the valve and allow manner similar to that of the embodiment of FIGS. 1-5.
power assistance. It is to be noted that use of a normally Operator Steering input to rack 12 produces a pressure
open Solenoid valve 33 allows the rack and pinion Steering differential between pressure sensors 80, 82. This pressure
arrangement to be effective, without power assistance, in the differential is Sensed by the control electronics, which pro
event of electrical power failure at the vehicle or failure at vide input to motor 142 for moving pistons 166, 170
the power assistance electrical control unit. 15 conjointly in a direction to reduce Such pressure differential.
FIGS. 6-8 illustrate a second embodiment 140 of the This piston movement assists the operator Steering input to
present invention. Reference numerals that are identical to the Steering System, as in the prior embodiment. FIG. 6 also
those used in the embodiment of FIGS. 1-5 indicate iden illustrates that the electro-hydraulic actuator System in
tical or functionally related parts. A power assist module 141 accordance with the present invention may receive external
includes an electric motor 142 having a Stator 144 and a control input not only from a steering wheel or yoke 204
rotatable armature 146. A sleeve 148 (FIG. 8) is press fitted asSociated with a vehicle Steering System, but also from a
or otherwise Secured within armature 146 so as to rotate joystick 206, a geographic positioning System 208 and/or a
conjointly with the armature within stator 144. Sleeve 148 voice input command module 210.
has internal threads mated with external threads on a lead
Screw 150. Leadscrew 150 extends from both axial ends of 25
AS indicated previously, the electronic control unit may be
motor 142. Armature 146 is rotatably mounted between a connected through vehicle bus interface 130 (FIG. 5) to as
pair of end bells 152, 154 by means of bearings 156 rotatably conventional multiplexed vehicle information network.
Supporting axially opposed ends of Sleeve 148. A resolver or On/off vehicle input information and vehicle speed infor
other suitable rotary position sensor 158 is mounted within mation may be obtained from the vehicle information net
a cap 159 secured to end bell 156 and operatively coupled work. There may be abidirectional eXchange of System data
to sleeve 148 for detecting rotary position of the sleeve. A over the vehicle network, So that the System control elec
pair of end housings 160, 162 are mounted on end bells 152, tronicS may share with a conventional vehicle onboard
154 respectively externally coaxially Surrounding the electronic control unit the power Steering System Status,
opposed ends of leadscrew 150. Housing 160 has an internal pressure data, actuator Sensor data, etc. System performance
chamber 164, within which is disposed a piston 166 opera 35
can then be monitored by Suitable Software, System diag
tively coupled to the associated end of leadscrew 150. nostics can be analyzed by Suitable Software, and System
Likewise, housing 162 has an internal chamber 168, within performance can be enhanced by changes in Such Software.
Both illustrated embodiments of the invention show use in
which is disposed a piston 170 operatively coupled to the a power-assisted vehicle Steering System, in which the
associated opposite end of leadscrew 150. Thus, rotation at hydraulic actuator is double-ended and integrated with an
armature 146 and sleeve 148 results in axial translation of 40
leadscrew 150 and pistons 166, 170 within their associated otherwise conventional rack and pinion Steering arrange
chambers 164, 168. The subassembly of pistons 166, 170 ment for connection to opposed Steerable vehicle wheels.
and leadscrew 150 is prevented from rotating with sleeve However, the hydraulic actuator could be single-ended or a
148 by means of a pin 220 (FIGS. 8 and 9) extending rotary-type actuator without departing from the principles of
through an anti rotation collar 220 secured to end bell 152, 45
the invention in their broadest aspects.
and an elongated slot 224 (FIGS. 8-10) in leadscrew 150. There has thus been disclosed an electro-hydraulic actua
The axially outer end of housing 160 terminates in a port tor System that fully Satisfies all of the objects and aims
cap 172 having a fluid passage 174 for connection to fluid previously set forth. The invention has been disclosed in
line 31 or 32 (FIG. 1) through a fitting 175 (FIG. 7). conjunction with electro-hydraulic power-assisted vehicle
Likewise, housing 162 has a port cap 176 with a fluid 50 Steering Systems, but finds ready application in other System
passage 178 for connection to the other fluid line 31 or 32 applications as described. AS applied Specifically to power
(FIG. 1) through a fitting 179. Fluid pressure sensors 80, 82 Steering Systems, elimination of the conventional rotary
are also mounted on the port caps and connected to fluid pump removes a major Source of fluid-borne noise and
passages 178,174 respectively. Piston 170 has a magnet 180 improves fuel economy on the order of four to Seven
at its periphery adjacent to the internal wall of chamber 168. 55 percent. A number of modifications and variations have been
A magnetic position Sensor, generally indicated at 182, is discussed. Other modifications and variations will readily
externally mounted on housing 162 for tracking position of Suggest themselves to perSons of ordinary skill in the art in
piston 170 within chamber 168. Sensor 182 includes a View of the foregoing description. The invention is intended
magnet 184 disposed within a non-magnetic keeper 186. to embrace all Such modifications and variations as fall
Keeper 186 is slidably longitudinally captured between a 60 within the Spirit and broad Scope of the appended claims.
What is claimed is:
pair of sensor strips 188, 190. Keeper 186 has a pair of 1. An electro-hydraulic actuator System that comprises:
laterally extending wiperS 226, 228 that slidably engage
strips 188, 190 respectively. Strips 188, 190 comprise vari a hydraulic actuator having a pair of fluid chambers and
able resistance Strips that provide electrical output signals being operable to provide an actuator output as a
indicative of position of keeper 186 and magnet 184 65 function of fluid preSSures in Said chambers,
between the strips. Strips 188, 190 are captured within a an electric-hydrostatic actuator including an electric
U-shaped housing 192, and a cover 194 is positioned over motor responsive to motor control signals for providing
 US 6,575,264 B2
10
output at a motor shaft, piston means coupled to Said 14. The system set forth in claim 13 wherein said central
shaft, and hydraulic cylinder means mounted on Said chamber and Said piston are non-round in lateral croSS
motor and cooperable with Said piston means for pro Section.
Viding a pair of pump fluid cylinderS respectfully 15. The system set forth in claim 8 wherein said housing
coupled to said fluid chambers of said hydraulic has a pair of fluid ports coupled to opposed sides of Said
actuatOr, piston.
a Solenoid valve connected between Said actuator cham 16. The system set forth in claim 8 wherein said cylinder
bers and responsive to Valve control Signals for feeding means comprises a housing mounted at each end of Said
fluid between Said chambers Short circuiting Said motor with Said leadscrew extending into each said housing,
cylinders, a piston in each said housing coupled to an end of Said
a pair of pressure Sensors coupled to Said chambers for leadscrew, and a fluid port at each Said housing coupled to
providing respective pressure Signals as functions of one side of the associated piston.
fluid pressure in Said chambers, and 17. The system set forth in claim 2 wherein said hydraulic
control means responsive to Said pressure Signals for actuator comprises: an elongated rack adapted to be con
providing Said valve control Signals and Said motor 15 nected at opposite ends to Steerable wheels of a vehicle, Said
control Signals. rack having a Series of teeth along a Section of its length, a
2. The system set forth in claim 1 wherein said electric rotatable pinion in mesh with the rack teeth and adapted to
motor comprises a rotary motor, and wherein Said motor be operably connected by a column to a steering wheel of the
shaft comprises a leadscrew operatively coupled to Said vehicle So as to receive vehicle operator Steering input, Said
piston means for moving Said piston means linearly in Said rack extending lengthwise within an elongated housing
cylinders as a function of rotary output of Said motor. constructed to form an elongated power cylinder and having
3. The system set forth in claim 2 wherein said leadscrew thereon Spaced apart first and Second circular interior por
comprises a rotary leadscrew disposed in Stationary position, tions of reduced diameter defining the axially opposite ends
and wherein Said piston means is axially movable along Said of Said power cylinder and having a Sealed engagement with
rotary leadscrew. 25 the rack in order to close opposite ends of Said power
4. The system set forth in claim 2 wherein said motor cylinder, and a piston carried by Said rack within Said power
includes a rotatable sleeve having an internal thread, cylinder having a Sealed engagement with the interior of the
wherein Said leadscrew is axially movable as a function of cylinder and Separating the cylinder into first and Second
rotary position of Said sleeve, and wherein Said piston means power assist working chambers filled with hydraulic fluid.
is Secured to an end of Said leadscrew. 18. A power Steering apparatus comprising:
5. The system set forth in claim 4 wherein said leadscrew a hydraulic actuator having a pair of power assist cylinder
is Secured against rotation within Said hydrostatic actuator. chambers and operable to generate assisting power,
6. The System set forth in claim 2 wherein said piston a hydrostatic actuator for supplying pressurized fluid to
means is mounted against rotation within Said cylinder Said power assist chambers,
CS. 35
7. The system set forth in claim 6 further comprising a an electric motor for operating Said hydrostatic actuator,
position Sensor coupled to Said piston means, and including a control valve mechanism operable by a System control
a magnet carried by Said piston means and a magnetic ler for bypassing between Said pair of power assist
position Sensor operatively magnetically coupled to Said cylinder chambers of Said hydraulic actuator the pres
piston means through a wall of Said cylinder means. 40 Surized fluid Supplied by Said hydrostatic actuator,
8. The system set forth in claim 2 wherein said cylinder pressure Sensors for detecting differential pressure
means comprises a housing mounted on an end of Said motor between pressures in Said pair of power assist cylinder
with Said leadscrew extending into Said housing, and a chambers, and
piston coupled to Said leadscrew and slidably disposed in a motor control responsive to the output of Said pressure
Said housing. 45 Sensors for controlling Said electric motor thereby to
9. The system set forth in claim 8 wherein said housing cause Said motor to drive Said hydrostatic actuator in
comprises an extrusion having multiple internal chambers accordance with Steering wheel position So as to return
extending through said extrusion, Said piston being disposed the differential pressure to a predetermined first value,
in one of Said chambers and other of Said clambers com Said hydroStatic actuator comprising a double-acting
prising at least one fluid passage to Said one chamber. 50 actuator piston and cylinder unit having a pair of
10. The system set forth in claim 9 wherein said extrusion working chambers Separated by Said actuator piston
has a central chamber in which said piston is slidably and respectively communicating with Said pair of
disposed and at least one peripheral chamber, and wherein power assist cylinder chambers, Said electric motor
Said housing further comprises at least one end member being operable bidirectionally axially to drive a lead
mounted on Said extrusion having at least one fluid port and 55 Screw on which Said piston is mounted for travel in
internal passage means connecting Said at least one port to response to axial motion of Said leadscrew.
at least one of Said chambers. 19. An electro-hydraulic power Steering System that com
11. The system set forth in claim 10 wherein said control prises:
means is disposed in one of Said peripheral chambers. an elongated rack adapted to be connected at opposite
12. The system set forth in claim 11 wherein said control 60 ends to Steerable wheels of a motor Vehicle, Said rack
means includes a Sensor for monitoring position of Said having a Series of teeth along a Section of its length,
piston in Said central chamber. a rotatable Steering gear in mesh with the rack teeth and
13. The system set forth in claim 12 wherein said piston adapted to be operably connected to a steering wheel of
includes a magnet, and wherein Said Sensor includes means the vehicle by a shaft So as to receive vehicle operator
for magnetic coupling to Said piston through a wall of Said 65 Steering input, Said rack extending lengthwise within an
extrusion that Separates Said one peripheral chamber from elongated housing constructed to form an elongated
Said central chamber. power assist cylinder,
 US 6,575,264 B2
11 12
a piston carried by Said rack and Separating Said power with Said leadscrew extending into Said housing, and a
assist cylinder into first and Second power assist work piston coupled to Said leadscrew and Slidably disposed in
ing chambers filled with hydraulic fluid, Said housing.
an electric-hydrostatic actuator including an electric 24. The system set forth in claim 23 wherein said housing
motor responsive to motor control signals for providing comprises an extrusion having multiple internal chambers
an output to a motor Shaft, piston means coupled to Said extending through Said extrusion, Said piston being disposed
in one of Said chambers and other of Said clambers com
shaft, and hydraulic cylinder means mounted on Said
motor and cooperating with Said piston means for prising at least one fluid line to Said one chamber.
providing a pair of pump fluid cylinderS respectively 25. The system set forth in claim 24 wherein said extru
coupled to first and Second power assist working Sion has a central chamber in Said piston is slidably disposed
chambers, and at least one peripheral chamber, and wherein Said
a Solenoid valve connected between Said chambers and housing further comprises at least one end member mounted
responsive to valve control Signals for feeding fluid on Said extrusion having at least one fluid port and internal
passage means connecting Said at least one port to at east one
between said chambers, 15 of Said chambers.
a pair of pressure Sensors coupled to Said power assist 26. The system set forth in claim 25 wherein said control
working chambers for providing respective pressure means is disposed in one of Said peripheral chambers.
Signals as a function of fluid pressure in Said chambers, 27. The system set forth in claim 26 wherein said control
which in turn are responsive at least in part to Steering means includes a Sensor for monitoring position of Said
input through Said Shaft, and piston in Said central chamber.
control means responsive to Said pressure Signals for 28. The system set forth in claim 27 wherein said piston
providing Said valve control signal and Said motor includes a magnet, and wherein Said Sensor includes means
control Signal. for magnetic coupling to Said piston through a wall of Said
20. The system set forth in claim 19 wherein said electric extrusion that Separates Said one peripheral chamber from
motor comprises a rotary motor, and wherein Said motor 25 Said central chamber.
shaft comprises a leadscrew operatively coupled to Said 29. The system set forth in claim 28 wherein said central
piston means for moving Said piston means linearly in Said chamber and Said piston are non-round in lateral croSS
cylinders as a function of rotary output of Said motor. Section.
21. The system set forth in claim 20 wherein said lead 30. The system set forth in claim 23 wherein said housing
Screw comprises a rotary leadscrew disposed in Stationary has a pair of fluid ports coupled to opposed sides of Said
position, and wherein Said piston means is axially movable piston.
along Said rotary leadscrew. 31. The system set forth in claim 23 wherein said cylinder
22. The system set forth in claim 20 wherein said motor means comprises a housing mounted at each end of Said
includes a rotatable sleeve having an internal thread, motor with Said leadscrew extending into each said housing,
wherein Said leadscrew is axially movable as a function of 35 a piston in each said housing coupled to an end of Said
rotary position of Said sleeve, and wherein Said piston means leadscrew, and a fluid port at each Said housing coupled to
is Secured to an end of Said leadscrew. one side of the associated piston.
23. The system set forth in claim 20 wherein said cylinder
means comprises a housing mounted on an end of Said motor k k k k k