ACURA NSX 1991 Service Repair Manual

5. Sea t th e externa l circli p i n th e groov e o f th e in -
termediat e shaft .
CAUTION : Instal l th e circli p wit h th e radiuse d sid e
facin g out .
EXTERNA L
CIRCLI P
6. Pres s th e oute r sea l int o th e bearin g suppor t usin g
the specia l tools .
Press
DRIVE R07749-0010000
PINION COVE RDRIVER ATTACHMEN T07LAD-PW50500
OUTE R SEA LReplace .
HUB DIS/ASSEMBL Y BAS E07GAF-SD40700
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Special Tool s
17-55
17-6 3
17-2 3
17-6 1, 17-44
17-6 0
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Component Location s
Index
NOTE :
• I f a n intac t airba g assembl y ha s bee n remove d fro m a scrappe d ca r o r ha s bee n foun d defectiv e o r damage d durin g transit ,
storag e o r service , i t shoul d b e deploye d (se e sectio n 24 ).
• Befor e removin g th e gearbox , remov e th e ignitio n ke y t o loc k th e steerin g shaft .
• Afte r installin g th e gearbox , chec k th e whee l alignmen t an d adjus t i f necessary .
EPS CONTRO L UNI TReplacement , pag e 17-6 4
STEERIN G GEARBO XRemoval/Installation , pag e 17-5 5Illustrate d Index , pag e 17-5 9Pinio n Preloa d Inspection , pag e 17-6 0Rack Guid e Scre w Adjustment , pag e 17-6 0
STEERIN G WHEEL /AIRBAG ASSEMBL YRemoval, pag e 17-4 5Disassembly , pag e 17-4 6Installation , pag e 17-4 7
STEERIN G COLUM NRemoval , pag e 17-4 9Inspection , pag e 17-5 1Installation , pag e 17-5 2
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System Description

Steering Column

The NSX/NSX-T has a till/telescopic steering column. The tilt/telescopic mechanism makes it possible to adjust the steer-

ing wheel in fore and aft, and up and down directions.

Tilt Mechanism

In the upper portion of the steering column is a joint on the steering shaft. This joint allows the steering wheel to be

adjusted
up or
down.
When
the
tilt
lever
is
operated,
the
lock
gears
are
detached from
the
column gear
to
release
the
lock.

The column moves upward or downward on two pivot bolts. When the tilt lever is returned to a fixed position after select-

ing the steering wheel height, the lock gear is engaged with the column gear to secure the column.

TILT LEVER

PIVOT

BOLT
COLUMN

GEAR

TILT LEVER

LOCK GEAR
JOINT

PIVOT

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Telescopic Mechanism

The upper steering shaft is divided into two shafts, connected by splines, making it possible for the shaft to telescope

while transmitting the rotation of the steering wheel. When the telescopic lever is lowered, the lever pivot turns in a direc-

tion to loosen the stopper shim at the tip of the lever pivot, allowing the shaft to telescope. The telescopic stroke is limited

by the slot and stopper on the movable shaft. After selecting a steering wheel position and locking the telescopic lever, the

stop shim presses, against the movable shaft, holding it in position.

STOP

SHIM

TELESCOPIC LEVER
STOP

UPPER

STEERING SHAFT

SPLINES

LEVER

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System Descriptio n
Energy-absorbin g Steerin g Column/Whee l
Both th e steerin g colum n an d steerin g whee l ar e designe d to absor b impac t energ y durin g a collision .
Steerin g Whee l
Th e steerin g whee l absorb s th e energ y o f a collisio n throug h th e deformatio n o f th e spok e portion . Shoul d th e impac t
absorbin g capacit y o f th e colum n sid e decreas e du e to th e deformatio n o f th e vehicl e bod y durin g a collision , th e steerin g
whee l wil l hel p absor b th e impact .
Steerin g Colum n
Th e steerin g colum n is fastene d o n th e bod y throug h a U-shape d plate , an d th e lowe r par t o f th e colum n is inserte d int o a
lowe r holder . Du e t o thi s construction , th e steerin g colum n wil l slid e i n it s axia l directio n whe n a larg e impac t i s give n in
th e axia l directio n o f th e column . Sinc e th e U-shape d plat e i s fastene d t o th e body , th e U-shape d plat e i s ben t an d
deforme d alon g th e guid e whe n th e colum n slide s i n it s axia l direction . Throug h th e deformatio n o f th e plate , th e energ y
i s absorbe d an d th e colum n slide s forward . Whe n expose d t o a greate r impact , a shea r pi n wil l brea k an d th e energ y i s
absorbe d b y th e lowe r shaft .
UNDE R NORMA L CONDITIO N
U-PLATE
U-PLAT EGUIDEAt TIM E O F IMPAC T
The U-plate s absor b a n energ ywhile the y ar e straightene d b ythe uppe r bracket .
UNDER NORMA L CONDITIO N
SHEAR PIN S
At TIM E O F IMPAC T
STEERIN G JOIN T
UNDE R NORMA L CONDITIO N
SPOKE
At TIM E O F IMPAC T
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Electrical Power Steering (EPS)

Outline

The NSX/NSX-T uses an electric motor-driven power steering, which possesses the characteristics best suited for a mid-

engine automobile. This system is a power-assisted steering device, with a motor inside the steering gearbox driven by

the EPS control unit. Its distinctive features are described below:

• Minimized loss of engine horsepower and decreased fuel consumption.

• A linear steering feel and the reduction of kickback.

• The system is compact and lightweight because it requires no complicated hydraulic piping, etc.

ALTERNATOR

TRANSMISSION

CONTROL MODULE (TCM)

EPS CONTROL UNIT

VEHICLE

SPEED SENSOR

PULSE UNIT (MT)

BATTERY

STEERING GEARBOX
STEERING WHEEL

STEERING

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System Description

Major Components

The Electrical Power Steering system is composed of the following major components:

• A steering gearbox that converts rotary operation of the steering wheel into transverse operation via a rack and pinion

mechanism. Steering sensors and an actuating motor are incorporated.

• A control unit that computes the optimum amount of power assistance, taking into account steering torque, steering

speed, and vehicle speed. Self-diagnosis functions are included.

• A power unit that drives the motor according to the signals from the EPS control unit. A current sensor is built in to

give feedback information to the EPS control unit. Two relays shut off the power if a problem in the system occurs.

• The countershaft speed sensor on the automatic transmission or the differential speed sensor on the manual transmis-

sion sends a vehicle speed signal to the EPS control unit. Also the speedometer sends a vehicle speed signal to the EPS

control unit. The two signals are used as a double-check.ProCarManuals.com

System Operation

Manual Steering Operation

Steering wheel input rotates the pinion of the gearbox through a universal joint. Due to the rack and pinion mechanism,

the rotation of pinion is converted into a transverse motion at the rack, which steers the front wheels throught the tie-rods

and knuckles the same as an ordinary rack and pinion system.

Assisting Operation

In addition to the manual steering operation, the steering sensor on the pinion shaft transmits a signal to the EPS control

unit when it receives a steering input. The EPS control unit calculates an adequate motor control with addition of vehicle

speed signals. Based on the signal from the sensors, the EPS control unit drives the motor inside the gearbox. The torque

generated by the motor is transmitted to a ball screw, through gears, and converted into an assisting thrust in the axial

direction of rack. The assisting thrust acts in the steering direction and lessens the steering force required at the steering

wheel.

EPS CONTROL UNIT

RECIRCULATING

BALL SCREW

STEERING WHEEL
RACK

STEERING SENSOR

(Build in the rotation sensor

and torque sensor)

MOTOR

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System Description

Function and Operation

Steering Sensor

The steering sensor consists of a torque sensor, an

interface, and the rotation sensor.

Torque Sensor

The torque sensor converts steering torque input and its

direction to voltage signals, in conjunction with the

interface.

A torsional force caused by steering operation is con-

verted to an axial movement of a slider core. A variable

differential transformer is installed around the slider

core.

Within the transformer are three coils, a primary coil on

the inside, and two secondary coils, one for right turns

and one for left turns.

Alternating current is passed through the primary coil

when the system is energized. The amount of mutual

induction from the primary coil to the secondary coils

changes depending on the position of the slider coil.

The input shaft and the slider are one piece. Rotation of

the shaft moves the slider in a circular direction. The

pinion is turned via the torsion bar. The slider core is

installed on the pinion shaft on grooves, and turns with

the pinion shaft.

When there is little resistance, the input shaft torsion

bar, pinion shaft, and the slider core turn together to the

same angle. The slider core does not move up/down.
TORSION BAR

INPUT

SHAFT

INTERFACE

CIRCUIT

SPIRAL

GROOVE

ROTATION

SENSOR

GUIDE

PIN

TRANSFORMER

PINION GEAR

WING

When there is resistance on the input shaft (hard to steer situation), and the slider pin is turned at an angle by the steering

wheel, the torsion bar is twisted due to the resistance. Accordingly, the pinion shaft turns at a smaller angle. The differ-

ence in the turning angles changes the position of the slider pin in the groove, forcing the slider core upward or down-

ward, depending on the direction of the direction of the turn.

PRIMARY COIL

UPPER SECONDARY COIL

LOWER SECONDARY COIL

SLIDER
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