ACURA NSX 1997 Service Repair Manual

Special Tool s
17-53
17-6 1
17-23
17-59, 17-42
17-58
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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 vehicl e 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 .
STEERING GEARBO XRemoval/Installation , pag e 17-5 3
Illustrate d Index , pag e 17-5 7
Pinio n Preloa d Inspection , pag e 17-5 8
Rac k Guid e Scre w Adjustment , pag e 17-5 8
STEERIN
G COLUM N
Removal , pag e 17-4 7
Inspection , pag e 17-4 9
Installation , pag e 17-5 0
STEERIN G WHEEL /AIRBAG ASSEMBL YRemoval, pag e 17-4 3
Disassembly , pag e 17-4 4
Installation , pag e 17-4 5
EP
S CONTRO L UNI T
Replacement , pag e 17-62
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System Description

Steering Column

The NSX/NSX-T has a tilt/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.ProCarManuals.com

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 stop shim at the tip of the lever pivot, allowing the shaft to telescope. The telescopic stroke is limited by

the slot and stop 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.ProCarManuals.com

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 in it s axia l directio n whe n a larg e impac t i s give n i n
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 .
The U-plate s absor b a n energ ywhile the y ar e straightene d b ythe uppe r bracket .
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Electrical Powe r Steerin g (EPS )
Outlin e
The NSX/NSX- T use s a n electri c motor-drive n powe r steering , whic h possesse s th e characteristic s bes t suite d fo r a mid -
engin e automobile . Thi s syste m is a power-assiste d steerin g device , wit h a moto r insid e th e steerin g gearbo x drive n b y
th e EP S contro l unit . It s distinctiv e feature s ar e describe d below :
• Minimize d los s o f engin e horsepowe r an d decrease d fue l consumption .
• A linea r steerin g fee l an d th e reductio n o f kickback .
• Th e syste m is compac t an d lightweigh t becaus e it require s n o complicate d hydrauli c piping , etc .
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System Descriptio n
Major Component s
The Electrica l Powe r Steerin g syste m is compose d o f th e followin g majo r components :
• A steerin g gearbo x tha t convert s rotar y operatio n o f th e steerin g whee l int o transvers e operatio n vi a a rac k an d pinio n
mechanism . Steerin g sensor s an d a n actuatin g moto r ar e incorporated .
• A contro l uni t tha t compute s th e optimu m amoun t o f powe r assistance , takin g int o accoun t steerin g torque , an d vehi -
cl e speed . Self-diagnosi s function s ar e included .
• A powe r modul e i n th e EP S contro l uni t tha t drive s th e moto r accordin g t o th e signal s fro m th e EP S contro l unit . A cur -
ren t senso r i s buil t i n t o giv e feedbac k informatio n t o th e EP S contro l unit . Tw o relay s shu t of f th e powe r i f a proble m
i n th e syste m occurs .
• Th e countershaf t spee d senso r o n th e automati c transmissio n o r th e differentia l spee d senso r o n th e manua l transmis -
sio n send s a vehicl e spee d signa l t o th e EP S contro l unit . Als o th e speedomete r send s a vehicl e spee d signa l t o th e EP S
contro l unit . Th e tw o signal s ar e use d a s a double-check .
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System Operatio n
Manual Steerin g Operatio n
Steerin g whee l inpu t rotate s th e pinio n o f th e gearbo x throug h a universa l joint . Du e t o th e rac k an d pinio n mechanism ,
th e rotatio n o f pinio n is converte d int o a transvers e motio n a t th e rack , whic h steer s th e fron t wheel s through t th e tie-rod s
an d knuckle s th e sam e a s a n ordinar y rac k an d pinio n system .
Assistin g Operatio n
In additio n t o th e manual steering operation , th e steerin g senso r o n th e pinio n shaf t transmit s a signa l t o th e EP S contro l
uni t whe n i t receive s a steerin g input . Th e EP S contro l uni t calculate s a n adequat e moto r contro l wit h additio n o f vehicl e
spee d signals . Base d o n th e signa l fro m th e sensors , th e EP S contro l uni t drive s th e moto r insid e th e gearbox . Th e torqu e
generate d b y th e moto r i s transmitte d t o a bal l screw , throug h gears , an d converte d int o a n assistin g thrus t i n th e axia l
directio n o f rack . Th e assistin g thrus t act s i n th e steerin g directio n an d lessen s th e steerin g forc e require d a t th e steerin g
wheel.
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System Description

Function and Operation

Steering Sensor

The steering sensor consists of a torque sensor, an

interface.

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.

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.ProCarManuals.com

Interface Circuit

The interface circuit is housed inside the steering gearbox near the pinion. It rectifies and amplifies the signals from the

torque sensor, and transmits the steering signals to the EPS control unit.ProCarManuals.com