steering wheel ACURA NSX 1997 Service Repair Manual

Component Locatio n
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 23 ).
• Befor e removin g th e gearbox , remov e th e ignitio n ke y t o loc k th e steerin g shaf t fro m turning .
• Afte r installin g th e gearbox , chec k th e whee l alignmen t an d adjus t i f necessary .
STEERING WHEEL/AIRBA G ASSEMBL Y
Removal , pag e 17-43
Disassembly/Reassembly , pag e 17- 44
Installation , pag e 17-45
STEERIN G COLUM N
Removal , pag e 17-47
Inspection , pag e 17-49
Installation , pag e 17-50
STEERIN G GEARBO XRemoval/Installation , pag e 17-1 9
Disassembly , pag e 17-2 2
Inspection , pag e 17-2 1Reassembly , pag e 17-2 5
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3-14
Design Specification
ITEMMETRICENGLISH
AIR CONDITIONINGCooling capacity
Conditions:
Compressor RPM
Outside air temperature
Outside air humidity
Condenser air temperature
Condenser air velocity
Blower capacity4,000 Kcal/h 15,872 BTU/h
1,800 rpm
27 °C 81 °F
50 %
35 °C 95 °F
4.5 m/sec 14.8 ft/sec
420 m
3/h 15,540 cu-ft/h
Independent double wishbone with compli-
ance pivot, coil spring with stabilizer
Independent double wishbone,
coil spring with stabilizer
Telescopic, hydraulic nitrogen gas-filledSUSPENSIONType, front
Type, rear
Shock absorber, front and rear
Evaporator Type
Air temperatureCorrugated fin type
19.5 °C 67 °F
Compressor Type/Make
No. of cylinders
Capacity
Max. speed
Lubricant capacity
NOTES
Swash-plate type/DENSO
10
155.3 cc/rev 9.47 cu-in/rev
7,600 rpm
160 mL 5 1/3 fl oz,
5.6 lmp oz
At 12 V
Air-mix type
Sirocco fan
178 W/12 V
Infinity variable
460 m
3/h 16,247 cu-ft/h
DENSO ND-OIL8
Condenser TypeCorrugated fin type
Temp. control
Blower Type
Motor input
Speed control
Max. capacity
At 13.5 V
Refrigerant Type
Quantity
Dry, single plate, poly-V-belt drive
40 W/12 VCompressor clutch Type
Power consumption
Electric, power assisted, rack and pinion
18.6
3.24
368 mm 14.5 inSTEERING
SYSTEMType
Overall ratio
Turns, lock-to-lock
Steering wheel dia.
HFC-134a (R-134a)
850+0g 30.0+0oz–50–1.8
(cont’d)
*04-NSX (61SW004)SEC03(01-16) 9/22/04 1:49 PM Page 3-14
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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 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

Self-Diagnosis Function

The EPS control unit monitors the system inputs and outputs, and the driving current of the motor. If there is a problem in

the system, the control unit turns the system off by actuating the relay. Power assist stops and normal manual steering

operation resumes. The control unit also turns the EPS indicator light on to alert the driver, and memorizes the problem in

the form of a code. Connecting the terminals of the service check connector with the SCS service connector (special tool)

enables the EPS indicator light to blink the problem code when the ignition switch is turned on (II).

Unloader Control

If the steering wheel is turned fully and held in the full-lock position, the steering torque reaches the maximum point, and

an over-current flows to the motor. The control unit detects this and reduces the current flow to the motor.

Average Moving Current Control

The electric current flow to the motor is estimated from the current values detected by the current sensor, and the average

current is obtained at two second intervals. The motor driving current is suppressed when the average current value

exceeds a predetermined marginal value. The control unit regulates the motor current during continuous loading to sup-

press any excessive temperature rise in the motor.ProCarManuals.com

Steering Gearbox

Motor and Power Assist Mechanism

A motor is housed inside the gearbox housing. It consists of a yoke with a permanent magnet fixed in it, a rotor with a

field coil, and brushes which pass electricity to rotor commutators. The motor is on the rack shaft of the steering gearbox.

The drive current from the control unit flows through the power relay and fail-safe relay to the brushes of the motor.

The drive current flows to rotor commutators through brushes, exciting the field coil of the rotor and rotates the rotor with

the magnetic action of the permanent magnet inside the yoke. The rotor rotates in the opposite direction when the direc-

tion of drive current is reversed.

The rotation torque of the motor is transmitted to the ball screw throught the helical gear. The rotation torque on the ball

screw is converted into assist thrust in the direction of steering rack by the recirculating ball screw. The mechanical advan-

tage of the recirculating ball screw, compaired to a conventional rack and pinion, acts to reduce the steering force to the

steering rack through the joint, to lessen the steering effort required at the steering wheel.

Recirculating Ball Screw

The recirculating ball screw is constructed so that steel balls roll between the screw shaft and the nut, and those coming

out of the screw face enter the screw groove again through a tube for recirculation. The rotation torque on the shaft is

converted into thrust in an axial direction as the slope of the screw shaft presses against the nut through the steel balls.

Since the torque conversion is made in this method through the screw shaft and the steel balls, the friction is small, high

transmission efficiency is obtained for both the forward and backward directions, and the steering feels identical to the

ordinary manual steering.

Furthermore, since the force from the backward direction (force pressing the steering rack) is converted into the rotation

torque of the screw shaft, instantaneous kick-back from the road surface will rapidly rotate the motor. In such a rapid rota-

tion, the inertia of the motor increases, which acts to reduce the kick-back. Any great kick-back will be transmitted from the

steering rack to the torque sensor on the pinion, which acts to twist the pinion shaft in the same direction as the input

direction of kick-back. As a result, the motor operates the kick-back to reduce assist force.ProCarManuals.com

Inspection
Steering Whee l Rotationa l Pla y
1. Plac e th e fron t wheel s i n a straigh t ahea d position ,
an d measur e th e distanc e th e steerin g whee l ca n b e
turne d withou t movin g th e fron t wheels .
2 . I f th e pla y exceed s th e servic e limit , chec k al l steer -
ing components .
Power Assis t Chec k Wit h Vehicl e
Parked
Turn th e steerin g whee l wit h a sprin g scale . Rea d th e
measuremen t whe n th e fron t wheel s o r steerin g whee l
start t o move .
Steerin g Gearbo x Adjustmen t
1. Loose n th e rac k guid e scre w locknut .
Seriou
s burn s ma y resul t i f yo u touc h an y
coolin g component s whe n th e coolin g syste m is hot .
2. Tighten , loose n an d retighte n th e rac k guid e scre w
two time s t o 4 N- m (0. 4 kgf-m , 2. 9 Ibf-ft) , the n bac k i t
of f
3. Tighte n th e locknu t o n th e rac k guid e scre w wit h
th e specia l tool .
4 . Chec k fo r tigh t o r loos e steerin g throug h th e com -
plete turnin g travel .
5. Rechec k steerin g assist .
LOCKNU T WRENCH , 4 0 m m
0791 6-SA5000 1
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