10. steering system

8/2/2019 10. Steering System

1/27

10

STEERING SYSTEMOUTLINE 10- 2OUTL INE OF CONSTRUCT ION .. . ... 10- 2STRUCTURAL V IEW 10- 2SPECIFICATIONS 10- 3POWER STEERING 10- 4OUTLINE 10- 4O IL PASSAGE 10- 5STEER ING G EAR ANDREACTION FORCE CHAMBER 10- 6OIL PUMP UNIT 10- 7ELECTRICAL SYSTEM 10-15MANUAL STEER ING CAPAB IL IT Y 10-22OPERATION 10-23MANUAL STEERING 10-26STEER ING GEAR 10-26

67Ul0X501


2/27

OUTLINEOUTLINE OF CONSTRUCTION1. The steering gear box has been changed from a ball-and-nut type to a rack-and-pinion type.2. Vehicle speed and steering angle sensing power steering is adopted.3. Tilt steering is a new feature. The steering wheel can be tilted about 5 degrees.4. The control unit has a self-diagnostic capability for the electrical steering components.

S7G10X-S01STRUCTURAL VIEW

Steering wheel

OiIPU~

$teerin~


3/27

SPECIFICA TIONSType

I , Manual steering Power steeringItem

I Outer diameter mm (in) I 380 (14.96)ISteering wheel ,..--- -rI Turns lock to lock I 3.6 j 2.7I II Shaft type CollapsibleISteering shaft and joints JOint type Cross joints (2)I

Tilt angle degree 5Type Rack and pinionSteering gear

I ISteering ratio 20.0 15.2Inner I 36 :!: 2

Maximum steering angle Outer 32 :!: 2Toe-in mm (in) 3 :!: 3 (0.12 :!: 0.12)

Wheel alignment Camber angle 22' :!: 30'I Caster angle 440' :!: 45'Capacity liter I 0.80

Power steering fluid (US quarts, Imp quarts) I (0.85, 0.70)Type I ATF type F (M2C33-F)I

57G10X502 Steering ratio: the turning angle of the tires relative to the turning angle of the steering wheel.

10-3


4/27

POWER STEERINGOUTLINE

S te pp in g mo to rP re ss ur e r es pons e v alv e\

\Angle s en so rContro l u nit

67U10X-505This power steering system changes its steering assist power according to vehicle speed, steeringwheel turning angle and road resistance.When the vehicle is stopped or running at low speed, more power assistance is provided and lesseffort is required of the driver.When the vehicle speed is high, less power assistance is provided and more driver effort is required.More effort is required at high speeds as the steering angle increases.With these functions. the system provides the driver with a rigid, stable, yet easy- handling feeling.The required steering effort is decided according to the oil pressure applied to the reaction force chamberin the steering gear housing. The oil pressure to the reaction force chamber is controlled by the vehi-cle speed signal and the steering wheel turning angle signal. This is done by means of the controlunit and the stepping motor. Oil pressure to the reaction force chamber is also controlled by the pres-sure response valve according to road resistance.

10-4


5/27

OIL PASSAGES te er in g g ea r

Pressure response valvePiston

Cont ro l u n it

The oil from the main pump is led to the rack housing through the control valve. The oil moves therack bar and also is led to the pressure response valve. Here oil moves the piston which controls thehydraulic pressure activated within the reaction force chamber.The oil from the sub-pump is led to the reaction force chamber, pressure response valve and steppingvalve (rotated by the stepping motor), thus changing the steering effort.

10-5

67U10X-529


6/27

STEERING GEAR AND REACTION FORCE CHAMBER

pressure

S te er in g sha ftTorsion

Cont ro l v alv e a ss emb ly

67U10X-506This rack-and-pinion type of steering gear construction is basically the same as that of the 323 and626, except that a new reaction force chamber has been provided at the lower part of the control valve.The reaction force chamber has been added in order to change the driver's steering effort accordingto driving conditions.Inside the reaction force chamber there are four small pistons which push against the steering shaft;hydraulic pressure is led to each piston from a sub-pump.During low-speed driving when the hydraulic pressure becomes low, the pressure upon the steeringshaft is reduced, and the torsion bar can be twisted easily so, the required steering effort becomes small.During high-speed driving when the hydraulic pressure becomes high, each piston exerts pressureupon the steering shaft, and the required steering effort to twist the torsion bar becomes large.

10-6


7/27

Oil PUMP UNIT

S te pp in g mo to rS te pping v alv e

P re ssu re r esponsevalve

S ub -p ump flow con tro l v alv eM ain p um p flo w co ntro l v alv e

O il p re ssu re sw itch

67U10X-507A stepping motor, stepping valve and pressure response valve are provided at the upper part of theoil pump unit.Inside, there are a vane-type main pump and sub-pump, as well as a flow control valve to regulatethe amount of discharge of these two pumps.The stepping valve controls the oil pressure of the sub-pump path by being driven by the geared step-ping motor. .The stepping motor adjusts according to the signal received from the control unit.The pressure response valve controls the oil pressure of the sub-pump path by opening or closingthe oil passage.

10-7


8/27

Flow Control Valve

Plug

Plug

S P r i ~ \ 1Sub-pump flow control valve

Main pump flow control valve

67U10X508Flow control valves for main pump and sub-pump maintain a flow of fluid at 5.5 liters/min (1.43 USgal/min, 1.21 Imp gal/min) for main pump, 2.0 liters/min (0.52 US gal/min, 0.44 Imp gal/min) for sub-pump to the control valve of the steering gear. It allows excessive fluid to return to the suction sideof the oil pump unit.

10-8


9/27

OperationAt low speed

Orifice

SpringAt high speed

Oil tank & pump!

OrificeSpring

67U10X-509

Main pump flow control1. At low speed:Oil discharged from the main pump flows into the rack housing through the flow control valve andcontrol valve.2. At high speed:When pump speed increases, the discharge pressure becomes higher, and a hydraulic pressuredifference develops with the orifice to the control valve as the boundary.The hydraulic pressure prior to passage through the orifice becomes higher than the hydraulic pres-sure after passage through the orifice.The hydraulic pressure prior to passage through the orifice is applied to the right side of the flowcontrol valve, and hydraulic pressure after passage through the orifice is applied to the left sideof the flow control valve.When the hydraulic pressure difference before and after the orifice becomes great, the flow controlvalve is forced to move to the left by depressing the spring. By this action, oil escapes to the suctionside of the pump.In this way, the flow of excess oil to the power steering gear control valve is prevented.

10-9


10/27

At low speed

T o re actio n fo rce ch amb er

Spring

F low con tr olvalve

At high speed

Orifice/

O il ta nk & pump

57G10X-503

Sub-pump flow control1. At low speed:Oil discharged from the sub-pump flows into the reaction force chamber through the orifice.2. At high speed:When the pump speed increases, the discharge pressure becomes higher. A hydraulic pressuredifference also develops with the orifice as the boundary.The hydraulic pressure prior to passage through the orifice becomes higher than the hydraulic pres-sure after passage through the orifice.The hydraulic pressure prior to passage through the orifice is applied to the lower side of the controlvalve. Hydraulic pressure after passage through the orifice is applied to the upper side of the con-trol valve.When the difference of hydraulic pressures before and after the orifice becomes great, the flow controlvalve is forced to move upward by depressing the spring, and discharged oil escapes to the suc-tion side of the pump.In this way, the flow of excess oil to the reaction force chamber is prevented.

10-10


11/27

-

Main pump flow control valve

F low con tr ol v alv e O il ta nk& pump

Spring

Sub-pump flow control valve

Spring

S te el b all

F low con tr ol v alv e

57G10X508Relief pressure controlMain pump flow control valve:If the wheels are held at the stops during steering, the pressure of the hydraulic system increasesinfinitely. The pressure of oil discharged from the oil pump is constantly pressing the steel ball. Whenthe pressure becomes greater than the set load of the relief spring, the pressure relief valve functions.Sub-pump flow control valve:If for some reason clogging occurs in the sub-pump path, the oil pressure in the sub-pump path rises.This high oil pressure pushes the steel ball, allowing the oil flow into the oil tank.Relief pressure:Main pump flow control valve: 7,848 kPa (80 kg/cm2, 1,137 psi)Sub-pump flow control valve: 3,924 kPa (40 kg/cm2, 569 psi)

10-11


12/27

Pressure Response Valve

67U10X-512

The pressure response valve is installed at the upper part of the oil pump unit.This valve, controlled by main pump pressure, functions to control the hydraulic pressure applied tothe reaction force chamber (at the lower part of the steering gear).The objectives of the installation of the pressure response valve are as described below:When the road resistance is small, such as on a snow-covered road, the required steering effort isreduced to let the driver sense that there is little road resistance. When the road resistance is high,the opposite is true.In other words, this valve compensates to give a more natural steering wheel response (such as youmight get with normal steering) in situations like an icy road, gravel road, etc.Changes of the hydraulic pressure (from the main pump) applied to the pressure response valve oc-cur in response to changes in the road surface resistance.When the road surface resistance is high, a greater force is required in order to turn the tires. Forthis reason, hydraulic pressure within the rack housing increases, and hydraulic pressure in the mainpump path becomes higher.On the other hand, when the road surface resistance is Iowa lesser force is required to turn the tires.In this situation, hydraulic pressure in the main pump path becomes lower.

10-12


13/27

OperationA

From sub-pump ---, .-- To reaction force chamber

From m ain pum p -_--.oJ

BtF--

67U10X-513

When hydraulic pressure in main pump path is high (illustration A)When the hydraulic pressure is high, the piston within the pressure response valve is pushed tothe right. As a result, the passage from the sub-pump to the oil tank closes.As a result, the hydraulic pressure within the reaction force chamber increases, and the steeringeffort of the steering wheel becomes greater.When hydraulic pressure in main pump path is low (illustration B)When the hydraulic pressure is low, the piston within the pressure response valve is pressed toleft by spring force, thus opening the passage from the reaction force chamber to the oil tank. Asa result, the hydraulic pressure within the reaction force chamber does not increase and the steer-ing effort of the steering wheel becomes less.

10-13


14/27

Pressure Switch

O il p ump d is cha rg e p re ss ure

Conta ct p oin t

The pressure switch detects the operational pressure of the power steering system. This switch sendsa signal to the idle-up system to increase engine speed when the pump discharge pressure is morethan 3,041 - 3,826 kPa (31 - 39 kg/cm2, 441 - 555 psi).

10-14

67U10X-514


15/27

ELECTRICAL SYSTEMControl Unit

IGN

Engine -speed s ignalS te pp in g mo to r

Rotor

o

67U10X-515The control unit detects the signals from the speed sensor, steering-angle sensor, and engine-speedsensor. Based upon these signals, the control unit regulates hydraulic pressure by rotating the step-ping motor. This rotation changes the opening degree of the stepping valve.The control unit also includes a fail-safe function. If, for any reason, no signal is sent from the vehiclespeed sensor, the signal from the engine speed sensor would be detected, and the hydraulic pres-sure would be regulated based upon that signal. Therefore, the appropriate steering wheel effort wouldbe provided.

Contr ol u nit

S pe ed s en so r

10-15


16/27

Self-diagnosis functionFault Condition Buzzer signal

Abnormal engine- The buzzer sounds when vehicle-speed signal is input but no en- I J 1 f I J 1 f l J U U I L J U lpeed signal gine speed signal is input (short circuit, broken wire, etc.)Abnormal stepping The buzzer sounds when the stepping motor does stepping notmotor signal respond to the signal from the control unit (broken wires or short I J l J U 1 J U J 1 I L l l J U l .circuit in coils or harnesses).Abnormal steering The buzzer sounds 60 seconds after broken wire or short circuit oc- J I f U U l J U l r u l n lensor signal curs to sensors or harnesses when vehicle speed is over 40 km/h(25 mph)Abnormal speed In case broken wires or short circuits occur to sensors or harnesses, I J U U U U W U Lensor signal the buzzer sounds 60 seconds after the engine speed signal of2,200 rpm continues for 18 seconds. IAbnormal control The buzzer sounds if the micro-computer malfunctions and cannotunit control the system.

And the buzzer sounds when there are circuit troubles other than J l J l r u u l I U r u Licro-com puter.Fail-safe function

I IFault Description I Power steering effectIMalfunction of Vehicle-speed signal is input but engine-speed signal is not I Normal controlenginespeed input

!ensor iMalfunction of No vehicle-speed signal but engine-speed signal Below Steering effort adjust to asvehicle-speed of more than 2,200 rpm received for over 18 80 km/h if vehicle speed 80 km/hsensor seconds (50 mph) (50 mph)

I Above Steering effort maintained80 km/h as if at vehilce speedI (50 mph) when failure occurred.

Malufunction of No steering angle signal is input when vehicle speed is over Vehicle speed control onlysteering-angle 40 km/h (25 mph).sensorMalfunction of Abnormal signal caused by damage, disconnection, short- Power supply to steppingstepping motor circuit , etc. of stepping motor circuit motor cancelled and steer-input ing effort adjusted to as ifvehicle speed 80 km/h

(50 mph)Malfunction of Control unit malfunction Power supply to steppingcontrol unit motor cancelled and steer-

ing effort adjusted to as ifvehicle speed 80 km/h(50 mph)

57G10X504

10-16


17/27

Steering control unit- control function

V eh ic le s pe ed co ntro l(])~:le n

(]) e n~ (]):l . . .e n 0-e n . . .(]) (]). . . . S tr aig ht a he ad po sitio n .00- E(]) c ao . s : :. .0 o- (])c: o0 . . . .:;::: .oc a c ::(]) 0a: :;::;oc a(])a:

Veh ic le s pe ed

S te erin g a ng le c on tro l

1 00 km /h ( 63mph)8 0km /h (SOmph)

40km/h (2Smph)

S te er in g a ng le

57G10X505Vehicle speed control function ...The control unit uses information from the vehicle speed sensor to regulate the turning angle of thestepping motor. This motor functions to control the hydraulic pressure applied to the reaction forcechamber according to the vehicle speed.Steering angle control function ...The control unit uses information from the steering angle sensor to regulate the turning angle of thestepping motor. This motor also functions to control hydraulic pressure applied to the reaction forcechamber according to the turning angle of the steering wheel.This control system functions when the vehicle speed is above 40 km/h (25 mph).

10-17


18/27

Stepping Motor

Coi l

S te pp in g mo to r S te pp in g mo to r

W in du p s prin g

Rotor

PinionRotor

P erm a ne nt m a gn et

67U10X519

The stepping motor is composed of a coil, a stator, a wind-up spring, and a rotor composed of a per-manent magnet. This motor is located at the upper part of the oil pump unit.The coil is 4 layers of coiled wire and is separated into two (upper and lower) parts within the steppingmotor.The rotor is unified with the shaft and has 12 N poles and 12 S poles. At one end of the shaft is apinion which drives the stepping valve. At the other end is the wind-up spring.If power is lost to the stepping motor, the wind-up spring functions to close the oil passage by rotatingthe stepping valve.

10-18


19/27

Operation

o

Electrode of rotor

(2)(1)

Electrode of stators

(4)3)

1.When there is power to coils (A) and (C) in the circuit, the rotor stops in the condition shown in illus-tration (1).2. Then, when the power to coil (A) stops and power is provided to coils (8) and (C), the poles of thelower stator of the upper part change from S to N. The result is that the S poles are attracted andthe rotor turns in the left direction shown in illustration (2).3. When (in the condition 2. above) power to coil (C) stops and power is provided to coils (8) and(0), the poles of the uppersta.tgrofthelOW$pspt:lrt change from N to S. The result is that the rotorturns further to the left as in illustration (3).4. When (in the condition 3. above) power to coil (8) stops and power is provided to coils (A) and(0), the poles of theloW~I'$tatorQfth$JoW$tipa,rt change from N to S. The result is that the rotorturns further to the left as in illustration (4).5 As described in 1. to 4. above, the rotor rotates as a result of the switching of the power supplyin sequence to coils (A) to (0). The turning angle for each time is 7.5.

10-19RX-l TRAINING MANUAL (3122)Rl5.\Il$qJ,a.N~~

67U10X-520


20/27

Stepping Valve

GearsStepping valve

Stepping motor

From sub-pump

When vehicle speed is low When vehicle speed is high

Section A-A Section A-A

67U10X521

The stepping valve is driven, via two gears, by the stepping motor. The turning angle of the steppingmotor is reduced 1Ii 0 by the gears, and this is transmitted to the stepping valve.The stepping valve adjusts the sub-pump system hydraulic-circuit pressure. This adjusted pressureis led to the reaction force chamber.

10-20


21/27

Angle Sensor

Angle sensor

3600 1800 00 1800Left turning Steering angle

3600Right turning

57G10X506

The angle sensor is installed on the steering shaft and sends the steering wheel turning angle signalto the control unit.The angle sensor has shared functions:1. Cancellation of the turn-signal lever2. Auto-adjusting suspensionNoteAlign the arrow heads when installing this sensor.

10-21


22/27

MANUAL STEERING CAPABILITY

In put sha ft Pinion

Tor sion barS ection A -A

67U10X-523

Even if there is no pressure because the engine is stopped or in the event of a pump malfunction,oil leakage, or any other reason, manual steering will still be possible because the input shaft is incontact with the pinion.

10-22


23/27

OPERATION

z : : : : z : : : : z : : : : : . : : : : H ig h p re ss ure o il P re s su re r es pon s e v alv e

Sub -pump

Re ac tio n fo rc e chamber

Re ac tio n fo rc echamber

57G10X-507

When turning (to the left) at low speed...For this power steering system, the effort required to turn the steering wheel has been reduced inorder to make steering easier at times when the steering resistance is great, such as when movingthe vehicle into a garage, etc.1. When the steering wheel is turned to the left, the rack bar does not move immediately.2. This is because there is road resistance transmitted from the tires, and also because the pinion isengaged with rack bar and does not follow the steering wheel angle.3. Therefore, only the input shaft is rotated and the torsion rod directly connected to the input shaftis distorted.4. At this time, a phase shift .occurs between the input shaft and the valve sleeve.5. Meanwhile, high-pressure oil flows into the right cylinder via the valve sleeve port.6. Consequently, the rack bar is moved to the left, the wheels are turned to the left via the knuckle arm.7. On the other hand, oil in the left cylinder is returned back to the oil tank.8. The pressure response valve closes the sub-pump path due to rising oil pressure in the steeringhousing.9. Because the stepping motor has fully opened the stepping valve, the hydraulic pressure in the reactionforce chamber of the steering gear does not increases. As a result, the steering operation becomeslighter.

10-23


24/27

Reac tio n fo rc e chambe r

: : : z : : : :: z : : : : . :: : : : z w H ig h p re ss ure o il Pressure response valve

Sub-pump

67U10X525

During straight-ahead driving at medium or high speed ...In order to further improve handling stability at medium and high speeds while driving straight, steer-ing wheel operation becomes heavier.1. As a result of the vehicle-speed signal from the control unit, the stepping motor rotates the steppingvalve, causing the oil passage to become more constricted. As a result hydraulic pressure in thepassage from the sub-pump increases.2. This causes the hydraulic pressure in the reaction force chamber of the steering gear to increase.3. Because the four pistons in the reaction force chamber push against the input shaft of the steeringshaft, operation of the steering wheel becomes heavy.

10-24


25/27

::::.:::::::::::::.:::igh pressure oil Pressure response valve

Reaction force chamber

Sub-pump Stepping valve

M force chamber

When turning (to the left) at medium or high speed...During turning (to the left) at medium or high speed, the flow of oil is the same as during low-speedturning, except that the operation of the steering wheel ismade heavier in order to prevent oversteering.1. As a result of the vehicle-speed signal and steering-angle signal from the control unit, the steppingmotor rotates the stepping valve, causing the oil passage to become more constricted. As a result,the hydraulic pressure in the passage from the sub-pump increases.2. This causes the hydraulic pressure in the reaction force chamber of the steering gear to increase.3. In addition, the hydraulic pressure in the passage to the main pump increases as a result of theincrease of hydraulic pressure in the right cylinder of the steering housing during turning.4. As a result, the hydraulic pressure in the reaction force chamber increases even further. Also, be-cause the four pistons in the reaction force chamber push against the input shaft of the steeringshaft, the operation of the steering wheel becomes heavy.

10-25

67U10X-526


26/27

MANUAL STEERINGSTEERING GEAR

Pinion

Tie rodR ack bar

67U10X-527The steering gear is a constant-gear-ratio type. The pinion gear is supported by the two upper andlower ball bearings.The method used for support of the rack bar has been changed from the system in which supportwas only by the support yoke (the method used for the 626 and 323) to a system in which supportis by the support yoke and ball bearinqs.

10-26


27/27

Support of Rack Bar

Ba ll bea ri ng

S upport y ok eSpr ing

S uppo rt y ok e

!~ IBa ll b e ar ing

P re vio us ty pe ra ck a nd p in io n

The method for support of the rack bar has been changed.Previous method ...The entire part from the center of the rack bar (with the vehicle in the straight-ahead condition) to theend of the rack bar (with the vehicle being turned) was supported only by the support yoke.New method ...The center part of the rack bar is supported by the support yoke (in the same way as the previousmethod). but the end of the rack bar is supported by ball bearings.Advantages of the new method ...1. Improvement of transmission efficiency of steering effort. because sliding contact has changed torolling contact.2. Improvement of rack bar wear resistance. because twisting of the rack bar as it moves is eliminated.

67U10X528

10. steering system

Documents