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VGRS (Variable Gear Ratio Steering) System General The steering gear ratio will be changed in accordance with the vehicle speed
a

Vehicle speed low

a+

Vehicle speed high

a

Low Ratio (Quick)

High Ratio (Slow)

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VGRS System System Diagram (Main Signal)

Engine ECU (ECM)
Engine Speed

Steering Angle Sensor

Steering Angle

Control Signal

VGRS Actuator
Lock Mechanism Rotational Angle Sensor

Steering Wheel Neutral Position Vehicle Speed Engine Speed Etc.

Skid Control ECU

VGRS Actuator Operating Angle

VGRS ECU

VGRS Actuator Actual Operating Angle

Control ECU

Wheel Angle (Steering Angle + VGRS Suspension Actuator Operating Angle)

Temp. Sensor

VGRS Warning Light DLC3

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Combination Meter

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VGRS System Component Location

VGRS Warning Light Steering Angle Sensor

VGRS Actuator
VGRS ECU

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VGRS System Steering Gear Ratio

Comparison of the gear ratio
Steering Gear Ratio
Slow

Gear Ratio : 19.8 Lock to Lock : 3.8

VGRS system not operates

Gear Ratio : 17.3 Lock to Lock : 3.3

Quick

Gear Ratio : 18.0 Lock to Lock : 3.5

: 03 Model with VGRS System : 02 Model

Gear Ratio : 12.4 Lock to Lock : 2.4

Vehicle Speed

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VGRS System Normal Operation

Steering Angle Sensor

VGRS Actuator Motor Gear

Control Signal (Target Operating Angle) Actuator Operating Angle

VGRS ECU
Map Calculate actuator target operating angle

Steering Angle Skid Control ECU Vehicle Speed

Vehicle Speed

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VGRS System Cooperative Control of Brake Control System For example, in order to enable quicker steering when braking suddenly (VSC active)
Drives steering effort
Effectiveness of Cooperative Control of Brake Control System Slippery Surface

Braking

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VGRS System VGRS Actuator

Steering Wheel
Rubber Coupling

VGRS Actuator

Spiral Cable Lock Mechanism DC Motor Reduction Mechanism

Rack & Pinion

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VGRS System Spiral Cable Flexible flat cable is used

Control Signal

VGRS ECU

Power Source Motor

Rotational angle and rotational direction of the DC motor

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VGRS System Lock Mechanism This mechanism locks the motor shaft if the system fails
A A Cross Section
Lock Holder (Motor Shaft) Solenoid

A
Motor Shaft Lock Lever (Housing)

Return Spring

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VGRS System Lock Mechanism

Solenoid ON Solenoid OFF

Unlock
System is Normal

Lock
Engine is stopped System inoperative (Fail Safe)

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VGRS System Motor A compact high-output low-noise DC brush-less stepper motor

Motor Shaft DC Motor

Magnet
Coil

Reduction Mechanism

Rotational Angle sensor (Three Hole ICs) is included in the motor

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VGRS System Reduction Mechanism The strain wave gearing type reduction mechanism is used
Steering Wheel Motor

Stator Gear Wave Generator

Stator Gear

Flexible Gear
Flexible Gear Driven Gear

Driven Gear Output Shaft

Wave Generator

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VGRS System Reduction Mechanism Components

Stator Gear (input) Flexible Gear Driven Gear (output) Wave Generator (input)

Steering Wheel

Rack & Pinion

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VGRS System Reduction Mechanism Components

Stator Gear (input ) Flexible Gear Driven Gear (output) Wave Generator (input)

Teeth Coupled to the housing of the VGRS actuator (Steering wheel input) Number of teeth: 102

Teeth Flexible metal body Gear teeth are meshed with the inside of both stator gear and driven gear Number of teeth: 100

Teeth Coupled to the output shaft of the VGRS actuator (Steering gear output) Number of teeth: 100 Consists an ovalshaped cam and bearing rotated by the DC motor -

The difference of number of teeth

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VGRS System Reduction Mechanism Construction

Stator Gear Flexible Gear Wave Generator

Meshing

Not meshing View from stator gear side (Steering wheel side)
Ball Bearing is between flexible gear and wave generator

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VGRS System Reduction Mechanism Operation of strain wave gearing

The flexible gear is flexed into an oval shape by wave generator The teeth of flexible gear meshes with the teeth of stator gear and driven gear
The wave generator rotates

The meshed area of the flexible gear and stator gear and driven gear moves in sequence
The wave generator makes one turn

View from stator gear side The driven gear and flexible gear have the same (stator gear fixed) number of teeth, so their rotational movements are
identical

The flexible gear moves by 2 teeth because the flexible gear has 2 fewer teeth than the stator gear

The driven gear moves by 2 teeth (=Actuator output)

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VGRS System Reduction Mechanism

Motor Shaft

Flexible Gear

Wave Generator

Stator Gear

View from stator gear side

Ball Bearing (Between flexible gear and wave generator)

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VGRS System Reduction Mechanism Operation of strain wave gearing

102 teeth The wave generator makes one turn

Moves 2 teeth

Click Picture

100 teeth

Every time motor rotates, flexible gear and stator gear shifts by two teeth

The shift is used as actuator output

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VGRS System Reduction Mechanism Gear ratio

102 teeth Wave generator (motor) rotates 50 times

Flexible gear rotates one time

100 teeth

Gear Ratio

50
Motor

1
Flexible Gear

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VGRS System Operation (Left turn when the vehicle speed is low) The motor rotates the clockwise and adds steering angle
Steering wheel 1 rev.

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VGRS System Operation (Left turn when the vehicle speed is mid.) The motor does not operate and no assist
Motor 0 rev. / Steering wheel 1 rev.

Click Picture

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VGRS System Operation (Left turn when the vehicle speed is high) The motor rotates the counterclockwise and reduces steering angle
Steering wheel 1 rev.

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VGRS System VGRS Warning Light VGRS warning light comes ON when the system has a malfunction

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VGRS System VGRS ECU (Fail-safe 1)

Malfunction Parts Fail-safe Operation VGRS Warning Light DTC Memory Condition

Steering Angle Sensor Malfunction DC Motor Malfunction VGRS ECU Malfunction DC Motor Circuit Malfunction Lock Mechanism Circuit Malfunction Vehicle Speed Signal Malfunction Skid Control ECU Communication Signal Malfunction System stop (Lock mechanism)

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VGRS System VGRS ECU (Fail-safe 2)

Malfunction Parts Fail-safe Operation
VGRS Warning Light DTC Memory Condition

DC Motor Overheat (approx. 100C *1) VGRS ECU Overheat (approx. 100C) PIG Power Source Drop Voltage Malfunction VGRS Actuator Malfunction *2

First, the control is stopped; then, the control resume after the system resumes its normal operation

*1: The temperature presumed from the motor drive current *2: Specific examples 1) When the steering operated while the output of the power steering pump is unstable, immediately after starting a cold engine 2) If the driver attempts to operate the steering wheel further after is has been steered entirely to the rock end

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VGRS System Diagnosis DTCs 1/3

DTCs C1511 / 11 C1515 / 15 C1516 / 16 C1521 / 21 C1522 / 22 C1527 / 27 C1528 / 28 C1531 / 31 C1532 / 32 C1533 / 33 VGRS ECU Malfunction VGRS Actuator Malfunction Detection item Steering Angle Sensor Malfunction VGRS Actuator Neutral Position undone

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VGRS System Diagnosis DTCs 2/3

DTCs C1541 / 41 C1549 / 49 C1551 / 51 C1552 / 52 C1554 / 54 C1555 / 55 Detection item Skid Control System Malfunction Skid Control System Communication Malfunction IG Power Source Voltage Malfunction DC Motor Power Source Voltage Malfunction Power Source Relay failure Predriver Source Relay Failure

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VGRS System Diagnosis DTCs 3/3

DTCs C1561 / 61 C1567 / 67 C1568 / 68 C1569 / 69 Detection item Lock Mechanism Malfunction Lock Mechanism Insertion Malfunction Lock Holder Deviation Detection Lock Mechanism Release Incomplete

Test Mode

C1571
C1572 C1575 C1576

Vehicle Speed Sensor Malfunction (FLO)

Vehicle Speed Sensor Malfunction (FRO) Steering Angle Sensor Malfunction DC Motor Revolution Angle Sensor Malfunction

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VGRS System Initialize Initialize VGRS ECU, after exchange VGRS ECU or VGRS actuator

Remove Install

Remove Install

Initialize VGRS ECU

When the VGRS ECU initialize is undone, the DTC (C1515 or C1516) is memorized