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Tire Pressure Monitoring

Tire Pressure Monitoring

Systems

Systems

Informal Document No.20 (53rdGRRF, 3-7 February 2003, Agenda Item 8)

1.

1.

Background

Background

2. System Classification

2. System Classification

3. Direct TPMS

3. Direct TPMS

3

3

-

-

1. Typical Example of the Direct Type

1. Typical Example of the Direct Type

3

3

-

-

2. New Development of Direct TPMS

2. New Development of Direct TPMS

4. Indirect TPMS

4. Indirect TPMS

4

4

-

-

1. Typical Example of the Indirect Type

1. Typical Example of the Indirect Type

4

4

-

-

2. Detection Methods of Indirect TPMS

2. Detection Methods of Indirect TPMS

4

4

-

-

3. Variety of Indirect TPMS

3. Variety of Indirect TPMS

4

4

-

-

4. New Development of Indirect TPMS

4. New Development of Indirect TPMS

4

4

-

-

5. Future Development of Indirect TPMS

5. Future Development of Indirect TPMS

5. Summary of System Classification

5. Summary of System Classification

6. Summary

(2)

1.

1. Background

Background

1) TPMS of conventional tires recently came into use on vehicles

mainly as a convenience device for drivers.

2) On the other hand, a

FMVSS 138

rule on TPMS was published

on June 5, 2002 and offers manufacturers 2 options:

- Option 1: TPMS to warn within 10 minutes after the inflation pressure

in one or more (up to four) of the vehicle’s tires, becomes

equal to or

less than 25%

below the recommended pressure.

- Option 2: TPMS to warn within 10 minutes after the inflation pressure

in one of the vehicle tires falls to equal or be

less than 30%

below the vehicle manufacturer’s recommended pressure.

3) By

March 1, 2005

reconsideration will be given to establishing the

performance requirement for the period beginning

November 1, 2006

.

4) There is a discussion concerning TPMS also in Europe.

We believe it is helpful to present an understanding of the

TPMS technologies of both

direct type and

indirect types

.

Direct TPMS Indirect TPMS

- High cost

- Sensor batteries have to be changed periodically.

- Using ABS sensors means only a small on-cost.

Detection Accuracy

Convenience Cost

- Depends on tire characteristics.

▲Tire pressure on each wheel can be displayed.

▼Additional sensors needed with snow tires (user’s on-cost)

▼Wheel type is restricted by integrated sensor/valve

2.

2.

System Classification

System Classification

- Absolute pressure measurement - Relative tire pressure - Absolute pressure (estimated) - More accurate method.

Reliability - High reliability because there is

no additional hardware.

▼In some cases, it may be difficult to guarantee the TPMS

performance on all replacement tires

(3)

3.

3.

Direct TPMS

Direct TPMS

ECU Warning Lamp Instrument Panel Pressure display Tire Rim Sensor / Transmitter TRANSMITTER Pressure and Temperature Sensors + Signal conditioning

Battery Tire Valve

3

3-

-1.

1.

Typical Example of the Direct Type

Typical Example of the Direct Type

Direct type: a system using the actual measurement

of tire pressure.

Sensor & Transmitter

(4)

4 Antenna System

1 Antenna System

3

3-

-2.

2.

New Development of Direct TPMS

New Development of Direct TPMS

Sensor / Transmitter

Antenna

Warning Lamp

Antenna &Receiver / ECU Sensor / Transmitter Warning Lamp

For cost reduction, the number of the antenna is reduced

from 4 to 1.

Receiver / ECU

COST REDUCTION

4.

(5)

Warning Lamp

Wheel Speed Sensor Toothed Rotor TPMS Logic

Tire

Instrument Panel Lower Panel

4

4-

-1.

1.

Typical Example of the Indirect Type

Typical Example of the Indirect Type

Set Switch

Indirect type: a system using the wheel speed signals

from the ABS.

ABS ECU

Relative detection Only one wheel deflation can be detected.

4

4-

-2.

2.

Detection Methods of Indirect TPMS

Detection Methods of Indirect TPMS

α=VFR VRL VFL VRR VRR VFR VRL VFL

Rolling Radius Method

Rolling Radius Method

(Conventional)

(Conventional)

R

R

(6)

System

A

A Direct DetectDirect Detect

Detection

speed range 1 wheel deflation:15 to 120km/h

1 wheel deflation: 15 to 120km/h Up to 4 wheels deflation: 15 to 100km/h Up to 4 wheels deflation: 0 to 250km/h Deviation of accuracy (approx.) ±10% at best ±10% at best ±5%

Detection Time 2 to 10min 2 to 10min 15sec to 1min

Characteristic Input signal Antenna Air pressure sensor Receiver Wheels

detection In combination Independent Independent

r

r’

Frequency A m pl it u d e of th e w h eel s p eed Pressure goes down ← ←← ←

4

4-

-3.

3.

Variety of Indirect TPMS

Variety of Indirect TPMS

Wheel speeds Wheel speeds Tire pressure

r

r’

Rolling radius Rolling radius + Resonance freq

B

B

Indirect Detect Indirect Detect

System Direct DetectDirect Detect

Detection speed range Up to 3 wheels deflation: 15 to 250km/h Up to 4 wheels deflation: 15 to 100km/h Up to 4 wheels deflation: 0 to 250km/h

Detection Time 2 to 5min

Characteristic Input signal Antenna Air Pressure sensor Receiver Wheels

detection Independent Independent

r

r’

Frequency A m pl it u d e of th e w h eel s p eed Pressure goes down ← ←← ←

4

4-

-3.

3.

Variety of Indirect TPMS

Variety of Indirect TPMS

continuedcontinued

Wheel speeds +

Stability Control System signals Tire pressure

Rolling radius + Resonance freq

Up to 3 wheels: 15 to 250km/h

2 to 5min In combination Wheel speeds +

Stability Control System signals

r

r’

Rolling radius C C DD Indirect Detect Indirect Detect Deviation of accuracy (approx.) ±10% at worst ±10% at worst ±5% 15sec to 1min.
(7)

4

4-

-4.

4.

New Development of Indirect TPMS

New Development of Indirect TPMS

using resonance frequency

using resonance frequency

Up to 4 tires with pressure deficiencies can be detected by the resonance frequency method.

Torsion spring constant is reduced with deflation of tire and consequently the resonance frequency drops

1)

1)

Resonance Frequency Method

Resonance Frequency Method

Independent and absolute detection

Even natural leak deflation of any tire(s) can be detected

Frequency A m pl it ude of w h e e l sp eed Standard Pressure Low Pressure

Tire resonance phenomenon might be not measurable in the situations below.

- high speed - low aspect ratio tires

4

4-

-4.

4.

New Development of Indirect TPMS

New Development of Indirect TPMS

using resonance frequency

using resonance frequency

3)

3)

Concerns

Concerns

2)

2)

Actual vehicle data

Actual vehicle data

Wheel speed signal

time w h eel s pee d 100 200 300

Tire Pressure(kPa)

28 30 32 34 36 38 40 0 0 0 0 10101010 202020203030 403030404040 505050506060 706060707070 Frequency (Hz) 400 400 400 400 300 300 300 300 200 200200 200 100 100 100 100 0 0 0 0 200kPa 100kPa ■ Gain F requ ency ( Hz ) Frequency analysis

(8)

<Concern>

It is difficult to judge whether a difference of wheel speed results from low pressure or from slipping under acceleration.

Development

Engine torque information distinguishes low tire pressure from wheel slip caused by acceleration.

<Concern>

It is difficult to judge, whether a difference of wheel speed results from low pressure or is being caused by cornering.

Development

Cornering information used in Stability Control Systems distinguishes low tire pressure from cornering.

4

4-

-4.

4.

New Developments of Indirect TPMS

New Developments of Indirect TPMS

using additional signals

using additional signals

クルーガー 中央道 2名乗車 40Nm<Te<70Nmのデータ採用 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 0 600 1200 1800 2400 3000 time(sec) st210 ra160 クルーガー 中央道 2名乗車 トルク選別なし -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 0 600 1200 1800 2400 3000 time(sec) st210 ra160 No engine torque signal used

Engine torque signal used

By using Stability Control System’s signals, up to 3 deflated tires can be detected. 1)

1) Two Two ‘‘low tireslow tires’’on the same axle on the same axle (Front or Rear)(Front or Rear)

2)

2)Two Two ‘‘low tireslow tires’’on the same side on the same side (Right or Left)(Right or Left)

Ro lli n g r a d iu s ch a n g e Ro lli n g r a d iu s ch a n g e

4

4-

-5.

5.

Future Development of Indirect TPMS

Future Development of Indirect TPMS

BS POTENZA RE01 CN T-Contact CH95 DL LEMANS LM702 GY EAGLE LS300 ML pilot SPORT OT DIGNEO PL P-ZERO NERO TY TRAMPIO Vimode YH DNA dB

The effective rolling radius is altered as the tire pressure changes. The value of the change depends on vehicle speed, load and tire variation. 1)

1)Tire characteristic for indirect TPMSTire characteristic for indirect TPMS Load=290kg -0.01 -0.009 -0.008 -0.007 -0.006 -0.005 -0.004 -0.003 -0.002 -0.001 0 100 110 120 130 140 150 160 170 180 190 200 210 220 230 Pressure (kPa) R o lli ng radi u s ch ange 30km/h 100km/h

(9)

It is possible to make progress in the performance of indirect TPMS by developing in future, the combination of TPMS and tires.

Identification of

Tire

characteristics

Standardization

of tire radius change

Tire Development Tire Development TPMS Logic TPMS Logic Development Development Use of Stability Control Signals Resonance frequency method

To ensure operation with all replacement tires

To ensure operation with all replacement tires

To inform the driver that TPMS and tires are matched

To inform the driver that

TPMS and tires are matched detection accuracy To improve

To improve detection accuracy

4

4-

-5.

5.

Future Development of Indirect TPMS

Future Development of Indirect TPMS

continuedcontinued

2)

2)To improve the performance of indirect TPMS To improve the performance of indirect TPMS

Future

Direct TPMS Indirect TPMS

- High cost

- Sensor batteries have to be changed periodically.

- Using ABS sensors means only a small on-cost.

Detection Accuracy

Convenience Cost

- Depends on tire characteristics.

▲Tire pressure on each wheel can be displayed.

▼Additional sensors needed with snow tires (user’s on-cost)

▼Wheel type is restricted by integrated sensor/valve

5.

5.

Summary of System Classification

Summary of System Classification

- Absolute pressure measurement - Relative tire pressure - Absolute pressure (estimated) - More accurate method.

Reliability - High reliability because there is

no additional hardware.

▼In some cases,it may be difficult to guarantee the TPMS performance on all replacement tires

(10)

1)

Both direct and indirect systems are able to contribute to

the real world safety with regard to tire deflation

- Independent wheel detection

- Tire pressure detection level

2)

For

direct TPMS

the cost will become lower in future.

For

indirect TPMS

it is possible to make progress with

the performance in future, by developing TPMS and

tires in combination.

6.

References

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