Evaluation Of 2 Motor Hybrid Architectures

Evaluation of 2-Motor

Hybrid Architectures

James PotterZF Special Driveline Technology

Hybrid Systems Contents

� Single Planetary Gear Set Systems

� Input Summing Hybrid

� Output Split Hybrid

�Dual Planetary Gear Set Systems

� Compound Split Hybrid

� Triple Planetary Gear Set Systems

� Compound Split Hybrid

� Two-Mode Hybrid

MG1MG2

Input Summing Hybrid System

� Hybrid Vehicle Applications� Ford Escape

� Toyota Prius Synergy Drive

� Features� Electric CVT – Single planetary transmission

� Generator can directly power the traction motor

� No torque converter → E-CVT launch

� PowerSplit Myth

� The PowerSplit system is advertized by both Toyota and Ford as a combination of both the parallel and series hybrid. However, even though there are operational points where the generator can absorb 100% of the engine power transferred into the system, the engine remains mechanically coupled to the drive axle. This pseudo-series hybrid operational point is unsustainable due to the variance in efficiency between the mechanical and electrical paths, therefore, the system would vary between charge depleting, charge neutral and charge increasing states.

� The PowerSplit argument can be applied to any two or more motor system, as long as one of the motors (generators) is attached to a different system node, relative to the traction motor, allowing one motor to act as a generator while the other motor provides motoring/tractive torque.

Input Summing Hybrid SystemMotor Power Ratio

PowerSplit Hybrid System

-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.02.53.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Transmission Torque Ratio

Po

wer

Ra

tio

, P M

oto

r/P

En

gin

e

PM1/Peng

PM2/Peng

Cross-Over Point

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

Ratio: Sun/Ring Gear Teeth

Co

up

lin

g P

oin

t

Prius & Escape

Coupling Point

Expected overall ratio spread ≈0.7:1 15:1

( )1

11 1RingSun

Ring

Engine

MG

NNRatio

N

P

P

+−=

Input Summing Hybrid SystemMotor Speed Gains

-25

-20

-15

-10

-5

0

5

10

15

0246810121416

Transmission Torque Ratio

Moto

r Speed G

ain

MG1

MG2

MG1 limits speed when;

Ratio < 0.4 and

Ratio > 4.0

Note: Assumes a maximum motor speed of 15,000 rpm

Prius & Escape

Output Split Hybrid System

MG1 MG2

� Hybrid Vehicle Applications

� Chevrolet Volt

� Features

� Motor integration ease

� Poor launch drivability

� Not practical at high torque ratios

The Volt avoids the launch issues by using a

brake to lock the ring gear during low speed

operation.

Output Split Hybrid SystemMotor Power Ratio

Output Split Hybrid System

-5

-3

-1

1

3

5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Ratio

Po

wer

Rati

o, P M

oto

r/P

En

gin

e

PM1/Peng

PM2/Peng

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Planetary Ratio, NSun/NRing

Co

up

lin

g P

oin

t

Coupling Point

Expected overall ratio spread ≈0.7:1 15:1

+

⋅−=

)(12

RingSun

Ring

Engine

M

NN

RatioN

Power

Power

Output Split Hybrid SystemMotor Speed Gains

-5

0

5

10

15

20

25

30

35

0246810121416

Transmission Torque Ratio

Moto

r Speed G

ain

MG1

MG2

MG2 limits speed when the torque ratio is less than 0.6

Compound Split Hybrid System

� Hybrid Vehicle Applications

� Lexus HS250h & RX400h

� Toyota Camry & Highlander

� Features

� Similar to the Prius Input

Summing system. The

traction motor operates

through a planetary rather

than a fixed gear set.

� Increased torque range of low

motor power requirements

� No Torque Converter → E-

CVT launch

� Efficient power ratios

� Minimal speed limitations

MG1MG2

MG1MG2

RX400h & Highlander

HS250h & Camry

Compound Split Hybrid SystemMotor Power Ratio

Compound Split Hybrid Systems

-8

-6

-4

-2

0

2

4

6

8

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Po

wer R

ati

o,

P M

oto

r/P

En

gin

e

PM1/Peng

PM2/Peng

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Planetary Ratio, NSun/NRing

Coupling P

oin

t

Expected overall ratio spread ≈0.7:1 15:1

Coupling Point

( )

+⋅−=

1

11 1RingSun

Ring

Engine

MG

NNRatio

N

P

P

Compound Split Hybrid SystemMotor Speed Gains

HS250h & Camry

-25

-20

-15

-10

-5

0

5

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Mo

tor S

peed

Ga

in

MG1

MG2

MG2 limits speed when the torque ratio is less than 0.6:1

Compound Split Hybrid SystemMotor Speed Gains

-30

-20

-10

0

10

20

30

40

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Moto

r S

peed G

ain

MG1

MG2

MG2 limits speed when the torque ratio is less than 1:1

RX400h & Highlander

Compound Split Hybrid System

MG1 MG2

CBLowCBHigh

To engage the low gear range, Toyota opens the conventional

planetary gearset’s brake 1 and locks brake 2, resulting in a

reduction gear ratio of 3.900. For high gear, brake 1 is locked

and brake two is open, with a reduction gear ratio of 1.900.

(The Rx 400h uses a fixed reduction ratio of 2.478.) The

result is that the motor in the 450h acts as a single high-

torque and high-speed motor. Motor size can then be reduced

enough to fit the transmission in the GS450h floor pan tunnel

� Hybrid Vehicle Applications

� Lexus GS450h, LS600h

� Features

� Low range is similar to the

RX400h system

� No Torque Converter → E-

CVT launch

� Increased complexity, with

added efficiency over Input

and other compound split

systems

� Efficient power ratios

� Reduction Ratios

• Low Gear 3.9:1

• High Gear 1.9:1

Compound Split Hybrid SystemMotor Power Ratio – Low Range

GS450h & LS600h in Low Range

-8

-6

-4

-2

0

2

4

6

8

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Pow

er R

atio, P

Moto

r/P

Engin

e

PM1/Peng

PM2/Peng

( )1

11 1RingSun

Ring

Engine

MG

NNRatio

N

P

P

+−=

Coupling Point

Expected overall ratio spread ≈

0.7:1

15:1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Planetary Ratio: NSun/NRing

Coupling P

oin

t

1.9:1 3.9:1Low Range

Compound Split Hybrid SystemMotor Power Ratio – High Range

GS450h & LS600h in High Range

-6

-4

-2

0

2

4

6

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Po

wer

Ra

tio

, P

Mo

tor/P

En

gin

e

PM1/Peng

PM2/Peng

−=

2

32 11

Ring

Ring

Engine

MG

N

N

RatioP

P

1.9:10.7:1

High Range

Compound Split Hybrid SystemClutch Slip Speed Gain

0

1

10

100

03691215

Transmission Torque Ratio

Clu

tch

Sli

p S

pee

d G

ain

CBLow

CBHigh

0.7

GS450h & LS600h

Engineω⋅142.2

Compound Split Hybrid SystemMotor Speed Gains

-20

-15

-10

-5

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Mo

tor

Sp

eed

Gain

MG1

MG2-Low

MG2-High

MG2 limits speed in;

- low range when the torque ratio is less than 1.0

- high range when the torque ratio is less than 0.5

GS450h & LS600h

xx4th Gear

xx3rd Gear

xEVT2

xx2nd Gear

xx1st Gear

xEVT1

CB4

C234, EVT2

C13

CB12R,

EVT1

Note: Gear-to-gear shifts are possible, however, the typical

shift sequence is to go from gear-to-EVT, then to the next gear.

Second gear is the hand-off from EVT1 to EVT2.

C234, EVT2

MG2MG1

CB4

C13

CB12R, EVT1

Two-Mode Hybrid System� Hybrid Vehicle Applications

� Allison EV Drive

� BMW X6

� Chrysler Aspen, Durango

� GM Tahoe, Yukon

� Mercedes ML450

� Features

� Electric & Mechanical Oil Pump

� Damper (GM only)

� No Torque Converter → E-CVT1 launch

� Synchronized Shifting

� Clutch-to-Clutch Powershift (BMW only)

� Race Start (BMW & Mercedes)

� Significant motor power requirements at high torque ratios

� High parasitic losses in all ratios, except at or near 3rd gear (Direct ratio)

Two-Mode Hybrid SystemE-CVT Low Range Motor Power Ratio

E-CVT Low Range (Mode 1)

-150

-100

-50

0

50

100

150

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Pow

er R

ati

o, P

Mo

tor/P

En

gin

e

MG1

MG2

Mode 1 Coupling Point Sensitivity

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Planetary Sun-to-Ring Gear Ratio

Coupling P

oin

t

NSun1/NRing1

NSun2/NRing2

NSun3/NRing3

Coupling Point

Expected overall ratio spread ≈

1.8:1

15:1

( )

( )

( )

++

−

−⋅=

K

NN

NN

Ratio

N

NNN

CCRatio

Power

Power RS

SRS

SRSOut

MG 33

321

121

211

EVT1

Two-Mode Hybrid SystemE-CVT High Range Motor Power Ratio

E-CVT High Range (Mode 2)

-6

-4

-2

0

2

4

6

0 2 4 6 8 10 12 14 16

Transmission Torque Ratio

Po

wer

Rati

o, P

Mo

tor/P

En

gin

e

MG1

MG2

Mode 2 Coupling Sensitivity

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Planetary Ratio, Sun-to-Ring Gear

Coupling P

oin

t NSun1/NRing1

NSun2/NRing2

NSun3/NRing3

NSun1/NRing1

NSun2/NRing2

NSun3/NRing3

Coupling Points

0.7:1

( ) ( )

( )

+

+−⋅⋅

−−=

KN

KNRatioK

Ratio

NN

N

N

P

P

Ring

SunSunRing

Sun

Ring

In

MG

2

112

1

22

Node 1

Node 2

1.8:1

Released Clutch Slip Speeds

0

1

2

3

4

5

6

7

8

EVT-1 EVT-1 1st Gear EVT-1 2nd Gear EVT-1 3rd Gear EVT-2 EVT-2 EVT-2 4th Gear EVT-2

Transmission Mode & Gear

Clu

tch S

lip

Sp

eed

Gain

0

2

4

6

8

10

12

14

16

Tra

nsm

issi

on T

orq

ue

Rati

o

CB12R

C13

CB234

CB4

Ratio

Engine Speed

Two-Mode Hybrid SystemClutch Slip Speed Gains

Torque Ratio

Two-Mode Hybrid SystemMotor Speed Gains

Motor Speeds Across Torque Range

-10

-5

0

5

10

15

20

EVT-1 1st Gear 2nd Gear EVT-2 EVT-1 3rd Gear EVT-2 4th Gear EVT-2

E-CVT Mode & Gear Ratio

Tra

nsm

issi

on

Torq

ue

Rati

o

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Moto

r S

pee

d G

ain

Ratio

MG1

MG2

Engine Speed

~ Motor Speed Limit

The EVT1 to EVT2 hand-off occurs at 2nd

gear, therefore, this EVT1 ratio will not

occur.