Traction Drive Speed Reducer for high speed traction motor · 2019-12-17 · (Speed reducer for ultra-high speed e-motor) Ultra-high speed e-motor Overall Volume-30% Conventional

Copyright NSK Ltd. All Rights Reserved

Traction Drive Speed Reducer for

high speed traction motor

International Automotive Congress 2019

APTT-02-19543

Dec. 4 , 2019

AUTOMOTIVE BUSINESS DIVISION HQ.

AUTOMOTIVE Technology Development Ctr.

2Copyright NSK Ltd. All Rights Reserved Speedy Open Creative No. APTT-02-19543

Agenda

1. Outline of NSK’s activity for EV drive system

2. Traction Drive Speed Reducer

Traction drive technology overview

High speed capability / efficiency / quietness

3. Summary






3. Summary


1-1. NSK’s future vision for EV

Ball screw for e-brake booster

Key components for eAxle

Steer by wire

Parallel Link Active SuspensionWheel Hub motor

Electrification of “Driving”, “Steering” & “Braking”

Braking

Driving Steering

Steering

Driving

Traction DriveSpeed Reducer

TorqueSensor

Power Flow Switching Device

(Electric shift actuator)

C : Connected

A : Autonomous

S : Shared & services

E : Electrification

NSK’s future vision for EV

Focus on “Autonomous” and “Electrification”

Today’s topic


1-2. NSK’s development for EV drive system

InverterBatteryInfrastructure

3 core items of EV

Highly efficient

operation of e-motor

Motor loss

reduction

Running resistance

reduction

Regenerative efficiency

improvement

Increase cruising range Minimize electric power consumption

Increase power

density

Weight

reduction

New solution for eAxle

system and components

Friction

reduction

Continuous improvement

of bearing performance

NSK’s development for EV drive system

Low

NVH

eAxle

Improvement

of quietness

Improvement

of driving

performance

e-motorGearbox

EV xxx V


1-3. Highlighted technical trends of eAxle

Current : Gearbox with fixed reduction ratio

Near future : 15,000 ~ 20,000rpm

Current : 10,000 ~ 13,000rpm

Future : 15,000 ～ 30,000rpm

18,000rpm 21,000rpm18,000rpm17,000rpm 20,000rpm

10,500rpm 11,400rpm 12,000rpm 13,500rpm

?

2X,000rpm

?

X0,000rpm

・・・

Near future ~ : Gearbox Gearbox or transmission

2spd.

Development of high speed e-motor up to 30,000rpm

is increasing to improve the power density

(Downsizing & weight reduction)

Development of multiple speed transmission

(Mainly 2-speed) is increasing to improve the driving

performance and cruising range

2spd.

2spd.2spd.

2spd.

2spd. 2spd.

B-CVT

30,000rpm

Speed increase of e-motor Replace gearbox with transmission

Focus on the development for speed increase of e-motor and 2-speed transmission


1-4. NSK’s development for eAxle

High speed e-motor up to 30,000rpm

for improving the power density (Downsizing & weight reduction)

Multiple speed transmission (Mainly 2-speed)

for improving driving performance and cruising range

TDSR** Traction Drive Speed Reducer

(Speed reducer for

ultra-high speed e-motor)

Ultra-high

speed e-motor

Overall

Volume

-30%

Conventional e-motor

Downsizing of packaging with TDSR and ultra-high

speed e-motor

Power transmission with low NVH by traction drive

2-speed transmission(Large gear step ratio)

Friction plates

(Brake and clutch)

PFSD*

* Power Flow Switching Device

High-functional electric

shift actuator

Seamless shifting at large gear step by torque feedback

control with Torque Sensor

Shift actuation of clutches only with 1-small e-motor by PFSD

・Installable to the powertrain

・None contact sensing

・Small size

Torque

Sensor

Downsized eAxle with TDSR 2-speed eAxle with Torque Sensor & PFSD

NSK’s development

Speed increase of e-motor Replace gearbox with transmission

Traction drive

Power transmission by shear force of

traction oil film between 2 elements,

which solidifies under high pressure

Drive roller Driven roller

Tangential force

Clamping

force

Oil film






3. Summary


2-1. Traction drive overview : Principle & application

Generator

●Application 2

Kawasaki Heavy Industries,Ltd.

T-IDG®

(Toroidal CVT)

●Application 1

Nissan Motor Co.,Ltd

EXTROID-CVT ®

(Toroidal CVT)

Drive roller Driven roller

Thin oil film

thickness is 1 μm

Tangential force for

transmitting torqueFt = μt・Fc

μt ; Traction coefficient

Fc ; Clamping forceCreep : Cr

Thin oil film

Tangential force：Ft

Drive roller

Driven roller

Clamping force : Fc

・Power is transmitted by shear force of oil film between 2 rollers

・Key technology on traction oil which behaves as solid material

under high pressure

PrincipleTraction drive

ApplicationTraction drive


2-2. Reliability in automotive market

Traction oil durability

×104

0.000

0.050

0.100

0 4 8 12 16

Mileage ，km

Tra

ctio

n c

oef

fici

ent

at

12

0o

C

●： Fleet

◇： Bench80,120, 140oC

Pressure (Pmax)

Velocity

Oil Temp.

1.24 GPa

6.8 m/s

5.0%Slip Ratio

80,120, 140oC

Pressure (Pmax)

Velocity

Oil Temp.

1.24 GPa

6.8 m/s

5.0%Slip Ratio

Driver

Driven

Traction coefficient was not changed

before and after endurance test

Traction surface durability

300:1

Magnification

1000:1

Running sectionNon-running section

Observation

area

Grinding direction Grinding

mark

Oil film in

operation

Evaluation of traction coefficient by Idemitsu Kosan Co., Ltd.

Grinding marks remained, so existence of

oil film in operation was confirmed

Traction Drive is reliable for automotive market because traction oil and traction surface keep original properties

Toroidal CVT disc after running

118,500 km in the market


2-3. Comparison between traction drive and gear

Contact patch・Low sliding speed・Smooth and silent

Normal force

Tangential force

DriveDriven

Traction drive Gear

High speed operation +++ - - -

Sliding speed @50m/s 0.1 [m/s] 20～30 [m/s]

Quietness (NVH) +++ - - -

Vibration in meshing order No Yes

Backlash (rattle noise) No Yes

Torque capacity (vs weight) + ++

Normal force / tangential force 15～20 < 2

Clamping mechanism Required Not required

Advantage of traction drive High speed capability High quietness (Low NVH) High controllability due to backlash-less


2-4. High speed capability

Fluid temp ; 100degC

Operating zone

Traction curve

Traction drive characteristic (traction curve)

Sliding speed at operating condition is quitelow (approx. 0.2% of creep ratio)

Traction drive characteristics under operating condition are almost unaffected by tangential speedIt keeps similar property as 10m/s even in 70m/s

Traction drive device is able to operate under high speed condition keeping high performance


2-5. Traction Drive Speed Reducer : structure & power flow

Specification

The pinion rollers are

held with the flexibility

on radial direction

Generation of clamping force linear to transmission torque

Optimum clamping force achieved with less creep and

frictional loss

Generation of clamping forceStructure of Traction Drive Speed Reducer

• Maximum input rotation speed : 32,000 [rpm]

• Capacity of transmit power : 125 [kW]• Reduction ratio : 4.0

• Weight of main components : 10 kg

Pinion roller

Carrier

Loading cam

Ring roller(Low speed side)

Sun roller(High speed side)

Input

Output

Fixed

Power pathways

Fa : Clamping force

T : Force by torque

θ : Cam angle

𝑭𝒂 = 𝑻/ 𝐭𝐚𝐧𝜽


2-6. Efficiency

Calculated efficiency at traction surface

Latest proto (Gen.3 modified)

Current proto (Gen.3)

Target

Measurement result

Target

Beyond 97 %

Next proto (Gen.4)Further optimization for efficiency improvement

The evaluation testing is to be started at Dec. 2019

Calculation

Next proto (Gen.4)

Good correlation between

calculation and measurement result Latest proto (Gen.3 modified)

Latest proto (Modified current proto)

Partially achieved the target efficiency (96% 98.5% )**

** Achieve full range with next proto


Gen.4 Gen.3

Output Side

Carrier(Fixed)Loading Cam（Torque-sensitive

clamping mechanism）

Sun Roller

(High speed side)

Pinion Roller

Ring Roller

(Low speed side)

Power 150kwMax torque 130Nm / Max rotation speed 30,000rpmReduction ratio 5.0 / Weight 9.3kg

Gen.4 prototype

2-7. Next prototype Gen.4

Contact

profile

optimization


1st meshing order

2nd meshing order

Planetary gear

TDSR

2-9. Quietness

Traction Drive Speed Reducer

(TDSR)

NVH comparison test between

planetary gear and TDSR (Proceeding)

Planetary gear

Verification test Initial testing result (Vibration comparison)

Input torque :

20 Nm

Acceleration pick-up

(Side of test-box)

Input speed :

7500 rpm

Sun roller rotating speed [rpm]

Vib

ration [

m/s

2]

Order [-]

Even at rotation speeds less than 10,000rpm,

significant reduction in vibration was observed

Vib

ration [

m/s

2r]

Acceleration pick-up

(Side of test-box) Planetary gear

TDSR


Inverter

E-motor

Φ200

14

0

Volume = 14.8 L

140

296

175

Volume=9.54L(1.64 + 7.90 L)

・110kw

・320Nm

・10,500rpm

StatorStator

Φ200

Φ252

Φ210

Φ156

Φ150

・150kw

・130Nm

・30,000rpm

TDSR

Even with higher power, 36% downsizing of e-motor incl. TDSR could be achieved

36% Down

22886

TDSRe-motor

NSK TDSR + Ultra-high speed e-motorConventional e-motor

2-10. NSK’s downsizing assumption


2-11. Proposal : Installation of Traction Drive Speed Reducer to eAxle

Vehicle

performance

20,000rpm or higher

NSK eAxle concept with TDSR

Reduction ratio

= 16.0 (Overall)

Superior

quietness

2 lay

axes*2

Improved

power density

of e-motor*1

Current eAxle

e-motor

eAxle

system

Calculation base

Vehicle segment : C

Vehicle weight : 1,600 kg

Wheel radius : 0.34 m

e-motor : 150 kW

Downsized

system *1,*2

13,000rpm

Vehicle speed

Drive

(w

he

el) t

orq

ue

Reduction ratio

= 10.5 (Overall)

3 lay

axes

160

km/h

Acceleration

(0.65G)

3,450Nm

Traction Drive

Speed Reducer

Reduction ratio

of TDSR= 5.0

Vehicle speed

Drive

(w

he

el) t

orq

ue

160

km/h

Acceleration

(0.65G)

3,450Nm






3. Summary


3. Summary

• Traction Drive Speed Reducer (TDSR) enables power transmission with higher reliability

and quietness under extremely high speed operation like 20000rpm or higher.

• High-speed traction motor equipped with TDSR is expected to be approximately 30-40%

smaller and lighter than conventional traction motor.

• Gen.3 TDSR partially achieved 98.5% of efficiency and Gen.4 TDSR with further

improvement is expected to achieve full range by end of 2019.

Traction Drive Speed Reducer


Seamless 2-speed eAxle concept : Technical specification

Technical specification

Max. e-motor power 150 kW

Max. e-motor torque 130 Nm

Max. e-motor speed 30,000 min-1

Reduction ratio of

traction drive speed reducer5.0

Reduction ratio of

2-speed transmission

Low: 2.5

High: 1.0

Max. drive torque 4,000 Nm

Max. vehicle speed 250 km/h

Traction Drive Speed

Reducer


Thank you for your attention.

Documents

Traction Drive Speed Reducer for high speed traction motor · 2019-12-17 · (Speed reducer for ultra-high speed e-motor) Ultra-high speed e-motor Overall Volume-30% Conventional