Electric Inverter A/C System for
TOYOTA PRIUS Hybrid Vehicle
Speaker
Ken Matsunaga DENSO CORPORATION
Kiwamu Inui
TOYOTA MOTOR CORPORATION
Presentation Outline
1. Development Background
2. Merits of Electrically Driven Compressors
3. Structure of Electric Inverter A/C System
4. Key Technology for Engine Stoppage
5. Conclusions
Development Background
Air Conditioner Types Confronting Engine Stoppage
Idle Stop（12V）
ＭＨＶ（42V）
Belt driven ＭＧ １Motor
Generator
Powerful Starter
Component
Type
Ａ／Ｃ
Type
2Motor Generator
（Ｐｒｉｕｓ）
Trans
Mission
12V
Ａｌｔｅｒ
engine
CL
MG2
CVT
12V
STARTER
Generation
of Electric
ｉｔｙ
ＳＨＶ（202～288V）
Small
Cold-Storage
SA
４２Ｖ
MG
MG
MG1
Trans
Mission
Middle
Large
Combined Use of
Belt driven and Electrically
drive
（２Way Compressor）
Electrically
Drive
Merits of Electrically Driven Compressors
Temperature [ ℃ ] Humidity[％RH]
100
0
60
Room
Room Humidity
Humidity
50
40
A/C turned on with engine
start according to the cabin
temperature rising up
30 Engine
drive
drive
Electrically
ｄｒｉｖｅ
20
10
0
Outlet Temperature
100
200
Time[s]
300
400
Speed[km/h]
Comparison of Air-conditioning Comfort between
Engines Belt and Electrically Driven Compressors
Merits of Electrically Driven Compressors
Impact on Fuel Consumption
For Electrical Drive
Engine Running Rate [－]
For Engine Belt Drive
A/C Off
Simulation
Vehicle Model:SUV
Running Mode：City Mode
Engine Drive Full Electrical
Drive
0.6
0.4
0.2
Q（
ｋW)
28℃ No Sunshine 30℃ Half Sunshine 35℃ Full Sunshine
Recycled Air
Fresh Air
Half Recycled
Air
Merits of Electrically Driven Compressors
Impact on Fuel Consumption
Power Consumption Rate [-]
Generator loss
Inv/Motor loss
Compressor loss
Cycle Efficiency
1.5
Engine
Drive
Vehicle Model：SUV
Mode ：City Mode
Generator Efficiency ０．８５
Full Electrical
Electrically
Drive
1.0
0.5
0.0
28℃ No Sunshine
Fresh Aｉ
r
30℃ Half Sunshine 35℃ Full Sunshine
Half Recycled Air Recycled Air
Merits of Electrically Driven Compressors
Fuel consumption effect （L/km）
Fuel Consumption Effect
Summer condition
Engine Driven
19% Electrically
Driven
Old PRIUS
New PRIUS
Structure of Electrical Inverter Air Conditioning System
Condenser
Electrically
Driven
Compressor
Inverter
Engine
Electrically Driven
Water Pump
Refrigerant Flow
Engine
Cooling
Water Flow
Fresh air
Fresh / Re-circulated Ａ
ｉｒ
Two Layer Flow A/C Unit
Re-circulated Air
Buttons for A/C and
Thermal Control
Button for Fresh/Re
-circulation Switching
Optimum Humidity Control
with Humidity Sensor
Structure of Electric Inverter A/C System
Compressor Specifications
Compact and Highly Efficient
Scroll Compressor
Items
Specifications
Inverter
(18 cm3/r)
ES18
Model
Cooling Performance
3.4kW
(at 7500r/min)
Size
φ 109×182
Mass
4.8kg (without
inverter)
Compact and Highly Efficient
DC Brush less Motor
（cm3）
3000
<Compressor Volume>
<Compressor Mass>
12
40%
Reduction
2000
8
53%
Reduction
4
1000
0
（kg）
Conventional
Electrically
Driven Compressor
New Development
for PRIUS
0
Conventional
Electrically
Driven Compressor
New Development
for PRIUS
mm
Key Technology for Engine Stoppage
C ondenser Fan ：
6V ×2
B low eｒ
：
Lo
M ode ：
FA C E FR ES H
M axC ool
Exteri
Exterior
or
60
B ackground N oise
50
40
0
2000
4000
6000
8000
C om pressor Speed（
r/m in）
N oise LeveldB （
A）
60
IInteri
nterior
or
Compressor
Speed（r/min）
N oise LeveldB （
A）
Electrically Driven Compressor System Noise
Level
H eat Load ：
35℃
70
7500
f(NV)
＝ａ
b
ｃ
（ｒｐｍ）
f(NV)
a
50
b
Speed（ｋｍ／ｈ）
B ackground N oise
40
30
0
2000
4000
6000
C om pressor Speed（
r/m in）
8000
Conclusions
• Cooling possible even during engine stoppage
• Fuel consumption improvements
• Adopted for the first time in September 2003
• Wide adoption expected in future