NEW PRODUCTElectric Oil Pump for Vehicle Idle Reduction System
The growing trend of energy conservation andenvironmental regulation reinforcement of recent years
has influenced automotive manufacturers to actively
adopt new technologies effective for better fuel efficiency
of vehicles. As a technology which improves the fuelefficiency of gasoline-driven vehicles by 5 to 10%, an idle
reduction system which stops the engine when a vehicle
is stationary has been commercialized and vehicles which
adopt this system are becoming more and more popular.
This paper introduces a new electric oil pump for vehicle
idle reduction systems developed and mass producedby JTEKT. The newly developed electric oil pump issmaller, lower cost and more energy efficient than ourconventional electric oil pump.

Intended Use of Electric Oil Pump
In a vehicle equipped with an idle reduction system,
hydraulic pressure decreases when the engine is stopped.
As such, when the vehicle starts to move again, thehydraulic pressure response is delayed, impeding thevehicle's motion. The role of the electric oil pump is tosecure the minimal necessary hydraulic pressure andavoid impeding vehicle motion.

Features1. In the control circuit of the electric oil pump, dischargepressure is estimated from oil temperature, motor speed
and current. Power consumption has been reduced
by up to 47% as a result of lowering the motor speed
and suppressing excess hydraulic pressure when thedischarge pressure exceeds the necessary level.
Suppressing excess output through excess output suppression
control and reducing power consumption of the diagonal area
electric oil pump output
characteristic line
Load characteristic line (maximum leakage)
Necessary

Discharge flow rate

performance
scope

Load characteristic line (normal leakage)
Load characteristic line (minimum leakage)

With excess output
suppression control

Electric oil pump

Performance
Compared with JTEKT's conventional electric oil
pump, the newly developed electric oil pump is smaller
yet achieves higher output per volume.

Without excess output
suppression control

Discharge pressure

2. Suppression of motor heat generation made it possible
to adopt a plastic stator frame. Also, by reviewing eachindividual part, the size of the electric oil pump was
reduced 30% compared with the conventional products.
2) Reduced bolts andwaterproof parts(1) Made one solid unit
by adhering bracket
to the stator frame.
(2) Formed connector
and the stator frame
together as one solidunit.

100
Developed productOutput, %Higher efficiency

1208060
Current product40200607080901001101) Shift to a plastic stator
frame
Reduced machining andnumber of bolts byencasing a stator frame
core in the plastic stator
frame through in-moldforming.

120Size, %Downsizing

JTEKT CORPORATIONJTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)67NEW PRODUCTBracket adhered
to the stator frame

Connector integrated plastic
stator frame with an in-moldstator frame core

ECU
Flat motor
Internal gear pump
Discharge port

Inlet port

Structure
1. By making a rotor hollow, bearings are allowed to bepositioned inside the rotor, and reduce resulting inshortening the axial directional length of the rotor by32%.
2. A magnetic cage is adopted, which has reduced costby completely eliminating bonding process. Also, bychanging from ring magnet to segment magnet shape,
usage of neodymium magnet has been reduced by 30%.
①Axial direction reduction (32%)②Upper space secured③Reduced inertia with hollow rotor

Ring magnet[Conventional part]

Shift to segment magnet[Developed part]

Driveline System Engineering Dept. 2, Automotive
Systems Business Headquarters

JTEKT CORPORATION68

JTEKT ENGINEERING JOURNAL English Edition No. 1010E (2013)