19-10-2012, 05:27 PM
Brushless Motors for In-Tank Fuel Pumps
Brushless Motors for In-Tank Fuel Pumps.pdf (Size: 5.93 MB / Downloads: 73)
ABSTRACT
Traditional in-tank gasoline and diesel fuel pumps require
high power, 120 W or more, in fuel systems that have high
flow requirements, high pressure requirements, or both. One
method to reduce power consumption is to improve
efficiency by using a brushless motor rather than the
traditional brush style motor. The brushless motor technology
also eliminates the brush to commutator interface which
improves the pump's robustness to fuel and reduces flow
variation. Additional benefits are provided by the controller
which provides motor commutation since it enables closed
loop pump speed control, pump diagnostics, and the
opportunity for additional sensor interfaces to improve the
fuel delivery system architecture. This paper describes the
brushless motor technology, design optimization strategy for
fuel pump applications, selected design, and resulting torque
and efficiency performance improvements.
INTRODUCTION
Most automotive fuel systems use a Fuel Delivery Module
with components to filter and pump gasoline at a specified
pressure and flow rate from the fuel tank to the engine. The
FDM uses a reservoir assembly to maintain a fuel supply at
the pump inlet and support components such as pressure
regulators and/or limiters, filters, level sensor, and the
electrical and hydraulic connections that pass-through the
tank. Current systems predominantly use passive electrical
components such as Brush Pumps and resistive fuel level
sensors that are independently connected to a voltage supply
and body control module respectively. The high flow levels
of these systems require high power pumps that may operate
continuously at maximum speed conditions.
BRUSHLESS PUMP TECHNOLOGY
Brushless DC permanent magnet motors are attractive
alternatives to existing brush motors due to their flexible
design, low part count, low friction torque, and high
efficiency. These motors have gained market share in recent
years primarily due to cost improvements for the control
electronics that provide the added benefit to tune the motor
drive currents for optimal system performance and may
include motor diagnostics. The Delphi brushless pump uses a
three phase motor configuration as show in Figure 3. This
solution uses a multi-pole magnet in the rotor assembly and
the stator includes the magnetic core with windings in three
phases. Motor commutation is achieved by a sensorless
approach that measures a voltage signal induced by the back-
EMF in an open winding during pump rotation.
BRUSHLESS PUMP BENEFITS
BL motors in fuel pumps provide improvements in torque
performance, power efficiency, flow stability over time, and
robustness to fuels. This leads to reductions in CO2 emissions
and improvements in the FDM performance, durability and
reliability. Since the fuel pump in the FDM application does
not require precise position control and pump operating
speeds are at levels that provide stable back emf signals, this
application can minimize the cost impact by eliminating the 3
Hall switches for motor commutation and using a sensorless
speed measurement approach.