Lift Pump Soft-Start Voltage Control for In-Rush Current Reduction

Solution Overview

Problem

Existing fuel lift pump systems experience issues with in-rush currents and pressure spikes due to sudden voltage changes, which can damage electrical components and cause fuel metering errors, especially during low engine loads or idle conditions.

Innovation Solution

Limiting the lift pump voltage to a lower level when powering on, maintaining it at that level for a duration, and then gradually increasing it to reduce in-rush currents and prevent pressure spikes in the fuel rail.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the lift pump voltage is stepped up from 0V to maximum voltage when powering on, then the lift pump can quickly provide fuel pressure, but in-rush currents increase causing damage to electrical circuitry and electromagnetic interference

Engineering Contradiction:

Improvefuel pressure build-up speedVSAvoidin-rush currents

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by implementing a soft-start mechanism that gradually increases voltage from 0V to maximum voltage over a predetermined time period. This preliminary gradual voltage increase prevents in-rush currents and electromagnetic interference before they can occur, while still achieving the necessary fuel pressure build-up speed for system operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies dynamics by making the voltage supply dynamic rather than static. The controller adjusts the voltage level over time based on the startup phase, transitioning from low voltage to maximum voltage. This dynamic voltage control eliminates harmful in-rush currents while maintaining the capability to quickly establish required fuel pressure when needed.

Inventive Principle:

Principle #15Dynamics

2Speed

If the lift pump voltage is stepped up from 0V to maximum voltage when powering on, then the lift pump can quickly provide fuel pressure, but pressure spikes occur in the fuel rail causing fuel metering errors

Engineering Contradiction:

Improvefuel pressure build-up speedVSAvoidfuel metering accuracy

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by implementing a soft-start mechanism that gradually increases voltage from 0V to maximum voltage over a predetermined time period. This preliminary gradual voltage increase prevents in-rush currents and electromagnetic interference before they can occur, while still achieving the necessary fuel pressure build-up speed for system operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies dynamics by making the voltage supply dynamic rather than static. The controller adjusts the voltage level over time based on the startup phase, transitioning from low voltage to maximum voltage. This dynamic voltage control eliminates harmful in-rush currents while maintaining the capability to quickly establish required fuel pressure when needed.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the lift pump is operated continuously with feedback control, then fuel rail pressure is maintained at desired levels, but energy consumption increases during low engine loads

Engineering Contradiction:

Improvefuel rail pressure controlVSAvoidelectrical power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies periodic action by switching between two operational modes based on engine load conditions. During high engine loads, the system operates in continuous feedback control mode for reliable pressure maintenance. During low engine loads, it transitions to intermittent periodic operation where the pump cycles on and off, significantly reducing electrical power consumption while still meeting fuel delivery requirements.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies partial action by providing just enough fuel pressure during low-load conditions rather than maintaining full pressure continuously. The controller determines when reduced or intermittent pump operation is sufficient, allowing the system to use partial action (intermittent pumping) instead of excessive continuous action, thereby reducing energy consumption while maintaining adequate fuel supply.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS9995237B2Systems and methods for operating a lift pump

Publication Date: 2018.06.12 FORD GLOBAL TECH LLC

AI summary

Methods and systems are provided for operating a lift pump of an engine fuel system. In one example, a method may comprise limiting a lift pump voltage to a lower first level when powering on a lift pump from off. The method may further comprise maintaining the lift pump voltage at the lower first level for a duration before increasing the lift pump voltage above the first level.