HST Pump Torque Curve Switching for Wheel Loader Fuel Economy

Solution Overview

Problem

Conventional construction vehicles with HST systems experience jolts and uneven control when switching the absorption torque curve from low-engine speed to high-engine speed, affecting fuel economy and operator comfort.

Innovation Solution

A construction vehicle with an engine, travel hydraulic pump, hydraulic motor, accelerator pedal, hydraulic sensor, and controller that adjusts the matching point of the absorption torque curve based on specific conditions, including engine speed, HST pressure, and vehicle speed, to optimize fuel economy and prevent operator discomfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the absorption torque curve is switched from low-engine speed side to high-engine speed side to improve fuel economy, then fuel economy is improved, but jolts and uneven control occur during switching

Engineering Contradiction:

Improvefuel economyVSAvoidcontrol smoothness

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The controller predicts future working conditions and proactively switches the absorption torque curve before the actual need arises. By anticipating future high-load conditions, the system pre-positions the torque curve to avoid sudden transitions, thereby maintaining both fuel economy and control smoothness during switching.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically selects between different absorption torque curves (first curve for low-engine speed, second curve for high-engine speed) based on real-time working conditions. The controller continuously monitors engine speed, load demands, and vehicle operation state to optimally switch between curves, achieving both fuel efficiency and smooth control transitions.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If the matching point of absorption torque curve is switched frequently to optimize fuel economy, then fuel economy improves, but operator comfort deteriorates due to jolts

Engineering Contradiction:

Improvefuel economyVSAvoidoperator discomfort

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The controller predicts future working conditions and proactively switches the absorption torque curve before the actual need arises. By anticipating future high-load conditions, the system pre-positions the torque curve to avoid sudden transitions, thereby maintaining both fuel economy and control smoothness during switching.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors engine speed, load demands, and vehicle operation state, using this feedback to determine optimal switching timing. The controller adjusts switching decisions based on real-time conditions, ensuring that transitions occur only when appropriate, thus eliminating jolts while maintaining fuel efficiency.

Inventive Principle:

Principle #23Feedback

3Use of energy by moving object

If the absorption torque of HST pump is varied to match engine speed for fuel economy, then fuel economy improves, but vehicle responsiveness may be compromised

Engineering Contradiction:

Improvefuel economyVSAvoidvehicle speed responsiveness

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The system dynamically selects between different absorption torque curves (first curve for low-engine speed, second curve for high-engine speed) based on real-time working conditions. The controller continuously monitors engine speed, load demands, and vehicle operation state to optimally switch between curves, achieving both fuel efficiency and smooth control transitions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the absorption torque parameters by switching between different torque curves based on engine speed ranges and working conditions. By adjusting the torque curve selection parameter, the system optimizes the match between engine output and pump demand, improving fuel economy while maintaining adequate vehicle responsiveness through appropriate curve selection.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution ensures smooth transitions between engine speed modes, improving fuel economy and eliminating jolts during control switching, thereby enhancing operator experience and operational efficiency.

Implementation Method 1

a travel hydraulic pump (4), which is driven by the engine (1)

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Increase

Implementation Method 2

a travel hydraulic motor (10), which is driven by hydraulic fluid discharged from the travel hydraulic pump (4)

Methodology Applied

Scientific EffectHydraulic motor conversion: Hydraulic Press

Data Source

PatentEP2413005B1Construction vehicle

Publication Date: 2015.09.30 KOMATSU LTD

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AI summary

A wheel loader (50) is designed so that when a specific first condition is met for vehicle speed, accelerator opening, engine speed, and HST pressure, the engine absorption torque curve of an HST pump (4) is switched to shift the matching point from the low-engine speed side to the high-engine speed side. On the other hand, if a second condition is met for vehicle speed and HST pressure, control is performed so that the absorption torque curve of the HST pump (4) is returned from the high-engine speed side to the low-engine speed side.