Wheeled Work Vehicle Shift Control to Reduce Downshift Shock

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Solution Overview

Problem

Wheeled work vehicles experience shocks during transmission shifts from high to low speed, which can affect the operability of front work implements and decrease work efficiency.

Innovation Solution

A wheeled work vehicle configuration that includes a prime mover, hydraulic pump, travelling hydraulic motor, transmission with at least two speed stages, a travelling control valve, changeover valve, and a controller. The controller switches the travelling control valve to a neutral position before shifting the transmission from high to low speed, allowing the rotational speed of the travelling hydraulic motor to decrease before resuming normal operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the tilting angle of the travelling hydraulic motor is decreased to suppress shock at transmission shifting from high to low speed, then the shock at shifting is reduced, but the operability of the front work implement is affected

Engineering Contradiction:

Improveshock at transmission shiftingVSAvoidoperability of front work implement

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The controller temporarily switches the travelling control valve to a neutral position before the transmission shifting occurs, preemptively reducing the rotational speed of the travelling hydraulic motor. This preliminary action ensures that when the shifting happens, the speed difference between input and output shafts is minimized, suppressing shock without affecting work implement operability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The neutral position of the travelling control valve acts as an intermediary state that temporarily decouples the hydraulic pump from the travelling hydraulic motor during the shifting process. This intermediary state allows the motor speed to be reduced independently of the work implement hydraulic system, resolving the contradiction between shock suppression and operability maintenance

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the tilting angle of the travelling hydraulic pump is changed according to the travelling hydraulic motor to suppress shock, then the shock at shifting is reduced, but the work implement operation is affected

Engineering Contradiction:

Improveshock at transmission shiftingVSAvoidwork efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The control system is segmented into independent control paths: the travelling control valve controls the travelling hydraulic motor separately from the work implement hydraulic pump. This segmentation allows the travelling system to adjust its tilting angle for shock suppression while the work implement system maintains independent operation, preventing interference with work efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #10Preliminary action

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

This configuration alleviates the shock experienced during transmission shifts from high to low speed without affecting the operability of the work implement, thus maintaining work efficiency.

Implementation Method 1

a hydraulic pump (51) driven by the prime mover (28); a travelling hydraulic motor (52) driven by hydraulic fluid supplied from the hydraulic pump (51)

Methodology Applied

Scientific EffectHydraulic fluid pressure: Pressure Gradient

Implementation Method 2

a travelling control valve (53) that controls a direction and a flow rate of the hydraulic fluid to be supplied from the hydraulic pump (51) to the travelling hydraulic motor (52)

Methodology Applied

Scientific EffectHydraulic flow control: Fluid Spray

Data Source

PatentEP3832032B1Wheeled work vehicle

Publication Date: 2025.02.19 HITACHI CONSTRUCTION MACHINERY CO LTD

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AI summary

A wheeled work vehicle includes: a transmission transmitting the rotational power of a travelling hydraulic motor to wheels; a travelling control valve having an interruption position that interrupts supply of hydraulic fluid from a hydraulic pump to the travelling hydraulic motor; a shift changeover valve that shifts the speed stage of the transmission by the position of the shift changeover valve being selectively switched; and a controller that controls the travelling control valve and the shift changeover valve. The controller switches the travelling control valve to the interruption position, then switches the position of the shift changeover valve such that the speed stage of the transmission is shifted to the low speed stage, and switches the travelling control valve from the interruption position to an original position side before the switching in a case where the controller shifts the transmission from the high speed stage to the low speed stage.