Hydraulic Motor Control Circuit with Intermediate Spool Positioning
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Solution Overview
Problem
Existing hydraulic control circuits for radial piston motors suffer from abrupt load alternations and shock during speed shifting, leading to loss of controllability, especially on rough terrain.
Innovation Solution
A hydraulic control circuit with a proportional speed control valve and a control unit that uses a time-related control current function to smoothly transition the speed control valve spool between full-torque, reduced-torque, and intermediate positions, reducing hydraulic shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If speed control valves are used to switch between pre-defined displacement values, then speed shifting functionality is achieved, but abrupt load alternations and hydraulic shock occur causing loss of controllability
Solution Approach 1:
The patent applies dynamics by making the valve spool continuously movable between end positions instead of fixed switching positions. The electrically adjustable pilot valve enables dynamic, continuous adjustment of the pilot pressure, which in turn continuously positions the control valve spool between full-torque and reduced-torque positions, eliminating abrupt transitions and hydraulic shock while maintaining speed shifting functionality.
2Ease of operation
If valve arrangement is used to change absorption volume of motor, then speed control is enabled, but quick de- or acceleration creates high shock detectable by driver
Solution Approach 1:
The patent uses an intermediary approach by introducing a pilot pressure system controlled by an electrically adjustable pilot valve. This pilot pressure acts as an intermediary control mechanism that smoothly adjusts the main control valve spool position, enabling gradual absorption volume changes in the motor rather than abrupt switching, thus eliminating driver discomfort while maintaining ease of operation.
3Temperature
If hydraulic fluid viscosity varies with temperature, then system responds to temperature changes, but response time increases causing freewheeling sensation
Solution Approach 1:
The patent applies parameter changes by using an electrically adjustable pilot valve that can modify the pilot pressure parameters in response to temperature changes. This electrical control mechanism compensates for viscosity variations caused by temperature, maintaining consistent response time and eliminating the freewheeling sensation while preserving temperature adaptation capability.
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 effectively smoothes the speed shifting behavior of hydraulic motors, reducing hydraulic shock and maintaining vehicle controllability even on challenging terrain.
Implementation Method 1
a control valve spool (38) continuously switchable by means of a force generated by a pilot pressure (52)
Implementation Method 2
a continuously, electrically adjustable pilot valve (50) having an electrical actuator (54)
Implementation Method 3
Hydraulic motors, in particular radial motors, e.g., orbital motors or radial piston hydraulic motors
Data Source
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AI summary
Hydraulic control circuit for a hydraulic motor operable at least at two displacements, comprising a proportional speed control valve with a control valve spool continuously moveable by means of a force generated by a pilot pressure being controlled by a continuously, electrically adjustable pilot valve having an electrical actuator, wherein the control valve spool is moveable between a full-torque end position, a reduced-torque end position, and at least one intermediate position. A time related control current function is provided for controlling the current applied to the electrical actuator for controlling the pilot pressure comprising a pre-current portion with a constant nonzero current.