Open-Centre Hydraulic Distributor for Stable Negative Pump Control
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Solution Overview
Problem
Existing negative control systems for hydraulic pumps in open centre hydraulic distributors suffer from instability and imprecision, particularly in electric vehicles, leading to inefficiency and increased energy dissipation, which is not compatible with the stringent energy efficiency requirements of small-sized machines.
Innovation Solution
An open centre hydraulic distributor system with a slide valve and valve device that maintains a pressure difference threshold, combined with a directional valve and negative control line, providing precise and stable negative control of the pump, reducing energy dissipation and improving control precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional negative control system is used in small-sized machines, then the system can control pump flow rate, but the control precision and stability are insufficient leading to energy dissipation
Solution Approach 1:
A pilot valve is introduced as an intermediary component to control the main spool of the directional valve. The pilot valve receives the negative control signal and uses it to precisely position the main spool, thereby improving control precision and stability while reducing energy dissipation through more accurate flow rate control.
Solution Approach 2:
The conventional direct mechanical control system is replaced with a hybrid system combining negative pressure control and pilot valve actuation. This substitution enables more precise control of the main spool position through the pilot valve's response to negative control signals, enhancing both stability and precision.
2Productivity
If the free circulation line is completely closed to maximize pump displacement, then the flow rate to users increases, but the control stability deteriorates due to pressure imbalance
Solution Approach 1:
The system implements feedback through the negative control line that continuously monitors the pressure downstream of the directional valve and adjusts the pilot valve accordingly. This feedback mechanism maintains pressure balance and control stability even when the free circulation line is closed and pump displacement is maximized.
Solution Approach 2:
The pilot valve acts as an intermediary between the negative control signal and the main spool, providing fine-tuned control that maintains stability during the transition to maximum pump displacement. This intermediate control stage prevents direct pressure imbalances that would occur with abrupt spool positioning.
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 system achieves more precise and stable negative control of hydraulic pumps, reducing energy dissipation and enhancing control precision, making it suitable for electric vehicles and small-sized machines with minimal energy consumption.
Implementation Method 1
a slide valve arranged on the free circulation line downstream of said at least one directional valve; a valve device configured to be activated when on the free circulation line a threshold value is reached that is given by the difference between a pressure value upstream and a pressure value downstream of said at least one directional valve, and to maintain said pressure difference equal to the threshold value
Implementation Method 2
a negative control line to pick up a pressure signal from the free circulation line in a position downstream of said at least one directional valve and upstream of the slide valve, said negative control line being intended to bring a pressure signal to the pump to perform the control of the negative type
Implementation Method 3
at least one directional valve so fitted as to intercept the free circulation line and the delivery line, said at least one directional valve comprising an actuator that is movable between at least a first and a second position and so configured that the movement from the first to the second position narrows a transit area of the free circulation line and opens a transit area of the delivery line
Data Source
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AI summary
Open centre hydraulic distributor (10) of a fluid, comprising: - a free circulation line (L2) that connects a supply line (L1) for supplying a fluid from a pump (P) of the negative control type to at least one discharge (T1, T2); - a delivery line (L3) that connects the supply line (L1) to one or more users (A1, B1, A2, B2) downstream of the distributor (10); - at least one directional valve (SV1, SV2) that intercepts the free circulation line (L2) and the delivery line (L3), and configurable in a first and a second position so that the movement from the first to the second position narrows a transit area of the free circulation line (L2) and opens a transit area of the delivery line (L3); - a slide valve (1) arranged on the free circulation line (L2) downstream of the directional valve (SV1, SV2); - a valve device (2) that is activated when a threshold value given by a pressure delta between upstream and downstream of the directional valve (SV1, SV2) is reached on the free circulation line (L1), and maintains this pressure delta equal to the threshold value; - a negative control line (L4) to pick up a pressure signal from the free circulation line (L2) in a position downstream of said at least one direction valve (SV1, SV2) and upstream of the slide valve (1).