Pilot Flow Restriction in Pressure Control Valves at Neutral

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Solution Overview

Problem

Existing hydraulic valves experience high pilot oil flow between the supply pressure port and the tank port when in the neutral position, leading to energy loss and increased costs due to the need for multiple valves in transmission applications.

Innovation Solution

A pressure control valve with a pilot flow control assembly that includes a first and second control element, defining a restricted pilot flow path with a varying restriction as a function of the spool position, significantly reducing pilot flow when the valve is in the neutral position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the size of the pilot stage orifice is decreased to reduce pilot flow leakage, then the pilot flow is reduced, but the response time of the valve is negatively affected and the main spool shifts much slower

Engineering Contradiction:

Improvepilot flow leakageVSAvoidresponse time

Core Design Contradiction:

Loss of energyVSSpeed

Solution Approach 1:

The pilot stage orifice is divided into two separate orifices (first pilot stage orifice and second pilot stage orifice) arranged in series. This segmentation allows each orifice to be optimized for different functions: the first orifice controls flow rate while the second orifice maintains adequate sizing for response time, eliminating the need to reduce a single orifice size which would compromise both leakage and response time

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A pilot pin is introduced as an intermediary component between the two pilot stage orifices. The pilot pin can selectively block the first pilot stage orifice when the spool is in the neutral position, directing pilot flow through only the second orifice to minimize leakage. When the spool moves, the pilot pin repositions to open both orifices, ensuring adequate flow for fast response time

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If the pilot stage orifice size is decreased to reduce leakage, then pilot flow leakage is reduced, but the orifice becomes more prone to blockage from contamination

Engineering Contradiction:

Improvepilot flow leakageVSAvoidorifice blockage resistance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The pilot stage orifice is segmented into two separate orifices arranged in series, each with adequate sizing that resists blockage from contamination. This eliminates the need to use a single small orifice which would be prone to blockage, while still achieving leakage reduction through the series arrangement and selective blocking mechanism

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pilot pin acts as a controllable intermediary that can selectively close the first orifice. By having the ability to close one orifice, the system can direct flow through the second adequately-sized orifice, preventing contamination blockage issues that would occur with a single small orifice

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If a secondary leakage reducing valve is integrated into the pilot stage to control leakage, then pilot flow leakage is reduced, but the valve becomes costly and complex

Engineering Contradiction:

Improvepilot flow leakageVSAvoidvalve structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The leakage control function is merged with the existing spool valve mechanism by using the pilot pin (already part of the spool assembly) to control the first pilot stage orifice. This integration eliminates the need for a separate secondary leakage reducing valve, reducing complexity while maintaining leakage control functionality

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The pilot pin is given multiple functions: it serves as both a positioning element for the spool and a controllable shutter for the first pilot stage orifice. This multi-functionality eliminates the need for dedicated leakage control components, simplifying the overall valve structure while achieving leakage reduction

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces pilot flow by up to 90%, minimizing energy loss and reducing the need for costly secondary valves, while maintaining desired performance characteristics.

Implementation Method 1

the first control element and the second control element define, when the spool is in the neutral position, a restricted pilot flow path along the pilot flow passage including a restriction that varies as a function of the spool position

Methodology Applied

Scientific EffectFluid flow restriction through varying orifice size: Pressure Drop

Data Source

PatentUS12234842B2Pressure control valve with reduced pilot flow and hydraulic control system with the same

Publication Date: 2025.02.25 HYDRAFORCE INC

AI summary

A hydraulic valve comprises a proportional piloted valve that controls pressure and includes means for restricting pilot flow through the pilot flow passage. The means for restricting pilot flow defines a restriction in the pilot flow passage when a movable spool disposed in an axial bore of the body of the valve is in a neutral position. The restriction varies as a function of spool movement such that flow of hydraulic fluid through the pilot flow passage is variably restricted as a function of the position of the spool over its range of travel.