Pilot Pressure Valve Control for Low-Flow Tilt Cylinder Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing fluid pressure control devices for fork lifts face instability in operation, particularly when the pump is driven at low rotation or when the working fluid is supplied to actuators other than the tilt cylinder, leading to insufficient pressure and failure to operate the tilt cylinder even when commanded to do so.
Innovation Solution
The fluid pressure control device incorporates a control valve with a switching valve and throttle portions, where the pressure upstream of the throttle is led to a pilot chamber to control the flow of working fluid, ensuring the tilt cylinder can operate even at low fluid flow rates by adjusting the switching valve and throttle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching valve is operated by pilot pressure from the parallel passage, then misoperation is prevented and tilt-lock function is achieved, but the tilt cylinder cannot be operated when pump rotation is low or fluid is supplied to other actuators with priority
Solution Approach 1:
A pilot valve is introduced as an intermediary component between the main control valve and the switching valve. The pilot valve receives fluid from the first supply passage and controls the pilot pressure that actuates the switching valve. This intermediary allows the switching valve to be controlled by a dedicated pilot pressure source rather than relying solely on pressure from the parallel passage, enabling tilt cylinder operation even when pump rotation is low or other actuators have priority fluid supply.
2Reliability
If the return passage is shut off by the switching valve holding tilt-lock position, then misoperation is prevented, but the tilt cylinder cannot be operated even when fluid control valve is switched to tilt-down position
Solution Approach 1:
The switching valve is designed to dynamically change its position based on pilot pressure variations. When pilot pressure increases (through the throttle portion and pilot passage), the switching valve moves from the tilt-lock position to the tilt-down position, opening the return passage. This dynamic response allows the system to maintain stability during normal operation while enabling rapid response when tilt operation is commanded, resolving the contradiction between operation stability and response speed.
3Reliability
If the pressure in the parallel passage does not rise sufficiently, then the switching valve remains continuously at tilt-lock position, but this prevents tilt cylinder operation even when pump is driven
Solution Approach 1:
The fluid control system is segmented into multiple independent control paths: the main control valve controls fluid supply to the tilt cylinder, while the pilot valve separately controls pilot pressure to the switching valve. The throttle portion creates a localized pressure zone in the pilot passage that is independent of the parallel passage pressure. This segmentation allows the switching valve to be actuated through the pilot pressure path even when the parallel passage pressure is insufficient, resolving the contradiction between maintaining locked state and enabling actuator drive 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
This configuration enhances the stability of the fluid pressure control device's operation by allowing the tilt cylinder to function reliably even at low fluid flow rates, preventing misoperation and ensuring consistent performance.
Implementation Method 1
a throttle portion configured to throttle the flow of the working fluid supplied to the first actuator from the first supply passage, and the pressure on an upstream side of the throttle portion is led to the pilot chamber
Implementation Method 2
a switching valve configured to control a flow of a working fluid to the discharge passage from the first actuator in accordance with a pressure in a pilot chamber to which a part of the working fluid supplied from the first supply passage to the first actuator is led
Data Source
AI summary
A fluid pressure control device includes a neutral passage, a control valve provided in the neutral passage, a first supply passage, and a discharge passage, the control valve has, a switching valve configured to control a flow of a working fluid to the discharge passage from the first actuator in accordance with a pressure in a pilot chamber to which a part of the working fluid supplied from the first supply passage to the first actuator is led, and a throttle portion configured to throttle the flow of the working fluid supplied to the first actuator from the first supply passage, and the pressure on an upstream side of the throttle portion is led to the pilot chamber.