Forklift Hydraulic Control for Simultaneous Speed
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Solution Overview
Problem
Conventional hydraulic devices for forklifts face difficulties in simultaneously operating multiple hydraulic mechanisms, such as lifting and tilting, at their instructed speeds due to the single hydraulic pump and electric motor configuration, leading to inefficient control and potential speed mismatches.
Innovation Solution
A hydraulic control device with multiple hydraulic mechanisms, including lifting/lowering and tilting hydraulic cylinders, a discharge control mechanism, proportional valves, and a controller, which adjusts the flow rate and valve open degrees based on operation speed differences to ensure simultaneous operation of multiple subjects at their instructed speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single hydraulic pump and electric motor are used to operate multiple hydraulic mechanisms, then the device complexity is reduced, but the ability to operate multiple operation subjects at their instructed speeds simultaneously deteriorates
Solution Approach 1:
The patent implements dynamic speed priority assignment where the controller dynamically determines which operation subject receives priority speed control based on real-time operational needs. The system switches between priority modes (e.g., fork lowering priority vs. mast tilting priority) to ensure that at least one operation maintains its instructed speed while another operates with available hydraulic flow.
Solution Approach 2:
The system changes operational parameters by dynamically adjusting the hydraulic pump's rotation speed and the electric motor's output based on the priority assignment and current operational state. This allows the single pump-motor unit to adapt its performance characteristics to meet the speed requirements of different operation subjects at different times.
2Speed
If the electric motor is controlled according to one operation subject's speed instruction, then that operation subject operates at the instructed speed, but other operation subjects cannot operate at their instructed speeds simultaneously
Solution Approach 1:
The controller dynamically switches between different speed priority assignments based on operational context. When fork lowering is prioritized, the motor controls speed for fork lowering while mast tilting operates with available flow. When mast tilting is prioritized, the control assignment reverses. This dynamic reassignment enables both operations to achieve their instructed speeds at different times, improving overall productivity.
Solution Approach 2:
The system incorporates feedback from speed sensors and operation instructions to continuously monitor the actual speeds of different hydraulic mechanisms. The controller uses this feedback to determine when to switch priority assignments, ensuring that operations can achieve their target speeds efficiently while maintaining safe and productive forklift operation.
3Ease of operation
If hydraulic oil flows directly from the lifting/lowering hydraulic cylinder to the hydraulic pump during fork lowering, then the lowering operation is simple, but power consumption increases and leakage occurs when the pump rotation speed does not match the required speed
Solution Approach 1:
The patent introduces a hydraulic accumulator as an intermediary between the lifting/lowering hydraulic cylinder and the hydraulic pump. During fork lowering, hydraulic oil flows through the accumulator which can store or release hydraulic energy as needed. This intermediary component buffers the speed mismatch between the pump and the lowering operation, preventing direct connection problems while maintaining operational simplicity.
Solution Approach 2:
The system changes the hydraulic flow path parameters dynamically. When the pump rotation speed matches the required lowering speed, hydraulic oil flows directly to the pump. When speeds don't match, the controller redirects flow through the accumulator or adjusts pump speed to minimize energy loss and prevent leakage, while maintaining the simple lowering operation interface.
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
Enables effective and efficient operation of multiple hydraulic subjects, such as forks and masts, by managing hydraulic oil flow and motor speed to maintain instructed speeds, reducing power consumption and leakage, and stabilizing the forklift's performance.
Implementation Method 1
The flow rate control valve opens at an open degree that is in accordance with a pressure difference between a front side and a rear side of the proportional valve
Implementation Method 2
The hydraulic pump generates rotation to operate a hydraulic cylinder (lift cylinder) that lifts and lowers a fork
Implementation Method 3
The discharge control mechanism allows hydraulic oil to be discharged from the lifting/lowering hydraulic cylinder to the hydraulic pump when lowering the fork
Data Source
AI summary
A hydraulic control device for a forklift includes: a plurality of hydraulic mechanisms including a lifting/lowering hydraulic cylinder and a tilting hydraulic cylinder; a hydraulic pump; an electric motor; a discharge control mechanism; a proportional valve; a flow rate control valve; and a controller. When the lifting/lowering hydraulic cylinder performs a lowering operation of the fork and a hydraulic mechanism other than the lifting/lowering hydraulic cylinder simultaneously performs a further operation, the controller controls an open degree of the proportional valve in accordance with a rotation speed difference of a required lowering operation rotation speed for the hydraulic pump, which is required to perform the lowering operation at an instructed speed that is in accordance with an operation amount of the lifting/lowering control member, and a required further operation rotation speed for the hydraulic pump, which is required to perform the further operation.