Mower Cutting Unit Hydraulic Lift Rate Control for Reduced Bouncing
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Solution Overview
Problem
Existing grass mowing machines face challenges in adjusting lift rates of cutting units due to variations in weight and engine speed, leading to undesirable mowing conditions.
Innovation Solution
An adjustable lift rate system using a proportional solenoid valve to divert hydraulic fluid, allowing operators to adjust lift rates via a display and manual controls, with features like ramped current profiles to control lift and lower speeds, ensuring consistent operation across varying engine speeds and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lift rate is increased to improve productivity, then the mowing efficiency is improved, but the cutting units bounce and impact against stops causing instability
Solution Approach 1:
The system dynamically adjusts the proportional solenoid valve current based on real-time conditions (engine speed, lift position, selected rate) to modulate hydraulic flow. This dynamic control allows the lift rate to adapt continuously, providing fast lifting when needed while automatically reducing speed near the top position to prevent bouncing, thus resolving the contradiction between productivity and stability
Solution Approach 2:
The system incorporates feedback mechanisms by monitoring engine speed, cut unit position, and operator selections to continuously adjust the proportional solenoid valve current. This closed-loop control ensures that the lift rate responds appropriately to changing conditions, maintaining stability during high-speed operations and preventing impact at the extremes of motion
2Adaptability or versatility
If a fixed lift rate is used to simplify the system, then the device complexity is reduced, but the system cannot adapt to different mowing conditions and engine speeds
Solution Approach 1:
The system changes the electrical parameter (proportional solenoid valve current) based on operating conditions, engine speed, and selected lift rates. By varying the current parameter dynamically rather than using fixed mechanical adjustments, the system achieves high adaptability to different mowing conditions while keeping the physical structure relatively simple
Solution Approach 2:
The patent replaces complex mechanical lift rate adjustment mechanisms with an electronically controlled proportional solenoid valve. This substitution allows precise control of hydraulic flow through electrical current modulation, reducing mechanical complexity while enhancing adaptability to different operating conditions through electronic control
3Stability of the object's composition
If the lift rate is decreased to improve stability, then cutting unit bouncing is reduced, but the mowing productivity decreases
Solution Approach 1:
The system applies periodic modulation to the proportional solenoid valve current during the lifting cycle, particularly near the top and bottom positions. This periodic adjustment of flow rate creates a controlled rhythm in the motion, allowing fast lifting during the majority of the stroke for high productivity while automatically slowing near extremes to maintain stability and prevent bouncing
4Productivity
If high current is applied to the proportional solenoid valve to increase lift speed, then productivity is improved, but energy consumption increases
Solution Approach 1:
The system applies high current to the proportional solenoid valve only when and where needed - specifically during the majority of the lifting stroke when high speed is required for productivity. Near the top and bottom positions, the current is reduced to appropriate levels, avoiding excessive energy consumption during phases where high speed is unnecessary or counterproductive
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 provides operator-adjustable lift rates, maintaining consistent mowing performance by adapting to different conditions and engine speeds, reducing bouncing and impact on cutting units.
Implementation Method 1
The adjustment changes the current to a proportional solenoid valve to divert hydraulic fluid to bypass the hydraulic cylinders for the lift arms
Data Source
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AI summary
An adjustable lift rate system on a grass mowing machine (102) such as a riding greensmower having a lift and lower circuit (109) including a plurality of hydraulic lift cylinders (120, 122, 124) to lift and lower a plurality of cutting units, and a controller (110) providing a current to a proportional solenoid valve (128) to bypass the hydraulic lift cylinders. An operator control (112) may be used to adjust the current to the proportional solenoid valve to adjust the lift and lower rate of the cutting units.