Hydraulic Drive Wheel Pretensioning for Industrial Truck Stability
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Solution Overview
Problem
Industrial trucks face challenges in maintaining drive wheel load and lateral stability due to weight changes, such as those caused by replacing lead-acid batteries with lithium-ion batteries, which affect traction and stability during varying ground conditions and maneuvers.
Innovation Solution
The industrial truck employs a spring unit with a hydraulic cylinder and a switchable valve that continuously adapts to changing conditions, allowing the drive wheel to maintain necessary load and stability through hydraulic connection and mechanical pretension, with the valve opening in safe operating states to adjust to ground conditions and prevent lifting during hazardous states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the vehicle mass is reduced by using lithium-ion batteries instead of lead-acid batteries, then the energy efficiency and operational time are improved, but the drive wheel load decreases which affects traction capacity and lateral stability
Solution Approach 1:
The patent employs a spring unit that acts as a counterweight mechanism to compensate for the reduced vehicle mass. The spring unit is designed to apply a predetermined downward force on the drive wheel, effectively creating an artificial load that replaces the weight previously provided by the battery mass. This ensures that the drive wheel maintains sufficient contact force with the ground for adequate traction capacity and lateral stability during operation.
Solution Approach 2:
The invention changes the physical parameters of the drive system by introducing a mechanically adjustable spring unit. The spring constant and preload force can be specifically calibrated to match the required drive wheel load for the reduced vehicle mass. This parameter adjustment allows the system to maintain optimal traction characteristics despite the fundamental change in battery technology and associated mass reduction.
2Force
If the drive wheel load is increased to maintain traction capacity, then the lateral stability is improved, but the shock loads on the chassis increase during uneven terrain operation
Solution Approach 1:
The spring unit serves as a pre-configured cushioning element that is integrated into the drive wheel assembly. By designing the spring with appropriate stiffness and damping characteristics, it provides beforehand cushioning that absorbs shock loads generated during operation on uneven terrain. The spring continuously deflects and stores energy during impact events, preventing these shocks from being transmitted directly to the chassis and other vehicle components.
Solution Approach 2:
The spring unit acts as an intermediary element between the drive wheel and the chassis. It mediates the interaction forces by providing a compliant connection that can accommodate vertical movements and absorb impact energies. This intermediary spring mechanism allows the drive wheel to maintain high contact force for traction and stability while isolating the chassis from harmful shock loads during uneven terrain operation.
3Stability of the object's composition
If a rigid connection is used for the drive wheel to ensure lateral stability, then the stability is improved, but the adaptability to changing ground conditions deteriorates
Solution Approach 1:
The invention transitions from a rigid connection to a dynamic, compliant connection using a spring unit. This spring-based suspension system allows the drive wheel to dynamically adapt its vertical position in response to changing ground conditions while maintaining lateral stability through the restoring force of the spring. The system automatically adjusts to varying terrain profiles, obstacles, and ground hardness without requiring active control or rigid structural connections.
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 solution ensures consistent drive wheel load and lateral stability across varying conditions, preventing shock loads and maintaining traction and control during uneven terrain and maneuvers, without requiring sensors to detect unstable states.
Implementation Method 1
The drive wheel is pretensioned against the ground or ground surface by a spring unit
Implementation Method 2
The spring unit has a hydraulic cylinder and a switchable valve
Implementation Method 3
In its closed position, the switchable valve blocks the movement of the drive wheel in the direction of the hall floor
Data Source
AI summary
An industrial truck includes a vehicle frame and a drive unit. The drive unit includes a drive wheel movably mounted to the vehicle frame and a spring unit. The spring unit includes a hydraulic cylinder positioned between the vehicle frame and the drive unit and a switchable valve configured to define a blocked state. The spring unit is configured to pretension the drive wheel against a ground surface. When the switchable valve is in the blocked state, a one-sided movement of the hydraulic cylinder is blocked.