Vertical Rear-Axle Motor Layout for High-Steering Lift Trucks
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Solution Overview
Problem
Current electric lifting trucks face challenges in achieving small turning radii while maintaining energy efficiency and being usable on rough terrain, as existing solutions either compromise on steering angles or suffer from reduced energy efficiency due to the use of cardan shafts and interference issues with motor placement.
Innovation Solution
The electric lifting truck features a rear axle with steered wheels that are hinged to the frame and pivot around a longitudinal axis, with a rear electric motor mounted directly on the axle and a vertically oriented rotation axis, allowing high steering angles and eliminating interference, and enabling a large battery compartment by removing mechanical components from the central area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the electric motor is positioned away from the rear axle and connected by a cardan shaft, then the steering angles can be increased, but the energy efficiency is reduced and the footprint increases
Solution Approach 1:
The patent extracts the cardan shaft and intermediate transmission components from the system, positioning the electric motor directly on the rear axle to eliminate the inefficient mechanical transmission path while maintaining the ability to achieve high steering angles through direct drive architecture
Solution Approach 2:
The patent repositions the electric motor from a longitudinal arrangement (away from axle) to a direct axial mounting on the rear axle, changing the spatial dimension of motor placement to eliminate the need for cardan shafts while preserving steering capability
2Use of energy by moving object
If the electric motor is installed directly on the rear axle, then energy efficiency is improved, but the steering angle is reduced due to interference between wheels and motor
Solution Approach 1:
The patent employs a steerable rear axle assembly where the entire axle unit with mounted motor can pivot relative to the vehicle frame, allowing the wheels to achieve high steering angles dynamically without the motor body interfering with the wheel path during steering operation
Solution Approach 2:
The patent segments the rear axle into a steerable assembly that can pivot independently from the vehicle frame, separating the motor mounting position from the wheel contact path to eliminate interference while maintaining direct drive efficiency
3Ease of operation
If the motor is positioned away from the rear axle, then steering is enabled, but the footprint in the central area increases which hinders battery pack positioning
Solution Approach 1:
The patent removes the cardan shaft and intermediate transmission components that occupied central space, and repositions the electric motor directly on the rear axle, thereby extracting the space-hungry mechanical elements and freeing up the central area for battery pack installation
Data Source
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AI summary
An electric lifting truck, comprising a frame (12) carrying a pair of front drive wheels (14) and a rear axle (38) carrying a pair of rear steered drive wheels (16) driven by a rear electric motor (50), wherein the rear electric motor (50) is fixed to the rear axle (38) and is arranged with its own rotation axis (C) oriented vertically.