Traction Force Limiting Device for Working Machines
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Solution Overview
Problem
Conventional multi-step transmissions in working machines, such as graders, often lead to excessive traction force during downshifts, causing wheel slip, especially on varying ground conditions, which can result in re-working of already flattened sections.
Innovation Solution
A traction force limiting device with a continuously variable transmission that decouples rotational speed ratio from torque ratio using a variator, allowing for independent adjustment of torque ratio, and includes a computer unit to compare actual traction force with a set limit value, controlling the variator to prevent exceeding the limit, thereby preventing wheel slip without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-step transmission is used to prevent engine stalling, then the transmission can downshift to increase torque, but the traction force increases excessively causing wheel slip
Solution Approach 1:
The patent applies dynamics by implementing a continuously variable transmission (CVT) that allows continuous adjustment of the transmission ratio rather than discrete steps. This enables the transmission ratio to be dynamically optimized to prevent both engine stalling and excessive wheel slip, resolving the contradiction between reliability and harmful effects.
Solution Approach 2:
The patent changes the parameter of transmission ratio from discrete multi-step values to continuous variable values. By continuously adjusting the transmission ratio based on operating conditions, the system can prevent engine stalling while avoiding excessive traction force increases that cause wheel slip.
2Reliability
If the transmission ratio is increased during downshift to prevent stalling, then engine reliability improves, but traction force exceeds the limit causing wheel slip
Solution Approach 1:
The patent implements feedback control by continuously monitoring the actual traction force and comparing it with the limit value. When the actual traction force approaches the limit, the control unit adjusts the transmission ratio to prevent excessive traction force, thereby preventing wheel slip while maintaining engine operation stability.
Solution Approach 2:
The system dynamically adjusts the transmission ratio based on real-time feedback of traction force conditions, allowing the transmission to respond continuously to changing operating conditions rather than using fixed discrete steps.
3Object-affected harmful factors
If a traction control system with multiple sensors is implemented to detect drag force, then wheel slip can be avoided, but the device complexity and cost increase
Solution Approach 1:
The patent makes the existing transmission ratio sensor serve multiple functions: it not only controls the transmission operation but also provides the basis for determining actual traction force in the feedback control system. This eliminates the need for separate drag force sensors, reducing device complexity and cost while maintaining wheel slip prevention capability.
Solution Approach 2:
The system uses its own existing sensor infrastructure (transmission ratio sensor) to provide the information needed for traction force determination and control, rather than requiring external additional sensors. The transmission system essentially monitors and controls itself.
4Device complexity
If conventional multi-step transmission is used, then the structure is simple, but the traction force behavior causes wheel slip on varying ground conditions
Solution Approach 1:
The patent replaces the static multi-step transmission structure with a dynamic continuously variable transmission that can adapt its transmission ratio continuously according to varying ground conditions and operating requirements, providing both simplicity and adaptability.
Solution Approach 2:
The system changes the transmission ratio parameter from discrete fixed values to continuous variable values that can be dynamically adjusted to match varying ground conditions, improving adaptability without significantly increasing structural complexity.
Data Source
AI summary
A traction force limiting device for a working machine with a continuously variable transmission that comprises a variator for adjusting the rotational speed ratio of the transmission independently of the torque ratio of the transmission. The traction force limiting device has a traction force interface for providing information to determine a traction force of the working machine, a limit value interface for setting a traction force limit value of the working machine and a control interface for emitting a control signal to the variator. Additionally, the traction force limiting device has a computer unit designed, on a basis of information provided via the traction force interface, to determine the traction force, to compare the traction force determined with the traction force limit value set via the limit value interface, and to control the variator in such manner that the traction force does not exceed the traction force limit value.