Viscous Coupling Fan Speed Regulation in Construction Machines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Construction machines, such as road finishers, face inefficiencies in cooling systems due to rigid fan connections to diesel engines, leading to increased noise and hydraulic losses, and existing controllable fan systems react hectically to extreme conditions, affecting performance and fuel efficiency.
Innovation Solution
A controllable viscous coupling system connected between the drive unit and the fan, allowing independent fan speed control based on oil levels, minimizing torque transmission and power losses, and utilizing a controller to monitor temperatures and adjust fan speed for optimal cooling and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan is rigidly connected to the diesel engine, then the fan always assumes a fan speed that corresponds to the drive speed of the diesel engine, but this leads to increased noise and hydraulic losses
Solution Approach 1:
A viscous coupling is introduced as an intermediary between the diesel engine and the fan. This viscous coupling allows slip between the input and output shafts, enabling the fan speed to differ from the engine speed while still being driven by it. The viscous coupling transmits torque through viscous fluid, providing smooth torque transmission and eliminating the rigid connection that causes noise and hydraulic losses.
Solution Approach 2:
The system transitions from a static rigid connection to a dynamic viscous coupling that can adapt its torque transmission characteristics. The viscous coupling allows the fan speed to dynamically adjust based on operating conditions, reducing noise during low-load operations while maintaining adequate cooling when needed.
2Productivity
If a hydraulically driven fan is used with needs-based supply of cooling air, then cooling efficiency is optimized, but hydraulic losses increase and financial outlay increases enormously
Solution Approach 1:
The viscous coupling serves as a mechanical intermediary that replaces the complex hydraulic system. Instead of using hydraulic pumps and motors with associated losses, the viscous coupling directly transmits mechanical energy from the engine to the fan through viscous fluid, significantly reducing energy losses while maintaining the ability to optimize cooling air supply.
Solution Approach 2:
The invention uses a viscous fluid coupling mechanism that operates on fluid dynamics principles but avoids the complexities of hydraulic systems. The viscous fluid transmits torque through shear stress, providing a simpler, more efficient alternative to hydraulic fan drives with constant current pumps.
3Adaptability or versatility
If existing controllable fan systems are used, then fan speed can be adjusted, but they react hectically to extreme measured values, affecting performance
Solution Approach 1:
The viscous coupling provides inherent cushioning against extreme variations in engine speed and load. The viscous fluid acts as a buffer that smooths out torque fluctuations and prevents hectic reactions to transient conditions. This cushioning effect stabilizes fan operation while maintaining adaptability to changing cooling requirements.
Solution Approach 2:
The system changes the physical parameters of torque transmission by using viscous coupling characteristics. The torque transmission through viscous fluid naturally filters out extreme measured values and provides smooth, gradual adjustments in fan speed based on engine operating conditions, preventing hectic responses.
4Speed
If the viscous coupling is completely flooded with oil, then the desired fan speed can be achieved, but the upstream speed control needs a long time until the output speed reaches the target speed
Solution Approach 1:
The viscous coupling system dynamically adjusts its oil level based on operating conditions. During transient phases or idling, the oil level is reduced to minimize inertia and improve response time. During steady-state operation requiring precise speed control, the oil level is increased to achieve the desired fan speed. This dynamic adjustment of oil level optimizes both response time and speed control accuracy.
Solution Approach 2:
The system changes the oil level parameter in the viscous coupling to optimize performance for different operating conditions. By controlling the amount of viscous fluid in the coupling, the system can rapidly transition between different speed states while maintaining adequate torque transmission when needed.
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
A construction machine has automatic fan rotational speed regulation, a drive unit, and a cooling system with a fan to generate a cooling airflow. The cooling system comprises an adjustable viscous coupling connected on the input side to the drive unit and on the output side to the fan. An independent claim is included for a method for automatic regulation and control of a cooling system of a construction machine.