Key Takeaways & Executive Findings
- •• A new calculation model for hydro-viscous clutch (HVC) torque and bearing capacity is proposed, replacing the fixed contact area ratio with a discrete micro-ring area ratio (DMAR) integration method to account for radial groove distribution. • A 32-degree-of-freedom dynamic model of the HVC in a fan drive system is established, enabling prediction of dynamic responses during speed regulation and revealing oscillation phenomena at the engagement steady-state boundary. • The proposed model accurately predicts axial engagement force and speed regulation curves, validated by experimental data, demonstrating its effectiveness for engineering design. • The study establishes a numerical relationship between friction plate structure parameters, mechanical properties, and speed regulation performance, providing a theoretical basis for optimizing friction plate design and step-less speed regulation.
Abstract
This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches (HVC) used in high-power vehicles, which is important to investigate the step-less speed regulation characteristics in a fan drive system. However, most of the existing models ignore the distribution differences of groove area along the radial direction, which may lead to significant deviations in calculating the mechanical property of friction pairs related to operating conditions and the engagement process. To fill this gap, a new calculation model for bearing capacity and frictional torque of friction pairs with different oil grooves is proposed, in which the traditional fixed contact area ratio coefficient for oil groove measurement is replaced by a more precise discrete micro-ring area ratio (DMAR) integration method. Then, a 32-degree-of-freedoms dynamic model of HVC at a fan drive system is established for the prediction of dynamic responses during speed regulation. Results show that friction pairs with different oil grooves have a direct influence on frictional torque and bearing capacity through the change of DMAR along the radial direction. The friction pairs with different groove structures have oscillation phenomena at the engagement steady-state boundary. Furthermore, a step-less speed regulation experimental setup is established to verify the correctness of the proposed model. It is demonstrated that the axial engagement force and the speed regulation curve predicted by the proposed method are in good agreement with the experimental data. The results could effectively predict the engagement dynamic characteristics. The numerical relationship among the structure parameters, the mechanical properties of friction pairs, and the speed regulation characteristics of the system are established through the proposed model, which lays a theoretical foundation for the structure design of friction plates and optimization of step-less speed regulation performance.
1. Introduction
Hydro-viscous clutch (HVC) is an important component in high-power vehicles’ fan transmission for step-less speed regulation [1–4]. Relying on the oil film shear and the interaction of asperities on the friction elements’ surface, it can achieve torque transmission. The lubrication state transitions from fluid lubrication to mixed friction or boundary friction, i.e., the three working states of the clutch: separated, slipping, and locked [5–7]. Investigating the engagement dynamic characteristics of friction pairs with different oil grooves is conducive to improving the stability of speed regulation during soft start and ensuring the safe operation of the mechanical transmission system [8].
The construction of precise calculation models for torque and bearing capacity in different lubrication stages is the key to investigating the dynamic characteristics during the engagement process. Chen et al. [9] investigated the effect of surface texture parameters on the load-bearing capacity of fluid and torque through a finite element method. Xie et al. [10] developed a mathematical model for the calculation of bearing capacity and torque during the phase of fluid lubrication of friction pair in the radial groove considering viscous temperature characteristics, the relationship between the cavitation phenomenon and the transmission efficiency was studied [11, 12]. Newton’s law of internal friction is met during the phase of fluid lubrication, and the main factors affecting the magnitude of the shear moment are the effective area factor and velocity distribution [1]. Cui et al. [13] calculated the friction pair’s bearing capacity and transmission torque in the phase of mixed friction based on the mean shear stress model and fractal contact theory. Based on this, Ref. [14] i
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Lintao Duan, Layue Zhao, Liming Wang, Yimin Shao, Liuyang Guo, Shi Chen, Zaigang Chen (2025). A New Dynamic Model of Hydro-Viscous Clutch in a Stepless Speed Regulation Fan Drive System Considering Oil Groove Structures. Chinese Journal of Mechanical Engineering. https://doi.org/10.1186/s10033-025-01286-8
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Frequently Asked Questions
What is the main contribution of this paper?
The paper proposes a new dynamic model for hydro-viscous clutches that accounts for oil groove structures using a discrete micro-ring area ratio (DMAR) method, improving accuracy in predicting torque and bearing capacity during speed regulation.
How does the proposed model differ from existing models?
Existing models often use a fixed contact area ratio coefficient, ignoring radial variations in groove area. The proposed model replaces this with a more precise DMAR integration method, capturing the distribution differences along the radial direction.
What are the key findings of the study?
The study shows that different oil groove structures significantly affect frictional torque and bearing capacity through changes in DMAR. It also reveals oscillation phenomena at the engagement steady-state boundary and validates the model with experimental data.
What is the significance of the 32-degree-of-freedom dynamic model?
The 32-DOF model allows for detailed prediction of dynamic responses during speed regulation, capturing the complex interactions within the fan drive system and enabling accurate simulation of engagement dynamics.
How was the model validated?
A step-less speed regulation experimental setup was established, and the predicted axial engagement force and speed regulation curves were compared with experimental data, showing good agreement.
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