1.1 Analysis of Vehicle Thermal Management Requirements

The drive system of a vehicle comprises the drive motor, motor controller, and reducer. These components generate significant heat during operation, particularly under heavy loads. If the temperature rises too high, it can negatively impact motor performance, potentially causing damage or failure. Similarly, excessive temperature in the high-speed reducer’s lubricating oil can reduce its viscosity, compromising the lubrication effect. For electric vehicles, the lithium-ion power battery also generates heat during charging and discharging, especially during fast charging or high-power discharge. If the battery temperature becomes too high or low, it can affect both its lifespan and performance, and in extreme cases, lead to spontaneous combustion. Additionally, components like chargers, inverters, and DC transformers require effective cooling. This study focuses on the cooling needs of the drive system and power battery, with an in-depth analysis of the vehicle’s electronic water pump.

1.2 Cooling System Structure

Based on current research into electric vehicle cooling systems, this paper proposes the use of water cooling to regulate the temperature of the drive system and power battery. As illustrated in Figure 1, the vehicle’s cooling system is designed with one “large cycle” and two “small cycles.” In addition to the conventional water-cooling circuit that manages the temperature of the vehicle’s core components, the air-conditioning system within the passenger compartment is also integrated into the vehicle’s thermal management system. This enhances or shares the thermal load within the overall cooling cycle, ensuring efficient heat distribution and improved system performance.

2. Electronic Water Pump Scheme Design

The hydraulic and mechanical design of the electronic circulation water pump for vehicles closely resembles that of traditional mechanical water pumps, with the primary distinction being in the motor and its controller. Unlike mechanical pumps, the speed of the electronic water pump is decoupled from the engine’s speed and is instead controlled through precise matching control commands. Given the similar design and development processes for electronic water pumps used in both power battery cooling systems and drive system cooling systems, one of these applications can serve as the focus for research. In this case, the electronic coolant pump used in the drive system cooling is selected for analysis.

The vehicle’s electronic water pump comprises three main components: a centrifugal water pump, a brushless DC motor (BLDC motor), and a motor controller. The impeller of the water pump is integrated directly with the motor shaft, resulting in a compact design with minimal mechanical losses. The motor’s rotor drives the impeller, which draws the coolant in from a vertical direction and forces it against the inner wall of the pump’s volute. This process propels the coolant through the system, transferring both energy and fluid to the next stage in the cooling cycle.