Application of an electric four-way valve in BTMS
Ⅰ. Definition
An electric 4-way Valve (4WV) is a motor-driven, switchable flow-path direction, four-way fluid reversing valve in the BTMS water cooling circuit. It is a flow distribution/reversing execution component of the thermal management circuit. The medium is generally ethylene glycol-water coolant (cooling antifreeze).
Interface definition: 4 fluid interfaces, usually labeled A / B / C / D;
Drive form: built-in stepper motor/small brushless motor + reduction mechanism + sealed valve core (mostly rotating valve cores, a few slide valve structures);
Control method: The VCU/BCM/BTMS controller sends a PWM or angle signal, and the controller controls the valve core to rotate to a designated position to achieve channel switching. Some valves also support continuous adjustment of the intermediate opening (continuously adjustable four-way valve, which is different from the switch-type four-way valve that only has 2-speed switching).
Ⅱ. Working principle
Core principle: The motor drives the internal rotating valve core to rotate, relying on the diversion channel on the valve core to change the connection and pairing relationship between the four nozzles. The valve core sealing surface ensures cross-flow leakage control between different flow channels (leakage is a key indicator for BTMS selection)
Ⅲ. Core role in BTMS
1. Battery pack circuit flow reversal (the most classic use)
The water-cooling plate/water-cooling channel has forward flow and reverse flow. The four-way valve switches the direction of coolant in and out of the battery pack, enabling reverse flushing and leveling the temperature difference inside the battery pack.
2. Loop mode switching: cooling/preheating/waste heat coupling switching
Connect the battery circuit to the Chiller (water-cooled condenser/cooling unit), PTC heater, motor electronically controlled waste heat circuit, and heat pump circuit:
Cooling mode: Battery pack ↔ Chiller connection; low-temperature coolant takes away battery heat;
Preheating mode: The battery pack ↔ PTC / motor waste heat circuit is connected, and the high-temperature coolant heats up the battery;
The four-way valve can directly switch the heat source/cold source docking relationship without changing the main circuit pipeline by reversing the direction, replacing 2~3 three-way valves.
3. Circuit reconstruction of heat pump thermal management system (hybrid/pure electric high-end models)
In-vehicle integrated thermal management (battery + motor + air conditioning heat pump), the four-way valve is used to reconstruct the circuit:
During heat pump heating: let the electrically controlled waste heat of the motor be given priority to the battery;
The battery is hot, and the passenger compartment is cooled at the same time: the circuit is split, the battery is cooled by an independent chiller, and the air conditioner is cooled by the refrigerant circuit;
A single four-way valve realizes thermal circuit decoupling and coupling switching, simplifying integration.
4. Flow distribution (exclusive to a continuously adjustable four-way valve)
Not only on-off reversal, the middle position of the valve core can realize: mixing of one cold flow + one hot flow, fine-tuning the temperature of the battery coolant, dynamically adjusting the inlet water temperature, improving the smoothness of temperature control, and reducing frequent starts and stops of PTC and frequent starts and stops of Chiller.
