A Dual Proportional Valve, often referred to as a proportioning valve or combination valve, serves the purpose of managing and regulating the distribution of brake fluid pressure between the front and rear brake circuits in a vehicle's braking system. The primary objectives of a dual proportional valve are to optimize braking performance, prevent wheel lockup, and ensure balanced braking under different driving conditions. Here are the main purposes of a Dual Proportional Valve:

1. **Brake Pressure Regulation:** The dual proportional valve is designed to regulate the brake fluid pressure delivered to the front and rear brakes. This is crucial for achieving balanced braking performance and preventing the wheels from locking up during hard braking or under heavy loads.

2. **Optimal Brake Force Distribution:** Different vehicles have varying weight distributions, with the front and rear axles bearing different proportions of the total vehicle weight. The dual proportional valve adjusts the brake force distribution based on these weight variations, ensuring that both the front and rear brakes contribute appropriately to the overall braking effort.

3. **Prevention of Rear Wheel Lockup:** In certain braking conditions, particularly when the vehicle is lightly loaded, there is a risk of the rear wheels locking up prematurely. The dual proportional valve includes a proportioning function that reduces the brake pressure to the rear wheels, helping to prevent rear wheel lockup and maintain stability during braking.

4. **Compensation for Brake Pad Wear:** As brake pads wear over time, the braking characteristics can change. The dual proportional valve may include features to compensate for this wear, adjusting the brake pressure distribution to maintain optimal braking performance.

5. **Integration with ABS (Anti-lock Braking System):** In modern vehicles, the dual proportional valve may be integrated into the ABS system. ABS helps prevent wheel lockup during hard braking by modulating brake pressure rapidly. The dual proportional valve works in conjunction with the ABS system to optimize brake pressure distribution while ABS is active.

6. **Emergency Brake Force Distribution:** During emergency braking situations, the dual proportional valve ensures that the available brake force is distributed in a way that maximizes the vehicle's stability and control. This is crucial for avoiding skidding and maintaining steering responsiveness.

7. **Towing and Heavy Load Adjustments:** When a vehicle is towing a trailer or carrying a heavy load, the weight distribution changes. The dual proportional valve adjusts the brake force distribution to accommodate the additional load, optimizing braking performance under these conditions.

Overall, the Dual Proportional Valve plays a critical role in maintaining balanced and effective braking in various driving scenarios. It is an important component for vehicle safety, ensuring that the braking system responds appropriately to different loads and conditions.