Hill Holding Device: Design & Function Explained

Hill Holding Device

What is Hill Holding System?

Hill holding device is an auxiliary mechanical braking device used in earlier generation hydraulic braking system. It automatically prevents the vehicle from sliding down the hill or slope after it is fully stopped by the use of the vehicle’s service brakes and as long as the clutch is disengaged. The hill holding system essentially consists of a check valve in the fluid line just ahead of the brake master cylinder. It maintains the pressure as long as the driver holds the clutch disengaged. With this device in the braking system, the drive can take the foot off from the brake pedal and keep it on the accelerator as the clutch is engaged.

Hill Holding Device
Hill Holding Device


Furthermore, the above diagram shows the construction of a hill holding device. Cam D operates valve B through E as shown in the diagram. Ball C controls the passage between valves B and C. When the driver engages the clutch; it opens the passage between A and B. Thereby, allowing the fluid to pass from the manner cylinder to the brakes. When the driver stops the car by disengaging the clutch and applying the brakes, the device operates cam D so that it presses the valve C against seat A; thereby closes its passage.

In Hill Holding Device, the passage between B and C still remains open. This keeps the brake master cylinder in communication with brakes through the passage inside the valve B. However, this happens only when the car is in the forward motion. While going uphill if the driver disengages the clutch and applies brakes, due to the gravity action, the ball C will stop passage between C and B. It will also stop the passage between E and A which is closed by cam D.

Now, if the driver releases the brakes, even the fluid under pressure in brake lines remains there. It does not come back and brakes remain applied. However, the system automatically releases brakes when the driver engages the clutch and starts the vehicle. Bendix, Girling, and TVS are some of the leading manufacturers of brake components in the world.

Watch Hill holding Device in action here:

Read More: How Adaptive Brakes work in a car?>>

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