How does hill hold work

The time is now. As a subfunction of the ESP, the hill hold control records and stores the brake pressure, holds the car stationary on the slope and enables moving off without using the hand brake.

Rolling backwards is prevented for about two seconds after the brake has been released. Complete your user account. Personal information. Tell us the basic information about you. Don't worry, you can edit this information later. When the brake pedal is released, Hill Hold Control is activated, maintaining the appropriate brake pressure until the throttle is applied.

Therefore, if the conditions required to activate Hill Hold Control entrance criteria are satisfied, then the system will be activated whether the surface has a positive, negative or zero gradient.

These systems are more complex than basic systems. The sensors used in these systems are the same as the sensors used by the basic-level systems plus a clutch position switch for manual transmission vehicles , a longitudinal acceleration sensor and a sensor indicating when the vehicle is in reverse gear.

In the case where a vehicle is on an incline, three conditions must be satisfied:. When on a decline, an additional condition is required. The reverse gear must be engaged.

This indicates to the system that the driver is trying to back up a hill without rolling forward. And while once upon a time sturdy torque converters would keep automatic-transmission-equipped cars in place on a hill, today's newer automatic transmissions are more fuel-efficient and tend to rev lower, which means they can slip more. And so these days, we're often experiencing that anxious rollback moment, even in automatic-equipped cars.

Enter an awesome feature that is becoming more common: hill-hold, or hill-start assist technology, which makes navigating hilly terrain effortless, allowing drivers to get started without rolling backward or forward. In a vehicle equipped with hill-hold, a pitch sensor detects the tilt of the body when the car is stopped on a slope and sends a signal to the vehicle's brake hardware to keep the wheels clamped for a few seconds after the driver releases the brake pedal.

If the driveway to your home or parking garage is sloped, you understand how helpful this feature can be, especially on a rainy day or in slow traffic on long inclines, or when the person behind you inches too close in traffic. Electronic Control Unit ECU : This is the vehicle's embedded computer system that receives signals from the various sensors. The ECU decides when the brakes need to be applied based on that input. The ECU can also calculate the traveling resistance, which is a function of the car's weight determined by the pressure sensors and the slope of the hill that the car is on determined by the angle sensors.

Traveling resistance is used to calculate how much engine torque will be necessary to move the vehicle uphill. Brake actuator : An actuator is a device that converts an electrical signal into a physical movement. The brake actuator receives a signal from the ECU telling it to trigger the brakes. It then activates brake valves, sending brake fluid to the brakes to hold the vehicle in place, which keeps it from rolling back down the hill.

In the case of a hybrid vehicle, the electric motor may be used in place of the brake to apply sufficient forward motion to the vehicle to keep it from rolling backward. Once the driver starts to accelerate, the torque sensors help the ECU to determine if the engine's torque is sufficient to overcome the traveling resistance already calculated by the ECU.

If it is, then the ECU sends a signal to the brake actuator telling it to turn off the brakes and let the car move. Ideally, the driver should be aware of none of this. The release of the brakes should be so smooth that the driver is unaware that brake force was still being applied after the brake had been released. Only later will the driver realize that he or she never once had to worry that the vehicle was going to slide back down the hill and collide with the car behind it. Driving safety is rarely this painless.

Is the safety advantage supplied by hill-start control worth the extra cost of buying a car that comes equipped with it? We'll consider that question on the next page. The major benefits of hill-start control should be obvious. It makes driving easier in certain situations and it can promote driving safety, too. After all, nobody wants his or her car to roll backwards down a hill.

There are just too many possibilities for damage in that scenario. But hill-start control isn't just for the benefit of the driver of the car that that's equipped with the hill-start system. It's also for the benefit of the traffic behind it. For that reason, there may eventually come a day when all cars come with hill-start control and similar safety and regulatory devices as standard equipment simply as a matter of public safety. Driving safety is important to everyone. Another way that hill-start control helps out is that it means less wear and tear on other parts of the car, such as the handbrake, that you might use to do the same job manually.

And in a manual transmission-equipped car you don't have to ride the clutch when starting out on a hill, meaning there's less wear on the clutch. And by preventing the car from rolling backwards, hill-start control puts less strain on the engine and drive train, which would otherwise have to counteract the backward momentum of the car in order to bring it up to speed.