An electric parking brake has several advantages over a traditional all-mechanical design. Let's look at the operating principle of the electromechanical handbrake, the pros and cons. As illustrations of the device, materials from the VAG automaker were used, describing the design of the hand brake of the Passat B6 model.
In a mechanical parking brake system, the force on the brake pads is transmitted from the lever through a cable drive. In the design of the electromechanical handbrake, the lever is replaced with a button, and the force on the pads, at the command of the ECU, is created using an electric drive and a multi-stage gearbox.
Electronic parking brake device
The electric parking handbrake consists of several components.
- Button to enable the Auto Hold function. Allows you to activate the automatic parking brake when stopping the vehicle on a slope.
- A key that turns the electronic parking handbrake on and off.
- Clutch pedal position sensor. On cars with manual transmission, it is designed to automatically turn off cruise control and select the moment to turn off the handbrake when starting the car with the Auto Hold function enabled.
- Rear brake mechanisms.
- Electronic handbrake control unit.
- ABS control unit.
What to do
First of all, you need to check the battery. If everything is fine with it, and there is enough charge for normal operation, then the problem may be related to faulty wiring.
The second option is to carefully check the operation of the parking brake. To do this, you need to stand on an inclined surface, press the brake, put the car on the handbrake and check whether it will roll or not. To avoid an emergency, make sure in advance that there are no other cars nearby.
If the car starts moving, the handbrake is faulty. In this case, you will have to repair the parking brake by completely disassembling the box. If the car remains stationary, then the Electronic Parking Brake error is most likely due to the electronic sensor. It's much easier to fix than the box.
If you are an inexperienced driver and have little understanding of the car, then it is better to turn to professionals. If the car was purchased recently and the warranty period has not yet expired, then you need to contact the dealer. In other cases, it is better to go to a car repair service. You definitely cannot ignore the Electronic Parking Brake error. If you do not solve the problem in time, you may encounter unpleasant consequences on the road in the future.
Features of rear brake mechanisms
The main feature of the brake mechanisms is the presence of an electric motor and a multi-stage gearbox. The motor is a conventional DC motor. The gearbox allows you to regulate the braking force and at the same time increase the torque from the electric motor shaft. The gearbox consists of 3 parts.
1. Screw drive - a screw connection in which the rotation of the shaft provokes longitudinal displacement of the pressure nut. The special shape of the pressure nut housing and the inside of the brake piston makes it impossible for them to rotate relative to each other. At the same time, the possibility of longitudinal movement remains. The self-braking spindle thread prevents the pads from spontaneously opening after the actuator is turned off. Therefore, you can remove and put the car on the electronic handbrake only if there is power at the electric motor terminals.
2. Toothed belt drive . Consists of two pulleys connected by a timing belt. The ratio of the diameter of the small and large gears determines the reduced gear ratio.
3. Gearbox with movable gear . By means of a toothed belt, the torque from the electric motor is transmitted to a large toothed pulley. The movable gear leads prevent it from rotating relative to the body, so it can only swing on the axis of the large toothed pulley hub. The driven gear and driven shaft are rigidly connected to each other. The drive gear on the shaft is placed on a bearing.
The oscillating gear moves on the hub of a large toothed pulley. Thanks to the skew and special design, each rotation of the large toothed pulley leads to a change in the position of the floating gear. Due to the fact that the driven gear has 51 teeth, and the floating gear has only 50, one of the teeth of the swing gear always presses on the driven tooth. Each time the oscillating gear moves, the driven gear rotates through a small angle. This design makes it possible to increase the torque of the electric motor by 50 times in order to tightly clamp the disc with the brake pads.
Composition and purpose of individual EPB units
To perform almost all functions of a mechanically driven parking system in a car, the following is used:
- standard rear wheel disc mechanism with caliper and pads;
- electric motor and belt drive to the gearbox;
- planetary gearbox with oscillating gear and helical gear to the pad pusher on each rear wheel;
- a parking brake control unit with sensors and a button at the driver’s disposal.
The electronic unit interacts with the vehicle data bus, receiving signals from external sensors, engine and transmission control systems.
The pads are pressed against the discs using a servo drive with a high gear ratio formed by an electric motor, a total three-stage gearbox and an internal pad pusher. The external one is engaged through a floating caliper bracket. Operating modes are set by the control electronics and the driver.
Operating principle of the electronic handbrake
When the parking brake button is pressed, the handbrake control unit supplies power to the electric motor. The torque from the electric motor shaft, belt drive and floating gear is transmitted to the worm gear spindle. The pressure nut presses on the piston, pressing the pads.
When the handbrake is deactivated by pressing a key or in automatic mode, the ECU changes the polarity of the supply voltage at the terminals of the electric motor winding. The shaft rotates in the opposite direction, moving the pads away from the discs.
The control unit constantly monitors the voltage on the motor windings. When the current reaches a certain value, the unit understands that the pads have compressed the disk and turns off the actuator.
Video:Parking Brake, Handbrake, Scissor, Electric Handbrake
EPB error in Kia Optima and Hyundai SantaFe: what is it
Cars are becoming more and more electronic. Its rapid development makes people's lives easier in many aspects. And more and more electronic components are being installed in cars. The reason for this is clear: cars, although fast, are a dangerous way of transportation.
In the event of some kind of malfunction or driver error, not only those in the car, but also random people around can die. Previously, there were few ways to prevent this, except to teach everyone good driving, as well as car repair. Now you can stick sensors into every part of the machine and constantly monitor its condition.
What is more: advantages or disadvantages?
Electronic handbrake brakes (EPB) have made cars more comfortable to drive thanks to several points at once:
- cheaper production. When assembling a car, you do not need to mount the handbrake cable from the handle to the rear pads through a special tunnel in the body;
- improving interior ergonomics. The space concealed by the handle, casing and cable mechanism can now be more effectively used to accommodate other controls, a niche for things, and an armrest;
- more functionality. Thanks to the electronic handbrake control, it is now possible to implement assistance when starting on a road with a slope. The car no longer rolls away, there is no need to play with the clutch pedal, gas and handbrake lever. The ECU registers the start of movement using sensors and automatically releases the rear brake pads;
- the presence of self-diagnosis, which allows you to light a warning lamp on the dashboard if the electronic handbrake is not working properly.
The main disadvantage of the electromechanical system is the increased cost of maintenance. Due to the increasing complexity of the design, the reliability of the unit has also decreased. The wires and the electric drive itself are in extremely unfavorable conditions. Often the plastic casing of the accuator cracks, causing moisture and reagents to leak inside. Over time, corrosion blocks the operation of the electric motor. Diagnosing the cause of a malfunction of the electronic handbrake is more expensive.
Reasons for the error
Experienced drivers come up with several reasons why the EPB light may light up in a Kia Optima or Hyundai SantaFe:
- parking sensors or parking radar are installed incorrectly;
- there are problems with the battery (it may be giving out a low charge);
- The electronic sensor signaling an error has broken down;
- The parking brake has failed.
What does Auto Hold mode mean?
When Auto Hold mode is activated, the electronic handbrake system will hold the vehicle on a slope until the vehicle starts moving. The following parameters are taken into account by the control unit:
- tilt angle (read by longitudinal acceleration sensor);
- engine load (determined by the signal from the throttle position sensor);
- the desired torque, determined by the signal from the accelerator pedal position sensor;
- degree of clutch closure (only on cars with manual transmission). Determined by the signal from the clutch pedal position sensor. On cars with automatic transmission, the direction of movement is taken into account, determined by the signal from the selector position sensor and the presence of power to the reversing lights.
Please note that the electronic handbrake only activates the Auto Hold mode if the engine is running, the driver's seat belt is fastened, and all doors are locked.
Pros and cons of the EPB system
In terms of ease of use, an electric handbrake is incomparably better than a simple mechanical one. But we must remember about its weaknesses:
- if the battery is discharged, it will no longer be possible to remove the car from the brake; to reverse the electric motors, you need to have power from the on-board network;
- the electric brake has only two positions, on and off, it is impossible to regulate the force, as on mechanics;
- artificially causing the rear wheels to slide, as a mechanical brake allows, will also not work here;
- quite complex mechanisms appeared in the calipers, potentially reducing reliability, although corrosion-related failures were often observed in the cables;
- the cost of the system is many times higher, which has already been experienced by owners of used cars with an electromechanical parking brake;
- the pads have to be replaced using a scanner that switches the EPB into service mode;
- Having gotten used to the operation of automation, many drivers completely forget about the presence of a parking brake system in the car, which is undesirable; sometimes its operation can take you by surprise.
But in reality, in everyday driving, having EPD is one less thing to worry about. The car will always take care of keeping itself in place, both in traffic and in parking lots:
- easier starting on hills;
- collisions with obstacles are prevented if your foot is accidentally removed from the brake pedal and the selector is in position D;
- The parking brake is adjusted automatically, it is always ready to create maximum braking force;
- to the right of the driver there is no lever with a large working stroke, which frees up space in the cabin;
- Maintenance comes down to routine checks and replacement of brake pads.
Everything that was said with the mention of an automatic transmission also applies to a manual one. The only difference is the location of a separate sensor under the clutch pedal, which tells the electronics that the pedal is pressed and by how much. This will be required for smooth release of the brakes when starting off.
How to use - frequently asked questions
What should I do to apply the handbrake while parked?
It is enough to depress the brake pedal, then press the handbrake button. In this case, the ignition does not have to be turned on.
How to disable the electronic handbrake?
You can release the car from the handbrake only with the ignition on and the brake pedal pressed. When these conditions are met, press the power button for the electromechanical handbrake.
What is the algorithm for automatically disabling the electronic parking brake?
If you start the engine, put the automatic transmission in D/R mode and press the accelerator pedal, the parking brake will release automatically. On cars with manual transmission, the control unit determines the start of movement by pressing the clutch, engaging a gear and increasing load on the engine. This takes into account the tilt of the vehicle.
What happens if you use a modern electronic handbrake while driving?
If the car speed is less than 7 km/h, the ECU will block the pads using servos. If the speed is higher, the hydraulic drive of the brake system will be activated. In this case, holding the key will activate all 4 brake mechanisms.
After putting the handbrake on, the car sometimes tries to roll away after a while, after which it stops again - is this normal operation or a sign of a malfunction?
The system is operating normally. When the vehicle is stopped using the service brake, the ABS ECU closes the valves in the valve body, maintaining the braking force on the pads using a hydraulic drive. After some time, the system relieves pressure in the brake lines and engages the electromechanical drive. In some cases, due to misalignment in braking force calculations, this transition may be felt, but it is not something to worry about.
Things to remember
Although EPB can regulate itself, it will have to undergo periodic inspections. In this case, the car is installed on a stand and, using special diagnostic equipment, the mechanic checks the proper operation of the system.
If it's time to change the brake pads, you need to act very carefully. During any technical work, the electromechanical part must be in service mode. If you miss this point, there is a high risk that the electric handbrake will activate on its own during the work process and damage the vehicle or the mechanic himself.
