Electric park brake

Electric park brakes (EPB) are used on passenger vehicles to hold the vehicle stationary on grades and flat roads. This was accomplished traditionally using a manual parking brake. With electric park brakes, the driver activates the holding mechanism with a button and the brake pads are then electrically applied onto the rear brakes. This is accomplished by an electronic control unit (ECU) and an actuator mechanism. There are two mechanisms that are currently in production: 1. Cable puller systems and 2. Caliper integrated systems. EPB systems can be considered a subset of Brake-by-wire technology. First installed in the 2002 BMW 7 Series (E65), electric park brakes have since appeared in a number of vehicles. Electric park brake in the center console in a Volkswagen Touran Functionality Apart from performing the basic vehicle holding function required of park brakes, the EPB systems provide other functions like automatic release of the park brakes when the driver presses the accelerator, and re-clamping using additional force on detection of vehicle motion. Further, the hill-hold function, which applies brakes to prevent roll-back when pulling away on a gradient, can also be implemented using the EPB. Implementation The implementation of the control logic for the actuators is carried out by either using a stand alone ECU or by integrating it in the ECU for electronic stability control Standards The design of the electric park brakes should be compliant with: FMVSS 105 FMVSS 135 ECE 13H References http://www.volkswagenag.com/content/vwcorp/info_center/en/publications/2012/11/VIAVISION_No_09_November_2012.bin.html/binarystorageitem/file/VIAVISION_GB.pdf a b http://www.sae.org/events/bce/presentations/2009/jscheon.pdf http://www.volkswagen.co.uk/technology/parking-and-manoeuvring/electronic-parking-brake  http://www.trw.com/braking_systems/electric_park_brake  http://www.vda.de/en/publikationen/publikationen_downloads/detail.php?id=1163  http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.105  http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.135  http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/R13hr2e.pdf

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Parking brake

In road vehicles, the parking brake, also called hand brake, emergency brake, or e-brake, is used to keep the vehicle stationary and in many cases also perform an emergency stop. Parking brakes on older vehicles often consist of a cable connected to two wheel brakes at one end and the other end to a pulling mechanism which is operated with the driver's hand or foot. The mechanism may be a hand-operated lever, at floor level beside the driver, or a straight pull handle located near the steering column, or a (foot-operated) pedal located beside the drivers leg. In most automobiles the parking brake operates only on the rear wheels, which have reduced traction while braking. Some automobiles have the parking brake operate on the front wheels, for example most Citroens manufactured since the end of World War II, and the early models of the Saab 900. Hand brake lever from a Geo Storm. In this photo, the lever mechanism is shown not installed in the car. Brake warning light ISO symbol used to indicate that the parking brake is applied The most common use for a parking brake is to keep a vehicle motionless when it is parked. The park brake has a ratchet or other lockingmechanism that will keep it engaged until manually released. On vehicles with automatic transmissions, this is usually used in concert with a parking pawl in the transmission. Electric park brake switch of a Volkswagen Touran Electric parking brake A recent variation is the electric parking brake. First installed in the 2001 BMW 7 Series (E65), electric park brakes have since appeared in a number of vehicles. Two variations are available: In the more-traditional "cable-pulling" type, an electric motor simply pulls the parking brake cable on the push or pull of a button rather than a mechanical pedal or handle in the cabin. A more complex unit  (first seen on the 2003 Audi A8) uses a computer-controlled motor attached to each of the two rear brake calipers referred to as the Motor on Caliper(MoC) system. It is expected that these systems will incorporate other features in the future. Jaguar, Landrover, BMW, Renault, Subaru and VW already have a system where the parking brake engages when the engine is stopped and is released when the gas pedal is pressed. An extension of this system, called the hill-hold function, prevents roll-back when stopping and starting on a hill. The OEM can easily turn off the system. Some electric parking brakes function similar to "park" on an automatic transmission and will not engage when the vehicle is in motion, there is...

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Brake bleeding

Brake bleeding is the procedure performed on hydraulic brake systems whereby the brake lines (the pipes and hoses containing the brake fluid) are purged of any air bubbles. This is necessary because, while the brake fluid is an incompressible liquid, air bubbles are compressiblegas and their presence in the brake system greatly reduces the hydraulic pressure that can be developed within the system. The same methods used for bleeding are also used for purging, where the old fluid is replaced with new fluid, which is necessary maintenance. The process is performed by forcing clean, bubble-free brake fluid through the entire system, usually from the master cylinder(s) to the calipers of disc brakes (or the wheel cylinders of drum brakes), but in certain cases in the opposite direction. A brake bleed screw is normally mounted at the highest point on each cylinder or caliper. There are four main methods of bleeding: The pump and hold method, the brake pedal is pressed while one bleed screw at a time is opened, allowing air to escape. The bleed screw must be closed before releasing the pedal. In the vacuum method, a specialized vacuum pump is attached to the bleeder valve, which is opened and fluid extracted with the pump until it runs clear of bubbles. In the pressure method, a specialized pressure pump is attached to the master cylinder, pressurizing the system, and the bleeder valves are opened one at a time until the fluid is clear of air. In the reverse method, a pump is used to force fluid through the bleeder valve to the master cylinder. This method uses the concept that air rises in liquid and naturally wants to escape up and out of the brake system. Close-up of a disk brake bleed screw Vacuum bleeding a disk brake caliper Pressure bleeding a brake system If bleeding brakes because of master cylinder replacement the master cylinder is usually "bench bled" before installation. Typically by securing it on the bench, filling it with fluid, connecting fittings and hoses to route fluid from the outlet ports on the master cylinder back to its reservoir, and repeatedly depressing the master cylinder plunger until bubbles are no longer seen coming from the hoses. Different vehicles have different bleeding patterns. Brakes are usually bled starting with the wheel that is furthest from the master cylinder and working towards the wheel closest to the master cylinder. References Brake Bleeding Methods by Phoenix Systems

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Air brake (road vehicle)

An air brake or, more formally, a compressed air brake system, is a type of friction brake for vehicles in which compressed airpressing on a piston is used to apply the pressure to the brake pad needed to stop the vehicle. Air brakes are used in large heavy vehicles, particularly those having multiple trailers which must be linked into the brake system, such as trucks, buses, trailers, and semi-trailers, in addition to their use in railroad trains. George Westinghouse first developed air brakes for use in railway service. He patented a safer air brake on March 5, 1872. Westinghouse made numerous alterations to improve his air pressured brake invention, which led to various forms of the automatic brake. In the early 20th century, after its advantages were proven in railway use, it was adopted by manufacturers of trucks and heavy road vehicles. Truck air actuated disc brake. Design and function Air brake systems are typically used on heavy trucks and buses. The system consists of service brakes, parking brakes, a control pedal, and an air storage tank. For the parking brake, there's a disc or drum brake arrangement which is designed to be held in the 'applied' position by spring pressure. Air pressure must be produced to release these "spring brake" parking brakes. For the service brakes (the ones used while driving for slowing or stopping) to be applied, the brake pedal is pushed, routing the air under pressure (approx 100–120 psi or 690–830 kPa or 6.89–8.27 bar) to the brake chamber, causing the brake to be engaged. Most types of truck air brakes are drum brakes, though there is an increasing trend towards the use of disc brakes in this application. The air compressor draws filtered air from the atmosphere and forces it into high-pressure reservoirs at around 120 psi (830 kPa; 8.3 bar). Most heavy vehicles have a gauge within the driver's view, indicating the availability of air pressure for safe vehicle operation, often including warning tones or lights. A mechanical "wig wag" that automatically drops down into the driver's field of vision when the pressure drops below a certain point is also common. Setting of the parking/emergency brake releases the pressurized air in the lines between the compressed air storage tank and the brakes, thus allowing the spring actuated parking brake to engage. A sudden loss of air pressure would result in full spring brake pressure immediately. A compressed air brake system is divided into a supply system and a control system. The supply system compresses, stores and supplies high-pressure air to the control system as well as to additional...

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Inboard brake

An inboard braking system is an automobile technology wherein the disc brakes are mounted on the chassis of the vehicle, rather than directly on the wheel hubs. The main advantages are twofold: a reduction in the unsprung weight of the wheel hubs, as this no longer includes the brake discs and calipers; also, braking torque applies directly to the chassis, rather than being taken through the suspension arms. Inboard brakes are fitted to a driven axle of the car, as they require a drive shaft to link the wheel to the brake. Most have thus been used for rear-wheel drive cars, although four-wheel drive and some front-wheel drives have also used them. A rare few rear wheel drive racing cars (e.g., the Lotus 72) have also used inboard front discs, accepting the need to provide a drive shaft to gain the unsprung weight and braking torque advantages. McLaren M23 rear brakes Inboard brakes for early racing cars have rarely used drum brakes, although nearly all inboard brakes date from the disc brake era. Alfa Romeo 75 rear transaxle Excepting the case of vehicles with beam axles and vehicles having no suspension, in practice it is normal for inboard brakes to be mounted rigidly with respect to the body of the vehicle, often to the differential casing. This is done to move the weight of the braking mechanism from being carried by the wheels directly (unsprung weight), to being carried indirectly by the wheels via the suspension (sprung mass). This then necessitates a means of transferring braking torque from the brake mechanism to the wheel, which is capable of operating despite the relative movement between body and wheel. Driven wheels already have shafting (or chains in older vehicles) which serve this purpose so there is no penalty for them, but undriven wheels require a similar mechanism which is then called a brake shaft. The benefit of such a system is primarily the reduction of unsprung weight which improves handling and ride. The suspension does not have to resist twisting when the brakes are applied. The wheels don't enclose the brake mechanism allowing greater flexibility in wheel offset, and placement of suspension members. It is also much easier to protect the brake mechanism from the outside environment, and protect it from water, dust, and oil. Of secondary importance is flexible brake pipes are avoided; rigid pipes allow increases in brake fluid pressure, allowing for a smaller disc to manage a given braking torque. The mechanical disadvantages are largely those of added complexity. Undriven wheels require a brake shaft. Mounted inboard, it is...

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Hydraulic brake

A hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing glycol ethers or diethylene glycol, to transfer pressure from the controlling mechanism to the braking mechanism. A schematic illustrating the major components of a hydraulic disc brake system. History Fred Duesenberg originated hydraulic brakes on his 1914 racing cars and Duesenberg was the first automotive marque to use the technology on a passenger car in 1921. This braking system could have earned him a fortune if he had patented it. In 1917 Malcolm Loughead (who later changed the spelling of his name to Lockheed) developed a hydraulic brake system. "Lockheed" is a common term for brake fluid in France. The technology was carried forward in automotive use and eventually led to the introduction of the self-energizing hydraulic drum brake system (Edward Bishop Boughton, London England, June 28, 1927) which is still in use today. Construction The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following: Brake pedal or lever A pushrod (also called an actuating rod) A master cylinder assembly containing a piston assembly (made up of either one or two pistons, a return spring, a series of gaskets/ O-rings and a fluid reservoir) Reinforced hydraulic lines Brake caliper assembly usually consisting of one or two hollow aluminum or chrome-plated steel pistons (called caliper pistons), a set of thermally conductive brake pads and a rotor (also called a brake disc) or drum attached to an axle. The system is usually filled with a glycol-ether based brake fluid (other fluids may also be used). At one time, passenger vehicles commonly employed drum brakes on all four wheels. Later, disc brakes were used for the front and drum brakes for the rear. However disc brakes have shown better heat dissipation and greater resistance to 'fading' and are therefore generally safer than drum brakes. So four-wheel disc brakes have become increasingly popular, replacing drums on all but the most basic vehicles. Many two-wheel vehicle designs, however, continue to employ a drum brake for the rear wheel. The following description uses the terminology for / and configuration of a simple disc brake. System operation In a hydraulic brake system, when the brake pedal is pressed, a pushrod exerts force on the piston(s) in the master cylinder, causing fluid from the brake fluid reservoir to flow into a pressure chamber through a compensating port. This results in an increase in the pressure of the entire hydraulic system, forcing fluid through the hydraulic lines toward one or more calipers where it acts upon one or more caliper pistons sealed by one or more seated O-rings (which prevent leakage of...

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Sensotronic Brake Control

Sensotronic Brake Control (SBC) is an electro-hydraulic brake system developed by Daimler and Bosch. The SBC system was introduced on the R230 SL-class, which went on sale in Europe in October 2001. How it works In a hydraulic brake system, the driver applies force by a mechanical link from the pedal to the master brake cylinder. In turn the master brake cylinder develops hydraulic pressure in the wheels. In contrast, the electro-hydraulic brake SBC provides the brakes with a brake fluid supply from the hydraulic high-pressure reservoir, which is sufficient for several braking events. A piston pump driven by an electric motor supplies a controlled brake fluid pressure between 140 and 160 Bar in the gas diaphragm reservoir.  When the driver presses the brake pedal - or when ESP intervenes to stabilize the vehicle - the SBC control unit calculates the desired target brake pressures on each individual wheel. Through the use of independent pressure modulators the system regulates the hydraulic pressure at each wheel. These four pressure modulators consist of one inlet and one outlet valve, controlled by electronic output stages. The system employs a travel sensor and a pressure sensor at the pedal to measure the speed and force of the driver's command. The control unit processes this information and generates the control signals for the wheel pressure modulators. Normally, the master brake cylinder is detached from the brake circuit. A pedal travel simulator creates normal pedal feedback. If ESP intervenes, the high-pressure reservoir supplies the required brake pressure quickly and precisely to selected wheels, without any driver involvement. Advantages and disadvantages With fine-grained control of pressure at each wheel, SBC offers a unique platform in which to implement skid protection and traction control compared to cf. Anti-lock braking system(ABS) and Electronic Stability Program (ESP), respectively. Moreover, the system offers innovative functions to reduce the driver's workload. These include Traffic Jam Assist, which brakes the vehicle automatically in stop-and-go traffic once the driver takes his or her foot off the accelerator. The Soft-Stop function - another first - assists with smooth stopping in town traffic. In case of computer failure, SBC reverts to a hydraulic master cylinder, but driver effort and stopping distance is reported to increase. In case of pump failure the high-pressure reservoir is capable of retaining enough pressure to stop the vehicle electronically. Information on other types of failure remain an open question. Industry recognition In 2001 the µ-Club, an association of international experts in the field of brake technology, honored Robert Bosch and Daimler Chrysler for...

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