Hydraulic retarder is an auxiliary braking device commonly used in large vehicles.
We all know that large vehicles have a large self weight and often require more braking force when braking than regular vehicles. Once encountering a long downhill section, the brake is prone to temperature rise and heat attenuation under long-term friction braking, and in severe cases, it can also lead to brake failure. The hydraulic retarder can to some extent avoid brake wear and overheating caused by prolonged or frequent brake application, achieving smooth braking of the vehicle.
In fact, hydraulic retarder is just one type of vehicle retarder, and common retarders also include engine retarder and eddy current retarder.
1. The engine retarder belongs to the first stage retarder, which can change the operation of the engine exhaust valve after starting, turning the engine into an air compressor that absorbs power, and then transmitting the deceleration force to the driving wheel.
Engine retarders can be divided into three types: engine exhaust butterfly valve brake, air release engine brake, and compression release engine retarder.
The first level retarder has a small braking force and cannot meet the legal requirements for vehicle braking. It can only be used in conjunction with other auxiliary braking systems. In addition, due to high noise, high maintenance costs, and the failure of the transmission during shifting, its development and popularization are limited.
2. The eddy current retarder belongs to the secondary retarder. The electromagnetism principle is used to convert the kinetic energy of the vehicle into heat energy for release, so as to achieve the purpose of deceleration and braking.
Eddy current retarder is a non-contact deceleration device typically installed between the drive axle and gearbox. It has the advantages of high braking efficiency, short operating response time, non-contact/zero wear/extremely low failure rate, etc. It can extend the service life of vehicle brakes, reduce comprehensive vehicle costs, and improve vehicle safety, economy, environmental protection, stability, and comfort.
On the other hand, the eddy current retarder has a larger size, higher requirements for installation space, larger self weight, consumes electrical energy, significant thermal attenuation, and is easily affected by the surrounding environment temperature.
At present, the eddy current retarders in China are mainly installed on buses and passenger vehicles, with the majority of applications in these two fields, especially in some high-end passenger cars where almost all eddy current retarders are installed.
3. The hydraulic retarder is also a two-stage retarder, which first appeared in Germany and was used to assist in deceleration on trains. It was later used on trucks.
According to different media, hydraulic retarders can be divided into two types: oil medium and water medium. At present, the most common one in the market is the oil medium retarder, whose market value is generally about 13000 yuan to 30000 yuan; The water medium retarder has advantages such as smaller self weight, faster response speed, high torque, less power consumption, and convenient maintenance, but its price is generally around 30000 to 50000 yuan. In addition, there are many technical difficulties in lubrication and high-temperature evaporation, so it has not yet been popularized.
In order to meet the installation needs of different vehicle models such as trucks, buses, light trucks, and specialized vehicles, hydraulic retarders have been introduced in series, parallel, and independent installation methods, allowing owners to freely choose according to the vehicle model.
It is worth mentioning that the market share of hydraulic retarders used to be far behind that of eddy current retarders. However, with the continuous improvement of related technologies, the price difference between the two is becoming smaller and smaller. Hydraulic retarders can provide greater braking torque with smaller quality, and have strong continuous braking ability, simple maintenance, low cost, good heat dissipation effect, and can smoothly assist vehicle braking while reducing the wear of the main brake, Extend the service life of tires, improve vehicle operation efficiency, and reduce comprehensive vehicle costs.
Some people think that hydraulic retarders are used when going downhill for a long time. This viewpoint is correct, but it is not accurate. If it is only used on long downhill slopes, the value of the liquid buffer can be at most half utilized. Car owners can collect fuel in advance and move the retarder handle to slow down in some foreseeable non emergency braking situations, such as toll booths, traffic lights, traffic jams, and other road sections, in order to reduce the number of brake applications.
Be careful not to use the hydraulic retarder when in neutral, and be cautious/disable the hydraulic retarder when encountering slippery, icy, or dark icy roads. If the hydraulic retarder cannot achieve deceleration after being used, for example, when the vehicle is fully loaded downhill, the hydraulic retarder is already in a constant speed range, but the vehicle speed is constantly increasing. At this time, the waiting driver should decisively press the brake pedal to brake, and do not directly set the hydraulic retarder to the highest gear. This is because pulling the hydraulic retarder to the highest gear suddenly enters the fully open state, which can easily cause excessive deceleration, cause the vehicle to roll over, and the water temperature will also rise sharply, causing the hydraulic retarder to continue to heat up Loss of braking force. So, although liquid buffering is good, it still needs to be applied properly.
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