為了滿足現代物流對時效性的苛刻追求，重卡的行駛速度變得更快，載重能力變得更高，同時車輛出色制動安全性能越發重要了。夏季行車時特別在長下坡路段行駛時，最令卡車司機擔心的就是安全制動和剎車問題。頻繁的剎車產生的高溫對主車制動系統帶來極大的挑戰，一旦制動器因熱衰退而失效，后果不堪設想。
交通安全倍加重視的今天，人們對于卡車制動安全的考慮比以往更加深入，除了主車制動系統在不斷改進技術，輔助制動裝置也越來越多的出現。除了發動機輔助制動制動系統的出現，另外一種高效的輔助制動裝置——液力緩速器也開始嶄露頭角。
液力緩速器可以在長下坡過程中大幅較少剎車裝置的使用，從而避免因長時間制動引起制動效果熱衰退剎車失靈的重大安全問題，大大提升行車安全性，同時可以緩解司機緊張的情緒和駕駛疲勞強度，下坡從容應對。
● 液力緩速器工作原理
液力緩速器，簡單點說就是通過液力裝置降低車輛行駛速度，由緩速器本體、操縱裝置、電子控制單元等部件組成，緩速器本體結構中，轉子和定子共同組成工作腔，當液力緩速器工作時，電子控制系統控制比例閥向工作液施加氣壓使油液充入工作腔。
轉子隨輸出軸的轉動帶動油液的旋轉，而定子是固定的，會對油液產生反作用力，這個反作用力同樣傳遞到轉子，阻礙它的轉動，從而實現對車輛的減速作用。在這個過程中，轉子轉動的能量通過經過油液的阻尼作用轉變成了熱量，由于工作液在運動中使進出口形成壓力差，促使介質循環，流經熱交換器時，車輛動能轉變成的熱量被來自發動機冷卻系統的冷卻水帶走而散掉。
緩速力矩的大小取決于工作腔內介質(機油)的壓力和數量，以及傳動軸的轉速。油槽中的介質由比例閥控制的壓縮空氣壓入工作腔，壓縮空氣的壓力不同供入工作腔的介質量也不同，從而產生緩速力矩也不同。液力緩速器一般都有多個檔位可選，還有很恒速功能，可以設定速度勻速下坡。
根據安裝方式的不同，液力緩速器可分為串聯式和并聯式兩種形式。串聯式安裝可安裝在傳動軸與變速箱之間，占用一定的軸向空間，再加裝需要對傳動軸的長度進行簡單的調整。并聯式則是與變速箱組成一個整體，通過齒輪傳遞動力。
另一種電渦流緩速器是利用電磁學原理把汽車行駛的動能轉化為熱能散發掉，從而實現減速和制動作用的裝置。與電渦流緩速器相比液力緩速器制動扭矩范圍更大，可達4000NM，而質量大約是電渦流緩速器的1/3左右。液力緩速器一般是與發動機共用冷卻系統，散熱能力強大，在緩速器的工作范圍內，即使長時間工作，最高溫度一般能控制在180攝氏度以下。而電渦流緩速器工作溫度可高達600度，利用風冷散熱，液力緩速器的冷卻性能要大大優于電渦流緩速器。尤其在長下坡路段，持續制動能力可以得到保證。所以液力緩速器更適合重型卡車上使用。
In order to meet the needs of modern logistics on the aging process of the pursuit of harsh and heavy truck speed became faster loading capacity becomes higher, at the same time, the vehicle excellent braking safety performance is more and more important. Especially in the summer driving downhill running, most truck drivers worried about is the safety brake and brake problems. Frequent brake and the generation of high temperature of main vehicle brake system bring great challenges, once the brake due to thermal degradation and failure, the consequences could be disastrous.
Pay attention to traffic safety doubly today, people consider the truck brake safety goes deeper than ever before, in addition to the main vehicle brake system in the continuous improvement of technology, the auxiliary brake device is more and more appear. In addition to the emergence of engine auxiliary braking system, also a kind of efficient auxiliary braking device, hydraulic retarder also began to emerge.
Hydraulic retarder can at the long downhill process significantly less brake device used to avoid braking effect heat recession brake failure of major security problems caused due to braking for a long time, greatly enhance the driving safety, also can alleviate the driver nervous mood and driving fatigue strength, downhill calmly.
The working principle of the hydraulic retarder
Hydraulic retarder, simple said is through the hydraulic device and reduces vehicle speed, consists of a retarder body, an operating device, electronic control unit and other components, retarder body structure, rotor and stator composed working chamber, when the work of hydraulic retarder, electronic control system proportional control valve to the working fluid applied pressure and the oil liquid is filled into the cavity.
Rotor with the output shaft rotates to drive the rotation of the oil, and the stator is fixed, will have a reaction to the oil, the reaction also transferred to the rotor, hinder its rotation, so as to realize the vehicle deceleration. In this process, the energy of the rotation of the rotor through after the role of oil damping change into heat, due to the working fluid in motion in the import and export to form a pressure difference, prompting the circulation of the medium, when passing through the heat exchanger, the vehicle kinetic energy into heat from engine cooling system cooling water away and evaporate.
Slow speed torque depends on the size of the working medium in the cavity (oil) pressure and quantity, and the speed of drive shaft. In the oil tank medium is controlled by proportional valve of compressed air pressure in working chamber, the pressure of compressed air into the working chamber for different dielectric quality is different, resulting in slow speed torque is also different. The hydraulic retarder generally have multiple gear optional, there is a constant function, can set the speed downhill.
According to the installation of different types of hydraulic retarder type and parallel type can be divided into two types of series. Between the tandem installation can be installed in the transmission shaft and the gear box, occupy axial space, adding to the length of the drive shaft for easy adjustment. The parallel connection type is composed of a whole with the gearbox, and the transmission power is transmitted through the gear box.
Another kind of eddy current retarder is the principle of electromagnetism the vehicle kinetic energy is transformed into heat energy dissipated, so as to realize deceleration and braking device. Hydraulic retarder braking torque range greater than and electric eddy current retarder, up to 4000NM, and quality about is about 1 / 3 of the eddy current retarder. Hydraulic retarder is generally and common engine cooling system and heat dissipation capability is strong, in the scope of work of the retarder, even if the work for a long time, the highest temperature can generally be controlled at 180 degrees Celsius below. And the working temperature of the electric eddy current retarder can be up to 600 degrees, using air cooling, the cooling performance of hydraulic retarder to is much better than that of eddy current retarder. Especially in the long downhill section, continuous braking ability can be guaranteed. So the hydraulic retarder is more suitable for the use of heavy truck.
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