所有汽車廠商都希望在不明顯增加成本的情況下讓自己的產(chǎn)品更加脫穎而出。雖然直接利用軟件來控制精密系統(tǒng)可以在一定程度上實現(xiàn)這個目標(biāo)，但僅憑機械手段“改變”這些系統(tǒng)可能存在一定困難，特別是當(dāng)人們對“改變”的主觀意愿是“優(yōu)化”的情況下。
駕乘性能的優(yōu)化是一個明顯的例子。中國底盤系統(tǒng)供應(yīng)商京西重工（BWI Group）推出了一款精密的磁流變懸架控制系統(tǒng)MagneRide，這款產(chǎn)品的客戶包括奧迪（Audi）、凱迪拉克（Cadillac）、雪佛蘭（西爾維拉多皮卡和巡洋艦）及法拉利等多個高端品牌。但除此之外，京西重工還推出了一款更加平價的懸架控制系統(tǒng)，目標(biāo)車型是旨在提升駕乘體驗的中級轎車。
液壓止動系統(tǒng)（Hydraulic Compression Stop）
為了在不犧牲操控和安全性能的前提下優(yōu)化車輛的駕乘體驗，京西重工計劃將從常規(guī)的止動模塊設(shè)計入手。具體來說，工程師計劃用一款液壓止動系統(tǒng)（HCS）取代硬止動模塊的設(shè)計，從而優(yōu)化傳統(tǒng)被動減振器的性能。
“在高端市場中，MagneRide等自適應(yīng)性懸架技術(shù)幾乎可以協(xié)助車輛在駕乘舒適度和車身控制之間達到完美平衡。”京西重工集團技術(shù)開發(fā)經(jīng)理Roman Bielak表示，“現(xiàn)在，擺在被動減振器面前的挑戰(zhàn)是如何在保持價格優(yōu)勢的前提下，盡量縮小與自適應(yīng)性懸架系統(tǒng)之間的性能差距。HCS系統(tǒng)的出現(xiàn)就是實現(xiàn)這一目標(biāo)的重要一環(huán)。”
Bielak告訴《汽車工程》，這款HCS系統(tǒng)經(jīng)過專門設(shè)計，旨在車輪的完整振幅范圍內(nèi)優(yōu)化車輛的減震性能，盡量減少路面振動傳入車內(nèi)：“與傳統(tǒng)的止動模塊相比，新系統(tǒng)在改裝調(diào)試方面的靈活度更高，可以優(yōu)化車輛的動態(tài)性能，而且還能通過降低車輪在極限位置時的車身峰值受力，優(yōu)化整車的NVH性能。”
據(jù)了解，京西重工的HCS系統(tǒng)按計劃將于2018進入生產(chǎn)。該系統(tǒng)背后的設(shè)計理念是降低系統(tǒng)在極限壓縮狀態(tài)下的峰值負(fù)荷。這樣一來，底盤設(shè)計師就可以更充分地利用減振器行程，改善車上人員的舒適度和底盤性能。此外，這還可有助于降低車身重量，而且不會對車輛的駕乘或操控性能產(chǎn)生影響。
Bielak表示，“如果有一輛滿載的汽車行駛在顛簸道路上，那這輛車的懸掛系統(tǒng)極有可能達到下極限。此時，HCS系統(tǒng)就可以避免車輛將負(fù)載壓力轉(zhuǎn)移到車身結(jié)構(gòu)上。”
京西重工HCS系統(tǒng)以集團的液壓反彈止動技術(shù)（HRS）為基礎(chǔ)，而后又進行了一系列改造，從而將系統(tǒng)的重點從反彈轉(zhuǎn)為壓縮。HRS和HCS系統(tǒng)均可以在懸掛處于極限位置時，將能量分散至液態(tài)阻尼液中，從而降低沖擊對車身的影響。目前，京西重工正在向多家廠商演示HCS系統(tǒng)。
HCS系統(tǒng)目前有兩種配置，分別適用于高/低阻尼要求下的應(yīng)用。高阻尼系統(tǒng)增加了一個密封液壓腔，腔體存在一條旁路通向減振器的液壓閥。這個獨立的腔室可以產(chǎn)生非常高的阻尼力，但并不會影響懸架行程其余部分的減振表現(xiàn)。
在需求較低的低阻尼系統(tǒng)中，京西重工集團采用了一條阻尼管開大小兩口的設(shè)計。其中，較大的口充當(dāng)主阻尼閥，較小的口可在達到指定閾值時開始工作，防止系統(tǒng)進入極限位置。
可應(yīng)用于混動和電動車
Bielak解釋說，這種設(shè)計可以給減振器的調(diào)試帶來更大的靈活度，但他也解釋說，系統(tǒng)的最大阻尼不能超過極限范圍，這樣才能保證基礎(chǔ)減振器的性能不會受到充油的影響。
“為了滿足不同車型的特定要求，我們開發(fā)了兩款HCS系統(tǒng)。”Bielak指出，“這兩種系統(tǒng)都可以優(yōu)化車輛的舒適性和耐久性，但其中一款在微調(diào)方面的潛力較大，另一款則可以提供更大的阻尼。”
Bielak補充說，雖然HCS系統(tǒng)最初是針對中檔轎車設(shè)計的，但由于該系統(tǒng)不需要對懸掛系統(tǒng)做大規(guī)模的改動，因此還可以用于現(xiàn)有車型的混動或電動版本。“該技術(shù)可以很好地應(yīng)對電動車大型電池組帶來的額外重量，”Bielak表示，“還可以將懸掛系統(tǒng)的噪聲控制在較低水平，從而保證電動模式下的安靜駕乘體驗。”
目前，京西重工的潛在客戶（并未透露客戶信息）正在考察低阻尼版的HCS系統(tǒng)。集團已證實該系統(tǒng)將于2018年進入生產(chǎn)。
Achieving product differentiation without adding significant cost is on the wish list of all automakers. While targets can be reached to some degree by applying clever software changes to sophisticated systems, using purely mechanical solutions as an alternative to those systems may be difficult, particularly in that subjective area categorized as “refinement.”
Ride refinement is a prime example. China-based chassis systems’ supplier BWI Group produces the sophisticated magneto-rheological suspension control, MagneRide, used by a growing list of brands including Audi, Cadillac, Chevrolet(Silverado pickups and Corvettes) and Ferrari. But BWI is also developing what it believes will be a cost-effective system aimed at raising the ride quality of mid-class premium cars.
Enter the HCS
It is doing so by focusing its R&D on the conventional bump stop as a route to improving ride comfort without degrading vehicle handling and safety. BWI engineers plan to extend the performance of conventional passive dampers by replacing hard bump stops with an hydraulic compression stop (HCS) integrated into the damper.
“At the top end of the market, adaptive suspension technology such as MagneRide virtually eliminates the compromise between ride comfort and body control,” explains Roman Bielak, BWI Group’s Technology Development Manager. “The challenge with passive dampers is to retain the price advantage while closing the performance gap to adaptive systems. HCS is an important step towards this.”
It is designed to better optimize damping over the full amplitude of wheel travel to secure improved road isolation: “The new system is not only more tunable than traditional bump stops, leading to better vehicle dynamic performance, but improves NVH by reducing peak forces transmitted to the vehicle body at the limit of travel,” Bielak told Automotive Engineering.
Thinking behind the HCS, due to enter production in 2018, is to soften the load spikes that normally occur at the limit of compression. This would allow chassis designers to make greater use of the available damper travel to improve occupant comfort and chassis refinement. It would also complement and facilitate reduced weight of a vehicle’s body without affecting ride quality or handling, because the strength and stiffness requirements of body structure at the tower would be lower for the same standard of refinement and durability.
“A heavily laden vehicle that is more likely to bottom its suspension on bumpy roads can do so without transmitting damaging loads into the body structure,” says Bielak.
The HCS, now being demonstrated to OEMs, is a development of BWI Group’s established hydraulic rebound stop (HRS) technology, which has been re-optimized for use in compression rather than rebound. Capability of both HRS and HCS is to reduce the shocks transmitted to the vehicle body at the limits of suspension travel by dissipating the energy hydraulically in the damper fluid.
HCS is being developed in two configurations to suit applications requiring either high or low damping levels. The high level is achieved by adding a sealed hydraulic chamber with a by-pass to the damper’s existing compression valve. The separate chamber allows very high damping forces to be generated without influencing damping over the remainder of the suspension travel.
For applications requiring lower levels of damping, BWI Group uses a damper tube swaged to give two diameters. The larger diameter is the main damper valve, the smaller engages a second valve at the chosen threshold of travel, before the limiting stroke is reached.
Hybrid and EV opportunities
Bielak explains this design gives greater opportunity for damper tuning. But he explained that the maximum damping force must be limited so that oil aeration does not degrade the base damper performance.
"We are developing two HCS technologies because different vehicle applications each have specific priorities," he noted. "Both approaches improve the comfort, refinement and durability of the vehicle but one offers greater potential for fine tuning while the other provides higher levels of damping.”
He added that although aimed initially at mid-range premium passenger cars, he believes that HCS could be particularly helpful when applied to hybrid or electric vehicles derived from existing models, because it avoids any major suspension changes. “The technology copes well with the additional weight of a large battery pack," he said, "and satisfies the lower cabin noise levels required when driving in electric mode by ensuring equally low levels of transmitted noise from the suspension.”
Potential customers (at present not named by BWI Group) for the system are currently evaluating the low-damping variant of HCS, which has been confirmed for production in 2018.
Author: Stuart Birch
Source: SAE Automotive Engineering Magazine
京西重工集團直接將高阻尼液壓止動系統(tǒng)（HCS）整合在減振器內(nèi)，替代傳統(tǒng)設(shè)計中的硬止動模塊。
如圖所示，在低阻尼系統(tǒng)中，京西重工采用了一根阻尼管開兩大小口的設(shè)計。
京西重工集團技術(shù)開發(fā)經(jīng)理Roman Bielak表示，現(xiàn)在，擺在被動減振器面前的挑戰(zhàn)是如何在保持價格優(yōu)勢的前提下，盡量縮小與自適應(yīng)性懸架系統(tǒng)之間的性能差距。
京西重工集團推出的精密磁流變懸架控制系統(tǒng)MagneRide（如圖所示）。