在非公路用车的市场中，关于混合动力设备最有趣的一点应该是其形形色色、五花八门的架构和储能方式。

“在其他行业，特别是乘用车行业内，混合动力车的架构都比较类似。”咨询公司Ricardo Strategic Consulting副总裁Mark Kuhn在接受SAE杂志访问时表示，“但非公路设备却不一样，单以储能方式为例，你就可以选择液压能量回收、机械能量回收、电容和电池等各种不同的技术。”

Kuhn指出，约翰迪尔(Jone Deere)的一些装载机，比如644 K和944 K型，甚至根本不会进行储能，而是会将回收的动能立即使用掉。

“在设计这些设备时，我们发现储能部件（比如电池）是最为昂贵的部分，而放弃储能功能可以有效降低成本，且并不会影响车辆的实质性能。”不断采用创新手段以降低成本、提高效益，这就是非公路设备技术如此丰富多彩的原因。

约翰迪尔的工程基建和林业产品营销经理John Chesterman表示，“约翰迪尔进行了多方面的考虑，最终选择了混合动力技术。”除了降低燃料消耗，其他考量因素还包括：弱化车速与发动机转速之间的关联、进行牵引力控制、进行拉力控制、提高设备耐久性，以及简化操作等。

Chesterman表示，“944K型装载机采用独立的轮内电机，可预防车轮打滑，而这是其他品牌的同级别装载机在进行重载挖掘或推动时非常容易出现的问题。这种设计可以减少轮胎磨损，从而降低客户的轮胎使用成本。”他同时指出，在设备上也会采用油冷系统、无刷交流电机和发电机，并对这些部件进行密封，以抵御灰尘和潮气侵入。此外，使用轮内电机的意味着设备不再需要倒车档位。

 “在需要倒车时，我们可以直接改变电机的方向，”他说，对拥有四个反向器的V型装载机而言，这很容易做到。“我们的客户发现，操作约翰迪尔混合动力装载机要容易得多，一天下来工作轻松了不少。”Chesterman补充说，944K混合动力装载机的用户对设备的低油耗、总体表现和操作简便等特性相当满意。

里卡多（Ricardo）公司的Kuhn表示，“我认为在施工机械设备中应用混合动力技术，有助于该技术从公路用车向非公路设备的扩展。其结果非常显著，你可以看看当今工程机械设备的动力系统，多数都采用了混动技术。”这种设计已经经过质量验证，因而技术风险更低。

采埃孚(ZF)就是一个很好的例子。公司非公路设备部副总裁Udo Kneitz表示，“我们可以在自己的研究范围内，探索各种各样的趋势，公司高级研发团队会关注并分析多种储能技术的发展。”

他认为，混合动力和电动系统都在不断发展。“这种趋势非常明显，在常用PTO设备的农机领域尤其如此。”

采埃孚的努力没有白费，其ZF-TERRA+系统在农机领域获得了成功。有一种值得关注的混合动力技术，可以将发电机模块整合至设备的变速箱外壳内，支持辅助系统的供电。为了增强TERRA+系统的功能，采埃孚还有一款控制单元，用于进行能量与混合动力的智能管理。这款控制单元可以避免设备以地能效的方式工作，从而使车辆取得最高的能源效率。

采埃孚的电气化和混合动力设计，均在公司提高效率的全面战略举措之列。Kneitz表示，采埃孚同时也需要一些其他基础技术。

Kneitz认为，“在全机械液压式功率分流CVT变速器的研发中，我们迈出了公司技术发展蓝图上的第一步。”他指的是公司适用于农机设备的TERRAMATIC CVT变速器。目前，这款设备的最新版可以输出450hp的动力。

Kneitz表示，“在我们看来，如果为了节能、降耗、提高效率而采用混合动力技术，最重要的一点就是升级动力传动系统。”他同时指出，采埃孚TERRA+仅仅是电气化进程中的一个例子。采埃孚还在为TERRAMATIC变速器加装60-kW的发电机，这也同样是公司产品电气化进程中的项目之一。

Kneitz同时指出，除了农机领域之外，这种混合动力技术在其他行业也颇具潜力。“我们也必须着眼于建筑机械领域，开发适合这些设备使用的混合动力系统，让它们在未来的建筑工地上大显其能。这项技术的发展一方面需要市场需求的驱动，另一方面需要政府排放法规的支持。”他说，“采埃孚的混合动力模块搭配了一款高效电机，采用并联混合动力模式，根据尺寸不同，输出功率可达85到120kW不等。”在Kneitz看来，一旦市场做好电气化准备，采埃孚就能立刻行动。

作者：Bruce Morey
来源：SAE《非公路工程》杂志
翻译：SAE 上海办公室

Hybrid variety in off-highway

Perhaps the most interesting point about hybrids in the off-highway market is the sheer variety of architectures and energy storage choices.

“Other industries, especially passenger cars, feature similar architectures of hybrid electric vehicles,” stated Mark Kuhn, Vice President for Ricardo Strategic Consulting, in interview with SAE Magazines. “Not so in off-road, where you have hydraulics, mechanical energy recovery, and ultracapacitors as well as batteries.”

He pointed out that some wheeled loaders from John Deere, such as the 644 K or 944 K, do not store any energy at all, but re-deploys any regenerative braking energy instantaneously.

“When they designed this, energy storage (e.g., batteries) was the most expensive component and eliminating it reduced the cost while still providing substantial benefit,” he said. Coming up with novel ways to reduce cost and provide benefit is the driver behind variety.

“John Deere chose electric hybrid technology for several reasons,” said John Chesterman, Product Marketing Manager, for John Deere Construction & Forestry. Beyond reducing fuel consumption are a number of other reasons including: decoupling the engine speed from vehicle speed, traction control, rim pull control, durability, and ease of operation.

“The 944K with individual wheel motors can control the wheels from spinning out like they do on the other competitor’s loaders in this size class in heavy digging or pushing applications. This reduces tire slicing and tire costs for our customers,” said Chesterman. He also noted that they use oil cooled, brushless ac electric motors and generators that are sealed from dirt and moisture, and using motors means no reverse shifting.

“We simply reverse the direction of the electric motor,” he said, quite a convenience with a typical v-pattern truck load with four reversals. “[Our customers] have found that the John Deere hybrid wheel loaders are much easier to operate and reduce the amount of fatigue over the course of a day of operating.” He added that users of the 944K Hybrid are happy with the low fuel consumption, overall performance, and ease of operation.

“I think the ability to apply hybrid electrics for off-road construction equipment is an easier transfer of that technology from on- to off-road. As a result, if you look at all the hybrid architectures that are in equipment today, most of them are hybrid electrics,” said Ricardo's Kuhn. There is lower technical risk because it is more of a known quantity.

ZF is a good example of this. “We can exploit all kind of trends within our development landscape. [Many types of] energy storages are analyzed and monitored by the corporate advanced engineering of ZF,” explained Udo Kneitz, Executive Vice President ZF Off-Highway Systems.

He sees both hybridization and electrification as growing in off-highway. “This trend is to be seen especially in the agricultural segments where PTO-powered implements are very common,” he said.

This approach has its pay-off in the agricultural segment with its ZF-TERRA+ system. This is an interesting idea for electrical hybridization, incorporating a generator module integrated into a transmission housing to power auxiliary electrical loads. As an enhancement to the TERRA+, ZF offers a control unit for intelligent energy and hybrid management. The control unit is intended to avoid vehicle conditions with poor efficiency, thus achieving best operational performance.

For ZF electrification and hybridization are elements of a comprehensive plan for improving efficiency. According Kneitz, other baseline technologies were needed as well.

“With the development of fully mechanical-hydrostatical power split CVT transmissions we did a first step along our technology roadmap,” he said, referring to the TERRAMATIC CVT for agricultural equipment. The latest version is rated at 450 hp.

“To upgrade driveline technology in our eyes is the basis for any meaningful hybridization in terms of saving energy or fuel and increasing efficiency,” he said. He also noted that ZF TERRA+ is only one example for the electrification of implements. Adding a 60-kW generator system integrated into this TERRAMATIC transmission is yet another.

Kneitz also acknowledges the potential in other industries beyond agriculture. “We will see also hybrid systems for construction machinery driveline systems and drives on future construction sites. This technology evolution needs to be driven by market demand with reasonable total costs of ownership on the one hand and governmental emissions regulations on the other,” he said. “The ZF hybrid module works as a parallel hybrid with an efficient electric machine, providing up to 85 or 120 kW performance, depending on the size.” As far as he is concerned, as soon as the market signals its readiness, ZF will be too.

Author: Bruce Morey
Source: SAE Off-Highway Engineering