汽车专业 机械 毕业设计翻译外文翻译

集成式发动机辅助混合动力系统 摘要 本论文介绍了用于和开发Honda Insight发动机的技术，一种新的发动机辅助混合 动力汽车，其总开发目标是在广泛的行驶条件下达到当今Civic消耗量的一半，实现35km/L（日本10-15模式），3.4L/km（98/69/EC）的消耗量。为了达到这个目标，加入了许多用于 包装和集成发动机辅助系统以及改善发动机效率的新技术，开发了一种新的集成式发动机辅 助混合动力发动机系统。这是结合了一种低空气阻力的新型轻稆车身开发的。环境性能目标 也包括了低排放（日本2000年的一半，EU2000标准的一半），高效率和杨回收性。对 消费的关键特性全面考虑，包括碰撞安全性能，操纵性和运行特性。 1． 绪论 为减小汽车对社会和环境的冲击要求其更干净并且能量效率更高更节能，空气质量更好。降 低CO2排放问作为全球环境焦点提出，解决这些问题的方法之一就是混合动力汽车。 Honda已开发并向遍及全球的几大市场输入Insight，新一代车辆设计。 Insight将混合动力系与先进的车身技术特性相结合以符合取得实际的最高燃油经济性的总目标。 混合动力系是发动机的辅助并联平行结构，把IMA叫做集成式发动机辅助。此动力系将把 一个高效电动机与一个新型小排量VTEC发动机结合起来，很轻的铝车身，改良的空气动 力学以实现3.4L/100km(CO2：80g/km)98/69/EC燃油经济性。低排放性能也已达到EU排放水平为目标。 除减速能的重用之外，集成式发动机在典型的市区行驶加速时提供大助力扭矩，显著地减小 了发动机拜师，提高了发动机效率。接近56kW每吨的功率/质量比保证了稳定的爬坡能力 和高速的常速行驶能力。新发动机技术包括促进高效快速的催化剂活性化的一种新VTEC（电子控制可变配气相位和气门升程）缸盖设计，促进稀薄燃烧能降低排放的新型稀NOx催化转化器，广泛的减摩及减重特色也用于其中。 2． 开发目标及开发理念 开发目的在于达到极低燃油消耗量。我们定下的目标是当今产品Civic燃油经济性的两倍，Honda的典型高燃油经济性轿车——7.0L/100km(93/116/EC)，因而Insight在世界汽油机轿车中拥有最低的燃油消耗量。排放性能由于低燃油消耗量的缘故而趋于牺牲，但是，我们仍决 定配备其它大多数批量生产的汽车所具备的低排放性能，在回收性（另一重要环境问题）， 碰撞安全性能以及操纵性和造型等汽车的基本性能方面也有考虑。综上所述，我们的开发目 标如下： 世界最好燃油消耗性能 超低排放 超回收性 全世界最高碰撞安全性能水平 先进造型 实用特色和操纵灵敏性 舒适的带有个性使用空间的二座结构 3． 降低燃油消耗量的策略 为了建立起取得低燃油消耗目标的技术途径，我们对一辆装配1.5L发动机听Civic基型车辆能量消耗进行细节。为取得低燃油消耗和其它上述目的，我们发现将目标效率如图形1 所示粗略地分为三部分是十分有用的。划分如下： 发动机自身热效率的改善 混合动力装置制动能量再生和怠速止挡应用 降低重复和减小空气阻力和滚动阻力的车身技术 图1. 两倍于CIVIC燃油经济性的目标 我们开发这种新集成式发动机辅助动力系瞄准为21世纪汽车动力系建立一个基准。这种动力系适合于下一代汽车，同时达到了极低3.4L/100km极低的燃油消耗量和低废气排放性能。本篇论文对新开发的IMA系统作了报告，包括用于Honda Insight的稀燃发动机，电动机功率控制单元，蓄电池技术和废气排放控制技术。 4． IMA系统的目的 为达到目的世界最低燃油消耗量，在开发下一代IMA 混合动力系统时我们尽可能多地结合已取得的技术方法。为达到这个目标，建立了以下四个系统开发主题： 减速能量的再生 发动机效率的改善 怠速止挡系统运用 动力系尺寸、重量的减小 5． 1系统结构 图2. IMA 系统 图 3IMA系统的发动机速度 (rpm)/输出特性曲线 如图2所示，IMA系统以发动机作为主动力源，加速时用电动机作为辅助动力 源。用电动机作为辅助动力源简化了整个系统并可采用轻型紧凑的发动机，蓄电 池和功率控制单元（PCU）。 在发动机与变速器间布置了一个永磁直流无电刷电动机，减速时为每个传动装置 计算出减速比，PCU控制发电机发电（再生能量）对镍金属氢蓄电池充电，加 速时由油门开度，发动机参数，蓄电池充电状态计算出辅助动力提供量（此后称 辅助），PCU控制蓄电池流向驱动马达的电流量。 5. 2再生减速能量 通过回收再生减速能量可在加速时补充发动机输出并减小油耗量。减小包括发动 机摩擦损失在内的工作能量损失引起的阻力可增加可用的再生能，尤其是使发动 机拜师减少到最小是减小摩擦的有效措施。降低发动机排量还有其它好处，例如 减轻重量增加热效率。IMA系统通过优化发动机和变速箱参数有效地增加了减 速时的再生能量。 5．3减小发动机排量 改善混合动力系燃油经济性中减小发动机排量是一个十分重要的因素。但是现代 汽车须在广泛的动态范围内运行，减小排量就等于降低汽车的基本性能特征。如 图3所示的输出特性曲线，利用电动机的大转矩性能特征IMA系统在低速范围内辅助发动机。电动机在低转速时能将总转矩提高50%，IMA系统取得了快速重启和不可思议的平滑启动成果。高转速范围时用电子控制可变配气相位和气门 升程发动机提高输出。因此保证了足够的峰值功率，便可用一个新的1.0L小排量发动机。 4稀燃发动机运行 5．基于节气门开度，以电动机辅助，创造出十分线性的转矩特性，由此改善了操纵灵活性。除 此之外，电动机辅助在中载条件下可扩大稀燃运行范围，显出了新开发稀烯发动机的潜力。 5．5怠速止推系统 制动时停止发动机而不是怠速空转也是减小消耗量的有效措施。如图4所示，为了以最小消 耗量重启发动机，发动机须在打火前通过集成式发动机快速转到600rpm或更高的的转速。 加上发动机停止运行空转省油，可以使消耗量最小。在执行怠速止挡时须注意许多问题，包 括判断驾驶者停车趋向，重启准备，提供减速平滑感，发动机停止时最小化车身振动。 Figure 4.Time (sec) The number of cranking in the engine start 图4 起动电机的转矩 5． 电动机辅助机构 6． 1开发目标 通过限速IMA电动机功能在阻力和再生两方面，确立的开发主题以取得以下两点： 简单紧凑结构 系统重量不大于整车质量的10% 6．2直流无电刷电动机 薄且紧凑的直流无电刷电动机具有发动机辅助和能源再生功能安装在曲轴上（图5），加速时辅助电动机是减小消耗量的十分有效的措施。这是一种高效、紧凑、轻型、永磁型三相同 步电动机，最大输出功率为10kW。除了开发技术以减轻重量、提高效率之外，我们也尽可 能把电动机做得最薄以获得紧凑的动力系。熔模铸造法用于转子，靠安装在曲轴上的弯曲而 旋转。与正常铸造产品相比取得了高强度更轻的重量。转子磁铁方面，对HONDA EV PLUS的烧结钕磁铁作了进一步的改良，扭转强度提高了近90%，热阻也得到改良。这种设计也 使电动机无需冷却系统。发明了一种有凸极集中绕组的可拆式定子结构并用于减小电动机的 轴向宽度。比传统波形绕法，如图6所示。除此之外，从铜极引出的集中配电母线卡环可用 于向定子两端线圈供电的线束固定，这使结构变得极简单紧凑。这些改良得到了一个厚度仅 60mm的极薄电动机，与传统技术相比在厚度减小了40%。 图5 电机剖面图 Wave winding Salient pole winding 图6 绕阻比较 图7 电机的剖视图 6．3镍金属氢蓄电池 镍金属氢蓄电池用于存储和为电动机辅助提供电力。这是一种先进的蓄电池，它安装于 HONDA EV PLUS电动汽车上，已经在高能蓄电池中取得了成就。这种混合动力汽车蓄电池 以稳定输出为特色，而不管蓄电池充电状态如何，且在应用中十分耐用。蓄电池是20个模块的集成结构，每个模块包括以网格状串联的6个D型单电池，这120个1.2V的单电池全 部以串联方式联结形成了总电池容量为144V的容量。 6．4功率控制单元（PCU） PCU精确控制电动机辅助/再生并向12V动力源提供动力，它具备内置冷却功能。这就使其 有一轻型，有效紧凑的结构。使用高效率冷却肋片和镁冷却套集成的购销风冷系统使重量显 著减轻。驱动马达的变压器是PCU内部最重要的元件，将开关元件集成为郑重三相交流的 单独模块，而在EV PLUS上都是分立的。驱动电路最小分并以高密度集成为IC。这些改良 不仅使重量显著减轻，也改变了功率转化效率，更好的是，采用高效相控驱动电动机降低了 发热量，使其可以用轻型简单的风冷系统。 Figure 8.Inverter Cut view of PCU Heat Sink case 图8 7发动机 7．1开发目标 为了在广泛的工况下获得低油耗以下四点作为开发主题： 热效率改善 减小机械损失（与传统设计相比小10%） 减小尺寸和降低重量（同类产品中最轻） EU2000标准的一半 7．2发动机总观及其规格 发动机规格如#表格#1所示，其主要新特色和他们的目的如表格2所示。首先，配备IMA系 统的汽车以接近1000cm3的排量为最佳，因此选择了3缸发动机以使燃烧室的面容比最小，并减小机械损失。 7．3油耗 由于在低转速时电动机辅助加强和VTEC发动机充足的峰值输出功率使得在电动机辅助动 力系中可以大大地减小发动机排量。这款发动机的一个重要特色是通过稀燃技术而有显著的 改善的燃烧率。采用了包括进气涡流口新气缸内强化涡流技术以达到这点，通过改良指示效 率而获得的紧凑燃烧室和高压缩比对其也有帮助。这导致了与传统稀燃发动机相比更短的燃 烧时间，在更高的空燃比下使其在更稀的范围内燃烧，显著地降低了油耗。这种强涡进气口 和紧凑的燃烧室结果是在传统VTEC稀燃技术上的革新。传统VTEC发动机中，涡流是靠在低速工况下关闭一个进气阀门产生的，然而在新发动机中进气阀和进气口被排式竖直结构 以在可燃物流向气缸时产生强涡流。 传统VTEC结构中进排气摇臂各由独立的摇臂轴支撑，如图10所示，新VTEC机构将其合成一根单独的摇臂轴，显著地减小了尺寸，还将气门角从460减小为300，容许强旋涡形气门及更紧凑的燃烧室。 图9 发动机的侧视图 图10 气缸的剖面图 7．4减小机械损失 除了改良指示热效率，减小机械损失对改善燃油经济性也很重要，为了达到这个目标，采用 了以下低磨擦技术： 同轴滚子VTEC机构 活塞微波纹处理 偏置气缸结构 低张力活塞环 连杆渗碳 同轴滚子VTEC结构Honda S2000（大功率跑车发动机）技术向单凸轮轴VTEC机构的改进。通过凸轮轴上的摇臂滑动区域使用滚针轴承可将凸轮轴驱动机构损失减小70%。另外，将VTEC开关活塞加入滚针轴承内轴同时减小了尺寸与重量。 图11 VTEC滚子剖面图 活塞微波纹处理由创造微波表面的活塞裙部处理组成，它提高了油膜抑制性能，使用低摩擦 损失机油时将减小近30%的摩擦，这些功效开发了 标准相符的0W-20级低粘度油，其摩擦减小效用是发动机马达试验测量的，测试结果如图12所示。现今发动机技术中，HTTS处于极限摩擦值进精度为7.5Mpa，同先进低摩擦发动机结合应用，极限值比 当今的发动机低得多。如图13所示，低摩擦技术大大地减小了发动机的总摩擦力。总的来 说，与传统1.0L发动机相比降低了10%以上。 图12 摩擦减小中的极限 图13 发动机摩擦 7．5减小重量 总观了发动机中几乎所有零件结构和材料，带着创造世界1.0L产品中最轻的发动机目的，减轻重量甚至延伸到了骨架式结构技术和材料技术领域，如用于S2000的连杆渗碳。表面强 化处理大大加快了发动机的营运速度，我们以此为IMA发动机制造出更细的连杆，与传统连杆相比重量减轻了近30%。 图14 磁性油底壳 大多数油底壳是用钢板或铝合金制造，传统的镁材料已经有高温机油承受能力的问题，与传 统材料相比，能在1200C以上温度承受显著落差的蠕变强度，我们开发的新型铝制的底壳 （图14）能承受高达1500C的蠕变强度。油底壳用有铝制垫片的钢制螺栓固定以防止电蚀。 此油底壳经铝制的轻35%，在重量的减轻是与两金属比质量相比的 为进一步扩大 塑制零件的应用，塑制材料在进气歧管、缸罩、水泵、皮带轮等进气系统零件中得到采用， 这些变化使发动机自重小于60kg是世界1.0L产品中最小的。 7．6废气排放性能 本发动机采用能同时达到稀燃和低排放的技术，显著地降低了NOx排量，排气系统发动机后置改善服燃烧（图15）。除此之外，将排气歧管集成在缸盖上，新开发了一种能在稀燃工 况时吸收NOx的催化剂，能降低NOx排放。 Figure 15. Section view of emission system 图15 排放系统的剖面图 7．6．1集成排气歧管和缸盖 传统缸盖每个气缸独立的排气门，在缸盖上再安装一排气歧管将这些排气门合起来。如图 16所示，Insight缸盖有内置的排气门合并的结构，大大地减轻了重量。小小的热辐射表面 减小了废气热损失，使催化过程更早进行。 图16 气缸盖主视图 7．6．2稀NOX催化剂 Insight催化系统包含了NOX吸附材料的三元催化转化器，如图17所示。 Figure 17. Exhaust gas purification mechanism 图17 废气净化装置 在稀燃工况下，废气中的NOX被催化剂吸附。传统三元催化在稀燃工况下，能小量降低 NOX，把大部分HC、CO氧化成CO2和H2O。由于废气中有大量的氧，所以相对少地降低 NOX，大部分NOX都存储于吸附材料表面。在理论空燃比和更高时，废气被阻挡，利用 HC和CO作为还原剂将吸附的NOX还原为氮，同时吸附过程也在进行。因此，利用有NOX吸附作用的三元催化器可有效地降低NOX、HC和CO。此催化剂在稀燃和理论配比工期况 下表现出良好的转化性能，在NOX吸附量满载前有必要再生大气。稀燃时催化剂直接吸收 NOX，在理论配比时将NOX还原为无害的氮排出，此催化剂以稀燃工况直接吸附NOX于表面为特征，而不是作为化合物吸附于表面内，方便了减小转化，提供了更高的高温承受能 力。此催化器将稀燃工况下的NOX排量降低了传统的1/10。值得一提的是其吸附转化性能 对燃料中硫含量十分敏感，因为硫会与NOX争夺吸附空间。传统催化器在稀燃运行时基本 没有降低NOX排量，因此需减小稀燃范围以降低NOX排量。此催化剂确保了稀燃工况下 改善燃油经济性，达到了EU2000标准，是遵守世界排放标准的高效稀燃发动机。 7． 结论 本论文总观了新开发电动机辅助混合动力系，对其各元件及效率与排放性能作了描述。此动 力系同时满足了极低油耗和低排放，达到了轻型紧凑的质量，我们相信此系统能推动21世纪的汽车技术。 Development of Integrated Motor Assist Hybrid System: Development of the ‘Insight’, a Personal Hybrid Coupe Kaoru Aoki, Shigetaka Kuroda, Shigemasa Kajiwara, Hiromitsu Sato and Yoshio Yamamoto Honda R&D Co.,Ltd. Copyright ?2000 Society of Automotive Engineers, Inc. ABSTRACT This paper presents the technical approach used to design and develop the powerplant for the Honda Insight, a new motor assist hybrid vehicle with an overall development objective of just half the fuel consumption of the current Civic over a wide range of driving conditions. Fuel consumption of 35km/L (Japanese 10-15 mode), and 3.4L/100km (98/69/EC) was realized. To achieve this, a new Integrated Motor Assist (IMA) hybrid power plant system was developed, incorporating many new technologies for packaging and integrating the motor assist system and for improving engine thermal efficiency. This was developed in combination with a new lightweight aluminum body with low aerodynamic resistance. Environmental performance goals also included the simultaneous achievement of low emissions (half the Japanese year 2000 standards, and half the EU2000 standards), high efficiency, and recyclability. Full consideration was also given to key consumer attributes, including crash safety performance, handling, and driving performance. 1. INTRODUCTION To reduce the automobile’s impact on society and the environment requires that it be increasingly cleaner and more energy efficient. The issues of energy conservation, ambient air quality, and reduction in CO2 emissions are increasing raised as global environmental concerns. One solution for dealing with these issues is the hybrid automobile. Honda has developed and introduced to several major markets worldwide the Insight, a new generation of vehicle design. The Insight combines a hybrid power train with advanced body technology features to meet an overall goal of achieving the highest fuel economy practical. The hybrid power train is a motor assist parallel configuration, termed IMA for ‘Integrated Motor Assist’. This power train combines a highly efficient electric motor with a new small displacement VTEC engine, a lightweight aluminum body, and improved aerodynamics to realize 3.4L/100km (CO2:80g/km) on 98/69/EC fuel economy. Low emissions performance was also targeted with emission levels achieving the EU2000. In addition to recapturing deceleration energy, the integrated motor provides high torque assist during typical urban driving accelerations. This allows a significant reduction in engine displacement and higher engine efficiency. Sustained hill climbing performance and high speed cruising capability are assured by a power-toweight ratio of approximately 56kW per metric ton. New engine technology includes the application of a new VTEC (Variable valve Timing and valve lift, Electronic Control) cylinder head design promoting high efficiency and fast catalyst activation, and a new lean NOx catalyst system which promotes lean burn combustion and a reduction in emissions. Extensive friction and weight reducing features are also applied. 2. DEVELOPMENT TARGETS AND CONCEPT Development was aimed at the achievement of extremely low fuel consumption. We set a target of twice the fuel economy of the current production Civic, Honda’s representative high fuel economy car at 7.0 L/100km (93/116/ EC). As a result, the Insight has the lowest fuel consumption in the world, among gasoline passenger cars. Exhaust emission performance often tends to be sacrificed for the sake of low fuel consumption. However, we also decided to match the low emissions performance achieved by other mass production cars. Consideration was also given to recyclability (another important environmental issue), crash safety performance, and the basic car characteristics including handling and styling. Summarizing the above, our development targets were as follows: , The best fuel consumption performance in the world , Ultra-low exhaust emissions , Superior recyclability , The world's highest level of crash safety performance , Advanced styling , Practical features and responsive handling , Comfortable two-seat configuration with personal utility space 3. POLICIES FOR FUEL CONSUMPTION REDUCTION In order to establish the technical approach for achieving the fuel consumption target, we conducted a detailed analysis of the energy consumption of the base car, a Civic equipped with a 1.5 liter engine. We found that it was useful to divide the targeted efficiency gains roughly into thirds, as shown in Fig. 1, in order to achieve the low fuel consumption and numerous other above-mentioned goals. These divisions are as follows. , Improvement of the heat efficiency of the engine itself , Recovery of braking energy and employment of idle stop using a hybrid power plant , Car body technologies including reduction of weight and reduced aerodynamic and rolling resistance. Figure 1. Target of double the fuel economy of CIVIC Aiming to establish a benchmark for 21st century automobile power trains, we developed this new Integrated Motor Assist power train. This power train simultaneously achieves both extremely low fuel consumption of 3.4L/100km, and low exhaust gas emission performance, befitting a next-generation car. This paper reports on the newly developed IMA system, including the lean burn engine, electric motor, power control unit, battery technology, and exhaust emission control technology used in the "Honda Insight". 4. AIM OF THE IMA SYSTEM While developing this next-generation IMA hybrid system, we incorporated as many currently achievable technologies and techniques as possible, in order to achieve the "world's lowest fuel consumption". The following four system development themes were established in order to meet this target. 1. Recovery of deceleration energy 2. Improvement of the efficiency of the engine 3. Use of idle stop system 4. Reduction of power train size and weight 5. OVERVIEW OF THE IMA SYSTEM 5.1. SYSTEM CONFIGURATION – As shown in Fig. 2, the IMA system uses the engine as the main power source and an electric motor as an auxiliary power source when accelerating. Using a motor as an auxiliary power source simplifies the overall system and makes it possible to use a compact and lightweight motor, battery, and power control unit (PCU). Figure 2. IMA System A permanent magnet DC brushless motor is located between the engine and the transmission. When decelerating, the rate of deceleration is calculated for each gear and the PCU controls the motor to generate electricity (recover energy), which charges a nickel-metal hydride battery. When accelerating, the amount of auxiliary power provided (hereafter called "assist") is calculated from the throttle opening, engine parameters, and battery state of charge. The PCU controls the amount of current flowing from the battery to the drive motor 5.2. RECOVERY OF DECELERATION ENERGY – Recovering deceleration energy through regeneration makes it possible to supplement the engine’s output during acceleration and reduce the amount of fuel consumed. Reducing resistance due to running losses, including engine frictional losses, increases the available energy for regeneration. In particular, minimizing the engine displacement is an effective means of reducing friction. Engine displacement reduction also has several other benefits, such as weight reduction and increased thermal efficiency. The IMA system effectively increases the amount of regeneration during deceleration by optimizing the engine and transmission specifications. 5.3. REDUCTION OF ENGINE DISPLACEMENT – Reducing engine displacement is a very important factor in improving fuel economy of a hybrid drive train. However, modern automobiles have to perform over a wide dynamic range. Reducing the displacement is equivalent to lowering the basic performance characteristics of the car. As shown in the output characteristics graph in Fig. 3, the IMA system assists the engine in the low rpm range by utilizing the hightorque performance characteristic of electric motors. The motor can increase overall toruque by over 50% in the lower rpm range used in normal driving. Output in the high rpm range is increased by using a Variable valve Timing and valve lift Electronic Control (VTEC) engine. Thus sufficient peak power is assured and makes it possible to use a new, small displacement 1.0 liter engine. Figure 3.Engine speed (rpm) Output performance of IMA SYSTEM Assist from the electric motor while accelerating is a very efficient means of reducing the amount of fuel consumed. 5.4. ACHIEVING LEAN BURN ENGINE OPERATION – Assist from the electric motor, based upon the throttle opening, creates quite linear torque characteristics. This, in turn, improves driveability. In addition, motor assist is also provided under moderate load conditions to broaden the lean-burn operating range, bringing out the full potential of the newly developed lean burn engine. 5.5. IDLE STOP SYSTEM – Stopping the engine rather than idling at stops is also an effective means for reducing fuel consumption. In order to restart the engine with the minimum amount of fuel consumption, the engine is quickly cranked to 600 rpm or more by the hightorque integrated motor before ignition occurs, as shown in Fig. 4. This makes it possible to minimize the amount of fuel consumed, in addition to the fuel saved by not running the engine at idle. There are many issues to be considered when performing idle stop. These include judging the driver's intent to stop, preparing for the restart, providing a smooth feeling of deceleration, and minimizing vibration of the car body when the engine stops. Figure 4.Time (sec) The number of cranking in the engine start This IMA system results in the achievement of both very quick restarts and exceptionally smooth starts. 6. MOTOR ASSIST MECHANISM 6.1. DEVELOPMENT OBJECTIVES – By limiting the IMA motor functions to assistance and regeneration, development themes were established to achieve the following two points. 1. A simple and compact structure 2. A system weight of 10% (80 kg) or less of the completed car weight 6.2. THIN PROFILE DC BRUSHLESS MOTOR – A thin and compact DC brushless motor with engine assist and energy regeneration functions was coupled to the engine crank-shaft (Fig. 5). Figure 5. Section view of Motor This is a high efficiency, compact, and lightweight permanent magnet-type three-phase synchronous electric motor with a maximum output of 10 kW. In addition to developing technologies to reduce the weight and increase efficiency, we also aimed to make the motor as thin as possible in order to achieve a compact power train. Lost wax precision casting process was used for the rotor, rotating by bending coupled to the crankshaft. This achieves high strength and lighter weight (approximately -20%) compared with normal cast products. For the rotor magnets, further improvements were made to the neodymium-sintered magnets used in the HONDA EV PLUS, realizing approximately 8% greater torque density and improved heat resistance. This design also results in a motor structure that does not require a cooling system. A split stator structure with salient pole centralized windings was developed and used to reduce the motor axial width. A split stator was adopted to drive the rotor. This makes it possible to use the salient pole centralized windings, which are both more compact and efficient than the conventional coil wave winding method, as shown in Fig. 6. In addition, centralized distribution bus rings (Fig. 7) formed from copper sheets were used for the harness that supplies electricity to the coils on both sides of the stator. This results in an extremely compact and simple structure. These improvements achieve an extremely thin motor with a width of only 60 mm. This represents a 40% reduction in width compared to conventional technology. Wave winding Salient pole winding Figure 6. Compare of winding Figure 7. Cut view of Motor 6.3. NICKEL-METAL HYDRIDE (NI-MH) BATTERY – A nickel-metal hydride battery is used to store and provide electrical energy for the motor assist. This is an advanced battery which has already achieved proven results in the high specific energy version used for the HONDA EV PLUS electric vehicle. The hybrid vehicle battery features stable output characteristics, regardless of the state-of-charge status. It is also extremely durable in this application. The battery pack has an integrated structure consisting of 20 modules, each having six D-size cells connected in series, arranged in a lattice formation. These 120 1.2 V cells are all connected in series for a total battery pack voltage of 144 V. 6.4. POWER CONTROL UNIT (PCU) – The PCU performs precise control of motor assist/regeneration and supplies power to the 12 V power source. It has built-in cooling functions, which give it a lightweight, efficient and compact structure. Significant weight reduction was achieved by integrating an air cooling system using highly efficient cooling fins and a magnesium heat sink case. The inverter for the drive motor, which is the most important component within the PCU, has switching elements integrated into a single module for generating the three-phase AC current. These were separate components on the EV PLUS. The drive circuit has been miniaturized and converted to an IC using high density integration. These improvements have resulted not only in significant weight reduction, but have also improved the power conversion efficiency. Further, using phase control to drive the motor at very high efficiencies reduces the amount of heat produced and makes it possible to use a lightweight and simple air-cooling system. (Fig. 8) Figure 8.Inverter Cut view of PCU Heat Sink case 7. ENGINE 7.1. DEVELOPMENT OBJECTIVES – The following four points were set as development themes in order to achieve low fuel consumption over a wide range of operating conditions. 1. Improvement of thermal efficiency 2. Reduction of mechanical losses (-10% compared with conventional designs ) 3. Reduction of size and weight (lightest weight in its class) 4. Achievement of half the EU2000 standards 7.2. ENGINE OVERVIEW AND SPECIFICATIONS – The engine specifications are shown in Table 1 and the main new features and their purposes are shown in Table 2. First, a displacement of approximately 1000 cm3 was considered optimal for this vehicle with the IMA system, so a 3-cylinder engine was selected to minimize combustion chamber surface-to-volume ratio and mechanical losses. (Fig. 9) 7.3. FUEL CONSUMPTION – Engine displacement could be reduce considerably in the motor assist powertrain because of the motor assist enhancement of low rpm torque, and also VTEC for sufficient peak power output from the engine. A key feature of this engine is the significant improvement in combustion efficiency through lean burn technology. Technologies adopted to make this possible include new intake swirl ports, which enhance the swirl (mixture formation) inside the cylinders. A compact combustion chamber and a high compression ratio also help by improving the indicated heat efficiency. This result in significantly shorter combustion times compared to conventional lean burn engines, allowing combustion in a leaner range with a higher air-fuel ratio. This significantly improves the fuel consumption. The new high swirl ports and compact combustion chamber are evolutions based on conventional VTEC lean burn technology. In the conventional VTEC engine, swirl is produced by keeping one intake valve closed in low speed operating conditions. However, in this engine the intake valves and intake ports are arranged more vertically to produce strong eddies in the mixture flowing into the cylinders. The conventional VTEC configuration has the inlet and exhaust rocker arms each supported by a separate rocker shaft. The new VTEC mechanism shown in Fig.10 combines these into a single rocker shaft, thus realizing a significant reduction in size. In addition, it narrows the valve included angle from 46? to 30?, allowing a high swirl port shape and a very compact combustion chamber. Figure 9. Cutaway view of engine Figure 10. Section view of cylinder 7.4. REDUCTION OF MECHANICAL LOSS – In addition to improvement of the indicated heat efficiency, reduction of mechanical loss is also important to improve fuel economy. To achieve this, the following the low friction technologies were used. , Roller coaxial VTEC mechanism , Piston micro-dimple treatment , Offset cylinder structure , Low tension piston rings , Carburized connecting rods The roller coaxial VTEC structure (Fig. 11) is an adaptation of technology used in the Honda S2000 (high output sportscar engine) to a single-cam VTEC mechanism. The camshaft drive loss was reduced by 70% using a needle roller bearing in the area where the rocker arm slides on the camshaft. In addition, simultaneous reduction in both weight and size were achieved by incorporating the VTEC switching piston into the roller bearing inner shaft. Piston micro-dimple treatment consists of treating the surface of the piston skirt to create a micro-dimple surface. This increases the oil film retention performance and can reduce friction by approximately 30% when lowfriction oil is used. Figure 11. Section view of Roller VTEC These effects resulted in the development of a 0W-20 grade low viscosity oil that complies with ILSAC standards. The friction reducing effects of super-low viscosity oil were measured by engine motoring. These measurement results are shown in Fig. 12. In the current technology engine, the HTHS viscosity at the limit friction value was approximately 2.5 mPas. Being used together with the advanced low friction engine, the limit value was lower than the current technology engine These low friction technologies have vastly reduced the overall engine friction, as shown in Fig. 13. In total, they have realized a reduction in friction of 10% or more compared to a conventional 1.0 liter engine design . Figure 12. Limit in friction reduction Figure 13. Engine friction 7.5. WEIGHT REDUCTION – The structure and materials of almost all parts in this engine have been reviewed with the aim of creating the lightest engine in the world in the 1.0 liter class. This weight reduction extends even to the "skeleton structure technology" and "materials technology" fields carburized connecting rods as used on the S2000 (high output sportscar engine). Carburization strength enhancement technology contributes greatly to increasing engine operational speed. We applied this strength enhancement technology to create a slim connecting rod design for the IMA engine. This resulted in a weight reduction of approximately 30% compared to conventional connecting rods. Most oil pans are made of steel plate or aluminum alloy. Conventional magnesium materials have had problems withstanding the high temperatures of engine oil. In contrast to conventional materials, which experience a significant drop in creep strength at 120?C or higher, we have developed a new magnesium oil pan (Fig. 14) which ensures sufficient creep strength up to 150?C. Figure 14. Magnesium Oil Pan This oil pan is fastened using steel bolts with aluminum washers to prevent galvanic corrosion. The oil pan weight is 35% lighter than an aluminum oil pan, for a reduction in weight that is comparable to the ratio between the specific masses of the two metals. In order to expand the application of plastic parts, plastic materials were adopted for the intake manifold, cylinder head cover, water pump pulley, and intake system parts. These changes brought the discrete dry weight of the engine to less than 60 kg, which is the lightest weight in the world for the 1.0 liter class. 7.6. EXHAUST EMISSION PERFORMANCE – Technology for simultaneously achieving both lean burn and low exhaust emissions was adopted in this engine, achieving a notable reduction in NOx emissions. Combustion was improved by putting the exhaust system to the rear of the engine (Fig. 15). In addition, the exhaust manifold was integrated with the cylinder head and a NOx adsorption catalyst which reduces NOx emissions during lean burn operation was also newly developed. Figure 15. Section view of emission system 7.6.1. Integrated Exhaust Manifold and Cylinder Head – Conventional cylinder heads have independent exhaust ports for each cylinder and a separate exhaust manifold acts to converge these exhaust ports into a single port is then mounted to the head. However, the new head on the Insight has a structure which converges the exhaust ports into a single port inside the head, as shown in Fig. 16. This greatly reduces the weight. In addition, the small heat radiating surface area reduces the exhaust gas heat loss, thus enabling early catalyst activation. Figure 16. View of Head 7.6.2. Lean NOx Catalyst – The catalyst system on the Insight combines a conventional three-way catalyst with NOx adsorbing materials. The NOx conversion mechanism of the newly developed catalyst is shown in Fig. 17. The NOx in the exhaust gas is adsorbed and separated by the NOx adsorption action of the catalyst during lean engine operating conditions. Conventional three-way catalyst operation reduces part of the NOx to nitrogen and oxidizes most of the HC and CO to CO2 and H2O during lean operation. However, since the exhaust gas contains large amounts of oxygen, there is relatively little NOx reduction with the three-way catalyst and most of the NOx is stored on the surface of the adsorbing material. When the exhaust is held at the theoretical air fuel ratio (stoichiometry) or richer air-fuel ratio, the adsorbed NOx is reduced to nitrogen using HC and CO as reducing agents. The adsorbent is regenerated at the same time. Thus, NOx, HC and CO are effectively converted using the three-way catalytic action of the catalyst combined with the NOx adsorber. This type of catalyst exhibits superior conversion performance during both lean operation and stoichiometric operation by switching between lean and stoichiometry operating conditions. It is essential to create a regenerative atmosphere before the NOx adsorption capacity becomes overloaded. This catalyst directly adsorbs NOx during lean burn engine operation and the adsorbed NOx is then reduced and exhausted as harmless nitrogen (N2) during stoichiometric operation. Figure 17. Exhaust gas purification mechanism This catalyst is characterized by the direct adsorption of NOx to the catalyst surface during lean operation. Adsorption on the catalyst surface, instead of absorption as a compound inside the surface, facilitates conversion during reduction and also provides superior durability at high temperatures. This adsorptive type catalyst reduces NOx emissions during lean burn operation to 1/10 the level of the conventional three-way catalyst. It should be noted that the adsorption and conversion performance of this type of catalyst is sensitive to sulfur levels in the fuel, as sulfur can compete for the active NOx adsorbing sites. As a conventional three-way catalyst has virtually no NOx reduction during lean-operation, the lean burn operating range typically has to be reduced to keep NOx emissions down. Use of an adsorptive type catalyst maintains the full lean burn range and improves fuel economy, even while reducing NOx. This vehicle can also satisfy the EU2000 standards, making this a highly efficient lean burn engine that complies with exhaust emissions standards throughout the world. 8. CONCLUSION This paper presents a general overview of the recently developed motor assist hybrid powertrain, as well as a description of its various components and its output and emission performance. This hybrid power train simultaneously achieves ultra low fuel consumption and low exhaust emissions. It also achieves a compact, lightweight power train layout. We believe this system advances 21st century automotive technology toward regional and global environmental goals. REFERENCES 1. Aoki, Kaoru, et al.: "Development an Integrated Motor Assist Hybrid System", JSAE No. 98-99 161 2. Yamaguchi, Tetsuro: "CVT Control in the HONDA Hybrid 'IMA'", No. 9908 JSAE SYMPOSIUM, Latest Motive Power Transmission Technologies '99, p.3740 3. Ohno, Hiroshi, et al.: "Development of a NOx Adsorptive Reaction Type Three-Way Catalyst", HONDA R&D Technical Review, Vol. 11 No. 2 (October 1999), p.45-50 4. Fukuo, Koichi, et al.: "Development of the Ultra Low Fuel Consumption Hybrid Car 'Insight'", HONDA R&D Technical Review, Vol. 11 No. 2 (October 1999), p.1-8 5. Hideki Tanaka, et al .: "The Effect of 0W-20 Low Viscosity Engine Oil on Fuel Economy”, SAE Paper No.1999-01-3468,Fuels and Lubricants meeting and Exposition, Toronto, Ontario, Canada, October 1999. 6. Aoki, Kaoru, et al.: "An Integrated Motor Assist Hybrid System", SAE Paper No.2000-01-2059, Government / Industry Meeting, Washington, D.C., USA