单模复合动力分流混合动力系统开发及热平衡技术研究

【作者】 韩兵；

【导师】 蔡忆昔；

【作者基本信息】 江苏大学 ， 动力机械及工程， 2011， 博士

【摘要】 能源和环境问题给汽车研发提出新的挑战,驱动系统电动化已经成为汽车动力系统的发展趋势,行星齿轮动力分流变速箱技术成为国际主流的深度混合动力系统方案。混合动力分流系统集成串联和并联混合动力方案的优点,能更好地适应行驶路况,同时实现整车的无级变速。动力分流变速箱技术包括动力分流系统的方案设计、机械结构设计、电机系统开发、独立液压系统开发以及整车控制策略开发,是高密度的集成技术体系。本文研究动力分流系统的设计技术、核心控制算法以及基于动力分流系统控制策略的混合动力变速箱热平衡管理技术。研究动力分流系统的基本动力分流模式特性,从传动系统效率和扭矩输出能力角度评估各种可能的结构方案,分析结论可以作为动力分流系统方案设计的基本依据。介绍单模和双模动力分流系统的设计方法及换挡元件的应用技术,采用双离合器技术、连接轴切换、电机转速解耦等设计技术开发多款单模和双模动力分流系统方案,提高了单模动力系统扭矩输出能力和高车速传动系统效率。设计基于拉维纳复合行星齿轮机构的新型四轴动力分流机构,并开发采用该动力分流机构的单模复合动力分流系统,填补同类混合动力分流产品的空白,也是目前第一款三自由度动力分流系统。研究动力分流传动系统的刚度匹配技术,建立动力分流传动系统的参数化振动模型,实现传动系统刚度的优化匹配。动力分流系统的控制技术是产品硬件开发的重要中间环节,不仅可以验证动力系统的设计方案,而且还为各子系统提供设计载荷谱。动力分流系统的控制技术主要包括工作点优化、驱动模式管理和各部件的扭矩平衡控制。对于行星齿轮动力分流系统而言,各传动轴之间的扭矩平衡控制是动力系统控制的关键技术,其核心内容是确定各种扭矩平衡模式的控制参数解耦条件。开发适用于产品设计的动力分流系统控制策略,仿真分析动力系统在典型标准工况下各部件的工作载荷,并作为产品设计和校核的载荷条件,电机和传动系统的损失功率谱作为动力箱热平衡管理系统的设计依据,为液压系统开发提供流量和压力要求。混合动力变速箱的热平衡管理系统主要研究维持动力电机和传动系统热平衡状态的管理技术,包括动力箱热平衡功率分析、液压冷却系统方案设计及液压元件设计。混合动力箱的热功率主要来源于内部电机的损失功率,其大小取决于动力系统控制策略对电机工作点的控制,因此动力箱的热平衡技术是建立在动力系统控制策略之上的管理技术。设计动力电机的喷淋直冷方案,实现电机的完全油冷。考虑到动力箱内部集成两个制动器元件,需要设计高压闭合油路,因此在液压系统设计时开发了具有电机冷却、传动系统润滑及换挡高压控制油路的集成液压方案,同时简化了动力箱的结构设计和油路布置。深度混合动力系统的多种工作模式使得液压系统的设计不同于传统自动变速箱,设计机械油泵和电机油泵组成的双液压源方案,满足动力系统在纯电动和混合驱动模式下的流量需求。机械油泵采用主减速齿轮驱动,其输出流量与车速成比例关系,只有当车速较低机械油泵无法满足需求流量时,电机油泵才起动进行流量补偿。当车速达到一定时将由机械油泵单独提供系统需求流量,电机油泵停止工作,该方案可以通过油泵排量的优化设计降低液压系统的溢流损失。采用先导式电磁阀设计双压力水平的液压控制油路,实现系统高低油压的自动控制,只有在制动器闭合时液压系统才工作在高压状态,在制动器打开时液压系统只工作在满足冷却润滑要求的低压状态,最大程度地降低了液压系统的功率消耗。根据液压系统各油路的设计压力,通过理论计算确定各液压元件的结构尺寸,采用有限元技术分析液压阀板油道的密封性能,优化固定螺栓分布使其对阀体产生的压紧应力覆盖整个油路,避免低应力区域造成流量泄漏。建立冷却润滑油路的流量分配模型,研究不同油温下各冷却润滑油路流量和压力的变化特性,实现电机和齿轮冷却润滑流量的比例分配。采用多学科仿真软件ITI-SimulaitonX建立完整的液压系统动态仿真模型,验证液压系统原理方案、液压元件尺寸设计以及液压系统在各种油温和行驶状态下的流量与压力变化特性。对混合动力变速箱进行台架和整车试验,测试整个动力系统功能以及动力箱的热平衡状态和液压系统流量压力是否满足设计要求。设计液压系统专用试验台架,单独测试液压系统各油路的流量和压力特性,试验结果表明液压系统的输出流量和电磁阀压力调节方案达到了样机设计要求。进行动力箱冷却润滑油路的观察试验,评估各油路的流量分配。在试验台架上进行动力动力箱的大负荷温升试验,确定行星齿轮机构必需的冷却润滑流量和电机实际需求的冷却流量,积累试验数据优化电机冷却流量分配,通过反复试验均衡大小电机的温度变化防止单个电机提前过热。对动力系统样车进行转鼓试验,测试动力系统在实际运行中的整体性能和动力箱的温度变化,测试结果表明动力系统能够实现各种设计功能,动力箱处于良好的热平衡状态,满足动力系统长时间工作的热平衡冷却要求。混合动力分流变速箱技术作为汽车驱动系统发展的重要方向,已经成为国内外汽车公司的研究热点,目前国内尚没有该类产品上市。本文研究了动力分流系统开发的核心技术,形成完整的动力系统设计规范,对于类似行星齿轮动力分流系统的开发具有指导作用。更多还原

【Abstract】 As the fear of environment pollution as well as the energy crisis, the pressure for the reduction of fuel consumption and exhaust emissions becomes a new challenge for all vehicle manufacturers. Developing the electrified vehicle power-train becomes the main trend of present vehicle technology. Among the various power-trains for hybrid electric vehicle, the planetary gear power split hybrid system, which is also known as series/parallel hybrid, has been widely regarded as the most promising hybrid configuration. Power split hybrid systems are more beneficial because they have the advantages of both series and parallel types, and enable the e-CVT function. The key development technology of power split hybrid system includes the power split configuration design, electric motor system, hybrid transmission thermal management technology and the control algorithm, which are studied in this thesis.Power circulation characteristics of the basic power split modes are analyzed, and the performance in the transmission configuration design is estimated according to the power-train efficiency and torque output ability, which can be used to guide the development of power split system. Design regulations for single mode and two mode hybrid systems and the application of shifting elements are summarized. Dual clutch technology, electric motor speed decouple technology, fixed gear driving mode, etc. are used to perfect the operating modes of power split system. Several single mode and two mode hybrid systems are designed, and the recommended single mode system has a highly flexible configuration, which is especially practical for improving the torque output ability and the high vehicle speed power-train efficiency. A new single mode hybrid system which utilizes an innovative four-shaft power split device based on the Ravigneaux compound planetary gear set is introduced. This hybrid configuration is the first single mode power split production with compound power split mode, which is also the first three-degree-of-freedom hybrid system. Torsional vibration analysis method for power split hybrid power-train is studied. Parametric power-train vibration model is built to optimize the resonant frequency through the torsional damper stiffness match.Control strategy development is a key step of the power split hybrid transmission design, which can be used to verify the power-train performance and supply the load cycle for all the mechanical parts design. The control strategy includes driving power interpretation, driving mode management and torque balance technology. As to all kinds of the planetary gear power split system, the torque balance technology is the necessary technology. Torque balance modes of different driving modes are studied to decouple the control parameters of the power split hybrid system. Control strategy of the compound power split system is developed to simulate the performance under different standard load cycles. Simulation data is also applied to guide and check the design of all the mechanical parts. The loss power spectrum of electric motors and power-train is used to develop the transmission thermal balance management system and confirm the oil flow and pressure requirement of the hydraulic system.Thermal balance management system is mainly used to keep the thermal balance status of the hybrid transmission, which includes the thermal power calculation, hydraulic system principle design and the hydraulic parts design. The thermal energy of the hybrid transmission is mainly from the electric motor loss power and the power-train friction loss power. Therefore, the thermal management technology can be considered as a control technology based on the system control strategy. The two electric motors rotate in the oil mist and are fully oil-cooled through the direct spray cooling mode. ATF oil is injected directly onto the cable ends of the motor stators to absorb the motor loss power. A high pressure oil circulation is needed to supply pressure oil for brake elements. So a multi-function integrated hydraulic system is designed including the cooling circulation and high pressure control elements. The integrated hydraulic system is practical to simplify the transmission structure and the layout of oil channels in the transmission housing.The hydraulic system design of full hybrid transmission is different from that of conditional automatic transmission, because in some driving modes the combustion engine can be stopped. Because of this reason, a new oil supply system of two oil pumps is designed. A first oil pump is located below the output-gear and becomes driven by that shaft, so it can be running even when the combustion engine stands still. A second pump is defined as an assistante one driven by a small electric motor which is only activated at reverse vehicle speed and when the flow rate from the first pump is not enough. The rotating speed of electric pump is controlled to compensate the required oil flow and ensure the necessary oil flow for motor cooling and power-train lubrication. Self-adapted pressure regulation circuit is designed for the brake element engagement via solenoid valves which only happens in the electric driving mode and the overspeed mechanical point driving mode. Otherwise the oil pressure is controlled around the low cooling-lubrication level. The pressure control circulate can be used to decrease the power consumption of hydraulic system.Dimensions of the hydraulic valves are design by theoretical calculation. Finite element techonolgy is applied to check the channel leakage of hydraulic block and optimize the layout of connecting bolts. Oil flow distribution model is established to distribute the oil flow and to observe the flow and pressure characteristic under different oil temperature and different driving modes. Dynamic simulation model of the whole hydraulic system is built to investigate the function of hydraulic principle, valve dimensions and characteristics of oil flow and pressure with ITI-SimulationX. Simulation results indicate the hydraulic system is practical and the element design parameters can reach the design requirement.Bench test and hybrid vehicle test are made to check the hybrid system function and the performance of hydraulic system. A special hydraulic test bench is built to test the oil flow and pressure characteristics. The hydraulic test results indicate the output cooling flow and pressure control principle are practical, which reach the requirement of the first prototype production. Full load bench test is designed to check whether the cooling oil flow for electric motors and planetary gear is enough or not. Test data is recorded and used to modify the oil distribution calculation results. The cooling flow for two motors and planetary is adjusted according to the test results. Vehicle test is carried out to check the real performance of the power split hybrid system and the thermal status of the transmission. Vehicle test results indicate the hybrid system can complete all the design functions and driving modes, and temperature level of the hybrid transmission is in the good condition.In recent years, more and more attention is paid to the research of power split hybrid transmission, which has become one important direction of vehicle power-train development. Unfortunately, so far there is no this kind of hybrid transmission. The key technologies of power split hybrid transmission are studied in this thesis, which can be used to guide the similar hybrid transmission development.更多还原