压电晶体喷油器及驱动策略的研究

【作者】 何正胤；

【导师】 周文华；

【作者基本信息】 浙江大学 ， 动力机械及工程， 2008， 硕士

【摘要】 高压共轨系统是柴油机燃油喷射系统的发展趋势。为了满足越来越严格的发动机排放法规的要求,对燃油喷射过程进行全方位的柔性控制越来越普遍地应用于柴油机高压共轨系统。压电晶体执行器与电磁阀执行器相比,在很多方面都有着先天的优越性,是高压共轨系统喷油器理想的执行器。本论文选题紧跟柴油机燃油喷射系统的发展趋势,具有深远的意义。对压电晶体性质的研究始于十九世纪末期,人们已经对压电晶体的压电效应、逆压电效应等性质进行了大量的研究。本文在这些研究的基础上,结合柴油机高压共轨系统应用环境,从理论上分析了压电执行器运动状况与所处电磁环境的关系。设计一个驱动电路首先应该提出对该驱动电路的要求。本文在充分理解柴油机高压共轨系统对喷油器执行器的要求的基础上,结合执行器本身的条件,对驱动电路提出了要求。驱动电路控制压电晶体执行器的充放电过程,实际上是对压电晶体执行器运动状态的控制。针对压电晶体执行器的要求和特性,作者提出了“初期开环控制加速,中期闭环控制匀速伸长,末期开环控制减速”的简单而可行的控制策略。结合控制策略和驱动要求,作者对驱动电路进行了模块化设计。文中提出了几套驱动策略,包括电压驱动方式、电流驱动方式和时间控制驱动方式。在对电压驱动方式和电流驱动方式两者对压电晶体执行器进行充电的过程的研究中作者发现,两者的驱动效果差别很小。同时还发现,随着时间的增加,开关管打开进行充电的时间越来越长,得出了时间控制驱动方式响应速度较慢的结论。本论文最后选择了电流驱动方式在压电晶体执行器充电、放电(即喷油器开始喷油和停止喷油)的全过程进行了试验验证,结果证明该方案满足预期要求。更多还原

【Abstract】 Common-rail system is the development trend of the diesel fuel injection system. In order to meet increasingly stringent emissions regulations, full range of flexible control is being more widely used in Common-rail system. Compared with the electromagnetic valve actuator, piezo actuator has a lot inherent advantages, and is the ideal actuator for injectors in common-rail system. This paper keeps up with the trend of the development of diesel fuel injection system and with far-reaching significance.Researches on piezo began in the late 19th century. People have done a lot of studies on the piezoelectric effect, the reverse piezoelectric effect, and other properties of piezo. Based on these studies and the application in the common-rail system, this paper has analyzed the relationship between the piezo actuator’s movement and the electromagnetic environment in which the piezo stay.The design of a driving circuit should first put forward the request. Based on request of common-rail application and the actuator’s properties, this paper has given some request on the driving circuit. The author proposed a "speeding up in a open-loop control at the beginning, keeping uniform elongation in a closed-loop control within the medium-term, and at the end decelerating in a open-loop control", a simple but practical control strategy. And also has made a modular design of the driving circuit.This paper has put forward several driving-strategy, including the voltage-driven approach, the current-driven approach and the timing-control driving approach. In the Studies on the comparison of the performances of the voltage-driven approach and the current-driven approach in the charging of piezo, author found that these two approaches had little difference. Also found that the switch opened a longer time with the increasing of time. Hence the timing-control driving approach must have a longer charging time. At the end of this paper, the author made a verification of the final choice of the current-driven approach in the implementation of the piezo charge and discharge with some experimentation. The results show that the solution is expected to meet the requirements.更多还原