拖拉机双离合器自动变速器换挡品质评价指标

针对双离合器自动变速器拖拉机在田间高负载作业工况下进行换挡时,原换挡品质评价指标不能充分考察对性能的影响,提出了变速器输出转矩传递系数和变速器输出转矩2个评价指标。归纳了奇数挡和偶数挡离合器接合与分离时序对换挡品质影响规律,建立了拖拉机DCT换挡动力学模型和换挡品质仿真模型。以东方红1804拖拉机为研究对象,对其犁耕工况进行了仿真分析,结果表明:当离合器油压上升滞后时间分别为0、0.1及0.2 s时,对应的变速器最小输出转矩传递系数分别为0.42、0.36及0.12,变速器最小输出转矩分别为2 257、1 932及725 N·m,产生的动载荷逐渐增大,拖拉机动力性变差;提出的2个换挡品质评价指标可较好地对换挡过程中产生的动载荷和拖拉机动力性进行评价,对原换挡品质评价指标进行了补充,完善了拖拉机DCT换挡品质评价体系。该研究为拖拉机双离合器自动变速器换挡控制策略制定提供了理论依据。

Evaluation indexes of shifting quality for dual clutch transmission for tractor

Abstract: When the tractor assembled with dual-clutch automatic transmission shifts under the condition of working with heavy load in the field, the original shifting quality evaluation indices can't fully investigate their impacts on the performance, so 2 evaluation indices, which are transfer coefficient of transmission's output torque and transmission's output torque, are proposed. The transfer coefficient of transmission's output torque is used to evaluate dynamic load which is produced in shifting process of the tractor assembled with dual-clutch automatic transmission; and the transmission's output torque is used to evaluate power in shifting process of the tractor assembled with dual-clutch automatic transmission. The pattern has been concluded that the superposition degree of 2 groups of clutches (one group is connected with odd gear input shaft, and the other is connected with even gear input shaft) has an effect on shifting quality. In the shifting process of the tractor with dual-clutch automatic transmission, in order to ensure ride comfort, power performance and durability of the transmission system, 2 groups of the clutches should have appropriate superposition in the separation and combination processes. If the superposition degree of 2 groups of clutches is insufficient, it could cause transfer coefficient of transmission's output torque and transmission output torque to decrease and even make power performance and durability of the transmission system enter a poor condition; if the superposition degree of 2 groups of clutches is excessive, it could cause jerk degree and sliding-friction work to increase, even make ride comfort enter a poor condition and shorten the service life of clutch. The dynamic equations of the shifting process of the tractor assembled with dual-clutch automatic transmission have been built and the shifting process has been analyzed. The shifting process is divided into 5 stages. The change trend of the speed and torque of the clutch and engine in each stage is analyzed. Based on the Matlab/Simulink/Stateflow software platform, the simulation model of the whole shifting process has been built. Dongfanghong-1804 tractor is selected as the reference object, and its shifting process has been simulated in plowing conditions. Relevant simulation results indicate that when the lag time of clutch's oil pressure rising is 0, 0.1 and 0.2 s, the corresponding minimum transfer coefficients of transmission's output torque are 0.42, 0.36 and 0.12, respectively, and the corresponding minimum torques output by transmission are 2 257, 1 932 and 725 N·m, respectively. According to the analysis of simulation data, as the lag time of clutch's oil pressure rising extends, the decline degree of transfer coefficient of transmission's output torque becomes larger to cause dynamic load to increase gradually, and the transmission's output torque becomes smaller to make tractor's power performance worse. The 2 new shifting quality evaluation indices can fully evaluate tractor dynamic and dynamic load which is generated in the process of shifting; they are good compliments to original shifting quality evaluation indices and improve the shifting quality evaluation system of the tractor assembled with dual-clutch automatic transmission. Above all, the results of this paper provide some theoretical basis for formulating shifting control strategy of the tractor with dual-clutch automatic transmission.