Effect Of Position Errors Of Coupler On Dynamic Performance Of Heavy Haul Locomotive

Active development of heavy haul railway transportation technology is one of the necessary conditions to promote the rapid growth of the national economy. Increasing the axle load and enlarging the train formation are the two most common ways to expand the capacity and improve the efficiency of heavy haul railway transportation. However, whatever for increasing the axle load or enlarging the train formation, it will cause more severe longitudinal impulses to the heavy haul trains under braking conditions. These impulses are likely to cause many problems such as coupler broken and draft gear damages. And more seriously, it would lead to train derailment and threatens to the life safety of the staff. So, the dynamic problems related to heavy haul trains under braking conditions have attracted wide attentions. In order to solve the problem of large and unidirectional transverse displacement of the eight-axe locomotive car-body under braking, geometric parameters were measured firstly and then the dynamic performances of the locomotives were investigated experimentally. Finally, the dynamic performances of the locomotives were calculated under conditions with different lateral deviation distances and running speed.The working mechanism of the 13A/QKX100 coupler/draft gear system is introduced in this paper. The car-body stable mechanism and the effect of the position errors of coupler box on the car-body stability of locomotives are studied under the action of longitudinal braking forces. The analysis shows that the position errors of the coupler box, the friction coefficient of coupler tail and the secondary suspension lateral stiffness are the key parameters affecting the stability of locomotives.In order to verify the main factors affecting the coupler angle and the car-body’s transverse displacement, a series of geometric measurements were carried out in a locomotive factory. The results indicate that the position error of the coupler box is large and unidirectional. Besides, a layer of grease between the coupler tail and the draft gear follower is obsevered. What’s more, in both the experiment on the factory line and measurements in the locomotive depot, the non-uniform wear between the coupler tail and the draft gear follower is found. The analysis result shows that the position error of the coupler box occurred in the production process affect the stability of locomotives. The main reason for the observed unidirectional transverse displacement of the locomotive car-body and the non-uniform wear of the coupler tail and the draft gear follower is the unidirection of the position error. The layer of grease leads to the insufficient friction between the coupler tail and the draft gear follower, which will decrease the coupler stability.A field test was carried out to study the dynamic characteristic of the locomotive lateral displacement under different braking conditions. In the test, coupler force, coupler yaw angle and car-body’s transverse displacement were measured. The measured results indicate that the coupler angle and car-body’s transverse displacement will be bigger under braking when the coupler force become lager. In addition, the coupler angle and the car-body’s transverse displacement have unidirectional feature under several conditions.With the 13A/QKX100 coupler/draft gear system and a certain type of heavy haul locomotive as the research object, a train dynamic model composed of 2 eight-axe locomotives connected by coupler/draft gear system was established based on the field test and geometric measrement results. Then compariosons between the calculated results and the tested results were made to verify the effectiveness of this dynamic model. Then the model was applied to calculate the effect of the position errors of the coupler box on the dynamic performance of the locomotives under braking. It is indicated that the coupler angle and the car-body’s transverse displacement will be larger and the running safety will be deteriorated under braking when the coupler box center lines deviate more from the car body underframe center line. In order to ensure the running safety for the studied train, the deviation distance should be as small as possible.