Engine and reducer are installed in the machine room. The brakes and other components of the traction machine are traction drive power. The traction rope is connected to one end of the car through the traction sheave and one end is connected to the counterweight. In order to make the hoistway hoistway and hoistway separately along the hoistway rubbing machine placed on the guide wheel, the two separated. The weight of the car and counterweight causes the traction rope to be compressed in the traction sheave groove to create friction. In this way, the rotation of the motor drives the traction sheave to rotate, driving the rope, dragging the car and making relative movement with respect to the weight. In other words, the car rises, the weight decreases; the weight increases, the car drops. Therefore, the car reciprocates along the shaft track, and the elevator performs vertical transportation.
The relative movement between the car and the counterweight is achieved by the friction between the traction rope and the traction sheave. This force is called drag force or driving force. The load of the elevator car in operation and the position of the car as well as the operating direction are all changing. In order to make the elevator in all circumstances have enough traction, the national standard GB 7588-2003 "elevator manufacturing and installation of safety norms" provides:
The traction condition must be satisfied: T1 / T2≤efα
Where T1 / T2 is the case where the car with 125% rated load is at the lowest landing and the empty car is at the highest landing, the larger static tension of the traction ropes on both sides of the traction sheave is Small static tension ratio.
C1 - with acceleration, deceleration and lift special installation conditions related to the coefficient, commonly known as the dynamic coefficient
C2 - The influence coefficient of the change of the section of traction sheave due to wear (for semicircle or kerf: C2 = 1, for V-groove: C2 = 1.2).
efα, f is the equivalent friction coefficient of the traction rope in the traction groove, and α is the wrap angle of the traction rope on the traction sheave. efα is called the drag coefficient. It limits the ratio of T1 / T2. The larger the efα, the greater the allowable value of T1 / T2 and the allowable value of T1-T2, which means the greater the traction capacity of the elevator. Therefore, the traction coefficient of an elevator represents the traction capacity of the elevator.