Main drive of rapier loom-electromagnetic clutch and brake
The electromagnetic clutch is a transmission device that uses electromagnetic attraction to pressurize one or several pairs of friction surfaces to generate friction torque to transmit power. There are single-piece and multi-piece types, dry type and wet type. The dry type friction disc is not immersed in lubricating oil and is cooled by air convection, while the wet type is immersed in oil, and the oil plays a cooling and lubricating role. Dry single-chip electromagnetic clutches are commonly used in loom transmission. It has only one friction surface, simple structure, good heat dissipation effect, and no viscosity caused by lubricating oil between the friction surfaces, so it responds quickly, moves sensitively, has no idling torque, and can withstand The high-frequency clutch action is suitable for occasions requiring quick response and frequent actions. These characteristics are in line with the needs of loom transmission. But it is easier to wear than a wet clutch, which is the disadvantage of this form. Figure 1-38 is an example of the structure of a dry single-plate electromagnetic clutch, which is an electromagnetic clutch with static coil, excitation, and automatic wear adjustment. The yoke 4 embedded with the coil 5 is mounted on the rotor 1 through the ball bearing 2, and then fixed on the stationary part of the machine through the bracket. The friction plate 6 is embedded in the end face of the rotor, and the armature 7 is installed on the spline hub 10 opposite the rotor, and can slide axially along the spline hub. The spline hub is also equipped with a flange 9, which can be directly connected to the transmission gear or pulley.
After the coil is energized, the yoke 4 is excited, forming a magnetic circuit 3 between the yoke 4, the rotor 1, and the armature 7, thereby attracting the armature and making the armature and the rotor close to each other. At this time, the two rotating parts are connected by friction, and the torque can be transmitted from the active side to the passive side. When the current is cut off, the armature and the friction plate are separated by the reaction force of the spring leaf 11. Because it is equipped with an automatic gap adjustment device, the gap between the armature and the friction plate can always be kept constant. 8 is the gap adjustment device and 12 is the mounting plate. The working principle of dry single-disc brake is the same as that of clutch. If the rotor in the clutch is fixed on the yoke and becomes a stator, it becomes a brake. From the overall structure point of view, the clutch and brake can operate separately and function independently, or they can be together to have the functions of both. The single-acting type with separate actions, as shown in Figure 1-39, has a relatively simple structure, simple installation, easy adjustment and maintenance, and a low price, but the installation location is large and the combination is not tight. The working principle of this form of electromagnetic separator is as follows: the clutch mounting plate 2 is fixed on the belt pulley 1, the disk 2 can drive the clutch armature 3 to rotate through the pin, and a leaf spring is sandwiched between them; the rotor 4 uses an adapter sleeve 5 is fixed on the main shaft, and the clutch coil and yoke 6 are fixed on the bracket and do not rotate. When the clutch coil 6 is energized, the magnetic force passes through the rotor 4 and tightly attracts the armature 3 to the rotor, thereby driving the main shaft to rotate; When the braking signal is obtained, the clutch coil 6 is powered off, the magnetic attraction disappears, and the armature 3 is separated from the rotor and resets under the action of the leaf spring. At the same time, the brake coil 7 is energized, attracting the brake armature 9 to fit against the stator. 8, the spindle is braked through the coupling disc 11. The stator 8 is fixed to the frame, and friction materials are embedded on the friction surfaces of the stator and the rotor. The gap between the friction surfaces is marked in the figure. The gap value is 0.3~0.5mm. After long-term operation and wear, when the value exceeds 1mm, or when oil stains adhere to it, it should be adjusted and cleaned. Oil stains can be used with three Wipe off with a rag soaked in vinyl chloride and other organic solvents.
The clutch and brake together are double-acting, as shown in Figure 1-40. This form has a compact structure, a closed shape, and a small volume. It is mostly installed on high-speed shafts and is widely adopted by high-speed shuttleless looms. Structurally, the clutch plate 3 and the brake plate 6 are connected to the middle seat 4 with pins, and the middle seat is fixed with the output shaft with a tapered tensioning ring; relative to the middle seat, the two friction plates can only move axially. Micro movement, no circumferential movement, there is a spring separating the middle seat and the clutch friction plate. In this way, torque can be transmitted without hindering the attraction of the electromagnet. In the example in the picture, the gap between the friction surfaces is controlled very small, only 0.4±0.1mm, with a compact structure and flexible movement. The engagement torque Mm of the clutch is related to the usage state. When starting, the clutch is in a slipping state, and the binding force at this time is the dynamic friction torque Md, which should be larger than the loom load resistance torque at startup, and the difference is the acceleration torque. When the start-up is completed and the loom enters normal speed for steady-state operation, the clutch will be fully engaged without slipping. Its combined torque is the static friction torque Mj, which should be greater than the maximum torque of the loom during normal operation. Load resistance moment. Usually the static friction torque Mj is given in the product specifications of the clutch factory, and the dynamic friction torque is introduced in detail in the technical information. The commonly used rated static moment values of shuttleless looms are as follows: high-end rapier looms are 400~500N m, air-jet, water-jet, and medium-speed rapier looms are 350~400N m, and popular rapier looms are 250N m; consumption The power used is 40~70W, and the power supply is 24V DC. DC electromagnetic coils are inductive circuits. When the current changes sharply, a back electromotive force will occur in the circuit due to self-induction, preventing the current from changing immediately. This is the transition phenomenon of the DC magnetic circuit. For the electromagnetic clutch, there will be a transition time after the voltage is applied until the armature is released, which is unfavorable for the fast response required by the loom. In order to shorten the above process and improve sensitivity, some special circuits can be used at the beginning of starting or braking. For example, during starting, fast excitation circuits, over-voltage excitation circuits or capacitor fast excitation circuits can be used; over-voltage methods are commonly used among them. A kind of, both in the initial stage of starting, the clutch coilAdding a high voltage 2 to 3 times the rated voltage for a short time shortens the attraction time, causes the combined torque to rise rapidly, and speeds up the starting process; when braking, the clutch coil should be powered off in time, in order to suppress the clutch coil disconnection at this moment. The generated overvoltage can be generated by various methods such as discharge control loops, parallel resistors, and parallel capacitors. The capacitor fast excitation circuit is charged when the loom is running, and discharges the brake coil with high voltage during braking to accelerate the braking process. High-speed shuttleless looms also use super starting torque motors to further speed up the starting process to adapt to high speeds. The starting torque of this motor can be 8 to 12 times the normal value. Due to the adoption of an electromagnetic clutch to control the starting and braking of the loom, as well as the application of other electromechanical combination devices, the operation of the loom can be operated with buttons and is easy to operate. Commonly used button types include: start, shut down, emergency shut down, inching, rear center position, idle, slow reverse, etc. The above are buttons for controlling the main transmission. In addition, there are some buttons for controlling auxiliary mechanisms, such as search engines. Weft reversal and forward rotation, electronic warp let-off forward and reverse rotation, electronic take-up forward and reverse rotation, etc. Depending on the transmission and design of the loom, the button types of various models are slightly different.
AAAEHRYJUTUTHYER
Extendedreading:https://www.tpu-ptfe.com/post/7738.html
Extendedreading:
Extendedreading:
Extendedreading:
Extendedreading:
Extendedreading:
Extendedreading:
Extendedreading:
Extendedreading:
Extendedread
