Adjustment of elevator brake clearance
With the increasing number of high-rise buildings in my country, elevators are widely used as an important means of transportation. The smooth operation and precise stopping of elevators are inseparable from the reliable operation of the elevator brakes. The core component of the elevator brake is the electromagnetic brake system in the brake. The elevator brake system is the most important safety and security component in the elevator. It is installed next to the motor, at the brake wheel where the motor shaft is connected to the worm shaft. It is the brake system that keeps the elevator car stationary when the elevator stops. However, the brake gap is the key to ensuring the brake. Starting from the working principle and structural action principle of the brake system, this article explains the methods, standards and inspections for adjusting the elevator brake gap, and provides some reference for many elevator maintenance personnel.
- 1.Working principle of elevator brake brake
The elevator brake is mainly composed of two parts: brake electromagnet and brake shoe brake.
The brake electromagnet consists of three parts: iron core, armature and coil. The brake shoe brake includes a brake wheel, brake shoe and spring, etc. The brake wheel and the motor are installed on the same shaft.
The automatic system of the elevator is generally an electromechanical brake (friction type). The main components of this system are electromagnets, brake arms, springs, brake wheels, brake shoes, etc.
When the elevator is in a stagnant state, the elevator traction motor disconnects the switch or contactor, the motor loses power, and the electromagnetic brake coil also loses power. The armature is separated from the iron core under the action of the spring tension. No current passes, and the brake magnet has no attraction. However, under the action of the brake spring, the brake shoe will tightly control the brake wheel, and the motor will be braked and stop the motor and brake coil, thereby keeping the elevator in a static state; when the elevator starts to run, the motor is in a powered state, and the electromagnetic force generated will push the brake shoe away. The elevator traction motor is powered on, and the electromagnetic brake coil is also powered, the armature is attracted, and the spring tension is overcome to separate the brake shoe from the brake wheel, and the elevator operates well. When the elevator rises or falls to a specified floor, the current of the motor disappears quickly, and the corresponding electromagnetic force disappears accordingly, thereby restraining the brake shoe and the brake wheel tightly together through the brake spring, so that the elevator falls to the corresponding floor. When the elevator is operating normally, the current passes through the brake coil, and the brake magnet core is magnetic, causing the brake spring to lose pressure, the brake pad and the brake spring to separate, and the brake wheel and the brake pad to separate, thereby ensuring the normal operation and operation of the elevator.
1.3 Working characteristics of electromagnetic brake The elevator brake mainly presents two states: release and brake. When the elevator is operating normally, the brake is released to keep the elevator running; when the elevator has a power outage and stops operating, the brake is engaged to maintain the safety and stability of the elevator. Its advantages are strong braking force, safety and reliability, and no accidents due to sudden power failure. The disadvantages are that the brake is large in size, the brake is severely worn, and vibration will be generated during rapid braking.
2 .Adjustment of the motor brake gap When the brake is operating normally and the brake core is not severely worn, the gap between the brake core and the magnet box is generally 20 mm. At the same time, the two brake levers evenly support the weight of the brake core. During the daily inspection process, the inspector manually opens the brake and uses a feeler gauge to check the brake lining gap to ensure that the 0.15mm thick feeler gauge can pass very smoothly and the 0.25mm thick feeler gauge cannot pass. Run the elevator in manual mode or detection speed and verify that the brake shoe is evenly attracted and has a gap of 0.125 to 0.250 mm with the brake disc. Use the brake opening adjustment bolt to set the brake shoe to open. The gap between each brake shoe and the brake disc must be the same.
2.2 Methods for adjusting the brake gap 2.2.1 Preparation for gap adjustment Since the elevator is a special equipment, it is necessary to strictly follow the standard in the process of adjusting the brake gap. First, stop the elevator, confirm that the mechanical and electrical shutdown, lock the main power switch, and hang the "under maintenance" and "strictly prohibited from starting" warning signs.
Before adjustment, carefully check the remaining thickness of the brake lining (that is, the minimum thickness of the brake lining) and check the protective disc. If the edge of the protective disc has touched the positioning pin mark, the brake disc must be replaced.
Adjust the air gap of the brake: tighten the three (four) bolts until the air gap is zero, then loosen the bolts in the opposite direction at an angle of 120°, and use a feeler gauge to check the brake gap (at least check three points), which should be uniform and meet the specified value; if not, please readjust; however, due to different models of brakes, the angle of reverse loosening and the gap of the brake are also different. During the adjustment process, it should be adjusted according to the standard air gap provided by the elevator manufacturer. During the adjustment, remove the brake switch mounting bracket and adjust the fixed position of the brake switch to ensure that there is still a stroke of 0.5 to 1.0 mm after the switch is pressed when the brake is manually opened. There must be a gap of about 2 to 2.5 mm between the brake discs. In particular, it is necessary to check that the iron cores on both sides of the brake move synchronously when the brake is powered on and closed in the hot state. However, after the adjustment is completed, the maximum stroke of the brake (the moving distance of the brake push rod when powered on) cannot exceed 3.5 mm. The basis for adjusting the brake gap is that the wear of the brake shoe does not exceed the limit. If the gap between the two moving iron cores cannot be adjusted too large due to structural factors, the method of adjusting while wearing can be adopted. If the brake shoe wear does not exceed 1mm, the gap between the two moving cores will be reduced by 2.5mm. At this time, the gap between the two moving cores can be restored to the original size by adjusting the adjustment screws on both sides (one side is screwed out 1.25mm). When the brake shoe is worn, the gap between the brake shoe and the brake disc increases (that is, the two moving cores move outward respectively). During the adjustment, if the brake shoe and the brake disc are not constrained from moving outward, no matter how much wear there is, the brake arm will not be pushed open and the brake will not fail. If the brake shoe and the brake disc are limited in the amount of outward movement, the brake arm will be pushed open.
2.3 Detection after brake gap adjustment Whether the brake gap adjustment is successful or not still needs to be tested. The most commonly used detection method is the dynamic brake sliding test. After all the initial adjustments are completed, a brake sliding test must be performed, such as a full-load and full-speed safety clamp test, a counterweight balance coefficient, etc.
During the test, first fully load the car, run the elevator from the top of the shaft downward, and after reaching the contract speed, use the emergency stop switch to make the car stop urgently and make the brake work. At this time, the two brake arms work at the same time. Record the sliding distance of the brake to make the sliding distance (tested by PMT) meet the following requirements. Generally, when the elevator running speed is 1.0m/s, the full-load sliding distance is between 400 and 450mm; when the running speed is 1.5m/s, the full-load sliding distance is between 1100 and 1200mm; when the running speed is 1.75m/s, the full-load sliding distance is between 1600 and 1700mm. If the test exceeds this range, it can be considered that the brake adjustment is unsuccessful and needs to be readjusted.
The adjustment of the elevator brake clearance is directly related to safe operation. Every person engaged in elevator installation, maintenance, testing and inspection should pay enough attention to the wear of the elevator brake shoe and the clearance adjustment. At the same time, daily inspections should be carried out. If the brake shoe is severely worn, it should be replaced in time. Clearance adjustment alone cannot guarantee the safe braking of the elevator.
