The premise of driving is to go straight, and if you deviate, you will drive in a corner. Generally, when a car is driving on an open straight road 100m, the maximum deviation should be controlled within 0.5m to 1m to be normal. If this index is exceeded, it is necessary to go to a professional maintenance station for a comprehensive inspection, because deviation can easily lead to many dangers, and the consequences can never be ignored.
Reason: As long as the car deviates, most drivers will think it is time to do four-wheel alignment. In fact, there are several different forms of deviation, including acceleration deviation, driving deviation and braking deviation. We often say that running deviation usually refers to driving deviation. There are many reasons for running deviation, such as tire running deviation caused by insufficient air pressure, different degrees of tread wear, suspension system design problems or suspension damage, deformation and displacement. In short, there are many reasons for deviation, but four-wheel alignment is the same as treating a headache as a cold, and all deviation phenomena can not be solved by just doing four-wheel alignment or moving a balance weight.
Generally speaking, the problems mainly focus on tires and suspension.
Tire: First check the rated tire pressure given by the manufacturer. Most family cars are set between 2.0bar and 2.5bar, and the air pressure values of the front and rear wheels are different. If the tire pressure is not equal, it will definitely lead to deviation; In order to make better use of tires, the position of tires should be changed every 20 thousand kilometers, because the wear degree of driving wheels is always greater than that of other wheels, and different friction forces will directly lead to deviation.
The correct replacement method is to cross the diagonal and switch back and forth; If new tires need to be replaced, tires of the same brand and pattern should be replaced, and it is best to replace four tires at the same time; Another common reason may be that the four-wheel alignment is not accurate. The camber of the front wheel and the camber of the kingpin are incorrect, or the toe angle is not equal to the left and right, which will also cause deviation. The way to avoid it is to drive less on the road and slow down when crossing the pit. As long as it is driving normally, you don't need to do four-wheel alignment for a year or two. But if something happens, you must go to a professional maintenance station for testing. Although some small detection points are cheap, they are not allowed to be adjusted and will recur soon.
Suspension: Under normal circumstances, the probability of deviation of new cars due to suspension system failure is very low, because the vehicles before leaving the factory have been strictly tested and adjusted by the manufacturers. However, it does not rule out problems with the original design. For example, the motion interference between the guide rod of the suspension and the pull rod of the steering system will affect the running deviation of the vehicle. The former is caused by manufacturing and adjustment errors, while the latter is caused by original factory design, and the latter mostly leads to right deviation. There are more reasons for the deviation of old cars. In addition to the above, the frame deformation, front axle displacement, negative toe-in and hanging arm, the difference between the two front leaf spring shrapnel, and the looseness of the ball pin of the horizontal tie rod will all cause deviation, so the old car should be analyzed in detail. If the running deviation is aggravated during braking, it is necessary to check the braking system, because the braking force of the left and right wheels is not equal, which will also lead to running deviation. First of all, it is necessary to visually check whether the front wheel brake disc is oily, wet and hardened; Check whether each brake cylinder leaks oil, whether the brake caliper fixing plate is loose, whether the friction plate returns smoothly, and whether the clearance between the friction plate and the brake disc (drum) is consistent under the condition that the brake disc and the brake disc are normal.
Secondly, the quality of the steering system will also affect the straight-line driving of the car. Loose joints caused by excessive wear clearance or wear of bearings, kingpins and bushings will cause the car to shake its head while driving, and it is impossible to maintain the normal motion track. If the steering knuckle arm and steering knuckle are bent and deformed, it will generally cause the car to travel in one direction. The most serious thing is that the ball head of the tie rod will loosen after serious wear, leading to steering failure and the car completely out of control.
Danger: if the deviation is light, the tire will be chewed and scrapped, and if it is serious, it will lead to dangerous situations such as flat tire and out-of-control vehicle. According to the survey, for ordinary family cars, the probability of 150km/h puncture is less than 20%; Deviation is not the kind of fault that can make the car break down immediately, but there are still many hidden dangers when the car is driving for a long time. If there is deviation, it should be checked and repaired.
Belt deviation
Belt deviation is the most common fault in the operation of belt conveyor, which is extremely harmful. Judging from the actual operation, the influence of belt deviation on the operation and production of belt conveyor mainly includes the following aspects:
1, system failure caused by deviation affects production efficiency. When the belt deviates to a certain extent, the belt will trigger the emergency stop device to prevent the operating system from stopping due to the deviation and affect the production process.
2, causing abnormal damage to the main parts of the equipment. First of all, the belt deviation increases the axial force borne by the roller and idler, which causes the roller deviation and the idler bearing damage; Secondly, the deviation of the belt causes the material to spill on the return belt, which causes abnormal wear of the belt and the drum and shortens the service life of the drum and the belt; In addition, the abnormal friction between the running belt and the bracket leads to the edge wear of the belt, which affects its service life.
3, easy to form a security risk. Due to the seriousness of the belt, the material of the belt turns over, which leads to the unilateral stress of the belt exceeding the longitudinal tension of the belt, thus causing the safety hazards such as transverse tearing of the belt.
4. It pollutes the environment and affects the quality of conveyed materials. Materials often cause coal dust in the process of scattering and cleaning, which pollutes the environment; At the same time, the overflow of materials also affects the quality of transported goods.
It can be seen that in the actual operation process, the belt deviation not only causes great damage to the belt conveyor itself, but also has potential safety hazards, affects production efficiency, transports goods quality, pollutes the environment and other problems.
Reasons for belt conveyor deviation: There are two direct reasons for belt conveyor deviation: First, the driving force on both sides of the conveyor belt is unbalanced; Second, the idler or roller exerts a transverse force on the conveyor belt.
1. There are many factors that lead to the unbalanced force on both sides of the conveyor belt: (1) Inconsistent force on both sides of the conveyor belt is caused by the installation error of the tensioner of the belt machine, which leads to the deviation of the conveyor belt. Improper installation or adjustment of the tensioner is the most basic reason for the inconsistent force on both sides of the conveyor belt. (2) Deviation caused by uneven joint of conveyor belt. Dislocation of belt vulcanization joint or belt itself is not straight, which leads to uneven tension on both sides of the belt, and the belt deviates to the side with high tension, especially at the belt joint or the belt is not straight. (3) Deviation caused by belt slack. After running for a period of time, the conveyor belt will be permanently deformed or aged due to stretching, which will reduce the tension of the conveyor belt, relax the conveyor belt, cause uneven stress distribution inside the conveyor belt, and also cause the conveyor belt to deviate to varying degrees. (4) Deviation caused by uneven distribution of materials. If the belt does not run off during idling, it will run off during heavy load, indicating that the material is unevenly distributed on both sides of the belt. This kind of deviation is the most common in the practical use of belt conveyor. The uneven distribution of materials is mainly caused by the incorrect falling direction and position of materials. If the mineral material is biased to the left, the belt will be biased to the right. Or conversely, the friction between idlers on both sides of the belt from Dallas to the auditorium (5) is unbalanced, and the pressure of rubber plates on both sides of the guide groove is uneven, resulting in inconsistent driving force and resistance on both sides of the belt, resulting in belt deviation. (6) Deviation caused by the adhesion between the roller and the idler. After the belt conveyor runs for a period of time, due to the certain viscosity of the materials, some of them will stick to the rollers and idlers, which will enlarge the local diameter of the rollers or idlers, resulting in uneven tension on both sides of the belt and belt deviation. The deviation caused by this factor generally occurs in short-distance belt transportation.
2. The conveyor belt deviates due to the lateral force generated by the roller or roller: (1) The roller and roller are not installed correctly, and the belt will be subjected to lateral force during operation. The verticality error between the installation position of the bearing roller and the center line of the conveyor is large, or the verticality error between the roller axis and the center line of the belt conveyor is too large, resulting in the belt deviating to one side in the bearing section. The deviation is the most serious at the installation position of reversing roller and idler, and it is lighter when the bearing section or return section advances. The deviation caused by the inclination of the driving drum will make the deviation more and more serious. (2) Deviation caused by frame deformation. The skew of the frame includes the skew of the center line of the frame and the inclination of both sides of the frame, both of which will cause the belt to be subjected to lateral force, thus causing serious deviation and being difficult to adjust.
In addition, the mechanical vibration of the belt conveyor during operation is inevitable. The faster the belt runs, the greater the vibration and the greater the belt deviation. In the belt conveyor, the vibration caused by the radial jump of the idler has the greatest influence on the deviation of the conveyor belt.
Common treatment methods of belt conveyor deviation
For the deviation phenomenon of belt conveyor, corresponding countermeasures need to be taken to adjust. The key is to eliminate the unbalanced driving force on both sides of the conveyor belt and the lateral force on the belt. For the deviation caused by installation error, we must first eliminate the installation error; Reconnect the reconnection of the belt joint; Plastic the deformed frame, and if it is serious, it must be reinstalled. For deviation, the specific adjustment method is as follows:
1, adjust the idler gear set.
When the conveyor belt of the belt conveyor deviates from the center of the whole belt conveyor, adjust the position of the idler group to adjust the deviation. In order to facilitate adjustment, the mounting holes on both sides of the roller bracket are machined into long holes. The specific method is shown in Figure 3. If the conveyor belt is biased to the A side, the idler pulley set on the A side moves forward in the direction of the conveyor belt, or the idler pulley set on the B side moves backward. This method can eliminate the deviation of belt conveyor caused by frame skew, uneven distribution of mineral materials and vibration.
2. Adjust the positions of the driving roller and the reversing roller.
The adjustment of idler is an important part of belt conveyor deviation adjustment. The axes of all drum installation positions in the belt conveyor must be perpendicular to the center line of the belt conveyor in the length direction. If the deflection is too large, deviation will inevitably occur. For the drum at the head of the belt conveyor, if the conveyor belt is biased to the A side of the drum, the A side bearing seat should move forward or the B side bearing seat should move backward to realize the relaxation of the A side conveyor belt or the tension of the B side. The adjustment method of the tail drum is just the opposite to that of the head drum. Due to the limited adjustment distance of the driving drum, in general, after the axis of the driving drum is adjusted to be perpendicular to the length direction of the belt conveyor, the position of the bearing seat of the tail reversing drum is adjusted by using the screw tensioner or the heavy hammer tensioner. This method can effectively eliminate the belt deviation caused by belt slack and frame skew.
3. Install the self-aligning idler assembly.
In the middle of the whole belt conveyor, self-aligning idler groups are often installed to prevent the conveyor belt from running off. The principle of anti-deviation is to adjust the deviation of the belt by blocking or generating lateral thrust through the rotation of the idler in the horizontal plane to center the belt automatically. Generally, when the total length of the belt conveyor is short or the belt conveyor runs in both directions, it is more reasonable to adopt this method, because the shorter belt conveyor is more prone to deviation and is not easy to adjust. It is best not to use this method for long belt conveyor, because the use of self-aligning idler groups will have a certain impact on the service life of the belt.
4. Adjustment of tension
According to the form of tension, it can be divided into: heavy hammer tension (including tail heavy hammer tension and middle heavy hammer tension) and mechanical tension (generally screw tension). The two reversing rollers at the upper part of the tension part of the heavy hammer should be perpendicular to the vertical line of gravity in addition to the length direction of the belt, that is, to ensure that the axis line is horizontal. When screw tensioning is used, the two bearing seats of the tensioning roller should translate at the same time to ensure that the roller shaft is perpendicular to the longitudinal direction of the belt. The specific adjustment method of belt deviation is similar to the adjustment at the drum.
5. Adjustment of the influence of feeding position at transfer point on belt deviation
In the conveying system of belt conveyor, the blanking height of transfer point has a great influence on the deviation of belt, especially when the projection of two belt conveyors on the horizontal plane is vertical. Generally, the relative height of the upper and lower belt conveyors at the transfer point should be considered. The lower the relative height, the greater the horizontal velocity component of the material, and the greater the lateral impact on the lower belt, making it difficult for the material to center. The material on the cross section of the belt deflects, which eventually leads to the deviation of the conveyor belt. If the material shifts to the right, the belt shifts to the left, and vice versa. In the installation process, the relative height of two belt conveyors should be increased as much as possible if conditions permit. At the same time, the shape and size of the upper and lower funnels, guide grooves and other parts should be carefully designed. Generally, the width of the guide groove is about 2/3 of the width of the belt. In addition, in order to reduce or avoid the deviation of the belt, a material retaining plate can be added to stop the material and change the falling direction and position of the material.