Design reasons and countermeasures 1. Gear Reducer Internal Gear Accuracy Grade When designing a reducer, the designer often considers economic factors to determine the gear accuracy level as economically as possible. Ignoring the accuracy level is a sign of noise and backlash of the gear. The American Gear Manufacturing Association used a lot of gear studies to determine that high-precision grade gears produced much less noise than low-precision grade gears. Therefore, if the conditions permit, the accuracy level of the gear should be increased as much as possible, which can reduce the transmission error and reduce the noise. 2. The internal gear width of the reducer increases the gear width when the reducer transmission space permits, which can reduce the unit load under constant torque. Reduce tooth deflection, reduce noise excitation and reduce transmission noise. Research by H. Opatz in Germany shows that when the torque is constant, the gradient of the small tooth width is higher than that of the large tooth width noise curve. At the same time, increasing the width of the gear can also increase the bearing capacity of the gear and increase the bearing moment of the reducer. 3. The gear pitch and pressure angle of the internal gear of the reducer can ensure that there are more teeth at the same time, the overlapping of the gears increases, the deflection of the single gear is reduced, the transmission noise is reduced, and the transmission precision is improved. The smaller pressure angle has a larger gear contact angle and lateral overlap ratio, so the running noise is smaller and the precision is higher. 4. The internal gear shift coefficient of the reducer is selected correctly and reasonably to select the displacement coefficient, not only can make the center distance, avoid gear root cutting, ensure the satisfaction of concentric conditions, improve the gear transmission performance and improve its carrying capacity and increase the service life of gears. Backlash, temperature rise and noise can also be effectively controlled. In the closed gear drive, the main failure mode of gears with hard tooth surface (hardness 350HBS) is the root-base fatigue fracture. This kind of gear transmission design is generally performed according to the bending fatigue strength when selecting the displacement coefficient. It should be ensured that the meshing teeth have the same bending strength. The main failure mode of gears with soft tooth surfaces (hardness: 350HBS) is fatigue pitting. This type of gear transmission design is generally carried out according to the contact fatigue strength. When selecting the displacement factor, it should be ensured to be as large as possible. Contact fatigue strength and fatigue life. Reasonable choices for the restriction coefficient are: 5. The internal gear tooth shape trimming (trimming and root trimming) and top chamfering of the gear reduce the tooth profile of the tooth top to be slightly convex than the correct involute curve. When the gear tooth surface is deformed by an external force, interference with the meshed gear can be avoided, noise can be reduced, and gear life can be extended. Care must be taken not to trim excessive amounts. Over-trimming is equivalent to an increase in tooth profile error and will have an adverse effect on meshing. 6. Analysis of sound radiation characteristics of gears When selecting gears with different structural forms, an acoustic radiation model is established for a specific structure, dynamic analysis is performed, and the noise of the gear transmission system is pre-evaluated. In order to meet the user's different requirements (use of the site, whether there is no operation, whether in urban areas, whether there are specific requirements for aboveground and underground structures, whether there is noise protection, or no other specific requirements) to meet. 7. The speed of the power source of the speed reducer The experiment on the speed reducer under different speed conditions shows that the noise will increase as the input speed of the speed reducer increases. 8. Deceleration case body structure Experimental studies have shown that the use of a cylindrical box is good for shock absorption. Under the same conditions, the cylindrical box is 5 dB lower than the noise level of other types of box. The resonance test is performed on the deceleration case body to find out the resonance position and add appropriate ribs (plates), which can improve the rigidity of the case, reduce the vibration of the case, and achieve noise reduction. In the multi-stage transmission, the change of the instantaneous transmission ratio is required to be as small as possible to ensure smooth transmission, low impact and vibration, and low noise. Manufacturing reasons and countermeasures 1. The internal gear error of the reducer affects the tooth error, base pitch deviation, tooth pitch error, and radial runout error of the gear during the gear manufacturing process. This is the main error in the planetary reducer drive noise. It is also a problem to control the transmission efficiency of planetary reducer. The simple description of the tooth error and the tooth error is now provided. 2. Assembling concentricity and balancing the misalignment of the assembly will result in an unbalanced shafting operation, and noise will be aggravated due to loosening of the loose half of the teeth. Imbalance in high-precision gear assembly will seriously affect the accuracy of the drive system. 3. Gear internal gear hardness With the development of gear hardened tooth surface technology, its large load carrying capacity, small size, light weight, and high transmission accuracy make its application areas increasingly widespread. However, in order to obtain hardened carburized hardened carburized gears, the gears are deformed, resulting in increased gear transmission noise and shortened life. In order to reduce noise, the tooth surface needs to be finished. In addition to the traditional tooth grinding method, a hardened tooth scraping method has been developed to reduce the gear bite and impact by correcting the tooth tip and tooth root, or reducing the teeth of both the main and passive wheels. , thereby reducing gear transmission noise. 4. The accuracy of the reducer system index before assembly and the matching methods of the parts (completely interchangeable, grouped, single-selected, etc.) will affect the accuracy level of the system after assembly. The noise level is also within the range of influence. Therefore, the calibration (or calibration) of the system's indicators after assembly is critical to control system noise. Installation reasons and countermeasures 1. Vibration reduction and blocking measures When installing the reducer, it is necessary to avoid resonance between the airframe and the base support and the connecting element to generate noise. One or more gears often occur inside the speed reducer within a certain speed range. In addition to the design reason, the gearbox does not return to the resonance position during installation. And there is a direct relationship between taking corresponding vibration reduction or blocking measures. Some reducers that require low transmission noise and vibration should use high-toughness, high-damping basic materials to reduce noise and vibration. 2. Partial geometric accuracy adjustment Because the geometric accuracy during installation does not meet the requirements of the standard, resonance of the reducer components occurs and noise is generated. This should improve the installation process, increase the tooling, and ensure that the overall quality of the assembly personnel is direct. relationship. 3. Loose parts are loosened during installation due to the looseness of individual parts (such as bearing pre-tightening mechanism, shafting positioning mechanism, etc.), which results in inaccurate positioning of the system, meshing in abnormal positions, and movement of the shafting system to generate vibration and noise. This series needs to start from the design structure, try to ensure the stability of the connection of various agencies, using a variety of connection methods. 4. Damage to the transmission components During installation, the transmission components are damaged due to improper operation, resulting in inaccurate movement of the system or instability of movement; high-speed moving parts cause oil film vibration due to damage; artificially created moving parts are unbalanced; all generate vibration and noise. These reasons must be paid attention to and avoided during installation. Damaged parts that cannot be repaired must be replaced to ensure a stable noise level for the system. Use maintenance reasons and countermeasures Although the correct use and maintenance of the reducer can not reduce the noise level of the system and ensure the transmission accuracy, it can prevent the degradation of its indicators and increase the service life. 1. The internal cleaning of the internal clean reducer is the basic condition for its normal operation. The entry of any contaminants will affect and damage the drive system, resulting in noise. 2. The working temperature guarantees the normal working temperature of the reducer, avoids deformation of the parts caused by excessive temperature rise, ensures the normal meshing of the gears, and thus prevents noise from increasing. 3. Prompt lubrication and proper use of oil Improper lubrication and incorrect use of grease will inevitably cause damage to the reducer. At high rotational speeds, the gear tooth surface friction generates a large amount of thermal energy. Improper lubrication will cause tooth damage, affect accuracy, and increase noise. The design requires a proper clearance for the gear pair (meshing the gap between the non-working surfaces of the gear teeth to compensate for thermal deformation and storage of grease). The correct use and selection of lubricating grease can ensure the safe and effective operation of the system, delay the deterioration trend and stabilize the noise level. 4. Correct use of the reducer The correct use of the reducer can minimize damage to parts and ensure a stable noise level. The noise of the reducer will increase with the increase of the load, so it should be used within the normal load range. 5. Regularly maintain and maintain regular maintenance (change oil, replace worn parts, loose fasteners, clear internal debris, adjust gaps of parts to standard values, check geometrical accuracy, etc.) The speed reducer resists noise level deterioration and maintains a stable use. in conclusion The transmission noise control of the reducer is a system engineering. It involves the design of the transmission system (gears, boxes, couplings, bearings, etc.), manufacture, installation, use, maintenance, and updating. It is not only for the designer, but also for the manufacturer. Many requirements have also been put forward for the installation and use of maintenance. 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1 Ensure that the cut gear does not cut;
2 to ensure the smoothness of the gear transmission, the degree of coincidence must be greater than 1, the general requirement is greater than 1.2;
3 to ensure a certain thickness of the tooth top;
4 When a pair of gears are meshed and driven, if the involute of one tooth crest is in contact with the transition curve of the other root, the common line of the two tooth profiles at the contact point cannot pass through because the transition curve is not involute. Nodes, which cause changes in the gear ratio, may also cause the two wheels to become stuck. This "transition curve interference" must be avoided when selecting the displacement factor.
Gears with small tooth profile error and small tooth surface roughness have a 10 dB lower noise than ordinary gears under the same test conditions. For gears with small pitch error, the noise level is 6~12dB smaller than that of a common gear under the same test conditions. However, if there is a pitch error, the impact of the load on the gear noise will be reduced.
Tooth error will cause transmission power not to be transmitted through the full width of the tooth, the end face of the contact area turning tooth or that end face, due to the local force increased bending of the tooth, resulting in increased noise level. However, at high loads, tooth deformation can partially compensate for toothing errors.