The relation between the metabolism and the cytotoxic effects of bisphenol A (BPA, 2,2-bis(4-hydroxyphenyl)propane) has been studied in freshly isolated rat hepatocytes and isolated hepatic mitochondria. The incubation of hepatocytes with BPA (0.25–0 mM) elicited a concentration- and time-dependent cell death, accompanied by losses of intracellular ATP and total adenine nucleotide pools. BPA at a low-toxic level (0.25 mM) in the hepatocyte suspensions was rapidly converted to its major conjugate, BPA-glucuronide, and other minor products without marked loss of cell viability, although at a toxic level (0.5 mM), more than 65% of the compound presented in an unaltered form 2 h after the incubation. Addition of salicylamide (2 mM), non-toxic to hepatocytes during the incubation period, enhanced BPA-induced cytotoxicity and reduced the loss of BPA and the formation of BPA-glucuronide. The addition of BPA to isolated hepatic. Reagents,Resin Flame Retardant,Highly Effective Deodorant,Dispersant For High Temperature Dyeing Jiangxi Hongjiu New Material Technology Co.,Ltd. , https://www.hongjiutech.com
During the loading operation, if the gear shaft has no axial limit, the axial force of the gear shaft will be unbalanced, and the center surface of the left and right rotating teeth will be offset (string axis), so that both ends of the left and right rotating teeth will enter the normal meshing. The balance of axial forces. Finally, the influence of mutual position error on contact accuracy can be offset. In the case of single-stage gear transmission, in the case of no axial limit, the mutual position error can be overcome by the series shaft, so that the left and right teeth are normally meshed, thereby offsetting the influence of mutual position error on the contact accuracy. However, when there is an axial limit, it will not be able to string, which will cause its mutual positional error to be unavoidable, resulting in a contactless trace and contact spot on the left and right teeth.
The series double arc gear reducer is mainly driven from two stages. The drive shaft and the driven shaft are axially positioned, and the intermediate shaft floats. For active drive, from the string. Since the intermediate shaft has both the active gear and the driven gear, the amount of the two trains will be mutually restricted and cannot be satisfied at the same time. The axial force of the driven stage drive is greater than the axial force of the active stage drive, and the driven stage gear takes precedence when the intermediate shaft is strung. It can be seen that the two-stage gear transmission with axial limit can not overcome the mutual position error of the left and right teeth, and the contact accuracy (contact trace and contact spot) will be related to the mutual position error of the left and right teeth. The magnitude of the axial force varies randomly.
Analysis of the influence of the basic tooth profile error on the contact accuracy The arc gear manufacturing has its particularity compared with the involute gear. Due to the complex tooth shape, it is impossible to carry out comprehensive and accurate measurement like the involute tooth shape, and its accuracy grade is only divided into five grades; the molding mechanism research is also complicated. This paper only needs to determine that the quality of the hob largely determines the accuracy of the tooth profile.
The newly produced double circular hob basic tooth shape has relevant standard control, and the error is small and negligible. However, when the hob is sharpened, especially after multiple sharpenings, its basic tooth shape will change. The circular arc gear machined by the hob with the basic tooth shape change will have a tooth shape that will change with the change of the hob. The basic tooth shape of the machined gear is caused by the error of the basic tooth shape of the hob. error. The pair of gears in which the basic tooth shape has an error meshes, which inevitably causes an error in the contact accuracy. The theory in this area has been clearly discussed in the process of the exhibition process. Measures to Control and Improve Contact Accuracy In order to control and improve contact accuracy, measures must be taken from design, process, and tooling.
Measures to overcome and reduce the mutual position error of the left and right teeth. The positional errors of the left and right rotators are basically inconsistent in the design, processing and assembly of the factory. Measures must be taken to ensure the uniformity of the three benchmarks: First, in the design process of the reducer box, the reference of the three-axis positioning dimension is unified, so that the reference of the three-axis and the herringbone gear on the shaft is unified to the herringbone ideal. The symmetry centerline; the second is to unify the design basis and process benchmark in the process of the herringbone tooth. In addition to the uniformity of the benchmark selection, it is necessary to make some necessary tooling to ensure. Improve the forming and assembly process The double circular arc gear reducer produced by our factory adopts the left and right rotating teeth herringbone shunting arrangement. The left and right rotating gears on the intermediate shaft are hot-fitted in place, so that the selection of the process method will bring about the left and right rotation. The problem of the positional error of the teeth.
Process method 1: The left and right rotating gear teeth on the intermediate shaft are separately processed into position, and then hot-fitted. After the actual measurement, the maximum time reaches 11, which inevitably brings the error of contact accuracy. Therefore, the assembly method must be changed. According to the equipment status of our factory, we changed the hot-packing to cold-press forming assembly, so that the relevant contact accuracy error can be effectively controlled and mastered.
Process method 2: The left and right rotating gears are hot-fitted in place, although the problem of reference parallelism will occur, but the tooth-shaped scribing and the machining-to-tool are carried out according to the second requirement of the “unified standardâ€, thereby eliminating the assembly process. The positional errors of the left and right teeth are mutual. Increasing the roughness of the scribe surface improves the roughness of the scribe line surface of the workpiece, which can improve the quality of the scribe line, facilitate the alignment and feed of the hobbing, reduce the hobbing error and improve the machining accuracy.
Research on Gear Contact Accuracy and Management Scheme