Abstract
Stepped hydrostatic thrust bearings used in metal-cutting machines are characterized by high load capacity and damping, which ensure the stable operation of structures. However, in comparison with throttle thrust bearings, they have a high compliance. It is preferable that, in addition to the main bearing function, a modern hydrostatic bearing has the ability to provide low (including negative) compliance for the implementation of an adaptive function in order to actively compensate for the deformation of the machine resilient system, thereby increasing the accuracy of metalworking. This paper considers the design of a stepped hydrostatic thrust bearing, which, in order to reduce the compliance to negative values, features a technical improvement consisting of the use of an active displacement compensator on an elastic suspension. In this paper, the results of mathematical modeling and theoretical research of stationary and non-stationary modes of operation of the adaptive thrust bearing are presented. The possibility of a significant reduction in the static compliance of the structure, including the negative compliance values, is shown. It was found that negative compliance is provided in a wide range of loads, which can be up to 80% of the range of permissible bearing loads. The study of the dynamic characteristics showed that with a targeted selection of parameters that ensure optimal performance, the adaptive thrust bearing is able to operate stably in the entire range of permissible loads. It has been established that an adaptive stepped hydrostatic thrust bearing with a displacement compensator has a high stability margin, sufficient to ensure its operability when implementing the adaptive function.
Highlights
Stepped hydrostatic bearings are used in metal-cutting machines and, when compared with similar throttle bearings, are characterized by their increased load capacity [1,2,3]
A formal analysis of the static characteristics of an active stepped thrust bearing shows that the use of a displacement compensator makes it possible to realize an adaptive function by providing a negative compliance mode
This paper considers the design and carries out a theoretical study of the static and dynamic characteristics of an adaptive stepped hydrostatic thrust bearing with an active displacement compensator on an elastic suspension
Summary
Stepped hydrostatic bearings are used in metal-cutting machines and, when compared with similar throttle bearings, are characterized by their increased load capacity [1,2,3]. The use of membrane or elastic regulators make it possible to reduce the static compliance to negative values (in the latter case, the increments of the load and the gap in the load-bearing fluid layer have the same signs), which ensures the adaptive function of such bearings Such designs are too energy intensive as a result of the need to significantly increase the lubricant flow rate using the input regulators to reduce compliance. The preferred means of reducing the compliance of the bearings is the use of compensators for the movement of the movable element (shaft) [29,30,31] Such designs allow for a decrease in compliance to negative values, which allows them to be used as supporting systems, and as automatic strain relief compensators of the technological system of machine tools, in order to reduce the time and increase the accuracy of metalworking, thereby realizing the mentioned adaptive function. This paper considers a mathematical model of the unsteady state of the thrust bearing and calculates and studies its static and dynamic characteristics
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