DEVELOPMENT OF INFINITELY STIFF HYDROSTATIC JOURNAL BEARINGS FOR HIGH SPEED SPINDLES UNISNG MINIATURIZED SELF-CONTROLLED RESTRICOTRS

近年来，由于减少了制造过程中的污染，干切削法的发展受到了极大的关注。在干切削加工中，需要一种高速主轴，它能在高速下实现大刚度、高精度和低功耗。在这项研究中，我们提出了一种新型的带有微型自控节流阀的无限刚性静压轴承，以实现上述轴承性能。在高速主轴静压轴承中，通常采用低粘度的润滑剂，以避免轴承功率消耗的增加。因此，有必要对所提出的用于低粘度润滑剂的静压轴承的轴承特性进行研究。我们得到了以下结果。(1)采用粘度小于10cst的润滑剂时，润滑剂的惯性效应对轴承性能有很大影响。(2)润滑剂的惯性降低了静刚度。(3)所提出的轴承即使在使用低粘度润滑剂的情况下也能稳定运行。其次，我们讨论了减小润滑剂的惯性效应的新方法，因为这种效应降低了静刚度。结果表明，用多孔限流器代替毛细限流器，可以大大提高结构的静刚度。这是因为多孔节流器可以避免由于润滑剂的惯性效应而在毛细管节流器入口处产生的孔口效应。研究了采用多孔材料自控节流器的静压轴承的静、动态特性。此外，将该自控节流器应用于静压滑动轴承，从理论和实验两个方面研究了该轴承的静态特性。结果表明，采用低粘度润滑剂的自控式节流静压径向轴承在实现高刚度、高精度和低功耗方面是非常有效的。

Recently, development of dry cutting method has been strongly desired because of reducing pollution in manufacture. In dry cutting, a high speed spindle is needed which can achieve large stiffness, high accuracy and low power consumption in high speeds. In this research, we propose a new type of infinitely stiff hydrostatic bearing with a miniaturized self-controlled restrictor in order to achieve the bearing performances mentioned above.In a hydrostatic bearing for high speed spindles, low viscous lubricant is usually adopted to avoid an increase of bearing power consumption. Therefore, it is necessary to investigate the bearing characteristics of the proposed hydrostatic bearing for low viscous lubricant. We obtained the following results. (1).The inertia effect of lubricant is greatly influenced on the bearing characteristics when the lubricant with viscosity of less than 10 cSt is adopted. (2).The inertia of lubricant reduces the static stiffness. (3).The proposed bearing can stably operate even when low viscous lubricant is used.Next, we discuss the new method to reduce the inertia effect of lubricant because this effect decreases the static stiffness. As a result, it was found that the static stiffness is greatly improved by using a porous restrictor instead of a capillary restrictor. This is because the porous restrictor can avoid the orifice effect, which occurs at the inlet of a capillary restrictor due to the inertia effect of lubricant. We investigated the static and dynamic characteristics of hydrostatic bearing with a self-controlled restrictor using a porous material. In addition, we applied this self-controlled restrictor to the hydrostatic journal bearing, and studied the static characteristics of the bearing, theoretically and experimentally. It was consequently found that the hydrostatic journal bearing with self-controlled restrictor using low viscous lubricant is very effective in achieving high stiffness, high accuracy and low power consumption.