Various “contactless” bearing mechanisms including hydrodynamic and magnetic bearings are provided for a rotary pump as alternatives to mechanical contact bearings. In one embodiment, a pump apparatus includes a pump housing defining a pumping chamber. The housing has a spindle extending into the pumping chamber. A spindle magnet assembly includes first and second magnets disposed within the spindle. The first and second magnets are arranged proximate each other with their respective magnetic vectors opposing each other. The lack of mechanical contact bearings enables longer life pump operation and less damage to working fluids such as blood.

Rotary blood pump

Surface texturing is a surface modification approach, resulting in an improvement in tribological performance such as friction and wear resistance. Surface texturing can be performed either as a protruded or recessed asperity, with the latter being more popular due to advantages in terms of micro-lubrication and ease of manufacturing. There are a number of ways of material preparation for surface texturing, with the laser surface texturing being the most popular because of its flexibility and high accuracy. The performance of textured surface depends on the geometrical characteristics of the surface texture and the operating condition of the bearing components. In hydrodynamic and mixed lubrication, microcavity in negative surface texture acts as a reservoir for fluid lubricant, while in boundary lubrication, it traps wear particles to reduce further abrasion. In the past, tremendous amount of research effort has been put into the study of surface texturing, with an aim to investigate the underlying effect of surface texturing on tribological performance. This paper presents a critical review of research and development on surface texturing over the past decades, highlighting design, optimization and fabrication of surface texture, and their effects on tribological performance in terms of friction and load bearing capacity under different lubrication regimes. Numerical modelling approaches involving Reynolds and Navier–Stokes equations employed to understand and determine the tribological behaviour are discussed and compared with respect to experimental investigations. Thin film coatings on textured surface have been found to be a promising means to further reduce friction and increase wear life.

Recent development on surface texturing in enhancing tribological performance of bearing sliders

The potential use of laser surface texturing (LST) in hydrodynamic journal bearings is examined theoretically. The regular surface texture has the form of micro-dimples with preselected diameter, depth, and area density. It can be applied to only a certain portion of the bearing perimeter (partial LST) or the full bearing perimeter (full LST). The effect of such a texture on load capacity and on the attitude angle of the journal bearing is investigated in the present work. The optimum parameters of the dimples and favorable LST mode for maximum load capacity have been found.

A Laser Surface Textured Journal Bearing

Chaos and bifurcation of a flexible rub-impact rotor supported by oil film bearings with nonlinear suspension

This paper proposes a method to calculate the characteristics of a coupled fluid dynamic journal and thrust bearing of a hard disk drive (HDD) spindle motor The governing equations for the journal and thrust bearings are the two-dimensional Reynolds equations in the θz and r0 planes, respectively. The finite element method is appropriately applied to analyze the coupled bearing under the conditions of the continuity of mass and pressure at the interface between the journal and thrust bearings. The pressure in the coupled bearing was calculated by applying the Reynolds boundary condition. The validity of this application was verified by comparing the analytical results of the flying height at various rotating speeds with experimental results. The characteristics of the coupled journal and thrust bearing were also investigated due to the Reynolds and Half-Sommerfeld boundary conditions and the coupled and separate analysis. This research demonstrates that the proposed method can accurately and realistically describe the coupled fluid dynamic bearing in a HDD system.

Finite Element Analysis of the Coupled Journal and Thrust Bearing in a Computer Hard Disk Drive

This research investigates the dynamic characteristics of a herringbone grooved journal bearing with plain sleeve (GJPS) and a plain journal bearing with herringbone grooved sleeve (PJGS) under static and dynamic load. FEM is used to solve the Reynolds equation in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors of a journal, such as orbit or rotational speed, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. Numerical results are validated by the experimental results of prior researchers. A GJPS produces less friction torque than a PJGS so that the GJPS consumes less input power than the PJGS. Under static load, the PJGS converges to the fixed equilibrium position, but the GJPS has a whirling motion due to the rotating groove even at the steady state, which produces the excitation frequencies corresponding to the integer multiple of the rotor speed multiplied by the number of grooves. The variation of rotational speed of a GJPS is always less than that of a PJGS due to less friction torque. Under the effect of mass unbalance, the excitation frequencies of the reaction force in a GJPS and a PJGS are the rotational frequency due to mass unbalance and its harmonics due to the nonlinear effect of fluid film. However, the GJPS has relatively big amplitude corresponding to the multiples of the number of grooves, in comparison with the amplitudes at the adjacent harmonics.

Nonlinear Dynamic Analysis of a Hydrodynamic Journal Bearing Considering the Effect of a Rotating or Stationary Herringbone Groove

This paper presents an analytical method to investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill's infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.

J. W. Yoon

Papers

Nonlinear Dynamic Analysis of a Hydrodynamic Journal Bearing Considering the Effect of a Rotating or Stationary Herringbone Groove

Stability Analysis of a Hydrodynamic Journal Bearing With Rotating Herringbone Grooves