Entwicklungspotenziale für stufenlose Getriebe

Proceedings of the Institution of Mechanical Engineers, Part C:

2012

This article presents a practical approach to leakage flow analysing for various types of hydraulic pumps. In this study, the influence of pump-operating conditions such as operating pressures, pump speeds and oil temperature on the leakage flow characteristics is investigated and a mathematical model to calculate the leakage flow is proposed. Currently, an external gear, an internal gear or a vane pump is commonly used for an automatic transmission. These pumps have their own leakage flow characteristics, which depend not only on pump-operating conditions but also on structures and dimensions of the pumps. For various pumps having different constructions, the delivery pressure and the oil temperature differently affect the leakage flow characteristics and especially the delivery pressure also changes the clearances causing the leakage flow. A mathematical model for the leakage flow, which takes into account a change in the thickness of clearance according to the delivery pressure, represents accurately the actual leakage flow characteristics in various pumps. Also, it clarifies the influence of the pump-operating conditions on their leakage flow characteristics. In the external and internal gear pumps, the leakage flow would not approach zero due to an existence of the orifice flow leakage almost independent of the viscosity of oil, even at an extremely low oil temperature. This leakage flow influences significantly the volumetric efficiency at a low oil temperature in the gear pumps.

Section: Inaguma 985mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A practical approach for analysis of leakage flow characteristics in hydraulic pumps

Proceedings of the Institution of Mechanical Engineers, Part C:

2012

“…Also, the vane pump has recently been used for a continuously variable transmission because of its higher efficiencies compared with an internal gear pump, which is commonly used for an automatic transmission [1][2][3]. The performance of a hydraulic pump affects the efficiency of such systems, and an improvement in the mechanical efficiency by reducing the friction torque is also important for the vane pump.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Friction Torque in Vane Pumps by Using Physical Vapour Deposition-Coated Vane

Proceedings of the Institution of Mechanical Engineers, Part C:

2010

This paper presents a method of reducing friction torque in a hydraulic vane pump through a short-period pump operation by using physical vapour deposition (PVD)-coated vanes. It is well known that the friction torque in a vane pump as well as in other hydraulic machines can be reduced by running-in through a long-time pump operation. This paper revealed that the reduction in the friction torque was derived from lowered friction between a cam contour and vane tips owing to the smoothed surface of a cam contour.Commonly, it was difficult to obtain such an effect through a short-period pump operation. The author has attempted to lessen the surface roughness of the cam contour and to decrease the friction torque of a vane in a short period of time by using vanes coated with an extremely hard PVD layer on their tips. In this study, three kinds of coatings of chromium nitride (CrN), titanium carbonitride (TiCN), and diamond-like carbon (DLC) by PVD were examined.It was found that the TiCN-coated vane was excellent in smoothing the surface roughness of the cam contour and in reducing the friction torque of the vane in a short period of time. It was also shown that the reduced friction torque of the vane depended essentially on the smoothness of the cam contour surface. In addition, the difference of the friction at the vane tip between an ordinary vane and coated vanes was indistinct for the same surface roughness of the cam contour below 0.8 μm Rz.

“…[1][2][3][4][5][6] Also the vane pump has recently been used for a continuously variable transmission operated at the maximum pressure of 5 MPa because its efficiencies are higher than those of an internal gear pump, 7 which is commonly used for an automatic transmission. 8,9 In these systems, reduction in the vibration and the noise during pump operation is desired. 10,11 In addition, for keeping a good stability of the hydraulic control, the pump is often required to have low delivery pressure ripples.…”

Section: Introductionmentioning

confidence: 99%

Influence of leakage flow variation on delivery pressure ripple in a vane pump

Proceedings of the Institution of Mechanical Engineers, Part C:

Nakamura²

2013

This article describes the theoretical analysis and experimental verification of the influence of variations of leakage flow as well as ideal flow on delivery pressure ripple in a balanced vane pump. The analytical model for simulating the delivery pressure ripple of the pump is simplified. It is composed of only the ripple of the ideal flow based on the theoretical pump displacement determined from geometrical pump dimensions, the leakage flow variation dependent on the pump dimensions including clearances and pump-operating conditions, an oil chamber volume in the pump and the impedance of a hydraulic circuit with a throttle valve set close to a pump outlet. The purpose of this study is to predict the pump delivery pressure ripple at the design stage of the vane pump. This article reveals that the delivery pressure ripple can be theoretically predicted through the calculations of the leakage flow as well as the ideal flow. The waveform of the delivery pressure ripple calculated agrees well with the measured one. The leakage flow variation significantly affects the delivery pressure ripple and it can be also calculated accurately from the pump dimensions including the clearances and pump-operating conditions. In addition, the components of the leakage flow are clarified and their effects on the delivery pressure ripple are investigated.