Abstract:The ideal variable displacement pump for a displacement control circuit is efficient across a wide operating range and readily mounted on a common shaft with multiple pumps. This paper presents a novel variable displacement pump architecture for displacement control circuits that uses the concept of alternating flow (AF) between piston pairs that share a common cylinder. The displacement is adjusted by varying the phase angle between the piston pairs. When the pistons are in phase, the pump displacement is at … Show more
“…The model showed that AF pump could theorically be more efficient than the other variable displacement technologies, especially at low displacement [13]. The efficiency of the prototype presented in [14] proved to be about 90% at full displacement and 65% at a displacement ratio of 36%, which is rather promising for a prototype. A considerable part of the losses were related to the chain drive and to the AF pipes.…”
Section: Alternating Flowmentioning
confidence: 87%
“…Conversely, when the phase angle 𝜑 = 0 a maximum pumping flow is generated by the AF pump since all the cylinders are in phase and synchronised. This specific continuously variable displacement technology has been tested on a prototype by Li et al [13,14] with two pumps, made of four reciprocating cylinders, and whose main shafts are synchronised by a chain drive. The phase angle had to be adjusted manually by removing the chain and turning the shaft angle of one of the two pumps.…”
The hydraulic motor is one of the main parts of hydrostatic transmission implemented in some off-road vehicles for instance. It uses hydraulic power to convey energy from the generator of the machine to the wheels and other actuators. As the hydraulic circuit may contain several hydraulic actuators, each of them needs to be controlled independently since the only control of the pump displacement may impact the entire circuit and all its actuators simultaneously.
To properly drive the vehicle, the hydraulic actuators have to be accurately controlled. This paper aims to present a state-of-the-art of the different ways of changing hydraulic pumps/motors displacement ratios because it is one of the most important parameter to control the torque/speed (resp. pressure/flow rate). Some hydraulic machines enable a continuous change of this displacement ratio thanks to their specific architectures, whereas other machines use hydraulic valves to pilot this ratio. Most of the technologies, from variable displacement axial solutions to new digitally modulated displacement machines will be presented and compared. Digital Displacement solutions and their valve timing control solutions will then be depicted. Finally, technological locks in Digital Displacement will be exposed based on the modeling of a radial piston motor.
“…The model showed that AF pump could theorically be more efficient than the other variable displacement technologies, especially at low displacement [13]. The efficiency of the prototype presented in [14] proved to be about 90% at full displacement and 65% at a displacement ratio of 36%, which is rather promising for a prototype. A considerable part of the losses were related to the chain drive and to the AF pipes.…”
Section: Alternating Flowmentioning
confidence: 87%
“…Conversely, when the phase angle 𝜑 = 0 a maximum pumping flow is generated by the AF pump since all the cylinders are in phase and synchronised. This specific continuously variable displacement technology has been tested on a prototype by Li et al [13,14] with two pumps, made of four reciprocating cylinders, and whose main shafts are synchronised by a chain drive. The phase angle had to be adjusted manually by removing the chain and turning the shaft angle of one of the two pumps.…”
The hydraulic motor is one of the main parts of hydrostatic transmission implemented in some off-road vehicles for instance. It uses hydraulic power to convey energy from the generator of the machine to the wheels and other actuators. As the hydraulic circuit may contain several hydraulic actuators, each of them needs to be controlled independently since the only control of the pump displacement may impact the entire circuit and all its actuators simultaneously.
To properly drive the vehicle, the hydraulic actuators have to be accurately controlled. This paper aims to present a state-of-the-art of the different ways of changing hydraulic pumps/motors displacement ratios because it is one of the most important parameter to control the torque/speed (resp. pressure/flow rate). Some hydraulic machines enable a continuous change of this displacement ratio thanks to their specific architectures, whereas other machines use hydraulic valves to pilot this ratio. Most of the technologies, from variable displacement axial solutions to new digitally modulated displacement machines will be presented and compared. Digital Displacement solutions and their valve timing control solutions will then be depicted. Finally, technological locks in Digital Displacement will be exposed based on the modeling of a radial piston motor.
“…As shown in Figure 2, due to the action of the two check valves and the compressibility of water, the pressure versus time curve in the piston chamber is close to trapezoidal. 23,24 There are two O-rings used to seal the pressure of the piston chamber. This article selects the second sealing ring as the research object because of its larger sealing area.Figure 2.Physical model of the port valve of piston pump.…”
For ultrahigh-pressure piston pumps, in the reciprocating action of the piston, the fretting between the static face seal and the mating surface occurs with the change of the pressure in the piston chamber. This phenomenon will seriously affect the service life of the seal ring and lead to the failure of the pump. However, the failure of static seals used to seal ultrahigh-pressures is usually studied from the directions of shear, stress, or rubber material. These studies cannot explain the failure phenomenon of the sealing ring found in our experiment. This paper analyzed the failure of the face seal ring in a piston pump with a maximum pressure of 120 MPa. A two-dimensional axisymmetric finite element model was established based on the Mooney-Rivlin constitutive relation of the rubber material, and the fretting conditions of the sealing ring were analyzed. Combined with the wear scars observed by the scanning electron microscope the face seal ring’s dynamic failure mechanism on the ultrahigh-pressure piston pump was determined. A better sealing scheme was proposed and verified by the duration test of the pump, which provided a basis for the design of the sealing of the ultrahigh-pressure fluid with high-frequency fluctuations.
“…By adjusting the phases, the piston strokes, and their velocities, each piston output flows intermittently in order to obtain a substantially constant discharge rate. Furthermore, a novel variable displacement pump architecture (Foss et al, 2017) was designed for displacement control circuits that uses the concept of alternating flow (AF) between piston pairs that share a common cylinder. The AF pump was constructed from two inline triplex pumps, which is efficient across a wide operating range.…”
Section: Introductionmentioning
confidence: 99%
“…To make the piston pump adapt to the developmental needs of the modern industrial sector, high efficiency and energy saving, small flow, and pressure pulsation are the goals of piston pump design (Gandhi et al, 2014;Huang et al, 2017;Wilhelm and Van De Ven, 2014b). Initially, most of the piston pumps were driven by the crank-connecting rod mechanism.…”
Abstract. An analytical method for programming piston displacements for constant flow rate piston pumps is presented. A total of two trigonometric transition functions are introduced to express the piston velocities during the transition processes, which can guarantee both constant flow rates and the continuity of piston accelerations. A kind of displacement function of pistons, for two-piston pumps, and two other kinds, for three-piston pumps, are presented, and the physical meaning of their parameters is also discussed. The results show that, with the given transition functions, cam profiles can be designed analytically with parameterized forms, and the maximum accelerations of the pistons are determined by the width of the transition domain and the rotational velocities of the cams, which will affect contact forces between cams and followers.
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