variable displacement hydraulic pump animation price

The displacement of a pump is defined by the volume of fluid that the gears, vanes or pistons will pump in one rotation. If a pump has a capacity of 30 cm3, it should treat 30 ml of fluid in one rotation.

In axial piston variable pumps, the flow is proportional to the drive speed and the displacement. The flow can be steplessly changed by adjusting the swivel angle. Axial piston variable ...

... axial piston pump type V60N is designed for open circuits in mobile hydraulics and operate according to the swash plate principle. They are available with the option of a thru-shaft for operating additional ...

Variable displacement axial piston pumps operate according to the bent axis principle. They adjust the geometric output volume from maximum to zero. As a result they vary the flow rate ...

... piston pump type V30D is designed for open circuits in industrial hydraulics and operate according to the swash plate principle. They are available with the option of a thru-shaft for operating additional ...

... circuit axial piston pumps are used as hydrostatic transmission components in self-propelled machines and for rotary drives in both fixed and mobile equipment of all kinds.

Axial piston twin flow pump. With a very high performance in all job conditions. Due to its twin flow configuration this pump allows a great variety of solutions in different job applications.

Air hydraulic pump, double pneumatic motor, double effect, foot operated with lock-up function, lever distributor valve (4/3), 10L tank, oil flow 8.5 / 0.26 l / min

... customer system options for mechanical, hydraulic and electric input solutions are available. Further special regulating features like torque control and pressure cut-off are also available. The reliable ...

... needs of truck hydraulics, the TXV variable displacement pumps with LS (Load Sensing) control allow flow regulation to suit the application requirements. The pump ...

... rev. displacements, these pumps are designed to operate in both directions of rotation (clockwise or counter-clockwise). Only one reference regardless of direction of rotation. The TXV indexable pumps ...

... PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design ...

Variable displacement pumps in closed loop; 3 basic design units and 8 max. displacement sizes of 14, 18, 21, 28, 35, 46, 56, 64 cc/rev; various control options; max. ...

Parker P2/P3 High Pressure Axial Piston Pumps are variable displacement, swashplate piston pumps designed for operation in open circuit, mobile hydraulic ...

... Series pump offers variable displacement axial piston pumps for open-circuit applications. Featuring a compact footprint and continuous operating pressure ...

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

With fast control response and superior performance, the PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design — while thriving on low-viscosity fluids.

When you need peak performance from a variable-displacement axial-piston pump, the Oilgear pump PVV line is ready. No matter what pressure and flow demands you face, these pumps rise to the challenge.

When you need peak performance from a variable-displacement axial-piston pump, the Oilgear pump PVV line is ready. No matter what pressure and flow demands you face, these pumps rise to the challenge.

When you need peak performance from a variable-displacement axial-piston pump, the Oilgear pump PVV line is ready. No matter what pressure and flow demands you face, these pumps rise to the challenge.

When you need peak performance from a variable-displacement axial-piston pump, the Oilgear pump PVV line is ready. No matter what pressure and flow demands you face, these pumps rise to the challenge.

Quiet operation, high efficiency and compact design — all available at a competitive price. That’s what Oilgear PVWC closed-loop, hydrostatic axial-piston hydraulic pumps bring to the table. All designed around our proven rotating group.

Quiet operation, high efficiency and compact design — all available at a competitive price. That’s what Oilgear PVWC closed-loop, hydrostatic axial-piston hydraulic pumps bring to the table. All designed around our proven rotating group.

Quiet operation, high efficiency and compact design — all available at a competitive price. That’s what Oilgear PVWC closed-loop, hydrostatic axial-piston hydraulic pumps bring to the table. All designed around our proven rotating group.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids—and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Designed to be cost-effective, stable and low-maintenance, PVWJ is a variable-displacement axial-piston pump with a medium control response. Like all Oilgear pumps, it thrives on low-viscosity fluids — and comes in a variety of frame sizes and available displacement rates.

Extremely effective across numerous industrial applications that require quick response in extreme environments, the XD5 series of pumps offer lightning-fast control response on both low-viscosity fluids and standard hydraulic oil. Engineered to handle the most challenging environments, they have been designed to be a high-performance solution for demanding mobile applications.

Designed to be cost effective, stable and low-maintenance, the PVWJ is a variable displacement axial piston pump with a medium control response. Like all Oilgear pumps, it thrives on low viscosity fluids and comes in a variety of frame sizes and available displacement rates.

PVWJ pumps were design and manufactured in such a way that we can offer customers greater flexibility to selectively match pressure and capacity for their specific application.

We offer 3 frame sizes and a total of 10 displacement rates, coupled with a variety of optional controls. The PVWJ family of pumps provides easy field interchangeability.

All Oilgear pumps are designed to thrive on low-viscosity fluids such as high water content and fire resistant fluids, like Skydrol™, Stack Magic™, Erifon™ and 98/2.

As with all Oilgear pumps, all contact surfaces such as the cylinder surface running on the valve plate and the pistons running on the swashblock surface are all hardened for incredible durability.

The PVWJ range provides a broad range of controls and porting options to take on your most demanding applications. For low to medium horsepower equipment, the PVWJ pumps are uniquely designed for enhanced stability and less maintenance. Further to that, they’re also a much quieter option for your operations (achieved with the use of static seals (O-rings) to reduce control noise.

Quiet in operation, super high efficiency, compact design, competitive pricing and impressive lead time are the key attributes of the Oilgear PVWJ open loop piston pump. Available in 10 displacement sizes, the PVWJ pumps offer a large selection of readily interchangeable controls. With improved response controls and reduced noise levels, its rugged cylinder design enhances performance.

The patented, pressure lubricated swashblock design offers high performance for high-cycling operations. It also contributes to the pump’s ability to run on low-viscosity fluids, including high water content, fire-resistant and other special fluids.

Zeus Hydratech fully supports the Oilgear PVWJpump product line and is the only valid source for OEM parts in the South of the UK. All Oilgear repairs are machined and tested per our original factory specifications.

The Muncie PV Series Piston Pumps is warranted against any defect in material and workmanship which existed at the time of sale by Muncie, according to the following provisions, subject to the requirements that the Valve must be used only in accordance with catalogue and package instructions. The Valve is warranted for a period of one year from date of installation. If during the warranty period the Valve fails to operate to Muncie’s specifications due to a defect in any part in material or workmanship that existed at the time of sale by Muncie, the defective part will be repaired or replaced, at Muncie’s election, at no charge, if the defective part is returned to Muncie with transportation prepaid.

Piston design - Solid, hollow, or with piston rings. The design and weight of the pistons will have a major effect on pump efficiency. The Parker F11 design with its lightweight head and retained balls can reach significantly higher speeds than swashplate pumps with their longer, heavier pistons.

Some pumps and motors can run over-centre, which means they can provide flow or rotate their drive shaft in both directions. These are commonly used in closed circuit, mobile vehicle drives systems.

Bent axis designs tend to have much heavier duty shaft bearings than swashplate pumps. This is because they are more commonly used as motor drive units and have to take the wheel loads against their shaft. Swashplate pumps, on the other hand, tend to be driven through flexible couplings that will remove any side loads, so the internal bearing is sized just to take the internal loads from the dynamic and pressure loading forces.

Noise level can be an issue with piston pumps. The noise is generated by the discontinuities in the flow e.g. as the pistons move forward and backward they create a pulsating flow that passes into the complete hydraulic system and vibrates or radiates from other components further down the circuit. This flow discontinuity is further complicated by the supply port which connects and disconnects each piston as it rotates. The timing of the opening and closing can create other, higher frequency flow discontinuities. Often different timing plates are available for different operating conditions e.g. fixed speed or variable speed applications.

Case leakage line pressures are critical for controlling the pressure balance of the slipper against the suction pressure. Care should be taken with some pump controllers as the valves exhaust into the pump casing and can create dangerous pressure spikes. Make sure case drain lines are sufficiently sized. One possible solution may be to use a more compliant, clear plastic hose for the case leakage line which will have the effect of damping out these peaks before damage the slippers. Case leakage line temperatures are also a good way of monitoring the health of the pump as discussed in the vane pump section.

If you are in doubt about the most appropriate pump to use in your application then always talk to manufacture or distributor who should be able to offer the most appropriate pump range and advise the expected service life.

Friction torque vs. pressure gain coefficient at maximum displacement — Proportionality constant at maximum displacement between friction torque and pressure gain

Angular velocity threshold for pump—motor transition — Shaft angular velocity at which to initiate a smooth transition between pump and motor modes

An axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a hydraulic motor or an automotive air conditioning compressor.

An axial piston pump has a number of pistons (usually an odd number) arranged in a circular array within a housing which is commonly referred to as a cylinder block, barrel. This cylinder block is driven to rotate about its axis of symmetry by an integral shaft that is, more or less, aligned with the pumping pistons (usually parallel but not necessarily).

Mating surfaces. One end of the cylinder block is convex and wears against a mating surface on a stationary valve plate. The inlet and outlet fluid of the pump pass through different parts of the sliding interface between the cylinder block and valve plate. The valve plate has two semi-circular ports that allow inlet of the operating fluid and exhaust of the outlet fluid respectively.

Protruding pistons. The pumping pistons protrude from the opposite end of the cylinder block. There are numerous configurations used for the exposed ends of the pistons but in all cases they bear against a cam. In variable displacement units, the cam is movable and commonly referred to as a yoke or hanger. For conceptual purposes, the cam can be represented by a plane, the orientation of which, in combination with shaft rotation, provides the cam action that leads to piston reciprocation and thus pumping. The angle between a vector normal to the cam plane and the cylinder block axis of rotation, called the cam angle, is one variable that determines the displacement of the pump or the amount of fluid pumped per shaft revolution. Variable displacement units have the ability to vary the cam angle during operation whereas fixed displacement units do not.

Reciprocating pistons. As the cylinder block rotates, the exposed ends of the pistons are constrained to follow the surface of the cam plane. Since the cam plane is at an angle to the axis of rotation, the pistons must reciprocate axially as they precess about the cylinder block axis. The axial motion of the pistons is sinusoidal. During the rising portion of the piston"s reciprocation cycle, the piston moves toward the valve plate. Also, during this time, the fluid trapped between the buried end of the piston and the valve plate is vented to the pump"s discharge port through one of the valve plate"s semi-circular ports - the discharge port. As the piston moves toward the valve plate, fluid is pushed or displaced through the discharge port of the valve plate.

Effect of precession. When the piston is at the top of the reciprocation cycle (commonly referred to as top-dead-center or just TDC), the connection between the trapped fluid chamber and the pump"s discharge port is closed. Shortly thereafter, that same chamber becomes open to the pump"s inlet port. As the piston continues to precess about the cylinder block axis, it moves away from the valve plate thereby increasing the volume of the trapped chamber. As this occurs, fluid enters the chamber from the pump"s inlet to fill the void. This process continues until the piston reaches the bottom of the reciprocation cylinder - commonly referred to as bottom-dead-center or BDC. At BDC, the connection between the pumping chamber and inlet port is closed. Shortly thereafter, the chamber becomes open to the discharge port again and the pumping cycle starts over.

Variable displacement. In a variable displacement pump, if the vector normal to the cam plane (swash plate) is set parallel to the axis of rotation, there is no movement of the pistons in their cylinders. Thus there is no output. Movement of the swash plate controls pump output from zero to maximum. There are two kinds of variable-displacement axial piston pumps:

direct displacement control pump, a kind of axial piston pump with a direct displacement control. A direct displacement control uses a mechanical lever attached to the swashplate of the axial piston pump. Higher system pressures require more force to move that lever, making direct displacement control only suitable for light or medium duty pumps. Heavy duty pumps require servo control.linkages and springs and in some cases magnets rather than a shaft to a motor located outside of the pump (thereby reducing the number of moving parts), keeping parts protected and lubricated and reducing the resistance against the flow of liquid.

Pressure. In a typical pressure-compensated pump, the swash plate angle is adjusted through the action of a valve which uses pressure feedback so that the instantaneous pump output flow is exactly enough to maintain a designated pressure. If the load flow increases, pressure will momentarily decrease but the pressure-compensation valve will sense the decrease and then increase the swash plate angle to increase pump output flow so that the desired pressure is restored. In reality most systems use pressure as a control for this type of pump. The operating pressure reaches, say, 200 bar (20 MPa or 2900 psi) and the swash plate is driven towards zero angle (piston stroke nearly zero) and with the inherent leaks in the system allows the pump to stabilise at the delivery volume that maintains the set pressure. As demand increases the swash plate is moved to a greater angle, piston stroke increases and the volume of fluid increases; if the demand slackens the pressure will rise, and the pumped volume diminishes as the pressure rises. At maximum system pressure the output is once again almost zero. If the fluid demand increases beyond the capacity of the pump to deliver, the system pressure will drop to near zero. The swash plate angle will remain at the maximum allowed, and the pistons will operate at full stroke. This continues until system flow-demand eases and the pump"s capacity is greater than demand. As the pressure rises the swash-plate angle modulates to try to not exceed the maximum pressure while meeting the flow demand.

Designers have a number of problems to overcome in designing axial piston pumps. One is managing to be able to manufacture a pump with the fine tolerances necessary for efficient operation. The mating faces between the rotary piston-cylinder assembly and the stationary pump body have to be almost a perfect seal while the rotary part turns at perhaps 3000 rpm. The pistons are usually less than half an inch (13 mm) in diameter with similar stroke lengths. Keeping the wall to piston seal tight means that very small clearances are involved and that materials have to be closely matched for similar coefficient of expansion.

The pistons have to be drawn outwards in their cylinder by some means. On small pumps this can be done by means of a spring inside the cylinder that forces the piston up the cylinder. Inlet fluid pressure can also be arranged so that the fluid pushes the pistons up the cylinder. Often a vane pump is located on the same drive shaft to provide this pressure and it also allows the pump assembly to draw fluid against some suction head from the reservoir, which is not an attribute of the unaided axial piston pump.

Internal lubrication of the pump is achieved by use of the operating fluid—normally called operating temperature, limited by the fluid, of about 120 °C (250 °F) so that using that fluid as a lubricant brings its own problems. In this type of pump the leakage from the face between the cylinder housing and the body block is used to cool and lubricate the exterior of the rotating parts. The leakage is then carried off to the reservoir or to the inlet side of the pump again. Hydraulic fluid that has been used is always cooled and passed through micrometre-sized filters before recirculating through the pump.

Despite the problems indicated above this type of pump can contain most of the necessary circuit controls integrally (the swash-plate angle control) to regulate flow and pressure, be very reliable and allow the rest of the hydraulic system to be very simple and inexpensive.

Axial piston pumps are used to power the hydraulic systems of jet aircraft, being gear-driven off of the turbine engine"s main shaft, The system used on the F-14 used a 9-piston pump that produced a standard system operating pressure of 3000 psi and a maximum flow of 84 gallons per minute.

Automotive air conditioning compressors for cabin cooling are nowadays mostly based around the axial piston pump design (others are based on the scroll compressor or rotary vane pump ones instead) in order to contain their weight and space requirement in the vehicle"s engine bay and reduce vibrations. They"re available in fixed displacement and dynamically adjusted variable displacement variants, and, depending upon the compressor"s design, the actual rotating swashplate either directly drives a set of pistons mated to its edges through a set of hemispherical metal shoes, or a nutating plate on which a set of pistons are mounted by means of rods.

An irregular performance of a mechanical-type constant power regulator is considered. In order to find the cause of an irregular discharge flow at the cut-off pressure area, modeling and numerical simulations are performed to observe dynamic behavior of internal parts of the constant power regulator system for a swashplate-type axial piston pump. The commercial numerical simulation software AMESim is applied to model the mechanical-type regulator with hydraulic pump and simulate the performance of it. The validity of the simulation model of the constant power regulator system is verified by comparing simulation results with experiments. In order to find the cause of the irregular performance of the mechanical-type constant power regulator system, the behavior of main components such as the spool, sleeve, and counterbalance piston is investigated using computer simulation. The shape modification of the counterbalance piston is proposed to improve the undesirable performance of the mechanical-type constant power regulator. The performance improvement is verified by computer simulation using AMESim software.

The pressure regulators of swashplate-type variable displacement axial piston pumps (VDAPP) control the swivel angle, which changes the amount of flow rate to hydraulic circuits. The pressure regulator is operating in accordance with the dynamic response of the discharge pressure, and it supplies pilot flow rate to the control piston which regulates the swivel angle of swashplate. The pressure regulator is mainly divided into the three types depending on the operating method, that is, a flat cut-off type, a differential cut-off type, and a constant power type.

The pressure regulators are usually used to save energy of hydraulic systems in the industrial field. As the hydraulic power unit used for movable equipment has increased, the pressure regulators have been applied in such systems in order to protect prime mover. Most movable hydraulic power unit consist of motor, pumps and reservoir (MPR). An overload of the pump can cause damage to the electric motor and its circuits under a variety of load conditions. To avoid these problems, power regulation of the pump is needed in order to respond to wide varieties of loads without exceeding the maximum power range of the prime mover. In this study, we applied the constant power regulator to the VDAPP so that the angle of the swashplate is automatically decreased according to an increase of the load pressure.

Recently, electronic regulators have been studied and commercialized [1–4]. However, the mechanical regulators are mainly applied in the industrial field because a proportional reducing pressure valve which is used as main part of the electronic regulator has relatively poor durability than mechanical regulator. In recently developed hydraulic regulator systems, both the electrical and mechanical regulators are applied to hydraulic regulator system. In those hydraulic regulator systems, the mechanical regulator is used as emergency equipment so that it only works when the electronic regulator fails. Due to the relatively exceptional durability, the mechanical regulator system is especially adopted to construction equipment and combat vehicles, which are used for long periods in poor conditions.

A schematic diagram of a swash plate VDAPP with a constant power regulator is shown in Figure 1. Figure 2 represent hydraulic circuit of the constant power regulator system. The constant power regulator system consists of five parts, that is, a regulator assembly (A), a control cylinder assembly (B) which controls the angle of the swash plate, a counterbalance assembly (C), a swash plate (D), and a piston (E). As shown in Figure 3, the regulator assembly consists of a spool and sleeve. A flow area of the regulator system is determined by relative displacement between spool and sleeve. Figures 4 and 5 show the detailed structure of the control cylinder and counterbalance.

As shown in Figure 8, the swash plate is held in a certain swivel angle. In this area, the discharge pressure of the pump does not feed back into the control cylinder. This causes the swash plate to rotate in a maximum angular displacement. As a result, the pump can supply the maximum flow rate to a load system unless the discharge pressure of VDAPP is sufficiently increased to a certain level by a load. At the maximum flow rate section shown in Figure 9, the discharge flow rate cannot be feed into the control cylinder because the spool blocks the path of the sleeve.

In the constant power area shown in Figure 11, the spool is moved by the pilot pressure which is equal to load pressure, and the spool displacement makes the flow path to the control cylinder open. Then, the flow is supplied to the control cylinder. Therefore, the swivel angle is decreased, and the discharge flow rate of the pump is reduced. When the swivel angle is decreased, the sleeve reduces or blocks the flow to the control cylinder by the movement of the counterbalance piston. Therefore, the displacement of the control cylinder is adjusted according to the load variation. Consequently, the increase of the load pressure decreases the discharge flow rate of VDAPP, and that makes output power of VDAPP constant because the output power of VDAPP is determined by the product of load pressure and discharge flow rate.

As previously described, these characteristics of the pump-regulator assembly are determined by the interaction of the spool and sleeve. The pilot pressure generated by the load pressure of the system affects the spool.

In the VDAPP, the displacements of the control cylinder and the counterbalance piston are the same due to kinematic constraint. Therefore, (2) can be expressed as

where is the pressure in control cylinder, is the pressurized area of the control cylinder, is the mass of the control cylinder, is the viscous friction coefficient between the control cylinder and a sleeve, is the spring constant, is the initial displacement, is the displacement of control cylinder, and is the spring constant of the reaction spring for the sleeve of the constant power mechanical regulator.

where is the effective bulk modulus, is input flow rate to control cylinder, is output flow rate from control cylinder to reservoir, is the pressurized area of control cylinder, and is leakage coefficient of the control cylinder. At mechanical-type constant power regulators, the control flow varies according to the relative displacement between the spool and sleeve. Thus,

where is flow coefficient of orifice, and represent the orifice areas, is discharge pressure of the hydraulic pump, and is density of working fluid.

The displacement of the control cylinder, in (4), is determined by the resultant force on the swash plate as shown in Figure 15. The various forces are expressed in the form of a complex nonlinear model. In this study, in order to derive more accurate results, the VDAPP was also implemented using AMESim software.

A VDAPP with a mechanical regulator system was established using AMESim simulation software, which allows a very accurate implementation of the response of a nonlinear system. In the field of hydraulic component design, AMESim is widely used to optimization and performance improvement as a review of the actual system [5]. Figure 16 shows an AMESim diagram for the analysis of the system performance of an MPR system that consists of nine pistons.

The maximum swivel angle was set to 16°, which is the same as in the real component, and the exclusion volume was set to 11.6 cm3/rev. All parameters of the VDAPP are the actual design values used in the experimental equipment. The experimental equipment was modeled by considering the nonlinear behavior of the MPR pump system.

If the pump is composed of an odd number of pistons, the number of discharging pistons is determined by the rotation angle of the piston, which located at regular intervals on the plate as follows [11]:

Figure 17 shows the simulation result when the pump is driven at 4500 rpm under no-load condition. The discharge flow rate is the sum of the flow rate of each piston. The pulsation in flow rate is observed in simulation result as shown in Figure 17. This simulation results also show that the average value of the discharge flow rate 49.8 L/min is less than the theoretical one 52 L/min because the internal leakage through the gap between the piston and cylinder block is considered in computer simulation.

Figure 19 shows the hydraulic circuit of test rig for VDAPP. The angular velocity of the electric motor is regulated as 4500 rpm, and the load pressure is adjusted by adjustable relief valve which installed in the discharge line of the VDAPP. The discharge pressure is slowly increased during 45 seconds. The load pressure, the discharge flow rate, and the angular velocity and the torque of the electric motor are acquired by data acquisition board in real time.

Also, the displacement of the counterbalance piston in this simulation is shown in Figure 24. This result is in good agreement with the designed dimension of the real system.

On the other hand, an irregular fluctuation in displacement of the counterbalance piston causes pulsation of the discharge flow rate of the VDAPP. As discussed in previous section, the displacements of the control cylinder and the counterbalance piston are the same due to kinematic constraint. The pressures in the control cylinder affects to the displacement of it. The pressure in control cylinder is regulated by the balance of inlet/outlet flow rate in the volume of control cylinder. In addition, the inlet flow rate to the control cylinder is decided by the relative displacement between the spool and sleeve. Therefore, the discharge flow rate of the VDAPP is influenced by the relative displacement between the spool and sleeve in the constant power regulator.

Figure 25 shows the simulation results of the displacements of the spool and sleeve versus time. The simulation results in Figure 24 show that the displacement of the sleeve and spool is distinguished at about 35 seconds. This means that the orifice is open on this point, but counterbalance piston does not move until 44 seconds. This phenomenon can be explained as follows. Though the pilot flow rate is supplied to the control cylinder at about 35 seconds, the amount of inlet flow rate is less than that of leakage from control cylinder. Therefore, the pressure in control cylinder does not rise. The relative displacement between spool and sleeve becomes sufficiently larger at around 44 seconds. At this time, the inlet flow rate is larger than the leakage from control cylinder. Therefore, the pressure in control cylinder is rising and the counterbalance piston starts to move and a constant output control begins.

The fluctuation in displacement of the spool and sleeve remarkably appears in the pressure cut-off area from 56 to 58 seconds. At this period, the displacement of the counterbalance piston also oscillates, and the irregular discharge flow rate of the VDAPP is observed. This phenomenon seems to be accrued due to the discontinuous shape at the edge of the counterbalance piston because the reacting spring force of the sleeve acting on the counterbalance piston disappears immediately at this region.

In this study, the constant power mechanical regulator system with variable displacement axial piston pump is considered. The constant power mechanical regulator with VDAPP has a problem of pulsation in the discharge flow rate at the cut-off area. In order to solve the problem, the internal behavior of the constant power regulator with VDAPP is analyzed by modeling the system using the AMESim software. The theoretical analysis of constant power regulator is induced for precise modeling, and the internal dynamics of un-measurable components are studied. The validation of the simulation model is confirmed by comparing the simulation results with the experimental output of the real system. By analyzing the dynamics of the unmeasurable internal components, it is found that the irregular discharge flow rate is caused by the discontinuous shape at the edge of the counterbalance piston. Therefore, we proposed the rounded shape for the edge of the counterbalance piston. The effect of the redesigned shape is implemented by AMESim simulation, and the validation is verified by computer simulation. The future work is experimental confirmation of the redesigned shape.

A device that changes the flow of fluid while converting mechanical energy into hydraulic energy is known as a variable displacement pump. During operation, the pump"s displacement can be adjusted, allowing for a different volume of fluid to be pumped with each revolution of the pump"s input shaft. In the field of automotive technology, the axial piston pump is a type of variable displacement pump that is frequently employed. This particular pump is made up of a number of pistons housed within cylinders that are aligned parallel to one another and rotate around a central axis. Pistons are connected to a moveable plate that is located at one end. Because of the angle that the plate is at, the rotating pistons move in and out of their cylinders as the plate rotates. Each bottle is connected to the fluid connection and supply lines in a randomized order by the rotary valve that is situated at the opposite end of the electrical panel. Continuous adjustments to the piston stroke can be made by adjusting the angle at which the swashplate is positioned.

Hydraulic pumps can be divided into two primary categories: those with positive displacement and those with non-positive displacement. Both positive displacement hydraulic pumps and non-positive hydraulic pumps create a flow that is constant, but a positive displacement pump produces a flow that is approximately constant at a constant rate regardless of the pressure. In the subsequent part, we are going to talk about a particular type of positive displacement pump known as a variable displacement pump. The variable displacement pump is responsible for the transfer of mechanical energy, such as the spinning of an engine, into hydraulic energy. However, there are also variable piston pumps that may be made to operate in the opposite direction. It is the process of changing the form of energy from hydraulic to mechanical (hydraulic motor function). During operation, the variable displacement pump allows for adjustments to be made to both the flow rate and the output pressure. Pumps like these are frequently used to provide power to a wide variety of tools. However, in comparison to other pumps, this one has a higher level of complexity and a higher price tag.

There are variable things that the hydraulic pump is responsible for when it is operating but two of them are most important. First, the movement of its moving parts produces a vacuum at the pump"s inlet, which enables the fluid to be pushed from the tank to the pump"s inlet line by the force of air pressure. Second, the motion of the mechanism causes this fluid to be pushed back into the hydraulic system while it is being delivered to the pump outlet.