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Fixed displacement pumps will continue to be a popular choice for hydraulic system designers for decades to come. These pumps are used in almost every industrial and mobile market segment and are generally less expensive than comparable variable displacement type pumps. Fixed displacement “Vane Type” pumps are especially popular because of their low noise characteristics as well as their inherent repair features. The demand for “Vane Type” fixed displacement pumps continues to grow in all market segments. Because of this continued demand, a new design of “fixed displacement vane pumps” is being developed. These pumps, designated the VPF Series, are targeted to offer continuous operating pressures up to 280 BAR with displacements from 40 to 215 cc/rev.

J I Case Company has produced four-wheel-drive agricultural tractors since 1964. In 1984 however, the flagship of the Case fleet changed hands. Rising labor costs and larger farming operations spearheaded the need for a more efficient larger tractor. January 1984 marked the introduction of the largest four-wheel-drive tractor in the history of Case, the 4994, a 400-gross engine horsepower tractor, Figure 1. Sheer horsepower alone however, would not meet the requirements of today's farming operations. Case Engineering realized that tomorrows tractors must have sufficient power to handle the wide variety of attachments available. They also realized that along with the unmatched power must come precise control of the attachment. These advancements in farming have required improvements to the tractor hydraulic system. This paper describes the hydraulic system of the 4994, Case's new flagship.

In order to reduce fuel consumption, companies have been looking at hybridizing vehicles. So far, two main hybridization options have been considered: electric and hydraulic hybrids. Because of light duty vehicle operating conditions and the high energy density of batteries, electric hybrids are being widely used for cars. However, companies are still evaluating both hybridization options for medium and heavy duty vehicles. Trucks generally demand very large regenerative power and frequent stop-and-go. In that situation, hydraulic systems could offer an advantage over electric drive systems because the hydraulic motor and accumulator can handle high power with small volume capacity. This study compares the fuel displacement of class 6 trucks using a hydraulic system compared to conventional and hybrid electric vehicles. The paper will describe the component technology and sizes of each powertrain as well as their overall vehicle level control strategies.

A distributed sensor is created to sense the rate of change in deflection of beam-like structures such as crane booms. This sensor will be useful in electrohydraulic compensation of boom deflections. The sensor is made of an array of strain-sensitive segments such as strain gages or piezoelectric film. In this example, segments of piezoelectric film convert strains on the surface of a vibrating beam into electrical outputs. These outputs are connected to low impedance signal conditioners. The output of the signal conditioners are then interpolated with a weighting vector that incorporates Lagrange polynomials, specified boundary conditions, and the desired location(s) of measurement. A simple linear combiner circuit combines the electrical outputs into the deflection velocity at the desired points.

Valve blocks are the key parts in hydraulic systems. A feature-based product model is the foundation of the CAD/CAM system for valve blocks--VBCADAM. This paper mainly analyses the design procedure of valve blocks, the application of feature-based design and modeling, object-oriented approach in the development of VBCADAM, such as feature definition and classification, the frame description of features, structure of product model and also the application of the product model in VBCADAM.

A new hydraulic system was developed using off-the-shelf components to gain lower effort steering, push-button machine function controls, and improved reliability. The ability to alter or add to the system (flexibility) is a requirement. The hydraulic control requirements for this vehicle are similar to other self-propelled machines. The inherent flexibility of this system may make it adaptable, at least in part, to other vehicles.

Production cost analyses show a potential economic advantage for thegiant loaders on large jobs. This paper presents a cost comparison between the Model 475 tractor shovel, a smaller tractor shovel, and a swing shovel. Evolutionary events and designs leading to the creation of the 475 are presented and discussed. Design considerations and specific features of this unit are pointed out. Some of these are: loader linkage design, hollow boom construction, split hydraulic system, and a hydraulic power assist for operator controls. Prototype testing and changes are discussed and explained.

This paper describes the design strategy adopted for developing a new high performance actuation system referred to as the ElectroHydraulic Actuator (EHA). The design approach can be divided into fives phases that include: pre-conceptual analysis, conceptual design, preliminary design, detailed design and, integration and test. An important aspect of the design process is the use of modeling and simulation for the analysis, sizing and selection of off-the-shelf parts, and for the detailed design of new custom made components. EHA is based on hydrostatic transmission. It is a unique device with its own characteristics and requires hydraulic components that are specifically tailored to its needs. A prototype of EHA has been produced and has demonstrated an extremely high level of performance. The performance of this prototype complies with design requirements and validates the chosen design approach.

An experimental methodology is proposed to measure the rollover propensity of road tankers when subjected to lateral perturbations derived from steering manoeuvers. The testing principle involves subjecting a scaled down sprung tank to the elimination of a lateral acceleration, to analyze its rollover propensity as a function of various vehicle's operational and design parameters. Initial acceleration is generated through putting the scaled tank on a tilt table supported by a hydraulic piston. The controlled release of the fluid in the hydraulic system generates a perturbation situation for the tank, similar to the one that a vehicle experiences when leaving a curved section of the road and going to a straight segment. Durations for the maneuver and initial tilt angles characterize both the corresponding intensities of the steering maneuver.

Conventional accumulator charging valves operate automatically and reliably in constant flow industrial hydraulic systems. By contrast, these valves do not necessarily perform reliably in variable flow mobile hydraulic systems because the accumulator circuit charging pump flow changes with the engine speed. Occasionally, the valve sticks in a transitional condition which neither allows the accumulator to fully charge nor lets the charge pump unload. This paper describes the operation of conventional and mobile type accumulator charging valves and describes how the spool design pilot circuit valve improves the reliability of the mobile machine accumulator charging valve.

A multi-sensing device with a piezoresistive pressure sensor for hydraulic system control was developed, applied to a hydraulic belt conveyor and tested. One single pressure sensor was installed inside a hydraulic motor. By analyzing the output signals, the following engineering variables were measured and could be analyzed: running speed, torque, absolute displacement, horsepower, pressure, mass flow rate of conveyed materials and even malfunction diagnosis. High speed resolution, torque and mass flow rate measurements are focused on in this paper. Based on data sampling rates and windows, high resolution speed data from a hydraulic motor sensor was measured. Relationships between mass flow rates on the conveyor belt and torques due to loading under various situations are presented.

Abstract Three-dimensional patterns representing crosshatched plateau-honed cylinder bores based on two-dimensional Fast Fourier Transform (FFT) of measured surfaces were generated and used to calculate pressure flow, shear-driven flow, and shear stress factors. Later, the flow and shear stress factors obtained by numerical simulations for various surface patterns were used to calculate lubricant film thickness and friction force between piston ring and cylinder bore contact in typical diesel engine conditions using a mixed lubrication model. The effects of various crosshatch honing angles, such as 30°, 45°, and 60°, and texture heights on engine friction losses, wear, and oil consumption were discussed in detail. It is observed from numerical results that lower lubricant film thickness values are generated with higher honing angles, particularly in mixed lubrication regime where lubricant film thickness is close to the roughness level, mainly due to lower resistance to pressure flow.

Most fertilizer application systems are not capable of variable rate adjustments “on-the-fly”. To change the application rate, the farmer must dismount the tractor and change the gear ratio mechanically (i.e. via gears, chains, etc.). Air seeder manufacturers have come up with their own unique solutions to address this problem, usually involving electrohydraulics. At present there are older seeding units that perform adequately, but do not have the variable rate option. A retrofit is therefore very desirable for these units. In this paper, the feasibility of a simple hydraulic proportional valve and variable speed motor circuit is employed to replace the gears and chains. The unit is integrated with a microcontroller to provide compensation to the nonlinear properties of a proportional valve, and in turn provide a very accurate feedrate. In addition, direct user input from the cab of the tractor is possible, allowing on-the-go rate changes.

This paper presents a theoretical and experimental study on the determination of the efficiency of a hydraulic gear pump based on an analysis of the hydraulic fluid temperature at the inlet and outlet ports. Considering the thermodynamics and fluid mechanics equations, the steady state behavior of the gear pump is described for different wear conditions. The model establishes the relationship between the inlet and outlet temperatures and the main variables such as pressure, torque, flow, and angular speed and, consequently, the pump efficiency.

This paper provides a review of the solubility parameter theory and its application to predicting elastomer/fluid compatibility. Emphasis is placed on describing the theory and translating the results of swell data into a more easily understood method than has previously been used. Numerous solubility parameters arc presented as well as swell test details. The swell data results are then used to determine solubility parameters which, upon comparison with other fluid or elastomer solubility parameters, determine compatibility. This procedure is especially important because it enables the results of swell tests to be used to identify elastomer/fluid compatibility of molecularly complex fluid additives or special elastomer mixtures.

Presenting a brand new approach to heat exchangers for engines, transmissions, hydraulic systems, etc. This new heat exchanger is made of only two pieces of circular extruded aluminum profiles: Core and shell. No soldering: The core and the shell is assembled by a minimum of automated work. In an oil to water cooling application, the active surface on the oil side of the core is enlarged by fins 0.2 mm thick, 0.3 mm spacing, and 3 mm high. The fins are made in unique production machines and enlarge the active surface area approximately five times compared to a conventional heat exchanger of the same dimensions. The principle utilizes the low pressure drop at laminar flow and avoids the disadvantage of low heat transfer after a certain laminar flow length. The result is approximately three times higher oil heat dissipation, combined with very low oil pressure drop, compared to conventional technique.

A new type of screw pump has inherent design features (e.g. balanced design, low bearing loads, wear-adjustable rotors, low rubbing loads, …) which may allow efficient, reliable, and maintainable operation in numerous applications, particularly for pumping low-viscosity fluids. Initial tests on an 87 gal/min prototype pumping lubricating oil at pressures up to 500 lb/in2 and speeds up to 1800 rev/min achieved good performance with little wear over 3400 hours of operations. Performance projections indicate volumetric efficiencies of 50 percent should be reached using the existing prototype pumping 1200 lb/in2 water in one stage.

Pulse width modulation (PWM) has been used to alter the performance of on-off hydraulic control valves to make them perform as proportional type flow control valves. Nonlinear performance resulting from time delays in valve switching as well as valve wear due to continuous cycling continue to persist as operational problems. This paper examines a new technique called modified PWM control. The method was found to provide accurate control with a minimum of valve chatter.

Anybody knows that contamination in oil is always harmful to hydraulic and lubricating systems. Contaminants inevitably exist in the oils of hydraulic and lubrication systems and cause tribological problems. In order to prevent such tribological problems due to contaminants, various oil cleaners have been developed and applied to hydraulic and lubricating systems. They have greatly contributed to improving the reliability of the systems. Since sophisticated hydraulic systems with proportional valves or servo valves, which are sensitive to oil contamination, became popular, fine filters like 3 micron or 1 micron are additionally used. However contamination problems have been revived. The authors have investigated the causes of hydraulic and lubricating problems and found that polymerized oil oxidation products were as harmful as solid particles. They are of molecular size and cannot be removed by mechanical filtration.

Underwater bulldozers have been built for development of the ocean floor. Yet it is impractical for a diver to operate an underwater bulldozer from within the vehicle. Remote control of a bulldozer is extremely difficult due to complicated relationships between vehicle inclination, blade cylinder deflection, and the terrain profile in front of the bulldozer. In this paper a nonlinear automatic feedback blade control system is designed to replace direct operator control of the blade. To accomplish this design, mathematical models were developed for the vehicle dynamics and the hydraulic system dynamics of a typical bulldozer. Since both subsystem models are complicated nonlinear ones, the blade control system was designed using only a simplified hydraulic system model. The performance of the complete nonlinear system with the blade feedback control system added was then investigated using a hybrid computer simulation compared to available experimental data using a skilled operator.