Double Pump — Closed Center Ford Tractor Hydraulic System

<div class="htmlview paragraph">In February of 1987, Dresser introduced a pair of new mechanical drive, off-highway trucks designed to operate in the 35 to 60 ton, rear-dump, classes. These trucks, designated 140M and 210M, replaced three previous models while covering the same payload range. One distinctive feature of these new vehicles was their hydraulic system and in particular the brake control portion of this system.</div> <div class="htmlview paragraph">This new hydraulic brake control system can be described as a closed-center arrangement using a pressure-compensated, variable displacement pump as an energy source with accumulator-based energy reserves for independent and redundant circuits. In the basic version, a pair of pressure regulating valves are used to control system pressure at the brakes. These valves can be actuated in</div> <div class="htmlview paragraph"> <figure id="F1" class="figure"> <div class="graphic-wrapper"><img class="article-figure figure" src="911834_fig0001.jpg" alt="No Caption Available"/></div> </figure> </div> <div class="htmlview paragraph">tandem by a treadle (foot pedal) or separately by hydraulic pilot pressure. A single, filtered hydraulic fluid is used throughout the system and is stored in a single reservoir vented to atmosphere.</div> <div class="htmlview paragraph">The basic system is capable of accommodating multiple-axle (i.e. more than two) arrangements but was originally applied to a two-axle vehicle using dry, disc-type (caliper and rotor) brakes on all wheels. In February of 1990, the Model 140M and 210M trucks were revised to offer rear axle oil-cooled brakes as an option. The brake control system was subsequently modified to provide for this change primarily by the use of an additional pressure regulating valve and redundant circuitry.</div> <div class="htmlview paragraph">Both the original and latest versions of this system are characterized by their use of a unique emergency brake control system. Through the use of logic-type control valves, a loss of hydraulic pressure in one circuit is used to force the remaining high pressure circuits into actuating the brakes. This paper will describe the arrangement and operation of this hydraulic brake control system and its function as an integral part of the overall vehicle hydraulic system.</div>

<div class="htmlview paragraph">Small electro-hydraulic actuators have started to replace systems with centralized hydraulic power supply in some areas. Therefore the most common systems with a variable speed electric motor in combination with a fixed-displacement pump and a constant speed motor with a variable displacement pump were compared using the load cycle of the aileron of a civil aircraft. For this load cycle the configuration with fixed displacement pump and the variable speed electric motor showed the same dynamic and a much better energetic performance than the variant with a constant speed motor and a variable displacement pump. The energy consumption could be reduced by 55 % using the motor speed as the control input. With a logic that changes the control input between motor speed and swashplate angle as a funktion of the actual motor speed the energy consumption could be reduced by another 24 %.</div>

As a rule, hydrostatic transmissions are more efficient than equivalent valve-operated flow controls. The choice of pump configuration can, however, significantly affect power efficiency. In Section 5.2, four basic valve control circuits were described; meter-in, meter-out, meter-in/meterout and bleed-off. In the bleed-off circuit, the pump operates as a flow source, in the other three cases the pump acts as a pressure source. We shall now examine several types of pump arrangement with special emphasis on power dissipation and efficiency. The five basic circuit arrangements are: (1) Fixed displacement pump at constant supply pressure. (2) Pressure-compensated variable displacement pump. (3) Fixed displacement pump with pressure match. (4) Variable displacement pump with power match. (5) Fixed displacement pump with bleed-off. Circuits (3) and (4) can further be broken down into either fixed or variable pressure or power match.

<div class="htmlview paragraph">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, <span class="xref">Figure 1</span>.</div> <div class="htmlview paragraph">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.</div> <div class="htmlview paragraph">This paper describes the hydraulic system of the 4994, Case's new flagship.</div>

<div class="htmlview paragraph">Heat generated in hydraulic systems can be responsible for reduced life of equipment. Current Industry trends look to load-sensing variable-displacement pumps and closed-center valves to combat the problem. A comparison is made between the load-sensing variable-displacement pump with closed-center control valves and the fixed-displacement pump (both wet and dry valve types) with open-center control valves, to determine the heat generation tradeoffs. The use of tanks, lines and cylinders as a heat radiator is considered. Heat generated by high-pressure leakage of driven members is addressed. The primary focus of this paper is on packer and body hydraulics of refuse trucks.</div>

<div class="section abstract"> <div class="htmlview paragraph">This SAE Standard covers complete general and dimensional specifications for 37 degree flared and flareless types of hydraulic tube fittings and O-ring plugs. Also included are pipe fittings and adapter unions for use in conjunction with these tube fittings. These fittings are intended for general application in hydraulic systems on industrial equipment and commercial products.</div> <div class="htmlview paragraph">These fittings are capable of providing leak-proof, full-flow connections in hydraulic systems operating at working pressures as specified in SAE J1065, “Pressure Ratings for Hydraulic Tubing and Fittings.”</div> <div class="htmlview paragraph">Since many factors influence the pressure at which a hydraulic system will or will not perform satisfactorily, the values shown in SAE J1065 should not be construed as a guaranteed minimum.</div> <div class="htmlview paragraph">For any application, it is recommended that sufficient testing be conducted and reviewed by both the user and fitting manufacturer to assure that performance levels will be safe and satisfactory.</div> <div class="htmlview paragraph">The standard is divided into six sections as follows:</div> </div>

<div class="htmlview paragraph">The conventional circuits for tractor loader backhoes generally consist of fixed displacement pump and valves that bypass excess flow resulting in poor efficiency. Poor machine controllability, high operator actuating forces, lack of pressure compensation and other problems have warranted development of better hydraulic circuits.</div> <div class="htmlview paragraph">These and many more handicaps are overcome in Vickers new design of sectional directional valves assisted by a load sensing variable displacement pump.</div> <div class="htmlview paragraph">An overview of possible alternate circuits is presented here with a description of the features of a new CMX sectional valve and its application in a tractor loader backhoe circuit.</div>

<div class="section abstract"><div class="htmlview paragraph">The fuel economy of the internal combustion engine becomes progressively critical, especially with the stringent standards set by the government. To meet the government norms such as CAFE (Corporate Fuel Average Economy), different technologies are being explored and implemented in internal combustion engines. Several technologies such as variable oil pump, map controlled PCJ (Piston Cooling Jet), variable or switchable water pump & ball bearing turbocharger etc. This study investigates the effectiveness of implementing map-controlled PCJ implemented for a 1.5-litre 3-cylinder diesel engine.</div><div class="htmlview paragraph">PCJ’s are major consumers of oil flow and map-controlled PCJ is used by many OEM’s e.g., Ford EcoSport to reduce the oil pump flow. In map-controlled PCJ, the oil to the PCJ is controlled using a solenoid valve. The solenoid valve can be completely variable or ON/OFF type. In our application, the ON/OFF type solenoid value is used to regulate the oil flow to PCJ. Conventionally, the oil to the PCJ is supplied at all operating conditions of the engine, even when the piston temperature is within the material acceptable limit. This adds to the parasitic loss of the internal combustion engine, due to the high friction power consumed by the oil pump to meet the oil flow rate requirement. Using the solenoid-controlled PCJ along with Variable Displacement Oil Pump (VDOP), the flow to the PCJ can be shut down at certain operating conditions such as high speed, and low load conditions. Using the VDOP, the total oil flow rate can be reduced whenever there is no flow to the PCJ, this will help to reduce engine friction load & improve the overall fuel economy.</div><div class="htmlview paragraph">The objective of the paper is to show the systemic approach, design modifications & challenges involved in the implementation of the map controlled PCJ. The final engine with the map-controlled PCJ along with VDOP is evaluated in the NEDC (New European Driving Cycle) drive cycle to understand the benefits & an overall fuel economy of 1 – 2 % was observed. Results are discussed in detail, which have enabled to take required decision on implementation of Map Controlled PCJ in the specific engine application.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In order to illustrate the constant development of the automatic transmission controls area, this paper describes how the garage shift calibration works in vehicles with transverse front wheel drive powertrains.</div><div class="htmlview paragraph">A garage shift (GS) is the turbine speed transient commanded by the shift lever movement from Park to Drive or Reverse, from Neutral to Drive or Reverse, from Drive to Reverse, from Reverse to Drive, or from Drive or Reverse to Neutral [<span class="xref">1</span>].</div><div class="htmlview paragraph">A usual metric to verify the garage shift comfort is the data acquisition of the fore-aft acceleration on the seat track, but also the shift time should be considered, as well as the clutch energy and the repeatability of the shift feeling for different temperatures and engine idle speed levels.</div><div class="htmlview paragraph">This paper demonstrates the transmission calibration strategies to determine a sensitive and a non-sensitive garage shift and its interactions with the engine calibration.</div><div class="htmlview paragraph">Many factors may affect the garage shift calibration, like hardware controls (software and calibration), hydraulic system (fluid and actuators), clutches (design and friction material) step ratios, and non-transmission factors such as idle control and engine torque signal accuracy [<span class="xref">2</span>]. The vehicle’s sensitivity to torsional driveline inputs and the powertrain mounts configuration also influence the shift quality perception.</div></div>

<div class="htmlview paragraph">Presenting a brand new approach to heat exchangers for engines, transmissions, hydraulic systems, etc.</div> <div class="htmlview paragraph">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.</div> <div class="htmlview paragraph">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.</div> <div class="htmlview paragraph">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.</div> <div class="htmlview paragraph">The inner surface of the core, the water side, is extremely tolerant to dirty water and gives negligible pressure drop.</div> <div class="htmlview paragraph">This new heat exchanger is made of only one metal, aluminum. The characteristics of corrosion are therefore easy to define.</div>

<div class="section abstract"><div class="htmlview paragraph">GREATER ease of servicing is one of the ultimate goals in the development of dry-type air cleaners. The authors acknowledge, however, that the oil-bath cleaner is a rugged proved component that has done a good job for the farmers who serviced it properly.</div><div class="htmlview paragraph">This paper describes studies made in Illinois of oil-bath and dry air cleaners in field service. At the same fuel/air ratios, the maximum horsepower of a test engine was greater with the dry-type filter than with the oil-bath cleaner.</div><div class="htmlview paragraph">It was found that with AC fine dust and steady airflow, the oil-bath cleaners had significantly lower efficiencies than the dry-type filter. At less than rated airflow the efficiency of the oil-bath cleaner decreased while that of the dry filter remained high.</div></div>

<div class="htmlview paragraph">A farm tractor protection cab made of thin steel sheet pressings is described. The cab is designed and produced using entirely automotive-type procedures. Curved glasses and a dampening suspension of the glasses are found to be an important means of achieving a low noise level in the cab.</div> <div class="htmlview paragraph">Using the pressing technique when producing a steel cab makes it possible to give the various cab details rigidity with a minimum of material. When welded together, these details form a very stiff cab body, which gives the necessary mechanical strength.</div> <div class="htmlview paragraph">The curved surfaces, the radii, and the round forms, which from a tooling point of view are natural for pressed steel parts, also have a vibration-dampening effect on the entire cab construction, thus making it easier to design a quiet tractor cab.</div> <div class="htmlview paragraph">Mounted on a farm tractor of conventional design, the cab meets the noise rating number ISO N85.</div>

<div class="section abstract"><div class="htmlview paragraph">Over the past few years, drastic steps have been taken to regularize emission norms for various segments in India. One of the major reforms done was separating construction equipment and agricultural vehicles to differentiate and define regulations effectively. Transition Emission Measure TREM IV emission norms have been implemented in India, and TREM V will also be launched soon. These changes to emission norms have increased the need for the implementation of after-treatment systems (ATS) in off-highway vehicle applications. Earlier, these systems were widely used for on highway vehicles. These emission norms target hydrocarbons, particulate matter, nitrogen oxide and carbon monoxide. Due to which, the demand for diesel oxidation catalysts (DOC) and diesel particulate filters (DPF) has increased in construction equipment and agricultural vehicles.</div><div class="htmlview paragraph">Although ATS has been in use for a long time, there are certain challenges associated with its integration into vehicles. As the space available on the vehicle is limited and there are high-temperature neighboring components, this can impact performance and increase safety-related risks for the end user. This study focuses on the integration challenges of ATS in tractor applications. Due to the limited available space, ATS must be integrated under the bonnet of vehicles for some applications. During static regeneration, the high temperature from the ATS heats up the bonnet and can pose a safety risk to the end user operating the vehicle. Some of the best practices to control heat rise from ATS have been discussed in this paper.</div><div class="htmlview paragraph">To understand the heat transfer in the actual application around ATS, a comprehensive repeatable test was done on the actual vehicle to collect critical information during various operating cycles of the vehicle. Air velocity was also measured during vehicle operation to understand the impact of forced convection on ATS. Validation of the actual test with steady state CFD simulation helped understand heat transfer on ATS. Validated CFD thermal model helps in comparing various design changes and identify thermal risks during high temperature conditions. A close correlation between the test and CFD simulation also helped in understanding the risk of high temperatures on the bonnet of vehicles. The modeling approach, test setup details, and critical factors affecting the performance of ATS have been discussed in detail in this study.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The most widely used type of windshield wiper system employs a coil spring for wiper arm pressure generation. This spring is fixed between the arm head (fixed part) and wiper arm (moving part) and the tension in the spring is responsible for pressure generation. The present arrangement although being unsophisticated design, has following drawbacks: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Inability to change wiper arm pressure according to change in vehicle speed.</div></li><li class="list-item"><div class="htmlview paragraph">Inability to provide constant arm pressure during the complete range of motion along varying curvature of windshield.</div></li><li class="list-item"><div class="htmlview paragraph">Inability to reduce/remove the continuous pressure on wiper blade when vehicle is parked for long durations resulting in permanent deformation of wiper blade rubber.</div></li></ul></div><div class="htmlview paragraph">This paper describes how electromagnets can be used to overcome the above stated inherent limitations of the windshield wiper system. An electromagnet is a device which produces magnetic field on application of electric current. It consists of electrical conductor wound around a magnetic core. Unlike a permanent magnet whose magnetic field is fixed, the magnetic field produced by electromagnets can be changed or even reversed very quickly by controlling the input current. Since, magnetic fields attract or repel each other depending upon their direction, hence, electromagnets can be used to produce variable force of attraction or repulsion. This enables electromagnets to be used as a spring with adjustable stiffness.</div></div>

<div class="htmlview paragraph">The present work concerns the analysis of a concept for a new variable valve actuation system for internal combustion engines, denoted HVC (Hydraulic Valve Control system). The system is an electro-hydraulic device which aims at minimizing the power consumption required for the valve actuation. Unlike lost motion devices, where the excess pumped oil is wasted in order to control the lift profile, the HVC system uses a reduced quantity of energy to ensure the actual lift profile. For that reason interesting potentialities to increase the global fuel conversion efficiency of the engine are expected, in addition to the benefits deriving from the control flexibility.</div> <div class="htmlview paragraph">The HVC system has been modeled by means of an hydraulic simulation tool, useful for the dynamic analysis of mechanical and hydraulic systems. In this work the main elements of the device will be described and their relevant modeling parameters will be discussed. The model has been validated by means of experimental lift data obtained in a prototype test bench. In order to properly tune the numerical model various operating conditions have been concerned.</div> <div class="htmlview paragraph">The system shows a high flexibility in the control of the lift and timing. The predicted power consumption is very attractive. The main effects of the oil pressure and of the oil temperature are discussed.</div>