Performance,Testing,of,Tractor,Hydraulic,Fluids,to,Simulate,In-Use,Conditions In addition to

　　Abstract:Tractor hydraulic fluids are tested to maximize their performance levels and to ensure manufacturer′s standards are met. Common tractor hydraulic fluid tests include: Gear Wear Protection, Brake Chatter Reduction, Wet-Clutch Capacity, and Pump Performance tests. These tests are run by Southwest Research Institute, in the U.S.A., for tractors built by John Deere and Case-New Holland. This paper details current methods for evaluating tractor hydraulic fluids. The tests that are described utilize full size equipment and were developed by the tractor′s original equipment manufacturers (OEMs).
　　Key words：performance testing; tractor hydraulic fluid; in-use condition
　　中图分类号：TE626.38 文献标识码：A
　　
　　0 Introduction
　　
　　Tractor hydraulic fluids (THFs) are unique products that lubricate highly stressed gears, axles, wet-clutches, and bearings in transmissions, oil-lubricated brake systems, and hydraulic pumps. Testing tractor hydraulic fluids requires the use of procedures specifically designed to evaluate fluid properties that are unique to tractor fluids. These properties are not found in gear lubricants, transmission fluids, and engine oils.
　　Many tractor hydraulic fluid test procedures have been developed to replicate problems that have occurred on equipment in the field. Test procedures are commonly developed to screen out fluids that will allow the equipment to exhibit undesirable operating characteristics or cause the equipment to fail prematurely. Development of the specific procedures and regulations for testing tractor hydraulic fluids often follows a different course of action than the test development of other classes of lubricating oil. While testing procedures for passenger car motor oils, gear lubricants, and automatic transmission fluids are typically developed by standards organizations and committees, testing procedures for THFs are almost always developed by the original equipment manufacturer. It is not unusual for each manufacturer to develop their own series of requirements specific to the needs of their equipment. Overviews of several current tractor hydraulic fluid test procedures are presented in this paper.
　　
　　1 Discussion
　　
　　Tractor Hydraulic Fluid testing services can be categorized into two types of tests： field tests and laboratory tests. Within the laboratory test category, most manufacturers′ specifications call for a series of both bench and dynamic test procedures. Bench tests are performed solely to evaluate the test fluid′s properties in relation to oxidation, viscosity, and other similar chemical and physical properties. This discussion will focus on the dynamic laboratory test procedures set forth by the OEMs.
　　1.1 John Deere Tractor Tests
　　The most common specifications in the field of THF testing are those set forth by John Deere. The current JDM J20specifications have been in existence for decades. Claiming to have met the requirements set forth in these specifications requires the successful completion of each test outlined in the JDM J20 specifications, including the tests described below.
　　1.1.1 JDQ-84: Sauer-Danfoss Dynamic Corrosion Test
　　Conducted for the John Deere JDQ-84 specification, the objective of this test is to identify oils that, when contaminated with limited amounts of water, can serve as a suitable fluid for hydrostatic transmissions and hydraulic pumps found on agricultural and industrial off-highway equipment. The test is designed to screen out oils that cause corrosion of copper-containing metals, which are common in high-pressure pumps. The oil′s performance is quantified by three factors: the change in volumetric efficiency of the pump during the test, the condition of the pump parts after the test is complete, and the results of post-test chemical analysis of the test oil.
　　The test apparatus consists of a Sauer-Danfoss Series 90 pump driven by an electric motor at constant speed. A large stainless steel fluid reservoir contains the test fluid. The test is run for 225 hours at constant input speed, constant pump charge pressure, constant pump case pressure, constant working loop temperature, and constant reservoir temperature. The pump output pressure varies throughout the test according to the values outlined in Table 1.
　　When the test is complete, the pump parts are rated based on their condition in comparison to those used in periodic reference oil tests. The passing reference oil consistently performs well, while the failing reference oil has never completed the procedure. This is a result of premature wear on the pump hardware as seen in Figure 1. Prior to the test, all critical brass components are measured to the nearest 0.0001-inch (0.00254 mm) as a standard to compare to post-test component measurements. When compared to the passing reference oil, successful test oils will have similar levels of distress on the brass and steel components, as well as a flow loss of less than 10%.
　　1.1.2 JDQ-94: Power Shift Transmission Clutch and Friction Test
　　The objective of this test is to assess the effect of a tractor hydraulic fluid on clutch stall time, dynamic friction coefficient, and clutch disc wear on a power shift transmission (PST) in accordance with the John Deere JDQ-94 specifications.
　　The test is conducted on a computer-controlled test stand using a modified 15-speed John Deere 4850 transmission, powered by a six-cylinder diesel engine, as seen in Figure 2. An eddy current dynamometer coupled to the output shaft of the transmission provides the loading.
　　A control system automatically cycles the transmission through 2000 clutch slipping cycles, each lasting eight seconds. Each test cycle consists of a partial engagement in which the clutches absorbs heat energy followed by a cool-down period in which the clutches are fully engaged. During these cycles the lube oil temperature, dynamometer torque, dynamometer speed, engine speed, and transmission ratio are held constant.
　　During the test slipping cycles, the clutch plates can become glazed and worn, like the one shown in Figure 3, causing a reduction in friction coefficient and torque holding capacity. The clutch′s ultimate capacity is measured by performing stall tests after the 2000 slip cycles are complete.
　　To perform the stall tests, the transmission is placed in 12thgear and the engine is set to a constant speed, with the dynamometer load set at its maximum limit. When the clutch is engaged, the engine should stop within 5 seconds. If the engine does not stall, the test is halted. If the engine stalls, the dynamometer load is removed, the engine is restarted, and the stall procedure repeated. Three stall tests are preformed and the results are used to calculate a friction coefficient and stall time. Successful completion of the test requires these values to fall within a predetermined range based on the performance set forth by passing reference oils.
　　1.1.3 JDQ-95/102: Spiral Bevel and Final Drive Gear Wear
　　This 50-hour test evaluates the effectiveness of tractor hydraulic fluids in protecting spiral bevel gears and final drive planetary reduction gears from scoring, surface distress, and wear. This test is performed in accordance with the John Deere JDQ-95 and JDQ-102 specifications. The test fixture is a drive axle assembly powered by a six-cylinder diesel engine through a power shift transmission. Two low-speed, high-torque brake dynamometers absorb the axle output power. These dynamometers are seen attached to the axle housing ends in Figure 4.
　　Before going through the JDQ-95 procedure, the test fluid is sheared to decrease its viscosity, thus simulating use of a used fluid during the gear wear test. This shearing sequence, known as the JDQ-102 procedure, is performed on a specialized test fixture.
　　The 50-hour JDQ-95 test is run in two parts. The first 20 hours are run at high speed, high torque, and high temperature. This is when scoring usually occurs. The ring and pinion are visually inspected for scoring after 2 and 20 hours. The last 30 hours of the test are run at lower speed, while the axle loading and temperature are maintained at the same levels.
　　When the test is complete, the axle is disassembled so that both the ring and pinion from the spiral bevel drive gear set may be inspected. Gear tooth wear is also measured on five teeth equally spaced around the sun pinion shafts. A comparison, like that in Figure 5, is then made between the gear wear caused by the test oil and passing reference oil.
　　1.1.4 JDQ-96: 1400 Series Axle Brake Chatter, Capacity, and Durability
　　The objective of this procedure is to assess the effect of test oils on brake noise and torque capacity as compared to those values demonstrated by a known, high quality reference oil.
　　This test uses a full-size John Deere 4640 tractor, with a modified power shift transmission, as the power source. This drives a 1400 series industrial axle equipped with annular wet disc brakes. The brake, as seen in Figure 6, consists of a rotating steel disk with paper friction material bonded to it, that is clamped between a stationary steel piston and backing plate. This axle also has a spiral bevel gear set and planetary reduction gears like those of the JDQ-95 axle.
　　This test procedure consists of 30,000 brake engagements. At 1,000, at 10,000, at 20,000, and finally at 30,000 brake engagements, a series of brake chatter checks are performed. Different wheel speeds, brake application pressures, and temperatures are evaluated during the chatter checks. The test report contains a comparison of the candidate oil′s brake chatter, brake capacity, and brake disk wear to the five most recent reference runs. An example of this comparison is provided in Figure 7.
　　1.2 Case-New Holland Tractor Tests
　　Case New-Holland (CNH) has also developed a common set of testing procedures to evaluate tractor hydraulic fluids. Unlike the John Deere procedures, several of the CNH tests utilize complete tractors as their test fixtures. Several of these procedures are discussed in detail below.
　　1.2.1 New Holland Ford 8340 16×16 Transmission Driveline Stall Test
　　This test evaluates the tractor′s clutch capacity to determine if the clutch can transmit enough torque to stall the engine in case of an overload. The test is run on a Ford 8340 tractor with a 16×16 transmission.
　　With the tractor anchored, 400 engine stalls are performed; 100 stall cycles in each of four different gears. Each gear is selected to maximize the load on one of four clutch packs in the transmission. At the completion of the test, all clutch plates must still be functional.
　　1.2.2 New Holland Ford 8340 16×16 Transmission High-Energy Clutch Test
　　This is a clutch life test, run with a controlled load, to evaluate the effects of a hydraulic fluid on clutch torque capacity and durability. This test is run for 450 clutch slip cycles, using two different transmission ratios. The use of different ratios ensures that both of the transmission′s two clutch packs are tested. The input power, input torque, and transmission sump temperature are held constant throughout the entire test. Clutch application pressure is modulated to maintain a consistent torque. The test fixture used for this procedure is shown in Figure 8.
　　The test is run until the torque capacity of the clutch can no longer support the required input torque, or until the 450 cycles are achieved. A clutch passing the test must still be functional when the test is complete.
　　1.2.3 New Holland Jenkins Cycle Test
　　This is a 660-hour drive train endurance test that evaluates the effect of the candidate hydraulic fluid on the transmission, final drive gears, and bearings. The test is primarily performed using a Ford 8340 tractor with a 16×16 transmission. However, since this procedure is performed on the universal tractor axle dynamometer shown in Figure 9, it can also be applied to any large tractor.
　　Prior to each procedure, the test tractor is rebuilt with new gears and bearings. The tractor is then operated on a universal tractor axle dynamometer through a series of six, 110-hour cycles, for a total test length of 660 hours. During the test, the tractor is run in all 16 forward speeds and several reverse speeds. The tractor′s output power and driveline fluid temperature are held constant. Acceptance criteria are based on the condition of the gears, bearings, and other lubricated hardware when inspected in a post-test evaluation.
　　
　　2 Conclusion
　　
　　Although the field of tractor hydraulic fluid testing has a well-established history, the development of new fluids as a result of updated equipment, emerging technologies, and changing market trends, demands continuous testing to ensure compliance with performance standards.
　　The tractor OEMs are constantly developing new equipment, often requiring the existing fluid specifications,and their related tests, to be updated. Staying on the forefront of these changes is an absolute necessity, one that can be accommodated by focusing on the implementation of highly adaptable, universal test fixtures.
　　The future of tractor hydraulic fluids points towards increased development and testing of fluids designed to return higher operating efficiencies and longer equipment life. With the widespread usage of these fluids comes a new set of challenges and operating conditions that must not only be accounted for by equipment manufacturers, but also test developers.
　　These trends point towards a number of pending changes, updates to existing test procedures, as well as the development of new tests in the near future. These are all trends that make the tractor hydraulic fluid testing field a candidate for new growth and investment.
　　Acknowledgements
　　This paper has been received great help from John Deere Company, Case-New Holland Company and Mr. Lochte Mike from Southwest Research Institute in providing references and supports. We′d like to send our gratitude to their contribution here.
　　收稿日期:2009-10-23。
　　
　　作者简介：Brian J. Bentley，male, graduated from Dwight Look College of Engineering, Texas A&M University, College Station, one of the top engineering colleges worldwide. He holds the Bachelor of Science in Mechanical Engineering. He is an engineer of Specialty and Driveline Fluid Evaluations Section of Fuels and Lubricants Research Division, Southwest Research Institute.