Introduction. The article deals with the development of a device for evaluating technical condition on of volumetric hydraulic drives made in Russia and abroad at repair and service centres. Materials and Methods. The study uses the statements of theoretical mechanics and hydrodynamics, the basic principles of mechanisms and machines production. For technical condition evaluating of volumetric hydraulic drives, the method of hydraulic loading of hydraulic motor was applied. Reliability of results was confirmed during experimental settings of the hydraulic loading device stand. Results. A stand design with the hydraulic loading device was developed and put into practice for new technical condition evaluating of volumetric hydraulic drives, made in Russia and abroad, at repair and service centres. A property of the stand is the use of the hydraulic loading method when the torque (braking) moment on the shaft of the tested hydraulic rotor is created using a hydraulic machine. The stand consists of data processing and measurement units. The data processing unit is based on a multifunctional data acquisition board connected with a personal computer. The structure of the data measurement unit includes a frequency converter connected to an electric motor, a drive shaft for connecting the shaft of the tested hydraulic pump; hydraulic system having a hydraulic tank; suction, control, drain, and discharge lines and reversible flow chokes installed in discharge lines and connected with the hydraulic pump and hydraulic rotor; loading device with the reversible hydraulic pump, drive shaft joined with the shaft of the tested hydraulic motor. Additionally, reversible throttle flow meters are connected via special ports and electric lines to the data acquisition board. The developed stand allows evaluating the technical condition of most widespread models of volumetric hydraulic drives used in modern agricultural and road construction equipment. The stand is characterized by good energy efficiency, simplicity of design, low costs, good technical characteristics that make it competitive. Discussion and Conclusion. The new stand design with the hydraulic loading device allows implementating of the dynamic testing methodology and guarantees high accuracy of evaluating the technical condition of the most widespread Russian and foreign volumetric hydraulic drives at repair and service centres. Further improvement of the evaluating the technical condition of volumetric hydraulic drives is related to the development of specialized software for processing and analysing test results in real-time.

Currently, manufacturers for a reliable assessment of the technical condition of volumetric hydraulic drives use the dynamic test method, which allows you to determine the torque (braking) moment on the shaft of the tested hydraulic motor. There are diffi culties in reliably determining the value of the developed torque (braking) moment. (Research purpose) The research purpose is in constructing a mathematical model of the relationship between the developed torque (braking) moment of a volumetric hydraulic drive and the parameters of a hydraulic loading device. (Materials and methods) The article presents a hydraulic loading device that provides the necessary braking torque on the shaft of the tested hydraulic motor. Authors conducted one-factor and multifactor experiments-dynamic tests of the new Sauer-Danfoss series 90 volumetric hydraulic drive using a hydraulic loading device. The torque (braking) was monitored using a non-contact digital torque sensor M 425 3-A datum electronics and a digital indicator with LCD display (Results and discussion) As a result of one-factor passive experiments, the factors infl uencing the optimization parameter and the ranges of their variation were determined. A mathematical model of the relationship between the developed torque (braking) moment of a volumetric hydraulic drive and the parameters of a hydraulic loading device was obtained by a multi-factor active experiment. The article presents a complete planning matrix for a multi-factor active experiment, which refl ects the sequence of all possible combinations of factors that affect the optimization parameter. The most signifi cant factors affecting the value of the developed torque (braking) moment were: the pressure drop and the temperature of the working fluid in the hydraulic lines of the hydraulic loading device. (Conclusions) The mathematical model allows us to determine with high accuracy the developed torque (braking) of the volumetric hydraulic drive.

Currently, manufacturers for a reliable assessment of the technical condition of volumetric hydraulic drives use the dynamic test method, which allows you to determine the torque (braking) moment on the shaft of the tested hydraulic motor. There are difficulties in reliably determining the value of the developed torque (braking) moment. (Research purpose) The research purpose is in constructing a mathematical model of the relationship between the developed torque (braking) moment of a volumetric hydraulic drive and the parameters of a hydraulic loading device. (Materials and methods) The article presents a hydraulic loading device that provides the necessary braking torque on the shaft of the tested hydraulic motor. Authors conducted one-factor and multi- factor experiments-dynamic tests of the new Sauer-Danfoss series 90 volumetric hydraulic drive using a hydraulic loading device. The torque (braking) was monitored using a non-contact digital torque sensor M 425 3-A datum electronics and a digital indicator with LCD display (Results and discussion) As a result of one-factor passive experiments, the factors influencing the optimization parameter and the ranges of their variation were determined. A mathematical model of the relationship between the developed torque (braking) moment of a volumetric hydraulic drive and the parameters of a hydraulic loading device was obtained by a multi-factor active experiment. The article presents a complete planning matrix for a multi-factor active experiment, which reflects the sequence of all possible combinations of factors that affect the optimization parameter. The most significant factors affecting the value of the developed torque (braking) moment were: the pressure drop and the temperature of the working fluid in the hydraulic lines of the hydraulic loading device. (Conclusions) The mathematical model allows us to determine with high accuracy the developed torque (braking) of the volumetric hydraulic drive.

Introduction. Developing and adapting domestic technologies aimed at the maintenance and repair of foreign equipment is impossible without design documentation. The object of the study was the volumetric hydraulic drive Sauer-Danfoss of 90 series consisting of a hydraulic pump 90R100 and a hydraulic motor 90M100. The purpose of the study is to determine the nominal dimensions and permissible variations in dimensions of critical parts that affect efficiency of the foreign hydraulic drive. Materials and Methods. The first series of bench tests was devoted to finding the ranges of variation of significant factors influencing the volumetric efficiency. In the second series, there were constructed regression models and by using the steepest ascend method, there were determined the values of critical parts wear and clearances in the critical parts connections affecting efficiency of the hydraulic drive Sauer-Danfoss. The nominal values of dimensions and permissible variations in dimensions of the hydraulic drive critical parts were determined by the dimensional analysis method. Results. The bench tests made it possible to determine the ranges of changes in critical parts wear and clearances in the critical parts connections of volumetric hydraulic drives that affect the volumetric efficiency. There has been proposed and implemented a comprehensive approach to determining the nominal dimensions and permissible variations in dimensions of critical parts of foreign equipment units. This approach suggests a combination of experimental studies (bench tests) and the method of dimensional analysis. For the new volumetric hydraulic drive Sauer-Danfoss series 90 the following values are received: diameter of a hole in the cylinder block under the piston 22,7+0,006 mm, piston diameter 22,7–0,004 mm, diameter of a hole in the rear cover under the spool 9,5+0,004 mm, spool diameter 9,5–0,0025 mm. Discussion and Conclusion. There have been determined the nominal values of dimensions, permissible variations in dimensions of critical parts, and the values of technological clearances in the critical parts connections of the new volumetric hydraulic drive Sauer-Danfoss series 90 that affect its efficiency. The results obtained are the basis for the development of technology to restore the efficiency and increase the durability of the volumetric hydraulic drive units of foreign origin.

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