Calculation of volumetric hydraulic drive of automobile crane

Contents

Contents

Introduction

1. Initial data for calculation of hydraulic drive

2. Principle Hydraulic Diagram

3. Calculation of volume hydraulic drive

3.1. Determination of hydraulic drive and pump power

3.2. Pump selection

3.3. Determination of internal diameter of hydraulic lines, liquid speeds

3.4. Calculation of pressure losses in hydraulic lines

3.5. Calculation of hydraulic motor

3.6. Thermal calculation of hydraulic drive

Conclusion

List of used literature

Introduction

The course design of volumetric hydraulic drives contributes to the generalization and consolidation of theoretical knowledge of students, is aimed at developing the skills of students' independent creative work, using reference literature, GOST, normals, performing calculations, drawings and compiling text design documents.

The object of the course design is the hydraulic drive of the automobile crane. The purpose of the calculation is to determine the parameters of the hydraulic drive, standard sizes and the nomenclature of the hydraulic equipment used .

By volumetric hydraulic drive is meant a set of devices, which include one or more volumetric hydraulic motors designed to drive mechanisms and machines using working fluid under pressure.

The modern level of development of construction and road engineering is characterized by the wide use of a volumetric hydraulic drive. The wide use of the hydraulic drive is due to a number of advantages over other types of drive:

1. High compactness with small weight and overall dimensions of hydraulic equipment compared to the weight and overall dimensions of mechanical drives of the same power, due to the absence or use in a smaller number of elements such as shafts, gear and chain reducers, couplings, brakes, ropes, etc.

2. Possibility of realization of large gear ratios. In a volumetric hydraulic drive using high-torque hydraulic motors, the gear ratio can reach 2000.

3. Small inertia, providing good dynamic properties of the drive. This makes it possible to reduce the cycle time and increase the performance of the machine, since the actuation and reversal of the working elements are carried out in a fraction of a second.

4. Stepless speed control that increases drive engine utilization, simplifies drive automation, and improves driver operating conditions.

5. Convenience and ease of control, which cause a small energy consumption by the machine operator and create conditions for automation not only of individual operations, but also of the entire process performed by the machine.

6. Independent arrangement of the assembly units of the drive, allowing them to be placed most expediently on the machine. The pump is usually installed at the drive engine, hydraulic motors - directly at the actuators, control elements - at the driver's console, hydraulic actuators - in the place most convenient according to the conditions of the layout.

7. Reliable protection against overloads of the drive engine, drive system, metal structures and working elements due to the installation of safety and overflow hydraulic valves.

8. Simplicity of mutual conversion of rotational and translational movements in systems of pump - hydraulic motor and pump - hydraulic cylinder.

9. The use of unified assembly units (pumps, hydraulic motors, hydraulic cylinders, hydraulic valves, hydraulic distributors, filters, pipeline connections, etc.), which allows reducing the cost of the drive, facilitating its operation and repair, as well as simplifying and reducing the process of designing machines.

Initial data for calculation of hydraulic drive

Calculation of volumetric hydraulic drive

To calculate the hydraulic drive, the following basic initial data are required: output parameters of the actuator hydraulic motors (values of torque and rotation speeds of the shaft); operating modes, hydraulic circuit diagram; nominal pressure in the hydraulic system; boundary ambient temperatures, etc.

When calculating the hydraulic drive, a number of assumptions are taken, the main of which are the following: working fluid is considered incompressible; liquid temperature, basic physical properties of the liquid (density, viscosity, etc.) are assumed to be constant; the steady-state operation mode of the hydraulic drive is considered; hydraulic resistance coefficients are constant; fluid flow rupture during hydraulic drive operation does not occur; supply of the pump feeding the hydraulic system is constant.

3.1. Determination of hydraulic drive and pump power

Power of hydraulic drive is determined by specified loads and speeds of hydraulic motors providing drive of actuators.

3.4. Selection of hydraulic equipment, operating fluid conditioners

Hydraulic equipment (distributors, check valves, hydraulic locks, safety valves, etc.) is selected according to the nominal pass and nominal pressure. An additional parameter for hydraulic equipment is the nominal flow rate of working fluid.

The conditional passage dy dg GOST 1651680 refers to the diameter of a circle rounded to the nearest value from the established row, the area of ​ ​ which is equal to the area of ​ ​ the characteristic flow section of the device channel or the area of ​ ​ the flow section of the connected pipeline.

Since the nominal pressure pnom = 15 MPa, we select the hydraulic distributor whose technical characteristics are given in Table 1.

Air conditioners are selected depending on the requirements; applied to working fluid purity according to the following parameters: nominal pass, nominal filtration fineness, nominal throughput capacity and nominal pressure. Therefore, before selecting them, it is necessary to establish requirements for filtration fineness due to the type of the selected pump.

Selection of working fluids is made on the basis of analysis of operating modes and operating conditions of hydraulic drive taking into account design features of installed hydraulic equipment, mainly design features of used pump. The operating fluid shall meet the requirements.

3.4. Calculation of pressure losses in hydraulic lines

Determination of pressure losses during fluid movement in hydraulic lines is necessary for more accurate calculation of hydraulic motor, as well as for determination of hydraulic efficiency of hydraulic drive.

Pressure losses are determined separately for each hydraulic line (suction, pressure, drain) at a certain working fluid temperature.

3.6. Thermal calculation of hydraulic drive

The thermal calculation of the hydraulic drive is given in order to determine the temperature of the working fluid, the volume of the hydraulic tank and to determine the need for special heat exchange devices.

The main reasons for heat generation in the hydraulic drive are: internal friction of the working fluid, throttling of the liquid during the passage of various elements of the hydraulic drive, friction in hydraulic equipment, etc.

The amount of heat generated in the hydraulic drive per unit time is equivalent to the power lost in the hydraulic drive.

Conclusion

In this course project, it was proposed to perform the calculation of an automobile crane. During the work, the capacities of the hydraulic drive and pump were determined. The choice of the gear pump NSh50A3 is made. Internal diameters of suction, pressure and drain hydraulic lines are determined, as well as speed of liquid movement along them. Hydraulic equipment and operating fluid were selected. Pressure losses in the hydraulic lines were calculated, the MGP80 hydraulic motor was selected, and the hydraulic drive was also heat calculated.

List of used literature

Calculation of volumetric hydraulic drive of transport and technological machines during course and diploma design: Methodological guidelines/Comp. N.S. Galdin. - Omsk: SibADI, 2013. – 28 pages.

Alekseeva T. V., Galdin N. S., Sherman E. B., - Hydraulic machines and hydraulic drive of mobile machines: Training Manual. - Novosibirsk: - Publishing house Novosib. Unta, 1994. - 212 sec. - ISBN 5-7615-0228-

Tasks for course work on hydraulic drive of road construction machines/Comp.; T.V. Alekseeva, N.S. Galdin, V.S. Bashkirov, V.P. Sharonov; SibADI. - Omsk, 1984.- 36 s.

Appendices to tasks for heading work on hydraulic drive of road building machines/Comp.; T.V. Aleksavva, N.S. Galdin, V.S. Bashkirov, V.P. Sharonov; SibADI.- Omsk, 1984.- 36 s.

Elements of volumetric hydraulic drives of construction and road

machines and their choice in course and degree design,

Part II; Hydraulic Equipment: Methodological Guidelines/Comp.: T.V. Alekseeva, V.S. Bashkirov, N.S. Galdin; SibADI. - Omsk, 1983. - 30 s.

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