Axially adjustable piston pump - course design

Contents

Introduction

Overview and analysis of existing diagrams and constructs

Selection of diagram of the designed hydraulic machine and description of its operation

Calculation of hydraulic machine parameters

Calculation of hydraulic machine efficiency

Strength calculation of hydraulic machine parts

Calculation of thermal mode of hydraulic machine

Conclusion

List of sources used

Project Description

Explanatory note 52 p., 22 Fig., 11 sources

AXIAL PISTON PUMP, INCLINED CYLINDER BLOCK, PISTON, PUMP FEED, NOMINAL PRESSURE, GEOMETRICAL PARAMETERS, HYDRAULIC SCHEMATIC DIAGRAM, ASSEMBLY DRAWING, PUMP EFFICIENCY

Subject of investigation is adjustable axial-piston pump with inclined cylinder block for hydraulic drive of machine with two hydraulic cylinders.

The purpose of the work is to develop and design an adjustable axial-piston pump with an inclined cylinder block for the hydraulic drive of the machine.

During the work, an analysis of literary and patent sources was carried out, the main geometric parameters of the pump were calculated, the strength calculation of the main parts of the pump was carried out, and the energy and thermal calculations of the pump were carried out.

As a result of the development and design of an axial-piston pump with an inclined cylinder block, a pump with a working volume of 50 cm3, a nominal pressure of 25 MPa and a maximum pressure of 32 MPa was first designed.

The designed and designed pump can be used in hydraulic drives of machines.

Introduction

Over the past 30 years, hydraulic drive has been widely used on earth-moving, lift-transport and other machines (excavators, auto graders, loaders, etc.).

Hydraulic drives of the undercarriage and working bodies are used in agricultural engineering on tractors, combines and agricultural machines with active drive of working bodies. Using a hydraulic drive allows increasing the productivity of machines and equipment, reducing their overall dimensions and weight, obtaining new characteristics of machines, expanding the possibilities of automating machines and mechanisms. Simultaneously with the expansion of the field of application of the hydraulic drive, the output of hydraulic equipment is significantly increased.

Characteristic features of the development of the hydraulic drive are: increased unit power, reduced noise and increased durability of hydraulic machines. Besides, increase of unit power, as grafted, is achieved by increase of nominal pressure in hydraulic systems and rotation speed of drive shafts of pumps and hydraulic motors, and expansion of speed range is provided, both due to increase of its upper boundary, and due to reduction of lower boundary, stable minimum rotation speed.

The creation of hydraulic machines (primarily hydraulic motors) with a stable minimum rotation speed will significantly simplify the kinematic goals of the actuators, increase the efficiency of the drive, reduce its weight and dimensions.

The hydraulic machine (hydrocar) is called the car intended for transformation of mechanical energy to energy of moving liquid or on the contrary. Depending on the type of energy conversion, hydraulic machines are divided into pumps and hydraulic motors.

A pump is a hydraulic machine for creating a flow of working fluid by converting mechanical energy into the energy of a moving fluid. Hydraulic motors are used to convert energy of working fluid flow into mechanical energy of hydraulic machine outlet link.

According to the principle of action, hydraulic machines are divided into two classes: dynamic and volumetric. Energy conversion in dynamic hydraulic machines occurs when the amount of fluid movement changes. In volumetric hydraulic machines, energy is converted as a result of periodic change of volume of working chambers hermetically separated from each other.

In volumetric pumps, liquid moves due to periodic change of volume of chamber occupied by it, which alternately communicates with pump inlet and outlet. Volumetric hydraulic machines can in principle be reversible, that is, operate both as a pump and as a hydraulic motor. However, the reversibility of specific hydraulic machines is associated with the features of their design.

In modern technology, many varieties of hydraulic machines are used. Volumetric and vane pumps and hydraulic motors became most widespread.

Currently, axial-piston hydraulic machines of the MN type with an inclined block have become widespread in mechanical engineering. These hydraulic machines are designed to operate at an ambient temperature of - 50 to + 50 ° C, and can operate on mineral oils having a temperature of - 40 to + 70 ° C.

A rotary axial-piston hydraulic machine is a machine in which the working chambers rotate relative to the axis of the rotor, and the axes of the pistons or plungers are parallel to the axis of rotation or make an angle with it less than 45 °. An important parameter for many applications is the acceptability (speed) of the pump when regulating the supply. The change of supply from zero to maximum is carried out in some types of axial-piston hydraulic machines for 0.04 s and from maximum to zero - for 0.02 s.

The most common number of cylinders in axial piston machines is 7-9, the diameters of hydraulic machine cylinders are usually in the range from 10 to 50 mm, and the working volumes of machines are in the range from 5 to 1000 cm3. The maximum angle between the axes of the cylinder unit and the inclined washer is usually 18 ° in the pumps.

Selection of diagram of the designed hydraulic machine and description of its operation

Let us consider the operating principle of the hydraulic system, the diagram of which is shown in the drawing.

The hydraulic system operates as follows. At closing of this or that limit switch by working element, control signal is supplied to control device, from where it is supplied to certain electromagnet of one of hydraulic distributor.

At the initial moment of time, the accumulator is charged and then, the pressure switch RD generates a signal going to the electromagnet E1 of the distributor R1 of the cylinder D1. The slide valve moves and the cylinder D1 moves rapidly, which is controlled by the throttle DP2 installed at the outlet. When the limit switch KV2 is reached, the signal for actuation of P3 distributor E3 is transmitted slowly to the limit switch KV3.

At achievement of the KB3 limit switch the signal on inclusion of E4 of the P2 distributor is given and inclusion of E6 of the P4 distributor happens movement Ts2 to the speed which is provided by a throttle of DR4 and regulators of an expense of RR. At achievement of the KB5 limit switch the signal on inclusion of E7 of the P4 distributor is given, there is a working giving which speed is determined by RR expense regulators.

Upon reaching the limit switch KV6, a signal is given to disconnect E7 of the five-way distributor P4, an operating supply occurs, the speed of which is determined by the flow controllers PP. At achievement of the KB7 limit switch the signal on inclusion of E5 of the five-running P2 distributor is given and there is a fast withdrawal of a cylinder of Ts2 to the KB4 limit switch. Speed of quick withdrawal is controlled by throttle DP3.

The KB4 limit switch makes inclusion of electromagnets of E2. There is a fast withdrawal of a cylinder of Ts1 to the KB1 limit switch. Movement of cylinder D1 at fast retraction is controlled by throttle DP1 installed at the outlet.

If necessary, the cycle will repeat.

Work of all hydraulic system can be stopped by means of installation of P1 and P2 distributors in neutral situation, and by means of the safety valve of indirect action of RC at inclusion of an electromagnet of E8. This valve is also used to protect the hydraulic system from overloads that may occur when an unplanned overload on a working member, when pipelines or hydraulic equipment is contaminated, etc. The valve actuation pressure, i.e. the maximum possible pressure in the hydraulic system, is adjusted using the MN control pressure gauge.

The hydraulic system uses two filters for cleaning working fluid from contaminants - at the inlet (after the pump) and on the drain line to the tank. Filter contamination control - visual.

For an analogue for designing a hydraulic machine, we take patent F04B1/26; RU 2275531 C1 (see Figure 1.13) [10]. The principle of pump operation is as follows. proposed axial-piston hydraulic machine with adjustable working volume has housing, shaft with flange installed in housing of hydraulic machine in bearings, rotating block of cylinders with pistons pivotally connected to flange of shaft, distributor interacting with cylinder block. Distributor is installed in housing with the possibility of movement along surface of rotation. Differential piston of pump displacement control system interacts with distributor by means of pin, in which slide valve is installed, which rests on arm of double-arm lever. Opposite arm of lever is spring-loaded. Axis of lever rotation is arranged in zone of maximum volume of hydraulic machine so that at increase of hydraulic machine working volume, i.e. at increase of angle of cylinder block inclination distance from spool axis to axis of double-arm lever rotation decreases accordingly. Control plunger is installed between spring and double-arm lever and rests on lever through thrust bearing. In the bearing there is a hole communicating with the hole in the plunger, which communicates with the chamber, into which liquid is supplied under pressure. Increased sensitivity and efficiency of hydraulic machine when used in transmissions due to provision of function of hyperbolic dependence of working volume on pressure.

The following changes were made to the design of the pump: two roller conical bearings were replaced with one ball radial and two ball radial-thrust bearings. The double-arm lever of the pump displacement control system is located at the top in the control system housing (see assembly drawing).

Conclusion

During the course project, an axial-piston adjustable pump with an inclined block was calculated, and its connection scheme was chosen.

In addition, the existing axial piston machines were reviewed and analyzed. Patent search and analysis was carried out. Strength calculation of pump parts was also performed. The volumetric efficiency has been determined to be ¼ 0 = = 0.995, the mechanical efficiency is ¼ m = 0.99, the hydraulic efficiency is ¼ g = 0.994, and the total efficiency of the pump?? = 0.979. Design working volume of the pump V0 = 50 cm3.

All heat energy from the pump is removed through its surface and working fluid, as a result of which the cooler may not be connected to the system.

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