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The working fluid (in the hydraulic drive) - liquid used as an energy carrier. As the working fluid used mineral, synthetic and semi-synthetic oils, water-oil emulsions, oil-in-water emulsion.

Requirements for working fluids:

Working fluids for hydraulic systems must meet the following requirements:
• viscosity in the desired range of values;
• high viscosity index (minimal dependence of viscosity on temperature);
• good lubricating properties;
• chemical inertness to the materials from which the elements are made of hydraulic drive;
• High Bulk modulus;
• high resistance to chemical and mechanical degradation;
• high thermal conductivity and specific heat capacity and low coefficient of thermal expansion;
• high flash point;
• non-toxic.

The functions of the working fluids

One of the functions of operating fluids - protection against corrosion of parts of hydraulic drive, so working fluids typically contain anticorrosion additives. Another function of the working fluid - heat exchange between the elements of the hydraulic system, as well as the heat exchange with the environment. As working fluid is carried out reliable lubrication of rubbing surfaces of parts of the hydraulic system components.

Accident prevention
Not Refer a mix between a different brand of working fluids, including, it is not recommended to mix different brands of mineral oils. This can cause foaming of the working fluid, which would entail a violation of the hydraulic actuator.


Literature
1. Lepeshkin AV, Mihailin AA, AA Sheipak ​​Hydraulics and gidropnevmoprivod: Tutorial, Part 2. Hydraulic Machines and gidropnevmoprivod. / Ed. A. Sheipak. - M .: MGIU, 2003. - 352 p.
2. hydraulics, hydraulic machines and hydraulic drives: A Textbook for engineering schools / TM Basta, S. Rudnev, BB Nekrasov et al. - 2nd ed., Rev. - M .: Mechanical Engineering, 1982.
3. Skhirtladze AG, Ivanov VI, CARE VN Hydraulic and pneumatic systems. - 2nd edition, enlarged. M .: IC MSTU "STANKIN", "Janus-K", 2003 - 544 p.

 Wikipedia

http://ru.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B1%D0%BE%D1%87%D0%B0%D1%8F_%D0%B6%D0%B8%D0%B4%D0%BA%D0%BE%D1%81%D1%82%D1%8C

 

Hydraulic drive (hydraulic) - a set of devices intended for propulsion machinery by hydraulic power.

Hydraulic drive is a kind of "water box" between the drive motor and the load (machinery or equipment) and performs the same function as the mechanical transmission (gearbox, belt drive, crank mechanism and so on. D.).

The functions of the hydraulic drive


The main function of the hydraulic drive, as well as mechanical transmission - converting mechanical characteristics of the drive motor in accordance with the requirements of the load (transformation of the form of motion of the output level of the engine, its parameters, as well as regulation, overload protection, etc.). Another function of the hydraulic drive - is the transfer of power from the drive motor to the working parts of the machine (eg, shovels - the transfer of power from the internal combustion engine to the bucket or hydraulic motor to drive the boom to the turret hydraulic motor, etc.).


Generally, in hydraulic power transmission is as follows:
1. The drive motor transmits torque to the pump shaft, which imparts energy working fluid.
2. The working fluid for hydraulic line through the regulatory apparatus enters the hydraulic motor, where the hydraulic power is converted into mechanical.
3. Thereafter, the working fluid of a hydraulic line back to the tank or directly to the pump.

Types of Hydraulic

Hydraulic drives can be of two types: hydrodynamic and displacement.

• In hydrodynamic drives used mainly kinetic energy of the fluid flow (and hence velocity of the fluid in the hydrodynamic drive large compared with speeds in bulk hydraulic drive).
• In bulk hydrodrives uses the potential energy of the working fluid pressure (hydraulic drives in bulk fluid velocity is not great - about 0.5-6 m / s).
Volumetric hydraulic drive - is hydraulic, which uses three-dimensional hydraulic machines (pumps and hydraulic motors). Volumetric called hydraulic machine, workflow which is based on the alternate filling of the working chamber and the fluid displaced by it from the oven. By volumetric machines include, for example, piston pumps, axial piston, radial piston, Gear pump and others.
One of the features that distinguishes the hydrodynamic volumetric hydraulic - high pressure hydraulic systems. Thus, the nominal pressure in the hydraulic excavator can be up to 32 MPa, and in some cases, the operating pressure may be more than 300 MPa, while hydrodynamic machines generally operate at pressures not in excess of 1.5-2 MPa.
Volumetric hydraulic much more compact and less weight than the hydrodynamic, and therefore it is most prevalent.

Resources fluid supply differ Drives

Hydraulic pump

In the hydraulic drive pump, is most prevalent in the art, the mechanical energy is converted into hydraulic pump, an energy carrier - the working fluid is pumped through the pressure line to the hydraulic motor, where the energy of the fluid flow is converted into mechanical. The working fluid (hydraulic fluid), giving their energy hydraulic motor, or returns back to the pump (closed loop hydraulic drive) or in the tank (open or open circuit hydraulic drive). In the general case of the hydraulic drive pump includes hydraulic transmission, hydroapparatuses, air conditioning working fluid gidroёmkosti and hydraulic lines.
The most widely used in hydraulic got axial piston, radial piston, vane and gear pumps.

Bulk hydraulic

In the main hydraulic drive working hydraulic fluid is pumped pumping stations in the pressure line to which users connect hydraulic energy. In contrast, the hydraulic drive pump, in which, as a rule, there is one (at least 2-3) hydraulic energy generator (pump) in the main hydraulic circuit of such generators may be a large number, and also hydraulic power consumers may be enough.

Hydraulic accumulator

In battery hydraulic drive, hydraulic fluid is fed into the hose from the pre-charged accumulator. This type of hydraulic drive is mainly used in machinery with intermittent operation.
The structure of the hydraulic drive
Mandatory elements are hydraulic drive pump and hydraulic motor. The pump is a hydraulic power source and hydraulic engine - its user, i.e. converts hydraulic energy into mechanical energy. Motion control of output links hydraulic motors is done either by control apparatus - chokes, valves et al., Or by changing the parameters of the hydraulic and / or pump.

As an obligatory component of the hydraulic drive are hydraulic line, which moves in the hydraulic fluid.

Critical to the hydraulic drive (primarily volume) is cleaning the working fluid from the contained therein (and constantly produced during operation) abrasive particles. Therefore, the hydraulic drive system is required to contain a filtering device (eg, oil filters), although in principle hydraulic some time and can work without them.
Since the hydraulic drive operating parameters substantially dependent on the working temperature of the hydraulic fluid in the hydraulic system, in some cases, but not always, the temperature control system is set (heated and / or cooling devices).

Sphere of application


Volumetric hydraulic drive is used in mining and road construction machines. Currently, more than 50% of the total fleet of mobile road construction machinery (bulldozers, excavators, graders, etc.) Is hydroficated.


In the machine tool hydraulic drive is also widely used, but in this area he feels strong competition from other types of drive [1].


Widely spread in hydraulic aviation. Saturation of modern aircraft hydraulic system is such that the total length of pipelines modern airliner can reach several kilometers.

In the automotive industry the most widely used as power steering, significantly increasing ease of driving. These devices are a kind of servo hydraulic drives. Hydraulic actuators are used in many other fields of engineering (aviation, tractor, industrial equipment, etc..).

Literature
1. hydraulics, hydraulic machines and hydraulic drives: A Textbook for engineering schools / TM Basta, S. Rudnev, BB Nekrasov et al. - 2nd ed., Rev. - M .: Mechanical Engineering, 1982.
2. Geyer VG, VS Doolin, Dawn AN Hydraulics and hydraulic: Textbook for universities. - 3rd ed., Rev. and add. - M .: Nedra, 1991.
3. Yufin AP Hydraulics, hydraulic machines and hydraulic. - M .: Higher School, 1965.
4. Alekseev T. Hydraulic and hydro Earthmovers. M., "Engineering", 1966. 140 p.
5. T. M. Basta Hydraulic actuators aircraft. 4th edition, revised and enlarged. Publishing House of the "Engineering", Moscow 1967
6. Lepeshkin AV, Mihailin AA, AA Sheipak ​​Hydraulics and gidropnevmoprivod: Tutorial, Part 2. Hydraulic Machines and gidropnevmoprivod. / Ed. A. Sheipak. - M .: MGIU, 2003. - 352 p.
7. Skhirtladze AG, Ivanov VI, CARE VN Hydraulic and pneumatic systems. - 2nd edition, enlarged. M .: IC MSTU "STANKIN", "Janus-K", 2003 - 544 p.
8. Podlipensky Victor Semenovich. Hydraulic and pneumatic.


 Wikipedia
http://ru.wikipedia.org/wiki/%D0%93%D0%B8%D0%B4%D1%80%D0%BE%D0%BF%D