Hydraulic coupling of fan drive - JP

Introduction.

Statistics on the change in the fleet of cars show that the average age of used cars is declining and does not exceed 8-12 years in recent years. At the same time, due to the improvement in the quality of cars, the main costs of their repair fall on the second half of this period.

The service market of all countries is characterized by a general picture - customers who bought a car from an official dealer are well in tech. service during the warranty period. However, after the expiration of the warranty period, up to half of these customers prefer to contact independent repair companies and small specialized workshops .

Demand for equipment service is constantly increasing for the following reasons:

- the fleet of machines will grow for many more years, as the developing economy requires more and more equipment;

- hundreds of new enterprises that purchase machinery will not acquire a repair base, counting on the service of manufacturers;

- old enterprises, trying to reduce the cost, get rid of repair shops, preferring to service machines in service companies;

- large enterprises, maintaining repair capacity, do not want to have stocks of parts, preferring urgent deliveries;

- consumers of the latest models cannot repair them themselves without wanting to spend on special equipment and training repairmen;

- private car owners, for whom the market has tightened the conditions of earnings, but also provided opportunities for their increase, do not want to spend time repairing cars.

The market economy requires minimizing the cost of any product in order to win competitions at prices from competitors. For all enterprises, a noticeable share of the fleet is foreign-made equipment, therefore, an important area of ​ ​ reducing cost is reducing the downtime of machines in repair. Only in large enterprises can this be ensured by the activities of their own well-equipped repair bases. For the rest, the maintenance of repairmen, relevant premises and equipment is a heavy burden. More and more owners of equipment understand the disadvantage of maintaining repair shops.

Private car owners also do not have free time to repair them - in the market conditions it is increasingly difficult to earn money, it takes more and more time to ensure normal living conditions.

Hired drivers, whose labor tensions increase from year to year, increasingly object to performing repairs on their own - this is not their specialty.

When organizing the repair of modern KamAZ cars and their units, which have a complex design and new additional systems, it was necessary to change the existing process of repair of engines and units based on the analysis of faults and defects of parts, assemblies and units at car repair enterprises; Implement best repair practices; to get and manufacture the additional equipment, the equipment, devices, strippers and the tool.

High-quality overhaul of car units is of great economic importance. The main factor in increasing the economic efficiency of overhaul of car units is the use of the residual resource of parts. About 75% of the parts after disassembly of the units going to overhaul have a large

residual resource and can be reused without restoration or after restoration at costs not exceeding 4060% of the list value of new parts.

Consequently, repair of machines even by replacing some parts and assemblies that have a small resource is always feasible and justified from an economic point of view. That is why during operation, cars undergo periodic maintenance and, if necessary, ongoing repairs - TR, which is carried out by replacing individual parts and units that have failed to work. This allows you to keep the car fleet in a technically serviceable condition.

In an economic downturn, the issue of repairing worn-out parts by restoring the original dimensions in various ways becomes relevant. All worn parts can be conditionally divided into three groups.

The first is parts that have completely exhausted their resource and must be replaced by new ones. The number of such parts is relatively small and is about 2530%. Parts of this group include pistons, piston rings, bearing inserts, various rubber products, rolling bearings, etc.

To the second, parts with an amount of approximately 3035% are parts that can be used for further operation without repair. This group includes all parts whose working surface wear is within acceptable limits.

The third group includes the remaining parts - approximately 4045%, which can be reused only after their restoration. This group includes most of the most complex and expensive parts - cylinder blocks, block heads, elbows and distributors.

new shafts, crankshafts of gearboxes and rear axle, shafts of checkpoint, etc. The cost of restoring these parts does not exceed 1545% of their cost during manufacture, and the resource, when using modern restoration methods, is practically not inferior to the new ones .

The vehicle brake system is critical to road safety. Wheel brakes are subject to such requirements as stable efficiency, smooth operation, resistance to pollution and corrosion, maximum reliability, strength, wear resistance, ease of maintenance and repair.

To date, in our country, with the transition to market relations, repair enterprises have almost ceased to exist, but the need for high-quality repairs, especially ongoing repairs, remains. But to carry out such repairs, the enterprise must have the necessary equipment, materials, capacities, premises not leased and, of course, qualified personnel. The current repair plants cannot provide the necessary level of repair due to outdated equipment, lack of materials, poor quality of components, lack of capital investments, low-skilled personnel. The quality of repair of machines does not meet the requirements of today. The standard established that the engine resource of cars after overhaul should be at least 80% of the resource of the new machine. Currently, this figure is at the level of 6065%. Improving the quality and cost of repairs is a priority task for repair production, as well as, in the context of the financial crisis, and for enterprises that operate and maintain machines - these tasks must be solved on the basis of the application of the latest achievements in science and technology.

To increase labor productivity at the repair enterprise, improve the quality of products and reduce the cost of repair, it is necessary to steadily introduce mechanization tools, various types of labor work, constantly improve the technology of disassembly, washing, defects, assembly, painting, drying, rolling; wide use of advanced repair technologies, introduction of reasonable time standards for these works.

At present, the issue of strengthening the connection of advanced science with production, the introduction of 21st century technologies is especially acute.

Only with such a partnership, as well as with improved training of workers and engineering personnel, it is possible to improve the state of repair production, improve the quality and reliability of repaired machines.

The cost of restoring parts is always lower than the cost of new spare parts, and with the use of modern technologies can reach the same resource, and sometimes higher. In this regard, the repair of units and assemblies will be constantly relevant.

The goals and objectives of pre-diploma practice are to acquire skills and skills in working in production as an engineering and technical worker, familiarize with the structure and organization of the enterprise's work, and with regulatory and technical documentation. During practice, I also consolidated theoretical knowledge of car maintenance and repair, directly took part in the operations of the technological process, for some time I worked as an understudy for a replacement foreman.

2.2.1 Washing of parts.

After disassembly of machines and units, parts are cleaned, degreased and washed. Cleaning and washing of parts has a great impact on the quality of major repairs. Complete removal of all contaminants improves the quality of the defect, increases the service life of the parts, reduces the occurrence of scrap. The rational choice of the method of washing and cleaning depends on the type of contaminants, the size, the configuration of the parts and the places of deposits of contaminants, economic considerations, but the main factor determining the choice of the method is the type of contaminants.

Pollution of road machines operating in difficult conditions of road construction can be divided into the following types: deposits of non-world origin (dust, dirt, etc.) and oil mud; lubricant residues; carbonaceous deposits; scale; corrosion; process deposits during repair; deposits of cement mortar and concrete.

Deposits of non-world origin and oily-mud are formed on the outer surface of parts of machines and units. Dust, dirt during the operation of machines fall on dry and oily surfaces. Such contaminants are removed relatively easily.

Residues of lubricants are available on all parts of machines that work in an oil medium, this is the most common type of pollution, the removal of which requires special preparations and cleaning conditions, washes.

Carbonaceous deposits are products of thermal oxidation of lubricants and fuels. They are formed on parts of internal combustion engines and, depending on the oxidation state, are divided into deposits, lacquer films, sediments and asphalt-resin substances, in addition, carbon deposits include residues of bitumen and asphalt concrete mixture that remain on the external surfaces of parts of road machines when working with these materials.

Scale is deposited on the internal surfaces of parts of the engine cooling system and is formed as a result of the release of calcium and magnesium salts when water is heated to a temperature of 70-85 ° C. The thermal conductivity of the scale is many times lower than the thermal conductivity of the metal, so even a minimum scale layer significantly worsens the heat exchange conditions, leads to overheating of engine parts, especially parts of the connecting rod group and cylinders. As a result, engine power is reduced, fuel and lubricant consumption is increased, and wear rate of parts is increased. Scale removal is a relatively complex and time consuming process.

Corrosion - iron oxide hydrate is formed as a result of chemical and electrochemical destruction of the surfaces of parts of the engine cooling system and all other metal surfaces.

Process contaminants on parts and units are generated during repair, assembly and running-in of units. These are the remains of lapping pastes, grinding wheels, metal chips, etc. They must also be removed in a timely and thorough manner, as they can cause intense wear on the friction surfaces of the parts.

Methods of removing contaminants. Physicochemical, ultra-sound and mechanical methods of washing and cleaning parts were most widely used in repair production.

The physicochemical method of washing and cleaning (jet and in baths) consists in the fact that contaminants are removed from the surfaces of parts with aqueous solutions of various preparations or with special solvents under certain conditions. The main modes of high-quality washing and purification with aqueous solutions are: high temperature of the detergent chemical solution (80-95 ° C), flow or jet of the solution at significant pressure and effective detergents.

Ultrasonic method of washing and cleaning is based on transmission of energy from ultrasound emitter through liquid medium to surface to be cleaned.

Vibrations of 20-30 kHz cause large accelerations and lead to the appearance of small bubbles in the liquid medium, during the rupture of which large hydraulic shocks occur, destroying carbonaceous deposits on the surfaces of the parts for 2-4 minutes, and oil films for 30-40 seconds. The PMS4 converter is attached to the bottom of the welded metal bath and is powered by an ultrasonic generator USG2.5. During operation, the converter is cooled by running water, which is supplied through the pipeline and drained through the pipeline. The terminal block is used to connect the converter to the generator. When using an aggressive detergent solution, a vinyl plastic tank is installed in a metal bath, the space between them is filled with water. Cleaned parts are suspended in bath in lattice basket with cells not less than 3X3 mm. The ultrasonic method is used mainly for cleaning small parts of a complex configuration (parts of carburetors, fuel pumps, electrical equipment, etc.). For ultrasonic degreasing of parts, a solution of the following composition can be recommended: soda ash - 30 g/l; trisodium phosphate - 30, emulsifier OP10 - 5 - 10 g/l.

The solution temperature shall be 50-55 ° C. The use of ultrasonic washing and cleaning of parts (especially small ones) gives a significant economic effect by accelerating the cleaning process and improving the quality of repair of the machine as a whole.

Essence of mechanical method consists in cleaning of part surface by hand with scrapers, brushes or mechanized-bone crumbs, abrasive and other materials supplied together with air, water or detergent solution.

Cleaning fluids and drugs. As washing liquids, aqueous solutions of caustic soda (sodium hydroxide), soda ash (sodium dioxide) with an additive of emulsifiers (liquid glass, household soap, trisodium phosphate) and with anticorrosion additives (chrompic, sodium nitrite) and preparations Tractorin, ML51, ML-52, LABAMID101, LABAMM-203 are used.

Aqueous alkaline solutions are heated to a temperature of 80-95 ° C. When the heating temperature decreases to 70 ° C and lower, the viscosity of the oil deposits remains increased, which makes their separation difficult and worsens the quality of washing. Due to the strong corrosive effect, alkaline solutions (with the presence of sodium hydroxide) intended for washing ferrous metal parts cannot be used for aluminum alloy parts. After washing with alkaline solutions, the parts should be washed with clean water.

Synthetic drugs Tractorin, ML51, ML-52, MS-6 and MS-8 are the most effective detergents that the chemical industry produces. The use of these preparations is economically advantageous compared to expensive caustic soda. Their main advantages over aqueous alkali solutions are low toxicity, good solubility in water, and the possibility of application for parts made of ferrous and non-ferrous metals. In addition, after the use of these drugs, it is not necessary to wash the parts with water.

Preparations "Tractorin," ML51 and MS-6 are used in machines and installations for inkjet washing of parts. The preparation ML52 and MS-8 are used for cooking parts from strong carbonaceous deposits in baths. The temperature of the solutions from these preparations is 70-80 ° C. The degreasing time is 8-20 minutes. The concentration of the aqueous solution is 20-30 g/l.

Preparation AM15, which is a solution of surfactants in organic solvents (xylene, olisarin oil and oxyethylated alcohol), is used to clean parts from strong resinous deposits in baths, as well as to restore the throughput of coarse filters.

Labamid101 and Labamid203 are designed to remove oil and carbonaceous deposits of various parts. Labamid101 is used as aqueous solutions of the concentration of Labamid203 and is used as aqueous solutions of the concentration of 25-35 g/l at a temperature of 80-100 ° C in bathroom washing machines .

Equipment. The choice of equipment depends on the type of contamination of the parts, their sizes, detergents and the capacity of the repair plant. For washing, degreasing and cleaning parts in the repair industry, jet washing machines of the conveyor type, batch chamber washing machines, baths and special installations (for cleaning parts from coke, scale, etc.) were the most common.

Conveyor-type inkjet washing machines designed for washing units, assemblies and parts can be one-, two- and three-chamber. Single-chamber machines are designed for washing with water or degreasing with solutions that do not require subsequent rinsing with water. Single-chamber conveyor washing jet machine designed for degreasing parts using non-aggressive solutions (Tractorin, ML51, MS-6), eliminating the need for subsequent rinsing of parts. Washing device for this machine is made in the form of pumping hydrant. Parts are moved by plate-type conveyor. Conveyor belt speed is 0.1-0.6 m/min. The detergent solution in this machine is heated by steam to a temperature of 75-85 ° C. Large parts are installed directly on conveyor plates, and small ones are supplied to washing machine in mesh baskets.

Two-chamber machines are used to wash parts and units with alkaline solutions in the first of the chambers, followed by washing with hot water in the second.

Three-chamber machines have three washing zones. In the first zone, soils are softened using a washing solution, in the second - thoroughly washed and in the third - rinsed with hot water. Conveyor-type machines are economically feasible in large repair plants.

In batch chamber washing machines, parts are washed with one solution followed by rinsing with hot water. In the latter case, there are two baths: for detergent solution and hot water. These machines are used in small repair enterprises and repair workshops of operating farms.

Baths are the simplest washing plants. Most often they are used to digest parts in alkaline or acid solutions. Baths are made of steel; they consist of two compartments of one for detergent solution, the other for water. The baths are covered from above with a double-leaf cover.

Cleaning parts from scale. Cleaning of water jacket of engine units and cylinder heads is performed at special installations. The unit is installed on roller table 3 and with the help of a hose connected to the side flange of the unit, a solution of trisodium phosphate heated to 60-80 ° C is pumped through its jacket at a rate of about 3-5 kg per 1 m3 of water. It can be used to remove scale and 8-10% hydrochloric acid solution. To protect the internal surfaces of the parts from corrosion, 3-4 g of urotropin per 1 liter are added to the solution as an inhibitor. The solution is heated to 50-60 ° C. The duration of washing depending on the thickness of the scale layer can be within 10-70 minutes. After removing the scale, the internal cavities of the parts must be washed with clean water.

Cleaning of internal surfaces of radiators is carried out by 5% caustic soda solution heated to 60-80 ° С. The soda solution is kept in the radiator until the scale layer is completely removed, after which the internal cavities are washed with hot water.

Workstations. Workstations for washing, degreasing and cleaning of parts are usually organized in washing departments of dismantling shops. Location of equipment at workplaces shall comply with sanitary standards and safety requirements. To lift large heavy parts as well as baskets with parts, workplaces shall be equipped with lifting mechanisms.