Cardan shaft Gazelle

Introduction

The constant lack of maintenance of spare parts is a serious factor in the decrease in technical readiness of the automobile fleet. The expansion of the production of new spare parts is associated with an increase in material and labor costs. At the same time, about 75% of the parts rejected during the first overhaul of cars are repairable or can be used without restoration at all. Therefore, a viable alternative to expanding the production of spare parts is the reuse of worn-out parts restored during the repair of cars and its units.

It is known from repair practice that most parts rejected by wear lose no more than 1-2% of the original mass. At the same time, the strength of the parts is practically preserved. For example, 95% of the parts of internal combustion engines are rejected with wear not exceeding 0.3 mm, and most of them can be reused after recovery.

From the point of view of material-intensive reproduction of machines, the economic feasibility of repair is due to the possibility of reusing most parts both suitable and extremely worn out after restoration. This makes it possible to carry out repairs in a shorter time with lower costs of metal and other materials compared to the costs of manufacturing new machines.

The high quality of repaired cars and units places increased requirements on the resource of restored parts. It is known that in cars and units after overhaul, the parts work, as a rule, in significantly worse conditions than in new ones, which is associated with a change in the basic dimensions, displacement of the axes in the body parts, a change in the lubrication supply conditions, etc. In this regard, part repair technologies should be based on coating and post-treatment methods that would not only preserve, but also increase the life of repaired parts. For example, when restoring parts by chromium, plasma and detonation spraying, induction and laser surfacing, contact welding of a metal layer, their wear resistance is significantly higher than that of new ones.

The restoration of automotive parts has become one of the most important indicators of the economic activity of large repair, specialized small enterprises and cooperatives. In fact, a new industry has been created - the restoration of worn-out parts. For a number of the most important metal-intensive and expensive parts, the secondary consumption of restored parts is much more than the consumption of new spare parts. For example, restored engine blocks are used 2.5 times more than received new, crankshafts - 1.9 times, gearbox crankshafts - 2.1 times more than new ones. The cost of recovery for most recoverable parts does not exceed 75% of the cost of new parts, and the cost of materials is 15-20 times lower than for their manufacture. The high economic efficiency of enterprises specializing in the restoration of automotive parts ensures their competitiveness in market production.

Abroad also focuses on technology and the organization of part recovery. In highly developed countries - the USA, England, Japan, Germany - repairs are mainly carried out at car manufacturers. Expensive, metal-intensive, mass automotive parts are restored - crankshafts and camshafts, cylinder liners, block blocks and block heads, connecting rods, brake drums, etc. The repair base is a motor and aggregate repair enterprises of manufacturers of new machines, independent intermediary companies. For example, in the United States, about 800 firms and companies are engaged in the restoration of parts. These include both specialized firms and companies that produce components for automotive enterprises, in the total volume of production of which 10-40% is accounted for by the production of restored parts. The repair fund is parts from decommissioned cars that are supplied by manufacturers or firms specializing in the processing of unsuitable cars. In the United States, 25 per cent of vehicle spare parts requirements are met as a result of the refurbishment of parts.

Analysis of operability and reliability of vehicle transmission - 32217

Cardan gears are used in car transmissions for power communication of mechanisms whose shafts are not coaxial or located at an angle, and their mutual position can change during movement. The gearboxes may have one or more gearboxes connected by gearboxes and intermediate supports. Gearboxes are also used to drive auxiliary mechanisms, for example, winches. In some cases, the steering wheel is connected to the steering gear by means of a cardan transmission.

Cardan transmissions are subject to the following requirements:

torque transmission without creating additional loads in the transmission (bending, twisting, vibration, axial);

possibility of torque transmission with provision of equality of angular speeds of drive and driven shafts regardless of angle between connected shafts;

high efficiency;

quietness;

minimum size and mass;

simplicity of device and maintenance;

processability;

repairability;

low noise level.

The GAZ 32217 uses an open-type cardan transmission, single-shaft with two cardan hinges.

Operation and maintenance of cardan transmission

During operation it is necessary to tighten nuts of bolts that attach the propeller shaft flange to the rear axle drive gear flange with torque of 27-30 Nm (2.73.0 kgfm).

In 20 thousand. km of mileage (when driving on dirty roads through 10 tons. km) lubricate the gearbox by getting the lubricant out of the cross cuffs.

Lubricate the gearbox with TAD17I or Omskoil oil - SuperT oil.

It is strictly forbidden to use solidol or other greases, since they do not enter the needles of the bearings during operation, solidify in the channels of the cross, preventing the subsequent passage of liquid grease.

Analysis of cardan transmission design

The development of structures of cardan hinges of unequal angular speeds is associated with a continuous improvement in their operational properties: reliability, the possibility of transmitting rotation at an increased angle between shafts, and increasing efficiency.

The requirement to ensure high efficiency of the cardan hinge is due to the need to increase its wear resistance, and therefore durability.

Cardan hinges of unequal angular speeds on needle bearings used in modern cars meet the requirements provided that the hinge has a rational design, the production technique is strictly observed, and the needle bearings are reliably clamped.

The efficiency of the cardan hinge depends on the angle y between the shafts to be connected. As the angle increases, the efficiency decreases sharply. In some cars, to reduce this angle, the engine is arranged with a slope of 2... 3 °. Sometimes, for the same purpose, the rear axle is set so that the driving shaft of the main gear receives a slight slope. However, it is unacceptable to reduce the angle between the shafts to zero, since this can lead to a rapid failure of the hinge due to the brinelling effect of the bearing needles on the surfaces with which they contact.

The brinellating action of the needles increases with a large total needle gap, when the bearing needles are pumped and a high pressure is created on the spike. The total needle gap in the cardan joints of various cars varies widely (0.1... 1.5 mm). The total needle gap is considered to be less than half the diameter of the bearing needle. In most cardan hinges of cars and trucks, bearings are used, the diameter of the needles of which is 2... 3 mm (the diameter tolerance is not more than 5 μm, and the length is not more than 0.1 mm). Needles for bearing are selected with the same dimensions according to tolerances. You cannot rearrange or replace individual needles.

Cardan joint crosspiece must be strictly centered. This is achieved by precisely fixing the bearing cups by means of locking rings. The gap between the ends of the spikes of the spider and the bottoms of the cups is unacceptable, as this leads to a variable imbalance of the cardan shaft during its rotation. At the same time, excessive tightening of cups can cause gouging of the ends of the spikes and the bottom of the cups, as well as skewing of the needles.

Reliability of cardan joint is determined primarily by reliability of needle bearings and their resource. In addition to brinellation, fatigue painting (pitting) on needle-contacting surfaces is also possible, due to high contact stresses. In this regard, the spikes of the crosspiece of the cardan hinge are made of highly alloyed steel, and the working surface of the cups and spikes is cemented.

Analysis of cardan transmission operability

The design operability analysis consists of quantitative analysis of parameters that determine the reliability of the design. The analysis of the gearbox should assess the degree of synchronization of the rotation of the shafts that are connected to it, how the absence of beating of the shafts and resonance phenomena is ensured, as well as ensuring the rigidity and reliability of the gearbox transmission of this car.

Part Defects and Sorting

Parts of a car after washing and cleaning from contamination in accordance with the process are subjected to defects, i.e., inspection to detect defects.

The main tasks of defective and sorting parts:

inspection of parts for determination of their technical condition;

sort parts into 3 groups:

suitable for further use;

to be restored further;

unsuitable;

accumulation of information on the results of defects and sorting in order to use it in improving technological processes and to determine the ratios of serviceability, changeability and restoration of parts;

Sorts parts by recovery route.

The work on the defects and sorting of parts has a great impact on the efficiency of car repair production, as well as on the quality and reliability of repaired cars. Therefore, the parts should be sorted in strict accordance with the specifications.

Parts are defected by means of their external inspection, as well as by means of special tools, devices, instruments and equipment.

Results of defects and sorting are fixed by marking parts with paint. At the same time, parts suitable for further use are noted with green paint, red - unsuitable, yellow - requiring restoration.

Quantitative parameters of parts defection and sorting are also recorded in puncturing lists. This data, after statistical processing, allows you to determine and correct the factors of serviceability, changeability and restoration of parts.

Choosing a Rational Way to Eliminate Part Defects

The correct choice of methods to eliminate defects should ensure the maximum service life of the part after restoration at the lowest repair cost.

Analyze existing recovery methods

Restoring parts is important. The cost of restoring parts in 2... is 3 times lower than the cost of their manufacture. This is due to the fact that the cost of materials, electricity and labor is significantly reduced during the restoration of parts.

The efficiency and quality of the repair of the parts depends on the method adopted. The most widely used methods for restoring parts are the following: machining; welding and surfacing; spraying; galvanic and chemical treatment; pressure treatment; use of synthetic materials.

The numerous technological methods used in the restoration of parts are explained by the variety of production conditions and defects for which they are used. Depending on the nature of the defects to be eliminated, all part recovery processes are grouped into two main groups:

repair of parts with mechanical damages;

restores parts with worn out surfaces (resizing part work surfaces).

The first group includes methods of restoring parts having cracks, holes, fractures, deformations, as well as corrosion damages. To the second - having changes in dimensions and geometric shape of working surfaces in the form of ovality, cone-shaped, corset, etc.

The use of a repair method also depends on the material from which the part to be restored is made.

Welding and surfacing are the most common methods of restoring parts. Welding is used to eliminate mechanical damages of parts (cracks, holes, etc.), and surfacing - to apply coatings in order to compensate for wear of working surfaces. Both manual and mechanized welding and surfacing methods are used at repair enterprises. Among mechanized surfacing methods, automatic arc surfacing under flux and in the medium of protective gases and vibration-arc surfacing have found the most application. Currently, promising welding methods such as laser and plasma welding are used in the restoration of parts.

About 40% of the parts are recovered by these methods. The wide application of welding and surfacing is due to the simplicity of the process and the equipment used, the ability to restore parts from most metals and alloys used in the automotive industry, high productivity and low cost.

When restoring parts, the following types and methods of welding and surfacing are used:

manual arc welding;

gas welding;

semi-automatic welding in carbon dioxide medium;

semi-automatic welding with PANCH11 wire;

semi-automatic welding with powder wire;

vibration surfacing;

automatic surfacing under the flux layer;

electrical contact welding.

Other methods and types of welding and surfacing are rarely used in the restoration of automotive parts.

Soldering is a process in which the connection of heated parts of a metal occurs as a result of the introduction of an intermediate metal or alloy (solder) interacting with the base metal into the gap between them and forming a liquid metal interlayer, the crystallization of which leads to the formation of a solder joint between the connected parts. Most often used in the restoration of permanent connections.

Spraying (application of gas-thermal coatings) as a method of restoring parts consists in the fact that molten metal is sprayed onto the appropriately prepared surface of the metal using a special apparatus with compressed air or inert gas. After spraying, the part is processed for the required size. At the same time, a layer with a thickness of 0.03 mm to several millimeters can be applied to the worn out surface without causing overheating of the metal. This method is very promising. Depending on the method of melting the metal, the following types of spraying are distinguished:

arc

gas flame;

high-frequency;

detonation;

plasma.

The essence of the process consists in melting the starting material (powder or wire) and transferring it to the restored surface of the part with a jet of gas (air).

Galvanic and chemical treatment is based on the deposition of metal on the surface of parts from salt solutions by a galvanic or chemical method. In repair practice, the most widely used are:

electrolytic chroming;

remaining;

electronic saturation.

Polymer materials are increasingly used in the restoration of parts. They are used to eliminate mechanical damages on parts, to compensate for wear of working surfaces of parts (composition based on epoxy resins), as well as to connect parts by gluing, for example, gluing friction linings.

Chrome plating, iron plating and chemical nickel plating are most commonly used to compensate for wear of parts. Application of protective coatings on the surfaces of parts is carried out using galvanic processes (chroming, nickel plating, galvanizing, copper plating), as well as chemical ones (oxidation and phosphating).

Mechanical machining is used as an independent method of repairing parts, as well as when processing parts for repair dimensions and when installing additional repair parts. By treating the parts for the repair dimension, the geometric shape of their working surfaces is restored, and by installing the additional repair part, the dimensions of the part correspond to the dimensions of the new part. In addition, mechanical machining is necessary in some cases when repairing parts in other ways

Restoration of parts by plastic deformation is based on the use of the properties of metals to change the geometric shape and dimensions under pressure of external forces without destruction. Depending on the design of the parts, such types of plastic deformation as crimping, rolling, draught, drawing, etc. are used.

An option for repair by placing an additional repair part is a method of repair by replacing a worn or damaged part of the part with a specially made additional part.

Synthetic materials (plastics) are used for gluing, repair of worn-out parts, leveling of cabin surfaces, bodies, plumage and other parts before painting, in case of technical damages, as well as when eliminating mechanical damages (cracks, holes) in the body parts. By means of adhesive compositions, parts or parts of parts made of metals and non-metallic materials are joined together in various combinations. Parts with breakdowns and debris are repaired by this method. Gluing is also used to produce permanent joints of parts during assembly

Electrical processing is based on the phenomenon of metal destruction during an electric spark discharge. This type of treatment can be used as a stand-alone method of repairing worn and damaged parts, as well as operations related to the preparation or final processing of parts repaired in other ways. The workpiece may be made of any metal or alloy; the material for the tool can be brass, copper, cast iron, aluminum and its alloys, etc.

Hardening treatment is one of the final stages of restoring parts and aims to achieve the given physical and mechanical properties.

The listed methods of restoring parts provide the required level of quality and reliable operation of parts during the established inter-repair runs of cars. The required level of quality of the restored parts is achieved with the correct selection of the technological method, as well as control of the processes of coating and subsequent processing of the parts. The quality of the restored parts is affected by the properties of the starting materials used in the coating application and processing modes.

Selecting a Method for Restoring Cardan Shaft Cross Necks

The durability of repaired cars depends to a large extent on the ways in which the parts are repaired and how it is organized.

The application of the most effective methods ensures long service life of parts, reduces the consumption of spare parts, materials, labor costs, etc. Along with the use of rational methods, for high-quality restoration of parts with the least labor and resources, the organization of production is of great importance - centralized restoration of parts in specialized plants and workshops, well equipped with modern equipment, devices, tools.

The choice of restoration methods depends on the structural and technological features and working conditions of the parts, the amount of their wear, the operational properties of the methods themselves, determining the durability of the repaired parts, and the cost of their restoration. The structural and technological features of the parts are determined by their structural characteristics: geometric shape and dimensions, material and heat treatment, surface hardness, manufacturing accuracy and surface cleanliness, the nature of the interface (type of fit), working conditions - the nature of the load, the type and type of friction, the amount of wear during the operational period. Knowledge of the structural characteristics of parts and their technological features and operational properties makes it possible in the first approximation to solve the question of the applicability of one or another of them to the method for restoring individual parts. Using this analysis, you can determine which parts can be restored in all or several ways and which in their structural characteristics in only one way. This criterion allows you to determine the applicability of recovery methods to specific parts and can be called a technological criterion or an applicability criterion. For example, using this criterion, it can be said in advance that parts of a small diametrical size, having high surface hardness and little wear, are irrationally restored by metallization and surfacing - manual electric arc and automatic under a flux layer.

The criterion of applicability cannot be numerically expressed and is essentially preliminary, since it cannot solve the issue of choosing a rational method of restoring parts if several of these methods are used. The applicability criterion allows you to classify parts by repair method and identify a list of parts that can be repaired in different ways. The latter facilitates further work on choosing a rational method.

Estimation of recovery methods from the point of view of the operability of the parts provided by them can be made using the criterion of durability determined by the coefficient of durability. The durability of parts restored in one way or another depends on the operational properties of the methods. The most rational ways here will be those that ensure the greatest durability of the restored part.

Based on the data described above, we define a method for recovering the crosspiece necks of the cardan shaft. According to the technical requirements: ensuring high hardness and wear resistance of the working surface of the cardan shaft cross, as well as specified dimensional accuracy, the most suitable methods for eliminating the defect are surfacing.

It will be apparent from the foregoing material that there are a significant number of different methods of welding and welding the parts. And if the choice of welding is not particularly difficult, since it is quite easily determined by the welding method itself, the material and configuration of the parts, as well as the nature of the defect, this cannot be said with respect to the choice of the build-up method.

The choice of the build-up method presents known difficulties, since it depends on a large number of factors. When choosing the method of surfacing parts, it is necessary to take into account:

part material, its chemical composition and properties;

thermal treatment and surface hardness of the part, possibility of their restoration after surfacing;

working conditions of the part (nature of load and fit, overall and geometric shape of the restored part);

value and wear pattern of the part, thickness of the surfacing layer;

permissible values of deformation of the part, reduction of surface hardness and fatigue strength;

machining of built-up metal and deformed section;

surfacing capacity, labor-intensive and cost-effective recovery of the part by surfacing (including all process operations).

Manual electric arc surfacing and automatic surfacing under the flux layer should be used to restore large-sized parts with high wear and relatively low surface hardness (not higher than HB 350-400). These include parts made of low carbon steels 10, 20, 30 and medium carbon steels 40, 45, 50G, as well as low alloy steels ZOKh and 40X. Since manual surfacing with electrodes OZN300, OZN-400, U340 p/b, TsN250, K-2 does not provide the production of built-up metal with high physical and mechanical properties compared to automatic surfacing under the flux layer and is inferior to it in productivity, it is obvious that restoration

parts must be automatically built-up. This especially applies to large-scale repair production. Manual electric arc surfacing is used for non-essential parts.

Responsible parts with small diametrical dimensions, made of cemented carbonaceous steels 20, 25 and low alloyed 18ChGT, 18ChNBA, 12ChN4A, 20ChNM, 20X and others, having high surface hardness after heat treatment (within HRC 40-60) and relatively small wear, it is advisable to restore carbon dioxide by welding in the medium. The same group includes parts made of steels 40, 45, 50G, 40X, having high surface hardness after hardening, i.e., operating under static loads. The use of electric pulse surfacing to restore dynamically loaded parts is impractical.

Parts with small diametrical dimensions and wear, with different surface hardness, can be restored by gas-electric surfacing (in the medium of carbon dioxide) using appropriate grades of electrode wire.

The choice of the build-up method must be made taking into account its economic feasibility. Thus, mechanized build-up methods are the most progressive not only in terms of wear resistance, but also in terms of economic indicators.

According to the above information, a rational and cost-effective method of recovery is surfacing in the environment of carbon dioxide.

Description of method of recovery of parts by semi-automatic surfacing in carbon dioxide environment

Semi-automatic surfacing in a carbon dioxide medium can restore parts with small diametrical dimensions (10 mm), with a layer of small thickness from 0.8 to 1.0 mm, as well as internal surfaces. Surfacing is carried out both by superimposing the rollers along the screw line (in case of restoration of cylindrical surfaces) and by longitudinal rollers (in case of restoration of planes and splines). For surfacing, semi-automatic A547p or surfacing heads used for surfacing under a flux layer are used. Current sources and gas equipment can be the same equipment as for welding in the medium of carbon dioxide.

Welding of parts of small diametrical dimensions is carried out at direct current usually at reverse polarity. If it is necessary to obtain a built-up metal with higher wear resistance compared to the base metal, it is advisable to apply the build-up at a direct current of direct polarity. In this case, the penetration depth of the base metal is smaller, therefore, and the proportion of the base metal in the formation of the roller will be smaller compared to the proportion of the electrode metal that the doped wire can be. Depending on purpose of a detail, material and heat treatment the following brands of an electrode wire can be applied to building up: Sv08GS, Sv-YuGS, Sv08G2SA, Sv-ZOHGSA, Sv10H13. The wire used must have an increased deoxidizer content. Both solid and powder wire can be used. Thus, the use of Sv2X13 wire allows to obtain hardness of the weld metal up to HRC 55.

Surfacing in the medium of carbon dioxide is more productive than manual arc surfacing by 3-5 times and allows you to obtain built-up metal of higher quality. As compared to electro-pulse surfacing, the method also has the advantage that the surfaced metal is obtained without cracks and is characterized by high hardness and wear resistance.

The installation for gas-electric surfacing includes: a lathe with a reduction gear that reduces the number of revolutions of the part, an electrode wire supply mechanism installed on the machine support, a hardware box, a welding converter, a cylinder with carbon dioxide, a reduction gear with a flowmeter, a dryer, a gas heater and rubber hoses for its supply. The sequence and technique of applying the annular and longitudinal rollers will remain the same as in automatic surfacing under the flux layer.

Description of accessory structure

The following devices are used as accessories used in restoring parts:

machine tools (used to install blanks in machines);

measuring devices (designed for manual or mechanized inspection of machined surfaces).

The reasonable use of machine tools allows to obtain high technical and economic indicators. The accuracy of processing parts according to the parameters of deviation of dimensions, shape and arrangement of surfaces increases (on average by 20... 40%) due to the use of devices. This, in turn, will make it possible to reasonably reduce the requirements for the qualification of employees (on average per grade), objectively regulate the duration of operations and prices, and expand the technological capabilities of the equipment.

Measuring devices are used both for direct control of the surface during its processing, and for control of the parameters of the finished part (dimensions, shape and mutual arrangement of surfaces).

From the data given in item 1, it is known that the cardan shaft spider has high requirements for accuracy of manufacture, surface cleanliness, mutual arrangement of the surfaces of the spikes of the spider and its axes.

Consider a measuring device that is used to control the perpendicular of the axes of the cross after machining (permissible non-perpendicular to not more than 0.1 mm at the ends of the spikes).

Accessory consists of mounting plate and indicator fixed on bracket. An adjustment screw is used to adjust the position of the indicator. On the mounting plate with the specified accuracy there are two prisms designed to fix the cross, as well as two knives for accurate installation of the cross (the axes of prisms and knives are mutually perpendicular to the accuracy of 0.01mm).

The crosspiece to be controlled is installed on knives and fixed in prisms, after which the perpendicular axis of the crosspiece is checked with an indicator. The operation is repeated for the second axis.

If the non-perpendicular axes exceed the permissible value, the cross is married and sent for revision.