Development of caterpillar tractor running gear

Contents

Contents:

Introduction

1.1 Machine Specification

1.1.1 Type, purpose and location in the machine system

1.1.2 Traction and speed parameters during tractor operation on the rod

1.1.3 Indicators characterizing cross-country ability and stability

tractors

1.1.4 Tractor weight indices

1.1.5 Tractor Technical Care

1.1.6 Reliability, durability, wear resistance

1.1.7 Working and Safety Conditions

1.1.8 Unification with other types of tractors

1.1.9 Tractor engine

1.1.10 Power transmission and brakes

1.1.11 Undercarriage

1.2 Terms of Reference

1.3 Technical Solutions

1.3.1 Classification of caterpillar chains

1.3.2 Composite track of rail type with raised

closed hinges

1.3.4 Rail-type cast tracks

1.3.5 Tracks with RMSH

1.3.6 Rubber-reinforced caterpillars

1.3.7 Patent Study

1.3.7.1 Advanced Track Chain Hinge

1.3.7.2 Widened link of caterpillar chain

1.3.7.3 Track of caterpillar chain

1.3.7.4 Vehicle track chain

1.3.7.5 Track chain link

1.3.7.6 Track link with reverse deflection limiter

1.3.8 Trends in the development of tracked tractor propulsion structures

1.4 Design Development

1.4.1 Track chain hinge design

1.4.2 Calculation of forces and stresses acting in the hinge

1.4.3 Distribution of Tracked Propulsion Pressures on Soil

1.4.4 Design of track link

1.5 Checking calculations of the machine main units

1.5.1 Clutch calculation

1.5.2 Determination of loads on shaft bearing supports

1.5.3 Determination of secondary shaft speed

on individual transmissions

1.5.4 Distribution of tractor operation time in separate gears

1.5.5 Definition of bearing life

1.5.6 Calculation of rear axle bearings

1.5.7 Determination of speed of crown gear and satellites

on individual transmissions

1.5.8 Definition of bearing life

1.5.9 Gear calculation

1.5.10 Calculation of geometric parameters

1.5.11 Determination of gear speed on separate gears

transfers

1.5.12 Calculation for contact endurance of active surfaces

teeths

1.5.13 Calculation of contact strength at maximum action

loadings

1.5.14 Calculation for deep contact endurance

1.5.15 Calculation for depth contact strength under action

maximum load

1.5.16 Calculation of teeth for endurance during bending

1.5.17 Maximum load bending strength calculation

1.5.18 Define criteria for shaft calculation

1.5.19 Static strength calculation

1.5.20 Determination of criteria for semi-axis calculation

rear axle

1.5.21 Static strength calculation

1.5.22 Fatigue strength calculation

1.6 Traction calculation

2.1 Safety analysis of the developed facility

2.2 Ensuring safety of the developed facility

2.3 Safety requirements during loading, transportation

2.4 Design Safety Requirements

2.5 Safety Requirements for Caterpillar Propulsion System Test

2.6 Production sanitation

2.7 Fire Safety

3.1 Part Assignment

3.2 Constructability Analysis

3.3 Calculation of the dimension chain

3.4 Definition of production type

3.5 Selection of the optimal method of obtaining the workpiece

3.6 Selection of process bases

3.7 Selection of processing methods

3.8 Process Route Selection

3.9 Allowances

3.10 Calculation of cutting mode during turning

3.12 Process Automation

3.13 Calculation of equipment utilization factor

4.1 Organization of the research and development process

4.2 Marketing Research

4.3 Expert assessment of the competitiveness of the goods

4.4 Calculation of research and development costs

4.5 Calculation of cost and price of the designed product

4.6 Project Cost Effectiveness Assessment

4.7 Estimate of project profitability

List of literature used

Introduction

With the intensification of agricultural production, one of the defining requirements for agricultural machinery is to increase its productivity. However, at the same time, the machines are complicated and their functional capabilities are expanded, which is associated with an increase in the number of their units (assembly units) and mass. This causes an increase in the mechanical effect of running systems on the soil. The latter leads to an increase in soil compaction and other negative consequences that reduce its fertility and crop yields.

The mechanical effect of propellers on the soil cannot be considered only from the side of the sealing effect, since at the same time its structure is intensively destroyed under the influence of their slipping.

The creation of new machines is both a technical and an economic task, since the tractors being developed must not only be more advanced in technical characteristics, but also provide higher economic indicators for all types of work in various soil-climatic zones, which are characterized by both the variety of crops cultivated, and the resistivity of soils to processing and abrasiveness.

The task of the designer is to create machines that provide a given increase in productivity when achieving the highest technical level, quality and reliability.

When substantiating the parameters of the designed machines, the scale of their production, it is necessary to take into account that the designed object is part of an ordered hierarchy of objects and, on the one hand, is part of a higher level system, and on the other, a system for lower level objects. So, the tractor is included in the machine-tractor unit, which, in turn, is included in the machine system, at the same time it is a system for components (assemblies and parts) that form it.

Shortening the development and development of new equipment, increasing its productivity and reliability requires the development of computer-aided design systems, the use of design methods based on unified block-modular and basic structures, and complex automation of machines using built-in microprocessors.

Optimizing machine parameters requires a reasonable choice of optimization criteria. The complexity and breadth of the problem practically excludes optimization according to only one criterion, since such a solution may not be optimal for some other, sufficiently significant criteria. Obviously, the orientation towards multi-criteria optimization with independent criteria is the most correct.

Of particular importance in the conditions of complex automation of production is the processability of the design, its quantitative evaluation using computers.

Traction chain properties of caterpillar traction machine are one of its main indicators. A tracked tractor or tractor is designed as a traction machine of a certain purpose, such as: general-purpose agricultural, steep, industrial for construction or road work, trackwork, transport, swamp or reclamation. The purpose of the tractor determines typical operating conditions, i.e. soil conditions, speed and traction resistance of the trailed or mounted machine. The task of the designer is to select such optimal design parameters of the chassis and the tractor as a whole that would provide the best traction qualities of the tractor. Since the tractor is used in a wide range of traction force on the hook, which is from 0.4 to 1.2 of the nominal traction force, the main requirement for the undercarriage is to provide a high value. in this range of thrust under different soil conditions.

For special tractors, such as transport tractors, marsh tractors and others operating under a variety of conditions, it is more important to ensure that the tractor is penetrable in difficult soil conditions, that is, to ensure its reliable adhesion to the soil, estimated by the coefficient of adhesion.

Traction and coupling properties of tractor are interconnected. Ensuring a reliable adhesion of the agricultural tractor to the soil under extreme operating conditions leads to a decrease in its slip at typical operating modes.

Some experts believe that modern tracked tractors already have good coupling properties. However, it is not taken into account that further improvement of the coupling qualities of an agricultural tractor due to the design allows to reduce its weight, that is, save metal and fuel. The better the adhesion of the tractor to the soil, the more stable the rectilinear movement of the tractor and the easier to automate its driving. The lower the rolling resistance of the tractor, the greater the resistance of the working machine it can overcome, i.e., have a higher specific traction force on the hook (tractor weight utilization factor), by which the adhesion of the tractor to the soil is often evaluated.

Machine Specification

1.1.1 Type, purpose and location in the machine system

Tractor of class 4 tons of traction - caterpillar, general purpose, for work in agriculture with hinged (including front and side suspension), half-weight, trailed, hydrofied, combined machines and tools. The tractor is designed to perform plowing of medium and heavy soils to a depth of 350 mm, soil discing, continuous cultivation, sowing, harvesting, transport, road-excavation, work in irrigated agriculture and work with loading materials. To carry out arable land or deep arable land, the tractor must be well aggregated with eight hull under normal handling.

On the basis of the tractor, the creation of a swamp and steep-slope modification with speed and power parameters established in accordance with the requirements of the institutions and departments using this tractor should be provided.

1.1.2 Traction and speed parameters during tractor operation on the rod

Parameter name Index

Nominal tractive force, kN:

- nominal 40

- maximum (long-term operation) 60

1.1.3 Indicators characterizing tractor cross-country ability and stability

Parameter name Index

Longitudinal base, mm 1800-1900

Gauge, mm 1300 - 1400

Ground clearance, mm 430 - 450

Weight of removable ballast loads, kg 400 - 500

Track width, mm 460 - 480

Length (with hinged device in transport position), mm 5600

Width, mm 1800-1900

Height, mm 3000 - 3100

Operating weight without ballast loads, kg 7600 - 7700

Mean soil pressure (without ballast loads), kPa 30 - 40

1.1.4 Tractor weight indices

The structural weight of the tractor shall be minimal. The weight load required to provide the required tractive force is achieved when the tractor is fully equipped in working condition with additional balancing.

1.1.5 Tractor Technical Care

Tractor maintenance costs shall not exceed 4-5% of the total operating time. This should be achieved by the introduction of automatic adjustment of mechanisms, reduction of lubrication leaks, introduction of joints with constant lubrication, centralization of lubrication of individual mechanisms with automatic refueling, increasing periods between lubricants, increasing the volume of the fuel tank, creating convenience and easy access to lubricated and adjustable points, introduction of bolted connections that do not require periodic tightening, good seals that do not allow leakage of fuel and lubrication. Lubrication of all tractor units shall be performed by no more than three types of lubricants.

1.1.6 Reliability, durability, wear resistance

Reliability, durability, wear resistance of tractor units and assemblies (with the exception of hull parts) shall be such that the following service life is ensured before overhaul: engine for at least 5000 hours, transmission for at least 6000 hours, running gear for at least 4000 hours on black earth soils and at least 2000 hours on sandy soils. Body (basic) parts shall be operated without replacement throughout the life of the tractor.

1.1.7 Working and Safety Conditions

The tractor design should meet the "Uniform safety requirements for agricultural tractors, self-propelled chassis, self-propelled vehicles and other agricultural machines and tools."

1.1.8 Unification with other types of tractors

Maximum possible unification shall be provided for the main units and parts with tractors of other classes. It should be possible to create tractor modifications for operation in mountain conditions and swampy soils as unified as possible by this basic model.

1.1.9 Tractor engine

Parameter name Index

Engine type diesel

Rated power, hp 110 - 120

Specific flow rate at rated power, g/kWh 250 - 260

Torque margin factor,% 20 - 25

Crankshaft speed, rpm 1800 - 2000

Working volume, l 10 - 15

Number of cylinders 4 - 6

Adaptability factor not less than 1.15

Crankcase oil consumption during warranty period

service life, in% of fuel consumption not more than 2.5

The starting device shall ensure reliable starting of the main engine from the driver's seat (starting engine with electric starter controlled from the driver's seat). Provide device that prevents engine starting, if there is no oil in the system, at superheated engine. Starting qualities shall meet the temporary requirements for the starting system of tractor and combine engines.

1.1.10 Power transmission and brakes

The power transmission of the tractor is a mechanical multi-stage gear with remote switching on the go without stopping the tractor. The turning mechanism must provide stable rectilinear movement when the point of application of traction force is shifted up to 150 mm from the longitudinal axis of the tractor and smooth turns of the tractor at the ends of the races, with units whose working elements do not switch off (dental harrows, disc harrows, etc.). Brakes that guarantee a reliable fixed holding of the tractor on the stability limits of lifts and descents.

1.1.11 Undercarriage

The running apparatus and tractor suspension shall ensure the necessary operating conditions of the tractor driver and the safety of the machine during operation at increased speeds during agricultural operations and transportation of mounted tools. Tractor track design shall ensure normal operation in winter and summer conditions. It shall be possible to install special tracks for work with artificial coating. The frequency of lubrication replenishment in the running system is no more than after 1000 hours.

Technical solutions

1.3.1 Classification of caterpillar chains

The caterpillar chain is the main element of the caterpillar propulsor, through which the main positive qualities of the caterpillar tractor are realized.

Usually, a propulsor with two tracks is installed on the tractor. There are designs of articulated tractors with four tracks.

Caterpillars are used to create a large supporting surface, which provides the necessary pressure on the soil at a significant weight of the tractor and its reliable adhesion to the soil, as well as to create endless rail tracks for rolling the supporting rollers of the propeller and converting the torque supplied to the driving wheels into a traction force moving the tractor unit.

Given the purpose of the tracks and the heavy external conditions of their work, they are subject to a number of additional requirements: they must have increased strength and wear resistance with as little material capacity as possible; be extremely simple and inexpensive to manufacture, operate and repair.

Modern caterpillars are classified, first of all, by the type of their general design. The first are traditional, consisting of separate metal hinged links, and the second are monolithic rubber-reinforced (RAG), which were not previously used on domestic tractors.

Further main classification of metal caterpillars is carried out according to the structural implementation of their links - they are composite and whole-cast. In addition, the links of caterpillars can be distinguished: by the type of treadmill of support rollers - rail and flat; by location of hinge on link - raised and lowered; by hinge type - closed, open, elastic (rubber-metal).

It should be noted that a particular link design usually has several qualification features at once.

1.3.2 Composite track of rail type with raised closed hinges

A composite link of a rail-type caterpillar with a raised closed hinge on agricultural tractors historically appeared earlier than a cast flat link. It consists (fig.1.1, a) of two separate stamped cheeks (rails) 6 and 7 of mirror configuration, connecting parts - bushing 11 and pin 12, support profile plate 8 (commonly called shoe) and bolts 5 with washers 9 and nuts 10.

Machined and thermally treated cheeks 6 and 7 each have two holes: large - for pressing of bushing 11 and small - for connecting pin 12 of links. Bushings and pins are made, as a rule, of low-carbon steels, followed by cementation and hardening of friction surfaces. In addition, a small annular recess "A" is made on the inner machined plane of the cheek at the small hole, as shown in the hinge section (Fig. 1.1.6). When assembling the track, the right 6 and left 7 cheeks are first pressed on the ends of the sleeve 11 so that its edges somewhat protrude beyond the outer machined planes of the cheeks. In subsequent assembly, the connecting pin 12 freely passes through the hole of the sleeve 11, and on its protruding ends sequentially press the next pair of cheeks with the connecting sleeve, etc. Thus connected cheeks of links form running track for support rollers in the form of rails. Therefore, such links were called "rail type."

Shoe 8 with transverse grouser "B" made of shaped steel is attached to lower surface of each pair of cheeks (Fig.1.1, a) by means of bolts 5, nuts 10 and lock washers 9.

The joints of the rail links are usually of a closed type and are raised above the surface of the shoe. Closed hinge is provided by the fact that (Fig.2.9, b) projecting ends of bushings 11 enter annular recesses "A" of complex external cheeks 6 and 7, forming labyrinth seal "B" preventing ingress of external abrasive into its inner part.

Since the links are pressed by a large force, of the order of 1000 kN, one of its links is made easily closing to install the caterpillar or remove it from the propeller. In this unit (Fig.1.1), the sleeve 3 is made shorter so that it does not extend beyond the holes of the cheeks into which it is pressed, and the ends of the connecting pin 2 are most often made with conical holes and a longitudinal cut. When caterpillar is closed, connecting pin 2 freely enters small holes of external cheeks and connecting bushing 3, after which stop cones 1 are pressed into its ends, which wedge ends of pin in holes of cheeks. In order to press out the cones 1 when disassembling the track, threaded holes "D" are made in them, closed during operation usually with wooden plugs. Additional rings (washers) 4 replacing missing protruding ends of connecting bushing 3 provide for creation of labyrinth seal of closed hinge of closing link.

The track in question has a pin engagement with the driving wheel of the propeller, where the role of the pin is performed by the outer surface of the link coupling bushing.

The main advantages of composite track tracks of the rail type are: the presence of a closed hinge that isolates its internal friction surfaces from the ingress of abrasive on them, which significantly reduces their wear and increases the durability of its operation; raising the hinge above the shoe, which also prevents it from getting abrasive into it; a cleaner track raised above the ground provides less resistance to rolling of the support rollers; better repairability, which allows replacing worn-out parts of the composite link and, if necessary, increasing (decreasing) the support surface of the shoes or installing additional rubber linings on them for tractor movement along paved roads.

The main disadvantages of these caterpillar links are: large metal consumption (reaching up to 25% of the mass of the tractor); the greater complexity and labour intensity of their manufacture compared to whole-cast caterpillar links; complexity in operation, requiring special press devices for their disassembly and assembly during repair.

However, despite the disadvantages noted, composite rail tracks are very widely used on tractors, especially large traction classes operating on sandy soils, mainly due to the high durability of closed type hinges and the repairability of composite links of tracks.

To increase the durability of hinges and reduce friction power losses in them, the best of their designs (Fig.1.2) use liquid lubrication of friction pairs and additional seals. In these joints, the connecting sleeve 2 is the same in length as in the closing unit, not extending beyond the opening of the cheek 3, but with carefully machined ends used as friction surfaces of the end seal. Sides of rubber sealing rings (4) with squeezed rubber ring (8) are pressed to them and to end face of bore in cheek (5). Simultaneously, the seal 4, being on the surface of the polyurethane thrust rings 9, further protects the inner cavity of the hinge from the penetration of the abrasive therein.

The connecting pin 6 is made hollow for filling the lubricant and with a hole 10 for feeding it on the friction surface of the hinge. Rubber plugs 7 with a lubricant injection hole closed with a plastic plug are pressed into the ends of pin 6.

1.3.3 Caterpillars with cast links

All-cast links of caterpillars are made by casting from high-manganese steels and, like a treadmill, they are flat or rail.

Flat unprocessed links of caterpillars for pin engagement (Fig.1.3, a) are cast shaped plates with treadmills 1, which in the middle part are connected by a wide link - eye 2, which is a pin for engagement with the driving wheel. To prevent caterpillar from leaping during operation, guide ridges 3 are cast on the links for rolling the support rollers. The links are connected to each other by means of cemented and hardened steel pins 6 freely inserted into holes 4 of connecting lugs and fixed in them by means of washers 7 and cotter pins 8. The number of lugs depends on the width of the link, but they prefer to be made as large as possible, since this reduces the concentration of stresses on their edges due to bending of the finger, which slightly increases the durability of the open-type hinge. Typically, five and seven-ear hinges are used.

For better engagement of links with soil on the side of lugs facing it there are tides - grousers in the form of spurs 5.

Flat cast links of caterpillars for ridge engagement (Fig.1.3, b) have treadmills 1 similar to those previously discussed. The main differences of this link from the previous one consist in the presence of a central ridge 2 located between the treadmills and serving to engage the link with the driving wheel and the direction of movement of the support rollers, and in the presence of one continuous transverse grouser 3.

The advantage of cast flat links over composite rail links is their ease of manufacture and maintenance, low cost and relatively low weight.

The main disadvantage of these links is the low durability, not exceeding on ordinary soils 1200... 2000 h., And on sandy sinking even to 250... 350 h. The main reason for this is an open hinge of low location, which allows the abrasive to freely penetrate into the lugs and wear them and connecting fingers quickly, making the link unreremontable, which generally leads to an increase in the cost of tractor operation.