Restoration of tractor drive retraction bracket

Contents

Kinematic Mechanism Analysis

Power analysis of the mechanism

Dynamic Mechanism Analysis

Involute Gear Design

Synthesis of cam mechanism

List of literature

Application

Introduction

Repair of automotive equipment is an objective necessity, which is due to technical and economic reasons.

Firstly, the need of the national economy for vehicles is partially satisfied through the operation of repaired cars and tractors. Secondly, repair ensures the continued use of those elements of the machines that are not completely worn out. As a result, a significant amount of past labor remains. Thirdly, repairs contribute to saving materials going to the manufacture of new equipment. When restoring parts, the consumption of materials is 20... 30 times lower than when making them.

Numerous studies have shown that the first overhaul, as a rule, is more profitable than the purchase of a new vehicle in all aspects of the cost-effectiveness of public labor. This is due to two possible circumstances:

- actual costs for the first overhaul of most types of machinery and equipment do not exceed 3040% of their book value, while repeated repairs are much more expensive;

- Most types of machines undergo the first overhaul, as a rule, before moral wear.

The total number of parts in modern cars and tractors is thousands of items. However, the number of parts that limit their service life until overhaul does not exceed several dozen items. The object is to increase the durability of these parts to the level of providing the longest life of the machine.

In addition to finding ways and methods to increase reliability, which is embedded in the design of the vehicle during design and is introduced in the field of production, it is necessary to find ways and methods to solve the same problem in the field of operation and repair. The actual service life before major repairs depends on how reasonably the life of cars will be used in operation.

Car repair production, having received significant development, has not yet fully realized its potential opportunities. In terms of its efficiency, organizational and technological level, it is still lagging behind the main production of the automotive industry. The quality of repairs remains low, the cost is high, the level of mechanization reaches only 25... 40%, as a result of which labor productivity is twice as low as in the automotive industry. The automotive repair plant (ARP) is equipped mainly with universal equipment of a large degree of wear and tear and low accuracy. These are the negative aspects of the modern state of car repair production and determine the ways of its development.

Arrangement, analysis of operation and characteristics of main causes of assembly unit operability loss

The tapping bracket is a part of the MTZ80 tractor clutch release mechanism. The bracket is a bearing part. On the hollow cylindrical neck of the bracket, a retraction sits freely, which moves along it when the clutch pedal acts on the shutdown fork through the push-pull rod system and controls the operation of the pressure disk. A tubular shaft of the rear BOP drive passes through the through axial hole, which rotates on a bearing pressed into the bracket on the side of the flange. A gland is installed between the bearing in the groove of the bracket, which prevents ingress of lubricant from the bearing on the clutch disk. Transmission drive shaft passes through tubular shaft of VOM drive. With an annular recess, the bracket assembly is installed in the clutch housing and is attached to it through a flange connection with three bolts.

During tractor operation, the bracket receives significant axial forces and torsional vibrations due to uneven rotation of the engine crankshaft. Because of this, the internal surfaces for the bearing and gland wear. Due to the intensive operation of the clutch release mechanism, wear of the surface of the bracket neck occurs at the point of movement of the tap. The bracket is made of grey cast iron CH 18, in which carbon is mostly in the form of graphite. This material is easily machined by cutting and weldable, but under impact loads it breaks down, in the place of fracture it has a gray color

The tapping bracket of the MTZ80 tractor clutch disengagement mechanism, entering the overhaul, has the following defects:

Wear of the outer cylindrical surface for installation in the coupling case on the flange side.

Wear of inner cylindrical surface for bearing installation.

Wear of groove surface for gland.

Local wear of outer cylindrical neck for retraction.

Choosing a Rational Way to Eliminate Basic Part Defects

The next step is to analyze how to restore the part and select the most rational methods.

Such a defect as surface wear through thickness can be repaired by surfacing followed by machining by turning and grinding. Wear of surfaces for roller bearing of NLG and for gland is restored by surfacing with subsequent grinding.

You must select the best methods to repair the required defects. According to the part drawing, the class and group to which the part belongs by structural and technological characteristics are selected. The part to be restored belongs to the fourth group of third-class parts. To select competitive recovery methods, the design and technological characteristics of the parts are used, taking into account the eight most important features: shape, dimensions, coating thickness, surface hardness, fatigue strength of the part material, and the nature of the acting loads. Based on these features, possible methods of restoring parts and specific indicators of the technical level of technology, economic efficiency and technical level of the part after restoration are determined. After analyzing the durability indicators for this class of parts after repair, it is most advisable to use the surfacing with Sv.0G2C GOST 224670 wire in carbon dioxide GOST 105086 in order to restore such defects as wear of surfaces for bearings and mating parts, followed by running and grinding. Prior to build-up, the parts are properly geometrically shaped by machining.

The part recovery process consists of the following:

1. cleaning of parts from dirt and oil;

2. grinding of parts surface with sandpaper;

3. assembly of parts on special suspensions;

4. isolation of places not subject to build-up;

5. surfacing with Sv.0G2S wire, GOST 224670 in carbon dioxide, GOST 105086.

6. washing with hot water;

7. removal of parts with suspension and removal of insulation;

8. quality control of build-up;

9. machining - semi-finished and tillage, material of the cutting part of T15K6 tool at abundant cooling;

10. machining - grinding the parts to the required size with an electrocorundum stone with a graininess of 4660 μm, with abundant cooling.

11. quality control of surfaces.

The surfaces should be smooth, without a large number of tubers, dentrides, breaks, exfoliation and other types of defects.

Assembly technology of the assembly. Basing Individual Joint Assembly Methods

The initial data for the design of the assembly process are the assembly drawing of the assembly and the specification for the assembled assembly. It is advisable to present the assembly process as a structural diagram. In the assembly diagram, the process is depicted in the form of a line to which the attachable units, parts, and fastening elements adjoin.

The bracket is a bearing part. On the hollow cylindrical neck of the bracket, a retraction sits freely, which moves along it when the clutch pedal acts on the shutdown fork through the push-pull rod system and controls the operation of the pressure disk. A tubular shaft of the rear BOP drive passes through the through axial hole, which rotates on a bearing pressed into the bracket on the side of the flange. A gland is installed between the bearing in the groove of the bracket, which prevents ingress of lubricant from the bearing on the clutch disk. Transmission drive shaft passes through tubular shaft of VOM drive. With an annular recess, the bracket assembly is installed in the clutch housing and is attached to it through a flange connection with three bolts. The diagram of the assembly is shown in the graphic part.

Conclusion

During the course design process, the process of restoring the tapping bracket of the MTZ80 tractor clutch mechanism was developed. The part operation conditions and possible defects were analyzed. The bracket defect map has been developed. Possible recovery methods for each defect were analyzed.

The main defect is wear of the surfaces for the bearing and gland, for the clutch housing and retraction. From the possible methods of restoring the main defect, the optimal method was chosen - a method of welding with wire in a carbon dioxide medium with subsequent machining at a nominal size.

The main time to restore the part was 30.18 minutes. The necessary equipment, process equipment, cutting and measuring tools are selected for performance of technological operations. Processing modes and technical time standards for performance of technological operations were calculated.

The technical and economic evaluation of the project was carried out according to the main indicators, which makes it possible to talk about a fairly high economic efficiency of restoring the retraction bracket by the selected methods and means of production.