Development of brake bench - PU, Drawings

Summary

1. Degree project scope:

1) Graphic part - 11 sheets, including:

- structural part of 8 sheets

- process part 3 sheets

2) Explanatory note - 143 sheets.

The note presents calculations for all parts of the project, as well as the necessary diagrams and figures, and for some calculations summary tables.

2. The thesis project I presented addressed the topic:

Car Brake Diagnostic Post with Test Bench Development

The structural part contains the substantiation of the technological decisions made by me, the technological characteristics of the test bench for testing brakes and its purpose, device and maintenance. I also made calculations of the main parameters of the brake bench, chain transmission, as well as kinematic and power calculation of the lifting mechanism.

The process part contains my developed technological process of the operation of assembly of the brake bench drive shaft, as well as the production of bushing and roller chains.

In the economic part, I calculated the efficiency of investments, the payback period and the annual economic effect of the reorganization of the diagnostic post for the braking mechanisms of cars.

In the section "Ecology and life safety," safety requirements for the operation of the brake bench were developed, characteristics of meteorological conditions in the working area of ​ ​ the room were given, and fire and electrical safety conditions were developed. Also, in accordance with SNiP 052395 "Natural and artificial lighting," the calculation of internal artificial lighting was carried out and the main lighting values ​ ​ of artificial lighting and the power of the lighting installation of the room were determined.

Introduction

During the transition of the economy of our country to market relations, the development of the automotive service of road transport and the tasks of increasing the economic efficiency of work and reducing the labor intensity of its maintenance and repair are new.

The efficiency of the use of vehicles depends on the perfection of the organization of the transportation process and the properties of cars to maintain within certain limits the values ​ ​ of the parameters characterizing their ability to perform the required functions. During the operation of the vehicle, its functional properties are constantly deteriorated due to wear, corrosion, damage to parts, fatigue of the material from which they are made, etc. Various faults (defects) appear in the car, which reduce the efficiency of its use. To prevent the appearance of defects and their timely elimination, the car is subjected to maintenance and repair.

Productivity in road transport is also directly dependent on the technical condition of cars, their readiness to reliably, qualitatively, economically and safely carry out the transport process. The condition of cars, in turn, depends on the organization, technology and quality of work during their diagnosis, maintenance and repair.

Maintenance - a complex of operations or an operation to maintain the operability or correct a car when used for its intended purpose, when standing, storing or transporting. Maintenance is a preventive measure and is carried out forcibly as planned through certain periods of use of the car, depending on its type and operating conditions.

Repair is a set of operations to restore serviceability or operability and restore the life of a car or its components. Repair is performed during maintenance. There are two types of repairs: current (TR) and capital (CR).

Maintenance and repair works are preceded by an assessment of its technical condition: diagnostics.

Diagnostics, being a subsystem of information for production control, is at the same time, as already stated, an element of the maintenance and maintenance system itself (mainly allocated in maintenance) and a subsystem for monitoring the quality of work and technical condition of cars not only at ATP but also outside them. Due to the possibility of determining a fault without disassembly, they are detected during regular diagnostics before the failure occurs, which allows you to plan their elimination, prevents progressive wear of parts and reduces the total consumption for maintenance and maintenance. Diagnostics also contribute to reducing fuel consumption and other operational materials, environmental pollution, as well as improving traffic safety, technical readiness of the automobile fleet and other technical and economic indicators of its use.

Analyzing the experience of the development of the car maintenance and repair industry in foreign countries and in Russia, the following conclusions can be drawn in terms of equipping enterprises with diagnostic and repair equipment:

1) Enterprises for maintenance and repair of cars are equipped with more and more advanced production equipment, new technological processes are introduced, labor intensity of production is reduced and quality of works is improved.

2) In car maintenance, diagnostic methods using electronic equipment are increasingly being introduced.

3) The use of modern equipment for maintenance and repair of cars provides and accelerates many technological processes, but requires the maintenance personnel to assimilate a certain range of knowledge and skills: knowledge of the car structure, the main technological processes of maintenance and repair, the ability to use modern instrumentation, tools and devices.

4) Well-organized maintenance and timely diagnosis of cars with highly qualified performance of work make it possible to increase the durability of cars, reduce from simple, increase the time between repairs, which, in turn, significantly reduces non-production costs and increases the profitability of motor vehicles.

1.2. Purpose of braking bench

Automatic braking bench is designed to control the efficiency of the braking systems of passenger cars of subcategory M1 according to GOST 25478-82 with a weight in running order of up to 2.5 tons and a gauge of 950-1750 mm in conditions of motor transport enterprises and maintenance stations.

The stands are intended for operation in the designated territories of motor vehicles whose electric networks are not connected to the networks of residential buildings.

The test bench can be operated in rooms that meet the requirements of accommodation category 4 in the climatic design of U and UHL as per GOST 1515069.

In terms of resistance to mechanical impacts, the bench design is ordinary as per GOST 1299776.

The design of the brake stand provides for the maintenance of cars of different types and bases.

1. 1. Justification of technical solutions

As mentioned above, productivity in road transport is directly dependent on the technical condition of cars, which, in turn, depends on the organization, technology and quality of work during their maintenance and repair.

Knowledge of this dependence, i.e. quantitative and qualitative characteristics of regularities of changing parameters of technical condition of units, units and the whole car as a whole allows to control operability and technical condition of the car during operation, to maintain and restore its operability.

Modern and high-quality maintenance is the main means of maintaining the car in its proper technical condition. The use and introduction of the latest diagnostic tools that allow you to monitor the technical condition of the car on the basis of external signs, without disassembly, as well as equipment for maintenance and repair made using advanced technologies allows you to significantly reduce the cost of service and improve the quality of service for cars.

Diagnostics make it possible to detect malfunctions and determine the life of failure-free operation of the car until partial or complete loss of its operability. It is carried out on specialized stands using a large number of both built-in and mounted sensors using a large number of electronics.

At first, the condition of the braking system was assessed by measuring the braking distance at a certain speed. Measurements were considered invalid if the driver had to turn the steering wheel to hold the vehicle in a straight line. On paper, this looked very convincing, but in the conditions of mass maintenance and technical inspections, it was simply impossible to perform all the test conditions correctly. Try to find a horizontal and clean platform on which you can accelerate the car to 30, and since 1985 - to 40 kilometers per hour, and so that there is still room for braking!

In addition, how to measure the exact value of the braking, and not stopping path? If you make each driver slow down after crossing a line, then the result of the measurement will depend more on whether this driver slept or spent a stormy night and responds to everything like a dinosaur. It is clear that neither money nor other opportunities were enough to organize the check according to all the rules. Therefore, the check was reduced to a pure formality: a small acceleration and braking until the wheels were blocked. If the length of the black strips on the asphalt is approximately the same, the brakes are in order.

In the already mentioned 1985, a new method for measuring brake performance - by deceleration - was added to the rules. But for this, the same platform was required, and also a special device - a decelerometer. This method is much more accurate, since wheel locking is not the most effective way to stop the car, and here braking is possible on the verge of yuz. And the response time of the driver does not matter. Nevertheless, such methods of verification were very dependent on the weather and other external factors.

The increase in the number of cars has led to an increase in traffic density and the need to use a quick and accurate method to assess the technical condition of the car and, in particular, its brakes. The most accurate and detailed measurement results can be obtained on a special stand.

Stands are of two types - platform and roller. When using the former, the car accelerates to a relatively high speed and brakes on special platforms associated with the measuring system. In the second, the movement is imitated by the rotation of the drums on which the wheels rest. In both cases, the maximum force with which the surface engages the wheel is measured.

Landing stands allow to obtain approximate values of braking forces for wheels of one axle, but at the same time there are several difficulties. Firstly, the results are distorted if you stop at the stand unevenly or turn the steering wheel during braking. Secondly, to perform braking precisely on a site about a meter long, especially with rear wheels, under the power of only a high-skill driver. Finally, thirdly, checking the parking brake involves increased danger, since it may not be strong enough to stop the car within the allotted area. In order not to expose themselves and others to danger, it is recommended to use site stands only for operational control of cars.

It is much safer and more accurate to check the braking system on roller stands. The car is standing, and it does not matter whether its braking system is serviceable; he will not harm anyone.

All this is well and easily feasible for single-axle vehicles. For all-wheel drive cars, this technology can give a significant error. This is due to the features of their transmissions. As you know, all-wheel drive machines come with a permanent and disconnectable drive to the second axle. In the latter case, you simply need to turn off all-wheel drive. The most difficult are machines with permanent all-wheel drive. The presence of a constant connection between all four wheels leads to the fact that the braking torque from one wheel is transferred to another in accordance with the degree of blocking of the inter-axle and inter-wheel differentials. For example, the Torsen inter-axle differential installed on the Audi Quattro has a blocking factor of about 30%. Accordingly, the wheels of one axle will brake the wheels of the other axle thirty percent even if the brake pedal is not pressed, and the inter-wheel differential will simply divide this moment equally between the right and left wheels. At the same time, the relative value of the difference in braking forces on the wheels will decrease, and the measurement result will not reflect the real state of things. To overcome this error, additional equipment is used when working with all-wheel drive cars.

To assess the technical condition of the braking systems of cars at ATP and STO, roller (drum) stands are mainly used. Of the roller stands, the predominant majority use stands based on the power method of diagnosis.

The power method allows determining the braking forces of each wheel at a given pressure on the brake pedal, measuring the response time of the brake drive, and assessing the condition of the brake drums and linings.

More reliable is the inertial diagnostic method on special roller inertial stands. They measure the braking distance on each individual wheel, the time of actuation of the brake drive and deceleration (maximum and on each wheel separately). Due to the complexity, high cost and lower processability in operation, these stands are used extremely limited.

Power roller stand consists of support device, main (stationary) and remote control and indication panels, pedameter and (if necessary) safety devices.

The support device of the power roller stands is most often made in the form of two independent units, which allows them to be conveniently placed on the inspection ditch, without cluttering it and providing free access to the control points of the braking mechanisms. Roller assembly consists of two rollers interconnected by chain transmission, reduction motor and force-measuring sensor. When measuring the braking force, torque from the output shaft of the reduction motor is transmitted to the driving and driven rollers. The reactive moment of the gear motor housing is sensed by a force measuring sensor, the output of which is proportional to the braking force.

The test bench developed in this project for checking the brakes of cars is a stationary roller, based on the power diagnostic method. It consists of a support device, main and remote control and indication panels.

It allows you to diagnose cars with a total weight of up to 2.5 tons. Support device is made in the form of two independent units. Roller assembly includes two rollers interconnected by chain transmission, reduction motor and lifting device.

A feature of this braking bench is a lifting device consisting of a lifting roller driven by an electric motor using eccentrics.