1. 研究目的与意义（文献综述）

1, research status
With the development of economy, automobiles have become one of the most important modes of transportation in today's society. The phenomenon that comes along with them is people's attention to the dynamics, economy, safety and comfort of automobiles. The function of the automobile brake system is to make the car run at proper deceleration until it stops; when driving downhill, the car is kept at an appropriate stable speed; the car is reliably parked in place or on a slope. Therefore, it is necessary to fully consider the various performances of the brake control mechanism and the brake actuator, and then design the brake of the automobile to meet the requirements for safe driving of the vehicle. According to the relevant information, in the accident caused by the vehicle's own problems, the accident caused by the failure of the brake system is 45% of the total. It can be seen that the brake is an extremely important system for ensuring the safety of driving. In addition, the quality of the brakes directly affects the average vehicle speed and the transportation efficiency of the vehicle, which is an important factor in ensuring the economic benefits of transportation. The brake is the most important safety component in the automotive brake system. It is of great significance to perform in-depth analysis of the vehicle brake.
At present, almost all brakes used in automobiles are friction-type, which can be divided into two major categories: drum type and disc type. The main advantage of disc brakes is that they are generally free of friction and help the effect, so the brake performance is less affected by the friction coefficient, that is, the performance is more stable; after the performance of water immersion is less, and only need to brake once or twice to return to normal In the case of the same output braking torque, the size and mass are generally small; the thermal expansion of the brake disc along the thickness direction is very small, and the brake pedal stroke will not be significantly increased like the thermal expansion of the brake drum. Too large; easier to achieve automatic gap adjustment. The brake can be quickly braked at a high speed, and the heat dissipation effect is better than the drum brake. The constant of the braking performance is good, and it is easy to install advanced electronic equipment like ABS. The main advantage of a drum brake is that the brake shoe wears less, the cost is lower, and maintenance is easier. Although in the field of automotive brakes, disc brakes will gradually replace drum brakes is an inevitable trend, but at this stage, drum brakes still occupy a very important position. In the braking process of a four-wheeled vehicle, due to the inertia, the load of the front wheel usually accounts for 70%-80% of the total load of the car. The braking force of the front wheel is larger than that of the rear wheel, and the rear wheel plays an auxiliary braking role. In order to save costs, manufacturers use the front disc rear drum braking method. Nowadays, the most widely used car is the front disc rear drum or full disc brakes, of which 20% of cars use front disc rear drum brakes. Although the entire drum brake in the car industry has basically been eliminated, but in commercial vehicles, due to the heavier load, the friction needed is larger, and the drum brake is widely used, and in the electric bus, it is generally With disk brakes, the vehicle controller will issue commands to the motor controller for energy recovery to assist the brakes.
Compared to disc brakes, drum brakes have much lower braking performance and heat dissipation. Drum brakes have poor braking force stability and vary greatly in braking force on different road surfaces and are not easily controlled. Due to poor heat dissipation performance, a large amount of heat will accumulate during the braking process. Brake shoes and brake drums are prone to extremely complicated deformation under the influence of high temperature, and are prone to brake decay and chattering, resulting in braking efficiency. decline. In addition, after the drum brakes have been used for a period of time, the gaps of the brake shoes should be regularly adjusted.
In view of the above drawbacks, drum brakes are now taking some improvement measures: 1) Reasonably determine the diameter of the brake drum 2) Reasonably determine the width of the friction lining 3) Reasonably determine the heat dissipation structure of the hub 4) Reasonably select the tire and wheel rim 5) Install the valve Mouth retaining card 6) Adopt current advanced technology to prevent the wheel from overheating, such as automatic adjustment arm using brake clearance and using retarder.
2. The basis, purpose and significance of the topic
Electric buses mainly refer to pure electric buses, all of which use electric energy to drive. Such products have low noise, high driving stability, and zero emissions. The electric bus refers to a bus powered by a car. The electric bus is equipped with a suitable on-board battery or cable-powered device to provide electric energy to drive the bus. The electric bus has good power performance, continuous mileage of 500 kilometers, long battery life (more than two years) and low cost, and is well equipped with the vehicle. Vehicles that meet the requirements of road traffic and safety regulations. Electric bus is the national 863 plan put forward a new generation of electric vehicle technology as the main direction of China's automotive technology innovation. It plans to focus on the industrialization technology platform of electric vehicles in the “Eleventh Five-Year Plan” period, and strive to achieve a major breakthrough, to seize the new A new generation of electric vehicle industry technology highs, diversification of transport energy structure, maintain national energy security, reduce vehicle emissions, ensure sustainable social development, improve China's auto industry's ability for independent innovation, and realize the leap-forward development of the automotive industry. The requirements of the electric vehicle for its transmission system are good torque control capability, high torque density, operational reliability and efficiency as high as possible throughout the entire speed range, so as to ensure that the vehicle has good dynamic performance and controllability. When the vehicle-mounted power battery fails to make a breakthrough, the vehicle's driving range is extended. Researching and developing a high-level motor drive control system is of great significance to improving the level of China's electric vehicle drive system and the industrialization of electric vehicles. With the improvement of performance and cost reduction of permanent magnetic materials, permanent magnet synchronous motors are gradually becoming one of the mainstream motors of electric vehicle transmission systems due to their high efficiency, high power factor and high power density.
Brakes are an extremely important system for ensuring the safety of driving. In addition, the quality of the brakes directly affects the average vehicle speed and the transportation efficiency of the vehicle, which is an important factor in ensuring the economic benefits of transportation. The brake is the most important safety component in the automobile brake system. It is of great significance to carry out in-depth analysis of the pure electric bus brake.

2. 研究的基本内容与方案

second, the design (thesis) main content:
(1) analyze the structural pattern of the brake system (including the automatic brake actuator) and components of the automatic driving pure electric bus;
(2) determine the structural design scheme of the brake system and components of the self-driving pure electric bus;
(3) determine the technical parameters of the brake system and its components;
(4) design and analysis of braking system and its components;
(5) determine the specific structural size parameters of the brake system components;
(6) drawing brake system structure diagram, brake assembly drawing, automatic brake actuator assembly drawing and main parts drawing.
third, the technical program

1: considering the bus location, consideringthe stability of braking performance, dual circuit brake system of type x; dueto the advantages of pneumatic brake system driving force in small can producethe braking force is large enough, the general bus, vehicle quality largetrucks, at present almost all the air brake system, brake pressure theadvantages are as follows:

when braking, the driver only needs tomanipulate the brake control valve, and the driving force is completelyproduced by the air pressure, thus the power saving is manipulated.

the compressed air produced by the gas supplyequipment can be used to drive other auxiliary devices (such as the wiper, thedoor opening and shutter, etc.).

3. 研究计划与安排

v. schedule
1~2 (19th and 20th weeks of the 7th semester): determine graduation design topics, graduation design assignments (related parameters), and collection of information on campus
3 (1st week of 8 semesters): plan conception, literature search, completion report

(2-3 weeks of 8th semester): off-campus internship, off-campus data collection, completion of internship report

4 (4th week of 8 semesters): foreign language translation, data recollection
the
5~7 (5th to 7th week of 8 semesters): design calculation, sketching

4. 参考文献（12篇以上）

6. references
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