Briefly describe the characteristics of the electro hydraulic braking system of hybrid electric vehi

It is characterized by the ability to accurately perceive the priority of the driver's control pedalsIt is converted into an electrical signal and transmitted to the electronic control unit, which automatically adjusts the brake pressure of the wheels according to different driving conditions. This system shortens the reaction time and avoids the danger of the driver unconsciously reducing the braking force due to vibrations caused by the reaction force of the hydromechanical braking system.

Main advantages: 1. Compact structure, improved braking efficiency;

2. The control is convenient and reliable, and the braking noise is significantly reduced;

3. There is no need for a vacuum device, which effectively reduces the kicking of the brake pedal and provides a better pedal feeling.

Comparison of electro-hydraulic braking system technology products.

Traditional electronically controlled hydraulic braking system, electronically controlled vacuum power assist system and electro-hydraulic power assist system 3 kinds of electronically controlled hydraulic braking system technical routes are different, brake control mode and so on are different, and also have their own advantages and disadvantages. The traditional electronically controlled hydraulic braking system appeared earlier, but its structure is complex, the technical difficulty is high, and the reliability needs to be improved, so it is only applied in some high-end models and a few Japanese cars.

The electronically controlled vacuum booster system has a simple structure and low cost, and is the most mainstream electronically controlled vacuum braking system solution on the market. The electro-hydraulic power assist system is only launched in recent years and gradually improved the braking system, its braking efficiency is high, can integrate a variety of brake assist functions, for new energy vehicles to achieve maximum energy **, is expected to be the mainstream electro-hydraulic braking system in the future.

The general working principle of the braking system is to use the friction between the non-rotating elements connected to the body (or frame) and the rotating elements connected to the wheels (or transmission shafts) to prevent the rotation or rotation of the wheels.

The working principle of hydraulic brakes is as follows:

1. The brake is composed of a yoke, an excitation coil, a spring, a brake disc, an armature, a spline sleeve, a mounting screw, etc., and the brake is installed at the rear end of the flange (or motor) of the equipment; The transmission shaft is connected with the spline sleeve and the brake disc;

2. When the excitation coil of the brake is connected to the rated voltage (DC), the electromagnetic force attracts the armature, so that the armature is separated from the brake disc (released), then the transmission shaft runs normally with the brake disc or starts, when the transmission system is separated or powered off, the brake is also powered off at the same time, and the spring is pressed on the armature at this time, forcing the friction torque between the brake disc and the armature and the flange to make the transmission shaft stop quickly;

3. When the heat dissipation environment of the brake is poor and the transmission shaft is working continuously for a long time, if the conditions permit, the voltage can be converted to 70%-80% of the rated voltage after the brake works, so as to reduce the heat.

Photo by Li Yuanli of Pacific Automobile Network).

The full hydraulic braking system consists of: filling valve, accumulator, foot valve, caliper disc brake (or other forms of brake), as well as brake tail light switch, pressure switch, etc. The pressure oil is fed to the accumulator through the filling valve and then goes all the way to the foot valve, which is actually a proportional reversing valve for the foot pedal, and then enters the brake next to the tire.

When the braking force is insufficient, the accumulator can supply oil for a short time.

There is also a brake in the form of an air pusher. The vacuum booster pump on the engine generates pressure gas, pushes the brake cylinder, and the right side of the brake oil pot enters the brake cylinder, which serves the purpose of increasing force, and then enters the brake.

Most of today's brakes are disc brakes rather than drum brakes.

Automotive electronic control systems can be divided into the following four parts:

1) Centralized control system for engine and power transmission. Including centralized engine control system, automatic transmission control system, brake anti-lock and traction control system, etc.;

2) Chassis integrated control and safety system. Including vehicle stability control system, active body attitude control system, cruise control system, collision avoidance warning system, driver intelligent support system, etc.;

3) Intelligent body electronic system. Automatic seat adjustment system, intelligent headlight system, car night vision system, electronic door lock and anti-theft system, etc.;

4) Communication and infotainment systems. Including intelligent car navigation system, voice recognition system,"on star"system (with automatic call for help and query and other functions), automobile maintenance data transmission system, car audio system, real-time traffic information consultation system, dynamic vehicle tracking and management system, information service system (including network, etc.), etc.

The following is a brief introduction to the automotive electronic control devices in some areas that are currently more common and mature.

a) Engine control part.

1.Electronically controlled ignition (ESA).

The system allows the engine to work under the best ignition advance angle under different speeds, air intake and other factors, so that the engine can output maximum power and torque, while reducing fuel consumption and emissions to a minimum. The system is divided into two types of control: open-loop and closed-loop. The closed-loop control system of the electronically controlled ignition device is fed back through the detonation sensor, and the control accuracy of the ignition time is higher than that of the open loop, but the exhaust gas purification is poor.

2.Electronically Controlled Gasoline Injection (EFI).

According to the signals transmitted by each sensor, the system can effectively control the air-fuel ratio of the mixture, so that the air-fuel ratio of the engine can reach the best value under various working conditions, so as to achieve the effects of increasing power, reducing fuel consumption and reducing exhaust pollution. The system can be divided into two types of control: open-loop and closed-loop. Closed-loop control is based on open-loop control, under certain conditions, the computer corrects the fuel supply according to the oxygen concentration signal output by the oxygen sensor, so that the air-fuel ratio of the mixture is kept in an ideal state.

3.Exhaust gas recirculation control (EGR).

In this system, a part of the exhaust gas is introduced into the fresh mixture on the intake side for re-combustion to suppress the generation of nitrogen oxides, which are harmful gases in the engine. The system can adjust the exhaust gas circulation rate involved in exhaust gas recirculation in a timely manner according to the working conditions of the engine, so as to reduce the harmful gas nitrogen oxides in the exhaust gas. It is an effective means of exhaust gas purification.

4.Idle Speed Control (ISC).

The system can make the engine idle speed in the best state according to the engine coolant temperature and other relevant parameters, such as air conditioning switch signal, power steering switch signal, etc.

In addition to the above control devices, the control content of the engine part includes: engine output, cooling fan, engine displacement, valve timing, secondary air injection, engine pressurization, oil and gas evaporation control and system self-diagnosis.

In addition, with the further development of computer technology, computers will take on more important tasks in modern automobiles, such as controlling the volume and shape of the combustion chamber, controlling the compression ratio, and detecting the increasing mechanical wear of automobile parts.

2) Chassis control.

The braking force of the left and right wheels is evenly distributed during braking.

Easy access to the correct distribution of braking power to the front and rear wheels.

When the car vibrates or the suspension is deformed, it will not brake on its own, nor will it affect the original braking efficiency.

The sealing requirements are strict, and there is "no leakage" in the pipeline, and if there is an oil leak, the whole system will fail.

The viscosity of the brake fluid changes with the change of the external temperature of the car, the viscosity is very high at low temperature, and the gas resistance may evaporate at high temperature, which seriously affects the braking effect.

It cannot be held for a long time to act as a brake, so that the brake pedal needs to be pressed constantly.

It can be used in combination with various boosters, or use two-stage and multi-stage pumps to form a variety of servo braking systems to obtain greater braking force.

Hydraulic braking is when the driving brake, the medium that transmits the pedal force is hydraulic oil! The basic working principle is that there is a booster cylinder and four working cylinders! Anyone who knows a little about hydraulics understands... I won't go into details!

Booster cylinder, also called master cylinder! The working cylinder, which is the caliper we see with the disc brakes of the car!