In the past, domestic ABS production enterprises were small in scale, with few supporting facilities and few mature technologies. So far, only one enterprise in Zhejiang Asia Pacific has produced qualified ABS products, with an annual sales volume of over 65,438+10,000 sets. On the contrary, ABS technology abroad is very mature, and China is still in the primary stage of development. With the support of foreign batch and large scale, the ABS cost of multinational companies is lower than that of domestic enterprises. The cost for domestic enterprises to produce a set of ABS is around 800 yuan. At present, most enterprises can only enter the supporting system of their own brand passenger cars. The price quoted by multinational companies to independent brand automobile manufacturers has dropped to 500 ~ 600 yuan, which has caused great competitive pressure to domestic related enterprises.
At present, most domestic enterprises with good ABS product research and development are private enterprises. These private enterprises have a big gap between their own capital accumulation and technology accumulation and foreign brands, and they will encounter many difficulties in the process of independent research and development. They can continue to invest in ABS products, which requires considerable capital and market grasp. Professor Fang Yonglong told reporters that even in ABS products, some manufacturers still need to import key parts from abroad. Domestic automobile enterprises, especially passenger car enterprises, also have doubts about the performance stability of domestic brands, making foreign brands still occupy the main market.
It is predicted that by 20 10, the total demand of automobile ABS in China will exceed 6 million sets, and the average annual growth rate of the market will exceed 30% in the next few years. To promote the development of China's automobile ABS industry, on the one hand, the government should strengthen guidance; On the other hand, enterprises need to improve their technological development capabilities and product quality, as well as the intensity of publicity and promotion.
At present, compared with the whole vehicle procurement, the government has little support for the independent brand procurement of independent brand auto parts. First, there are few domestic enterprises producing core spare parts, and the scale is small, which has not yet formed. As far as ABS industry is concerned, we should speed up the industrialization process of our own brand ABS. In the future, the matching degree between self-owned brand ABS and the whole vehicle will be higher and higher, and the product development between parts enterprises and automobile manufacturers should be carried out together to form a complete supporting system.
Theoretical basis and working principle of anti-lock braking system
The tangential friction between two objects is determined by the vertical force (the gravity of the car to the ground) and the friction coefficient. The sliding friction coefficient is generally a fixed value, and the static friction ranges from zero to the maximum static friction coefficient. The maximum static friction coefficient is greater than the sliding friction coefficient under the same conditions except tangential relative motion and static state, that is, the maximum static friction coefficient is greater than the sliding friction coefficient (this is the braking force that the automobile can achieve).
The ABS anti-lock braking system tries to change the sliding friction between the wheel and the ground into static friction when the vehicle is braking (at this time, the contact part between the wheel and the ground remains relatively static, and the car does not stop, but the wheel rolls instead of locking, and the braking system can apply braking force to the wheel within the maximum static friction, and the static friction between the wheel and the ground is rolling friction at this time), thus increasing the braking force.
ABS anti-lock braking system
The Chinese translation of "ABS" is "anti-lock braking system". It is an automobile safety control system with the advantages of anti-skid and anti-lock braking. ABS is an improved technology based on conventional braking devices, which is divided into mechanical and electronic types. Modern cars are equipped with a large number of anti-lock braking systems. ABS not only has the braking function of ordinary braking system, but also can prevent the wheel from locking, so that the car can still turn under braking conditions, ensure the stability of the braking direction of the car and prevent side slip and deviation. ABS is the most advanced braking device with the best braking effect in automobiles at present.
In the past, consumers used to regard ABS as an important indicator when buying a car. With the development of technology, at present, most domestic cars adopt ABS as the standard configuration. However, many drivers are not very clear about the understanding and correct use of ABS, and even have some misunderstandings about ABS. Some drivers think that ABS is a device to shorten the braking distance. The braking distance of vehicles equipped with ABS on any road surface must be shorter than that of vehicles without ABS. Some people even mistakenly think that the braking distance on ice and snow pavement can be equivalent to that on asphalt pavement. There are also some drivers who believe that as long as ABS is equipped, even if driving at high speed on rainy days or icy roads, there will be no loss of control of vehicles. ABS has not greatly improved the limit of automobile physical properties as some people think. Strictly speaking, the function of ABS is mainly to ensure the maneuverability and stability of the vehicle itself when braking within the physical limit performance. At the same time, it can also prevent the pure slip of the tire during acceleration, and improve the acceleration performance and handling stability.
Application of ABS
The full name of ABS is anti-lock braking system or anti-skid braking system, which can effectively control the wheels to keep rotating, improve the braking stability of vehicles and the braking performance of vehicles in bad road conditions. ABS constantly detects the rotational speed of each wheel through the rotational speed sensor installed on each wheel or transmission shaft, and the computer calculates the wheel slip rate at that time and compares it with the ideal slip rate, so as to make a decision to increase or decrease the braking pressure of the brake, and order the actuator to adjust the braking pressure in time to keep the wheel in an ideal braking state.
1906 ABS obtained the patent for the first time, and1936abosch registered the "mechanical" patent to prevent the wheels of motor vehicles from locking. All early designs have the same problem: too complicated, easy to fail and too slow to operate. 1947 the world's first ABS system was first applied to the B-47 bomber. Teldix company began to study this project on 1964, and its ABS research was quickly taken over by Bosch. Within two years, the first batch of ABS test vehicles have the function of shortening the braking distance. The steering and stability of the vehicle are also guaranteed when turning, but about 1000 analog components and safety switches were used at that time, which means that the reliability and durability of the electronic control unit called ABS 1 system can not meet the requirements of mass production and needs to be improved. Bosch's technology in developing electronic engine management, digital technology and the arrival of integrated circuits (ICs) have reduced the number of electronic components to 140.
1968 ABS began to study and apply to automobiles. 1975 due to the adoption of the American federal motor vehicle safety standard 12 1, many heavy trucks and buses are equipped with ABS. However, due to many technical problems in the braking system and the opposition of the truck industry, the standard was revoked in 1978. In the same year, Bosch, as the first company in the world to launch an ABS system with electronic control function, began to install this ABS 2 system as an optional configuration, and assembled it on a Mercedes-Benz S-Class sedan, and then quickly installed it on a BMW 7 Series luxury car. After this period, the further research and design of ABS in the United States decreased, but manufacturers in Europe and Japan continued to carefully develop ABS.
Since 1980s, American automobile manufacturers have shown new interest in ABS in American automobile market, because all cars imported from America are equipped with ABS. With the rapid development of microelectronics technology and people's strong demand for automobile driving safety, ABS devices have been further widely used in the world automobile industry. 1987, about 3% cars in the United States were equipped with very reliable ABS. In the following time, developers focus on simplifying the system. In 1989, Bosch engineers successfully installed the hybrid control unit directly on the hydraulic module. In this way, they do not need a wiring harness connecting the control unit and the hydraulic module, nor do they need a connector, so the overall weight of the ABS 2E is significantly reduced.
1993, Bosch engineers created ABS 5.0 with new solenoid valves, and developed versions 5.3 and 5.7 in the following years. The main features of the new generation ABS 8 are greatly reducing the weight, reducing the volume, increasing the memory and adding more functions, such as electronic distribution of braking pressure, thus replacing the mechanical mechanism to reduce the braking pressure of the rear axle. At that time, the predictions of some auto industry analysts were confirmed: after the mid-1990s, most cars and trucks in the world market will be equipped with ABS.
Function of ABS
The main function of ABS is to improve the braking performance of the whole vehicle, improve the driving safety, prevent the wheels from locking when braking (that is, stop rolling), ensure that the driver can still control the direction when braking, and prevent the rear axle from slipping. Its working principle is: in the case of emergency braking, once the wheel is found to be locked, the computer immediately controls the pressure regulator to release the pressure of the wheel brake cylinder, so that the wheel can resume rotation and achieve the purpose of preventing the wheel from being locked. The working process of ABS is actually a cyclic working process of "locking-releasing-locking-releasing", which keeps the vehicle rolling in the critical locking gap all the time, effectively overcomes the vehicle deviation caused by wheel locking during emergency braking, and prevents the occurrence of out-of-control situations.
ABS can be divided into mechanical type and electronic type. Mechanical ABS has a simple structure, and the braking force can be simply adjusted mainly by using its own internal structure. The working principle of the device is simple, there is no sensor to feed back signals such as road friction and wheel speed, and it works entirely by preset data. Whether it is a waterlogged pavement, an icy pavement, a muddy pavement or a good cement asphalt pavement, its working mode is the same. Strictly speaking, this kind of ABS can only be called "advanced braking system". At present, only some low-end pickup trucks and other models in China still use mechanical ABS.
Mechanical ABS only uses the physical characteristics of components for mechanical movement, while electronic ABS uses computers to analyze and calculate various data to get results. Electronic ABS consists of wheel speed sensor, wire harness, computer, ABS hydraulic pump, indicator light and other components. According to the signal of the wheel speed sensor of each wheel, the computer can apply different braking force to each wheel, so as to achieve the effect of scientific and reasonable distribution of braking force.
The earliest ABS system was a two-wheel system. The so-called two-wheel system is to install ABS on the two rear wheels of the car. Because the two rear wheels share a brake hydraulic pipeline and a control valve, it is also called "single channel control system". This system selects the braking pressure according to the state of the wheel with less adhesion among the two rear wheels, which is the so-called "low selection principle". That is to say, when one rear wheel of ABS vehicle adopts the principle of low selection and tends to lock, the system can only release pressure to both rear wheels at the same time. Because the front wheel has no anti-lock function, it is difficult for the two-wheel system to achieve the best braking effect.
With the development of related technology, a "three-channel control system" appeared later. Based on the two-wheel system, the two front wheels are independently controlled by two independent pipelines. Although the rear wheel still adopts the principle of "low selection", this system has the main characteristics of modern ABS because it realizes the steering function during emergency braking and the function of preventing the rear axle from slipping. Up to now, there are still vehicles in the market using this three-channel control ABS system.
At present, the most common vehicles are equipped with four sensors and four channels of ABS system, and each wheel is controlled by an independent hydraulic pipeline and solenoid valve, so that the independent control of a single wheel can be realized. This structure can achieve good anti-lock function.
Two control modes of ABS
1. two-parameter control
ABS controlled by two parameters consists of speed sensor (speed radar), wheel speed sensor, control device (computer) and actuator. Its working principle is that the vehicle speed and wheel speed signals are respectively input into the computer by the vehicle speed sensor and the wheel speed sensor, and the actual slip rate is calculated by the computer and compared with the ideal slip rate 15%-20%, and then the braking force of the brake is increased or decreased by the solenoid valve.
This kind of resistance sensor usually uses Doppler velocimetry radar. When the car is running, the Doppler radar antenna constantly emits electromagnetic waves to the ground at a certain frequency, and at the same time receives the reflected electromagnetic waves. By measuring the difference between automotive radar transmission and reception, the speed of the car can be accurately calculated. The wheel speed sensor is installed in the transmission housing and driven by the transmission output shaft. It is a pulse motor, and its frequency is directly proportional to the wheel speed.
The actuator consists of solenoid valve and relay. The solenoid valve adjusts the braking force to maintain the ideal slip rate. This kind of ABS can ensure the ideal control of slip rate and has good anti-lock braking performance, but due to the addition of a speed measuring radar, the structure is more complicated and the cost is higher. For example, the patent (patent number 9222 1809.9) reported by Shen Shusheng, an automobile magazine.
2. Single parameter control
The purpose is to control the angular deceleration of the wheel, control the braking force of the wheel and realize anti-lock braking. Its structure is mainly composed of wheel speed sensor, controller (computer) and solenoid valve.
Attached Figure 1 The wheel speed sensor consists of a sensor and a ring gear steel ring (see Figure 2).
1 .cable 2. Permanent magnet 3. A housing 4, an induction coil 5, and a polar shaft 6. ring gear
In order to accurately measure the wheel speed, there should be a gap of 1 mm between the sensor head and the wheel gear ring. In order to avoid the influence of water, mud and dust on the sensor, the sensor should be filled with butter before installation.
Solenoid valve is used for pressure adjustment of wheel brake. For a four-channel braking system, one wheel has a solenoid valve; Three-channel braking system, one for each front wheel and one for two rear wheels. The solenoid valve has three hydraulic holes, which are respectively connected with the master brake cylinder and the wheel brake cylinder, and can realize the pressure adjustment functions of boosting, maintaining and reducing pressure. The working principle is as follows.
1) Boost: When the solenoid valve is not working, the brake master cylinder interface is directly connected with each brake cylinder interface. Due to the force of the main spring, the oil inlet valve opens and the braking pressure increases.
2) Pressure maintenance: When the pressure in the wheel brake cylinder increases to a certain value, the oil inlet valve is cut off and closed. The bracket is kept in the middle state, and the three holes are sealed with each other to maintain the braking pressure.
3) Depressurization: When the solenoid valve works, the bracket overcomes the elasticity of two springs, opens the unloading meat, and reduces the pressure of the brake cylinder. Once the pressure is reduced, the solenoid valve is switched to the pressure holding state or the pressurization preparation state.
The main task of the control device ECU is to calculate, analyze, amplify and judge the signals sent back by the sensors of each wheel, and then the output stage outputs command signals to the solenoid valve to perform the task of brake pressure adjustment. The electronic control device consists of four parts: input stage A, controller B, output stage C and voltage stabilizing protection device D. 。
The electronic controller drives the solenoid valve at a frequency of 4- 10 1tz, which the driver cannot do.
This single-parameter control mode of ABS is widely used at present because of its simple structure and low cost.
Most Chrysler luxury cars in the United States are equipped with ABS with this single parameter control mode. It is equipped with wheel speed sensors on all four wheels of the car. The distribution valve (see Figure 5) is a three-channel distribution valve located under the brake oil pump assembly.
Fig. 2 A 45-tooth or 100-tooth gear ring is mounted on the wheel shaft, and the sensing head of the wheel speed sensor is mounted on the top of the gear ring. When the wheel rotates, the sensor constantly generates a voltage signal, which is input into the computer, and compared with the ideal speed in RoM, the speed increase or deceleration of the wheel is calculated, and the command of boosting or depressurizing is sent to the solenoid valve to control the braking force of the cylinder. Get out of ABS misunderstanding
The misunderstandings about ABS at the beginning need to be explained. If the wheels lock when the car brakes, the lateral adhesion that the car can get is the smallest. At this time, due to the imbalance of road adhesion coefficient, automobile braking force, suspension imbalance, automobile tire pressure, road curvature, bump or slope, the automobile may slip, tail flick or get out of control. In addition, because the front wheel of the vehicle is locked, the car will lose its steering ability. An anti-lock braking system with excellent performance can control the slip rate of automobile wheels between 20% and 30% when braking. In this state, the wheels can give consideration to the relative maximum longitudinal braking force and lateral grip, effectively ensuring that the vehicle will not get out of control. In addition, under the condition that the front wheel is not locked, the car can turn according to the driver's wishes because of its certain grip, thus controlling the vehicle. In order to control the wheel slip rate in an ideal state and pursue the stability of the vehicle, some longitudinal braking force may be sacrificed. Therefore, when ABS works, the braking distance will not be shortened on all roads.
On ice and snow roads, the adhesion provided by the ground is much smaller than that provided by ordinary roads. ABS can only adjust the braking force of the car on the basis of this adhesion, and will not produce additional braking factors. Therefore, the braking distance on the ice and snow road can only be said to be shorter than that when the wheel is held, and it is still much longer than that on the general road.
In fact, the actual road is very complicated, such as the unbalanced adhesion coefficient of the road surface, the curvature of the road surface or the cross slope of the road surface, and even the tire pressure of the car. There are many factors that can make the car slip when braking, and these factors cannot be overcome by ABS itself. Therefore, if the vehicle brakes suddenly when the speed is too fast on the ice and snow road, when one of the above factors is encountered, when the centrifugal force of the vehicle is greater than the maximum lateral force provided by the ground, the vehicle will become out of control, which is very dangerous.
In short, no equipment is omnipotent, and drivers must achieve safe driving through their own subjective initiative. Even the ABS with excellent performance has limited effect on the stability of vehicles under working conditions, especially when driving on gravel roads or ice and snow roads, it is necessary to keep enough distance between vehicles, slow down and do not rely entirely on ABS system.
Get out of ABS misunderstanding
The misunderstandings about ABS at the beginning need to be explained. If the wheels lock when the car brakes, the lateral adhesion that the car can get is the smallest. At this time, due to the imbalance of road adhesion coefficient, automobile braking force, suspension imbalance, automobile tire pressure, road curvature, bump or slope, the automobile may slip, tail flick or get out of control. In addition, because the front wheel of the vehicle is locked, the car will lose its steering ability. An anti-lock braking system with excellent performance can control the slip rate of automobile wheels between 20% and 30% when braking. In this state, the wheels can give consideration to the relative maximum longitudinal braking force and lateral grip, effectively ensuring that the vehicle will not get out of control. In addition, under the condition that the front wheel is not locked, the car can turn according to the driver's wishes because of its certain grip, thus controlling the vehicle. In order to control the wheel slip rate in an ideal state and pursue the stability of the vehicle, some longitudinal braking force may be sacrificed. Therefore, when ABS works, the braking distance will not be shortened on all roads.
On ice and snow roads, the adhesion provided by the ground is much smaller than that provided by ordinary roads. ABS can only adjust the braking force of the car on the basis of this adhesion, and will not produce additional braking factors. Therefore, the braking distance on the ice and snow road can only be said to be shorter than that when the wheel is held, and it is still much longer than that on the general road.
In fact, the actual road is very complicated, such as the unbalanced adhesion coefficient of the road surface, the curvature of the road surface or the cross slope of the road surface, and even the tire pressure of the car. There are many factors that can make the car slip when braking, and these factors cannot be overcome by ABS itself. Therefore, if the vehicle brakes suddenly when the speed is too fast on the ice and snow road, when one of the above factors is encountered, when the centrifugal force of the vehicle is greater than the maximum lateral force provided by the ground, the vehicle will become out of control, which is very dangerous.
In short, no equipment is omnipotent, and drivers must achieve safe driving through their own subjective initiative. Even the ABS with excellent performance has limited effect on the stability of vehicles under working conditions, especially when driving on gravel roads or ice and snow roads, it is necessary to keep enough distance between vehicles, slow down and do not rely entirely on ABS system.
Common sense of ABS use
Now basically all passenger cars are equipped with ABS system, which plays a great role in improving the active safety performance of vehicles, but if it is used improperly, the effect will be greatly reduced. Here, we summarize the principle of using ABS as "four musts and seven don 'ts".
Four elements
1. Always keep pressing the brake pedal to ensure sufficient and continuous braking force and make ABS work effectively.
2. Keep enough safe distance. In general, the minimum distance between cars should not be less than 50m. When the vehicle speed exceeds 50km/h, the minimum distance is the same as the vehicle speed. For example, the minimum vehicle distance is 100 m when 100 km/h and 120 m when 120 km/h. ..
3. Be familiar with ABS in advance, so that you can get ready to adapt to the brake pedal jitter when ABS works.
4. Read the driver's manual in advance to learn more about the various operating instructions provided by the automobile manufacturer that installed ABS.
Seven don't.
1. Don't think that you can drive at will with ABS. ABS is not absolutely safe. If the vehicle brakes too hard and too fast, it will still slip. Therefore, even if your car is equipped with ABS, you still need to drive carefully.
2. Don't use the "point brake" brake. When vehicles without ABS are braking on wet roads and at high speed, it is necessary to use the method of "point braking" to achieve the purpose of safe braking. After the installation of ABS, because ABS can automatically adjust the braking force, when implementing emergency braking, you can step on the pedal to the bottom without releasing it, so you don't have to worry about the wheel locking and slipping, otherwise the braking distance will be greatly extended.
Don't be scared by the jitter of ABS. When ABS works, it will hear the noise, which is generated by the solenoid valve and hydraulic pump in the hydraulic control system. Don't panic because there is something wrong with the brake system, and don't take your feet off the brake pedal. At this time, you still have to trample the brake pedal to death, regardless of it.
4. Don't ignore the inspection of ABS indicator light. Under normal circumstances, after the ignition switch is turned on, this light should be on; It goes out automatically after about 3 seconds. In this process, in essence, the electronic control device checks the wheel sensor and the control valve of the hydraulic regulator according to the self-checking procedure. If this light doesn't light up all the time, it means there is something wrong with ABS.
Don't panic at 5.5. ABS indicator does not go out. When the ABS breaks down during driving, the anti-lock braking system will automatically connect the oil circuit of the original braking system, and the original braking system on the car still works, but there is no ABS, so it is enough to pay attention to maintenance.
6. Do not change the computer unit of ABS without permission. If the computer finds a fault, the whole ABS unit should be replaced.
7. For the vehicle equipped with ABS, but want to modify it, please do not remove the nut connecting the brake pipe and ABS unit.
ABS is divided into electronic ABS and mechanical ABS.
1, electronic ABS is designed according to different models, and its installation requires professional technical force. If you switch to another car, you must change the circuit design and battery capacity, which is not universal; Mechanical ABS is multifunctional, can be used in any vehicle with hydraulic braking device, and can be changed from one vehicle to another, and the installation only takes 30 minutes.
2. Electronic ABS is bulky, so the finished car may not have enough space to install electronic ABS. In contrast, mechanical ABS is small in size and takes up less space.
3. The electronic ABS starts to work at the moment when the wheel is locked, and it can work 60~ 120 times per second according to different vehicle speeds; Mechanical ABS starts to work when braking, and moves 6~ 12 times per second.
The applicable characteristics of mechanical ABS need to be set in advance. On the pavement with water, ice and snow, gravel and asphalt, the friction coefficient of tires is different, and the braking force required at different speeds is also different. There is no real-time measurement feedback system and only depends on the preset terbium value, so the application range is narrow and the braking effect will be reduced.
You should be very careful when buying mechanical ABS anti-lock braking system. Fake ABS products are similar in appearance and structure, but inferior products are difficult to withstand the corrosion and high pressure of brake oil for a long time, and rubber will age and deform with time and lose its due performance.
The genuine rubber valve capsule can withstand high pressure per square inch 1 1000 pounds when immersed in brake oil, and will not deform for a long time. The price of imported mechanical ABS is about 2000 yuan, and domestic ABS is only 200 yuan.
What is ABS?
ABS can be installed on any vehicle with hydraulic brakes. It uses a rubber airbag in the valve body to apply brake oil pressure to the valve body of ABS when braking. At this time, the airbag uses the middle air interlayer to back pressure, so that the wheel can avoid the dead point. When the wheel is about to reach the next dead center, the pressure of brake oil makes the airbag repeatedly act, such as
In this way, you can move 60 120 times a second, which is equivalent to constantly braking and relaxing, which is similar to a mechanical "point brake". Therefore, ABS anti-death system can avoid out-of-control direction and wheel sideslip during emergency braking, so that wheels will not lock up during braking and tires will not rub against the ground at [1] point, thus increasing friction, making braking efficiency reach over 90%, reducing braking consumption and prolonging the service life of brake drum, brake disc and tires by two times. The anti-skid performance of vehicles equipped with ABS on dry asphalt pavement, rainy day and snowy day reaches 80%90%, 30% 10% and 15%20% respectively.