1. Classified by the source of braking force
According to the source of braking force, the braking system is divided into three types: human braking, assisted braking, and human + assisted braking.
1) Human brake
Human transmission of force through machinery or hydraulic oil is called human braking, which is only suitable for small cars, not for cars and trucks.
2) Power-assisted braking
The truck uses the pressure difference between the compressed air of the air compressor (relative pressure is 5 to 8 bar) and the air atmospheric pressure (relative pressure is o).
Power assist, due to the large pressure difference, can reduce the size of the servo mechanism to achieve braking.
3) Manpower + booster braking
The car uses the pressure difference between the vacuum source (---0.3bar) and atmospheric pressure (relative pressure is o) to assist, called vacuum assist pressure
The maximum difference is 0.7 bar, and the braking is the superposition of manpower and vacuum braking force, which is a common way for car braking. When the vacuum boost fails, only.
With manual braking, the braking distance is significantly increased. There are three types of vacuum sources: for gasoline engines, use the vacuum degree of the intake manifold when the engine is working; for diesel
The machine adopts a vane vacuum pump driven by the back of the generator or the end of the camshaft; electric vacuum pumps can also be used. Now the car is equipped with an automatic transmission
In order to increase the brake boosting effect, there is also a design method that uses an electric vacuum pump to assist the engine's intake manifold to form a vacuum source.
2. Classified by the brake transmission medium
The brake system is divided into mechanical type, hydraulic type, pneumatic type, an electromagnetic type according to the different braking force transmission media. Among them, low-speed agricultural vehicles-part of them are mechanical, and most of them use hydraulic power transmission methods; all cars use hydraulic power transmission methods; light trucks can use hydraulic or air pressure as the power transmission medium, and heavy trucks all use air pressure as the power transmission medium. The difference of the brake transmission medium leads to the difference of various brake master cylinders, brake cylinders, clutch master cylinders, and clutch cylinders.
3. Classified according to the number of master cylinders (air brake is divided by the number of closed pipes divided by the four-way valve)
The hydraulic power transmission brake system is divided into two types: single pipeline and double-pipeline braking. When the master cylinder adopts one pipeline, it is called single pipeline braking, and two pipelines are used.
The pipeline is called a two-pipe brake. Before the 1980s, automobile braking systems were mostly single circuits (also called single pipelines). In a single-circuit braking system, the master cylinder has a
The output port is connected to the brake pipeline to provide braking force to all-wheel brakes. Although the structure of the braking system is simple, it only needs to be anywhere in the system.
Damaged air or oil leakage will cause the entire braking system to fail, that is, "brake failure". In order to break reliably, countries have successively adopted "redundant technology",
The dual-circuit braking system is enforced through regulations to ensure the reliability of the braking system and ensure driving safety. Dual circuit braking system is also called dual pipeline
A braking system refers to two independent circuits composed of hydraulic or pneumatic pipes of all service brakes of the whole vehicle. Braking of the dual-circuit braking system
The main cylinder has 2 independent working chambers, which are respectively connected to the pipelines of their respective circuits. If one of the circuits fails, the other--intact circuit can still be used to start
Braking effect.
At present, only a very small number of light and low-speed trucks are still using single-line hydraulic braking, and all cars use hydraulic dual-line braking. Pneumatic brake trucks
Using the brake valves of the upper and lower chambers cannot be equivalent to dual-pipe braking, because the brake valves themselves do not generate braking force. So it should be closed according to how much the four-way valve is divided
To determine the number of pipelines, multi-axle trucks will have two pipelines or three pipelines for braking, and the remaining pipeline is used for auxiliary braking control.
The foot brake valve of the air brake system is equivalent to the hydraulic brake master cylinder, and the brake chamber of the air brake system is equivalent to the brake wheel of the hydraulic brake system
Cylinder. At present, the foot brake valve of the pneumatic brake system is divided into upper and lower pipelines, the lower pipeline is for front steering wheel braking, and the upper pipeline is for rear-wheel braking.
4. Classified according to the pipeline layout of the dual-circuit brake system
The dual-circuit braking system has the following 5 different piping arrangements.
1) Type II (front and rear)
Type II pipeline arrangement means one circuit is connected to the wheel brakes of the front axle (axle), and the other circuit is connected to the wheel brakes of the rear axle (axle), as shown in Figure 4-
As shown in 1(a), the front axle wheel brakes and the rear axle wheel brakes each use one circuit.
Type II pipeline layout is simple and can be used in conjunction with traditional single-wheel cylinder (or single-brake chamber) drum brakes. The cost is low. It is currently used in various types of steam
It is widely used on trucks, especially trucks. The failure of a set of circuits and the loss of the braking force of the front or rear axle wheels will reduce the braking efficiency of the entire vehicle. Rear brake back
When the road fails, for a car without an ABS device, once the front wheel is locked, it is easy to lose the turning braking ability. The most serious is the front axle brake failure, no ABS
The installed car will not only lock up the rear wheels and lose stability, but also because the parking brake device works through the rear axle, even if the parking brake is applied
Car braking cannot compensate for the loss of front axle braking force.
2) X type (diagonal type)
One circuit connects the left front wheel and the right rear wheel brake, and the other circuit connects the right front wheel and the left rear wheel brake, as shown in Figure 4-1(b). Front axle
The wheel brake on one side of the rear axle belongs to the same circuit as the wheel brake on the opposite side of the rear axle.
X-type pipeline layout is simple. When braking straight ahead, if any set of circuits leaks, the remaining total braking force can maintain 50% of the normal value without loss
Stability, because there is no braking force-the wheels on the side can withstand lateral forces. However, once a certain pipeline is damaged and liquid leakage occurs, the braking force on both sides will be lost.
Balance. At this time, the front wheel will rotate around the kingpin toward the side with a large braking force, and the brake will deviate. But you can adjust the kingpin offset to make it a negative value (ie
The front-wheel grounding point is on the inner side of the intersection of the kingpin extension line and the ground, up to 20mm). At this time, the unbalanced braking force causes the wheel to rotate in the opposite direction to avoid both sides.
The uneven braking force causes braking deviation. However, the value of the kingpin offset should not be too small, otherwise, it will not only make the steering heavy but also make the tire and the road
There will be greater slippage between them, which will aggravate tire wear.
The piping layout of the dual-circuit brake system should be I or X. For commercial vehicles with heavy rear wheels such as medium and heavy loads, type I cloth should be used.
For cars with eccentric centers of mass, such as passenger cars and light-duty cars, an X-type layout is often adopted.
5. Classified according to the presence or absence of electronic control system
The braking system is divided into traditional braking systems and electric control systems according to whether there is an electronic control system. The electronic control system is divided into ABS and ABS/ESP.
Kind of electronic control system.
In the design of the traditional braking system, in terms of time control, the metering valve is designed according to the principle that the rear wheels are braked normally and the front wheels are braked later than the rear wheels. This function is in
The electric control system is no longer used on cars, and there is no metering valve function in the software. In terms of braking intensity control, the braking force of the rear wheels is less than that of the front wheels (to prevent the rear wheels
A tail-flick accident occurs due to lock-up), in principle, a proportional valve or a load-sensing proportional valve should be designed.
After adopting the electronic control ABS system, the rear wheel adopts the low selection principle, which is the electronic braking force distribution function, so there is no measurement in the electronic control system
Valves and proportional valves. When the electric control system is ABS/ESP type, in addition to the brake pressure adjustment function of ABS in the service brake, in the automobile
When the car is turning, the ESP function provides automatic braking "part of the wheel" to realize the driver's intention path tracking function.
6. According to whether the service brake system has energy feedback braking function classification
According to whether the service brake system has an energy feedback braking function, it can be divided into mechanical friction braking and hybrid braking. Electric cars and hybrid cars
The car has two types of braking: mechanical friction and energy regeneration.