Shulou(Shulou.com)11/24 Report--

The original title: "the world is too unfair to the brakes"

The world is too unfair to the brakes: people seldom look at it except when it is called "failure".

Like many things in the world, "stopping" is sometimes more difficult than "moving", and stopping is often more difficult than running fast. For people who switch to racing cars, braking may even be one of the highest priority and most effective upgrades.

In the early years, consumers would also pay attention to the difference between disc brakes and drum brakes, as drum brakes were eliminated at mainstream prices and disappeared for a time, leaving only the performance-oriented high-end market to care about details such as the number of caliper pistons, ventilation punching and so on. But in fact, even if it is not "high play", the braking system is worth exploring.

Before or after calipers, it can explain why today's modern passenger cars have basically entered the era of disc brakes (not to mention the reverse movement of individual drum brakes for the time being). What we are more familiar with is the diameter of the brake disc and the size of the caliper. Can explain the advantages and disadvantages of a car's braking performance, and then imply the overall performance of the vehicle.

In addition to these more intuitive and actual ratios, the position of the front wheel brake calipers will also reveal some additional vehicle information. Generally speaking, the front wheel calipers of the front drive of the horizontal engine are mostly located on the front side of the car, while the front calipers of the rear drive of the longitudinal engine are mostly on the rear side (of course, there are no lack of special cases).

This difference is mainly related to the engine room layout of fuel vehicles.

The engine of the front drive of the horizontal engine is usually located in front of the front axle, and because the traverse occupies a large lateral space, the front wheel steering lever usually has to be arranged behind the front axle, which leads to the front brake calipers are mostly positioned in the front (front direction).

For the dynamic performance of the vehicle, this is not an ideal arrangement.

The steering lever is located behind the wheel contact, and the steering rod of the outer wheel with greater steering pressure is subjected to thrust rather than more stable pulling force, which has a natural adverse effect on steering stability. So today's Zhiji L7, Weilai ET5 and so on, have begun to promote and emphasize their own steering lever front selling point.

Due to the longitudinal engine rear-drive model with gearbox and transmission shaft running through the center of the vehicle, the front wheel steering gear and steering rod are no longer easy to be arranged behind the axle, and most of them will choose the front steering rod. So the steering lever occupies the space in front of the wheel steering knuckle, and the front brake calipers tend to be arranged on the rear side (rear direction).

After the Kia Stinger removes the engine, the transmission causes the steering lever to be difficult to rear, but for the brake itself, the front wheel caliper is back to the front of the car, which is not ideal when using air flow while driving; on the contrary, the rear caliper has a certain natural advantage in heat dissipation. Rear front wheel calipers are also helpful for vehicle weight distribution, especially for high performance sports cars with lighter vehicle and higher brake ratio. Front wheel caliper rear + rear wheel caliper front is almost a standard operation.

In the era of electric cars, many of the exclusive pure electric platforms that really let go of their hands and feet have skimmed the structural constraints of the era of fuel cars. Although Volkswagen's MEB platform is still positioned as an economical car, the ID.3 and ID.4 not only adopt the rear-drive configuration, but also use the steering gear / steering lever in the front and calipers in the rear.

Floating does not float, depends on what is said in the brake circle "slang", "floating" is a common word. For the two most important parts of the disc brake system: brake disc and caliper, the meaning of the word floating is different.

For brake discs, or brake discs, "floating discs" are advanced types that are different from conventional fixed brake discs. The conventional brake disc is generally a monolithic structure, the central part does not actually participate in the brake friction, and the volume change is relatively small in the whole working process, but the outer ring will heat up sharply and the volume will expand greatly under the intense braking.

The temperature difference and expansion difference between the internal and external parts will lead to tension and deformation, which will affect the performance and safety.

As a result, there is a floating brake disc in which the wheel mounting part of the inner ring is separated from the brake friction part of the outer ring, and different materials are usually selected (such as carbon ceramic for the outer ring). There is a margin of expansion in the connection structure between the two, which allows the outer ring to heat up and expand under severe friction and improve the working limit of the braking system.

For brake calipers, fixed calipers or fixed calipers or opposite calipers are an advanced choice relative to conventional floating calipers. Conventional calipers will only set pistons on one side (usually the inside of the wheel), especially for ordinary household cars with low performance requirements, the single-piston calipers naturally can only be one-sided pistons.

Conventional unilateral piston (not necessarily single piston) calipers are called "floating" because of their working principle: at the beginning of the establishment of braking force, the brake pads on one side of the piston are ejected to contact the brake disc, and then the ejection of the piston stops. The caliper floats to the inside to make the outer brake pads touch the brake disc, so it is called floating calipers.

This structure only depends on mechanical action, and the outer part of the caliper does not need to arrange oil pipes, and the structure is relatively simple; but it is obvious that the braking force on both sides is not uniform, which affects the braking effect and makes the brake oil more likely to overheat. Floating calipers are generally only used in household models can be understood.

For higher performance requirements, fixed calipers with pistons on both sides are required, that is, the so-called opposite calipers. When pistons are arranged on both sides, the brake disc can be clamped inward from both sides at the same time, so that there is no need for calipers to have "floating" ability, that is, fixed calipers are commonly known as fixed calipers.

It is not difficult to see the advantages and disadvantages of the fixed caliper. In contrast to the floating caliper, it can provide more average and stable braking force and higher performance limit, but it needs to leave more space on the outside of the brake disc. The inside of the caliper, especially the outside, requires more complex oil circuit layout, and the cost is naturally higher.

With the increasing trend of electrification, the problems of disc brakes in front of them were put aside, and the drum brakes unexpectedly returned to view. Volkswagen used drum brakes on the rear wheels of the MEB platform (which is now available), and as a result, it was unsurprisingly rejected. However, the rear wheel braking system of electric vehicles with rear motors is weakened, which is a phenomenon in line with technological evolution.

The third-generation Formula E Electric Formula one, which will be launched in 2023, will completely eliminate the rear wheel (hydraulic) brakes and rely entirely on the kinetic energy recovery braking force of the rear motor. The front configuration of Volkswagen MEB (not listed on the market) no longer has a rear motor, although the positioning of the model is lower than that of ID.3 and ID.4, it uses the rear disc brake instead.

When the "electrified brake" of kinetic energy recovery enters the game, the small matter of stopping is not a razor, but tends to become more complicated.

This article comes from the official account of Wechat: autocarweekly (ID:autocarweekly), article | Aohu

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