Why can't the car doors always be opened after a collision?

What on earth is the safety level of new energy vehicle doors? Consumers' doubts have never dissipated.

Recently, a collision accident involving a Xiaomi SU7 Ultra in Chengdu has drawn attention. According to the official report, after the collision, the accident vehicle crossed the central green belt of the road and caught fire.

From the videos taken by on - lookers, it can be seen that after the accident, some kind - hearted people tried to rescue the passengers. However, several adult men pulled the door handle with all their might but still couldn't open the accident vehicle's door.

The accident is still under investigation, and many details remain unclear. But the safety issue of new energy vehicles has once again become the focus of millions of consumers.

36Kr has previously published multiple reports on door locks and hidden door handles. However, the safety topic always deserves more attention. In this article, we will continue to explore: How to open new energy vehicle doors in emergency situations?

The car doors will automatically unlock when the airbags are deployed

The car door lock is a complex and precise physical structure, mainly composed of two parts. One part is the lock. Whether it is unlocking or locking with a key, remote control, mobile phone remotely, or through the in - car central control screen, all these operations are performed on the lock part. The other part is the latch. Pulling the door handle is to unlock the latch and open the door.

That is to say, there are two key steps to successfully open a car door: the first step is to unlock the lock, and the second step is to open the latch.

The original intention of the car door lock was to prevent the car from being driven away by others at will and allow the people inside the car to choose to lock the door for self - protection. Therefore, in most cases, whether the door is locked or not is controlled by the car owner and the people inside the car.

However, after a collision accident, the people inside the car may fall into a coma. If the door lock can still only be controlled by the people inside the car, the rescue difficulty will increase significantly. In case of an accident, the door may need to be cut to rescue the people, and the vehicle's property value will also be lost.

Therefore, car manufacturers have designed a sophisticated emergency automatic locking and unlocking mechanism: using the ignition of the airbag as the starting condition for the emergency procedure of the door lock.

The airbag is the highest - level program in the overall vehicle safety.

The collision sensor and the airbag system usually have the highest - level operating authority. The accuracy of the sensor, the transmission speed of the wiring harness used, and the precision of the controller all meet the highest standards.

When a vehicle collision occurs, after the collision sensor senses the change in state, it will determine whether to activate the airbag through the program set by the manufacturer. If the collision conditions are sufficient to trigger the airbag, it will ignite, and then the airbag will deploy.

At the moment when the airbag ignites, the door locking program will be triggered, and the door will lock immediately. This moment is usually accompanied by multiple functions such as the tightening of the seat belt and the seat lumbar support. The purpose is to fix the position of the people inside the car and prevent secondary injuries.

Only when the sensor that detects the vehicle's state senses that the vehicle has stopped will it send a signal to unlock the door, facilitating the rescue by people inside and outside the car.

"Whether in regulations or in practice, this step generally only unlocks the door, and the door remains closed. Someone inside or outside the car needs to pull the door handle to open it," an engineer told 36Kr. Due to the complex accident environment, actively popping open the door may cause other injuries.

The airbag is a one - time device. After it deploys in an accident, the car owner needs to return to the after - sales service center to replace the airbag device.

An engineer told 36Kr that for an economy car equipped with 10 airbags, the cost of reinstalling the airbags is about 10,000 yuan. "All the airbags and wiring harnesses need to be reinstalled and debugged."

If the airbag fails to deploy in a major accident, it cannot protect the passengers inside the car. If it deploys in a minor collision, it may block the driver's line of sight or cause objects on the dashboard to fly out, causing other injuries to the people inside the car.

Therefore, car manufacturers are very cautious when setting the airbag deployment program.

If the accident is not serious and the airbag does not need to deploy, the people inside the car are likely to be conscious and can unlock the door by themselves to complete the rescue. In this case, the emergency procedure of the door lock does not need to be activated.

Binding the vehicle's automatic locking and unlocking program with the airbag program is a mature and widely - verified common practice. Then why are there still situations where the door cannot be opened after an accident? Analyzed from the principle and practice, there are mainly two types of situations:

The door lock circuit is the first line of defense and requires multiple redundancies

The first situation is that the automatic locking and unlocking program fails and fails to unlock the door successfully.

The operation of the vehicle's automatic locking and unlocking program requires the power supply, the controller, and the wiring harness between them to remain intact and function properly. However, after a severe vehicle collision, each link in this process may be damaged. Once a certain link is damaged, the vehicle's locking and unlocking program will fail.

To improve safety and reduce the risk of the locking and unlocking program failure, car manufacturers usually adopt the method of redundant power supply and redundant wiring.

For example, the door lock is connected to two sets of power supplies: the high - voltage battery and the low - voltage small battery, and two wiring harnesses in different positions are arranged. In this way, if the front compartment of the vehicle is damaged in a collision, the power supply and wiring in the rear compartment are still connected. The same applies if the rear compartment is damaged. However, this method will double the cost for the manufacturer.

Some car models have a third set of power supply and wiring specifically for the door lock. The door locks of the four doors form a separate circuit, and the power supply is placed under the second - row seats of the vehicle. This method provides more protection. Even if the low - voltage small batteries in the front and rear compartments of the vehicle are damaged at the same time, the separate power supply under the second - row seats can still operate.

An engineer told 36Kr that three - way power supply cannot guarantee 100% non - damage. However, if the vehicle collision causes the bottom of the second - row seats to deform, the rescue difficulty will not be just about whether the door can be opened.

In addition, some car models adopt a physical emergency structure. After a collision occurs, the unlocking signal drives the lever structure to achieve physical unlocking. The engineer told 36Kr that some enterprises cannot fully trust the pure electronic structure. When the cost allows, manufacturers are willing to seek more possibilities in the physical structure.

Pure electronic door handles pose risks, and mechanical structures are indispensable

The second situation is that the door lock's locking and unlocking program can operate and unlock the door, but the door cannot be opened.

As mentioned above, the car door lock is divided into two parts: the lock and the latch. To open the door, you not only need to unlock the lock but also open the latch. The door handle is the way to open the latch.

The traditional mechanical pull - type door handle is a pure physical structure, with the handle and the latch connected by a lever or a pull - rope. As long as the rescue personnel pull the mechanical door handle, they can unlock the latch.

However, many cars now use pure electronic door handles. The Xiaomi SU7 is an example.

Lei Jun specially introduced the semi - hidden door handle design of the Xiaomi SU7 at the press conference. He said that there is a button inside the semi - hidden handle. Users can touch the button by putting their hands inside the door handle to open the door.

This is a door handle structure that has no physical pull - rope and is only driven by a motor. To successfully open this door, in addition to protecting the vehicle's automatic locking and unlocking program, you also need to protect the door button, the motor, and the wiring harness between them.

In an emergency, the more links there are, the greater the risk, especially for electronic structures.

The physical structure only needs to ensure that the pull - rope is strong enough, but the electronic structure needs to protect the integrity and effectiveness of the handle button, the intermediate wiring harness, and the handle motor. The difficulty and risk are imaginable.

An engineer told 36Kr that the maximum speed of most family cars can reach over 180 km/h. To ensure that the door will not come off at high speed, the door latch and the sealing strips around the door frame form a very firm sealing structure.

"Taking the electronic door handle as an example, if the motor fails, even if it is a semi - hidden door handle with a point of force, you still can't open the door because the latch is not unlocked at all."

If the vehicle uses an external physical door handle, as long as the door handle does not fall off, external rescuers can open the door through the door handle.

If both the inside and outside door handles of the current vehicle are electronic structures, there is still a final line of defense inside the car: there is a mechanical inside door handle at the driver's seat position inside the car.

In most car models, this door handle is not controlled by the door lock and can be opened at any time by pulling. In case of an accident, you can use a window breaker to smash the driver's window and use the mechanical handle inside the driver's seat to open the door.

An engineer told 36Kr that if the door is only slightly deformed and there is a physical door handle, there is a possibility of opening the door with great force. That is to say, the mechanical door handle does provide a more solid safety bottom line.

So how can consumers judge whether a vehicle has a mechanical door handle during the car - buying process? The mechanical door handle is connected by a pull - rope or a lever, and there must be space for "pulling" outward to open the door.

At the end of September this year, the Ministry of Industry and Information Technology issued a draft for comments on the mandatory national standard "Safety Technical Requirements for Automobile Door Handles". The draft clearly states that both the inside and outside door handles of a car should have a physical structure. After the draft comes into effect, the mechanical outside door handle will become a standard configuration.

However, once the vehicle speed is too high and the door is severely deformed after a collision, it doesn't matter whether the locking and unlocking program can operate or whether the door handle is mechanical or electronic. Obeying traffic rules and driving safely are the core elements of vehicle safety.

After the "show - off competition" in pursuing a sense of technology and the drag coefficient, the new energy vehicle industry is now returning to the essence of safety. The car door handle may be a starting point. After that, both car manufacturers and consumers will dig deeper and pay more attention to every detail of vehicle safety.