[Technology] Cars have become an indispensable part of our lives. The combination of steering wheel+shift lever+pedal seems to have become a natural way to control cars, but their respective mechanisms are rarely understood. Take the steering wheel in our hands as an example, the majority of riders are still vague about the common concepts of various steering systems, such as "the difference with hydraulic power" and "what is the variable power", and so on. Below, we will systematically introduce various common steering systems, answer these questions, and discuss the mysteries and mysteries of various steering systems with you.

　

　　Because of the long space, this paper introduces our most common system now, interprets "where does the power come from" and introduces the classification of power steering system.

　　Power steering, as its name implies, is to resist steering resistance by increasing external force, so that drivers can complete steering with less force. It is also called power steering. It was originally designed to make some large vehicles with heavy weight operate more easily, but now it has become very popular. It makes driving easier and easier, and makes vehicles more agile and improves safety to some extent. Power steering can be divided into two categories according to the different sources of power-hydraulic power and electric power.

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　　The origin of hydraulic power steering can be traced back to February, 1902. Frederick W. Lanchester of Britain invented "Cause the steering mechanism to be actuated by hydraulic power", that is, the hydraulic driving steering mechanism. After that, inventors in the United States and Canada successively registered patents for similar inventions. In automobile production, the commercial production of hydraulic power steering system was first realized, and it was named Hydraguide hydraulic steering system, and it was installed on Chrysler’s sixth generation Imperial in 1951. With the development of technology, the steering system with electronic pump instead of mechanical pump appears, so the current hydraulic power is mainly divided into mechanical hydraulic power and electronic hydraulic power. In addition, the electronic servo hydraulic power steering system is derived from the mechanical hydraulic power.

　

　　Let’s look at the main principle of mechanical hydraulic power steering, which is based on mechanical rack-and-pinion steering mechanism, and adds a whole set of hydraulic system, including liquid storage tank, hydraulic booster pump, mechanical valve connected with steering column, hydraulic cylinder on steering mechanism and the one that can push steering rod, etc.

　　The hydraulic pump provided by mechanical power steering is driven by a belt, which means that the steering pump can only run when the engine is running, which is why the steering wheel power disappears after the engine is turned off. On the steering machine, there is a mechanical valve that can rotate with the steering column. When the steering wheel does not rotate left and right, the pressure in the chambers on both sides of the piston is consistent and in a balanced state. When the steering wheel rotates, the mechanical valve connected to the steering column will be opened or closed accordingly, and the oil on one side will return directly to the oil storage tank without passing through the hydraulic cylinder, and the oil on the other side will continue to be injected into the hydraulic cylinder, so that the pressure difference between the two sides of the piston will be pushed under the action of hydraulic force, and then the auxiliary force will be generated to push the steering rod to steer the wheels, which greatly reduces the force required for us to turn the steering wheel.

　　Another advantage of hydraulic power steering system is to improve comfort and safety. When the wheels jump violently and the tires turn involuntarily when encountering potholes, the vibration can be well buffered and absorbed by the action of hydraulic pressure on the piston, which greatly reduces the vibration transmitted to the steering wheel. At the same time, this structure also improves the safety. For example, when a vehicle using the traditional rack-and-pinion mechanism turns, the tire suddenly changes direction when it encounters a pothole, and the rack will drive the gear to reverse the steering wheel, resulting in the situation of "beater", which is easy to hurt the driver’s hand, so there will be no such problem in a hydraulically assisted vehicle.

　　Mechanical hydraulic booster features:The whole system is a mechanical structure, from the mechanical hydraulic pump driven by the belt to the hydraulic mechanical valve body on the steering column, without any electronic system, with mature and stable technology, high reliability and wide application range. Even if the hydraulic system of the vehicle fails and loses power, it can still rely on the traditional rack and pinion mechanism for steering. Disadvantages are complex structure, large space occupation and high manufacturing cost, which also makes the maintenance difficult and costly. And because the hydraulic pump is driven by the engine belt, it will consume part of the power of the engine, which will affect the fuel economy and the power of the vehicle, especially for small-displacement vehicles with relatively weak power. In addition, the strength of the mechanical hydraulic power-assisted system is not adjustable, so it is difficult to take into account the different requirements for pointing accuracy when driving at low speed and high speed.

● Electro-hydraulic booster

　　The so-called Electro-hydraulic power steering (EHPS for short) has exactly the same principle as mechanical hydraulic power steering, but the biggest difference from mechanical hydraulic power steering is that instead of using a hydraulic pump driven by an engine through a belt, it is replaced by an electric pump.

　　The advantages of electro-hydraulic power assist are firstly reflected in energy consumption. First, the electronic pump driven by electric energy uses the electric energy output by the generator and the battery, and no longer consumes the power of the engine itself. The start and stop of the electronic pump are all controlled by the electronic system. When it is not steering, the electronic pump is turned off, unlike the mechanical hydraulic power assist pump, which is always linked with the engine, further reducing energy consumption.

　　Secondly, the electronic control unit of the electro-hydraulic power steering system can change the power of steering assistance by processing the information of sensors such as speed sensor, lateral acceleration sensor and steering angle sensor, and changing the flow rate of the electronic pump in real time, that is, the function of variable power assistance with speed. Of course, it is not only the electro-hydraulic power assist that can realize the variable power assist with speed. We will introduce various "variable" power assist steering systems in detail in later articles.

　　Electro-hydraulic power assist has been gradually popularized since the late 1990s, and brands such as,,,,, and have models using electro-hydraulic power assist system. We are familiar with, and other models use such a system.

"Triumph, old models and other models use electro-hydraulic power."

　　Why can’t electro-hydraulic assist replace mechanical hydraulic assist?

　　No matter from the aspects of technology, function or economy, electro-hydraulic power assistance has more advantages than mechanical hydraulic power assistance. However, at present, electro-hydraulic power assistance has not been able to replace mechanical hydraulic power assistance for the following reasons:

　　1. The cost of electro-hydraulic booster is higher. Compared with the mechanical hydraulic power-assisted system, after adding the electronic control system and replacing it with the electronic pump, the manufacturing cost of electronic hydraulic power-assisted system is higher, the technology is more complicated, and the difficulty and cost of maintenance are also increased.

　　2. The reliability is not as good as that of mechanical hydraulic booster. In addition to the failure of steering mechanism and hydraulic mechanism, electro-hydraulic power assist also increases the possibility of electrical system failure, so its reliability is not as good as that of traditional hydraulic power assist system.

　　3. The assistance is limited. Although the use of electronic pump has obvious advantages, it needs to be driven by the electric energy of the generator, and the vehicle-mounted generator itself and the maximum current it can provide are limited, so the power of the electronic pump is also limited, and the load it can carry is also limited. Therefore, at present, most of the models that use electro-hydraulic power are medium-sized vehicles. For vehicles that need greater assistance, the electro-hydraulic assistance system is beyond the reach.

　　4. Evolved mechanical hydraulic booster system. With the development of technology, the variable speed function of electro-hydraulic power-assisted system has been realized on the evolved mechanical hydraulic power-assisted system (using solenoid valve body technology), and even a variable speed ratio system has been derived from the mechanical hydraulic power-assisted steering system, so the mechanical hydraulic power-assisted system with higher reliability and load-bearing capacity is still welcomed by manufacturers.