The device and the principle of operation of the carburetor

Until the mid-80's gasoline internal combustion engines for cars and light trucks were massively equipped with carburetors. Such engines operate on the principle of combustion of pre-prepared by an external device fuel-air mixture in the engine cylinders. This working mixture consists of drops of fuel and air. The carburetor is responsible for the process, which implies the formation of a mixture of these components in the right proportions for maximum efficiency of the internal combustion engine. The simplest carburetor is a mechanical dosing device.

A little history

Early developments at the dawn of the engine era used light gas as fuel. Carburetors were simply not needed for such engines at an early stage. Light gas entered the cylinders due to rarefaction, which was formed during engine operation. The main problem with this fuel was its high cost and a number of difficulties in the process of use.

The second half of the XIX century was that period, when inventors, engineers and mechanics around the world have tried to replace expensive light gas with more economical ones, cheap and affordable type of fuel for an internal combustion engine. The best solution was to use the usual liquid fuel for us today.

It is worth considering, that such fuel cannot ignite without the participation of air. An additional device was required to prepare the mixture of air and fuel. Little of, but it was necessary to mix air with fuel in the right proportions.

To solve this problem, the first carburetor was invented. The device saw the light of day 1876 year. The inventor of the early carburetor model was the Italian inventor Luigi De Christopheris. In its design and principle of operation, the first carburetor had a number of significant differences from more modern counterparts. To obtain a high-quality fuel-air mixture, the fuel in the first device was heated, and its vapors mixed with air. For a number of reasons, this method of forming a working mixture is not widespread.

Developments in this area have continued, and a year later, talented engineers Gottlieb Daimler and Wilhelm Maybach designed the internal combustion engine., who had a carburetor, operating on the principle of fuel spraying. This device formed the basis for all subsequent developments.

modernization

The main direction of further work of engineers was the maximum automation of all mixing processes. The best minds of many car and related equipment companies have worked to improve the design of the carburetor.. For this reason, you can find many simple and complex models of carburetors from many global manufacturers.

Further development

Carburetors began to be actively replaced by injection systems only at the end of the XX century. Until now, the design of the carburetor has been greatly improved. The last round of the evolution of carburetor injection was carburetors under the control of electronics. Such carburetors had several solenoid valves, whose work was controlled by a special control device. For example, we can mention the carburetor brand Hitachi. In the design there were almost 5 valves, and the valves were controlled electronically.

The latest generation of structurally complex carburetors perfectly demonstrates the already mentioned Hitachi carburetor model. This carburetor was installed on Nissan cars in the late 80's and early 90's. The complexity of this generation of carburetors lies in the large number of auxiliary devices, especially if you compare the Hitachi product with the primitive "Solex", which was put on VAZ.

Auxiliary devices were responsible for stabilizing the carburetor in different modes. Such modes and features of operation include a sharp discharge of gas, idling mode during downtime on cars with automatic transmission, leveling and stabilization of revolutions of the power unit after inclusion of the climatic installation, as well as many others.

Perfected carburetor of recent generations basically consisted of numerous devices. We will name only some of them for reference:

1. Outdoor air temperature control system ;.
2. Intake manifold heater;
3. Fuel shut-off valve;
4. The valve of the mixture enrichment device;
5. Bimetal spring of the air damper in the device of the throttle opening mechanism;
6. High idle system, etc.;

Such devices correspond to the latest "electronic" carburetors. Additional elements in these models were made in the form of separate analog devices. The devices were controlled by the simplest electronics or worked on the principle of self-regulation (bimetallic spring).

It is noteworthy, that simple mechanical carburetors are very versatile devices and can be installed with an adapter on different car models. A great example is the same well-known to domestic motorists carburetor "Solex".

Carburetor and injector

Later, in the history of fuel and blending systems, mono-injection first appeared (monoinjector), and fully electronic injection and productive fuel injectors have finally supplanted obsolete carburetors.

The main advantage of the injector is a much more accurate and timely dosing of fuel to obtain the desired proportions of the fuel-air mixture. The emergence and introduction of affordable microprocessors in the automotive industry has eventually led to, that the need for a complex carburetor and additional devices in its design has simply disappeared. All functions of the individual elements of the carburetor took over a single control unit (ECU), and in the design of the injector installed simple devices.

It is a mistake to believe, that the injector is a more economical solution compared to the carburetor. A well-built carburetor shows similar fuel consumption. The popularity of distributed injection is due to ??team, that such mechanism of fuel supply is capable to correspond to all rigid modern norms and requirements on environmental friendliness of the internal combustion engine. The carburetor cannot meet such requirements, due to its design features and performance of jets.

Today, carburetor injection is found only on those engines, the main purpose of which is the target installation of special equipment. The reason for this decision was the vulnerability of electronic injection systems during difficult operating conditions. Electronic components and injector modules suffer from high humidity and contamination, and the injectors are sensitive to fuel quality. For example, it is worth saying, that it is definitely better to install a mechanical carburetor on a special vehicle when using one in the swamps, which will not burn out. This carburetor can always be easily serviced, clean and dry if necessary.

types of carburetors

As we have said, the process of modernization of carburetors has generated a large number of types of this device from different manufacturers. All this variety of carburetors can be divided into three groups:

• bubbling;
• membrane-needle;
• float;

The first two types of carburetors have long been virtually non-existent, so we will not dwell on these constructions. It is better to consider a float carburetor, which can still be seen in various modifications on civilian cars of the 90s today.

Float carburetor device

The main task of the carburetor is to mix fuel and air. Different models of carburetors carry out this process on a similar principle. The float carburetor consists of the following elements:

• float chamber;
• float;
• locking needle float,
• cracks;
• faucet chamber;
• sprayer;
• venturi tube;
• choker;

The float carburetor is arranged as follows, that a special highway is connected to its float chamber. Fuel is supplied to the carburetor from this line from the fuel tank. The amount of fuel in the chamber is regulated by two elements, which are interconnected. We are talking about floats and needles. A drop in the fuel level in the float chamber means, that the float will go down together with the needle. This is how it will turn out, the lowered needle will open access for penetration into the chamber of the next portion of fuel. When the chamber is filled with gasoline, the float will rise, and the needle will block fuel access in parallel.

At the bottom of the float chamber is the next element called the nozzle. The nozzle serves as a calibrator and provides fuel metering. Through the nozzle the fuel enters the atomizer. This is how the required amount of fuel is moved from the float chamber to the mixing chamber. The process of preparation of the working fuel-air mixture takes place in the mixer chamber.

Structurally, the mixer chamber has a diffuser. The specified element is created for that, to increase the speed of air flow. The diffuser is responsible for creating a vacuum in the immediate vicinity of the spray. This helps to extract fuel from the float chamber, and also contributes to its better dispersion in the mixer chamber. This is the basic device of a simple float carburetor.

Choker: cold start and idle

And the amount of working fuel-air mixture, which will enter the engine cylinders, will depend on the position of the throttle. The damper has a direct connection to the accelerator pedal. But that's not all.

Some cars with carburetors had an additional device to control the throttle. This element is well known to fans of the old "classics" from VAZ. In the people motorists nicknamed this device "suction", and the device itself is designed for cold start. The element is made in the form of a special lever, which is located at the bottom of the torpedo on the driver's side.

The lever allows you to further control the throttle. If you pull the "suction" on yourself, in this case the damper is closed. This allows you to limit air access and increase the level of vacuum in the carburetor mixer chamber.

Gasoline from the float chamber at high vacuum is extracted into the mixing chamber much more intensely, and insufficient amount of air forces the carburetor to prepare for the engine enriched working mix. This mixture is best suited for a confident start of a cold engine.

It is worth noting, that the cold start was the first in the whole structure to be further modernized, already familiar to us under the name "suction". Simple carburetors deservedly include the once common and popular carburetor "Solex", to which the line of classic VAZ cars owes a lot.

The operation of the carburetor engine in idle mode is as follows:

• the carburetor is equipped with special additional air jets. These nozzles are responsible for supplying a strictly dosed amount of air;
• the air passes under the throttle valve and then according to the operating algorithm is mixed with gasoline. The whole process takes place then, when the accelerator pedal is not squeezed and released;

This is the basic device and the principle of operation of the float carburetor.

Strengths and weaknesses of the device

The main advantage of the carburetor is its affordable maintainability. To date, there are special repair kits on sale, which allow you to turn the carburetor in order quickly enough. An arsenal of any special equipment is not required to repair the carburetor, and to repair the device in the presence of certain skills and abilities under the power of almost any motorist.

Mechanical carburetor is not so afraid of dirt and water, since their impact cannot permanently disable it. At the same time it lies as strong, and the weak side of the device. The carburetor needs to be adjusted and cleaned quite often in comparison with injection, but it is more durable than electronic solutions under a number of such conditions, relating to severe or even extreme operating conditions.

Additional advantages of the carburetor include its lower sensitivity to low quality fuel, and the cleaning process will not be difficult. Although the carburetor is a relatively complex device, but it is much easier to diagnose and maintain faults than a clogged or faulty injection system.

The main disadvantages of the carburetor include the need for regular cleaning and adjustment. The carburetor can bring surprises during operation, as there is a dependence on external weather conditions. In winter, condensate can accumulate in the carburetor housing and then freeze. In heat, the carburetor is prone to overheating, which leads to intensive evaporation of fuel and a drop in engine power.

The last argument against the carburetor is the increased toxicity of the exhaust, which led to the rejection of its use on modern cars around the world. Today, the carburetor is justifiably considered a hopelessly outdated "classic" solution.