Internal combustion engine cooling system: how is it arranged and should it be flushed in winter? Chapter i. Internal combustion engine Engine cooling system Definition

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The modern car enthusiast is more and more interested in the device of the car. In studying car device, it is difficult to ignore such an important part as maintaining the temperature regime in the car engine. CO (Engine Cooling System), the most important component of any machine. The wear and productivity of the engine of the machine depend on the correctness of its functioning. Serviceable CO, significantly reduces the load on the working elements of the engine. To maintain the correct functioning of the system, it is necessary to have a good understanding of its components. After reviewing the helpful materials, you will be able to serve COs competently.

During the operation of the car, the working parts of the engine are capable of gaining a high temperature. To avoid overheating of the working parts, the car is equipped with a cooling system. The cooling system of the car significantly reduces the temperature of the working parts of the engine. Maintaining optimal temperature conditions is due to working fluid... The working mixture circulates through special conductors, preventing overheating. The system, on all vehicles, performs a number of additional functions.

Cooling system functions.

Optimization of the temperature of the mixture for lubricating the working parts of the car.
Exhaust gas temperature regulation in the exhaust system.
Lowering the temperature of the mixture for the automatic transmission.
Lowering the air temperature in the car's turbine.
Heating the air flow in the heating system.

Today, there are several types of cooling systems. Systems, in particular, are separated from the method of lowering the temperature of the working parts.

Types of cooling systems.

Closed. In this system, the temperature drop is due to the working fluid.
Open (Air). In an open system, the temperature is reduced by air flow.
Combined. The cooling system under consideration combines two types of cooling. Particularly from the system manufacturer, the cooling is done jointly or sequentially.

The most popular in mechanical engineering has become the engine cooling system using coolant. The cooling system under consideration has become the most effective and practical for operation. The cooling system evenly lowers the temperature of the working parts of the engine. Let's consider the device and the way of functioning of the system, using the most popular example.

Regardless of the features of the engine, the design and functioning of the cooling system does not differ much. Thus, engines with different kind fuels have an almost identical temperature control system. The cooling system includes components that ensure its functioning. Each component is extremely important for full-fledged work. In case of malfunction of one component, the correct optimization of the temperature regime is violated.

Components of cooling systems.

Coolant heat exchanger.
Oil heat exchanger.
Fan.
Pumps. In particular, from the OS model, there may be several of them.
Working mixture tank.
Sensors.

For the functioning of the working mixture, there are special conductors in the system. The control of the system operation is carried out thanks to the central control system.

The heat exchanger lowers the temperature of the liquid by a flow of cold air. To change the heat output, the heat exchanger is equipped with a certain mechanism, which is a small tube.

Together with the standard transmitter, some manufacturers equip the system with a heat exchanger for oil and recycled gases. The oil heat exchanger reduces the temperature of the fluid that lubricates the working components. The second is necessary to lower the temperature of the exhaust mixture. Exhaust Circulation Regulator - Reduces the production temperature of the combined fuel and air. This reduces the amount of nitrogen produced during the operation of the engine. A special compressor is responsible for the correct operation of the device in question. The compressor sets the working mixture in motion, moving it through the system. The device is built into the OS.

The heat exchanger is responsible for the opposite action. The device produces an increase in the temperature of the air flow operating through the system. To ensure maximum productivity, the mechanism is located on the coolant outlet from the vehicle engine.

Expansion barrel designed to fill the system with a working mixture. Thanks to this, fresh coolant enters the conductors, restoring the volume of the used one. Thus, the level of the mixture always remains necessary.

The movement of the coolant takes place thanks to the central pump. Depending on the manufacturer, the pump is driven in different ways. Most pumps are driven by a belt or gear. Some manufacturers equip the OS with another pump. An additional pump is required when equipping the mechanism with a compressor to cool the air flow. The engine control unit is responsible for the functioning of all pumps in the system.

A thermostat is provided to create the optimum fluid temperature. This device detects the volume of liquid (moving through the radiator) that needs to be cooled. Thus, the necessary temperature conditions are created for the correct operation of the engine. The device is located between the radiator and the mixture conductor.

Large displacement motors are equipped with electric thermostats. This view devices change the temperature of the liquid in several stages. The device has several modes of operation: free, closed and intermediate. When the load on the engine becomes full, thanks to the electric drive, the thermostat is brought into free mode. In this case, the temperature drops to required level... In particular, from the pressure on the engine, the thermostat operates in the mode of maintaining the optimum temperature.

The fan is responsible for improving the efficiency of regulating the temperature of the liquid. The fan drive differs depending on the OS model and manufacturer.

Fan drive types:

Mechanics. This type of drive establishes continuous contact with the hardened shaft of the engine.
Electrician. In this case, the fan is driven by an electric motor.
Hydraulics. Special coupling with hydraulic drive, directly activates the fan.

Due to the possibility of adjustment and a variety of operating modes, the most popular is the electric drive.

Sensors are important components of the aggregate. Level and temperature sensor coolant, allow you to monitor the necessary parameters and restore them in a timely manner. Also, the device contains a central control unit and adjustment elements.

The coolant temperature sensor determines the indicator of the working fluid and converts it into digital format for transmission to the device. At the radiator outlet, a separate sensor is installed to expand the functionality of the cooling system.

The electrical unit receives readings from the sensor and transmits it to special devices. The block also changes the indicators for the impact, determining the required direction. For this, there is a special software installation in the block.

To carry out actions and adjust the temperature of the coolant, the mechanism is equipped with a number of special devices.

OS executive systems.

Thermostat temperature regulator.
Main and secondary compressor switch.
Fan mode control unit.
The block that regulates the operation of the OS after the engine stops.

The principles of the cooling system.

The control over the operation of the cooling system is carried out by the central engine control unit. Most cars are equipped with a system based on a certain algorithm. The necessary conditions the work and period of certain processes are determined using the appropriate indicators. Optimization takes place based on the indicators of the sensors (temperature and coolant level, lubricant temperature). Thus, optimal processes are set for maintaining the temperature regime in the car engine.

The central pump is responsible for the constant movement of the coolant along the conductors. Under pressure, the liquid moves continuously along the conductors of the OC. Thanks to this process, there is a decrease in the temperature of the working parts of the engine. Depending on the characteristics of a particular mechanism, several directions of movement of the mixture are distinguished. In the first case, the mixture is directed from the initial cylinder to the final one. In the second, from the outlet collector to the inlet.

Based on the temperature readings, the liquid flows in a narrow or wide arc. When starting the engine, working elements and liquid, including, have a low temperature. To increase the temperature quickly, the mixture moves in a narrow arc without cooling the radiator. During this process, the thermostat is in closed mode. Thus, operational warming up of the engine is achieved.

As the temperature of the engine elements rises, the thermostat goes into free mode (opening the cover). At the same time, the liquid begins to pass through the radiator, moving in a wide arc. The air flow in the radiator cools the heated liquid. An auxiliary cooling element can also be a fan.

After creating the required temperature, the mixture passes into the conductors located on the engine. While the vehicle is running, the temperature optimization process is constantly repeated.

On vehicles equipped with a turbine, a special cooling mechanism with two levels is installed. In this, there is a separation of the coolant conductors. One of the levels is responsible for cooling the car engine. The second one cools the air flow.

The cooling device is especially important for the proper operation of the vehicle. If it malfunctions, the engine may overheat and fail. Like any component of a car, the OS requires timely maintenance and care. One of the most important elements for maintaining the temperature regime is the coolant. This mixture must be changed regularly, according to the manufacturer's recommendations. In the event of malfunctions in the OS, it is not recommended to operate the car. This can expose the engine to high temperatures. In order to avoid serious malfunctions, it is necessary to quickly diagnose the device. Having studied the device and the principle of operation, you can determine the nature of the malfunction. If serious malfunctions occur, consult a professional. This knowledge will also be useful to you in this. Service the device in a timely manner and you will significantly increase its service life. Good luck with the useful material.

Normal functioning power plant car is possible only at a certain temperature. For most cars, the optimal temperature range is 80-90 degrees. C. At a lower rate, the mixture formation in the cylinders worsens, and the high temperature leads to the expansion of the metal, which can cause jamming of the components.

General arrangement of the cooling system

To keep the temperature of the power plant in the optimal range, a cooling system is included in the design of the motor. It is thanks to it that heat is removed from the most heated elements - the cylinders.

Types of cooling systems

Total on engines internal combustion two types of cooling are used - air and liquid.

Air cooling system, its design, disadvantages

Device air system engine cooling

Due to a number of shortcomings, road transport the air system is not widespread, although structurally it is much simpler than the liquid one. Its main element is the cooling fins on the cylinders.

The heat released from the cylinders was distributed to these fins, and the air flow passing through them carried it out. To create a flow, the system design could additionally include a turbine - a special impeller driven by crankshaft and a sleeve with which the generated air flow was directed to the cylinders. This is the whole structure of the air system.

On vehicles, the air system is practically not used because:

it is impossible to adjust the temperature regime (in winter the motor did not reach the required temperature, and in the summer it overheated very quickly);
to ensure an even distribution of the air flow, each cylinder stood separately;
when parked with the engine running, even in the presence of a turbine, the air flow is very weak, which leads to rapid overheating;
it is impossible to arrange interior heating.

Because of these shortcomings, the air system is not used on cars, although there were still isolated cases - ZAZ-968 "Zaporozhets" had just such a cooling system. But it is widely used in motor vehicles and equipment equipped with 2-stroke motors (chainsaws, brushcutters, walk-behind tractors, etc.).

Video: Engine cooling system. Device and principle of operation

Device, design, principle of operation

Liquid cooling system

Dignity fluid system cooling is precisely the ability to maintain the temperature in a given range, therefore it is better than air. But the design of this system is much more complicated.

It includes:

Cooling jacket
Water pump
Thermostat
Radiators
Connecting pipes
Fan

In this case, the main working element of such a system is special liquid-, with the help of which heat is removed. Previously, it was used instead plain water, but due to the low temperature threshold of freezing and the formation of scale, the water was gradually abandoned.

1. Cooling jacket

The cooling jacket is a special system of channels in the cylinder block and the block head through which fluid moves. If we consider everything in a simple way, then it looks like this: there is a block in which the cylinders are installed, as well as the main components and mechanisms. A shell is made on top of this block, and the space between them is used as channels for fluid movement. This design allows the fluid to wash over the cylinders, pass next to the units installed in the block and the head, which ensures heat removal from them.

2. Pump

It looks like this water pump

A water pump is installed in the cooling jacket. It consists of a drive gear (pulley) and an impeller, which is placed inside the shirt, fitted on one axis. It is driven from the crankshaft using a belt.

It is the water pump that circulates the fluid through the system. Receiving rotation from the crankshaft, the impeller forces the fluid to move through the channels of the jacket.

3. Radiator

At the same time, antifreeze circulates not only through the shirt. If this were the case, then the liquid would have nowhere to give heat, that is. To prevent this from happening, it is included in the design.

It is a structure of two tanks - one is supplied with liquid from the jacket, and from the second it returns back. These tanks are connected to each other by a large number of tubes through which the liquid moves between them. So that the radiator is made of metals with high thermal conductivity (copper, aluminum, brass). Also, in order to increase heat transfer between the tubes, special tapes are located, laid in a certain way and having a large number of points of contact with the tubes.

The liquid passing through the tubes gives off some of the heat to the tapes. The air passing through the radiator removes heat and removes it to the environment. To ensure good air flow, the radiator is installed in the front of the car. The radiator with the cooling jacket is connected by means of rubber pipes.

Separately, we note that thanks to the liquid system, it was possible to provide and. For this, another radiator was included in the cooling system, which was placed in the cabin. Structurally, it is the same as the main radiator, but smaller in size. The air flow for it is created using an electric motor with a fan.

Video: Engine overheating. Consequences of overheating.

4. Thermostat

The cooling system must ensure the fastest possible output of the power plant to the optimal temperature regime. And to ensure this, a thermostat is included in the design. To understand what it is for - a little theory.

If the design of the system consisted only of a jacket and a pump, then the engine would overheat very quickly, since the liquid moved only through the channels in the block and there would be nowhere to remove heat.

The device and principle of operation of the thermostat

To avoid this, a radiator was included in the design. But due to its presence, the volume increased, besides, the purpose of the radiator is to remove heat, so the engine will reach the desired temperature for a very long time, especially in winter.

To ensure a quick access to the required temperature, the cooling system was divided into two rings - small (only the cooling jacket and pump are involved) and large (jacket + pump + radiator).

The thermostat is also engaged in the division into rings. It is a valve that is triggered by an increase in temperature. On different cars, its response temperature is different, but in general it works in the range - 85-95 degrees. WITH.

The thermostat housing is usually located on the cylinder block near the channel leading to the radiator. While the temperature of the motor is low, the thermostat closes this channel and the liquid moves only along the jacket. As the temperature rises, this valve begins to open gradually, letting the liquid through the large ring, with the involvement of the radiator. When a certain temperature value is reached, it opens completely, and the liquid already moves only along the large ring.

5. Fan, sensors

The principle of operation of the cooling fan

It so happens that the air flow is not enough to ensure normal heat dissipation from the radiator. For example, this happens in a traffic jam when the engine is constantly running, but there is no oncoming air flow, since the car is immobilized.

To prevent the liquid from overheating, a fan is used to create a forced air flow. It is located behind the main radiator and is driven by an electric motor. Its inclusion in work is carried out due to the temperature sensor installed in the radiator.

Additionally, the design also includes a temperature one, which transmits temperature data to dashboard in the cabin, so the driver can constantly monitor the temperature regime of the motor and notice the appearance of a malfunction in a timely manner, due to which the temperature of the motor "went up".

The main malfunctions of the cooling system

There are not so many malfunctions in the engine cooling system, but the consequences from them can be very serious. The main ones are:

Leakage of coolant;
Malfunction of the pump, thermostat;
Damaged sensor wiring.

Video: All causes of engine overheating and boiling. Elimination of the causes of overheating of the VAZ NIVA engine

Liquid leakage can occur due to breakdown of the cooling jacket, cylinder head gaskets, rubber pipes, radiator, or due to unreliable fastening of the connection points.

It is not difficult to identify this malfunction, since as a result of a leak under the car, a puddle of coolant will form. If the leak is not eliminated in a timely manner, then most of coolant may leak out and the system will no longer be able to maintain temperature.

Pump failure is often associated. This is accompanied by traces of smudges on the drive side, increased noise during engine operation, and uneven wear of the drive belt.

If the pump is not replaced in a timely manner, there is a possibility that it will jam and break. drive belt, and this is already fraught with quite serious problems, since often the timing belt is also put into operation with this belt.

The problem with a thermostat is usually that it gets stuck in one position. Because of this, the transfer of fluid between the rings is not carried out, it moves either only along a small one, or along big circle.

Damage to the wiring or sensors leads to the fact that the readings to the dashboard are not transmitted or do not correspond to reality, and the fan does not turn on at the required time or it works constantly, which is why the temperature regime is disturbed.

Most serious car malfunctions are related to engine overheating. The temperature of the gases in the cylinder reaches 2000 g. When fuel burns, a large amount of heat is generated in the cylinder, which must be removed and thereby prevent overheating of engine parts.

Cooling systems design principles

A decrease in the efficiency of the cooling system leads to an increase in the temperature of the pistons, a decrease in the clearances between the piston and the cylinder. Thermal clearances decrease to zero. The piston touches the cylinder walls, scuffing is formed, the overheated oil loses its lubricating properties and the oil film breaks. This mode of operation can lead to engine seizure. Overheating is accompanied by uneven expansion of the block head, mounting bolts, engine block, etc. In the future, engine destruction is inevitable: cracks in the block head, deformation of the junction planes of the head and the cylinder block itself, cracks in valve seats, etc. - even unpleasantly listed, all this, so it is better not to bring it to this!

The engine and oil cooling system is designed to prevent such a development of events, but in order for the system to cope with the tasks set, it is necessary to use high-quality coolant (coolant). Low-freezing coolants are called antifreeze- from the English word "antifreeze". Previously, coolant was prepared on the basis of aqueous solutions of monohydric alcohols, glycols, glycerol, and inorganic salts. Currently, preference is given to monoethylene glycol, a colorless syrupy liquid with a density of about 1.112 g / cm2 and a boiling point of 198 g. The task of the coolant is not only to cool the engine, but also not to boil in the entire temperature range of the engine and its components, to have a high heat capacity and thermal conductivity, not to foam, not to have a harmful effect on pipes and seals, and to have lubricating and anti-corrosion properties.

In the 70s, antifreeze was produced based on an aqueous solution of monoethylene glycol with a crystallization onset temperature of 40 grams. It did not require dilution with water when added to the cooling system. This drug is called ANTISOL- by the name of the laboratory "Technology of Organic Synthesis". Because the name is not patented, then TOSOL is a ready-to-use product, and "antifreeze" is a concentrated solution (although TOSOL is also antifreeze).

Ready-made antifreezes are colored for safety and choose bright colors: blue, green, red. During operation, antifreeze loses beneficial features- anti-corrosion properties decrease, the tendency to foaming increases. The service life of domestic coolants is from 2 to 5 years, imported 5-7 years.

The figure below shows a diagram of the vehicle's cooling system. There is nothing special or complicated in the cooling system, and nevertheless ...

Rice. 1 - engine, 2 - radiator, 3 - heater, 4 - thermostat, 5 - expansion tank, 6 - radiator plug, 7 - upper pipe, 8 - lower pipe, 9 - radiator fan, 10 - fan switch on sensor, 11 - sensor temperature, 12 - pump.

When the engine is started, the pump (water pump) starts to rotate. The pump drive can have its own pulley, driven in rotation by the accessory belt, or driven by the rotation of the timing belt. The cooling system contains an impeller that rotates and sets the coolant in motion. To warm up the engine quickly, the system is "short-circuited", i.e. the thermostat is closed and does not allow liquid to enter the cooling radiator. As the temperature of the coolant rises, the thermostat opens, transferring the system to another state when the coolant passes along a long path - through the radiator of the cooling system (the short path is blocked by the thermostat). Thermostats have various characteristics discoveries. Usually the opening temperature is printed on the edge. Probably not worth explaining the design of the radiator. A fan switch is installed at the bottom of the radiator. If the coolant temperature reaches a certain value, the sensor will close, and since it is electrically connected to open the power supply circuit of the electric fan, then when closed, the cooling system fan should turn on. As the coolant cools down, the fan turns off, and the thermostat blocks the long path for a short one. It's simple, but not very ...

Such a scheme is the basis, but life does not stand still and various manufacturers are improving cooling systems. On some cars, you will not find a sensor for turning on the cooling fan, because the fan is switched on from the ECU by the engine, depending on the readings of the coolant temperature sensor. It is worth paying attention to the situation in which, when the ignition is wedged in, the cooling system fan immediately turns on. Either the temperature sensor is faulty, or its circuits are damaged, or the ECU itself is faulty by the engine - it "does not see" the engine temperature and, just in case, turns on the fan right away.

On some cars, on the way to the heater, special solenoid valves are installed that allow or block the path of the coolant (BMW, MERCEDES). Such valves sometimes "help" the cooling system to fail.

Troubleshooting the cooling system

Specialists of the firm "AB-Engineering" under the leadership of Khrulev A.E. developed a table of the causes and consequences of engine overheating. Myself engine overheating- this is the temperature regime of its operation, characterized by the boiling of the coolant. But overheating is not the only problem. The operation of the engine at a constantly low temperature is also considered a malfunction, because in this case, the engine operates at an unusual temperature regime. Failure of a thermostat, electric fan or viscous clutch, thermal switches, etc. will lead to abnormal operation of the cooling system. If the driver detects signs of a violation in time thermal conditions engine operation and will not allow irreversible processes, then the repair of the cooling system will not be expensive and time-consuming. Therefore, we strongly recommend that you (and your clients) pay attention to the temperature conditions of the engine.

BUT. The first step is to check the connection diagram of the cooling system pipes, if the car is not new or has been repaired after being repaired at another service.

To some, such a proposal will seem ridiculous, but life has shown the opposite, examples:

the car assembled after overhaul had a connection between the crankcase ventilation system pipe and the expansion tank of the cooling system;
an installed non-standard fan with blades directing the air flow in the wrong direction;
the blades of the electric fan rotate freely on the shaft of the switched off engine;
the connectors of the electric fan are loose or cut off, etc.

Inspect the radiator for external blockages. Inspect areas and paths for free cooling of the engine. A negative example is the powerful underside protection that blocks the airflow from the underside of the engine. Sometimes a breakdown of the bumper, the lower part of which has air flow guides to the engine, leads to overheating (VW Passat B3).

B. After inspection, it is necessary to check the coolant level in the system, the presence and serviceability of the radiator cap valves and expansion tank, the integrity of the pipes and hoses. Clarify what kind of antifreeze or just water is poured into the system, because boiling point for each liquid is different.

If the first two points (A or B) revealed any malfunctions, they must be eliminated or taken into account when passing the "verdict". When adding coolant, keep in mind that not all vehicles are designed according to the “just add water” principle. For example on BMW car(M20, E34) when adding coolant, it is necessary to turn on the ignition and set the stove temperature regulators to the "maximum warmth" mode so that the stove valves turn on and open for the coolant to move through the system; in addition, it is necessary to raise the radiator up, because the expansion tank, built into the radiator by the "miracle designers" of Germany, is located below the level of the cabin stove and it is often airy.

If there is a suspicion that the engine is airy (there is air in the system that impedes the movement of fluid), it is necessary to unscrew the special plugs of the cooling system to release the air. They are usually located at the top of the engine cooling system. Start the engine, turn on the interior heaters, turn on the fan. Observe the warming up of the engine, components and assemblies. If there is an expansion tank in the system, then check the fluid circulation, i.e. its movement through the system. When the engine speed is added up to 2,500 - 3,000, a powerful jet of coolant must enter the reservoir. Air can escape from the unscrewed (not completely!) Plugs for some time, and as soon as the liquid pours out, the plugs must be tightened. As the engine warms up, warming air should flow from the interior heater. If the engine is warming up, and the air from the heater is cold, then this is the first sign of "airing" of the cooling system. Stop the engine and take steps to troubleshoot the problem.

With a working thermostat (the opening temperature can vary from 80 to 95 degrees), after warming up, the lower radiator pipe should have approximately the same temperature as the upper one. If this is not the case, then there is poor circulation of the coolant through the radiator.

If the thermostat is in good working order, the cooling fan should turn on some time after opening it. If a non-electric fan is installed in the system, then it is necessary to check the sensor for switching on the electromagnetic clutch circuit or the operation of the viscous clutch. In the event of a malfunction of the viscous clutch, the cooling fan on a hot engine can be stopped and held by hand (when stopping, be careful - stop with a soft object so as not to damage the fan impeller or hand). It is necessary to check the air pressure and its temperature - hot air must be directed to the engine.

The pressure in the cooling system should rise slowly as the engine warms up and drop slowly after the engine is turned off. If the upper pipe leading to the radiator swells when the engine speed rises, it is necessary to check whether some of the exhaust gases enter the cooling system. This is usually noticeable by the oil film in the expansion tank or the blistering of the coolant. At the same time, white smoke is usually intensely emitted from the muffler from the heated and evaporating coolant entering the engine cylinders. In this case, it is necessary to check the oil filler neck of the engine and a white emulsion has sat down on it, then the coolant is not only in the engine cylinders, but also in the lubrication system (you must stop moving). Here are a few examples from the practice of various services that "speak" of the fact that engine diagnostics is inseparable from diagnostics of all vehicle systems, including the cooling system.

A \ m MAZDA 626 - the owner complains of uneven engine speed or increased speed idle move... Checking the control system (and self-diagnostics) did not reveal a malfunction. Pay attention to the increased voltage on temperature sensor coolant.

The control system adds the amount of fuel, because reacts to high voltage at the sensor (engine cold). It turned out that there is little liquid in the cooling system, the sensor is "bare". The coolant level is simply added to the normal level and the rpm is normalized.

А \ m FORD - the coolant got into the oil in an unconventional way - through the oil cooling system located around the oil filter.

A \ m FORD - after warming up the engine, one cylinder stopped working. Replacing the spark plug and other work led to a positive result (it had nothing to do with the determination of the malfunction, it was just that the engine cooled down during the work) - the cylinder began to work and the client left. The next day he is with us again. It turned out - a crack in the head of the block in the area of the exhaust valve of the inoperative cylinder. As long as the engine is cold, everything is normal. When warmed up, the crack grew and began to let coolant into the cylinder. The mixture became lean and interruptions began, and then the cylinder was completely turned off.

There are many such examples, they are in the practice of every auto repairman. The main conclusion should be made by everyone who is seriously engaged in car repair - to notice and analyze everything significant and insignificant, because these positions can be abruptly reversed.

The cooling system is designed to cool engine parts that are heated as a result of engine operation. On the modern cars the cooling system, in addition to the main function, performs a number of other functions, including:

Depending on the cooling method, the following types of cooling systems are distinguished: liquid (closed), air (open) and combined. In a liquid cooling system, heat from the heated parts of the engine is removed by a fluid flow. The air system uses airflow for cooling. The combined system combines fluid and air systems.

On cars, the most common liquid cooling system. This system provides uniform and efficient cooling and also has a lower noise level. Therefore, the design and principle of operation of the cooling system are considered on the example of a liquid cooling system.

The design of the cooling system of gasoline and diesel engines are similar. The engine cooling system includes many elements, including a coolant radiator, an oil cooler, a heater heat exchanger, a radiator fan, a centrifugal pump, as well as an expansion tank and a thermostat. The cooling system diagram includes a "cooling jacket" of the engine. Control elements are used to regulate the operation of the system.

The radiator is designed to cool the heated coolant with an air stream. To increase heat transfer, the radiator has a special tubular device.

Along with the main radiator, an oil cooler and an exhaust gas recirculation cooler can be installed in the cooling system. The oil cooler serves to cool the oil in the lubrication system.

The EGR cooler cools the exhaust gases, thereby reducing the combustion temperature of the air-fuel mixture and the formation of nitrogen oxides. The operation of the exhaust gas cooler is ensured by an additional coolant circulation pump included in the cooling system.

The heat exchanger of the heater performs a function opposite to the radiator of the cooling system. The heat exchanger heats the air passing through it. For efficient operation, the heater heat exchanger is installed directly at the outlet of the heated coolant from the engine.

To compensate for changes in the volume of coolant due to temperature in the system, an expansion tank is installed. The system is usually filled with coolant through an expansion tank.

The circulation of the coolant in the system is provided by a centrifugal pump. In everyday life, a centrifugal pump is called pomp... The centrifugal pump can have a different drive: gear, belt, etc. On some turbocharged engines, an additional coolant circulation pump is installed to cool the charge air and the turbocharger, which is connected by the engine control unit.

The thermostat is designed to regulate the amount of coolant passing through the radiator, which ensures the optimal temperature regime in the system. The thermostat is installed in the pipe between the radiator and the "cooling jacket" of the engine.

Powerful engines are fitted with an electrically heated thermostat that provides two-stage coolant temperature control. For this, the thermostat has three operating positions: closed, partially open and fully open. When the engine is fully loaded, the electric heating thermostat opens it completely. In this case, the temperature of the coolant decreases to 90 ° C, the propensity of the engine to detonate decreases. In other cases, the coolant temperature is maintained within 105 ° C.

The radiator fan serves to increase the intensity of cooling the liquid in the radiator. The fan can have a different drive:

mechanical ( persistent connection with crankshaft engine);
electric ( controlled electric motor);
hydraulic ( fluid coupling).

The most widespread is the electric fan drive, which provides ample opportunities for regulation.

Typical cooling system controls are the coolant temperature sensor, the electronic unit control and various executive devices.

The coolant temperature sensor records the value of the monitored parameter and converts it into an electrical signal. To expand the functions of the cooling system (cooling the exhaust gases in the exhaust gas recirculation system, regulating the operation of the fan, etc.), a additional sensor coolant temperature.

The signals from the sensor are received by the electronic control unit and converted into control actions on the actuators. As a rule, an engine control unit with the appropriate software installed is used.

The following actuators can be used in the control system: thermostat heater, auxiliary coolant pump relay, radiator fan control unit, engine cooling relay after stopping.

How the cooling system works

The operation of the cooling system is provided by the engine management system. In modern engines, the operation algorithm is implemented based on mathematical model, which takes into account various parameters (coolant temperature, oil temperature, outside temperature, etc.) and sets the optimal conditions for switching on and the operating time of structural elements.

The coolant in the system has forced circulation, which is provided by a centrifugal pump. The movement of fluid is carried out through the "cooling jacket" of the engine. This cools the engine and heats up the coolant. The direction of fluid movement in the "cooling jacket" can be longitudinal (from the first cylinder to the last) or transverse (from the exhaust manifold to the intake).

Depending on the temperature, the liquid circulates in a small or large circle. When the engine is started, the engine itself and the coolant in it are cold. To speed up engine warm-up, the coolant moves in a small circle, bypassing the radiator. The thermostat is closed at the same time.

As the coolant heats up, the thermostat opens and the coolant moves in a large circle through the radiator. The heated liquid passes through the radiator, where it is cooled by the counterflow of air. If necessary, the liquid is cooled by an air flow from the fan.

After cooling, the liquid is returned to the "cooling jacket" of the engine. During engine operation, the coolant cycle is repeated many times.

On turbocharged vehicles, a dual-circuit cooling system can be used, in which one circuit is responsible for cooling the engine, the other for cooling the charge air.

Cooling system is a set of devices that provide forced removal of heat from heating engine parts.

The need for cooling systems for modern engines caused by the fact that the natural dissipation of heat by the outer surfaces of the engine and heat dissipation into the circulating engine oil do not provide optimal temperature conditions for the engine and some of its systems. Overheating of the engine is associated with a deterioration in the process of filling the cylinders with a fresh charge, oil burning, an increase in friction losses and even piston seizure. On the gasoline engines there is also a danger of glow ignition (not from a spark plug, but due to high temperature combustion chambers).

The cooling system should ensure automatic maintenance of the optimal thermal regime of the engine at all high-speed and load modes of its operation at an ambient temperature of -45 ... + 45 ° С, rapid engine warming up to working temperature, minimum power consumption for driving the system units, low weight and small dimensions, operational reliability, determined by the service life, simplicity and ease of maintenance and repair.

Air and liquid cooling systems are used on modern wheeled and tracked vehicles.

When using an air cooling system (Fig. A), heat from the cylinder head and block is transferred directly to the air blowing around them. Through the air jacket formed by the casing 3, the cooling air is driven by the fan 2 driven from the crankshaft using a belt drive. To improve heat dissipation, the cylinders 5 and their heads are equipped with ribs 4. The intensity of cooling is regulated by special air dampers 6, which are automatically controlled by air thermostats.

Most modern engines have a liquid cooling system (Fig. B). The system includes cooling jackets 11 and 13, respectively, of the cylinder head and block, radiator 18, upper 8 and lower 16 connecting pipes with hoses 7 and 15, liquid pump 14, distribution pipe 72, thermostat 9, expansion (compensation) tank 10 and fan 77 Cooling liquid (water or antifreeze - non-freezing liquid) is in the cooling jacket, radiator and pipes.

Rice. Schemes of air (a) and liquid (b) engine cooling systems:
1 - belt drive; 2, 17 - fans; 3 - casing; 4 - ribs of the cylinder; 5 - cylinder; 6 - air damper; 7, 15 - hoses; 8, 16 - upper and lower connecting pipes; 9 - thermostat; 10 - expansion tank; 77, - cooling jacket for the head and cylinder block; 12 - distribution pipe; 14 - liquid pump; 18 - radiator

When the engine is running, a crankshaft-driven liquid pump circulates coolant in the system. Through the distribution pipe 12, the liquid is directed first to the most heated parts (cylinders, the head of the block), cools them and through the pipe 8 enters the radiator 18. In the radiator, the liquid flow branches through the tubes into thin streams and is cooled by air blown through the radiator. The cooled liquid from the lower radiator tank through the pipe 16 and hose 15 again enters the liquid pump. The flow of air through the radiator is usually created by a fan 77 driven by a crankshaft or a special electric motor. On some tracked vehicles, an ejection device is used to ensure air flow. The principle of operation of this device is to use the energy of the exhaust gases flowing out at high speed from the exhaust pipe and entraining air with them.

Regulates the circulation of fluid in the radiator, maintaining the optimum engine temperature, thermostat 9. The higher the temperature of the fluid in the jacket, the more open the thermostat valve and more fluid enters the radiator. At a low engine temperature (for example, immediately after starting it), the thermostat valve is closed, and the liquid is directed not into the radiator (along a large circulation circle), but directly into the pump intake cavity (along a small circle). This allows the engine to warm up quickly after starting. Cooling intensity is also regulated by louvers installed at the inlet or outlet of the air duct. The greater the degree of shutter closing, the less air passes through the radiator and the worse the cooling of the liquid.

In the expansion tank 10, located above the radiator, there is a supply of liquid to compensate for its loss in the circuit due to evaporation and leaks. In the upper cavity of the expansion tank, steam generated in the system is often removed from the upper radiator header and the cooling jacket.

Compared to air cooling, liquid cooling has the following advantages: easier engine start-up at low ambient temperatures, more uniform engine cooling, the possibility of using block cylinder designs, simplified layout and the ability to

isolation of the air path, less noise from the engine and lower mechanical stresses in its parts. At the same time, the liquid cooling system has a number of disadvantages, such as a more complex design of the engine and system, the need for coolant and more frequent oil changes, the risk of fluid leakage and freezing, increased corrosive wear, significant fuel consumption, more complex maintenance and repair. , as well as (in some cases) increased sensitivity to changes in ambient temperature.

Liquid pump 14 (see fig. B) circulates the coolant in the system. Centrifugal vane pumps are commonly used, but gear and piston pumps are sometimes used. Thermostat 9 can be one- and two-valve with a liquid thermo-force element or an element containing a solid filler (ceresin). In any case, the material for the thermo-power element must have a very high coefficient of volumetric expansion, so that when heated, the valve stem of the thermostat can move a fairly large distance.

Practically all engines of liquid-cooled ground vehicles are equipped with so-called closed cooling systems, which do not have a constant connection with the atmosphere. In this case, excessive pressure is formed in the system, which leads to an increase in the boiling point of the liquid (up to 105 ... 110 ° C), an increase in cooling efficiency and a decrease in losses, as well as a decrease in the likelihood of air and vapor bubbles in the liquid flow.

Maintaining the necessary overpressure in the system and providing access to atmospheric air during vacuum is carried out using a double vapor-air valve, which is installed at the highest point of the liquid system (usually in the filler cap of an expansion tank or radiator). The steam valve opens, allowing excess steam to escape to the atmosphere if the pressure in the system exceeds atmospheric by 20 ... 60 kPa. The air valve opens when the pressure in the system decreases by 1 ... 4 kPa compared to atmospheric (after stopping the engine, the coolant cools down and its volume decreases). The pressure drops at which the valves open are provided by the selection of the valve spring parameters.

In a liquid ventilation cooling system, the radiator is surrounded by a flow of air generated by a fan. Depending on the relative position of the radiator and fan, the following types of fans can be used: axial, centrifugal and combined, creating both axial and radial air flows. Axial fans are installed in front of the radiator or behind it in a special air supply channel. The air is supplied to the centrifugal fan along the axis of its rotation, and it is removed along the radius (or vice versa). When the radiator is in front of the fan (in the suction area), the air flow in the radiator is more uniform, and the air temperature is not increased due to its stirring by the fan. When the radiator is behind the fan (in the discharge area), the air flow in the radiator is turbulent, which increases the cooling intensity.

On heavy wheeled and tracked vehicles, the fan is usually driven from the engine crankshaft. Cardan, belt and gear (cylindrical and bevel) transmissions can be used. In order to reduce the dynamic loads on the fan in its drive from the crankshaft, unloading and damping devices are often used in the form of torsion rollers, rubber, frictional and viscous couplings, as well as hydraulic couplings. To drive the fan of relatively low-power motors, special electric motors are widely used, which are powered from the on-board electrical system. This generally reduces the weight of the power plant and simplifies its layout. In addition, the use of an electric motor to drive the fan makes it possible to regulate its rotation frequency and, consequently, the cooling intensity. If the coolant temperature is low, the fan can be turned off automatically.

Radiators connect the air and fluid paths of the cooling system to each other. The purpose of the radiators is to transfer heat from the coolant to the atmospheric air. The main parts of the radiator are the inlet and outlet headers, as well as the core (cooling grille). The core is made of copper, brass or aluminum alloys. By the type of core, the following types of radiators are distinguished: tubular, tubular-plate, tubular-tape, plate and honeycomb.

In cooling systems for wheeled and tracked vehicles, tubular-plate and tubular-tape radiators are most widely used. They are tough, durable, manufacturable and have high thermal efficiency. The tubes of such radiators, as a rule, have a flat-oval cross-section. Plate-tube radiators can also consist of tubes of round or oval cross-section. Sometimes flat-oval tubes are placed at an angle of 10 ... 15 ° to the air flow, which promotes turbulence (swirl) of the air and increases the heat transfer of the radiator. Plates (tapes) can be smooth or corrugated, with pyramidal projections or bent notches. Corrugation of the plates, the application of notches and protrusions increase the cooling surface and provide a turbulent flow of air flow between the tubes.

Rice. Grilles of tubular-plate (a) and tubular-tape (b) radiators