Many vehicle owners who are equipped with a "incomplete" drive (which at some point becomes complete) heard of the Viscounts (that is, the viscous coupling), but have a very troubled idea of \u200b\u200bthe principle of operation of such a node. In our article we will try briefly and intelligibly to tell about the device of this part of the transmission and the algorithm of its functioning.

Structurally viscous coupling (VM) is a hermetic case, as a rule, cylindrical shape. Inside it has round perforated steel discs (with a small gap between them). Half of these plates is connected to the leading (input) shaft, the rest - with the slave (output). Moreover, discs have different hole geometry. Plates with slots are installed on the entrance shaft, on the weekend with "holes". Disks inside the case are installed so that they alternate: first one "presenter", then one "slave" and so on. Mechanically both shaft are not interconnected.

The entire inner volume (and intervals between the discs) is filled with a special fluid (so-called silicone oil) based on polydimethylsiloxane.

For what it applies

IN modern cars Viscosity clutches are used for:

• temporary translation into the All-wheel drive mode (AWD);
• blocking of the mid-scene differential.

Let us dwell on these moments in more detail.

Translation of vehicle in AWD mode

Many modern crossovers or "parcktails", as well as some minivans, sedans or hatchbacks, are equipped with a so-called temporarily connected full wheel drive. The axis of the differential of the lead (usually the front) bridge is connected via the Viscuft with a similar node rear wheels. Under normal conditions, both shaft rotate at the same speed. The viscosity of silicone fluid does not change, but, consequently, the transmission of torque on rear axle not happening. As soon as the front wheels begin to slip, the work "turns on" the Viscounts. Then the car goes back to the standard front-wheel drive mode.

On a note! In vehicles equipped with temporarily connected full-wheel drive through the Viscounts, the diameter of the front and rear wheels must necessarily be the same. This will avoid false positives of VM (for example, when driving on the highway). If you set the leading front wheels of a smaller diameter (in this case, they will do more turns In a minute than the rear), at certain speeds, the movement of the Viscouft may "think" that they are running and connecting the four-wheel drive at the most inopportune moment.

Inside, the Viscuft is dilatated liquid (J), the viscosity of which increases at times as the intensity of stirring is accelerated. If speed vehicle Stable (when the machine does not raise), then JR has a liquid consistency and the plate rotate the same (parallel to each other). There is only a minimum mixing of the liquid. As a result of the slip, the leading shaft begins to rotate very quickly (consequently, the plates on it), and the slave, practically, is without any movement. Next occurs very intensive mixing of J, a sharp increase in its viscosity. Also observed the heating of the fluid and its expansion, as a result of which the plates begin to press a lot to each other (they, almost "glued" together). The transmission of the rotational torque from the drive shaft on the slave, the car ceases to be stopped, the rotation speed of both shafts is stabilized, the viscosity of the fluid is significantly reduced, its mixing is stopped and rear axle Disabled. That is, "everything comes back to their circles."

Blocking inter-axis differential

One of the inalienable nodes of the transmission is differential. It is intended to rotate with different angular velocities when turning the wheels, as they (right and left) in the implementation of such a maneuver pass different along the path. On some cars there is a blocking of differential using an integrated viscous coupling. This function is very useful if one of the leading wheels (for example, hitting a wet or slippery portion of the road leaf) begins to slip. In this case, VM blocks differential. On both wheels are transmitted the same torque. After the "problem" portion of the road is overcome, the disks of the Viscouft "are separated" and the differential goes into normal mode Work.

On a note! On SUVs (for example, Subaru Forester. or BMW 325IX E30) equipped with a constant system full drive, VM "works" when slipping one of the leading bridges. Technologically integrated into the central differential and blocks it to align the speed of rotation of the front and rear shafts.

Major malfunctions Viscouft

Immediately it is worth noting that manufacturers of cars equipped with viscous products indicate in the technical documentation that this node is not subject to repair, and in case of interruptions in its work, it is subject to replacement for a new one.

Two main faults that may occur during the operation of VM:

• The disruption of the tightness of the body of the product, as a result of which silicone oil flows out. In this case, the Viscounts simply stops working, and does not "turn on" a temporary full drive mode or does not block differential.
• Hardening silicone fluid and, as a result, the loss of its "unique" properties (this can occur due to frequent overheating of the unit, for example, with permanent roadway). Causes such a malfunction to the fact that both shaft are in constant engagement. But, the elements of the transmission (gearbox of the leading bridge, gearbox and so on) vehicles with a temporarily connected full drive initially not designed for such constant increased loads and can quickly fail. Therefore, at the first sign that the liquid "crossed" into a solid state, the Viscuft must be replaced urgently. Inaction can lead to very expensive repair.

Advantages and disadvantages

Among the advantages of VM should be noted:

• Simplicity of design. Really, automatic inclusion node to work occurs without the use of any special sensors (measuring the speed of rotation of the wheels) or electronic block Control.
• Low cost.
• Durability. Under the observance of the rules of operation recommended by the manufacturer, the service life of the viscous coupling is designed for the entire period of "life" of the car.
• No need periodic maintenance.
• High body strength. Its design can withstand pressure even at 15 ÷ 20 atm (the increase occurs due to heating and fluid expansion).

And now about the disadvantages:

• Inertial response. Before the Viscounts automatically "connect" to work four-wheel drive, the time required to increase the viscosity of silicone fluid and "engagement" of the shafts is passed.
• Maintainability (or rather, its absence). The product is disposable and when the breakdown is to be replaced.
• The dependence of the efficiency of the connected full drive from the intensity of the protrusion of the drive wheels.
• The inability of continuous long-term operation in off-road conditions.

In the design of the cooling system of the car there is such an interesting mechanism as the viscous food. Automotive forums often ask questions related to this mechanism. We made conclusions about the need for a detailed study of this topic.

What is the viscous fan

Under such a strange name implies a special mechanism on which the function of selective transmission is determined by external conditions and. The coupling has a view of a hermetic case. Inside it there are discs, broken into two rows. One row of disks connect with the slave shaft, respectively, the second row is associated with the master. The design of the mechanism provides for the possibility of alternating the disks among themselves. Their design has holes and protrusions.

Inside the Viscuft, there is a special fluid with a viscous structure, because the mechanism is often called viscous. Most often, silicone is used for the manufacture of this substance. The fluid is characterized by unique features that determine its effective use. The possibilities of this substance are reduced to the following:

• with an increase in the intensity of the mixing, the viscosity rate increases;
• when heated, the expansion coefficient increases.

Such features define the principle of operation of the Viscounts, which will be studied next.

Where is Viscounts

This mechanism takes place between the car cooling radiator and. It performs a number of important features:

1. Monitoring the speed of rotation of the blades of the fan, which cools the power unit of the car.
2. Ensuring the efficiency of the engine by activating the fan to the desired moments.
3. Reducing the load, which is experiencing a power unit.

The coupling can be attached to the flange shaft, which, in turn, is installed on the pulley of the pump. Also, the shaft may sound on the pump shaft. Next, you need to deal with how the cooling fan is working.

How the cooling fan viscous

Acquaintance with the viscous fan will be impossible without studying the principle of operation of this mechanism. In the inexperienced motorist, this process may seem complicated, although, in fact, everything works simply and understandable. The principle of operation The cooling fan is based on the functioning of a bimetallic sensor. It is ahead of the viscose fan. This element reacts to a temperature that is transmitted through the cooling system radiator.

1. At low temperature, the sensitive sensor causes the valve to shrink. This leads to the preservation of oil inside the Viscouft within the tank. The coupling on the fan is deactivated and continues to rotate only by 20% of the intensity of rotation of the motor.
2. When the temperature is raised to the working level, the sensor expands and causes the valve to rotate. This leads to the movement of the oil through the chamber to the outer edges. The adhesion with the fan is activated and the speed of rotation of the coupling increases from 20% to 80%.

When the TC is moving at a constant speed, the rotation of the disks is uniform and is not accompanied by stirring the oil between them. If the difference occurs between speeds (slave and master), the discs also begin to work in different modes. This leads to an increase in the viscosity of silicone fluid. In such a state, it has an impact on the transmission of torque.

When a large difference occurs between the speeds of rotation of the discs, the liquid becomes almost hard, which leads to the blocking of the Viscounts. The device of the Viscouft fan studied, now it is necessary to learn how to check the serviceability of this mechanism.

How to check the viscous coupling

Performance of the ventilator of the fan must be checked on cold and hot force aggregate. This is evidenced by operating allowances for the repair of the vehicle. With a cold motor, Peregazovka will not change the frequency of the clutch rotations. In the case of a hot motor, this indicator will increase greatly.

Also, a longitudinal backlash is also checked, when the detection of which will have to perform work to eliminate it. Availability outsided sounds During rotation, the coupling will talk about the fault of bearings.

The main causes of malfunction

The mechanism may fail for several reasons. We allocated the main and most common:

• the use of tires of various sizes, which also have different levels of worn out;
• leakage of fluid from the coupling;
• wear of parts as a result of intensive operation, the effects of aggressive factors and high temperature;
• incorrect alignment of the drive mechanism;
• the loss of the properties of the bimetallic sensor, which may appear as a result of the clutch jams;
• faulty bearing.

Signs of malfunction

The first and most important feature that may indicate the faulty state of the Viscounts, is excessive heating of the motor. Such a situation may occur as a result of fluid leakage or the lack of timely response of the bimetric plate. The motor temperature rises, and the fan does not work at all or functions on low revs, therefore, the unit cooling is not ensured.

It also happens that with a cold engine, the fan rotates for full force. Such a situation may arise due to a damaged gel, breakdowns of a number of mechanism nodes or turning the lubricant into a solid substance.

What can cause defective Viscounts

The working stock of the Viscounts on average is 200 thousand km. After that, the mechanism requires increased attention. You need to constantly monitor the moment of its operation, especially in summer. It is also required to check operating temperature Motor in traffic jams. If the values \u200b\u200bclose to critical are noted, it will have to be seriously engaged in the Viscounts. The new item costs a lot, and it is often not possible to find the desired model. Therefore, many car owners are solved on the installation electrical system. In any case, it is impossible to ignore this situation, because you can face the following troubles:

• overheating of the motor;
• reducing the service life of the pump;
• increase.

Each of you is warned about the danger, which carries a faulty vescilla of the fan of the car cooling system. You should not neglect the verification and troubleshooting, otherwise you can face very expensive and time-consuming engine repair.

Recently, crossovers are increasingly popular, or so-called parquets. These cars differ from the present SUVs not only the absence of a carrier frame (here this function is performed by the body), but also a "dishonest" full-wheel drive with electronic locks. And it is connected automatically. To associate two axes, the Viscounts are used. What is this element, not every motorist knows. In today's article, we will consider this mechanism in more detail.

Characteristic

Why serves the Viscounts? What is this mechanism?

The viscous coupling is a device for automatic transmission torque through viscous properties. In other words, the connection of the second axis of the car is produced by changing the density of the fluid, which is filled inside this coupling.

What fluid

It is located in a closed case of the device called the Viscounts. What it is? Inside the coupling there is a dilatant liquid, which is made on the basis of silicone.

It has special properties. In calm condition, it is liquid. But as soon as the molecules are mixed, it changes its density. The dilatancy fluid is poured for the entire service life of the mechanism.

Device and principle of operation

The viscous coupling on the principle of the hydrotransformer is working, which has automatic transmission. In both cases, the torque is transmitted by liquid. However, the coupling is arranged a little differently, rather than the torque converter. It is a hermetic closed case. Inside it rotates the leading and slave impellers (two turbines). When the shafts of the wheels rotate synchronously, the composition inside is in a liquid state. As soon as one axis of Zabuxed, the torque of one turbine is transmitted to another. The liquid is mixed and becomes solid. Thus, the transmission of torque on the axis is renewed. As soon as the car overcame the obstacle, stirring stops. The torque is again transmitted to one axis.

But this is not a single scheme of the viscous coupling device. Some instead of turbines have leading and led friction discs (see photo below).

They work according to the same principle. Inside the dilatancy fluid is also poured. When the shafts rotate at different speeds, it is mixed and becomes dense (it expands). So, the torque is aligned, and both wheels (in front and rear) rotate the same one. Due to the expansion of fluid, the slave and the leading discs are pressed to each other.

As you can see, the device of the mechanism is quite simple. The element serves sufficiently long, so the repair of the Viscounts may be needed not soon.

Where is used?

There are two main directions where the viscous food is used. What is it for the spheres? Below we will look at:

• Cooling system. The viscous coupling is used to comprising cooling the radiator. The mechanism is installed on the rod and drives from crankshaft With the help of belt transmission. From above to the item install a multilave fan. How it works? The stronger the pulley rotates, the faster the liquid is thick in the coupling. Thus, on medium and high revolutions The engine radiator is cooled forced. With a drop of revolutions, the heat exchanger is cooled naturally. The fan stops its work. Now this cooling method is practically not used. The viscous clutch was replaced by electric fans. They are powered by the engine temperature sensor. The element is not associated with crankshaft Engine and is more technological.
• Connecting a full drive. And if in the first case, the problem could be solved by electronics, then transfer the torque to the second axis will not be able to transmit. Therefore, the main sphere of applying a viscous coupling is crossovers.

Benefits

What are the advantages of this mechanism? Consider a few of them:

• Easy design. The device has a liquid and two turbines (or discs), tightly closed in the case.
• Strength. The housing in the couphe is able to withstand pressure up to 20 atmospheres. Therefore, you should not be afraid for the fact that the liquid once flows from the outside.
• Practicality. It can work on both the dirt road and on the asphalt (for example, if you are moving with slipping). Does not require electronics. Connecting and disable drive occur in automatic mode.

disadvantages

Despite such significant advantages, it is worth noting the shortcomings of the viscous coupling:

• Low maintainability. In case of failure, the viscous coupling is completely replaced. The cost of such a detail is large enough. Repair Viscouft is not performed.
• Small efficiency of the full drive. Both wheels will rotate at the same speed only when the car will be strongly designed. There can be no speech about the rigid inter-axis blocking.
• The impossibility of forced connection. For example, you need to cross the Brod. It is desirable to have a constant four-wheel drive. However, the viscous clutch will not give you this. Wheels will rotate fully only after you are in charge.
• Reduced road lumen. The body of the mechanism is quite large, which puts the question of the characteristics of the crossover.
• Small overheating resistance. For a long time, the element in the full drive mode cannot (the properties of the liquid change, the bearing is wedge). Otherwise, it will fail. Therefore, it is not worth a bounce on off-road for a long time.

Removing the Vussophy UAZ do it yourself

Let's look at how to extract this item along with the fan, on the example of cars of the Ulyanovsk Automobile Plan. So, for convenience, you need to remove the radiator and the fan casing (blinds). Next, with the key of 12, two mounting bolts pulley pump are unscrewed. Please note: on the nut of the viscous clutch there is a left-sided thread. Therefore, it is necessary to unscrew it clockwise, but to twist - on the contrary. After that, the clutch fastening nut is unscrewed by a key. Hold the crankshaft pulley from scrolling. If the nut is with difficulty, you can use the hammer. Carefully apply shock in the direction of turning. Next, the coupling is successfully removed from the pump shaft. The key to 13 unscrew the 4 fastening screws. Give the mechanism outward and put a new one.

The installation of the item is made in the reverse order. Bolt rods screwed into their place with pliers with thin sponges. Next clutches, fastening nuts twist "by hand". Watch the bolt on the couphe itself is not needed. It is self-tasking when the engine is started.

So, we found out what the Viscounts represents.

Now cursovovers have received great popularity in the automotive market. They have both complete and monoprifer. It connects with the help of such a device as the Viscounts. The principle of operation of the aggregate is further in our article.

Characteristic

So, what is this element? The Viscouft is an automatic mechanism for transmitting torque by means of special liquids. It is worth noting that the principle of operation of the Viscuft of the full drive and the fan is the same.

Thus, the torque on both elements is transmitted using working fluid. Below we will look at what it represents.

What is inside?

Inside the housing of the coupling is used liquid on silicone basis. It has special properties. If it does not rotate and not heated, it remains in a liquid state. As soon as the energy of torque is incorporated, it expands and becomes very dense. With an increase in temperature, it looks like frozen glue. As soon as the temperature drops, the substance turns into a liquid. By the way, she is flooded for the entire service life.

How does it work?

What is the product called "Viscounts" principle of work? According to the action algorithm, it looks like a hydraulic transformer automatic box. Here also torque is transmitted using fluid (but only by means transmission Oil). There are two types of wicked. Below we will look at them.

First Type: Impeller

It includes a metal closed case. The principle of operation of the Viscounts (cooling fan including) is the action of two turbine wheels. They are located opposite each other. One is on the leading shaft, the second is on the slave. The housing is filled with silicone-based liquid.

When these shafts rotate with the same frequency, the stirring of the composition does not occur. But as soon as the slip appears, the temperature inside the housing grows. The liquid becomes thick. Thus, the leading turbine wheel enters the clutch with the axis. Connects as soon as the car left off-road, the speed of rotation of the impeller is restored. The temperature drop is reduced with a drop of fluid. In the car turns off the four-wheel drive.

Second Type: Disc

There is also a closed case here. However, in contrast to the first type, there is a group of flat disks on the lead and driven shaft. What is this Viscounts of the principle of operation? Disks rotate in silicone fluid. As soon as the temperature grows, it expands and presses these elements.

The coupling begins to transmit torque on the second axis. This is happening only when the car has dropped and there is a different frequency of rotation of the wheels (until one stand, the second drops). In both types are not used automatic electronic systems. The device works on the rotation energy. Therefore, the viscous food of the fan and the full drive is distinguished by a long service life.

Where is used?

At first, we first note the element that is used in the engine cooling system. The principle of operation of the ventilator fan is based on the work of the crankshaft. The coupling itself is attached to the rod and has the higher the crankshaft turnover, the stronger the fluid was heated in the coupling. Thus, the relationship became tougher, and the element with the fan began to rotate, cooling the engine and the radiator.

With a drop of revolutions and a decrease in the temperature of the coupling fluid ceases its work. It is worth noting that the viscous fan is no longer used. On the modern engines Apply electronic impeller with a temperature sensor. They are no longer connected with the crankshaft and work separately from it.

Four-wheel drive and viscous

The principle of operation is the same as the fan. However, the detail is not in open space, and under the bottom of the car. And, in contrast to the first type, the wssoculation of the full drive does not lose its popularity.

Now it is installed on many crossovers and off-roads with a disconnected drive. Some use electromechanical analogs. But they are much more expensive and less practical. Among decent competitors, it should be noted that there is a mechanical blocking that is on "Niva" and "UAZ". But due to urbanization, manufacturers have abandoned the present blocking, which rigidly connects both axes and increases the car's permeability. The driver himself can choose when he needs a four-wheel drive. If it is required to overcome the off-road "PARKTER", it will quickly get stuck and after sinking it will earn the rear axle. But to get out of strong dirt it will not help him.

Benefits

Let's consider the positive aspects of the Viscounts:

• Easy design. Inside, only a few impeller or disks are used. And all this is activated without electronics, by physical expansion of the fluid.
• Cheapness. Due to the simple design of the Viscounts, it practically does not affect the cost of the car (if it concerns the option "Four-wheel drive").
• Reliability. The coupling has a durable housing that maintains pressure up to 20 kilograms per square centimeter. Installed for the entire service life and does not require periodic replacement of the working fluid.
• Can work in any road conditions. It does not give slip on the dirt or when driving through the snow. The outer temperature does not matter to heat the working fluid.

disadvantages

It is worth noting the lack of maintainability. Viscounts are installed forever.

And if it failed (for example, due to mechanical deformations), it changes entirely. Also, motorists complain about the lack of ability to connect a four-wheel drive independently. The coupling introduces the second axis in the engagement only when the car already "buried". It does not allow the car easily overcome mud or snow obstacles. The next minus is low ground clearance. For the node you need a large case. And if you use a small viscous coupling, it will not transmit the desired torque force. And the last drawback is the fear of overheating.

It is impossible to buck for a long time. Otherwise, there is a risk of increasing the Viscuft. Therefore, this type of "dishonest" drive is not welcomed by off-Round lovers. With long loads, the node simply encourages.

Conclusion

So, we found out how the Viscounts of the full drive and the fan works. As you can see, the device due to the special fluid can transmit torque at the desired time without attracting additional sensors and systems. This is very

The viscous coupling or viscous food is a device transmitting torque from one shaft to another due to the viscous properties of a special fluid inside the coupling. This mechanism He got widespread in the technique, but motorists he is more familiar as a device in the car transmission. This is a simple and inexpensive mechanism that is capable of providing both automatic and automatically connected four-wheel drive in most modern crossovers. Consider the principle of operation, the design, as well as the advantages and disadvantages of the popular transmission mechanism.

Principle of operation of the Viscounts

The viscous coupling is a hermetic case, inside of which perforated discs and dilatant liquid (material based on silicone, having a high viscosity). One part of the disks is rigidly connected to the drive shaft, the other with the differential housing.

General view of Viscounts

When the car moves along the smooth road surface, the differential and drive shaft rotate synchronously. Perforated discs are also rotated as a whole. If the car begins to buck, the wheels of one axis begin to rotate quickly, and the other axis becomes fixed. At this point, the drives associated with the drive shaft are starting to rotate quickly and stir dilatant liquid. As a result, the silicone substance is quickly thickened and hardening, blocking differential. The torque is transmitted to the second axis, thereby "connecting" a four-wheel drive that helps the car to cope with off-road. After overcoming the obstacle, the silicone fluid returns to the original state, the Viscouft is unlocked, and the rear axle is turned off.

Device and main components

The main components of the viscous clutch are flat perforated discs, dilatated liquid and airtual body.
A package of disks with holes is divided into two groups: one group is connected to the drive shaft, the other with the slave shaft. All discs are at a minimum distance from each other, while leading and driven alternate.
Dilatant liquid filling inner space Viscounts, is an organic substance based on silicone. With active stirring and heating, the substance is thickened and goes into a solid state. After expanding and solidifying silicone material, the pressure on perforated discs is greatly increasing, which is why they are pressed against each other. It is after that the rear axle of the machine is included in the work.

Advantages and disadvantages

First of the advantages of Viscounts:

• simplest design;
• durable case withstanding pressure up to 20 atmospheres;
• affordable cost due to ease of design;
• does not require maintenance, usually operated without breakdowns throughout the service life of the car.

Basic Disadvantages of Viscounts:

• the impossibility of repair (if the viscous coupling broke, it is changed to a new one);
• danger of overheating during long work;
• there is no possibility of manual lock;
• incomplete automatic blocking;
• triggering with the receipt;
• incompatibility with;
• lack of complete drive control;
• large couplings greatly reduce clearance.

Application of Viscounts

Viscous coupling, mainly installed on cars with increased patency As an automatic lock (for example, on cars Jeep Grand. Cherokee I. Range Rover. HSE). However, the Viscouft can also be used together with a gear free differential, acting as a role. auxiliary mechanism automatic lock.
Note that the coupling with dilatated liquid is the easiest and cheapest way to associate both axes of the car. The effectiveness and accuracy of this mechanism in most cases is enough to prevent the front wheels of the machine with respect to the rear pavement on the usual road surface. However, now automakers are increasingly abandoning the installation of the Vicility due to their incompatibility with the ABS system.