Kamaz's hydraulic coupling: how to ensure trouble-free operation of the cooling fan?

The system of cooling cars KamAZ is arranged on a classical principle. But there are also features. One of them - the presence of a hydraulic clutch fan. Thanks to the proper operation of this unit, the cooling system of the truck under load works as efficiently as possible.

Hydraulic coupling designation

The most important unit for ensuring efficient engine cooling is the hydraulic coupling. KAMAZ without it would have a continuously running cooling fan. The meaning of it - at the right time to turn on the fan, and then turn it off. After all, at the moments of warming up the engine, as well as during the cold operating time of the car, there is absolutely no need for blowing.

The direct purpose of the fluid coupling is to transmit the torque of the engine's crankshaft to the cooling fan at the right time . It also significantly quenches the sudden changes in crankshaft operation and serves as a good damper for driving the fan.

How this unique cooling system node works will be clear from its structure.

The device of the hydraulic coupling of KamAZ

A hydraulic coupling will only work if there is oil inside the working space. KamAZ has the best designs for this. The coupling is based on two wheels: the master (9) and the slave (10). The drive wheel has 33 blades and is connected to the engine crankshaft via the splined part of the shaft (7). The driven wheel has 32 blades and is inextricably linked to the driven shaft (16), which in turn drives the cooling fan. The drive shaft (7) rotates in bearings 8 and 19, and the driven shaft, in turn, in bearings 4 and 13.

The clutch impellers do not touch each other without oil. That is, in the off state, only the driving wheel rotates. The slave can also be turned passively, thanks to the rotation of the fan when the cooling radiator louver is open. A reliable coupling body consisting of a cover (1) and a casing (2) is provided with a hydraulic clutch of the fan. KamAZ has a well-designed leakage protection system. To prevent oil leakage, the hydraulic coupling has two seals (17, 20) and a gasket (18).

In order for the oil to enter the hydraulic coupler at the right time, there is a hydraulic switch with a "flag" for three positions. We will analyze this simple, but at the same time, integral component in more detail.

Hydraulic Clutch Switch

A metal housing with a temperature sensor directly connected to the coolant is the hydraulic coupling switch. KamAZ has the following temperature regime: when the temperature of antifreeze or antifreeze rises to 83-86 ° C (hot or cold switch), the working mass in the sensor begins to melt and expand, pushing the rod. The channel for oil entering the hydraulic coupling opens. When the coolant temperature returns to the opposite position, the spring returns the opening rod of the switch.

What do the three positions of the hydraulic switch? "Flag" of the switch makes it possible to select three main operating modes:

• auto;
• Constantly open option;
• Permanently closed.

It is clear that the automatic mode is the main working mode and, if the fan's hydraulic clutch is in good condition, does not switch to other positions. In the event of a malfunction in the switch (which is quite possible), it is set to the "permanently open" mode. And at the first opportunity, the switch is replaced.

The third mode of the hydraulic clutch switch - "permanently closed", is used in case of overcoming by the car of deep fords. In these cases, the work of the fan is not just not needed, but will only harm.

Principle of operation of the hydraulic clutch of the fan

Now, after the internal structure of the hydraulic clutch has become clear, it is quite simple to understand how it all works. In the automatic mode, the hydraulic coupling starts to move, specifically, the fan turns on, when the coolant temperature rises to 83 ° C or 86 ° C. The fan, blowing, blows the radiator, thereby cooling the antifreeze and maintaining the optimum engine temperature.

When the temperature of the antifreeze is lowered, the hydraulic clutch switch is activated, and it turns off the fan rotation. After that, it can only rotate passively, from the flow of incoming air due to the movement of the car (with the radiator blinds open).

Also now it becomes clear how to ensure the uninterrupted operation of the cooling fan. The easiest way is to set the "switch" of the hydraulic switch to the "permanently open" position. The fan will constantly rotate, as the oil will be constantly in the hydraulic coupling, and it will operate continuously, as long as the engine crankshaft rotates.

Features and weaknesses of the hydraulic coupling

The hydraulic clutch is a fairly complex unit, and it may seem that this is not a very reliable design. But in practice, the hydraulic coupling itself does not break. Its reliability is exceptionally high. A weak point in the torque transmission system from the crankshaft is the inclusion of the hydraulic clutch. KamAZ has a fairly weak switch hydraulic coupling. It is the element that can lower the entire cooling system of the car.

In the hood itself, seals and bearings can theoretically degrade. But these components are selected on the basis of typical loads, plus some margin of safety. For their failure, there must be an unplanned impact. In cases of the same operation of the car and with regular maintenance, the hydraulic coupling can work without repair and replacement.

Hydraulic coupling advantages

If we consider other types of couplings in the fan drive, namely electric and viscous coupling, the advantages of the fluid coupling are obvious on the face.

• There is no whole electrical circuit for controlling and controlling the operation of the unit.
• Higher reliability of the design, which increases the time of trouble-free operation during engine operation.
• Turning the fan on and off at the coupling is the fastest.

All the obvious advantages of the hydraulic clutch significantly worsen not the most reliable element of the system - its switch. In practice, different methods are used to raise the overall reliability. One of these is the use of a switch from Ural-4320.

How to identify a malfunction?

There are several factors in order to ensure a long and trouble-free operation of the hydraulic coupling. KamAZ is very reliable, but there are nuances. First of all, it is, of course, the operating switch of the hydraulic coupling. In practice, most problems arise precisely because of its incorrect work. This turns this part into a consumable element, along with engine filters.

The next factor is the quality of the engine oil. There is a good all-season engine oil - there will be a normal efficient operation of the hydraulic clutch. KamAZ is not so demanding in everything, but not in this case. This must be taken into account during the winter operation of the car.

Another point to note is a regular inspection of the engine cooling system for leaks. Any traces of coolant or oil must be eliminated in a timely manner. The slightest leak without intervention can disable the entire engine.

The deterioration of the hydraulic coupling can easily be determined by reducing the cooling fan speed. If it does not rotate at all on the hot engine - the breakdown is obvious. It's good if the fan drive belt is simply worn or loose. If it is an oil seal seal, KamAZ will require more laborious work.

How to replace the hydraulic coupling?

Long operation without any interference from the hydraulic coupling. KamAZ-740 can afford it. But sooner or later everything wears out. If this happened and the further efficiency of the cooling system in question, it is necessary to dismantle the element.

The installation site of the fan drive and hydraulic coupling significantly complicates the replacement work. First of all you need to get access to the engine. In the case of KamAZ, this is done by lifting the cab. The sequence of work to replace the hydraulic clutch may look like this:

• To drain motor small;
• Remove the attachment belt;
• Unscrew the cooling fan;
• Remove the oil pan;
• Remove the cooling radiator;
• Remove the oil cooler;
• Dismantle the oil filter;
• To provide access to the front cover of the unit, by raising the engine;
• Remove the front cover together with the hydraulic coupling.

After the hydraulic coupling is removed, the degree of wear and types of defects are revealed. If possible, some elements are replaced. But considering the laboriousness of the operation to replace the coupling, it is recommended to replace the whole assembly. It is even better and easier to make a replacement of the hydraulic clutch assembly with the front cover of the unit.

After the reverse assembly procedure has been performed, it is necessary to check the tightness of the system and then only the operation of the hydraulic coupling. When replacing a node, you must select the original part and do not look for adventure in the selection of any analogues.

Preventive maintenance and maintenance

Sufficiently long time ensures the correct and uninterrupted operation of the hydraulic coupling drive. KamAZ as a whole has a good margin of safety. And for this to continue as long as possible, there is no need for special maintenance. The prevention of malfunctions consists in the general regular inspection, scheduled maintenance with qualitative replacement of oils and other technical liquids.

Also, when operating and servicing the fluid coupling, always pay attention to its weak points - the switch. Timely replacement of a faulty circuit breaker can greatly facilitate the operation of the unit as a whole.

Instead of concluding

The reliable unit in the cooling system is the hydraulic coupling. KamAZ with timely maintenance allows it to work without fail in the entire cycle of engine operation. In the case of replacing the coupling, it is recommended to completely replace the original assembly with the front cover of the cylinder block.