What is the function of the crankshaft pulley in a car?

There are quite a few parts in the car that, even when disassembled, may not be easy to notice. One of these parts is the crankshaft pulley - a small disc-shaped product that performs a very important task. Namely, torque transmission. In this article we will look at this problem “under a microscope” and also determine how to determine a faulty crankshaft pulley. We will also answer questions about the need to replace it and present a methodology for selecting spare parts. Let us note in advance that a pulley that does not attract attention quite rarely fails, however, in the event of a breakdown, the problem cannot be ignored - the performance of several car systems decreases.

Important Features

The operation of individual automobile units is provided by energy that is transmitted from the rotating crankshaft. For example, the rotation of the wheels is ensured by a complex system of gears and shafts, but the pump, air conditioner, timing belt and generator rotate from the crankshaft pulley. This small part is characterized by high strength and low fault tolerance. In fact, it can last as long as a car will last until it is sent for recycling.

In fact, there are many types of crankshaft pulleys for cars. At least in the sense in which the manufacturer sees it, each group of engineers has the right to resort to their own design solutions and create their own pulley options. Today there are not many varieties of this part left, but the division into types has a justification. Each pulley is adapted to certain operating conditions of the vehicle, so it is important for the driver to understand that a pair of pulleys cannot always be interchangeable. In part, this simplifies the buyer’s task, since it is enough to search for the pulley using the vehicle data or its identification number.

Purpose and device

The crankshaft pulley is a disk-shaped product. In the center there is a special hole, with the help of which the entire part can be mounted on the front part of the crankshaft. There is also a small groove intended for installing the so-called key. There are grooves on the outer part of the pulley. As the car enthusiast has probably already guessed, the grooves are made for drive belts.

In the vast majority of cases, the outer part of the pulley is a disk with a periphery, which are connected by especially durable rubber. You can notice small notches and pits on the pulley - they are needed so that the part, which is mostly a heavy metal product, is balanced . A well-balanced pulley copes with the following tasks:

• Belt cooling;
• Depreciation in cases where the nature of rotation changes;
• Transferring energy to attachments through a belt drive;
• Balancing the crankshaft as it works.

Ideally, a crankshaft pulley lasts ten years. The duration of operation is influenced by many factors, including the nature of the operation of the power unit and the condition of adjacent components. The pulley is not a serviceable part, and ideas about its repair are far from reality - the part needs to be restored and balanced, which can sometimes be as difficult as turning a new product from a solid metal blank. When making pulleys at the factory, casting and filigree turning are used, which not every craftsman can handle. So if the crankshaft pulley fails , you need to get a new one.

Application of pulleys

Wedge drives are one of the most widely used in a wide variety of mechanisms and devices with high torque and angular velocity. First of all, these are internal combustion engines. In addition, V-belt pairs are used in areas such as:

• fans and air conditioners;
• compressor units, both piston and screw;
• transport systems of buildings: elevators, escalators, travelators;
• agricultural machinery;
• road construction equipment;
• mining machines;
• industrial technological installations;
• machines;
• Appliances;
• hand power tools;

and in many other industries.

Gear drives are used in cases where it is necessary to transmit significant torque without slipping. The toothed belt drive does not require much tension for good traction. It produces significantly less radial load on the axle than other belt drives.

The following drives are used in:

• automobile engines, for the gas distribution mechanism;
• power drives of machine tools and industrial mechanisms;
• in technological installations of the food, pharmaceutical, chemical industries.

Poly V-ribbed pulleys do an excellent job in so-called serpentine transmissions, when one drive supplies rotational energy to many consumers, and at the same time follows a very winding trajectory. Poly V-ratio transmissions allow you to transmit significant torques and achieve high speeds without increasing dimensions.

They are used both in heavy engineering and in the production of household appliances.

CVT drive wheels are used wherever it is necessary to smoothly change speed and torque without stopping rotation or removing the load. They are popular in areas such as:

• transmissions of cars, motorcycles, and other wheeled vehicles;
• conveyors;
• precision machines for processing metal, wood and other materials;
• agricultural machinery.

A modern variator surpasses both manual and hydraulic transmissions in its performance characteristics.

Flat drives are used where it is necessary to transmit rotation over significant distances (up to 7-9 m) and absorb shocks, jolts and other dynamic loads transmitted from the drive shaft to the driven shaft (or in the opposite direction). They apply:

• in pressing and other forging equipment;
• in sawmill drives;
• in technological equipment of the textile industry;
• in powerful centrifugal pumps.

Round belt drives are used for light-duty transmissions in precision instruments, consumer electronics and appliances.

They also easily intersect and, with the help of additional passive pulleys, allow you to connect the driven and drive shafts, located in different planes and at an angle to each other, and also change the direction of rotation.

Types of pulleys

As we wrote earlier, automakers can introduce various pulleys into the design of their cars. Although a part from a car of one brand may not be externally different from a part from another, there is always a difference. And the point here is not only in form, but also in balancing . However, pulleys are divided into several types. Namely:

1. Under the V-belt. It is pulleys for such a belt that are installed on the vast majority of cars, trucks, and sports cars. The belt pulley is the same one-piece or all-welded part mentioned above. A key on the crankshaft prevents the pulley from turning, and the part itself is secured with a nut (in rare cases, a bolt);
2. Toothed pulley. Modern timing belts do not always use a chain drive. In order to facilitate the entire system, the designers decided to use special belts. The toothed pulley has teeth on its outer rim that engage grooves on the inner surface of the belt. Despite the apparent vulnerability of the teeth, they hardly wear out;
3. Damper pulley. Toothed pulleys made it possible to solve the problem of mismatched rotation angles, and damper pulleys make it possible to solve the problem of impulse mechanical influences that inevitably arise in the gas distribution system of a car. Such a pulley has a rubber layer that separates the working disk and the inner race - the damper.

All three pulleys have their advantages and disadvantages. It is important to understand that the design of the pulley also depends on how the elements adjacent to them are arranged and what are the features of their operation. The same damper pulleys made it possible to solve the problems of mechanical impacts and vibrations that occur when starting the engine and changing the frequency at which the crankshaft rotates. At the same time, the pulley damper fails quite quickly. Let's pay a little more attention to this.

Pulley concept

It is designed to transmit torque from the drive shaft to the driven shaft. To operate such a drive, both shafts are placed in parallel. A flat wheel is put on and secured to each shaft; they are placed in the same plane. The wheels are connected by an endless flexible drive belt. When the drive pulley rotates, the friction force causes the belt to move, covering part of its surface. This motion is transferred to the driven pulley, causing it to rotate.

Belt drives are common among household appliances, mechanisms of low- and medium-power machine tools, and in various internal combustion engines.

It has the following advantages:

• simple device;
• the ability to transmit significant power, modern V-belt pairs transmit up to 400 kW;
• high rotation speed, up to 50 m/s;
• smooth and quiet running;
• damping of vibrations and jerks of the drive shaft during rotation transmission;
• slippage under overloads acts as a safety mechanism.

The pulley itself is a disk on a shaft. It consists of two main parts: the rim and the hub. The rim is the outer part of the part. It engages with the belt and, depending on the type of drive, can be flat or have a recess in the shape of the belt. The side projections above the rim are called cheeks. They keep the belt from slipping. If the drive is wedge, then the cheeks are made inclined; they have an additional function - they increase the engagement area.

If a gear drive is used, then teeth of the appropriate shape are made on the surface of the rim.

If several streams are used in parallel, several grooves are made on the rim.

The hub is the inner part of the pulley. It has a hole for mounting on the shaft. Often the rim and hub are cast, turned, or milled as a single piece.

To reduce the weight of the product, voids are left in the body of the pulley, forming spokes. When made from wood, the presence of knitting needles was determined by the manufacturing technology.

To ensure the interchangeability of pulleys, their standard sizes, technological requirements, and markings are standardized. They are described in GOST 20889-94. “Pulleys for driving V-belts” and in GOST R 50641-94 (ISO 4183-89).

Download GOST 20889-88

Download GOST 50641-94

Standard markings include the following parameters:

• number of streams;
• profile of the drive belt used;
• diameter (calculated by cord);
• sleeve designation.

Thus, the marking 8 SPC 500 indicates an eight-lane pulley for an SPC profile with a diameter of 500 mm.

The rules for depicting pulleys in the drawing have also been standardized. The drawing must be constructed so that the product can be manufactured to exactly the same shape and size.

Damper or solid pulleys?

In practice, it has been proven that it is quite simple to neutralize engine vibrations using a torsional vibration damper . Such dampers are widely used in diesel cars, while they are not so common in gasoline cars (usually in trucks and buses). On passenger cars, the crankshaft pulley is usually all-metal, which is its Achilles heel - vibrations freely transmitted from the engine lead to rapid wear of the pulley, as a result of which it does not reach the 10 years of operation guaranteed by the manufacturer. The advantages of the damper pulley are:

• Engine noise is reduced;
• The amplitude of torsional vibrations is reduced by 2-5 times - this increases the survivability of the pulley and adjacent units (only the damper wears out quickly);
• Shock loads are effectively absorbed;
• Increases fuel efficiency and environmental friendliness of the vehicle.

Spare parts for Renault 10

Towing cables
1.3

Spare parts for Renault 10

Steering rack/mechanism oil seal (see standard sizes) 1.1
Contrary to the assurances of some car enthusiasts, the damper cannot seriously reduce the load on the belt. However, a pulley with a damping insert has several more significant disadvantages:

• It is more expensive than an all-metal pulley;
• The damper becomes unusable over time (the rubber insert cracks or breaks).

Despite the disadvantages, damper pulleys perform better than non-damper pulleys. One of their problems is the need for preventative replacement . As soon as the rubber element cracks, the entire pulley ceases to perform its main tasks. Please note: Modern fuel efficient engines are built to fit damper pulleys only.

And let’s immediately touch on another question: what is a lightweight pulley? This is the name given to a part made of aluminum alloy. Usually it has a damping element, but exceptions sometimes occur. For example, in the USA, the alloys from which some automobile engine parts are made are called alloys for aviation applications. They are durable, resistant to temperature changes and very lightweight. Aluminum pulleys introduce peculiarities into the operation of the engine (it slows down faster after the driver releases the gas pedal) and copes worse with vibrations (solved by installing a damper).

Pulley design

For the manufacture of belt drive pulleys, steel, cast iron, light alloys, wood and plastics are used. The outer part of the pulley with the belts installed is the rim, and the central part placed on the shaft is the hub. To connect the rim to the hub, spokes or a disk are used. If it is possible to put the pulley on the shaft from the end, it is made one-piece, otherwise it is made detachable. As a rule, the connector is made along the spokes.

For flat belt pulleys, the rim may be cylindrical or slightly convex. The convexity is provided in order to center the belt. Since a bulge on the rim negatively affects the life of the belt, usually only the drive pulley has a bulge on the rim. For V-belt drive pulleys, the rim is equipped with wedge-shaped grooves.

Classification of pulleys with a damping element

If you compare the silent block and the mentioned part, you can find many similarities: the same “pie” of metal parts and the elastic element that separates them, the same layout that takes into account the perception and damping of vibrations with minimal harm to the part. Pulleys with dampers are also divided into several types. Each subsequent type is much more complex than the previous one and often much more expensive:

1. Single pulley damper. These are 2 metal plates made of aluminum or steel and 1 rubber element connecting them. Most diesel and gasoline cars have just such pulleys;
2. ICE pulley for stop-start system. By using a damper of a more complex design, the pulley can withstand a significant number of internal combustion engine starts without breakdown;
3. Double pulley damper. Often installed on high-performance diesel vehicles. It consists of 7-8 parts made of metal and 2 parts made of rubber.

The quality of the damping element is a key factor in choosing a pulley. The fact is that it is slightly deformed exactly as many times as the mixture is ignited in the internal combustion engine cylinders. Simply put, during the course of a thousand-kilometer distance, the damper can be deformed ten million times (almost always less, but the count still goes into the millions). The condition of the damper after such a rigorous test will determine whether the pulley needs to be replaced.

Types of pulleys

Over thousands of years of use, designers have developed many designs of belt pulleys. Their classification is carried out according to various criteria.

Depending on the type of belt used, there are:

Wedge-shaped

The most common type of product. Used with V-belts. The side cheeks provide additional engagement area, increasing the transmission capabilities of torque and rotation speed.

The inclination of the groove must be indicated on the part drawing.

In order to reduce the dimensions of the transmission or increase its power, several streams are launched in parallel. Such pulleys are called multi-grooved; they have the appropriate number of grooves. Sometimes a single belt with several wedge-shaped protrusions is put on such a pulley. This is a poly-V transmission.

In the drawing it is permissible to give a detailed image of one groove and indicate their number. Detailing of the rest in the drawing is not required

If the permissible load is exceeded in an emergency, slipping begins, protecting the equipment from damage.

V-belt transmissions allow you to transmit the highest torque.

Serrated

There are toothed projections on the inner surface of the belt; teeth corresponding to their pitch are also made on the surface of the rim. Gear-belt pairs do not slip and can transmit more torque. They are also distinguished by the accuracy of transmitting the angular position of the shaft, therefore they are used in gas distribution mechanisms of internal combustion engines. The downside is the lack of a protective function against overloads. The rim is made by milling. There is also production by the rolling method. The detail drawing must indicate the exact parameters of the tooth, its pitch, height, and profile.

Flat-shaft

A classic design used in the very first gears. Absorbs vibration and dynamic loads from the drive shaft. They are characterized by low noise, limited torque and rotation speed.

Using additional rollers, you can connect driven and drive shafts that are in different planes, not coaxial, and change the direction of rotation. In this way, cardan and worm gears can be replaced. The drawing of such a product is the simplest, but it should indicate the radii of the rim and cheeks, if provided. Sometimes cheeks are not provided, and the rim profile is made convex. In this case, its radius should be indicated on the drawing.

Round belt

The groove in the rim has a semicircular profile. Such belt drives are used for low transmitted torques and rotational speeds. They also allow you to change the direction of rotation and connect axes located in different planes. In the drawings of such parts, only the radius of the groove is indicated.

CVT

These are the most complex devices in design. The rim is made in the form of a cone with a conical moving cheek. The V-belt ring has the ability to move along the cone in the axial direction, from a smaller radius to a larger one. The second pulley has a reverse taper, and the drive on it moves from a smaller radius to a larger one. In this case, the transmission ratio changes. The cheeks of both pulleys can move in the opposite direction, changing the gear ratio in the opposite direction.

The advantage of the design is that the gear ratio can be changed without stopping rotation and without removing the load from the drive. It can be difficult to understand the operating principle of a device from a drawing. Three-dimensional modeling allows you to supplement models with kinematic simulations that clearly demonstrate the interaction of mechanism parts.

Pulleys are also distinguished by the method of placement on the shaft:

• Under the sleeve. Allows you to secure the drive on any standard shaft by selecting a bushing of the appropriate internal diameter. If the seat is damaged, it is enough to replace the bushing, which makes repairs easier and faster.
• Under boring. Available with a small central hole. It is bored or drilled to fit the diameter of the shaft. If damaged, it is difficult to repair.
• Fixed diameter. Usually equipped with a groove for keyed fastening or splines. Very simple and quick installation and dismantling. Requires exact matching of diameters. Allows the production of molded parts.

Crankshaft damper pulley malfunctions

Only an external inspection will help determine with accuracy whether the pulley is suitable or needs to be replaced. However, before approaching the crankshaft, you should still pay attention to some things that indicate a faulty pulley. Namely:

• The appearance of vibrations in the cabin;
• The appearance of a knock, the frequency of which changes as the engine speed increases or decreases;
• Drive belt whistle;
• Stopping the motor.

Here's what you can see during an external examination:

1. Deformation and melting of rubber (usually due to oil leaks);
2. Cracks in the rubber, hub, and also in the spinning areas;
3. Damper separation;
4. Cracks on the belt.

Regarding the last point: normally, the belt becomes covered with cracks only after the expiration of the service life declared by the manufacturer. If cracks appear prematurely , we can talk about a pulley failure. Checking the damper is quite easy:

1. Get close to the damper and draw a line with a marker from the edge to its center;
2. After starting the engine, also turn on the air conditioning;
3. Muffle the engine and inspect the pulley again. If the line is straight, then everything is fine with him. But if you notice two mismatched marks, then the rubber pulley inserts no longer fulfill their role.

There are many reasons why the damper pulley fails. To prevent early failure, make sure the part does not come into contact with alkali, oil or acid. Check adjacent parts, in particular, pay attention to units powered by the crankshaft. Entrust the installation of the pulley to trusted specialists or do it yourself - for the work you only need a dismantling kit (usually each pulley manufacturer produces its own kit), a wrench and a hammer.

Features of replacing the crankshaft pulley

The need to accurately synchronize the operation of the crankshaft and camshaft of a car engine puts forward a number of specific requirements for replacing the crankshaft pulley. In particular, it is recommended to use special tools or devices to check the degree of tension of the timing belt, the tightening force of the nut (or bolt) securing the pulley, and to set a certain position of the crankshaft and camshaft. Timing belts also have special marks for their correct installation. Under no circumstances should oil or other technical liquids come into contact with the pulley and belt - in addition to having a negative effect on the material of the belt and pulley, they can lead to belt slippage and disruption of the synchronization of engine shafts.

Modern cars often have a special crankshaft position sensor that simply will not allow the engine to start with the crankshaft and camshafts in incorrect positions - this is done to prevent costly damage to the crank group that can result from careless maintenance.

One of the main technical features of dismantling the crankshaft pulley is the strong tightening of its fastening. The fastening thread is cut in such a way that the direction of unscrewing coincides with the direction of rotation of the shaft and pulley - this is done so that the pulley fastening does not unwind on its own. As a rule, dismantling the crankshaft pulley is possible only in the inspection hole. This often requires removing the wheel closest to the crankshaft pulley.

If you have a pneumatic impact wrench, removing the crankshaft pulley fastening is not a big problem. For Soviet and Russian cars, there is a folk recipe for unscrewing the crankshaft pulley using a starter (ATTENTION, we publish this method for general information, but we recommend that you do not risk your car, but entrust the replacement of the crankshaft pulley to qualified and experienced craftsmen with the appropriate equipment):

1. First of all, you need to determine in which direction the shaft and pulley on your car’s engine rotate, and accordingly, in which direction you need to unscrew the pulley mount.
2. Moisten the nut (bolt head) with a special liquid such as WD-40.
3. The car is installed on the inspection hole, the wheels are fixed.
4. If necessary, remove the wheel closest to the crankshaft pulley.
5. A wrench with a long handle (or extended using improvised means) is placed on the crankshaft nut (bolt). The handle of the key must be rested against the floor or spar in the direction of rotation, making sure that such support is safe.
6. Measures are taken to prevent the car from starting (the wire or terminal from the ignition is removed, each car model has its own method).
7. The generator belt is removed.
8. Turning on the ignition for a short time causes the crankshaft to turn, the key handle rests on the floor, the nut (bolt) is torn off, and then unscrewed with a regular key.

Making the right choice

Selecting a crankshaft pulley without a damper or with a rubber element is quite simple. But remember: a mistake in choosing will mean that the part either cannot be installed, or it will work with noise and will accelerate the wear of the car elements adjacent to it. Here's how to look for a pulley:

• By VIN code . This is a very accurate method, using which you can easily find original spare parts and even the closest analogues;
• By pulley code . Since car enthusiasts do not know exactly the codes of the spare parts they are looking for, they have to turn to electronic catalogues, social networks and thematic forums where they can be found. We recommend electronic catalogs that specify the compatibility of spare parts with specific car models - this is exactly the catalog Avto.pro has;
• According to the car . We are talking about the make, model of the car, engine data, body and year of manufacture. This method is usually used by car enthusiasts who start their search in online stores.

Searching by pulley parameters does not always give reliable results. Car enthusiasts need to clarify the applicability of the parts found. It is enough to take an existing pulley, determine its geometric parameters and compare it with the proposed ones. If everything matches, we advise you to check compatibility again by going through the catalogs and looking at the spare parts codes.

When choosing a pulley, also keep in mind the mounting bolts used. The fact is that the bolt is screwed in with a fairly high tightening torque, as a result of which it approaches its deformation limit. Simply put, a reused bolt is longer than a new one. As a rule, pulleys are sold complete with special washers and bolts.

Brand tour

There are many manufacturers of automotive crankshaft pulleys. It is important for a car enthusiast to determine the best manufacturer - only his product will last a long time. We focus on such a seemingly trivial issue because many car enthusiasts buy cheap analogues of dubious quality . Good analogues are offered by the following companies:

• SNR (France);
• Corteco (Germany);
• SKF (Sweden);
• NTN (Japan).

Typically, pulleys from these companies are included in the original package. The cost of the part is quite high, but it is more than justified. Budget analogues can be offered by the following companies:

• SWAG (Germany);
• Magneti Marelli (Italy);
• Febi (Germany);
• SAT (China);
• Contitech (Germany).

If a car enthusiast decides to give preference to a budget option , then he should be aware of the risks. Periodic inspection of the pulley will become mandatory. Good analogues can be found at Contitech, Magnetti Marelli, but you may not be so lucky with Febi. The red price for the pulley is the one set by the sellers for the product from Febi - we absolutely do not recommend taking anything cheaper.

Conclusion

The crankshaft pulley is definitely not a part you should skimp on. Purchasing analogues from suppliers for the conveyor is acceptable. It is easy to select this part, guided by the car data or catalog number. Beware of fakes! They are easily betrayed by poor quality packaging, poor quality of work with metal and rubber, as well as inconsistency of codes and concealment of important information from the buyer. Usually the country of manufacture of the counterfeit is not indicated. And remember: there are no eternal dampers. If the description of a damper pulley states that the damper itself is eternal, then the pulley simply may not have one - this is a rare, but still common, scheme to deceive buyers online.

Main types of pulleys

1. Wedge. Torque is transmitted using V-belts. Used for ventilation, mining, agricultural and other equipment.

2. Serrated. The torque is transmitted using timing belts. Rotational motion is transmitted through the meshing of the belt teeth and pulley. Used in printing, food, textile, industry, etc.

3. Poly-wedge. They perfectly combine reliable power transmission and elasticity. Withstanding harsh operating conditions, they are often used in drives in mechanical engineering.

4. CVT. A variator is a mechanical transmission that provides a stepless change in the gear ratio within a certain control range. They are used in drives of cars, conveyors, machine tools, agricultural and other equipment.

5. Flat-shaft. They are used in flat belt transmission. Scope of application – production of bodies, various machine tools, generators, ventilation units, agricultural machines, etc.

6. Round belt pulleys. With their help, low power transmission is ensured. Features of round belt transmission are flexibility and elasticity.

In general, pulleys are made from different materials, finding wide application in industry.

In any internal combustion engine, the drive of the main and auxiliary mechanisms is carried out from the crankshaft using a pulley and belt. Read about what a crankshaft pulley is, what types it exists, how it works and functions, as well as how to replace and repair the pulley.