The device and principle of operation of the crankshaft position sensor
Car device,  Vehicle electrical equipment

The device and principle of operation of the crankshaft position sensor

To improve the efficiency, economy and environmental friendliness of modern transport, car manufacturers are equipping cars with an increasing number of electronic devices. The reason is that the mechanical components responsible, for example, for the formation of sparks in the cylinders, which were equipped with old cars, were notable for their instability. Even a slight oxidation of the contacts could lead to the fact that the car simply stopped starting, even for no apparent reason.

In addition to this disadvantage, mechanical devices do not allow fine tuning of the power unit. An example of this is the contact ignition system, which is described in detail. here... The key element in it was a mechanical distributor-breaker (read about the distributor device in another review). Although with proper maintenance and the correct ignition timing, this mechanism provided a timely spark to the spark plugs, with the advent of turbochargers, it could no longer work as efficiently.

The device and principle of operation of the crankshaft position sensor

As an improved version, engineers have developed contactless ignition system, in which the same distributor was used, only an inductive sensor was installed in it instead of a mechanical breaker. Thanks to this, it was possible to achieve greater stability of the formation of a high-voltage pulse, but the remaining disadvantages of the SZ were not eliminated, since a mechanical distributor was still used in it.

To eliminate all the disadvantages associated with the operation of mechanical elements, a more modern ignition system was developed - electronic (about its structure and principle of operation is described here). The key element in such a system is the crankshaft position sensor.

Consider what it is, what is the principle of its operation, what it is responsible for, how to determine its malfunction, and what its breakdown is fraught with.

What is DPKV

The crankshaft position sensor is installed in any injection engine running on petrol or gas. Modern diesel engines are also equipped with the same element. Only in this case, on the basis of its indicators, the moment of injection of diesel fuel is determined, and not the supply of a spark, since the diesel engine works according to a different principle (a comparison of these two types of motors is here).

This sensor records at what moment the piston of the first and fourth cylinders will take the desired position (top and bottom dead center). It generates pulses that go to the electronic control unit. From these signals, the microprocessor determines the speed at which the crankshaft rotates.

The device and principle of operation of the crankshaft position sensor

This information is needed by the ECU to correct the SPL. As you know, depending on the operating conditions of the engine, it is required to ignite the air-fuel mixture at different times. In contact and non-contact ignition systems, this work was performed by centrifugal and vacuum regulators. In the electronic system, this process is performed by the algorithms of the electronic control unit in accordance with the firmware installed by the manufacturer.

As for the diesel engine, the signals from the DPKV help the ECU to control the injection of diesel fuel into each individual cylinder. If the gas distribution mechanism is equipped with a phase shifter, then on the basis of pulses from the sensor, the electronics changes the angular rotation of the mechanism valve timing changes... These signals are also needed to correct the operation of the adsorber (in detail about this system is described here).

Depending on the car model and the type of on-board system, the electronics are able to regulate the composition of the air-fuel mixture. This allows the engine to run more efficiently while using less fuel.

Any modern internal combustion engine will not function, since the DPKV is responsible for the indicators, without which the electronics will not be able to determine when to supply a spark or diesel fuel injection. As for the carburetor power unit, there is no need for this sensor. The reason is that the process of VTS formation is regulated by the carburetor itself (read about the differences between injection and carburetor engines separately). Moreover, the composition of the MTC does not depend on the operating modes of the unit. Electronics allows you to change the degree of enrichment of the mixture, depending on the load on the internal combustion engine.

The device and principle of operation of the crankshaft position sensor

Some motorists believe that the DPKV and the sensor located near the camshaft are identical devices. In fact, this is far from the case. The first device fixes the position of the crankshaft, and the second - the camshaft. In the second case, the sensor detects the angular position of the camshaft so that the electronics provide more accurate operation of the fuel injection and ignition system. Both sensors work together, but without a crankshaft sensor, the engine will not start.

Crankshaft position sensor device

The sensor design may vary from vehicle to vehicle, but the key elements are the same. DPKV consists of:

  • Permanent magnet;
  • Housings;
  • Magnetic core;
  • Electromagnetic winding.

So that the contact between the wires and the sensor elements does not disappear, they are all located inside the case, which is filled with a compound resin. The device is connected to the on-board system through a standard female / male connector. There are lugs in the body of the device for fixing it in the workplace.

The sensor always works in tandem with one more element, although that is not included in its design. This is a toothed pulley. There is a small gap between the magnetic core and the pulley teeth.

Where is the crankshaft sensor

Since this sensor detects the position of the crankshaft, it must be in close proximity to this part of the engine. The toothed pulley is installed on the shaft itself or the flywheel (in addition, about why a flywheel is needed, and what modifications there are, it is described separately).

The device and principle of operation of the crankshaft position sensor

The sensor is fixed motionlessly on the cylinder block using a special bracket. There is no other location for this sensor. Otherwise, it will not be able to cope with its function. Now let's look at the key functions of the sensor.

What is the function of the crankshaft sensor?

As already mentioned, structurally, the crankshaft position sensors may differ from each other, but the key function for all of them is the same - to determine the moment at which the ignition and injection system should be activated.

The principle of operation will differ slightly depending on the type of sensors. The most common modification is inductive or magnetic. The device operates as follows.

The reference disk (aka a toothed pulley) is equipped with 60 teeth. However, in one part of the part, two elements are missing. It is this gap that is the reference point at which one complete revolution of the crankshaft is recorded. During the rotation of the pulley, its teeth alternately pass in the zone of the magnetic field of the sensor. As soon as a large slot without teeth passes by this area, a pulse is generated in it, which is fed through the wires to the control unit.

The device and principle of operation of the crankshaft position sensor

The microprocessor of the on-board system is programmed for different indicators of these pulses, in accordance with which the corresponding algorithms are activated, and the electronics activate the desired system or adjust its operation.

There are also other modifications of the reference discs, the number of teeth in which may be different. For example, on some diesel engines, a master disc with a double skip of teeth is used.

Types of sensors

If we divide all sensors into categories, then there will be three of them. Each type of sensor has its own principle of operation:

  • Inductive or magnetic sensors... Perhaps this is the simplest modification. Its work does not require connection to an electrical circuit, since it independently generates pulses due to magnetic induction. Due to the simplicity of the design and the large work resource, such a DPKV will cost little. Among the disadvantages of such modifications, it is worth mentioning that the device is highly sensitive to pulley dirt. There must be no foreign particles, such as an oil film, between the magnetic element and the teeth. Also, for the effectiveness of the formation of an electromagnetic pulse, it is necessary that the pulley rotates quickly.
  • Hall sensors... Despite the more complex device, such DPKV are quite reliable and also have a large resource. Details about the device and how it works are described in another article... By the way, several sensors can be used in the car that work on this principle, and they will be responsible for different parameters. For the sensor to function, it must be powered. This modification is rarely used to lock the crankshaft position.
  • Optical sensor... This modification is equipped with a light source and receiver. The device is as follows. The pulley teeth run between the LED and the photodiode. In the process of rotation of the reference disk, the light beam either enters or interrupts its supply to the light detector. In the photodiode, pulses are generated based on the effect of light, which are fed to the computer. Due to the complexity of the device and vulnerability, this modification is also rarely installed on machines.

Symptoms of a malfunction

When some electronic element of the engine or a system associated with it fails, the unit starts to work incorrectly. For example, it can troit (for details on why this effect appears, read here), it is unstable to idle, start up with great difficulty, etc. But if the DPKV does not function, the internal combustion engine will not start at all.

The sensor as such does not have any malfunctions. It either works or it doesn't. The only situation where the device can resume operation is contact oxidation. In this case, a signal is generated in the sensor, but its output does not occur due to the fact that the electrical circuit is broken. In other cases, a faulty sensor will have only one symptom - the motor will stall and will not start.

If the crankshaft sensor does not work, the electronic control unit will not record a signal from it, and the engine icon or the inscription "Check Engine" will light up on the instrument panel. A breakdown of the sensor is detected during the rotation of the crankshaft. The microprocessor stops recording impulses from the sensor, so it does not understand at what moment it is necessary to give a command to the injectors and ignition coils.

The device and principle of operation of the crankshaft position sensor

There are several reasons for sensor breakage. Here is some of them:

  1. Destruction of the structure during thermal loads and constant vibrations;
  2. Operation of the car in wet regions or frequent conquest of the fords;
  3. A sharp change in the temperature regime of the device (especially in winter, when the difference in temperatures is very large).

The most common sensor failure is no longer related to it, but to its wiring. As a result of natural wear and tear, the cable can wear out, which can lead to a loss of voltage.

You need to pay attention to DPKV in the following case:

  • The car does not start, and this can be regardless of whether the engine is heated or not;
  • The crankshaft speed drops sharply, and the car moves, as if the fuel has run out (fuel does not enter the cylinders, since the ECU is waiting for an impulse from the sensor, and no current flows to the candles, and also due to the lack of an impulse from the DPKV);
  • Detonation (this occurs mainly not due to sensor breakage, but due to its unstable fixation) of the engine, which will immediately let you know about corresponding sensor;
  • The motor constantly stalls (this can happen if there is a problem with the wiring, and the signal from the sensor appears and disappears).
The device and principle of operation of the crankshaft position sensor

Floating revs, reduced dynamics and other similar symptoms are signs of failure of other vehicle systems. As for the sensor, if its signal disappears, the microprocessor will wait until this pulse appears. In this case, the on-board system "thinks" that the crankshaft is not rotating, so neither a spark is generated, nor fuel is sprayed into the cylinders.

To determine why the motor has stopped working stably, it is necessary to carry out computer diagnostics. How it is carried out is A separate article.

How to check the crankshaft sensor

There are several ways to check DPKV. The very first thing to do is a visual check. First you need to look at the quality of the fastening. Due to the rattling sound of the sensor, the distance from the magnetic element to the surfaces of the teeth is constantly changing. This can lead to incorrect signal transmission. For this reason, the electronics can incorrectly send signals to the actuators. In this case, the operation of the motor may be accompanied by completely illogical actions: detonation, a sharp increase / decrease in speed, etc.

If the device is properly fixed in its place, there is no need to speculate about what to do next. The next stage of the visual inspection is to check the quality of the sensor wiring. Usually, this is where the detection of sensor defects ends, and the device continues to work properly. The most effective test method is to install a known working analog. If the power unit began to work correctly and stably, then we throw away the old sensor.

The device and principle of operation of the crankshaft position sensor

In the most difficult situations, the winding of the magnetic core fails. This breakdown will help to identify a multimeter. The device is set to resistance measurement mode. The probes are connected to the sensor in accordance with the pinout. Normally, this indicator should be in the range from 550 to 750 Ohm.

In order not to spend money on checking individual equipment, it is practical to carry out routine preventive diagnostics. One of the tools that can help identify hidden problems in various electronic equipment is an oscilloscope. How this device works is described here.

So, if some sensor in the car fails, then the electronics will go into emergency mode and will work less efficiently, but in this mode it will be possible to get to the nearest service station. But if the crankshaft position sensor breaks down, then the unit will not work without it. For this reason, it would be better to always have an analog in stock.

Additionally, watch a short video on how DPKV works, as well as DPRV:

Crankshaft and camshaft sensors: operating principle, malfunctions and diagnostic methods. Part 11

Questions and answers:

What happens when the crankshaft sensor fails? When the signal from the crankshaft sensor disappears, the controller stops generating a spark pulse. Because of this, the ignition stops working.

How to understand that the crankshaft sensor has died? If the crankshaft sensor is out of order, the car will either not start or stall. The reason is that the control unit cannot determine at what moment to create an impulse to form a spark.

What happens if the crankshaft sensor does not work?  The signal from the crankshaft sensor is needed to synchronize the operation of the fuel injectors (diesel engine) and the ignition system (in gasoline engines). If it breaks down, the car won't start.

Where is the crankshaft sensor located? Basically, this sensor is attached directly to the cylinder block. In some models, it stands near the crankshaft pulley and even on the gearbox housing.

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