Crankshaft position sensor
Encyclopedia
A crank position sensor is an electronic device used in an internal combustion engine
to monitor the position or rotational speed
of the crankshaft
. This information is used by engine management systems to control ignition system
timing and other engine parameters. Before electronic crank sensors were available, the distributor
would have to be manually adjusted to a timing mark
on the engine.
The crank sensor can be used in combination with a similar camshaft
position sensor to monitor the relationship between the piston
s and valves
in the engine, which is particularly important in engines with variable valve timing
. This method is also used to "syncronise" a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also commonly used as the primary source for the measurement of engine speed in revolutions per minute
.
Common mounting locations include the main crank pulley
, the flywheel
, the camshaft
or on the crankshaft itself. This sensor is the most important sensor in modern day engines. When it fails, there is a chance the engine will not start, or cut out while running.
is used, which is placed adjacant to a spinning ferrous
disk. Alternatively, other detection principles can be employed i.e. optical or inductive
.
Some engines, such as GM's Premium V family
, use crank position sensors which read a reluctor ring integral to the harmonic balancer
. This is a much more accurate method of determining the position of the crankshaft, and allows the computer to determine within a few degrees the exact position of the crankshaft (and thereby all connected components) at any given time.
s to monitor the position of the crankset
, usually for the cadence
readout of a cyclocomputer
.
's use the information transmitted by the sensor to control parameters such as ignition timing and fuel injection timing. The sensor output can also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four stroke engine.
s where the crank position sensor is located in the distributor, effectively driven by the timing belt. Other locations include: The front of the crank on the engine block below or next to the water pump, on the main crank pulley or near the flywheel..
s, the pistons fire, or the acceleration behavior. If the engine is revved up with a bad
or faulty sensor, it may cause misfiring, motor vibration or backfires. Accelerating might be hesitant, and abnormal shaking during engine idle might occur. In the worst case the car may not start.
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
to monitor the position or rotational speed
Rotational speed
Rotational speed tells how many complete rotations there are per time unit. It is therefore a cyclic frequency, measured in hertz in the SI System...
of the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
. This information is used by engine management systems to control ignition system
Ignition system
An ignition system is a system for igniting a fuel-air mixture. Ignition systems are well known in the field of internal combustion engines such as those used in petrol engines used to power the majority of motor vehicles, but they are also used in many other applications such as in oil-fired and...
timing and other engine parameters. Before electronic crank sensors were available, the distributor
Distributor
A distributor is a device in the ignition system of an internal combustion engine that routes high voltage from the ignition coil to the spark plugs in the correct firing order. The first reliable battery operated ignition was developed by Dayton Engineering Laboratories Co. and introduced in the...
would have to be manually adjusted to a timing mark
Timing mark
A timing mark is an indicator used for setting the timing of the ignition system of an engine, typically found on the crankshaft pulley or the flywheel, being the largest radius rotating at crankshaft speed and therefore the place where marks at one degree intervals will be farthest apart.On older...
on the engine.
The crank sensor can be used in combination with a similar camshaft
Camshaft
A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.-History:An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The camshaft was later described in Iraq by Al-Jazari in 1206. He employed it as part of his automata,...
position sensor to monitor the relationship between the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s and valves
Tappet
A tappet is the noise made by a worn cam follower, however the term is widely used to represent the cam follower itself. In mechanical engineering it is a projection which imparts a linear motion to some other component within an assembly...
in the engine, which is particularly important in engines with variable valve timing
Variable valve timing
In internal combustion engines, variable valve timing , also known as Variable valve actuation , is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine...
. This method is also used to "syncronise" a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also commonly used as the primary source for the measurement of engine speed in revolutions per minute
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...
.
Common mounting locations include the main crank pulley
Pulley
A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...
, the flywheel
Flywheel
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia, and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed...
, the camshaft
Camshaft
A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.-History:An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The camshaft was later described in Iraq by Al-Jazari in 1206. He employed it as part of his automata,...
or on the crankshaft itself. This sensor is the most important sensor in modern day engines. When it fails, there is a chance the engine will not start, or cut out while running.
Types of Sensor
Commonly a hall effect sensorHall effect sensor
A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall effect sensors are used for proximity switching, positioning, speed detection, and current sensing applications....
is used, which is placed adjacant to a spinning ferrous
Ferrous
Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound ....
disk. Alternatively, other detection principles can be employed i.e. optical or inductive
Inductive sensor
An inductive sensor is an electronic proximity sensor, which detects metallic objects without touching them.The sensor consists of an induction loop. Electric current generates a magnetic field, which collapses generating a current that falls asymptotically toward zero from its initial level when...
.
Some engines, such as GM's Premium V family
GM Premium V engine
The Northstar engine series of automobile engines is General Motors' most technically complex 90° V engine architecture. The family is most associated with Cadillac's Northstar V8, but the family has also seen use at Oldsmobile...
, use crank position sensors which read a reluctor ring integral to the harmonic balancer
Harmonic balancer
A harmonic balancer is a device connected to the crankshaft of an engine to reduce torsional vibration and serves as a pulley for drive belts....
. This is a much more accurate method of determining the position of the crankshaft, and allows the computer to determine within a few degrees the exact position of the crankshaft (and thereby all connected components) at any given time.
Other Applications
Another type of crank sensor is used on bicycleBicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
s to monitor the position of the crankset
Crankset
The crankset or chainset , is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain, which in turn drives the rear wheel...
, usually for the cadence
Cadence (cycling)
In cycling, cadence is the number of revolutions of the crank per minute; roughly speaking, this is the rate at which a cyclist is pedalling/turning the pedals...
readout of a cyclocomputer
Cyclocomputer
A cyclocomputer or cyclometer is a device mounted on a bicycle that calculates and displays trip information, similar to the instruments in the dashboard of a car. The computer with display, or head unit, usually is attached to the handlebar for easy viewing.-History:In 1895 Curtis Hussey Veeder...
.
Purpose
The functional objective for the crankshaft position sensor is to determine the position and/or rotational speed (RPM) of the crank. Engine Control UnitEngine Control Unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
's use the information transmitted by the sensor to control parameters such as ignition timing and fuel injection timing. The sensor output can also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four stroke engine.
Physical location
The rotating disc of the sensor system does not necessarily have to be mounted directly on the crankshaft but can also be driven by a chain or toothed belt off the crankshaft as is the case in some HondaHonda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...
s where the crank position sensor is located in the distributor, effectively driven by the timing belt. Other locations include: The front of the crank on the engine block below or next to the water pump, on the main crank pulley or near the flywheel..
Problems encountered
Sometimes the sensor may become burnt or worn out. The most likely causes of crankshaft position sensor failure are exposure to extreme heat when you have a gasket or crank problem, corruption from oil or other engine fluids that leaked onto the sensor, or wear over a long period of time. When it goes bad, it stops transmitting the signal which contains the vital data for the ignition and other parts in the system.Signs of a problem
A bad crank position sensor can worsen the way the engine idleIdle
Idle is a term which generally refers to a lack of motion and/or energy.- Uses :In describing a person or machine, idle means the act of nothing or no work...
s, the pistons fire, or the acceleration behavior. If the engine is revved up with a bad
or faulty sensor, it may cause misfiring, motor vibration or backfires. Accelerating might be hesitant, and abnormal shaking during engine idle might occur. In the worst case the car may not start.