The oil pump in internal combustion engine circulates engine oil under pressure to rotary bearings, sliding pistons and engine camshafts. It lubricates the pads, allowing the use of higher capacity fluid bearings and also helps in cooling the engine.
As well as its main purpose for lubrication, pressurized oil is increasingly used as a hydraulic fluid to run small actuators. One of the first important uses in this way is for hydraulic tappets in camshaft actuation and valves. Increasingly common uses may include tensioners for timing belts or variators for variable valve timing systems.
Video Oil pump (internal combustion engine)
Pompa
The types of pumps used vary. Gear pump trochoid pumps and vane pumps are all commonly used. Plunger pumps have been used in the past, but these are now only rarely used, for small machines.
To avoid the need for priming, the pump is always installed low, either submerged or around the oil level on the sump. Short pickup pipes with simple wire mesh strands reach the bottom of the sump.
Pump driver
For simplicity and reliability, mechanical pumps are used, driven by a mechanical geartrain of the crankshaft. Reducing pump speed is very advantageous and very common to drive the pump from the cam (if it is mounted on the cylinder block) or distributor shaft, which rotates at half speed of the machine. Placing low-down oil pumps using a near-vertical drive shaft, driven by helical tilt gears from the camshaft. Some engines, such as the Fiat 1964 camat cam machine, started as an OHV engine with oil pump driven from a conventional camshaft in a cylinder block. When the twin overhead cam engine is developed, the previous oil pump arrangement is retained and the ridge shaft becomes a shortened stub shaft. Even when the position of the distributor is removed from the previous mounting block to be mounted on the cylinder head camshafts, the oil pump drive remains in the same position, the unused distributor position is now covered by the blanking plate. Small engines, or scooters may have an internal gear pump mounted directly on their crankshaft.
For reliability, it is rare to use an external drive mechanism, either a separate belt drive or an external gear, although camshaft-based pumps often rely on the same timing belt. An additional separated belt is sometimes used where a dry sump pump has been added to the machine during adjustment.
Electric oil pump is not used, again for reliability. Some 'turbo timer' electric turbo pumps are sometimes installed on turbocharged engines. This is the second oil pump that keeps running after the engine stops, providing cooling oil to the turbocharger's hot pad for a few minutes, while it cools. It is a complementary pump and does not replace the main pump, mechanical, and oil.
Maps Oil pump (internal combustion engine)
Lubrication System
The oiling system overcomes the need to properly lubricate the engine while walking. Properly lubricate the engine not only reduces friction between moving parts but also the main method where heat is removed from pistons, bearings, and shafts. Failure to properly lubricate the engine will result in engine damage. The oil pump forces the motor oil through the ducts in the engine to distribute the oil properly to different engine components. In a general lubricating system, oil is removed from the oil tube (oil pan, in US English) through a wire screen that removes pieces of debris that are larger than oil. The flow made by the oil pump allows the oil to be distributed around the engine. In this system, oil flows through an oil filter and sometimes an oil cooler, before passing through the engine oil line and dispersed to lubricate pistons, rings, springs, valve sticks, and more.
Oil pressure
The oil pressure produced in most engines should be about 10 psi per every 1000 turns per minute (rpm), peaking at about 55-65 psi.
Local pressure (in crankshaft and bearing journals) is much higher than 50, 60 psi & amp; c. arranged by the pump assistance valve, and will reach hundreds of psi. This higher pressure is developed by the relative speed in units of feet per second (rather than the RPM or direct-size journals) of the crankshaft journal itself against bearings, bearing width (for nearest pressure leaks), oil viscosity, and temperature, balanced against bearing delivery (leakage rate).
All the pump pressure is "filling the hole" and refreshing the oil in the circular space faster than the leaking one. This is why low-speed engines have relatively large journals, with just the size and pressure of simple pumps. Low pressure indicates that the leakage of the bearing is higher than the pumping rate of the pump.
Measuring pressure
The oil pressure at the pump outlet, which opens the pressure relief valve, is just the flow resistance caused by the clearance and restriction of the bearing.
The oil pressure gauge, or warning light, only puts pressure on the point at which the sender enters the part of the compressed system - not everywhere, not average, or a general overview of systemic stress.
Although often compared to hydraulic engineering theory, this is not a "closed system" where oil pressure is balanced and identical everywhere. All machines are "open systems", because oil returns to the pan by a series of controlled leaks. The most distant bearing from the pump always has the lowest pressure due to the large number of leaks between the pump and the bearing. Excess bearings increase the loss of pressure between the first and last bearing in the circuit.
Depending on the conditions, the engine may have an acceptable gauge pressure, and still only 5 psi pressure on one connecting rod, which will fail under high loads.
The real pressure is created by resistance to the flow of oil around the engine. Thus, the oil pressure may vary during operation, with temperature, engine speed, and wear on the engine. Cooler oil temperatures can cause higher pressure, because the oil is thicker, while higher engine speeds cause the pump to run faster and push more oil through the engine. Because the normal engine temperature and engine speed is higher when the ignition is turned on, it is normal to see higher oil pressure when the engine is turned on rather than at normal operating temperature, where normal oil pressure typically falls between 30 and 45 psi. Too much oil pressure can create unnecessary work for the engine and even add air into the system. To ensure that the oil pressure does not exceed the maximum value, once the pressure exceeds a predetermined limit, the spring pressure relief valve discards the excess pressure well into the suction side of the pump, or directly back into the oil or tank pan.
High Oil Pressure
The end result of the oil pressure is too high is the front or rear main engine seal will be blown and/or blow the oil out plug. In other words every chance of getting into a sealed crankcase could somehow be detonated. High oil pressure often means very high pressure at cold start, but this is a design flaw rather than the automatic consequence of high pressure. Observation "if you raise the maximum pressure, cold pressure becomes too high" accurate, but not accidental.
Even stock pumps (apart from brands and models) do not have enough relief valve capacity: the relief port is too small to handle the volume of cold oil. This is why there is a significant difference between cold & amp; hot oil, high & amp; Low RPM & amp; c., but there is usually no problem with the stock machine because of the above-mentioned spring-pressure relief valve. Properly designed relief ports (not found in production machines) will flow whatever oil volume the tooth will pass through, regardless of the viscosity or the temperature of the oil, and the meter reading will be slightly different.
The oil pressure is monitored by the oil pressure delivery unit, usually fitted to the engine block. This can be either a spring pressure sensor or an electronic pressure sensor, depending on the type of delivery unit. Problems with the oil pressure delivery unit or the connection between them and the driver's display may cause abnormal oil pressure readings when the oil pressure is received perfectly.
Low Oil Pressure
There are only 4 reasons for low oil pressure. 1) no oil or low oil in the machine 2) worn or broken oil pump or pressure drop valve spring breaker 3) worn main bearings (the big end has nothing to do with the oil pressure since most of the pressure for this is supplied by centrifugal force) and 4) fracture or blockage of oil gallery. Low oil pressure can cause engine damage. The first thing that fails is a cam carrier bearing if the vehicle is an OHC because it is fed through the barrier and low pressure will expose the top of the lube machine. If the pistons have crown jets for example scania, can cause piston/liner nip. Also crankshaft and bearing connecting rods will confiscate. The indication of low oil pressure may be that the warning light is on, the low pressure reading on the gauge, or the clinking sound of the machine. Low oil pressure is a problem that must be addressed immediately to prevent serious damage.
The main cause of low oil pressure in the engine is the wear on the vital part of the machine. Over time, the engine pads and seals are damaged. Wear and tear can cause these parts to eventually lose their original dimensions, and this increase in permits allows greater oil volume to flow over time which can greatly reduce oil pressure. For example, a 0.001 inch fading from the main engine bearing can cause a 20% loss in oil pressure. Simply replacing worn bearings can fix this problem, but on older machines with much wear and tear there is not much that can be done apart from actually overhauling the machine.
Particles in oil can also cause serious problems with oil pressure. After the oil flows through the engine, the engine returns to the oil pan, and can carry a lot of debris. The debris can cause problems with the oil pickup screen and the oil pump itself. The holes in the oil pickup screen are about 0.04 inches square (0.26 cm 2 ). This size hole only picks up larger pieces of debris and allows many small pieces to flow through it. The holes on the screen are very large (relative to the debris) because at low temperatures and slow engine speeds, the oil is very thick and requires large openings to flow freely. Even with large holes in the screen, it can still get clogged and cause low oil pressure. The 0.005-inch-thick layer (0.13 mm) on the screen can reduce the hole size to about 0.03 inch square (0.19 cm 2 ), which in turn reduces the flow of oil by 44 percent.
Even after passing through the oil pickup screen and oil filter, the flakes can remain inside the oil. It is important to replace oil and oil filters to minimize the amount of impurities that enter through your machine. These dangerous ruins along with normal engine wear in high mileage engines lead to an increase in the distance between bearings and other moving parts.
Low oil pressure may be just because there is not enough oil in the sump, because the combustion of oil (usually caused by wearing a piston ring or a worn valve seal) or leakage. The piston rings serve to seal the combustion chamber, and remove the oil from the cylinder's internal walls. However, when they wear, its effectiveness decreases, which leaves the oil on the cylinder wall during combustion. In some engines, burning a little oil is normal and should not cause an alarm, while burning lots of oil is a sign that the machine may need repair.
Oil Pump on High Performance Machine
Not all machines have the same oiling requirement. High-performance machines, for example, place a higher pressure on the lubricating system. In this case, the lubricant system must be very strong to prevent engine damage. Most engines in cars on the road today do not run far beyond 5,000-6,000 rpm, but that's not always the case in performance engines, where the engine speed can reach up to 8000-9000 rpm. In a machine like this, it is important that the oil circulates fairly quickly, or the air can get trapped in the oil. Also, to free up power, some machines in performance apps run lower heavy oils, which require less power to run oil pumps. The general oil weight in the engine today is usually 5w30 or 10w30 oil, while the performance engine may use 0w20 oil, which is less viscous.
The wet and dry sump system
Conventional wet sump machine has one oil pump. Generally located at the bottom of the machine, usually below and/or on one side of the crankshaft. On a dry sump machine, at least two oil pumps are required: one for pressing and distributing oil around the engine components, and at least one other 'collecting pump' to evacuate the oil accumulated at the bottom of the engine. This scavenger pump is sometimes (but not always) located on the engine 's sump, and most importantly, the flow rate capacity of this scavenger pump must exceed the pump that suppresses and distributes the oil throughout the machine.
Due to the external oil reservoir being dry, excess air can get out of the oil before the oil is pumped back through the engine. Dry sumps also allow more power because they reduce the amount of windage, oil into rotating assemblies, and vacuum from the scavenger pumps that increase the seal of the ring. Dry sumps are more popular in racing applications due to increased power and reduction of oil spills that will reduce the oil pressure. The disadvantages of dry piles are weight gain, additional parts, and more opportunities for leaks and problems to occur.
See also
- Ring oiler
References
External links
- Machine Failure
Source of the article : Wikipedia
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