Why is crankcase oil supplied to sleeve bearings?

  • Thread starter marellasunny
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In summary, the crosshead in a reciprocating engine eliminates sideways pressure on the piston, caused by the connecting rod. The oil used in journal bearings acts as a cushion to soften the impact, preventing any damage from rod to crank.
  • #1
marellasunny
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(Diagram attached)
Why is crankcase oil supplied to sleeve bearings in the connecting rod?Does the oil film act like in a journal bearing?

I was reading about compressors and there is a mechanism called a 'crosshead'(see diagram) that converts rotary to reciprocating motion. Its funny how oil is used instead of real bearings.
 

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  • #2
Bearings require lubrication or they will seize, thus destroying the engine.
 
  • #3
but,there are no needle/round bearings in the crosshead.Its just oil flowing throw the crank pin that is taking-up all the rotation,which is what surprises me.
I would imagine the same lubricating mechanism in a IC engine for automobiles. Since there always exists the phenomenon of blow-by in IC engines,what is to ensure that the crank oil always reaches the pin in the first place?
 
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  • #4
marellasunny said:
there is a mechanism called a 'crosshead' that converts rotary to reciprocating motion.
marellasunny,

A crosshead is a mechanism used in large reciprocating engines and reciprocating compressors to eliminate sideways pressure on the piston, caused by the connecting rod.

http://en.wikipedia.org/wiki/Crosshead

http://marinediesels.info/2_stroke_engine_parts/crosshead.htm

The connecting rod connects the piston to the crankshaft... the connecting rod is actually what converts the rotating motion of the crankshaft into linear motion (reciprocating motion).
Or, vice versa... linear into rotating motion.

http://en.wikipedia.org/wiki/Connecting_rod

http://en.wikipedia.org/wiki/Connecting_rod#Internal_combustion_engines

http://en.wikipedia.org/wiki/Connecting_rod#Compound_rods

The bearings are 'real'... they're called plain bearings, or journal bearings, as opposed to rolling-element bearings.

http://en.wikipedia.org/wiki/Journal_bearing#Two-piece

http://en.wikipedia.org/wiki/Rolling-element_bearing

http://en.wikipedia.org/wiki/Bearing_(mechanical)

And, yes... they ride on a film of oil, supplied by the engine oil pump.

http://en.wikipedia.org/wiki/Plain_bearing#Fluid_lubrication

http://en.wikipedia.org/wiki/Oil_pump_(internal_combustion_engine)



OCR
 
  • #5
marellasunny said:
but,there are no needle/round bearings in the crosshead.Its just oil flowing throw the crank pin that is taking-up all the rotation,which is what surprises me.
I would imagine the same lubricating mechanism in a IC engine for automobiles. Since there always exists the phenomenon of blow-by in IC engines,what is to ensure that the crank oil always reaches the pin in the first place?

Why do you think that "blow-by" would interfere with journal bearing lubrication?
 
  • #6
the exhaust gases mix with the oil and make it more viscous than needed.
Now,the question is whether journal bearings would survive in such extreme conditions...why would engineers take the risk of the crosshead with a journal than the usual needle?
 
  • #7
why would engineers take the risk of the crosshead with a journal than the usual needle?
What is the risk?
 
  • #8
I would imagine the load placed on the needle bearing would render it useless. The oil acts as a cushion to soften the impact as to prevent any damage from rod to crank
 

1. Why is crankcase oil supplied to sleeve bearings?

Crankcase oil is supplied to sleeve bearings to provide lubrication and reduce friction between the bearing and the rotating shaft. This helps to prevent wear and damage to both the bearing and the shaft, ensuring smooth operation and extending the lifespan of the equipment.

2. What is the role of crankcase oil in sleeve bearings?

The main role of crankcase oil in sleeve bearings is to act as a lubricant, reducing friction and wear between the bearing and the rotating shaft. It also helps to dissipate heat generated by the friction, preventing overheating and potential damage to the bearing and shaft.

3. How does crankcase oil affect the performance of sleeve bearings?

Crankcase oil plays a crucial role in the performance of sleeve bearings by reducing friction and ensuring smooth operation, which can improve efficiency and reduce energy consumption. It also helps to prevent wear and extend the lifespan of the bearings, ensuring reliable performance over time.

4. What happens if crankcase oil is not supplied to sleeve bearings?

If crankcase oil is not supplied to sleeve bearings, the bearing and rotating shaft will experience increased friction and wear. This can lead to overheating, damage to the bearing and shaft, and potentially cause equipment failure. Regular oil maintenance and replacement is essential to prevent these issues.

5. How often should crankcase oil be supplied to sleeve bearings?

The frequency of supplying crankcase oil to sleeve bearings can vary depending on factors such as the type of bearing, operating conditions, and oil quality. It is generally recommended to follow the manufacturer's guidelines and perform regular oil analysis to determine the appropriate oil change interval for optimal performance and longevity of the bearings.

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