Design of shaft pin and bearing of construction machinery

1. bearing design of working device:

There are many kinds of bearing for working device, which can be divided into copper bearing, stainless steel bearing, composite joint bearing and so on. According to its lubrication mode
It is divided into dry friction bearing, oil bearing, incomplete oil film bearing, fluid film bearing and so on
For incomplete oil film lubrication, copper, steel, copper base steel back self-lubrication and other bearings have been used. Copper bearing has good toughness and resistance
Generally abrasive,
The shaft has a good protective effect,
But the resistance to deformation is poor,
Easy deformation after long use, resulting in bearing
Diameter expansion, resulting in structural parts shaking; Steel bearing high strength, good wear resistance, deformation resistance, but the surface heat treatment process
Demand is high; Copper base steel-backed self-lubricating bearing has the advantages of steel bearing and copper bearing, and oil groove lubrication and self-lubricating are combined at the same time.
Can effectively avoid the burning of the bearing, but its process is complex, the cost is high.
Bearing design is primarily concerned with the service life of the bearing,
Its life is determined by the wear amount of bearing inner diameter except for burning.
The wear amount is mainly affected by the friction condition, and the friction is also affected by the load, speed, impurities, surface roughness, working temperature, different operating modes, lubricants and other conditions, so the wear amount can only be a theoretical estimate, the life of the shaft sleeve
It depends on the complicated conditions. It is difficult to predict the wear condition if the wear changes sharply due to poor oil supply and impurity infiltration.
Under normal circumstances, wear amount of copper bearing (ZcuAll0Fe3Mn2) can be approximated by the following equation:
W = K * V * P T
W: wear (mm)
K: friction coefficient [mm/(N/mm2·m/min·hr)]
P: carrying capacity (N/mm2)
V: linear velocity (m/min)
T: wear time (hr)
Where, K = Ci * K, K is the friction coefficient under ideal state, K = (1 ~ 5) * 10-8 [mm/(N)/ mm2·m/min·hr)】
Ci is equal to C0 times Cl times C2 times C3
2. Bearing pressure P
Usually the so-called load bearing pressure refers to the bearing under the load,
The maximum load supported by the bearing divided by the area under pressure,
So the area under pressure,
When the bearing is cylindrical, the projected area of the load direction in contact with the bearing is taken.
3. Velocity V
The heat generated by the bearing,
It is mainly caused by the friction of the bearing. According to the experience, the rise of the temperature of the friction surface,
sliding
The influence of velocity V is far greater than that of bearing pressure P.
So you can see,
The life of the bearing is mainly determined by the value P by V.
At the same time, PV value determines the heat output of the bearing.
When bearing luck
Turn,
Bearing temperature is affected by the heat generated by friction and heat emission.
It usually stabilizes at some temperature,if There are impurities invading during the continuous operation.The performance of lubricating oil will be reduced,And because of the friction powder,

Material in the At this time, the deformation of the friction surface changes, the friction coefficient increases, the temperature of the bearing rises, resulting in damage to the friction surface, the guideIn this case, the lower the operating temperature of the bearing, i.e., the lower PV value is used, the better the bearing load performance is.Life is extended, so use a lower PV value as far as possible at design time.
Ii. Shaft pin design:
(1)In general, the shaft material is 35 # or above high quality carbon structural steel, alloying elements can also be added to improve its heatTreatment performance: after surface treatment such as quenching and tempering, the hardness of the material exceeds the hardness of the bearing to achieve an ideal effect;When a hard object invades, it can be inserted into the bearing without damaging the shaft. Otherwise, the fatigue life of the shaft will be reduced.

(2)When the surface roughness of shaft is large, the protruding part of shaft and shaft sleeve will cut off the oil film, resulting in direct contact between the two. Therefore, improve the surface roughness of the shaft, minimize the oil film gap, and make it close to the fluid lubrication state, so as to improve the service life of the shaft sleeve. Generally, the surface roughness of the shaft should be at Ral. More than 6.

Engineering machinery reliability of working device of hydraulic engineering machinery performance influence is very big, the operation condition of the working device at work for low-speed overloading, it’s on the shaft pin and bearing performance of work put forward very high requirements, and in engineering machinery design, the weight of the working device on the premise of can meet the design performance parameters should be as small as possible, so the reasonable design of shaft and bearing is important for engineering mechanical engine performance.


Post time: Dec-07-2018
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