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Depiction of shafts and bearings for hydraulic excavator working equipment
Source: China Bearing Network Time: 2017-11-23
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First, the depiction of the bearing:
The bearing of the working equipment is complex; according to its data, it can be divided into copper bearing, steel bearing, composite bearing, etc. According to its smooth method, it can be divided into dry conflict bearing, oil bearing, incomplete oil film bearing, fluid film bearing, etc.: The smooth method of bearing is used to make the oil film smooth. The copper, steel and copper-based steel are used for self-smoothing. The copper bearing has excellent resistance; the wear resistance is normal; the shaft has good protection; The deformation can be poor; the deformation is easy after long-term use; the inner diameter of the bearing is expanded; the structural member is shaken, the steel bearing has high strength; the wear resistance is good; the deformation resistance is strong; but the process demand for external heat treatment is high, the copper-based steel back Since the smooth bearing has the advantages of steel bearing and copper bearing; the oil groove is smooth and self-smooth; it can be used to avoid the burning of the bearing; but the process is messy; the cost is higher.
The primary consideration of the bearing is the service life of the bearing; its life is determined by the wear of the inner diameter of the bearing in addition to the scorch. The amount of wear is mainly affected by the conflicting conditions; and the collision is subject to load, speed, impurities, rough appearance. Degree, operating temperature, different working methods, smoothing agents and other conditions; therefore; the amount of wear can only be a theoretical estimate; the life of the bushing depends on various messy conditions. If the oil supply is poor; impurities Entry causes the wear to change drastically; it is difficult to guess the wear condition.
Under normal conditions; the wear of the copper bearing (ZcuAll0Fe3Mn2) can be approximated by:
W=K×P×V×T
W: wear amount (mm)
K: Conflict coefficient [mm/(N/mm20?æš?æšæ¤‹??ç‘é¢??br> P: carrying capacity (N/mm2)
V: line speed (m/min)
T: wear time (hr)
In the formula, K=Ci×k; k is the conflict coefficient under the ambition; K=(1~5)×10-8[mm/(N/mm20?æš?æšæ¤‹??ç‘é¢??br> 1, Ci=C0×Cl×C2×C3
2, bearing pressure P
Generally speaking, the bearing pressure refers to the bearing load receiving load; the maximum load of the bearing support divided by the pressure area; the so-called pressure area; when the bearing is cylindrical; take the projection area of ​​the load direction with the bearing touch.
3, speed V
The heat generated by the bearing; firstly caused by the conflicting effect of the bearing; available on the basis of experience; the rise of the temperature of the conflict surface; the influence of the sliding speed V is much greater than the influence of the bearing pressure P.
It can be seen that the life of the bearing is determined by the value of P×V. The PV value determines the heat generation of the bearing. When the bearing is working, the bearing temperature is affected by the heat and heat generated by the conflict; usually at a certain temperature. Stabilize; if the work continues, there will be impurities intrusion; the function of the smooth oil will decrease; together with the influence of the conflicting powder; the fatigue of the data; the deformation of the conflict surface will change at this moment; the conflict coefficient will improve; the temperature of the bearing will rise; Conflict surface damage; incurs scorch; according to this situation; the lower the working temperature of the bearing; that is, when the low PV value is used; the load of the bearing is better; the life is extended; so the lower PV can be used in the depiction. value.
Second, the depiction of the axis:
(1) Under normal conditions, the material of the shaft should be made of high-quality carbon structural steel of 35# or higher; it can also participate in the improvement of the heat treatment function of the alloy elements; the data can be treated after quenching and tempering, and the hardness exceeds the hardness of the bearing. Compared with the ambition, when there is a hard object intrusion; the hard object can be embedded in the bearing; without damaging the shaft, otherwise the fatigue life of the shaft will be reduced.
(2) When the outer surface roughness of the shaft is large; the protrusions of the shaft and the sleeve may block the oil film; the two sides are directly touched. Thus; the appearance roughness of the shaft is improved; the oil film gap can be reduced; Smooth condition; this can improve the service life of the bushing; in general, the outer surface roughness of the shaft should be in Ral. 6 or more.
(3) Electroplating the shaft that does not accept the alternating load; not only can it improve its corrosion resistance; and it can be useful to avoid rough wear;
Third, the shaft and bearing public service cooperation:
Under normal conditions; the outer ring of the bearing and the structural member are medium-sized press-fit cooperation; the inner ring of the bearing and the shaft cooperate with the gap made by the base hole; the inner ring of the bearing has an oil groove; smooth grease is smooth. The shaft and the bearing The cooperation gap is too large; there is a large impact load; it seriously affects the service life of the shaft and the structural member, and the cooperation gap between the shaft and the bearing passes. The 蚰岩å•çº¬æ™Œæ¦·Ç–å¨œè ¡ãƒå‡°å²·å²·å²·å²¢å²¢æ¹Ž 湎 湎 㤠㤠㤠晌榷ǖ 晌榷ǖ 晌榷ǖ 晌榷ǖ è ¡ã• èµ¡è‰¿ 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 赡艿 . . . . . . h h h h h h h h h h h h h h h h h h
Hs: minimum oil film thickness (mm)
Y12: Relative flexural deformation of the two faces of the bearing Ra1: Surface roughness of the shaft Ra2: Surface roughness of the bearing â–³L: Straightness of the shaft in the bearing â–³D: Roundness of the inner ring of the bearing â–³: Bearing after installation The amount of bore reduction is now calculated for the minimum cooperation gap between the shaft and the bearing of the XCMG 220LC-6 type maneuvering arm and the arm joint:
When the diameter of the shaft with a diameter of 90 is 90, the minimum safety value of the oil film is hs=6 (μm); the deflection of the shaft is analyzed: the system pressure of the hydraulic system is: 31.4×106 Pa; the cylinder diameter of the cylinder is 140 mm.
The thrust of the cylinder is: F = π × 70 × 70 × l0 - 6 × 31.4 × 106 = 4.8 × 105 (N)
According to the force analysis of the stick; Pl=P2=3.06×l05; then Rl=R2=3.06×105;
The load of the shaft is symmetrically distributed; now when X is at (0 207); the bending moment equation is M(x)=R1×X-××(X-37)×(X-37) then Y(X)=+cx+D =
-+x-x.茫 is obtained by X=0; Y(x)=0 is obtained: D=0; X=0; θ(x)=0 is obtained: c=0
So: Y(x)=×-+X-X
Where E=270 (GPa)
I=×D4=×(180)4=5.15×107(mm4)
y(37)==7.5×10-7(mm)
Y(157)==6.7×10-5(mm)
So; Y12=Y(157)-Y(37)
=6.625×10-5(mm)
The surface roughness of the shaft is Ra1=1.6(μm)
Bearing surface roughness: Ra2 = 1.6 (μ m)
The straightness of the shaft in the bearing is △L=20(μm)
The roundness of the inner ring of the bearing â–³ D = 15 (pm)
Maximum shortening of inner bore of bearing after installation △=×δmax
Where δmax is the maximum interference of the outer diameter of the bearing; δmax=45(μm)
DB is the outer diameter of the front bearing before pressing; DB=110 (mm)
Do is the inner diameter of the bearing before pressing; d0=90 (mm)
Calculated by △: 0.91 × 45 = 40 (μm)
Therefore; the minimum gap that constitutes the oil film is:
Hmim=hs+y12+Ra1+Ra2+â–³L+â–³D+â–³
=6+6.625×10-2+1.6+1.6+20+15+40
=84.9 (μm)
The selected public service is 90; the minimum gap is 122μm; it is suitable to see this gap.
In the depiction of the shaft and the bearing; firstly, we must consider the working conditions; secondly, on the basis of satisfactory use of the function; the service life of the shaft and the bearing is slightly longer and the service life of the whole machine can be used; Best plan.
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