Turbocharger (For 4Tne106T); Structure And Functions; Structural And Functional Outline - Komatsu 4D98 Series Shop Manual

8. Turbocharger (for 4TNE 106T)
8.1 Structure and Functions
(1) Structural and functional outline
(1 .I) Turbine
The exhaust gas from the engine is accelerated at the nozzle portion in the turbine housing
and blown onto the turbine impeller to rotate the turbine shaft.
This is called the turbine. A seal ring and heat insulating plate are installed to prevent the
bearing from adverse influence of the gas.
(1.2) Compressor
The compressor impeller installed on the turbine shaft rotates with the shaft to suck and com-
press air for feeding into the intake manifold.
This is called the blower or compressor.
(1.3) Bearings
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Thrust bearing:
As the turbine shaft is constantly applied with a thrust force, this bearing prevents the shaft
from being moved by the thrust force.
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Radial bearing:
A floating bearing is adopted. Since the bearing moves with the turbine shaft as the oil films
are formed both inside and outside the bearing, the bearing sliding speed is slower than the
turbine shaft speed, resulting in higher dynamic stability.
(1.4) Compressor side sealing mechanism
To prevent the intake air and oil from leaking, a seal ring and a seal plate are provided to form
a double wall structure on the rear side of the compressor impeller.
(1.5) Waste gate
When the blower side pressure (intake air pressure) exceeds the specified level, the exhaust
gas at the turbine inlet is partially bypassed to the exhaust discharge side to control the turbine
rpm so as to maintain the intake pressure at the specified level for improving the response to
load variation in the low to medium speed range and to minimize black smoke generation.
It consists of a control assembly separated from the turbocharger and a valve assembly in-
stalled in the turbine impeller chamber.
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