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Development of a Laser-Hardened Cylinder and An Ion-Plated Piston Ring
Technical Paper
1994-25-0267
Sector:
Event:
ISATA 1994
Language:
English
Abstract
The diesel engine which produces less CO2 in its exhaust
emissions is now attracting wide attention, as it contributes to
the environmental protection. In the light commercial vehicles
market, indirect injection (IDI) diesel engine which is
advantageous for reducing not only NOx emission but also
vibration and noise is in general use. The growing market demands
are also for higher output.
To meet these market needs, we, Mitsubishi Motors Corporation,
have developed the 4M40 engine which employs the IDI combustion
system and also uses turbocharger with intercooler to provide
higher output. The 4M40, which provides the highest specific output
in its class, has been installed into the "Pajero."
Generally, IDI turbocharged, (IDI/TC) engine involves very high
piston thermal load which makes it difficult to increase its output
because of higher possibilities of wear and scuffing of the
cylinder and piston ring, particularly the top ring. To improve the
durability and reliability of the cylinder, the laser-hardening
method has been adopted for the 4M40 engine. The 4M40 is the
world's first automotive engine that employs the method,
although there are some instances of marine engines using the
method. To improve the durability and reliability of the top ring,
a better surface treatment method, CrN ion plating, which makes it
possible to produce a thicker film, has been developed and adopted
for treatment of the top ring sliding surface in place of the
conventional ion plating technique by which the maximum possible
film thickness was slightly more than 110 μm. Adoption of these
techniques has successfully made the 4M40 a highly durable engine
which offers a higher output. Here is a report on how these new
techniques were developed.