Yanmar 4LHA-DTP, Operation Manual

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Chapter 7 Reduction and Reversing Gear
1. Construction
4LHA Serie:
Marine Gear Model
KM 5 A
1. Construction
1-1 Construction
The clutch is a cone-type, mechanically operated clutch.
When the drive cone (which is connected to the clutch shaft
by the lead spline) is moved forward or backward, its taper
contacts with the clutch gear and transfers power to the
output shaft.
The construction is simple when compared with other types
of clutch and it serves to reduces the number of compo-
nents, making for a lighter, more compact unitwhich can be
operated smoothly. Although it is small, the power trans-
mission efficiency is high even under a heavy load. It is
also durable and reliable because high grade materials are
used for the shaft and gear, and a taper roller bearing is
incorporated. Power transmission is smooth because
connection with the engine is made through the damper
disc.
• The drive cone is made from special aluminum bronze
which has high wear-resistance and durability. The
drive cone is connected with the clutch shaft. The taper
angle, diameter of the drive cone, twist angle, and dia-
meter of the involute spline, are designed to give the
greatest efficiency, thus ensuring that the drive cone can
be readily engaged or disengaged.
• Helical gears are used for greater strength. The inter-
mediate shaft is supported at 2 points to reduce deflec-
tion and gear noise.
• The clutch case and mounting flange are made from an
aluminum alloy of special composition to reduce weight.
This is non-corrosive in seawater.
• The damper disc is fitted to the input shaft, so power
can be transmitted smoothly. Springs of different streng-
ths are used for the damper disc so that two stages of
torque and twist angle are applied. That is, in the first
stage, only the weak spring is used, and the strong spring
comes into action for a torque higher than a predetermin-
ed value.
This prevents gear noise due to torsional vibration, as
well as absorbing shock when engaging.
Stage arrangement
Absorbs shock
when engaging
Twist angle 6
There is a small clearance between the dipstick and the
inside of the dipstick tube. A small hole in the dipstick
works as a breather.
• When the load on the propeller is removed, the engage-
ment of the drive cone and the clutch gear is maintained by
the shifter and V-groove of the drive cone. Even when the
drive cone's tapered area and V-groove are worn, this
engagement is maintained by the shift lever device.
Accordingly no adjustment of the remote control cable is
required.
• The cup spring on the rear of the clutch gear absorbs
rotational fluctuations and stabilizes the engagement of
the drive cone and the clutch gear. Thus, the durability
of the cone against wear is enhanced.
7-1-1