Isuzu N-Series. Manual - part 214
HYDRAULIC BRAKES 5A-15
Operation of Auto-adjuster
The entire auto-adjust mechanism is incorporated into
the wheel cylinder assembly, and the adjust operation is
carried out only when in the forward movement.
The operation of the auto-adjuster is as follows:
• When fluid pressure is applied to the oil chamber
(A), the piston, which is resistant to the over-travel
spring installed between the bracket (14) and the
adjust lever (6), is forced out to the brake shoe (18)
side. (The piston and bracket are welded into a
monolithic construction.)
• When force delivered by the over-travel spring (18)
is intensified as the piston (2) moves, the balance
maintained with the lever return spring (7) installed
between the adjust lever (6) and lever pin (10) is
destroyed, and the adjust lever (6) with the lever
pin (10) as a pivot, rotates the adjust gear (11) in
the rotational direction.
• When the shoe clearance (clearance between the
brake shoe and the brake drum) gets to the speci-
fied value, the adjust lever (6) adjusts the shoe
clearance by driving one gear tooth or more of the
adjust gear (11) in the rotational direction through
the force of the over-travel spring (8).
• When the brake shoe (18) comes into contact with
the brake drum, the frictional force generated be-
tween the adjust screw (13) and the adjust nut (12)
gets larger, and the adjust gear (11) cannot be ro-
tated by the force of the over-travel spring (8). (The
adjust gear and the adjust nut are welded into a
monolithic construction.) That is, the automatic ad-
justment of the shoe clearance is carried out until
the brake shoe comes in touch with brake drum.
However, over adjust can be avoided since this au-
tomatic adjustment will not be performed for the in-
creased amount of the piston shift caused by the
deformation of the drum and shoe after their con-
tact.
• When the fluid pressure is released from the oil
chamber (A), the force by which the lever return
spring (7) rotates the adjust gear (6) adversely gets
weaker than the frictional force generated between
the adjust screw (13) and the adjust nut (12),there-
fore, the adjust lever (6) slides on the adjust gear
(11) to get back to its former state before operation
and this operation is completed with the adjust
gear (11) left in the state in the rotational direction
into which its has been driven.
Legend
A. Oil chamber
B. Rotational direction of the drum (forward)
N5A0059E