Maeda MK0003, Руководство по обслуживанию, Страница: 105 / 348

2-77
[3] Actuation of acceleration positioner
By applying a current to solenoid (SOL11), this operating section moves spool (2) in commensurate with the input
current, and by means of the linked acceleration wire, it allows the engine to vary its revolution speed, in order to
control the pump discharge rate.
1. When magnetic proportional reducing valve solenoid is not excited
For the pilot pressure (primary pressure) from pilot line, the path to secondary side pilot chamber (a) is closed by
reducing valve spool (1). On the other hand, pilot chamber (a) is connected to drain port (c) by way of the internal
path of reducing valve spool (1). Consequently, the pressure of pilot chamber (a) becomes equal to that of spring
chamber (b) (drain pressure), and thus spool (2) is pushed leftward by return spring (3).
2. When magnetic proportional reducing valve solenoid is excited
Applying a current to solenoid (SOL11) of magnetic proportional reducing valve (4) allows the reducing valve
spool (1) to be pushed down by push pin (5) for an amount corresponding to the current value to control the
secondary pressure in pilot chamber (a).
Also, as a result of reducing valve spool (1) being pushed down, the path that has connected the pilot chamber
(a) with spring chamber (b) is closed, and consequently the hydraulic oil that has entered pilot chamber (a) acts
on piston (6) so that the spool (2) connecting with piston (6) is moved rightward to the location where balanced is
established with the force of return spring (3).
Thus, since the input current and the stroke of spool (2) are in a proportional relationship, an engine revolution
speed commensurating with the input current can be obtained, and thus the discharge rate of the pump can be
controlled.
SOL11
From pilot line
Primary
pressure
Engine
1. Reducing valve spool
2. Spool
3. Return spring
1. Reducing valve spool
2. Spool
3. Return spring
4. Magnetic proportional reducing valve
5. Push pin
6. Piston
From pilot line
Primary
pressure
Engine
Acceleration wire