Fig. 1 Autocontrol power lift system
1. Hydraulic pump
2. Control valve
3. Lifting cylinder
4. Electronic unit
5. Draft sensor
6. Position sensor
7. Switch panel
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Model Code Page
32. Electro---hydraulic power lift
8. 11. 1990
6000--8400 320 1
1
2
3
4
5
6
7
1. Autocontrol --- hydraulic lift, elec-
trical system
Note! Hydraulic system of the power lift is described in sec-
tion 90. This Autocontrol---hydraulic lift is the same as on Val-
met 505---905 tractors.
The Valmet Autocontrol is an electrically controlled hydraulic
lift. All mechanical levers have been replaced with knobs and
switches. Ideal mixing/sensitivity values for draft control have
been pre---programmed and can be controlled with one
switch.
Operation:
The pump (1) draws oil from the oil reservoir and delivers it to
the control valve (2). The control valve directs the oil to the lift-
ing cylinders (3) for the operation of the lifting arms (lifting,
lowering and holding functions). The values set on the switch
panel (7), and the actual values detected by the draft sensors
(5) and position sensor (6), are fed into the electronic unit (4).
This unit determines the differences between the two sets of
signals (i.e. from the sensors and switches) and feed the
necessary control signal to the control valve solenoid.
The position sensor (6) is in permanent contact with an eccen-
tric on the lift shaft. When the lower links are lifted or lowered
the eccentric moves the pin, which sends a signal to the elec-
tronic unit; thus the hydraulic lift always ”knows” the position
of the lower links.
The lower links are connected to the draft sensors (5). When
the draft force in the lower links increases the loading on the
draft sensors also increases. This loading is then converted
into electrical signals by the draft sensors.
These signals are amplified by an electronic device which is
built into the the draft sensors. The signals are sent to the Au-
tocontrol hydraulic lift. If the draft force increases the hydraulic
lift will raise the implement, the draft control sensitivity de-
pending on the setting of the switches in the cab.
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