829
Model Code Page
46. Power take ---off
1. 11. 1998
6000--8750 460 15
1. 1. 1995
PTO clutch cushioning valve, ---660070
(picture 11).
The cushioning valve is fitted in the gearbox housing and it is
accessible when a small cover on the gearbox LH side is
removed. Before removing the cover, the gearbox oil must be
drained.
When PTO solenoid valve opens oil flows under pressure to
the PTO clutch. When the pressure has reached 0,5---0,6
MPa, valve ball (1) opens. At the same time oil flows past
needle (2) to piston (3). After 0,7---1 second the pressure is
equalized and ball (1) closes. The engaging pressure then
rises to a normal value of about 1,8 MP a.
Note! The PTO engagement can further be made slower by
fitting a ø 2 mm restriction into the gearbox housing, see
page 462/8.
PTO clutch cushioning valve, 660071---
(picture 12).
From tractor ser. no. 660071 the cushioning valve is in---built
intheservovalveblockontheLHsideofthegearbox.The
cushioning valve end plugs are fitted on the top side of the
valve block, see pictures on pages 420/17A and 17B point 8.
When the PTO is engaged, the solenoid valve directs oil to the
PTO clutch and to the cushioning valve. The cushioning valve
spring (below piston 4) has its maximum length and raising
pressure in the lower passage opens valve ball 5 and oil can
flow to the tank. At the same time oil flows by valve ball 6 into
the upper passage.
Pressure oil moves piston 4 downwards and spring force
which affects the ball 5 increases . Oil flow to tank decreases
and clutch pressure rises slowly to its max. value (1,8 MPa).
When the PTO is disengaged, oil returns via solenoid valve to
the tank passage 7. Pressure in the lower passage decreases
and oil can flow from the upper passage by ball 6. Piston 4
returns quickly to the original position.
This construction facilitates the function of the valve when the
PTO is engaged quickly again.
From tractor ser. no 661798 incl. the cushioning valve has
been modified so that the engagement of the PTO is ”softer”.
The spring on ball (5) has been changed so that the spring
wire diameter is now 1,0 mm (earlier 1,1 mm). In addition, the
restriction on ball (6) has been changed. The new restriction
has a groove of 0,4 mm (earlier 0,5 mm).
These modifications can also be done forthe earliermanufac-
tured tractors.
The spare part number of the new spring is 30626810.
The spare part number of the new restriction is 32720410.
Note! In order to improve further the engagement of the PTO,
a new restric tor has been fitted into the servo valve block and
an extra passage has been drilled, see page 420/17A point
17and page 420/17B point 17. The restrictor canbe fitted also
on the earlier manufactured tractors. The spare part number
of the restrictor is 31742320 (ø1,2 mm).
Note! HiTech tractors have not the cushioning valve, but t he
PTO engagement is controlled by a proportional solenoid
valve which in turn is controlled by the Autocontrol V control
unit (see code 370).
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