Farmer 400
Fav 700
Fav 900
Steering / General system
Functional description
A
General
Fav 900 chassis number 23/3001 and up
04.12.2000
4000
000001
A
a
1/3
Capitel
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Date
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Functional description
Text-module
Comparison with Fav 500, Xylon, Fav 800 etc.:
Bullet-List
Unchanged:
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Same function
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Same pressure values
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Same principle
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First priority in hydraulic system and immediate operational readiness when engine is running
(i.e. independently of other systems)
Bullet-List
New:
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All the main control components are now flange-mounted on the central control block ZSB
(e.g. priority valve, see Fig. 1) or incorporated internally.
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The pressure-relief system for the auxiliary pump DBV-L (see Fig. 2) is generally no longer in the
steering unit LE nor provided in the form of a separate external valve, but is incorporated in the
central control block ZSB.
Bullet-List
Test instructions / cross-references:
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The hydraulic function of the steering system must not be viewed in isolation, see general test
instructions "Test instructions and log for general hydraulic functions" 9600/E/-----
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The "Performance test / Overview" 4000/E/---- sheet provides an initial guide.
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The "Auxiliary pump PL and priority valve" 4000/E/----- special test instructions can be used to
connect the auxiliary pump to the circuit.
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Please see "Control system function charts" for the different operational statuses when steering.
Bullet-List
Available pumps:
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The steering system has two pumps available to it, with the LS pump PR (=inclined-disc axial-flow
piston pump) servicing the steering system in the "normal scenario".
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Both pumps are isolated from each other in terms of both pressure and volume by the non-return
valves RV3 and RV4, i.e. the auxiliary pump PL does not feed into the LS pump PR and the LS
pump PR does not feed into the auxiliary pump PL. The non-return valves RV3 and RV4 are integral
components of the central control block ZSB
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LS pump PR (=inclined-disc axial-flow piston pump):
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The maximum working pressure of the LS pump PR is fixed at the pump controller; this pressure
must never be increased (rise in oil temperature, consequential damage and voiding of warranty)
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Auxiliary pump PL (= gear pump = fixed-displacement pump)
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The auxiliary pump PL pumps oil constantly, independently of the engine speed; it is therefore part of
the hydraulic system's cooling circuit.
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The auxiliary pump PL only takes over responsibility for steering in the "need scenario". If the tractor
also has a hydraulic trailer brake, the auxiliary pump generates the instantaneous pressure in the
trailer brake.
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The commonly used name "steering pump" is therefore not appropriate; the term "auxiliary pump" is
better and will be used in future.
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Pressure relief for the auxiliary pump PL is provided by the DBV-L valve in the central control block
ZSB (see Fig. 2).
Bullet-List
Steering / "normal scenario"
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The LS pump PR normally services the steering system.
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The LS pump makes its maximum working pressure (=200 bar) available to the steering system.
Bullet-List
Steering / "need scenario"
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A need only arises if the LS pump PR is exhausted by the current oil demand, and the steering
system still requires a higher pressure.
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The priority valve PVL ensures that the auxiliary pump PL is automatically connected to the circuit.
