Branson F36r - Page 290

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CHAPTER 6 HYDRAULIC SYSTEM 3015R(h)/3515R(h)/4015R(h)/F36R(h)/F42R(h) TRACTOR
6
5
1
2
3
4
K20W602A
(1) Spool
(2) Sleeve
(3) Pin
(4) Leaf spring
(5) Drive shaft
(6) Gerotor (inner rotor)
The steering wheel is engaged with the steering valve spool with splines. Therefore, when the steering wheel
isturned,thespoolisturnedaswell.Thespool(1)iscoveredwiththesleeve(2)andthesearexedbythe
pin (3). Therefore, when the spool is turned by the steering wheel, this pin is rotated as well to turn the sleeve.
Theinsidediameterofthepinholeofthesleeveismatchedtotheoutsidediameterofthepin,sothepintsto
the hole tightly. However, the pin hole of the spool is larger than the pin. Therefore, when the spool is rotated,
the sleeve cannot be rotated with the spool immediately, but it is rotated approx. 10 degrees (the amount
of free play of the spool pin hole) behind the spool. For example, when the steering wheel is being turned
clockwise, the sleeve is turned approx. 10 degrees behind the spool, so the holes for the right turn among the
holes of the sleeve and spool are aligned to supply hydraulic oil to the steering cylinder for right turn. When the
steering wheel is stopped, the spool is stopped simultaneously but the sleeve turns 10 degrees further before
stopping. This is because the leaf spring binds the spool and sleeve and it exerts a force to return the relative
positions of the spool and sleeve to the neutral positions. Since force of this spring is not so strong, so it does
not have any effect when the steering wheel is being turned. However, when the steering wheel is stopped,
it returns the spool and sleeve to the neutral position. Then, the neutral holes among the several holes of the
spool and sleeve are aligned, so the steering cylinder does not move, keeping its original position.
On the other side, when the steering wheel is turned, the spool rotates and turns the sleeve through the pin, but
it turns the drive shaft (5) as well. Then, this drive shaft turns the inner rotor (6) of the Gerotor pump under the
steering valve. This Gerotor pump is to enable steering even when the engine is stopped. When the steering
wheel is turned, the rotor in the Gerotor is rotated to produce and supply hydraulic oil to the steering cylinder.