Draft Control - Kubota M6800S Workshop Manual

M6800 · M6800S · M8200 · M9000, WSM

(2) Draft Control

Draft control is a system in which the lift arms (implement) automatically rise when the implement's traction load is
increased and lower when the traction load is decreased. By maintaining a constant traction load, it prevents the
tractor from slipping and over-load.
There are two types of traction load sensing system: top link sensing system and lower link sensing system. These
tractor are equipped with the top link sensing type.
When using the draft control, the draft control lever should be set in the draft range, and the position control lever
should be set at the lowest position.
Draft Control System
(1) Spool Retainer
(2) Draft Control Shaft
(3) Draft Link
(4) Draft Link 2
1. When the draft control lever is moved to the draft range, the draft control shaft (2) rotates clockwise and draft link
2 (4) approaches to the draft cam (11).
(Reference)
• Draft control sensitivity can be regulated by changing the distance between draft link 2 (4) and the draft cam (11)
using the draft control lever.
2. Traction load of the implement acts as torsion force to the torsion bar (5) via the top link bracket (7).
When traction load increases, the torsion bar is twisted depending on the load, and this twist is transmitted to the
draft control rod (12), draft cam (11), draft link 2 (4), connector (10), holder (9), and spool holder (1), thereby
causing the spool (8) to be forced in.
As a result, a Raising circuit is formed.
3. As the lift arms (implement) are raised, traction load reduces. Therefore, the draft control rod (12) returns. As a
result of this, the spool (8) is forced out by the return spring which allows a Lowering circuit to be formed again,
thereby causing the lift arm to move downward.
(Reference)
• The spring installed inside the holder (9) is a safety device which functions when the draft control rod (12) is pushed
in excess of the specified spool stroke.
(5) Torsion Bar
(6) Top Link
(7) Top Link Bracket
(8) Spool
(9) Holder
(10) Connector
(11) Draft Cam
(12) Draft Control Rod
8-M20
HYDRAULIC SYSTEM
(a) Motion when traction load
increases
(b) Motion when traction load
decreases
KiSC issued 03, 2008 A