Suzuki kq750 Service Manual page 649

6C-3 Power Assisted Steering System:
Detecting Principle
The column shaft is connected to the input shaft by means of serration. The output shaft and input shaft are connected
via torsion bar. When torque is inputted from the column shaft, a relative angular displacement occurs between the
input shaft and the output shaft due to twist of the torsion bar. As the sleeve is engaged with a fixed pin, such an
angular displacement of the sleeve is converted to a linear displacement due to helical spline arrangement.
By the return spring of torque sensor lever, the sleeve is always forced to one side within its annular groove. The
sleeve's linear displacement causes the torque sensor lever to turn, which is then converted to a voltage signal to
supply to EPS control unit.
The torque sensor is a double circuit of main and sub, when the handlebars is in neutral position (no torsional torque
applied to the steering wheel), each torque sensor (main and sub) output is 2.5 V and in this state the EPS control unit
determines the steering torque as 0. During operating the handlebars, the EPS control unit processes the main torque
sensor input signal to determine the steering torque required for the current condition. The relation between the
steering direction of the EPS control unit and the output voltage is as follows: The direction is determined to be right
turn steering "a" if the main torque sensor output voltage is lower than 2.5 V and to be left turn steering if the voltage is
higher than 2.5 V for controlling the steering direction in the case of normal steering operation.
Conversely, the direction is determined to be left turn steering "b" if the sub torque sensor output voltage is lower than
2.5 V and to be right turn steering if the voltage is higher than 2.5 V for controlling the steering direction.
Column shaft
Torsion bar
Sleeve
Output shaft
" b "
Input shaft
Helical spline
Pin
Main
Left steering
Steering torque
" a "
" b "
Pin
Voltage
2.5 V
Sleeve
Sub
Neutral position
Right steering " a "
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