HONDA Insight - Manual (Page 31)

31
Electronic Construction
The EPS control unit is mounted inside the car on the right side bulkhead, underneath the dash. It
receives input from the vehicle speed sensor and torque sensor mounted on the steering pinion shaft.
The torque sensor is identical in construction to the unit on the S2000. The pinion shaft engages the
pinion gear via a torsion bar, which twists slightly when there is a high amount of steering resistance. The
amount of twist is in proportion to both the amount of resistance to wheel turning, and to the steering force
applied. A pin on the torsion bar engages a diagonal slot in the sensor core, which moves up or down
depending on the amount of torsion bar twist, and the direction of rotation. Two coils surrounding the core
detect both the amount, and the direction of movement.
Using this information, the EPS control unit determines both the amount of steering assist required, and
the direction. It then supplies current to the motor for steering assist. The amount of assist is also modified
in proportion to vehicle speed to maintain good steering feel.
Torque Sensor
The torque sensor is a device to detect steering turning direction and read resistance. The sensing
section of the torque sensor consists of two coils and a core (slider). The steering input shaft and pinion
gear are connected via a torsion bar. The slider is engaged with the pinion gear in a way that it turns
together with the pinion gear but can move vertically. A guide pin is provided on the input shaft and the pin
is in a slant groove on the slider.
When road resistance is low, the steering input shaft, pinion gear and slider turn together without the
slider's vertical movement.
When road resistance is high, the torsion bar twists and causes a difference of steering angle between
the input shaft and pinion gear. In other words, the turning angle of the guide pin and slider differ, and the
guide pin forces the slider to move upward or downward.