Hyundai Santa Fe (2006 year). Manual - part 16
AT -16
AUTOMATIC TRANSAXLE (F4A51)
VFS (VARIABLE FORCE SOLENOID)
VRS Function
The spool rod in VFS is not duty cycled like one of PWM,
it minutely vibrates at the range between the control port
and exhaust port to control the hydraulic pressure. That is,
it uses the equilibrium effect between the spring force and
the magnetic force, the spring force is mechanical charac-
teristics decided at the stage of design and the magnetic
force is controlled by TCM. This electrical magnetic force
is proportional to the current. So TCM will control the cur-
rent.
In case of VFS valve, the electrical ‘ time constant’
is
considered to decide the frequency for the current not to
be fluctuated even though turns on or off the input signal.
The electrical ‘ time constant’
is much more fast than
one of mechanical so the frequency of VFS is extremely
higher than the conventional PWM type.
VFS
ATF TEMP SENSOR
EKRF081A
Characteristics of Bosch VFS:
Supply pressure : 700∼1600kPa
Control pressure: typically 600∼0 kPa
Current range: typically 0∼1,000 mA
Dither frequency: Up to 600 Hz
Dimension: 32 mm protrusion reach 42 mm
Control
Supply
Exhaust
EKRF082A
The reducing pressure will be supplied to the ‘ Supply’
port of the VFS valve on the above illustration to control
the line pressure.
REDUCING PRESSURE
FUNCTION
Adjusting screw for reducing pressure
EKRF083A
As same as one of Alpha or Beta automatic transaxle sys-
tem, this reducing valve length can be adjusted by rotating
the screw on the picture. As you rotate the screw toward
clockwise by 90˚ , the reducing pressure will increase
about 1.0bar. However, the reducing pressure is used
just as a ‘ supply pressure’
for the solenoid valves (ex-
cept Low＆Reverse, Reduction and Damper Clutch control
solen), so this may not be handled to rotate in the field ser-
vice shop. VFS is operated based on the ‘ supply pres-
sure’
and it outputs the ‘ control pressure’
to control
the regulator valve indirectly. While developing the VFS
system, the line pressure was used as a ‘ supply pres-
sure’
for VFS and other solenoid valves but it has been
changed into additional ‘ reducing pressure’
because
the line pressure is variably changed by VFS so the control
pressure becomes unstable and some hydraulic pressure
oscillation occurred. That is why the reducing pressure
has been added in the hydraulic circuit of VFS system for
both 4th and 5th speed A/T.
<Valve body>
Reducing
valve
EKRF084A