4 Hägglunds VFWCB 600 | Freewheeling valve
Bosch Rexroth AB, 06.2024, RE 15380
3 Functional description
General
Hägglunds motors CA, Quantum and CBm can be operated
in free-wheeling mode by retracting the pistons and allo-
wing the cylinder block to freely rotate on its bearings.
The valve is designed for use with the motors and provides
free-wheeling of the motor by means of disconnecting the
motor from the main lines and connecting both motor
ports to T, which has to be drained to tank. The valve can
be mounted directly onto the motor and can be used in
both open and closed loop applications.
Maximum operating pressure is 350 bar (5076 psi) and
maximum flow 1000 l/min (264 gpm). Nominal flow is 600
l/min (156 gpm).
The valve is available in three main congurations:
1. VFWCB 600 E Free-wheeling valve electrically
operated
2. VFWCB 600 H Free-wheeling valve hydraulically
operated
3. VFWCB 600 M Free-wheeling valve manually operated
Various options are available referring to the order code.
Note!
Only one valve is to be used on the Hägglunds CBm.
For more than one valve, contact your Bosch Rexroth
representative!
Function
A system is required to ensure that the motor is in statio-
nary position before switching from free wheeling position
into drive position. Free-wheeling is achieved by maintain-
ing pressure into the motor case causing the piston to be
lift off the cam ring and pushed in to the cylinder block.
The rotating section of the motor comprising the cylinder
block, pistons and cam rollers can then rotate on the main
bearings without oil flow through the motor main ports.
This case pressure is generated by ensuring that there is a
flow through the motor case. The case pressure shall be
controlled with a pressure relief valve on the motor case
drain line, maintaining a pressure of 1,0 bar (14,5 psi) to
1.5 bar (22 psi), (one of the D ports). A typical response
for a Hägglunds CA210 motor with casing flow of 60 l/min
(16 gpm) would be 1 seconds to change into free-whee-
ling mode.
Before the motor is put into free-wheeling the pilot control
valve (3) is operated, which switches the main spool (1)
and connects the motor ports AM and Cm to T. T has to be
connected to tank.
The shuttle valve (2) allows pilot pressure to be selected
from the high pressure motor line.
Shifting from free-wheeling into operation during running
will not be allowed due to risk for motor damage. For this
reason the pilot control valve (3) has a detent function in
order to avoid unintentional shifting during operation if for
example there is a power failure to the solenoid.
When using the internal pilot valve it is important to
ensure that minimum pilot pressure is available, so that
drive or free-wheeling mode is fully engaged before driving
the motor. External pilot pressure via Px or Pa and Pb is
recommended for open loop system.
For additional information regarding free wheeling see
data sheet, section technical data, for respective motor.
NOTICE
Shifting from free wheeling position into drive position
during running of motor
Damage on piston parts and camring
▶ Shifting from free-wheeling position into drive position
must only be carried out when the motor is standing
still