Body Vacuum Transducer

Design


The vacuum transducer is used for actuating the vacuum units. This is done by producing a control pressure in line with the electric input signal from the engine control module and passing this to the downstream actuator.







A magnetic field is produced in the coil (e) which varies the gap (s) in proportion to the control current of the engine control module. The control vacuum is a measure for the magnitude of the output signal

No signal from control module
The gap (s) is at its largest in the deenergized state.
A pressure balance can now take place from ATM through the orifice plate (g) and the drillings in the housing (c), on through the restriction drilling (n), through the filter (f) to OUT.
As atmospheric pressure also acts on the valve (b) from below through the centrally positioned drilling in the housing (c), the valve is able to close with the aid of the force of the spring (o) and the suction pressure from VAC.
Air is admitted to the vacuum unit.







Signal from control module
If the coil (e) is now supplied with control current, a magnetic field is produced in the armature (I), as a result of which the orifice plate (g) is pulled against the seat of the brass sleeve (h). The drilling to ATM is closed off.
As the atmospheric pressure no longer acts on the lower chamber (m) of the diaphragm (d), the spring (a) is able to push down the diaphragm, and also the valve (b) and the passage from VAC is opened. The vacuum now passes from VAC through the restriction drilling (n), on through the filter (f) to the respective vacuum unit. It is not possible to assure a constant vacuum supply because of the permanently varying control current in the coil.