VPD Variable Power Divider

Independent speed.  Buzzword: VPD. Variable Power Divider

 

General information

The motivation. Speedometer, tachometer, clutch, gear shift: in conventional manual transmissions vehicle speed and engine speed are coupled. We sought solutions that enable adapting speed without depending on motor speed – and rapid shifting: VPD transforms a drive with gear shift into an continuously variable  system.

The principle. VPD is a hydrostatic-mechanical power-split transmission. It is installed between a diesel engine and a conventional automatic or manual transmission and splits the drive power between auxiliary drive and vehicle drive. In work mode the auxiliary drive is directly coupled to the engine. Output speed to the vehicle transmission is adopted steplessly in the power superposition system.

The benefit. VPD drivers can immediately adapt their speed – regardless of enigne speed. This is the ideal solution for municipal and cleaning vehicles as well as for airport fire-fighting vehicles.

Applications

Each power class is a class of its own. Buzzword: challenge.

The VPD transmission is suited for municipal applications, street-sweeping and cleaning vehicles and fire-fighting vehicles in pump-and-roll operation, where using the fire-fighting pump in combination with controlled vehicle motion is a particular challenge.

Street sweeper

VPD 2500 front view

VPD 2500 rear view

Airport fire-fighting vehicle

VPD 4000 direct mount

VPD 4000 remote mount






Figure: Transmission schema VPD

Technical description

Special solutions for special challenges.  VPD in Modus 2.


Functional description of VPD power-split transmission.

Core principle. A planetary transmission enables variably setting the rotational speed ratio between transmission input and transmission output shaft within defined spreads. This functionality converts a conventional drive train with stepped translation ratios to an infinitely variable (stepless) drive train.

The functional principle of VPD power split in pictures:

speed diagram

power flow




Operating mode. VPD transmission has two distinct functional modes:

Mode 1: In normal operation the PTO drive train is shut off; the translation ratio between the diesel engine and the main transmission in the VPD transmission is set to 1. Driving and shifting is the same as for a vehicle without a VPD transmission.

Mode 2: In work mode the diesel engine is regulated to the required rotational speed for adding the auxiliary drive and die PTO clutch is closed. In the VPD transmission the change in diesel engine speed can be compensated for in the realm of available power limits; driving operation of the vehicle remains fully functional after activating the auxiliary drive.
After activation of the auxiliary load, the diesel engine is accelerated to the required rotational speed. Auxiliary aggregates such as pumps and ventilators run in the required operating ranges.

Electronic controls. From activation of the auxiliary load and setting of the diesel RPM to the required value, the electronic controls of the VPD transmission take over control of the translation ratio between the diesel engine and the input shaft of the vehicle drive. The driver simply enters the target speed via the gas pedal or speed control.

Free of friction and wear. VPD transmission adapts the rotational speed to the vehicle drive based on the setpoint – wear-free because there is no friction clutch. Thus vehicle speed can be adapted to requirements permanently without the danger of overheating.  



VPD transmission is available in two power classes:

VPD2500. Designed for use in municipal and cleaning vehicles, available as sandwich or direct-mount version.

VPD 2500 - Sweeper

   
Rated input speed 2600 rpm
Maximum input torque 800 Nm
Rated input power 180 kW
T/M Ratios 2,23 to 1.01
PTO Ratio 0,71
PTO Power  120 kW
Flange to Engine SAE 3
Flange to Transmission (direct mount) SAE 3


VPD4000.
Designed for use in airport fire-fighting vehicles (crash trucks or ARFF vehicles)

VPD 4000 - Crash Truck

   
Rated input speed 2100 rpm
Maximum input torque 3200 Nm
Rated input power 600 kW
T/M Ratios 1,8 to 0,71
PTO Ratio 0,49
PTO Power  300 kW
Flange to Engine SAE 1
Flange to Transmission (direct mount) SAE 1


Figure: VPD transmission schema

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