Design and function of tandem pump - RA4600FBL0060X(46-0060)

Designation plate (Vickers/Luk) 

Fig 1: Identifying Tandem Pump Designation Plate (Vickers/Luk)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Tandem pump model 

Fig 2: Description Of Tandem Pump Designation Plate Numbers (Vickers/Luk)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Designation plate (Zahnradfabrik Friedrichshafen) 

Fig 3: Identifying Tandem Pump Designation Plate (Zahnradfabrik Friedrichshafen)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Tandem pump model 

Fig 4: Description Of Tandem Pump Designation Plate Numbers (Zahnradfabrik Friedrichshafen)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The tandem pump is driven as in the case of the power steering pump via a poly V-belt. An automatic retensioner ensures an even preload on the poly-V belt.

Fig 5: Identifying Tandem Pump Drive, Line Routing

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The poly V-belt pulley (48) is secured to the drive shaft flange with three hexagon bolts (48a).

Fig 6: Identifying Poly V-Belt Pulley (48) And Drive Shaft Flange Bolts (48A)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 7: Identifying Tandem Pump Components

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Both systems are driven by the same drive shaft (3).

The servo system corresponds to the power steering pump in terms of drive, design and function (vane-type pump).

The radial piston pump for the level control, ASD, ADS and 4MATIC systems is driven via the eccentric section (4). The piston (5) is shifted into a stroke motion by the eccentric.

The eccentric (4) of the radial piston pump is connected to the drive shaft (3) via the shear pin (8) which shears in the event of overload. The vane-type pump for the power steering continues to remain operative in this event.

Two different flow rates are achieved using the minimum of space by means of two independent systems.

Steering gear oil is used for the servo circuit in the case of power steering; by contrast the radial piston pump works with hydraulic fluid.

Sealing 

The complete pump assembly is sealed by O-rings.

Sealing the drive shaft (3) and the separation of both systems is achieved by double-lipped radial sealing rings (11, 14).

Line routing 

The line routing and location of the servo circuit is the same as for the power steering pump. The radial piston pump is supplied with hydraulic fluid from a separate reservoir (2) via the hose line (A).

Fig 8: Identifying Reservoir (2) And Hose Line (A)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The pressure line (P) supplies the individual systems depending on the vehicle equipment - ASD, ADS, 4MATIC and level control - with a maximum oil pressure up to 150 bar.

Location M 104

Fig 9: Identifying Pressure Line, Pressure Oil Pump/Level Controller And Oil Reservoir

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 10: Identifying Oil Delivery Of Radial Piston Pump

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The spring-loaded pistons (5) more axially due to rotation of the eccentric drive shaft (3). With the travel of the piston to the lower dead-center position, a vacuum is created due to the increase in volume in the piston chamber. This causes the oil to flow in through the transverse bores in the piston which connects the cylinder chamber to the inlet side shortly before the lower dead-center position. On the power stroke the full cylinder chamber is sealed due to the overlapping of the bores shortly after the lower dead-center position.

Oil is pushed out to the pressure side via spring loaded exhaust valves.

Constant oil flow at variable speed is achieved by suction control. As speed increases, the opening time of the transverse bores in the piston is reduced so that the suction vacuum is no longer adequate to completely fill the cylinder chamber in the short time interval. The decreasing partial filling has the effect of keeping the flow rate as well as the required power almost constant as speed increases.

The pressure of the radial piston pump is limited by pressure relief valves in the control units of the connected systems (ASD, ADS, 4MATIC and level control). A performance and pressure test must not therefore be performed directly on the radial piston pump section of the tandem pump.