Location
W55.90-1109-08
5 | Hydraulic motor (right) | 6 | Hydraulic motor (left) |
The hydraulic motor (5) is mounted on the right side of vehicle and hydraulic motor (6) on the left side of vehicle, at each wheel hub.
Task
The hydraulic motors (5, 6) drive the front wheels. The hydraulic fluid volumetric flow required here is generated by the hydraulic pump.
The hydrostatic auxiliary drive must have been activated by the driver beforehand.
Body
W55.90-1126-09
Shown on left hydraulic motor (6) |
5 | Hydraulic motor (right) | 10 | Cam ring | 15 | Piston housing | ||
6 | Hydraulic motor (left) | 11 | O-ring | 16 | Wheel flange | ||
7 | Bolt | 12 | Bolt | 17 | Steering knuckle | ||
8 | Cover | 13 | Distributor | 18 | Split bearing shells | ||
9 | O-ring | 14 | O-rings |
The hydraulic motors (5, 6) here are so-called radial-piston motors, that are used as a wheel hub motor. The piston housing (15) is rigidly mounted through the gearing to the steering knuckle (17). The cam ring (10) is bolted to the wheel flange (16) and thereby firmly connected to the front wheel. The housing of the distributor (13) is bolted to the steering knuckle (17). The distributor (13) distributes the volumetric flow through oil holes to the individual radial pistons in the piston housing (15). The wheel flange (16) and the steering knuckle (17) are movably connected to each other through the wheel bearing. The hydrostatic actuated radial pistons in the piston housing (15) generate a rotation and thereby a torque on the cam ring (10). This rotational movement of the cam ring (10) is supported by the wheel bearing and transferred to the front wheel.
The piston housing (15) does not turn, the component that turns here is the cam ring (10).
Function
Freewheel switch position |
10 | Cam ring |
15 | Piston housing |
15.1 | Radial piston |
15.2 | Radial piston |
15.3 | Radial piston |
15.4 | Radial piston |
15.5 | Radial piston |
15.6 | Radial piston |
15.7 | Radial piston |
15.8 | Radial piston |
15.9 | Radial piston |
15.10 | Radial piston |
17 | Steering knuckle |
b1 | Control pressure |
e1 | Unpressurized |
W55.90-1097-76
The control line routes control pressure (b1) through the steering knuckle (17) between the piston housing (15) and the cam ring (10). The control pressure (b1) pushes the radial pistons (15.1 to 15.10) back into the piston housing (15) thereby preventing any contact between the radial pistons (15.1 to 15.10) and the cam ring (10). A volumetric flow is not introduced through the high-pressure lines.
This switch position reduces the friction in the hydraulic motors (5, 6) when the hydrostatic auxiliary drive is not active.
Forward drive switch position |
10 | Cam ring |
15 | Piston housing |
15.1 | Radial piston |
15.2 | Radial piston |
15.3 | Radial piston |
15.4 | Radial piston |
15.5 | Radial piston |
15.6 | Radial piston |
15.7 | Radial piston |
15.8 | Radial piston |
15.9 | Radial piston |
15.10 | Radial piston |
17 | Steering knuckle |
a1 | High pressure |
b1 | Control pressure |
e1 | Unpressurized |
W55.90-1127-76
The figure can only show one moment in time in the working cycle of the radial pistons (15.1 to 15.10). To ensure that drive is uniform 4 radial pistons (15.1 to 15.10) are always in the working cycle. With one turn of the cam ring (10) each of the radial pistons (15.1 to 15.10) runs through the complete working cycle 8 times. In the figure, the radial pistons (15.3, 15.4, 15.8, 15.9) are in the working cycle, the radial pistons (15.1, 15.2, 15.6, 15.7) are in the exhaust cycle and the radial pistons (15.1 to 15.10) are at the TDC. In this figure, none of the radial pistons (15.1 to 15.10) are in the BDC.
The volumetric flow is introduced through the high-pressure lines. The perforated plate in the hub (13) supplies high pressure (a1) through holes to the radial pistons (15.3, 15.4, 15.8, 15.9) whose rollers are in a downward incline in the cam ring (10). The radial pistons (15.3, 15.4, 15.8, 15.9) press their rollers up against the incline in the cam ring (10). The cam ring (10) turns away, transfers the rotational movement onto the front wheel and thereby onto the distributor (13).
When the rollers of the radial pistons (15.3, 15.8) reach the end of the incline in the cam ring (10) (BDC), the distributor (13) here then interrupts the high pressure (a1) and opens the oil duct control pressure (b1) to be able to eject the hydraulic fluid. At the same time, the radial pistons (15.5, 15.10) have high pressure (a1) applied to them through the distributor (13) which moves them into the working cycle. The radial pistons (15.1 and 15.6) are now close to TDC and therefore ready for the working cycle when the radial pistons (15.4, 15.9) reach the BDC. This working cycle is repeated by all the radial pistons (15.1 to 15.10) all the way round.
In the exhaust cycle the rotation of the cam ring (10) pushes back the corresponding radial pistons (15.1 to 15.10). The hydraulic fluid flows out of the pressure chamber into the return line. The figure shows the radial pistons (15.1, 15.2, 15.6, 15.7).
The forward or rearward drive of the front wheels is realized by a reversal of the flow direction for the volumetric flow in the hydraulic pump.
The high pressure (a1) of approx. 420 bar enables an output of approx. 40 kW per hydraulic motor (5, 6) to be reached. The maximum torque is approx. 12,000 Nm.
The rotational speed or torque of the front wheels is increased or lowered by the volumetric flow.