Axial Piston Pumps have compact design.

Press Release Summary:

Suited for demanding applications and control of working equipment, variable displacement axial piston pumps feature aluminum alloy casing and taper roller bearing used to accommodate thrust load. To accommodate radial load, products utilize CARB toroidal roller bearing type: C 2207 TN9/C3 lubricated by complete oil immersion. Bearing is self-aligning and accommodates misalignment between shaft and housing. Speed is rated to 2,500 rpm.

Original Press Release:

Increasing the Power Density in Axial Piston Pumps

Bosch Rexroth AG situated in Germany, a member of the Bosch Group, is a leading supplier of industrial motion and control components and services. Compact size and high power density, economy and reliability are characteristic advantages for their hydrostatic transmissions, together with the fact that the products meet the demand for high speed and high torque, as well as optimum efficiency.

The application

Rexroth axial piston pumps are designed for demanding applications and easy control of working equipment, e.g. loading cranes, generator drives, compressor drives, drives for air conditioning systems, fan drives, etc.

The latest generation of Rexroth variable displacement axial piston pumps is suitable for various branches. For mobile equipment pumps, low weight and high power density are particularly important. The casing is therefore made of aluminium alloy.

The rated power per weight unit for the Rexroth variable displacement axial piston pump series is presently unmatched in the mobile hydraulic pump market.

In conventional bearing arrangements a taper roller bearing is used for accommodating thrust load and a cylindrical roller bearing, close to the drive-end of the shaft, for accommodating radial load. However, analysis showed that the cylindrical roller bearing would be exposed to misalignment, due to unavoidable deflections, which could shorten bearing service life. To obtain the full service life using this bearing type, the housing would have to be made stronger and heavier which would have added to the cost as well as creating a lower power density and higher fuel consumption.

The solution

To overcome this problem SKF engineers replaced the cylindrical roller bearing with a CARB toroidal roller bearing type: C 2207 TN9/C3. This bearing is housed in an aluminium alloy housing and is lubricated by complete oil immersion. Speed is up to 2,500 r/min. The bearing is self-aligning and accommodates misalignment between the shaft and housing without any reduction in bearing service life.

The benefits

Three other benefits from using an SKF CARB bearing were:

o Cost savings by letting the bearing "absorb" the deflections rather than providing stiffening through modified design

o The high real radial load carrying capacity enabled high power density design of the pump which in turn gave a reduction in "build-in" space

o Reduced fuel consumption and increased vehicle payload, as a consequence of the lightweight design that lets the bearing accommodate any deflections

Field experience with the new bearing arrangement is very good and the pump unit meets the long service life requirements set by Bosch Rexroth AG.

For further information please contact your local SKF sales office, the following websites or

Colin T. Roberts
SKF Group Technical Press

About SKF:

SKF is the leading global supplier in the rolling bearing business. It is evolving into a knowledge engineering company supplying many different industries with products and solutions based on one or more of the following technologies; rolling bearings, seals, mechatronics, lubrication systems, and services such as engineering consultancy and plant asset reliability optimisation

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