Cost effective thanks to high power
density and high efficiency

High speed QXM internal gear motors for fan,
blower and compressor drives in mobile machines

By no means just ‘field, forest and meadow technology’, but instead perfectly designed to fulfil the requirements of modern machines – that describes the QXM series of internal gear motors. Technologically innovative and already field tested, these internal gear motors deliver very high overall efficiencies over a wide speed range. In addition, they offer excellent startup performance and operate quietly. These factors are the ideal prerequisites for application in the fan, blower and compressor drives of mobile machines.

For several years the QXM42 high-speed motor has been used with the greatest success for saw drives in forestry harvesters. In this application, it runs at speeds of up to 10,000 rpm and impresses users with its high efficiency and long service life. The QXM42 high-speed motor is supplied with displacements of 20, 25 or 32 cm³/rev. In comparison with the hydraulic motors previously employed, the use of internal gear technology has yielded increased machine operating hours and decreased fuel consumption. These positive experiences provided the impulse for the development of other internal gear motors for mobile machines.

With the QXM12 and QXM22, two smaller motors with displacements of between 3 and 8 cm³/rev are now available. Running at speeds of up to 6,000 rpm, these small motors prove that they can deliver high power levels. The motors achieve a hydro-mechanical efficiency of 92% at pressures up to 180 bar. Acceleration from 0 to 6,000 rpm in 100 ms can be achieved. With a weight of just 3 kg, the internal gear motor thus has a power/weight ratio similar to that of a Formula 1 racing car.

Technical refinements reduce operating costs

Intelligent and sustainable production is becoming increasingly important in agriculture. Demands for energy-saving and environmentally friendly concepts are satisfied by the technical refinements of the internal gear motors. In particular, comparisons with the drive technologies that are conventionally applied, such as external gear and piston motors, come out clearly in favour of the QXM concept. Efficiency, startup behaviour, operational safety and noise levels are at the forefront in such comparisons.

The design of the internal gear motors enables the flow in the inlet and outlet areas to be guided in the direction of motion of the gear set. There is therefore no radial impact of the oil flow such as occurs with external gear motors, so turbulence and flow losses are significantly lower. Compared to axial piston units, no displacement elements are accelerated and decelerated during each revolution. Both of these effects have a positive influence, particularly in the upper speed range, and are one reason for the significantly higher hydro-mechanical efficiency of the QXM.

Quiet running, good startup behaviour
and long service life

Pulsation and the associated noise generated by the drive unit are another important issue. The recommended applications such as fan, blower and compressor drives can operate very quietly with motors from the QXM12 and QXM22 ranges. The reduced noise generation is the result of the long pressure build-up region along the crescent, a large-diameter pinion for slow opening and displacement, and special gear-tooth profiling to ensure low torque fluctuations. To sum up, less pulsation is created and the motor runs more quietly. In addition, the motor starts smoothly because the rotating components of pinion and ring gear can move freely in the non-compensated chamber system. Thus, the subject of unwanted stick-slip effects does not even arise, which makes the startup behaviour of the QXM clearly superior when compared with external gear or axial piston motors.

The sophisticated QXM motor concept impresses not only with its design details but also with the operational reliability of the range. The motors consist of just a few components that are made of high-strength materials. This makes it extremely sturdy right from the start. While continuous high speeds of more than 3,000 rpm are problematic for other motors, the QXM is just getting into its stride. Field experience has shown that, in spite of the high working speed of 6,000 rpm, these motors achieve significantly higher levels of reliability and a longer service life. The basis for this is the forced lubrication of the hydrodynamic plain bearings in the non-compensated system, which virtually excludes any possibility of thermal overload of the lubricating film. In addition, the QXM motor is equipped with an integral roller bearing in the vicinity of the shaft sealing ring. This provides the optimum axial and radial shaft guidance for absorbing external forces from fans or blowers, and at the same time it prevents the QXM motor shaft from vibrating, which in turn increases the protection against external leakage.

 
Application examples

• Radiator fan drives in tractors and forestry harvesters

• Radiator fan drives in self-propelled harvesters

• Radiator fan drives in construction machines

• Blower and grain-distribution spinner drives in sowers

• Compressor drives for air-conditioning systems in road-building machines

• Blower drives for road sweepers

The merits of the QXM range are particularly desirable in these applications because the motors meet the need for demand-regulated, and therefore efficient and economic, operation. And in the case of radiator fan drives for diesel engines, QXM motors of course support compliance with the existing emissions regulations as specified in Interim Tier 4 and with the Final Tier, Stage IV that comes into force in 2014.

QXM benefits at a glance

• Ideally suited for high-speed operation

• Extremely high power density

• Energy savings thanks to outstanding efficiencies

• Long service life even with the most unfavorable operating
  conditions and at maximum speeds

• Minimal noise level