Greater flexibility in automatic transmissions thanks to the pendulum-slider oil pump

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Stuttgart, September 2011—MAHLE's patented controlled pendulum-slider oil pump has already proven itself in combustion engines. Depending on the control strategy and driving cycle, it alone reduces the CO2 emissions of a vehicle by three to four percent. When used in automatic transmissions, the controlled pump offers enormous advantages with respect to fuel efficiency and variable shifting and control strategies.

In the MAHLE pendulum-slider oil pump, pressure and volume flow are generated only as demand requires, reducing the required power consumption to a minimum. The main advantages over other controlled oil pumps, such as external-gear pumps and vane pumps, include:

  • Ability to withstand dirt (such as particles or soot)
  • High overall efficiency over the entire service life
  • Suitable for high rotational speeds
  • Various control strategies can be used, short adjustment and response time

The short adjustment times and control flexibility provide interesting potential in the increasingly popular automatic transmission. In contrast to applications in the combustion engine, the prominent controlling variable in automatic transmissions is not the oil pressure, but the required volume flow.

A simple type of control can be achieved by fitting a baffle on the outlet of the MAHLE pendulum-slider oil pump, which limits the volume flow to a maximum level. As soon as the volume flow of the pump exceeds the maximum flow rate at the baffle, the control valve shifts on the pump and the volume flow is reduced. Comparing a pendulum-slider oil pump that is thus actively controlled with a passively controlled vane pump, the two pumps almost have identical power consumption at an oil temperature of 30 degrees Celsius and low pressure. At greater systems pressures, the savings potential of the MAHLE pump increases significantly above approx. 2,000 rpm. At greater oil temperatures, the power consumption at all measured systems pressures above just 3,000 rpm is only half that of the competing pump, which can be attributed to the high volumetric efficiency of the pendulum-slider oil pump.

Bidynamic pressure pump
MAHLE has developed the pendulum-slider oil pump further into a bidynamic pressure pump. This pump uses the additional delivery chambers below the pendulums to build up a separate high-pressure delivery stage, which can be used for shifting automatic transmissions, for example. The main chamber, with greater volume flow (low-pressure delivery stage), serves for lubricating and cooling. The pressure build-up in the high-pressure chambers is achieved by pistons at the feet of the pendulum that seal off the delivery chambers more tightly than the conventionally shaped pendulum foot.

MAHLE has demonstrated the flawless function of this "double" oil pump in prototypes. The low-pressure stage delivers 20 liters of oil per minute, at a pressure of 10 bar, while the high-pressure stage delivers 2 liters of oil per minute at 60 bar. Thus, the bidynamic pump can excellently be used in hybrid drives, for example, and supply to separate oil circuits.

MAHLE's controlled pendulum-slider oil pump thus provides significant advantages when used with automatic transmissions, both with respect to further fuel savings, and by supporting variable shifting and control strategies. Its reliability and high efficiency over its entire service life has already been demonstrated millions of times over in applications as a lubricating oil pump in combustion engines.

The MAHLE Group is one of the 30 largest companies in the automotive supply industry worldwide. With its two business units Engine Systems and Components and Filtration and Engine Peripherals, MAHLE ranks among the top three systems suppliers worldwide for piston systems, cylinder components, as well as valve train, air management, and liquid management systems. MAHLE's industrial activities are combined in the Industry business unit. These include, among others, the areas of large engines, industrial filtration, as well as cooling and air conditioning systems. The Aftermarket business unit serves the independent parts market, supplying MAHLE products in original equipment quality. In 2010, the MAHLE Group generated sales of approximately EUR 5.3 billion; around 47,000 employees work at over 100 production plants and eight research and development centers.