ZF manages systems technology

ZF's Multitrac axle has high planetary ratios in the wheel ends for a compact differential design. Its limited-slip differential and operator-controlled differential lock/unlock system increase traction and mobility.

The ZF Group (Booth S-15421) is one of those companies that have been around about as long as the transportation industry. In its long history, it has supplied parts and technology to all of the Big Three: automotive, aerospace, and off-highway. It is today a 6.5 billion Euro ($5.8 billion, 2000 figure) company that is still entwined with transportation, and it is still around today because it has managed to evolve along with the industry.

The industry over time has moved up and down and sideways. What changes is the angle of movement. There are, after all, 360 ways to move from the center of a circle. At the center of ZF's off-highway (construction, agriculture, marine, etc.) circle are, officially, driveline technology and axle systems. Without undermining drivelines and axles, technology and systems are the keywords here, especially during a show as large and influential as CONEXPO. It has become increasingly difficult for suppliers—and not only because of the current economic downswing—to come to a show and announce, "Here's a new product." Much of this change has been because of the necessity of a systems engineering philosophy, a change in focus ZF made after experiencing low profits in the 1980s. Looking externally, the OEM became the company's most important customer, with ZF managing the progress of the entire driveline, from project planning to development, testing, manufacture, and assembly.

The steering cylinder in ZF's Multisteer axle is integrated in the axle body.

Like any company that has survived as long as it has, ZF will always have new products to showcase in a setting like CONEXPO, some for the aftermarket. However, because of collaborations with OEMs, a company's newest products often remain unseen by the average show-walker. But it is not possible to keep all "behind the curtain."

ZF spends between 4 and 5% of its yearly sales for research and development activities. Part of its attention has been directed toward driveline technology for wheeled excavators from 4 to 25 t (4.4 to 27.6 ton), including the development of hydrostatic-mechanical drives. Claiming to be the "leading manufacturer of drivetrains for wheeled excavators," ZF's package consists of Multisteer and Multitrac axles, a range of AVG and HL transmissions, and DR-series swing drives.

For crawler excavators, ZF offers the RLV series of track drives that combines a planetary transmission with a slow-speed hydrostatic motor.

The one-speed AVG 185 is used for wheeled excavators up to about 10 t (11 ton). Its speed is infinitely variable via an accelerator pedal. Produced in volume in five different ratios, the transmissions have an input speed of 4500 rpm at a max torque of 1250 N•m (920 lb•ft). The two-speed HL transmission is for larger excavators. Depending on the total ratio of the two gears, either the speed range or the tractive effort can be increased. With a top speed of about 35 km/h (22 mph), a ZF downshift inhibitor protects the transmissions and hydraulic motor from overspeeding. Depending on the type of excavator, the one- and two-speed transfer boxes can be mounted separately from the axle or flanged directly to the rigid axle.

Designed with finite element methods, the Multitrac (rigid axle) and Multisteer (steering axle) are available in seven configurations for wheeled excavators from 2.5 to 25 t (2.8 to 27.6 ton). Both axles were designed with a high planetary ratio in the wheel heads. Due to the lower ratio of the bevel gear set, a smaller ring can be used in the housing. The multi-disc brakes are integrated into the axles for protection against dust and dirt. In the Multisteer axle, the steering cylinder is integrated in the axle body and placed behind the axle. The symmetrical steering kinematics allow the same steering angle on both the left and right side. The two-speed planetary DR swing drives are for excavators from 13 to 25 t (14.3 to 27.6 ton).

ZF engineers have also developed a new drive system for tracked excavators that has been approved for production. The goals for the design of the new RLV system included a higher travel speed, better efficiency, and improved tractive effort. Engineers combined a specially designed planetary transmission with a slow-speed hydrostatic motor. The result was a travel speed up to 6 km/h (3.7 mph) with very low internal speeds. The concept allowed the integration of an automatic parking brake and brake-valve system. With a "major portion" of its design patented, the RLV-450 will be the first series transmission, followed by the RLV-350B and RLV-550.

The ZF ECOMIX PLM series of mixer drives are mounted on a pedestal with the output flange connecting directly to the mixing drum.

Higher power needs and tougher duty cycles have put increased demands on mixer-drum drives, of which ZF claims to hold 70% of the market. One of the products that ZF will present at the show is its new ZF ECOMIX PLM 7 and PLM 9 transmissions for truck mixers with a drum capacity up to 7 to 10 m³ (9.4 to 13.4 yd³). ZF engineers integrated a slow-speed hydraulic radial-piston motor and a rear-fitted planetary transmission into a complete drum drive together with filter, fan, and cable harness. The cooling system can also be integrated, or fitted at another location of the mixer frame for additional space. An electric motor and water pump can be installed separately. Like many other ZF systems, the transmission and motor share a common oil system to eliminate the risk of filling with the wrong lubricant. The transmission consists of only two housing halves, reducing the number of sealing points.

The displacement of the motors for the PLM 7 and PLM 9 is 1.08 and 1.45 L, respectively. The PLM 7 has an output torque of up to 42,000 N•m (31,000 lb•ft), and the PLM 9 up to 60,000 N•m (44,300 lb•ft). As an economic alternative to the PLM series and offering more "widely proven technology," ZF now offers the P-Series, comprised of a two-stage planetary gearbox and driven by an external hydraulic motor.

- Jean L. Broge

Poclain Hydraulics debuts skid-steer-loader motor

Poclain Hydraulics' new ML06 motor has 12 kg (26 lb) less mass than an equivalent MS motor, while delivering 330 rpm, nearly twice the speed.

Designed exclusively for use in skid-steer loaders using cam-lobe radial piston technology, Poclain Hydraulics (Booth S-13671) had its engineers design its new ML series motors from scratch to nearly double the speed of its MS series, but make it cheaper to the end customer. The first of the motors, the ML06, is designed to power the dual-chain drive to the two wheels of each side of a loader with operating capacities from 770 to 1180 kg (1700 to 2600 lb).

The ML06 incorporates patented Soft-Shift two-speed technology that softens the shifting of the transmission and does not require additional equipment beyond standard two-speed-motor design. The high-speed range sends a hydraulic pilot signal to the speed selector port integral to the motor. The shift mechanism is completely internal to the motor. The downshift from high to low speed is cushioned for smoother driving. The speed ratio of the two-speed motor is optimized between 1.5:1 and 1.7:1, which corresponds to typical working speed of 11-13 km/h (7-8 mph) and travel speeds to 22 km/h (14 mph).

At 0.63 L and 278 kPa (5800 psi), the ML06 is 330-mm (13-in) long from rear cover to shaft end. All porting is arranged to accommodate flexible hosing connections. Its construction includes two speeds, a spring-applied hydraulically released brake, and dual-sprocket output shaft. The integral dual-sprocket output shaft reduces the number of assembly components and the overall shaft size. With a smaller width required for the sprocket assembly, the chaincase width can be reduced to increase space availability in the engine compartment. According to Poclain, when compared to sprockets mounted onto splined output shafts, the one-piece forged shaft of the ML06 provides a smaller diameter sprocket profile for increased chain reduction to the driven sprockets, thus increased torque output at the wheels. The motor is available with a variety of sprocket configurations that accommodate multiple chain sizes and chain-reduction ratios for various OEM applications.

The distribution valving of the motor is plate-style and pressure-biased. The pistons in the cylinder block are equipped with what Poclain describes as "automotive-style" piston rings, which compensate for piston-bore wear by expanding and maintaining low motor internal leakage. The company claims that the radial-piston design of the motor eliminates the high-pitched whine associated with gearboxes operating at high speeds. The internal parts also move at up to 1/20th the speed of a high-speed motor, allowing the indirect noise generated by hydraulic oil turbulence to be reduced.

The ML06 was designed with both hot- and cold-weather applications in mind. A dedicated-valve design reduces temperature levels in the hydraulic circuit in hot weather and during high-speed vehicle operation. For cold-weather operation, an integral hot-oil-exchange valve sends oil to the cooler while eliminating valve shifting out of synch, common to standard "shuttle-valve" designs, according to Poclain.

The ML06 was tested at Poclain's proving grounds in Verberie, France, and will be manufactured at the company's facility in Sturtevant, WI.

- Jean L. Broge