Driver, maintenance issues shape new designs

Driver comfort and low maintenance requirements are the forces driving contemporary clutch design. The industry continues to develop models for improved clutch action and feel. Also, in keeping with the trend for increased engine-horsepower ranges and falling peak-torque engine speeds, clutch manufacturers have moved toward the use of soft spring rate damper discs to prevent torsional vibrations and extend the life of driveline components.

Sales of the newer generation of self-adjusting clutches, and the even more recently released maintenance-free clutches, are also taking off as fleet managers strive to reduce vehicle downtime and labor costs.

Proper adjustment and lubrication, according to Eaton Clutch Div., is the key to maximizing clutch life. Since some fleets prefer to perform their own maintenance, Eaton offers a choice in products, including 14- and 15.5-in. Easy-Pedal, and adjustment-free Eaton Fuller Solo models.

Last year, Eaton unveiled a new generation of medium- and heavy-duty Solo clutches that not only are self-adjusting, but also require no lubrication, making the Angle-Spring, pull-type clutches truly maintenance-free.

Solo 15.5-in. adjustment-free clutches with extended lube option use Eaton's "soft-rate" seven-spring design and V.C.T. (Vibration Control Technology). For medium-duty trucks, the "soft-rate" damper now has a maximum torque rating of 1,150 lb.-ft., enabling higher-horsepower engines to use the option instead of upgrading to a 15.5-in. heavy-duty cast iron product.

Eaton's plans for the future are to further integrate the clutch and transmission as a system, especially as automated transmissions gain in popularity.

Haldex Brake Systems supplies a wide range of 13-, 14-, and 15-in. push- and pull-type, single- and two-plate clutch assemblies. Following the industry's example, the company is currently adapting its 15/380 clutch system to include long-turn dampening centers. The DLPS (Drive Line Protection System) clutch for Class 8 trucks will have a capacity rating up to 2,200 lb.-ft. of torque and will be introduced by the end of this year.

The DLPS pull-type clutch is unique in its design, especially in the disc assembly, where Haldex has sintered ceramic-type buttons directly on the clutch disc carrier. The result is 18% more area, which translates into improved mileage, better clutch engagement qualities, and less wear.

The unit also features Haldex's proven direct-pressure stamped cover with no internal adjustment. Adjustment is required at the sleeve assembly only. DLPS models will have the same installation parameters as Haldex's existing group of 15-in. clutches.

Meritor Automotive also offers a comprehensive clutch line, which includes diaphragm-spring, two-plate, pull-type clutches available in 14- and 15.5-in. sizes with ceramic or molded organic facings.

The newest product in Meritor's lineup is the AutoJust clutch, a self-adjusting clutch designed to eliminate periodic wear adjustments. AutoJust also provides fleets a simplified means of checking remaining clutch life with wear sensors located in four quadrants instead of just one.

To minimize torsional vibrations in higher-horsepower engines, Meritor manufactures a seven-spring Long Travel Damper (LTD) clutch disc for torque capacities up to 1,860 lb.-ft. For even larger engines (up to 600 hp.), Meritor offers the Lite Pedal clutch with a torque capacity rating of 2,050-lb.-ft.

Valeo Clutches & Transmissions manufactures a range of single-plate diaphragm-spring clutches, including 13-in. push-type and 14-in. pull-type models for medium-duty trucks as well as 16-in. and 17-in. pull-type clutches for heavy-duty vehicles. The 16- and 17-in. heavy-duty clutches are standard with Valeo's GD long travel "soft rate" damper.

The advantages of Valeo's thicker, single-plate design are improved clutch engagement and disengagement, and better heat dissipation, which reduces the chance for warping - a major cause of clutch drag and subsequent shifting problems.

To help simplify maintenance, Valeo has designed its clutches so that adjustment is done at the release bearing, not the clutch itself; the procedure requires only one person.

New for Valeo is a 17-in. self-adjusting clutch, which is being tested and going into production in Europe. It's also being considered for opportunities in North America.