The world innovation of the ZF Group, the TraXon automatic commercial vehicle transmission, excels with its numerous technological innovations and a modular construction kit of drive elements. The complete system and its individual components have been developed for sustainability. Thus, also the single and twin disc clutches represent the latest state of the art: They are adjusted to engines that comply with the latest Euro 6 exhaust emission standard and meet the trend towards diesel units with lower operating speeds. Besides that, the clutches feature low wear and thus facilitate economic commercial vehicle maintenance. The ConAct pneumatic release cylinder that is integrated in the TraXon as standard also contributes to that.
Due to their functions, the clutches are direct subjects to the impacting driving powers. This basic rule also applies to an automatic commercial vehicle transmission such as the ZF TraXon, where the engaging and disengaging processes are performed electromechanically or pneumatically - independent of the driver - therefore, they are very short and precise. For the new TraXon automatic transmission system, ZF has also revised the range of available dry clutches.
The product range of available single and twin disc clutches – for high-torque applications – covers a wide application range up to 2,950 lb-ft (4,000 newton meters) of engine torque to be transmitted and is thus well prepared for future requirements.
The clutch, consisting of the clutch disc with torsional damper and facings, the clutch cover, and the ConAct release cylinder, represents a system within the system. In case of the single and twin disc clutches for the TraXon automatic transmission system, ZF brings some innovations onto the market, also in this classic drive-off element category.
In this context, new torsional dampers are used which meet the requirements of the trend towards higher engine torques in combination with lower operating speeds. In fact, fuel consumption can be cut by reducing the operating speed in highway traffic, but at the same time, the vibration load at the interface between engine and transmission increases. ZF will use new torsional dampers with lower spring rates for its dry clutches in future and that way, the company can compensate for the significantly higher stress on the torsional dampers during operation with high torques and reduced speed. Thanks to the very robust construction, this goal could be achieved without having to increase the stiffness in the clutch disc. This would have led to worse NVH (noise, vibration, harshness) characteristics of the complete driveline.
In an automated transmission system for commercial vehicles, the control electronics takes over the control of the engaging and disengaging processes as well as the gear changes. These are then performed by mainly pneumatic actuators. By using the ConAct pneumatic clutch cylinder, ZF brings an especially powerful actuator for clutch actuation into operation. As a result of the concentric construction and its coaxial arrangement in relation to the transmission input shaft, it offers not only advantages regarding installation length and weight, but also reduces the number of system components required. The ConAct release cylinder shows significant advantages also with regard to its functions when it comes to clutch service life and sensitiveness of the clutch control mechanism - compared to the systems previously used in automated transmissions.