chapter  7
94 Pages

Mechatronic Driveline Systems

The definitions of simple, combined, and integrated driveline systems were given in Section 1.2 (see Figure 1.34). Power-dividing units (PDUs) and driveline systems as a whole that are purely mechanical systems were analyzed in the previous chapters. Mechatronic driveline systems are a new direction in the application of mechatronics to the development of automotive systems. Several examples of mechatronic systems were given in Table 1.17. This chapter examines the sources and causes for the appearance of mechatronic systems and the principal directions of their development. This will clarify the need for the separate consideration of mechatronic systems and the structure and content of the subsequent sections of this chapter. It is commonly assumed that the beginning of the era of electronics and electronic control

systems that started making their way into all domains of economic activity, including the automotive industry, was in the 1950s. The most active application of electromechanical and electronic devices for controlling work processes of individual units and systems of ground vehicles, including cars, trucks, and buses started in the second half of the 1980s. As the different electromechanical (hydraulic and pneumatic) systems started developing, it became obvious that (i) the development of mechanical and electrical=electronic subsystems must be based on new principles that would lead to the creation of designs in which each of the subsystems would ensure conformance to the functioning requirements of the other subsystems, and (ii) different vehicular systems cannot ensure better vehicle performance if they do not interact with one another. Item (i) can be clarified by reference to the requirement of zero-lateral-gap meshing of

gears (no backlash) that are used in systems with electronic control. Another example may consist of magneto-rheological and electro-rheological fluids that are only recently coming into use in vehicular systems but give rise to a long series of new requirements to the design of mechanical subsystems. The appearance of these requirements and their actual implementation brought about continually new engineering solutions of mechanical subsystems that ensure the mechanical isolation of such fluids, the prevention of chemical interaction with the surfaces of the surrounding parts while at the same time retaining the properties of the fluids, and ensuring the functional properties of the entire system. It may be stated with sufficient justification that the mutual entry and the combination

of the principles of the design of mechanical, electrical, and electronic units and systems has resulted in the appearance of mechatronics, a science that integrates the above scientific disciplines and further develops each one in combination with the others.

This was facilitated by the development of computer science, and information and electronic technologies. In explaining item (ii), various protocols (e.g., the CAN Protocol) that were developed in

order to ensure and coordinate the functioning of the vehicle’s systems can be pointed out. Electronic differential locking devices started appearing during the 1970s and 1980s.

Locking in these designs was usually triggered by detecting differences in the angular velocities of the wheels and unlocking-after some time had elapsed. Gradually, the control of a single differential was replaced by the control of interaxial and interwheel coupling units. Table 7.1 presents examples of driveline systems of 4 2 and 4 4 vehicles and the designations of these systems given by their manufacturers. These systems came to be known in the engineering literature as ‘‘torque vectoring’’ and

‘‘torque management.’’ As an illustration, consider one of the designs of the 4MATIC system by A. Zomotor et al. (1986) that has been in use since the 1980s. The schematic diagram of this system is shown in Figure 7.1. It is comprised of a transfer case with asymmetrical spur gear interaxle differential 3

(the gear ratio of the mechanism is 65=35 1.86). Its crown gear is coupled to engine 1, its carrier to rear-axle differential 8, and its sun gear to front-axle differential 2. The interaxle differential is equipped with a normally engaged locking friction clutch that couples the differential’s carrier to the hollow shaft of its sun gear. This friction clutch is locked and unlocked by hydraulic power cylinder 4. The interaxle differential is also equipped with a front-axle drive friction clutch. It is locked and unlocked by hydraulic power cylinder 5. The rear-axle differential includes two multidisk friction clutches that are compressed, under certain conditions, by hydraulic cylinders 6 and 7. The operation of hydraulic cylinders 4 through 7 is controlled by an electronic system consisting of a microprocessor 13 with an additional memory device. The microprocessor, with induction sensors 9 and 10 of the rear-wheel rpm and induction sensors 11 and 12 of the front-wheel rpm and