autoregion international 2/2020 - Greater Region Mobility Innovation

18 One-Way Clutch for Hybrid and Electric Vehicles By Dr. Friedrich Brezger, Advanced Product Engineering, BorgWarner in Ketsch and Alexander Moser, Supervisor Advanced Product Engineering, BorgWarner in Ketsch BorgWarner‘s Multi Mode Clutch Module (MMCM) offers an advanced shifting solution for the growing hybrid and electric vehicle market. This shiftable form-locked one-way-clutch offers clockwise or counter-clockwise modes, both locked and free, which are designed to meet the needs of today‘s high-efficiency vehicle propul- sion systems. Introduction & Function Clutch systems, such as the dog or friction clutch, have been used in transmissions for many years. The friction clutch provides slip with high control when used in start-up of dual clutch transmissions, while also enabling the damping of combustion engine vibrations by allowing continuous slip. The dog clutch offers the benefit of virtually no drag torque in the disengaged mode as well as naturally bistability. The MMCM synergizes the big ad- vantages of single direction synchronization with high efficiency by having practically no drag torque and maintaining bistability. BorgWarner has developed this technology to provide enhanced performance over tra- ditional clutch systems. This shiftable pawl clutch is comprised of both an Outer and Inner Race, Pawls and a Cam. The Pawls (see Figure 1) allow the MMCM to operate as a One-Way Clutch (OWC) with a passive shift where it automatically switches to the opposite mode, either overrun or block. The Cam is used to control the Pawls’ movement, allowing up to 4modes to be employed: OWC clockwise, OWC counter clockwise, block and free. Clutch Comparisons BorgWarner, who pioneered the develop- ment of one-way clutches decades ago, cur- rently manufactures all three types of the one-way clutch including the sprag clutch, roller clutch and pawl clutch (see Figure 2). The Sector Clutch uses a solenoid as actua- tor and is comprised of the Pawls, actuation bar and a position sensor to track the Pawls’ position. The Sector Clutch assembly nests its electro-mechanical actuator in an egg-shaped design. Since only a small area for a box in one radial direction is needed, this clutch system requires less space around the circumference as compared to the MMCM. MMCM Transmission Applications There are many potential benefits to the use of a shiftable transmission in electric vehicles. These include system efficiency, range, total Images/Graphics: © BorgWarner Figure 1: The Multi Mode Clutch Module (MMCM) features four modes – OWC counter clockwise, free and locked, and OWC clockwise – with a rotating Cam to switch between modes. S H A R E