Simplicity and Strength
In conventional one-way clutches on the market today (sprag and roller clutches), the lock-up function relies upon a wedging action of several small sprags/rollers between an inner and outer race. The precision of this event requires highly accurate machined surfaces be used for each of the components. In addition, this lockup configuration induces a high ratio of radial forces in order to transmit the required tangential force or useful torque (see diagram). The resulting radial forces create high surface stresses at each contact point and hoop stresses in both races, requiring all the materials to be hardened and relatively free of defects.
Conventional Roller Clutch
Conventional Sprag Clutch
Alternatively, the Means Mechanical Diode uses rectangular 'struts' that engage precisely in the direction of the torque load. Since the struts are oriented to hold the load more directly, you need very few of them to engage at once - in fact only one in most applications and never more than two. This means lower contact loads and virtually no hoop stresses. The final result: you have a clutch with fewer pieces, can be designed to handle higher loads, can be built out of lower strength materials, tolerates higher surface variation and therefore lends itself to a still unexplored level of design variations and manufacturing techniques.
Means Mechanical Diode
Designed for Speed
The Mechanical Diode's performance advantages are not limited to its strength in lock-up conditions. In fact, with the relatively small number of components, well-developed part geometries, and sufficient oil flow the Mechanical Diode can withstand higher overrun speeds for longer durations than the corresponding roller/sprag clutch designs which are susceptible to vibration and instability. This ability is due to the oil that the clutch naturally pumps through its internal geometry. This keeps a boundary layer of oil between each of the components and stabilizes the entire system. This effect becomes more pronounced at higher overrun speeds thereby allowing the clutch to run at a very high rpm. A secondary effect of the oil utilization is less free-wheel drag and consequently improved transmission efficiency.
Early applications of the Mechanical Diode were drop-in black box replacements of conventional one-way clutches in order to solve warranty issues, realize marginal cost savings, reduce rotational mass, and/or reduce drag force. Later applications were identified earlier in the design cycle where the Mechanical Diode could be designed directly into the application and therefore realize additional benefits of reduced design envelopes, additional design flexibility, incorporation directly into other neighboring components, and to meet higher demands placed on transmissions in trucks, high-performance cars and sports utility vehicles.
Today we are exploring how the technology can be adapted to torque converters, differentials, and a number of other applications outside of the automotive industry.
Although the Means Mechanical Diode has established itself as a proven technology over the past two decades, it is still a relatively new technology that continues to advance - especially in comparison to the matured technologies of the sprag and roller clutches that have been around for over 50 and 100 years respectively. Means is finding ways to integrate the Mechanical Diode with its other technologies and deliver full module packs to its customers. We are also adding more innovative functions to the clutch, such as the selectivity switch of the Controllable Mechanical Diode.
With so many great ideas and opportunities for this product, it may hold the solution to your biggest design challenges. Feel free to contact our dedicated MD Clutch Department to discuss your particular application or setup a visit to tour our facilities in person. We look forward to hearing from you soon!
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