Propulsion Systems

Engineering Solutions

Driven by the need to improve fuel economy, today’s powertrain requirements are increasingly complex. For more than twenty years, Means has focused on leading the research, development, and manufacturing of advanced mechanical and electro-mechanical clutch systems. As a result, more than 30 million Means clutches can be found in the field.

Means’ commitment to innovation has positioned it as an industry leader in powertrain solutions. In fact, Means Controllable Mechanical Diode (CMD) will be the world’s first production Selectable One-Way clutch, a technology that offers OEM transmission manufacturers a solution that will reduce system mass, improve driveline efficiency, and offer packaging and design flexibility.

Modal Operation

Our Clutch System business unit began with our Mechanical Diode (MD) product-line, however, our technology has evolved to allow for multi-modal controllability. Our CMD (Controllable Mechanical Diode) Selectable One-Way Clutch can be configured into numerous modal combinations including one or all of the different modes below. This capability is fully dependent on an OEM’s system needs and specifications. 

 

MODE CLUTCH FUNCTION DESCRIPTION

A

One-Way Clutch - Clockwise

Overrun in Clockwise direction, locked in the Counter-Clockwise direction

B

One-Way Clutch - Counter Clockwise

Overrun in Counter - Clockwise direction, locked in the Clockwise other direction

C

Locked Clutch

Clutch Cannot Move in Either Direction

D

Open Clutch

Clutch Moves Freely in both Directions

 The assembled clutch, individual components, and modal functions as controlled by the clutches struts and slide plate.

Clutch including modes A, B, and D

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CMD - Selectable One Way Clutch – Components
CMD – Components

There are 3 primary CMD Components: The Selector Plate to the left, the Notch Plate in the center, and the Pocket Plate to the right.

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CMD – Selectable One Way Clutch – Pocket Plate
CMD – Pocket Plate

The CMD Pocket Plate carries 2 additional critical components – struts and springs.  The T-shaped struts, and the springs that sit in the pockets underneath of the struts, are the foundation of our Mechanical Diode OWC design. 

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CMD – Selectable One Way Clutch – Selector Plate
CMD – Selector Plate

The CMD Selector Plate is what controls our Selectable One-Way Clutch, and shifts the clutch interchangeably from modes A, B, and D. The shift is enacted by a tangential force applied to the lever attached to the clutch. 

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CMD – Selectable One Way Clutch – Notch Plate
CMD – Notch Plate

The Notch Plate carries torque from the Pocket Plate through the struts. The direction of the torque depends on what mode the has been selected. 

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CMD – Selectable One Way Clutch – Selector in Reverse
CMD – Selector Plate in Reverse Position

This example illustrates the Selector Plate function in the reverse position. The Selector Plate has covered the forward struts, which creates OWC functionality – locking in the counterclockwise direction and overrunning in the clockwise direction. 

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CMD – Selectable One Way Clutch – Selector in Neutral
CMD – Selector Plate in Neutral Position

This example illustrates the Selector Plate function in the neutral position. The Selector Plate has covered both forward and reverse struts, which creates overrun functionality in both directions.

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CMD – Selectable One Way Clutch – Selector in Forward
CMD – Selector Plate in Forward Position

This example illustrates the Selector Plate function in the forward position. The Selector Plate has covered the reverse struts, which creates OWC functionality – locking in the clockwise direction and overrunning in the counterclockwise direction.

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CMD – Selectable One Way Clutch – Forward Selection
CMD – Forward Selection

This image illustrates a CMD with a Forward mode selection. The modal selection requires less than 20 Newtons of force for engagement, and single digit Newtons of force to hold in place. 

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CMD – Selectable One Way Clutch – Neutral Selection
CMD – Neutral Selection

This image illustrates a CMD with a Neutral mode selection. This modal selection does not require any engagement, and only single digit Newtons of force would be required for provisional position holding.

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CMD – Selectable One Way Clutch – Reverse Selection
CMD – Reverse Selection

This image illustrates a CMD with a Reverse mode selection. The modal selection requires less than 20 Newtons of force for engagement, and single digit Newtons of force to hold in place.

Actuation Types

Many different devices including solenoids, hydraulic valves, linear actuators, and DC Motors can actuate our clutches. They are actuated in two ways. Functionally, we refer to these two methods as Tangential and Axial actuation.

Tangential CDM Selectable One Way Clutch Actuation

TANGENTIAL ACTUATION  Tangential force is applied to the selector plate (orange). As the selector plate shifts, the struts (green) are allowed to emerge and can engage in torque transfer. Tangential designs have utilized technologies such as solenoids, dc-motors, and hydraulic accumulators.  

 


Axial CDM Selectable One Way Clutch Actuation

AXIAL ACTUATION  Axial force is applied to the actuator plate (orange). As the plate shifts, the springs (red) push forward the struts (green), and are in position to engage in torque transfer. Axial designs have utilized technologies such as linear actuators and hydraulic pistons.

Benefits

A CMD can provide considerable advantages with respect to drag torque efficiency. This can translate to about 100 W energy savings at freeway speeds, when compared to a Roller / Friction Pack combination. The data below demonstrates the drag torque benefit of a CMD as compared to the roller one-way clutch / friction clutch combination it replaces in the low reverse position of a planetary automatic transmission. 

 

Transmission Efficiency (Drag Torque / Spin Loss)

 

DRAG TORQUE

   

 

ENERGY LOSS (WATTS)

 Roller / Friction vs. CMD Watts

 

 

 

Mass and Packaging Efficiency

Our high-volume production clutches are excellent examples of our ability to provide extra value to our customers. The example below not only provides one-way clutch functionality, but also offers the ability to serve as a backing plate for an adjacent friction clutch and a hub for an additional friction clutch pack. This allows our customers to reduce complexity and save both mass and system cost in transmissions. The clutch’s torque density also enables it to be manufactured with an Aluminum Pocket Plate resulting in 0.6 Kg mass-reduction on a rotating component, which further enhances OEM fuel economy targets. 

 

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Aluminum Pocket Plate – Mass Savings
Aluminum Pocket Plate

The inner diameter of this production MD One-Way Clutch was able to utilize Aluminum. This resulted in a system mass savings of 0.6 kg for the automatic planetary transmission.

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Rotating Mass Reduction – Inertia Improvements
Rotating Inertia Improvement

The MD One-Way Clutch’s torque density allows for the use of aluminum components. The production design above was able to use aluminum for the rotating Pocket Plate, which in addition to mass savings helped reduce transmission rotating inertia.

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Added Backing Plate Functionality
Backing Plate Functionality

The MD One-Way Clutch’s design flexibility offers additional benefits. This production design integrated a backing plate for an adjacent frictions clutch, which enables reduced complexity in the transmission.

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Added Center Hub Functionality
Center Hub Functionality

The MD One-Way Clutch’s design flexibility offers added benefits. This production design utilizes a center hub for a wet clutch – improving transmission packaging. 

Applications

Means MD technology has been installed in millions of automatic planetary transmissions.  Additionally, the technology is proving to be a very good fit in power-split HEVs, stop/start systems, and axle disconnects.

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Planetary Automatic
Mass Advantage
Drag Torque Advantage
Packaging / Space Advantage
BOM Reduction due to Superior Packaging
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Power Split Hybrid
Low Lubrication Needs
Modal Flexibility Translates to System Efficiency
Electric Controllability / Actuation
Near 0 Wattage Drag Torque Loss
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Stop / Start Systems & EBoosting
High RPM Capability
Small Package
Flexible Integration
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Axle Disconnect
Torque Dense
Electric Actuation
Modal Flexibility