EV Propulsion Systems

Electric Vehicle Propulsion Systems

Sustainable Driving with Efficient EV Propulsion Systems

Superior Performance with Advanced Electric Vehicle Propulsion Systems

Hybrid Dual-Clutch Transmission


The integration of advanced transmission systems plays a pivotal role in enhancing vehicle performance and efficiency. Clutch transmissions, particularly dual-clutch systems, are increasingly being adopted in electric and hybrid vehicles to offer seamless power delivery and improved driving dynamics. These transmissions enable quicker and smoother gear shifts, which are essential for optimizing the electric powertrain's efficiency and responsiveness. By utilizing dual-clutch technology, electric vehicles can achieve better acceleration, enhanced energy recuperation, and overall improved drivability.

How Dual Clutch Transmission (DCT) work?

Dual Clutch Transmission 6 speed basic designImage from: auto.howstuffworks.com
In a DCT system, the two clutches are connected to two separate sets of gears. The odd gear set is connected to one of the clutches and the even gear set to the other clutch. It is necessary to preselect the gears to realize the benefits of the DCT system. Accordingly, the off-going clutch is released simultaneously as the on-coming clutch is engaged. This gives the uninterrupted torque supply to the driveline during the shifting process. This pre-selection of gears can be implemented using complicated controllers such as fuzzy logic or simple ones such as selections based on the next anticipated vehicle speed.

What is the difference for Hybrid Dual Clutch Transmission (HDTC)?

An HDCT incorporates the features of a DCT but is specifically designed to work in conjunction with a hybrid powertrain. In addition to the internal combustion engine, an HDCT integrates an electric motor and a hybrid power system, such as a battery pack. This allows for the seamless blending of power from both the internal combustion engine and the electric motor.


Key features of an HDCT compared to a standalone DCT

Hybrid Power Integration 

HDCT is part of a hybrid powertrain wherein it can manage the distribution of power between the internal combustion engine and the IPM electric motor. This integration enables electric-only driving, hybrid driving modes, and regenerative braking.

Energy Recovery

HDCT, being part of a hybrid system, can take advantage of regenerative braking to recover and store energy in the battery packs. This contributes to overall energy efficiency and fuel savings.

Electric-Only Mode

In certain driving conditions, an HDCT-equipped hybrid vehicle can operate solely on electric power, utilizing the electric motor without engaging the internal combustion engine. EV Propulsion System

Enhanced Fuel Efficiency

The hybridization allows for optimized power conversion delivery based on driving conditions, contributing to improved fuel efficiency and reduced emissions.


Engine and Motor Operation

In a hybrid system, the motor supports the engine, improving driving performance and fuel consumption by regenerating with the motor and storing energy in the battery, using this to drive like an EV and for accelerating. The one-motor two-clutch hybrid system can separate the engine from the drivetrain as necessary. It can utilize the engine and motor as power sources, from running just on the motor to using both motor and engine for full acceleration, achieving a more efficient drive as per the situation. During regeneration and electric-mode driving, the engine is completely disconnected from the drive-train, resulting in zero loss from engine friction.

The operation of the clutches varies based on the driving situation, utilizing the engine and motor in different ways as follows:


Dual Clutch Transmission Scenario 1: Motor Drive (Electrical energy is delivered from the lithium-ion battery) Clutch #1 Disconnected, Clutch #2 ConnectedDual Clutch Transmission Scenario 2: Engine Drive (Engine power is delivered directly to the transmission) Clutch #1 Connected

Scenario 1: Motor Drive (Electrical energy is delivered from the lithium-ion battery)
Clutch #1 Disconnected, Clutch #2 Connected

Efficient use of battery power | Zero engine friction and noise | Ideal for low-speed or idle situations
Scenario 2: Engine Drive (Engine power is delivered directly to the transmission)
Clutch #1 Connected

Immediate power transfer due to the absence of a torque converter | Enhanced driving performance | Suitable for high-speed and high-power demands


Dual Clutch Transmission Scenario 3: Engine + Power Assist DriveDual Clutch Transmission Scenario 4: Regeneration, Decelerating

Scenario 3: Engine + Power Assist Drive (Both engine and motor power are delivered for acceleration)
Clutch #1 Connected

Utilizes high-output lithium-ion battery for additional power | Optimal for overtaking and rapid acceleration needs
Scenario 4: Regeneration, Decelerating (Engine rpm is zero, eliminating engine friction)
Clutch #1 Disconnected, Clutch #2 Connected

Efficient battery charging from the motor | Reduces wear and tear on the engine | Ideal for energy recovery during deceleration or stationary periods                        

Components System & Material Solutions

Clutch Assembly


Clutch Assembly Components
Image from: https://www.linkedin.com/pulse/clutch-components-alice-lan/
The clutch assembly is  responsible for engaging and disengaging the engine's power to the transmission. It allows the driver to smoothly switch gears while the vehicle is in motion, providing control over the vehicle's speed and power delivery. The components are the clutch disc, pressure plate, flywheel, bearing, and clutch pedal. In operation, pressing the clutch pedal disengages the clutch, allowing the driver to change gears without transmitting power to the wheels. Releasing the pedal re-engages the clutch, connecting the engine's power to the transmission and, ultimately, the wheels.

Silyl-Modified Polymers (SMP) and Polyurethane (PU) Adhesives and Sealants for Bonding of Clutch Plates 

These adhesives provide strong, durable bonds necessary for attaching friction materials to the clutch plates. Their resistance to high temperatures and environmental stressors ensures longevity and reliability.

BS7000F SMP series are fire-safe (meeting EN 45545 standards) and remain elastic over a wide temperature range (-40°C to 100°C), making them suitable for the temperature variations.

BS 9000 Series are PU based chemistry adhesive which has high strength and thixotropy


Transmission Housing


BMW DCT transmission housing
Image from BMW DCT transmission
The transmission housing protects and supports the transmission's internal components, including gears, shafts, bearings, and the clutch assembly. It prevents contaminants like dirt and water from entering, ensuring the system's longevity and reliability. Additionally, the housing contains transmission fluid, which lubricates and cools the internal parts, reducing friction and preventing overheating. Made typically from aluminum or cast iron, it also provides mounting points to securely attach the transmission to the vehicle's chassis and engine, facilitating efficient power transfer from the engine to the drivetrain.

Polyurethane (PU) Adhesives for Transmission Housing

PU adhesives (BS900) are particularly suited for bonding components within the transmission housing, where their high strength and resistance to oil and heat come into play.

Polyurethane and Silicone Sealants

These sealants are used to create tight seals in the transmission housing, preventing oil leaks and ensuring that the internal components are protected from external contaminants.

Valve Body & Pump Housing

12-17 BMW M5 M6 S63 Dual Clutch DCT Trans GS7D36BG Mechantronics Valve Body  OEM | eBayImage from BMW Valve Body
The valve body is the central control unit that directs hydraulic fluid to various valves to manage gear changes, ensuring smooth and timely shifts based on the vehicle’s speed and load. The pump housing encases the transmission pump, which circulates transmission fluid throughout the system to lubricate, cool, and operate the transmission components. Made from durable materials like cast aluminum or cast iron, the pump housing ensures the pump functions efficiently, providing a steady fluid flow essential for the transmission’s operation and longevity.

Flat Gaskets:

Provide static seals between stationary parts of the DCT to prevent the leakage of transmission fluid and other contaminants.

LINQSEAL GS-PTFE boasts outstanding dielectric properties and remarkable temperature stability, ranging from –180 °C to 260 °C. Its unparalleled chemical resistance extends to acids, bases, and solvents.

LINQSEAL GS-VMQ possesses excellent resistance to extreme temperatures from –55 °C to  210 °C. It also exhibits low compression sets, meaning it maintains its shape and sealing properties over time, ensuring reliable performance throughout the operational life of the system. 

Flat gaskets made of PTFE or FKM are used in sealing valve bodies and pump housings due to their excellent chemical resistance and ability to withstand high temperatures and pressures.

LINQSEAL GS-EPDM is highly recommended as outdoor sealing material. These gasket's rubber material exhibits high resistance to a wide range of environmental factors, including heat, cold, ozone, steam, electricity, UV rays, abrasion, and water, making it a preferred choice for various outdoor and challenging conditions.

LINQSEAL GS-FKM are composed of a fluorocarbon rubber, which stands out as a premier elastomer due to its remarkable chemical resistance. It is a sealing material in the aerospace sector for auxiliary power units, connectors, line fittings, hydraulic actuators, pumps, valves, and oil reservoirs.


Thermal Interface Materials Application on HCDT Components


  Operating Temperature, oC Materials Use
Clutch Components 150 - 200 Thermal Grease
Phase Change Materials
Power Electronics (Inverter and Motor Controller) (-40) - 100

Phase Change Materials
Epoxy Molding Compounds
Busbar Coating Powders

Power Electronics ( Semiconductor Devices) ex. IGBTS, MOSFETS (-40) - 150 Phase Change Materials
PTM6000HV (Optimized for IGBT printing)
Transmission Fluid Temperature Control 70 - 100 Phase Change Materials
Thermal Gap Pads
Thermal Grease
Electric Motor | Generator (-40) - 100 Phase Change Materials
Thermal Gap Pads
Thermal Grease