Understanding Clutch 1 in Nissan's Hybrid CVT Systems
This analysis explores the crucial functions of Clutch 1 in Nissan's hybrid Continuously Variable Transmission (CVT) systems, specifically the RE0F02/3H (JF019E) model utilized in popular vehicles such as the Nissan Rogue, Pathfinder, and Infiniti QX60. The article details how this multi-plate dry clutch, positioned strategically within the traction motor, orchestrates the complex interplay between the engine, electric motor, and transmission to deliver power, initiate engine starts, and manage the charging of the lithium-ion battery. The dynamic and frequent engagement of Clutch 1 under diverse operating scenarios is underscored as a significant factor contributing to its operational demands and potential for wear.
At the core of these hybrid powertrains lies the Jatco RE0F02/3H CVT, also known as JF019E. Unlike traditional transmissions, this system integrates a traction motor where a torque converter would typically reside. This motor plays a pivotal role, allowing power to be delivered to the transmission from either the electric motor or the conventional internal combustion engine. The design of the transmission itself shares considerable similarities with Jatco's RE0F10D/E CVT 8, particularly evident in the identical appearance of their valve bodies. However, a key distinction lies in the nomenclature: what is commonly known as a lockup solenoid in other systems is referred to as a Clutch 1 solenoid in this hybrid variant.
The Clutch 1 solenoid is directly responsible for engaging and disengaging Clutch 1, a multi-plate dry clutch assembly situated at the front of the traction motor. The hub of this clutch is connected to a shaft driven by a torsional drive plate, which in turn is bolted to the engine's crankshaft. This mechanical linkage allows for the transfer of power and the initiation of engine rotation. Furthermore, the transmission incorporates a second clutch, designated Clutch 2, which functions as both a reverse brake and a forward drive clutch. Under specific operating conditions, Clutch 2 is designed to slip, a process that generates heat and necessitates additional cooling. To mitigate this, an electric cooling pump is installed near the transmission's sump. This pump circulates fluid, passing it through a pipe that runs adjacent to the solenoid pass-through case connector and is positioned beneath the heat exchanger. A temperature sensor in this vicinity provides crucial input to the vehicle's computer, signaling when to activate the cooler motor to maintain optimal operating temperatures.
The Hybrid Powertrain Control Module (HPCM) serves as the central intelligence for this sophisticated system. Located at the rear of the vehicle, a lithium-ion battery supplies power, managed by the HPCM through an inverter. The HPCM issues commands to the inverter, dictating whether the traction motor or the engine should power the transmission, or if the Li-ion batteries require charging. For instance, to start the engine, the HPCM directs the traction motor to rotate. This action generates hydraulic pressure within the transmission, and the Clutch 1 solenoid engages Clutch 1, which then rotates the engine, enabling it to start. The vehicle also retains a conventional starter motor for specific situations, such as extremely cold weather. The HPCM is programmed to initiate engine starts via Clutch 1 under conditions like an open hood, or when the selector lever is in park, the driver's seatbelt is unbuckled, and the driver's side door is open. When the Li-ion battery's charge is low, and the gasoline engine is running, Clutch 1 can engage the traction motor to recharge the battery, both while the vehicle is stationary in park or actively being driven. Conversely, when the Li-ion battery holds sufficient charge to propel the vehicle using the traction motor alone, the gasoline engine automatically shuts off, and Clutch 1 disengages. During deceleration, both Clutch 1 and the gasoline engine remain inactive. Regenerative braking then harnesses the kinetic energy from the wheels, converting it into electrical power through the traction motor to recharge the Li-ion battery.
The examples presented illustrate the dynamic and multi-faceted operation of Clutch 1 within these advanced hybrid CVT systems. Its constant engagement and disengagement across a spectrum of driving scenarios highlight its pivotal, yet demanding, role in optimizing power delivery, fuel efficiency, and battery management. This active involvement also points to why Clutch 1 is a component prone to significant wear and tear over time, making its understanding crucial for maintenance and diagnostic purposes.