Design of a Disconnect Clutch and Actuator for a 48V P4 Electric Drive Transmission

Abstract

The vehicle industry is making great strides in electric and hybrid technologies, representing a significant step towards reducing emissions from personal vehicles.

In order to make the transition to new hybrid technologies as convincing as possible, well-functioning and smooth transitions between traditional combustion engines and electric motors are required. So-called mild hybrids enable a cost-effective method to electrify existing drivetrains, as a smaller electric motor can be used separately from the combustion engine drivetrain.
Due to the reduced size of the electric motor, it is not able to rotate at the high top speeds of many modern personal vehicles. This necessitates a means to disconnect the electric motor from the wheels. This disconnect device is conceptualized in this report.

The aim of this thesis is to develop the disconnect system, which incorporates both the mechanical configuration and the actuator providing force transfer. A requirement is the use of a dog clutch.

The product development process of the report follows the methodology produced by K. T. Ulrich and S. D. Eppinger, resulting in seven promising concepts of which two were chosen for detailed design. A total of 34 concepts were screened. Despite being removed, some concepts show additional potential and are recorded in a concept library. Placements of the disconnect system, as well as actuator technologies were evaluated.

The two chosen concepts, concept WY - First Pinion and V - GenVI Hydro Sleeve, present two different methods for disconnection placed at different positions along the drivetrain. This enabled both effective work with one concept for each thesis student, and freedom of choice for BorgWarner during evaluation.
The thesis continued into the phase of detailed design but further work is required before the concepts can be verified and finished.

Popular Abstract

New ways to disconnect electric motors in hybrid drivetrains are vital for hybrid vehicles. Two intriguing ideas have been conceptualized; One using a frictionless solenoid plunger, the other a fast-acting hydraulic system.

This project conceptualized and explored new ways of imple- menting a disconnect system in mild hybrid electric vehicles. The concepts were developed with the extensive use of the method outlined by [1].

The first concept, First Pinion, is placed at the pinion of the electric motor output axle. This helps reduce the force required for a disconnect operation, while also making the system as compact as possible. By utilizing a coaxial solenoid in which the plunger is free to rotate, the frictional contacts of the system have effectively been eliminated. Guiding surfaces make sure the construction is kept stable even at the maximum 20 000 rpm of the electric motor. See figure 1. The second concept developed is the GenVI Hydro Sleeve and can be seen in figure 2. It is placed next to the differential on the rear driveshaft of the vehicle. It utilizes a hydraulic pump to move the two halves of the dog clutch together with high force. This creates interference and torque is transmitted from the electric motor to the driven wheel. By placing the disconnect at this position, most parts of the drivetrain can be disengaged when not in use.

The seamless integration of electric motors in hybrid vehicles is an important step towards lowering the carbon emissions of personal vehicles. Well-functioning and smooth transitions between the two different drivetrains are essential for a convincing driving experience. Mild hybrids are an economic and straight-forward method for electrifying vehicles, utiliz- ing a smaller electric motor only for assisting operations during driving. A downside of the smaller motor is the restrictions on its rotational speed, which amounts to the motor being damaged if used during the high velocities of modern vehicles. A driveline disconnect is a vital safety measure in modern hybrid vehicles. By disconnecting the electric motor from the driveline connecting the motor to the wheels, the electric motor is only used for its rated speeds. The disconnect also increases efficiency, as fewer parts of the driveline are spinning.

The concepts were developed using an iterative process and were chosen after careful evaluation against a broad range of concept ideas. Over thirty concepts were generated. The concepts were first screened, using a comparison with a reference product, and finally scored against weighted criteria. A variety of actuator technologies were considered and evaluated during a scoring process. Hydraulic, solenoid, and electromagnetic systems were found to be attractive candidates. By choosing two different placements with their own respective designs, there is room for flexibility and customer-specific alteration during future development.

• author: Blomqvist, Oscar and Schneider, Matthis
• supervisor: Per-Erik Andersson
• organization: Innovation
• course: MMKM05 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Driveline disconnect, hybrid technology, P4-architecture, electric rear axle, product development.
• language: English
• id: 9021692
• date added to LUP: 2020-06-24 08:39:54
• date last changed: 2020-06-24 08:39:54