Supercharger Drives

Hannu Jääskeläinen

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• Introduction
• Mechanical Drives
• Electric Motors
• Hydraulic Motors

Introduction

A critical component of any supercharger is the drive. Superchargers are typically driven via a mechanical drive—usually a belt—connected to the engine’s crankshaft. An electric motor can also be used to drive the supercharger, especially if the vehicle already has an electrical system with sufficient capacity. At one time, hydraulic drives were also considered a possibility.

In some cases, the supercharger drive also performs additional functions. These may include:

• Engagement/disengagement—The drive must engage the supercharger when boost is required and disengage it when it is not. Especially for passenger cars, the engagement/disengagement should be transparent to the driver and not yield any undesirable noise, vibration or harshness (NVH).
• Speed control—The drive may be called upon to vary the supercharger speed independently from the engine’s speed.

Mechanical Drives

A belt drive coupling of the supercharger to the crankshaft with no clutch or variable speed transmission is the simplest mechanical drive for a supercharger. The selection of the pulley sizes on the supercharger and crankshaft fix the speed ratio of the supercharger relative to the engine. Adding a clutch or variable speed transmission can add additional operational flexibility to a mechanically driven supercharger.

Torsional Coupling. A torsional coupling can sometimes be mounted on the supercharger input shaft to help improve the supercharger sound quality, Figure 1 [2803]. The coupling allows limited rotation of the input shaft relative to the supercharger compressor. In some cases, the torsional coupling can also lock-up to act as a solid connection when higher torque is transmitted to the supercharger.

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